FIELD OF THE INVENTION

[001] The present disclosure, in general, relates to iron ore sintering and more particularly, to a real time system and method thereof to measure and control permeability of a sinter bed in a sinter machine to increase productivity of the sinter machine.
BACKGROUND OF THE INVENTION
[002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[003] In iron ore sinter plant, green sinter mix is prepared by mixing and proportioning of ingredients of size 0-8 mm of iron ore fines, coke breeze, fluxes and plant reverts. Suitable amount of water is added to the mix which is then produced in the form of granules of size 4-8 mm. The green sinter mix is charged on to the sinter machine, consisting of moving grates called pallet cars. Air is sucked through the bed. Sintering starts by igniting the top layer of the bed which forms a sustainable flame front. The flame front moves continuously downward under the effect of suction and sintering takes place in layer by layer. The process is driven by the heat carrying capacity of the air passing through the granular solid mass.
[004] The rate of sintering is dependent on the amount of air passing through the bed at a given time. The ease of air to pass through the bed is given by the term “Permeability” which is defined as the air flow through a unit cube of material under a unit pressure gradient. It is derived from the Ergun function for fluid flowing through a packed bed. In practice, bed permeability (P) is directly related to the amount of (ease of) passing air through the sinter bed and therefore the production of the sinter machine. So, Permeability (P) is a parameter, all sinter plant operators would like to know and control to achieve maximum production from a given set of condition and a given sinter machine. Many researchers and plant operators have tried to measure P over last 50 years or so, but the task remained elusive due to the fundamental difficulty in measuring the air flow through the sinter bed.
[005] A known method in the prior art is that of off-line measurement where the flow is measured off-line by taking a sample of the green mix in a container and applying suction to it. Although this method gives a permeability value, the method has several drawbacks. Firstly, the permeability is only indicative as the operator does not get the real value after charging the material on sinter bed. Secondly, the method is off-line and gives discrete values in time scale.
[006] Another known method in the prior art is that of measurement in surge hopper above the sinter machine. In accordance with this method, a pressure measuring device is installed in the surge hopper above sinter machine. It is a contact type probe and faced a serious difficulty as green mix is sticky in nature and creates build up on the measuring device. Therefore, this method is not preferred. (Patent No.- 199446 (Filed on 7th July 2006))
[007] Another common method known in the prior art is use of Anemometer. Many operators tried measuring the air velocity on top of the sinter bed as it comes out of the ignition furnace. The method has several drawbacks. Firstly, air velocity above the sinter bed is of the order of 0.4 - 0.6 m/s and it varies from side to the center of the bed. Hence getting accurate and representative measurement is not possible. Secondly, in most of the anemometers, accuracy is low due to the lower velocity range and there is no streamline flow above the bed. Hence this method also failed to give an accurate measurement of permeability. Such use of Anemometer is disclosed in US patent no.3,265,377 titled ‘Method of and apparatus for regulating the speed of sintering strands’.
[008] A further method as known in the prior art is that of using pitot tubes. Use of pitot tubes in the wind box down comer just after the ignition furnace was tried long back by E. W. Voice et. al., 1953. Like other known method this also suffers from several drawbacks. Firstly, the air drawn in to the wind box just after ignition contains very high amount of dust particles. These tend to choke the opening of the pitot tube. Secondly, the pitot tube gets damaged due to erosion by impact of these particles moving at a speed of 15-20 m/s.
[009] A still further method of using sensors is discussed in the Canadian patent publication no. 949175A titled ‘Process and apparatus for the control of the speed of movement of sinter strand’. In accordance with the disclosure, the position of burn through is determined in the travel of moving sinter strand by noting the change in relative permeability through differential pressure sensor by at least two sensors in a moving structure along the moving direction over sinter strand. Also speed of the sinter strand can be regulated so that burn through will happen at a predefined position. US patent application no. 281,501 discloses a flowmeter based on differential pressure to measure air flow rate.
[010] In the above discussed prior arts, there lies a drawback that there is no system/method for reliable measurement of flow of air (F) through the sinter bed to determine the permeability of the sinter bed. Thus, there is a requirement of a system and method thereof that can measure permeability of sinter bed in real time.
OBJECTIVES OF THE INVENTION
[011] It is therefore the object of the invention to overcome the aforementioned and other drawbacks existing in prior art.
[012] The primary object of the invention is to provide a real time system and method for measuring flow of air through sinter bed in a sinter machine.
[013] Another object of the invention is to provide a system and method that can utilize air drawn in wind box(s) of a sinter machine containing high amount of dust particles to measure the flow of air through sinter bed in a sinter machine.
[014] Yet another object of the invention is to provide a system and method to measure permeability of sinter bed in a sinter machine.
[015] Yet another object of the invention is to provide a system and method that can control sinter bed permeability to increase the production of a sinter machine in real time.
[016] These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.
SUMMARY OF THE INVENTION
[017] The present invention provides for a real time system and method thereof to measure and control sinter bed permeability in a sinter machine.
[018] In accordance with an embodiment, a real time system to measure and control permeability of a sinter bed in a sinter machine comprising a plurality of wind box is provided. The real time system comprises of a first sensing unit disposed in a wind box down comer to send a first information on a continuous basis and a second sensing unit disposed vertically downwards to the first sensing unit i flow path of air from sinter bed to send a second information on a continuous basis. The system further comprises of a processing unit adapted to receive and process the first information and second information to determine air flow rate through the sinter bed on a continuous basis and to determine the permeability of the sinter bed based on air flow rate on a continuous basis. The real time system also comprises of a display unit comprising a graphical user interface adapted to display the permeability of the sinter bed on a continuous basis.
[019] In accordance with said embodiment, the display unit of the real time system is adapted to take instructions from a sinter plant operator to control the permeability of the sinter bed.
[020] In accordance with said embodiment, the first sensing unit and second sensing unit are infrared based sensing unit and are disposed in the wind box down corner number 3 or the down corner just after the ignition furnace of the sinter machine. The first sensing unit and second sensing unit are disposed a predetermined distance apart.
[021] In accordance with said embodiment, the real time system also comprises of a power supply unit.
[022] In accordance with another non-limiting embodiment, a real time method to measure and control sinter bed permeability in a sinter machine is provided. The method comprises the steps of receiving a first information from a first sensing unit on a continuous basis, receiving a second information from a second sensing unit on a continuous basis, calculating air flow rate through the sinter bed using the first information and second information, determining the permeability of the sinter bed using the air flow rate, and controlling the permeability of the sinter bed to increase sinter production of the sinter machine.
[023] In accordance with said embodiment, the first information and second information is monitoring of turbulence in air flow from sinter bed, wherein the turbulence is created by dust particles and condensed water droplets in air flow from sinter bed.
[023] In accordance with said embodiment, controlling the permeability comprises taking instructions from a sinter plant operator to vary green mix moisture and to vary packing density of the sinter bed.
[024] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.
[025] It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.
[026] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.
BREIF DESCRIPTION OF THE DRAWINGS
[027] The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and processes that are consistent with the subject matter as claimed herein, wherein:
Figure 1: illustrates an exemplary sinter plant comprising of a sinter machine, as known in the art;
Figure 2: illustrates an exemplary sintering process detailing the different stages of sintering;
Figure 3: illustrates thermal zones of sintering process as known in the art;
Figure 4: illustrates a real time system, in accordance with an exemplary embodiment of the present disclosure;
Figure 5 (a) and (b): illustrates time delay (T) or lag between two crests of received modulated signals obtained from two infrared based sensing units, in accordance with an exemplary embodiment of the present disclosure;
Figure 6: provides a flowchart depicting the method steps, in accordance with an embodiment of the present disclosure;
Figure 7: illustrates trend of uncontrolled permeability during 50% (app.) empty of single, two pallets and sinter bed forcing, in accordance with an exemplary embodiment of the present disclosure.

Figure 8: illustrates trend of permeability in controlled condition, using the real time permeability measured values, in accordance with an exemplary embodiment of the present disclosure.
Figure 9: illustrates trends of sinter bed permeability, flue gas velocity and suction at wind box number 3, in accordance with an exemplary embodiment of the present disclosure; and
Figure 10: illustrates trends of Mixing Drum Water Flow, Burn Through Temperature, in accordance with an exemplary embodiment of the present disclosure.
[028] The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION OF THE INVENTION
[029] While the embodiments of the disclosure are subject to various modifications and alternative forms, specific embodiment thereof have been shown by way of example in the figures and will be described below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alterative falling within the scope of the disclosure.
[030] As used in the description herein and throughout the claims that follow, the meaning of "a," "an," and "the" includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise.
[026] The terms "comprises", "comprising", or any other variations thereof used in the disclosure, are intended to cover a non-exclusive inclusion, such that a device, system, assembly that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to the system, or assembly, or device. In other words, one or more elements in a system or device proceeded by "comprises... a" does not, without more constraints, preclude the existence of other elements or additional elements in the system, apparatus or device.
[031] Hereinafter a real time system and method thereof to measure and control permeability of sinter bed in sinter machine will be discussed in more detail.
[032] Referring to figure 1 which illustrates an exemplary sinter plant. A green sinter mix is prepared by mixing and proportioning of ingredients of size 0-8 mm of iron ore fines, coke breeze, fluxes and plant reverts. Suitable amount of water is added to the mix which is then produced in the form of granules of size 4-8 mm. The green sinter mix is charged on to the sinter machine, consisting of moving grates called pallet cars. Air is sucked through the bed. Sintering starts by igniting the top layer of the bed which forms a sustainable flame front. The flame front moves continuously downward under the effect of suction and sintering takes place in layer by layer. The process is driven by the heat carrying capacity of the air passing through the granular solid mass. The process is depicted in Fig. 2 and Fig. 3.
[033] The rate of sintering is dependent on the amount of air passing through the bed at a given time as per Fig. 2 and 3. The ease of air to pass through the bed is given by the term “Permeability” which is defined as the air flow through a unit cube of material under a unit pressure gradient. It is derived from the Ergun Function. The formula for permeability, in JPU is given by Eqn.

Where,
P = Permeability expressed in Japanese Permeability Unit (JPU)
F = Wind volume passing through the bed, Nm3/min
A = Area through which air is passing, m2
h = Bed height (thickness of green mix), mm
s = Applied suction, mm Water Gauge
[034] In practice, bed permeability (P) is directly related to the amount of (ease of) passing air through the sinter bed and therefore the production of the sinter machine
[035] Referring to figure 4, a real time system (100) providing reliable measurement of air flow through sinter bed is illustrated. The measurement of air flow in accordance with an embodiment is done in the down comer of wind box (50) number 3, i.e., just after the ignition furnace because:
air velocity in the wind box down comer is of the order of 15-20 m/s. Most instruments work with higher accuracy at this range; and
there is clear demarcation of the area (complete area of the wind box) through which air is drawn, so higher accuracy in applying the permeability formula.
[036] The real time system (100) comprises of a first sensing unit (10) disposed in a wind box down comer (50) to send a first information on a continuous basis, a second sensing unit (20) disposed vertically downwards to the first sensing unit (10) in flow path of air from sinter bed to send a second information on a continuous basis, a processing unit (30) adapted to receive and process the first information and second information to determine air flow rate (F) through the sinter bed on a continuous basis and to determine the permeability (P) of the sinter bed based on air flow rate (F) on a continuous basis and a display unit (40) comprising a graphical user interface adapted to display the permeability (P) of the sinter bed on a continuous basis. The display unit (40) is adapted to take instructions from a sinter plant operator to control the permeability (P) of the sinter bed.
[037] The sensing units (10, 20) are non-contact type infrared sensing device to measure the air flow rate (F). The working used is similar in principle to the technique of flow measurement by the injection of chemical dye or radioactive tracers, where the velocity is derived from the transport time of the tracer between two measuring points a known distance apart. Instead of an artificial tracer being added, the naturally occurring turbulence of the gas stream is used as the tracer. This flow turbulence causes fluctuations to occur in infrared radiation emitted by the gas. This continuously variable turbulent pattern is monitored by two infra-red based sensor unit (10, 20) mounted typically 1m apart along the direction of air flow. An electronic correlation technique is used to continuously compare the two sensor signals i.e. first information and second information to determine the time delay between them imposed by the gas velocity.
[038] Typical signals from the sensor unit 10 and 20 are shown in Fig. 5. The signal from sensor unit (20) shows a strong similarity to that from sensor unit (10) but is delayed by a time t, the time taken for the gas to flow from point of mounting of sensor unit 10 to 20. Continuous determination of the sensor signal time delay by the signal processor unit produces a continuous measurement of gas velocity since:
Velocity V = L/t
L is the separation distance between the two sensor unit (10, 20); t is the time delay measured by the infrared sensors (10, 20).
[039] Referring to figure 6 which illustrates a flowchart of a real time method (200) to measure and control sinter bed permeability in a sinter machine in accordance with an embodiment. The method comprises the steps of:
receiving a first information (201) from a first sensing unit on a continuous basis,
receiving a second information (202) from a second sensing unit on a continuous basis,
calculating (203) air flow rate (F) through the sinter bed using the first information and second information,
determining (204) the permeability (P) of the sinter bed using the air flow rate, and
controlling (205) the permeability (P) of the sinter bed to increase sinter production of the sinter machine.
[040] The first information and second information is monitoring of turbulence in air flow from sinter bed, wherein the turbulence is created by dust particles in air flow from sinter bed. Controlling the permeability comprises taking instructions from a sinter plant operator including varying green mix moisture and varying packing density of the sinter bed.
Advantages of the present disclosure:
[037] The present disclosure provides for a non-contact type measurement.
[038] The present disclosure utilizes the wave signature created by dust particles at a temperature of about 85 °C which is ideal to create the desired signal for turbulence, the infrared sensors to pick up accurately
[039] The present disclosure provides for a real time system and method that is ideally designed to work in an environment existing in the wind box down comer of a sinter machine.
[040] The present disclosure provides for a real time system and method that is suitable for hot, dusty aggressive gases and provides for measurement under multi-phase environment.
[041] The present disclosure provides for a real time system and method that is reliable on-line measurement system for sinter bed permeability. The real time system and method makes it possible to run sinter machine in a steady state for a longer time. In many instances, process disturbances can be detected early and then can be avoided. Such avoidance or adjustment was not possible earlier without the on-line permeability measurement.
[042] The present disclosure provides for a real time system and method that facilitates sinter plant operator to control the permeability by varying the green mix moisture and varying the packing density of the sinter bed by varying the speed of the feed roll.
[043] The present disclosure provides for a real time system and method that facilitates availability of the relevant parameters to control sinter bed permeability to be visible to sinter plant operator on a real-time basis on display device. By operating sinter machine within the desired range of permeability value, there is a gain in sinter machine production and productivity. A productivity gain of 0.5 t/m2/d is possible just by eliminating the process abnormality. The real time permeability measurement and control system is a great enabler to attain the steady state operation of sinter plant, which ensures better quality of sinter. Operators are enabled to take early corrective measure and thereby eliminate long unsteady state of operation leading to lower productivity and poor quality of sinter which help sinter operators achieve optimal permeability for any given lot of raw sintering mix.
[044] The present disclosure is now explained with the help of a non-limiting example.
[045] Infrared correlation based non-contact flow device has been implemented to detect air flow through the wind box #3 of sinter machine #2 at SP1, Tata Steel Limited Jamshedpur Works. With the air flow reading obtained from the sensor, JPU (Japanese Permeability Unit) has been calculated as per equation 2 given above. The constants used in this case is specific to machine dimensions of Jamshedpur Works. These will change for any other machine as per the design parameters.
JPU (Japanese Permeability unit) for SP#1, Machine 2:

JPU (Japanese Permeability unit)
=e(F/A) ?(h/s)?^0.6
= e (F/5)(490/s)0.6
=8.23 e(F/s0.6)
where
e=((10132.5-s)*298)/((273+t)*10132.5)
• F=air flow rate in m3/min=To be taken from flow device=Variable
• A=cross sectional area of the bed (m2) = 2.5X2=5 m2- Constant for a given machine
• h=height of the bed in mm; 490 mm- Constant for a given machine
• S=suction pressure in mm of H2O = taken on-line from pressure transmitter in wind box# 3 (or the WB after ignition hood) in mm H2O=Variable
• t= Temperature in 0C in wind box #3-Variable
• e=factor to multiply with volume to get nominal volume at NTP
condition (Nm3/min)
[041] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles, ‘a', or "an" limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations).
[046] It’s reading is helpful to understand the process of sinter making. Following has been tested for following mentioned conditions.
1. Bed void around 50% as per Fig. 7. Due to decrease in sinter bed depth the permeability shoots up to around 7.3% from it’s initial value.
2. Due to sudden close of water addition in secondary mixer, feed roll speed has been decreased and this in turn created drop in the permeability around 40% from it’s initial value as per Fig. 7.
[047] Figure 8illustrates trend of permeability in controlled condition, using the real time permeability measured values. As seen from trends of Fig 9 and Fig. 10, Mixing Drum Water Flow, BTP, Sinter bed Permeability (JPU), Flue Gas Velocity, Suction at WB#3, variation is less after 13/12/18, 10.15 am to end. Moreover, this time zone is indicating good BTP zone from 210 to 240 degree centigrade, which means stable and quality region of sinter making for this specific machine. It may be different for different machines. Additionally, it has been observed that Flue Gas Velocity and Sinter Bed Permeability trends are likewise which is logical. Also it has been observed that trends of the suction in wind box #3 varies almost inversely with the Sinter Bed Permeability which is a physical phenomenon, not difficult to understand by those closely associated with the art.
[048] The above description does not provide specific details of manufacture or design of the various components. Those of skill in the art are familiar with such details, and unless departures from those techniques are set out, techniques, known, related art or later developed designs and materials should be employed. Those in the art are capable of choosing suitable manufacturing and design details.
[049] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.
[050] The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.
[051] While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

We claim:

1. A real time system (100) to measure and control permeability (P) of a sinter bed in a sinter machine comprising a plurality of wind box (WB), the real time system comprises:
? a first sensing unit (10) disposed in a wind box down comer (50) to send a first information on a continuous basis,
? a second sensing unit (20) disposed vertically downwards to the first sensing unit (10) in flow path of air flow from sinter bed to send a second information on a continuous basis,
? a processing unit (30) adapted to receive and process the first information and second information to determine air flow rate (F) through the sinter bed on a continuous basis and to determine the permeability (P) of the sinter bed based on air flow rate (F) on a continuous basis,
? a display unit (40) comprising a graphical user interface adapted to display the permeability (P) of the sinter bed on a continuous basis.
2. The real time system (100) as claimed in claim 1, wherein the display unit (40) is adapted to take instructions from a sinter plant operator to control the permeability (P) of the sinter bed.
3. The real time system (100) as claimed in claim 1, wherein the first sensing unit (10) and second sensing unit (20) are infrared based sensing unit.
4. The real time system (100) as claimed in claim 1, wherein the first sensing unit (10) and second sensing unit (20) are disposed in the wind box down comer number 3 of the sinter machine.
5. The real time system (100) as claimed in claim 1, wherein the first sensing unit (10) and second sensing unit (20) are disposed a predetermined distance apart.
6. The real time system (100) as claimed in claim 5, wherein the predetermined distance is 1 meter.
7. The real time system (100) as claimed in claim 1, comprises of a power supply unit (60).
8. A real time method (200) to measure and control sinter bed permeability in a sinter machine comprising the steps of:
? receiving a first information (201) from a first sensing unit on a continuous basis,
? receiving a second information (202) from a second sensing unit on a continuous basis,
? calculating (203) air flow rate (F) through the sinter bed using the first information and second information,
? determining (204) the permeability (P) of the sinter bed using the air flow rate, and
? controlling (205) the permeability (P) of the sinter bed to increase sinter production of the sinter machine.
9. The real time method (200) as claimed in claim 8, wherein the first information and second information is monitoring of turbulence in air flow from sinter bed.
10. The real time method (200) as claimed in claim 8, wherein the turbulence is created by dust particles in air flow from sinter bed.
11. The real time method (200) as claimed in claim 8, wherein controlling the permeability comprises taking instructions from a sinter plant operator.
12. The real time method (200) as claimed in claim 8, wherein the instructions from the sinter plant operator includes varying green mix moisture and varying packing density of the sinter bed.