Gas contains both hydrogen sulfide and sulfur dioxide

What kind of gas is it? If it’s coke oven gas, it is produced during coal charging, but in very small quantities; ammonia is removed long before that.

Coke oven gas, but the amount of sulfur dioxide is greater than that of hydrogen sulfide

It may be due to leaks in the coke oven structure or problems with the operational procedures (such as too low pressure or even negative pressure in the gas collection system; the pressure difference causing air from the combustion chamber to enter the carbonization chamber or air being drawn in through the coal loading holes at the top of the oven), which results in air entering the carbonization chamber and leading to the oxidation of sulfur in the gas to sulfur dioxide.

If there is negative pressure, wouldn’t it be very dangerous for air to get in?

There is a leakage in the furnace structure, allowing air (oxygen) to enter the carbonization chamber from the outside or from the combustion system; this causes hydrogen sulfide to be converted into sulfur dioxide: H2S + 0.5O2 = H2O + SO2

Negative pressure in the carbonization chamber of a coke oven is an almost inevitable phenomenon. Unless the pressure control system for the gas collection pipes is excellent, and given the increasingly strict environmental regulations, the set pressure for these pipes tends to become lower and lower. As a result, it is normal for negative pressure to occur in the carbonization chamber when the pressure in the gas collection pipes is low or even negative; the issue lies rather in the extent of that negative pressure and its duration. The risk caused by negative pressure is generally not that great, and it certainly doesn’t reach the upper limit of the explosion threshold.

It can be analyzed through the readings from the gas oxygen analyzer to determine whether the assumption of air entering the gas negative pressure system can be verified.

Our unit also experienced two other types of improper operations that led to high oxygen levels in the gas. One approach is intentional: at the end of the carbonization phase, coal injection holes are opened without switching the rise tube flap, with the aim of burning the graphite on the roof ； One possibility is careless operation: the high-pressure ammonia is not turned off in time after coal loading is completed, and the excessive use of high-pressure ammonia results in negative pressure in the corresponding carbonization chamber. It’s also possible that there is a problem with the ammonia valve, which prevents the high-pressure ammonia from being shut off. The latter case can be accurately identified through the high-pressure ammonia flow trend chart. Both of the above situations can cause fluctuations in the oxygen content in the gas; operational issues with the coke oven can be identified by examining the patterns of variation in the oxygen content charts.

If it leaks, then the sulfur dioxide level shouldn’t be very high

If air is drawn in under negative pressure, the sulfur dioxide content should be low. Since sulfur dioxide is oxidizing, could it react with hydrogen sulfide?