Problems with the flash vaporization arrangement
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This post was last edited by lflsedin on 2015-8-13 at 13:36. In the flash vaporization systems designed by Hualu Design Institute, the high-pressure flash vaporizer is usually located at the highest point of the slag-water framework; the low-pressure flash vaporizer is situated to the west, while the vacuum flash vaporizer is at the bottom. This layout facilitates the drainage, by gravity, of the substances in the high- and low-pressure flash tanks into the vacuum flash vaporizer when the gasifier is shut down, after which they are pumped to the sedimentation tank using a feed pump. It also helps to prevent the situation where the high-pressure flash tank becomes overfilled due to insufficient pressure when the system is started up and water is introduced. However, currently GE and domestic institutions such as Tianchen Design Institute typically use a layout in which low-pressure flashing is located at the top layer of the residue water tank, vacuum flashing is in the middle, and high-pressure flashing is at the bottom. Although this arrangement reduces wear on the pipelines connecting the high-pressure and low-pressure flashers and makes full use of the pressure difference and height difference between the two tanks, it can easily lead to problems during startup and shutdown: due to insufficient pressure, the water from the high-pressure flasher cannot flow into the low-pressure flasher, resulting in a large amount of residue accumulating in both tanks, which causes many difficulties in subsequent cleaning tasks! I hope everyone can discuss the advantages and disadvantages of these two layouts, especially their respective design intentions, so as to facilitate deeper exchanges and learning among us!
Personally, I think Hualu’s design is reasonable. The possible problem is that after feeding the material in, there is both a height difference and a pressure difference between the wash tower and the high-flash tank; if the black water cannot be drained, it will cause blockages
Tianchen’s design is really terrible; at the beginning of feeding material into the vaporization furnace, due to the low temperature of the black water, the high flash tank often gets full, and pressure cannot build up, which prevents the water from being discharged to the low flash tank.
I agree with you; the drainage from the scrubber tower is indeed a problem in the early stages of operation. In both Tianchen’s and Hualu’s designs, the scrubber tower is located on the ground level, which is lower than the level of the high flash point. It’s therefore not possible to drain the water from there to the area where the high flash point is located. It seems that dealing with the drainage from the scrubber tower might be more difficult in Hualu’s cases compared to Tianchen’s.
That’s what we do as well: after feeding the material, we open the low-pressure nitrogen supply on the high-flash tank when draining water from it, maintaining a pressure of 5 to 6 kilograms in the high-flash tank so that the water can be directed to the low-flash tank. However, it’s quite troublesome to open and close the valves on the low-pressure nitrogen blind flange whenever starting up or shutting down the system! The most critical issue is that the sludge present in the high-flash tank isn’t easy to transfer to the low-flash tank. Every time we stop the operation, we have to open the manhole in the high-flash tank; there’s a lot of sludge there that needs to be cleaned manually. However, with the design of the high-flash tanks used by Hualu, there’s almost no sludge at all – the tanks remain very clean.
We don’t need to turn on the nitrogen pressure at all; if the water from the vaporization furnace and the scrubber tower can be drained to the high flash point, then the pressure at that level will rise, and the water will be pushed down to the low flash point. The flash tank needs to be cleaned when parking.
This post was last edited by xklcj on 2015-8-12 at 14:26. Your high flash pressure builds up quite quickly; here we often encounter situations where the high flash pressure rises too slowly, and if no pressing is done, it can easily lead to the high flash tank becoming full! Why does your high flash pressure rise so quickly? How did you handle this issue, or are there any other measures? I’d like to share it with everyone! Thanks!
At the pressure increase points of the vaporizer and scrubber tower, switch to high flash mode; close the high flash vent valve before feeding material
Where have the wash towers gone before reaching the high flash point? After our washing tower is started up, no water is discharged; it only switches to high flash mode when the pressure is sufficient. However, the drainage pipes of the washing tower often get clogged, which is quite troublesome!
It goes straight to high flash point; we’ve encountered that issue too, but fortunately it doesn’t happen often