Coke Oven Machines
Coke Oven Machines
Coke oven machines are an integral part of any coke oven battery. These machines charge the ovens with the coal feedstock, push the coke from the ovens after coking, and feed it to the coke quenching process. In recent times, coke oven machines are acquiring a more prominent role in the coke making process. The increasing dimensions of coke oven chambers and the demand for the high performance have spurred the development of complex coke oven machines.
Apart from the traditional handling of the coal and coke flow, coke oven machines are to meet the requirements for automation, productivity, safety, and user friendliness. Nowadays, where there can be upto 150 pushing cycles per day, so called ‘single spot operation’ of these machines, which involves no additional travelling, has become standard norm for each cycle.
The operators’ cabins of the coke oven machines besides being fully air conditioned are to be equipped with modern control units which include comprehensive PLC (programmable logic controller) systems connected to the control and monitoring units of the coke oven battery for ensuring safe operation. The automation and control systems of the coke oven machines are preferably to be complemented with advanced digital features so as ensure the safe operation of the battery with all travelling steps being fully automated and accurately scheduled. The travelling and all related operation steps of the coke oven machines are to be designed to allow for fully automated operation so that the pushing schedule can be controlled and adjusted.
In the present day environment of stringent environmental regulations, the coke oven machines are also deeply involved in all environmental and process control aspects. Hence, all the machines are to be equipped with highly efficient emission control systems, so that the environmental regulations are met. This means that all the machines are required to be designed taking into maximum consideration of pollution control regarding (i) emission during charging, (ii) emission on top coke side door when opening the door, (iii) emission during coke pushing on coke side, and (iv) emission at oven doors during the period of technology.
The different types of coke oven machines used for the by-product coke oven batteries are (i) coal charging car, (ii) coke pusher machine for the top charged ovens, (iii) coal stamping cum coke pusher machine for stamped charge ovens, (iv) coke guide and transfer car, (v) coke quenching car or coke bucket car with electric locomotive, and (vi) door service car.
Coal charging car
Coal charging car is used to charge coal blend into the coke oven by means of traditional devices of gravitation type charging or forced charging of coal by screw or rotary feeders. The coal charging car is designed for single spot operation and equipped with the technologies related to pollution control, and safe and efficient operations.
The main operations performed by the coal charging car include (i) collection of coal blend from coal tower gates, (ii) travelling over battery top and charging of coal blend into the coke oven, (iii) extraction / installation of lids of charging hatches, (iv) control of stand-pipes and injection valves, and (v) cleaning of elbows and wells of stand-pipes. The main functional units of the charging car are (i) travel drives (bogies), (ii) charging weighing hoppers, (iii) lid cleaners, (iv) frame cleaners, (v ) screw feeders (or rotary feeders) for controlled charging, (vi) rotary gates, (vii) sealed telescopes, (viii) lid lifters, (ix) auxiliary lid lifters at coke oven N+2 (the oven charged by the machine during previous sequence), (x) lid luting system, and (xi) oven top vacuum cleaner.
Drives of screw feeders (or rotary feeders) are with frequency regulation of rotation speed which provides the optimal charging speed. Control system is executed by PLC. Hydraulic drives are widely used in the design of machine mechanisms. Weighing of blend in bunkers is provided by means of load cells which are installed under supports of bunker. The signals are transferred to the display in operator’s cabin. Values of weigh scales are used for controlled charging of bunkers of the coal charging car as well as charging of coke oven with the required quantity of coal blend.
The coal charging car travel drive normally has 16 wheels which are supported in 4 numbers four-wheel bogies. Each four-wheel bogie consists of 2 numbers two-wheel bogies. One wheel in each two-wheel bogies is driven. The whole system is connected to the machine framework through a spring loaded suspension beam which has the aim to eliminate all the vibrations and reduce the loads to oven roof refractory. In case of failure of one electrical motor, the machine is able to operate at a reduced speed. Drive of coal charging car can also be hydraulic drive.
The controlled charging system for the coal charging car has been developed with the objective to reduce the emissions occurring during charging of the batteries down to a level tolerated by the environmental regulations with a minimum of investment and operational cost. This is normally used in combination with the single oven pressure control system. This state-of-the-art for the coal charging in the coke oven battery ensures very good performance and long lasting operation at the design conditions. This system is based on the concepts consisting of (i) optimal cleaning of charging frames, (ii) frame cleaners assurance that the contact surface with the telescope tip is always perfect cleaned since the scraping is performed through a specially designed brushes actuated by a rotary drum, and (iii) perfect gas tight charging system.
The charging equipment creates a sealed connection between the charging hole frame and the telescope and has gas tight seals at all telescope links and at the discharge gate as well as at the coal hopper filling opening. This charging equipment is gas tight upto an over-pressure of 20 mm water gauge. The seal between charging hole frame and telescope and between bottom and top telescopes is normally created by using hydraulic cylinder to press the two metal parts against each other. The cylinder force is applied during the entire charging process. However, the sealing system does not conflict with the self adjustment features of the telescope in case there is an off-set between the centre of the charging hole lid and the centre of the telescope or a deviation in the lid elevation. The connection between the top telescope and the screw feeder outlet is created with the help of a well protected compensator.
The discharge gate used in the gas tight charging equipment, which is a new development, is integrated in the screw feeder outlet and prevents the coal from spilling onto the oven deck. During charging, it opens the screw feeder outlet completely. The gate is actuated from the outside of the screw feeder construction. The seal with the coal hopper filling opening is created with the help of a coal plug, i.e. after charging, a certain amount of coal remains both in the screw feeder and in the hopper. Fig 1 shows coal charging car and coal charging system.
Fig 1 Coal charging car and coal charging system
Continuously controlled coal charging is done by the coal charging car. Levelling and charging at the same time creates a blockage of the gas passage, causing an over-pressure at the telescope, on the one hand, and the built-up of peak amounts of charging gas which is to be conveyed through the standpipe, on the other hand. In order to overcome this bottleneck, a charging system which minimizes the number of levelling strokes is used. As an optimum, the charging process takes place without levelling at the same time, i.e. only when charging is completed, one levelling stroke is to be carried out. The possibility to use the system of charging without levelling at the same time, of course, depends on the oven geometry.
The coal peaks inside the coke oven are to be built up in such a way that the volume of the coal piles an top of the levelling line balances the volume of the valleys below the levelling line. During the entire charging time, a free gas passage between coal pile and oven roof is to be provided. The coal pile is normally built up inside the tapered charging hole without blocking the gas passage. Another pre-condition is that a free space between top of leveller bar and oven roof is provided during levelling. Only a charging system with a high accuracy in building up the coal piles inside the coke oven can achieve such a constant free gas passage.
Efficient levelling of the coal inside the coke oven is done by the pusher machine. The leveller bar installed in the pusher machine is normally designed to work in perfect combination with the charging car and its shape ensures a minimum bending during levelling and a good resistance to thermal stress.
The rotary magnetic lid lifters guided by the centering pins and installed on the charging lids, can follow the eventual misalignment occurring to the lids themselves. The lids are equipped with detection devices capable to verify the presence and correct engagement of the lids. For all the other functional units of the charging car, the hydraulic actuation is arranged above the top platform, in order to be completely protected from flames and heat.
A second row of lid lifters called auxiliary lid lifter are arranged at coke oven N+2 in order to manipulate the lids opened for decarbonizing operations. The special electro-magnets are arranged on a cardanically suspended cross beam. Because of the cardanic suspension, the lids are concentrically replaced even when they have not concentrically been lifted.
Lid luting system consists of special designed horizontal tanks which have the scope to distribute the luting liquid along the four charging holes thus avoiding sticking problems. The mixture is prepared by a stationary device installed on coal tower and loaded onto the coal charging machines on shift basis.
Oven top vacuum cleaner installed on the coal charging car is a fully automatic device capable to operate at oven N-2. This device is mainly made of three components namely (i) two shuttle suction tips moving along the oven roof, (ii) the main duct, and (iii) one bag filter placed on the machine main platform. The design of the oven top vacuum cleaner is such that the movable shuttle is connected to the fixed part (bag filter) without a flexible hose. In this way the maximum reliability is assured.
Coke pusher machine
The coke pusher machine travels along the length of the battery and carries out various functions such as (i) remove and replace coke oven doors, (ii) push out hot coke from the oven, (iii) open and close leveller bar doors, (iv) level the coal charge in the oven, (v) clean doors, frame and flash plates, (vi) degraphitize the oven ceiling, and (vii) remove the coke spillage. The pusher machine is located at the coke oven battery side and is normally designed for the single spot operation. The drives of machine can be hydraulic or electro-mechanical. Operator’s cabin, and the hydraulic and electronic equipment cabins are normally equipped with air-conditioners.
The main functional units of the coke pusher machine are (i) travelling mechanism, (ii) pushing mechanism, (iii) door latch unscrewing mechanism, (iv) door snatching mechanism, (v) door turning mechanism, (vi) travelling mechanism for door extractor installation, (vii) door cleaning mechanism, (viii) door frame and flash plate cleaning mechanism, (ix) levelling mechanism, (x) leveller bar door opening mechanism, (xi) coal charge spillage collecting system, (xii) coke spillages collecting device with quenching system, (xiii) degraphitizing mechanism.
The task of the pushing equipment is to push the ready carbonized coke out of the coke oven, through the coke guide into the quenching car. The pusher device is situated on the lower machine platform and consists of (i) the pusher bar drive, (ii) the pusher bar, and (iii) the pusher bar head (ram) with the plough shoe and roof decarbonizing system. Two fixedly installed pipes on each side of the pusher bar supply the degraphitizing air to nozzles at the top of the pusher bar head with the functions of (i) oven top decarbonizing, and (ii) stand pipe decarbonizing. The height adjustable sliding shoe underneath the front part of the pusher ram is normally equipped with a changeable wearing plate. It supports the pusher bar inside the oven during pushing. The pusher head is also normally equipped with a height adjustable mechanical carbon scraper.
The job of the levelling device is to level the coal peaks inside the coke oven after charging so as to achieve an even top surface of the charged coal inside the coke oven. The levelling device is situated on the upper machine platform, with its centre-line two oven pitches away from the centre-line of the pusher bar on the pusher bar right side when facing the oven and consists of (i) leveller bar drive, (ii) leveller bar, (iii) leveller bar support roller, (iv) leveller door manipulator, (v) smoke sleeve and the spillage coal collection system, and (vi) movable platform in the smoke sleeve area.
The leveller door manipulator is installed at the utmost front end of the leveller bar, facing the coke oven. It opens and closes as well as unlocks and locks the leveller door. In order to avoid the escape of flames and smoke through the open leveller door, a smoke sleeve with an air curtain is normally provided. Also, a spillage coal chute is situated in front of the smoke sleeve. This chute swings towards the oven door and collects as well as guide spillage coal from the leveller door opening to the leveller coal bunker.
The leveller bar support rollers are installed in several roller stands. The rollers itself are manually adjustable to compensate all deviation. The ladder type leveller bar is of welded construction and is furnished with a changeable front portion. The leveller bar design and the levelling procedure are chosen with respect to minimize the bars deflection.
The pusher machine is equipped with a device which collects the spillage coke resulting from the oven servicing. After the oven has been closed, the collected spillage coke is transferred through a chute into a storage bin at the pusher machine. The device is located underneath the pusher bar and consists of a movable and tiltable spillage coke collection pan with an integrated quenching system, a transfer chute, and a spillage coke storage bin with discharge gate. Whenever necessary, the storage bin can be emptied with the help of a hydraulic cylinder operated clamshell gate at the designated positions into a dedicated stationary box.
The door extractor is positioned in a steel structure beside the pusher bar and consists of (i) a robust travel beam with guide rollers, which is rested in a carriageway, (ii) the swivel arm, which is attached through the upper and lower pivot bearings to the front portion of the travel beam, and (iii) the door extractor head, which is attached through a pivot bearing to the swivel arm. All travelling and lifting movements are effected by means of hydraulic cylinders.
Turning the door in and out of the axis of coke oven is executed through a curved track. The door extractor is provided with a door position detection and memory system capable to memorize the height and inclination of each oven doors. The inclination and height detection and memorizing system ensures the highest possible cleaning efficiency of the door cleaner, prevents damages to the door sealing strip during door extraction, has the capability to handle considerably inclined doors, and provides high longevity of the whole construction.
The door cleaner is installed in the steel structure on the side of the door extractor. After the door has been extracted and the door extractor has been returned to its home position, the door is pivoted by 90 degree through the curved track to be in line with the centre line of the door cleaner. Also, the door extractor moves the door in height and inclination into the cleaning position to achieve high cleaning efficiency.
Door cleaning takes place while the coke is being pushed and the frame is being cleaned.The door-cleaning device consists of a cleaning head and a long travel jib with steel structure. The cleaner head is made of a robust hollow profile design and is attached to the moving device by stable guide frame. The guide frame also accommodates the hydraulic cleaning cylinder as well as the spring-suspended guide rollers of the tool holder and the top and bottom horizontal cleaners. The vertical cleaning cylinder is adjustable and is mounted on shock absorbing elements. All scrapers are arranged on spring loaded adjustable devices in order to allow a smooth and safe cleaning action.
The frame cleaner is positioned in a steel structure beside the pusher bar, but on the other site as the door extractor and consists of (i) a robust travel beam with guide rollers, which is rested in a carriageway, (ii) the swivel arm, which is attached through the upper and lower pivot bearings to the front portion of the travel beam, and the frame cleaner head, which is attached through a pivot bearing to the swivel arm. The cleaner head is supported by a hollow profile structure is hinged at the pivoting part by means of a stable guiding frame. Fig 2 shows a coke pusher machine.
Fig 2 Coke pusher machine
Coal stamping cum coke pusher machine for stamped charge ovens
A coke oven battery with stamp charging is configured to charge coal from a side of the coke oven and put the coal into the oven in a pressed cake form. In a stamp charge coke oven, coal is compacted into a rectangular parallelepiped cake in a chamber by a stamping machine.
Stamping equipment can be located in a building intended to this purpose or in the charging / pushing machine. The stamping process consists in general in introducing the coal blend previously ground to a specific size within a steel box as successive layers which are rammed mechanically. It can be applied vertically or horizontally. Additionally, vibration can be applied to facilitate the accommodation of the particles. A horizontal box is filled with the coal blend, with defined grain size distribution and moisture content, in three equal layers. Compaction and vibration is applied, through 24 plates covering all the surface of the cake, during two minutes for each layer, to support the transfer from the box to the oven. Two aspects which are to be taken into the account are densification and mechanical properties. Fig 3 shows coal stamping cum coke pusher machine.
Fig 3 Coal stamping cum coke pusher machine
Coke guide and transfer car
Coke guide and transfer car is designed for servicing the coke side of the coke oven battery. The main operations to be fulfilled by the coke guide car are (i) extraction and installation of door, (ii) approach-withdrawal of coke guide cage to oven, (iii) directing coke descent in coke transfer car, (iv) cleaning of doors and frames, (v) collecting of dust-gas mixture, and (vi) removal of coke spillage.
Considering the importance of the emission control, operation reliability, and low maintenance, nowadays coke guide and transfer car has (i) installation of a pushing emission control system with land based filter plant connected to the machine’s hood system, (ii) installation of a door emission collection system which collects the emission escaping from the open oven chamber and from the door in cleaning position and conveyed by thermal effect to the top of the machine, (iii) installation of a spillage coke collection device, (iv) installation of door cleaner, and (v) installation of frame cleaner.
The main functional units of the coke guide and transfer car include (i) travel drives (bogies), (ii) hood system, (iii) coke guide, (iv) coke spillages collecting device, (v) door extractor, (vi) door cleaner, and (vii) frame cleaner. Even if it is installed on the ground, the pushing emissions control system is considered as a part of the integrated coke guide and transfer car since it is capable to minimize the emissions during pushing. The design of the bag filter, the collector as well as the belt lifter device performs as a unique system with the coke guide and transfer car. Fig 4 shows the coke guide and transfer car.
Fig 4 Coke guide and transfer car
The coke guide is arranged at the machine’s centre on the track located in the upper machine frame. The inner walls of the coke guide are built up with replaceable U-channels to form a smooth surface. The coke guide trough arranged underneath the sidewalls, which is furnished with replaceable floor and side plates. The coke guide is advanced and returned by means of two hydraulic cylinders. During coke pushing, the coke guide is locked through a hydraulically operated device.
The coke guide is housed-in by stainless steel plates to avoid escaping of emissions. On the rear end, the housing extends into the main hood. On the front end, on the vertical portion of the coke guide housing spring loaded sealing strips are installed which are pressed against the buck stays during forward movement of the coke guide car. A coke breaker is mounted at the coke guide rear end upper part to transfer the coke cake safely into the coke receiving car.
The coke guide and transfer car has a hood for door emission collection. The coke guide and transfer car is equipped with a door emission collection system. It is the task of the system to collect the emission from the open oven and which are transferred by thermal effect to the top of the machine as well as those emissions which are escaping from the door in cleaning position and to transfer them through the belt lifting car and suction duct to the land based filter plant of the pushing emission control system. Special type whirl hoods and booster fans are used for supporting the suction.
The main hood at the coke guide and transfer car is located above the car. The hood is of welded construction and is suspended in the machine supporting structure. It is the main task of the hood to collect all emissions escaping from the top opening of the coke receiving car, from the breaking coke when it leaves the coke guide, and from the coke guide housing and to transfer the dust laden air due to the suction caused by the exhaust fan of the filter plant through the belt lifting car into the collection duct along the battery.
The coke guide and transfer car is equipped with a device, which collects the spillage coke resulting from oven servicing. The device is located in front of the retracted coke guide and consists out of a movable and tiltable spillage coke collection pan. At the end of door cycle, the collected residues are dumped directly into the coke guide, ready to be pushed into quenching car at the following pushing cycle.
Regarding the door extractor as well as the door and frame cleaners, the same technology as being used for the pusher machine is used on the coke guide car and coke transfer car unit. This has the advantage of minimizing the spare parts, since most of the components are common.
Coke quenching car or coke bucket car with electric locomotive
In case of wet quenching, two different types of wet quenching cars are used. These two types are one which is used for conventional top spray quenching and the second which is used for coke stabilizing quenching. These cars are of robust design or can be self-propelled or locomotive driven.
The conventional quenching car is a fixed sloped bottom car with a pneumatically or hydraulically operated discharge gate. The flap opening mechanism is self-locking, so that no uncontrolled opening of the gates can occur.
The coke stabilizing quenching car has a fixed sloped bottom and is fitted with all facilities for coke box flooding and quick water drainage. The coke box is closed by two gates. The inner gate holds the coke inside the box, but lets the water drain. The outer gate holds the water inside the box.
In case of wet quenching and coke stabilizing quenching, the coke box of the quench car consists of the floor irons and covering plates which are laid upon them. The floor irons are laid on respective supports at the loading and unloading side and are secured with brackets which hold them in their position. Due to this, a quick exchange of the floor irons is possible without having to touch the base structure. In order to avoid the entrance of quenching water and coke through the horizontal joints of the steel plates and onto the bogie dedicated drainage channels are provided. With the help of this particular design the complete bogie and its structure are effectively protected from quenching water influence.
Coke dry quenching bucket cars are designed for receipt of coke having the temperature of 1,000 deg C to 1,050 deg C from the chamber of coke oven battery in its coke bucket and transports the bucket with coke by means of electric loco to the coke dry cooling plant for lifting and discharging of coke into quenching chambers of coke dry cooling plant. The bucket is designed to have a maximum of durability. Fig 5 shows coke quenching cars.
Fig 5 Coke quenching cars
The locomotive is normally designed to drive conventional wet quenching car, coke stabilizing quenching car, or hot coke bucket car. It is equipped with all on-board systems necessary to feed power and compressed air to the driven cars and can be operated in four different modes namely (i) man less (fully automatic), (ii) semi-automatic, (iii) inter-locked manual mode, and (iv) repair / maintenance mode. In case of wet quenching and coke stabilizing quenching, the locomotive has also the function to supply electrical power and compressed air to the discharging flaps driving system.
Door service car
To ensure a trouble-free coke oven battery operation, regular monitoring and maintenance of the oven doors is absolutely essential. For this purpose, it is necessary to undertake all the required adjustments and to carry out needed repairs on the individual doors without interrupting the actual operation of the coke ovens. This is done with the help of the door service car. Fig 6 shows a door service car.
Fig 6 Door service car
With the help of the door service car, all necessary maintenance work can be carried out at the oven doors without utilizing movable platforms, scaffolding, or other temporary devices. The door service car normally hangs from a T-support, which is mounted with cantilever to the battery’s buckstays. It is travelled by an electric drive with feed by on board batteries. When not in operation, the door service car is parked in coal tower area and is connected to the power network in order to keep the batteries always charged.
The door service car is normally equipped with adjustable service platforms which ensure easy access to any part of the oven doors which needs servicing. All tools and monitoring devices required for this special kind of work – up to and including an appropriate energy supply is made available on the door service car.