Step-by-step treatment and recycling method for treating copper or iron slag through waste acid

Abstract

The invention discloses a step-by-step treatment and recycling method for treating copper or iron slag by waste acid, which comprises the following steps of: carrying out solid-liquid separation on copper or iron-containing waste acid which is circulated for multiple times, and precipitating to obtain copper arsenate or iron arsenate; concentrating and crystallizing the liquid obtained after solid-liquid separation to obtain a solid-phase mixture; the solid-phase mixture is subjected to microwave heating at the heating temperature of 50-450 DEG C, and crystal water, fluorine and chlorine in the solid-phase mixture are removed; the treated solid-phase residues are subjected to roasting decomposition, the roasting temperature is 200-1250 DEG C, the obtained solid-phase copper or iron oxide is reused for waste acid neutralization treatment, and sulfur oxide is reused for an acid making working section. According to the method, through step-by-step chemical precipitation-roasting, efficient separation and open circuit of fluorine, chlorine and arsenic in the waste acid are achieved, closed-loop circulation of high-value materials is achieved, and low-cost and full-quantitative utilization of the waste acid is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of industrial sewage treatment, and in particular relates to a step-by-step treatment and recycling method for copper or iron slag treated with waste acid. Background Art

[0002] As a wastewater of key concern generated during the smelting of non-ferrous metals and the production of pyrite acid, dirty acid originates from the purification process of sulfur- and heavy metal-containing flue gas. It has problems such as high acid concentration, high heavy metal content, and strong corrosiveness of fluoride and chloride ions. At present, quicklime is mainly used to neutralize and precipitate dirty acid. This method produces a large amount of slag such as calcium sulfate, and is classified as hazardous waste because the slag contains heavy metals such as arsenic, resulting in high processing and management costs for enterprises. Low-cost and environmentally friendly treatment of dirty acid has become a technical difficulty that needs to be urgently solved in many industries such as the non-ferrous industry and pyrite acid production.

[0003] The traditional roasting process has the problem of contact heat exchange, which is prone to equipment corrosion and scaling and slagging. At the same time, slagging reduces the conductivity coefficient, resulting in large losses in roasting equipment, high energy consumption, and high operating costs. Zhejiang University's doctoral dissertation "Research on the Thermal Treatment and Slagging Characteristics of Typical Hazardous Wastes in a Two-Stage Rotary Kiln Incineration System and Its Application" pointed out that the current research on the incineration characteristics and ash characteristics of hazardous wastes is not in-depth, and the rotary kiln incineration system lacks the necessary guidance during operation. In actual applications, there are problems such as poor hazardous waste incineration effect, slagging in the rotary kiln, corrosion of refractory materials, and substandard pollutant emissions. For this reason, it is very necessary to develop a waste acid treatment method with high treatment efficiency, low cost, and no solid waste treatment. Summary of the invention

[0004] The purpose of the present invention is to provide a step-by-step treatment and recycling method for copper or iron slag treated with contaminated acid, aiming to use microwaves and roasting to quickly decompose copper sulfate and ferric sulfate in steps, generate copper oxide and iron oxide for recycling to form a closed loop, open the circuit of arsenic in the form of ferric arsenate, and remove fluorine and chlorine, so as to achieve low-cost and solid waste-free treatment of contaminated acid.

[0005] The object of the present invention is achieved by comprising the following steps: S1, separating the copper or iron-containing waste acid after multiple cycles into solid and liquid, precipitating it into copper arsenate or iron arsenate, and forming an open circuit of arsenic; S2, concentrating and crystallizing the liquid obtained after the solid-liquid separation in step S1 to obtain a solid phase mixture containing iron sulfate / copper, fluoride and chloride salts, etc.; S3, subjecting the solid phase mixture of step S2 to microwave heating at a heating temperature of 50°C to 450°C to remove crystal water, fluorine and chlorine in the solid phase mixture, wherein the crystal water is removed in the form of water vapor, the fluorine is removed in the form of hydrofluoric acid, and the chlorine is removed in the form of hydrochloric acid; S4. The solid phase residue treated in step S3 is roasted and decomposed at a roasting temperature of 200°C to 1250°C. The obtained solid phase copper or iron oxides are recycled for waste acid neutralization treatment, and the sulfur oxides are recycled for acid production.

[0006] Preferably, the concentration and crystallization in step S2 is evaporation concentration, cooling crystallization, adding seed crystals or salting-out crystallization.

[0007] Preferably, the microwave heating in step S3 is microwave direct heating or microwave indirect heating; wherein, before microwave indirect heating, a microwave absorbing material is added to the solid phase mixture.

[0008] Preferably, the microwave heating utilizes electromagnetic waves with a frequency of 300 MHz to 300 GHz.

[0009] Preferably, the absorbing material is graphene, carbon black, ferrite ceramic or silicon carbide ceramic.

[0010] Preferably, the calcination in step S4 is carried out in a medium frequency furnace or a high frequency furnace.

[0011] Preferably, the operating frequency of the medium frequency furnace is 300HZ~1000HZ, and the operating frequency of the high frequency furnace is 1000HZ~30000HZ.

[0012] Technical principle of the present invention: (1) Copper / iron oxides can react with sulfuric acid in waste acid to generate soluble copper sulfate and ferric sulfate / ferrous sulfate solution. Copper / iron ions react with arsenate to generate copper arsenate / ferric arsenate precipitates. After solid-liquid separation, an open circuit of arsenic is formed. The specific reaction equation is: (2) Under the action of a rapidly changing high-frequency electromagnetic field, microwaves convert the field energy of the microwave field into thermal energy within the medium, raising the temperature of the material and removing the water of crystallization from copper sulfate and ferric sulfate / ferrous sulfate. At the same time, under high temperature conditions, the fluorine and chlorine components escape in the form of hydrochloric acid and hydrofluoric acid, thus opening the circuit of the fluorine and chlorine components.

[0013] (3) Medium frequency furnaces and high frequency furnaces convert electrical energy into thermal energy through electromagnetic induction. Copper sulfate, ferrous sulfate, and ferrous sulfate will decompose at high temperatures to produce copper / iron oxides, thereby achieving the purpose of rapid decomposition of sulfates. When heated, copper sulfate pentahydrate crystals first lose their crystal water, and the reaction equation is: , Continue heating to 650℃ and the decomposition equation of anhydrous copper sulfate is: , If the temperature continues to rise, sulfur trioxide will partially decompose: .

[0014] The decomposition temperature of ferric sulfate is about 300-500℃, and the equation is: , At about 500℃, the decomposition equation of ferrous sulfate is: .

[0015] Compared with the prior art, the present invention has the following technical effects: 1. The present invention uses microwave heating to heat the water treatment slag containing copper, iron, arsenic, etc. produced by the treatment of waste acid, so that the dipole molecules in the medium move to generate internal friction heat, and the heating speed is fast and uniform, so that the volatile components in the material are quickly removed and dried, and the water, fluorine and chlorine in the mixed slag are quickly separated; the roasting realizes the rapid decomposition of iron / copper sulfate; the copper oxide / iron generated by the present invention is recycled to form a closed-loop cycle, arsenic is open-circuited in the form of ferric arsenate, and fluorine and chlorine are volatilized and removed in the form of hydrochloric acid and hydrofluoric acid, so as to realize the low-cost and full-quantity utilization of waste acid; 2. The present invention not only realizes the efficient separation and open circuit of fluorine, chlorine and arsenic in the waste acid through step-by-step chemical precipitation-roasting, but also realizes the closed-circuit circulation of high-value copper materials; 3. The present invention can use medium frequency furnaces, high frequency furnaces, etc. to achieve non-contact rapid heating and rapid decomposition of water treatment slag; medium frequency furnaces and high frequency furnaces use electromagnetic induction to convert electrical energy into thermal energy and convert industrial frequency current distribution into medium frequency and high frequency current, and have the advantages of high heating efficiency, simple operation, energy saving and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0017] The present invention is further described below in conjunction with the accompanying drawings, 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.

[0018] Example 1 The waste acid produced by a copper smelter has an acid concentration of 10% and contains harmful components such as fluorine, chlorine and arsenic. Figure 1 As shown, the step-by-step treatment and recycling method of the contaminated acid treated copper slag in this embodiment comprises the following steps: S1. The copper-containing waste acid after multiple cycles is separated into solid and liquid to precipitate into copper arsenate, and the arsenic removal rate reaches more than 80%; S2, evaporating and concentrating the nearly saturated copper sulfate solution obtained after solid-liquid separation in step S1, cooling it to crystallize and then filtering it to obtain a solid phase mixture containing copper sulfate, fluorine chloride salt, etc.; S3, the solid phase mixture of step S2 is subjected to medium-temperature microwave indirect heating in a microwave oven, carbon black is added as a microwave absorbing material in an amount of 5wt%, and the heating temperature is 50°C, so that the crystal water in the solid phase mixture is removed, and the fluorine and chlorine are volatilized and removed in the form of hydrochloric acid and hydrofluoric acid respectively; S4, the solid phase residue treated in step S3 is roasted in a medium frequency furnace at a temperature of 300°C and an operating frequency of 300HZ, and is decomposed into copper oxide, sulfur dioxide and sulfur trioxide; the obtained solid phase copper oxide is recycled for waste acid neutralization treatment, and sulfur dioxide and sulfur trioxide are recycled for acid production section; After one cycle, the acid concentration in the waste acid is reduced by 1% and is reused for washing and purifying sulfur-containing flue gas.

[0019] Example 2 The waste acid produced by a lead-zinc smelter has an acid concentration of 11% and contains harmful components such as fluorine, chlorine and arsenic. The step-by-step treatment and recycling method of waste acid treated iron slag in this embodiment includes the following steps: S1. The iron-containing waste acid after multiple cycles is separated into solid and liquid and precipitated into ferric arsenate, and the arsenic removal rate reaches more than 85%; S2, adding electrolyte salting-out agent sodium chloride to the nearly saturated ferrous sulfate and ferrous sulfate solution obtained after solid-liquid separation in step S1 for salting-out crystallization, and then filtering to obtain a solid phase mixture containing ferrous sulfate, ferrous sulfate, fluorine chloride, etc.; S3, the solid phase mixture of step S2 is subjected to medium-temperature microwave indirect heating in a microwave oven, and ferrite ceramic is added as a microwave absorbing material in an amount of 20wt%, and the heating temperature is 300°C, so that the crystal water in the solid phase mixture is removed, and the fluorine and chlorine are volatilized and removed in the form of hydrochloric acid and hydrofluoric acid respectively; S4, the solid phase residue treated in step S3 is roasted in a high frequency furnace at a roasting temperature of 650°C and an operating frequency of 20000HZ, and is decomposed into iron oxide, sulfur dioxide and sulfur trioxide; the obtained solid phase iron oxide is recycled for waste acid neutralization treatment, and sulfur dioxide and sulfur trioxide are recycled for acid production section; After one cycle, the acid concentration in the waste acid is reduced by 4% and is reused for washing and purifying sulfur-containing flue gas.

[0020] Example 3 The copper-containing waste acid produced by a certain enterprise has an acid concentration of 15% and contains harmful components such as fluorine, chlorine and arsenic. The step-by-step treatment and recycling method of waste acid treated copper slag in this embodiment is based on Example 1, and the difference from Example 1 is that: silicon carbide ceramic is added as an absorbing material in step S3, the amount is 30wt%, the heating temperature is 260°C, the working frequency in step S4 is 600HZ, and the roasting temperature is 1250°C; The arsenic removal rate reaches over 75%; after one cycle, the acid concentration in the waste acid drops by 5% and can be reused for washing and purification of sulfur-containing flue gas.

[0021] Example 4 The waste acid produced by a tin smelter has an acid concentration of 5% and contains harmful components such as fluorine, chlorine and arsenic. The step-by-step treatment and recycling method of waste acid treated iron slag in this embodiment is based on Example 2, and the difference from Example 2 is that carbon black ceramic is added as an absorbing material in step S3, with an amount of 20wt%, the heating temperature is 150°C, and the operating frequency in step S4 is 2000HZ; The arsenic removal rate reaches over 90%; after one cycle, the acid concentration in the waste acid drops by 3% and can be reused for washing and purification of sulfur-containing flue gas.

[0022] Example 5 The step-by-step treatment and recycling method of the contaminated acid treated iron slag in this embodiment is based on the embodiment 1, and the difference from the embodiment 1 is that the heating temperature of step S3 is 50°C, the roasting temperature of step S4 is 200°C, and the working frequency is 300HZ.

[0023] Example 6 The step-by-step treatment and recycling method of the contaminated acid treated iron slag in this embodiment is based on the embodiment 1, and the difference from the embodiment 1 is that the heating temperature of step S3 is 450°C, the roasting temperature of step S4 is 1250°C, and the operating frequency is 1000HZ.

[0024] Example 7 The step-by-step treatment and recycling method of the contaminated acid treated iron slag in this embodiment is based on the embodiment 1, and the difference from the embodiment 1 is that the heating temperature of step S3 is 250°C, the roasting temperature of step S4 is 725°C, and the operating frequency is 650HZ.

[0025] Example 8 The step-by-step treatment and recycling method of the dirty acid treated iron slag in this embodiment is based on the embodiment 1, and is different from the embodiment 2 in that the heating temperature in step S3 is 400°C, the roasting temperature in step S4 is 850°C, and the operating frequency is 1000HZ.

[0026] Example 9 The step-by-step treatment and recycling method of the waste acid treated iron slag in this embodiment is based on the embodiment 1, and is different from the embodiment 2 in that the heating temperature in step S3 is 350°C, the roasting temperature in step S4 is 700°C, and the operating frequency is 30000HZ.

[0027] Example 10 The step-by-step treatment and recycling method of the contaminated acid treated iron slag in this embodiment is based on the embodiment 1, and is different from the embodiment 2 in that the heating temperature in step S3 is 200° C., the roasting temperature in step S4 is 1200° C., and the operating frequency is 15500 Hz.

Claims

1. A method for stepwise treatment and recycling of copper or iron slag treated with dirty acid, characterized in that The following steps are involved: S1, separating the copper or iron-containing waste acid after multiple cycles into solid-liquid and precipitating it into copper arsenate or iron arsenate; S2, concentrating and crystallizing the liquid obtained after solid-liquid separation in step S1 to obtain a solid phase mixture; S3, subjecting the solid phase mixture of step S2 to microwave heating at a temperature of 50°C to 450°C to remove crystal water, fluorine and chlorine in the solid phase mixture; S4. The solid phase residue treated in step S3 is roasted and decomposed at a roasting temperature of 200°C to 1250°C. The obtained solid phase copper or iron oxides are recycled for waste acid neutralization treatment, and the sulfur oxides are recycled for acid production.

2. The method for stepwise treatment and recycling of waste acid treated copper or iron slag according to claim 1, characterized in that The concentration and crystallization in step S2 is evaporation concentration, cooling crystallization, adding crystal seeds or salting out crystallization.

3. The method for stepwise treatment and recycling of waste acid treated copper or iron slag according to claim 1, characterized in that The microwave heating in step S3 is microwave direct heating or microwave indirect heating; wherein, before microwave indirect heating, a microwave absorbing material is added to the solid phase mixture.

4. The method for stepwise treatment and recycling of waste acid treated copper or iron slag according to claim 1 or 3, characterized in that The microwave heating utilizes electromagnetic waves with a frequency of 300 MHz to 300 GHz.

5. The method for stepwise treatment and recycling of waste acid treated copper or iron slag according to claim 3, characterized in that The wave absorbing material is graphene, carbon black, ferrite ceramic or silicon carbide ceramic.

6. The method for stepwise treatment and recycling of waste acid treated copper or iron slag according to claim 1, characterized in that The calcination in step S4 is carried out in a medium frequency furnace or a high frequency furnace.

7. The method for stepwise treatment and recycling of waste acid treated copper or iron slag according to claim 6, characterized in that The working frequency of the medium frequency furnace is 300HZ~1000HZ, and the working frequency of the high frequency furnace is 1000HZ~30000HZ.

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