Recycling treatment process for chlorohydric acid pickling liquid waste

Abstract

The invention discloses a recycling treatment process for chlorohydric acid pickling liquid waste. The process comprises the following steps: adjusting the acidity of CaCO3 of the chlorohydric acid pickling liquid waste to 99.65-124.56g/L; adding ferrous chloride so as to enable ferrite to be in a saturation condition; heating to the bubble point, then feeding the mixture into a rectifying tower and separating, wherein the pressure in the rectifying tower is 61.05-67.50Kpa; recovering a 10-15% diluted hydrochloric acid liquid and ferrous chloride crystals. Through reasonable parameter control and decompressing and rectifying processes, hydrochloric acid liquor applicable to acid pickling steel pieces as well as a coagulant capable of being used for sewage and wastewater treatment or a chemical raw material ferrous chloride can be recovered just by means of materials generated in the steel piece acid pickling process without spending other raw materials, so that the cost is greatly saved. The process is process-investment-saving, low in energy consumption and easy for mastering of operation, and can be continuously operated or intermittently operated in batches, thereby realizing automatically controlled operation.

Description

technical field [0001] The invention relates to a recycling treatment process of hydrochloric acid pickling waste liquid, which is mainly suitable for resource utilization of hydrochloric acid pickling waste liquid in small and medium-sized steel enterprises. Background technique [0002] Steel parts need to use sulfuric acid or hydrochloric acid to remove the oxide scale on the steel surface before hot-dip galvanizing. Compared with sulfuric acid pickling, hydrochloric acid pickling is faster and the surface quality of steel is better. Therefore, many steel enterprises choose hydrochloric acid for pickling. The rate slows down, the pickling effect is affected, and new hydrochloric acid must be replaced to maintain a suitable pickling speed. Hydrochloric acid pickling produces hydrochloric acid pickling liquid containing free hydrochloric acid with a weight ratio of 5% to 7% and iron content of 100 to 140g / L, which is hydrochloric acid pickling waste liquid. The domestic ir...

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

[0006] 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

[0007] 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

[0008] 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.

[0009] 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 pickling waste liquid, hydrochloric acid will be encountered. - 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, CN103288232A adopts salt-adding distillation technology, adding calcium chloride and magnesium chloride to change the gas-liquid equilibrium curve of hydrochloric acid-water, improving the distillation effect, increasing the concentration of recovered hydrochloric acid, and the residual liquid can be used to prepare compound Coagulant, but this method adopts atmospheric batch distillation, which consumes a lot of energy and has low productivity; adding calcium chloride and magnesium chloride will increase the operating cost

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