Practical approaches and methods for starting a coke oven with initial coal loading without releasing waste gas before operation

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Starting up a coke oven is a highly complex process that mainly includes steps such as the trial operation of various system equipment, switching the coke oven to normal heating mode, the first loading of coal and connection of the gas collection pipes, and the first extraction of coke. It involves significant safety and environmental risks. The raw gas generated during the initial coal charging is released through the rising pipe; it can only be integrated into the pipeline system once certain conditions are met, which not only pollutes the environment but also wastes energy. 1 Preparatory work before coal loading: All thermal-related works must be completed prior to starting up the coke oven; the coke oven heating system, locomotive system, etc. must be in a condition that permits the operation of the coke oven. Relevant processes such as coal handling, gas purification, and dry quenching of coke must also be ready for normal production of the coke oven. 1.1 Initial commissioning of the gas collection system 1) The initial commissioning of the gas collection system includes processes such as air leakage testing of the gas collection system, supply of steam via steam pipes, supply of water via industrial water pipes, supply of ammonia water via ammonia pipes, ammonia water spraying tests, and supply of water to the water seal in the rising pipe. 2) Adjust various types of valves or flaps, such as the gas collection pipe control flap, suction pipe butterfly valve, bridge pipe flap, and vent pipe flap; conduct pressure testing on the gas collection pipe, suction pipe, high and low pressure ammonia pipes, steam pipes, and industrial water pipes to ensure the system’s airtightness. 3) Turn on the low-pressure ammonia, adjust the valve for low-pressure ammonia, and maintain the pressure of low-pressure ammonia at the gas collection point at 0.2 to 0.3 MPa. Once the low-pressure ammonia circulation is operating normally, high-pressure ammonia is turned on, with the pressure of high-pressure ammonia maintained above 2.5 MPa. Check the spraying pattern of the ammonia nozzle; it should spray evenly in the correct direction, and ammonia must not be sprayed into the rising pipe. At the same time, check for any leaks in the ammonia pipeline, and close the valve after testing the spray. 4) After the insulation layer of the steam pipeline is installed, steam is introduced; the industrial water system is thoroughly inspected, and water is supplied to the water seal at the rising pipe. 1.2 N2 purging operation: Before loading coal into the coke oven, it is necessary to purge the gas conduit from the coke oven’s gas collection system to the exhaust fan with N2, in order to remove the air from the coal gas pipeline. Once the oxygen content is within acceptable levels, the pressure is maintained. During coal loading, the generated waste gas is used to displace N2, thereby completing the replacement and connection of the gas system. 2 Initial coal charging and raw gas extraction operations 2.1 Requirements for initial coal charging 2.1.1 Requirements for the coaling used in the furnace: At the beginning of operation, the coaling used in the furnace should have good coking properties, high shrinkage, and a volatility content of over 28%, in order to facilitate proper sealing of the furnace. 2.1.2 Principles for initial coal charging During the initial coal charging process in a coke oven, the following principles must be followed in order to prevent or minimize gas leakage from the rising pipe as well as smoking and ignition at the oven door. 1) Implement an operation mode in which the coke oven does not release gases. Smokeless coal charging is carried out using high-pressure ammonia water, and the water seal valve flaps are opened in a timely manner before coal is charged into each carbonization chamber to connect with the gas collection pipe. 2) The coal loading amount shall be about 10% less than that in normal operation; coal shall be loaded in an uneven manner without opening the small furnace door, in order to reduce air intake. 3) After coal loading, adjust the blade edges of the furnace door on the machine side online, address any leaks in the furnace body promptly, and prevent smoking or fires from occurring. 2.2 Waste Gas Discharge Operation 2.2.1 Waste Gas Discharge Operation Before connecting the waste gas, set the automatic venting pressure to 500 Pa and put the automatic ignition venting device in automatic mode ； Before coal loading, remove the temporary blind plate from the riser pipe of the coal charging chamber and close the riser pipe cover. After coal loading, adjust the amount of circulating ammonia water sprayed into the carbonization chamber to ensure normal spraying, close the nitrogen filling valve on the gas collection pipe, closely monitor the pressure in the gas collection pipe, and timely adjust and control the amount of gas generated at the vent valve in order to gradually displace N2 from the gas collection pipe, suction pipe, and main suction duct. As the coal charging operation proceeds continuously, the raw gas is introduced into the gas collection pipe, and a combustion test is conducted at the release valve of the chemical cross-cooler. Once the test is successful, the release valve is gradually closed, while the inlet valve of the cross-cooler is gradually opened to full capacity, allowing the raw gas from the coke oven to enter the chemical cross-cooler. The outlet valve of the cross-cooler is then opened slowly; by controlling the opening degree of this valve and adjusting the opening degree of the coke oven’s flaps, the pressure before the cross-cooler is maintained at around 200 Pa. After the waste gas is connected, maintain the pressure in the gas collection pipe at 120–150 Pa, and control the opening degree of the flap between 30% and 45%. Once the pressure in the gas collection pipe is stable, the automatic adjustment flap for the gas collection pipe can be activated to achieve automatic control of its pressure. 2.2.2 Precautions for export operations 1) The coke oven must have its gas collection pipe relief valves, the rising pipe covers of the ovens that have been loaded with coal, and the flaps of the bridge pipes that have not undergone coal loading operations secured. 2) Implement isolation and safety warning measures for the connecting pipes to ensure the safety of the gas system as well as the safety of workers involved in construction and production activities in the area.