What is the approximate temperature of the inner wall of the coke oven rising tube?
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The temperature of the raw gas coming out of the carbonization chamber is about 700°C. Then it directly enters the riser pipe. What is the temperature of the inner wall of the riser pipe? Is it possible that dropping to 270°C will cause a large amount of graphite to be generated?
The gas temperature in the rising tube changes with different coking time. Normally, the maximum temperature should be lower than 800 degrees. If the temperature at the fire hole rises around 630 degrees, the temperature will drop (heat dissipation in the rising tube). However, I personally think that it will not drop to 270 degrees even if it is lowered! ! ! Could it be the area before the circulating ammonia water was sprayed? !
"This is the first time I have heard that dropping to 270°C will lead to the formation of large amounts of graphite. Generally speaking, the higher the temperature, the more intense the formation of graphite.
Although graphite grows faster at high temperatures, it is not a unilateral reason. According to reliable theoretical analysis, the growth rate of graphite in the rising tube has a great relationship with the temperature difference of the inner wall. If the riser tube can be insulated, it will be very effective in controlling the growth of graphite. When the temperature of the inner wall is low, it is easy for tar and other condensation deposits, and when the temperature is high, cracking occurs to produce graphite. Both factors equally lead to accelerated graphite growth.
Mentioned in the textbook: When the inner wall temperature of the rising pipe is about 260--270°C, the sediment grows rapidly. If the cast iron rising pipe is insulated with cement-expanded perlite, the inner wall temperature rises to 460--470°C, and the sediment is less and loose. Based on these phenomena, it can be considered that the conditions for the formation of sediment conditions (commonly known as graphite) are:: First, the inner wall temperature is low, causing some high-boiling point tar fractions in the raw gas to condense on the inner wall surface. ； The second is that radiation or convection causes the condensed high-boiling tar fraction to undergo pyrolysis and thermal polycondensation to solidify. This temperature is at least above 550°C. The question is, can the temperature of the riser tube be reduced to 270°C?
The temperature at the riser bridge pipe should be around 600, and the temperature in the straight pipe section should be a little higher.