Reasons for difficulty in pushing coke out from large areas of coke ovens and quick solutions

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Packed coke ovens have significant advantages over top-charging coke ovens in terms of conserving coking coal resources, improving coke quality, reducing production costs, and increasing corporate profits; therefore, many coking enterprises use the packed coking process for production. However, once it becomes difficult to push coke out on a large scale in a rammed coke oven, due to the high bulk density of the rammed coal cakes, using conventional manual methods for removing the coke results in a long processing time and significant difficulties, thereby severely affecting normal production operations. 1. Analysis of the reasons for difficulty in pushing coke out of rammed coke ovens. When large-scale difficulties arise in pushing coke out of rammed coke ovens, it is necessary to rule out the impact of defects in individual carbonization chambers; therefore, a thorough analysis should be conducted from three aspects: coal blending quality, fluctuations in furnace temperature, and equipment defects, in order to identify the main causes and take targeted measures to address them. 1.1 Reasons related to coal blending quality: The quality of the coal used in blending is extremely important. When the volatility of the coal is low, its shrinkage rate is small, and its cohesion is poor, it becomes difficult for the coke to shrink during the coking process, which can lead to difficulties in removing the coke from the furnace. 1.2 Reasons for furnace temperature fluctuations: A too low or too high temperature in the coke oven can lead to over-oxidation or under-oxidation of the coke, resulting in poor contraction of the coke or excessive fragmentation of it; in severe cases, it can make it difficult to remove the coke from the oven. 1.3 The cause of equipment defects is the widening of the coal box width, which increases the width of the coal cake and can also lead to difficulties in pushing the coke out. 2. Quick solution: Once a situation arises where it is difficult to push the coke out on a large scale, personnel should be immediately mobilized to analyze and test the quality of the coal mixture, measure the width of the coal bins, and analyze changes in furnace temperature, so as to obtain accurate data and make timely adjustments to prevent the situation from worsening further. 2.1 If the quality of the coal mixture changes, it is necessary to adjust the ratio of coal used in firing promptly, empty the existing coal in the coal tower, and use appropriate raw coal. 2.2 If the furnace temperature fluctuates, the heating regime should be adjusted promptly to stabilize it. 2.3 If the equipment has defects, the width of the coal tank should be adjusted to meet the design specifications. Along with the adjustments mentioned above, the key issue to address is how to remove the coke from the existing furnace chambers where it is difficult to extract. It is not recommended to use manual methods for removing the coke. Our plant has encountered situations where it was difficult to remove coke on a large scale; in such cases, we adopted a method involving cooling and contraction – by lowering the furnace temperature, the coke and the furnace walls contract, thereby increasing the distance between them, which allowed us to successfully remove the coke from all 100 furnace chambers with difficulties. The specific implementation is as follows. (1) Reduce the consumption of coke oven gas to lower the overall furnace temperature. (2) Based on the temperature measurement data, for the furnaces with excessively high temperatures, the gas control valves should be closed to rapidly lower the temperature. (3) Open the rising pipe and dust removal hole covers of the coke ovens that are difficult to cool, in order to achieve rapid cooling. (4) When the temperature of the coke oven in question drops to around 1100°C or when the temperature control period exceeds four hours, it is necessary to check the coke contraction gaps from the top of the oven and on the machine side to determine whether conditions are suitable for removing the coke. At our plant, when the furnace temperature drops to around 1050°C, it is difficult to push the coke chamber out smoothly. The cooling and contraction coke pushing method is simple, fast, and practical; it can significantly reduce waste of manpower and resources. However, the reduction in furnace temperature, along with the opening of the rising pipe and dust removal hole covers, causes the gaps between bricks to widen and the sealing graphite to burn, resulting in leaks in the coke oven and black smoke coming from the chimney. By reducing the furnace temperature while strengthening the adjustment of the upper large spring, increasing the protective pressure and raising the pressure in the gas collection ducts (by 40–50 Pa compared to normal operation), high-level heating of the coke oven can be ensured, and the leakage issues will be eliminated in a short time, returning things to normal levels. 3. Conclusion In summary, in ramming coking, more attention should be paid to daily production management to avoid situations where coke is difficult to push out. In the event of large-scale difficulty in pushing coke, the above methods can be used to handle the situation quickly and effectively.