How is a distillation tower designed?
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I don’t understand now what the relationship is between the number of trays and the diameter of the tower? And the design principles of distillation towers? We currently have one set of floating valve columns and one set of vertical sieve plate columns, but I don’t understand the design principle behind these columns. I would appreciate it if someone with expertise could explain it to me. Or where can I find relevant information to consult? The concepts explained in Chemical Engineering Principles aren’t very clear.
Distillation is used to separate liquid mixtures that contain liquefiable gas mixtures. Driven by an energy agent, the gas-liquid phases are brought into direct contact and separated multiple times, and separation of various components is achieved by taking advantage of their differences in volatility
This issue cannot be explained in just one or two sentences; go and read a book on Principles of Chemical Engineering to see how the number of theoretical plates is calculated and converted. .
Distillation is a method for separating mutually soluble liquid mixtures. The separation is based on the different volatilities of various liquids; when the mixture is partially vaporized, the composition of the gas phase differs from that of the liquid phase. Separation is achieved by taking advantage of the differences in volatility among the components in the mixture. In the distillation column, above the feed location of the column, the heavier components contained in the rising vapor are transferred to the liquid phase, while the lighter components in the reflux liquid are transferred to the gas phase. This exchange of substances causes the concentration of lighter components in the rising vapor to increase gradually. As long as there is sufficient interphase contact area and an adequate amount of liquid reflux, the vapor that reaches the top of the column will consist of highly pure lighter components. The upper half of the column thus achieves the purification of the rising vapor. Below the feed plate of the column, the lighter components in the descending liquid are transferred to the gas phase, while the heavier components in the rising vapor are transferred to the liquid phase. With sufficient contact area between the two phases and an appropriate amount of rising vapor, the concentration of lighter components in the liquid that reaches the bottom of the column can be reduced to very low levels, thereby yielding highly pure heavier components. The lower half of the column carries out the process of concentrating the heavier components in the descending liquid. (Note: The upper half of the column does not include the feed plate; the feed plate is part of the lower half of the column.)
Thank you all, but my question is why are there 70 layers in the tray? Why 85 floors? I don’t understand now why they designed it this way; so why not use 50 layers or these 60 layers?
Is it to first calculate the theoretical number of theoretical plates, and then convert it based on specific circumstances?
There are several indicators for hydraulic control; you can understand them by looking at textbooks on chemical engineering principles
Based on the processing volume of the product to be separated and the required purity level, along with the gas-liquid equilibrium data of the mixture to be separated and the feed conditions, the number of theoretical plates needed is calculated, which is then converted into the actual number of plates
Based on your material composition, feed rate, reflux, the relationship between gas and liquid equilibrium, and the gas in the tower. The operational relationship between the liquid and gas phases: First, the theoretical number of theoretical plates is calculated; then, based on certain conditions, the theoretical number of plates is determined, after which the actual number of plates is computed.
I have a question: textbooks on chemical engineering principles cover theoretical aspects; just knowing about trays and heights isn’t enough to know how to design tower diagrams.
This question is extremely difficult to answer; the method of calculation depends on the properties of the material and the desired purity of the separation. For example, in alcohol distillation, if ordinary-grade alcohol is required, the number of plates in the distillation tower is usually 68–70 (for differential pressure distillation); for higher-grade alcohol, this number rises to 76–82 plates (also under differential pressure distillation). As for towers used in the petrochemical industry, the number of plates can even reach 100! As for how to calculate it, design institutes now have software!