Claims:WE CLAIM:

1. A system for automated control of heating in coke oven battery comprising

a coke oven battery heating controlling processor embodying computing sequences enabled for operating in feed-forward action and calculating heat demand of an oven of the coke oven battery for coal carbonization and producing coke as soon as it is charged with coal based on actual heat consumed by the oven till its charging;

a pyrometer interfaced to the processor for evaluation of actual thermal condition of the coke oven battery and feedbacking the same to the processor enabling the computing sequences to operate both feed-forward as well as feedback mode and finally adjust heating pause time for the oven for actual control of battery heating.

2. The system as claimed in claim 1, wherein the pyrometer installed at the entrance of quenching tower of the oven to evaluate the thermal condition of the coke oven battery by measuring actual temperature of coke after it is pushed out from the oven.

3. The system as claimed in claim 1 or 2, wherein the processor is configured to determine thermal regime of the battery based on actual heat demand in terms of heating gas flow and pressure.

4. The system as claimed in anyone of claims 1 to 3, wherein the pause time which corresponds to the time between two gas reversals when both the flow of gas and air the oven is stopped for a moment is delayed by the to control the heat input to the battery whereby after completion of the heating pause time, air flappers of other side opens followed by gas cock opening of other side completing one reversal cycle.

5. The system as claimed in anyone of claims 1 to 4, wherein the calculated pause time is downloaded to Winch Reversal PLC means, which interacts with the battery winch reversal electrical mechanism to introduce additional heating pause time.

6. The system as claimed in anyone of claims 1 to 5, wherein the processor including a heterogeneous control in configured to receive process parameters relating to thermal condition of the coke oven battery and thereby calculates actual heat consumed in last reversal and net cumulative heat consumed by the ovens till its charging along with the heat demand of the battery for the next reversal at every winch reversal.

7. The system as claimed in anyone of claims 1 to 6, wherein the process parameters relating to thermal condition includes coke mass temperature, coking index, charging time, pushing time, average charge weight, waste gas temperature, coal moisture, heating gas calorific value, heating gas / waste gas / distillation gas chemical analysis, chemical composition of heating gas.

Dated this the 28th day of March, 2018

Anjan Sen
Of Anjan Sen & Associates
(Applicants Agent)
IN/PA-199
, Description:FIELD OF THE INVENTION:

This invention relates to automated control of heating in coke oven battery. More specifically the present invention is directed to develop an automated computer based heating control system of coke oven battery involving pause time control technique in heterogeneous control system architecture with multi-vendor process control.

BACKGROUND OF THE INVENTION:

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. Some of the systems are based on coke mass temperature but does not take care of coking index. Other systems are based on regenerator top temperature and does not takes care of actual coke temperature or coking index. The total software and hardware is such system are imported and indigenous know-how is not available.

Some controls systems are based on direct regulation of heating gas flow and battery draft. However these systems suffer from one drawback that actual battery thermal regimes are changed at every reversal, which sometime disturbs the battery regulation. Moreover these systems are not applicable in sub-batteries having common chimney as described above.

The available 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 automatic control systems commercially available in the market are either feedback or feed-forward in nature. But to achieve optimum battery performance, it is essential to have both feed-forward (Heat Demand) and feed-back (coke mass temperature).

OBJECTIVE OF THE INVENTION:

It is thus the basic object of the present invention is to develop a system for automated control of heating in coke oven battery which would be adapted to operate based on actual process condition and heat demand calculations.

Another object of the present invention is to develop a system for automated control of heating in coke oven battery which would be adapted to operate considering coke mass temperature, actual progress of carbonisation, and the quality of coke.

Yet another object of the present invention is to develop a system for automated control of heating in coke oven battery which would be adapted to involve both feed-forward (Heat Demand) and feed-back (coke mass temperature) in heat controlling operation to achieve optimum battery performance.

A still further object of the present invention is to develop a system for automated control of heating in coke oven battery which would be adapted to implement an on-line heating control of coke oven battery by introducing variable heating pause time in a heterogeneous process control environment.

SUMMARY OF THE INVENTION:

Thus according to the basic aspect of the present invention there is provided a system for automated control of heating in coke oven battery comprising

a coke oven battery heating controlling processor embodying computing sequences enabled for operating in feed-forward action and calculating heat demand of an oven of the coke oven battery for coal carbonization and producing coke as soon as it is charged with coal based on actual heat consumed by the oven till its charging;

a pyrometer interfaced to the processor for evaluation of actual thermal condition of the coke oven battery and feedbacking the same to the processor enabling the computing sequences to operate both feed-forward as well as feedback mode and finally adjust heating pause time for the oven for actual control of battery heating.

In a preferred embodiment of the present system, the pyrometer installed at the entrance of quenching tower of the oven to evaluate the thermal condition of the coke oven battery by measuring actual temperature of coke after it is pushed out from the oven.

In a preferred embodiment of the present system, the processor is configured to determine thermal regime of the battery based on actual heat demand in terms of heating gas flow and pressure.

In a preferred embodiment of the present system, the pause time which corresponds to the time between two gas reversals when both the flow of gas and air the oven is stopped for a moment is delayed by controlling the heat input to the battery whereby after completion of the heating pause time, air flappers of other side opens followed by gas cock opening of other side completing one reversal cycle.

In a preferred embodiment of the present system, the calculated pause time is downloaded to Winch Reversal PLC means, which interacts with the battery winch reversal electrical mechanism to introduce additional heating pause time.

In a preferred embodiment of the present system, the processor in configured to receive process parameters relating to thermal condition of the coke oven battery and thereby calculates actual heat consumed in last reversal and net cumulative heat consumed by the ovens till its charging along with the heat demand of the battery for the next reversal at every winch reversal.

In a preferred embodiment of the present system, the process parameters relating to thermal condition includes coke mass temperature, coking index, charging time, pushing time, average charge weight, waste gas temperature, coal moisture, heating gas calorific value, heating gas / waste gas / distillation gas chemical analysis, chemical composition of heating gas.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:

Figure 1 shows a preferred architecture of Heterogeneous Process Control System for heating control of the coke oven battery in accordance with the present invention.

Figure 2 shows Major Input / Output of the System in accordance with the present invention.

Figure 3 shows Block Schematic of Control System in accordance with the present invention.

Figure 4 shows Result of Heat Demand / Loss Calculation in accordance with the present invention.

Figure 5 shows computer screen shot of developed Human Machine Interface main screen in accordance with the present invention.

Figure 6 shows Flow Chart of Heating Control System in accordance with the present invention

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS:

As stated hereinbefore, the present invention discloses a system for automated control of heating in coke oven battery involving pause time control technique in heterogeneous control system architecture with multi-vendor process control.

The present invention can be implemented in a coke oven with twin flue underjet type heating System wherein the coke oven battery is divided in two blocks A and B each having plurality of ovens. Each oven includes coal charge capacity and sandwiched between two heating walls. Either Coke Oven (CO) gas or Mixed Gas (a mixture of gas emanating from Blast Furnace and Coke Oven and mixed in a certain proportion) gas is burnt inside the vertical flues. There is a common flue gas chimney located at one end of battery which caters to both the heating blocks. 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 is 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 which is pushed out through the quenching car and taken to quenching tower for quenching with water. Quenched coke is sent to Blast Furnace for production of hot metal.

The optimum heating control of the ovens is one of the crucial operations, which delineate the entire coal carbonization process in Coke Oven Battery. Optimum heating control by way of ensuring complete combustion, minimizing sensible heat being taken away by the waste gas and reducing heating time schedule has a crucial role in lowering the energy inputs and improving the coke quality. 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 etc. This invention exemplifies a stupendous in-house effort in terms of marshalling multidisciplinary resources in the fields of heat transfer & combustion, kinetics, reaction dynamics of carbonisation process, control system, sensors and the three levels of automation with intricate mathematical modeling.

Heating control in a coke oven battery is generally accomplished by directly controlling fuel gas flow and battery draft. However, in the aforesaid type of Coke Ovens this method of heat input control is not possible. This is because each sub-battery is heated by a different fuel – either coke oven gas or blast furnace gas but since the chimney is located at one end of the battery, the draught is common to both the sub-batteries. This gives rise to a unique situation that if say, as per model calculation the coke oven gas pressure and consequently the draught is adjusted in block A, the draught in block B also changes and disturbs the heating in that block. Hence a different methodology is adopted through which actual heat input control to the battery is regulated by manipulating the duration of flow of heating gas. This is done by pause time control during winch reversal. Pause time is the time between two gas reversals when both the flow of gas and air is stopped for a moment. During winch reversal process, initially gas cock of one side is closed followed by air purge. Then air flappers of the same side closes. This is the time when flow of both gas and air ceases in the battery. This is called Heating Pause. In normal sequence it takes place only for few second. However the present control system extends and adjusts this pause time to control the heat input to the battery. After completion of heating pause, air flappers of other side opens followed by gas cock opening of other side. This completes one reversal cycle.

The invention relates to data acquisition through state-of-the-art PLC means and control of battery heating by adjustment of pause time as calculated by a processor of the present system embodying mathematical model. This system can be implemented in any coke oven having similar heating system.

The processor of the developed heating control system includes Level-II tier of automation hierarchy. The Level-II system is seamlessly integrated with heterogeneous Level-I process control and Instrumentation system through OPC based driver software. The Oven Identification related data is provided from OPTO 22 PLC installed in each oven machine linked with a central co-ordination PLC in control room through wireless communication. The block schematic of control system architecture is shown in Figure-2. All the aforesaid DCS & PLC are networked with one SIEMENS scheduling PLC through which COHC system is linked using OPC. OPC interface is an integral part of Level-II model for seamless data integration between Level I and II. Figure – 1 depicts the architecture of heterogeneous control system.

This technology program exemplifies a stupendous effort in terms of marshalling multidisciplinary resources in the fields of heat transfer & combustion, kinetics, reaction dynamics of carbonization process, control system designing, sensors and the three levels of automation with intricate mathematical modeling. The system has been put in place for efficient battery heating, which involves accurate information on heating gas, waste gas and raw gas chemical composition, temperature, charge weight, pushing & charging time, different phases of coal carbonization, coke mass temperature etc.

The mathematical model, which is the core of the system, is based on the philosophy of continuous supply of heat to battery as per actual process demand. Figure – 6 depicts Flow Chart of Integrated Control System including heat demand and consumption model. The system is both feed-forward as well as feedback in nature. Initiating feed-forward action, the model calculates heat demand of an oven as soon as it is charged with coal. This facilitates model to compute heat requirement for coal carbonization, just when heating is started in the oven. However this calculation is based on theoretical mathematical model. However, actual installation is for an industry where many un- deterministic features also influences the battery heating for example heat loss due to leakages etc. To compensate these factors, actual battery thermal condition is evaluated by measuring actual temperature of coke (Coke Mass Temperature) after it is pushed out from an oven. This works as feedback signal of actual thermal condition of battery and takes care of any such un-deterministic features as mention above. Hence the control system is both feed-forward as well as feedback in nature.

Meticulous prediction of battery thermal regime requires a precise knowledge about several process parameters like coke mass temperature, coking index, charging time, pushing time, average charge weight, waste gas temperature, coal moisture, heating gas calorific value, heating gas / waste gas / distillation gas chemical analysis etc. The chemical composition of heating gas is also used for computation of gas calorific value. The system includes input means to receive all laboratory analysis data regarding chemical composition of heating gas, waste gas, raw gas and coal / coke properties from DSP’s ERP system. The actual oven pushing time, actual charging / leveling time and average charge weight is furnished by Oven Identification PLC’s installed on respective oven machines through wireless communication. The architecture of control system is depicted in Figure 1.

The coke mass temperature of coke pushed from individual ovens is measured by a pyrometer installed at the entrance of quenching tower. The instrumentation system also records process parameters like tunnel temperature, heating gas flow / pressure, battery draught etc, pushing / charging current etc. The block schematic of control system is depicted in Figure 3.

The system is both feed-forward as well as feedback in nature. Initiating feed-forward action, the model calculates heat demand of an oven as soon as it is charged with coal. The system incorporates feedback corrections with respect to final coke mass temperature and actual coking index.

The process model is based on meticulously worked out mass balance equations. The total heat energy imparted in the battery by combustion of heating gas is mainly consumed by following components:

- Coal – Coke Carbonization process
- Product of coal distillation like benzol, tar, moisture etc.
- Heat loss through Waste gas
- Heat loss through surface radiation

The heat demand of battery is computed by determining the heat requirement of each of the aforesaid components. The model calculates this during every winch reversal for all the ovens charged in between previous to current reversal. The result of various heat demand calculations as computed by process model is shown in Figure 4.

The system works through perfect symbiosis between calculated theoretical heat demand and actual heat consumed. At every winch reversal, the system calculates the actual heat consumed in last reversal and net cumulative heat consumed by the ovens till its charging. From the above figures, the system calculates the actual heat demand of the battery for the next reversal. The expected pushing times of each ovens as received from Oven Identification System is also considered for the aforesaid computation. The thermal regime of the battery is calculated from actual heat demand in terms of heating gas flow and pressure. However, the calculated heating gas flow is compensated with feedback signals of actual coke mass temperature to integrate the thermal condition of battery.

The actual control of battery heating is achieved by adjusting the heating pause time. Pause time is the time between two gas reversals when both the flow of gas and air is stopped for a moment. During winch reversal, initially gas cock of one side is closed followed by air purging. Then air flappers of the same side closes. This is the time when flow of both gas and air ceases in the battery. This is called Heating Pause. In normal sequence it takes place only for few second but the control system introduces additional heating pause time to control the heat input to the battery. After completion of heating pause, air flappers of other side opens followed by gas cock opening of other side. This completes one reversal cycle. From the compensated thermal regime, model calculates the heating pause time. The calculated pause time is downloaded to Winch Reversal PLC system, which interacts with battery winch reversal electrical mechanism to introduce additional heating pause time. However, a provision of cascade, auto and manual mode of operation has been kept. In cascade mode of operation, the predicated pause time by heating control model is directly downloaded to winch reversal PLC for control, thus providing a close loop control. The computer screen predicting the heating gas flow and pause time is shown in following Figure – 5.

In addition to prediction and control of battery heating, the system generates HMI screens for convenience of battery operation and analysis of battery health conditions. The main computer screen predicting the heating gas flow and pause time is shown in Figure – 5. Some salient features has been described below:

- Oven Pushing & Charging status and actual coking time
- Oven wise battery heating status indicating remaining coking time left
- Oven-wise display of actual coke mass temperature and average charge weight
- Display of winch reversal times

As indicated in Figure 1, the system receives process information from heterogeneous process control systems like PLC, DCS etc. All these control systems are based on vendor specific operating system and software, which cannot directly communicate with each other. Our system software has been developed under VC++ environment, which needs to be integrated with all these process control system. The integration has been accomplished using the concept of OPC (Object linking and embedding for Process Control). The OPC based interface software provides bi-directional data access with all the process control equipment. As this is an integral part of the invention, the data from these multi-vendor systems is directly made available to the system database.

Best Mode of Working the Invention:

The PLC system is envisaged through a heterogeneous network of PLC’s as indicated in Figure – 1. The process model is implemented in a high end server grade computer. The model software is written in VC++ (Microsoft Visual Studio.Net). The bidirectional data communication between VC++ and Level- I control system has been achieved through an OPC (OLE for Process Control) client software developed in VC++ and is an integral part of model. SIEMENS SIMATIC-NET has been used as OPC server. At every winch reversal, the model reads all the process related data from PLC and calculates heating pause time for next reversal. It immediately downloads the calculated pause time to winch reversal PLC, which actually controls the winch reversal mechanism.

The computer screen predicting the heating gas flow and pause time is shown in following (Figure – 5).

Identify the Novel Features:

The novel features of the invention are explained below and protection shall be sought.

a) On-line battery heating control using real time process and laboratory data through heterogeneous DCS, PLC and ERP system etc.
b) Seamless process integration using in-built OPC based client software
c) Model based prediction of battery thermal regime
d) Neutral Pause Time based battery heating control
e) Dedicated HMI for monitoring and analysis of battery heating