Stabilization of oxygen pressure during gasification
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This post was last edited by huchsh on 2010-3-17 09:10. I have some questions after reviewing some materials recently and would like to discuss them with everyone. The materials state that maintaining a stable oxygen pressure in the gasification process is crucial for the proper operation of the facility; any abnormalities in the air separation unit can lead to fluctuations in oxygen pressure, which in turn affects the normal progress of gasification. To stabilize the oxygen pressure, oxygen buffer tanks are installed before oxygen enters the gasification section. In addition, some manufacturers install pressure control valves on the main oxygen pipeline, which function as safety valves. When the oxygen pressure suddenly rises, these valves open. Thanks to safety programming, the oxygen flow control valve in the pipeline leading to the gasification furnace closes at the same time the safety valve opens, and this flow control valve only reopens once the safety valve returns to its normal state! This process is very brief, lasting only about two or three seconds, but I wonder what effect it has on the vaporization furnace during the time when the flow valve is closed? Is that dangerous? Is it necessary to do this? The facility where we work doesn’t have that safety valve! I heard that there is a system at the oxygen separation unit to maintain stable oxygen pressure!
The oxygen pipeline coming from the air separation unit is equipped with a vent line; the set pressure of this oxygen pipeline is adjustable, and when overpressure occurs, the pressure relief valve opens to release pressure and maintain stable pipeline pressure. If the oxygen flow control valve is closed, why doesn’t the machine shut down?
Set automatic adjustment of the oxygen pipeline pressure; generally, the oxygen pipeline has a large capacity, and especially when a single gasification furnace stops operating, this does not have a significant impact on the system, allowing the oxygen pressure to be maintained at a stable level. Manufacturers that use fewer gasification furnaces rely mainly on liquid oxygen pumps to regulate the oxygen supply; when the gasification process is under increased load, the air separation unit must operate in conjunction to maintain stable oxygen pressure. An excessively low oxygen pressure difference affects the atomization of the burner.
Air separation oxygen supply systems all have pressure retention devices; isn’t it unnecessary to exert so much effort in vaporization? What are the capacities of your air separation and gasification units, and what are the processes used?
This post was last edited by xklcj on 2010-3-17 07:44. 4# luanma_chen uses Texaco’s technology, while the air separation unit is from Hangyang; there are two units in total, each with a capacity of 30,000 standard cubic meters per hour. There are three gasification furnaces, each with a diameter of 3200 millimeters and a capacity of 58 cubic meters per hour for coal slurry!
Hehe, it’s a big furnace; ours is much smaller
2# xuqinger: I also think the system will cause the vehicle to stop operating when there is no oxygen flow – the interlock mechanism that triggers an alarm when oxygen flow is low is very important and is usually activated during normal operation. Without any oxygen flow, the system will definitely stop working. But my supervisor said that since others have such a system, there must be a way to deal with it; perhaps the interlock that triggers an alarm when oxygen flow is low is disabled simultaneously when the flow control valve is closed, and it gets reactivated automatically once the flow control valve is opened! I don’t know if that’s the case!
If it’s done as mentioned above, by removing the interlock, it might work. Just like during feeding, with high temperatures in the furnace, the coal slurry is fed into the furnace first, and then the oxygen flow control valve is opened to allow oxygen to enter the furnace. The key question is: who would dare to disable the low oxygen flow shutdown interlock before the safety valve trips?
Closing the oxygen control valve prevents high-temperature syngas from within the gasifier from flowing back into the oxygen system; nitrogen purging should be carried out while closing it； Additionally, if the safety valve reseats, it can easily cause the oxygen pump to vaporize.
During the shutdown of the oxygen flow valve, the amount of oxygen supplied to the burner in the gasification furnace drops to zero; as a result, such a burner with zero flow rate will immediately shut down.
I think both the system for pressure control and the users should have their own methods: when pressure is high, in the system case it’s necessary to close the valves and allow air to escape, while users need to close their valves to maintain stable pressure