FIELD OF THE INVENTION
The present invention relates in general to coke oven batteries for producing high quality coke to be fed into the blast furnace to maximise its effect on blast furnace operations and improve the hot metal quality, and in particular to an improved 1.0 MTPA top charged coke oven battery with 49.8 M3 hot oven volume to make the coke-making cheaper, user friendly as well as environment friendly. The battery produces high quality coke while providing the lowest amount of impurities, higher thermal energy, higher metal reduction and optimum permeability for the flow of gaseous and molten products.
BACKGROUND OF THE INVENTION
Coke is produced by high temperature carbonization of pulverized coking coal (-3 mm size). In this process, coal is heated in absence of air up to a temperature of 10000C -10500C to form lumpy coke. Coke is the most important raw material that is fed into the blast furnace in terms of its effect on blast furnace operation and hot metal quality. The coke making process generates several by-products which may be solid, liquid, gaseous or plastic in nature. Many of these by-products are toxic and dangerous for the environment. They have to be handled with great care and control. A high-quality coke should be able to support a smooth decent of the blast furnace burden with as little degradation as possible while providing the lowest amount of impurities, highest thermal energy, highest metal reduction and optimum permeability for the flow of gaseous and molten products.
Coke is produced in batteries, each of which has a plurality of slot type ovens for carbonization of coal. Coal (coming from the coal preparation plant and stored in coal tower) is charged to each oven sequentially and heated in the absence of air for a specific period of time (known as coking period) to drive out the volatile matter present within coal. When the gas evolution and subsequent coal carbonization is complete, coke is pushed out of the oven, cooled suitably through wet/dry method and finally sent to the blast furnace via coke handling plant. Evolved gases from the ovens are taken to by¬product plant for recovery of various valuable chemicals like tar, ammonia, naphthalene, benzene, sulphur, toluene, xylene etc. The cleaned coke oven gas still has a high calorific value and is supplied back to the coke oven as a heating fuel. Hence coke oven battery can be operated without any external source of fuel. Surplus coke oven gas is utilized in other units of the plant. However, provision is also generally kept for utilising blast furnace gas (BFG)/ Mixed gas (MG) as alternate fuel.

Following types of machinery are used for the coke oven operation as described below:
a) Charging car-it receives coal from coal tower located nearby and charges the same into the individual ovens.
b) Pusher car-it pushes the ready coke out of the oven and also levels the coal inside an oven during charging.
c) Transfer/Guide car-it guides the coke which is pushed out of an oven onto the receiving quenching car/Coke car.
d) Quenching car (in case of wet quenching)-it receives hot coke from the ovens, takes it to the quenching tower for cooling and finally disposes the cold coke to coke wharf.
e) Coke car (in case of dry quenching)-it takes hot coke from oven to the coke dry cooling plant (CDCP). Cooled coke is directly charged to conveyors from CDCP for onward transmission to Blast Furnace via coke handling plant.
One coke oven battery is generally operated with the help of one working + one standby set of such machines. However, in general for a pair of Coke oven, 2 sets of Working + 1 set of Standby oven machines will be used.
A coke oven battery is designed on the target coke output per year. Accordingly, the effective volume of a single oven, number of pushing/charging required per day, total number of ovens in a battery, scheduled carbonization time (coking period) etc. are decided.
Since long, efforts are being made worldwide to make the coke-making process cheaper, more and more user friendly as well as environment friendly. Development of batteries with larger oven volume is a very effective way to achieve the same.
Although batteries have been in operation for several decades, the batteries of the prior art suffer from several drawbacks. Mostly, they fail to meet the increased demand of coke. A coke oven battery, apart from the ovens, has several other components like heating walls, regenerators, gas supply system, waste gas system including tunnels and chimney, gas off-take system, reversing mechanism, oven machines etc. The design and size of each and every such component of the battery is dependent on the number of ovens, dimensions and capacity of each oven directly or indirectly. For example, the capacity of the oven decides the amount of coal to be charged in it which in turn stipulates the amount of gas evolved and the gas off-take system of the battery is designed accordingly. It also

decides the amount of coke to be pushed from an oven which decides the details of the oven machine design as well as or coke cooling/quenching system. Again, the oven width decides the coal carbonization time, and thereby the heating system.
Repeated failure of buckstays/tie rods is also a predominant hazard, especially in an aged battery. Another problem is leakage from the regenerator face and the oven roofing, causing undue gas as well as heat loss in a traditional coke oven battery. This also deteriorates the working condition.
Thus, there is a great need in the industry for a coke oven battery that can produce coke in a more environment friendly, efficient and economic way. The present invention seeks to overcome not only the above, but also other drawbacks of the prior art. This will become clear from the description of the invention that follows.
OBJECTS OF THE INVENTION
The main object of the present invention is to provide a coke oven battery which makes coke making cheaper, user friendly as well as environment friendly.
Another object of the invention is to provide a coke oven battery to make high quality coke to support smooth decent of the blast furnace burden with as little degradation as possible.
A further object of the invention is to provide a coke oven battery having a 1.0 MTPA coke oven plant with 49.8 m3 hot oven volume so that high quality coke can be obtained while generating lowest amount of impurities, highest thermal energy, highest metal reduction and optimum permeability for the flow of gaseous and molten products.
Another object of the invention is to provide a coke oven battery having PLC controlled hydraulic reversing winch with auto change-over facility from one heating gas to another heating gas.
Yet another object of the invention is to provide a high oven-volume coke oven battery to get target coke output per year with less number of ovens, less number of operations, less pollution, less infrastructural and operational costs.
A further object of the invention is to provide a coke oven battery to increase the average battery life by incorporating sturdy box type buckstays having high section modulus.

Another object of the invention is to provide a coke oven battery to keep the coke swelling pressure during carbonization introducing wider ovens.
Another object of the invention is to provide a coke oven battery to provide oven anchorage system with totally concealed intermediate springs inside the buckstays to protect them from external hazardous conditions.
Another object of the invention is to provide a coke oven battery to keep the number of springs per buckstay optimum and keep at the minimum level through proper load analysis and simulation software.
Another object of the invention is to provide a coke oven battery to reduce chances of environmental pollution through reduction in the total leaking surface area (e.g. oven doors, charging lids, A.P. caps etc.)
Another object of the invention is to provide a coke oven battery which uses stainless steel sheet in regenerator face wall and oven roof section to stop leakage of gas from coke oven battery.
Another object of the invention is to provide a coke oven battery to reduce the average power consumption of the battery by reducing operations like pushing, charging, quenching etc.
Another object of the invention is to provide a coke oven battery to achieve higher productivity (1.0 MPTA) of high quality coke by using less number of ovens (76 numbers) through less number of pushing (<100/day).
Another object of the invention is to provide a coke oven battery to provide a coke oven battery that is cheaper due to less number of ovens, equipment cost, infrastructural and operating cost, space requirement etc.
How the objectives as mentioned above are achieved will be clear from the following description. In this context, it is clarified that the description provided is non-limiting and is only by way of explanation.

SUMMARY OF THE INVENTION
An improved top charged coke oven battery is provided with PLC (programable logic control) controlled hydraulic reversing winch having four foot mounted hydraulic cylinders. These cylinders impart reciprocal motion to cause reversal of the heating system every 20 minutes. The oven anchorage consists of buckstays, flash plates, cross and longitudinal tie rods, and springs adapted to maintain a positive pressure on the refractory to avoid opening of joints or cracks due to temperature changes. Stainless steel sheet is provided within the brick work of the regenerator face walls and oven roof sections to significantly improve the heat efficiency of the battery.
The battery has a hot volume of 49.8 M3 to achieve a productivity of 1.0 MPTA with less than 100 pushing per day.
The reversal of heating system is used to heat the battery through either odd number of flues or even number of flues of heating walls alternatively. During one reversal, heating will be through odd flues. In the next reversal, heating shall be through even flues. This is required to maintain uniform temperature along the length and height of heating walls. This reversal will be applicable to heating with either coke oven gas or mixed gas.
The total cycle of operation of the winch is completed in 225 seconds including 45 seconds of operation time, 60 seconds of warning and waiting time and a normal pause time of 120 seconds.
The reversal of the heating system is caused by sequential actuation of hydraulic cylinders which are actuated by intermittent energisation of a direction control valve, which is controlled by the PLC based on commands/field switch inputs.
The buckstays are of welded box type construction without any splicing joint in critical zone and are well ventilated. The buckstays on the pusher side and the coke side are held at the battery top level and nozzle decking level by the cross tie rods at each level loaded through helical springs.
A method for reversing operation with coke oven gas heating (Reversal-I) of the improved top charged coke oven battery as described above comprises of the steps of:

- identification of the positions of first, third and fourth cylinders by the actuation of limit switches PS 2, PS 5 and PS 9 respectively;
- starting of movement of the first cylinder towards the pause position to stop the heating gas and stopping when limit switch PS 3 is actuated;
- starting of movement of the third cylinder and stopping when limit switch PS 6 is actuated;
- starting of movement of the fourth cylinder and stopping when limit switch PS 7 is actuated, resulting in reversal of combustion air and waste gas withdrawal; and
- starting of movement of the first cylinder and stopping it when limit switch PS 4 is actuated, thereby opening gas cocks and starting Reversal-II heating, which is recognised by the actuation of limit switches PS 4, PS 6 and PS 7.
A method for reversing operation with mixed gas heating (Reversal-II) of the improved top charged coke oven battery as described above comprises of the steps of:
- starting of movement of the second cylinder towards the pause position to stop the heating gas and stopping it when limit switch PS 12 is actuated;
- starting of movement of third cylinder and stopping when limit switch PS 6 is actuated, resulting in reversal of combustion air and waste gas withdrawal; and
- starting of movement of the second cylinder and stopping when limit switch PS 13 is actuated, thereby opening the gas cocks and starting the Reversal-II heating which is recognised by the actuation of limit switches PS 13 and PS 6.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The nature and scope of the present invention will be better understood from the accompanying drawings, which are by way of illustration of a preferred embodiment and not by way of any sort of limitation. In the accompanying drawings:-Figure 1 shows the elevation view of the hydraulic reversing system of the 1.0 MTPA coke oven battery according to the present invention.
Figure 1A is a enlarged view of the portion marked as X in figure 1. Figure 1B is a enlarged view of the portion marked as Y in figure 1. Figure 1C is a enlarged view of the portion marked as Z in figure 1.

Figure 2 shows the elevation view of the 1.0 MTPA coke oven battery with cross tie rod arrangement for oven anchorage system.
Figure 3A shows enlarged view of the portion marked as A in figure 2.
Figure 3B shows enlarged view of the portion marked as B in figure 2.
Figure 4A shows the elevation view of the top cross tie rod in hot condition.
Figure 4B shows the plan view of the top cross tie rod in hot condition.
Figure 5 shows the arrangement of SS foil at oven roofing.
Figure 6A shows the arrangement of SS foil at regenerator face wall.
Figure 6B shows the view along line X-X of figure 6A.
Figure 7 is a schematic diagram of the reversing operation of the coke oven battery with coke oven gas & mixed gas heating.
DETAILED DESCRIPTION OF THE INVENTION
Having described the main features of the invention above, a brief and non-limiting description of a preferred embodiment will be given in the following paragraphs with reference to the accompanying drawings.
In all the figures, like reference numerals represent like features. Further, the shape, size and number of the devices shown are by way of example only and it is within the scope of the present invention to change their shape, size and number without departing from the basic principle of the invention.
Further, when in the following it is referred to “top”, “bottom”, “upward”, “downward”, “above” or “below”, “right hand side”, “left hand side” and similar terms, this is strictly referring to an orientation with reference to the apparatus, where the base of the apparatus is horizontal and is at the bottom portion of the figures. The number of components shown is exemplary and not restrictive and it is within the scope of the invention to vary the shape and size of the apparatus as well as the number of its components, without departing from the principle of the present invention.
All through the specification, the technical terms and abbreviations are to be interpreted in the broadest sense of the respective terms, and include all similar items in the field known by other terms, as may be clear to persons skilled in art. Restriction or limitation if

any referred to in the specification, is solely by way of example and understanding the present invention.
The battery according to the present invention has the following specifications. However, the invention is equally applicable to batteries having other specifications as well.
i) Oven characteristics / dimensions
Description Features
Number of ovens 76 (2 x 38)
Useful oven length between door plugs 16.192 m
Oven height 7.000 m
Useful oven height 6.700 m
Average width of oven 460 mm
Pusher side width of oven 430 mm
Coke side width of oven 490 mm
Oven taper 60 mm
Oven useful volume (hot) 49.8 m3
Oven pitch 1450 mm
Number of heating flues 34 no's in 17 pairs
No. of charging holes per oven 4
ii) Operational characteristics
Description Features
Schedule no. of pushing/ charging per day 98
Dry coal charge per oven (with coal dry bulk density 36.9 t
0.74 t/m3)
Coke per pushing (@76% of coal charge) 28 t
Design Coking period 18.5 hr
Dry coal throughput per annum with 25% V.M 13,17,840 t
Gross Coke production per annum 10,01,560 t
BF Coke (25 to 80 mm) per annum @88% of gross coke 8,81,375 t Average coke oven gas production (@320 Nm3/t of dry 48,140 Nm3/hr coal charge)
Heating mode envisage CO/BF/Mixed gas
COG mode of heating
i) Specific heat consumption i) 540-560 Kcal/Kg of
wet coal
ii) COG consumption (with CV 4100-4200 ii) 21,893 Nm3/hr
Kcal/ Nm3)
iii) 26,247 Nm3/hr
iii) Excess CO gas generation
Mixed gas mode of heating (with CV 1000 Kcal/ Nm3) i) 600 Kcal/Kg of wet
i) Specific heat consumption coal
ii) 99,546 Nm3/hr
ii) Mixed gas consumption
iii) COG consumption (with CV 4200 Kcal/ iii) 5,856 Nm3/hr
Nm3)

iv) BF gas consumption (with CV 800 Kcal/ iv) 93,690 Nm3/hr
Nm3)
v) 42,285 Nm3/hr
v) Excess CO gas generation
It may be clearly understood that the above figures are illustrative in nature and may vary in actual performance of the invention.
We now refer to the accompanying drawings.
A. PLC CONTROLLED HYDRAULIC REVERSING WINCH
This is depicted in Figure 1.
In order to maintain the uniformity of heating and thermal regime, coke oven battery heating system is subjected to reversal of heating path and burning of alternative flues as heating fuel for heating the wall alternatively with a time interval of every 20 minutes.
Reversing winch cylinders impart reciprocal motion to the reversing mechanism pull rods, chains, gas cock levers and pull rods of waste heat boxes and air inlet boxes, which make the reversal of heating system every 20 minutes.
1. System description:
The hydraulic reversing winch system basically comprises of four number of foot mounted hydraulic cylinders (1, 2, 3, 4). Out of them, two cylinders (1, 2) are telescopic cylinders of stroke 610 mm (305 mm+305mm) to control CO gas and mixed gas reversals. The other two cylinders (3, 4) are of stroke 610 mm and 400 mm stroke respectively, to control reversal of waste heat boxes and one air flap of Air inlet boxes and controlling the second air flap of Air inlet box respectively.
Telescopic cylinder for coke oven gas reversals - (1)
Telescopic cylinder for mixed gas reversals - (2)
Waste heat valves and one air flap for mixed gas reversals - (3)
Second air flap for coke oven gas reversals - (4)
For CO gas reversal, cylinders (1), (3) and(4) are in operation and for Mixed gas reversals, cylinders (2) and(3) will be in operation. This is best shown in figure 1A.

With this arrangement, auto change over from CO gas heating to mixed gas and vice versa is possible.
The reversing winch/cylinders are driven by a hydraulic power pack. Reversing winch power pack and accumulator stand for power pack are housed in a single room adjacent to the hydraulic reversing winch.
The total cycle of operation of the winch is normally completed in 225 seconds including 45 seconds of operation time, warning and waiting time of 60 seconds and a normal pause time of 120 seconds.
The hydraulic system is controlled by reversing winch control panels. This control panel is a composite line up of panels for controlling the hydraulic pumps and the solenoid valves for the hydraulic cylinders, which cause the actual movement of the winch. There are two sections in the reversing winch control panels, namely power (MCC) and control (PLC). PLC panel is located in main control room and is actuated through remote I/O for reversing operation.
The power section is housed in panel-1 and it contains the feeders for the hydraulic pumps, incoming feeder, control transformer and accessories. In panel-2 the PLC for reversing winch control and control-gears for process control, indication and annunciation are housed.
The remote I/O is housed in the rooms located near the reversing winch of battery. In the same room MCC Panel for Hydraulic pumps shall be also be placed. In the power pack room, there is a local push button station for control of hydraulic pumps. Along with the hydraulic system, field switches (Limit switches) are provided which will provide the necessary information to the PLC for process monitoring and control.
There are two 11KW rated hydraulic pumps in the system. Out of the two hydraulic pumps, one is working and the other is kept as standby.
Out of these two hydraulic pumps, only one can be started at a time from local control post (LCP). Whichever pump is started first becomes the operating pump, and the other one automatically becomes the standby pump. No automatic switch over to standby pump will take place in case of tripping of the operating pump. It is advisable to change the operating pump from time to time to keep both the pumps is good working condition.

When the pump cycle is switched on by pressing the corresponding “start” pushbutton for the pump, the “pump on” lamp (inside the start pushbutton) starts flashing. When the pump is actually running and charging up the accumulator, the “pump on” lamp inside the start pushbutton becomes steady on.
Pumping cycle will stop/trip out if the stop pushbutton is pressed, oil level is very low, oil temperature is high, header line pressure after initial starting bypass is low, or if pump electrical trip takes place. Apart from these, the pump will also stop in case the lockout pushbutton for the running pump is actuated. One such lockout station is individually provided for each pump. This lockout pushbutton contact is hardwired with the pump control circuit for added safety. Generally, it is actuated before taking up any maintenance work.
After the cycle starts, the pump is actually permitted to run if the suction line valve for the pump is open and tank oil level is above the low level. However, during actual running of the pump, if the suction valve is closed or the oil level goes below permissible low level, the pump will stop but the cycle will continue to remain active. Occurrence of such fault will be annunciated in the annunciation fascia provided on the control panel-2 door. After such fault has occurred, if the fault condition is removed, then the pump will again start up based on accumulator oil level interlock till the pump running cycle is aborted.
Pump on, off and trip indications are provided both on the local control panel (LCP) as well as in the control panel of PLC.
2. REVERSING WINCH OPERATION
Reversing operation is caused by sequential actuation of hydraulic cylinders (cylinders 1, 2, 3 and 4) actuated by intermittent energisation of a direction control valve, which is controlled by the PLC, based on commands/field switch inputs. In this connection, it may be noted that there are two hypothetical positions for the hydraulic cylinders, namely green pipe position (Reversal-1) and red pipe position (Reversal-II). Each of these two positions is determined by conditions of a set of end limit switches (PS1 to PS13), best shown in figure 7.
Reversal-1 corresponds to heating of even number of heating walls with even flues and odd number of heating walls with odd flues.

Reversal-2 corresponds to heating of even number of heating walls with odd flues and odd number of heating walls with even flues.
PS-1 to PS-13 are the total number of limit switches mounted on the reversing winch for both coke oven gas heating and mixed gas heating. These limit switches provide the necessary feedback to the PLC regarding the positioning of the hydraulic cylinders, thereby heating the system.
A. Reversing operation with coke oven Gas heating:
The operational principle is represented schematically with the help of fig. 7.
For CO gas reversal, Cylinders 1, 3 and 4 are in operation.
Reversal – I
For this, position of cylinder 1, cylinder 3 and cylinder 4are identified by the actuation of Limit switches PS 2, PS 5 and PS 9 respectively.
Reversal - I to Reversal -II:
Once the reversal is actuated, the process for movement of Hydraulic cylinders to reach the condition/position of Reversal-II from Reversal-I starts.
During this, cylinder 1 starts moving towards the pause position to stop the heating gas. The cylinder 1 will stop once the limit switch PS 3 is actuated.
Thereafter cylinder 3 starts moving and will stop once the limit switch PS 6 is actuated. Subsequently, cylinder 4 will start moving and will stop once the limit switch PS 7 gets actuated. This results in reversal of combustion air and waste gas withdrawal.
Finally, cylinder 1 will start moving and will stop once the limit switch PS 4 is actuated and gas cocks will be opened.
This is the position, where the Reversal-II heating will start, which is recognised by the actuation of limit switches PS4, PS6 and PS7.

Reversal - II to Reversal- I
Once this reversal is initiated after a certain interval, the above sequence will be reversed and Reversal-I heating will be started once the actuation of limit switches PS 2, PS 5 and PS 9 are made.
B. Reversing operation with Mixed Gas heating
For mixed gas reversals, cylinders 2and3are in operation. Cylinder 4 will be stopped at the actuation of limit switch PS8.
Reversal – I
For this, position of cylinder 2 and cylinder 3 shall be identified by the actuation of Limit switches PS 11 and PS 5 respectively.
Reversal - I to Reversal -II
Once this reversal is actuated, the process will start for movement of the hydraulic cylinders to reach the condition/position of Reversal-II from Reversal-I.
During this, cylinder 2 will start moving towards the pause position to stop the heating gas. Cylinder 2 will stop once the limit switch PS 12 will be actuated.
Thereafter cylinder 3 will start moving and will stop once the limit switch PS6 is actuated. This results in reversal of combustion air and waste gas withdrawal.
Finally, cylinder 2 will start moving and will stop once the limit switch PS 13 is actuated and gas cocks are opened.
This is the position, where the reversal-II heating will start and the same is recognised by the actuation of limit switches PS13 and PS6.
Reversal - II to Reversal- I
Once this reversal is initiated after a certain interval, the above sequence will be reversed and reversal-I heating will be started once the limit switches PS 11 and PS 5 are actuated.

Reversing modes
Reversing cycle can be initiated from the remote I/O panel in following modes
1) Auto Mode
2) Manual mode.
3) Manual mode with inching.
4) Emergency operation during power failure
5) Operation through Hydraulic Cylinders
Other interlocks
Further, the following interlocks shall be included in the circuit to initiate Reversing.
1. CO Gas/ BF Gas valves are open (Motorized actuators).
2. CO gas pressure is in order.
3. Draft in Regenerator is in order.
4. CO/BF Gas Motorized gate valves shall close automatically, after reversing winch comes to Neutral position, if the gas pressure in the pipeline falls below the Set point. This signal/contact comes from Inst. PLC of instrumentation system.
Oven anchorage system:
We now refer to Figure 2, 3A, 3B, 4A and 4B. They show the arrangement of oven anchorage system.
The battery oven anchorage consists primarily of buckstays, flash plates, cross and longitudinal tie rods, helical springs, etc. The anchorage system maintains a positive pressure on the refractory to avoid opening of joints or cracks due to temperature changes. They are of rugged construction to withstand the stresses and loads. Suitable protection is provided with stainless steel pipe sleeves for the full length of upper cross tie rods. Material of construction of the cross tie rod is chrome molybdenum steel. A set of regenerator bracings is provided for loading on the main walls and dividing the walls of the regenerators.
Buttress walls are connected together at the top by longitudinal tie rods. To ensure proper loading, adequate (at least seven) number of longitudinal tie roads are provided with helical springs.
Buckstays are provided to transmit load on the heating walls through the flash plate.

They are of rugged construction to withstand the stresses and loads during heating up and battery operation. Buckstays are of welded box type construction without any splicing joint in critical zone and are well ventilated. Buckstays on the pusher side and the coke side are held at the battery top level and nozzle decking level by suitable cross tie rods at each level loaded through helical springs. There are no joints in the cross tie rods. Buckstays are made to restart the bottom on the nozzle decking. The transfer of load from buckstay to flash plates and to main wall is through a number of helical springs located inside the buckstay on the pusher side and the coke side.
A set of regenerator bracings are provided for loading on the main and the dividing regenerator walls, to take care of the differential expansion characteristics of refractory of this region.
PROVISION OF STAINLESS STEEL SHEET:
This is depicted in Figures 5, 6A and 6B.
The regenerator face walls and oven roof sections are traditionally potent sources of leakage in any coke oven battery, causing undue gas and heat loss. It also deteriorates the working condition. To solve this problem,
The present invention incorporates several novel and inventive features, some of which are mentioned in the non-limiting list below. Other such features and advantages will be clear to a person skilled in the art from the description provided above.
1. Large oven volume: The coke oven battery according to the invention is of substantially higher annual capacity (1 MTPA) with large oven volume (49.8 m3 hot) as compared to any conventional coke oven battery. This offers the following advantages:
i) Higher productively through less number of pushing: Due to higher
coke output per pushing, high productivity (1.0 MTPA) is achieved
through comparatively less number of pushing (<100/day). This
provides great convenience to the battery operators.
ii) Less pollution: Number of ovens required is less, and hence the total
leaking surface (e.g. Oven doors, charging lids, A.P. caps etc.) is less which reduces the chances of pollution to a great extent.

iii) Less power consumption: Due to less number of operations like
pushing, charging, quenching etc., average power consumption of
the coke oven battery is also less.
iv) Improved average life: Due to less number of operations, wear and
tear of the ovens and the equipment is less. This enhances the
average battery life.
v) Lower cost: Due to less number of ovens, equipment cost,
infrastructural and operating costs, space requirement etc., i.e., the total cost of the battery is lower. 2. Auto change over facility between heating modes: Both coke oven gas as well as mixed gas are used as heating media in the coke oven battery of the present invention. For smooth and reliable operation of the reversing mechanism, PLC controlled hydraulic reversing winch with auto change-over facility is provided for switching from coke oven gas heating to mixed gas heating and vice versa by merely pressing a button switch. 3.
4. Oven anchorage system: Repeated failure of buckstays/tie rods is a predominant hazard especially in an aged battery of the prior art. Improper loading practice on brickwork (through buckstays and accessories) adds to this misery even more. Sturdy box type buckstays having high section modulus have been provided to eliminate such problems and to increase the average battery life.
5. Provision of PLC controlled hydraulic reversing winch.
6. Provision of stainless steel sheet within the brick work of the regenerator face walls and oven roof sections to prevent undue gas and heat loss and thereby improve the heat efficiency of the battery significantly.
The present invention has been described with reference to some drawings and a preferred embodiment purely for the sake of understanding and not by way of any limitation and the present invention includes all legitimate developments within the scope of what has been described herein before and claimed in the appended claims.

We claim:
1. An improved top charged coke oven battery provided with PLC controlled hydraulic reversing winch having four foot mounted hydraulic cylinders (1, 2, 3, 4) which impart reciprocal motion to cause reversal of the heating system every 20 minutes and an oven anchorage consisting of buckstays, flash plates, cross and longitudinal tie rods, and helical springs adapted to maintain a positive pressure on the refractory to avoid opening of joints or cracks due to temperature changes and stainless steel sheet (5) is provided within the brick work of the regenerator face walls and oven roof sections to significantly improve the heat efficiency of the battery.
2. The improved top charged coke oven battery as claimed in claim 1, wherein the battery has a hot volume of 49.8 M3 to achieve a productivity of 1.0 MPTA with less than 100 pushings per day.
3. The improved top charged coke oven battery as claimed in claim 1, wherein said reversal of heating system is adapted to use to heat the battery through either odd number of flues or even number of flues of heating walls alternatively.
4. The improved top charged coke oven battery as claimed in claim 1, wherein the total cycle of operation of the winch is completed in 225 seconds including 45 seconds of operation time, 60 seconds of warning and waiting time and a normal pause time of 120 seconds.
5. The improved top charged coke oven battery as claimed in claim 1, wherein said reversal of the heating system is caused by sequential actuation of hydraulic cylinders (1, 2, 3, 4) actuated by intermittent energisation of a direction control valve, which is controlled by the PLC based on commands/field switch (PS1 – PS13) inputs.
6. The improved top charged coke oven battery as claimed in claim 1, wherein said buckstays are of welded box type construction without any splicing joint in critical zone and well ventilated, the buckstays on the pusher side and the coke side being held at the battery top level and nozzle decking level by said cross tie rods at each level loaded through helical springs.

7. A method for reversing operation with coke oven gas heating (Reversal-I) of the
improved top charged coke oven battery as claimed in claims 1-6 comprises of the
steps of:
- identification of the positions of cylinder (1), cylinder (3) and cylinder (4) by the actuation of limit switches PS 2, PS 5 and PS 9 respectively;
- starting of movement of cylinder (1) towards the pause position to stop the heating gas and stopping it when limit switch PS 3 is actuated;
- starting of movement of cylinder (3) and stopping when limit switch PS 6 is actuated;
- starting of movement of cylinder (4) and stopping when limit switch PS 7 is actuated, resulting in reversal of combustion air and waste gas withdrawal; and
- starting of movement of cylinder (1) and stopping when limit switch PS 4 is actuated, thereby opening gas cocks and starting Reversal-II heating, which is recognised by the actuation of limit switches PS 4, PS 6 and PS 7.
8. A method for reversing operation with mixed gas heating (Reversal-II) of the
improved top charged coke oven battery as claimed in claims 1-6 comprises of the
steps of:
- starting of movement of cylinder (2) towards the pause position to stop the heating gas and stopping it when limit switch PS 12 is actuated;
- starting of movement of cylinder (3) and stopping when limit switch PS 6 is actuated, resulting in reversal of combustion air and waste gas withdrawal; and
- starting of movement of cylinder (2) and stopping when limit switch PS 13 is actuated, thereby opening the gas cocks and starting the Reversal-II heating which is recognised by the actuation of limit switches PS 13 and PS 6.