The sieve plate distillation device with continuous feeding and discharging is in stable operation process, and the pressure of the condensing system can be studied by steady-state process. At 20℃, butadiene saturated vapor pressure is 0.24Mpa, hexane saturated vapor pressure is 0.016Mpa,

The sieve plate distillation device with continuous feeding and discharging is in stable operation process, and the pressure of the condensing system can be studied by steady-state process. At 20℃, butadiene saturated vapor pressure is 0.24Mpa and hexane saturated vapor pressure is 0.016Mpa. Assuming that the condensate consists of 30% butadiene and 70% hexane, the calculated saturated vapor pressure of the liquid phase is only 0.083Mpa, which is much different from the tower pressure of 0.3Mpa, indicating that unknown gas C should exist in the condensate system. The partial pressure Pc is 0.217Mpa, accounting for about 72.3% of gas phase concentration.

The analysis data of sieve plate distillation experimental equipment confirmed that the unknown gas C in the condenser is mainly N2 non-condensable gas, and the actual content is close to the theoretical derived data of the unknown gas. So we know that N2 is the noncondensing gas in the system. The raw material crude solvent oil of the original dehydrating tower comes from the tank farm. In order to prevent volatilization, N2 is used to maintain pressure in the storage tank. Therefore, trace N2 is dissolved in the raw material and brought into the dehydrating tower. N2 could not be detected by routine analysis of feed samples.

According to the supercooling phenomenon of condensate in dehydrating tower, the cavitation formation process is explained as follows:

The pressure of the condenser is ΣPi. In the presence of noncondensed gas, the partial pressure is PN2, so the total pressure is the sum of the two partial pressures: P=ΣPi+PN2.

In the condenser of the sieve plate distillation experimental device, the non-condensing gas as a light component has the characteristics of upward natural flow. If the gas and liquid in the condenser share an outlet, the gas will not be automatically discharged from the lower port, and it will remain in the container. This is the equipment cause of accumulation of noncondensable gas. Condenser is a kind of heat exchanger with special requirements. Not all heat exchangers can be used as condensers.

The pressure control of sieve plate distillation experimental device is designed for the regulation of condensable gas, while ignoring the objective existence of non-condensable gas. Such a regulation system can not distinguish the nature of the gas that causes the pressure to rise, so it helps the accumulation of non-condensable gas in the condenser while reducing the temperature, which is the technological reason for the accumulation of non-condensable gas.