Purified methanol quality

Ethanol is extracted from the side stream of the atmospheric tower in the distillation unit to maintain the ethanol content in purified methanol. Reduce side reactions during synthesis and lower the ethanol content in crude methanol

Synthesis requires control of low temperature and low CO content, which reduces the ethanol content in the product. Distillation increases the reflux ratio and adjusts the appropriate extraction point to ensure the concentration of ethanol obtained. Secondly, it is necessary to control the temperature of the tower axe appropriately; if that’s not possible, a small amount of ethanol can be discharged along with the wastewater.

At a low H2:C ratio, the system’s energy consumption is high and the one-way conversion rate decreases; at a high H2:C ratio, the one-way conversion rate increases, but side reactions also increase. Moreover, an excessively high ratio can lead to carbon deposition, thereby shortening the catalyst’s lifespan. Therefore, it is necessary to adjust the H2:C ratio to an appropriate level for methanol synthesis. The purity of the recycle gas is also an important factor affecting ethanol production; hence, it is essential to regularly clean the methanol coolers, lower the temperature of the recycle gas, and improve the separation efficiency of the methanol separator. All these measures can help reduce the ethanol content in crude methanol, which in turn helps to lower the ethanol content in refined methanol. The key to reducing ethanol content in methanol lies in methanol distillation – by increasing the reflux based on the load of the distillation tower, it is possible to keep the area where ethanol gets concentrated in the middle and lower parts of the distillation tower； Increase the recovery of fusel oils and control the temperature in the middle section of the atmospheric distillation column, so that the ethanol-enriched zone is concentrated at the outlet for fusel oils ； Water is added to the pre-distillation tower to reduce the concentration of crude methanol; by diluting the ethanol present in the concentrated crude methanol with water, it is possible to control the upward movement of ethanol into the refined methanol during the distillation process. Due to the varying specific parameters of different systems, it is necessary for each system to optimize itself based on its own characteristics by focusing on the aspects mentioned above; this will lead to a significant reduction in the ethanol content in methanol within those systems. These are all my experiences from working in methanol distillation; I’m glad to discuss these systems with you all, as it may be helpful to you. According to the American AA standards, the ethanol concentration in methanol must be kept below 10 ppm; for crude methanol, where the ethanol content is above 1000 ppm, it is very difficult to meet the AA standards using three-column distillation! Pressure towers are very ineffective for separating ethanol! Separation in a atmospheric pressure column is easier compared to that in a pressurized column. The domestic quality standards for methanol do not specify any limits on the ethanol content! (Trading negotiations) + ?# Z0 V4 P9 z P; w Therefore, in the design of many methanol projects in China, the AA standards from the United States are often adopted, which ends up tying those projects down and restricting their development. ) l& u g, s; D) J Further investigation reveals that a 200,000-ton methanol production facility in China uses natural gas as raw material. The ethanol concentration in the crude methanol is around 200 ppm; through careful control and increased processing costs, it is possible to reduce this concentration to 30 ppm in the refined methanol product. However, during normal production, the ethanol concentration in the methanol product remains above 100 ppm. Methanol with an ethanol concentration of 30 ppm has a selling price that is 500 yuan per ton higher than that of methanol products with an ethanol concentration of 100 ppm. It’s because the processing cost is much higher. When methanol is produced using coal as a raw material, the ethanol concentration in the crude alcohol is above 1000 ppm, and the ethanol content in the final methanol product is typically between 600 and 800 ppm. In any case, it cannot reach a quality level of 10 ppm

Reply to 4# pdslht: Share your own experiences; many things are already outdated. These days, there are too many factories that can achieve an ethanol level of less than 10PPM.

By ruling out synthesis-related issues, lowering the reactor temperature, increasing reflux, and adjusting the side-stream extraction from the atmospheric pressure tower, ethanol can be controlled

Using 4-column distillation, it can be kept below 10 ppm.