Process for preparing cadmium sulfide through combination of lead and zinc smelting slag

Abstract

The invention discloses a process for jointly preparing cadmium sulfide from lead-zinc smelting slag, which comprises the following steps: firstly, carrying out neutral leaching on the lead smelting slag, carrying out filter-pressing solid-liquid separation on leached ore pulp to obtain a leaching solution A and lead-rich slag, returning the lead-rich slag to a lead smelting system to recover lead, grinding the zinc smelting slag through wet ball milling, adding caustic soda flakes into the ore pulp to carry out alkaline leaching, and carrying out solid-liquid separation on the leached ore pulp to obtain cadmium sulfide; carrying out filter pressing solid-liquid separation on the obtained leaching ore pulp to obtain a leaching solution B and zinc-rich slag, returning the zinc-rich slag to a lead smelting system to recover valuable metals such as zinc, silver and gold, carrying out mixed reaction on the leaching solution B and the leaching solution A, carrying out filter pressing after the reaction to obtain a cadmium sulfide product and a cadmium-settled solution, returning part of the cadmium-settled solution to the zinc smelting slag to carry out alkaline leaching, and recycling the cadmium-settled solution. Sodium salt crystallization products and condensate water are produced partially through evaporative crystallization. According to the method, cadmium sulfide is produced through combined treatment of neutral leaching and alkaline leaching, so that elements such as lead, zinc, gold and silver in the two materials are effectively enriched, the enrichment rate of lead and zinc and the recovery rate of cadmium are high, and the process is short.

Description

Technical Field

[0001] The invention relates to the technical field of chemical production, and in particular to a process for preparing cadmium sulfide based on lead-zinc smelting slag. Background Art

[0002] The sulfide filter residue produced by oxygen pressure leaching is a hazardous waste. The hot filter residue is rich in valuable metals such as lead, zinc, gold, silver, and indium, and the sulfur is mainly elemental sulfur, with a content of up to 63%. It is a difficult-to-treat metallurgical waste residue. Long-term storage will cause environmental pollution and loss of valuable metals. Reasonable harmless treatment of hazardous waste residues and recovery of valuable metals from them have great contributions to environmental protection and economic benefits. At present, there are deficiencies in the methods of treating zinc hazardous waste residues at home and abroad, such as high energy consumption of rotary kiln treatment of hazardous waste residues, low recovery rate of valuable metals, short furnace life of fuming furnace treatment, and large loss of Ausmelt furnace consumables. There are many problems in using oxygen-enriched side blowing-fuming zinc extraction process to treat zinc smelting sulfide filter residue: First, the added value of the produced sulfuric acid is low, and the environmental protection requirements and disposal costs are high. Second, due to the high sulfur content in the slag, which is mainly elemental sulfur, elemental sulfur is easy to volatilize into the flue during the smelting process, causing blockage of the equipment and affecting production. Third, the slag contains 1.7g / t gold and about 140g / t silver. It is difficult to enrich and recover them through pyrometallurgical treatment, which will cause loss of valuable metals.

[0003] At the same time, the content of cadmium in the earth's crust is extremely small, accounting for about 0.005‰. It is mainly associated with lead and zinc ores and exists in the form of cadmite in nature. In the process of lead smelting, cadmium is mainly enriched in bottom-blown smelting ash, and mainly exists in the form of cadmium sulfate, cadmium sulfide, etc. The recovery of cadmium in bottom-blown ash is mostly done by weak acid leaching. The leaching solution is replaced with zinc powder to obtain sponge cadmium. The amount of zinc powder added is 1.1 times the cadmium content. The price of zinc powder is higher than that of cadmium metal. Therefore, the method of replacing cadmium with zinc powder is costly.

[0004] Therefore, in order to achieve the enrichment and recovery of valuable metals in zinc smelting sulfide filter residues and lead smelting bottom-blown soot, the development of a process for the joint preparation of cadmium sulfide from lead and zinc smelting slag has important economic and social effects. Summary of the invention

[0005] In view of the defects of the prior art, the present invention provides a process for preparing cadmium sulfide by co-using lead-zinc smelting slag, which has a short process flow, high lead-zinc enrichment rate and cadmium recovery rate, and can effectively utilize lead-zinc smelting slag resources.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solution: a process for preparing cadmium sulfide by combining lead and zinc smelting slag, characterized in that the process is carried out according to the following steps:

[0007] Step 1: Grind the zinc smelting slag with a wet ball mill, control the grinding concentration to 70-75%, and control the particle size to 100 mesh accounting for more than 45%;

[0008] Step 2: transport the slurry obtained in step 1 to an alkaline leaching tank, add caustic soda flakes and water, control the leaching slurry concentration to 25%-30%, the reaction time to 0.5-1h, the reaction temperature to 60-80°C, and after the reaction is completed, use a filter press to separate the solid and liquid to obtain zinc-rich slag and leachate B;

[0009] Step 3: transport the lead smelting slag to a neutral leaching tank, add water, control the leaching pulp concentration to 30%-35%, the reaction time to 1-1.5h, the reaction temperature to 50-60°C, and after the reaction, use a filter press to separate the solid and liquid to obtain lead-rich slag and leachate A;

[0010] Step 4: The leachate B obtained in step 2 and the leachate A obtained in step 3 are transported together to a mixed reaction tank for precipitation reaction, the reaction time is 1-1.5 hours, the reaction temperature is room temperature, the volume ratio of leachate B to leachate A is 1-1.5:1, and after the reaction is completed, a filter press is used for solid-liquid separation to obtain a cadmium sulfide product and a cadmium precipitation liquid;

[0011] Step 5: returning a portion of the cadmium precipitation solution obtained in step 4 to step 2 as slurry conditioning water for adjusting alkaline leaching, and using the remaining portion for evaporation crystallization to produce sodium salt crystals and condensed water;

[0012] Step 6: The condensed water obtained in step 5 is returned to step 1 as slurry adjusting water for adjusting the grinding concentration.

[0013] In step 1, the zinc smelting slag is the leaching slag produced by oxygen pressure leaching of zinc concentrate, and then the sulfur concentrate is obtained by sulfur flotation. The sulfur concentrate is purified by melting filtration to produce a sulfide filter residue, and its main components are: S 50-60%, Fe 7-10%, Zn 5-10%, Au 1.5-2%, wherein the main phase of S is: sulfur in elemental sulfur accounts for 80-94.65%, sulfur in sulfide accounts for 2-10%, and sulfur in sulfate accounts for 2-10%.

[0014] In step 2, the amount of caustic soda added is adjusted according to the sulfur content in the zinc smelting slag, and the molar ratio of sulfur to sodium hydroxide is 5:3. The obtained leaching solution B is mainly a mixed solution of Na2S4 and Na2S2O3, and the sulfur content is 15-20g / L.

[0015] The zinc-rich slag obtained in step 2 mainly comprises: Zn 13-15%, Au 2-3.5 g / t, and S 15-20%.

[0016] The lead smelting slag in step 3 is cadmium-containing ash produced by bottom-blowing smelting slag from lead concentrate, and its main components are: Cd 15-20%, Pb 40-45%, and the cadmium phase is mainly cadmium sulfate. The obtained leaching solution A is mainly a cadmium sulfate solution, containing 40-60g / L cadmium. The lead-rich slag obtained in step 3 contains 0.4-1% Cd and 50-70% Pb.

[0017] The cadmium content in the cadmium precipitation solution obtained in step 4 is 0.05-0.1 g / L.

[0018] The sodium salt crystals produced by evaporation and crystallization in step 5 are mainly mixed crystalline salts of Na2S, Na2S4 and Na2S2O3 remaining in the reaction, containing 20-50% sulfur.

[0019] The process of the present invention has the following advantages over the prior art:

[0020] First, based on the fact that the sulfur in the zinc smelting sulfide filter residue is mainly elemental sulfur, it reacts with sodium hydroxide to produce Na2S X The main product of Na2S4 is obtained by controlling the molar ratio of sulfur and sodium hydroxide to 5:3. Cadmium in the bottom-blown ash of lead smelting mainly exists in the form of cadmium sulfate. Cadmium sulfate is soluble in water and cadmium sulfate solution is obtained by neutral leaching. Na2S4 is hydrolyzed to produce HS - and S 2- , compared with the S produced by Na2S hydrolysis 2- The volume ratio of leachate B to leachate A is controlled to be 1-1.5:1 based on the mechanism of more moles, and the content of Cd and S in leachate A and B is effectively utilized to achieve the output of CdS products. On the one hand, the valuable metal elements in the zinc smelting sulfide filter residue are enriched, and the enrichment ratio reaches 2-2.5. On the other hand, the cadmium in the bottom-blown ash of lead smelting is recovered, and the lead-zinc smelting slag resources are recycled.

[0021] Second, the obtained crystalline product is mainly a mixed crystalline salt of Na2S, Na2S4 and Na2S2O3 remaining in the reaction, containing 20-50% sulfur, which can be used as a flotation agent to replace Na2S. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0023] The following is combined with Figure 1 The present invention is further described by specific embodiments:

[0024] Example 1

[0025] The main components of zinc smelting sulfide filter residue are: S 51%, Fe 7.4%, Zn 5.2%, Au 1.5%, among which the main phases of S are: sulfur in elemental sulfur accounts for 83%, sulfur in sulfide accounts for 3%, and sulfur in sulfate accounts for 3%. The main components of lead smelting cadmium-containing ash are: Cd 15%, Pb 40%, and the cadmium phase is mainly cadmium sulfate.

[0026] Follow these steps:

[0027] Step 1: Grind the zinc smelting slag with a wet ball mill, control the grinding concentration to 70%, and control the particle size to 100 mesh, accounting for 45%;

[0028] Step 2: transport the slurry obtained in step 1 to an alkaline leaching tank, add caustic soda flakes and water, control the leaching slurry concentration to 25%, the reaction time to 0.5h, the reaction temperature to 60°C, and after the reaction, use a filter press to separate the solid and liquid to obtain zinc-rich slag and leaching solution B;

[0029] Step 3: transport the lead smelting slag to a neutral leaching tank, add water, control the leaching pulp concentration to 30%, the reaction time to 1 hour, the reaction temperature to 50°C, and after the reaction, use a filter press to separate the solid and liquid to obtain lead-rich slag and leachate A;

[0030] Step 4: transporting the leachate B and the leachate A to a mixed reaction tank for precipitation reaction. The reaction time is 1 hour, the reaction temperature is room temperature, and the volume ratio of the leachate B to the leachate A is 1:1. After the reaction is completed, a filter press is used for solid-liquid separation to obtain a cadmium sulfide product and a cadmium precipitation liquid;

[0031] Step 5: returning part of the cadmium precipitation liquid obtained in step 4 to step 2 as slurry adjusting water for adjusting alkaline leaching, and using the remaining part for evaporation crystallization to produce sodium salt crystals and condensed water;

[0032] Step 6: The condensed water obtained in step 5 is returned to step 1 as slurry adjusting water for adjusting the grinding concentration.

[0033] In step 2, the amount of caustic soda added is adjusted according to the sulfur content in the zinc smelting slag, and the molar ratio of sulfur to sodium hydroxide is 5:3.

[0034] result:

[0035] The obtained leaching solution B is mainly a mixed solution of Na2S4 and Na2S2O3, and contains 16g / L sulfur. The main components of zinc-rich slag include: Zn 13.4%, Au 2.3g / t, S15%. The obtained leaching solution A is mainly a solution of cadmium sulfate, containing 40g / L cadmium. The obtained lead-rich slag contains 0.4% Cd and 53% Pb. The cadmium content of the obtained cadmium precipitation liquid is 0.06g / L. The sodium salt crystals produced by evaporation crystallization are mainly mixed crystalline salts of Na2S, Na2S4 and Na2S2O3 remaining in the reaction, containing 24% sulfur. The cadmium sulfide product contains 76% cadmium and the sulfur resource utilization rate is 82%.

[0036] Example 2

[0037] The main components of zinc smelting sulfide filter residue are: S 55%, Fe 8.2%, Zn 7.8%, Au 1.8%, among which the main phases of S are: sulfur in elemental sulfur accounts for 90%, sulfur in sulfide accounts for 7%, and sulfur in sulfate accounts for 3%. The main components of lead smelting cadmium-containing ash are: Cd 18%, Pb 43%, and the cadmium phase is mainly cadmium sulfate.

[0038] Follow these steps:

[0039] Step 1: Grind the zinc smelting slag with a wet ball mill, control the grinding concentration to 78%, and control the particle size to 100 mesh, accounting for 52%;

[0040] Step 2: transport the slurry obtained in step 1 to an alkaline leaching tank, add caustic soda flakes and water, control the leaching slurry concentration to 28%, the reaction time to 0.8h, the reaction temperature to 70°C, and after the reaction, use a filter press to separate the solid and liquid to obtain zinc-rich slag and leachate B;

[0041] Step 3: transport the lead smelting slag to a neutral leaching tank, add water, control the leaching pulp concentration to 30%, the reaction time to 1.3h, the reaction temperature to 55°C, and after the reaction, use a filter press to separate the solid and liquid to obtain lead-rich slag and leachate A;

[0042] Step 4: leachate B and leachate A are transported together to a mixed reaction tank for precipitation reaction. The reaction time is 1.3 hours, the reaction temperature is room temperature, and the volume ratio of leachate B to leachate A is 1.3:1. After the reaction is completed, a filter press is used for solid-liquid separation to obtain a cadmium sulfide product and a cadmium precipitation liquid;

[0043] Step 5: returning part of the cadmium precipitation liquid obtained in step 4 to step 2 as slurry adjusting water for adjusting alkaline leaching, and using the remaining part for evaporation crystallization to produce sodium salt crystals and condensed water;

[0044] Step 6: The condensed water obtained in step 5 is returned to step 1 as slurry adjusting water for adjusting the grinding concentration.

[0045] In step 2, the amount of caustic soda added is adjusted according to the sulfur content in the zinc smelting slag, and the molar ratio of sulfur to sodium hydroxide is 5:3.

[0046] result:

[0047] The obtained leachate B is mainly a mixed solution of Na2S4 and Na2S2O3, and contains 18g / L sulfur. The main components of zinc-rich slag include: Zn 15.6%, Au 3.5g / t, S18%. The obtained leachate A is mainly a solution of cadmium sulfate, containing 48g / L cadmium. The obtained lead-rich slag contains 0.6% Cd and 62% Pb. The cadmium content of the obtained cadmium precipitation liquid is 0.08g / L. The sodium salt crystals produced by evaporation crystallization are mainly mixed crystal salts of Na2S, Na2S4 and Na2S2O3 remaining in the reaction, containing 33% sulfur. The cadmium sulfide product contains 78% cadmium and the sulfur resource utilization rate is 84.5%.

[0048] Example 3

[0049] The main components of zinc smelting sulfide filter residue are: S 58%, Fe 9%, Zn 9%, Au 1.9%, among which the main phases of S are: sulfur in elemental sulfur accounts for 94%, sulfur in sulfide accounts for 0.2%, and sulfur in sulfate accounts for 19%. The main components of lead smelting cadmium-containing ash are: Cd 18%, Pb 45%, and the cadmium phase is mainly cadmium sulfate.

[0050] Follow these steps:

[0051] Step 1: Grind the zinc smelting slag with a wet ball mill, control the grinding concentration to 75%, and control the particle size to 100 mesh, accounting for 55%;

[0052] Step 2: transport the slurry obtained in step 1 to an alkaline leaching tank, add caustic soda flakes and water, control the leaching slurry concentration to 30%, the reaction time to 1 hour, the reaction temperature to 80°C, and after the reaction is completed, use a filter press to separate the solid and liquid to obtain zinc-rich slag and leachate B;

[0053] Step 3: transport the lead smelting slag to a neutral leaching tank, add water, control the leaching pulp concentration to 35%, the reaction time to 1.5h, the reaction temperature to 60°C, and after the reaction, use a filter press to separate the solid and liquid to obtain lead-rich slag and leachate A;

[0054] Step 4: transporting the leachate B and the leachate A to a mixed reaction tank for precipitation reaction. The reaction time is 1.5 hours, the reaction temperature is room temperature, and the volume ratio of the leachate B to the leachate A is 1.5:1. After the reaction is completed, a filter press is used for solid-liquid separation to obtain a cadmium sulfide product and a cadmium precipitation liquid;

[0055] Step 5: returning part of the cadmium precipitation liquid obtained in step 4 to step 2 as slurry water for adjusting alkaline leaching, and using part of the evaporative crystallization to produce sodium salt crystals and condensed water;

[0056] Step 6: The condensed water obtained in step 5 is returned to step 1 as slurry adjusting water for adjusting the grinding concentration.

[0057] In step 2, the amount of caustic soda added is adjusted according to the sulfur content in the zinc smelting slag, and the molar ratio of sulfur to sodium hydroxide is 5:3.

[0058] result:

[0059] The obtained leachate B is mainly a mixed solution of Na2S4 and Na2S2O3, and contains 19g / L sulfur. The main components of zinc-rich slag include: Zn 14.9%, Au 3.5g / t, S20%. The obtained leachate A is mainly a solution of cadmium sulfate, containing 56g / L cadmium. The obtained lead-rich slag contains 0.8% Cd and 68% Pb. The cadmium content of the obtained cadmium precipitation liquid is 0.1g / L. The sodium salt crystals produced by evaporation crystallization are mainly mixed crystalline salts of Na2S, Na2S4 and Na2S2O3 remaining in the reaction, containing 48% sulfur. The cadmium sulfide product contains 76.8% cadmium.

[0060] The present invention has been described in detail above. The above description is only a preferred embodiment of the present invention and should not limit the scope of implementation of the present invention. That is, all equivalent changes and modifications made within the scope of this application should still fall within the scope of the present invention.

Claims

1. A process for preparing cadmium sulfide from lead and zinc smelting slag, characterized in that: Follow these steps: Step 1: Grind the zinc smelting slag with a wet ball mill, control the grinding concentration to 70-75%, and control the particle size to 100 mesh accounting for more than 45%; Step 2: transport the slurry obtained in step 1 to an alkaline leaching tank, add caustic soda flakes and water, control the leaching slurry concentration to 25%-30%, the reaction time to 0.5-1h, the reaction temperature to 60-80°C, and after the reaction is completed, use a filter press to separate the solid and liquid to obtain zinc-rich slag and leachate B; Step 3: transport the lead smelting slag to a neutral leaching tank, add water, control the leaching pulp concentration to 30%-35%, the reaction time to 1-1.5h, the reaction temperature to 50-60°C, and after the reaction, use a filter press to separate the solid and liquid to obtain lead-rich slag and leachate A; Step 4: The leachate B obtained in step 2 and the leachate A obtained in step 3 are transported together to a mixed reaction tank for precipitation reaction, the reaction time is 1-1.5 hours, the reaction temperature is room temperature, the volume ratio of leachate B to leachate A is 1-1.5:1, and after the reaction is completed, a filter press is used for solid-liquid separation to obtain a cadmium sulfide product and a cadmium precipitation liquid; Step 5: returning a portion of the cadmium precipitation solution obtained in step 4 to step 2 as slurry conditioning water for adjusting alkaline leaching, and using the remaining portion for evaporation crystallization to produce sodium salt crystals and condensed water; Step 6: The condensed water obtained in step 5 is returned to step 1 as slurry adjusting water for adjusting the grinding concentration.

2. The process for preparing cadmium sulfide from lead-zinc smelting slag according to claim 1, characterized in that: In step 1, the zinc smelting slag is the leaching slag produced by oxygen pressure leaching of zinc concentrate, and then the sulfur concentrate is obtained by sulfur flotation. The sulfur concentrate is purified by melting filtration to produce a sulfide filter residue, and its main components are: S 50-60%, Fe 7-10%, Zn 5-10%, Au 1.5-2%, wherein the main phase of S is: sulfur in elemental sulfur accounts for 80-94.65%, sulfur in sulfide accounts for 2-10%, and sulfur in sulfate accounts for 2-10%.

3. The process for preparing cadmium sulfide from lead-zinc smelting slag according to claim 1, characterized in that: In step 2, the amount of caustic soda added is adjusted according to the sulfur content in the zinc smelting slag, and the molar ratio of sulfur to sodium hydroxide is 5:

3. The obtained leaching solution B is mainly a mixed solution of Na2S4 and Na2S2O3, and the sulfur content is 15-20g / L.

4. The process for preparing cadmium sulfide from lead-zinc smelting slag according to claim 1, characterized in that: The zinc-rich slag obtained in step 2 mainly comprises: Zn 13-15%, Au 2-3.5 g / t, and S 15-20%.

5. The process for preparing cadmium sulfide from lead-zinc smelting slag according to claim 1, characterized in that: The lead smelting slag in step 3 is cadmium-containing fly ash produced by bottom-blowing smelting slag of lead concentrate, and its main components are: Cd 15-20%, Pb 40-45%, and the cadmium phase is mainly cadmium sulfate. The obtained leaching solution A is mainly a solution of cadmium sulfate, containing 40-60g / L cadmium.

6. The process for preparing cadmium sulfide from lead-zinc smelting slag according to claim 1, characterized in that: The lead-rich slag obtained in step 3 contains 0.4-1% Cd and 50-70% Pb.

7. The process for preparing cadmium sulfide from lead-zinc smelting slag according to claim 1, characterized in that: The cadmium content in the cadmium precipitation solution obtained in step 4 is 0.05-0.1 g / L.

8. The novel process for preparing cadmium sulfide from lead-zinc smelting slag according to claim 1, characterized in that: The sodium salt crystals produced by evaporation and crystallization in step 5 are mainly mixed crystalline salts of Na2S, Na2S4 and Na2S2O3 remaining in the reaction, containing 20-50% sulfur.

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