Reasons for excessive sulfur removal in low-temperature methanol washing
Thread Content
I would like to ask the experts in this forum to help with an analysis. In coal-to-methanol plants, low-temperature methanol washing is used to replenish methanol in the system during normal operation. During this methanol replenishment process, the sulfur content at the outlet rises sharply from the normal level of 0.04PPM to 1PPM (which is significantly above the specified limit of 0.1PPM); it then gradually returns to its normal level after the replenishment is complete. This phenomenon has occurred on several occasions during methanol replenishment. After ruling out various potential faults, all other parameters remain normal. Could someone please help identify the cause of this issue? Have you encountered such a situation? How is it all handled? Thank you so much.
No one has replied to me; I’ll add more and provide further data to rule out possibilities. The process is Linde low-methane process, handling 420,000 standard cubic meters of feed gas. The make-up fluid is directly added to the storage tank at the inlet of the lean fluid pump; there is a separate make-up pipeline. The methanol used for make-up is high-purity methanol, and there is no risk of contamination of the methanol. The amount of methanol added at one time is approximately 20 tons, with a flow rate of around 10 tons per hour. The temperature is 35 degrees, while the temperature of the fluid once it enters the storage tank is 55 degrees.
The addition of fresh methanol resulted in a higher temperature of the methanol-poor stream; the temperature of this stream entering the absorption tower before and after methanol addition can be compared.
Thank you for your reply. Explanation: The temperature of the fresh methanol added is 30 degrees, and it is added to the methanol-depleted tank at 55 degrees; therefore, the issue you mentioned regarding an elevated temperature in the methanol-depleted tank will not occur.
Let me add more data on the impurities in the formic acid solution: water: 0.05%, ammonia: 40 mg/l, hydrogen sulfide: 63 mg/l, pH: 8.34
Is there a connection between the fresh methanol pipeline and the contaminated methanol pipeline?
Please check the second floor for supplements; there is no connection.
Don’t directly refill the methanol tank; by refilling it in the hydrogen sulfide concentration tower, that problem won’t occur. Also, refill it at a slower rate – five to six cubic meters per hour is sufficient.
May I ask, why can’t it be added to the lean methanol tank? Could you tell me the reason?