Method for preparing high-purity refined methanol by three-tower rectification

Abstract

The invention discloses a method for preparing high-purity refined methanol by three-tower rectification, which is used for preparing high-purity refined methanol by treating a methanol crude product by using a three-tower rectification method. The method comprises the steps of: based on diluted alcohol water or soft water as an extraction agent, distilling in a pre-separating tower to remove low-boiling substances in the methanol crude product and water-insoluble gas so as to obtain pre-separated methanol; sending pre-separated methanol into a pressurizing tower for pressurized rectification treatment, cooling light components at the tower top of the pressurizing tower, returning a part of the light components to the tower top of the pressurizing tower for refluxing, and collecting the rest of the light components as the refined methanol product; sending heavy components at the tower bottom of the pressurizing tower into a main rectifying tower for rectification, cooling light components at the tower top of the main rectifying tower, returning a part of the light components to the tower top of the main rectifying tower for refluxing, and collecting the rest of the light components as the refined methanol product; and discharging the main rectifying tower bottom liquid as waste liquid. By using the 'three-tower rectification' method, the problem that methanol azeotropes cannot be separated in the methanol products is effectively solved, the purity of the obtained refined methanol product reaches more than 99.9%, the mass percent concentration of methanol in the discharged waste liquid is smaller than 1.0%, and the pollution of effluents to the environment is reduced because the methanol content is low.

Description

technical field [0001] The invention relates to the technical field of methanol production, in particular to a method for preparing high-purity refined methanol through three-tower rectification. Background technique [0002] As one of the important basic organic chemical raw materials, methanol plays a very important role in the world economy. With the increasing shortage of energy in the world, methanol has gradually developed into an important energy substitute, and the industry of chemical products such as dimethyl ether and olefins synthesized from methanol has also developed rapidly. At present, my country's methanol production capacity has accounted for 1 / 4 of the world's total production capacity, with a total capacity of more than 29 million t / a. With the rapid development of methanol derivatives and their downstream products and the application of methanol fuel, the demand for methanol will increase. Therefore, improving the quality of methanol products and reduci...

AI Technical Summary

Problems solved by technology

[0004] At present, the common problem faced by methanol rectification is the methanol azeotrope impurities in crude methanol, such as dimethyl carbonate, etc. These impurities will form a mixture with methanol at the same boiling point, which is extremely difficult to separate. The current distillation purification method cannot separate these impurities. Methanol azeotrope impurity, so that the purity of the methanol product can not be improved, the best level of the produced methanol product can only reach 99.5% purity, and the quality is difficult to stabilize

Moreover, the alcohol content in the methanol rectification raffinate is high, and the mass percentage concentration of methanol in the raffinate is generally above 3%, which seriously pollutes the environment during the discharge process.

In addition, steam consumption has never been able to make a breakthrough. Currently, steam consumption per ton of methanol rectification is generally 1.5 to 1.8 tons