I have a question about vacuums
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I have a question regarding vacuum conditions. It involves a reactor with a volume of 14 m3, operating at a temperature of 340 degrees. The reactor releases 750 kg/h of condensable gases with an average molecular weight of 100; at the same time, 200 Nm3/h of air is introduced into the reactor. The desired pressure inside the reactor is 500 Pa (absolute pressure). I am considering using DN600 pipes with a length of 10 meters. My question is: 1) Is the flow capacity of these pipes sufficient? 2) What is the pressure drop of the pipeline? 3) Is it feasible to use a spray condenser along with three-stage steam ejectors to maintain vacuum? If it works, how to choose?
Let me estimate the pipe diameter: Assuming an average molecular weight of air of 29, the flow rate under standard conditions (200 NM3/h) converts to a mass flow rate of 200/22.4*29 = 258.9285 kg/h. The total amount of gas that needs to be transported is 258.9285 kg/h + 750 kg/h = 1008.9285 kg/h. The density of the gas under actual conditions is: (1008.9285*273*500) / (101.33*1000*22.4*613) = 0.099 kg/m3. If the gas flow velocity is 20 m/s, then the pipe diameter is: D2 = (4*1008.9285) / (3600*20*3.14*0.099), which gives D = 0.425 m. Choosing a DN600 pipe provides sufficient headroom. I’m not sure if this is correct
Under such high vacuum conditions, the ideal gas law may not be appropriate. We have a vacuum evaporator with an evaporation capacity of around 2200 kg of water vapor, a temperature of approximately 130°C, and a pressure of about 0.0033 MPa (absolute pressure). The design in China specifies a pipe diameter of DN800, while the German design uses a pipe diameter of DN900. The situation described by the poster is less generous in terms of volume, but it has a higher vacuum level and temperature. It is recommended to increase the pipe diameter further; although this entails additional investment, it will ensure normal operation in the long term.