Daily Question: Methanol and Purification Technology Forum Edition 20191103

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Reasons for the unsatisfactory water solubility of pure methanol product and solutions. Water solubility is also known as turbidity. The product quality requirements for pure methanol specify that it can be mixed with water in any proportion without becoming turbid. If the pure methanol product contains organic impurities that are insoluble or poorly soluble in water, upon addition of water, these impurities will precipitate as gel-like particles, resulting in turbidity. Water extraction is an important method for separating and removing these impurities. However, the amount of water added generally should not exceed 20% of the crude methanol feed. Increasing the amount of water further does help in removing organic impurities, but it may overwhelm the capacity of the pre-tower, increase energy consumption in terms of heat and kinetic energy, which is not economical. It also poses certain difficulties in controlling other process conditions of the tower. However, if the system has excess low-pressure steam, it can still be considered comprehensively.