4.3 Analysis of coke side collapse in rammed coke ovens
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Since the commissioning of our plant’s 4.3-type ramming coke ovens (2*75 chambers, with an average width of 500 mm for the coke side, 510 mm on the machine side, and 490 mm on the coal side; the height of the coal cakes is 4 meters, and the cycle time is 24 hours), I have roughly estimated the rate of coke collapse on the coke side: it is around 6% per month. Although we made various efforts in the early stages, these efforts managed to reduce the coke collapse rate by less than 1 percentage point. Based on the actual conditions of our factory, I would like to discuss the reasons for the collapse of coke ovens in these types of ovens. I am also hoping to get the help of colleagues from Haichuan to keep the rate of oven collapse at its lowest level. Equipment issues: 1. After the coal carrier’s coal-supporting plate delivers the coal cake into the carbonization chamber and then retracts, the coal cake tends to lean against the door on the coke side due to inertia. As a result, after the coke matures, it also leans against the furnace door; when the door is opened, the coke at the top of the furnace begins to collapse. 2. The forward limit adjustment of the coal-supporting plate is not proper; when the coal-supporting plate delivers the coal cake to the side of the carbonization chamber facing the coke, the gap between the coal cake and the furnace door on that side is too large, which makes it easier for the aforementioned problem to occur. 3. When the coal support plate enters and exits the carbonization chamber, its movement is not very smooth, which causes longitudinal cracks to form in the coal cake from the top to the bottom during loading. As a result, cracks appear in the coal cake on the side facing the coke at a distance of around 1–1.5 M (this was the actual situation during the early stages of operation in our plant). When the coal support plate is retracted, the coal cake rests against the furnace door on the coke side. Note: Earlier, before coke was taken out of our plant, it was possible to clearly see through the smoke exhaust holes on the coke side of the furnace roof that there were cracks about 10 centimeters long in the coke cake at a distance of around 1–1.5 meters from the furnace door, which effectively illustrates the issue mentioned above. Heat regulation issue: 1. For coke ovens, vertical heating is necessary; however, it cannot be controlled too poorly or too well – either the upper part of the coke burns too much or the lower part burns too much. 2. Burner temperature: While ensuring that the coke is properly cooked, the burner temperature can be reduced appropriately. 3. Straight-run temperature. Solution: 1. Precisely calculate and measure the gap between the coal support plate and the door on the coke side; reduce this gap as much as possible while maintaining safety (30–50 mm is ideal). Our factory is currently implementing this approach. 2. The issue of uneven operation of the coal carrying plate – it has been resolved through equipment modifications, so I won’t go into details. (Our factory has basically resolved this issue; however, the coal cakes still have cracks, though their width is much smaller than before.) 3. Regarding temperature control, in addition to regulating vertical heating and the temperature at the furnace tip, if the temperature in the combustion chamber remains high for an extended period over 24 hours – that is, if the temperature exceeds the standard level by more than 20 degrees in three measurements – and no action is taken promptly, it can cause the coke in the adjacent carbonization chambers to collapse more easily. Note that I say “more easily,” not absolutely: I’ve done some estimates, and the rate of coke collapse due to excessive temperatures is around 30%). Therefore, improving temperature control in these three aspects can help reduce the occurrence of coke collapse to a certain extent. 4. Reduce the height of the coal cake on the coke side; the height of the coal cake on this side in our plant is less than 100 mm lower than that on the middle side. Reducing the height of the coal cake on the coke side by an additional amount, say around 1 meter, could help prevent the coke from collapsing. (Theoretical analysis; no specific data available. It’s presented for reference only. I recall that tamping coke ovens with a rating of 3.8 are less prone to coke collapse, and there must be reasons for that.)
Here’s some advice: I’ve worked on several coke ovens (serving multiple factories), all of 4.3 meters in length. On one hand, it’s necessary to strictly control the temperature at the oven tip; on the other hand, an appropriate standard temperature should be set. As for the height of the coal cake, it should be 3.8 meters on the machine side, 4 meters in the middle, and 3.9 meters on the coke side. There should be no problem in handling the above three aspects well.
Could you specify how wide each section is: 3.8 meters on the machine side, 4 meters in the middle, and 3.9 meters on the coke side? The machine and coke side of our plant is also around 1M, compared to the middle part. Do you have data on coke collapse on the side of a tamped coke oven? By adjusting the height of the coal briquettes and controlling the temperature properly, can coking failure be well controlled? This post was last edited by Topc on 2008-1-8 22:20 ]
Coking failure is not just a temperature issue; it is also related to the compaction of the coal cake. I’m on a business trip outside right now; I don’t have the previously recorded data with me
Okay, let’s keep in touch more often when we have time :lol. It’s easy to analyze the reasons, but finding solutions to the problems is harder, haha. Our workshop plans to make addressing the issue of coked coke a key focus for 2008; therefore, it’s necessary to establish relevant goals and implementation plans for this task, and I hope to get your help with that. If the height of the coal briquettes is reduced too much, it has an impact on production; therefore, I cannot simply propose this solution – it must be feasible before it can be submitted to the factory management
The furnace type is the same. We encounter this situation here as well; it is greatly influenced by the coal supporting equipment, the temperature at the furnace tip, the ramming method, and the time taken. First, check and rule out any issues with the coal supporting plates as well as the gap between the coal box and those plates. Additionally, with the coal mixture remaining unchanged and the furnace temperature constant, you can observe the performance of coal compaction during each shift. Check whether the compaction fails in every shift, or if it occurs mainly in certain shifts, and whether there are any shifts in which little collapse occurs. Pay specific attention to the time taken for compaction in each shift: how high the layer of bottom coal is placed, and how long it takes to compact that layer; as well as how long it takes to compact the upper layer of coal. It’s not acceptable if the compaction of the bottom coal takes too long, especially when the coal is wet, as increased friction between the coal cake and the coal plate when lifting it leads to a reverse force that causes the cake to collapse. The same reason applies when the cake collapses on the machine side
Now, the higher-level control system can directly view the data
Comparing the coal feeding rates might also help identify some issues (suggestion; I don’t have detailed data)
I support the view from the 6th floor. Also, have you measured the height difference between the coal support plate and the bottom of the carbonization chamber? If it’s too large, it will definitely suffer from focus failure. .
I support your view. Let’s see if there’s any more.