Title of Invention	PLC BASED DATA ACQUISITION AND CONTROL SYSTEM FOR ON-LINE GAS PRESSURE AND DRAUGHT CONTROL IN COKE OVEN BATTERY.
Abstract	An arrangement for online control of coke oven battery heating gas pressure and battery draught involving both feed back and feed forward strategy comprising Programmable and Logic Controller (PLC) (6) based data acquisition system adapted to receive signals of parameters selected from Coke Mass Temperature; Goose-neck temperature (8); Coking Index; Heating gas; Calorific value; Coal Moisture; Heating Gas Flow; Heating Gas Pressure; Battery Draught; Tunnel Temperature; Winch reversal and comprising means (9) for storage and display of the data thus acquired; and means for communicating with the control system (7) of the arrangement; and a control system (7) adapted to receive inputs from the PLC and predict heating gas pressure and battery draught values comprising means for processing heat demand values given by the equation.

Title of Invention

PLC BASED DATA ACQUISITION AND CONTROL SYSTEM FOR ON-LINE GAS PRESSURE AND DRAUGHT CONTROL IN COKE OVEN BATTERY.

Abstract

An arrangement for online control of coke oven battery heating gas pressure and battery draught involving both feed back and feed forward strategy comprising Programmable and Logic Controller (PLC) (6) based data acquisition system adapted to receive signals of parameters selected from Coke Mass Temperature; Goose-neck temperature (8); Coking Index; Heating gas; Calorific value; Coal Moisture; Heating Gas Flow; Heating Gas Pressure; Battery Draught; Tunnel Temperature; Winch reversal and comprising means (9) for storage and display of the data thus acquired; and means for communicating with the control system (7) of the arrangement; and a control system (7) adapted to receive inputs from the PLC and predict heating gas pressure and battery draught values comprising means for processing heat demand values given by the equation.

Full Text	Field of invention : The present invention relates to an arrangement for online control of coke oven battery heating gas pressure and battery draught involving both feed back and feed forward strategy. More particularly the present invention relates to an arrangement comprising a system for data acquisition of actual coke mass temperature, coking index, heating gas calorific value, coal moisture and the like by PLC system and a control system so as to provide on-line control and prediction of battery thermal regime considering all the above mentioned parameters. This arrangement can be implemented in any coke oven having similar heating system. Background and prior art: The known art of battery heating control is through manual adjustment of thermal regime based on battery pushing schedule. In some automatic heating control, heat demand is always considered the same for all the ovens. Average temperature of heating wall is measured by manual measurement of burner base temperature of a few selected vertical flues with hand held optical pyrometer. This method of measurement is labour intensive, subjective and does not always co-relate well with coke temperature inside the oven. However, in some coke oven battery automatic control of battery is available through imported system. Some imported system are based on coke mass temperature but does not takes care of coking index. Other systems are based on regenerator top temperature and do not take care of actual coke temperature or coking index. The total software and hardware in such systems are imported and indigenous know-how is not available. Drawbacks of the Known Art: The manual control system is not based on actual process condition and heat demand calculations but depends on the experience of shop operators. Hence it is not accurate and utilises more energy. Also as there is no check for coke mass temperature and actual progress of carbonisation, the quality of coke is inferior and inconsistent. Even the imported automatic control systems commercially available in the market are either feedback or feed-forward in nature. But to achieve optimum battery performance, it is 2 essential to have both feed-forward (Heat Demand) and feed-back (coke mass temperature and coking index). Objects of the Invention : Thus an object of the present invention is to provide an arrangement comprising a Programmable and Logic Controller (PLC) based data acquisition system for acquisition of data on parameters selected from heating gas, waste gas and distillation gas chemical composition, coke mass temperature, different phases of carbonisation, coal-coke properties and the like and communicating them to control system"; and a control system adapted to process the data from the PLC based data acquisition system and predict heating gas pressure and battery draught, said arrangement providing for on-line control of coke oven battery heating gas pressure and battery draught. Another object of the invention is to provide an arrangement for on-line control of coke oven battery heating gas pressure and battery draught such that it utilizes both feed back and feed forward control strategy. Summary of the Invention Thus according to main aspect of the present invention there is provided an arrangement for on-line control of coke oven battery thermal regime and battery draught comprising: i) Programmable and Logic Controller (PLC) based data acquisition system adapted to receive signals of parameters selected from Coke Mass Temperature; Goose-neck temperature; Coking Index; Heating gas; Calorific value; Coal Moisture; Heating Gas Flow; Heating Gas Pressure; Battery Draught; Tunnel Temperature; Winch reversal and comprising a) means for storage and display of the data thus acquired; and b) means for communicating with the control system of the arrangement; and 3 ii) a control system adapted to receive inputs from the PLC and predict heating gas pressure and battery draught values comprising means for processing heat demand values, heat consumption values and correcting the same based on feed back inputs. Detailed Description of Invention : The arrangement of the present invention is implemented in a coke oven which is side fired pair vertical re-circulation type battery comprising of 65 ovens. Each oven is sandwiched between two heating walls. There are 28 vertical flues in each heating wall. Either Coke Oven (CO) gas or Blast Furnace (BF) gas is burnt inside the vertical flues. Coal is charged inside the oven from oven top after closing both side doors and coal is heated in absence of air by the heat transferred from heating wall. During coking, raw Coke Oven gas generated inside the oven which escapes through ascension pipes and collecting main to the exhauster house. After a certain period of time, called Coking Period, coal is converted into coke and is pushed out to the quenching car which takes it to quenching tower for quenching with water. Quenched coke is sent to Blast Furnace for production of hot metal. Optimum control of coke oven battery thermal regime is one of the key factors in coal carbonisation process. Meticulous control of heating requires knowledge about heating gas, waste gas and distillation gas chemical composition, coke mass temperature, different phases of carbonisation, coal-coke properties and the like. The arrangement of the present invention comprises PLC based data acquisition system which acquires data on various parameters by several means for the same. These are stored and then communicated to the control system of the arrangement of the present invention. The control system processes these data and predicts the heating gas pressure and battery draught. These preliminary predictions are modified and corrected. Final values are communicated to the PLC based data acquisition system These are finally communicated to controls for heating gas pressure and battery draught. The arrangement thus uses both feed back and feed forward modes. 4 The PLC based data acquisition system of the arrangement present invention comprises various means which acquires the following process information and communicates them to control system :- - Coke Mass Temperature. - Goose-neck temperature. - Coking Index. - Heating gas Calorific value. - Coal Moisture. - Heating Gas Flow (Coke Side and Pusher Side). - Heating Gas Pressure (Coke Side and Pusher Side). - Batter Draught (Coke Side and Pusher Side). - Tunnel Temperature (Coke Side and Pusher Side). - Winch reversal. The PLC based data acquisition system is also adapted to receive data based on the pushing current which indicate the pushing force required to push the coke from the pusher car by means of system as mentioned in our co-pending application No. 360/Kol/2004 which is incorporated here by way of reference. There are different methods of measuring coke temperature. One way of measuring coke temperature is by putting temperature measurement system in guide car. However, it is found that such installations are difficult to maintain and fails soon due to heat and dust as coke falls in quenching car. Hence in the present invention temperature measurement means is installed at the roof of quenching tower. The means for measuring coke mass temperature Infra-Red pyrometer. The coke mass temperature is measured in quenching car when it enters the quenching tower for quenching. The signal is transmitted to PLC. The temperature of distillation gas at goose-necks are measured by means of chromel-alumel thermocouples mounted at the base of accession pipe. This section is most suitable area for measuring the temperature. The trend of distillation gas temperature provides a direct information about progress of coal carbonisation. The highest 5 temperature achieved (tmax_temp) and the time required to reach such temperature (tmax_time) are thus determined and from these data the Coking index is derived from these data by means of software using the equation: Coking index = Coking period Time to reach peak raw temperature(tmax_time). where coking period = next_time (i) - last time (i): where 'next_time' is next pushing time and 'iasl_time' is the last charging time as mentioned in our co-pending application No. 364/Kol/2004 which is incorporated here by way of reference. Heating gas calorific value is measured by means of on-line CV analyser, which takes gas samples from main gas pipe line before it enters the battery. Means for measuring coal moisture is microwave sensor installed over conveyor belt just before coal tower. Other parameters are measured by conventional means. The PLC receives all the signals from the above mentioned means and stores them by means of continuous data base and event database (as mentioned in our co-pending application No. 364/Kol/2004 which is incorporated here by way of reference) for display of historical trend. The data storage is ensured irrespective of HMI as all the data are stored in PLC. This is in contrary to conventional system, where data is stored HMI (Human Machine Interface). Very fast scan rate in order of 50 ms is achieved due to the fast scanning rate of PLC. Further alt the signals from the PLC are communicated to control system whenever requested. This is done through a specially developed software using OPC (OLE for Process Control). PLC driver means serves as an OPC server while control system acts as OPC client. The data acquisition system also receives set points of gas pressure and battery draught from control system through this driver software and downloads them to respective loop controllers for necessary action. The control system of the arrangement of the present invention comprises means for both feed forward and feedback mode of operation. In the feed forward part, the means for 6 determining the heat demand comprises the heat demand model. This model computes by means of a software the heat demand of battery/ovens during individual oven charging from heat balance equations taking data from data acquisition system as explained above and chemical composition of heating gas, waste gas and distillation gas as fed by operators. Surface heat losses and heat losses from waste gases are also considered to arrive at net heat demand of battery/ovens by the said module by means of computers. This is calculated from the equation as provided in our co-pending application No. 0363/Kol/2004. Where, Ht = Total heat demand of battery Qd (Oven1) = Heat demand of oven Qi.wg = Waste gas heat loss / oven Shi = Surface heat loss / oven N = Total No, of Ovens Heat demand per oven (Qd(Oven1)} is based on several parameters like Coal/coke properties, heating gas parameters, waste gas parameters, raw gas parameters, air data etc. The salient parameters are indicated below : 1) Coal / Coke Parameters : Coal Volatile Matter % Coal Ash % Coal Moisture % Coal Temperature % Coke Temperature % 2) Heating Gas Parameters : 7 Heating Gas Composition (CH4,CO,CO2,CmHm, H2, N2, O2) Heating Gas Temperature Heating Gas Flow 3) Waste Gas Parameters ; Waste Gas Composition (H2, CO, CO2, N2, O2) Average tunnel temperature 4) Raw Gas Parameters : Raw Gas Composition (CH4, CO, CO2, CmHm,, H2, N2, O2) Raw Gas Temperature 5) Air Data : Air Moisture Air Temperature Heat demand of an oven is calculated by the following equation : where, qdx = heat demand of individual carbonization products per ton of dry coal charge. qo - heat of reaction Mcharge = Weight of dry coal charge qdx can be calculated by following equation : 9 where, Yx = Yield of component "x" in Kg/Ton of dry coal charge. Cpx = Heat Capacity of component "x" in KJ/Kg/°C Waste gas heat loss is calculated by following equation Where, Vhg = Specific consumption of heating gas in m3/ton of dry coal charge Vwg = Actual Volume of waste gas per m3 of moist heating gas Cpwg = Output of moist waste gas, m3/m3 of heating gas twg = Waste gas temperature at exit Vwg is calculated by calculating excess air co-efficient and knowing the reaction of various gaseous components with O2. To calculate surface heat loss, oven surface is divided into various parts like oven roof, heating chamber roof, charging hole, inspection hole, heating wall lintel (coke side and pusher side), doors (coke side and pusher side), heating walls (coke side and pusher side), regenerator face walls etc. Heat loss from individual parts is calculated and added to calculate total heat loss from oven surface. Surface heat loss from a specific oven part can be calculated as follows : 9 where, Shlr is rate of surface heat loss from a specific oven part in Joule/sec, K1 is coefficient of heat conducted by convection, K2 is coefficient of heat conducted by radiation, T1 is surface temperature and T2 is ambient temperature (both in degree Kelvin), and A is surface area of specific part (in m2). For K1 and K2 we specifically have: where, H is total height of oven, w is wind speed, and C is coefficient of heat radiation by a black body ( watts/m2/ °C ). Surface heat loss from a particular oven part "Shlr" for total coaking period "CPD" can be calculated from following equation : Total surface heat loss from the oven is calculated by adding equation (7) for all the parts of the oven. The means for determining the heat consumption comprises the heat consumption model. In the heat consumption model, taking on-line data of heating gas fed per reversal and its calorific value, heat consumed per reversal is computed by means of computers using the software as indicated in our co-pending application No. 0363/Kol/2004 which is incorporated here by way of reference. 10 The total heat consumed is calculated by the following equation : Where, Vhg = volume of total heating gas consumed during the reversal (20 minutes) in m3. Chg = Average calorific value of heating gas during the reversal. Preliminary heat demand for the next reversal is computed from comparing the heat demand and heat consumption values and hence preliminary heating gas pressure and draught for the next reversal are predicted by means of software. These preliminary predictions are modified depending on the actual values obtained from the feed back module comprising feed back loops - coking index and pushed out coke temperature by means of software. It has been found by experimentation that coking index for optimum battery performance should be in the range of 1.38 - 1.42. Hence, if average coking index of ovens is beyond this range, preliminary predicted pressure and draught are revised by some value which has been found by experimentation. Likewise, average pushed out temperature of coke should be in the range of 980-1020°C. If actual pushed out temperature of coke is beyond this range, preliminary predicted pressure and draught is corrected by some factors which are found by trails. The corrected values thus obtained by processing the predicted values and the actual values by the software are communicated to the data acquisition PLC system by driver. These final corrected values are downloaded to data acquisition system and communicated to the gas flow control and draught control for actuating the respective butterfly valves. The predicted data generated is shown in Table 1 below: 11 12 The invention is now described by means of non limiting illustrative accompanying drawings. Brief description of accompanying drawings : Figure 1: Graphical representation of coke mass temperature profile Figure 2: Graphical representation of raw gas temperature profile Figure 3; Schematic view of the arrangement of present invention Detailed description of accompanying drawings Figure 1: The actual coke mass temperature is depicted by 1. The running average (2) is also indicated in the figure as derived from the PLC based data acquisition system of the arrangement of the present invention. Figure 2: The raw gas temperature profile at goose neck is indicated. The data acquisition system of the arrangement of the present invention calculates the peak temperature (tmax_temp) 3, time to reach the peak temperature (tmax_time) 4 from the raw gas temperature profile. The coking period 5 is also derived from the temperature profile as next_time - last_time i.e. next pushing time minus last pushing time. The coking index is then given by 4/5. The desired coking index calculated is 1.28 to 1.32. Figure 3: The PLC based data acquisition system (6) receives signals from field instrumentation, normalises the signals and sends it to control system (7) for prediction of gas pressure battery draught. Coke mass temperature is one of the crucial signal for control system. The data acquisition system calculates the running average of instantaneous signal and final average temperature. The gooseneck temperature parameter (8) is vital for coking control methodology. In each and every oven of battery, raw gas is evolved during coke making process. This gas is passing through Ascension Pipe (AP) and collected by hydraulic main. Raw gas temperature of an oven can be measured by putting thermocouple in AP. The mv signal is generated by data acquisition system. Coking index is a crucial 13 parameter used in the feedback loop for determination of the pressure and draught by control system. The coking index provides an index of coke readiness. There are eighteen nos. of thermocouples installed in the standpipes of ovens. Coking process has unique repetitive characteristics of raw gas temperature with time as shown in figure 2. After charging of the oven, within 11 to 16 hours the raw mass temperature reaches its peak and thereafter it gradually reduces till the oven pushing. The coking period with respect, to the 11 to 16 hours is 17 to 22 hours approximately. The parameters calculated by the PLC are the peak temperature (tmax_temp), time to reach this peak temperature (tmax_time) and the schedules coking period. The data acquisition system is implemented through Control Logix PLC of Rockwell Automation make. The data acquisition system is networked with Computer (9) for HMI i.e. means for display of above mentioned parameters in different forms like trend, graphics, bar graphs etc. The HMI platform is Rs View32®, which is a Rockwell Software product. The PLC (6) receives inputs from various means like CV analyzer (10), quenching tower pyrometer (11), moisture analyzer (12). These data are processed and delivered to the control system (7) by PLC driver which serves as the OPC server while the control system serves as the OPC client. There are three models in the control system which predicts the heating gas pressure and battery draught for the current winch reversal Heat Demand Model, (13), Heat Consumption Model (14) and Feedback models including coke mass temperature feed back (15) and coking index feedback (16) Heat demand model (13) calculates the heat demand of an oven as soon as it is charged. This calculation is based on several mass balance equations based on parameters as communicated by data acquisition system. In addition, it also depends on chemical composition of heating gas, waste gas and distillation gas. These data are fed by operator based on laboratory analysis. Heat consumption model (14) keeps a track of actual heat consumed by the battery. Based on the heat demand and consumption, the control system calculates the balance heat required by the battery and heat demand for the current 14 reversal. This is further modified by feedback models (15 and 16). The first correction is based on coke mass temperature and the second correction is based on coking index.. These corrected values are then communicated to the PLC through the driver (not shown). It then actuates the gas flow control (17) and the draught control (18). These then effect the respective valves and effects the on line control as provided by the arrangement of the present invention. 15 We Claim: I. An arrangement for on-line control of coke oven battery thermal regime and battety draught comprising: i) Programmable and Logic Controller (PLC) based data acquisition system adapted to receive signals of parameters selected from Coke Mass Temperature; Goose-neck temperature; Coking Index; Heating gas; Calorific value; Coal Moisture; Heating Gas Flow; Heating Gas Pressure; Battery Draught; Tunnel Temperature; Winch reversal and comprising a) means for storage and display of the data thus acquired; and b) means for communicating with the control system of the arrangement; and ii) a control system adapted to receive inputs from the PLC and predict heating gas pressure and battery draught values comprising means for processing heat demand values given by the equation Where, H1 = Total heat demand of battery Qd (Oven1) = Heat demand of oven Qi.wg = Waste gas heat loss / oven Shi = Surface heat loss / oven N = Total No. of Ovens 16 heat consumption values given by the equation : Where, Vhg = volume of total heating gas consumed during the reversal in m3. Chg = Average calorific value of heating gas during the reversal. 2. Arrangement as claimed in claim 1 wherein the control system is adapted to predict heating gas pressure and battery draught values by processing the inputs from the heat demand model and the heat consumption model by means of the software. 3. Arrangement as claimed in claims 1 to 2 wherein the control system is adapted to modify the preliminary predictions depending on the actual values obtained from the feed back models comprising feed back loops - coking index and pushed out coke temperature by means of software and generate corrected values. 4. Arrangement as claimed in claims 1 to 3 wherein the PLC is adapted to receive corrected values of gas pressure and battery draught from control system by means of driver and to download them to respective controllers for necessary action. 5. Arrangement as claimed in claims 1 to 4 wherein means of communication, of signals using OPC (OLE for Process Control ) from the PLC comprise PLC driver adapted to serve as the OPC server and the control system adapted to serve as the OPC client. 6. Arrangement as claimed in claims 1 to 5 wherein the control system comprises heat demand model which computes the heat demand by processing the data from PLC 17 based data acquisition system and chemical composition of heating gas, waste gas and distillation gas as fed by operators. 7. Arrangement as claimed in claim 1 wherein the means for storage of data in the PLC is event database and continuous database 8. Arrangement as claimed in claim 1 to 7 wherein the means for measuring coke mass temperature is Infra-Red pyrometer from which the input is received by the PLC. 9. Arrangement as claimed in claim 1 to 8 wherein the means for measuring temperature of distillation gas at goose-necks is chromel-alumel thermocouples mounted at the base of accession pipe from which the input is received by the PLC. 10. Arrangement as claimed in claim 1 to 9 wherein the heating gas calorific value is measured by means of on-line CV analyser, which takes gas samples from main gas pipe line before it enters the battery from which the input is received by the PLC. 11. Arrangement as claimed in claim 1 to 10 wherein the means for measuring coal moisture is microwave sensor installed over conveyor belt just before coal tower from which the input is received by the PLC. An arrangement for online control of coke oven battery heating gas pressure and battery draught involving both feed back and feed forward strategy comprising Programmable and Logic Controller (PLC) (6) based data acquisition system adapted to receive signals of parameters selected from Coke Mass Temperature; Goose-neck temperature (8); Coking Index; Heating gas; Calorific value; Coal Moisture; Heating Gas Flow; Heating Gas Pressure; Battery Draught; Tunnel Temperature; Winch reversal and comprising means (9) for storage and display of the data thus acquired; and means for communicating with the control system (7) of the arrangement; and a control system (7) adapted to receive inputs from the PLC and predict heating gas pressure and battery draught values comprising means for processing heat demand values given by the equation.

Full Text

Field of invention :
The present invention relates to an arrangement for online control of coke oven battery heating gas pressure and battery draught involving both feed back and feed forward strategy. More particularly the present invention relates to an arrangement comprising a system for data acquisition of actual coke mass temperature, coking index, heating gas calorific value, coal moisture and the like by PLC system and a control system so as to provide on-line control and prediction of battery thermal regime considering all the above mentioned parameters. This arrangement can be implemented in any coke oven having similar heating system.
Background and prior art:
The known art of battery heating control is through manual adjustment of thermal regime based on battery pushing schedule. In some automatic heating control, heat demand is always considered the same for all the ovens. Average temperature of heating wall is measured by manual measurement of burner base temperature of a few selected vertical flues with hand held optical pyrometer. This method of measurement is labour intensive, subjective and does not always co-relate well with coke temperature inside the oven. However, in some coke oven battery automatic control of battery is available through imported system. Some imported system are based on coke mass temperature but does not takes care of coking index. Other systems are based on regenerator top temperature and do not take care of actual coke temperature or coking index. The total software and hardware in such systems are imported and indigenous know-how is not available.
Drawbacks of the Known Art:
The manual control system is not based on actual process condition and heat demand calculations but depends on the experience of shop operators. Hence it is not accurate and utilises more energy. Also as there is no check for coke mass temperature and actual progress of carbonisation, the quality of coke is inferior and inconsistent. Even the imported automatic control systems commercially available in the market are either feedback or feed-forward in nature. But to achieve optimum battery performance, it is

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essential to have both feed-forward (Heat Demand) and feed-back (coke mass temperature and coking index).
Objects of the Invention :
Thus an object of the present invention is to provide an arrangement comprising a Programmable and Logic Controller (PLC) based data acquisition system for acquisition of data on parameters selected from heating gas, waste gas and distillation gas chemical composition, coke mass temperature, different phases of carbonisation, coal-coke properties and the like and communicating them to control system"; and a control system adapted to process the data from the PLC based data acquisition system and predict heating gas pressure and battery draught, said arrangement providing for on-line control of coke oven battery heating gas pressure and battery draught.
Another object of the invention is to provide an arrangement for on-line control of coke oven battery heating gas pressure and battery draught such that it utilizes both feed back and feed forward control strategy.
Summary of the Invention
Thus according to main aspect of the present invention there is provided an arrangement for on-line control of coke oven battery thermal regime and battery draught comprising:
i) Programmable and Logic Controller (PLC) based data acquisition system adapted to receive signals of parameters selected from Coke Mass Temperature; Goose-neck temperature; Coking Index; Heating gas; Calorific value; Coal Moisture; Heating Gas Flow; Heating Gas Pressure; Battery Draught; Tunnel Temperature; Winch reversal and comprising
a) means for storage and display of the data thus acquired; and
b) means for communicating with the control system of the arrangement; and

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ii) a control system adapted to receive inputs from the PLC and predict heating gas pressure and battery draught values comprising means for processing heat demand values, heat consumption values and correcting the same based on feed back inputs.
Detailed Description of Invention :
The arrangement of the present invention is implemented in a coke oven which is side fired pair vertical re-circulation type battery comprising of 65 ovens. Each oven is sandwiched between two heating walls. There are 28 vertical flues in each heating wall. Either Coke Oven (CO) gas or Blast Furnace (BF) gas is burnt inside the vertical flues. Coal is charged inside the oven from oven top after closing both side doors and coal is heated in absence of air by the heat transferred from heating wall. During coking, raw Coke Oven gas generated inside the oven which escapes through ascension pipes and collecting main to the exhauster house. After a certain period of time, called Coking Period, coal is converted into coke and is pushed out to the quenching car which takes it to quenching tower for quenching with water. Quenched coke is sent to Blast Furnace for production of hot metal.
Optimum control of coke oven battery thermal regime is one of the key factors in coal carbonisation process. Meticulous control of heating requires knowledge about heating gas, waste gas and distillation gas chemical composition, coke mass temperature, different phases of carbonisation, coal-coke properties and the like.
The arrangement of the present invention comprises PLC based data acquisition system which acquires data on various parameters by several means for the same. These are stored and then communicated to the control system of the arrangement of the present invention. The control system processes these data and predicts the heating gas pressure and battery draught. These preliminary predictions are modified and corrected. Final values are communicated to the PLC based data acquisition system These are finally communicated to controls for heating gas pressure and battery draught. The arrangement thus uses both feed back and feed forward modes.

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The PLC based data acquisition system of the arrangement present invention comprises various means which acquires the following process information and communicates them to control system :-
- Coke Mass Temperature.
- Goose-neck temperature.
- Coking Index.
- Heating gas Calorific value.
- Coal Moisture.
- Heating Gas Flow (Coke Side and Pusher Side).
- Heating Gas Pressure (Coke Side and Pusher Side).
- Batter Draught (Coke Side and Pusher Side).
- Tunnel Temperature (Coke Side and Pusher Side).
- Winch reversal.
The PLC based data acquisition system is also adapted to receive data based on the pushing current which indicate the pushing force required to push the coke from the pusher car by means of system as mentioned in our co-pending application No. 360/Kol/2004 which is incorporated here by way of reference.
There are different methods of measuring coke temperature. One way of measuring coke temperature is by putting temperature measurement system in guide car. However, it is found that such installations are difficult to maintain and fails soon due to heat and dust as coke falls in quenching car. Hence in the present invention temperature measurement means is installed at the roof of quenching tower. The means for measuring coke mass temperature Infra-Red pyrometer. The coke mass temperature is measured in quenching car when it enters the quenching tower for quenching. The signal is transmitted to PLC. The temperature of distillation gas at goose-necks are measured by means of chromel-alumel thermocouples mounted at the base of accession pipe. This section is most suitable area for measuring the temperature. The trend of distillation gas temperature provides a direct information about progress of coal carbonisation. The highest

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temperature achieved (tmax_temp) and the time required to reach such temperature (tmax_time) are thus determined and from these data the Coking index is derived from these data by means of software using the equation:
Coking index = Coking period
Time to reach peak raw temperature(tmax_time). where coking period = next_time (i) - last time (i): where 'next_time' is next pushing time and 'iasl_time' is the last charging time as mentioned in our co-pending application No. 364/Kol/2004 which is incorporated here by way of reference.
Heating gas calorific value is measured by means of on-line CV analyser, which takes gas samples from main gas pipe line before it enters the battery. Means for measuring coal moisture is microwave sensor installed over conveyor belt just before coal tower. Other parameters are measured by conventional means.
The PLC receives all the signals from the above mentioned means and stores them by means of continuous data base and event database (as mentioned in our co-pending application No. 364/Kol/2004 which is incorporated here by way of reference) for display of historical trend. The data storage is ensured irrespective of HMI as all the data are stored in PLC. This is in contrary to conventional system, where data is stored HMI (Human Machine Interface). Very fast scan rate in order of 50 ms is achieved due to the fast scanning rate of PLC. Further alt the signals from the PLC are communicated to control system whenever requested. This is done through a specially developed software using OPC (OLE for Process Control). PLC driver means serves as an OPC server while control system acts as OPC client. The data acquisition system also receives set points of gas pressure and battery draught from control system through this driver software and downloads them to respective loop controllers for necessary action.
The control system of the arrangement of the present invention comprises means for both feed forward and feedback mode of operation. In the feed forward part, the means for

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determining the heat demand comprises the heat demand model. This model computes by means of a software the heat demand of battery/ovens during individual oven charging from heat balance equations taking data from data acquisition system as explained above and chemical composition of heating gas, waste gas and distillation gas as fed by operators. Surface heat losses and heat losses from waste gases are also considered to arrive at net heat demand of battery/ovens by the said module by means of computers. This is calculated from the equation as provided in our co-pending application No. 0363/Kol/2004.

Where,
Ht = Total heat demand of battery
Qd (Oven1) = Heat demand of oven
Qi.wg = Waste gas heat loss / oven
Shi = Surface heat loss / oven
N = Total No, of Ovens
Heat demand per oven (Qd(Oven1)} is based on several parameters like Coal/coke properties, heating gas parameters, waste gas parameters, raw gas parameters, air data etc. The salient parameters are indicated below :
1) Coal / Coke Parameters :
Coal Volatile Matter % Coal Ash % Coal Moisture % Coal Temperature % Coke Temperature %
2) Heating Gas Parameters :

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Heating Gas Composition (CH4,CO,CO2,CmHm, H2, N2, O2) Heating Gas Temperature Heating Gas Flow
3) Waste Gas Parameters ;
Waste Gas Composition (H2, CO, CO2, N2, O2) Average tunnel temperature
4) Raw Gas Parameters :
Raw Gas Composition (CH4, CO, CO2, CmHm,, H2, N2, O2) Raw Gas Temperature
5) Air Data :
Air Moisture Air Temperature
Heat demand of an oven is calculated by the following equation :

where,
qdx = heat demand of individual carbonization
products per ton of dry coal charge.
qo - heat of reaction
Mcharge = Weight of dry coal charge
qdx can be calculated by following equation :

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where,
Yx = Yield of component "x" in Kg/Ton of dry coal
charge.
Cpx = Heat Capacity of component "x" in KJ/Kg/°C
Waste gas heat loss is calculated by following equation

Where,
Vhg = Specific consumption of heating gas in m3/ton of dry
coal charge
Vwg = Actual Volume of waste gas per m3 of moist
heating gas
Cpwg = Output of moist waste gas, m3/m3 of heating gas
twg = Waste gas temperature at exit
Vwg is calculated by calculating excess air co-efficient and knowing the reaction of various gaseous components with O2.

To calculate surface heat loss, oven surface is divided into various parts like oven roof, heating chamber roof, charging hole, inspection hole, heating wall lintel (coke side and pusher side), doors (coke side and pusher side), heating walls (coke side and pusher side), regenerator face walls etc. Heat loss from individual parts is calculated and added to calculate total heat loss from oven surface. Surface heat loss from a specific oven part can be calculated as follows :

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where, Shlr is rate of surface heat loss from a specific oven part in Joule/sec, K1 is coefficient of heat conducted by convection, K2 is coefficient of heat conducted by radiation, T1 is surface temperature and T2 is ambient temperature (both in degree Kelvin), and A is surface area of specific part (in m2). For K1 and K2 we specifically have:

where, H is total height of oven, w is wind speed, and C is coefficient of heat radiation by a black body ( watts/m2/ °C ).
Surface heat loss from a particular oven part "Shlr" for total coaking period "CPD" can be calculated from following equation :

Total surface heat loss from the oven is calculated by adding equation (7) for all the parts of the oven.

The means for determining the heat consumption comprises the heat consumption model. In the heat consumption model, taking on-line data of heating gas fed per reversal and its calorific value, heat consumed per reversal is computed by means of computers using the software as indicated in our co-pending application No. 0363/Kol/2004 which is incorporated here by way of reference.

10
The total heat consumed is calculated by the following equation :

Where,
Vhg = volume of total heating gas consumed during the
reversal (20 minutes) in m3.
Chg = Average calorific value of heating gas during the
reversal.
Preliminary heat demand for the next reversal is computed from comparing the heat demand and heat consumption values and hence preliminary heating gas pressure and draught for the next reversal are predicted by means of software. These preliminary predictions are modified depending on the actual values obtained from the feed back module comprising feed back loops - coking index and pushed out coke temperature by means of software. It has been found by experimentation that coking index for optimum battery performance should be in the range of 1.38 - 1.42. Hence, if average coking index of ovens is beyond this range, preliminary predicted pressure and draught are revised by some value which has been found by experimentation. Likewise, average pushed out temperature of coke should be in the range of 980-1020°C. If actual pushed out temperature of coke is beyond this range, preliminary predicted pressure and draught is corrected by some factors which are found by trails. The corrected values thus obtained by processing the predicted values and the actual values by the software are communicated to the data acquisition PLC system by driver. These final corrected values are downloaded to data acquisition system and communicated to the gas flow control and draught control for actuating the respective butterfly valves.
The predicted data generated is shown in Table 1 below:

11

12
The invention is now described by means of non limiting illustrative accompanying drawings.
Brief description of accompanying drawings :
Figure 1: Graphical representation of coke mass temperature profile Figure 2: Graphical representation of raw gas temperature profile Figure 3; Schematic view of the arrangement of present invention
Detailed description of accompanying drawings
Figure 1: The actual coke mass temperature is depicted by 1. The running average (2) is also indicated in the figure as derived from the PLC based data acquisition system of the arrangement of the present invention.
Figure 2: The raw gas temperature profile at goose neck is indicated. The data acquisition system of the arrangement of the present invention calculates the peak temperature (tmax_temp) 3, time to reach the peak temperature (tmax_time) 4 from the raw gas temperature profile. The coking period 5 is also derived from the temperature profile as next_time - last_time i.e. next pushing time minus last pushing time. The coking index is then given by 4/5. The desired coking index calculated is 1.28 to 1.32.
Figure 3: The PLC based data acquisition system (6) receives signals from field instrumentation, normalises the signals and sends it to control system (7) for prediction of gas pressure battery draught.
Coke mass temperature is one of the crucial signal for control system. The data acquisition system calculates the running average of instantaneous signal and final average temperature. The gooseneck temperature parameter (8) is vital for coking control methodology. In each and every oven of battery, raw gas is evolved during coke making process. This gas is passing through Ascension Pipe (AP) and collected by hydraulic main. Raw gas temperature of an oven can be measured by putting thermocouple in AP. The mv signal is generated by data acquisition system. Coking index is a crucial

13
parameter used in the feedback loop for determination of the pressure and draught by control system. The coking index provides an index of coke readiness. There are eighteen nos. of thermocouples installed in the standpipes of ovens. Coking process has unique repetitive characteristics of raw gas temperature with time as shown in figure 2. After charging of the oven, within 11 to 16 hours the raw mass temperature reaches its peak and thereafter it gradually reduces till the oven pushing. The coking period with respect, to the 11 to 16 hours is 17 to 22 hours approximately. The parameters calculated by the PLC are the peak temperature (tmax_temp), time to reach this peak temperature (tmax_time) and the schedules coking period.
The data acquisition system is implemented through Control Logix PLC of Rockwell Automation make. The data acquisition system is networked with Computer (9) for HMI i.e. means for display of above mentioned parameters in different forms like trend, graphics, bar graphs etc. The HMI platform is Rs View32®, which is a Rockwell Software product. The PLC (6) receives inputs from various means like CV analyzer (10), quenching tower pyrometer (11), moisture analyzer (12). These data are processed and delivered to the control system (7) by PLC driver which serves as the OPC server while the control system serves as the OPC client.
There are three models in the control system which predicts the heating gas pressure and battery draught for the current winch reversal Heat Demand Model, (13), Heat Consumption Model (14) and Feedback models including coke mass temperature feed back (15) and coking index feedback (16)
Heat demand model (13) calculates the heat demand of an oven as soon as it is charged. This calculation is based on several mass balance equations based on parameters as communicated by data acquisition system. In addition, it also depends on chemical composition of heating gas, waste gas and distillation gas. These data are fed by operator based on laboratory analysis. Heat consumption model (14) keeps a track of actual heat consumed by the battery. Based on the heat demand and consumption, the control system calculates the balance heat required by the battery and heat demand for the current

14
reversal. This is further modified by feedback models (15 and 16). The first correction is based on coke mass temperature and the second correction is based on coking index..
These corrected values are then communicated to the PLC through the driver (not shown). It then actuates the gas flow control (17) and the draught control (18). These then effect the respective valves and effects the on line control as provided by the arrangement of the present invention.

15
We Claim:
I. An arrangement for on-line control of coke oven battery thermal regime and battety draught comprising:
i) Programmable and Logic Controller (PLC) based data acquisition system adapted to receive signals of parameters selected from Coke Mass Temperature; Goose-neck temperature; Coking Index; Heating gas; Calorific value; Coal Moisture; Heating Gas Flow; Heating Gas Pressure; Battery Draught; Tunnel Temperature; Winch reversal and comprising
a) means for storage and display of the data thus acquired; and
b) means for communicating with the control system of the arrangement; and
ii) a control system adapted to receive inputs from the PLC and predict heating gas pressure and battery draught values comprising means for processing heat demand values given by the equation

Where,
H1 = Total heat demand of battery
Qd (Oven1) = Heat demand of oven
Qi.wg = Waste gas heat loss / oven
Shi = Surface heat loss / oven
N = Total No. of Ovens

16

heat consumption values given by the equation :
Where,
Vhg = volume of total heating gas consumed during the
reversal in m3.
Chg = Average calorific value of heating gas during the
reversal.
2. Arrangement as claimed in claim 1 wherein the control system is adapted to predict heating gas pressure and battery draught values by processing the inputs from the heat demand model and the heat consumption model by means of the software.
3. Arrangement as claimed in claims 1 to 2 wherein the control system is adapted to modify the preliminary predictions depending on the actual values obtained from the feed back models comprising feed back loops - coking index and pushed out coke temperature by means of software and generate corrected values.
4. Arrangement as claimed in claims 1 to 3 wherein the PLC is adapted to receive corrected values of gas pressure and battery draught from control system by means of driver and to download them to respective controllers for necessary action.
5. Arrangement as claimed in claims 1 to 4 wherein means of communication, of signals using OPC (OLE for Process Control ) from the PLC comprise PLC driver adapted to serve as the OPC server and the control system adapted to serve as the OPC client.
6. Arrangement as claimed in claims 1 to 5 wherein the control system comprises heat demand model which computes the heat demand by processing the data from PLC

17
based data acquisition system and chemical composition of heating gas, waste gas and distillation gas as fed by operators.
7. Arrangement as claimed in claim 1 wherein the means for storage of data in the PLC is event database and continuous database
8. Arrangement as claimed in claim 1 to 7 wherein the means for measuring coke mass temperature is Infra-Red pyrometer from which the input is received by the PLC.
9. Arrangement as claimed in claim 1 to 8 wherein the means for measuring temperature of distillation gas at goose-necks is chromel-alumel thermocouples mounted at the base of accession pipe from which the input is received by the PLC.
10. Arrangement as claimed in claim 1 to 9 wherein the heating gas calorific value is measured by means of on-line CV analyser, which takes gas samples from main gas pipe line before it enters the battery from which the input is received by the PLC.
11. Arrangement as claimed in claim 1 to 10 wherein the means for measuring coal moisture is microwave sensor installed over conveyor belt just before coal tower from which the input is received by the PLC.
An arrangement for online control of coke oven battery heating gas pressure and battery draught involving both feed back and feed forward strategy comprising Programmable and Logic Controller (PLC) (6) based data acquisition system adapted to receive signals of parameters selected from Coke Mass Temperature; Goose-neck temperature (8); Coking Index; Heating gas; Calorific value; Coal Moisture; Heating Gas Flow; Heating Gas Pressure; Battery Draught; Tunnel Temperature; Winch reversal and comprising means (9) for storage and display of the data thus acquired; and means for communicating with the control system (7) of the arrangement; and a control system (7) adapted to receive inputs from the PLC and predict heating gas pressure and battery draught values comprising means for processing heat demand values given by the equation.

Documents:

00361-kol-2004-abstract.pdf

00361-kol-2004-claims.pdf

00361-kol-2004-correspondence.pdf

00361-kol-2004-description(complete).pdf

00361-kol-2004-drawings.pdf

00361-kol-2004-form-1.pdf

00361-kol-2004-form-18.pdf

00361-kol-2004-form-2.pdf

00361-kol-2004-form-3.pdf

00361-kol-2004-letters patent.pdf

00361-kol-2004-p.a.pdf

361-KOL-2004-FORM 27.pdf

361-KOL-2004-FORM-27.pdf

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Patent Number

207095

Indian Patent Application Number

361/KOL/2004

PG Journal Number

21/2007

Publication Date

25-May-2007

Grant Date

23-May-2007

Date of Filing

28-Jun-2004

Name of Patentee

STEEL AUTHORITY OF INDIA LTD., RESEARCH & DEVELOPMENT CENTRE FOR IRON & STEEL, AND A GOVT. OF INDIA

Applicant Address

RESEARCH AND DEVELOPMENT CENTRE FOR IRON AND STEEL DORANDA RANCHI 834002

Inventors:

#	Inventor's Name	Inventor's Address
1	MITRA SOMNATH	RESEARCH AND DEVELOPMENT CENTRE FOR IRON AND STEEL DORANDA RANCHI
2	MAJUMDER SUSANTA	RESEARCH AND DEVELOPMENT CENTRE FOR IRON AND STEEL DORANDA RANCHI
3	BHASKAR UJJWAL	RESEARCH AND DEVELOPMENT CENTRE FOR IRON AND STEEL DORANDA RANCHI
4	CHAKRABORTY BASUDEV	RESEARCH AND DEVELOPMENT CENTRE FOR IRON AND STEEL DORANDA RANCHI
5	GUPTA ASHUTOSH	RESEARCH AND DEVELOPMENT CENTRE FOR IRON AND STEEL DORANDA RANCHI

PCT International Classification Number

G 06 B 19/05

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA