Sulfur content in the purified gas from low-temperature methanol washing
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Dear sea friends, happy New Year! Our company uses the Lurgi process package for low-temperature methanol washing. It has been over one and a half years since the system was put into operation, and throughout this time the trace sulfur content in the purified gas has consistently been above the specified limits. We have tried various methods, but the sulfur content in the purified gas has not improved, and even the patent holder’s attempts to resolve the issue were unsuccessful. It is generally believed that the sulfur content in the raw gas supplied from the upstream gasification process is too high, usually around 1200 ppm, with levels as high as 2000 ppm (the design value being 800 ppm). Judging from the trends in the removal of the lean methanol filter in recent instances (assuming that the sulfur content in the purified gas remains high), as soon as trace amounts of sulfur are removed by the filter, the online instrument measuring this sulfur content starts to show a gradual decrease. Could it be that the sulfur present in the lean methanol vaporizes due to the reduced pressure in the filter, enters the top of the absorption tower, and then ends up in the purified gas? What else is the reason? The quality of the methanol-poor material was analyzed; it was found that it contained a type of large-molecule sulfur that cannot be removed through thermal regeneration. Engineers sent it to the China National Petroleum Research Institute in Beijing for testing, and the results are still pending. I was wondering if any of your colleagues have encountered similar situations? What is analyzed in lean methanol? Is there organic sulfur? Thank you! :)
Wait for the analysis results of the samples to come in, and stay vigilant. Both of these instances of exceeding the limits were caused by internal leakage in the heat exchanger; there are no other issues.
Following with interest; looking forward to future updates. Thank you
The decarburization section of low-temperature methanol washing has a high efficiency; if the methanol-depleted stream is of satisfactory quality and the tower is operating properly, the purified gas cannot contain sulfur. If there is no issue with the methanol at the outlet of the methanol regeneration tower, it is possible to check the rich-lean liquid heat exchanger on the pipeline leading to the absorption tower for any internal leaks.
Well, during the major maintenance in August 2017, it was found that the methanol heat exchangers were indeed leaking; there was a gap the size of a coin on the tube sheet. Yet even after repairs, the sulfur level remained high.
It’s likely that the lean methanol and rich methanol streams have mixed together in certain areas
This post was last edited by hai8487 on 2018-1-12 08:45. It is possible that the thiol and thioether compounds in the lean methanol cannot be completely removed in the regeneration tower, which affects the efficiency of methanol in removing sulfur. You said that after the methanol filter is installed, the sulfur content in the purified gas will decrease – by how much? Has it been used for cutting over a long period of time, and what are the results?
It was sent to the company’s analysis and testing laboratory, where it was found that there were no thiol or thioether compounds present. The precision filter was not in operation for a long time; the maximum duration of its operation was around 4 to 5 days. As soon as the filter started operating, the total sulfur content in the purified gas began to decrease, dropping from 0.18 ppm to around 0.11 ppm, after which further reduction was not possible.
Could you send a photo of the scrubber tower for me to see?
Could you send a photo of the scrubber tower for me to see?
What is the sulfur content in lean methanol? Should the pressure in the flash section of the thermal regeneration tower be adjusted appropriately? Can the heat regeneration temperature be increased?