DESCRIPTION METHOD FOR PROCESSING COAL AND COAL PROCESSING SYSTEM
Technical Field [0001]
The present invention relates to a method for processing coal and a coal processing system for efficiently utilizing the coal, particularly so-called low-grade coal at a low cost in a coal utilization plant.
Background Art [0002]
Due to globally growing energy demand, utilization ratio of the low-grade coal is increasing year by year, regarding coal as a fuel used in a coal-fired thermal power plant, and such a tendency is expected to be further stronger from now. [0003]
However, a fuel consumption rate of the coal-fired thermal power plant is reduced the low-grade coal with high moisture is used. Particularly, in a coal utilization plant using pulverized coal, the coal is mixed with high-temperature air for combustion and dried, crushed, and thereafter introduced into a boiler. Therefore, increase of moisture in the coal as a fuel directly leads to deterioration of the fuel consumption rate. In addition, under an influence of a drying ability of a mill or the like, it is necessary to limit
an amount of using such a low-grade coal. [0004]
In order to avoid such a circumstance, for example, a drying method of coal and a drying plant are known as disclosed in Patent Document 1 described below. When the aforementioned low-grade coal is dried, this drying plant
dries the low-grade coal at 80°C to 150°C by utilizing combustion exhaust gas which has passed through an air heater of a boiler of the coal-fired thermal power plant, and after drying, feeds the exhaust gas (emission gas) to an electric dust collector (electric dust collector unit) of the coal-fired thermal power plant. [0005]
Then, after pulverized coal and the like brought by the exhaust gas are removed by the electric dust collector, the exhaust gas is discharged through a desulfurizer. Further, a scrubber (washing dust collector) that performs a so-called wet treatment is also known as a dust collector for removing the pulverized coal and the like brought by the exhaust gas. Various kinds of type are used in this scrubber, such as a water-storage type for collecting dust by allowing the exhaust gas to pass through pooled water; a pressurized water type for ejecting pressurized water into a flow of the exhaust gas; and a charging type and a rotation type. [0006]
Normal transport of coal (coal feed) to such a coal-fired thermal power plant is performed, for example
as shown in Fig. 11. Specifically, in a coal mixing step 503, bituminous coal 501, i.e., high-grade coal, and sub-bituminous coal 502, i.e., low-grade coal, are blended (mixed) in a coal collection relay plant 500 called a coal center, with a mass ratio of approximately 8:2, for example. Thereafter, in a transporting step 504 or a belt conveyor or the like, blended (mixed) coal is transported to a cement production plant 600 or a coal-fired thermal power plant 700 as a coal utilization plant. Then, as shown in FIG. 11, the transported coal is used for a fuel in sintering step 601 or in the cement production plant 600, and in boiler step 701 or the coal-fired thermal power plant 700. [Related Art Document] [Patent Literature] [0007]
[Patent Literature 1] Japanese Patent Application Laid-Open No. 10-281443
Summary of the Invention Technical Problem [0008]
However, in a conventional drying plant disclosed in the aforementioned Patent Document 1, drying with high thermal efficiency is realized in the coal-fired thermal power plant. However, an efficient process is not necessarily achieved, due to fluctuation of operation conditions in the power generation plant.
[0009]
Further, since there are few reserves of a so-called high-grade coal such as bituminous coal, the price thereof tends to rise due to a steep rise of a coal price and an increase of energy demand of recent years. Therefore, there is a desire to utilize the low-grade coal with higher utilization efficiency, which has bountiful reserves that can be utilized at a moderate cost in an environmentally friendly manner. [0010]
Further, for example, in the conventional drying plant, the exhaust gas containing the pulverized coal after dry treatment is discharged through the electric dust collector and the desulfurizer, or the exhaust gas is discharged through wet treatment, thereby removing the pulverized coal or the like.
In the former case, the pulverized coal which failed to be removed may be discharged included in the exhaust gas of high temperature, thus posing a high possibility of causing an adverse influence on an environment or catching fire. In the latter case, due to wetting of the pulverized coal and the like, which are removed from the exhaust gas, a dry treatment needs to be performed again when the pulverized coal and the like are recovered and reused, thus involving a problem that efficient use of resources is not achieved and expansion of loss of energy is hardly prevented. [0011]
Further, for example, when the low-grade coal transported from the aforementioned coal collection relay plant 500 is dried and only the dried low-grade coal is fed to a fuel combustion boiler of the coal-fired thermal power plant 700 (boiler step 701), there is a possibility that dust is generated and a neighboring environment is contaminated. In addition, when the coal after blending (mixing) with the high-grade coal is dried before combustion in the coal-fired thermal power plant 700, an amount to be dried is increased, resulting in poor utilization efficiency. [0012]
Further, in the conventional drying plant, for example, the high-grade coal and the low-grade coal after dry treatment are mixed with each other, which are then utilized as a fuel of the coal-fired thermal power plant. However, various low-grade coal are dried together under uniform and fixed conditions. Therefore, for example, when there is a fluctuation in total moisture of the low-grade coal depending on the conditions, the total moisture of the coal, which is brought to the coal combustion boiler (fuel combustion boiler), is also fluctuated in some cases. In addition, there is not so much difference in total moisture before/after drying, because of low moisture that can be dried, depending on the type of the coal. [0013]
In this case, conditions of dry treatment applied
to the low-grade coal (such as heat quantity required for drying, and drying time), and operation conditions of the coal-fired thermal power plant (such as operation time and feed amount of the fuel), and so forth, need to be fluctuated frequently. Therefore, there is a problem that stable operation of the coal-fired thermal power plant is difficult, and utilization of additional staff or expansion of devices is necessary, thus raising a cost. [0014]
The present invention has been made in order to solve the above-described problem, and it is desired to provide a method for processing coal and a coal processing system capable of efficiently utilizing the low-grade coal in particular in a coal utilization plant, by efficiently drying the low-grade coal at a low cost in an environmentally friendly manner.
Further, according to the present invention, it is desired to provide a method for processing coal and a coal processing system capable of improving a thermal efficiency during combustion in the coal utilization plant because the total moisture of the coal can be reduced, in which the low-grade coal and the high-grade coal are mixed, and also capable of improving utilization ratio of the low-grade coal by suppressing an influence of the dust on an environment as much as possible, the dust being generated from the low-grade coal during transport.
Further, according to the present invention, it is
desired to provide a method for processing coal and a coal processing system capable of realizing stabilization of a quality of the coal and a reduction of total moisture of the coal, which is brought to the coal-fired thermal power plant and in which the low-grade coal and the high-grade coal are mixed with each other, and capable of improving the thermal efficiency by realizing an improvement of combustion efficiency, and also capable of operating the coal utilization plant at a low cost by stabilizing operating conditions of the coal-fired thermal power plant and reducing a heat quantity required for dry treatment. Solution to Problem [0015]
The present invention provides a method for processing coal by drying the coal and firing the coal in a coal-fired thermal power plant, comprising the steps of:
feeding the coal into a drying chamber of a paddle stirring type dryer, an inner portion of the paddle stirring type dryer is partitioned by a gas distribution plate into an upper drying chamber and a lower gas chamber, the drying chamber including a paddle shaft laid therein, the paddle shaft being rotatably provided in the drying chamber, and a plurality of paddles for stirring the coal being attached to the paddle shaft at constant intervals in an axial direction of the paddle shaft; and
feeding heat gas into the gas chamber from a heat
gas feeding plant different from the coal-fired thermal
power plant to dry the coal.
[0016]
Further, the method may also comprise the step of : mixing dry coal after drying with coal not to be processed different from the dry coal; and feeding the mixed coal to the coal-fired thermal power plant. [0017]
Further, the method may further comprise the step of : the exhaust gas containing pulverized coal discharged from a drying plant is mixing with other gas to cool. [0018]
Further, the method may also comprise the step of : before drying the coal, judging necessity of dry treatment for the coal, the necessity of the dry treatment being judged based on information regarding total moisture of coal before drying and equilibrium moisture; and drying coal to be processed having certain properties, when it is judged to require the dry treatment, to a certain state. [0019]
The heat gas feeding plant preferably functions as a cement production plant. Heat gas discharged from the cement production plant may include exhaust gas having a heat of about 400°C discharged from a preheating device such as a suspension preheater as a sintering step, and
exhaust gas having a heat of about 300°C discharged from
a cooling device such as a clinker cooler as a cooling step. Among these types of gas, the exhaust gas discharged from the sintering step has a low oxygen concentration of about several %, and may be preferable in terms of safety, as a heat source used for the dry treatment applied to the coal. However, in many cement production plants, a heat (exhaust heat) of the heat gas (exhaust gas) discharged from the sintering step is already utilized as air for drying in a crashing step, or for generation of electric power by collecting heat of the exhaust gas. Therefore, the heat gas is preferably the exhaust heat not utilized by the cement production plant. That is, for example, the heat gas is preferably the gas discharged from the clinker cooler as a cooling step (the exhaust gas of the clinker cooler). [0020]
Further, the coal is preferably dried, so that a temperature of the coal after drying is 70°C or less. The mixture of coal is preferably performed by feeding the dry coal to a transport unit for transporting the coal not to be processed. Other gas mixed with the exhaust gas after dry treatment is preferably air of an atmospheric temperature. The exhaust gas is preferably
cooled to a temperature of 75°C or less. Preferably, the method further comprises the step of separating pulverized coal from a mixed gas containing the exhaust gas containing the pulverized coal and other gas. [0021]
The necessity of the dry treatment is preferably judged based on the information regarding the total moisture of the coal and the equilibrium moisture of the coal. Further, the dry treatment is judged to be necessary, preferably, when a value obtained by subtracting the equilibrium moisture of the coal from the total moisture of the coal is 8 or more, and the dry treatment is judged to be unnecessary when the value is less than 8. The coal to be processed is preferably reformulated and molded into a pellet shape and/or a briquette shape. The dry treatment is preferably performed so that the total moisture of the coal after the dry treatment is beyond the equilibrium moisture of the coal. [0022]
Energy required for removing moisture adhered to the coal is comparable to an evaporation latent heat of water. In contrast, energy required for removing in-particle moisture (water of crystallization or internal water) other than the adhered water is greater than the energy required for removing the adhered moisture. Therefore, the coal with high adhered moisture is preferable as the coal to be processed or as a drying object. Since coal with a lot of moisture adhered thereto may enjoy a large amount of moisture decrease, a drying operation for such the coal may bring a great advantage, i.e., greater increase in heat generation. Therefore, the sub-bituminous coal or brown coal with a
lot of moisture adhered thereto is preferable as the coal to be processed. Meanwhile, the high-grade coal such as bituminous coal has less moisture adhered thereto, and therefore a merit of a drying operation for such coal is smaller. Accordingly, the bituminous coal is blended (mixed) with dry coal, as coal not to be processed. [0023]
The method for treating coal according to the present invention is a process of blending (mixing) dry coal obtained by drying coal to be processed with the coal not to be processed different from the dry coal. Meanwhile, a process of blending (mixing) the coal to be processed with coal not to be processed in advance, and thereafter drying the coal is used, an advantage of drying may become smaller. In addition, a quantity of the coal to be dried is increased, and the dryer and supplementary plants grow in size. This is not preferable. In the method for processing coal according to the present invention, the quantity to be dried can be reduced, and the dryer and supplementary plants can not be prevented from growing in size, as compared to the latter case. [0024]
Note that blending (mixing) ratio of the coal by mass ratio of the dry coal and the coal not to be processed different from the dry coal, may be set within a range of 8:2 to 2:8, preferably 8:2 to 3:7, and further preferably 7:3 to 5:5. If the mass ratio of the dry coal
with respect to the coal after blending (mixing) is beyond 8, the mass ratio of the dry coal is equal to the mass ratio of the coal after blending (mixing), and it is efficient to dry the coal after blending (mixing). This is not preferable. Further, if the mass ratio of the dry coal is below 2, the increase in heat generation by drying is small. This is not preferable, either. [0025]
Further, the present invention provides a coal processing system for drying the coal and firing the coal in the coal-fired thermal power plant. The system comprises a paddle stirring type dryer. The paddle stirring type dryer includes: an inner portion partitioned by a gas distribution plate into an upper drying chamber and a lower gas chamber; a paddle shaft provided rotatably and laid in the drying chamber; a plurality of paddles for stirring the coal attached to the paddle shaft at constant intervals in an axial direction of the paddle shaft; a feeding port for feeding the coal provided in the drying chamber; and a heat gas feeding port provided in the gas chamber to feed heat gas for drying the coal.
The heat gas feeding port being connected to an exhaust line for exhausting exhaust gas from a clinker cooler of a cement production plant. [0026]
Further, the present invention provides a processing system, including: a coal collection relay
plant;
a coal-fired thermal power plant; a coal dry treatment plant; and a cement production plant. A plural types of coal with different properties are transported to the coal dry treatment plant from the coal collection relay plant.
Before the coal is fired and utilized in the coal-fired thermal power plant, out of such plural types of coal, coal to be processed having certain properties is dried so as to be set in a certain state by using heat gas from the cement production plant. The dry coal after drying is mixed with coal not to be processed different from the dry coal, and is fed to the coal-fired thermal power plant. [0027]
Further, the present invention provides a coal processing system, including: a coal-fired thermal power plant; a coal dry treatment plant; and a cement production plant. Before a plural types of coal with different properties are fired and utilized in the coal-fired thermal power plant, the heat gas from the cement production plant is introduced to the coal dry treatment plant, and the coal to be processed with certain properties out of the plural types of coals is dried by the coal dry treatment plant. Also, other gas is mixed with exhaust gas generated during dry treatment, to thereby cool the exhaust gas. [0028]
Further, the system may also include: a coal collection relay plant; a coal-fired thermal power plant; a coal dry treatment plant; and a cement production plant. Before the coal is fired and utilized by the coal-fired thermal power plant, a plural types of coal with different properties are transported to the coal dry treatment plant from the coal collection relay plant. Then, the heat gas from the cement production plant is introduced to the coal dry treatment plant. Coal to be processed having certain properties, which is out of the plural types of coal is dried so as to be set in a certain state. The dry coal after drying is blended (mixed) with the coal not to be processed different from the dry coal, which is then fed to the coal-fired thermal power plant. [0029]
Preferably, the coal dry treatment plant is, for example, an inner portion of the paddle stirring type dryer is partitioned by a gas distribution plate into an upper drying chamber and a lower gas chamber, the drying chamber including a paddle shaft laid therein, the paddle shaft being rotatably provided in the drying chamber, and a plurality of paddles for stirring the coal being attached to the paddle shaft at constant intervals in an axial direction of the paddle shaft. [0030]
Further, the present invention provides a coal processing system, including: a coal-fired thermal power
plant; a coal dry treatment plant; and a cement production plant. Before a plural types of different coal with different properties are fired and utilized in the coal-fired thermal power plant, necessity of a dry treatment for the coal by the coal dry treatment plant is judged, and based on a judgment result of the necessity of the dry treatment, heat gas is introduced from the cement production plant, and coal to be processed having certain properties, when it is judged to require the dry treatment, is dried to a certain state.
Advantageous Effects of Invention [0031]
According to the present invention, there are provided the method for processing coal and the coal processing system capable of efficiently utilizing particularly the low-grade coal in the coal-fired thermal power plant, by efficiently drying the low-grade coal at a low cost in an environmentally friendly manner.
Further, according to the present invention, the total moisture of the coal can be reduced, the coal being in a blended (mixed) state of the low-grade coal and the high-grade coal. Therefore, improvement of thermal efficiency during combustion in the coal-fired thermal power plant is achieved, and also improvement of a utilization ratio of the low-grade coal is achieved by lessening an influence on an environment, namely, the influence of dust generated from the low-grade coal
during transportation can be lessened.
Further, the coal-fired thermal power plant can be safely operated by preventing the influence on the environment by the exhaust gas discharged during the dry treatment, or by preventing the possibility of ignition.
Further, according to the present invention, the stabilization of the quality and the reduction of the total moisture of the coal can be achieved, the coal being mixed and brought to the coal-fired thermal power plant, and the improvement of the thermal efficiency is achieved by realizing the improvement of the combustion efficiency, and also the coal-fired thermal power plant can be operated at a low cost by reducing a heat quantity required for drying the coal while stabilizing the operating conditions of the coal-fired thermal power plant.
Brief Description of the Drawings [0032]
FIG. 1 is a block diagram showing an example of an outline of an overall coal processing system for realizing a method for processing coal according to a first embodiment of the present invention.
FIG. 2 is an explanatory view for explaining an example of a coal dry treatment plant of the aforementioned system.
FIG. 3 is a block diagram showing an example of a flow of an overall coal processing system for realizing a
method for processing coal according to a second embodiment of the present invention.
FIG. 4 is a block diagram showing an example of an outline of the overall coal processing system.
FIG. 5 is an explanatory view for explaining an example of a coal dry treatment plant of the coal processing system according to the second embodiment of the present invention.
FIG. 6 is a block diagram showing an example of a flow of a method for processing coal and an overall coal processing system according to a third embodiment of the present invention.
FIG. 7 is a block diagram showing an example of an outline of the overall coal processing system.
FIG. 8 is an explanatory view for explaining an example of the coal dry treatment plant in the coal processing system.
FIG. 9 is a block diagram showing an example of a flow of a method for processing coal and an overall coal processing system according to a fourth embodiment of the present invention.
FIG. 10 is a block diagram showing an example of an outline of the overall coal processing system.
FIG. 11 is a block diagram showing an example of a flow of an overall conventional coal processing system.
Description of Embodiments [0033]
Preferred embodiments of a method for processing coal and a coal processing system according to the present invention will be described hereafter, with reference to the drawings. [0034] (First embodiment)
FIG. 1 is a block diagram showing an example of an outline of an overall coal processing system for realizing a method for processing coal according to a first embodiment of the present invention. As shown in FIG. 1, a coal processing system 1 includes: a coal-fired thermal power plant 100, a cement production plant 200 which is a heat gas feeding plant, and a coal dry treatment plant 300. [0035]
The coal-fired thermal power plant 100 is a plant for generating electric power by firing and utilizing a plurality of coal with different properties, including a power generating step similar to the power generating step of a publicly-known coal-fired thermal power plant. That is, in the coal-fired thermal power plant 100, coal fed thereto is first crushed into particles having a certain size, in crushing step 102 using a vertical mill or the like, and is fired at a temperature of about 1600°C by a pulverized coal combustion boiler in boiler step 103. [0036]
Then, a steam turbine is driven in power generating
step 104 using thermal energy generated by the boiler step 103, so that electric power is supplied. Note that in feed water heating step 105, feed water to a fuel combustion boiler is heated by a feed water heater utilizing bleed air from the steam turbine, so that a thermal efficiency can be improved in the power generating step 104.
[0037]
Meanwhile, nitrogen oxide is removed from exhaust heat (exhaust) gas generated in the boiler step 103, in denitrating step 106 using stack-gas denitrification apparatus or the like. The exhaust gas after removing nitrogen oxide, is further used for warming combustion air which is sent to the boiler step 103 under pressure, by using a gas air heater in heat recovering step 107. Thereafter, dust is collected by dust collecting step 108 using an electric dust collector for collecting dust that flows in the exhaust heat gas.
[0038]
Thereafter, sulfur oxide is removed from the exhaust heat gas by desulfurizing step 109 using stack-gas desulfurization apparatus or the like. The exhaust heat gas after removing sulfur oxide, is discharged into the atmosphere. Thus, electric power is generated by the coal-fired thermal power plant 100 of the coal processing system 1 according to the first embodiment.
[0039]
In this processing system 1, coal is dried by the
coal dry treatment plant 300 before it is fed to the crushing step 102. Here, the low-grade coal such as sub-bituminous coal or brown coal can be given as the dried coal. Such coal is dried so as to be reformed into a coal having certain moisture. [0040]
The certain moisture means as low moisture as possible, but not below equilibrium moisture of the coal. The equilibrium moisture mentioned here means the moisture set in an equilibrium state in an atmosphere (outlet of a dryer or storage silo, atmospheric air) to which the coal is exposed in a process of utilization.
It is desirable that the moisture of the dry coal be as low as possible, because higher heat can be generated by further removing the moisture of the coal. However, if the moisture of the dry coal discharged from the coal dry treatment plant 300 is below the equilibrium moisture of the coal in the atmosphere, the dry coal absorbs moisture in the atmosphere. [0041]
Accordingly, the moisture is set so as not to be below certain equilibrium moisture, to prevent reabsorption of moisture by the dry coal, and secure drying efficiency. The moisture not below the equilibrium moisture is moisture not less than the equilibrium moisture of the coal, and not more than 1.3 times of the equilibrium moisture thereof. Preferably, it is not less than the equilibrium moisture of the coal,
and not more than 1.2 times of the equilibrium moisture of the coal. For example, when the sub-bituminous coal with total moisture of 25 wt% and equilibrium moisture of 15 wt% is dried, certain moisture is as low as possible but not below 15 wt%, and for example in a range of 15 wt% to 19.5 wt%, preferably in a range of 15 wt% to 18 wt%. Note that the moisture not below the certain equilibrium moisture is varied depending on the kinds of the coal. Accordingly, an amount of coal feed, a temperature of dried heat gas, an amount of dried heat gas, and drying conditions of a drying plant such as a rotation speed of a paddle are suitably set, depending on total moisture of the coal. [0042]
Note that total moisture was measured so as to comply with JIS M8820 (cokes Coal and coke Determination of total moisture content of a lot) . A curve of equilibrium water-content ratio of the dry coal can be obtained by measuring the equilibrium moisture of the dry coal based on, for example, JIS A1475 (Method of test for hygroscopic sorption properties of building materials). The equilibrium water-content ratio of the dry coal is obtained from the curve of the equilibrium water-content ratio, and temperatures and relative humidity data in atmospheres (outlet of a dryer and storage silo, atmospheric air) to which the coal is exposed in a process of utilization of the dry coal. The obtained equilibrium water-content ratio means a
percentage of water mass based on total mass after drying. Therefore, the equilibrium moisture of the dry coal can be obtained by converting it to the percentage of the water mass based on the total mass before drying by the following formula (1). [0043] [Formula 1]
Equilibrium moisture (mass%) =equilibrium water-content ratio
÷(100 + equilibrium water-content ratio) x 100 (1)
[0044]
In this processing system 1, energy of the exhaust heat in the cement production plant 200 is utilized by the coal dry treatment plant 300. That is, the cement production plant 200 includes a producing step similar to a producing step of a publicly-known cement production plant, and in this producing step, raw materials such as limestone, clay, burstone, and iron are crushed by crushing step 201 using a mill, which are then sintered at a temperature of about 1450°C using a sintering furnace or the like, with the coal as a fuel in sintering step 202, to thereby obtain a cement clinker. Thereafter, the sintered cement clinker is cooled by cooling step 203 using a clinker cooler or the like, and gypsum or other mixed materials are mixed and crushed in finishing step 204, to thereby finish the clinker as powdery cement. [0045]
In such producing steps, particularly in the cooling step 203, the exhaust gas having a heat of about
300°C is discharged from the clinker cooler or the like. However, in the existing systems, the exhaust heat of such exhaust gas is hardly utilized, but is discharged. Accordingly, in this processing system 1, the exhaust heat of the exhaust gas can be utilized for the coal dry treatment by the coal dry treatment plant 300, with almost no necessity for remodeling the existing plant. [0046]
This is may promote energy saving in utilization of the coal, and it is possible to seek for improvement in fuel consumption rate. Also, the coal to be processed such as an inexpensive low-grade coal, which has bounty of recoverable resources, can be utilized likes high-grade coal. Therefore, life of coal resources can be extended. [0047]
Here, the coal dry treatment plant 300 for realizing the dry treatment applied to the coal will be described. FIG. 2 is an explanatory view for explaining an example of the coal dry treatment plant 300 of the coal processing system 1 according to the first embodiment of the present invention. Note that in the description hereafter, the same signs and numerals are assigned to portions overlapped on an already explained portion, and explanation thereof is omitted, and clear description is not made for a portion particularly not related to the present invention. [0048]
First, for example, the high-grade coal or the low-grade coal is fed to a bifurcated damper 3 from an existing coal feed line 2, and in this bifurcated damper 3, for example, the high-grade coal is sorted to the side of an existing coal feed line 4, and the coal to be processed such as low-grade coal is sorted to the side of an existing coal feed line 5. [0049]
Sorting by the bifurcated damper 3 is performed by controlling the bifurcated damper 3 by a controller 7, based on information of the total moisture of the measured coal, which is sent from a moisture meter 6 installed on the existing coal feed line 2 for example. The coal to be processed such as low-grade coal sorted to the side of the existing coal feed line 5 is charged into a receiving silo 9. [0050]
The coal to be processed charged into the receiving silo 9 is pulled out from the receiving silo 9 by a pull-out conveyor 12, and is transferred to a screw feeder 14 via a vertical conveyor 13. The coal to be processed transferred to the screw feeder 14 is charged into a dryer 20 via a rotary valve 15. [0051]
The dryer 20 includes a publicly-known paddle stirring type dryer for drying the coal to be processed while the coal to be processed on a gas (air) distribution plate 22 for example is stirred by paddles
21. The coal to be processed, which is stirred and dried (dry coal) is discharged from the dryer 20 by a discharge conveyor 17 via a rotary valve 16. In this example, preferably the coal is dried so that the temperature of the coal after drying becomes 70°C or less. Thus, a possibility of ignition of the dry coal can be effectively suppressed. For this purpose, drying conditions of a drying plant such as an amount of coal feed, a temperature of dried heat gas, an amount of the dried heat gas supply, and a rotation speed of the paddles are suitably set. Further, the temperature inside the dryer is preferably monitored.
Exhaust gas from the dryer 20 is sent to a bag filter 19 by a fan 18 with dust removed by the bag filter 19, and thereafter is discharged into the atmosphere from an exhaust duct 31 by a bag filter fan 30. [0052]
Inside of the dryer 20 is partitioned into an upper drying chamber and a lower air chamber by the gas (air) distribution plate 22. A plurality of slit-shaped openings are provided side by side on the gas (air) distribution plate 22. Also, a paddle shaft is laid in the drying chamber. It is provided in the drying chamber such that it may rotate at various speeds. A plurality of paddles 21 for stirring the coal to be processed are attached to the paddle shaft at certain intervals in an axial direction of the paddle shaft. The paddles 21 are attached with phases of attachment angles mutually
shifted, viewed from the axial direction of the paddles 21 arranged adjacent to each other in the axial direction of the paddle shaft. An amount of coal remaining in the drying chamber is adjusted by the number of times of rotations of the paddles, a scraping area of the paddles, an attachment position or a shape of a discharging port and the like. A bulk volume occupied by the coal remaining in the drying chamber is preferably in a range of 20 to 30 volume % of a volume of a column to which the paddles may reach. That is, a ratio of the coal remaining in the drying chamber against 100 volume % of a paddle stirring volume (a holdup rate) is preferably in a range of 20 to 30 volume %. [0053]
Each paddle 21 is attached to the paddle shaft, so as to be inclined with respect to an axial line of the paddle shaft, to add a stirring force axially to the coal to be processed. Also, it is attached to the paddle shaft such that its inclination angle can be adjusted. In addition, a feeding port and a discharging port for the coal to be processed are provided to one end side and the other end side of the paddle shaft of the drying chamber. Dried heat gas is introduced into the air chamber, and such dried heat gas is sprayed into the drying chamber at a high speed through slit-shaped openings on the gas (air) distribution plate 22, to thereby fluidize the coal to be processed. [0054]
For example, the coal to be processed is fluidized by the dried heat gas of about 100°C, and the paddles 21 are rotated in association with a rotation of the paddle shaft, to thereby scrape the coal to be processed, so that stirring of particles is satisfactorily performed. Then, the coal to be processed is dried while being moved in the axial direction of the paddle shaft by an action of the paddles 21 attached to the paddle shaft while inclined thereto. [0055]
The dry coal discharged from the dryer 20 is charged into a product silo 34 via a vertical conveyor 33 from the discharge conveyor 17. Note that dust (pulverized coal) collected by the bag filter 19 is also charged into the product silo 34 by a dust (pulverized coal) transfer system 35. [0056]
Then, product coal including the dry coal is fed to a vertical conveyor 38 from the product silo 34 by a transfer conveyor 37 having a quantitative feeding meter system 36, and is sent to an existing main coal feed line 39. Then, it is mixed with the high-grade coal such as bituminous coal on this line (coal mixing), and is fed to crushing step 102 of the coal-fired thermal power plant 100. Then, it is utilized by boiler step 103 as a fuel of a pulverized coal combustion boiler. Specific coal mixing method may include a method of feeding the dry coal to the bituminous coal which is transported by a
belt conveyor, and a method of feeding the dry coal to a joint portion, or a shoot portion, for example, of the belt conveyor for transporting bituminous coal. The bituminous coal and the dry coal are blended with each other by repeating a moving motion, a dropping motion, and a rolling motion on the belt conveyor by which the coal is transported. [0057]
In the coal dry treatment plant 300, when the dry treatment is applied to the coal to be processed by the dryer 20, the exhaust gas containing the exhaust heat which is discharged from the clinker cooler or the like in the cooling step 203 of the cement production plant 200 is supplied to the dryer 20 and utilized for drying.
Low-grade coal has a high spontaneous heating property, thus posing a risk that the low-grade coal may catch fire in the dryer by being dried. Therefore, as a safety measure against the ignition of the low-grade coal in the dryer 20, plant air such as nitrogen gas and atmosphere, and tap water (industrial water) are utilized. [0058]
The aforementioned exhaust gas contains termal energy. However, it is discharged without being used
even if it has a temperature of about 300°C when it is discharged from the clinker cooler or the like, for example. In the dryer 20 of the coal dry treatment plant 300 according to this example, it is utilized for the dry treatment of the coal to be processed, even if the
temperature thereof is decreased to about 80°C to 200°C
when it is introduced into the dryer 20. Then, the coal
to be processed is dried to certain moisture by the dry
treatment performed by the dryer 20.
[0059]
(Examples of a first embodiment)
Examples and a comparative example of the first embodiment will be described specifically hereafter.
As the dryer used in the examples and the comparative example, a paddle type dryer having a structure equivalent to the structure of the dryer 20 is used, and the examples and the comparative example are conducted under the following conditions. [0060]
The dryer used herein has a columnar drying chamber with an inner dimension of Φ268 mm x 740 mm. It also has a feeding port for coal to be processed with a dimension of Φ140 mm. The feeding port is placed directly above a position that is 50 mm away in a paddle shaft direction from a side wall of the drying chamber on a side of the feeding port of the coal to be processed. The dryer used herein has a semi-circular discharging port for discharging the coal to be processed. It has a dimension of 140 mm x 140 mm. The discharging port is placed on a side wall at a position 495 mm away in the axial direction of the paddle shaft, from the side wall of the drying chamber on the feeding port (at a position of angle 5° to 75° based on a horizontal reference). The
exhaust gas after removing dust using cyclone is released into the atmosphere through an exhaust gas line in an upper part of the discharging port. [0061]
Further, slit opening of 3 mm x 140 mm each are arranged at intervals of 45 mm on the gas (air) distribution plate between the drying chamber and the air chamber. Paddles of 75 mm x 75 mm each are arranged on the paddle shaft. The paddle shaft has an axial diameter
of Φ76.3. The paddles are arranged on the paddle shaft at intervals of 90 mm, with attachment angles viewed from
the axial direction mutually shifted by 120°. The paddle shaft thus arranged with paddles is laid in the drying chamber, and a screw feeder for feeding the coal to be processed is provided to an upper part of the feeding port of coal to be processed.
Note that in order to evaluate the safety of the dryer, the exhaust gas with dust removed was analyzed and the temperature of the dry coal was measured. [0062]
Properties of the coal to be processed (sub-bituminous coal) used in the examples and the comparative example are shown in the following Table 1. The total moisture was measured based on JIS M8820 (cokes Coal and coke -- Determination of total moisture content of a lot). Proximate analysis was done based on JIS M8812 (Coal and coke -- Methods for proximate analysis). Calorific Value was measured based on JIS M8814 (Determination of
Calorific Value of Coal and Coke). A particle size distribution was measured based on JIS M8801 (Coal -Testing Methods). [0063] [Table 1]
(Table Removed)
[0064]
The equilibrium moisture of the coal to be processed (sub-bituminous coal) used in the examples and the comparative example is shown in Table 2. The equilibrium moisture was calculated as follows. First, a correlating equation for obtaining the equilibrium moisture from temperature and relative humidity is prepared, based on data of equilibrium water-content ratio of the coal to be processed obtained pursuant to a desiccator method (measurement temperature: 20°C to 50°C
and relative humidity: 10% to 98%) of JIS A1475 (Method of test for hygroscopic sorption properties of building materials). Then, by substituting into this correlating equation the temperature and the relative humidity under an atmosphere condition (outlet of the dryer and atmosphere) in which the examples and the comparative example are executed, the equilibrium water-content ratio of the dry coal was obtained. Next, the equilibrium moisture was calculated from this equilibrium water-content ratio by using formula (1).
[0065]
As a dry heat source of the dryer, the temperature of the exhaust gas from the clinker cooler of the cement production plant was adjusted by air to about 80°C to about 180°C, and a flow rate thereof was set to 150 Nm3/h. A remaining time of the coal in the dryer was set to about 180 seconds by adjusting the number of times of rotation of the paddles.
[0066]
[Table 2]
(Table Removed)
[0067]
Results of a test performed under the aforementioned conditions are shown in Table 3. Note
that the volume of the drying chamber where the coal remains was determined based on a portion corresponding to a distance from a first slit of the gas distribution plate to the discharging port. In this example, a distance from the side wall of the drying chamber on the feeding port of the coal to be processed side, to 45 mm -495 mm in the axial direction of the paddle shaft, was used to determine an effective volume used for calculating a heat capacity coefficient. [0068] [Table 3]
(Table Removed)
[0069]
The examples and the comparative example will be described hereafter. (Example 1)
As a result of conducting a test by setting the
feed amount of the coal to 20.4 kg/h, and the temperature of the dry heat source to 82°C, it was found that the total moisture of the coal was 20.3 mass% after drying, while it was 32.5 mass% during feeding, and the heat capacity coefficient was 5612 kcal/m3hr°C. Further, the temperature of the coal at this time was 19.9°C. (Example 2)
As a result of conducting a test by setting the feed amount of the coal to 20.0 kg/h, and setting the temperature of the dry heat source to 121°C, it was found that the total moisture of the coal was 19.0 mass% after drying, while it was 33.1 mass% during feeding, and the heat capacity coefficient was 5236 kcal/m3hr°C. Further, the temperature of the coal at this time was 25.3°C. (Example 3)
As a result of conducting a test by setting the feed amount of the coal to 40.1 kg/h, and setting the
temperature of the dry heat source to 180°C, it was found that the total moisture of the coal was 18.4 mass% after drying, while it was 32.4 mass% during feeding, and the heat capacity coefficient was 5020 kcal/m3hr°C. Further, the temperature of the coal at this time was 40.1°C. (Comparative example)
As a result of conducting a test by setting the feed amount of the coal to 20.3 kg/h, and setting the temperature of the dry heat source to 180°C, it was found that the total moisture of the coal was 12.1 mass% after drying, while it was 32.9 mass% during feeding, and the
heat capacity coefficient was 2747 kcal/m3hr°C. Further, the temperature of the coal at this time was 79.0°C. [0070]
As described in Examples 1 to 3, it was found that by suitably controlling the feed amount of the coal to be processed and the temperature of the dry gas, the coal to be processed could be dried from the total moisture (about 32.8 mass%) to certain moisture, namely to as low moisture as possible but not below the equilibrium moisture (17.6 mass%) of the coal to be processed. Further, in the existing coal-fired thermal power plant, the temperature in a pulverized coal mill is controlled to 70°C or less to prevent the ignition of the coal in the mill. The temperature of the coal observed in Examples 1 to 3 was below such a control temperature and it was confirmed that there is no problem in terms of safety. [0071]
Meanwhile, according to the comparative example, the moisture of the dry coal is much below the equilibrium moisture, and therefore reabsorption of moisture by the dry coal occurs after drying. The reabsorption after drying is not preferable as a driving condition, because the reabsorption leads to a loss of drying energy. Further, the temperature of the dry coal is beyond the pulverized coal mill control temperature (70°C) of the coal-fired thermal power plant, and a method performed under such a driving condition cannot be
said to be a preferable method in terms of safety. [0072]
From the above-described results, it was found that the total moisture of the coal could be reduced to certain moisture by the dry heat source with a temperature of about 80°C to about 180°C having a lower temperature area than an estimated temperature of about
200°C to about 300°C of the exhaust gas from the clinker
cooler of the cooling step 203.
[0073]
As described above, there is no problem in terms of safety, in reducing the total moisture of the coal to be processed to certain moisture (beyond the equilibrium moisture), with a low level heat (for example, about 80°C to about 180°C) as a heat source, and according to the processing system 1 of the first embodiment, the thermal energy discharged from the cement production plant 200 is utilized by the coal-fired thermal power plant 100, thus making it possible to effectively utilize the low-grade coal as a fuel by drying it to a quality equivalent to the high-grade coal such as bituminous coal. [0074]
As described above, according to the method for treating coal and the coal processing system of the first embodiment, the low-grade coal can be utilized by reforming it to have a quality equivalent to the high-grade coal by using the existing plant, to thereby achieve expansion of the utilization of the low-grade
coal, thus making it possible to effectively utilize
resources.
[0075]
Further, there is a low possibility that ignition of the coal to be processed (dry coal) occurs after dry treatment, and the coal to be processed can be easily handled in the same way as the high-grade coal, and the exhaust heat of the exhaust gas discharged from the cement production plant can be utilized as energy for the dry treatment. Therefore, energy saving is achieved by effectively utilizing the thermal energy in an environmentally friendly manner, and a lower cost in utilizing the coal can be accelerated. [0076] (Second embodiment)
FIG. 3 is a block diagram showing an example of a flow of an overall coal processing system for realizing the method for processing coal according to the second embodiment of the present invention, and FIG. 4 is a block diagram showing an example of an outline of the overall coal processing system. As shown in FIGS. 3 and 4, a coal processing system 1A includes a coal-fired thermal power plant 100; a cement production plant 200 which is a heat gas feeding plant; a coal dry treatment plant 300; and a coal collection relay plant (coal center) 400 for collecting and relaying the coal used as a fuel by these coal-fired thermal power plant 100 and cement production plant 200.
[0077]
Then, for example as shown in FIG. 3, in this processing system 1A, the high-grade coal such as bituminous coal 401 collected by the coal collection relay plant 400, and coal to be processed 402, being the low-grade coal such as sub-bituminous coal or brown coal, are transported to the coal dry treatment plant 300 through an independent route. That is, the bituminous coal 401 is transported by transporting step 208 such as a belt conveyor, and the coal to be processed 402 is passed to drying step 209 by other belt conveyor or the like. [0078]
In the drying step 209 of the coal dry treatment plant 300, the exhaust heat from the cooling step 203 of the cement production plant 200 is introduced, and the dry treatment is applied to the coal to be processed 402, and the dry coal that has undergone the dry treatment by the drying step 209 is blended (mixed) with the bituminous coal 401 on a belt of a transport line that continues from the transporting step 208, which is coal transporting/mixing step 210, and thereafter is used as the coal for combustion by boiler (combustion) step 110 of the coal-fired thermal power plant 100. [0079]
The processing system 1A thus constructed will be further described hereafter. As shown in FIG. 4, the coal-fired thermal power plant 100 is a plant where
electric power is generated by firing and utilizing mixed coal in which a plurality types of coal with different properties are mixed as described in the first embodiment. It has a power generating step similar to a power generating step of a publicly-known coal-fired thermal power plant, and has a structure and a step equivalent to those of the coal-fired thermal power plant 100 of the processing system 1 according to the fist embodiment. Accordingly, in the coal-fired thermal power plant 100, the mixed coal fed from the coal dry treatment plant 300 is crushed first into a certain size in crushing step 102 using a vertical mill or the like. Thereafter, as described above, the boiler step (equivalent to the combustion step 110) 103, power generating step 104, feed water heating step 105, denitrating step 106, heat recovering step 107, dust collecting step 108, and desulfurizing step 109 are performed. Through these steps, electric power is generated in the coal-fired thermal power plant 100 of the coal processing system 1A according to the second embodiment. [0080]
In this processing system 1A, the coal to be processed 402 is dried by the coal dry treatment plant 300, before the coal is fed to the crushing step 102. Here, the coal to be processed402 to be dried here may include low-grade coal such as sub-bituminous coal or brown coal. Among such types of coal, an inexpensive low-grade coal containing high moisture is suitably used.
The coal to be processed 402 is dried so as to have the
aforementioned certain moisture.
[0081]
Here, the meanings of the certain moisture, equilibrium moisture, moisture not below the equilibrium moisture, and total moisture have been described in the first embodiment, and therefore explanation thereof is omitted. The drying conditions of the drying plant are suitably set according to the total moisture of the coal to be processed and the equilibrium moisture in the atmosphere. Further, the equilibrium moisture of the dry coal can be similarly obtained by the above-described formula (1). [0082]
Note that in the coal-fired thermal power plant 100 according to the second embodiment, among various coals with different properties, coal to be processed having certain properties such as sub-bituminous coal or brown coal, which is inexpensive low-grade coal containing high moisture and ifferent from the bituminous coal called high-grade coal, is dried in advance by the coal dry treatment plant 300 so as to be set in the above-described state. Thereafter, the coal blended with the high-grade coal is used as a fuel. In this processing system 1A, the coal transporting/mixing step 210 including this coal drying step (drying step 209) is performed not in the coal-fired thermal power plant 100 but in the coal dry treatment plant 300 by utilizing
exhaust heat energy of the cement production plant 200. [0083]
The structure, action, producing step and the like of the cement production plant 200 have been described above. In such a producing step, particularly in the cooling step 203, the exhaust gas having a heat of about 300°C is discharged from the clinker cooler or the like. However, actually most of the exhaust heat of such exhaust gas is discharged as it is without being utilized. Accordingly, in this processing system 1A, the exhaust heat of the exhaust gas can be utilized for the dry treatment applied to the coal to be processed 402 by drying step 212 of the coal dry treatment plant 300, with little modification of the existing plant. [0084]
For example, the bituminous coal 401 is transported as it is to the coal dry treatment plant 300 from the coal collection relay plant 400 through the transporting step 208, and the dry treatment is applied to the coal to be processed 402 by the drying step 209 by utilizing the thermal energy of the exhaust heat discharged from the cooling step 203 of the cement production plant 200. Then, the dried dry coal is mixed with the transported bituminous coal 401 by the coal transporting/mixing step 210, and thereafter is sent to the coal-fired thermal power plant 100. Specific coal mixing method may include a method of feeding the dry coal to the bituminous coal which is transported by a belt conveyor, and a method of
feeding the dry coal to a joint portion, or a shoot portion, for example, of the belt conveyor for transporting bituminous coal. The bituminous coal and the dry coal are blended with each other by repeating a moving motion, a dropping motion, and a rolling motion on the belt conveyor by which the coal is transported. [0085]
Thus, similarly to the aforementioned first embodiment, this may promote energy saving in utilization of the coal, and it is possible to seek for improvement in fuel consumption rate. Also, coal to be processed such as an inexpensive low-grade coal, which has bounty of recoverable resources, can be utilized like high-grade coal. Therefore, life of coal resources can be extended. [0086]
Here, the coal dry treatment plant 300 for realizing the coal transporting/mixing step 210 including the dry treatment applied to the coal to be processed 402 by the drying step 209 will be explained. FIG. 5 is an explanatory view for explaining an example of the coal dry treatment plant 300 of the coal processing system 1A according to the second embodiment of the present invention. [0087]
As shown in FIG. 5, first, the low-grade coal is fed to the bifurcated damper 3 from the existing coal feed line 2 that continues from the coal collection relay plant 400. In this bifurcated damper 3, for example, the
low-grade coal which does not undergo dry treatment is sorted to the side of the existing coal feed line 4. In addition, the coal to be processed, i.e., low-grade coal which should undergo the dry treatment is sorted to the side of the existing coal feed line 5. [0088]
Sorting by this bifurcated damper 3 is performed under control of the bifurcated damper 3 by the controller 7, based on the information of the measured total moisture of the low-grade coal, which is sent from the moisture meter 6 installed on the existing coal feed line 2 for example.
The low-grade coal sorted to the side of the existing coal feed line 4, is fed back to the coal collection relay plant 400 or used for other purpose of use, because such low-grade coal has excessively high total moisture or has a quality unworthy of treatment. [0089]
The coal to be processed that is sorted to the side of the existing coal feed line 5, is charged into the receiving silo 9. The coal to be processed charged into the receiving silo 9 is pulled out from the receiving silo 9 by the pull-out conveyor 12, and is transferred to the screw feeder 14 via the vertical conveyor 13. The coal to be processed transferred to the screw feeder 14 is charged into the dryer 20 via the rotary valve 15. [0090]
The dryer 20 includes the aforementioned publicly-
known paddle stirring type dryer for example, having the structure and the action described in the first embodiment, and is operated similarly to the first embodiment. Note that the coal to be processed is ejected into the drying chamber from the air chamber via the gas (air) distribution plate 22. The dry coal discharged from the dryer 20 is charged into the product silo 34 from the discharge conveyor 17 via the vertical conveyor 33, then fed to the vertical conveyor 38 in certain amounts from the product silo 34 by the transfer conveyor 37 having the quantitative feeding meter system 36, and drops onto high-grade coal (bituminous coal) which is placed on the existing main coal feed line 39 and is transported by the transporting step 208, and is blended (mixed) with the high-grade coal (bituminous coal) . This part corresponds to the aforementioned coal transporting/mixing step 210. Thus, the mixed coal which is mixture of the bituminous coal and the dry coal, is sent to the crushing step 102 of the coal-fired thermal power plant 100, and is utilized by the boiler step 103 as a fuel of a fuel combustion boiler. [0091]
Note that an accurate amount (such as 50 t/h) of the dry coal is dropped and fed to the existing main coal feed line 39 by the quantitative feeding meter system 36, the transfer conveyor 37, and the vertical conveyor 38, so that the ratio of the dry coal with respect to the bituminous coal by mass ratio in the coal
transporting/mixing step 210 is set to about 8:2 to 2:8, preferably 8:2 to 3:7, and further preferably 7:3 to 5:5. [0092]
When the dry treatment is applied to the coal to be processed by the dryer 20, the exhaust gas containing exhaust heat discharged from the clinker cooler or the like of the cooling step 203 of the cement production plant 200, is fed and utilized by the coal dry treatment plant 300.
Low-grade coal has a high spontaneous heating property, and there is a risk that the low-grade coal catches fire by being dried in the dryer. Therefore, nitrogen gas, industrial water and the like are utilized as fire extinguishing equipment against the ignition in the dryer 20.
Such exhaust gas is utilized for the dry treatment applied to the coal to be processed, even if the
temperature is decreased to about 80°C to about 200°C
when the coal to be processed is introduced into the
dryer 20 as described above. Then, the coal to be
processed is dried so as to have certain moisture by
receiving the dry treatment by the dryer 20.
[0093]
(Examples of a second embodiment)
The present invention will be specifically described hereafter, by examples and a comparative example of the second embodiment.
The examples and the comparative example use the
paddle stirring type dryer having a structure equivalent to the dryer 20, and are performed under conditions similar to those of the first embodiment.
Note that properties of the coal to be processed (sub-bituminous coal) used in the examples and the comparative example are shown in the aforementioned Table 1. Further, the equilibrium moisture of the coal to be processed (sub-bituminous coal) used in the examples and the comparative example is shown in the aforementioned Table 2, and is calculated by the aforementioned formula
(1) • [0094]
The dry heat source of the dryer, its flow rate, and the remaining time of the coal were set to the same conditions as those of the first embodiment. Dry air of the dryer (namely, exhaust gas introduced into the dryer 20) was set, so that the temperature was about 80°C to about 180°C and air flow rate was 150 Nm3/h. Results of the examples and the comparative example performed under the aforementioned conditions are shown in the aforementioned Table 3. Explanation for the examples and the comparative example of the second embodiment is similar to the explanation for the examples of the first embodiment, and therefore the explanation is omitted here. [0095]
As described in Examples 1 to 3, in the second embodiment as well, by suitably controlling the feed amount of the coal to be processed and the temperature of
the dry gas, the coal to be processed could be dried from the total moisture (about 32.8 mass%) to certain moisture, namely to as low moisture as possible but not below the equilibrium moisture (17.6 mass%) of the coal to be processed. Further, in the existing coal-fired thermal power plant, the temperature in the mill is controlled to
70°C or less to prevent the ignition of the coal in the pulverized coal mill. The temperature of the coal observed in Examples 1 to 3 was below such a control temperature and it was confirmed that there is no problem in terms of safety. [0096]
Meanwhile, in the comparative example, similarly to the first embodiment, the moisture of the dry coal was much below the equilibrium moisture, and therefore the reabsorption of moisture by the coal occurred after drying. Such reabsorption after drying leads to a loss of drying energy, and therefore is not preferable as a driving condition. Further, the temperature of the dry
coal was beyond the control temperature (70°C) of the pulverized coal mill of the coal-fired thermal power plant, and a method performed under such a driving condition cannot be said to be a preferable method in terms of safety. [0097]
From the above-described results, it was found that the total moisture of the coal could be reduced to certain moisture by dry air of about 80°C to about 180°
which is lower than an estimated temperature of about 200°C to about 300° of the exhaust gas from the clinker cooler of the aforementioned cooling step 203. [0098]
As described above, there is no problem in terms of safety in reducing the total moisture of the coal to be processed to certain moisture (beyond the equilibrium moisture), with a low level heat (for example, about 80°C to about 180°C) as a heat source. According to the processing system 1A of the second embodiment, by utilizing the thermal energy discarded from the cement production plant 200 in the coal dry treatment plant 300, the coal with high moisture (low-grade coal) is dried to have a quality equivalent to the high-grade coal such as bituminous coal and can be utilized as a fuel. [0099]
Thus, according to this processing system 1A, the total moisture of the coal used by the coal-fired thermal power plant 100 can be reduced, and therefore thermal efficiency at the time of combustion in the coal-fired thermal power plant 100 can be improved. In addition, the low-grade coal is dried in advance by the coal dry treatment plant 300 before being used in the coal-fired thermal power plant 100, and thereafter the coal mixed with the high-grade coal is fed to the coal-fired thermal power plant 100. Therefore, an influence of dust on the environment, which is generated from the low-grade coal during transportation, is reduced as much as possible,
and the utilization efficiency of the low-grade coal can
be improved.
[0100]
Further, in this processing system 1A, 30 mass% of the coal to be processed (dry coal) which was dried in an optimal state in Examples 1 to 3, was fed to 70 mass% of the high-grade coal such as bituminous coal which was placed on the existing main coal feed line 39 for feeding coal not to be processed and sent to the coal-fired thermal power plant 100. As a result, it was confirmed visually that the coals could be blended with each other by the coal transporting/mixing step 210 by repeating a moving motion, a dropping motion, and a rolling motion on the belt conveyor by which the coal is transported. Further, it was also confirmed that generation of dust could be prevented, compared with a case that only the low-grade coal was fed to the coal-fired thermal power plant 100. In addition, when the mixed coal was fired in a small scale combustion testing device, it was found out that the combustion performance was excellent. Accordingly, the total moisture of the mixed coal can be reduced while preventing the generation of dust, compared with a case that only the dried low-grade coal is fed to the coal-fired thermal power plant 100. Therefore, it was found that the total moisture of the coal fired in the coal-fired thermal power plant 100 could be reduced at a low cost, and the thermal efficiency could be effectively improved, and also a utilization ratio of the
low-grade coal such as sub-bituminous coal or brown coal
could be dramatically improved.
[0101]
As described above, according to the coal processing method and the coal processing system of the second embodiment, the coal to be processed of the low-grade coal can be utilized by reforming it to have the quality equivalent to the high-grade coal by using the existing plant, and therefore utilization of the low-grade coal can be expanded and effective utilization of resources can be realized. [0102]
Further, the coal to be processed (dry coal) after dry treatment has a low possibility of catching fire, easy to be handled, and can be handled in the same way as the high-grade coal. The exhaust heat of the exhaust gas discharged in the cement production can be utilized as the energy for the dry treatment. Therefore, energy saving is achieved by effectively utilizing the thermal energy in an environmentally friendly manner, and a lower cost in utilization of the coal can be promoted. [0103] (Third embodiment)
FIG. 6 is a block diagram showing an example of an overall flow of a coal processing system for realizing a method for treating coal according to a third embodiment of the present invention, and FIG. 7 is a block diagram showing an example of an outline of the overall coal
processing system. As shown in FIGS. 6 and 7, a coal processing system 1B includes: a coal-fired thermal power plant 100, a cement production plant 200 which is a heat gas feeding plant; a coal dry treatment plant 300; and a coal collection relay plant (coal center) 400 for collecting and relaying the coal used as a fuel in the coal-fired thermal power plant 100 and the cement production plant 200. [0104]
Then, in this processing system 1B, for example as shown in FIG. 6, the high-grade coal such as bituminous coal 401 collected in the coal collection relay plant
400 is transported to the coal-fired thermal power plant 100 through the transporting step 208 and the coal transporting/mixing step 210. Meanwhile, the coal to be processed 402, being the low-grade coal, such as sub-bituminous coal is transported to the coal dry treatment plant 300 by other belt conveyor or the like. [0105]
In the drying step 209 of the coal dry treatment plant 300, the heat gas from the cooling step 203 of the cement production plant 200 is introduced, to thereby apply the dry treatment to the coal to be processed 402, and the exhaust gas containing the pulverized coal discharged from the drying step 209 is cooled by other gas. Then, the dry coal that has undergone the dry treatment by the drying step 209 is blended (mixed) with the bituminous coal 401 on the belt of the transport line
that continues from the transporting step 208 which is the coal transporting/mixing step 210, and thereafter is used for a fuel by the boiler step 110 of the coal-fired thermal power plant 100, as the coal for combustion. [0106]
The coal combustion plant here may include, in addition to the coal-fired thermal power plant 100, a cement plant, an iron mill, and various types of factories. The coal to be processed which has undergone the dry treatment by the dry treatment plant is utilized as a fuel for a boiler or a fuel for heating. [0107]
The processing system 1B thus constructed will be further described in detail as follows. As shown in FIG. 7, as has already been described in the first and second embodiments, the coal-fired thermal power plant 100 is the plant for generating electric power by firing and utilizing a plurality of kinds of coal with different properties, including a power generating step similar to the power generating step of a publicly-known coal-fired thermal power plant, and has a structure and a step similar to those of the coal-fired thermal power plant 100 of the processing systems 1 and 1A according to the above embodiments. Accordingly, in the coal-fired thermal power plant 100, the coal obtained by blending (mixing) the dry coal, being the coal to be processed 402 fed from the coal dry treatment plant 300 and the bituminous coal 401, is first crushed to a certain size
in the crushing step 102 using the vertical mill or the like. Thereafter, as described above, the boiler step (equivalent to the combustion step 110) 103, power generating step 104, feed water heating step 105, denitrating step 106, heat recovering step 107, dust collecting step 108, and desulfurizing step 109 are performed. Through these steps, electric power is generated by the coal-fired thermal power plant 100 of the coal processing system 1B according to the third embodiment. [0108]
In this processing system 1B, similarly to the processing system 1A, the coal to be processed 402 is dried by the coal dry treatment plant 300, before being fed to the crushing step 102. The coal to be processed 402 which is dried here may include low-grade coal such as sub-bituminous coal. Among these, the low-grade coal containing high moisture is suitably used. The coal to be processed 402 is dried so as to have the aforementioned certain moisture. [0109]
Here, preferably the certain moisture is not below the equilibrium moisture of the coal to be processed in the atmosphere, and has as low moisture as possible. The equilibrium moisture means the moisture of setting the coal in an equilibrium state in a certain atmosphere, and the equilibrium moisture is affected by temperature and humidity in the atmosphere. The coal to be processed 402
which has undergone the dry treatment is discharged from an outlet of the dryer of the drying step 209, and thereafter is stored in a production silo. Then it is blended (mixed) with the sub-bituminous coal 401 on the belt conveyor and is transported to the coal-fired thermal power plant 100. The atmosphere of each process, namely the temperature and the humidity are different, and therefore the dry coal to be processed absorbs or releases moisture depending on the atmosphere of each process (moisture is fluctuated). [0110]
Then, as the moisture is removed from the coal as described above, higher heat generation can be achieved, and therefore it is desirable to set the moisture of the dry coal to be as low as possible. However, in order to avoid a waste of drying energy, the coal to be processed which is dried once should not absorb moisture again. Therefore, the moisture after drying the coal to be processed is preferably not below the equilibrium moisture on the belt conveyor, namely, in the atmosphere, which is a final stage of the aforementioned each process. [0111]
Note that the meaning of the moisture not below the equilibrium moisture and the drying conditions of the drying plant have been described in the second embodiment, and therefore explanation thereof is omitted here. The total moisture here is the moisture contained in the coal to be processed before or after the dry treatment. A
sample of the coal for measuring the moisture is picked before being transported to the drying step 209. The total moisture is measured pursuant to the aforementioned JIS M8820, and the equilibrium moisture is measured pursuant to the aforementioned JIS A1475 for example, with the coal to be processed used as a sample. Through these measurings, a curve of an equilibrium water-content ratio of the dry coal can be obtained. The equilibrium water-content ratio of the dry coal is obtained by the curve of the equilibrium water-content ratio obtained here and temperature and relative humidity data in the atmosphere to which the dry coal is exposed in a process it is utilized. The obtained equilibrium water-content ratio is a percentage of water mass based on a total mass after drying, and therefore the equilibrium moisture of the dry coal in the atmosphere can be obtained by the aforementioned formula (1). [0112]
Note that in the aforementioned coal-fired thermal power plant 100 according to the third embodiment, among various types of coal with different properties, the coal to be processed such as sub-bituminous coal, being inexpensive low-grade coal containing high moisture, different from the bituminous coal called high-grade coal, is subjected to dry treatment in advance by the coal dry treatment plant 300 so as to be set in the above-described state, namely, so as to have as low moisture as possible but not below the equilibrium moisture. In the
coal processing system 1B according to the third embodiment, the thermal energy discharged from the cement production plant 200 to the coal dry treatment plant 300 is utilized. [0113]
The structure, action, producing step and the like of the cement production plant 200 have been described above. In such a producing step, particularly in the cooling step 203, heat gas having a heat of about 300°C is discharged from the clinker cooler or the like. However, actually most of the heat of the heat gas is discharged as it is without being utilized. Accordingly, in this processing system 1B, the heat of the heat gas can be utilized for the coal dry treatment applied to the coal to be processed 402 by the drying step 209 of the coal dry treatment plant 300, with little modification of the existing plant. [0114]
Further, the bituminous coal 401 is transported to the coal dry treatment plant 300 from the coal collection relay plant 400 as it is by the transporting step 208, and the coal dry treatment utilizing the thermal energy of the heat gas discharged from the cooling step 203 of the cement production plant 200 is applied to the coal to be processed 402 by the drying step 209. Further, the exhaust gas containing the pulverized coal discharged from the drying step 209 is cooled by other gas. Then, the dried dry coal is blended (mixed) with the bituminous
coal 401 which is transported by the coal transporting/mixing step 210, and thereafter is sent to the coal-fired thermal power plant 100. [0115]
Thus, similarly to the first and second embodiments, by promoting energy saving in utilizing the coal, improvement of a fuel consumption rate is achieved and also the coal to be processed such as an inexpensive low-grade coal having bounty of recoverable resources can be utilized similarly to the high-grade coal. Therefore, life of coal resources can be extended. [0116]
Here, explanation will be given for the coal dry treatment plant 300 for realizing the coal transporting/mixing step 210 including the dry treatment applied to the coal to be processed 402 by the drying step 209. FIG. 8 is an explanatory view for explaining an example of the coal dry treatment plant 300 of the coal processing system 1B according to the third embodiment of the present invention. As shown in FIG. 8, the low-grade coal is first fed to the bifurcated damper from the existing coal feed line 2 that continues from the coal collection relay plant 400, and in this bifurcated damper 3, for example, the low-grade coal that has not undergone the dry treatment is sorted to the side of the existing coal feed line 4, and the coal to be processed, being the low-grade coal that should undergo the dry treatment is sorted to the side of the existing
coal feed line 5. [0117]
The coal to be processed sorted to the side of the existing coal feed line 5 is charged into the receiving silo 9. The coal to be processed charged into the receiving silo 9 is pulled out from the receiving silo 9 by the pull-out conveyor 12, and is transferred to the screw feeder 14 via the vertical conveyor 13. The coal to be processed transferred to the screw feeder 14 is charged into the dryer 20 via the rotary valve 15. [0118]
The dryer 20 is constructed as the publicly-known paddle stirring type dryer having the structure and the action described in the first and second embodiments, and is operated similarly. Here, the coal is preferably dried so that the temperature of the coal after drying is 75°C or less. The exhaust gas discharged from the dryer 20 is cooled to 75°C or less by air of an atmosphere temperature, being other gas introduced into the exhaust gas line, and is sent to the bag filter 19 by the fan 18. The pulverized coal is removed by the bag filter 19, and the exhaust gas is then discharged into the atmosphere from the exhaust duct 31 by the bag filter fan 30. [0119]
The exhaust gas line of the dryer 20 has a structure capable of introducing the air of the atmosphere temperature (atmosphere), being other gas different from the exhaust gas, for example, as shown in
the figure. Therefore, the exhaust gas is mixed with the atmosphere introduced by the exhaust gas line of the
dryer 20, and is cooled to the temperature of about 75°C or less. Therefore, the exhaust gas discharged into the atmosphere from the exhaust duct 31 has been already cooled and environmentally friendly, and thus even if the pulverized coal is slightly brought by the exhaust gas, there is almost no risk of ignition. [0120]
Further, preferably the step of removing the pulverized coal from the mixed gas of the exhaust gas containing the pulverized coal and other gas is further provided. [0121]
Further, since the exhaust gas is cooled to the temperature of 75°C or less by the exhaust gas line of the dryer 20, removing (separating) efficiency of the pulverized coal brought by the exhaust gas can be improved, and spontaneous ignition in the bag filter 19 can be prevented before it occurs. Therefore, an operation of the coal dry treatment plant 300 can be stably performed. [0122]
Note that although not shown, a dual pulverized coal removing structure may be provided, wherein a pulverized coal removing apparatus such as an electric dust collector or a cyclone separator is further installed at a front side of the discharging port of the
bag filter 19, in case the pulverized coal is still brought by the exhaust gas exhausted from the bag filter 19. [0123]
The structure and the action of the dryer 20 have already been described. As described above, the coal to be processed is dried while being moved in an axial direction of the paddle shaft, by an action of the paddles 21 attached to the paddle shaft while inclined to the paddle shaft. [0124]
Then, the dry coal discharged from the dryer 20 is charged into the product silo 34 from the discharge conveyor 17 via the vertical conveyor 33. Note that the pulverized coal collected by the bag filter 19 is also charged into the product silo 34 by the pulverized coal transfer system 35. [0125]
As described above, in order to remove the pulverized coal by the bag filter 19, the removed pulverized coal is set in a dry state. Even if the pulverized coal is directly charged into the product silo 34 by the pulverized coal transfer system 35, the total moisture of the mixed dry coal is not increased, compared with a case that the pulverized coal is removed by wet-type treatment such as a scrubber. Therefore, according to this processing system 1B, the step of re-drying the pulverized coal which is removed by the bag filter 19 is
not necessary, and an overall energy saving can be promoted. [0126]
Then, the dry coal is fed to the vertical conveyor 38 from the product silo 34 in certain amounts by the transfer conveyor 37 having the quantitative feeding meter system 36, and drops onto the high-grade coal (bituminous coal) which is placed on the existing main coal feed line 39 and is transported by the transporting step 208, and is blended (mixed) with the high-grade coal (bituminous coal). This part corresponds to the aforementioned coal transporting/mixing step 210. Thus, the blended (mixed) coal is sent to the crushing step 102 of the coal-fired thermal power plant 100, and is utilized by the boiler step 103 as a fuel of a fuel combustion boiler. [0127]
Note that an accurate amount (such as 50 t/h) of the dry coal is dropped and fed to the existing main coal feed line 39 by the quantitative feeding meter system 36, the transfer conveyor 37, and the vertical conveyor 38, so that the ratio of the dry coal with respect to the bituminous coal by mass ratio is set to about 8:2 to 2:8, preferably 8:2 to 3:7, and further preferably 7:3 to 5:5 in the coal transporting/mixing step 210. As a coal mixing method, the method is not limited to the above-described method, and for example, a method of feeding the dry coal to a joint portion of the belt conveyor by
which the bituminous coal is transported, such as a shoot portion for example, can be given as a coal mixing method. The moving motion, dropping motion, and rolling motion of the bituminous coal and the dry coal are repeated on the belt conveyor, to thereby blend the bituminous coal and the dry coal. [0128]
When the dry treatment is applied to the coal to be processed by the dryer 20, the heat gas discharged from the clinker cooler in the cooling step 203 of the cement production plant 200 is fed and utilized by the coal dry treatment plant 300.
Further, the low-grade coal has a high spontaneous heating property, and there is a risk that the low-grade coal catches fire by being dried by the dryer. Therefore, a device for feeding nitrogen gas, industrial water and the like is preferably installed as fire extinguishing equipment against the ignition in the dryer 20. [0129]
The heat gas is utilized for the dry treatment applied to the coal to be processed, even if the
temperature is decreased to about 80°C to about 180°C at the time of being introduced into the dryer 20 as described above. Then, the coal to be processed is dried so as to have certain moisture by the dry treatment performed by the dryer 20.
[0130]
(Examples of a third embodiment)
The present invention will be specifically described by using examples and a comparative example of the third embodiment.
As a dryer used in the examples and the comparative example, the paddle stirring type dryer having a structure equivalent to the structure of the dryer 20 was used, and the examples were conducted under similar conditions as those of the first and second embodiments. [0131]
The dryer used herein includes: a columnar drying chamber with an inner dimension of Φ268 mm x 740 mm; a feeding port for coal to be processed with a dimension of Φ140 mm directly above a position 50 mm away in the axial direction of the paddle shaft, from a side wall of the drying chamber on the coal-to-be-processed feeding port side; and a semi-circular coal to be processed discharging port for discharging the coal to be processed
with a dimension of 140 mm x 140 mm on the side wall at a position 495 mm away in the axial direction of the paddle shaft, from the side wall of the drying chamber on the coal-to-be-processed feeding port side (at a position of
angle 5° to 75° based on a horizontal reference), wherein air (atmosphere) of the atmosphere temperature can be introduced into the exhaust gas line in an upper part of the discharging port, and the exhaust gas is cooled to the temperature of 75°C or less and thereafter the exhaust gas with dust removed by cyclone is released into the atmosphere.
[0132]
Further, slit ports of 3 mm x 140 mm are arranged on the air distribution plate between the drying chamber and the air chamber at 45 mm intervals, and a paddle shaft is laid in the drying chamber, having paddles of 75 mm x 75 mm attached to the paddle shaft with axial diameter of Φ7 6.3 mm at intervals of 90 mm in a state that an attachment angle is shifted from each other by 120° viewed from the axial direction, and a screw feeder for feeding the coal to be processed is provided above the coal-to-be-processed feeding port. Note that in order to monitor the safety of the dryer, the temperature of the dry coal and the temperature of the exhaust gas in the upper part of the discharging port were measured. [0133]
Properties of the coal to be processed (sub-bituminous coal) used in the examples and the comparative example are shown in the aforementioned Table 1. Further, 17.6 mass% of the coal to be processed (sub-bituminous coal) used in the examples and the comparative example was used, which had the equilibrium moisture as shown in the aforementioned Table 2. Based on data of the equilibrium water-content ratio of the coal to be processed obtained pursuant to the desiccator method (measurement temperature: 20°C to 50°C and relative humidity: 10% to 98%), the equilibrium moisture was calculated by preparing a correlating equation for obtaining the equilibrium moisture from temperature and
relative humidity, then substituting into this correlating equation the temperature and the relative humidity under a condition (atmosphere) in which the examples and the comparative example were executed to thereby obtain the equilibrium water-content ratio of the dry coal, and obtaining the equilibrium water-content of the dry coal from this equilibrium water-content ratio by using formula (1). [0134]
A drying ability of the dryer was set so that a coal feed amount was about 20 kg/h to about 40 kg/h by adjusting the number of rotations of the screw feeder, which is a coal feeder. A dry heat source of the dryer, its flow rate, and a remaining time of the coal were set so as to be the same conditions as those of the first and second embodiments. [0135]
Results of the examples and the comparative example performed under the above-described conditions are shown in the aforementioned Table 3. Note that an effective volume used in calculating a heat capacity coefficient was determined, by using a portion corresponding to a distance from a first slit of the gas distribution plate to the discharging port of the volume of the drying chamber in which the coal remains, namely, in this example, a distance from 45 mm to 495 mm in the axial direction of the paddle shaft from the side wall of the drying chamber on the coal-to-be-processed feeding port
side. [0136]
The examples and the comparative example will be described hereafter. (Example 1)
As a result of conducting a test by setting the feed amount of the coal to 20.4 kg/h, and the temperature of the dry heat source to 82°C, it was found that the total moisture of the coal was 20.3 mass% after drying, while it was 32.5 mass% during feeding, and the heat capacity coefficient was 5612 kcal/m3hr°C. Further, the temperature of the coal at this time was 19.9°C. In addition, the temperature of the exhaust gas in the upper part of the discharging port was 55.4°C. (Example 2)
As a result of conducting a test by setting the feed amount of the coal to 20.0 kg/h, and setting the temperature of the dry heat source to 121°C, it was found that the total moisture of the coal was 19.0 mass% after drying, while it was 33.1 mass% during feeding, and the heat capacity coefficient was 5236 kcal/m3hr°C. Further, the temperature of the coal at this time was 25.3°C. In addition, the temperature of the exhaust gas in the upper part of the discharging port was 75.1°C. Accordingly, air was fed to the exhaust gas to thereby cool the temperature of the exhaust gas to 75°C or less. (Example 3)
As a result of conducting a test by setting the
feed amount of the coal to 40.1 kg/h, and setting the temperature of the dry heat source to 180°C, it was found that the total moisture of the coal was 18.4 mass% after drying, while it was 32.4 mass% during feeding, and the heat capacity coefficient was 5020 kcal/m3hr°C. Further, the temperature of the coal at this time was 40.1°C. In addition, the temperature of the exhaust gas in the upper part of the discharging port was 82.0°C. Accordingly, air was fed to the exhaust gas to thereby cool the temperature of the exhaust gas to 75°C or less. (Comparative example)
As a result of conducting a test by setting the feed amount of the coal to 20.3 kg/h and setting the temperature of the dry heat source to 180°C, it was found that the total moisture of the coal was 12.1 mass% after drying, while it was 32.9 mass% during feeding, and the heat capacity coefficient was 2747 kcal/m3hr°C. Further, the temperature of the coal at this time was 79.0°C. In addition, the temperature of the exhaust gas in the upper part of the discharging port was 109.0°C. As a result, both the coal and exhaust gas after drying exceeded 75°C. [0137]
As described in Examples 1 to 3, it was found also in the third embodiment that by suitably controlling the feed amount of the coal to be processed and the temperature of the dry heat source, the coal to be processed could be dried from the total moisture (about 32.8 mass%) to certain moisture, namely to as low
moisture as possible but not below the equilibrium moisture (17.6 mass%) of the coal to be processed. Further, in the existing coal-fired thermal power plant, the temperature in the mill is controlled to 75°C or less, preferably 70°C or less, and further preferably 50°C or less in consideration of the properties of the coal to be used, to prevent the ignition of the coal in the pulverized coal mill. The temperature of the coal observed in Examples 1 to 3 was below such a control temperature and it was confirmed that there is no problem in terms of safety. [0138]
Meanwhile, according to the comparative example, the moisture of the dry coal is further below the equilibrium moisture similarly to the first and second embodiments, and therefore reabsorption of moisture by the dry coal occurs after drying. The reabsorption after drying is not preferable as a driving condition, because the reabsorption leads to a loss of drying energy. Further, the temperature of the dry coal is beyond a maximum value (75°C) of the pulverized coal mill control temperature of the coal-fired thermal power plant, and hence the comparative example cannot be said to be a preferable method in terms of safety. [0139]
From the above-described results, it was found that the total moisture of the coal could be reduced to certain moisture by the heat gas of about 80°C to about
180°C having a lower temperature area than an estimated temperature of about 200°C to about 300°C of the clinker cooler heat gas discharged from the cooling step 203. [0140]
As described above, there is no problem in terms of safety, in reducing the total moisture of the coal to be processed to certain moisture (beyond the equilibrium moisture), with a low level heat (for example, about 80°C to about 180°C) as a heat source, and according to the processing system 1B of the third embodiment, the thermal energy discharged from the cement production plant 200 is utilized by the coal dry treatment plant 300, thus making it possible to effectively utilize the coal with high water-content (low-grade coal) as a fuel by drying it to have a quality equivalent to the high-grade coal such as bituminous coal. [0141]
Then, the exhaust gas from the dryer 20 is cooled to the temperature of 75°C or less, and thereafter is exhausted. Therefore, safe exhaust can be discharged by reducing a possibility of ignition of the pulverized coal in the exhaust gas, while drying the total moisture of the dry coal to certain moisture, namely, to as low moisture as possible but not below the equilibrium moisture. Thus, the coal to be processed can be dried to an optimal state from both aspects of the improvement of the drying energy efficiency and safety. [0142]
That is, the atmosphere is mixed with the exhaust gas generated during drying of the dry treatment by the dryer 20, to thereby cool the exhaust gas to the temperature of 75°C or less. Therefore, by preventing an influence on global warming by the exhaust gas discharged during drying and preventing the ignition of the pulverized coal brought by the exhaust gas of a high temperature, the coal-fired thermal power plant 100 and the coal dry treatment plant 300 can be stably operated, and the effective utilization of the low-grade coal can be safely and surely realized. [0143]
Thus, according to the coal processing system 1B of the third embodiment, coal to be processed, particularly of the low-grade coal, can be dried in the coal dry treatment plant 300 efficiently at a low cost in an environmentally friendly manner, and effectively utilized by the coal-fired thermal power plant 100. At the same time, by preventing influence on the environment and ignition by the exhaust gas discharged during drying, it is possible to stably operate the coal-fired thermal power plant 100 or the like. [0144]
Further, since the coal to be processed (dry coal) after dry treatment has an extremely low possibility of ignition, it can be handled easily in a similar way to handling the high-grade coal. Further, since the heat of the heat gas discharged from the cement production plant
200 can be utilized as energy for the dry treatment, energy saving is achieved with effective utilization of the thermal energy in an environmentally friendly manner, and a lower cost can be promoted in utilization of the coal. [0145]
Thus, according to this processing system 1B, the total moisture of the coal used by the coal-fired thermal power plant 100 can be reduced, and therefore thermal efficiency at the time of combustion in the coal-fired thermal power plant 100 can be improved. In addition, the low-grade coal is dried in advance by the coal dry treatment plant 300 before being used by the coal-fired thermal power plant 100, and thereafter the coal blended (mixed) with the high-grade coal is fed to the coal-fired thermal power plant 100. Therefore, the influence of the dust on the environment, which is generated from the low-grade coal during transportation, is reduced as much as possible, and improvement in utilization of the low-grade coal can be achieved. [0146]
As described above, according to the processing method and the processing system of the third embodiment, the low-grade coal can be effectively utilized by efficiently drying it at a low cost in an environmentally friendly manner, and the influence on the environment and the ignition of the exhaust gas discharged during drying can be prevented, thus making it possible to stably
operate a coal utilization plant. Further, according to the processing method and the coal processing system of the third embodiment, the coal to be processed, being the low-grade coal, can be utilized by reforming it to the quality equivalent to the high-grade coal by using the existing plant, thus making it possible to expand the utilization of the low-grade coal and realize the effective utilization of the resources. [0147] (Fourth embodiment)
FIG. 9 is a block diagram showing an example of a flow of an overall coal processing system for realizing the method for processing coal according to a fourth embodiment, and FIG. 10 is a block diagram showing an example of an outline of an overall coal processing system. As shown in FIGS. 9 and 10, a coal processing system 1C has a structure basically similar to the structure of the processing system 1B of the third embodiment, including a coal-fired thermal power plant 100; a cement production plant 200; a coal dry treatment plant 300; and a coal collection relay plant (coal center) 400. [0148]
Then, as shown in FIG. 9, in this processing system 1C, the high-grade coal such as bituminous coal 401 collected by the coal collection relay plant 400 is transported to the coal-fired thermal power plant 100 by the transporting step 208 and the coal
transporting/mixing step 210. Meanwhile, the coal to be processed 402, being the low-grade coal such as sub-bituminous coal, is transported to the coal dry treatment plant 300 by other belt conveyor or the like. [0149]
In the coal dry treatment plant 300, necessity of the dry treatment for the coal to be processed 402 as will be described later is judged by judging step 209P, and regarding the coal to be processed 402 judged to require the dry treatment, the heat gas is introduced from the cooling step 203 of the cement production plant 200, and the dry treatment is applied to the coal to be processed 402 by the drying step 209 of the coal dry treatment plant 300, and the exhaust gas containing the pulverized coal discharged from the drying step 209 is cooled by other gas. Then, the dry coal that has undergone the dry treatment by the drying step 209 is blended (mixed) with the bituminous coal 401 on the belt of the transporting line that continues from the transporting step 208, which is the coal
transporting/mixing step 210, and thereafter is used for the fuel by the boiler step 110 of the coal-fired thermal power plant 100, as the coal for combustion. As specific coal mixing methods include a method of feeding the dry coal to the bituminous coal which is transported by the belt conveyor, and a method of feeding the dry coal to the shoot portion for example, being the joint portion of the belt conveyor by which the bituminous coal is
transported. The bituminous coal and the dry coal are blended with each other by repeating the moving motion, the dropping motion, and the rolling motion on the belt conveyor by which the coal is transported. As the coal combustion plant, in addition to the coal-fired thermal power plant 100, a cement plant, an iron mill, and each kind of plants can be given, and the coal to be processed which has undergone the dry treatment in the coal dry treatment plant 300, is utilized as a fuel for a boiler or a fuel for heating. [0150]
The processing system 1C thus constructed will be further described in detail. As shown in FIG. 10, the coal-fired thermal power plant 100 is the plant for generating electric power by firing and utilizing a plurality of kinds of coal with different properties as described in the first to third embodiments, including the power generating step similar to the power generating step of the publicly-known coal-fired thermal power plant, and has a structure and a step equivalent to those of the coal-fired thermal power plant 100 of the processing system 1B according to the aforementioned embodiment. Accordingly, the crushing step 102, boiler step (equivalent to the boiler step 110) 103, power generating step 104, feed water heating step 105, denitrating step 106, heat recovering step 107, dust collecting step 108, and desulfurizing step 109 of the coal-fired thermal power plant 100 are just as described above, and through
these steps, electric power is generated by the coal-fired thermal power plant 100 of the coal processing system 1C according to the fourth embodiment. [0151]
In this processing system 1C, similarly to the aforementioned processing system 1B, the coal to be processed out of various types of coal is dried by the coal dry treatment plant 300 before being fed to the crushing step 102. As the coal to be processed which is dried here, the low-grade coal such as sub-bituminous coal or brown coal can be given. Among them, an inexpensive low-grade coal containing high moisture is suitably utilized. The coal to be processed is dried so as to have the aforementioned certain moisture. [0152]
Here, the certain moisture, the equilibrium moisture, the moisture not below the equilibrium moisture, the total moisture and the like have been described in the third embodiment, and therefore explanation thereof is omitted here, and the drying condition of the drying plant is suitably set according to the total moisture of the coal to be processed and the equilibrium moisture in the atmosphere. Further, the equilibrium moisture of the dry coal in the atmosphere can be similarly obtained by the aforementioned formula (1). The coal sample for measuring the total moisture is picked by the judging step 209P before being transported to the drying step 209. [0153]
Note that in the coal-fired thermal power plant 100 according to the fourth embodiment, necessity of the dry treatment is judged by the judging step 209P, regarding various types of coal with different properties to be dried by the coal dry treatment plant 300, and when the coal to be processed such as sub-bituminous coal, being an inexpensive low-grade coal containing high moisture, different from the bituminous coal called high-grade coal, is judged to require the dry treatment, the dry treatment is applied thereto in advance so as to be set in the above-described state, namely so as to have as low moisture as possible but not below the equilibrium moisture. In the coal processing system 1C of the fourth embodiment, the thermal energy discharged from the cement production plant 200 is utilized by the coal dry treatment plant 300. [0154]
The structure, action, producing step and the like of the cement production plant 200 are as described above. In such a producing step, particularly the heat gas
having a heat of about 300°C is discharged from the clinker cooler or the like of the cooling step 203. However, actually most of the heat of the heat gas is discharged without being utilized. Accordingly, in this processing system 1C, the heat of the heat gas can be utilized for the coal dry treatment applied to the coal to be processed 402 by the drying step 209 of the coal dry treatment plant 300, with almost no necessity of
remodeling the existing plant. [0155]
The bituminous coal 401 is transported as it is to the coal dry treatment plant 300 from the coal collection relay plant 400 by the transporting step 208, and among the coal to be processed 402, such coal to be processed 402 that is judged to require the dry treatment by the judging step 209P is subjected to the coal dry treatment in the drying step 209, by utilizing the thermal energy of the heat gas discharged from the cooling step 203 of the cement production plant 200. Further, the exhaust gas containing the pulverized coal discharged from the drying step 209 is cooled by other gas. Then, the dried dry coal is blended (mixed) with the bituminous coal 401 transported by the coal transporting/mixing step 210 and thereafter is sent to the coal-fired thermal power plant 100. [0156]
Thus, similarly to the aforementioned first to third embodiments, by promoting energy saving in utilization of the coal, improvement of a fuel consumption rate is achieved and also the coal to be processed such as an inexpensive low-grade coal having bounty of recoverable resources can be utilized similarly to the high-grade coal. Therefore, life of the coal resources can be extended. [0157]
Here, the coal dry treatment plant 300 for
realizing the coal transporting/mixing step 210 including the dry treatment applied to the coal to be processed 402 by the aforementioned judging step 209P and drying step 209 will be described using FIG. 8. As shown in FIG. 8, first, the coal is fed to the bifurcated damper 3 from the existing coal feed line 2 that continues from the coal collection relay plant 400, and in this bifurcated damper 3, coal not to be processed, which is not worth the dry treatment, is sorted to the side of the existing coal feed line 4, and the coal to be processed, which should undergo the dry treatment is sorted to the side of the existing coal feed line 5. [0158]
The coal to be processed sorted to the side of the existing coal feed line 5, is charged into the receiving silo 9. The coal to be processed charged into the receiving silo 9 is pulled out from the receiving silo 9 by the pull-out conveyor 12, and is transferred to the screw feeder 14 via the vertical conveyor 13. The coal to be processed transferred to the screw feeder 14 is charged into the dryer 20 via the rotary valve 15. [0159]
The energy required for removing the moisture adhered to the coal corresponds to about an evaporation latent heat of water, while much more energy than required for removing the adhered moisture is required for removing in-particle moisture (crystal water or pore water) other than adhered moisture. Therefore, the coal
with high adhered moisture is preferable as the coal to be processed which is a drying object. A reduction amount of the moisture can be increased in the coal with high adhered moisture, and therefore an increase amount of the heat generation becomes large, which is a merit that can be obtained by a drying operation. Meanwhile, the coal with little adhered moisture has little merit by the drying operation, and therefore is judged not to be worth the dry treatment, and is blended (mixed) with the dry coal, as coal not to be processed. [0160]
In the fourth embodiment, the adhered moisture of the coal is defined as a value obtained by subtracting the equilibrium moisture from the total moisture in the aforementioned judging step 209P, and the necessity of the dry treatment is determined by the value obtained by subtracting the equilibrium moisture from the total moisture of the coal. The total moisture is fluctuated depending on weather and season, and therefore it is measured every time the coal is used (every time the necessity of drying is determined). The equilibrium moisture is a specific value in each kind of the coal (coal brand). Therefore, there is no necessity of measuring the equilibrium moisture every time the coal is used. The equilibrium moisture in an external environment (by temperature and humidity) during usage of the coal can be obtained, by an estimation formula specific to the kind of the coal obtained in advance
based on equilibrium moisture data measured for every kind of the coal. The aforementioned value is calculated and determined, by using the "equilibrium moisture" as already known information for each kind of the coal (because measurement time requires several days or more in some cases), and by measuring the "total moisture" every time (because it is influenced by coal storage conditions and weather such as raining). Note that if the total moisture is measured pursuant to JIS, the measurement time of several hours or more is required, and therefore in some cases, a simple measurement method (such as a method omitting pre-treatment like crushing) can be used in some cases. [0161]
The equilibrium moisture is a specific value defined for each kind of the coal, and is varied by atmosphere temperature and humidity, and can be experimentally calculated for each kind of the coal as a function of temperature and humidity. Accordingly, when the kind of the coal to be used is determined, the equilibrium moisture can be calculated based on the atmosphere and conditions (temperature, humidity) at this time point (or by assuming the time point of using the coal). The necessity of the dry treatment is judged by whether or not the obtained value falls within a suitable range, the value being obtained by subtracting the "equilibrium moisture" obtained as described above, from the "total moisture" measured every time.
[0162]
Note that the judgment of the necessity of the dry treatment may be made by the judging step 209P based on the information regarding the total moisture of the coal and the equilibrium moisture. The following Table 4 shows the total moisture and the equilibrium moisture and the value obtained by subtracting the equilibrium moisture from the total moisture, regarding two kinds of coal with different qualities. Note that the total moisture was measured according to JIS M8820 (total moisture measurement method for coal and cokes - lots). Further, the equilibrium moisture is a value calculated by the aforementioned formula (1) prepared for each kind of the coal, under conditions of temperature of 30°C and relative humidity of 75% (average temperature and average relative humidity of the atmosphere). The total moisture is fluctuated depending on the coal storage status, and the equilibrium moisture is fluctuated depending on the temperature and the relative humidity of the atmosphere. Therefore, the value obtained by subtracting the equilibrium moisture from the total moisture is fluctuated depending on the coal storage status and the temperature and the relative humidity of the atmosphere. [0163]
In the fourth embodiment, the difference between the equilibrium moisture and the total moisture is defined as the adhered moisture, and the coal with high adhered moisture (coal with high reduction amount of
moisture per drying energy) is judged to be the coal which requires the dry treatment. The necessity of the dry treatment is preferably judged by the judging step 209P as follows: when the value obtained by subtracting the equilibrium moisture from the total moisture of the coal is 8 or more, the coal is judged to be the coal to be processed which requires the dry treatment, and when the value is less than 8, the coal is judged to be the coal not to be processed which requires no dry treatment. [0164]
Generally, the low-grade coal with high total moisture has the aforementioned value of beyond 8 and is judged to be the coal to be processed which requires the dry treatment in many cases. However, the value obtained by subtracting the equilibrium moisture from the total moisture is decreased by fluctuation of the coal storage status and the temperature and the relative humidity of the atmosphere, and the value is sometimes below 8. In this case, the coal is judged to be the coal not to be processed which requires no dry treatment.
Reversely, even in a case of the high-grade coal with low total moisture, if the value obtained by subtracting the equilibrium moisture from the total moisture is increased by fluctuation of the coal storage status and the temperature and the relative humidity of the atmosphere, and if the value is beyond 8, the coal is judged to be the coal to be processed. [0165]
[Table 4]
(Table Removed)
[0166]
Here, the total moisture of the coal is necessary in judging a sorting destination of the coal, and this total moisture is measured in advance by an analysis method such as JIS M8820 (total moisture measurement method of coal and cokes - lots), or is measured by other moisture measurement apparatus. As such moisture measurement apparatus, a halogen type moisture meter, an infrared ray type moisture meter and the like can be given. However, in order to prevent a change of properties of the coal, the drying temperature during
measurement of the moisture is preferably set to 107°C or less.
Note that although not shown, the moisture measurement apparatus is installed on the existing coal feed line 2, and a controller is further installed for controlling the bifurcated damper 3 based on the information regarding the total moisture of the coal obtained from the moisture measurement apparatus and the equilibrium moisture, and the necessity of the dry treatment is judged by the controller, and based on a judgment result, the bifurcated damper 3 can be controlled.
[0167]
For example, when it is judged that the value obtained by subtracting the equilibrium moisture from the total moisture of the coal is 8 or more, the coal is regarded as requiring the dry treatment and is sorted to the side of the existing coal feed line 5. Meanwhile, when it is judged that the value is less than 8, the coal is regarded as not requiring the dry treatment and the coal is sorted to the side of the existing coal feed line 4. Note that the coal sorted to the side of the existing coal feed line 4 is, for example, fed back to the coal collection relay plant and is stocked again for usage of other purpose of use. [0168]
Note that the dry treatment may be performed so that the total moisture of the coal after the dry treatment is beyond the equilibrium moisture.
Thus, it may be possible to prevent the reabsorption of moisture by the coal, which is dried once, before being utilized, and prevent a rise of the total moisture of the coal, and also prevent the waste of the drying energy. [0169]
The coal to be processed which is sorted to the side of the existing coal feed line 5 and requires the dry treatment, is charged into the receiving silo 9. The coal to be processed charged into the receiving silo 9 is pulled out from the receiving silo 9 by the pull-out
conveyor 12, and is transferred to the screw feeder 14 via the vertical conveyor 13. The coal to be processed transferred to the screw feeder 14 is charged into the dryer 20 via the rotary valve 15. [0170]
The dryer 20 is constructed as the publicly-known paddle stirring type dryer having the structure and the action described in the first to third embodiments, and is operated similarly. Then, the coal to be processed, which is stirred and dried, is discharged from the dryer 20 by the discharge conveyor 17 via the rotary valve 16. Note that the exhaust gas from the dryer 20 is sent to the bag filter 19 by the fan 18 with dust removed by the bag filter 19, and thereafter is discharged into the atmosphere from the exhaust duct 31 by the bag filter fan 30. [0171]
As described in the third embodiment, the coal is preferably dried by the dryer 20 so that the temperature of the coal after drying is 75°C or less. Thus, it may be possible to effectively prevent the possibility that the dried coal catches fire. Therefore, preferably, drying conditions of the drying plant such as an amount of the coal feed, temperature of dry heat gas, an amount of the dry heat gas supply, and the number of rotations of the paddles are suitably set, and the temperature inside of the dryer is monitored. [0172]
The exhaust gas of the dryer 20 is mixed with the atmosphere introduced by the exhaust gas line of the
dryer 20, and is cooled to the temperature of about 75°C or less. Accordingly, the exhaust gas discharged into the atmosphere from the exhaust duct 31 is already cooled and environmentally friendly, and therefore even if the pulverized coal is slightly brought by the exhaust gas, there is almost no risk of ignition. [0173]
In addition, preferably, the step of removing the pulverized coal from the mixed gas of the exhaust gas containing the pulverized coal and other gas is further provided. [0174]
Further, since the exhaust gas is cooled to the temperature of 75°C or less by the exhaust gas line of the dryer 20, removing (separating) efficiency of the pulverized coal brought by the exhaust gas can be improved, and spontaneous ignition in the bag filter 19 can be prevented before it occurs. Therefore, the operation of the coal dry treatment plant 300 can be stably performed. [0175]
Note that although not shown, a dual pulverized coal removing structure may be provided, wherein a pulverized coal removing apparatus such as an electric dust collector or a cyclone separator is further installed at a front side of the discharging port of the
bag filter 19, in case the pulverized coal is still brought by the exhaust gas exhausted from the bag filter 19. [0176]
The structure and the action of the dryer 20 have already been described. As described above, the coal to be processed is dried while being moved in the axial direction of the paddle shaft. The dry coal discharged from the dryer 20 is charged into the product silo 34 from the discharge conveyor 17 via the vertical conveyor 33. Note that the pulverized coal collected by the bag filter 19 is also charged into the product silo 34 by the pulverized coal transfer system 35. [0177]
As described above, in order to remove the pulverized coal by the bag filter 19, the removed pulverized coal is set in a dry state, and if the pulverized coal is directly charged into the product silo 34 by the pulverized coal transfer system 35, the total moisture of the mixed dry coal is not increased, compared with a case that the pulverized coal is removed by wet-type treatment such as a scrubber. Therefore, according to this processing system 1C, the step of re-drying the pulverized coal which is removed by the bag filter 19 is not necessary, and an overall energy saving can be accelerated. [0178]
Then, the dry coal is fed to the vertical conveyor
38 in certain amounts from the product silo 34 by the transfer conveyor 37 having the quantitative feeding meter system 36, and drops onto the high-grade coal (bituminous coal) which is placed on the existing main coal feed line 39 and is transported by the transporting step 208, and is blended (mixed) with the high-grade coal (bituminous coal). This part corresponds to the aforementioned coal transporting/mixing step 210. Thus, the blended (mixed) coal is sent to the crushing step 102 of the coal-fired thermal power plant 100, and is utilized by the boiler step 103 as the fuel of the fuel combustion boiler. [0179]
Note that an accurate amount (such as 50 t/h) of the dry coal is dropped and fed to the existing main coal feed line 39 by the quantitative feeding meter system 36, the transfer conveyor 37, and the vertical conveyor 38, so that the ratio of blending (mixing) of the dry coal with respect to the bituminous coal by mass ratio in the coal transporting/mixing step 210, is set to about 8:2 to 2:8, preferably 8:2 to 3:7, and further preferably 7:3 to 5:5. [0180]
When the dry treatment is applied to the coal to be processed by the dryer 20, the heat gas discharged from the clinker cooler or the like of the cooling step 203 of the cement production plant 200 is fed and utilized by the coal dry treatment plant 300.
Further, the low-grade coal has a high spontaneous heating property, thus posing a risk that the low-grade coal may catch fire in the dryer by being dried. Therefore, as fire extinguishing equipment against the ignition in the dryer 20, equipment for feeding nitrogen gas and/or industrial water or the like is preferably installed. [0181]
The heat gas is utilized for the dry treatment applied to the coal to be processed even if the temperature is decreased to about 80°C to about 180°C at the time point of being introduced into the dryer 20 as described above. Then, the coal to be processed is dried so as to have certain moisture by the dry treatment performed by the dryer 20. [0182] (Examples of a fourth embodiment)
The present invention will be specifically described hereafter by examples and a comparative example of the fourth embodiment.
As the dryer used in the examples and the comparative example, a stirring paddle type dryer having a structure equivalent to the structure of the dryer 20 was used, and the examples and the comparative example were conducted under similar conditions as those of the third embodiment. [0183]
The dryer used in this example is the same as the
dryer used in the example of the third embodiment. Further, properties of the coal to be processed (sub-bituminous coal) used in the examples and the comparative example are shown in the aforementioned Table 1. The measurement method of the total moisture or the like is also as described above. In addition, the equilibrium moisture was calculated by the aforementioned formula (1). [0184]
As described above, the coal to. be processed (sub-bituminous coal) used in the examples and the comparative example has the total moisture of 32.8 mass%, and the equilibrium moisture of 17.6 mass%, and the value obtained by subtracting the equilibrium moisture from the total moisture is beyond 8, and therefore such a coal is the coal that can be dried (coal to be processed). [0185]
The drying ability of the dryer, the dry heat source of the dryer, its flow rate, and the remaining time of the coal were set as the same conditions as those of the third embodiment. The results of the examples and the comparative example performed under the above-described conditions are shown in the aforementioned Table 3. The explanation for the examples and the comparative example is similar to the explanation for the examples of the third embodiment, and therefore the explanation is omitted. [0186]
As described in Examples 1 to 3, in the fourth
embodiment as well, it was found that by suitably controlling the feed amount of the coal to be processed and the temperature of the dry heat source, the coal to be processed could be dried from the total moisture (about 32.8 mass%) to certain moisture, namely to as low moisture as possible but not below the equilibrium moisture of the coal to be processed (about 17.6 mass%). Further, in the existing coal-fired thermal power plant, the temperature in the pulverized coal mill is controlled to 75°C or less, preferably 70°C or less, and further preferably 50°C or less in consideration of the properties of the used coal, to prevent the ignition of the coal in the mill. The temperature of the coal observed in Examples 1 to 3 was below such a control temperature and it was confirmed that there is no problem in terms of safety. [0187]
Meanwhile, according to the comparative example, the moisture of the dry coal is much below the equilibrium moisture similarly to the first to third embodiments, and therefore reabsorption of moisture by the dry coal occurs after drying. The reabsorption after drying is not preferable as a driving condition, because the reabsorption leads to a loss of the drying energy. Further, the temperature of the dry coal is beyond a maximum value (75°C) of a control temperature of the pulverized coal mill of the coal-fired thermal power plant, and a method performed under such a driving
condition cannot be said to be a preferable method in
terms of safety.
[0188]
From the above-described results, it was found that the total moisture of the coal could be decreased to certain moisture by the heat gas of about 80°C to about 180°C having a lower temperature area than an estimated temperature of about 200°C to about 300°C of the clinker cooler heat gas discharged from the cooling step 203. [0189]
As described above, there is no problem in terms of safety, in reducing the total moisture of the coal to be processed to certain moisture (beyond the equilibrium moisture), with a low level heat (for example, about 80°C to about 180°C) as a heat source, and according to the coal processing system 1C of the fourth embodiment, the thermal energy discharged from the cement production plant 200 is utilized by the coal dry treatment plant 300, thus making it possible to effectively utilize the high moisture coal (low-grade coal) as a fuel by drying it to have a quality equivalent to the high-grade coal such as bituminous coal. The other action effect is similar to that of the third embodiment. That is, according to the coal processing method and the coal processing system of the fourth embodiment, the low-grade coal can be effectively utilized by efficiently drying it at a low cost in an environmentally friendly manner, and the influence on the environment and the ignition of the
exhaust gas discharged during drying can be prevented, to thereby safely operate the coal utilization plant. Further, according to the coal processing method and the coal processing system of the fourth embodiment, the coal to be processed, being the low-grade coal, can be utilized by reforming it to have a quality equivalent to the quality of the high-grade coal. Therefore, expansion of the utilization of the low-grade coal is realized, and effective utilization of the resources is achieved. [0190]
As the coal to be processed to be dried, the low-grade coal such as sub-bituminous coal or brown coal with high adhered moisture is preferable as described above. However, the coal to be processed is not limited thereto. For example, the coal such as low-grade coal is reformed (moisture is reduced) by suitably combining each kind of operations such as heating, pressurizing, drying, and dehydrating, and simultaneously with change of properties or after change of properties, the coal is molded into a pellet shape and/or a briquette shape, and the coal thus molded can be used. The coal reformed and molded into the pellet shape and/or the briquette shape is stocked outside before being utilized by the coal-fired thermal power plant. The pellet-shaped and/or briquette-shaped coal having much moisture again due to rain water during stock is dried and can be utilized by the coal-fired thermal power plant as needed.
Description of signs and numerals [0191]
1 Coal processing system
2 Existing coal feed line
3 Bifurcated damper
4 Existing coal feed line
5 Existing coal feed line
6 Moisture meter
7 Controller
9 Receiving silo
12 Pull-out conveyor
13 Vertical conveyor
14 Screw feeder
15 Rotary valve
16 Rotary valve
17 Discharge conveyor
18 Fan
19 Bag filter
20 Dryer
21 Paddle
22 Gas (air) distribution plate

30 Bag filter fan
31 Exhaust duct

33 Vertical conveyor
34 Product silo
35 Dust (pulverized coal) transfer system
36 Quantitative feeding meter system
37 Transfer conveyor
38 Vertical conveyor
39 Existing main coal feed line
100 Coal-fired thermal power plant
102 Crushing step
103 Boiler step
104 Power generating step
105 Feed water heating step
106 Denitrating step
107 Heat recovering step
108 Dust collecting step
109 Desulfurizing step

200 Cement production plant
201 Crushing step
202 Sintering step
203 Cooling step
204 Finishing step

208 Transporting step
209 Drying step
210 Coal transporting/mixing step
300 Coal dry treatment plant
400 Coal collection relay plant
401 Bituminous coal (high-grade coal)
402 Coal to be processed (low-grade coal)

500 Coal collection relay plant
501 Bituminous coal
502 Sub-bituminous coal
503 Coal mixing step
504 Transporting step
600 Cement production plant
601 Transporting step

700 Coal-fired thermal power plant
701 Boiler step

CLAIMS
1. A method for processing coal by drying the coal
and firing the coal in a coal-fired thermal power plant,
comprising the steps of:
feeding the coal into a drying chamber of a paddle stirring type dryer, an inner portion of the paddle stirring type dryer is partitioned by a gas distribution plate into an upper drying chamber and a lower gas chamber, the drying chamber including a paddle shaft laid therein, the paddle shaft being rotatably provided in the drying chamber, and a plurality of paddles for stirring the coal being attached to the paddle shaft at constant intervals in an axial direction of the paddle shaft; and
feeding heat gas into the gas chamber from a heat gas feeding plant different from the coal-fired thermal power plant to dry the coal.
2. The method for processing coal according to
claim 1, further comprising the steps of:
mixing dry coal after drying with coal not to be processed different from the dry coal; and
feeding mixed coal to the coal-fired thermal power plant.
3. The method for processing coal according to
claim 1 or 2, further comprising the step of:
the exhaust gas containing pulverized coal discharged from a drying plant is mixing with other gas
to cool.
4. The method for processing coal according to any
one of claims 1 to 3, further comprising the step of:
before drying the coal, judging necessity of dry treatment for the coal,
the necessity of the dry treatment being judged based on information regarding total moisture of coal before drying and equilibrium moisture of the coal; and
drying coal to be processed having certain properties, when it is judged to require the dry treatment, to a certain state.
5. The method for processing coal according to any one of claims 1 to 4, wherein the heat gas feeding plant is a cement production plant.
6. The method for processing coal according to claim 2, wherein the mixing of the coal is performed by feeding the dry coal to transport equipment for transporting the coal not to be processed.
7. The method for processing coal according to claim 3, wherein the exhaust gas is cooled to a temperature of 75°C or less.
8. The method for processing coal according to claim 4, wherein the necessity of the dry treatment is
judged in such a manner that, the dry treatment is judged to be necessary when a value obtained by subtracting the equilibrium moisture of the coal from the total moisture of the coal is 8 or more, whereas the dry treatment is judged to be unnecessary when the value is less than 8.
9. The method for processing coal according to
claim 1, wherein the coal to be processed is coal
reformulated and molded into a pellet shape and/or a
briquette shape.
10. The method for processing coal according to claim 1, wherein the dry treatment is performed so that total moisture of the coal after the dry treatment is beyond equilibrium moisture of the coal.
11. A coal processing system for drying coal and firing the coal in the coal-fired thermal power plant,
the system comprising a paddle stirring type dryer,
the paddle stirring type dryer including:
an inner portion partitioned by a gas distribution
plate into an upper drying chamber and a lower gas
chamber;
a paddle shaft provided rotatably and laid in the
drying chamber;
a plurality of paddles for stirring the coal
attached to the paddle shaft at constant intervals in an
axial direction of the paddle shaft;
a feeding port for feeding the coal provided in the drying chamber; and
a heat gas feeding port provided in the gas chamber to feed heat gas for drying the coal,
the heat gas feeding port being connected to an exhaust line for exhausting exhaust gas from a clinker cooler of a cement production plant.