Where is the best place to add alkali liquid in the crude methanol distillation process?

Generally, we add it to the bottom of the pre-column because the main substances that affect the acidity of crude methanol are formic acid and acetic acid. They are both heavy components and are soluble in water, so adding them to the bottom of the tower can effectively prevent acid corrosion. If they are added to the top of the tower, it will easily cause light components to be carried and wasted.

We add it to the feed pipeline, which also needs to be protected from acid corrosion. It can also be mixed in advance, and the effect is very good.

Added to the top of the pre-tower, it can wash the low-boiling point acid produced by the hydrolysis of esters in the distillation tower and move down plate by plate to prevent corrosion of the tower wall and pipeline fittings. Adding it to the tower kettle can prevent the acidic components contained in the crude methanol from causing major corrosion to the tower kettle, but it cannot handle the low boiling point acid generated during the production process. The above is a simple comparison of the corrosion effects of the two alkali addition methods on the system.: In addition, a big problem with adding alkali to the top of the pre-column is that the neutralized low-boiling point acid cannot be discharged from the distillation system. Instead, it enters the distillation pressurized tower or normal pressure tower along with the column liquid. During the distillation process, the strong alkali and weak acid salt formed will inevitably decompose to produce low-boiling point acid, which will move up the trays layer by layer, eventually causing the acid value of the refined methanol product to exceed the standard. When alkali is added to the pre-tower still or feed line, the low-boiling-point acid decomposed from the pre-tower will be discharged with the venting of light components such as dimethyl ether. It will not accumulate in the system and be brought into the subsequent distillation tower, and ultimately will not affect the quality of the refined methanol product. Therefore, it is recommended to use pipeline alkali addition or pre-tower kettle alkali addition. The above is my personal opinion and is for reference only.

Agree with the fourth floor. Add alkaline solution along with crude methanol feed

The device I am in is adding alkali at the lower part of the middle part of the pre-tower because the organic acids contained in crude methanol are mainly formic acid and acetic acid, which are heavy components. Of course, there is also a small amount of low-boiling point acid. Organic acids have a relatively high content in the tower still. Adding alkali at the lower part of the middle part of the pre-tower can effectively prevent the corrosion of the tower still by organic acids and neutralize the low-boiling point acid in it.

The methanol pre-column generally has 48 trays, and the alkali liquid is usually added to the 36th (or 30th, or 40th, counting from bottom to top) tray along with the feed.

We also add in the feed. I personally think it is better to mix this way.

The alkali solution of my unit is added together with the crude methanol feed pipe.

Our factory adds it in front of the crude alcohol preheater, which is good... It was said before that the lye (soda ash) used contained more chloride ions than caustic soda, which affected the catalyst, so we later switched to caustic soda solution.

At present, what is the pH of methanol, that is, the pre-column reactor of your device, can it be controlled to 10?