TECHNICAL FIELD
The present invention relates to a coal fired boiler
plant and a coal drying method for a coal fired boiler
5 plant.
BACKGROUND ART
The coal that is used as fuel in electrical power
generating plant equipped with a coal fired boiler turbine
(hereafter simply referred to as a boiler) is classified as
10 high-grade, medium grade, and low-grade, depending on the
water content, coal rank, and the like.
Low-grade coal such as lignite and the like has high
water content and low coal rank and low calorific value
compared with high-grade coal, so in order to increase the
15 combustion efficiency of the boiler, it is desirable that
the coal be dried before being fed into the boiler.
Therefore, conventionally, the coal is dried by heating
it using steam extracted from the boiler.
Also, it has been proposed that coal be heated and
20 dried using combustion exhaust gas discharged from the
outlet of an econbmizer and denitrification plant provided
with the boiler (for example, see Patent Literature (PTL)
1).
CITATION LIST
25 PATENT LITERATURE
PTL 1
Japanese Unexamined Patent Application Publication No.
Hei 10-332134
30 SUMMARY OF INVENTION
TECHNICAL PROBLEM
However, because steam that is extracted from the
boiler is used to heat the coal, naturally, efficiency of
35 the boiler is reduced.
Also, the combustion exhaust gas discharged from the
outlet of the economizer or denitrification plant is at a
high temperature of from 350 to 550'~. If such a hightemperature
combustion exhaust gas is used as the heating
5 medium for drying the coal, hydrocarbon components are
volatilized from the coal during the process and are mixed
into the exhaust gas, and this has the problem that it has
an adverse effect on the performance of the exhaust gas
processing plant on the downstream side.
10 With the foregoing in view, it is an object of the
present invention to provide a coal fired boiler plant and a
coal drying method for a coal fired boiler plant that is
capable of properly drying the coal and increasing the
efficiency of the ,boiler while suppressing any reduction in
15 efficiensy of the boiler and suppressing the generation of
hydrocarbon gas components.
Solution t o Problem
In order to solve these problems, the following
solutions are adopted as the coal fired boiler plant and the
20 coal drying method for the coal fired boiler plant according
to the present invention.
The coal fired boiler plant according to a first aspect
of the present invention comprises: a coal dryer that dries'
coal; a boiler in which the coal that was dried in the coal
25 dryer is mixed with air for combustion and burned; an air
heater that heats the air for combustion supplied to the
boiler using combustion exhaust gas discharged from the
boiler; a precipitator that collects dust included in the
combustion exhaust gas; a desulfurization plant that
30 performs a desulfurization process on the combustion exhaust
gas; and heat recovery equipment that is provided on the
downstream side of the air heater in the direction of flow
of the combustion exhaust gas, and that heats a heating
medium with the combustion exhaust gas, wherein the coal
35 dryer dries the coal using the heat energy of the heating
medium that was heated in the heat recovery equipment.
By heating the coal using the heat energy of the
heating medium that was heated in the heat recovery
equipment, it is not necessary to use steam extracted from
3
the boiler, and it is possible to suppress the reduction in
efficiency of the boiler.
Also, the coqbustion exhaust gas from the boiler that
has passed through the air heat.er has a lower temperature of
5 from 130 to 170"~ compared with combustion exhaust gas
discharged from an economizer or a denitrification plant
(from 350 to 550°C). Therefore, it is possible to dry the
coal at a lower temperature, so it is possible to prevent
the generation of hydrocarbon gas components from the coal.
10 In the coal fired boiler plant according to the first
aspect of the present invention, the coal dryer can dry the
coal within the coal dryer by passing the heating medium
that has been heated in the heat recovery equipment through
a tubes provided within the coal dryer.
15 Also, the coal fired boiler plant according to the
first aspect of the present invention can dry the coal
within the coal dryer by heating a carrier air supplied from
the outside into the coal dryer using the heating medium
that was heated in*the heat recovery equipment.
20 The coal fired boiler plant according to the first
aspect of the present invention may further comprise an air
heater that heats carrier air supplied from the outside into
the coal dryer using steam that has been extracted by
extracting a portion of the steam generated by burning the
25 coal in the boiler.
In this case, a portion of the steam is extracted from
the boiler, but the steam that is extracted is used in an
auxiliary manner to dry the coal that is to be heated using.
the heat that is recovered in the heat recovery equipment.
30 Therefore, it is possible to minimize the quantity of steam
that is extracted compared with the case where the coal is
dried mainly using steam extracted from the boiler.
The coal fired boiler plant according to the first
aspect of the pr'esent invention can further comprise a
35 heating medium heater that further heats the heating medium
that has been heated in the heat recovery equipment using
steam that has been extracted by extracting a portion of the
steam generated by burning the coal in the boiler.
As a result, the coal can be more efficiently dried.
In the coal fired boiler plant according to the first
aspect of the present invention, the air heater may heat air
for combustion supplied to the boiler using combustion
5 exhaust gas discharged from the boiler, and a portion of the
air for combustion may be branched off, mixed with carrier
air that is supplied from the outside into the coal dryer,
and supplied into the coal dryer.
As a result,,the coal can be more efficiently dried.
10 Also, by adjusting the mixing ratio of the carrier air and
air for drying, the temperature can be adjusted as
appropriate.
In addition, in the coal fired boiler plant according
to the first aspect of the present invention, the
15 desulfurization plant performs a desulfurization process by
bringing the combustion exhaust gas into contact with
process water, and the coal fired boiler plant can further
comprise a spray dryer that evaporates wastewater obtained
by separating a gypsum component from the process water
20 after the desulfurization process, by bringing the
wastewater into contact with the combustion exhaust gas on
the upstream side of the desulfurization plant.
As a result, it is possible to reduce the wastewater
from the desulfurization plant.
In the coal fired boiler plant according to the first
aspect of the present invention, the exhaust air from the
coal dryer can be fed to the precipitator.
As a result, the fine coal included in the exhaust air
from the coal dryer can be collected by the precipitator.
30 The coal fired boiler plant according to the first
aspect of the present invention can further comprise a fine
coal recovery plant that recovers fine coal smaller than a
predetermined particle size from the coal that is included
in the exhaust air from the coal dryer, and the fine coal
35 recovery plant can supply the recovered fine coal to the
boiler together with the coal that has been dried in the
coal dryer.
In addition, 'in the coal fired boiler plant according
to the first aspect of the present invention, the exhaust
air from which the fine coal has been removed by recovering
the fine coal in the fine coal recovery plant can be fed to
5 the precipitator.
In the coal fired boiler plant according to the first
aspect of the present invention, the heat recovery equipment
can be disposed on the upstream side of the precipitator.
As a result, it is possible to reduce the temperature
10 of the combustion exhaust gas that is fed to the
precipitator. As a result, the dust collection performance
of the precipitator is improved, and the dust collection
efficiency is increased.
Of course, a configuration in which the heat recovery
15 equipment is disposed on the downstream side of the
t
precipitator is also possible.
The present invention of a second aspect also includes
a method of drying coal that is supplied to a boiler in the
coal fired boiler plant as described above, comprising:
20 heating a heating medium recovered in heat recovery
equipment that is provided on the downstream side of an air
heater in the direction of flow of combustion exhaust gas
using the heat energy of the combustion exhaust gas that is
discharged from the boiler as a result of combustion of the
25 coal in the boiler; and drying the coal supplied to the
boiler using the heat energy of the heating medium.
A d v a n t a g e o u s E f f e c t s of Invention
According to the present invention, it is possible to
properly dry coal and increase the efficiency of a boiler
30 while suppressing Sny reduction in efficiency of the boiler
and su2pressing the generation of hydrocarbon gas
components.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 illustrates a configuration of a coal fired
35 boiler plant according to a first embodiment of the present
invention.
F I G . 2 illustrates an application example of the coal.
fired boiler plant according to the first embodiment of the
present invention.
F I G . 3 illustrates an application example of the coal
5 fired boiler plant according to the first embodiment of the
present invention.
,
F I G . 4 illustrates an application example of the coal
fired boiler plant according to the first embodiment of the
present invention.
10 F I G . 5 illustrates a configuration of a coal fired
boiler plant according to a second embodiment of the present
invention.
F I G . 6 illustrates an application example of the coal
fired boiler plant according to the second embodiment of the
15 present invention.
F I G . 7 illustrates an application example of the coal
fired boiler plant according to the second embodiment of the
present invention.
F I G . 8 illustrates an application example of the coal
20 fired boiler plant*according to the second embodiment of the
present invention.
F I G . 9 illustrates a configuration of a coal fired
boiler plant according to a third embodiment of the present
invention.
25 F I G . 10 illustrates a configuration of a coal fired
boiler plant according to a fourth embcdiment of the present
invention.
F I G . 11 illustrates a configuration of a coal fired.
boiler plant according to a fifth embodiment of the present
30 invention.
DESCRIPTION OF EMBODIMENTS
The following is an explanation of a coal fired boiler
plant and a coal drying method for a coal fired boiler plant
according to the present invention, with reference to the
drawings.
F i r s t Embodiment:
A first embodiment of the present invention will be
described below using FIG. 1.
5 As illustrated in FIG. 1, a coal fired boiler plant 10A
mainly includes a coal dryer 11, a coal bunker 12, a coal'
mill 13, a boiler turbine (boiler) 14, an air heater 15,
heat recovery equipment 16, an electrostatic precipitator
17, a desulfurization plant 18, and a flue 19.
10 Coal that is pulverized in a coal crusher 20 is fed to
the coal dryer 11, and is transported by air as a carrier
gas bl~wn in by an air blower 21, and the coal dryer 11
dries the coal by a configuration that is explained in
detail later.
15 The coal bunker 12 temporarily stores the coal that is
dried in the coal dryer 11.
The coal mill 13 pulverizes the coal that is supplied
from the coal bunker 12, and converts it into coal powder
with a predetermined particle size.
20 The coal powder that is pulverized in the coal mill 13'
is fed to the boiler turbine 14, and in the boiler thereof,
it is mixed with air for combustion supplied from the
outside and burned, water is heated with the heat energy,
and steam is generated. The turbine of the boiler turbine 14
25 is driven by the steam that is generated, and this driving
power is used for the required work such as causing a
generator or the like to rotate. Here, there is no
limitation on the use of the driving power generated in the
boiler turbine 14.
30 Heat is exchanged in the air heater 15 between the
combustion exhaust gas discharged from the boiler unit of
the boiler turbine 14 and air for combustion supplied to the
boiler unit. As a result, the air for combustion is heated
by the sensible heat of the combustion exhaust gas, and
35 supplied to the boiler of the boiler turbine 14.
Here, heat is exchanged between the air for combustion
8
and the combustion exhaust gas discharged from the air
heater 15 so that the combustion exhaust gas is at a
temperature of from 130 to 170'~.
The heat recbvery equipment 16 recovers heat energy
5 from the combustion exhaust gas by heat exchange between the
combustion exhaust gas that has passed through the air
heater 15 and a cooling medium such as water or the like, so
that the temperature of the combustion exhaust gas is
further reduced. A fin-tube type of heat recovery equipment
0 in which heat is exchanged between a cooling medium that
flows within a tube and the combustion exhaust gas that
flows around fins provided integrally on the tubes, can be
used as the heat recovery equipment 16.
The electrostatic precipitator 17 collects dust in the
15 combustion exhaust gas that has passed through the heat
recovery equipment 16 using electrostatic forces.
The desulfurization plant 18 mainly carries out a
removal process (desulfurization process) to remove SO2 from
the combustion exhaust gas that has passed through the
20 electrostatic precipitator 17. There is no particular
limitation on the method of the desulfurization process in
this embodiment.
The flue 19 releases the combustion exhaust gas that
has been desulfurized into the atmosphere.
The coal fired boiler plant 10A has the following
configuration in order that the coal dryer 11 can perform
the drying process on the coal with higher efficiency.
In this embodiment, lines 30, 31 are provided between
the heat recovery equipment 16 and the coal dryer 11, and
30 coal within the coal dryer 11 is heated by the heat
recovered in the heat recovery equipment 16, so drying of
the coal is promoted.
Specifically,. the cooling medium such as water or the
like thst is heated by heat exchange with the combustion
35 exhaust gas in the heat recovery equipment 16 is fed by the
line 30 as a heating medium to the coal dryer 11. In the
coal dryer 11, the coal within the coal dryer 11 is directly
heated by the heat energy of the heating medium such as
water or the like &d from the heat recovery equipment 16.
If the coal dryei 11 is a rotary kiln type, the heating
medium is fed from the line 30 to tubes provided within the
5 rotary kiln, so that by heating the coal that passes around
the tubes, drying of the coal is promoted.
The heating medium that has lost its heat energy within
the coal dryer 11 is circulated to the heat recovery
equipment 16 via the line 31 using a pump 32.
5
10 Here, a bypass line 33 may be provided between the line
30 and the line 31, and control valves 34, 35 may be
provided on the bypass line 33 and the line 31. Opening and
closing and the degree of opening of the control valves 34,
35 are adjusted automatically by a temperature controller 37
15 based on the measurement results of a sensor 36 provided on
the combustion exhaust gas outlet side of the heat recovery
equipment 16. The temperature controller 37 adjusts the
opening and closing and the degree of opening of the control
valves 34, 35 so that the temperature of the combustion
20 exhaust gas on the outlet side of the heat recovery
equipment 16 is within a predetermined temperature range,
for example, from 85 to 95"~.
By controlling the temperature of the combustion
exhaust gas from the heat recovery equipment 16 as described
25 above, reduction in the fluidity of the ash collected in the
electrostatic pre?ipitator on the downstream side of the
heat recovery equipment 16 is prevented.
According to the configuration as described above, coal
within the coal dryer 11 is heated by heat recovered from
30 the combustion exhaust gas in the heat recovery equipment
16, so that drying of the coal is promoted. As a result, it
is not necessary to bleed steam from the boiler turbine 14,
so it is possible to increase the efficiency (output) of the
boiler turbine 14. Also, the calorific value of the coal is
35 increased by drying the coal, so from this point, also it is
possible to increase efficiency of the boiler turbine 14. As'
a result, less coal is needed to obtain the same output, so
it is possible to suppress the quantity of coal used in the
coal fired boiler plant 10A, and achieve lower costs.
10
In addition, by drying the coal, the combustion
conditions within *the boiler turbine 14 approach the ideal
combustion conditions, so it is possible to reduce the
quantity of combustion exhaust gas. As a result, it is
5 possible to reduce the quantity of supplementary makeup
water used for desulfurization in the desulfurization plant
18, and in this respect, also it is possible to achieve
lower costs.
Also, by drying the coal, the effect of reduction of
10 the quantity of mercury and NOx contained in the combustion
exhaust gas is expected.
Also, in the coal fired boiler plant 10A, the heat
recovery equipment 16 is provided on the upstream side of
the electrostatic precipitator 17, and as a result, the
15 temperature of the combustion exhaust gas fed to the
electrostatic precipitator 17 is reduced. As a result, the
dust collection performance of , the electrostatic
precipitator 17 is improved, and the dust collection
efficiency is increased. Also, as a result, it is possible
20 to minimize the quantity of SO3 in the combustion exhaust
gas.
Incidentally, in the coal fired boiler plant 10A that
is configured as described above, the temperature of the
exhaust gas from the boiler turbine 14 is low during
25 startup, so there is a possibility that the action and
effect as described above cannot be obtained sufficiently.
Therefore, during startup, heating of the coal as'
described above may be carried out after the load on the
boiler turbine 14 has increased, and the temperature of the
30 combustion exhaust gas has sufficiently increased.
Also, normally, an auxiliary boiler 14b for startup is
provided with the, boiler turbine 14, so during startup,
steam from the auxiliary boiler 14b can be supplied as a
heat source to the coal dryer 11, so it is possible to
35 promote drying of the coal.
(Application Examples of the First Embodiment)
The following are descriptions of several
configurations that can be added to the configuration of the
first embodiment as described above as application examples.
(Application Example 1)
In the coal fired boiler plant 10A illustrated in FIG.
2, in addition to the configuration described for the first
embodiment above, steam extracted from the boiler turbine 14
may be fed to an air heater 40 provided between the air
blower 21 and the &oal dryer 11 via a line 39. Then, in the
air heater 40, heat is exchanged between the extracted steam
and the air (carrier air) fed from the air blower 21 to the
coal dryer 11, and the air is heated.
Here, extracting of the steam from the boiler turbine
14 can be carried out at a suitable location, such as the
low-pressure side, medium pressure side, and the like. Also,
15 preferably, condensed water that has passed through the air
heater 40 is returned to the low-pressure side of the boiler
turbine 14.
As a result, the temperature of the air fed to the coal
dryer 11 is increased, and drying of the coal within the
20 coal dryer 11 is further promoted.
Heat exchange in the air heater 40 as described above
can be adjusted in accordance with the temperature of the
5
carrier air in the coal dryer 11. In this case, the
temperature of the air may be measured by a sensor 41A or
41B provided on the outlet side of the air blower 21, or on
the exhaust gas side of the coal dryer 11, and the quantity
of steam extracted from the boiler turbine 14 may be
adjusted by a temperature controller 42 and a valve 43 based
on the measurement results.
30 (Application Example 2)
Also, in the coal fired boiler plant 10A illustrated in
FIG. 3, in addition to the ~onfi~ura'tiodne scribed for the
first embodiment above, steam may be extracted from the
boiler turbine 14, and fed to a heating medium heater 45
35 provided on the line 30 that supplies the heating medium
from the heat recovery equipment 16 to the coal dryer 11 via
a line 44. Also, the heating medium is further heated in
this heating medium heater 45.
As a result, the temperature of the heating medium fed
to the coal dryer 11 is further increased, and drying of the
coal within the coal dryer 11 is further promoted.
5 Heat exchange in the heating medium heater 45 as
described above can be controlled by adjusting the quantity
of steam extracted from the boiler turbine 14 using a
temperature controller 47 and a valve 48 based on the
measurement results of a temperature sensor 46A provided on
10 the exhaust gas side of the coal dryer 11, or a heating
medium temperature sensor 46B provided on the line 30.
(Application ~xampef 3)
Also, in the coal fired boiler plant 10A illustrated in
FIG. 4, air for drying that has been heated using the
15 combustion exhaust gas from the boiler turbine 14 as a heat
source and generated in the air heater 15 can be fed to the
outlet side of the air blower 21 via a line 49.
As a result, the temperature of the air fed to the coal
dryer 11 is increased, and drying of the coal within the
20 coal dryer 11 is further promoted.
The supply of the air for drying as described above can
be controlled by adjusting the flow rate (mixing ratio) of
the air for drying supplied from the line 49 and the carrier
air supplied from the air blower 21. This can be achieved
25 using valves 53A, 53B and flow rate controllers 54A, 54B
provided on the outlet side of the air blower 21 and on the
line 49, so th'at their temperatures are within a
predetermined range using a temperature controller 52A or
52B that are based on the air temperature measured by a
30 sensor 51A or 51B provided, in this case, on the outlet side
of the air blower 21 or on the exhaust air side of the coal
dryer 11.
Second Embodiment:
Next, a second embodiment of the present invention will
35 be described below. In the following explanation of the
second embodiment, the configuration that is common with the.
first embodiment as described above is given the same
13
reference numerals in the drawings and its explanation is
omitted, and the explanation is focused on the differences
from the first embodiment as described above.
As illustrated in FIG. 5, a coal fired boiler plant 10B
5 according to this embodiment mainly includes the coal dryer
11, the coal bunker 12, the coal mill 13, the boiler turbine
14, the air heat.er 15, heat recovery equipment 16, the
electrostatic precipitator 17, the desulfurization plant 18,
and the flue 19.
10 In this embodiment, coal that has been pulverized in
the coal crusher 20 is fed to the coal dryer 11, and air fed.
from the air blower 21 is heated in a second air heater 60
to become heated air, and this heated air transports the
coal as carrier gas, and the coal dryer 11 dries the coal
15 using the heat of the heated air.
The second air heater 60 heats the air using a cooling
medium (heating meaium) such as water or the like as a heat
source that is heated by heat exchange with the combustion
exhaust gas in the heat recovery equipment 16. In other
20 words, the cooling medium such as water or the like that is
heated by heat exchange with the combustion exhaust gas in
the heat recovery equipment 16 is fed by a line 61 as the
heating medium to the second air heater 60. In the second
air heater 60, the air is heated to become heated air
25 through heat exchange between the air fed from the air
blower 21 and this heating medium.
The heating medium that has lost its heat energy in the
second air heater 60 is circulated to the heat recovery
equipment 16 via a line 62.
30 Here, as with the configuration illustrated in FIG. 1,
the bypass line 33 may be provided between the line 61 and
the line 62, and ~ontrol valves 34, 35 may be provided on
the bypass line 33 and the line 62. Opening and closing and
the degree of opening of the control valves 34, 35 are
35 adjusted automatically by a temperature controller 37 based
on the measurement results of a sensor 36 provided on the
combustion exhaust gas outlet side of the heat recovery
equipment 16. Using the temperature controller 37, the
opening and closing and the degree of opening of the control
14
valves 34, 35 are adjusted and the quantity of heating
medium circulating between the heat recovery equipment 16
and the second air heater 60 is controlled so that the
temperature of the combustion exhaust gas on the outlet side
5 of the heat recovery equipment 16 is within a predetermined
temperature range, for example, from 85 to 90'~.
t
According to the configuration as described above, the
air that is fed to the coal dryer 11 is heated by the heat
recovered from the combustion exhaust gas in the heat
10 recovery equipment 16. Within the coal dryer 11, drying of
coal is promoted by the contact between this air and the
coal. As a result, it is not necessary to extract steam from
the boiler turbine 14, so it is possible to increase the
efficiency (output) of the boiler turbine 14. Also, the
15 calorific value of the coal is increased by drying the coal,
so from this point, also it is possible to increase the
efficiency of the boiler turbine 14. As a result, less coal'
is needed to obtain the same output, so it is possible to
reduce the quantity of coal used in the coal fired boiler
20 plant 10B, and achieve lower costs.
In addition, by drying the coal, the combustion
conditions within ,the boiler turbine 14 approach the ideal
combusti3n conditions, so it is possible to reduce the
quantity of combustion exhaust gas. As a result, it is
25 possible to reduce the quantity of supplementary makeup
water used for desulfurization in the desulfurization plant
18, and in this respect, also it is possible to achieve
lower costs.
Also, by drying the coal, the effect of reduction of
30 mercury and NOx contained in the combustion exhaust gas is
expected.
Application Examples of the Second Embodiment:
The following are descriptions of several
configurations that can be added to the configuration of the
35 second embodiment as described above as application
examples.
(Application Example 1)
In the coal fired boiler plant 10B illustrated in FIG.
6, in addition to the configuration described for the second
embodiment above, steam extracted from the boiler turbine 14
5 may be fed to an air heater 40 provided between the second
air heater 60 and the coal dryer 11 via the line 39. Then,
in the air heater 40, heat is exchanged between the
extracted steam and the heated air (carrier air) fed from
the second air heater 60 to the coal dryer 11, and the
10 heated air is further heated.
As a result, the temperature of the air fed to the coal
dryer 11 is further increased, and drying of the coal in the
coal dryer 11 is further promoted.
Heat exchange in the air heater 40 as described above
15 can be adjusted in accordance with the temperature of the
carrier air in the coal dryer 11. In this case, the
temperature of the air may be measured by the sensor 41A or
41B provided on the outlet side of the second air heater 60
or on the exhaust gas side of the coal dryer 11, and the
20 quantity of steam extracted from the boiler turbine 14 may
be adjusted by the temperature controller 42 and the valve
43 based on the measurement results.
(Application Example 2)
Also, in the coal fired boiler plant 10B illustrated in
FIG. 7, in additi~n to the configuration described for the
second embodiment above, steam may be extracted from the
boiler turbine 14, and fed to the heating medium heater 45
provided on the line 30 that supplies the heating medium
from the heat recovery equipment 16 to the coal dryer 11 via
the line 44. Also, the heating medium is further heated in
this heating medium heater 45.
As a result, the temperature of the heating medium fed
to the second air heater 60 is further increased, the
temperature of the heated air is further increased, and
35 drying of the coal within the coal dryer 11 is further.
promoted.
Heat exchange in the heating medium heater 45 as
described above cah be controlled by adjusting the quantity
of steam extracted from the boiler turbine 14 using the
temperature controller 47 and the valve 48 based on the
measurement results of the temperature sensor 46A provided
5 on the exhaust gas side of the coal dryer 11, or a heating
medium temperature sensor 46B provided on the inlet side of
the coal dryer 11.
(Application Example 3)
Also, in the coal fired boiler plant 10B illustrated in
10 FIG. 8, air for drying that has been heated using the
combustion exhaust gas from the boiler turbine 14 as a heat
source and generated in the air heater 15 may be fed to the
outlet side of the second air heater 60 via the line 49.
As a result, the temperature of the air fed to the coal
15 dryer 11 is increased, and drying of the coal in the coal
dryer 11 is furthe: promoted.
In this case, the supply of this air for drying can be
controlled by adjusting the flow rate (mixing ratio) of the
air for drying supplied from the line 49 and the heated air
20 supplied from the air blower 21. This can be achieved using
the valves 53A, 53B and the flow rate controllers 54A, 54B
provided on the outlet side of the air blower 21 and on the
line 49, so that their temperatures are within a
predetermined range using the temperature controller 52A or
25 52B based on the air temperature measured by the sensor 51A
or 51B provided on the outlet side of the second air heater
60 or on the exhaust gas side of the coal dryer 11.
Third Embodiment:
Next, a third embodiment of the present invention will
30 be described below. In the following explanation of the
third exbodiment, the configuration that is common with the
first embodiment and second embodiment as described above is
given the same reference numerals in the drawings and its
explanation is omitted, and the explanation is focused on
35 the differences from the first embodiment and second
embodiment as described above.
The configuration of the third embodiment described
below can be added to any of the configurations illustrated
in FIGS. 1 through 8. In the following, an example is
described in which the configuration according to this
embodiment is added to the configuration illustrated in
FIG.5.
c
As illustrated in FIG. 9, a coal fired boiler plant 10C
according to this embodiment includes a gypsum separator 65
and a spray dryer 66, in addition to the configuration of
the coal fired boiler plant 10B illustrated in FIG. 5.
The gypsum separator 65 filters the wastewater from the
desulfurization plant 18, and separates into the gypsum
component and the filtrate. The filtrate (wastewater)
obtained from the gypsum separator 65 is fed to the spray
dryer 66.
The filtrate fed from the gypsum separator 65 and the
high temperature combustion exhaust gas from the boiler
turbine 14 are fed to the spray dryer 66. The filtrate and
the combustion exhaust gas are fed to the spray dryer 66,
and sprayed into the combustion exhaust gas on the outlet
side of the air hea,t er 15.
As a result, the water component of the filtrate
contacts the combustion exhaust gas and is evaporated. As a
result, it is possible to eliminate the wastewater from the
desulfurization plant 18. Also, it is possible to reduce the
temperature of the combustion exhaust gas on the upstream
side of the heat recovery equipment 16 by evaporating the
water component of the filtrate.
Fourth Embodiment:
Next, a fourth embodiment of the present invention will
be described below. In the following explanation of the
fourth embodiment, the configuration that is common with the
first through third embodiments as described above is given
the same reference numerals in the drawings and its
explanation is omitted, and the explanation is focused on
the differences frpm the first through third embodiments as
described above.
The configuration of the fourth embodiment described
18
below can be added to any of the configurations illustrated
in FIGS. 1 through 9. In the following, an example is
described in which the configuration according to this
embodiment is added to the configuration illustrated in.
5 FIG.5.
As illustrated in FIG. 10, a coal fired boiler plant
10D according to this embodiment includes a line 70 that
feeds exhaust gas from the coal dryer 11 to the inlet side
of the electrostatic precipitator 17, in addition to the
10 configuration of the coal fired boiler plant 10B illustrated
in FIG. 5.
By feeding the exhaust gas from the coal dryer 11 to
the electrostatic precipitator 17 via the line 70, in the
electrostatic precipitator 17, it is possible to recover the
15 fine coal included in the exhaust gas from the coal dryer
11.
As a result, it is possible to further clean the
exhaust gas discharged from the coal fired boiler plant 10D,
and prevent pollution of the atmospheric environment. In.
20 addition, it is not necessary to separately provide
equipment to recover the fine coal included in the exhaust
gas from the coal dryer 11, so it is possible to obtain the
effects described above at lower costs.
When fine coal is burned in the boiler turbine 14,
25 mercury is segreghted. Therefore, because the fine coal
included in the exhaust gas from the coal dryer 11 is
recovered in the electrostatic precipitator 17, mercury is
not released.
Fifth Embodiment:
30 Next, a fifth embodiment of the present invention will
be described below. In the following explanation of the
fifth embodiment, the configuration that is common with the
first through fourth embodiments as described above is given
the same reference numerals in the drawings and its.
35 explanation is omitted, and the explanation is focused on
the differences from the first through fourth embodiments as
described above.
The configuration of the fifth embodiment described
below can be added to any of the configurations illustrated
in FIGS. 1 through 10. In the following, an example is
described in which the configuration according to this
5 embodiment is added to the configuration illustrated in FIG.
As illustrated in FIG. 11, a coal fired boiler plant
10E according to this embodiment includes a configuration in
which exhaust gas from the coal dryer 11 is fed to a gas'
10 processing system (fine coal recovery plant) 80, in addition
to the configuration of the coal fired boiler plant 10B
illustrated in FIG. 5.
The gas processing system 80 separates the exhaust gas
from the coal dry~r 11 into a gaseous component and fine
15 coal that was contained in the exhaust gas.
The gas that has passed through the gas processing
system 80 is fed to the inlet side of the electrostatic
precipitator 17.
Also, the fine coal that is collected in the gas
20 processing system 80 is fed to the coal bunker 12.
By feeding the exhaust gas from the coal dryer 11 to
the electrostatic precipitator 17 via the gas processing
system 80 as described above, it is possible to further'
clean the exhaust gas discharged from the coal fired boiler
25 plant 10D, and prevent pollution of the atmospheric
environment.
In addition, it is possible to more effectively use the
coal by feeding , the fine coal collected in the gas
processing system 80 to the boiler turbine 14 via the coal
30 bunker 12.
In addition, by feeding the fine coal collected in the
gas processing system 80 to the coal bunker 12, it is
possible to prevent the coal powder from mixing with the ash
collected by the electrostatic precipitator 17.
35 The configurations described in each of the above
embodiments can be changed as appropriate provided they are
within the intent of the scope of the present invention.
20
For example, the configurations described for the first
through fifth embodiments above can be combined as
appropriate.
%
Also, in each of the embodiments, the heat recovery
5 equipment 16 is provided on the upstream side of the
electrostatic precipitator 17, but the electrostatic
precipitator 17 may be provided on the upstream side of the
heat recovery equipment 16.
Besides this, the configurations described in the
10 embodiments above can be adopted or discarded as desired, or
changed as appropriate into other configurations, provided
there is no deviation from the intent of the present
invention.
WE CLAIM:
1. A coal fired boiler plant, comprising:
a coal dryer that dries coal;
a boiler in which the coal that was dried in the
5 coal dryer is mixed with air for combustion and burned;
an air heater that heats the air for combustion
suppiied to the boiler using combustion exhaust gas
discharged from the boiler;
a precipitator that collects dust included in the
10 combustion exhaust gas;
a desulfurization plant that performs a
desulfurization process on the combustion exhaust gas;
and
heat recovery equipment that is provided on the
15 downstream side of the air heater in the direction of
flow of the combustion exhaust gas, and that heats a
heating medium with the combustion exhaust gas, wherein
the coal dryer dries the coal using the heat
energy of the heating medium that was heated in the heat
20 recovery equipment.
2. The coal fired boiler plant according to claim 1,
wherein the coal dryer dries the coal within the coal
dryer by passing the heating medium that has been heated
in the heat recovery equipment through a tubes provided
25 within the coal dryer.
3. The coal fired boiler plant according to claim 1,
wherein the coal is dried within the coal dryer by
heating a carrier air supplied from the outside into the
coal dryer using the heating medium that was heated in,
30 the heat recovery equipment.
4. The coal fired boiler plant according to any one of
claims 1 through 3, further comprising an air heater
that heats carrier air supplied from the outside into
the coal dryer using steam that has been extracted by
22
extracting a portion of the steam generated by burning
the coal in the boiler.
5. The coal fired boiler plant according to any one of
claims 1 through 4, further comprising a heating medium
5 heater that further heats the heating medium that has
been heated in the heat recovery equipment using steam
that has been extracted by extracting a portion of the
steam generated by burning the coal in the boiler.
6. The coal fired boiler plant according to any one of
10 claims 1 through 5, wherein the air heater heats air for
drying supplied to the coal dryer using combustion
exhaust gas discharged from the boiler, and
*
the coal dryer dries the coal within the coal
dryer using the air for drying that is fed into the coal
15 dryer.
7. The coal fired boiler plant according to claim 6,
wherein a portion of the air for combustion heated in
the air heater is branched off and mixed with the
carrier air that is supplied from the outside into the
20 coal dryer, and supplied into the coal dryer.
8. The coal fired boiler plant according to any one of
claims 1 through 7, wherein the desulfurization plant'
performs a desulfurization process by bringing the
combustion exhaust gas into contact with process water,
25 and
the coal fired boiler plant further comprises a
spray dryer that evaporates wastewater obtained by
separating a gypsum component from the process water
after the desulfurization process, by bringing the
30 wastewater into contact with the combustion exhaust gas
on the upstream side of the desulfurization plant.
9. The coal fired boiler plant according to any one of
claims 1 through 8, wherein the coal dryer feeds the
exhaust gas from the coal dryer to t.he precipitator.
35 10. The coal fired boiler plant according to any one of
claims 1 through 8, further comprising a fine coal
recovery plant that recovers fine coal smaller than a
predetermined particle size from the coal that is
included in the exhaust gas from the coal dryer, and
the fine coal recovery plant supplies the
recovered fine coal to the boiler together with the coal
5 that has been dried in the coal dryer.
11. The coal fired boiler plant according to claim 10,
wherein the exhaust gas from which the fine coal has
been removed by recovering the fine coal in the fine
coal recovery plant is fed to the precipitator.
10 12. The coal fired boiler plant according to any one of
claims 1 through 11, wherein the heat recovery equipment
is disposed on the upstream side of the precipitator.
13. The coal fired boiler plant according to any one of
claims 1 through 11, wherein the heat recovery equipment
15 is disposed on the downstream side of the precipitator.
14. A method of drying coal that is supplied to a boiler in
the coal fired boiler plant according to any one of
claims 1 through 13, comprising:
heating a heating medium recovered in heat
20 recovery equipment that is provided on the downstream
side of an air heater in the direction of flow of
combustion exhaust gas using the heat energy of
combustion exhaust gas that is discharged from a boiler
as a result of combustion of the coal in the boiler; and
25 drying the coal supplied to the boiler using the
heat energy of the heating medium.