Reheating of the coke oven

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Reheating of the coke oven: If reheating the coke oven is independent of whether the blower is running, that is, if the gas pipeline remains at a normal gas pressure, the gas can be directly supplied to the oven to resume heating. Whether heated with coke oven gas or lean gas, the gas can be fed directly into the furnace. It should be noted that previous regulations stipulated that after stopping heating, feeding blast furnace gas into a regenerator containing a large amount of air posed an explosion risk; it was necessary to first heat it with coke oven gas before switching to blast furnace gas. However, in daily production when using lean gas for heating, it is inevitable to feed the lean gas into a \"regenerator containing a large amount of air\"; that is, each time gas is exchanged, it is fed into a \"regenerator containing a large amount of air\". Actual sampling and testing showed that during the exchange process, exhaust gas samples were taken from the downward-flowing gas 3–5 seconds after the gas supply was turned off, and until the exhaust gas exchange was complete, the exhaust gas samples contained 60%–85% air. This is because after the gas is turned off during the exchange process, the resistance in the circulation system decreases, which increases the suction in the small flue; as a result, the amount of air entering increases to about 1.5 times the original level. After the exhaust gas exchange is complete, this sufficient amount of air allows the downward-flowing gas to pass through. The reason no explosion occurs under these conditions is that the mixing area of gas and air in the flow channel is small and is separated by the exhaust gases produced by combustion, preventing the formation of explosive gases; hence, no explosion takes place. Therefore, when resuming heating, even when using lean gas for heating, there is no need to switch to rich gas for heating; similarly, for single-heating type coke ovens, there is no need to first introduce a small amount of lean gas. The following discusses the detailed steps for reheating when using furnace gas for heating. 1. Start the blower: The blower should be started when there is a certain pressure in the air collection duct, which generally should be above 200 Pa. If the stop time of the blower is short, and the raw gas system up to the blower is still filled with qualified gas and the pressure in the gas collection pipe meets the requirements, the blower can be started. If the blower is shut down for an extended period, the waste gas system is not in a condition to be filled with qualified gas; it is necessary to push the coke back and load coal again, and guide the gas into the gas collection pipe and suction pipe until it reaches the blower. A burst test must also be passed, and the pressure in the gas collection pipe must reach the specified value before the blower can be started. Before pushing coke and loading coal, the ammonia spraying condition in the bridge pipe should be checked; coke pushing and coal loading can only proceed after confirming normal spraying. Starting the blower must be approved by the on-duty gas supervisor. If the vent pipe remains open after the blower is started, it should be gradually closed as the amount of gas drawn from the furnace increases, in order to maintain the pressure in the gas collection pipe at a level not lower than that during normal operation. If the pressure drops too low, the blower should be notified to make adjustments. 2. Purging of coal gas pipelines: If the blower is stopped for a short period of time and the pressure in the coal gas pipelines leading back to the furnace remains above 200 Pa, it is not necessary to purge the pipelines. Once the pressure in the branch pipes rises to an adequate level after the blower is started, the coal gas can be fed into the furnace. If the gas pipeline leading to the furnace is at a slight positive pressure when the blower starts, ventilation can be carried out at the end of the branch pipe for some time after the blower is started; only after a burst test is successful can the gas be fed into the furnace. When the blower is shut down for an extended period and the pressure in the coal gas pipeline returning to the furnace has dropped to atmospheric pressure, the gas in the pipeline should be replaced. (1) Before purging, check that the control valve is closed, ensure the water seal is filled with water, and open the vent pipe. (2) Purge all coal gas pipelines returning to the furnace with steam or an inert gas, and vent at the ends of the branch pipes. When using steam purging, the steam application time should not be too long; purging can be stopped as soon as steam appears in the vent pipe, and gas conversion steam can then be used. (3) Take gas samples before the vent pipe for an explosion test until it passes. The explosion test tube should be prepared in advance; the sample should be ignited in a location far away from gas sources, and testing is not allowed in basements, switchgear rooms, or flue corridors. 3. Supplying gas to the furnace: Once the above explosion test is successful, gas can be supplied into the furnace. Before feeding gas into the combustion chamber, restore the inlet opening degree and the suction force in the smoke ducts. Since this is a restart of heating, it can be fed into the furnace at once using the switch. It is also possible to manually feed air into the furnace in groups; this method is generally used when the furnace temperature is low, as it makes it easier to deal with burners that fail to ignite. When delivering gas, gradually close the vent pipe according to changes in gas pressure. When switching the furnace set to normal heating, pay attention to the following: (1) Do not resume heating of other furnace sets simultaneously. (2) No other furnace groups shall engage in gas exchange (except for coke oven groups). (3) Pushing coke out of the furnace shall not be carried out while purging the pipes or feeding gas into the furnace. (4) There shall be no open flames in the basement or near gas pipelines; welding and cutting operations are prohibited, and oxygen and gas cylinders must be removed from the furnace area. 4. Furnace unit monitoring: After gas is supplied to the entire furnace, adjust the opening degrees of each valve. Gas pressure or flow is automatically adjusted, and the flue suction is automatically adjusted to restore operation. The frequency of checking and monitoring the furnace temperature should be increased compared to normal production in order to prevent abnormal temperatures from occurring. Once the furnace temperature stabilizes, proceed with normal temperature measurement. Thereafter, adjustments were made gradually to achieve the appropriate damper opening, tuyere pressure, as well as suction in the air system and flue ducts.