Preheating burner sprayout accident
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Accident details: On the evening of December 26, 20XX, during the heating-up phase of Furnace No. 1, the furnace temperature was high, causing slag to flow down and get stuck at the slag outlet. This resulted in a reduction in the size of the slag outlet, leading to backfire. In order to control the furnace temperature, the control room did not reduce the fuel gas supply, while instructing the operators on site to increase the extraction rate. The slag opening is getting smaller, the tempering is increasing, and more suction is applied. Suddenly, the slag at the slag outlet was drawn away, causing the slag outlet to enlarge; a large amount of air entered the furnace, where it met the excess fuel gas and resulted in an explosion. The preheated burner was ejected outside the furnace, and the control system stopped the supply of fuel gas.
If there is an excess of fuel gas, shouldn’t the furnace go out?
It is estimated that the fuel gas mentioned here refers to the off-gas from methanol, which mainly consists of CO and H2. It can be heated up to the point where slag is formed; the temperature is already very high. It’s not easy to cause it to go out just because of a little air. As they put it, we experienced this once as well – the fuel gas burner got bent, which was quite serious
It’s time to stop supplying gas at this point; keeping adding gas will result in extremely high temperatures, which is dangerous! ! !
Since it’s capable of producing slag, the temperature must be at least 1000 degrees. With fuel gas present, it’s impossible for the fire to go out; otherwise it would be considered back-firing, as an excess of fuel gas in the furnace leads to partial oxidation reactions.
This is a typical operational accident; during the furnace heating phase, the temperature was not properly controlled. Why is this the case? For a normal shutdown of the gasification furnace, it is necessary to increase the temperature in order to melt the slag. During an emergency shutdown, there is no need to worry about severe slag formation. But why did this happen during furnace heating? I believe that in the later stages of furnace heating, due to the high temperatures, it is necessary to maintain a constant temperature to ensure the slag melts. If the heating rate and temperature fluctuations are too large during these later stages, it can lead to excessive melting of the slag, which in turn blocks the slag outlet. Therefore, it is essential to strictly control the heating rate and prevent large temperature fluctuations in the later stages of furnace heating. The constant temperature at 1000 degrees is maintained for a sufficient duration.
Sometimes that is the case, but production may stop unexpectedly; the furnace does not go through the slag removal process, and it has to be reheated, especially towards the end of the process. If the high-temperature period lasts too long, blockages can occur at the slag outlet, resulting in insufficient negative pressure in the furnace, inadequate heat supply, slow temperature rise, or no increase in temperature at all, or even a drop in temperature. If the start-stop plan keeps changing, this kind of situation is likely to occur
Work safety remains of top priority.