5% hydrochloric acid concentrated to 21%
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I recently conducted a simulation to see how 5% hydrochloric acid could be concentrated to 21%. The results of the simulation showed that the high-concentration hydrochloric acid solution is obtained from the bottom of the tower, while essentially only water is obtained from the top. After doing some research, I found that many people say the concentrated acid comes from the bottom of the tower; I really can’t understand this. I would appreciate it if experts could explain why this is the case. Azeotrope temperature: 109℃
Friends from Sichuan, just reading without answering! ! !
You’ll understand if you take a look at the boiling point curve of hydrochloric acid
At atmospheric pressure, when the hydrochloric acid concentration is below 19%, the mass proportion of water in the distilled material is greater than 81%, while the mass proportion of HCl is less than 19%； When the hydrochloric acid concentration is higher than 22%, the mass proportion of water in the distillate is less than 78%, while the mass proportion of HCl is greater than 22%. Is it clear now? To further dehydrate and concentrate HCl, an appropriate negative pressure can be applied, as reducing the boiling point of the dilute acid facilitates the evaporation of water.
As you yourself said, the boiling point is 109 degrees. So if it is heated to 100 degrees, will water or hydrochloric acid rise to the top of the tower? Therefore, the hydrochloric acid at the top of the tower will become more concentrated, right?!