Process design for distillation purification (high purity)
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Hello everyone. The crude material contains product A, impurity B, and impurities C1 and C2 (A, B, and C are all inorganic substances). How can distillation be used to achieve a purity level of 99.99%–99.999% for product A? Note: The crude material contains 98% of Product A (with a boiling point of 130°C). It also contains the low-boiling-point impurity B at 0.01% (boiling point of 59°C). The remaining components are high-boiling-point impurities C1 and C2, each present in amounts of 0.002% (with boiling points of 180°C and 300°C respectively). There are also some solid impurities dissolved in the liquid mixture; currently, low-boiling-point and high-boiling-point impurities are purified using separate floating valve columns. It should be noted that this design allows for the sacrifice of the main product A when removing low- and high-boiling-point impurities, meaning that a significant amount of Product A can be present among the impurities separated during distillation. I would appreciate some advice from those with more experience: 1. Is it better to use a floating valve tower or a packed tower? ； How should a column for removing high-boiling-point and low-boiling-point impurities be designed to meet the quality specifications? Thank you
This requirement is quite high; increasing the reflux and tower height results in substantial energy consumption and investment costs. Can it be solved by other methods, such as crystallization? With physical property data, quantitative calculation should be possible, leaving some margin as well. It can be achieved.
Your purity requirements are quite high; don’t simplify things. You should find a design institute or university to help you conduct software-based simulations in order to determine whether there are suitable towers and packing materials. Then conduct experiments with full reflux to verify it. This is not a casual question.
Reply to 2# jiafengwang: Thank you all for your suggestions. Crystallization is a good idea; some of the impurities can be removed this way, but those with very low melting points cannot be handled using this method
Could the adsorption method be considered?
Reply to 3# NSHYXFWB: Regarding the above issues, is it possible to compromise on the main component concentration when removing low-boiling-point impurities? In other words, the separated low-boiling-point impurities can contain a large amount of the main component, and this process can be repeated several times. Increase the reflux ratio to remove high-boiling-point impurities. To achieve a rate of over 99.99%
Reply to 5# scg_tju: What you said is quite innovative. What materials are generally used for adsorption?
From the perspective of distillation column equilibrium, your view that it’s not easy to achieve high purity at the bottom of the column is valid
Reply to 8# NSHYXFWB: Yes, when separating low-boiling-point impurities, it is only necessary to ensure high precision in the material at the bottom of the distillation tower; why is it so difficult to achieve this?
Reply to 7# zirconium: It depends on the system in question; it’s hard to say. There are some useful options available at present, but they seem to be few in number, as the adsorbents that have been developed lack versatility
I do know of a company that provides various adsorbents (our company has been using them). It might seem like advertising if I mention it directly, so if you need it, message me privately and I’ll send it to you!