What is an appropriate pressure level for the gas collection pipe? What are the reasons for too high or too low pressure? How should it be handled?

The poster should specify what type of furnace it is, as different furnace types have significant differences in exhaust pipe pressure. The excessive pressure is caused by a large amount of gas being generated in the carbonization chamber, and the raw gas in the gas collection pipe not being able to be discharged in time. However, the pressure inside the carbonization chamber should not be too high either; excessive pressure can cause the raw gas to escape into the atmosphere through the furnace door and other gaps. This not only leads to smoking and burning at the furnace door, damaging the equipment used to protect the furnace, but also deteriorates the operating conditions. The reason for too low pressure is the opposite: during the early stage of coking, gas leaks from the carbonization chamber into the combustion system, while in the late stage of coking, exhaust gases from the combustion system leak into the carbonization chamber. When the carbonization chamber is under negative pressure, air may be drawn into the chamber from the outside. In this case, during the early stages of coking, raw gas decomposes the hot furnace bricks to produce graphite, which gradually deposits in the gaps between the bricks, blocking those gaps and cracks ； At the late stage of coking, exhaust gases containing residual oxygen enter the carbonization chamber through the gaps between bricks; these gases first burn away the graphite deposited in those gaps, which is why the walls of the carbonization chamber are never airtight. As air leaks into the carbonization chamber, it causes the coke inside the furnace to burn. This not only increases the ash content of the coke, but also the ash resulting from the combustion of the coke erodes the furnace wall bricks at high temperatures, leading to damage to the furnace structure. Furthermore, the air that leaks in will burn part of the raw gas, resulting in a decrease in the production of chemical products and a lower calorific value of the gas; it also increases the amount of free carbon in the tar. When determining the pressure regime, the following principles must be followed: (1) The pressure at the bottom of the carbonization chamber should, under all circumstances (including normal operation, changes in coking time, delays in coke pushing, and cessation of heating), be higher than the pressure in the adjacent combustion system at the same elevation as well as the atmospheric pressure. (2) Within the same coking time, the pressure distribution in the vertical direction of the combustion system should remain stable. (3) The pressure at the top of the firebox should be close to ±0.

The pressure in the gas collection duct is not set arbitrarily; it changes according to the seasons. The general principle is to maintain a positive pressure at the bottom of the carbonization chamber (0-5 Pa). Excess pressure in the gas collection system can cause the coke oven to emit smoke and flames, polluting the environment, and it also results in the loss of valuable resources – gas ； If it is too small, a negative pressure will be generated in the coke oven, which will burn out the graphite in the furnace walls and lead to leaks in the oven structure; over time, this will also shorten the lifespan of the coke oven. As for how to handle it, we will follow the general principles.

A pressure of 60–80 Pa is appropriate; it is related to the amount of gas generated and can be adjusted through a small circulation system.

The furnace type is JN60-6. Our operating procedure specifies a pressure range of 80-120 Pa, but in practice we use a pressure range of 70-260 Pa

When determining the pressure in the gas collection pipe, the following principle must be followed: ensure that the pressure at the bottom of the carbonization chamber directly below the suction pipe is positive at the end of coking.

This depends on the type of furnace, the season, and the operating condition of the coke oven. Controlling the pressure in the gas collection ducts is primarily aimed at maintaining a positive pressure at the bottom of the carbonization chamber (0–5 Pa). If the pressure is too high, it can cause poor exhaust of raw gas from the coke oven, and even smoke and flames may emerge from the coal loading ports and furnace doors; on the other hand, if the pressure is too low, a negative pressure will occur in the carbonization chamber, which can lead to leaks in the furnace walls. Nowadays, most coke ovens are equipped with automatic pressure regulation devices at the U-tube sections. For ordinary coal-loading coke ovens, a pressure range of 80–120 Pa is suitable. Personal opinion, for reference only.