Dechlorination pretreatment method for zinc-containing dust

Abstract

The invention discloses a dechlorination pretreatment method for zinc-containing dust, and belongs to the technical field of metallurgy and secondary resource utilization. The method comprises the following steps: performing salt washing treatment on the zinc-containing dust by adopting a salt washing solution and a salt washing auxiliary agent, so that the chlorine element in the zinc-containing dust enters the solution in an ion form, filtering, leaving the zinc-containing dust in filter residues, leaving the chlorine element in filtrate, oxidizing the residual chlorine element in the filter residues through electrolysis, and entering electrolyte in an ion form, thereby obtaining the zinc-containing dust. According to the method, the zinc-containing dust escapes from the electrolyte in a gas form or escapes from the electrolyte in a gas form, the zinc-containing dust is left in the filter residue after filtration, the chlorine element is left in the filtrate, and the residual chlorine element in the filter residue is further volatilized and removed at a high temperature by reducing and roasting the filter residue and utilizing the volatility of chloride, so that the purpose of reducing the chlorine content of the zinc-containing dust to 0.1% or below is finally achieved. And corrosion to equipment and pipelines and serious influence on products caused by too high chlorine content of the zinc-containing dust are avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy and secondary resource utilization, and in particular relates to a dechlorination pretreatment method for zinc-containing dust. Background Art

[0002] During the blast furnace ironmaking process, the blast furnace gas is deeply dusted and purified by the bag filter to produce blast furnace gas ash. After the blast furnace gas ash is roasted in a rotary kiln, secondary smoke dust is produced. The secondary smoke dust contains a large amount of valuable metal elements. It is composed of carbon and oxides of Fe, Si, Al, Mg, Ca, and low-boiling point non-ferrous metals (Pb, Sn) and their oxides. It is one of the main solid wastes of steel enterprises. The secondary smoke dust of the rotary kiln contains iron, carbon and a small amount of non-ferrous metal elements, which are precious resources. If they cannot be effectively managed and utilized, it will not only cause waste of resources, but also cause great pollution to the environment. At present, most zinc-containing smoke dust has not been fully utilized, which not only causes large-scale land and water pollution, but also causes a large amount of valuable metal elements such as Zn, Fe and other resources in the smoke dust. Therefore, studying the extraction and separation of zinc in zinc-containing dust and the efficient recovery and utilization of valuable elements has important theoretical and practical significance for eliminating environmental impacts.

[0003] In China, zinc-containing dust is usually treated by wet process, and the process is generally leaching, purification, and electrolysis. Zinc-containing dust often contains a high content of chlorine. During the comprehensive utilization process, the Cl element will run through the entire wet process and enter the zinc sulfate solution. When electrolytically extracting zinc, excessive chlorine content will not only cause serious corrosion to equipment and pipelines, but also accelerate anode loss, seriously reduce the quality of zinc plates, and have a serious impact on the product. Therefore, in the process of wet zinc smelting, the concentration of chloride ions in the zinc sulfate solution needs to be strictly controlled within 100 mg / L, but it is difficult to remove chlorine in the existing zinc dust treatment process. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a dechlorination pretreatment method for zinc-containing dust. The method provided by the present invention can reduce the chlorine content of zinc-containing dust to below 0.1%.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a dechlorination pretreatment method for zinc-containing dust, comprising the following steps:

[0007] (1) mixing zinc-containing dust, a salt washing solution and a salt washing aid to perform salt washing treatment, and filtering to obtain a filtrate and a filter residue;

[0008] (2) mixing the filter residue obtained in step (1) with an electrolyte and performing electrolysis, and filtering to obtain a filtrate and a filter residue;

[0009] (3) The filter residue obtained in step (2) is subjected to reduction roasting to obtain dechlorinated zinc-containing dust.

[0010] Technical principle: The present invention proposes a combined pretreatment method of salt washing-electrolysis-reduction roasting, firstly, the zinc-containing dust is subjected to salt washing treatment with a salt washing solution and a salt washing auxiliary agent, so that the chlorine element in the zinc-containing dust enters the solution in the form of ions, and after filtration, the zinc-containing dust remains in the filter residue, while the chlorine element remains in the filtrate, and then the chlorine element remaining in the filter residue is oxidized by electrolysis to enter the electrolyte in the form of ions, or escapes from the electrolyte in the form of gas, and after filtration, the zinc-containing dust remains in the filter residue, while the chlorine element remains in the filtrate, and then the filter residue is reduction roasted, and the volatility of chloride is utilized to make the chlorine element remaining in the filter residue further volatilize and remove at high temperature, thereby finally achieving the purpose of reducing the chlorine content of the zinc-containing dust to below 0.1%.

[0011] Furthermore, in step (1), the solid-liquid ratio of the zinc-containing dust to the salt washing solution is 1:(2-10).

[0012] Furthermore, in step (1), the composition of the salt washing solution is NaSO3: 0.1-1 g / L, NaSO4: 0.1-1 g / L and NaNO3: 0.1-1 g / L; the pH value of the salt washing solution is 6-9.

[0013] Furthermore, in step (1), the salt washing auxiliary agent is H2O2 or SO2; the amount of H2O2 used is 0.5-2% of the volume of the salt washing solution; and the ventilation amount of SO2 is 0.5-2% of the volume of the salt washing solution.

[0014] Furthermore, in step (1), the temperature of the salt washing treatment is 40-80° C. and the time is 2 hours.

[0015] Furthermore, in step (2), the solid-liquid ratio of the filter residue to the electrolyte is 1:(2-10).

[0016] Furthermore, in step (2), the composition of the electrolyte is NaSO3: 10-100 g / L, NaSO4: 10-100 g / L and NaNO3: 10-100 g / L; the pH value of the electrolyte is 6-9.

[0017] Furthermore, in step (2), the anode used in the electrolysis is any one of graphite, pure lead and lead-silver alloy, and the cathode used in the electrolysis is any one of graphite, stainless steel and pure nickel;

[0018] The ratio of the area of ​​the anode or cathode to the volume of the electrolyte is 20 to 50 cm 2 / L.

[0019] Furthermore, in step (2), the cell voltage of the electrolysis is 2 to 4 V, and the current density is 20 to 500 A / m 2 ;

[0020] The electrolysis temperature is 40-80° C. and the time is 2 hours.

[0021] Furthermore, in step (3), the temperature of the reduction roasting is 400-700°C, and the time is 1-2 hours; the atmosphere of the reduction roasting is a mixture of CO and CO2 or H2; the volume ratio of CO and CO2 in the mixture of CO and CO2 is (10:90)-(20:80).

[0022] Compared with the prior art, the present invention has the following advantages and technical effects:

[0023] Zinc-containing dust often contains a high content of chlorine. During the comprehensive utilization process, the element Cl will run through the entire wet process and enter the zinc sulfate solution, which will have a serious impact on subsequent products. During the wet zinc smelting process, the concentration of chloride ions in the zinc sulfate solution needs to be strictly controlled within 100 mg / L. The dechlorination pretreatment method for zinc-containing dust provided by the present invention can reduce the chlorine content of zinc-containing dust to less than 0.1%, avoiding the corrosion of equipment and pipelines caused by excessive chlorine content of zinc-containing dust and the serious impact on products. In addition, the method provided by the present invention has the advantages of simple process, low cost, high efficiency and short time consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0025] Figure 1 The process flow chart of the dechlorination pretreatment method of zinc-containing dust in Examples 1 to 6 of the present invention;

[0026] Figure 2 The XRD diagrams of zinc-containing dust and dechlorinated zinc-containing dust in Example 1 of the present invention, wherein (a) is zinc-containing dust, and (b) is dechlorinated zinc-containing dust;

[0027] Figure 3 The XRD diagrams of zinc-containing dust and dechlorinated zinc-containing dust in Example 2 of the present invention, wherein (a) is zinc-containing dust, and (b) is dechlorinated zinc-containing dust;

[0028] Figure 4 The XRD diagrams of zinc-containing dust and dechlorinated zinc-containing dust in Example 3 of the present invention, wherein (a) is zinc-containing dust, and (b) is dechlorinated zinc-containing dust;

[0029] Figure 5 The XRD diagrams of zinc-containing dust and dechlorinated zinc-containing dust in Example 4 of the present invention, wherein (a) is zinc-containing dust, and (b) is dechlorinated zinc-containing dust;

[0030] Figure 6 The XRD diagrams of zinc-containing dust and dechlorinated zinc-containing dust in Example 5 of the present invention, wherein (a) is zinc-containing dust, and (b) is dechlorinated zinc-containing dust;

[0031] Figure 7 1 and 2 are XRD diagrams of zinc-containing dust and dechlorinated zinc-containing dust in Example 6 of the present invention, wherein (a) is zinc-containing dust and (b) is dechlorinated zinc-containing dust. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] The embodiment of the present invention provides a dechlorination pretreatment method for zinc-containing dust, comprising the following steps:

[0035] (1) mixing zinc-containing dust, a salt washing solution and a salt washing aid to perform salt washing treatment, and filtering to obtain a filtrate and a filter residue;

[0036] (2) mixing the filter residue obtained in step (1) with an electrolyte and performing electrolysis, and filtering to obtain a filtrate and a filter residue;

[0037] (3) The filter residue obtained in step (2) is subjected to reduction roasting to obtain dechlorinated zinc-containing dust.

[0038] In a preferred embodiment, in step (1), the solid-liquid ratio of the zinc-containing dust to the salt washing solution is 1:(2-10), and more preferably 1:(3-10). The present invention controls the solid-liquid ratio of the zinc-containing dust to the salt washing solution within the above range, thereby ensuring sufficient reaction of the chlorine element in the zinc-containing dust with the salt washing solution.

[0039] In a preferred embodiment, in step (1), the composition of the salt washing solution is NaSO3: 0.1-1g / L, NaSO4: 0.1-1g / L and NaNO3: 0.1-1g / L, more preferably NaSO3: 0.2-1g / L, NaSO4: 0.5-1g / L and NaNO3: 0.2-0.8g / L; the pH value of the salt washing solution is 6-9. The present invention uses a salt washing solution composed of NaSO3, NaSO4 and NaNO3 for salt washing treatment, which has the advantages of high chlorine removal efficiency and no effect on the quality of zinc-containing dust.

[0040] In a preferred embodiment, in step (1), the salt washing aid is H2O2 or SO2; the amount of H2O2 is 0.5-2% of the volume of the salt washing solution, and the volume concentration of H2O2 is 30%; the ventilation volume of SO2 is 0.5-2% of the volume of the salt washing solution. The salt washing aid in the present invention plays the role of oxidative dissolution. Using H2O2 or SO2 as a salt washing aid has the advantages of not introducing new impurities and high oxidative dissolution efficiency. The amount of salt washing aid will affect the dechlorination effect. If the amount of salt washing aid is too low, the oxidative dissolution of chlorine elements is insufficient, and the dechlorination efficiency is low. If the amount of salt washing aid is too high, the pH range of the salt washing solution will change and the zinc grade in the zinc-containing dust will be reduced.

[0041] In a preferred embodiment, in step (1), the salt washing treatment is carried out at a temperature of 40 to 80° C. for 2 hours. The present invention performs the salt washing treatment at the above temperature to ensure that the chlorine element in the zinc-containing dust fully reacts with the salt washing solution and the salt washing auxiliary agent.

[0042] In a preferred embodiment, in step (1), the filtrate is evaporated and crystallized to obtain sodium salt; the condensed water after the evaporation and crystallization is returned to prepare the salt washing solution, thereby realizing a closed-loop circulation of wastewater.

[0043] In a preferred embodiment, in step (2), the solid-liquid ratio of the filter residue to the electrolyte is 1:(2-10). The present invention controls the solid-liquid ratio of the filter residue to the electrolyte within the above range to ensure sufficient reaction of the chlorine element in the filter residue with the electrolyte.

[0044] In a preferred embodiment, in step (2), the composition of the electrolyte is NaSO3: 10-100 g / L, NaSO4: 10-100 g / L and NaNO3: 10-100 g / L, more preferably NaSO3: 10-80 g / L, NaSO4: 20-80 g / L and NaNO3: 20-80 g / L; the pH value of the electrolyte is 6-9. The present invention uses an electrolyte with the same composition as the salt washing solution to further remove the chlorine element from the zinc-containing powder, and controls the concentrations of NaSO3, NaSO4 and NaNO3 within the above range, which is beneficial to the oxidation and precipitation of the chlorine element and improves the efficiency of electrolytic dechlorination.

[0045] In a preferred embodiment, in step (2), the anode used for electrolysis is any one of graphite, pure lead and lead-silver alloy, and the cathode used for electrolysis is any one of graphite, stainless steel and pure nickel.

[0046] In a preferred embodiment, in step (2), the ratio of the area of ​​the anode and the area of ​​the cathode to the volume of the electrolyte is 20 to 50 cm 2 / L.

[0047] In a preferred embodiment, in step (2), the cell voltage of the electrolysis is 2 to 4 V, and the current density is 20 to 500 A / m 2 The present invention performs electrolysis under the above-mentioned cell voltage and current density, which is beneficial to the oxidation and precipitation of chlorine element and improves the electrolytic dechlorination efficiency.

[0048] In a preferred embodiment, in step (2), the electrolysis temperature is 40-80° C. and the time is 2 hours.

[0049] In a preferred embodiment, in step (2), the filtrate is reused in the electrolysis process.

[0050] In a preferred embodiment, in step (3), the reduction roasting temperature is 400-700°C, and the time is 1-2 hours; the reduction roasting atmosphere is a mixture of CO and CO2 or H2; the volume ratio of CO and CO2 in the mixture of CO and CO2 is (10:90)-(20:80). The present invention performs reduction roasting at the above temperature, which is conducive to the volatilization of chlorine and improves the dechlorination efficiency; if the reduction roasting temperature is too high, the zinc element will volatilize and reduce the zinc element grade in the zinc-containing dust; if the temperature is too low, the chlorine element will not volatilize sufficiently and the dechlorination efficiency will be low.

[0051] In a preferred embodiment, in step (3), after the reduction roasting is completed, the obtained roasted slag is subjected to neutral leaching with sulfuric acid, and the pH value of the leaching end point is 5-5.2, so as to obtain a leachate and a leachate residue; the chlorine content in the leachate is detected, and if the chlorine content in the leachate is greater than 150 mg / L, the roasted slag is returned to the salt washing process; if the chlorine content in the leachate is less than 150 mg / L, the dechlorination pretreatment of the zinc-containing dust is completed to obtain a dechlorinated zinc-containing powder.

[0052] Unless otherwise specified, the raw materials in the examples of the present invention were purchased from commercial sources.

[0053] Example 1

[0054] A dechlorination pretreatment method for zinc-containing dust, the process flow chart is shown in Figure 1 , the specific steps are as follows:

[0055] (1) adding zinc-containing dust to a salt washing solution at a solid-liquid ratio of 1:5, wherein the composition of the salt washing solution is NaSO3: 0.5 g / L, NaSO4: 0.5 g / L and NaNO3: 0.3 g / L, and the pH value of the salt washing solution is controlled at 7.5, and at the same time, adding H2O2 with a volume concentration of 30%, the addition amount being 0.5% of the volume of the salt washing solution, and stirring and mixing, and the temperature is controlled at 60°C for salt washing treatment, and the salt washing treatment is completed after 2 hours, and then the mixed slurry is filtered to obtain a filtrate and a filter residue; the obtained filtrate is evaporated and crystallized to produce sodium salt, and the condensed water after evaporation and crystallization is returned to prepare the salt washing solution, thereby realizing a closed-loop circulation of wastewater.

[0056] (2) Add the filter residue obtained in step (1) to an electrolyte at a solid-liquid ratio of 1:5, wherein the electrolyte composition is NaSO3: 50 g / L, NaSO4: 50 g / L and NaNO3: 50 g / L, and the pH value of the electrolyte is 6.3, and stir to obtain a mixed slurry. The obtained mixed slurry is electrolyzed, wherein the anode of the electrolysis is graphite, the cathode is stainless steel, and the ratio of the area of ​​the anode or the area of ​​the cathode to the volume of the electrolyte is 30 cm 2 / L. The cell voltage of electrolysis is 2.3V and the current density is 30A / m 2 , the temperature is 80° C. After 2 hours, the electrolysis is completed, and the mixed slurry after electrolysis is filtered to obtain a filtrate and a filter residue; the obtained filtrate is returned to the electrolysis process.

[0057] (3) The filter residue obtained in step (2) is subjected to reduction roasting at a temperature of 500° C. in a roasting atmosphere of a mixture of CO and CO2 (the volume ratio of CO to CO2 in the mixture of CO and CO2 is 10:90), and roasting for 1 hour to obtain dechlorinated zinc-containing dust.

[0058] The zinc-containing dust and the dechlorinated zinc-containing dust in Example 1 were subjected to XRD analysis, and the results are shown in Figure 2In the figure, (a) is zinc-containing dust, and (b) is dechlorinated zinc-containing dust. Figure 2 As can be seen from part (a) of the figure, before treatment, the zinc-containing dust phase contains KCl and PbCl2 chlorides, with a chlorine content of 0.45%. Figure 2 It can be seen from part (b) that after treatment, there is no KCl and PbCl2 chloride in the dechlorinated zinc-containing dust phase, the chlorine content is reduced to 0.08%, and the dechlorination efficiency is 82.2%.

[0059] Example 2

[0060] A dechlorination pretreatment method for zinc-containing dust, the process flow chart is shown in Figure 1 , the specific steps are as follows:

[0061] (1) adding zinc-containing dust to a salt washing solution at a solid-liquid ratio of 1:3, wherein the composition of the salt washing solution is NaSO3: 0.7 g / L, NaSO4: 0.5 g / L and NaNO3: 0.8 g / L, and the pH value of the salt washing solution is controlled at 6.5, and at the same time, adding H2O2 with a volume concentration of 30%, the addition amount of which is 1% of the volume of the salt washing solution, and stirring and mixing, and the temperature is controlled at 80°C for salt washing treatment, and the salt washing treatment is completed after 2 hours, and then the mixed slurry is filtered to obtain a filtrate and a filter residue; the obtained filtrate is evaporated and crystallized to produce sodium salt, and the condensed water after evaporation and crystallization is returned to prepare the salt washing solution, thereby realizing a closed-loop circulation of wastewater.

[0062] (2) Add the filter residue obtained in step (1) to an electrolyte at a solid-liquid ratio of 1:10, wherein the electrolyte composition is NaSO3: 80 g / L, NaSO4: 20 g / L and NaNO3: 100 g / L, and the pH value of the electrolyte is 9, and stir and mix to obtain a mixed slurry. The obtained mixed slurry is electrolyzed, wherein the anode of the electrolysis is pure lead, the cathode is pure nickel, and the ratio of the area of ​​the anode or the area of ​​the cathode to the volume of the electrolyte is 50 cm 2 / L. The cell voltage of electrolysis is 3.5V and the current density is 100A / m 2 , the temperature is 60° C. After 2 hours, the electrolysis is completed, and the mixed slurry after electrolysis is filtered to obtain a filtrate and a filter residue; the obtained filtrate is returned to the electrolysis process.

[0063] (3) The filter residue obtained in step (2) is subjected to reduction roasting at a temperature of 600° C. in a roasting atmosphere of a mixture of CO and CO2 (the volume ratio of CO to CO2 in the mixture of CO and CO2 is 20:80), and roasting for 1 hour to obtain dechlorinated zinc-containing dust.

[0064] The zinc-containing dust and the dechlorinated zinc-containing dust in Example 2 were subjected to XRD analysis, and the results are shown in Figure 3 In the figure, (a) is zinc-containing dust, and (b) is dechlorinated zinc-containing dust. Figure 3As can be seen from part (a) of the figure, before treatment, the zinc-containing dust phase contains KCl and PbCl2 chlorides, with a chlorine content of 0.45%. Figure 3 It can be seen from part (b) that after treatment, there is no KCl and PbCl2 chloride in the dechlorinated zinc-containing dust phase, the chlorine content is reduced to 0.06%, and the dechlorination efficiency is 86.7%.

[0065] Example 3

[0066] A dechlorination pretreatment method for zinc-containing dust, the process flow chart is shown in Figure 1 , the specific steps are as follows:

[0067] (1) adding zinc-containing dust to a salt washing solution at a solid-liquid ratio of 1:10, wherein the composition of the salt washing solution is NaSO3: 0.2 g / L, NaSO4: 1 g / L and NaNO3: 0.8 g / L, and the pH value of the salt washing solution is controlled at 7.5, and at the same time, adding H2O2 with a volume concentration of 30% and an addition amount of 1% of the volume of the salt washing solution, and stirring and mixing, and controlling the temperature at 50°C for salt washing treatment, completing the salt washing treatment after 2 hours, and then filtering the mixed slurry to obtain a filtrate and a filter residue; the obtained filtrate is evaporated and crystallized to produce sodium salt, and the condensed water after evaporation and crystallization is returned to prepare the salt washing solution, thereby realizing a closed-loop circulation of wastewater.

[0068] (2) The filter residue obtained in step (1) is added to an electrolyte at a solid-liquid ratio of 1:8, wherein the electrolyte composition is NaSO3: 20 g / L, NaSO4: 80 g / L and NaNO3: 50 g / L, and the pH value of the electrolyte is 6.3, and the mixture is stirred to obtain a mixed slurry. The obtained mixed slurry is electrolyzed, wherein the anode of the electrolysis is a lead-silver alloy, the cathode is graphite, and the ratio of the area of ​​the anode or the area of ​​the cathode to the volume of the electrolyte is 30 cm 2 / L. The cell voltage of electrolysis is 3.2V and the current density is 300A / m 2 , the temperature is 80° C. After 2 hours, the electrolysis is completed, and the mixed slurry after electrolysis is filtered to obtain a filtrate and a filter residue; the obtained filtrate is returned to the electrolysis process.

[0069] (3) The filter residue obtained in step (2) is subjected to reduction roasting at a temperature of 500° C. in a H 2 (100%) atmosphere for 1 hour to obtain dechlorinated zinc-containing dust.

[0070] The zinc-containing dust and the dechlorinated zinc-containing dust in Example 3 were subjected to XRD analysis, and the results are shown in Figure 4 In the figure, (a) is zinc-containing dust, and (b) is dechlorinated zinc-containing dust. Figure 4 As can be seen from part (a) of the figure, before treatment, the zinc-containing dust phase contains KCl and PbCl2 chlorides, with a chlorine content of 0.45%. Figure 4As can be seen from part (b) in the figure, after treatment, there is no KCl and PbCl2 chloride in the dechlorinated zinc-containing dust phase, the chlorine content is reduced to as low as 0.05%, and the dechlorination efficiency is 88.9%.

[0071] Example 4

[0072] A dechlorination pretreatment method for zinc-containing dust, the process flow chart is shown in Figure 1 , the specific steps are as follows:

[0073] (1) Adding zinc-containing dust to a salt washing solution at a solid-liquid ratio of 1:5, the salt washing solution comprises NaSO3: 1 g / L, NaSO4: 1 g / L and NaNO3: 0.2 g / L, the pH value of the salt washing solution is controlled at 6, and SO2 gas is introduced at a flow rate of 1% of the volume of the salt washing solution, and the mixture is stirred and mixed, and the temperature is controlled at 60°C for salt washing treatment. The salt washing treatment is completed after 2 hours, and then the mixed slurry is filtered to obtain a filtrate and a filter residue; the obtained filtrate is evaporated and crystallized to produce sodium salt, and the condensed water after evaporation and crystallization is returned to prepare the salt washing solution, thereby realizing a closed-loop circulation of wastewater.

[0074] (2) Add the filter residue obtained in step (1) to an electrolyte at a solid-liquid ratio of 1:5, wherein the electrolyte composition is NaSO3: 10 g / L, NaSO4: 50 g / L and NaNO3: 30 g / L, and the pH value of the electrolyte is 8.2, and stir and mix to obtain a mixed slurry. The obtained mixed slurry is electrolyzed, wherein the anode of the electrolysis is graphite, the cathode is stainless steel, and the ratio of the area of ​​the anode or the area of ​​the cathode to the volume of the electrolyte is 50 cm 2 / L. The cell voltage of electrolysis is 3.8V and the current density is 500A / m 2 , the temperature is 70° C. After 2 hours, the electrolysis is completed, and the mixed slurry after electrolysis is filtered to obtain a filtrate and a filter residue; the obtained filtrate is returned to the electrolysis process.

[0075] (3) The filter residue obtained in step (2) is subjected to reduction roasting at a temperature of 700° C. in a H 2 (100%) atmosphere for 1 hour to obtain dechlorinated zinc-containing dust.

[0076] The zinc-containing dust and the dechlorinated zinc-containing dust in Example 4 were subjected to XRD analysis, and the results are shown in Figure 5 In the figure, (a) is zinc-containing dust, and (b) is dechlorinated zinc-containing dust. Figure 5 As can be seen from part (a) of the figure, before treatment, the zinc-containing dust phase contains KCl and PbCl2 chlorides, with a chlorine content of 0.45%. Figure 5 It can be seen from part (b) that after treatment, there is no KCl and PbCl2 chloride in the dechlorinated zinc-containing dust phase, the chlorine content is reduced to 0.03%, and the dechlorination efficiency is 93.3%.

[0077] Example 5

[0078] A dechlorination pretreatment method for zinc-containing dust, the process flow chart is shown in Figure 1 , the specific steps are as follows:

[0079] (1) adding zinc-containing dust to a salt washing solution at a solid-liquid ratio of 1:10, wherein the composition of the salt washing solution is NaSO3: 0.6 g / L, NaSO4: 1 g / L and NaNO3: 0.3 g / L, and the pH value of the salt washing solution is controlled at 8.5, and SO2 gas is introduced at the same time, and the aeration amount of SO2 is 0.5% of the volume of the salt washing solution, and the mixture is stirred and mixed, and the temperature is controlled at 70°C for salt washing treatment. The salt washing treatment is completed after 2 hours, and then the mixed slurry is filtered to obtain a filtrate and a filter residue; the obtained filtrate is evaporated and crystallized to produce sodium salt, and the condensed water after evaporation and crystallization is returned to prepare the salt washing solution, thereby realizing a closed-loop circulation of wastewater.

[0080] (2) Add the filter residue obtained in step (1) to an electrolyte at a solid-liquid ratio of 1:10, wherein the electrolyte composition is NaSO3:100 g / L, NaSO4:100 g / L and NaNO3:20 g / L, and the pH value of the electrolyte is 6.8, and stir and mix to obtain a mixed slurry. The obtained mixed slurry is electrolyzed, wherein the anode of the electrolysis is graphite, the cathode is pure nickel, and the ratio of the area of ​​the anode or the area of ​​the cathode to the volume of the electrolyte is 50 cm 2 / L. The cell voltage of electrolysis is 2.8V and the current density is 80A / m 2 , the temperature is 80° C. After 2 hours, the electrolysis is completed, and the mixed slurry after electrolysis is filtered to obtain a filtrate and a filter residue; the obtained filtrate is returned to the electrolysis process.

[0081] (3) The filter residue obtained in step (2) is subjected to reduction roasting at a temperature of 700° C. in a roasting atmosphere of a mixture of CO and CO2 (the volume ratio of CO to CO2 in the mixture of CO and CO2 is 20:80), and roasting for 1 hour to obtain dechlorinated zinc-containing dust.

[0082] The zinc-containing dust and the dechlorinated zinc-containing dust in Example 5 were subjected to XRD analysis, and the results are shown in Figure 6 In the figure, (a) is zinc-containing dust, and (b) is dechlorinated zinc-containing dust. Figure 6 As can be seen from part (a) of the figure, before treatment, the zinc-containing dust phase contains KCl and PbCl2 chlorides, with a chlorine content of 0.45%. Figure 6 It can be seen from part (b) that after treatment, there is no KCl and PbCl2 chloride in the dechlorinated zinc-containing dust phase, the chlorine content is reduced to 0.07%, and the dechlorination efficiency is 84.4%.

[0083] Example 6

[0084] A dechlorination pretreatment method for zinc-containing dust, the process flow chart is shown in Figure 1 , the specific steps are as follows:

[0085] (1) The zinc-containing dust is added to a salt washing solution at a solid-liquid ratio of 1:10. The composition of the salt washing solution is NaSO3: 1 g / L, NaSO4: 0.5 g / L and NaNO3: 1 g / L. The pH value of the salt washing solution is controlled at 6. At the same time, SO2 gas is introduced. The aeration rate of SO2 is 2% of the volume of the salt washing solution. The mixture is stirred and mixed. The temperature is controlled at 80°C for salt washing. The salt washing treatment is completed after 2 hours. Then, the mixed slurry is filtered to obtain a filtrate and a filter residue. The obtained filtrate is evaporated and crystallized to produce sodium salt. The condensed water after evaporation and crystallization is returned to prepare the salt washing solution, thereby realizing a closed-loop circulation of wastewater.

[0086] (2) The filter residue obtained in step (1) is added to an electrolyte at a solid-liquid ratio of 1:10, wherein the electrolyte composition is NaSO3: 30 g / L, NaSO4: 50 g / L and NaNO3: 80 g / L, and the pH value of the electrolyte is 6.8, and the mixture is stirred to obtain a mixed slurry. The mixed slurry is electrolyzed, wherein the anode of the electrolysis is graphite, and the cathode is a graphite anode area or a cathode area to the electrolyte volume ratio of 50 cm 2 / L. The cell voltage of electrolysis is 3.2V and the current density is 200A / m 2 , the temperature is 80° C. After 2 hours, the electrolysis is completed, and the mixed slurry after electrolysis is filtered to obtain a filtrate and a filter residue; the obtained filtrate is returned to the electrolysis process.

[0087] (3) The filter residue obtained in step (2) is subjected to reduction roasting at a temperature of 700° C. in a H 2 (100%) atmosphere for 1 hour to obtain dechlorinated zinc-containing dust.

[0088] The zinc-containing dust and the dechlorinated zinc-containing dust in Example 6 were subjected to XRD analysis, and the results are shown in Figure 7 In the figure, (a) is zinc-containing dust, and (b) is dechlorinated zinc-containing dust. Figure 7 As can be seen from part (a) of the figure, before treatment, the zinc-containing dust phase contains KCl and PbCl2 chlorides, with a chlorine content of 0.45%. Figure 7 It can be seen from part (b) that after treatment, there is no KCl and PbCl2 chloride in the dechlorinated zinc-containing dust phase, the chlorine content is reduced to 0.05%, and the dechlorination efficiency is 88.9%.

[0089] Comparative Example 1

[0090] The difference from Example 4 is that in step (1), the salt washing solution consists of NaSO4: 2 g / L and NaNO3: 0.2 g / L, and the rest is the same as Example 4.

[0091] Comparative Example 2

[0092] The difference from Example 4 is that in step (1), the salt washing solution consists of NaSO3: 1 g / L and NaSO4: 1.2 g / L, and the rest is the same as Example 4.

[0093] Comparative Example 3

[0094] The difference from Example 4 is that in step (1), SO2 gas is not passed, and the rest is the same as Example 4.

[0095] Comparative Example 4

[0096] The difference from Example 4 is that in step (2), the filter residue obtained in step (1) is added to the electrolyte at a solid-liquid ratio of 1:12, and the rest is the same as Example 4.

[0097] Comparative Example 5

[0098] The difference from Example 4 is that in step (2), the electrolyte composition is NaSO4: 60 g / L and NaNO3: 30 g / L, and the rest is the same as Example 4.

[0099] Comparative Example 6

[0100] The difference from Example 4 is that in step (2), the pH value of the electrolyte is 10, and the rest is the same as Example 4.

[0101] Comparative Example 7

[0102] The difference from Example 4 is that in step (2), the cell voltage of electrolysis is 6V, and the rest is the same as Example 4.

[0103] Comparative Example 8

[0104] The difference from Example 4 is that in step (2), the electrolysis temperature is 30° C., and the rest is the same as Example 4.

[0105] Comparative Example 9

[0106] The difference from Example 4 is that in step (3), the calcination temperature is 350°C, and the rest is the same as Example 4.

[0107] The chlorine content and dechlorination efficiency of the dechlorinated zinc-containing powders obtained in Comparative Examples 1-9 are shown in Table 1.

[0108] Table 1

[0109] Chlorine content% Dechlorination efficiency % Example 4 0.03 93.3 Comparative Example 1 0.08 82.2 Comparative Example 2 0.06 86.7 Comparative Example 3 0.08 82.2 Comparative Example 4 0.07 84.4 Comparative Example 5 0.05 88.9 Comparative Example 6 0.07 84.4 Comparative Example 7 0.08 82.2 Comparative Example 8 0.06 86.7 Comparative Example 9 0.05 88.9

[0110] It can be seen from Table 1 that the composition of the salt washing solution, the addition of salt washing aids, the solid-liquid ratio of electrolysis, the composition and pH value of the electrolyte, the electrolysis conditions and the roasting temperature will affect the dechlorination efficiency. The dechlorination pretreatment method for zinc-containing dust provided by the present invention can reduce the chlorine content of zinc-containing dust to below 0.1%.

[0111] The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A dechlorination pretreatment method for zinc-containing dust, characterized in that: The following steps are involved: (1) mixing zinc-containing dust, a salt washing solution and a salt washing aid to perform salt washing treatment, and filtering to obtain a filtrate and a filter residue; (2) mixing the filter residue obtained in step (1) with an electrolyte and performing electrolysis, and filtering to obtain a filtrate and a filter residue; (3) The filter residue obtained in step (2) is subjected to reduction roasting to obtain dechlorinated zinc-containing dust.

2. The dechlorination pretreatment method for zinc-containing dust according to claim 1, characterized in that: In step (1), the solid-liquid ratio of the zinc-containing dust to the salt washing solution is 1:(2-10).

3. The dechlorination pretreatment method for zinc-containing dust according to claim 1 or 2, characterized in that: In step (1), the composition of the salt washing solution is NaSO3: 0.1-1 g / L, NaSO4: 0.1-1 g / L and NaNO3: 0.1-1 g / L; the pH value of the salt washing solution is 6-9.

4. The dechlorination pretreatment method for zinc-containing dust according to claim 1, characterized in that: In step (1), the salt washing auxiliary agent is H2O2 or SO2; the amount of H2O2 used is 0.5-2% of the volume of the salt washing solution; the ventilation amount of SO2 is 0.5-2% of the volume of the salt washing solution.

5. The dechlorination pretreatment method for zinc-containing dust according to claim 1, characterized in that: In step (1), the temperature of the salt washing treatment is 40-80° C. and the time is 2 hours.

6. The dechlorination pretreatment method for zinc-containing dust according to claim 1, characterized in that: In step (2), the solid-liquid ratio of the filter residue to the electrolyte is 1:(2-10).

7. The dechlorination pretreatment method for zinc-containing dust according to claim 1, characterized in that: In step (2), the composition of the electrolyte is NaSO3: 10-100 g / L, NaSO4: 10-100 g / L and NaNO3: 10-100 g / L; the pH value of the electrolyte is 6-9.

8. The dechlorination pretreatment method for zinc-containing dust according to claim 1, characterized in that: In step (2), the anode used in the electrolysis is any one of graphite, pure lead and lead-silver alloy, and the cathode used in the electrolysis is any one of graphite, stainless steel and pure nickel; The ratio of the area of ​​the anode or cathode to the volume of the electrolyte is 20 to 50 cm 2 / L.

9. The dechlorination pretreatment method for zinc-containing dust according to claim 1, characterized in that: In step (2), the cell voltage of the electrolysis is 2-4V, and the current density is 20-500A / m 2 ; The electrolysis temperature is 40-80° C. and the time is 2 hours.

10. The dechlorination pretreatment method for zinc-containing dust according to claim 1, characterized in that: In step (3), the temperature of the reduction roasting is 400-700°C, and the time is 1-2 hours; the atmosphere of the reduction roasting is a mixture of CO and CO2 or H2; the volume ratio of CO and CO2 in the mixture of CO and CO2 is (10:90)-(20:80).

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