Methanol Weekly Topic: What should be the water content control for pure methanol? 2015.12.07--12.13

Three questions: What should be the control level for the water content in pure methanol? In the methanol synthesis reaction, CO2 reacts with H2 to produce water and methanol; as a result, the methanol content in the crude methanol produced is approximately 94–95%. In a distillation system, the pre-distillation tower operates on the principle of extractive distillation, and the solvent used in this system is water. Therefore, to obtain high-quality purified methanol, it is necessary to keep the water content in it within certain limits (for industrial-grade products, this limit is less than or equal to 0.10%). Controlling this water content is also a very important factor. How to control it and what are the bases? The reasons for the high water content in pure methanol include the following: 1. The operation of the main distillation tower – among the three distillation towers, the pre-distillation tower is used to remove the light components from crude methanol, while the pressurized tower and the atmospheric pressure tower are used to remove the heavy components from it. Since water belongs to the heavy components in crude methanol, the operation of the main distillation tower directly affects the water content in pure methanol. Firstly, if the steam volume at the bottom of the pressurized tower is too high, it causes high temperatures at the bottoms of both the pressurized tower and the atmospheric pressure tower; as a result, heavier components rise upward, increasing the water content in the pure alcohol ； Secondly, the amount of purified methanol extracted is too high while the reflux amount is too low, resulting in poor quality of the purified methanol and a high water content. 2. A leak in the equipment on the purified methanol recovery line of the distillation system allowed water to enter the methanol, resulting in a high water content. Is it beneficial for olefins to use methanol with a low water content? It’s not very advantageous; there’s too much work

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It’s five percent; a certain level of moisture is acceptable

The water content in the pure alcohol produced by our factory is only around 0.01%. **The standard water content should be less than 0.1%; by controlling the temperature at the bottom of the tower appropriately, the reflux ratio can be reduced, thereby decreasing the water content in the product.

A moisture content of 5% no longer qualifies as pure methanol; it is referred to as crude methanol. The national standard requires that the moisture content in pure methanol be less than 0.1%. In reality, the products obtained through three-stage or four-stage distillation all have a moisture content of 0.01% or even lower