Methanol Technical Version Daily Question (Short Answer) [2018-1-29]
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The water solubility of pure methanol is not up to standard; how should this be addressed? ① The light components at the top of the tower are too high, so the initial distillate should be collected in an appropriate amount from the pre-tower condenser. ② The reflux ratio is low; increase the amount of reflux. ③ The collection temperature is too high; lower it. ④ Too little of the intermediate fractions are collected; increase the amount of fusel oil collected.
①The light components at the top of the tower are high; therefore, the initial distillate should be taken off from the pre-tower condenser in an appropriate manner. ② The reflux ratio is low; increase the amount of reflux. ③ The temperature at which distillation occurs is high; lower this temperature. ④ Few intermediate distillates are taken off; increase the amount of fusel oil taken off.
①The light components at the top of the tower are high; therefore, the initial distillate should be taken off from the pre-tower condenser in an appropriate manner. ② The reflux ratio is low; increase the amount of reflux. ③ The temperature at which distillation occurs is high; lower this temperature. ④ Few intermediate distillates are taken off; increase the amount of fusel oil taken off.
This post was last edited by tczxs on 2018-1-29 09:09. Answers: ① The light components at the top of the tower are too high; accordingly, the initial distillate should be collected from the pre-tower condenser in an appropriate manner. ② The reflux ratio is low; it should be increased. ③ The collection temperature is too high; it should be reduced. ④ Few intermediate distillates are being collected; more fusel oil should be collected.
The reflux ratio is low; increase the reflux volume. The extraction temperature is high; reduce the extraction temperature.
If the pure methanol product contains organic impurities that are insoluble or poorly soluble in water, upon addition of water, these impurities precipitate as gel-like particles, resulting in turbidity. The process of water extraction distillation is an important method for separating and removing these impurities. However, the amount of water added generally does not exceed 20% of the crude methanol feed volume. Increasing the amount of water added will certainly help in removing organic impurities, but it will reduce the production capacity of the pre-distillation tower, increase energy consumption in terms of heat and kinetic energy, and also pose certain difficulties in controlling other process conditions of the tower
Answer: The reasons are as follows: 1； Improper pretreatment led to some alkanes that form azeotropes with methanol being carried over into the product, affecting its water solubility. Treatment measure: Adjust the amount of extraction water appropriately based on the quality of crude methanol, and remove alkane impurities through extraction. Control the pre-column condensation temperature to allow light components to be discharged from the system smoothly 2; improper treatment in the main column results in heavy components being included in the product, affecting its water solubility. Remedial measures: Strictly control the operating conditions inside the tower; by adjusting the heat load and reflux rate, maintain an appropriate temperature on the sensitive plate to prevent the upward movement of heavier components. How to handle it: ① Control the operating temperature of the synthesis tower. ②Increase the reflux ratio. ③Reduce the reboiler steam volume. ④Control the operating temperatures of the pre-tower condenser and the expansion gas cooler. ⑤Strictly control the extraction of fusel oils.
1) Improper pretreatment of the tower resulted in some alkanes that form azeotropes with methanol being carried over into the product, affecting its water solubility. Treatment measure: Adjust the amount of extraction water appropriately based on the quality of crude methanol, and remove alkane impurities through extraction. Control the pre-column condensation temperature to enable light components to be discharged from the system smoothly. (2) Improper treatment in the main column results in heavy components being carried into the product, affecting its water solubility. Countermeasures: Strictly control the operating conditions inside the tower; by adjusting the heat load and reflux rate, maintain an appropriate temperature for the sensitive plates to prevent the upward movement of heavier components. Components that are generally similar in boiling point to methanol, such as esters, aldehydes, ketones, and ethers, as well as most compounds in the C5–C10 range, form azeotropic mixtures with methanol and end up in the extracted product, resulting in unsatisfactory water solubility. The main reason is related to the operation of the pre-tower, but the influence of the main tower cannot be completely ruled out. Generally, it could be due to the following reasons: 1. The amount of water used for extraction is not appropriate. 2. The temperature of the pre-tower condenser is not controlled properly. 3. Fusel oils were not removed in appropriate amounts. 4. Collect a small amount of the initial distillate from the pre-cooling reflux liquid. 5. The operation is unstable, and the system experiences fluctuations.
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What should be done if the water solubility of pure methanol is not satisfactory? Answer: ① The light components at the top of the tower are too high; accordingly, the initial distillate should be collected in an appropriate amount from the pre-condenser. ② The reflux ratio is low; increase the amount of reflux. ③ The collection temperature is too high; lower it. ④ Too little of the intermediate distillate is collected; increase the amount of fusel oil collected.