Title of Invention

A SYSTEM FOR AUTOMATIC CONTROL OF HEATING AND REGULATION OF COKE OVEN BATTERY

Abstract

A system for automatic control of the heating and regulation of a coke oven battery to obtain optimum battery performance. The system is a combination of feed forward and feed back mode of operation and comprises means adapted for computing the heat demand; means adapted for computing the heat consumption; and means adapted for comparing the heat demand and heat consumption taking into consideration coking index and pushed out coke temperature and adapted to control action for the next reversal.

Full Text

Field of the invention: The present invention relates to a system, for automatic control of the heating and regulation of a coke oven battery to obtain optimum battery performance. More particularly the present invention relates to a system for automatic control of the heating and regulation of a coke oven battery to obtain optimum battery performance such that the said system is a combination of feed forward and feed back mode of operation Background and prior art: In a coke plant, coal is coked by destructive distillation i.e., without combustion. This process is carried out in sealed, narrow, externally heated chambers called ovens from which the residue, coke, is subsequently pushed, quenched, and screened for use as fuel in the blast furnace. Ovens are erected in batteries of approximately 60-80 ovens placed side by side, with heating walls between each oven. Each heating wall has a row of 28 heating flues. Thus each row of flue serves to heat two adjacent ovens, except at the end of the battery. Beneath the oven chamber and heating flues are regenerator chambers containing checker work which reclaims heat from the outgoing waste gases and, upon reversal, gives up heat to the incoming combustion air or lean heating gas. The process of heating and regulation of coke ovens is of utmost importance and requires coordination of mainly three elements : gas supply, draft and air supply. An efficient heating system should ensure : 1. Complete combustion of fuel gas with a minimum of excess air to ensure coke quality and low specific heat consumption. 2. Uniform heat distribution throughout the oven such that coking proceeds evenly in all parts of the oven. 3. Minimum time between pushing and charging of ovens by proper scheduling. In conventional heating control, the heat required for coking is considered the same for all ovens. The heating regime is dictated by the coke production target based on which the average coking period and the average heating wall temperature to be maintained are deduced. The heating wall temperature is determined based on the manual measurement of the burner base temperature of a few selected vertical flues (control verticals) with hand- 2 held pyrometer once daily. Thus, conventional heating control is primarily based on the control vertical temperatures. These temperatures may not accurately reflect the actual temperature of the battery. Moreover, since they are measured manually, they are prone to subjectivity and human errors. The known systems suffer from the following draw backs : 1. The Heat required for each oven is assumed to be the same without taking into consideration the changes in the process variables. 2. Manual measurement of heating wall temperature in a few flues is non representative and subjective approach. 3. There is no way of knowing the status of carbonisation in the ovens. 4. Oven scheduling has to be done manually. Object of the invention Thus the main object of the present invention is to provide a system for automatic control of the heating and regulation of a coke oven battery based on synchronization of battery heat demand with the heat supply. A further object is to provide a system for automatic control of the heating and regulation of a coke oven battery without substantial manual intervention. Summary of invention Thus according to the main aspect of the present invention there is provided a system for automatic control of the heating and regulation of a coke oven battery to obtain optimum battery performance comprising : means for determining the heat demand taking into consideration the coking index; means for measuring the heat consumption taking into consideration the pushed out coke temperature ; and means for regulating the heat supply. Detailed Description : The system of the present invention does not require the measurement of control vertical temperatures. The system is based on continuous synchronisation of battery heat demand 3 with the heat supply. Heat demand, heat consumed and heat supply for each reversal is arrived at through a three level automation system to capture real- time data from the various processes. The actual progress of carbonization in the ovens is determined by the raw gas temperature measurement sensors in each oven and action is taken to ensure complete carbonization of coal before the coke is pushed. An oven identification system based on Infra-red transmitters and receivers incorporates the pushing/charging events specific to each oven into the heating and oven scheduling models as provided in our co-pending application No. 362/Kol/2004 and incorporated here by way of reference. Thus, the scope for manual intervention is reduced and subjectivity is eliminated. The invented heating control system is a combination of feed forward and feed back mode of operation (Figure 1). In the feed forward part, heat demand of battery/ovens is determined from heat balance equations taking on-line data of charge coal quality parameters. The basic heat demand equation can be defined by the following equation : Where, Ht = Total heat demand of battery Qd(Oven;) = Heat demand of oven Q1 wg = Waste gas heat loss / oven Shi = Surface heat loss / oven n = No. of ovens in a battery 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 °C Coke Temperature °C 4 2) Heating Gas Parameters : 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 : Qd(Oven1) = [qdcoke + qdrgas + qdbenzol + qdmmst - qdcoal - qdhg-qdair-qo] X Mcharge (2) where, qdx = heat demand of individual carbonization products per ton of dry coal charge. qo = heat of reaction Mcharge Weight of dry coal charge qd can be calculated by following equation : qdx = YxCpx (3) 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 Qi-wg = vhgx Vwg x CpWg x tWg KJ/ton of charge (4) 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 5 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 : Shll =[K,+ K2]xAx(T1-T2) (5) 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: K, = (H+3.6w)x 1.163 watts/m3/°C (6a) K2 = {(T1/100)4-(T2/100)4}/(T1 -T2 ) ........ (6 b) 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 "Shl_i" for total coaking period "CPD" can be calculated from following equation : Shi_, = [K1 + K2] x A x (T1 -T2). (CPDx3600xl0-3)/(16.4xl06) (7) 6 Total surface heat loss from the oven is calculated by adding equation (7) for all the parts of the oven. Shl = SShl_i , KJ/Ton of dry coal charge (8) The heat consumption is calculated by taking values of heating gas fed per reversal, its calorific value and event inputs from the oven identification system, heat consumed per reversal as provided in our co-pending application No. 0362/Kol/2004 which is incorporated here by way of reference. When an oven is charged, consumption model invokes the demand model to calculate the heat demand for that oven. The pushing time, charging time and average coking period from scheduling model is also taken into account, as provided in our co-pending application No. 364/Kol/2004 which is incorporated here by way of reference. The total heat consumed is calculated by the following equation : Qc battery = Vhg C hg (9) Where, Vhg = volume of total heating gas consumed during the reversal in m3. Chg = Average calorific value of heating gas during the reversal. Comparing the heat demand and heat consumption data, the model arrives at the preliminary heating gas flow, pressure and draught for the next reversal, as provided in our co-pending application No. 361/Kol/2004 which is incorporated here by way of reference. These preliminary predictions are modified depending on the values obtained from the feed back loops - coking index and pushed out coke temperature, where the coking index reflects the progress of coking in the ovens. Coking index (CI) is estimated by measuring raw gas (distillation gas) temperature at the base of ascension pipe. In this system, raw gas temperature measurement is done for two ovens in every pushing series. It is observed that temperature of the raw gas goes on increasing with the progress of carbonization, reaches a maximum (Tmax) at time say, tTmax and then drops abruptly. This time to reach Tmax signifies the time at which coke layers meet at the center of oven. Coking index is calculated by the following equation : 7 Cl' = 1 coking period ' tTmax ( 10) The coking index for individual ovens is calculated by PLC programme. The consumption model calculates the average coking index of entire battery. It has been found from experiments that for optimum performance of battery No. 3, BSP, coking index should lie between 1.35 and 1.40. The consumption model tunes the flow to keep the coking index between above mentioned range as provided in our co-pending application No. which is incorporated here by way of reference. These corrected values are then received by the gas flow, pressure and draught controllers, where control action for that reversal is finally taken. The invention is now described by way of non-limiting illustrative accompanying drawings. Description of the accompanying drawings: Figure 1 is a flow diagram indicating the control carried out by the present system of the invention. Figure 2 graphical representation of heat balance predicted by the heat demand model. Figure 3 schematic representation of the system involving various means. Figure 1 is a self-explanatory flow chart which shows that taking in data from the coal moisture level laboratory data regarding heating gas parameters, waste gas parameters and surface heat loss the head demand model predicts the heat demand. Taking inputs from the heat consumption model and dynamic scheduling modal the next pushing time is calculated. The heat energy required and gas flow required are also taking into account. The coking index values and the coking index correction as well as the heating gas calorific values are processed along with the gas flow required to predict the new flow. The coke end temperature correction from quenching tower sensor are also taken into account. New draught values and corrected flow inputs are considered along with excess air correction over the draught required to arrive at the corrected draught. 8 Figure 2 illustrates graphically the total heat balance by the heat demand model. The total heat demand is calculated from the coke parameters, raw gas parameters and the like. The waste gas loss and surface heat loss are then considered to arrive at the heat balance. Figure 3 illustrates the system for automatic control of heating and regulation of coke over battery to obtain optimum battery performance as per the present invention. The master control system communicates both ways with the heat control system where the master PLC (I) receives and stores data from the radio modem (2) which sends data regarding pusher car control and pushing force analysis (3). The master PLC also receives and stores data from oven identification system (4), quenching tower pyrometer (5), cv and waste gas analyzer (6), moisture analyzer (7) and processes the same and provides to the master control system (8). It also receives communication from master control system to control the gas flow by sending outputs to the gas flow control system (9). It also communicates both ways of coke oven scheduling model (10). The coking index values (11) are provided to the slave PLC (12), which along with the master PLC communicates both ways master control system. The control system processes the data from the heat calculation model (13) and accordingly directs the coke over scheduling (14) and coke ready model(15). The pusher car model (16) provides the pushing force analysis through another slave PLC (17) and communicates both ways to the master PLC via radio modem(2). The values from the pusher car model are displayed by operator's display. 9 We Claim I. A system for automatic control of the heating and regulation "of a coke oven battery to obtain optimum battery performance such that the said system is a combination of feed forward and feed back mode of operation comprising : means adapted for computing the heat demand; means adapted for computing the heat consumption; and means adapted for comparing the heat demand and heat consumption taking into consideration coking index and pushed out coke temperature and adapted to control action for the next reversal . 2. A system as claimed in claim 1 wherein the means for measuring heat demand of the battery is adapted to determine the heat demand based on equation (I) as given below: H1= S {Qd(Oven1)+q1-wg, + Shl} (1) Where, Ht = Total heat demand of battery Qd(Oven1) = Heat demand of oven qwg - Waste gas heat loss / oven Shl = Surface heat loss / oven n = No. of ovens in the battery 3 Amstcm as claimed in claim 2 wherein the heat demand per oven {Qd(Ove1)} is based-on several parameters like Coal/coke properties, heating gas parameters, waste gas parameters, raw gas parameters, air data and the like and is calculated based on equation (2) as given below Qd(Oveni) = [qdcoke + qdrgas+qdbenzol+qdmois- qdcoal- qdhg-qdair-qo] x M charge (2) where, qdx = heat demand of individual carbonization products per ton of dry coal charge. qo = heat of reaction Mcharge= Weight of dry coal charge 10 said qdx being determined by equation (3) : qdx = YxCpx (3) where, Yx = Yield of component "x" in Kg/Ton of dry coal charge. Cpx = Heat Capacity of component "x" in KJ/Kg/°C 4. A system as claimed in claim 2 wherein the waste gas heat loss is determined by equation (4). Qi.wg = vhg x Vwg x CpWg X twg KJ/ton of charge (4) where, Vhg = Specific consumption of heating gas in m3/ton of dry coal charge Vwg = Actual Volume of waste gas per m of moist heating gas Cpwg = Output of moist waste gas, m3/m3 of heating gas twg = Waste gas temperature at exit such that Vwg is computed by calculating excess air co-efficient and knowing the reaction of various gaseous components with O2. 5. A system as claimed in claim 2 wherein surface heat loss by radiation and convection from a specific oven part is determined by equation (5) : Shlr=[K1+ K2]xAx(T1-T2) (5) where, Shh 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 )where K1 and K2 are as under: K1 =(H+3.6w)x 1.163 watts/m3/°C (6a) K2 - C{T1/100)4-(T2/100)4}/(T1-T2) (6b) 11 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 ) 6. A system as claimed in claim 5 wherein surface heat loss from a particular oven part "Shl_l" for total coaking period "CPD" can be calculated from following equation : Shl_i = [K1 + K2] x A x (T1 -T2). (CPDx3600xl0-3)/(16.4xl06) (7) 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 )where K1 and K2 are as under: K1 =(H+3.6w)x 1.163 watts/m3 /°C (6a) K2 = C{(T1/100)4-(T2/100)4 }/(T1-T2) (6b) 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 ) 7. A system as claimed in claim 5 wherein the surface heat loss per ton of coal charge for all the parts of the oven is determined by equation (8) : Sh1 = SSh1_t , KJ/Ton of.dry coal charge (8) 8. A system as claimed in claim 1 wherein the heat consumption is determined by equation (9): Q c battery = Vhg X Qhg (9) Where, Vhg = volume of total heating gas consumed during the reversal in m3. Chg = Average calorific value of heating gas during the reversal. 9. A system as claimed in claim 5 wherein the heat consumption is determined by using on-line data of heating gas fed per reversal, its calorific value and event inputs from the oven identification system, to calculate heat consumed per reversal. 10. A system as claimed in any preceding claim wherein the means for computing the heat consumption is adapted to invoke the means for computing heat demand to calculate the heat demand for that oven when the said oven is charged. 1 ]. A system as claimed in any preceding claim wherein the means adapted for computing the heat demand comprises computer programme based on equation (1). 12. A system as claimed in any preceding claim wherein the means adapted for computing the heat consumption comprises computer programme based on equation (9). 13. A system as claimed in any preceding claim wherein the corrected values as generated from the means adapted for comparing the heat demand and heat consumption are then received by the gas flow, pressure and draught controllers, where control action for that reversal is finally taken. A system for automatic control of the heating and regulation of a coke oven battery to obtain optimum battery performance. The system is a combination of feed forward and feed back mode of operation and comprises means adapted for computing the heat demand; means adapted for computing the heat consumption; and means adapted for comparing the heat demand and heat consumption taking into consideration coking index and pushed out coke temperature and adapted to control action for the next reversal.

Documents:

00363-kol-2004 abstract.pdf

00363-kol-2004 claims.pdf

00363-kol-2004 correspondence.pdf

00363-kol-2004 description(complete).pdf

00363-kol-2004 drawings.pdf

00363-kol-2004 form-1.pdf

00363-kol-2004 form-18.pdf

00363-kol-2004 form-2.pdf

00363-kol-2004 form-3.pdf

00363-kol-2004 letters patent.pdf

00363-kol-2004 p.a.pdf

363-KOL-2004-(01-02-2012)-FORM-27.pdf

363-KOL-2004-FORM 27.pdf