Aspen is seeking help
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I built a benzene removal tower using Radfrac; the feed pressure was set at 200 kPa, whereas the value I found in the literature was 12 kPa. The pressure at the top of the tower was also 200 kPa. The values mentioned in the literature were much lower than this, and since the temperature at the top of the tower wouldn’t rise, it was necessary to increase the pressure. I tried various feed pressures; any value lower than 200 kPa resulted in simulation errors, with the message stating that the feed pressure was lower than the pressure across the tray That shows the temperature changes inside the tower as simulated, and it seems quite strange. Could some expert give me some advice? What’s wrong with my setup?
I changed the pressure at the top of the tower to 10 kPa; the temperature at the top of the tower is too low
I adjusted the tower pressure to its normal value, but the temperature at the top of the tower keeps from rising. What’s going on?
If the feed pressure is lower than the feed plate pressure, it generally does not cause any errors; at most, a warning is issued, and it has no significant impact on the simulation results. I think your feed temperature is too high, and the pressure at the top of the tower is also a bit high; 0.04–0.1 MPaa should be sufficient; there’s no need for it to be that high
That is, the output is insufficient. With constant pressure, temperature and composition are directly related to each other. If you set the pressure to 20 kPa and benzene is collected at the top of the tower, then the temperature at the top of the tower will likely be equal to the boiling point of benzene (20 kPa), so it won’t be too high
Okay, okay, I’ll adjust it. Thank you, big bro
Carefully check the input conditions – even a simple value like mass fraction can be set incorrectly, so it’s normal that the calculation doesn’t work. Generally, for such well-established substances, there are two reasons why the calculation fails: either the parameters aren’t set properly, or relevant literature hasn’t been taken into account (for example, maybe pure benzene isn’t required at the tower top, in which case the presence of some C11 compounds will naturally raise the temperature)
I’ve just started using this software, and there are many things I don’t understand. The top of the tower does not require pure benzene; it is a mixture of benzene, toluene, and xylene. There is one setting in my system that I don’t quite understand – the output volume from the bottom of the tower. I set it to 700, and this value allows for good separation of the components. I reduced the number of theoretical plates from 20 to 15, and there was basically no effect. One literature source suggests using 11 plates
First, you need to know what the purpose of designing this tower is (for example, to protect the top or the bottom of the tower). Establish corresponding design criteria, determine the minimum reflux ratio and the minimum number of theoretical plates (this can be done using simplified methods or other approaches such as the infinite tray theory). Then, select an appropriate reflux ratio (for example, 1.05 to 1.2 times the minimum reflux ratio). Based on these design criteria and the reflux ratio, find the suitable number of trays, and make further adjustments – all of these are concepts covered in chemical engineering principles
Thanks for the advice; I’ll run it through with Simple Tower then
What is the actual top temperature of the tower?