Control scheme for vinyl chloride distillation in the calcium carbide process

The principle of distillation involves purifying materials by increasing or decreasing temperature under constant pressure. Based on experience, the pressure at the bottom of the low-boiling-point column is maintained between 0.53 and 0.55 MPa, with a pressure difference of 0.03 within the column; the bottom temperature is around 40°C. For the high-boiling-point column, the pressure at the bottom is kept between 0.28 and 0.26 MPA, with a pressure difference of 0.02, and the bottom temperature is approximately 30°C (not strictly fixed). In the high-boiling-point column, the amount of hot water evaporated at the bottom of the column, and thus the bottom temperature, is adjusted accordingly based on the liquid level in the column. Furthermore, fine-tune the reboiler heating amount and the top reflux rate based on the high and low boiling point content of the product

Just by looking at the second floor, it’s clear that it’s not used for the distillation of vinyl chloride. 　　　　　　　　　　　　　　　　　　　　　　　　　The pressure controlled in the low-boiling tower is a bit high; the pressure difference is also a bit large. Additionally, temperature is proportional to pressure. The temperature in the high-boiling-point tower varies depending on the pressure, as well as on the concentration of high-boiling-point substances present. It can be said that at a given pressure, the higher the temperature at the bottom of the tower, the greater the amount of high-boiling-point substances present, which means it is time to discharge the residual liquid; otherwise, the tubes at the bottom of the tower may become clogged due to the carbonization caused by these high-boiling-point substances, thereby affecting heat transfer. Another one is the reflux ratio.