Sequence of oxygen and coal slurry introduction into the furnace

To ensure safety during feeding and prevent the coal slurry containing peroxides from entering the gasifier before oxygen, the coal slurry is generally introduced about 1 minute before oxygen; if oxygen has not been added by that time, the system shuts down automatically. When stopping, oxygen first, then slurry.

It’s definitely safer to let the coal slurry enter the furnace first. If oxygen entered first and then the coal slurry, that would surely lead to an explosion. As for the impact, if the coal slurry enters the furnace much earlier than oxygen, it means oxygen arrives too late, which will cause the system to shut down ； If it’s just a bit earlier, that’s normal. This is also the case in practical operation: during material feeding, the temperature of the vaporization furnace first drops significantly before rising again. Opinions from a beginner; experts are welcome to provide corrections~~~

To ensure safety, in Texaco gasification, the coal slurry is first fed into the furnace, followed by the use of oxygen pipelines to purge the furnace with high-pressure nitrogen, and finally oxygen is introduced into the furnace. As a result, after feeding begins in the gasifier, its temperature will experience a brief drop before rising again. To enhance the safety of the system, high-pressure nitrogen plugs are also installed between the upstream and downstream shut-off valves for oxygen. These plugs use high-pressure nitrogen to prevent oxygen from entering the furnace prematurely or from entering the gasification furnace in the event of a failure, thereby avoiding accidents; as a result, strict requirements are placed on the pressure of the high-pressure nitrogen used in these plugs.

If the coal slurry enters the furnace too early, an excessive amount of volatiles accumulates in the gasifier; these volatiles can be considered combustible gases. Could an explosion occur if oxygen is introduced into the furnace at this time?

Oxygen entering the furnace first: Impact – High-purity oxygen, with its strong oxidizing properties, causes the burners to erode at high temperatures. Additionally, the refractory materials also have a certain degree of heat resistance, but they may still be damaged if the slag present in the gasification furnace melts and falls off. Coal slurry entering the furnace first: Impact – If coal slurry enters the furnace for an extended period of time without oxygen entering as well, this can lead to a significant drop in furnace temperature, failing to meet the minimum requirements. Moreover, without the dispersion and atomization effect provided by external oxygen and central oxygen, the coal slurry may enter the gasification furnace in a columnar shape; if it hits the furnace walls directly away from the center line, the impact on the refractory bricks will be severe. Another point is that large clumps of coal particles can flow to the slag outlet and cause blockages; therefore, it’s necessary for the coal slurry to enter the furnace before oxygen. However, there are strict time requirements regarding this, and I won’t go into detail as to exactly how much ahead it should be:)

Oxygen does not enter the furnace first! Not to mention normal situations – even in most cases, coal slurry is fed into the furnace first!

Of course, that goes without saying – the coal slurry is fed into the furnace first; otherwise, an explosion would occur due to the lack of oxygen, haha

Can volatiles be considered combustible gases? If possible, then in general, when flammable gases react with oxygen in a combustion reaction, oxygen is introduced first and then the flammable gas. Why is that?

Volatile matter cannot be considered a flammable gas!

It’s definitely better for the coal slurry to enter the furnace first, as that is safer. If oxygen enters the furnace first, peroxide formation can occur, which may lead to an explosion in the carbon scrubber tower