Dissolution of nitrogen in liquid propylene in ASPEN
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This post was last edited by sqjshu on 2019-8-5 10:52. Recently, I was working on separating a product; in simplified terms, it involves 50,000 kg/h of propylene and 85,000 kg/h of nitrogen, which are flashed at 15°C and 2.42 Mpa. According to ASPEN’s property data, the saturated vapor pressure of propylene at this temperature is 0.9 MPa, while that of nitrogen is 90 MPa. But what comes out of the flashing is all gas phase, and they cannot be separated at all. What seems to be the problem? SRK, PENG-ROB, and NTRL have all been tried.
Based on rough calculations, at these temperature and pressure conditions, there is ~25 t/h of liquid phase, with 97% being propylene. Use SRK
I used SRK as well, but the results were not separated. The original intention was to use nitrogen for the stripping of propylene, but this approach ends up introducing new impurities as well
The boiling point of nitrogen at standard pressure is -196 degrees.
You need to look at the boiling point, not just the saturated vapor pressure.
This post was last edited by *amingteda on 2019-8-7 at 11:02. Under these conditions, this system is primarily in the gas phase, with very little liquid phase; most of the liquid phase consists of propylene, with trace amounts of nitrogen. A rough manual calculation will suffice: the partial pressure of nitrogen in the vapor phase is equal to its vapor pressure.