Does everyone know how to calculate the exhaust volume of the vacuum pump in a distillation system or a reaction system?
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I have been designing a reactor recently; it is a vacuum reactor, with methanol entering the reactor to undergo reactions, and then being pumped out from the top of the reactor by a vacuum pump. Knowing the amount of methanol that exits from the top of the reactor, where the pressure at the top is around 10 Kpa, how can one calculate the exhaust volume of the vacuum pump and select an appropriate one? Very little methanol can be cooled at the vacuum pump inlet; most of it likely condenses at the vacuum pump outlet. I consulted a senior engineer from a design institute, who said that in the case of distillation, it is generally 15% of the evaporation volume; this refers to the theoretical volume under standard conditions, not the volume under vacuum. So, in the case of complete failure to condense that I encountered with this vacuum pump, should I replace methanol with a substance of theoretical volume that is 10% higher to ensure proper condensation? ? ? ? :Q:Q:Q
This post was last edited by richardpai on 2018-9-20 09:28. There is already very little that can be condensed at the inlet; under vacuum conditions, organic substances tend to evaporate more easily, which can be explained using the theory of saturated vapor pressure. Methanol has a relatively low boiling point, so a lower temperature is required for pre-pump condensation. It is also possible to calculate how much can be condensed by knowing the gas temperature and flow rate at the exit of the condenser – values that can be measured in practice. As for condensation after pumping, theoretically speaking, a large amount of liquid will be condensed; moreover, it depends on the type of vacuum pump used – with water-ring pumps, much of the liquid condensed in the post-pump condenser is water.
We are going to conduct experiments; if the results are not satisfactory, we will scale it up to reach a guaranteed value
Is the reaction process continuous or batch? In a continuous process, to determine the pumping capacity of the vacuum pump, the evaporation rate of the system is determined through experiments or experience. The condensation efficiency of methanol can be ascertained by considering the temperature of the water in the condenser, and the pumping capacity of the vacuum pump can be calculated using gas laws. The suction pumps used can be dry pumps, screw vacuum pumps, or claw vacuum pumps; the exhaust gases can be recycled a second time via a condenser. To calculate the exhaust volume, please provide specific data.
I can help you do the calculations; under standard conditions, converted to operating conditions – low-vacuum dry vacuum pumps are designed for an operating vacuum level of -0.08 to -0.09 MPa. They have low motor power requirements, are air-cooled, and offer good cost-performance. They are used for recovering low-boiling-point substances such as propane, methanol, and ethyl acetate
Calculate using the ideal gas law. PV=nRT; a pressure of 10 kPa corresponds to a volume expansion of 10 times. Based on the mass of methanol, you calculate the ideal volume, which is m/M*22.4; this is the standard volume. If all the methanol is condensed in front of the vacuum pump, the amount of gas that needs to be pumped out by the vacuum pump is very small.