Principle of the MTBE light-end removal tower
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Our company has a C4 drying tower used to remove moisture from C4. It operates in a manner similar to the light-end stripping tower in the MTBE plant; the temperature at the bottom of the tower is 85 degrees, and the pressure is 6.5 kilograms. Under these conditions, water cannot vaporize. The feed contains 400 ppm of water, while the designed value for the water content in the output from the bottom of the tower is less than 1 ppm. At present, the plant has not yet been put into operation, so it’s not clear whether these requirements can be met. At the same time, I’m not very familiar with the operating principle of the tower; those who are experienced with MTBE would be kind enough to share their knowledge!
Working principle of the light-end removal tower: 1. The water in the feed to the light-end removal tower is trace saturated water present in the C4 fraction. 2. In pure water, water molecules are bonded together through hydrogen bonds; therefore, pure water has a high boiling point and relatively low volatility. 3. In tetrahydrocarbons, the water molecules present in trace amounts are surrounded by a large number of tetrahydrocarbon molecules; these water molecules are separated from one another, with no intermolecular bonding occurring between them. As a result, the volatility of these water molecules is **higher** than that of water in pure form, by a factor of over 400. It can even exceed the volatility of butene-1 in tetrahydrocarbons after ether removal. Since water can form heterogeneous azeotropes with tetrahydrocarbons, it is possible to remove water from tetrahydrocarbons after ether removal using a light-end removal tower.
The carbon tetrasaturated water, which cannot be completely dehydrated when at rest, has a concentration of 200-300 ppm; molecular sieves should be used to remove water from it