What are the advantages and disadvantages of installing a methanol recovery tower or a methanol stripping tower in the methanol distillation process?
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In the methanol distillation process, impurities are extracted from the side stream of the atmospheric pressure column and sent to the methanol recovery column; thereafter, pure methanol is obtained from the top of the recovery column, wastewater is produced at the bottom of the column, and impurities are obtained from the side stream. Wastewater is discharged from both the bottom of the atmospheric pressure tower and the bottom of the recovery tower ； Another method is the process of feeding the wastewater from the bottom of the atmospheric pressure tower into the methanol stripping tower, where methanol is stripped from the top of the stripping tower and the wastewater is discharged from the bottom; meanwhile, fusel oils are extracted from the side stream of the atmospheric pressure tower. What are the advantages and disadvantages of each of these two processes? Personally, I think the process using a methanol recovery tower is better; pure methanol can be obtained from the top of the tower, and the concentration of impurities in the waste stream is also reduced. But isn’t it more complex to operate compared to the stripping tower process (since it is necessary to ensure that the purity of methanol at the top of the atmospheric pressure tower is within acceptable limits, while also keeping the methanol content at the bottom of the tower below specified levels)? Stirred-tank stripping is easy to operate in methanol production, but the concentration of fusel oils drawn from the side stream of the atmospheric tower is low, and it also results in steam waste. What are the opinions of those who work in methanol distillation?
We use a stripping tower, with fusel oil coming out from the middle and wastewater from the bottom. The top vapor is washed and then vented. The washed water can be returned to the fusel oil collection tank, mixed together, and then discharged. I’ve never encountered the situation you mentioned of impurity oils being extracted from the middle section of an atmospheric pressure tower, but in that case, every temperature point in the entire tower would need to reach the specified temperatures in order to ensure that the purified methanol meets the required standards, right? In this case, wouldn’t fluctuations in the steam system or other utility systems have a significant impact on the finished product? We don’t have any online analysis for pure methanol here, so I personally think that if the first method is used, the finished product is likely to fail to meet the standards due to fluctuations in operating conditions.
The process of feeding methanol from the side stream of an atmospheric pressure column into a distillation column for recovery is probably a quite common technique, right?