The liquid level in the gasifier remains high and fluctuates frequently

We have encountered this situation as well; after a parking inspection, it was found that the quench chamber, along with the downcomer and upcomer, were filled with slag. Sometimes, by rapidly increasing or decreasing the pressure, the liquid level can return to normal, but the situation remains the same after a few days. It is likely caused by the gasifier operating for a long time or poor water quality in the system.

This post was last edited by wang06120325 on 2015-7-17 at 11:57. It happened once before as well, but not as severely as this time. The liquid level in the gasification furnace first rose and then fell; after two days, it dropped rapidly, with the load being around 30 cubic meters before the plant had to be shut down. When the manhole was opened, it was indeed found that sediment had formed in all the gaps inside. I think the impact of water quality must be significant to some extent. Changes in the ash melting point of different coal types, along with delays in taking action due to these changes, which lead to blockages at the slag outlet, are also factors that cannot be ignored. If the gaps become blocked, there is no choice but to shut down the system for repairs.

In this situation, increasing the drainage often still doesn’t help avoid the problem. But what is the mechanism behind the blockage between the downcomer and the upcomer? Could anyone explain in detail whether it is related to an excessive amount of quench water?

This probably has little to do with quenching water; if it is caused by an uneven distribution of the quenching rings, then there is no bubbling or deformation in the downcomer. The liquid slag in the gasification furnace, as it moves from the slag outlet to the quenching chamber, does not exhibit a simple laminar flow pattern; driven by the high-speed syngas, it splashes and collides with other particles, with some of it being quenched in the downcomer while some may be quenched in the quenching chamber. If syngas deviates from its path, this problem becomes even more severe; slagging is likely to occur in the downcomer and upcomer, and once slagging forms, it gradually spreads from a single point to an entire area. Our quench water flow rate is around 280. At this flow rate, it depends on how severe the deviation in flow is; if the deviation is significant enough to cause uneven heat transfer, it can easily lead to deformation of the downcomer or bubbling.

A blocked slag outlet affects the gas flow rate, leading to large fluctuations in the composition of the process gas, which in turn impacts the liquid level in the gasifier； Deformation of the downward tube, as well as bulging, can also cause instability and fluctuations in the liquid level of the vaporized fluid ； The water quality doesn’t matter much.

Yes, there was. Obviously, the downcomer has been pulled, and some of the gas does not pass through the water bath in the quench chamber; if you look closely, the temperature of the gas at the outlet of the vaporizer is a bit higher

Last night, the furnace level fluctuated five times within three hours, with the last fluctuation triggering an interlock shutdown. With the subsequent consecutive injections successful, I agree with what was said above regarding the somewhat high temperature at the syngas outlet; if there is a significant increase in this temperature, it’s very likely that the downcomer has started to bubble or even burn through. The situation isn’t likely to have reached that level yet, but caution is needed in handling it.

Once this situation occurs, it is advisable to reduce the load and then increase the operating temperature. Raise the load once the system stabilizes. The composition of the syngas has been quite volatile these past few days, and moreover, the temperature in the lockhopper is much lower than usual. This is likely not due to the coal quality alone; it’s probably the result of poor heat exchange caused by the deviation in flow. I checked the slag several times; there were strands in it, but not particularly many. There were quite a few small spherical pieces of slag, and the color of the slag was black. The occurrence of this globular slag is more or less related to the gas deflection. The wire inside is very likely to have been carried by the syngas to the slagged corners in the gaps between the downcomer and the upcomer. During the last maintenance visit, it was found that there was a considerable amount of wire drawing in the gaps between the downcomer and the upcomer.