Weekly Topic 4.10, Issue 22: Distribution of Demineralized Water in Methanol Distillation
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As the title suggests, let’s discuss the issue of the allocation of methanol distillation demineralized water, including the specific amounts used and their applications!
Under normal circumstances, the amount of demineralized water used in distillation is about 15–20% of the crude methanol. However, there are advantages to adding demineralized water from different locations; for example, adding it to the stripping tank or the pre-condenser reflux tank each has its own benefits. In our case, the ratio is approximately 5:1 between the reflux tank and the stripping tank
For distilled deionized water, we use it only in the stripping tank (with 6% crude methanol content), for preparing alkali solutions, as seal water for pumps (0.5 cubic meters), and in the exhaust gas scrubber tower (0.2 cubic meters)
Reply to 3# Shouhou: When do you plan to return the reflux tank? Without desalinated water?
Reply to 4# wawjia: It is generally not added; the pre-extraction reflux tank does not have an overflow port, and the liquid from our extraction tank returns to that reflux tank. So it’s better to add it from above.
Our setup is the opposite: the liquid in the return tank can be returned to the extraction tank intermittently or manually, so the desalinated water is mainly used in the return tank
Distilled deionized water, used in the stripping tank; alkali preparation, seal water for pumps
Under normal circumstances, the amount of demineralized water used in distillation is about 20% of that in crude methanol; it is mainly used to prepare alkaline solutions and to remove moisture from the pump water
The specific circumstances vary, so the amount of desalinated water added can differ. Using less desalinated water saves energy but increases the operational complexity; percentages between 13% and 22% are acceptable. Although the analysis tank contains desalinated water, it is generally not added there; instead, it is added to the reflux tank and the feed lines of the pre-distillation column. In cases where there is a vent gas washing tower, desalinated water is usually not sent back to the pre-distillation column either, otherwise the distillation conditions will fluctuate and the managers will start complaining again
The deionized water from our methanol distillation is mainly used in the pre-condenser reflux tank for extractive distillation; it is also used to prepare alkaline solutions, although this preparation is done intermittently rather than continuously.
Reply to 10# guojing9113: Where is the best place to add deionized water to the pre-tower? How can impurities be removed to ensure that the methanol’s water solubility meets the required standards?