A kind of hydrochloric acid waste liquid purification treatment method

Abstract

The invention discloses a purification treatment method for hydrochloric acid waste liquid. The method comprises the following concrete steps: (1) adjusting the acidity of hydrochloric acid waste liquid and then feeding ferrous chloride; (2) orderly heating saturated hydrochloric acid waste liquid to a bubble point through a heat exchanger and a preheater orderly, and condensing through the heat exchanger and a condenser orderly to obtain a recovered hydrochloric acid solution; (3) adding a coagulant aid and a dilute hydrochloric acid solution to a reaction tank to carry out flocculation reaction; and (4) enabling the flocculated dilute hydrochloric acid solution to flow to a distillation kettle through a tower plate, and heating and vaporizing again, and enabling the residual liquid inside the distillation kettle to flow to a crystallization kettle to be cooled and crystallized, so as to obtain ferrous chloride crystals. The problem that a hydrochloric acid-water constant boiling solution is difficult to separate is effectively solved by using a salting-out effect generated by the recovered ferrous chloride, the acidity of the hydrochloric acid waste liquid can be adjusted by using water or the hydrochloric acid waste liquid, and the cost is also greatly saved. The hydrochloric acid recovery effect is significantly improved after the acidity is adjusted and the coagulant aid is added, and the purification treatment method has good economic benefits and environmental benefits.

Description

technical field [0001] The invention relates to a waste liquid purification treatment method, in particular to a hydrochloric acid waste liquid purification treatment method, and belongs to the field of resource utilization of waste liquid. Background technique [0002] At present, the commonly used hydrochloric acid waste treatment methods include the traditional neutralization precipitation method and resource utilization technology. The neutralization precipitation method is currently the most commonly used method for treating waste acid in China. This method neutralizes the hydrochloric acid in the waste acid with alkaline substances such as alkali and lime, and at the same time precipitates ferrous ions. This method needs to consume a large amount of chemical raw materials such as alkali and lime, and the operating cost is high; hydrochloric acid and ferrous salt in waste acid cannot be recycled, and a large amount of waste residue will cause secondary pollution to the ...

AI Technical Summary

Problems solved by technology

The roasting method is industrially applied by large iron and steel enterprises, but this method requires a large initial investment, strict equipment and process requirements, and it is difficult for small and medium-sized enterprises to bear

In addition, incomplete absorption of hydrogen chloride furnace gas leads to excessive discharge of hydrogen chloride in the tail gas and iron oxide dust generated by roasting will cause secondary pollution

[0005] The ion exchange method and membrane separation method are limited by the high concentration of iron content, which is easy to cause resin and membrane pollution; the extraction method has high requirements for the preparation of the extractant and the regeneration of the extractant, and the recovery of hydrochloric acid for the pickling process may be due to residual Extractant affects product quality

The chemical conversion method is to convert all free hydrochloric acid and ferrous chloride into ferric chloride or ferrous sulfate. Since the conversion of ferric chloride needs to consume chlorine gas and the sale of ferric chloride is not good, it is now very use less

The ferrous sulfate method needs to replace ferrous chloride with sulfuric acid to produce ferrous sulfate. Because the crystallization temperature of ferrous sulfate is low, a set of ice machine system needs to be added, which requires large investment and high operating costs.

[0006] The distillation method is to put the pickling waste liquid into the distillation pot, heat it to boiling under constant pressure, so that the liquid is continuously vaporized, and the generated steam is recovered as dilute hydrochloric acid after condensation, and the ferrous chloride can be recovered by cooling and crystallizing the pot liquid. The advantage is that it does not consume chlorine, sulfuric acid, alkali, lime and other raw materials, and can recover hydrochloric acid and ferrous salt. It has the advantages of simple equipment and low treatment cost. However, when distilling hydrochloric acid waste liquid, it will encounter hydrochloric acid-water Azeotrope obstacle, resulting in low concentration of recovered hydrochloric acid and incomplete recovery

In order to solve the problem of hydrochloric acid-water azeotrope, salt-adding distillation technology is adopted, and calcium chloride and magnesium chloride are added to change the gas-liquid equilibrium curve of hydrochloric acid-water, improve the distillation effect, and increase the concentration of recovered hydrochloric acid. coagulant, but this method adopts atmospheric pressure intermittent distillation, which consumes a lot of energy and has low productivity; adding calcium chloride and magnesium chloride will lead to an increase in operating costs