Hydrochloric acid resolution and hydrochloric acid concentration
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I have been working on projects related to hydrochloric acid dissociation recently. Currently, hydrochloric acid dissociation is mainly carried out through conventional and advanced methods; conventional methods typically reach only a hydrochloric acid concentration of 20%, while advanced methods are more thorough and allow for the production of more HCl gas. All of these devices are in operation. But I have noticed that not all companies want pure HCl gas; what they want is concentrated hydrochloric acid. Generally, 20% hydrochloric acid can be partially distilled to obtain pure HCl gas, after which an HCl absorption process is carried out. But I wonder why it isn’t possible to obtain concentrated hydrochloric acid directly. In fact, distillation using steam heating can also be employed for the separation of hydrochloric acid; HCl is a non-condensable gas, and by controlling the amount of steam used, the top of the tower will contain a mixture of hydrogen chloride and steam, with a relatively high steam content. Through direct cooling and condensation, concentrated hydrochloric acid is obtained. The amount of HCl gas remaining is small, so it can be absorbed and concentrated using 20% hydrochloric acid.
If the process makes sense, you can take a look at the operating costs
OP, you must find your own question confusing, right? 1. Conventional treatment: Treating 31% concentrated hydrochloric acid results in HCl gas and 20% dilute hydrochloric acid. 2. Advanced treatment: Treating 20% dilute hydrochloric acid yields HCl gas along with waste acid at a concentration of less than 1%. Conventional treatment is generally used in devices that require HCl gas, while advanced treatment is used for waste acid processing; the HCl gas obtained from the advanced treatment of 20% waste acid can be further absorbed by water to produce 31% concentrated hydrochloric acid. Why not use 20% dilute hydrochloric acid to directly obtain 31% hydrochloric acid? ? 1. Do you mean direct distillation? ? No! ! Distilling 20% dilute hydrochloric acid itself is an azeotropic system; it is not possible to obtain HCl and water that can be condensed into 31% hydrochloric acid. 2. 31% concentrated hydrochloric acid can be produced by using 20% dilute hydrochloric acid to absorb additional HCl gas, but additional HCl gas is required.
With 20% hydrochloric acid, a thorough analysis shows that high-purity HCl gas can be obtained at the tower top; there is no doubt about this. You might not have understood what I mean; steam distillation simply lacks a reboiler, but it does not eliminate azeotropy. The HCL at the top of the tower contains a certain amount of water vapor. When we need to produce gas, we introduce a reflux flow (though it’s not a true reflux in the strict sense); when we only need a high-concentration hydrochloric acid, there is no need for such a reflux flow. By increasing the amount of secondary steam, more water vapor can be introduced into the tower. After the mixed gas phase at the top of the tower is cooled and condensed, a larger amount of hydrochloric acid can be obtained. It can reduce the subsequent absorption equipment and processes.