What causes sudden large-scale leakage in coke ovens?
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This post was last edited by dmz329227 on 2023-5-30 at 12:34. We have 5.5m ramming coke ovens; after changing the mixture ratio, there suddenly occurred widespread leakage – many viewing ports showed leakage with black smoke and flames emerging. The current required to push the coke increased by about 10A, but there was no difficulty in pushing the coke. May I ask what the specific cause might be? Has anyone ever encountered a situation where there is suddenly a large-scale leakage?
Perhaps due to changes in the ratio, the bulk density and compressibility of the coke change, resulting in an uneven pressure distribution within the furnace; this causes certain areas of the kiln to be subjected to excessive pressure, leading to leakage. It is recommended to check for issues such as excessive porosity or unevenness in the coke inside the furnace; the quality and stacking method of the coke can be adjusted accordingly, as well as the mixing ratio. At the same time, it is recommended to clean the slag promptly to ensure the compactness of the top slag and prevent unnecessary damage to the furnace. For such issues, professional engineers should be contacted promptly to handle them. .
Be more specific about the situation – what are the coal blending specifications?
The coal mix used in the furnace has been changed; the new coal variety has poor shrinkage and a high coking rate. Small coke cake and furnace wall contraction gaps are the direct causes of an increase in the coke pushing current. As the pusher current increases, the abrasion of the furnace wall graphite by the coke cake during pushing is the direct cause of the leakage. Precautionary measures taken by our plant: strictly controlling the time during which the furnace door remains open to prevent graphite damage, especially during the period when the furnace is empty after coke pushing; ensuring proper operation of the smoke guiding equipment, high-pressure ammonia solutions, and coal loading systems. Reducing the coal cake height by 20-30 cm creates conditions for graphite growth in the furnace roof space.
Personally, I think it’s not a problem with the coal blend; we should consider the process aspects. Is there negative pressure? Large-scale leakage occurs when the graphite is burned up, and if the graphite burns, then air must have gotten in.
It is rare for changes in the coal blending ratio to cause widespread leakage; generally, multiple factors coming together are required for such a situation to occur. During normal production, the coal blending ratio, thermal management, and operational procedures are all very stable. Changing the coal blending ratio generally occurs when it is necessary to extend the coking time, when there is an imbalance among the different types of coal and it is required to ensure a longer available time for these coals, or in order to reduce the costs associated with coal blending (which are essentially production costs). Therefore, your analysis cannot be based solely on changes in the coal blending ratio; for example, if the coking time is increased, has your heating regime been adjusted accordingly? Although there was no difficulty in pushing the coke, the current required for this process increased. The mechanical stress generated by pushing the coke contributes to the expansion of cracks in the furnace walls and to increased deformation of those walls; this effect is particularly severe when it is difficult to push the coke. The analysis is not necessarily correct; it is for reference only!
The reasons for leakage through the furnace walls of coke ovens are roughly as follows: 1. Unreasonable heating regime: (1) If the pressure at the observation holes is too high, that is, if the pressure in the combustion system is too high, exhaust gases (containing a certain amount of oxygen) flow from the combustion chamber to the carbonization chamber, burning the graphite in the gaps between the bricks； (2) The pressure in the gas collection pipe is high, that is, the pressure in the carbonization chamber is high, which causes raw gas to flow into the combustion chamber ； 2. Changing the cycle time – that is, after the standard temperature is altered, the iron components (spring tonnage) are not adjusted in a timely manner ； 3. A change in the coal blending ratio resulted in the new blend having lower shrinkage, which increased friction during coke pushing and led to the loss of graphite from the furnace walls.