Is it feasible to use methanol distillation to treat the methanol from low-temperature methanol washing?
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Our company is planning a major overhaul soon. During this overhaul, it is planned to send the methanol obtained from the low-temperature methanol washing process to the crude methanol storage tank, where it will be refined by the methanol distillation system. I am unable to determine whether: 1) the distillation system can refine the large amount of methanol from the low-temperature methanol washing process into high-quality refined methanol 2. What should be noted when distilling methanol from low-temperature methanol wash? 3. In our facility, the low-temperature methanol wash process often returns methanol to the crude methanol tank, and this is done due to high ammonia levels; high water content also leads to the return of methanol. I wonder how methanol is generally handled in the low-temperature methanol wash processes at other plants? Please share your respective experiences and lessons learned!
For methanol contaminated with high ammonia levels, strict requirements are applied in the distillation pre-treatment process; otherwise, it is easy for the alkalinity of the product to exceed the specified limits
Tell them to adjust the methanol regeneration tower and the water separation tower by themselves. If your requirements for methanol aren’t very strict, you can return it.
It is better not to return it; used low-temperature methanol wash contains many impurities, which will result in the distillation product not meeting the standards
It can be handled, but if the requirements regarding alkalinity are quite strict, then other solutions will have to be found
Personally, it’s better not to mix them. Low-temperature methanol washing contains many impurities in the methanol, and a distillation system cannot remove them all; it might be slightly easier to handle these impurities when the distillation unit is operating at reduced capacity. If possible, it would be better to send the methanol from low-temperature methanol washing directly to a storage tank, where it can be dehydrated and purified through distillation before being fed back into the purification system.
We once distilled methanol with a high ammonia content in crude methanol for some time; the non-condensable gases from this distillation process were sent to the purification exhaust gas scrubber, which resulted in the purified methanol having an increased total sulfur content due to the high ammonia level.
It’s best not to do this, as the pre-tower does not have a strong ability to remove S. We accepted that the finished cans would all get contaminated later on. The methanol we returned had unacceptable color and permanganic acid levels after distillation
I’ve heard of cases where the removal of methanol through low-temperature methanol washing led to failures in the potassium permanganate tests for the product, as well as excessive alkalinity levels. In our factory, we’ve experienced an increase in color intensity and failures in the acid value tests.
Similarly, we recently tried to monitor the level of the racemate oil tank fluid; this fluid also contained ammonia-containing methanol from the low-temperature methanol washing process. After only two days of monitoring, the potassium permanganate test showed poor results and the acidity level was above the acceptable limit.
It can be returned; generally, the products that pass the distillation process are fine, but those that do not meet the dual-methane standards are problematic