Knowing its reflux temperature, the top pressure can be determined
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As far as I know, in design, bubble point reflux is generally used; the pressure of the condensate in the total condenser is calculated based on the temperature of the condensate in the system and the composition at the top of the tower, using the bubble point equation. But in this design task, the temperature of the reflux stream has been set at 30 degrees as a cooled liquid reflux, not the bubble point temperature. So how can we determine the bubble point temperature of the condensate? (The material system is benzene-toluene, with a tower top composition of 0.983)
You say that “in design, it’s usually done with some kind of reflux,” but what I’ve seen is nothing like that. Most need to be supercooled. Since it has already dropped to 30 degrees, of course there is no connection with the temperature and pressure at the top of the tower.
Reply to 2# DXJ122: If it’s okay? Can the top pressure be determined directly based on the composition of the system at atmospheric pressure? Atmospheric distillation is used, but the pressure at the top of the column is generally slightly higher than atmospheric pressure. How should this pressure at the top of the column be calculated? Please ask a professional for advice!!
If the outlet of the condenser is connected to the atmosphere, it is what is known as atmospheric distillation. What you said, that \"atmospheric distillation is used, but the pressure at the top of the tower is generally slightly higher than atmospheric pressure,\" is correct in theory. The additional part is the resistance of the condenser, which is actually very small. If it is confirmed to be atmospheric distillation, you take the pressure at the top of the tower as atmospheric pressure, and by relating it to the composition, you can calculate the temperature at the top of the tower. Of course, if perfection is required, one calculates the resistance of the condenser and then increases the air pressure to obtain the pressure at the top of the tower.