A method for resource utilization of smelting waste acid

Abstract

The present application relates to smelting pollution treatment technical field, specifically related to a kind of resource utilization method of smelting waste acid.The resource utilization method of smelting waste acid of the present application includes the following steps: under the condition of 10~30 ℃, smelting waste acid is mixed with hydrogen sulfide, and first treatment liquid is obtained;The first treatment liquid and magnesium oxide are mixed, and second treatment liquid is obtained;The second treatment liquid is heated to above 100 ℃.The method of the present application realizes the efficient separation and resource utilization of arsenic, fluorine, chlorine impurity elements in smelting waste acid while high-value utilization of sulfuric acid in non-ferrous smelting waste acid, no waste residue is generated in whole process, no waste water and waste gas is discharged, with the advantages of short process, easy operation, low cost etc., and has important significance to the sustainable development of non-ferrous smelting industry.

Description

Technical Field

[0001] This invention relates to the field of pollution control technology in non-ferrous smelting, specifically to a method for the resource utilization of smelting waste acid. Background Technology

[0002] The raw materials for non-ferrous metal smelting are mostly sulfide ores. The sulfur dioxide flue gas produced during the roasting or smelting of sulfide ores needs purification before being used to produce acid. This purification process yields waste acid containing 5-10% acid and high levels of impurities such as fluorine, chlorine, and arsenic. Due to these impurities, this waste acid cannot be returned to the wet process system. Domestic and international waste acid treatment methods mostly employ the "lime neutralization" method, aiming to achieve standard wastewater discharge. This produces large quantities of hazardous waste acid sludge requiring waterproofing, seepage prevention, and dust control, occupying a large area and posing a significant environmental pollution risk. The sulfuric acid in the waste acid forms gypsum slag containing large amounts of heavy metals and calcium fluoride. Not only is the sulfuric acid resource not effectively utilized, but the gypsum slag requires costly outsourcing for disposal or storage. The neutralized liquid also needs further treatment through softening, multi-media filtration, ultrafiltration, reverse osmosis, and electrodialysis. The overall process is lengthy, costly, and labor-intensive, severely impacting the economic benefits of enterprises. Current technology uses a two-stage lime slurry neutralization process for wastewater. The first stage produces gypsum slag without heavy gypsum residue, while the second stage produces heavy gypsum slag. The liquid after the second stage neutralization is softened with CO2 and then reused in the system. However, in this method, fluoride from the wastewater enters the first-stage neutralization gypsum slag in the form of calcium fluoride, making resource utilization difficult. Heavy metals such as arsenic also enter the second-stage neutralization gypsum slag, which is also classified as hazardous waste. Chlorine remains in the liquid after the second stage neutralization. With increasingly stringent national environmental standards, existing treatment methods struggle to achieve stable wastewater discharge, especially in areas with special emission limits. This severely restricts the sustainable development of the non-ferrous smelting industry.

[0003] Therefore, strengthening research on the resource utilization technology of waste acid from non-ferrous smelting, and achieving the resource utilization of sulfuric acid, arsenic, fluorine, and chlorine in waste acid while efficiently separating heavy metals and fluorine and chlorine impurities, and realizing zero discharge of waste, not only effectively combines the economic benefits of enterprises with the ecological and environmental benefits, but also has great significance for the sustainable development of the non-ferrous smelting industry.

[0004] Therefore, there is an urgent need to develop a method for the resource utilization of smelting waste acid. Summary of the Invention

[0005] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, one object of this invention is to provide a method for the resource utilization of smelting waste acid, which has advantages such as a short process, ease of operation, and low cost.

[0006] Therefore, the first aspect of the present invention provides a method for the resource utilization of smelting waste acid, comprising the following steps:

[0007] At 10–30°C, smelting waste acid is mixed with hydrogen sulfide to obtain the first treatment solution;

[0008] The first treatment solution and magnesium oxide are mixed to obtain the second treatment solution;

[0009] The second treatment solution is heated to above 100°C.

[0010] The process of this invention includes: firstly, treating smelting waste acid with hydrogen sulfide to remove heavy metal elements such as arsenic, trace amounts of mercury, and trace amounts of zinc; then treating the arsenic-removed liquid (first treatment liquid) with magnesium oxide to produce magnesium fluoride product and a second treatment liquid; evaporating the second treatment liquid to remove chlorine, causing the chlorine to volatilize in the form of HCl and collecting it to produce hydrochloric acid product. This method of the invention achieves efficient separation and resource utilization of arsenic, fluorine, and chlorine impurities in waste acid while simultaneously utilizing sulfuric acid in non-ferrous smelting waste acid for high-value processing. The entire process generates no waste residue, and there are no wastewater or waste gas emissions. It has advantages such as a short process, ease of operation, and low cost, and is of great significance to the sustainable development of the non-ferrous smelting industry.

[0011] In some embodiments of the present invention, the mixing time of the smelting waste acid and hydrogen sulfide is 3 to 6 hours at a temperature of 10–30°C. The inventors have found that if the reaction temperature is too low or the reaction time is too short, the removal of arsenic, mercury, and zinc is ineffective; if the reaction temperature is too high, energy consumption will increase.

[0012] In some embodiments of the present invention, the first treatment solution and magnesium oxide are mixed at a temperature of 70–90°C. The temperature of 70–90°C can improve the defluorination efficiency of magnesium oxide while controlling costs.

[0013] In some embodiments of the present invention, the mixing time of the first treatment liquid and the magnesium oxide is 1 to 5 hours; in some preferred embodiments of the present invention, the mixing time of the smelting waste acid and hydrogen sulfide is 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5 hours.

[0014] In some embodiments of the present invention, the final pH of the mixture of the first treatment solution and the magnesium oxide is 4 to 6.

[0015] In some embodiments of the present invention, the purity of the magnesium oxide is ≥90%. Therefore, a better defluorination effect can be achieved while improving defluorination efficiency.

[0016] In some embodiments of the present invention, the first treatment solution is treated with magnesium oxide to obtain a second treatment solution and magnesium fluoride; the second treatment solution has a fluorine content ≤42.65 mg / L and a magnesium fluoride purity ≥95.97%. The present invention utilizes magnesium oxide to treat the first treatment solution while simultaneously producing magnesium fluoride, increasing the variety of products and improving the overall economic efficiency of the process. Furthermore, magnesium fluoride has wide applications in many industrial fields (such as metallurgy, ceramics, and electronics) and can be used as a raw material to further create value.

[0017] In some embodiments of the present invention, after obtaining the second processing liquid and before heating the second processing liquid, the second processing liquid is subjected to low-temperature evaporation and concentration at 70-90°C.

[0018] In some embodiments of the present invention, the low-temperature evaporation and concentration time is 1 to 5 hours.

[0019] In some embodiments of the present invention, the second treatment liquid is heated to above 100°C for 1 to 5 hours.

[0020] In some embodiments of the present invention, the second treatment liquid is heated to above 100°C to obtain a dechlorinated liquid. High-temperature evaporation can volatilize the chlorine in the second treatment liquid as HCl, yielding the produced hydrochloric acid product. After this dechlorination step is completed, the chlorine content in the dechlorinated liquid is ≤100 mg / L, and the HCl mass fraction in the produced hydrochloric acid product is greater than 31%.

[0021] In some embodiments of the present invention, the second treatment liquid is heated to above 100°C for high-temperature evaporation and concentration to obtain a dechlorinated liquid; the dechlorinated liquid is then cooled at a temperature of 20–48°C. This yields magnesium sulfate heptahydrate. Magnesium sulfate heptahydrate has applications in agriculture, medicine, printing and dyeing industries, realizing the resource utilization of elements such as magnesium and sulfur in waste acid.

[0022] In some embodiments of the present invention, the liquid obtained after solid-liquid separation is returned to the dechlorination step for evaporation and dechlorination. This further saves resources.

[0023] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0024] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0025] Figure 1 A flowchart of a method for resource utilization of smelting waste acid according to an embodiment of the present invention is shown. Detailed Implementation

[0026] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0027] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0028] The proportion of sulfide minerals in non-ferrous metal smelting raw materials is gradually increasing. As the grade of the ore decreases, the content of impurity elements such as arsenic, lead, and cadmium also gradually increases. Enterprises discharge large amounts of acidic wastewater containing arsenic, lead, and cadmium during the purification process; this is called waste acid. The arsenic concentration in waste acid is typically between 0.5 and 20 g / L. Due to the severely excessive levels of heavy metal ions such as arsenic, lead, mercury, and cadmium in waste acid, it can be discharged or reused after purification treatment. Current technology typically uses lime neutralization, which generates large amounts of hazardous gypsum waste that needs to be stockpiled.

[0029] Therefore, the first aspect of the present invention provides a method for the resource utilization of smelting waste acid, comprising the following steps:

[0030] At 10–30°C, smelting waste acid is mixed with hydrogen sulfide to obtain the first treatment solution;

[0031] The first treatment solution and magnesium oxide are mixed to obtain the second treatment solution;

[0032] The second treatment solution is heated to above 100°C.

[0033] The process of this invention includes: firstly, treating smelting waste acid with hydrogen sulfide to remove heavy metal elements such as arsenic, trace amounts of mercury, and trace amounts of zinc; then treating the arsenic-removed liquid (first treatment liquid) with magnesium oxide to produce magnesium fluoride product and a second treatment liquid; evaporating the second treatment liquid to remove chlorine, causing the chlorine to volatilize in the form of HCl and collecting it to produce hydrochloric acid product. This method of the invention achieves efficient separation and resource utilization of arsenic, fluorine, and chlorine impurities in waste acid while simultaneously utilizing sulfuric acid in non-ferrous smelting waste acid for high-value processing. The entire process generates no waste residue, and there are no wastewater or waste gas emissions. It has advantages such as a short process, ease of operation, and low cost, and is of great significance to the sustainable development of the non-ferrous smelting industry.

[0034] In some embodiments of the present invention, the smelting waste acid is zinc smelting waste acid and / or copper smelting waste acid. The main components of zinc smelting waste acid are H2SO4 40-60 g / L and As. 3-2-10g / L, Zn 2+ 30-60mg / L, F - 2-10g / L, Cl - 1-10 g / L. The main components of copper smelting waste acid are H2SO4 40-60 g / L and As. 3- 5-15g / L, Cu 2+ 2-10 mg / L, F - 2-10g / L, Cl - 1-10g / L.

[0035] The present invention does not impose any special restrictions on the source of the hydrogen sulfide. In some embodiments of the present invention, the hydrogen sulfide is in a gaseous state, preferably synthesized from sulfur and hydrogen.

[0036] In some embodiments of the present invention, the purity of hydrogen sulfide gas is ≥60%; in some preferred embodiments of the present invention, the purity of hydrogen sulfide gas is 62%. This effectively removes heavy metal impurities such as arsenic from smelting waste acid.

[0037] In some embodiments of the present invention, the mixing of smelting waste acid and hydrogen sulfide is achieved by passing hydrogen sulfide gas into the smelting waste acid.

[0038] In some embodiments of the present invention, the molar ratio of hydrogen sulfide to arsenic is 1:(1.5-3). As an example, the molar ratio of hydrogen sulfide to arsenic can be 1:1.5, 1:2, 1:2.5 or 1:3.

[0039] In some embodiments of the present invention, the mixing time of the smelting waste acid and hydrogen sulfide is 3-6 hours at a temperature of 10-30°C; in some preferred embodiments of the present invention, the mixing temperature can be 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, or 30°C; in some preferred embodiments of the present invention, the mixing time of the smelting waste acid and hydrogen sulfide is 3, 3.5, 4, 4.5, 5, 5.5, or 6 hours. The inventors have found that if the reaction temperature is too low or the reaction time is too short, the removal of arsenic, mercury, and zinc is ineffective; if the reaction temperature is too high, energy consumption will increase.

[0040] The reaction equations for hydrogen sulfide and impurities in smelting waste acid are shown below:

[0041] 2H3AsO3 + 3H2S = As2S3↓ + 6H2O

[0042] Hg 2+ +H₂S=HgS↓+2H +

[0043] Zn2+ +H₂S=ZnS↓+2H +

[0044] Cu 2+ +H₂S=CuS↓+2H +

[0045] In some embodiments of the present invention, after hydrogen sulfide removal, a first treatment liquid and arsenic sulfide slag and other heavy metal sulfides are obtained; the arsenic content in the first treatment liquid is ≤16mg / L; the arsenic sulfide slag contains ≥40% arsenic. The smelting waste acid treated with hydrogen sulfide effectively removes heavy metals such as arsenic, trace amounts of mercury, and trace amounts of zinc, reducing the emission of these heavy metals into the environment and lowering the risk of pollution to surrounding environments such as soil and water bodies. This is because these heavy metals are difficult to degrade in the natural environment, easily accumulate in organisms, and harm ecosystems and human health. The arsenic sulfide slag can be further recycled to recover arsenic, realizing the transformation of arsenic from pollutant to resource in the waste acid, improving resource utilization, and conforming to the concept of sustainable development.

[0046] In some embodiments of the present invention, the first treatment solution and magnesium oxide are mixed at a temperature of 70–90°C; in some preferred embodiments of the present invention, the mixing temperature is 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, or 90°C. A temperature of 70–90°C can improve the defluorination efficiency of magnesium oxide while controlling costs.

[0047] In some embodiments of the present invention, the mixing time of the first treatment liquid and the magnesium oxide is 1 to 5 hours; in some preferred embodiments of the present invention, the mixing time of the smelting waste acid and hydrogen sulfide is 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5 hours.

[0048] In some embodiments of the present invention, the final pH of the mixture of the first treatment solution and the magnesium oxide is 4 to 6. As an example, the final pH of the mixture of the first treatment solution and the magnesium oxide can be 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5 or 6.0.

[0049] In some embodiments of the present invention, after the first treatment solution and magnesium oxide are mixed for 1 to 5 hours, the pH of the system is 4.5 to 5.5.

[0050] In some embodiments of the present invention, the purity of magnesium oxide is ≥90%. In some preferred embodiments of the present invention, the purity of magnesium oxide is 92.34% or 94.65%. Therefore, a better defluorination effect can be achieved while improving defluorination efficiency.

[0051] In some embodiments of the present invention, the proportion of magnesium oxide particles with a particle size of -200 mesh is greater than 90%; the whiteness of magnesium oxide is ≥95%.

[0052] Magnesium oxide can react with fluorine in the first treatment solution, as shown in the following equation:

[0053] 2HF + MgO = MgF2↓ + H2O

[0054] In some embodiments of the present invention, the first treatment solution is treated with magnesium oxide to obtain a second treatment solution and magnesium fluoride; the second treatment solution has a fluorine content ≤42.65 mg / L and a magnesium fluoride purity ≥95.97%. The present invention utilizes magnesium oxide to treat the first treatment solution while simultaneously producing magnesium fluoride, increasing the variety of products and improving the overall economic efficiency of the process. Furthermore, magnesium fluoride has wide applications in many industrial fields (such as metallurgy, ceramics, and electronics) and can be used as a raw material to further create value.

[0055] In some embodiments of the present invention, after obtaining the second processing liquid, before heating the second processing liquid, the second processing liquid is subjected to low-temperature evaporation and concentration at 70-90°C.

[0056] In some embodiments of the present invention, the low-temperature evaporation and concentration time is 1 to 5 hours; the magnesium content in the liquid after low-temperature evaporation and concentration is controlled to be 50 to 150 g / L. As an example, the low-temperature evaporation and concentration time can be 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or 5 hours.

[0057] In some embodiments of the present invention, the second treatment liquid is heated to above 100°C for 1 to 5 hours; in some preferred embodiments of the present invention, the second treatment liquid is heated to 100 to 120°C; in other preferred embodiments of the present invention, the second treatment liquid is heated to 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119 or 120°C; and the heating time is 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5 hours.

[0058] In some embodiments of the present invention, the second treatment liquid is heated to above 100°C for high-temperature evaporation and concentration to obtain a dechlorinated liquid; the dechlorinated liquid is then cooled at a temperature of 20–48°C. High-temperature evaporation volatilizes the chlorine in the second treatment liquid as HCl, yielding the produced hydrochloric acid product. After this dechlorination step, the chlorine content in the dechlorinated liquid is ≤100 mg / L, and the HCl mass fraction in the produced hydrochloric acid product is greater than 31%.

[0059] In some embodiments of the present invention, the method for resource utilization of smelting waste acid further includes the following steps:

[0060] The cooled system undergoes solid-liquid separation to obtain magnesium sulfate heptahydrate; the solid-liquid separation is preferably performed by centrifugal filtration. This yields magnesium sulfate heptahydrate with a purity greater than 99.5% and an adsorbed water content of less than 20%. Magnesium sulfate heptahydrate has applications in agriculture, medicine, and dyeing industries, realizing the resource utilization of elements such as magnesium and sulfur in waste acid.

[0061] In some embodiments of the present invention, the liquid obtained after solid-liquid separation is returned to the dechlorination step for evaporation and dechlorination. This further saves resources.

[0062] The present disclosure will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be construed as limiting the scope of the disclosure. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0063] Example 1

[0064] This embodiment describes a method for the resource utilization of smelting waste acid, the process flow diagram of which is shown below. Figure 1 As shown, it includes the following steps:

[0065] (1) Arsenic precipitation by sulfide: Take 200 ml of zinc smelting waste acid 3 The main component concentrations are H2SO4 53.55 g / L and As 3+ 2.52g / L, Zn 2+ 36mg / L, Hg + 25mg / L, F - 8.69 g / L, Cl - 1.53 g / L; 62% pure hydrogen sulfide gas was introduced into the zinc smelting waste acid, with an excess of 1.5 times that of arsenic. The reaction temperature was 15℃, and the reaction was carried out for 3 hours. After the reaction was completed, a sulfidated liquid was obtained, which contained As. 3+ 8.68 mg / L, Zn 2+3.3 mg / L, Hg + 1.56 mg / L, the produced arsenic sulfide slag contains 40.35% arsenic;

[0066] (2) Defluorination: Add industrial light magnesium oxide (HG / T2573-2006 standard) with a purity of 92%, whiteness of 90%, and particle size of 92%-200 mesh to the arsenic-removed liquid. The reaction temperature is 85℃, the reaction time is 3h, the final pH is 4.6, and the reaction is stopped. The defluorinated liquid contains 42.65mg / L of fluoride and the purity of magnesium fluoride is 95.97%.

[0067] (3) Low-temperature evaporation and concentration: The defluorinated liquid is concentrated by steam at 85°C for 3 hours. The concentrated liquid contains 123.54 g / L of magnesium. After the first stage of low-temperature evaporation and concentration, the steam turns into condensate and is discharged through the pipeline.

[0068] (4) Two-stage high-temperature evaporation and concentration: After the first-stage low-temperature evaporation and concentration, the liquid continues to be concentrated in the dechlorination equipment at 105°C with steam for 2 hours. The evaporation tail gas is collected to produce hydrochloric acid product with a HCl mass fraction of 31.85%. The chlorine content of the concentrated liquid is 56.34 mg / L.

[0069] (5) Cooling and crystallization: Cool the dechlorinated liquid to 32°C. After cooling, filter the liquid with a centrifuge to produce magnesium sulfate heptahydrate with a purity of 99.68% and an attached water content of 18.56% and hydrochloric acid. The mother liquor from the crystallization is returned to the second-stage high-temperature evaporation and concentration process.

[0070] Example 2

[0071] This embodiment of a method for resource utilization of smelting waste acid includes the following steps:

[0072] (1) Arsenic precipitation by sulfide treatment: Take 150 ml of copper smelting waste acid 3 Its main components are H2SO4 46.54g / L and As. 3+ 10.82 g / L, Cu 2+ 65mg / L, Hg + 10mg / L, F - 2.71 g / L, Cl - 3.86 g / L. Hydrogen sulfide gas with a purity of 62% was introduced, and arsenic was added in excess at a ratio of 2.0. The reaction temperature was 28℃, and the reaction was carried out for 5 hours to obtain a sulfidated liquid. The sulfidated liquid contained As. 3+ 15.54 mg / L, Cu 2+ 2.78 mg / L, Hg + The concentration of arsenic in the arsenic sulfide slag produced was 0.56 mg / L, and the arsenic content was 43.58%.

[0073] (2) Defluorination: Add industrial light magnesium oxide (HG / T2573-2006 standard) with a purity of 93%, whiteness of 92%, and particle size of 95%-200 mesh to the arsenic-removed liquid. The reaction temperature is 76℃, the reaction time is 2h, the final pH is 5.0, the fluorine content of the defluorinated liquid is 36.12mg / L, and the purity of magnesium fluoride is 96.64%.

[0074] (3) Low-temperature evaporation and concentration: The defluorinated liquid is concentrated by steam at 80°C for 3 hours. The concentrated liquid contains 145.06 g / L of magnesium. After the first stage of low-temperature evaporation and concentration, the steam turns into condensate and is discharged through the pipeline.

[0075] (4) Two-stage high-temperature evaporation and concentration: After the first-stage low-temperature evaporation and concentration, the liquid continues to be concentrated in the dechlorination equipment at 113°C with steam for 3 hours. The evaporation tail gas is collected to produce hydrochloric acid product with a HCl mass fraction of 32.12%. The chlorine content of the concentrated liquid is 65.47 mg / L.

[0076] (5) Cooling and crystallization: Cool the dechlorinated liquid to 25°C. After cooling, filter the liquid with a centrifuge to produce magnesium sulfate heptahydrate with a purity of 99.75% and an attached water content of 17.36% and hydrochloric acid. The mother liquor from the crystallization is returned to the second-stage high-temperature evaporation and concentration process.

[0077] Comparative Example 1

[0078] The difference between this comparative example and Example 1 lies in the defluorination process, which specifically includes the following steps:

[0079] (1) Arsenic precipitation by sulfide: Take 200 ml of zinc smelting waste acid 3 The main component concentrations are H2SO4 53.55 g / L and As 3+ 2.52g / L, Zn 2+ 36mg / L, Hg + 25mg / L, F - 8.69 g / L, Cl - 1.53 g / L; 62% pure hydrogen sulfide gas was introduced into the zinc smelting waste acid, with an excess of 1.5 times that of arsenic. The reaction temperature was 15℃, and the reaction was carried out for 3 hours. After the reaction was completed, a sulfidated liquid was obtained, which contained As. 3+ 8.68 mg / L, Zn 2+ 3.3 mg / L, Hg + 1.56 mg / L, the produced arsenic sulfide slag contains 40.35% arsenic;

[0080] (2) Defluorination: Add industrial-grade calcium oxide with a purity of 95%, whiteness of 89%, and particle size of 96%-200 mesh to the arsenic-free liquid. The reaction temperature is 82℃ and the reaction is carried out for 3 hours until the pH of the system is 5.5. Then stop the reaction. The defluorinated liquid contains 18.37 mg / L of fluoride and the calcium fluoride purity is 32.42% (the remaining components are mainly calcium sulfate dihydrate).

[0081] (3) Low-temperature evaporation and concentration: The defluorinated liquid is concentrated at 85°C for 3 hours to produce a chlorine-free condensate recycling system;

[0082] (4) Two-stage high-temperature evaporation and concentration: After the first-stage low-temperature concentration, the liquid continues to undergo two-stage high-temperature evaporation and concentration at 105°C in the dechlorination equipment. After evaporation and concentration for 2 hours, the evaporation tail gas is collected, and dilute hydrochloric acid with a mass fraction of 18.56% HCl is produced. The liquid after evaporation and concentration contains 220.62 mg / L of chlorine.

[0083] Comparative Example 2

[0084] The difference between this comparative example and Example 1 lies in the evaporation and concentration process, which specifically includes the following steps:

[0085] (1) Arsenic precipitation by sulfide: Take 200 ml of zinc smelting waste acid 3 The main component concentrations are H2SO4 53.55 g / L and As 3+ 2.52g / L, Zn 2+ 36mg / L, Hg + 25mg / L, F - 8.69 g / L, Cl - 1.53 g / L; 62% pure hydrogen sulfide gas was introduced into the zinc smelting waste acid, with an excess of 1.5 times that of arsenic. The reaction temperature was 15℃, and the reaction was carried out for 3 hours. After the reaction was completed, a sulfidated liquid was obtained, which contained As. 3+ 8.68 mg / L, Zn 2+ 3.3 mg / L, Hg + 1.56 mg / L, the produced arsenic sulfide slag contains 40.35% arsenic;

[0086] (2) Defluorination: Add industrial light magnesium oxide (HG / T2573-2006 standard) with a purity of 92%, whiteness of 90%, and particle size of 92%-200 mesh to the arsenic-removed liquid. The reaction temperature is 85℃, the reaction time is 3h, the final pH is 4.6, and the reaction is stopped. The defluorinated liquid contains 42.65mg / L of fluoride and the purity of magnesium fluoride is 95.97%.

[0087] (3) Dechlorination: The defluorinated liquid is heated to 106°C in the dechlorination equipment and evaporated and concentrated for 5 hours; the evaporation tail gas is collected to produce hydrochloric acid product with HCl mass fraction of 30.85% and the evaporated and concentrated liquid contains chlorine of 76.24 mg / L, which is used as system makeup water for reuse.

[0088] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," "some implementations," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0089] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for the resource utilization of smelting waste acid, characterized in that, Includes the following steps: At 10~30℃, smelting waste acid is mixed with hydrogen sulfide to obtain the first treatment solution; The first treatment solution and magnesium oxide are mixed to obtain the second treatment solution; The second treatment liquid is heated to above 100°C and concentrated by high-temperature evaporation to obtain a dechlorinated liquid; the dechlorinated liquid is then cooled to obtain magnesium sulfate heptahydrate product. The cooling temperature is 20~48℃; The final pH of the mixture of the first treatment solution and the magnesium oxide is 4-6.

2. The method for resource utilization of smelting waste acid according to claim 1, characterized in that, The mixing time between the smelting waste acid and hydrogen sulfide is 3-6 hours.

3. The method for resource utilization of smelting waste acid according to claim 1, characterized in that, The first treatment solution and magnesium oxide were mixed at 70-90°C.

4. The method for resource utilization of smelting waste acid according to claim 1 or 3, characterized in that, The mixing time between the first treatment solution and the magnesium oxide is 1 to 5 hours.

5. The method for resource utilization of smelting waste acid according to claim 1, characterized in that, The purity of the magnesium oxide is ≥90%.

6. The method for resource utilization of smelting waste acid according to claim 1, characterized in that, Before heating the second treatment liquid, the second treatment liquid is concentrated by low-temperature evaporation at 70~90°C.

7. The method for resource utilization of smelting waste acid according to claim 6, characterized in that, The low-temperature evaporation and concentration time is 1~5 hours.

8. The method for resource utilization of smelting waste acid according to claim 1, characterized in that, The second treatment solution is heated to 100~120℃ for 1~5 hours.

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