Why is the material from the distillation tower taken out from the top of the tower directly, without passing through a condenser?
Thread Content
The condenser of this distillation tower is external and operates in full reflux mode. The overhead stream is taken directly from the top of the tower, and there are two issues: 1. Is stream 1 in the diagram the gas phase? 2. Are there any advantages to setting it this way?
It should be like this, but this diagram is missing some elements that need to be shown; it doesn’t hold up logically. It’s best to improve it to facilitate discussion. For reference.
Some details in the diagram attached by the original poster may not be clearly shown. If material 1 is the gas-phase side stream output, it has no practical meaning or represents a flawed design. Material 1 is only meaningful in terms of the liquid-phase side stream output, and there are also many practical application cases. It is mainly used in situations where there is a slight degree of decomposition or dehydration reactions in the product at the top of the tower. Due to the presence of a small amount of light components or water resulting from this decomposition, it is often not possible to obtain a product of satisfactory quality by simply taking it from the reflux tank after condensation at the tower top. In such cases, extracting the product through a liquid-phase side stream is the most effective way to solve this problem.
With this design, the vapor phase at the top of the tower should be difficult to condense, as its boiling point is often negative. There should be a vapor-liquid separation tank at the vapor outlet, and the vapor needs to be recovered using a compressor. The external condenser is used to recover the light components contained in the vapor, thereby preventing damage to the compressor
It appears that the material is drawn out via a bubble column, with a liquid phase layer at the top of the column; the drawing process is precisely controlled. As for the advantages, it is certain that a completely liquid substance is obtained.
This diagram is incomplete; Logistics 1 can be either a gas or a liquid – I have encountered both scenarios. In the case of a gas, the gas obtained at the top of the tower is sent directly to the downstream process without passing through a condenser, which allows for some energy savings. Of course, this depends on the requirements of the downstream process. For liquids, it involves collecting the liquid from the collection tray and controlling the liquid level in that tray