A method for recovering zinc from tin smelting dust by ammonia leaching-extraction process

Abstract

The invention discloses a method for recovering zinc in tin smelting dust by an ammonia leaching-extraction process, using an ammonia-ammonium mixed solution as a leachate, leaching for a certain time at a certain liquid-solid ratio under certain temperature conditions, and then performing liquid-solid separation; the obtained slag is washed and used as a tin smelting raw material, the leachate is added with zinc powder to replace the cadmium and then extracted and returned to leach, and the extracted organic phase is stripped with a dilute sulfuric acid solution and continues to be recycled as an extraction phase; finally, the zinc sulfate solution after stripping and enrichment is sent to electrolysis to recover cathode zinc, and the electrolyte can be used as a stripping solution after zinc is recovered by electrolytic deposition. The present invention provides a method for recovering zinc in tin smelting dust by an ammonia leaching-extraction process, while removing the harmful element zinc in the tin smelting dust, realizing the recovery of valuable metal zinc, and achieving the purpose of recovering zinc in tin smelting dust.

Description

Technical Field

[0001] The invention relates to the technical field of recovering valuable metals in tin smelting dust by using a wet process, and more specifically to a method for recovering zinc in tin smelting dust by using an ammonia leaching-extraction process. Background Art

[0002] With the gradual consumption of tin resources in large tin mines, the relatively large volume and fixed types of tin ore raw materials have gradually decreased. In recent years, the types of tin-containing materials in large tin smelters have become more and more complex, especially after the proportion of various types of tin secondary raw materials in tin smelters has gradually increased, resulting in the phenomenon of cyclic enrichment of one or more metal impurities that are not common in the traditional tin smelting field in the tin smelting process. In order to reduce the impact of these impurity metals on the product output, quality and production efficiency of each production section of the tin smelter, and in line with the principle of comprehensive recovery of valuable metals and improvement of smelting efficiency, it is urgently necessary to add a process for removing and recovering the impurity metals that are cyclically enriched in the tin smelting process in the tin smelting plant.

[0003] In the tin smelting process, the tin dust recovered from the flue gas during the smelting process is generally returned to the smelting furnace for smelting after granulation or humidification as a return product due to its high tin content (Sn ≥ 30%). Therefore, the phenomenon of cyclic enrichment of low melting and boiling point metal impurities is very likely to occur in this process. After a period of crude tin smelting production in a large tin smelting plant, zinc gradually enriched in the smelting dust, and the zinc content of the dust was generally 8wt.%-15wt.%, which not only caused the smelting furnace flue to be prone to nodule blockage, and the dust in the dust bin was prone to agglomeration and difficult to clean, but also increased the smelting energy consumption, thereby affecting the smelting production efficiency. In addition, the smoke dust with zinc enrichment in the smelting plant also showed enrichment of cadmium and chlorine, generally containing 1.5wt.%-5wt.% cadmium and 6wt.%-12wt.% chlorine. Among them, the impact of cadmium on tin smelting is similar to that of zinc, while chlorine will corrode smelting equipment, reduce the direct recovery rate of tin smelting, and endanger the normal operation of the low-concentration sulfur dioxide acid-making system in the tail gas treatment part of the smelting process. After the physical phase analysis of these tin smelting fumes containing harmful impurities of zinc, cadmium and chlorine, most of the zinc exists in the form of oxides, a small amount exists in the form of chlorides, most of the cadmium exists in the form of chlorides, and tin is basically in the form of oxides. Since most of the cadmium in this kind of fumes exists in the form of chlorides, the wet process is used to treat the fumes to recover zinc, and the purpose of removing cadmium and chlorine at the same time can also be achieved.

[0004] In the smelting industry, zinc enriched in smoke is generally recovered by wet leaching, and the more common one is sulfuric acid leaching. For example, lead smelters use sulfuric acid leaching-purification-electrolysis to recover zinc. However, this method is extremely inapplicable when treating low-zinc smoke (containing about 10% Zn) and containing high content of elements harmful to zinc recovery, such as iron, arsenic, and chlorine. Because these low-zinc smoke are treated by sulfuric acid leaching, not only is the zinc ion concentration in the leachate low, making it difficult to enrich, but also a large amount of harmful impurity elements such as iron, arsenic, and chlorine will be introduced into the leachate, making it very difficult to recover zinc from the clean liquid. The zinc-containing tin smoke produced by tin smelting, its zinc content characteristics and impurity characteristics are not suitable for direct leaching and recovery with common sulfuric acid, so it is necessary to find a new process route for recovering zinc from tin smelting smoke with low zinc content and high impurities.

[0005] The present invention provides a method for recovering zinc from tin smelting dust by an ammonia leaching-extraction process. Solving the problem that the impurity zinc in the tin smelting process is cyclically enriched in the smelting dust and has an adverse effect on the tin smelting process, and recovering zinc more effectively are problems that technicians in this field need to solve urgently. Summary of the invention

[0006] In view of this, based on the harm caused to the tin smelting production process by the enrichment of zinc in tin smelting dust, the present invention provides a method for recovering zinc in tin smelting dust through an ammonia leaching-extraction process, which can remove the harmful element zinc in tin smelting dust while realizing the recovery of valuable metal zinc, and achieve the purpose of recovering zinc in tin smelting dust.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A method for recovering zinc from tin smelting dust by an ammonia leaching-extraction process, the specific steps are as follows:

[0009] S1, preparing a mixed solution of ammonia water and ammonium chloride as a leaching solution for zinc-tin smelting dust, with a concentration of ammonia water of 2-6 mol / L and ammonium chloride of 2-6 mol / L, at a liquid-solid ratio of 4-6:1 at a temperature of 30-50°C, stirring and leaching for 1.5-3h;

[0010] S2, the leached slurry is subjected to liquid-solid separation by plate and frame filter pressing, the filter residue is washed to obtain dezincified tin dust which is returned to the tin smelting section as a raw material for tin smelting, the liquid-solid ratio during the filter residue washing is 3:1, the washing liquid is reused 5-10 times, and the reused washing liquid is used as a supplementary liquid for the leaching liquid containing zinc and tin smelting dust;

[0011] S3, zinc powder is added to the filtrate after solid-liquid separation according to the cadmium concentration to replace and remove cadmium, the molar ratio of zinc powder: cadmium is 1.05-1.1:1, P204 and kerosene are mixed in a volume ratio of 3:7 to obtain an organic phase as an extractant, the volume ratio of the organic phase to the filtrate obtained after cadmium removal is 1:1, the temperature is set at 30-45°C during the extraction process, the time is 0.5-1h, and then a three-stage countercurrent extraction and stripping is performed, 120-220g / L dilute sulfuric acid solution is used as the stripping solution, the volume ratio of the organic phase to the stripping solution is 1-2:1, the temperature is set at 30-45°C, the time is 0.5-1h, the stripping solution is continuously circulated to strip the zinc-carrying organic phase 3-5 times, and the zinc sulfate solution after stripping and enrichment is sent to the electrolysis section for electrolytic recovery of cathode zinc.

[0012] Preferably, the ammonium salt added to the leachate is one of ammonium chloride, ammonium sulfate, ammonium bicarbonate and ammonium carbonate.

[0013] By adopting the above preferred embodiment, the beneficial effects of the present invention are:

[0014] 1. Using ammonia-ammonium mixed solution as the leaching solution, this combination method can continue to add ammonia water to the solution when the ammonium salt is basically saturated, further increasing the total ammonia content (NH 3 +NH 4 + ), making the reaction more favorable to the formation of zinc-ammine complex [Zn(NH 3 ) n ] 2+ , so as to speed up the zinc leaching rate and improve the zinc leaching rate. The test shows that under a certain liquid-to-solid ratio, when the total amount of ammonia (molar amount) in the solution is 5-10 times the total amount of zinc (molar amount) in the reaction dust, the zinc leaching rate in the tin smelting dust can be maintained in the range of 80%-90%. And this leachate can selectively leach zinc and a small amount of cadmium, while tin and other impurities such as lead, iron, and arsenic basically do not enter the liquid. The test shows that the tin and arsenic content in the leachate is less than 0.1g / L, and the lead and iron content is less than 0.01g / L, so the tin can basically be fully recovered in the leaching slag, and a relatively pure zinc leachate can be obtained.

[0015] 2. Adding zinc powder to the ammonia leachate for displacement and impurity removal can simplify the impurity removal process compared to purification and impurity removal after stripping, because the stripping solution is dilute sulfuric acid. If the impurity removal is carried out in a dilute sulfuric acid solution, neutralization treatment must be carried out in advance.

[0016] 3. The present invention not only removes zinc from tin smelting dust, but also removes most of the cadmium and chlorine that are harmful to the tin smelting process, so that the dust can be more easily handled after being returned to the smelting process after being treated.

[0017] 4. The leachate can be returned to be used as leachate after extraction. The leaching residue washing liquid can also be used as leachate replenishing liquid after multiple washings. The electrolyte can be used as stripping liquid after zinc electrolysis. The extracted organic phase is recycled. This operation mode makes the solution utilization rate of each section higher and the amount of wastewater is very small.

[0018] 5. The extraction method can effectively enrich the zinc in the low-concentration zinc-containing leaching solution, making the leached zinc easier to recover in the form of a higher-value metallic zinc product. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0020] Figure 1 The accompanying drawing is a specific process flow chart of Example 1 of the present invention;

[0021] Figure 2 The accompanying drawing is a device connection diagram of Embodiment 1 of the present invention;

[0022] In the figure: 1-leaching tank, 2-corrosion-resistant pump for pumping leaching slurry, 3-plate and frame filter press for liquid-solid separation of leaching slurry, 4-slag washing tank, 5-corrosion-resistant pump for pumping slag washing slurry, 6-plate and frame filter press for liquid-solid separation of slag washing slurry, 7-replacement tank, 8-plate and frame filter press for separating and replacing slag, 9-plate and frame filter press for pumping the mixture of slag and liquid after replacement, 10-extraction and stripping tank, 11-electrolytic cell for electrolytic recovery of zinc. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention are described clearly and completely below. 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.

[0024] Embodiment 1:

[0025] Example 1 of the present invention discloses a method for recovering zinc from tin smelting dust by an ammonia leaching-extraction process, and the technical scheme adopted is as follows:

[0026] 300t of high-zinc-tin smoke with components of Sn 41.80wt.%, Zn 8.97wt.%, As 2.08wt.%, Cd 3.30wt.%, and Cl10.21wt.% was processed.

[0027] First configure NH 3 ·H 2 O and NH 4 The concentration of Cl in the leaching solution is 5 mol / L, and then the leaching is carried out for 2 hours under the conditions of liquid-to-solid ratio of 6:1, leaching temperature of 35°C, and stirring. After leaching, it is pumped into a plate-frame filter press for liquid-solid separation. The leached residue is washed at a liquid-to-solid ratio of 3:1, and then pumped into a plate-frame filter press for liquid-solid separation. Finally, the impure tin fume is returned to the tin smelting section. The washing liquid is repeatedly washed 8 times as a leaching liquid replenisher; the obtained leaching liquid contains Zn 10.2g / L, containing Cd2.8g / L, Zn leaching rate of 81%, after the leaching solution was replaced with zinc powder containing 1.1 times the cadmium content, the organic phase with a volume ratio of P204 to kerosene of 3:7 was used as the extractant, and zinc was extracted by three-stage countercurrent extraction under the conditions of a volume ratio of organic phase to solution phase of 1:1.2, a temperature of 40°C, and a time of 0.6h; a dilute sulfuric acid solution with a concentration of 150g / L was used as the stripping solution for stripping, the volume ratio of the organic phase to the solution phase of the stripping was 1:1, the reaction time was 0.5h, the temperature was 30°C, and the stripping solution was continuously circulated to strip the zinc-carrying organic phase for 5 times, and finally a zinc sulfate solution containing 52g / L of Zn was obtained; the zinc sulfate solution was then sent to the electrolytic zinc section for treatment, and finally zinc was recovered in the form of cathode zinc product, 20t of product zinc was produced, and the remaining electrolytic zinc waste liquid was used to treat the next batch of zinc-tin smoke stripping liquid.

[0028] Embodiment 2:

[0029] Example 2 of the present invention discloses a method for recovering zinc from tin smelting dust by an ammonia leaching-extraction process, and the technical scheme adopted is as follows:

[0030] 500t of high-zinc-tin smoke with the composition of Sn 40.69wt.%, Zn 9.36wt.%, As 1.27wt.%, Cd 3.50wt.%, and Cl9.37wt.% was processed.

[0031] First configure the NH 3 ·H 2 O 4mol / L, containing NH 4The concentration of Cl in the leaching solution is 6 mol / L, and then the leaching is carried out for 2 hours under the conditions of liquid-to-solid ratio of 6:1, leaching temperature of 45°C, and stirring. After leaching, it is pumped into a plate-frame filter press for liquid-solid separation. The leached residue is washed at a liquid-to-solid ratio of 3:1, and then pumped into a plate-frame filter press for liquid-solid separation. Finally, the impure tin fume is returned to the tin smelting section. The washing liquid is repeatedly washed 6 times as a leaching liquid replenisher; the obtained leaching solution contains Zn11.5g / L and Cd 3.6g / L, Zn leaching rate reaches 83%, after the leaching solution is replaced with zinc powder containing 1.1 times the cadmium content, the organic phase with a volume ratio of P204 to kerosene of 3:7 is used as the extractant, and zinc is extracted by three-stage countercurrent extraction under the conditions of a volume ratio of organic phase to solution phase of 1:1, a temperature of 40°C, and a time of 1h; a dilute sulfuric acid solution with a concentration of 120g / L is used as the stripping solution for stripping, the volume ratio of the organic phase to the solution phase of the stripping is 1.5:1, the reaction time is 1h, the temperature is 40°C, and the stripping solution is continuously circulated to strip the zinc-carrying organic phase 4 times, and finally a zinc sulfate solution containing 58g / L of Zn is obtained; the zinc sulfate solution is then sent to the electrolytic zinc section for treatment, and finally zinc is recovered in the form of cathode zinc product, 40t of product zinc is produced, and the remaining electrolytic zinc waste liquid is used to treat the next batch of zinc-tin smoke stripping liquid.

[0032] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0033] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for recovering zinc from tin smelting dust by an ammonia leaching-extraction process, characterized in that: The specific steps are as follows: S1, preparing a mixed solution of ammonia water and ammonium chloride as a leaching solution for zinc-tin smelting dust, with a concentration of ammonia water of 2-6 mol / L and ammonium chloride of 2-6 mol / L, at a liquid-solid ratio of 4-6:1 at a temperature of 30-50°C, stirring and leaching for 1.5-3h; S2, the leached slurry is subjected to liquid-solid separation by plate and frame filter pressing, the filter residue is washed to obtain dezincified tin dust which is returned to the tin smelting section as a raw material for tin smelting, the liquid-solid ratio during the filter residue washing is 3:1, the washing liquid is reused 5-10 times, and the reused washing liquid is used as a supplementary liquid for the leaching liquid containing zinc and tin smelting dust; S3, zinc powder is added to the filtrate after solid-liquid separation according to the cadmium concentration to replace and remove cadmium, the molar ratio of zinc powder: cadmium is 1.05-1.1:1, P204 and kerosene are mixed in a volume ratio of 3:7 to obtain an organic phase as an extractant, the volume ratio of the organic phase to the filtrate obtained after cadmium removal is 1:1, the temperature is set at 30-45°C during the extraction process, the time is 0.5-1h, and then a three-stage countercurrent extraction and stripping is performed, 120-220g / L dilute sulfuric acid solution is used as the stripping solution, the volume ratio of the organic phase to the stripping solution is 1-2:1, the temperature is set at 30-45°C, the time is 0.5-1h, the stripping solution is continuously circulated to strip the zinc-carrying organic phase 3-5 times, and the zinc sulfate solution after stripping and enrichment is sent to the electrolysis section for electrolytic recovery of cathode zinc.

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