Method for redox smelting of zinc sulfide concentrate

Abstract

The invention discloses a zinc sulfide concentrate redox smelting method, which relates to the technical field of thermometallurgy, and comprises the following steps: step 1, proportioning; step 2, performing granulation; step 3, oxidizing and smelting; 4, reduction smelting is conducted, specifically, the zinc oxide melt obtained after oxidative desulfurization is added into a reduction side-blown furnace, pea coal is added, the pea coal accounts for 15%-18% of the weight of the zinc oxide melt, oxygen-enriched air is introduced for reduction smelting, generator water gas is added into the upper space of the furnace, and the volume ratio of furnace gas (H2 + CO) / CO2 is controlled to be 1.5-2.0; step 5, fuming; step 6, condensation separation; and step 7, rectification. Generator water gas is added into the upper space of the reduction side-blown furnace, and the volume ratio of furnace gas (H2 + CO) / CO2 is controlled to be 1.5-2.0, so that oxygen-enriched air can be completely combusted to form a steady-state reducing atmosphere, and zinc steam is prevented from being oxidized.

Description

Technical Field

[0001] This invention relates to the field of pyrometallurgical technology, specifically to a method for redox smelting of zinc sulfide concentrate. Background Technology

[0002] Currently, hydrometallurgical zinc smelting is the dominant process in zinc production, accounting for over 80% of zinc products. Hydrometallurgical zinc smelting offers advantages such as wide raw material adaptability and good comprehensive recovery, but it also suffers from drawbacks including a long process flow, the need for pyrometallurgical treatment of hydrometallurgical slag, and high energy consumption. Pyrometallurgical zinc smelting includes two processes: electric arc furnace (EAF) zinc smelting and closed blast furnace zinc smelting. EAF zinc smelting offers advantages such as a shorter process flow and lower investment, but it suffers from low single-furnace capacity and high power consumption. Closed blast furnace zinc smelting offers advantages such as a short process flow and strong raw material adaptability, but it suffers from problems such as complex sintering and crushing processes, poor waste heat recovery, and high coke consumption in the blast furnace.

[0003] With the maturation and development of oxygen-enriched side-blown smelting technology, more and more smelting units are focusing on using this technology to process zinc-containing materials and achieve efficient zinc smelting. However, in existing technologies for processing zinc sulfide concentrate, it is often difficult to precisely control the batching ratio and smelting conditions, leading to low smelting efficiency and unstable product quality. Furthermore, during the reduction smelting of zinc in zinc sulfide concentrate, zinc vapor is easily oxidized to zinc oxide during condensation, which not only reduces zinc recovery but also increases the complexity and cost of subsequent processing. Summary of the Invention

[0004] The purpose of this invention is to provide a method for redox smelting of zinc sulfide concentrate to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for oxidation-reduction smelting of zinc sulfide concentrate, the principle of which is to use oxygen to oxidize and desulfurize the zinc sulfide concentrate at high temperature, and then reduce the zinc oxide after oxidation and desulfurization to produce zinc vapor, the chemical reaction formula of which is as follows: ZnS(s) + 1.5O2(g) = ZnO(s) + SO2(g) ZnO(s) + CO(g) = Zn(g) + CO2(g) To prevent zinc vapor generated during reduction smelting from oxidizing to zinc oxide during condensation, this invention introduces producer water gas into the upper space of the reduction side-blown furnace to maintain a stable reducing atmosphere. Specifically, this includes the following steps: Step 1: Batching. The zinc sulfide concentrate is batched with flux in the batching silo. The composition of the zinc sulfide concentrate is Zn: 48%-54%, Pb: 1%-3%, Fe: 5%-10%, S: 28%-35%. Step 2: Granulation. The prepared mixture is fed into a cylindrical granulator for granulation. The particle size of the granulated material should be 8-10mm, and the moisture content should be 8%-10%. Step 3: Oxidation smelting. The granulated material is mixed with 5-10mm coal granules and added to the oxidation side-blown furnace. The 5-10mm coal granules account for 6%-8% of the material weight. Oxygen-enriched air with an oxygen concentration of 70-80 vol% is introduced for oxidation smelting. The produced zinc oxide melt is sent to reduction smelting. Step 4: Reduction smelting. The zinc oxide melt after oxidation and desulfurization is added to the reduction side-blown furnace, along with 5-10mm granular coal, which accounts for 15%-18% of the weight of the zinc oxide melt. Oxygen-enriched air is introduced for reduction smelting, producing reduction flue gas. The composition of the reduction flue gas is Zn: 18-25 vol%, CO: 7-12 vol%, CO2: 20-26 vol%. Producer water gas is added to the upper space of the furnace, accounting for 40-60 vol% of the reduction flue gas volume. The volume ratio of furnace gas (H2+CO) / CO2 is controlled at 1.5-2.0. The zinc-containing steam furnace gas is sent to the lead rain condenser, and the reduction slag is sent to the fuming furnace for smelting. Step 5: Fuming. The reducing slag is fed into the fuming furnace, and pulverized coal is injected into the furnace for fuming and smelting. Step Six: Condensation and Separation. The zinc-containing vapor produced from the reduction side-blown furnace enters the lead rain condenser for cooling. The condensing medium is molten lead. The molten lead captures the zinc vapor to form a lead-zinc liquid, which enters the separation system. The furnace gas is burned to recover the calorific value. The lead and zinc are clarified and separated based on their different specific gravities. Step 7: Distillation. The crude zinc liquid condensed and separated from the lead rain condenser enters the distillation furnace.

[0006] Furthermore, in step one, the flux is limestone, quartz, iron filings, or iron sulfides.

[0007] Furthermore, in step three, the temperature of the oxidative smelting is 1200-1250℃, the time is 2-2.5h, and the dust-laden flue gas produced by the oxidative smelting is sent to acid production after waste heat recovery.

[0008] Furthermore, in step four, the oxygen concentration of the oxygen-enriched air introduced is 45-55 vol%, the reduction smelting temperature is 1250-1300℃, and the time is 2-2.5h.

[0009] Furthermore, in step four, the producer water gas is a mixed gas generated by reacting solid fuel coal with a gasifying agent and steam under high temperature conditions. The composition of the producer water gas is H2: 40% - 50 vol%, CO: 30% - 40 vol%, CO2: 5% - 10 vol%, and the temperature is 600-700℃.

[0010] Furthermore, in step five, the injected pulverized coal accounts for 18%-20% of the weight of the reducing slag, the controlled temperature of the fuming blowing is 1250-1300℃, and the time is 2-2.5h.

[0011] Furthermore, in step five, the dust-laden flue gas produced is sent to the flue gas treatment system after being collected by waste heat utilization, the zinc oxide obtained from the dust collection is returned to the batching, and the produced slag is sold after water quenching.

[0012] Furthermore, in step six, the lower layer of lead liquid is returned to the lead rain condenser for recycling, and the upper layer of zinc liquid enters the zinc storage tank to produce crude zinc liquid. The high-temperature lead liquid in the separation system is cooled by water vapor to 100-120℃.

[0013] Furthermore, in step seven, the distillation furnace includes a lead tower and a cadmium tower. Zinc liquid flows into the lead tower, where most of the zinc and the cadmium it contains evaporate in vapor form at a temperature of 750-850°C, while lead and other high-boiling-point impurities are discharged and separated as liquid alloys. The cadmium-containing zinc produced by the lead tower is introduced into the cadmium tower via a sluice box, where zinc and cadmium are separated at a temperature of 800-900°C, and pure zinc liquid enters the pure zinc tank from the bottom.

[0014] The technical effects and advantages provided by the present invention in the above technical solution are as follows: 1. Add producer water gas to the upper space of the reducing side-blown furnace. By controlling the volume ratio of furnace gas (H2+CO) / CO2 to 1.5-2.0, the oxygen-rich air can be completely burned and a stable reducing atmosphere can be formed, thus preventing the zinc vapor from being oxidized. 2. For zinc sulfide concentrate with a composition of Zn: 48%-54%, Pb: 1%-3%, Fe: 5%-10%, and S: 28%-35%, the efficiency and stability of the smelting process are ensured by precisely controlling the proportion of raw materials and smelting conditions, thereby improving product quality. 3. By using coal instead of coke, production costs are reduced, while the comprehensive utilization rate of resources is improved, resulting in good economic benefits. 4. Lead rain condensers have good adaptability to fluctuations in zinc vapor concentration, can handle large volumes of furnace gas, and are suitable for large-scale industrial production. 5. The side-blown furnace oxidation-reduction zinc smelting process is adopted. Zinc volatilizes in the form of steam. After condensation and recovery, the zinc recovery rate can reach more than 97%. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0016] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0017] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0018] The gas used in this invention is a mixed gas generated by reacting solid fuel coal with a gasifying agent and steam under high temperature conditions. Its main components include: H2: 40-50 vol%, CO: 30-40 vol%, CO2: 5-10 vol%.

[0019] The apparatus used in this invention includes: a batching silo, a cylindrical granulator, an oxidation side-blown furnace, a reduction side-blown furnace, a fuming furnace, a lead rain condenser, a separation system, and a distillation furnace.

[0020] Example 1: Please refer to Figure 1 This invention provides a method for redox smelting of zinc sulfide concentrate, comprising the following steps: Step 1: Batching. The zinc sulfide concentrate is batched with flux in the batching bin. The zinc sulfide concentrate has the following composition: Zn: 48%-54%, Pb: 1%-3%, Fe: 5%-10%, S: 28%-35%. The flux is limestone, quartz, iron filings or iron sulfides. Step 2: Granulation. The prepared mixture is fed into a cylindrical granulator for mixing and granulation to ensure that the material is mixed evenly and fully wetted. The particle size of the granulated material is 8mm and the moisture content is 8%. Step 3: Oxidation smelting. The granulated material is mixed with 5mm coal granules and added to the oxidation side-blown furnace. The 5mm coal granules account for 6% of the material weight. Oxygen-enriched air with an oxygen concentration of 70 vol% is introduced for oxidation smelting. The temperature is controlled at 1200℃ and the time is 2 hours. The dust-containing flue gas produced is sent to acid production after waste heat recovery and dust collection. The zinc oxide melt produced is sent to reduction smelting. Step 4: Reduction smelting. The zinc oxide melt after oxidation and desulfurization is added to the reduction side-blown furnace, along with 5mm coal granules, which account for 16% of the weight of the zinc oxide melt. Oxygen-enriched air with an oxygen concentration of 45 vol% is introduced for reduction smelting. The temperature is controlled at 1250℃ for 2 hours, producing reduction flue gas with the following composition: Zn: 18-25 vol%, CO: 7-12 vol%, CO2: 20-26 vol%. Meanwhile, producer water gas is added to the upper space of the furnace at 600℃, accounting for 40 vol% of the reduction flue gas volume. The volume ratio of furnace gas (H2+CO) / CO2 is controlled at 1.5-2.0. The produced zinc-containing steam furnace gas is sent to the lead rain condenser, and the produced reduction slag is sent to the fuming furnace for smelting. Step 5: Fuming. The reducing slag is fed into the fuming furnace, and pulverized coal is injected into the furnace for fuming and blowing. The temperature is controlled at 1250℃ for 2 hours. The pulverized coal accounts for 18% of the mass of the reducing slag. The dust-containing flue gas produced is sent to the flue gas treatment system after waste heat utilization and dust collection. The zinc oxide obtained from dust collection is returned to the batching. Step Six: Condensation and Separation. The furnace gas containing zinc vapor is sent to the lead rain condenser for cooling. The condensing medium is molten lead. The molten lead captures the zinc vapor to form a lead-zinc liquid, which enters the separation system. The furnace gas is burned to recover calorific value. Lead and zinc are separated by their different specific gravities. The lower layer of molten lead is returned to the lead rain condenser for recycling, while the upper layer of molten zinc enters the zinc storage tank to produce crude zinc liquid. The high-temperature molten lead in the separation system is cooled by 100°C using water vapor, and the waste heat can be used to generate electricity. Step 7: Distillation. The crude zinc liquid is fed into a distillation furnace for distillation. The distillation furnace includes a lead column and a cadmium column. The zinc liquid flows into the lead column, where most of the zinc and the cadmium it contains evaporates in vapor form at 750°C. The lead and other high-boiling-point impurities are discharged as liquid alloys and separated. The cadmium-containing zinc produced in the lead column is introduced into the cadmium column through a sluice. At 800°C, zinc and cadmium are separated. The pure zinc liquid enters the pure zinc tank from the bottom, thus obtaining distilled zinc.

[0021] Example 2: Zinc sulfide concentrate with a composition of Zn: 49%, Pb: 3%, Fe: 10%, S: 33% was subjected to oxidation-reduction smelting according to the steps described in Example 1 to generate reducing flue gas. The composition of the reducing flue gas was Zn: 19%, CO: 9%, CO2: 23%. Producer water gas with a composition of H2: 46%, CO: 39%, CO2: 8% was added to the upper space of the reduction furnace to obtain mixed furnace gas (H2+CO) / CO2=1.6. The zinc-containing steam furnace gas entered the lead rain condenser to recover zinc, and the resulting reducing slag was blown into the fuming furnace. The final zinc recovery rate was 97.2%.

[0022] Example 3: Zinc sulfide concentrate with the composition of Zn: 51%, Pb: 2%, Fe: 9%, S: 31% was subjected to oxidation-reduction smelting according to the steps described in Example 1 to generate reducing flue gas. The composition of the reducing flue gas was Zn: 21%, CO: 8%, CO2: 24%. Producer water gas with the composition of H2: 47%, CO: 37%, CO2: 7% was added to the upper space of the reduction furnace to obtain mixed furnace gas (H2+CO) / CO2=1.6. The zinc-containing steam furnace gas entered the lead rain condenser to recover zinc, and the resulting reducing slag was sent to the fuming furnace for smelting. The final zinc recovery rate was 98.0%.

[0023] Example 4: Zinc sulfide concentrate with the composition of Zn: 53%, Pb: 1%, Fe: 7%, S: 29% was subjected to oxidation-reduction smelting according to the steps described in Example 1 to generate reducing flue gas. The composition of the reducing flue gas was Zn: 24%, CO: 7%, CO2: 25%. Producer water gas with the composition of H2: 49%, CO: 35%, CO2: 6% was added to the upper space of the reduction furnace to obtain mixed furnace gas (H2+CO) / CO2=1.5. The zinc-containing steam furnace gas entered the lead rain condenser to recover zinc, and the resulting reducing slag was sent to the fuming furnace for smelting. The final zinc recovery rate was 98.4%.

[0024] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A method for redox smelting of zinc sulfide concentrate, characterized in that, Includes the following steps: Step 1: Batching. The zinc sulfide concentrate is batched with flux in the batching silo. The composition of the zinc sulfide concentrate is Zn: 48%-54%, Pb: 1%-3%, Fe: 5%-10%, S: 28%-35%. Step 2: Granulation. The prepared mixture is fed into a cylindrical granulator for granulation. The particle size of the granulated material should be 8-10mm, and the moisture content should be 8%-10%. Step 3: Oxidation smelting. The granulated material is mixed with 5-10mm coal granules and added to the oxidation side-blown furnace. The 5-10mm coal granules account for 6%-8% of the material weight. Oxygen-enriched air with an oxygen concentration of 70-80 vol% is introduced for oxidation smelting. The produced zinc oxide melt is sent to reduction smelting. Step 4: Reduction smelting. The zinc oxide melt after oxidation and desulfurization is added to the reduction side-blown furnace, along with 5-10mm granular coal, which accounts for 15%-18% of the weight of the zinc oxide melt. Oxygen-enriched air is introduced for reduction smelting, producing reduction flue gas. The composition of the reduction flue gas is Zn: 18-25 vol%, CO: 7-12 vol%, CO2: 20-26 vol%. Producer water gas is added to the upper space of the furnace, accounting for 40-60 vol% of the reduction flue gas volume. The volume ratio of furnace gas (H2+CO) / CO2 is controlled at 1.5-2.

0. The zinc-containing steam furnace gas is sent to the lead rain condenser, and the reduction slag is sent to the fuming furnace for smelting. Step 5: Fuming. The reducing slag is fed into the fuming furnace, and pulverized coal is injected into the furnace for fuming and smelting. Step Six: Condensation and Separation. The zinc-containing vapor produced from the reduction side-blown furnace enters the lead rain condenser for cooling. The condensing medium is molten lead. The molten lead captures the zinc vapor to form a lead-zinc liquid, which enters the separation system. The furnace gas is burned to recover the calorific value. The lead and zinc are clarified and separated based on their different specific gravities. Step 7: Distillation. The crude zinc liquid condensed and separated from the lead rain condenser enters the distillation furnace.

2. The method for redox smelting of zinc sulfide concentrate according to claim 1, characterized in that: In step one, the flux is limestone, quartz, iron filings, or iron sulfide.

3. The method for redox smelting of zinc sulfide concentrate according to claim 1, characterized in that: In step three, the temperature of the oxidation smelting is 1200-1250℃, and the time is 2-2.5h. The dust-laden flue gas produced by the oxidation smelting is sent to acid production after waste heat recovery and dust collection.

4. The method for redox smelting of zinc sulfide concentrate according to claim 1, characterized in that: In step four, the oxygen concentration of the oxygen-enriched air introduced is 45-55 vol%, the reduction smelting temperature is 1250-1300℃, and the time is 2-2.5h.

5. The method for redox smelting of zinc sulfide concentrate according to claim 1, characterized in that: In step four, the producer water gas is a mixed gas generated by reacting solid fuel coal with a gasifying agent and steam under high temperature conditions. The composition of the producer water gas is H2: 40% - 50 vol%, CO: 30% - 40 vol%, CO2: 5% - 10 vol%, and the temperature is 600-700℃.

6. The method for redox smelting of zinc sulfide concentrate according to claim 1, characterized in that: In step five, the injected pulverized coal accounts for 18%-20% of the weight of the reducing slag, the controlled temperature of the fuming blowing is 1250-1300℃, and the time is 2-2.5h.

7. The method for redox smelting of zinc sulfide concentrate according to claim 1, characterized in that: In step five, the dust-laden flue gas produced is sent to the flue gas treatment system after being collected by waste heat utilization. The zinc oxide obtained from the dust collection is returned to the batching process, and the produced slag is sold after water quenching.

8. The method for redox smelting of zinc sulfide concentrate according to claim 1, characterized in that: In step six, the lower layer of lead liquid is returned to the lead rain condenser for recycling, while the upper layer of zinc liquid enters the zinc storage tank to produce crude zinc liquid. The high-temperature lead liquid in the separation system is cooled by water vapor to 100-120℃.

9. The method for redox smelting of zinc sulfide concentrate according to claim 1, characterized in that: In step seven, the distillation furnace includes a lead tower and a cadmium tower. Zinc liquid flows into the lead tower, and at a temperature of 750-850°C, most of the zinc and the cadmium it contains evaporate in a vapor state, while lead and other high-boiling-point impurities are discharged and separated as liquid alloys. The cadmium-containing zinc produced by the lead tower is introduced into the cadmium tower through a sluice box, and zinc-cadmium separation is carried out at a temperature of 800-900°C. Pure zinc liquid enters the pure zinc tank from the bottom.

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