Clean production process for waste acid treatment

Abstract

The invention discloses a clean production process for contaminated acid treatment, which comprises the following steps: (1) after contaminated acid is subjected to heavy metal removal pretreatment, adding iron oxide / iron and copper oxide / copper into the contaminated acid to carry out neutralization reaction, and carrying out solid-liquid separation to obtain a ferric sulfate / ferrous sulfate solution and a copper sulfate solution; (2) concentrating and crystallizing the ferric sulfate / ferrous sulfate solution and the copper sulfate solution which are generated by neutralizing the waste acid; (3) roasting the ferric sulfate / ferrous sulfate and copper sulfate crystals step by step to remove crystal water; (4) carrying out high-temperature roasting on the ferric sulfate / ferrous sulfate or copper sulfate after the crystal water is removed, and decomposing into ferric oxide, copper sulfate, sulfur dioxide or sulfur trioxide; the obtained ferric oxide and copper oxide are recycled for neutralization treatment of waste acid after being recycled, and the obtained sulfur dioxide and sulfur trioxide can be recycled for sulfuric acid production. The waste acid is subjected to circulating neutralization treatment, so that the generation of traditional waste acid neutralization slag is avoided, and the resource utilization of sulfur is also realized.

Description

Technical Field

[0001] The invention belongs to the technical field of industrial sewage treatment, and in particular relates to a clean production process for sewage acid treatment. Background Art

[0002] Industrial activities such as non-ferrous metal smelting and pyrite acid production will produce a large amount of waste acid, with a sulfuric acid concentration of 10 to 200 g / L. Traditional lime neutralization treatment will not only produce a large amount of water treatment neutralization slag mainly composed of calcium sulfate, but also due to the lack of effective utilization methods, large-scale storage will not only occupy land and cause ecological damage, but also pose risks such as groundwater pollution and dust. China is short of sulfur resources, and a large amount of sulfate ions in waste acid exist in the form of calcium sulfate, resulting in a large waste of sulfur resources.

[0003] Iron and iron oxide, copper and copper oxide can react with sulfuric acid to undergo neutralization reaction. The reaction products, ferrous sulfate, ferrous sulfate and cupric sulfate, can be concentrated and crystallized, and then decomposed to generate iron oxide, cupric oxide, sulfur dioxide and sulfur trioxide by high temperature roasting. The iron oxide and cupric oxide can be recycled for neutralization of waste acid, while sulfur dioxide and sulfur trioxide can be directly fed into the sulfuric acid production line of the enterprise to realize resource utilization. Based on the above principle, the present invention proposes a clean production process for waste acid treatment, which uses iron oxide / iron and cupric oxide / copper to neutralize waste acid, and realizes closed-loop use of iron oxide and cupric oxide and resource utilization of sulfur by crystallization and roasting of ferrous sulfate, ferrous sulfate and cupric sulfate. Summary of the invention

[0004] The object of the present invention is to provide a clean production process for treating polluted acid: This method is implemented by the following steps: (1) After the waste acid is pretreated for heavy metal removal, iron oxide / iron and copper oxide / copper are added to the pretreated waste acid for neutralization reaction, and after sufficient reaction, solid-liquid separation is performed to obtain ferric sulfate / ferrous sulfate solution and copper sulfate solution; (2) concentrating and crystallizing the ferrous sulfate / ferrous sulfate solution and the copper sulfate solution obtained in step (1); (3) roasting the ferric sulfate / ferrous sulfate crystals and copper sulfate crystals obtained in step (2) at low temperature step by step to remove crystal water; (4) After the crystal water is removed, the ferrous sulfate / ferrous sulfate and cupric sulfate are subjected to high temperature roasting to decompose into iron oxide, cupric oxide, sulfur dioxide and sulfur trioxide; the obtained iron oxide and cupric oxide are returned to the neutralization treatment of the waste acid in step (1) for recycling; the obtained sulfur dioxide and sulfur trioxide can be reused in sulfuric acid production.

[0005] Preferably, the concentration of sulfuric acid in the waste acid in step (1) is greater than 5%.

[0006] Preferably, the iron oxide in step (1) is any one or more of ferric oxide, ferrous oxide, ferric carbonate or iron-containing oxide minerals, and the copper oxide is any one or more of copper oxide, cuprous oxide or copper-containing oxide minerals.

[0007] Furthermore, the iron-containing oxide minerals are minerals such as hematite, siderite, etc. containing ferric oxide, ferrous oxide, iron carbonate, metallic iron, etc., and the copper-containing oxide minerals are minerals such as cuprite, malachite, azurite, etc.

[0008] Preferably, the low-concentration ferric sulfate / ferrous sulfate solution and copper sulfate solution produced by the neutralization in step (1) can be recycled to the flue gas purification section to increase the sulfate concentration thereof, so as to facilitate the subsequent crystallization and concentration of ferric sulfate / ferrous sulfate and copper sulfate.

[0009] Preferably, the low-temperature roasting temperature in step (2) is 50-300°C, the high-temperature roasting temperature is 300-800°C, and further, the high-temperature roasting temperature is 450-600°C.

[0010] Principle of the present invention: (1) After the waste acid is pretreated by heavy metal removal, iron / iron oxide and copper / copper oxide are added to the waste acid, which react with sulfuric acid to generate ferric sulfate / ferrous sulfate and copper sulfate, and the waste acid is neutralized; (2) Concentrating and crystallizing the ferrous sulfate / ferrous sulfate solution and copper sulfate solution produced by neutralizing the waste acid, and calcining the ferrous sulfate / ferrous sulfate crystals and copper sulfate crystals at low temperature to remove crystal water; (3) calcining the ferrous sulfate / ferrous sulfate and copper sulfate after removing the crystal water to decompose them into iron oxide, copper oxide, sulfur dioxide and sulfur trioxide; (4) The iron oxide and copper oxide obtained by high-temperature roasting can be reused for the neutralization of waste acid; the sulfur dioxide and sulfur trioxide obtained by high-temperature roasting can be reused for sulfuric acid production.

[0011] Compared with the prior art, the present invention has the following beneficial effects: (1) No water treatment and neutralization waste residue generation. The present invention completely avoids the generation of CaSO4 neutralization waste residue, reduces the generation of solid waste, and avoids the problems of ecological damage, groundwater pollution, etc. caused by its storage.

[0012] (2) Sulfur recycling. Through high-temperature decomposition of ferrous sulfate / ferrous sulfate and copper sulfate, sulfur dioxide and sulfur trioxide are obtained for sulfuric acid production. This realizes the recycling of sulfur resources throughout their life cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0014] The present invention is further described below in conjunction with the embodiments, but the present invention is not limited in any way. Any changes or substitutions made based on the teachings of the present invention belong to the protection scope of the present invention.

[0015] Example 1 The waste acid produced by a copper smelter has an acid concentration of 3-10%. (1) After the waste acid is pretreated for heavy metal removal, ferric oxide and iron powder are added to the waste acid for neutralization reaction, and ferric sulfate / ferrous sulfate solution is obtained through solid-liquid separation; (2) Concentrating and crystallizing the ferrous sulfate / ferrous sulfate solution produced by neutralizing the waste acid; (3) calcining the ferric sulfate / ferrous sulfate crystals at a temperature of 10-200° C. to remove crystal water; (4) calcining the ferrous sulfate / ferrous sulfate after removing the crystal water at 300-550° C. to decompose it into iron oxide and sulfur dioxide; (5) The iron oxide obtained by high-temperature roasting can be reused for the neutralization of waste acid; (6) The sulfur dioxide obtained by high-temperature roasting can be reused in sulfuric acid production.

[0016] Example 2 The acid concentration of the waste acid produced by a lead-zinc smelter is 3-8%. (1) After the waste acid is pretreated for heavy metal removal, iron carbonate and iron powder are added to the waste acid for neutralization reaction to obtain a ferric sulfate / ferrous sulfate solution; (2) Concentrating and crystallizing the ferrous sulfate / ferrous sulfate solution produced by neutralizing the waste acid; (3) calcining the ferric sulfate / ferrous sulfate crystals at 50-200° C. to remove crystal water; (4) calcining the ferrous sulfate / ferrous sulfate after removing the crystal water at 350-650° C. to decompose it into iron oxide and sulfur dioxide; (5) The iron oxide obtained by high-temperature roasting can be reused for the neutralization of waste acid; (6) The sulfur dioxide obtained by high-temperature roasting can be reused in sulfuric acid production.

[0017] Example 3 The acid concentration of the waste acid produced by a pyrite mine is 5-15%. (1) After the waste acid is pretreated for heavy metal removal, copper oxide, copper powder and a mixture are added to the waste acid for neutralization reaction, and a copper sulfate solution is obtained by solid-liquid separation; (2) Concentrating and crystallizing the copper sulfate solution produced by neutralizing the waste acid; (3) calcining the copper sulfate crystals at 200-300° C. to remove crystal water; (4) the copper sulfate after the crystal water is removed is calcined at 560-800° C. to decompose it into copper oxide, sulfur dioxide and sulfur trioxide; (5) The copper oxide obtained by high-temperature roasting can be reused for the neutralization of waste acid; (6) The sulfur dioxide and sulfur trioxide obtained by high-temperature roasting can be reused in sulfuric acid production.

[0018] Example 4 The waste acid produced by a tin smelter has an acid concentration of 5-20%. (1) After the waste acid is pretreated by heavy metal removal, hematite, siderite, scrap iron, etc. are added to the waste acid for neutralization reaction, and ferric sulfate / ferrous sulfate solution is obtained by solid-liquid separation; (2) Concentrating and crystallizing the ferrous sulfate / ferrous sulfate solution produced by neutralizing the waste acid; (3) calcining the ferric sulfate / ferrous sulfate crystals at 200-300° C. to remove crystal water; (4) calcining the ferrous sulfate / ferrous sulfate after removing the crystal water at 450-750° C. to decompose it into iron oxide and sulfur dioxide; (5) The iron oxide obtained by high-temperature roasting can be reused in the neutralization of waste acid; (6) The sulfur dioxide obtained by high-temperature roasting can be reused in the production of sulfuric acid.

Claims

1. A clean production process for treating polluted acid, characterized by comprising the following steps: (1) After the waste acid is pretreated for heavy metal removal, iron oxide / iron and copper oxide / copper are added to the pretreated waste acid for neutralization reaction. After sufficient reaction, ferric sulfate / ferrous sulfate solution and copper sulfate solution are obtained by solid-liquid separation; (2) concentrating and crystallizing the ferric sulfate / ferrous sulfate solution and the copper sulfate solution obtained in step (1); (3) calcining the ferric sulfate / ferrous sulfate crystals and copper sulfate crystals obtained in step (2) at low temperature to remove crystal water; (4) After the crystal water is removed, the ferric sulfate / ferrous sulfate and copper sulfate are subjected to high temperature roasting to decompose into iron oxide, copper oxide, sulfur dioxide and sulfur trioxide; the obtained iron oxide and copper oxide are returned to the neutralization treatment of the waste acid in step (1) for recycling; the obtained sulfur dioxide and sulfur trioxide can be reused in sulfuric acid production.

2. The clean production process for waste acid treatment according to claim 1, characterized in that The iron oxide in step (1) is any one or more of ferric oxide, ferrous oxide, ferric carbonate or iron-containing oxide minerals, and the copper oxide is any one or more of copper oxide, cuprous oxide or copper-containing oxide minerals.

3. The clean production process for waste acid treatment according to claim 1 is characterized in that The low-concentration ferric sulfate / ferrous sulfate solution and copper sulfate solution produced by the neutralization in step (1) can be recycled to the flue gas purification section to increase the sulfate concentration thereof, so as to facilitate the subsequent crystallization and concentration of ferric sulfate / ferrous sulfate and copper sulfate.

4. The clean production process for treating polluted acid according to claim 1, characterized in that The low-temperature calcination temperature in step (3) is 50-300°C.

5. The clean production process for treating polluted acid according to claim 1, characterized in that The high temperature calcination temperature in step (4) is 300-800°C.

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