If the methanol-ammonia content in low-temperature methanol washing is too high, what causes the sulfur content at the top of the absorption tower to be excessive?
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If the methanol-ammonia content in low-temperature methanol washing is too high, what causes the sulfur content at the top of the absorption tower to be excessive?
Is it caused by the decomposition of (NH4)2S at the top? I want to know too. Generally, installing an ammonia washing unit before methanol washing prevents this problem
(NH4)2S cannot be stripped in the thermal flash tower, so it enters the decarburization tower where it decomposes and flashes to release H2S
(NH4)2S crystallizes at the top of the absorption tower, and the purified gas carries away the hydrogen sulfide that has been decomposed. As operation time increases, a small amount of ammonia is always introduced into the methanol wash, accumulating over time.
After ammonium sulfide is formed in the areas of high hydrogen sulfide concentration in the thermal regeneration tower, it enters the carbon dioxide absorption tower along with the methanol-poor stream, where it is separated out in the absorption tower; SO
Ammonia and hydrogen sulfide are used to produce ammonium sulfide at high temperatures; this compound is usually present in solution form and is unstable. It is carried to the absorption tower along with circulating methanol, where it decomposes into H2S and ammonia under the low-temperature conditions in the absorption tower, resulting in an excess of hydrogen sulfide in that tower
The ammonia washing unit cannot remove all of the ammonia; a small amount of ammonia still makes its way into the system. Over time, this leads to an excessive ammonia content in the circulating methanol
Our plant’s old system has been in operation for over 10 years without encountering this issue; probably because the volume is small and it goes away with the acidic gas
This is a problem of system balance; when that balance is disrupted, the ammonia content in the system’s methanol rises above the acceptable level. In general, ammonia in systems is burned for desulfurization recovery. When sulfur is recovered, methanol is carried along, which causes the liquid level in the sulfur recovery scrubber to rise. This issue varies from plant to plant, so it cannot be generalized
In our ammonia washing unit, the ammonia that is washed out is ultimately sent to coal slurry preparation; therefore, the ammonia is not discharged. The only way for ammonia to be removed is by burning it in sulfur recovery processes