A system for recycling waste hydrochloric acid in iron-containing industries

Abstract

The invention discloses a system for resourceful treatment of iron-containing industrial waste hydrochloric acid. A first acid pickling tower is used for carrying out acid pickling and concentrating on a hydrogen chloride-containing gas which escapes from a first deacidification tower and compressed by a compressor to obtain a finished product industrial hydrochloric acid; an aeration reactor is used for reacting a liquid waste of the first deacidification tower with crystal or a solution of ammonium bicarbonate, ammonium carbonate, sodium bicarbonate or sodium carbonate, generating ferrous hydroxide and ferric hydroxide and generating ammonium chloride or sodium chloride and ferric hydroxide under aeration oxidation and bubbling mixing conditions and sequentially conveying the solid-liquid mixture generated through reaction to a buffer tank and a solid-liquid separator; the buffer tank is used for removing foam, discharging separated carbon dioxide and excessive air or oxygen and separating out an ammonium chloride or sodium chloride solution; and the solid-liquid separator is used for separating out a ferric hydroxide solid product and ammonium chloride or sodium chloride crystal. The concentration of the hydrochloric acid recovered through the acid pickling tower is about 23%, about 95% of hydrochloric acid in the iron-containing waste hydrochloric acid is recovered and the purchase quantity of the hydrochloric acid is reduced.

Description

technical field [0001] The invention belongs to the field of environmental protection and relates to the treatment of industrial iron-containing waste hydrochloric acid, in particular to a system for recycling iron-containing industrial waste hydrochloric acid. Background technique [0002] As a commonly used chemical product, hydrochloric acid is widely used in carbon steel cold rolling, galvanizing and other processes. As a pickling medium, hydrochloric acid reacts with iron oxide on the surface of steel to generate ferrous chloride and ferric chloride and dissolve them in the acid solution. The hydrochloric acid waste liquid produced by this reaction contains about 5% hydrochloric acid and 10-12% ferrous chloride and ferric chloride. If this part of the iron-containing hydrochloric acid waste liquid is directly discharged, it will cause serious environmental damage to the discharge area. pollute. In addition, the waste acid liquid contains ferrous chloride and hydrogen ...

AI Technical Summary

Problems solved by technology

Thermal decomposition method and high temperature hydrolysis method can be divided into roasting method, fluidized bed method, etc. The working principle of these two methods is the same, both of which are to react waste hydrochloric acid containing ferrous chloride with oxygen at high temperature and absorb Concentrate volatilized hydrogen chloride, and the finished products are hydrochloric acid and iron red. The disadvantages are large investment, high operating cost, difficult technology, difficult management and maintenance

The extraction method uses an extract composed of an organic phase for countercurrent extraction, and the method of recycling the extract phase still has high investment and is inconvenient to operate, so it is not suitable

The membrane separation method uses membrane ions to selectively separate iron and acid. The disadvantage is that with the increase of the osmotic pressure of iron ions on both sides of the membrane, a large pressure energy input is required, and it has a great impact on the material and compressive performance of the membrane. High requirements are put forward, and the initial investment and operating costs are relatively high

Precipitation method is to utilize flocculant to flocculate ferrous chloride in waste hydrochloric acid. Although this method utilizes part of ferrous chloride in waste hydrochloric acid, there is still a small part of ferrous chloride in the remaining waste acid solution. This makes the purity level of the product generated by the subsequent waste acid treatment generally not high, which affects the performance of the product

The neutralization method uses alkali to react with waste hydrochloric acid. This is the oldest method for treating pickling waste liquid. However, because hydrogen chloride and ferrous chloride in waste acid liquid have not been utilized, and it is easy to cause secondary pollution, At present, this method is basically no longer used

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