Recycling method of waste acid from stainless steel acid washing process

An acid cycle and membrane stack technology, applied in the field of metallurgical environmental protection, can solve problems such as unfavorable energy saving, increase production cost, and environmental harm, and achieve the effects of avoiding the deterioration of pickling quality, improving productivity, and reducing production costs.

Inactive Publication Date: 2010-05-12
TONGJI UNIV +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The addition and subtraction neutralization method consumes a large amount of alkaline substances and produces a large amount of refractory sludge, which is costly and environmentally harmful, which is not conducive to energy saving and will increase production costs

Method used

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  • Recycling method of waste acid from stainless steel acid washing process
  • Recycling method of waste acid from stainless steel acid washing process
  • Recycling method of waste acid from stainless steel acid washing process

Examples

Experimental program
Comparison scheme
Effect test

Embodiment

[0032] The waste acid is neutralized by adding alkali, and the concentration of each index is as follows:

[0033] Before treatment: NO in waste acid 3 - Concentration 2.23mol / L, F - The concentration is 5.70mol / L; it contains a certain amount of metal ions (when KOH is added, a certain amount of water is added, so the concentration decreases).

[0034] Capacity: 1000L / h, NO 3 - : 1.86mol / L, F - : 4.75mol / L, K + : 6.61mol / L, the total of multivalent cations (Fe, Cr, Ni, Ca, Mg, etc.) is 1mg / L. The waste liquid does not contain membrane fouling substances such as oil, particulate polymers, and surfactants, and acidifiers that easily cause membrane degradation, and the waste liquid does not contain SS components. The liquid temperature is below 35°C.

[0035] After the bipolar membrane stack reaction, the indicators of acid solution, alkali solution and dilute salt solution are as follows:

[0036] Acid solution: 2000L / h, HF: 2.12mol / L, HNO 3 : 0.93mol / L; lye: 2000L / h,...

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Abstract

The invention relates to a recycling method of waste acid from a stainless steel acid washing process, comprising the following steps of: (1) adding water soluble alkali in waste acid to adjust the pH to alkalescence and enable metal ions to generate hydroxide deposition; (2) filtering the hydroxide deposition by adopting a press filtering method, discharging filter cakes outside and collecting the filtrate; and (3) pumping the filtrate into a bipolar-membrane membrane stack, applying electrolysis voltage at the two ends of the membrane stack to generate mixed acid, alkali and dilute salt solution to be respectively discharged through different pipelines. The mixed acid obtained from the method can be reused in an acid washing process, and the alkali can be reused for neutralizing the waste acid in the step (1). Therefore, the invention can realize regeneration of waste acid and the recycling of the alkali, avoid reducing acid washing quality, keep the stable components of acid washing solution and improve the acid washing quality. The invention also has the characteristics of reducing the acid consumption for acid washing, reducing the discharge of acid liquor, reducing the production cost, improving the environment, enhancing the production efficiency and the like.

Description

technical field [0001] The invention belongs to the field of metallurgy and environmental protection, and in particular relates to a method for recycling stainless steel pickling waste acid. Background technique [0002] In the stainless steel annealing and pickling line, the iron oxide scale and chromium-poor layer on the surface of the strip are usually removed by pickling, and the surface of the strip is passivated to improve the corrosion resistance of the steel plate. The important pickling is the mixed pickling of nitric acid and hydrofluoric acid. During the pickling process, the acid solution will react with iron, nickel, chromium, etc. in the base metal to form metal salts. As the content of metal ions increases, the free acid components in the acid solution decrease, the activity decreases, and the pickling effect decreases. At the same time, some insoluble substances will accumulate to form a large amount of acid mud, forming a large amount of waste acid. For th...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C23G1/36
Inventor 范建伟张杰刘祥虎孙宇程炜潘荣幸
Owner TONGJI UNIV
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