CN113023689A - Wet-method selenium refining process using lead-zinc smelting acid sludge as raw material - Google Patents
Wet-method selenium refining process using lead-zinc smelting acid sludge as raw material Download PDFInfo
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Abstract
The invention provides a wet-process refined selenium extracting process taking lead-zinc smelting acid sludge as a raw material, which sequentially comprises the steps of raw material treatment, granulation, roasting for removing mercury, sulfuric acid leaching, crude selenium recovery, preparation of refined selenium (a, heating reaction b, cooling for precipitation c, acidification d, washing e, drying) and the like. The process combines the processes of fire mercury removal and wet selenium extraction, acid sludge generated in the lead-zinc smelting process is used as a raw material, calcium is added to fix selenium and remove mercury, then refined selenium is extracted by a wet method, and finished selenium with the purity of more than 99% is obtained by raw material treatment, granulation, roasting mercury removal, sulfuric acid leaching, crude selenium recovery and refined selenium preparation and extraction.
Description
Technical Field
The invention provides a wet-method selenium refining process using lead-zinc smelting acid sludge as a raw material, and belongs to the technical field of mineral smelting.
Background
The selenium element has little content in the earth crust and is distributed and dispersed, most of the selenium is recovered from the by-product in the copper ore processing process, but the selenium is widely applied to the fields of electronics, glass, metallurgy, chemical industry, medical care, agriculture and the like. Selenium has photosensitivity and semiconductor properties and is commonly used in the electronics industry to make photovoltaic cells, photoreceptors, laser devices, infrared controllers, phototubes, photoresistors, optical instruments, photometers, rectifiers, and the like. The application of selenium in the field of electronic industry accounts for about 30% of the total demand, and high-purity selenium (99.99%) and selenium alloy are the main light-absorbing media in photoelectric copying machines and are used as photoreceptors of common paper copying machines and laser printers; selenium can improve the processing performance of steel, so that the selenium is often applied to metallurgical industry, 0.3-0.5 percent of selenium is added into cast iron, stainless steel and copper alloy, the mechanical performance of the cast iron, stainless steel and copper alloy can be improved, the structure is more compact, high-speed cutting can be carried out, the surface of a processed part is smoother, and the alloy consisting of selenium and other elements is often used for manufacturing low-voltage rectifiers, photocells and thermoelectric materials; in agricultural production, selenium can be added into a fertilizer to improve the selenium deficiency state of soil and promote plant growth; selenium is also used in cosmetics, and some cosmetics containing selenium have an anti-aging effect; in addition, the addition of selenium to the plating solution can improve the appearance of the plated article and is therefore also used in the electroplating industry.
The extraction process of selenium mainly comprises fire extraction of selenium and wet extraction of selenium. The pyrogenic selenium extraction process has been widely used in industrial production due to its strong adaptability to raw materials and simple operation, and has become a traditional selenium extraction process, and within a long period of time, the pyrogenic selenium extraction process has become the dominant process for extracting selenium from copper electrolysis anode mud. The common fire method selenium extraction process mainly comprises the following steps: the method comprises an oxidation baking process, a soda baking process, a sulfation baking process and a calcium and selenium adding baking process, wherein the oxidation baking process has the problems of low product taste and difficulty in separation of mercury and selenium; the soda baking process has the problems of large acid consumption and high difficulty of subsequent purification treatment; the sulfating baking process has the problems of large amount of waste gas and waste acid, and higher cost in the aspect of environmental management. The fire method selenium extraction process also has the defects of large smoke quantity and easy generation of SO2And SeO2And the problems of toxic gas, high energy consumption and the like are solved, and the further popularization and application of the pyrogenic selenium extraction process are seriously influenced by the defects. Compared with the fire method selenium extraction process, the wet method selenium extraction process has the advantages of low energy consumption, cleanness, environmental protection, low production cost and the like, so the wet method selenium extraction process gradually replaces the fire method selenium extraction process to become a dominant process for extracting selenium, and the improvement, popularization and development of the wet method selenium extraction process are worthy of researchTo a problem of (a).
Disclosure of Invention
The invention solves the defects in the prior art and provides a wet-method selenium refining process by taking lead-zinc smelting acid sludge as a raw material, the process takes acid sludge generated in the lead-zinc smelting process as a raw material, calcium is added to fix selenium and remove mercury, and then the refined selenium is extracted by a wet method, so that the purity of the finished selenium product reaches more than 99 percent, and the process has the advantages of low auxiliary material loss and production cost, simplicity in operation, low labor intensity, less smoke dust, cleanness, environmental friendliness and high economic benefit.
The technical scheme adopted for realizing the above purpose of the invention is as follows:
a wet-process selenium refining process taking lead-zinc smelting acid sludge as a raw material comprises the following steps: (1) and (3) raw material treatment: lead-zinc smelting acid mud and quicklime are uniformly stirred and mixed according to the mass ratio of 1: 2-1: 9;
(2) and granulating: the mixed material is granulated, and dust generated in the baking process can be reduced through granulation, so that the generation of mercury soot is reduced, and the generation rate of the activated mercury and the direct yield of the smelted mercury are improved;
(3) roasting to remove mercury: roasting the granulated material at 650-700 ℃ under an aerobic environment with 0.8-0.9 standard atmospheric pressure, reacting selenide with calcium oxide in the roasting process to generate mercury vapor and calcium selenite, condensing the mercury vapor after the mercury vapor escapes, liquefying the mercury vapor into liquid metal mercury after the mercury vapor is condensed, and leaching the roasted residue with sulfuric acid;
(4) and sulfuric acid leaching: adding water into the baking residues, wet-milling, putting into a sulfuric acid solution, wherein the liquid-solid ratio is 4: 1-5: 1, the initial sulfuric acid concentration of a sulfuric acid leaching solution is 270-310 g/L, the leaching temperature is 85-95 ℃, the leaching time is 4-5 h, and after the sulfuric acid leaching is finished, dissolving calcium selenite in the sulfuric acid solution, and reducing to obtain selenious acid;
(5) and recovering crude selenium: carrying out solid-liquid separation on the leaching solution after sulfuric acid leaching to obtain filtrate A, and introducing SO into the filtrate A2Reacting at the temperature of more than 70 ℃, and reducing to obtain crude selenium with the purity of more than 93 percent;
(6) and preparing refined selenium:
a. heating for reaction: leaching the reduced crude selenium in a sodium sulfite solution, heating and stirring during leaching, wherein the leaching time is 4-5 hours, the leaching temperature is 100-110 ℃, a sodium sulfide solution is added during leaching, sodium selenosulfate and indissolvable copper and mercury sulfides are generated after reaction, and solid-liquid separation is performed on a leaching solution to obtain a filtrate B;
b. cooling and precipitating: repeating the operations of heating, dissolving, cooling and separating out on the filtrate B until refined selenium with the purity of more than 99% is separated out, carrying out solid-liquid separation after the separation is finished to obtain refined selenium and mother liquor, washing the refined selenium, and storing the mother liquor in a centralized manner;
c. acidifying: after the mother liquor is stored for 5-7 days, adding sulfuric acid to carry out acidification reaction for 8-9 hours, generating refined selenium after the reaction is finished, and washing the refined selenium;
d. washing: washing with water, cooling, separating out and acidifying to obtain refined selenium;
e. drying: and drying the washed refined selenium to obtain the refined finished selenium product.
And (3) condensing in the step (3) by indirect cooling, wherein the indirect cooling is performed by condensing in a condensing tube at the temperature of 20-30 ℃, and the condensed tail gas enters into cleaning treatment.
And (3) recycling sulfuric acid generated by the reduction reaction in the step (5) for sulfuric acid leaching and acidification.
The particle size of the baking residues after wet grinding in the step (4) is 90-110 meshes.
And (5) performing solid-liquid separation by adopting vacuum filtration.
And (3) washing in the step (6) is used for removing sulfite and sulfuric acid attached to the refined selenium, the sulfite is reused for temperature rise reaction, and the sulfuric acid is reused for sulfuric acid leaching and acidified leachate.
And (4) reacting sulfur dioxide generated by acidification in the step (6) with sodium hydroxide to prepare sodium sulfite, and reusing the sodium sulfite as a leachate of the heating reaction.
The drying in the step (6) is electric heating, and the heating temperature is 95-110 ℃.
Compared with the prior art, the wet-process selenium refining process using the lead-zinc smelting acid sludge as the raw material has the following advantages: 1. the method provided by the invention has the advantages that the lead-zinc smelting acid sludge is used as the raw material to refine the refined selenium, so that the metal smelting waste is recycled, and the method is low in production cost, clean, environment-friendly and resource-recycling; 2. according to the invention, the acid mud is mixed, granulated and baked through a mercury removal process, dust generated by baking and baking time can be reduced through granulation, mercury is extracted through baking, and the generated baking residues can better react with sulfuric acid in the crude selenium recovery process; 3. according to the wet-method refined selenium process adopted after mercury removal, the refined selenium with the purity of more than 99% is refined through the operations of crude selenium recovery, temperature-raising reaction leaching, filtering, temperature-lowering precipitation, acidification, washing and drying, the process flow is simple, the operation is simple and convenient, the energy consumption is low, the refined selenium is high in purity, simultaneously, the generated dust and smoke are less, and the air environment of a working area is improved, so that the physical harm to workers is reduced, and the process has good popularization value and economic benefit; 4. the sulfuric acid and the sodium sulfite produced in the process can be recycled, so that the workload of waste cleaning and pollutant discharge are reduced, the production cost is reduced, and the environment is protected.
Drawings
FIG. 1 is a process flow diagram of a wet-process selenium refining process using lead-zinc smelting acid sludge as a raw material.
Detailed Description
The present invention will be described in detail with reference to specific examples.
Example 1
The invention provides a wet-process selenium refining process taking lead-zinc smelting acid sludge as a raw material, which has a process flow shown in figure 1 and comprises the following steps: (1) and (3) raw material treatment: lead-zinc smelting acid mud and quicklime are weighed according to the mass ratio of 1:7, 100g of acid mud and 700g of quicklime are uniformly mixed in a stirring mixer, and the main components in the acid mud are (%): pb36.31, Se35.24, Hg11.24, Fe10.37, Zn 6;
(2) and granulating: putting the mixed materials into a granulator to prepare small balls with the diameter of 7 mm; dust generated in the baking process can be reduced through granulation, so that mercury soot generation is reduced, and the generation rate of activated mercury and the direct yield of mercury smelting are improved;
(3) roasting to remove mercury: roasting the granulated material in a rotary kiln under an aerobic environment of 680 ℃ and 0.9 standard atmospheric pressure, wherein the retention time in the rotary kiln is 15min, selenide reacts with calcium oxide in the roasting process to generate mercury vapor and calcium selenite, the mercury vapor escapes and then enters a condensing pipe for condensation treatment, circulating cooling water is adopted in the condensing pipe to control the temperature to be 25 ℃, the mercury vapor is condensed into liquid metal mercury, and roasting residues enter a sulfuric acid leaching process; the roasting reaction separates mercury in the acid mud, and meanwhile, the selenium is oxidized to generate a stable compound to be stored in the roasting residue. The waste gas generated by baking and condensation is absorbed by hydrogen peroxide, sodium hypochlorite, sodium polysulfide and a Venturi wet dust removal and desulfurization device, and mercury soot is recycled for raw material treatment. The baking process involves the main equations:
HgSe+CaO+O2→Hg+CaSeO3
Hg(s)→Hg(g)
Se+CaO+O2→CaSeO3
MeSe+CaO+O2→MeSeO3(other selenides are oxidized)
(4) And sulfuric acid leaching: selenium mainly comprises CaSeO in roasting residue after roasting for removing mercury3Adding water into baking residues, wet-grinding until the granularity is 100 meshes, putting the baking residues into a sulfuric acid solution, leaching the sulfuric acid in a sealed tank at a liquid-solid ratio of 4:1 and an initial sulfuric acid concentration of a sulfuric acid leaching solution of 290g/L at a leaching temperature of 90 ℃ for 5h, wherein CaSeO is added3Can be better dissolved in sulfuric acid solution, and after the sulfuric acid leaching is finished, the calcium selenite is dissolved in the sulfuric acid solution and reduced to obtain the selenic acid. The main equations involved in the sulfuric acid leaching process are:
CaSeO3+H2SO4→CaSO4+H2SeO3
(5) and recovering crude selenium: carrying out solid-liquid separation on the leachate after sulfuric acid leaching through a vacuum filter vat to obtain filtrate A, and introducing SO into the filtrate A2At 75 ℃ CAnd (3) carrying out reaction, reducing to obtain crude selenium with the purity of 93%, and recycling sulfuric acid generated in the reaction process for sulfuric acid leaching and acidification in fine selenium preparation without discharging. The main equations involved in the reaction process are:
H2SeO3+2SO2+H2O→2H2SO4+Se
(6) and preparing refined selenium:
a. heating for reaction: and (2) putting the recovered crude selenium into a sodium sulfite solution for leaching, heating and stirring during leaching, wherein the leaching time is 5h, the leaching temperature is 110 ℃, adding a sodium sulfide solution during leaching, generating sodium selenosulfate and indissolvable copper and mercury sulfides after the reaction is finished, and performing solid-liquid separation on the leachate to obtain a filtrate B. The main reaction equations involved in the process are:
Na2SO3+Se→Na2SeSO3(temperature-elevating reaction)
b. Cooling and precipitating: and (3) repeating the operations of heating, dissolving, cooling and separating out of the filtrate B until refined selenium with the purity of more than 99% is separated out, carrying out solid-liquid separation after the separation is finished to obtain the refined selenium and mother liquor, washing the refined selenium, and storing the mother liquor with lower selenium content left after the refined selenium is separated out in a centralized manner. The main reaction equations involved in the process are:
Na2SeSO3→Na2SO3+ Se (Cooling reaction)
c. Acidifying: storing the mother liquor for 5 days, adding sulfuric acid to carry out acidification reaction for 9h, generating refined selenium after the reaction is finished, washing the refined selenium, discharging generated acidified waste liquid, and discharging SO generated by acidification2Reacting with NaOH under negative pressure to prepare sodium sulfite, and recycling to prepare sodium sulfite solution for heating reaction. The main reaction equations involved in the process are:
Na2SeSO3+H2SO4→Na2SO4+Se↓+SO2↑+H2o (acidification reaction)
SO2+2NaOH→Na2SO3+H2O (exhaust gas absorption reaction)
d. Washing: washing the refined selenium obtained by cooling, separating out and acidifying by water, removing sulfite and sulfuric acid attached to the refined selenium, reusing the sulfite for heating reaction, and reusing the sulfuric acid for sulfuric acid leaching and acidifying sulfuric acid solution.
e. Drying: and (3) putting the washed fine selenium into a drying box, wherein the drying box is electrically heated at 100 ℃, the dried fine selenium is an extracted finished product and is packaged as a final product, the drying box is closed, the specific gravity of the selenium is large, and no dust is emitted basically in the drying process.
In this example, 10.31g of mercury with a purity of 99% was finally obtained, the mercury recovery rate (mercury content of liquid metallic mercury/mercury content of acid sludge) was 90.8%, 33.95g of selenium with a purity of 99%, and the selenium recovery rate (selenium content of finished product selenium/selenium content of acid sludge) was 95.4%.
Example 2
The invention provides a wet-method selenium refining process by taking lead-zinc smelting acid sludge as a raw material, and a reaction equation related in the embodiment is consistent with that in the embodiment 1, and is not repeated herein. The method specifically comprises the following steps: (1) and (3) raw material treatment: lead-zinc smelting acid mud and quicklime are weighed according to the mass ratio of 1:7, 100g of acid mud and 700g of quicklime are uniformly mixed in a stirring mixer, and the main components in the acid mud are (%): pb36.31, Se35.24, Hg11.24, Fe10.37, Zn 6;
(2) and granulating: putting the mixed materials into a granulator to prepare small balls with the diameter of 7 mm; dust generated in the baking process can be reduced through granulation, so that mercury soot generation is reduced, and the generation rate of activated mercury and the direct yield of mercury smelting are improved;
(3) roasting to remove mercury: roasting the granulated material in a rotary kiln under an aerobic environment of 680 ℃ and 0.9 standard atmospheric pressure, wherein the retention time in the rotary kiln is 15min, selenide reacts with calcium oxide in the roasting process to generate mercury vapor and calcium selenite, the mercury vapor escapes and then enters a condensing pipe for condensation treatment, circulating cooling water is adopted in the condensing pipe to control the temperature to be 25 ℃, the mercury vapor is condensed into liquid metal mercury, and roasting residues enter a sulfuric acid leaching process; the roasting reaction separates mercury in the acid mud, and meanwhile, the selenium is oxidized to generate a stable compound to be stored in the roasting residue. The waste gas generated by baking and condensation is absorbed by hydrogen peroxide, sodium hypochlorite, sodium polysulfide and a Venturi wet dust removal and desulfurization device, and mercury soot is recycled for raw material treatment.
(4) And sulfuric acid leaching: selenium mainly comprises CaSeO in roasting residue after roasting for removing mercury3Adding water into baking residues, wet-grinding until the granularity is 100 meshes, putting the baking residues into a sulfuric acid solution, leaching the sulfuric acid in a sealed tank at a liquid-solid ratio of 4:1 and an initial sulfuric acid concentration of a sulfuric acid leaching solution of 290g/L at a leaching temperature of 90 ℃ for 5h, wherein CaSeO is added3Can be better dissolved in sulfuric acid solution, and after the sulfuric acid leaching is finished, the calcium selenite is dissolved in the sulfuric acid solution and reduced to obtain the selenic acid.
(5) And recovering crude selenium: carrying out solid-liquid separation on the leachate after sulfuric acid leaching through a vacuum filter vat to obtain filtrate A, and introducing SO into the filtrate A2The reaction is carried out at 75 ℃, crude selenium with the purity of 93 percent is obtained by reduction, and sulfuric acid generated in the reaction process is reused for sulfuric acid leaching and acidification in fine selenium preparation, and is not discharged.
(6) And preparing refined selenium:
a. heating for reaction: leaching the recovered crude selenium in a sodium sulfite solution, heating and stirring during leaching, wherein the leaching time is 5h, the leaching temperature is 110 ℃, a sodium sulfide solution is added during leaching, sodium selenosulfate and indissolvable copper and mercury sulfides are generated after the reaction is finished, and the leachate is subjected to solid-liquid separation to obtain a filtrate B;
b. cooling and precipitating: repeating the operations of heating, dissolving, cooling and separating out on the filtrate B until refined selenium with the purity of more than 99% is separated out, carrying out solid-liquid separation after the separation is finished to obtain refined selenium and mother liquor, washing the refined selenium, and storing the mother liquor with lower selenium content left after the refined selenium is separated out;
c. acidifying: storing the mother liquor for 6 days, adding sulfuric acid to carry out acidification reaction for 9h, generating refined selenium after the reaction is finished, washing the refined selenium, discharging generated acidified waste liquid, and discharging SO generated by acidification2Reacting with NaOH under negative pressure to prepare sodium sulfite, and recycling to prepare sodium sulfite solution for heating reaction.
d. Washing: washing the refined selenium obtained by cooling, separating out and acidifying by water, removing sulfite and sulfuric acid attached to the refined selenium, reusing the sulfite for heating reaction, and reusing the sulfuric acid for sulfuric acid leaching and acidifying sulfuric acid solution.
e. Drying: and (3) putting the washed fine selenium into a drying box, wherein the drying box is electrically heated at 100 ℃, the dried fine selenium is an extracted finished product and is packaged as a final product, the drying box is closed, the specific gravity of the selenium is large, and no dust is emitted basically in the drying process.
In this example, 10.38g of mercury with a purity of 99% was finally obtained, the mercury yield (mercury content of liquid metallic mercury/mercury content of acid sludge) was 91.42%, 34.38g of selenium with a purity of 99%, and the selenium recovery (selenium content of finished product selenium/selenium content of acid sludge) was 96.6%.
Example 3
The invention provides a wet-method selenium refining process by taking lead-zinc smelting acid sludge as a raw material, and a reaction equation related in the embodiment is consistent with that in the embodiment 1, and is not repeated herein. The method specifically comprises the following steps: (1) and (3) raw material treatment: lead-zinc smelting acid mud and quicklime are weighed according to the mass ratio of 1:7, 100g of acid mud and 700g of quicklime are uniformly mixed in a stirring mixer, and the main components in the acid mud are (%): pb36.31, Se35.24, Hg11.24, Fe10.37 and Zn 6.
(2) And granulating: putting the mixed materials into a granulator to prepare small balls with the diameter of 7 mm; dust generated in the baking process can be reduced through granulation, so that mercury soot generation is reduced, and the generation rate of activated mercury and the direct yield of mercury smelting are improved.
(3) Roasting to remove mercury: roasting the granulated material in a rotary kiln under an aerobic environment of 680 ℃ and 0.9 standard atmospheric pressure, wherein the retention time in the rotary kiln is 15min, selenide reacts with calcium oxide in the roasting process to generate mercury vapor and calcium selenite, the mercury vapor escapes and then enters a condensing pipe for condensation treatment, circulating cooling water is adopted in the condensing pipe to control the temperature to be 25 ℃, the mercury vapor is condensed into liquid metal mercury, and roasting residues enter a sulfuric acid leaching process; the roasting reaction separates mercury in the acid mud, and meanwhile, the selenium is oxidized to generate a stable compound to be stored in the roasting residue. The waste gas generated by baking and condensation is absorbed by hydrogen peroxide, sodium hypochlorite, sodium polysulfide and a Venturi wet dust removal and desulfurization device, and mercury soot is recycled for raw material treatment.
(4) And sulfuric acid leaching: selenium mainly comprises CaSeO in roasting residue after roasting for removing mercury3Adding water into baking residues, wet-grinding until the granularity is 100 meshes, putting the baking residues into a sulfuric acid solution, leaching the sulfuric acid in a sealed tank at a liquid-solid ratio of 4:1 and an initial sulfuric acid concentration of a sulfuric acid leaching solution of 290g/L at a leaching temperature of 90 ℃ for 5h, wherein CaSeO is added3Can be better dissolved in sulfuric acid solution, and after the sulfuric acid leaching is finished, the calcium selenite is dissolved in the sulfuric acid solution and reduced to obtain the selenic acid.
(5) And recovering crude selenium: carrying out solid-liquid separation on the leachate after sulfuric acid leaching through a vacuum filter vat to obtain filtrate A, and introducing SO into the filtrate A2The reaction is carried out at 75 ℃, crude selenium with the purity of 94 percent is obtained by reduction, and sulfuric acid generated in the reaction process is reused for sulfuric acid leaching and acidification in the preparation of refined selenium and is not discharged.
(6) And preparing refined selenium:
a. heating for reaction: leaching the recovered crude selenium in a sodium sulfite solution, heating and stirring during leaching, wherein the leaching time is 5h, the leaching temperature is 110 ℃, a sodium sulfide solution is added during leaching, sodium selenosulfate and indissolvable copper and mercury sulfides are generated after the reaction is finished, and the leachate is subjected to solid-liquid separation to obtain a filtrate B;
b. cooling and precipitating: repeating the operations of heating, dissolving, cooling and separating out on the filtrate B until refined selenium with the purity of more than 99% is separated out, carrying out solid-liquid separation after the separation is finished to obtain refined selenium and mother liquor, washing the refined selenium, and storing the mother liquor with lower selenium content left after the refined selenium is separated out;
c. acidifying: storing the mother liquor for 7 days, adding sulfuric acid to carry out acidification reaction for 9h, generating refined selenium after the reaction is finished, washing the refined selenium, discharging generated acidified waste liquid, and discharging SO generated by acidification2Reacting with NaOH under negative pressure to obtain sodium sulfite, and recycling to obtainSodium sulfite solution for temperature reaction;
d. washing: washing the refined selenium obtained by cooling, separating out and acidifying by water, removing sulfite and sulfuric acid attached to the refined selenium, reusing the sulfite for heating reaction, and reusing the sulfuric acid for sulfuric acid leaching and acidifying sulfuric acid solution;
e. drying: putting the washed fine selenium into a drying box, wherein the drying box is electrically heated at 100 ℃, the dried fine selenium is an extracted finished product and is packaged as a final product, the drying box is closed, the specific gravity of the selenium is high, and no dust is emitted basically in the drying process;
in this example, 10.28g of mercury with a purity of 99% was finally obtained, the direct yield of mercury (mercury content of liquid metallic mercury/mercury content of acid sludge) was 90.5%, 34.84g of selenium with a purity of 99%, and the recovery rate of selenium (selenium content of finished product selenium/selenium content of acid sludge) was 97.9%.
The invention provides a wet-method selenium refining process taking lead-zinc smelting acid sludge as a raw material, which is characterized in that quicklime is added through raw material treatment, the acid sludge can be dried, and heat transfer and mercury evaporation in a baking process are facilitated; dust generated in the baking process can be reduced through granulation, so that mercury soot generation is reduced, and the generation rate of activated mercury and the direct yield of mercury smelting are improved; roasting to remove mercury can shorten roasting time and refine to obtain liquid metal mercury; selenious acid is obtained by sulfuric acid leaching reduction; crude selenium with the purity of more than 93 percent is obtained by recovering the crude selenium; insoluble matters, copper, mercury and other impurities in the crude selenium are further removed through a heating reaction; cooling and separating out to obtain refined selenium with the purity of more than 99 percent; and (4) removing residues and moisture on the surface of the refined selenium through washing and drying, and finally packaging as a finished product. The invention combines the processes of fire mercury removal and wet selenium extraction, takes acid sludge generated in the lead-zinc smelting process as a raw material, adds calcium to fix selenium and remove mercury, and then carries out wet selenium extraction to obtain refined selenium, so that the purity of the finished selenium product reaches more than 99 percent, and the invention has the advantages of low auxiliary material loss and production cost, simple operation, low labor intensity, less smoke dust, cleanness, environmental protection and high economic benefit.
Claims (8)
1. A wet-process selenium refining process taking lead-zinc smelting acid sludge as a raw material is characterized by comprising the following steps:
(1) and (3) raw material treatment: lead-zinc smelting acid mud and quicklime are uniformly stirred and mixed according to the mass ratio of 1: 2-1: 9;
(2) and granulating: the mixed material is granulated, and dust generated in the baking process can be reduced through granulation, so that the generation of mercury soot is reduced, and the generation rate of the activated mercury and the direct yield of the smelted mercury are improved;
(3) roasting to remove mercury: roasting the granulated material at 650-700 ℃ under an aerobic environment with 0.8-0.9 standard atmospheric pressure, reacting selenide with calcium oxide in the roasting process to generate mercury vapor and calcium selenite, condensing the mercury vapor after the mercury vapor escapes, liquefying the mercury vapor into liquid metal mercury after the mercury vapor is condensed, and leaching the roasted residue with sulfuric acid;
(4) and sulfuric acid leaching: adding water into the baking residues, wet-milling, putting into a sulfuric acid solution, wherein the liquid-solid ratio is 4: 1-5: 1, the initial sulfuric acid concentration of a sulfuric acid leaching solution is 270-310 g/L, the leaching temperature is 85-95 ℃, the leaching time is 4-5 h, and after the sulfuric acid leaching is finished, dissolving calcium selenite in the sulfuric acid solution, and reducing to obtain selenious acid;
(5) and recovering crude selenium: carrying out solid-liquid separation on the leaching solution after sulfuric acid leaching to obtain filtrate A, and introducing SO into the filtrate A2Reacting at the temperature of more than 70 ℃, and reducing to obtain crude selenium with the purity of more than 93 percent;
(6) and preparing refined selenium:
a. heating for reaction: leaching the recovered crude selenium in a sodium sulfite solution, heating and stirring during leaching, wherein the leaching time is 4-5 hours, the leaching temperature is 100-110 ℃, a sodium sulfide solution is added during leaching, sodium selenosulfate and indissolvable copper and mercury sulfides are generated after the reaction is finished, and solid-liquid separation is performed on the leachate to obtain a filtrate B;
b. cooling and precipitating: repeating the operations of heating, dissolving, cooling and separating out on the filtrate B until refined selenium with the purity of more than 99% is separated out, carrying out solid-liquid separation after the separation is finished to obtain refined selenium and mother liquor, washing the refined selenium, and storing the mother liquor in a centralized manner;
c. acidifying: after the mother liquor is stored for 5-7 days, adding sulfuric acid to carry out acidification reaction for 8-9 hours, generating refined selenium after the reaction is finished, and washing the refined selenium;
d. washing: washing with water, cooling, separating out and acidifying to obtain refined selenium;
e. drying: and drying the washed refined selenium to obtain the refined finished selenium product.
2. The wet-process selenium refining process taking lead-zinc smelting acid sludge as a raw material according to claim 1, which is characterized in that: and (3) condensing in the step (3) by indirect cooling, wherein the indirect cooling is performed by condensing in a condensing tube at the temperature of 20-30 ℃, and the condensed tail gas enters into cleaning treatment.
3. The wet-process selenium refining process taking lead-zinc smelting acid sludge as a raw material according to claim 1, which is characterized in that: and (3) recycling sulfuric acid generated by the reduction reaction in the step (5) for sulfuric acid leaching and acidification.
4. The wet-process selenium refining process taking lead-zinc smelting acid sludge as a raw material according to claim 1, which is characterized in that: the granularity of the mercury-removing slag after wet grinding in the step (4) is 90-110 meshes.
5. The wet-process selenium refining process taking lead-zinc smelting acid sludge as a raw material according to claim 1, which is characterized in that: and (5) performing solid-liquid separation by adopting vacuum filtration.
6. The wet-process selenium refining process taking lead-zinc smelting acid sludge as a raw material according to claim 1, which is characterized in that: and (4) washing in the step (6) is used for removing sulfite and sulfuric acid attached to the refined selenium, the sulfite is reused for temperature rise reaction, and the sulfuric acid is reused for sulfuric acid leaching and acidification.
7. The wet-process selenium refining process taking lead-zinc smelting acid sludge as a raw material according to claim 1, which is characterized in that: and (4) reacting sulfur dioxide generated by acidification in the step (6) with sodium hydroxide to prepare sodium sulfite, and reusing the sodium sulfite as a leachate of the heating reaction.
8. The wet-process selenium refining process taking lead-zinc smelting acid sludge as a raw material according to claim 1, which is characterized in that: the drying in the step (6) is electric heating, and the heating temperature is 95-110 ℃.
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