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CN-116924492-B - Stainless steel pickling waste mixed acid treatment system and recovery method of nitric acid and hydrofluoric acid

CN116924492BCN 116924492 BCN116924492 BCN 116924492BCN-116924492-B

Abstract

The invention relates to a stainless steel pickling waste mixed acid treatment system and a method for recycling nitric acid and hydrofluoric acid, wherein the stainless steel pickling waste mixed acid treatment system comprises a waste acid storage tank, an electrolytic tank, an exhaust device, a spraying device, a filtering device, a cathode acid storage tank and an anode acid storage tank, wherein the electrolytic tank is provided with an anion membrane, the electrolytic tank is divided into a cathode chamber and an anode chamber, the cathode chamber is connected to the cathode acid storage tank through the exhaust device and the spraying device which are arranged correspondingly and is used for introducing hydrofluoric acid gas volatilized from the cathode chamber into the cathode acid storage tank, the anode chamber is connected to the anode acid storage tank through the exhaust device and the spraying device which are arranged correspondingly and is used for introducing nitric acid gas volatilized from the anode chamber into the anode acid storage tank, the cathode chamber and the filtering device are connected into a circulation loop and are used for circularly filtering cathode liquid, sediment in the cathode liquid is removed, the filtering device is also connected to the cathode acid storage tank, and the anode chamber is connected to the anode acid storage tank. The waste mixed acid treatment system can realize the recovery of nitric acid and hydrofluoric acid in waste mixed acid.

Inventors

  • WANG HONGJUN
  • LI YAQING
  • CHEN JINGHONG
  • YUAN YAO
  • CHEN YUAN

Assignees

  • 肇庆宏旺金属实业有限公司

Dates

Publication Date
20260508
Application Date
20230615

Claims (10)

  1. 1. The stainless steel pickling waste mixed acid treatment system is characterized by comprising a waste acid storage tank, an electrolytic tank, an exhaust device, a spraying device, a filtering device, a cathode acid storage tank and an anode acid storage tank, wherein the electrolytic tank is provided with an anion membrane, the electrolytic tank is divided into a cathode chamber and an anode chamber, the cathode chamber is connected to the cathode acid storage tank through the exhaust device and the spraying device which are arranged correspondingly, hydrofluoric acid gas volatilized from the cathode chamber is used for being introduced into the cathode acid storage tank, the anode chamber is connected to the anode acid storage tank through the exhaust device and the spraying device which are arranged correspondingly, nitric acid gas volatilized from the anode chamber is used for being introduced into the anode acid storage tank, the cathode chamber and the filtering device are connected into a circulation loop, the cathode solution is used for circularly filtering, sediment in the cathode solution is removed, metal ions in the waste acid in the cathode chamber are reduced into metal simple substances and are adhered to a cathode electrode plate in the electrolytic process, the metal attached to the cathode electrode plate is periodically cleaned, the filtering device is also connected to the cathode acid storage tank, the anode chamber is connected to the anode acid storage tank, after the power supply is supplied to the anode, and the anode solution enters the cathode acid storage tank through the filtering device; The anion membrane is an anion membrane with directional selective penetrability, anions can be selectively supplied to pass through the anion membrane from the cathode chamber to enter the anode chamber, NO 3 - preferentially passes through due to the selective penetrability of the anion membrane, NO 3 - enters the anode chamber in a large amount, F - is left in the cathode chamber in a large amount, waste mixed acid in a waste acid storage tank is placed in the cathode chamber, low-concentration nitric acid solution with the same liquid level is placed in the anode chamber, and the initial dilute nitric acid concentration of the anode solution is 0-80g/L.
  2. 2. A method for recycling nitric acid and hydrofluoric acid in stainless steel pickling waste mixed acid is characterized in that the stainless steel pickling waste mixed acid treatment system is provided, and comprises the following steps: (1) Carrying out coarse filtration on the stainless steel strip acid washing waste mixed acid, filtering and removing particles in the waste mixed acid, and discharging the waste mixed acid after coarse filtration into a waste acid storage tank for later use; (2) Placing waste mixed acid in a waste acid storage tank in a cathode chamber, and placing low-concentration nitric acid solution with the same liquid level in an anode chamber, wherein the initial dilute nitric acid concentration of the anode solution is 0-80g/L; (3) The cathode chamber is placed with a cathode electrode, the anode chamber is placed with an anode electrode, electrolysis is started, free NO 3 - in waste mixed acid passes through an anion membrane and enters the anode chamber, F - is left in the cathode chamber to realize separation of NO 3 - and F - , metal ions in waste acid in the cathode chamber are reduced into metal simple substances and are attached to a cathode electrode plate in the electrolysis process, and the metal simple substances attached to the cathode electrode plate are cleaned periodically; (4) Circularly filtering the liquid in the cathode chamber to remove the precipitate formed in the cathode chamber; (5) Gaseous hydrofluoric acid volatilized from the cathode chamber flows back to the cathode acid storage tank through the corresponding air draft device and the spraying device; (6) After the electrolysis is finished, the liquid in the cathode chamber is introduced into the filtering device for filtering and then enters the cathode acid storage tank to obtain hydrofluoric acid solution, and the liquid in the anode chamber enters the anode acid storage tank to obtain nitric acid solution.
  3. 3. The method for recovering nitric acid and hydrofluoric acid according to claim 2, wherein in the step (4), the external filter press is adopted for the filtration, and the chamber plate and the filter cloth are made of acid-resistant materials.
  4. 4. The method for recovering nitric acid and hydrofluoric acid according to claim 2, wherein the cathode electrode is made of stainless steel, copper or lead, and the anode electrode is made of lead dioxide or platinum.
  5. 5. The method for recovering nitric acid and hydrofluoric acid according to claim 2, wherein the concentration of nitric acid in the waste liquid of the stainless steel pickling in the cathode chamber in the step (2) is 40-120g/L, the concentration of hydrofluoric acid is 0-10g/L, and the concentration of metal ions is 50-200g/L.
  6. 6. The method for recovering nitric acid and hydrofluoric acid according to claim 2, wherein in the step (6), the concentration of the obtained hydrofluoric acid solution is 0 to 100g/L, and the concentration of the obtained nitric acid solution is 50 to 400g/L.
  7. 7. The method for recovering nitric acid and hydrofluoric acid according to claim 2, wherein in the step (3), The electrifying current of the electrolytic tank is 500-5000A/m 2 , the temperature in the electrolytic tank is 30-80 ℃, and the electrolytic time is 8-24 h.
  8. 8. The method for recovering nitric acid and hydrofluoric acid according to claim 2, wherein in the step (4), the precipitate is a hydroxide precipitate formed by a part of metal ions in the mixed acid.
  9. 9. The method for recovering nitric acid and hydrofluoric acid according to claim 2, wherein in the step (4), the obtained precipitate is a metal oxide and a metal hydroxide, and the precipitate is subjected to centrifugal dehydration.
  10. 10. The method for recovering nitric acid and hydrofluoric acid according to claim 2, wherein in the step (5), the volatilized nitric acid and hydrofluoric acid are additionally contained, and after the electrolysis is completed, the nitric acid and hydrofluoric acid are mixed with the solution in the anode chamber and the solution in the cathode chamber, and the mixture is reused as the mixed acid solution.

Description

Stainless steel pickling waste mixed acid treatment system and recovery method of nitric acid and hydrofluoric acid Technical Field The invention belongs to the technical field of waste acid treatment, and particularly relates to a stainless steel pickling waste mixed acid treatment system and a method for recycling nitric acid and hydrofluoric acid. Background In the manufacturing process of stainless steel, black and yellow oxide skin is generated on the surface, and the attractiveness and corrosion resistance of the material are affected, so that pickling passivation treatment is generally needed, and a new chromium-containing oxide film is generated while the surface glossiness is improved, so that the passivation and corrosion prevention purposes are achieved. In industrial production, the treatment is generally carried out using a sulfuric acid/neutral salt electrolysis+mixed acid pickling scheme. The mixed acid takes nitric acid and hydrofluoric acid as main components, can obviously improve the production quality of stainless steel, and the active ingredients of the mixed acid are gradually reduced along with the promotion of the reaction process, so that the activity is reduced along with the gradual reduction, and acid washing wastewater is generated. The acid liquor has very complex components and mainly comprises the following components: (1) The content of nitric acid in each liter of wastewater is about 20-200 g, the wastewater pipeline is easy to corrode after discharge, the problems of soil calcification and the like are caused, but the direct neutralization treatment cost is extremely high. (2) The content of hydrofluoric acid in each liter of wastewater is about 0-50 g, and fluorine element in the wastewater can enter animal and plant bodies through soil and water sources to cause metabolic disorder and even cell necrosis. (3) The metal ions, mainly iron, chromium, nickel, and the like, can destroy water ecology and cause human diseases. In recent years, as the requirements for the management of solid hazardous waste are increased and the cost of environmental protection treatment is increased, it is necessary to reduce the waste generated from acid washing wastewater. Meanwhile, in consideration of the requirements of environmental protection and sustainable development of resources, the mixed acid waste acid needs to be regenerated. The mixed acid recovery technology which is common worldwide at present mainly comprises the following three types: (1) In the resin adsorption method, acid components are adsorbed by anion exchange resin, and salt solution flows out from the other end of the resin bed, so that acid and the salt solution are separated, and purified acid liquor is returned to the pickling tank for continuous use. The purification process is simple, the operation is convenient, the occupied area is compact, the installation cost is low, the disposable investment is small, but only free acid in waste acid can be recovered, metal salt cannot be recovered, and the deacidified metal salt is discharged after further treatment. In addition, even after neutralization treatment, nitrate and fluoride cannot be eliminated, so that the influence on the environment is large, the difficulty in removing nitrogen is large, and the biological denitrification treatment process is complex. (2) The decompression evaporation method uses the difference of the boiling points of H 2SO4、HNO3 and HF, and the decompression distillation is carried out, H 2SO4 and nitrate and fluoride in the waste acid liquid are subjected to displacement reaction, HNO 3 and HF are generated and distilled out along with water, and the HNO 3 and the HF are condensed and recovered. The method can recover the free acid and the compound acid simultaneously, realizes full acid recovery and has high recovery rate, but the process has less application in practical engineering, mainly because the requirement on equipment is higher by carrying out reduced pressure distillation under the condition of strong acid. The technology is used by domestic minority enterprises, but the automation control degree is very low, mainly manual operation control is adopted, and the technology needs to be further developed. (3) Spray roasting acid regeneration technology, ruthner company in 1992 successfully used for recycling stainless steel mixed acid waste liquid, obtaining acid gas and metal oxide through high temperature and heating roasting, and spraying the acid gas to form regenerated acid. The free acid and the compound acid can be recovered simultaneously, the recovery rate is higher, the nickel-containing metal oxide produced simultaneously can be recycled, the wastewater treatment capacity is greatly reduced, and the economic value is higher. But the process flow is complex, the equipment is huge, the installation cost and the operation and maintenance cost are high, the one-time investment is large, and the method is suitable for recyc