Equipment for preparing magnesium metal by decomposing serpentine

Abstract

The utility model relates to the technical field of preparation of magnesium metal from serpentine, in particular to equipment for preparing magnesium metal by decomposing serpentine. Comprising a two-section countercurrent leaching reaction device, a leachate outlet of the two-section countercurrent leaching reaction device is connected with a solid-liquid separation washing device, and an overflow port of the solid-liquid separation washing device is sequentially connected with an iron removal device, a nickel precipitation device, an evaporation concentration device, a magnesium chloride drying device and a magnesium chloride electrolysis device. The system provided by the utility model has the characteristics of short growth process, small environmental pollution, low energy consumption, lower cost and the like, and develops a new development thought for comprehensive utilization of serpentine resources in China.

Description

Technical Field

[0001] This utility model relates to the technical field of preparing metallic magnesium from serpentine, and in particular to an apparatus for preparing metallic magnesium by decomposing serpentine. Background Technology

[0002] With the rapid development of modern industry, traditional metal resources are nearing depletion. Therefore, finding and developing new metal resources has become imperative.

[0003] Magnesium is one of the most abundant elements on Earth, accounting for 2.3% of its total content in surface mineral deposits, and also present in significant amounts in salt lakes and oceans. Therefore, accelerating the development of magnesium metal materials is one of the important measures to achieve sustainable development.

[0004] Traditional magnesium and magnesium-based materials primarily originate from magnesite-type magnesium carbonate ores, which require high-temperature roasting to convert them into magnesium oxide. Under current environmental regulations, this traditional production process has serious shortcomings and problems. First, it consumes a large amount of energy and generates significant amounts of carbon dioxide during roasting, thus putting considerable pressure on the supply of metallic magnesium and magnesium-based materials.

[0005] my country is rich in serpentine mineral resources, mostly ultramafic serpentine deposits, characterized by numerous, large-scale, widely distributed deposits with favorable geological conditions. Serpentine belongs to the 1:1 type layered silicate, composed of silicon-oxygen tetrahedral sheets and magnesium-oxygen octahedral sheets, mainly including fibrous serpentine, foliated serpentine, and lizardite. The main mineral composition of serpentine rock, serpentine tailings, and asbestos tailings is serpentine with minor amounts of magnetite, talc, brucite, dolomite, and calcite. The main chemical composition is SiO2 and MgO, with minor amounts of Fe2O3, Al2O3, NiO, and Cr2O3, among which magnesium oxide is the dominant metal oxide.

[0006] Currently, the common method for utilizing serpentine resources is to add organic and inorganic acids to serpentine raw materials and directly acid-leach them to prepare magnesium-containing compound products. However, this method still has problems such as environmental pollution and high energy consumption. Summary of the Invention

[0007] The technical problem to be solved by this utility model is to provide a device for preparing metallic magnesium by decomposing serpentine, which has less environmental pollution, less energy consumption, and lower cost.

[0008] This utility model is implemented as follows:

[0009] A device for preparing metallic magnesium by decomposing serpentine, the system comprising a two-stage countercurrent leaching reaction device, wherein the leaching outlet of the two-stage countercurrent leaching reaction device is connected to a solid-liquid separation and washing device, and the overflow port of the solid-liquid separation and washing device is sequentially connected to an iron removal device, a nickel precipitation device, an evaporation and concentration device, a magnesium chloride drying device, and a magnesium chloride electrolysis device.

[0010] Furthermore, the solid-liquid separation and washing device is a CCD thickener.

[0011] Furthermore, the gas outlet of the magnesium chloride drying device is connected to the hydrochloric acid absorption tower, and the hydrochloric acid outlet of the hydrochloric acid absorption tower is connected to the hydrochloric acid recovery inlet of the two-stage countercurrent leaching reaction device.

[0012] Furthermore, the magnesium chloride drying device includes a granulation centrifuge, an air fluidized bed dryer, and an HCl gas drying mechanism. The granulation centrifuge is connected to the air fluidized bed dryer through a particle transfer mechanism, and the outlet of the air fluidized bed dryer is connected to the inlet of the HCl gas drying mechanism.

[0013] Specifically, the air fluidized bed dryer includes a discharge hopper, a conveyor, a vibrating screen, a wet material bin, and a feed pipe arranged along the particle transport route.

[0014] Furthermore, the gas outlet of the magnesium chloride electrolysis unit is connected to the chlorine inlet of the hydrochloric acid synthesis unit via a chlorine compressor, and the hydrogen inlet of the hydrochloric acid synthesis unit is connected to the water electrolysis unit.

[0015] Furthermore, the magnesium chloride electrolysis device is further connected to the magnesium metal refining and casting device, the magnesium metal liquid outlet of the magnesium chloride electrolysis device is connected to the inlet of the magnesium metal refining device, and the magnesium metal refining device is transported to the casting device through a conveying device.

[0016] The advantages of this invention are: the system of this invention has the characteristics of short growth process, low environmental pollution, low energy consumption and low cost, which opens up new development ideas for the comprehensive utilization of serpentine resources in my country. Attached Figure Description

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0018] Figure 1 This is a schematic diagram of the structure of this utility model.

[0019] The diagram is labeled as follows: 1. Two-stage countercurrent leaching reaction device; 2. Solid-liquid separation and washing device; 3. Iron removal device; 4. Nickel precipitation device; 5. Evaporation and concentration device; 6. Magnesium chloride drying device; 7. Granulation centrifuge; 8. Fluidized bed dryer; 9. HCl gas drying device; 10. Magnesium chloride electrolysis device; 11. Hydrochloric acid absorption tower; 12. Chlorine compressor; 13. Hydrochloric acid synthesis device; 14. Water electrolysis device; 15. Metallic magnesium refining and casting device. Detailed Implementation

[0020] In the description of this utility model, it should be understood that the description indicating the orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this utility model and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this utility model.

[0021] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "set up," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0022] The technical solution of this utility model is as follows:

[0023] Please see Figure 1 As shown, this utility model discloses an apparatus for preparing metallic magnesium by decomposing serpentine. The system includes a two-stage countercurrent leaching reaction device 1. The leaching outlet of the two-stage countercurrent leaching reaction device 1 is connected to a solid-liquid separation and washing device 2. The overflow port of the solid-liquid separation and washing device 2 is connected to a metallic magnesium production line. The metallic magnesium production line includes an iron removal device 3, a nickel precipitation device 4, an evaporation and concentration device 5, a magnesium chloride drying device 6, and a magnesium chloride electrolysis device 7 connected in sequence.

[0024] Furthermore, the solid-liquid separation and washing device 2 is a CCD thickener.

[0025] Furthermore, the gas outlet of the magnesium chloride drying device 6 is connected to the hydrochloric acid absorption tower 8, and the hydrochloric acid outlet of the hydrochloric acid absorption tower 8 is connected to the hydrochloric acid recovery inlet of the two-stage countercurrent leaching reaction device 1.

[0026] Furthermore, the magnesium chloride drying device 6 includes a granulation centrifuge 61, an air fluidized bed dryer 62, and an HCl gas drying mechanism 63. The granulation centrifuge 61 is connected to the air fluidized bed dryer 62 through a particle conveying mechanism, and the outlet of the air fluidized bed dryer 62 is connected to the inlet of the HCl gas drying mechanism 63.

[0027] Specifically, the air fluidized bed dryer 62 includes a discharge hopper, a conveyor, a vibrating screen, a wet material bin, and a feed pipe (conventional, not shown) arranged along the particle transport route.

[0028] Furthermore, the gas outlet of the magnesium chloride electrolysis device 7 is connected to the chlorine inlet of the hydrochloric acid synthesis device 10 via a chlorine compressor 9, and the hydrogen inlet of the hydrochloric acid synthesis device 10 is connected to the water electrolysis device 11.

[0029] Furthermore, the magnesium chloride electrolysis device 7 is further connected to the magnesium metal refining and casting device 12.

[0030] The specific process steps of this utility model are as follows:

[0031] 1. Slurry storage and filtration

[0032] Serpentine ore is transported to the smelting yard, where it undergoes coarse and fine crushing to obtain serpentine ore with a particle size of approximately 10mm. This ore is stored in the coarse powder silo of the grinding system before entering the grinding system itself. The coarse powder is fed into the vertical mill via a quantitative feeder, belt conveyor, and bucket elevator. The fine powder is collected by a bag filter and then lifted to the fine powder silo via a pneumatic chute and bucket elevator for temporary storage, ensuring that over 85% of the fine powder has a particle size of 0.074mm. After being slurried in a slurry tank on the top of the silo, the fine powder is sent to the leaching unit.

[0033] 2. Hydrochloric acid leaching

[0034] A two-stage countercurrent leaching reactor is used, employing two stages of countercurrent atmospheric pressure hydrochloric acid leaching to ensure that most of the magnesium enters the leaching solution:

[0035] The pretreated slurry first enters the first-stage leaching process. The slurry temperature in the first-stage leaching is controlled at approximately 80℃–85℃, and the leaching time is 2–3 hours. Most metal oxides are leached in the first stage. After thickening in the first-stage leaching, the overflow is sent to neutralization and iron removal, with residual acid concentrations between 5-15 g / L. The underflow from the first-stage leaching is sent to the second-stage leaching process. The slurry temperature in the second-stage leaching is controlled at approximately 95℃–100℃, and the leaching time is 2–3 hours. The crude silica slag obtained after separation in the second-stage leaching is sent to a CCD washing facility; the overflow from the second-stage leaching is returned to the first-stage leaching process.

[0036] 3. CCD and silica slag filtration

[0037] The crude silica slag obtained from the leaching workshop is slurried and then subjected to countercurrent washing using a CCD thickener. The wash water comes from product wash water and the liquid after tail gas washing. To improve the CCD washing efficiency, the washing system adopts a 5-stage countercurrent washing method, with the washing ratio controlled at 2:1 (the weight ratio of wash water to solids entering the thickener). The overflow liquid from CCD1 is sent to the iron removal and nickel slurry workshop for slurrying of the second stage of iron removal, and then sent to the first stage of leaching. The underflow from CCD5 is filtered, and the crude silica containing water after filtration can be further used to produce silicon products.

[0038] 3.1 Magnesium Metal Production Process

[0039] 3.1.1 Iron removal and nickel plating workshop

[0040] The process of removing iron and precipitating nickel mainly involves using magnesium oxide slurry to neutralize the residual acid in a leaching overflow, then adjusting the pH value to remove impurities such as iron, aluminum, and silicon, and finally precipitating nickel to recover valuable metals.

[0041] The iron removal process employs a two-stage procedure. Magnesium hydroxide slurry is used as a neutralizing agent. After neutralizing residual acid, the final pH value of the first iron removal stage is controlled at 3.0–3.5, causing ferric iron and aluminum to hydrolyze and precipitate, while simultaneously removing silica through co-precipitation. The slurry after iron removal undergoes thickening separation. This process utilizes a first settling tank and a first settling thickener.

[0042] The final pH value of the second-stage iron removal process is 4.0–4.5. Compressed air is blown in to oxidize ferrous iron to ferric iron, further hydrolyzing the iron and aluminum in the first-stage slurry. The overflow from the second-stage iron removal process is sent to nickel precipitation. The underflow from the second-stage iron removal process is slurried with CCD6 overflow liquid and returned to the first-stage iron removal process to recover valuable metals such as nickel from the slag. This process uses an oxidation reaction iron removal tank.

[0043] Magnesium oxide slurry is also used as the precipitant for nickel precipitation. The final pH value of nickel precipitation is controlled at 8.0-8.5, causing nickel in the solution to form hydroxide precipitate, while a small amount of manganese also precipitates. After precipitation, the slurry is sent to a thickener for liquid-solid separation. The equipment used in this process is a second precipitation tank and a second precipitation thickener.

[0044] 3.1.2 Product Separation and Filtration

[0045] Product separation includes a first-stage iron removal product thickening separation, nickel plating thickening separation, filtration separation of the underflow after thickening, and product packaging.

[0046] The first stage of the iron removal process involves thickening and separating the product. The overflow from the thickener is then sent to the second stage of iron removal in the iron removal and nickel plating workshop. The underflow from the thickener enters the product filtration and washing process. After two stages of washing and two stages of pressure filtration, the resulting wet iron concentrate is sent to the iron concentrate drying workshop for drying. The washing process uses secondary steam condensate from magnesium chloride.

[0047] In the thickening and separation process of immersion nickel products, part of the overflow from the thickener is sent to the magnesium chloride evaporation workshop after precision filtration, while the remainder is used as a precipitant and flocculant preparation solution. The underflow from the thickener enters the product filtration and washing process, undergoing two stages of washing and two stages of pressure filtration to produce nickel products, which are then automatically packaged. The washing process uses the condensate from the secondary steam of magnesium chloride. The packaged nickel products can be stored in the nickel product warehouse.

[0048] The flocculant preparation mainly provides a usable flocculant solution for the operations of raw material thickening, CCD and product thickening separation processes, and pumps it to various flocculant application points.

[0049] 3.1.3 Evaporation and Concentration of Magnesium Chloride

[0050] Magnesium chloride solution, after storage and preheating, enters the evaporation and concentration unit. This unit employs quadruple-effect evaporation to obtain a magnesium chloride solution with a concentration of 48%-51%. The solution is then cooled and granulated in a granulation tower to obtain solid magnesium chloride (MgCl2) hydrate, which is conveyed to the magnesium chloride drying unit for drying. The condensate from the secondary steam after evaporation is returned to the system for use as slag washing water. The discharged mother liquor is returned to the iron removal and nickel precipitation workshop.

[0051] 3.1.4 Magnesium Smelting Process

[0052] 3.1.4.1 Magnesium chloride and excipient composition

[0053] (1) Magnesium chloride solution

[0054] The aforementioned method uses a forced circulation evaporator to evaporate and concentrate magnesium chloride, obtaining a magnesium chloride solution with a magnesium chloride content of 48%-51%, which is used as raw material for drying magnesium chloride.

[0055] Specifically, the magnesium chloride solution after wet purification contains approximately 25.44% MgCl2, and is concentrated using multi-effect forced evaporation to obtain a magnesium chloride solution of approximately 51%.

[0056] (2) Concentrated sulfuric acid

[0057] The aqueous chlorine gas produced by magnesium chloride electrolysis needs to be adsorbed and compressed.

[0058] 3.1.4.2 Magnesium Metal Smelting Process Flow

[0059] (1) Magnesium chloride drying system

[0060] Since the MgCl2 solution produced by wet evaporation and concentration has a content of about 51%, anhydrous magnesium chloride is obtained by using a process of cooling granulation + one-stage air fluidized bed dehydration + one-stage molten salt dehydration. The equipment used is a granulation centrifuge, an air fluidized bed dryer, and an HCl gas drying mechanism.

[0061] The purpose of granulation is to convert concentrated liquid brine into solid particles. Magnesium chloride brine enters a granulation centrifuge, where it is sprayed into the granulation tower as droplets. These droplets fall within the tower, coming into counter-current contact with the ambient air cooling airflow introduced through a louver system and in parallel flow with the airflow at the top of the tower. This controls the droplets' umbrella-shaped descent trajectory and the temperature of the air exiting from the top. As the droplets cool and crystallize, solid particles form. A discharge hopper at the bottom of the granulation tower receives the granulated wet particles. The particles exiting the tower are conveyed via a belt and bucket conveyor system to a set of vibrating screens to remove large particles. These large particles are then re-melted and re-granulated. The remaining particles are sent to a wet silo and then to an air fluidized bed dryer.

[0062] The primary purpose of the air dryer is to partially dry MgCl2 particles, reducing them from approximately 4.8 mol H2O / mol MgCl2 to approximately 1.8 mol H2O / mol MgCl2. Moist magnesium chloride particles containing water are fed into the air dryer through a feed pipe from the wet particle storage hopper. The particles are then fed into the top pan of a two-stage vertical fluidized bed using hot air, which is introduced from the bottom of each stage as the heating / drying medium. The compressed air is heated by an electric heater in the air dryer and supplied to a gill-shaped feeder in the top pan, ensuring the wet particles are evenly distributed across the surface of the fluidized bed.

[0063] The produced MgCl2 enters the hydrogen chloride drying tower to gradually remove water molecules from the MgCl2, obtaining magnesium chloride molten salt, which meets the needs of the electrolytic cell and improves the life of the electrolytic cell.

[0064] The drying process uses HCl gas, which is produced by high-temperature chemical synthesis of hydrogen gas from water electrolysis and Cl2 from magnesium electrolysis. After drying, the water-containing HCl gas undergoes multi-stage washing and concentration to obtain 36% hydrochloric acid, which is then returned to the leaching process.

[0065] (2) Magnesium smelting system

[0066] Magnesium electrolysis mainly involves electrolyzing MgCl2 from the drying system into metallic magnesium and chlorine. The magnesium is then refined and cast into ingots for sale, while the chlorine is produced by burning it with hydrogen in a synthesis process to produce HCl.

[0067] Electrolytic magnesium is produced using a multi-stage electrolytic cell, where MgCl2 is electrolyzed into Mg and Cl2. Chlorine gas is discharged through a chlorine pipe and sent to the chlorination section via the chlorine compressor chamber. Molten magnesium is periodically extracted using a vacuum magnesium extraction ladle.

[0068] The chlorine compressor is used to transport electrolytic chlorine gas. The medium in the chlorine compressor is concentrated sulfuric acid. The chlorine gas exiting the electrolytic cell contains electrolyte sublimations. The chlorine gas exiting the electrolytic cell passes through a chlorine branch pipe and is collected in the chlorine gas delivery main pipe. It then enters a bag filter to remove the sublimations before being sent by the chlorine compressor to the turbine chamber for pressurization and then to the hydrochloric acid synthesis unit.

[0069] (3) Magnesium refining system

[0070] Molten magnesium is pumped to a refining furnace, and refining flux is added at a rate of 20 kg per ton of magnesium. The mixture is then thoroughly stirred to achieve a purification effect. The refining time is approximately 10-20 minutes. The temperature is then controlled at 1013-1023 K, and the mixture is allowed to stand for 15-20 minutes to separate impurities from magnesium.

[0071] After refining, the molten magnesium is transported to a continuous casting machine for pouring. The continuous casting machine rotates slowly and continuously, and the cast magnesium metal cools rapidly. Sulfur powder is sprayed on the surface of the magnesium ingot to prevent magnesium oxidation, and finally magnesium ingots are formed.

[0072] 4. Products

[0073] The magnesium metal produced by this invention meets the relevant chemical composition requirements of the national standard "Primary Magnesium Ingots" (GB / T3499-2023). The surface of the crude magnesium ingot should be flat and clean, and it is not allowed to have residual solvent, inclusions, cold shuts, flash, shrinkage cracks, oxidation combustion products and other defects. It is not allowed to have residual acid, and there should be no moisture in the shrinkage cavities.

[0074] While specific embodiments of the present invention have been described above, those skilled in the art should understand that the specific embodiments described are merely illustrative and not intended to limit the scope of the present invention. Equivalent modifications and variations made by those skilled in the art in accordance with the spirit of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. An apparatus for preparing metallic magnesium by decomposing serpentine, characterized in that: It includes a two-stage countercurrent leaching reaction device, wherein the leaching outlet of the two-stage countercurrent leaching reaction device is connected to a solid-liquid separation and washing device, and the overflow port of the solid-liquid separation and washing device is sequentially connected to an iron removal device, a nickel precipitation device, an evaporation and concentration device, a magnesium chloride drying device, and a magnesium chloride electrolysis device.

2. The apparatus for preparing metallic magnesium by decomposing serpentine as described in claim 1, characterized in that: The solid-liquid separation and washing device is a CCD thickener.

3. The apparatus for preparing metallic magnesium by decomposing serpentine as described in claim 1, characterized in that: The gas outlet of the magnesium chloride drying device is connected to the hydrochloric acid absorption tower, and the hydrochloric acid outlet of the hydrochloric acid absorption tower is connected to the hydrochloric acid recovery inlet of the two-stage countercurrent leaching reaction device.

4. The apparatus for preparing metallic magnesium by decomposing serpentine as described in claim 1, characterized in that: The magnesium chloride drying device includes a granulation centrifuge, an air fluidized bed dryer, and an HCl gas drying mechanism. The granulation centrifuge is connected to the air fluidized bed dryer through a particle conveying mechanism, and the outlet of the air fluidized bed dryer is connected to the inlet of the HCl gas drying mechanism.

5. The apparatus for preparing metallic magnesium by decomposing serpentine as described in claim 1, characterized in that: The gas outlet of the magnesium chloride electrolysis unit is connected to the chlorine inlet of the hydrochloric acid synthesis unit via a chlorine compressor, and the hydrogen inlet of the hydrochloric acid synthesis unit is connected to the water electrolysis unit.

6. The apparatus for preparing metallic magnesium by decomposing serpentine as described in claim 1, characterized in that: The magnesium chloride electrolysis device is further connected to the magnesium metal refining and casting device. The magnesium metal liquid outlet of the magnesium chloride electrolysis device is connected to the inlet of the magnesium metal refining device. The magnesium metal refining device is transported to the casting device through a conveying device.

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