Failure analysis of condenser noncondensing gas in sieve plate distillation laboratory
The sieve plate distillation unit is in stable operation, and the condensing system pressure can be studied as a steady state process. At 20℃, the saturated vapor pressure of butadiene is 0.24Mpa, and that of hexane is 0.016Mpa.
The sieve plate distillation unit is in stable operation, and the condensing system pressure can be studied as a steady state process. At 20℃, the saturated vapor pressure of butadiene is 0.24Mpa, and the saturated vapor pressure of hexane is 0.016Mpa. Assuming that the condensate group becomes containing 30% butadiene and 70% hexane, the saturated vapor pressure of the liquid phase is only 0.083Mpa after calculation, which is very different from the tower pressure. This indicates that the condensate group becomes 30% butadiene and 70% hexane, and the saturated vapor pressure of the liquid phase is only 0.083Mpa.
The analysis data obtained from the sieve plate distillation apparatus confirmed that the unknown gas C in the condenser is N2,N2 is an uncondensed gas, and its actual content is close to the theoretical derived value. In this way, we know that N2 is the noncondensing gas in the system. The crude solvent oil of the raw material of the dehydrating tower comes from the tank farm. In order to prevent volatilization, N2 is used to maintain pressure on the storage tank, so that the dissolved N2 in the raw material can enter the dehydrating tower. N2 was not detectable in the routine analysis.
In view of the supercooling phenomenon of condensate in dehydrating tower, the venting process is described as follows:
The partial pressure and sigma Pi of each component are condenser pressure. The partial pressure of PN2 occurs due to the presence of noncondensed gas, so the total pressure is P=ΣPi+PN2.
Because the non-condensing gas as a light component in the condenser of the sieve plate distillation experimental device has the characteristics of natural upward flow, if the gas and liquid in the condenser share a common outlet, the gas will not automatically discharge from the lower port and stay in the container. It is the device responsible for the accumulation of noncondensing gas. A condenser is a heat exchanger with special requirements. Not all heat exchangers can be used as condensers.
The pressure control of sieve plate distillation experimental device is mainly designed for condensable gas regulation, ignoring the objective existence of non-condensable gas. This regulation system can not distinguish the nature of the gas that causes the pressure to rise, so it helps to reduce the temperature while the accumulation of non-condensable gas in the condenser, which is a technological reason for the accumulation of non-condensable gas.