Why do coke oven chimneys need to be in hot standby?
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I am an outsider when it comes to coking, so my questions are rather superficial; I hope experts can answer them: 1. Why do coke oven flues need to be kept warm in advance, instead of using a suction fan like in power plants? Is it because of the high electrical consumption of the blower? 2. What impact does the inability to discharge coke oven flue gas have on coke oven production?
Generally, there is waste heat recovery behind the flue; the exhaust fan is part of the waste heat recovery system, and it enters the chimney only after the heat has been recovered.
The coke oven is equipped with complex thermal systems, and its power source is the chimney, which relies on natural suction to expel the waste gases generated by the burning process in the coke oven. Therefore, in order for the chimney to have sufficient suction, it must be at a certain temperature! !
If the flue gas from the coke oven cannot be discharged, will the coke oven explode?
This question is posed in a rather odd way. If there is no power source to drive the exhaust gases out, then how can gas and air get in? If the gas has pressure, it can be introduced, but without a power source, air simply cannot enter the coke oven combustion system! !
Theoretically speaking, by installing exhaust fans at the top to draw out the coke oven flue gas, it is possible to meet the suction required for heating the coke oven, while also making rational use of the heat contained in that flue gas for preheating and recovery. Currently, exhaust fans are installed in both the waste heat recovery systems for coke oven flue gas and the desulfurization and denitration devices to draw out the flue gas from the coke ovens. However, heating the coke oven is a complex process; in the event of a failure in the exhaust fan, it is necessary to maintain an appropriate suction level in the flue ducts, to prevent situations where gas supply is interrupted too late or where there is severe leakage from the coke oven, which could result in the gas not being able to burn completely and thus the formation of explosive gases. Therefore, the coke oven chimney must be kept in hot standby. That is, after the recovery of waste heat from the flue gas, the temperature of the flue gas must not only be above the dew point temperature to reduce corrosion in the economizer, but it must also meet the suction requirements of the coke oven chimney. If the suction power of the chimney is too low, serious gas leaks and explosions can indeed occur.
Thank you to the moderator for the answer; I’ve learned something, thanks!
However, I heard from the workers in the coke oven area that when the entire plant loses power or its main equipment fails, it is necessary to completely close the dampers in front of the chimneys in order to maintain heat inside the coke ovens for an extended period of time. In this case, the flue gas should not be flowing. At this point, the gas supply must have been cut off, but leaks in the carbonization chamber cannot be completely avoided. Is there a risk of explosion at this time? If there is a risk of explosion, how should the risks be controlled?
The flue gas from coke ovens is expelled through negative pressure generated by thermal buoyancy; without this heat, the flue gas cannot be discharged properly
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When heating is stopped, the gas supply is cut off, but the exhaust gas still needs to be exchanged every hour or so, with the damper opening reduced to around 5-10 mm