The total condenser of the distillation tower is being replaced; I’m not sure by how much the tower pressure will increase
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We are a chemical plant that produces trichloroethylene. The full condenser in the intermediate tower is leaking. Since there are no spare units available for now, we are using other graphite heat exchangers as a temporary solution. However, the pipe connections do not match – the original full condenser had a DN150 connection, while the spare unit has a 50mm connection. Under full reflux conditions, the reflux rate is around 1.5–2 m3/h; the reflux liquid mainly consists of trichloroethylene, trichloroethane, tetrachloroethylene, and other substances. As this is an atmospheric pressure tower, I would like to ask: what will be the tower pressure if I replace the full condenser? How was it calculated: Q:Q
With such a question, it’s impossible to answer. Please provide the type, specifications, and dimensions of your heat exchanger, so that we can assist you better. We previously developed a set of TCE processes as well; will there be any issues with the product if you use atmospheric pressure distillation?
It’s a graphite block tubular heat exchanger; both heat exchangers are made of the same material, and their heat exchange area is 25 m2 each. The only difference is the diameter of the gas inlet – it used to be 150 mm, but now it’s 50 mm. I’m not sure how high the pressure inside the tower will rise after making this replacement. . As far as I know, domestic TCE plants all use atmospheric pressure distillation
Considering this heat exchange area, I think that if it is changed to DN50, the pressure drop across the entire heat exchanger could increase by 30–50 mbar (based on my personal experience). Whether this will affect the condensation process requires calculation using specialized software. In my design for TCE, distillation and purification are carried out using an evaporator; since there is mineral oil present in the distillate, a vacuum is used to some extent. This might differ from your process – it could be a relatively new technique in China.
In this way, the pressure buildup won’t be very high. Is there a formula for that?
Are you not sure what other data is needed?
I’m not entirely sure about this. I think it’s possible to calculate it: This represents local fluid resistance, with h=K×u2/2×ƿ(1+βt). The value of K depends on whether there is a sudden reduction in diameter; in such cases, K=0.7×(1-F1/F), where F1 is the exit area and F is the inlet area. K is approximately 0.47 in such situations. U represents the velocity at the narrowed section, and it can be estimated based on the normal flow velocity and the diameters of the pipes before and after the narrowing – around 30 m/s, which is an upward estimate. ƿ is the density of the gas; according to available data, it should be around 4.5. The values of βt are very small, so they can be ignored. Plugging these values in should give a result of 16 KPa. Please use this as a reference. The person who posted above certainly has a lot of experience; I might have overestimated the velocity.