Benzene melting point
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I would like to ask: for the benzene distilled by the extraction unit, it is required that its freezing point be no lower than 5.4°C. How can this freezing point be controlled?
It actually refers to the purity of benzene; the higher the purity of benzene, the higher its melting point.
If there are too many impurities in benzene, it will lower the crystallization point, right? The benzene tower top distillate is cooled by air cooling; then why are steam pipelines installed in the air cooler?
Prevent the atmospheric temperature from dropping too low, which could cause benzene to freeze in air cooling. At the same time, when freezing occurs in the air cooler, steam is introduced to heat it.
The medium coming out of the benzene tower is at 90°C, and its temperature remains at 25°C after air cooling. Under such conditions, is it still necessary to use steam for heating?
It should be about considering the issues that arise after the device is shut down for a long time
Although the temperature after air cooling is 25 degrees, local freezing can still occur if the ambient temperature is very low. Additionally, during temporary shutdowns when the environmental temperature is low, air cooling can also lead to freezing. In the north, steam needs to be used during winter; in the south, one should make a decision based on the local conditions. If the temperature is low and the installation is shut down, steam must be used.
There are several aspects to controlling the crystallization point: 1. High purity of benzene with low levels of non-aromatic compounds; 2. The benzene product contains little solvent; 3. Thorough separation of benzene from water. The air cooling system and steam pipelines in the benzene tower are used for heating purposes to prevent freezing. Benzene has a low crystallization point (5°C), making it prone to freezing, especially in northern regions where winter temperatures can drop well below zero degrees. Since the start of operations at our plant, there has been one instance of damage and leakage due to freezing in the air cooling system of the benzene tower. It is essential to pay close attention to maintaining an appropriate temperature during operation (above 20 degrees Celsius), particularly during periods of significant temperature drops or strong winds. During inspections, it is important to check the temperature at the exit of the air cooling system as well as the temperature of the pipe bundles
A steam pipeline is added to the air cooler as a measure to prevent freezing and condensation in winter; benzene has a low freezing point, so this system can be activated when winter temperatures drop below benzene’s freezing point.