How does Aspen calculate saturated vapor pressure?

There are quite a few methods, right? Flash evaporation works as well, and it can be used in property analysis as well. For example, after setting up the flash evaporation process, you can choose HCURVE or sensitivity analysis; once the process is completed, the pressure at which the gas phase fraction is 1 corresponds to the saturated vapor pressure

The original poster may not be very clear about the basic concepts; for benzene mixtures, it is only possible to calculate the saturated vapor pressure of each individual component. I doubt this was what the original poster intended Is the poster trying to calculate the bubble point pressure? Then it has nothing to do with your system pressure, right? I suggest the original poster search the forum for posts related to calculating bubble point pressure or bubble point temperature – there are many such posts. If they can’t be found, they can use the analysis tool in Aspen Properties; the poster can try it out. If they still don’t understand how to do it, they should just come to me. It is recommended that the original poster first understand the definitions of bubble point pressure, dew point pressure, and saturated vapor pressure.

It seems I didn’t explain it clearly enough. Hehe, it’s about the partial pressures of each component in this mixture when it reaches equilibrium at normal temperature and pressure. The mixture consists of benzene, toluene, ethylbenzene, and xylene. If we know the molar ratio of these components in the mixture, we can determine their partial pressure ratios in the gas phase, and thus calculate the distribution proportions of these substances in the gas phase. I’m not sure if it can be solved. :lol :lol :lol

I asked for the saturated vapor pressures of each component at normal temperature and pressure; when flash evaporation occurred, there was only a liquid phase and no gas phase – I don’t know why Hehe

Flash evaporation isn’t an option; with flash evaporation, you can’t specify the composition of the gas phase – you can only specify the temperature and pressure. That is known as isothermal flash evaporation, and your case doesn’t fall under that category. Your goal is to determine the composition of the gas phase at equilibrium with the liquid phase composition, and you don’t need to calculate partial pressures at all; you can directly find the composition of the gas phase at equilibrium. This is called bubble point calculation. However, this approach still differs from yours, as bubble point calculation allows you to specify only the liquid phase composition (which you have already specified), while for temperature and pressure, you can only specify one of them, not both. In fact, your calculation isn’t possible because once you specify the temperature, pressure, and composition, it’s impossible to determine whether the system will be in gas-liquid equilibrium. This is why flash evaporation isn’t an option for you. You can check out my other post on the analysis of degrees of freedom in gas-liquid equilibrium; another person might have the same problem as you. In short, you need to gain a further understanding of gas-liquid equilibrium calculations.

Gas, such as nitrogen, is added during flashing, thereby satisfying the conditions of a gas phase at normal pressure at room temperature.

To lsrwan, what is the link to your post on the analysis of degrees of freedom in gas-liquid equilibrium? Why wasn’t it found, ah?

Normal temperature and normal pressure can only be specified as one; otherwise, it’s impossible to calculate

I couldn’t find it at http://bbs.hcbbs.com/viewthread.php?tid=343190&page=1#pid1770199; I’m not sure why. Let’s see if there’s anything similar to your situation

At normal temperature and pressure, this system remains in the liquid phase; it is almost always in the liquid phase regardless of its composition. What is the meaning of this calculation then?