Three-column distillation of methanol

It’s just a slight negative pressure; improper operation may sometimes result in a slight positive pressure as well. After methanol vapor condenses into a liquid in the water cooler, negative pressure is naturally created within the space of the water cooler. Since the top of the water cooler is connected to the top of the atmospheric tower, negative pressure thus exists.

In addition to pressure, the temperature of the reactor also has an impact on pressure, as temperature affects the gas-liquid equilibrium of the liquid in the reactor, which in turn influences the pressure; therefore, it is necessary to control the temperature. .

1. Excessive venting, 2. Insufficient heat, 3. Too low reflux temperature, 4. Incorrect instrument readings

The temperature control of the tower top condenser is inadequate

Improper temperature control of the tower top condenser----------------- The temperature of the first-stage condenser in the pre-tower is usually controlled between 45 and 55 degrees, with it not exceeding 65 degrees. When water cooling is used, control is achieved by regulating the flow rate of the cooling water; but if an air cooler is used, how is the condensation temperature controlled? I hope everyone will discuss it

If it’s negative pressure, how can there be a vent? The main reason is the heat imbalance between the pressurized tower and the atmospheric pressure tower. This is especially caused by an excessively low reflux temperature and a large reflux flow rate in the atmospheric pressure column; however, this has no significant impact on operations, as the low operating pressure increases the relative volatility of the two substances, which is advantageous for our operations!

Generally, this kind of problem occurs due to excessive reflux during operation, which leads to too low a tower temperature and an imbalance between gas and liquid. It appears momentarily and does not last long, so it does not affect normal operation. However, it is necessary to adjust the heat balance; otherwise, defective products may be produced.

The external heat supply for the atmospheric pressure column comes entirely from the steam of the reboiler in the pressurized column, while the heat is removed by cooling water in the condenser at the top of the atmospheric pressure column. The negative pressure that occurs at the top of the atmospheric pressure tower is caused by either insufficient heat input or excessive heat removal. If the negative pressure is due to insufficient heat input, it will lead to a decrease in the reflux ratio at the tower top, which in turn results in a decline in product quality; in such cases, it is necessary to increase the amount of steam supplied to resolve the issue ； If it is due to excessive heat removal, it usually does not have a significant impact on product quality. Our company uses nitrogen injection as a solution; during this process, the valve opening should not be too large to prevent damage to the operation of the tower.

Why do you need to fill it with nitrogen? If the negative pressure is caused by excessive heat removal, filling it with nitrogen will not change the partial pressure of methanol vapor at the top of the tower, nor will it alter the material balance. Therefore, I personally believe that there is no need to use nitrogen when production is operating stably. Of course, it is possible to use accelerated energy transfer while driving.

The 7th and 10th floors make sense; taken together, they constitute the owner’s answer

I have a question: if four-column distillation is used, there is a pressure control valve at the top of the pressurized column that leads to the atmospheric pressure reflux cooler. I was wondering if other companies also use such valves. In our company, this valve has never been used. Why can’t this valve be opened to increase the pressure in the atmospheric pressure column when its pressure is low? What are the functions of the left and right sides of this valve?