Reasons for excessive oxygen content in coke oven gas, responsible departments, and control measures

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The oxygen content in coke oven gas is an important safety control parameter in the coking production process. An excessive oxygen level in the gas can result in the formation of explosive mixtures, leading to safety accidents. This paper conducts an in-depth analysis of the control measures for oxygen content in the negative-pressure coal charging system, providing ideas and strategies for controlling oxygen content in coking production practices, thereby facilitating safe production management in coking. With the development of China’s coking industry and the stringent safety management measures in place, the oxygen content in coke oven gas has increasingly gained attention as a crucial safety indicator in the coking process. Given that coke oven gas is toxic, flammable, and explosive, excessive oxygen levels can lead to the formation of explosive mixtures, potentially resulting in serious safety incidents such as explosions. However, during the coking production process, incidents of excessive oxygen levels occur from time to time, posing serious safety risks to subsequent processes. The following is an analysis and discussion of the reasons for excessive oxygen levels during production and the corresponding control measures. I. Analysis of the reasons for excessive oxygen content during coal loading and countermeasures (1) A malfunction occurred during coal loading, resulting in an excessively long loading time. At the beginning of coal loading, the pressure in the gas collection pipe is relatively high, mainly due to raw gas being drawn into the gas collection pipe ； Over an extended period of time, the pressure in the gas collection tube automatically adjusts to normal levels; as a result, the suction force increases, and large amounts of air are drawn into the system, leading to an excess oxygen level. Responsible positions: Coke pusher and coal loader driver, rammer driver. Control measures: The rammer operator should improve the quality of coal cake ramming in order to reduce the occurrence of cake collapse ； In the event of a malfunction during coal charging, the operator of the coke-pushing and coal-charging car should promptly inform the control room operator in the blower house. The control room operator shall then increase the pressure in the collecting main and make relevant records. (Previously, there was no notification or notifications were delayed; information was only provided when the chemical plant noticed any abnormalities and inquired about them. ) (2) The startup of high-pressure ammonia water is not carried out properly. When high-pressure ammonia is introduced into a coke oven, several problematic situations can arise: firstly, the high-pressure ammonia in one coke oven has not yet been turned off, while another coke oven already has high-pressure ammonia applied to it in preparation for coal loading ； Second, high-pressure ammonia water was turned on immediately, then turned off again, and turned on once more ； Third, during the coal loading process with high-pressure ammonia at one coke oven, high-pressure ammonia is also activated at another coke oven for a few minutes before it is turned off. Since the pressure in the gas collection pipe is automatically regulated, the improper activation of high-pressure ammonia solution causes the fan to adjust frequently, resulting in significant fluctuations in the pressure of the gas collection pipe. Air is drawn in when negative pressure occurs, which leads to an excess oxygen level. Responsible position: Top furnace operator. Control measures: When the coking time is extended, the top furnace operator should not activate the high-pressure ammonia solution for smoke guidance in advance; it should be activated only after the driver of the smoke guidance vehicle has positioned himself properly. Normal coking operations should resume with the usual procedures. (3) Start high-pressure ammonia solution in advance for coal loading. The side furnace door and dust removal holes of the coal loading machine have been opened; before the coal cake enters the carbonization chamber, high-pressure ammonia water is introduced, which can easily lead to the absorption of large amounts of air and result in an excessive oxygen level. Responsible position: Top furnace operator. Control measure: The top furnace operator should not turn on the high-pressure ammonia solution for coal loading in advance; it should be turned on only after the coal cake has been inserted. (4) The flap of the valve body for the operating furnace did not close in advance. After the coking time is extended, no raw gas is produced in the later stages of coking; yet there is still some time before coke pushing begins. At this point, if the negative pressure in the gas collection system increases or high-pressure ammonia water is introduced, air can easily enter through the furnace door and dust removal holes, resulting in an excessive oxygen content. Responsible position: Top furnace operator. Control measure: When the coking time increases, the top furnace operator should promptly close the flap of the furnace corresponding to the mature coke level, depending on its maturity status. II. Analysis of the reasons for excessive oxygen content during non-coaling processes and countermeasures (1) When cleaning the riser, high-pressure ammonia water is used to achieve \"fire suppression\". When cleaning the riser pipe, the valve flap is closed, while the dust removal hole cover and the riser pipe cover are both opened; then the air duct is activated to “suppress the fire” for the purpose of cleaning. Then, some of the riser workers, to save time, opened the valve flaps and released ammonia for cleaning (without having to move the air ducts back and forth or operate the valves), which caused a large amount of air to be drawn into the collection ducts, resulting in an excessive oxygen level. Responsible positions: shift leader, rising pipe operator, furnace top worker. Control measures: The shift leader should educate the workers and strengthen inspections; it is strictly prohibited for rising pipe operators to use high-pressure ammonia water instead of compressed air to extinguish fires” ； The furnace top worker must refuse to open high-pressure ammonia water in conjunction with the rising tube worker. (2) Air enters the tar box, gas collection pipe cleaning holes, etc. When the suction force in front of the cooler was high, the water seal in the tar box did not function properly, allowing air to be drawn in easily ； If the cleaning hole cover of the gas collection pipe is not properly sealed, or if the furnace door and the dust removal hole covers are not tightly sealed, air will also be able to enter when there is negative pressure in the gas collection pipe, all of which can lead to an excessive oxygen level. Responsible positions: Rising pipe operator, furnace top worker, furnace door operator, furnace door repairer. Control measures: The rising pipe operator should improve the management of the tar box to ensure its tightness, clean it regularly to maintain its openness, and keep proper records of inspections and any repairs carried out ； After the tar is removed from the gas collection pipe, the rising pipe must have its cleaning hole cover securely in place ； The furnace door repairer completes the repair of the furnace door to ensure that the edge is smooth ； The furnace door operators should intensify the cleaning of the furnace doors, while the furnace roof operators should pay more attention to the management of the dust removal hole covers to ensure their tightness.