Self-description of the coke oven exhaust gas system and data on commissioning trials
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(The double-bottom injection type coke oven) is akin to “reading the signs by observing the smoke.” The coke oven exhaust gas system plays a vital role in the coke oven; it includes components such as the combustion chamber, regenerator, chute area, small flues, exhaust gas trays, flues, and the main flue. Everything is interconnected; if there is a problem with any one component, it can affect the proper heating of the gas in the combustion chamber. The suction required for the flow of coke oven exhaust gas is generated by the exhaust gas at temperatures of 200 to 300 degrees Celsius in the chimney. By adjusting the dampers, the exhaust gas flaps, as well as the flaps of the individual smoke ducts and the main smoke duct, it is possible to change the suction in the coke oven, and thereby adjust the flow rate of the exhaust gas from the coke oven. With the coking time fixed, the opening degrees of these adjustment components remain essentially unchanged. In stable coking production, no smoke can be seen coming from the tall chimneys; the exhaust gas they emit is as clean as the gas used in household stoves. However, it sometimes emits some black smoke due to changes in the furnace condition or the occurrence of unexpected situations. What exactly can black smoke tell us for those of us working in the coking industry? I would like to share my views on the situation regarding a few coke ovens, for reference only. In the first case, there is leakage through the furnace wall. After coal is added to the carbonization chamber, both the amount of gas produced and the pressure on the surface of the furnace wall are high. In the event of a large leak, a large volume of raw gas passes through the furnace wall into the opposite vertical flue, disrupting the normal operation there. Neither the returned gas nor the raw gas can burn properly, and they mix with the exhaust gases as part of the downward-flowing air; some of this gas burns partially in the regenerative chamber, and the resulting smoke is then expelled through the chimney. It has a darker color and a short emission time, usually ranging from a few minutes to a dozen minutes. If the smoke production is heavy and intense, it indicates severe leakage through the furnace walls of the carbonization chamber. Secondly, the chimney is always filled with smoke; in the absence of leaks in the furnace walls, this may be due to insufficient combustion of the gas in the vertical flue. There may be a significant amount of leakage from the brick gas channels; that is, some of the gas enters the combustion chamber normally, while another portion leaks through the gaps in these brick gas channels into the regenerative chamber or small flue as a downward-flowing gas stream, resulting in incomplete combustion in most cases. In the third case, the amount of smoke emitted by the chimney changes regularly as the heating gas is exchanged, with the amount of smoke during a particular exchange always being higher. There are various reasons for this situation, most of which are related to the exhaust gas exchange equipment. For example, if a certain exhaust gas tray gets stuck frequently, it increases the negative pressure of the upward airflow, slowing down the movement of air upward; as a result, unburned gases are generated in the corresponding flue. B Some air dampers are not fully closed, resulting in insufficient suction in the corresponding downward-flowing flue. A failure in one of the exhaust trays prevented it from being lifted, which stopped the exhaust gases in the corresponding flame channel from being discharged; as a result, gas continued to flow into that flame channel, generating large amounts of black smoke. This smoke gradually spilled over into the upward airflow of adjacent rows through the ceiling space, disrupting the combustion in those flame channels. The extensive replacement of nozzles in basement D was carried out in a disorganized manner, resulting in an excessive amount of gas exchange and black smoke. The exchange valve of a certain upward airflow suddenly got stuck, causing gas to continue to be released from the corresponding flue during downward airflow. This released gas was drawn directly into the regenerator through its own inclined duct, resulting in a large amount of black smoke. In the fourth scenario, suddenly a large amount of black smoke emerges from the chimney. There are three scenarios: the pressure in the main pipe increases momentarily, the flow rate of gas entering the flue increases, resulting in black smoke; once the pressure in the main pipe returns to normal, the black smoke disappears on its own. There is a problem with the exhaust gas circulation system; the exhaust gas valve is in neither an open nor a closed state. As a result, the positive pressure at the top of the furnace increases, and black smoke accumulates in the vertical flue. After some time, the smoke starts to flow downward through the smaller flues. A circuit mix-up occurred in the C switch, causing air and gas to flow in opposite directions. There are some other situations that will not be discussed here. In short, the actual conditions of each coke oven, as well as the differences in employees’ operational skills and workshop management levels, lead to varying situations. Therefore, it is necessary for us to analyze these situations based on the actual conditions, rather than copying others or making arbitrary judgments. This post was last edited by goudan020 on 2009-3-6 19:49]
Commissioning trial operation of the coke oven: The trial operation of equipment related to the startup of the coke oven includes the trial operation of individual units as well as the coordinated trial operation of related equipment. Interconnected trial operation can only be carried out on the basis that the individual units have passed their trial operations. Equipment that needs to be tested under hot conditions cannot be tested under cold conditions. 1. Commissioning of switches and switching systems The commissioning of switches and switching systems must be completed entirely before normal heating is resumed. 2. Trial operation of coke oven moving equipment The coke oven moving equipment includes coke pushers, (or coal-loading coke pushers) and coal-loading cars, coke catchers, coke quenching cars (or coke tank cars), roof dust collection cars, etc. All these devices must be tested and operated properly before starting work. 1) Coke pusher (or coal-loading coke pusher), coke stopper – When using solid fuel for heating the furnace, load testing of the coke pusher and coke stopper can be carried out after removing the external furnace. If a gas fuel furnace is used, in addition to the traveling mechanism which needs to be tested after being switched to normal heating, all other mechanisms should also be tested in advance. Traveling mechanism: Operate continuously along the track more than 5 times until it meets the requirements. Check the sensitivity of the operation and braking systems, examine the distance between the coke pusher and the furnace body, adjust the position of the safety barriers, and check the sliding contact between the friction wires and the sliders. Air compressor: The trial operation time of the air compressor should be no less than 48 hours. Door opening mechanism: Tests are conducted on the furnace door frame at the furnace door repair station to check whether the operations for opening and closing the furnace door, as well as those of various devices, function properly. Pusher rod: Pushing operations are tested on the artificial carbonization chamber bottom installed at the pusher rod repair station. The toothed plate and the tooth wheel of the coke pushing rod must engage properly; there should be no misalignment ； The pusher rod must move smoothly, and its center line of movement must be accurate ； The travel distance must meet the design requirements ； The sensitivity and accuracy of the circuit breakers and limit switches must be high. The elevation of the push rod matches the thermal elevation at the end of heating the bottom of the carbonization chamber; that is, during the pushing process, the bottom surface of the push rod head is 20–25 mm higher than the bottom of the carbonization chamber. Therefore, it is necessary to ensure that the bottom surface of the push rod slider is lower by the same amount compared to the bottom surface of the push rod head. Since the push rod bends downward during the coke pushing process, the bottom surface of the slider should be 30–50 mm higher than the bottom surface of the carbonization chamber before it enters the latter. Flat coal device: Test the mechanism for opening and closing the small furnace door on the furnace door mounted on a fixed door frame, and adjust it until it is proper. Tests are conducted on flat coal rods at the flat coal rod replacement station to check the deviation and stability of their center lines, as well as the sensitivity of the limit switches and the accuracy of their travel distance. Focal guide device: Check the travel of the focal guide grid, the elevation of the base plate, and the relevant positions of the grinding plates. 2) Coal loading car and coal loading system: Before testing, all tracks and sliding wires were adjusted properly; the coal tower was cleaned thoroughly, and the manual operation of the coal tower’s discharge nozzle was found to be satisfactory. All components of the coal loading car were adjusted to meet the requirements after testing. Traveling mechanism: Operate back and forth along the track more than 5 times until it meets the requirements; check the operating condition as well as the condition of the sliding rails and make adjustments; also check the operation of the compressed air system. When checking the sliding contact between the slider and the friction wire, the coal car should be loaded with coal. Coal loading mechanism: Conduct opening and closing tests on the coal taking nozzles in the coal tower to check the sensitivity of the limit switches. Conduct lowering and lifting tests on the coal hopper gate sleeve to inspect the positions related to the furnace body. Conduct tests on the opening and closing of the coal hopper gates as well as tests on the function of the coal shaker. Conduct tests on disk or screw feeders. Conduct adjustments to the electromagnetic or mechanical mechanisms for opening the furnace lid, etc. Coal tower scale: Adjust it so that it can give accurate measurements. 3) Wet quenching cars and dry quenching systems Traveling mechanism: Operate back and forth along the tracks more than 5 times to check the stability of movement, verify whether there is any track damage, inspect the sliding condition between the contact wires and sliders, and check the sensitivity of the circuit breakers. Focusing mechanism: Check the flexibility of the focusing gate in opening and closing, as well as the accuracy of the limit switches. Dry quenching coke tank: Tests are conducted on the opening and closing of the gate at the bottom of the coke tank, on the pulling operation of the coke tank car, and on the lateral movement of the coke tank. Operations such as lifting, moving horizontally, lowering, and discharging coke (loading coal into the dry quenching tank) are repeated until the system is properly adjusted. 4) Trial operation of the tamping station for tamped coke ovens: Coal-retaining plate test: A no-load test using a coal-retaining plate is conducted on the bottom of the simulated carbonization chamber to check the center line, elevation, and stability, etc. Rammer: Conduct tests on the movement of the ramming hammer and the ramming process, as well as actual ramming tests using coal material with specific particle sizes and moisture levels. Test of ramming coal cakes at the bottom of a fake carbonization chamber, measurement parameters. 5) Roof smoke removal vehicle The roof smoke removal vehicle should be tested and adjusted. 3. Trial operation of the furnace door repair station: Each furnace door frame was tested simultaneously during the trial operation of the moving equipment; if any issues arose, they had to be addressed promptly. Individual test run of the winch: Perform various operations such as lifting and flipping the furnace door repeatedly until it meets the requirements. 4. Pre-production of the wet quenching system: (1) Before spraying water, check the spray pipes and nozzles inside the quenching tower; they are considered acceptable if all of them are unobstructed. (2) The coke quenching tower itself, spraying pipes, pump house, powder coke tank, and grab have all passed the acceptance tests. (3) Install the upper and lower pipes and connect them to water supply; fill the tank with water. (4) All water pumps, motors, and accessories have passed inspection. (5) The drain pipes must be unobstructed. (6) When putting it into operation in winter, the steam pipe for temporary heating should be connected and supplied with steam before filling the tank with water. The heating system in the pump room has been installed. (7) Conduct pre-production of the wet quenching system; after tuning, ensure normal spraying, with a total trial spraying time of no less than 2 hours. 5. Pre-production of the dry quenching system: (1) The dry quenching system has passed the acceptance inspection. (2) Conduct opening and closing tests on the coke discharge gate at the bottom of the coke drum. (3) Conduct traction operation tests and lateral movement operation tests. (4) Repeat the operations of lifting, translating, lowering the coke drum, loading coke, lifting, translating, lowering, etc., until it passes the debugging test. (5) Heat the dry quenching furnace to 800°C. 6. Pre-production of the gas collection system Pre-production of the gas collection system includes testing for leaks in the gas collection pipes, supplying air through the steam pipes, supplying water through the clean water pipes, supplying ammonia water through the ammonia pipes, conducting ammonia water spraying tests, as well as supplying and draining water through the water seals in the rising pipes. Generally, all tests should be completed 1 to 2 days before coal charging into the coke oven. (1) The intake pipe has passed the pressure test; after conducting final inspections of the collector pipe and intake pipe, the access hole is sealed and the cleaning hole is covered tightly, with a thorough inspection of components such as the joints. (2) The suction pipe disc valve operates smoothly, with clear markings for the fully open and fully closed positions. All instrument equipment in the control room has been installed and tested. (3) The flap switches for the bridge pipe and the vent pipe should be flexible. (4) The ammonia pipeline pressure test passed successfully; the ammonia nozzles are in good condition, the ammonia pressure gauge is functioning properly, and all valves operate smoothly. (5) The ammonia water pump room passed the load test successfully. (6) The steam pipes have passed the pressure testing, the insulation layer has been installed, and components such as pressure gauges and condensate drain pipes have been installed. (7) Conduct a comprehensive inspection of the clean water system; the pressure test passed. (8) Thoroughly inspect the distribution of blind plates in all pipelines; those that need to be removed should be removed. (9) When feeding steam into the steam pipe, slowly open the valve to gradually increase the pressure to the design pressure. Check the tightness of the pipelines and whether they are blocked. It is particularly important to open the valve on the condensate drain pipe to verify that the condensate system is unobstructed. In winter, attention should be paid to preventing freezing. (10) Testing the ammonia pipeline with ammonia: Gradually open the main ammonia valve and check for any leaks, addressing any such issues. Check whether the pressure of the ammonia solution meets the design requirements. When a coke oven to be put into operation shares an ammonia water pump with an already operating coke oven, it is also necessary to check whether this affects the ammonia water pressure of the already operating coke oven. (11) After the ammonia water is supplied, check the spraying condition of each nozzle under ammonia water pressure (0.1–0.15 MPa). The spraying area should be even, and ammonia solution must not be sprayed into the rising tube. If it does get sprayed into the rising tube, this is usually due to uneven machining of the flange surface where the ammonia nozzle is installed at the top of the bridge tube; this issue can be resolved by replacing the nozzle or adding shims. (12) After the ammonia water is supplied, it should be continuously circulated until operation begins. When it is necessary to stop the transport of ammonia due to repair work resulting from an accident, it is best to continuously feed clean water, especially in winter, to prevent the pipes or fittings from freezing. If the supply of ammonia solution is stopped for too long, an excessive amount of clean water will flow into the ammonia clarification tank, which is not desirable. The supply of clean water should be stopped and the pipes emptied. (13) Fill the clean water pipe with water to check for leakage points and address them promptly. (14) Supply water to the upward riser water seal cover, and complete the commissioning 1–2 days before startup. 7. Instruments: All coke oven instruments and analog sampling equipment have been installed and passed inspection, and the instrument calibration work has been completed. 8. Others In addition to the above, there are other devices such as dust collection systems, coal handling equipment, and lifting equipment, all of which should also be tested. The communication facilities within the factory must be functioning properly. 9. Joint trial operation of mobile equipment The joint trial operation of mobile equipment should be carried out after the fire bed is cleared and before coal is loaded. Select the carbonization chambers at both ends and the middle section for joint trial operation. The equipment should be operated in accordance with the procedures specified during normal production. Before the joint commissioning, each piece of equipment must undergo individual testing, and the coke pusher rod must be repeatedly tested in a simulated carbonization chamber bottom. The elevation of the fake carbonization chamber floor must be consistent with the hot-state elevation of the carbonization chamber floor. The ramming coke oven coal packing plate must also be tested by pushing it at the bottom of the pseudo-coking chamber. The sequence for the joint commissioning is as follows: (1) Remove the machine and the furnace door on the coke side. (2) To the upper guide groove. (3) Send a communication signal once the coke quenching vehicle (or coke car) reaches the position under the coke guide chute for receiving coke. (4) Push the coke after receiving the signal; if there are debris such as broken bricks at the bottom of the carbonization chamber during coke pushing, a wet straw bag can be wrapped around the end of the coke pushing rod to push the debris out of the carbonization chamber. (5) During coke pushing, the coke quenching vehicle moves to pick up the coke; after collecting the red coke, it goes to the coke quenching tower where water is sprayed to quench the coke and allow excess water to drain off, after which the coke is placed on the coke bed (if dry quenching is used, after collecting the red coke, the coke car moves to a lateral position, followed by a series of actions such as lateral movement, lifting, moving horizontally, lowering, and loading the coke). (6) After the coke quenching vehicle has collected the red coke, the coke pushing rod retracts, the guide grid of the coke stopper returns to its original position, the door on the coke side is closed, and a signal is sent to load coal. (7) The coal loading vehicle (empty) drives to the coal loading furnace to load coal, and returns to the coal tower after the operation is completed. In the case of ramming coal loading, after closing the furnace door on the coke side, try to push the coal floc plate without a coal cake from the machine side. (8) In the carbonization chamber of the coal-loading furnace, a test was conducted to open and close the small furnace door using a coke pusher; the coal leveling rod was extended to the entrance of the carbonization chamber and then retracted, without going inside the chamber (the operation test of the coal leveling rod was already carried out at the repair station). During ramming coal loading, after the coal-packing plate is retracted, close the furnace door on the shutdown side. Thus, the joint commissioning is complete. If any issues are detected during the commissioning, emergency repairs should be carried out immediately, followed by another attempt at commissioning.
Support, very objective and comprehensive!