I’m a beginner in Aspen; I have questions and would like some advice

The pressures of the condenser and reboiler are specified based on empirical values; in the simplified module, it is possible to set no pressure drop first, and then have the detailed module perform the calculations

Generally, the pressure at the top of the tower is determined first; the pressure at the bottom of the tower is 0.2–0.5 bar higher than that at the top (the tower pressure drop). The determination of the tower top pressure is generally based on the temperature of the refrigerant. For example, if the top of the tower requires condensation using condensate water, the minimum temperature is generally 40°C; therefore, the dew point of the stream at the top of the tower must be set at 40°C. Based on this dew point, the pressure required at the top of the tower can be calculated.

Thank you, sir. Based on experience, what are usually the pressures for these two points in a propylene distillation tower?

Thank you, sir. The pressure at the top of the tower needs to be calculated, right? Or based on production experience? I am currently simulating a propylene distillation column, with the requirement that the concentration of propylene in the top product be 99% and the recovery rate be 90%

The boiling point of propyl acetate is 56.5 degrees, so at normal pressure, the substance can be completely condensed once the temperature drops to around 56.5 degrees. In industry, cooling water is definitely used for cooling, and the lowest cooling temperature can reach 40 degrees. If pressure is applied, the operating temperature at the top of the tower can be higher. There are two issues at present: first, applying pressure is not conducive to distillation separation, and the energy consumption at the bottom of the tower increases ； On the other hand, increasing pressure can make the tower smaller, reducing equipment investment. Therefore, a trade-off is needed. This involves economic evaluation; relevant data and engineering experience can be referred to, and Aspen Economic Analysis can carry out such economic evaluation. Of course, the requirements are a bit high for beginners; thus, it can be assumed that the pressure at the top of the distillation column is 1 barg. In this case, the condensation temperature at the top of the column is around 60–70°C, with cooling water being used as the coolant (this is an estimate, not calculated using Aspen). Of course, there are quite a few design options for this, and there is no standard solution to practical engineering problems.