Patent Application
20160160319
The invention belongs to the field of comprehensive recovery of a zinc-containing secondary resource, and in particular relates to a treatment method of a chlorine-containing zinc oxide secondary material.
At present, about 14,000,000 t/a of zinc ingot are consumed in the world, wherein 50% of the zinc ingot are used for surface protection of steel; in recovering of galvanized steel, zinc volatilizes at high temperature and enters into steelmaking dust, and the dust is called as electric arc furnace dust (EAFD). In addition, zinc is also accompanied in various metal mineral resources, and the zinc invades into the smelting dust in a process of smelting those metals at high temperature; in some zinc-containing waste, lead and zinc volatilize into the dust through a high-temperature reducing volatilization way. The dust is a main source of secondary zinc resource; zinc exists in the zinc-containing materials in the form of oxide in common; meanwhile, the zinc-containing materials are different in chlorine content which exceeds the maximum amount allowed by zinc hydrometallurgy by tens to hundreds of times at most, and the zinc-containing materials contain lead, calcium, magnesium, iron, sodium, potassium, silicon dioxide, etc. When being treated by a current zinc hydrometallurgy technology, chlorine enters into solution, so that electrolysis process of the zinc cannot continue. Mineral zinc raw material is growing increasingly tense and is to run out around the world, while secondary zinc resource becomes more and accumulation of the secondary zinc resource causes increasing pressure on environment, so that people are urged to conduct a lot of researches on utilization of the secondary resource.
High chlorine content is a key factor that the current zinc smelting technology is unavailable to treat the secondary resource; to make the raw material adapt to technological requirements of zinc hydrometallurgy, current researches mainly focus on removal of chlorine in the raw materials. According to an existing treatment idea, chlorine of the materials is removed, and the current zinc smelting technology is employed after reducing chlorine content.
Chlorine is removed from the chlorine-containing zinc oxide respectively through pyrogenic dechloridation and wet dechloridation processes. The pyrogenic dechloridation, on the basis of a property of metal chloride which is easy to volatilize due to relatively high vapor pressure at high temperature, volatilizes and removes chlorine in the form of the metal chloride at high temperature. Generally, such dechlorinating equipment include multi-hearth furnace and waelz kiln. Some people also make studies on microwave dechloridation, which heats materials to 700-1100 DEG C. to volatilize the chlorine. The pyrogenic dechloridation has shortcomings such as high energy consumption, low metal recovery rate, a gas-phase pollution source and pressure on environment due to generation of dust higher in chlorine content, but the pyrogenic dechloridation is also widely adopted by various enterprises at present; after removing the chlorine, zinc oxide is applied to the existing zinc smelting process.
The wet dechloridation, on the basis of a property of being soluble in water of chloride, converts chlorine in solution. Generally, sodium carbonate (or ammonium carbonate) is used for treating materials, lead chloride and zinc chloride are converted into carbonate insoluble in water, and the chlorine enters into the solution in the form of sodium chloride. The wet dechloridation has the shortcomings of incomplete dechloridation, high reagent consumption, high cost and high dechloridation water consumption, and after removing chlorine, the liquid is mixing thin solution of sodium (potassium) chloride, sodium carbonate and sodium (potassium) sulfate. The dechloridation solution, which is non-recyclable and is inconvenient to recover chloride, is generally discharged. Therefore serious chlorine-containing wastewater discharge accompanies with the wet dechloridation.
Although the various disadvantages, the process of removing chlorine from the raw materials is a choice to treat chlorine-containing zinc oxide secondary resource at present. The chlorine-containing zinc oxide, after removing the chlorine, can be applied to the current zinc smelting process, and a certain amount of chlorine which is still kept in the raw materials is constantly accumulated in a leaching-electrolyte circulating process in zinc hydrometallurgy. Therefore, the chlorine shall be removed from circulating zinc sulfate solution. The chlorine in the zinc sulfate solution is removed on the basis that some oxides are low in solubility in the zinc sulfate solution and the chlorine is removed from the solution through generated chloride precipitate; generally, cuprous ion serves as a precipitate for precipitating chlorine ions; by precipitating the chlorine in the form of cuprous chloride, chlorine in the zinc sulfate solution is reduced so that electrolysis can be implemented normally. Sometimes, ion exchange, organic solvent chlorine extraction or other methods are available to transfer chlorine in the zinc sulfate solution to other solutions, so as to discharge the chlorine in the form of wastewater. Because of existence of the chlorine, the zinc hydrometallurgy process is complex and is increased in consumption of expensive copper; meanwhile, discharge of chlorine-containing wastewater is increased.
Therefore, the problem of high chlorine content in the secondary zinc oxide is still an issue in the zinc recycling field. Because such issue cannot be solved thoroughly and secondary zinc oxide resource cannot be effectively utilized for long time, so that utilization rate of zinc secondary resource is much less than that of other non-ferrous metals.
Whereas, in order to solve above said issues, the invention aims at providing an environment-friendly and energy-saving technology for chlorine-containing zinc oxide secondary resource. The inventor, on the basis of a lot of further studies and creative work, completes the invention.
The technical solution is:
A treatment method of chlorine-containing zinc oxide secondary material is characterized by the following steps:
(1) Leaching the chlorine-containing zinc oxide secondary material I through an acid solution to obtain leaching liquor and leaching residue;
(2) Selectively extracting zinc from leaching liquor obtained from the Step (1) through P204-kerosene solvent to obtain a zinc-containing organic phase as well as chlorine and acid containing raffinate;
(3) Implementing stripping-electrolysis zinc recovery to the zinc-containing organic phase obtained from the Step (2), and returning the organic phase after the stripping to the Step (2) to extract zinc;
(4) Taking the raffinate obtained from the Step (2) as the acid solution of the Step (1), returning to Step (1) and repeating steps (1)-(4);
(5) Taking out the raffinate obtained from the Step (4), when the chlorine ion of chlorine-containing aqueous phase in the step (2) achieves 50-80 g/L after circulating repeating steps (1)-(4), wherein the number of taking out the raffinate shall guarantee the chlorine content of the taken out raffinate is identical to that of raw material added in the Step (1) so as to keep chlorine ion adding and taking out balance; mixing the taken out raffinate with additional chlorine-containing zinc oxide secondary material II at liquid-solid ratio of 1-3:1; carrying out liquid-solid separation; leaching the separated deposit through acid raffinate of the Step (1);
(6) After finishing the Step (5) until separated solution contains 80-120 g/L of chlorine ion and 160-240 g/L of total salt content, removing impurities of chlorine-containing aqueous phase to obtain a KCl and NaCl mixing solution;
(7) Evaporating and concentrating the KCl and NaCl mixing solution obtained from the Step (6) to crystallize out KCl and NaCl products.
Preferably, in the Step (1), the leaching conditions are as follows: liquid-solid ratio is controlled according to leaching liquor that contains 25-28 g/L of zinc. Depending on different zinc contents of material, the liquid-solid ratio is controlled at 20-40:1; leaching is implemented in a mechanical stirring tank; and leaching end pH value is at 4.5-5.0.
Preferably, sulfuric acid serves as acid solution for primary leaching in the Step (1); the sulfuric acid shall be supplied if the acid from the raffinate of the Step (4) for leaching in the Step (1) is insufficient.
Preferably, in the Step (2), the P204-kerosene solvent is prepared by making volume percentage of an organic solvent P204 at 20-40% through 260# solvent kerosene.
Preferably, the stripping-electrolysis zinc recovery in the Step (3) is carried out by implementing stripping on zinc-containing organic phase through zinc electrolysis waste solution, wherein the stripping solution contains 100-120 g/L of Zn and 60-100 g/L of H2SO4, and electrolyzing zinc after deoiling.
Preferably, mixing in the Step (5) is carried out in a mechanical stirring tank or in a form of dump leaching; ore pulp shall be filtered to realize liquid-solid separation when the mixing is carried in the mechanical stirring tank.
Preferably, impurity removal in the Step (6) comprises the following steps:
1) neutralizing and removing heavy metal: adding lime and controlling pH value at 7.0-7.5;
2) neutralizing and removing Mg: adding lime and controlling pH value at 10;
3) removing calcium: adding Na2CO3.
The invention has the advantages as follows:
1. The invention avoids chlorine removal process from Step (1) to Step (7), thus omitting a raw material chlorine removal process, simplifying process, eliminating gaseous phase and aqueous phase pollution sources in the raw material chlorine removal process, saving energy consumption and reagent consumption in the chlorine removal process and greatly reducing production cost.
2. According to the invention, zinc is extracted and recovered from organic solvent in the Step (2), impurities are removed in the Step (6) and chloride is recovered in the Step (7), thus achieving a purpose of simultaneously implementing zinc recovery, chloride recovery and impurity removal.
3. According to the invention, chlorine in the chlorine-containing zinc oxide is converted into the solution through step (1), (2), (3), (4) and (5) and is enriched as a chloride solution high in concentration, so as to facilitate recovery of sodium chloride and potassium chloride from the solution.
4. According to the invention, chloride is recovered in the Step (7), so as to recover the chlorine in the raw material as a product, which not only guarantees a certain economic value but also thoroughly eliminates secondary pollution of the current dechloridation process.
5. The invention is free from process wastewater discharge, thus the company can realize the goal of zero emission of waste water.
6. According to the invention, zinc oxide secondary materials differing in chlorine content which chlorine content is 1-20% can be directly processed raw material relatively low in chlorine content is directly leached as operations in the Step (1), and raw material relatively high in chlorine content is processed by raffinate as operations in the Step (5) and is leached as the Step (1).
In order to clearly illustrate the technical solution of the embodiments of the invention or the existing technology, the drawings of the embodiments will be briefly described in the following; it is obvious that the described drawings are only related to embodiments of the invention; those skilled in the field can obtain other drawings depending on those drawings, without any inventive work.
The technical solutions of the embodiment will be described in a clearly and fully understandable way in connection with drawings related to the embodiments of the invention. It is obvious that the described embodiments are just a part but not all of the embodiments of the invention. Based on the described embodiments therein, those skilled in the art can obtain other embodiment(s), without any inventive work, which should be within the scope of the invention.
According to the process flowchart as shown in
(1) Leaching the chlorine-containing zinc oxide secondary material I through an acid solution to obtain leaching liquor and leaching residue;
(2) Selectively extracting zinc from leaching liquor obtained from the Step (1) through Pm-kerosene solvent to obtain a zinc-containing organic phase as well as a chlorine and acid containing raffinate;
(3) Implementing stripping-electrolysis zinc recovery to the zinc-containing organic phase obtained from the Step (2); returning the lean organic phase after the stripping to the Step (2) to extract zinc;
(4) Taking the raffinate obtained from the Step (2) as the acid solution of the Step (1), returning to Step (1) and repeating (1)-(4);
(5) Circulating the chlorine ion of chlorine-containing aqueous phase in the Step (2) for several times until chlorine ion achieves 50-80 g/L; taking out one part of the raffinate obtained from the Step (4), and mixing additional chlorine-containing zinc oxide secondary material at low liquid-solid ratio, separating precipitate, and adding the chlorine-containing zinc oxide secondary material of the Step (1), wherein the number of taking out the raffinate shall guarantee the chlorine content of the taken out raffinate is identical to that of raw material added in the Step (1) so as to keep chlorine ion adding and taking out balance;
(6) When chlorine-containing aqueous phase of the Step (5) contains 80-120 g/L of chlorine ion and 160-240 g/L of total salt content, removing impurities of chlorine-containing aqueous phase to obtain a KCl and NaCl mixing solution
(7) Evaporating and concentrating the KCl and NaCl mixing solution obtained from the Step (6) to crystallize out KCl and NaCl products.
Therefore, according to the process flow, actually, an acid wet treatment process of chlorine-containing zinc oxide (secondary material) is provided according to the invention. Further description will be made on the process flow below:
According to the invention, in stead of implementing dechloridation to the chlorine-containing zinc oxide (secondary material) in advance, the zinc oxide is directly leached through acid solution, so that such soluble materials as zinc, chlorine, potassium, sodium and magnesium in the zinc oxide are leached in the solution; the zinc is selectively extracted through P204-kerosene solvent so as to separate the zinc from Cr, K+, Na+, Mg2+ and the like. By implementing stripping-electrolysis zinc recovery from zinc-containing organic phase, the raffinate is returned once again to leach out chlorine-containing zinc oxide. Repeating in such way, Cl−, K+, Na+, Mg2+ and other ions in the solution are circulated and enriched, thus forming a complex chlorine salt-sulfate mixing system mainly containing Cl− ion and simultaneously including K+, Na+, Mg2+ and Zn2+ as well as little sulfuric acid.
After Cl−, K+, Na+ and Mg2+ in the solution achieve a certain concentration, partial zinc raffinate is taken out to recover chloride, thus realizing input and output balance in Cl−, K+, Na+, Mg2+ and other ions.
The taken out zinc raffinate contains free acid identical to extracted zinc ion in mole and not-extracted zinc; the taken out raffinate is mixed with excessive chlorine-containing zinc oxide raw material in the low liquid-solid ratio; acid of the solution is neutralized, zinc and sulfate radical are reduced, and chlorine ion concentration is further improved. The solution is neutralized by lime to remove Mg2+ and trace amount of heavy metal ion; the solution, after being processed, is a KCl and NaCl mixing high-concentration solution; the solution is concentrated and crystallized to generate potassium chloride and sodium chloride products.
Furthermore, principles and characteristics of the process flow according to the invention are described below, including preferred process conditions of steps (1)-(7). Equivalent or equal process conditions made by those skilled in the art through the principles and characteristics below shall be included within content scope and protection scope of the present invention.
The invention has the following characteristics:
1. Instead of pyrogenic or wet dechloridation in advance, acid leaching is directly implemented on the high-chlorine zinc oxide raw material.
Cl−, Zn2+, Mg2+, K+ and Na+ in the raw material enters into the leaching liquor; acid for leaching comes from circulating residual zinc raffinate, and sulfuric acid is supplied for insufficient part. Pb and Ca in the raw material enter into leaching residue in the form of sulfate together with SiO2; the sulfate in the solution will not be accumulated or enriched; the leaching residue serves as source of recovering lead.
Preferably, leaching conditions are as follows: liquid-solid ratio is controlled according to leaching liquor that contains 25-28 g/L of zinc; leaching is implemented in a mechanical stirring tank; and leaching end pH value is at 4.5-5.0.
To improve zinc leaching rate, zinc hydrometallurgy is available, which generally adopts multi-stage countercurrent leaching.
Leaching Reactions:
MO+H2SO4→MSO4+H2O
MO+2HCl→MCl2+H2O
PbO+H2SO4→PbSO4↓+H2O
PbCl2+H2SO4→PbSO4↓+2HCl
CaO+H2SO4+H2O→CaSO4.2H2O↓
M is Zn, Mg, etc., and KCl, NaCl as well as chloride of Zn and Mg can be directly dissolved in solution.
2. Zinc Recovery and Chlorine Circulation & Enrichment
Leaching liquor is filtered into clear solution and is mixed with P204 organic solvent; zinc is selectively extracted; free acid identical to the extracted zinc ion in mole is generated when extracting zinc; other ions such as Cl−, SO42−, K+, Na+ and Mg2+ are still kept in the solution; residual zinc raffinate is returned and leached, so that such irons as Cl−, K+, Na+ and Mg2+ are circulated and accumulated in a process of leaching→zinc extracting→re-leaching; reaction of extracting zinc is as follows:
ZnCl2+3HR→ZnR2.HR+2HCl
ZnSO4+3HR→ZnR2.HR+H2SO4
When extracting zinc, the organic solvent P204 and 260# solvent kerosene are mixed and the volume percentage of the organic solvent P204 falls within 20%-40%, such as 20%, 25%, 30%, 35% or 40%.
The stripping is carried out on zinc extracting organic phase through zinc electrolysis waste liquid; the stripping solution contains 100-120 g/L of Zn and 60-100 g/L of H2SO4, and zinc is electrolyzed after deoiling.
The solution is recycled for use; zinc is extracted through organic solvent for each recycling, while other soluble ions are accumulated in circulating liquid, thus forming a complex chlorine salt-sulfate mixing system mainly containing Cl− ion and simultaneously including SO42−, Zn2+, K+, Na+, Mg2+. Extraction system of zinc is different from the current salt-sulfate zinc extraction system, belonging to two different solution systems.
3. Control of Chlorine Ion
Through circulation in leaching→extracting→re-leaching, content of Cl− in the raw material is continuously increased in the circulating solution; partial chlorine-containing solution in the circulating liquid is taken out after reaching a certain concentration (such as 50-80 g/L) in accordance with Cl− input/output balance.
Specific treatment process adopts partial residual liquid after extracting zinc; the residual liquid is an acid solution which contains acid which is identical to extracted zinc ion in mole; meanwhile, the residual liquid contains different amounts of SO42− and Zn2+, K+, Na+, Mg2+, etc. The taking out solution is mixed with chlorine-containing zinc oxide raw material on a relatively low liquid-solid ratio; in this process, acid in the solution is neutralized; and partial Zn2+ is turned into alkaline zinc sulfate precipitate.
Neutralization Acid Reaction:
ZnO+2HCl→ZnCl2+H2O
ZnO+H2SO4→ZnSO4+H2O
Excessive ZnO will continue to react to generate alkaline zinc salt precipitate:
ZnSO4+ZnO+H2O→2Zn.SO4.(OH)2↓
Meanwhile, chloride in the raw material is dissolved in solution, so that chlorine ion in the solution is increased and chlorine in the raw material is reduced; after chlorine content is reduced, secondary zinc material is leached together with other chlorine-containing zinc oxide.
Treatment process of taking out raffinate can be implemented in the mechanical stirring tank or in a form of dump leaching; ore pulp shall be filtered to realize liquid-solid separation when the treatment process is carried in the mechanical stirring tank.
4. Recover KCl and NaCl from Chlorine-Containing Solution
Generally, treated solution contains 80-120 g/L of chlorine and 160-240 g/L of total salt, being high-concentration solution; the treated solution can serve as raw material for recovering KCl and NaCl or a condition for judging recovery.
The solution is purified into a KCl and NaCl mixing solution; the KCl and NaCl mixing solution is evaporated and concentrated to respectively crystallize out KCl and NaCl products.
A kind of preferable impurity removal process includes the follows: 1) neutralizing and removing heavy metal: adding lime and controlling pH value at 7.0-7.5 to form such heavy metal as Zn2+ in the solution into hydroxide precipitate; 2) neutralizing and removing Mg: adding lime and controlling pH value at 10 to form Mg into hydroxide precipitate; 3) removing calcium: precipitating little Ca2+ in the solution in the form of CaCO3 through Na2CO3. pH value of the solution is 10-11 after separating precipitate, and the solution is concentrated and crystallized to generate KCl and NaCl.
The present invention is further described through an embodiment below:
Some chlorine-containing zinc oxide secondary material is taken as a reagent, wherein chemical components (in percentage by weight) are as follows:
After being balanced in repeated circulation, the residual zinc raffinate contains the following components (Unit: g/L)
Step (1): leaching I 500 g of zinc-containing zinc oxide through the residual zinc raffinate, controlling zinc content of leaching post-liquid at 26 g/L, controlling liquid-solid ratio at 42, adding 21 L of residual zinc raffinate, slowly adding H2SO4 and controlling leaching end pH value at 5.0 to obtain leaching liquid which contains the following components: (unit: g/L)
Step (2): filtering clean leaching liquid, extracting zinc through 30% of P204-260# solvent oil, controlling phase ratio at 1:1 and extracting level on IV-level to obtain residual raffinate which contains 13 g/L of Zn and 0.4 mol/L of H+.
Step (3): stripping zinc from zinc extracting organic phase through zinc electrolysis waste liquid, wherein the stripping post-liquid contains 110 g/L of Zn and 85 g/L of H2SO4, and electrolyzing zinc after deoiling.
Step (4): in accordance with the Step (1) adding 34 g of chlorine, taking out 500 ml (about 34 g of chlorine) of residual zinc raffinate in the Step (2) for taking out, supplementing volume to 21 L for reset 20.5 L; returning to Step (1) and leaching; and repeating the steps.
Step (5): mixing the 500 ml of open residual raffinate and 200 g of chlorine-containing zinc oxide secondary material II at liquid-solid ratio of 2.5:1 for 30 min while stirring, and filtering to obtain 500 ml of solution which contains the following components: (unit: g/L)
Concentration of Cl−, K+ and Na+ in the solution are increased while Zn2+ and SO42− are reduced, and total salt content of the solution is 235.7 g/L; precipitate is 190 g weight after filtering and separating, which contains 31.5% of Zn, and Cl is reduced to 4.6% from 20.02%; and it shall implement leaching in the Step (1).
Step (6): purifying chlorine-containing aqueous phase which contains 132 g/L of chlorine ion after the Step (5) to obtain a KCl and NaCl mixing solution; the impurity removal process includes the follows: 1) neutralizing and removing heavy metal: adding lime and controlling pH value at 7.0-7.5 to form such heavy metal as Zn2+ in the solution into hydroxide precipitate; 2) neutralizing and removing Mg: adding lime and controlling pH value at 10 to form Mg into hydroxide precipitate; 3) removing calcium: precipitating little Ca2+ in the solution in the form of CaCO3 through Na2CO3.
Step (7): evaporating and concentrating the KCl and NaCl mixing solution obtained from the Step (6) to crystallize out KCl and NaCl products, wherein pH value of the mixing solution is 10-11.
The foregoing embodiments merely are exemplary embodiments of the invention, and not intended to define the scope of the invention; any modification, equal replacement, improvement, etc. shall be included in the protection scope of the invention.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2014/081557 | 7/3/2014 | WO | 00 |
