Three processes for methanol purification
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Three processes for methanol purification (double tower, high-quality three-tower distillation, energy-saving three-tower distillation). 1. Ordinary double-tower process: The ethanol content in refined methanol is related to the ethanol content in crude methanol; whereas the ethanol content in crude methanol is influenced by the synthesis conditions, such as pressure, temperature, the stage of catalyst use, the composition of the syngas, and the structure of the raw materials, among others. Crude methanol produced by the low-pressure process (including the high-pressure process using copper-based catalysts with light oil as raw material) contains 100–1000 ppm of ethanol, whereas crude methanol produced by the medium-pressure process (Methanol-to-Formaldehyde process) and the high-pressure process (also using copper catalysts) with coal as raw material can contain up to 400–2000 ppm of ethanol. Therefore, the ethanol content in pure methanol also varies significantly, generally ranging from 100 to 600 ppm, and sometimes it can reach as high as 1000 ppm. This is because in a double-column distillation system, the bottom of the main distillation column where the product is obtained is almost entirely water. Moreover, the volatility of ethanol is similar to that of methanol; as a result, ethanol cannot be concentrated in the column bottom. Therefore, some of the ethanol rises to the top of the column along with methanol, and a considerable amount of ethanol from the crude methanol ends up in the pure methanol. Based on domestic methanol production experience, the ethanol content in purified methanol can also be reduced using a double-column atmospheric distillation method
The energy-saving three-tower process can increase the purity of pure methanol to 99.95%
The information provided by the original poster seems to have been taken from the book \"Methanol Engineering.\" However, the poster did make an effort to research this topic. According to methanol standards, the concentration of high-quality methanol is 99.85%, but many manufacturers claim to be able to achieve a concentration of 5 nines; as for 4 nines, such claims are even rarer. So it seems that this person up top isn’t very familiar with methanol.
I carefully examined the distillation process in our plant and found that we mainly increase the reflux ratio of Tower 2 to control the quality of the product taken from this tower. Approximately 35% is extracted from the 2 towers. 3 steps yield 60%. It has been proven that our products can indeed achieve 99.95%. The majority of our factory’s products are also exported.
Hehe, ours can reach 4 nines, but unfortunately the ethanol content is a bit high. I don’t know how to solve this issue; I’m still trying to figure it out, which is frustrating…
It’s not true that the three-column process is always the best. Based on experience in our country, some manufacturers appear to use a three-column process, but in reality they use a two-column process; it’s just that there are three columns present. Whether to use a two-tower process or a three-tower process depends on the product quality requirements and the raw materials
The quality of 3 nines should be guaranteed
That’s great; I’ve learned a lot. It would be even better if a flowchart could be included
I’ve learned more knowledge again; thank you for your hard work!
The new distillation systems currently in use are all of the four-tower (or three-plus-one tower) type, namely the pre-tower, pressure tower, atmospheric pressure tower, and recovery tower (also known as a stripping tower). Their characteristic is that； 1 ； Boiling point feeding is employed; the feed to the pre-tower is heated to around 65°C by heat exchange with the steam condensate from the pressure tower and the recovery tower, while the feed to the pressure tower is preheated to around 110°C using the liquid from the bottom of the pressure tower. 2 ； The methanol vapor from the pressurized tower is sent to the reboiler of the atmospheric pressure tower, providing heat for that tower, 3 ； The fusel oils obtained from the atmospheric pressure column are sent to a recovery column for further distillation, thereby extracting the vast majority of the methanol contained in them. The characteristics of the four towers are ； Steam is utilized more efficiently, which further improves the quality of the spirit; in particular, the ethanol content is lower, the alcohol content in the wastewater is reduced, and consumption is decreased
The four-tower process seems reasonable from an introductory perspective; is it possible to calculate it theoretically?
The poster has some information on converting coke oven gas to water gas and would like to share it.
Double tower, high-quality three-tower distillation, energy-saving three-tower distillation