Question: What is the principle behind using calcium chloride for dehydration, and how should the waste residue be disposed of?
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Our company has a product that is sent to a chemical manufacturing firm for purification; the raw material contains 20% water, which forms an azeotrope with the main components. The company uses calcium chloride to absorb water; I would like to know the principle behind this. Is this a mature technology or one that is about to be phased out? What are its advantages and disadvantages? And can the waste residues be recycled? What to do if it cannot be recycled? I’m not in the chemical industry, so I don’t understand; I’d like to learn more. This post was last edited by thong0421 on 2009-3-21 19:47.]
Since calcium chloride is a desiccant, it can naturally absorb water; it is inexpensive, its production process is not advanced, and it can be recycled and reused after use.
I’m not sure if you’re trying to separate an isopropyl alcohol and water mixture, but regardless of what needs to be separated, using CaCl2 for dehydration is an outdated method. Nowadays, extraction distillation or azeotropic distillation is employed to separate such azeotic systems. If the volume of material is large, you might want to consult Tianjin Xintianjin Packing Company; their separation technologies and packing materials are of high quality in China. The phone number is 23301230, spoken to by Engineer Huang. PS: I know people from their company very well.
Vacuum distillation cannot separate your azeotropes; CaCl2-based dehydration is definitely an outdated method, unless the amount used is very small and suitable for laboratory use； As for the specific procedures, you need to get in touch with them directly; after all, this falls within their company’s area of responsibility, and it’s not appropriate for me to say more.
Thank you to the moderator. Mm-hm. This one. I thought I’d gain some knowledge. How does dehydration of CaCl2 manifest itself? It seems the boss is a bit interested in this. After dehydration, the water content of CaCl2 can be reduced to 0.05%, so I would like to know its advantages and disadvantages. This post was last edited by thong0421 on 2009-3-21 23:55.]
The CaCl2 process is far too outdated: it’s inconvenient to handle solid materials, dehydrating the CaCl2 solution is energy-intensive and leads to scaling; there are also issues regarding the disposal of waste residues, and improper operation often results in equipment blockages! But then again, what exactly is being separated? If it’s about recovering HCl from dilute hydrochloric acid, there’s no better way than to use CaCl2 ； If separating organic substances or azeotropes with water such as isopropanol, definitely avoid using CaCl2.
"The CaCl2 process is far too outdated: it’s inconvenient to handle solid materials, dehydrating the CaCl2 solution is energy-intensive and leads to scaling; there are also issues regarding the disposal of waste residues, and improper operation often results in equipment blockages! " Okay! What is separated occasionally is an azeotrope of organic matter and water, with the organic substance having a boiling point of 80 degrees Celsius.
Hehe, everything you said is correct. But if calcium chloride can be used for dehydration, then no other method will be chosen. Well, using calcium chloride for dehydration is cheap; saving money is what really matters.:lol
Firstly, it is a chemical reaction; generally, this reaction takes the form of CaCl2 + 2H2O == CaCl2·2H2O. However, at different temperatures, different hydrated compounds can be formed (with 1, 2, 3, or 6 molecules of water of crystallization). Moreover, anhydrous calcium chloride cannot be used to dry ammonia, ethanol, and certain organic substances such as lipids, as it forms complexes with them. Secondly: the products resulting from the reaction can be recycled. That is, calcium chloride dihydrate is reheated to 260–300°C and dried to remove water, thereby turning into white anhydrous calcium chloride.
It is an organic product obtained through vacuum distillation, with a purity of only 97%. To achieve a purity of 98%, the 1% of water present cannot be removed. After several rounds of recrystallization, the color of the product turns yellow. Could anyone suggest ways to get rid of this 1% of water?
It is estimated that the number of theoretical plates is insufficient; conducting more reflux cycles will not be very effective. It is recommended to replace the packing with a more efficient type or increase its height!