Prevention and treatment of graphite at the top of the coke oven charging chamber

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The 25th National \"Safety Production Month\" in 2026: Everyone should talk about safety and know how to handle emergencies; identify and eliminate potential risks and hazards. -------------------------------------------------- Thick layers of graphite on the top of the carbonization chamber is a common problem in the production of coke ovens. In the production management of coke ovens, various factors such as irregular coke oven suction pressure systems, improper heating procedures, and the failure to take cooling measures after the coal cakes collapsed lead to the accumulation of a thick layer of graphite on the top of the carbonization chamber. An increase in graphite leads to a rise in the temperature in the space above the furnace. When coal is added, this increase in graphite also creates resistance, resulting in the collapse of the coal briquettes and affecting production output. The collapse of these coal briquettes, in turn, causes an excess of space above the furnace, slowing down the flow of gas; the gas then undergoes secondary cracking, which further increases the amount of graphite, creating a vicious cycle. In the prevention and treatment of graphite issues, we must pay close attention to the production management of coke ovens; proactive prevention is far more crucial than dealing with problems after they occur. Therefore, I summarize my approaches to the prevention and treatment of graphite in coke oven production management as follows: 1. Prevention of graphite formation on the top of the carbonization chamber. From the perspective of coke oven production management, it is essential to ensure proper handling of the following aspects. 1.1 Pressure control of the gas collection duct The pressure in the gas collection duct is determined by maintaining the pressure at the bottom of the carbonization chamber directly below the suction duct at 5 Pa toward the end of coking. If the pressure in the gas collection duct is not properly controlled, the coke oven gas stays in the top of the carbonization chamber for too long, and fails to be discharged in a timely manner, which leads to secondary cracking of the coke oven gas. The main cleavage reaction equations are: C2H6 = C2H4 + H2; C2H4 = CH4 + C; CH4 = C + 2H2. 1.2 Control of the temperature at the gas outlet of the primary cooler: In the chemical product recovery workshop, the temperature at the gas outlet of the primary cooler should be maintained between 23 and 25°C. Excessively high temperatures can affect the flow of the gas, and the retention of gas can lead to further decomposition of the gas. 1.3 Control of the temperature in the furnace top space The temperature in the furnace top space refers to the temperature of the raw gas in the area above the carbonization chamber. According to the \"Regulations on the Technical Management of Coke Ovens,\" the temperature in the roof space should be maintained at 800±30°C, with a maximum of 850°C. If the temperature in this space is too high, coke oven gas undergoes secondary cracking at the top of the carbonization chamber, resulting in large amounts of deposited carbon adhering to that area. Excessively high temperatures also lead to poor quality of the tar recovered from the chemical processes; this is manifested by an increased specific gravity of the tar, higher viscosity, and difficulties in dehydration. 1.4 Appropriate standard temperature Setting an appropriate standard temperature is a very important aspect in production. If the standard temperature is set too high, it will result in excessive temperatures in the space above the furnace, causing the coke to over-cook; on the other hand, if the standard temperature is set too low, the coke will not cook properly. Therefore, it is particularly important to determine the standard temperature appropriately. The determination of the standard temperature can be based on the following aspects: 1.4.1 It can be determined based on the temperature at the center of the coke cake: The temperature at the center of the coke cake is an indicator of the maturity of the coke. In typical coke oven operations, the coke is considered mature when the temperature at its center reaches 1000±50°C. 1.4.2 The volatiles content of coke is used as a reference: it is generally specified that the volatiles content of coke should not exceed 1.9, while in our company’s production process, we require the volatiles content of coke to be between 1.2 and 1.5. 1.4.3 The temperature in the roof space of the furnace can also be used as a reference; generally, in coke oven production, this temperature should be maintained at 800±30°C. 1.5 Uniformity of temperature in the horizontal row Ensuring uniform temperature in the horizontal row is one of the most important aspects of thermal management in coke ovens. If the temperature is uneven in the horizontal direction, it will lead to chaotic heating in the entire combustion chamber’s vertical flue, resulting in uneven maturity of the coke cake; this in turn leads to overly high standard temperatures when setting them. This also leads to an increase in the temperature of the space above the furnace, causing secondary cracking of coke oven gas and accelerating the growth of graphite at the top of the carbonization chamber. 1.6 Proper implementation of the rising tube heating procedure: Open the covers of the rising tubes 10 to 20 minutes in advance according to the coke pushing schedule (no more than three at a time), close the water seal flaps on the bridge tubes simultaneously, open the covers of the dust removal holes located away from the rising tubes to allow air to flow in, thereby burning off the graphite at the top of the carbonization chamber. 1.7 Promptly clean the vertical flue in the combustion chamber at the site of collapse. During the coal loading process, if the compacted coal cakes collapse, it is necessary to take action promptly to address the situation in the vertical flue of the combustion chamber at that location. A common method is to reduce the amount of gas supplied, for example by inserting wires, in order to prevent excessive temperatures from affecting the temperature in the roof area of the furnace. 1.8 Improve the quality of coal cake compaction. 　　Improving the compacting quality of coal briquettes can effectively prevent an increase in the space above the furnace caused by the collapse of these briquettes, which in turn would lead to prolonged retention time of gas and subsequent secondary cracking. 2. Common methods for eliminating graphite For some time, our coke ovens faced issues due to a high proportion of weak coal in the coal mixture; this weak coal consumed a large amount of heat. To ensure the quality of the coke, we adopted a method of increasing the temperature during production. Additionally, since the ovens had not been in operation for long, the quality of ramming carried out by the rammers could not be guaranteed, which led to frequent coal collapse. As a result, carbon buildup at the top of the carbonization chamber became quite severe. 　　In coke oven production, common methods for removing graphite include: blowing compressed air at the graphite, cleaning the graphite by burning out the furnace, and using a scraper installed at the top of the coke pusher to remove graphite. The first two methods ultimately require manual tapping, but due to the long carbonization chamber of 5.5-meter coke ovens (with a length of 15.98 meters), manual cleaning or tapping is not very effective. The first two methods are somewhat effective for smaller coke ovens; in the past, we used the method of burning out the furnace to remove graphite from coke ovens with a carbonization chamber length of 2.8 meters, and it was quite effective. It presents certain difficulties for large blast furnaces. Our company’s 5.5-meter coke ovens use scrapers installed on top of the pusher heads, along with upward-flaming tubes, to deal with the graphite at the top of the carbonization chamber. 2.1 Scraping method for removing graphite In our pusher design, scrapers are installed at the two upper corners of the pusher rod; during the pushing process, these scrapers scrape graphite from the top of the carbonization chamber to create two grooves. However, the graphite in the central area cannot be removed in this way. Consequently, we added another scraper at the middle position on the upper part of the pusher rod, and the two scrapers are used alternately at these three positions. This way, the graphite can be removed. 2.2 Burning the rising tube: Open the covers of the rising tubes 10 to 20 minutes in advance according to the coke pushing schedule (no more than three at a time), close the water seal flaps of the bridge tube simultaneously, open the covers of the dust removal holes located away from the rising tubes, and introduce air to burn off the graphite at the top of the carbonization chamber. 　　By effectively combining the above two methods, we completely removed the graphite from the top of the carbonization chamber, thereby stabilizing the production of the coke oven.