How to choose azeotropic point
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Saddle nodes, unstable nodes and stable nodes, which one is better for simulation?
From what you're asking, I'm a bit of a layman. There is no question of choosing or not choosing an azeotropic point. 1. Which method to choose is mainly related to the material system. ； 2. Saddle point, unstable point, and stable point are concepts in the residual curve, which are mainly determined by the system, that is, the boiling point, azeotropic point, etc. of each component. The residual curve can be hand-drawn through these points for the conceptual design of the distillation sequence. You can check "Separation Process" by Liu Jiaqi (Tianjin University), which explains it very clearly.
I'm really not proficient in these. I haven't gone to work yet. I want to ask when doing aspen simulation. There are two azeotropes. So in the first distillation tower, one of the distillates at the top or bottom of the tower must be an azeotrope. Then which azeotrope, or which azeotropic point should be selected, will make the separation effect better.
Would you like to read the book I recommended? There is also an electronic version online. Azeotropy is a characteristic. As long as it contains two substances that exhibit azeotrope, the system must be an azeotrope system. When selecting an azeotrope to be taken from the top or bottom of the tower, the boiling point of the pure substance also needs to be taken into consideration. That is, all boiling points of pure substances (which may be unstable points or stable points) and azeotropic boiling points (usually saddle points) are listed, so that a preliminary separation sequence can be given.