Self-description of the coke oven exhaust gas system

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The coke oven exhaust gas system plays an important role in coke ovens; it includes components such as the combustion chamber, regenerator, chute area, small flue ducts, exhaust gas trays, flues, and 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 gases is generated by the exhaust gases 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 gases 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. But it sometimes emits some black smoke due to changes in the furnace conditions 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 significant leaks, large amounts of raw gas pass through the furnace wall into the opposite vertical flue, disrupting the normal operation there. Neither the return 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 black smoke is then expelled through the chimney. It has a darker color and a shorter 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 gas enters the combustion chamber normally, while another portion leaks through the gaps in these brick channels into the regenerator or smaller flue ducts as a downward-flowing gas stream, resulting in incomplete combustion in most cases. 　In the third case, the amount of smoke emitted from 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 malfunction 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 the 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 gas exchange volume that caused black smoke. The exchange valve of a certain upward airflow suddenly got stuck, causing gas to continue to be emitted from the corresponding flue during downward airflow. The emitted 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 cases that will not be discussed here. 　In short, the actual conditions of each coke oven, as well as differences in the operational skills of the staff and the level of workshop management, lead to varying situations. This requires us to analyze things based on the actual circumstances, rather than following templates or making arbitrary judgments.