Advantages of selecting three towers for methanol distillation

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Comparison between two-tower distillation and three-tower distillation

1, product quality

Three-tower distillation can produce high-quality methanol with low ethanol content, generally less than 100× 10-6, which can be kept below 50× 10 -6 most of the time, and the content of other organic impurities is also relatively reduced. The quality of refined methanol products is not only related to distillation process, but also related to methanol synthesis pressure, synthesis gas composition, synthesis [wiki] catalyst [/wiki], and even related to the material selection of synthetic tower and other equipment. The content of ethanol in methanol products is closely related to that in crude methanol. When the ethanol content in crude methanol is low, the ethanol content in refined methanol is naturally low. In the three-tower distillation, the quality of refined methanol extracted by atmospheric tower is better. The actual analysis results show that the ethanol content in refined methanol produced by atmospheric tower is extremely low, only/kloc-0 /×10-6 ~ 2×10-6, and sometimes it can't even be analyzed, while the ethanol content in refined methanol produced by pressure tower is mostly 20×10-6 ~ 80×.

2. Energy consumption

Methanol is a product with high energy consumption, and the energy consumption of rectification process accounts for 10% ~ 30% of the total energy consumption, so the energy saving and consumption reduction of rectification can not be ignored. The steam consumption of double-tower distillation per ton of refined methanol is about 1.8 ~ 2.0t, and many factories consume more than 2.0t. The difference between three-tower distillation and double-tower distillation is that two main distillation columns are used, one is operated under pressure and the other is operated under normal pressure. The condensation heat of steam at the top of the pressurized tower is used as the heat source of the atmospheric tower, which saves both steam and cooling water. Every refined 1t refined methanol saves about 1t steam, so the energy consumption of three-tower distillation is low.

3. Investment and operating expenses

The relationship between investment, operating expenses and energy consumption of double-tower distillation and three-tower distillation is closely related to the production scale.

With the increase of production scale, the economic benefit of three-tower distillation is more obvious.

The double-tower distillation process has the advantages of less investment, short construction period, simple equipment and convenient operation and management. Although the consumption is higher than that of the three-tower distillation process, when the production scale is below 50,000 tons/year, its technical and economic indicators are superior, and its energy-saving and consumption-reducing ways can adopt efficient fillers to achieve the purpose of reducing steam consumption. When the production scale is above 50,000 tons/year, the three-tower distillation technology should be adopted. Although the one-time investment is high, the operating cost and energy consumption are relatively low.