Preparation system of anhydrous magnesium chloride

Abstract

The utility model relates to a preparation system of anhydrous magnesium chloride, which comprises a high-concentration magnesium chloride solution preparation system, a primary fluidized bed drying system and a secondary fluidized bed drying system which are sequentially connected, the spray feeding device is connected with a high-concentration magnesium chloride solution preparation system through a pressure pump pipeline, and the secondary fluidized bed drying system is connected with an HCl gas heating and recycling system. According to the preparation system designed by the utility model, high-concentration magnesium chloride solution spray feeding is adopted, anhydrous magnesium chloride is produced through two-stage drying, the product purity is high, HCl gas is used as heating gas in the two-stage fluidized bed drying system, and the HCl gas is recycled, so that the consumption of the HCl gas is saved, and the harm to the environment is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of magnesium chloride production, in particular to a preparation system of anhydrous magnesium chloride. Background Art

[0002] Magnesium metal has the advantages of light weight, high strength, impact resistance and corrosion resistance. It is widely used in aviation, aerospace, modern automobiles, rail transportation, ships, national defense and military industries. At present, the process of preparing magnesium metal by electrolysis in industry is relatively reliable, and high-purity anhydrous magnesium chloride is the key to preparing magnesium metal by electrolysis. The existing preparation technologies of anhydrous magnesium chloride mainly include ammonia complex dehydration method, melt chlorination dehydration method and high-temperature dehydration under hydrogen chloride protective atmosphere. Among them, ammonia complex dehydration method is still in the research stage and has no industrial application. The melt chlorination dehydration method is to place MgCl2 powder (containing MgO and H2O) in a chlorination furnace with chlorine gas, and melt dehydrate at 810℃. This method has high energy consumption, large amount of chlorine gas is used, and serious environmental pollution.

[0003] Dehydration under hydrogen chloride atmosphere is currently the most advanced method for dehydrating magnesium chloride. This method is to obtain magnesium chloride hexahydrate by granulating a 33% MgCl2 solution, and then perform two-stage drying and dehydration. The first-stage drying is fluidized bed drying under air atmosphere. After the first-stage fluidized bed drying, magnesium chloride dihydrate particles can be obtained, and then the second-stage fluidized bed drying under HCl atmosphere is performed to finally obtain anhydrous magnesium chloride. This method has a long process flow, and the dehydration process parameters are difficult to control. In addition, the magnesium chloride particles obtained by granulation have poor strength and are easy to break to produce fine powder, which leads to easy blockage of the fluidized bed tray and frequent dead bed. At the same time, too much dust is entrained, resulting in high post-processing pressure, and the HCl gas is not effectively utilized after discharge, which has great environmental hazards. Summary of the invention

[0004] In order to solve the problems in the prior art, the utility model patent designs a preparation system of anhydrous magnesium chloride to solve the problems of long process flow, poor product quality, high energy consumption and low utilization rate of hydrogen chloride gas in the existing magnesium chloride dehydration process.

[0005] The technical solution adopted by the utility model is as follows: the preparation system comprises a high-concentration magnesium chloride solution preparation system, a primary fluidized bed drying system and a secondary fluidized bed drying system which are sequentially connected and arranged; the primary fluidized bed drying system is provided with a spray feeding device, the spray feeding device is connected to the high-concentration magnesium chloride solution preparation system through a pressurized pipeline, and the secondary fluidized bed drying system is connected to an HCl gas heating and recycling system.

[0006] Furthermore, the spray feeding device includes a feed pipe horizontally arranged at the feed end of the primary fluidized bed, a plurality of nozzles are arranged on the feed pipe, the feed pipe is connected to a pressurized pipeline and a high-pressure gas source, and the nozzle of the nozzle is arranged upward.

[0007] Furthermore, an air supply pipeline is connected to the air inlet end of the primary fluidized bed, and a first heater is provided on the air supply pipeline.

[0008] Furthermore, the air outlet end of the primary fluidized bed is connected to a spray tower and an induced draft fan via pipelines in sequence.

[0009] Furthermore, a spray device is provided in the upper part of the spray tower, the liquid inlet pipeline of the spray device is connected to the low-concentration magnesium chloride solution storage tank, and the liquid outlet pipeline at the bottom of the spray tower is connected to the high-concentration magnesium chloride solution preparation system.

[0010] Furthermore, the HCl gas heating and recycling system comprises a dust collector, a dehumidifying moving bed, a circulating fan and a second heater which are sequentially connected by pipelines, the air inlet end of the dust collector is connected to the air outlet end of the secondary fluidized bed, and the air outlet end of the second heater is connected to the air inlet end of the secondary fluidized bed.

[0011] Furthermore, the high-concentration magnesium chloride solution preparation system comprises a magnesium chloride refining device and a magnesium chloride evaporating device which are connected in sequence, and the magnesium chloride refining device is connected to a low-concentration magnesium chloride solution storage tank.

[0012] Furthermore, the dust collector is a cyclone dust collector.

[0013] Compared with the prior art, the improvement of the preparation system of anhydrous magnesium chloride designed by the utility model patent is:

[0014] First, the preparation system sets up a high-concentration magnesium chloride preparation system, and inputs a high-concentration (50%) magnesium chloride solution into the primary fluidized bed for spray granulation. Compared with the prior art that uses a low-concentration magnesium chloride solution of about 30% as the liquid, the magnesium chloride particles formed by granulation have less moisture and greater strength. Less moisture helps the magnesium chloride particles dry, and high strength can prevent the magnesium chloride particles from breaking during the fluidized drying process, generating less dust and reducing post-processing pressure.

[0015] Second, the spray granulation and drying of the high-concentration magnesium chloride solution in the primary fluidized bed of the preparation system are carried out simultaneously. The magnesium chloride solution is sprayed from the nozzle into the high-temperature primary fluidized bed, and undergoes a drying process at the moment of spraying, that is, the water in the magnesium chloride solution has not yet completely formed crystal water, and it is dried in the form of free water to obtain magnesium chloride dihydrate, and anhydrous magnesium chloride can be obtained through two-stage drying. Compared with the traditional preparation process of first granulating to form magnesium chloride hexahydrate, and then dehydrating the magnesium chloride hexahydrate to anhydrous magnesium chloride through two-stage fluidized bed drying, the process flow is short, the energy consumption is lower, and the purity of the prepared anhydrous magnesium chloride is also higher.

[0016] Third, the secondary fluidized bed drying system in the preparation system is equipped with an HCl gas heating and recycling system, which can dehumidify the wet HCl gas discharged from the secondary fluidized bed, thereby realizing the recycling of HCl gas. On the one hand, it can save the amount of HCl gas, and on the other hand, it can reduce the harm to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the preparation system of anhydrous magnesium chloride.

[0018] In the figure, 1 is a low-concentration magnesium chloride solution storage tank, 2 is a magnesium chloride refining device, 3 is a magnesium chloride evaporation device, 4 is a primary fluidized bed, 5 is a nozzle, 6 is a first heater, 7 is a spray tower, 8 is an induced draft fan, 9 is a secondary fluidized bed, 10 is a second heater, 11 is a cyclone dust collector, 12 is a moving bed, and 13 is a circulating fan. DETAILED DESCRIPTION

[0019] The utility model is further described below in conjunction with the accompanying drawings and specific embodiments. The technical solutions in the embodiments of the utility model are clearly and completely described, and the described embodiments are only embodiments of a part of the invention, not all of it. Based on the embodiments in the invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the invention.

[0020] like Figure 1 As shown, the utility model patent designs an embodiment of a system for preparing anhydrous magnesium chloride. In this embodiment, the preparation system includes a high-concentration magnesium chloride solution preparation system, a primary fluidized bed drying system and a secondary fluidized bed drying system which are sequentially connected.

[0021] The high-concentration magnesium chloride solution preparation system comprises a magnesium chloride refining device 2 and a magnesium chloride evaporating device 3 which are connected in sequence. The magnesium chloride refining device 2 is connected to a low-concentration magnesium chloride solution storage tank 1, and the magnesium chloride solution is subjected to impurity removal and static treatment. Then, the magnesium chloride evaporating device 3 evaporates and concentrates the refined low-concentration magnesium chloride solution to obtain a high-concentration magnesium chloride solution.

[0022] The primary fluidized bed drying system includes a primary fluidized bed 4, a spray feeding device and an exhaust gas treatment device, wherein the spray feeding device includes a feeding pipe horizontally arranged at the feeding end of the primary fluidized bed 4, and the feeding pipe is connected to the liquid outlet end of the magnesium chloride evaporation device 3 of the high-concentration magnesium chloride solution preparation system and a high-pressure gas source through a pressure pump pipeline. A plurality of nozzles 5 are arranged on the feeding pipe, and the nozzles of the plurality of nozzles 5 are all arranged upward to spray upward.

[0023] The air inlet end of the primary fluidized bed 4 is connected to an air supply pipeline, and a first heater 6 is arranged on the air supply pipeline, and the first heater 6 adopts a natural gas combustion furnace. The air outlet end of the primary fluidized bed 4 is connected to a spray tower 7 and an induced draft fan 8 in sequence through pipelines. A spray device is arranged on the upper inner side of the spray tower 7, and the liquid inlet pipeline of the spray device is connected to the low-concentration magnesium chloride solution storage tank 1 through a pressure pump, and the liquid outlet pipeline at the bottom end of the spray tower 7 is connected to the liquid inlet end of the magnesium chloride evaporation device 3 of the high-concentration magnesium chloride solution preparation system.

[0024] The secondary fluidized bed drying system includes a secondary fluidized bed 9 and an HCl gas heating and recycling system. The feed end of the secondary fluidized bed 9 is connected to the discharge end of the primary fluidized bed 4 through a feeding device. The HCl gas heating and recycling system includes a cyclone dust collector 11, a dehumidifying moving bed 12, a circulating fan 13 and a second heater 10 which are sequentially connected by pipelines. The air inlet end of the cyclone dust collector 11 is connected to the exhaust end of the secondary fluidized bed 9, and the air outlet end of the second heater 10 is connected to the air inlet end of the secondary fluidized bed 9.

[0025] When the preparation system of anhydrous magnesium chloride disclosed in the utility model patent is used, the MgCl2 solution (concentration of 30%) in the low-concentration magnesium chloride solution storage tank 1 enters from the top of the magnesium chloride refining device 2 and flows out from the bottom. A filter is arranged at the top of the refining device to remove floating impurities in the MgCl2 solution, and a cleaning port is arranged at the bottom to regularly clean the impurities precipitated inside; the refined MgCl2 solution enters the magnesium chloride evaporation device 3, and the temperature of the evaporation device is set to 160-180°C, which plays the role of evaporation and concentration of the MgCl2 solution, and the MgCl2 solution after evaporation and concentration can be maintained at a concentration of about 50%.

[0026] The air supply pipeline at the air inlet end of the primary fluidized bed 4 is provided with a blower, and the air supplied is heated by a natural gas combustion furnace. The heated air enters the primary fluidized bed 4 from the bottom, and is evenly distributed in the primary fluidized bed 4 through the air distribution plate. The temperature inside the primary fluidized bed 4 is maintained at 160-180°C during the drying process. The 50% concentration MgCl2 solution after evaporation and concentration is sprayed upward from the nozzle 5 into the primary fluidized bed 4 under the action of compressed gas to form MgCl2 particles. Due to the high temperature inside the fluidized bed, part of the water inside the MgCl2 solution will evaporate at the moment of spraying, and then a fluidized state will be formed under the action of hot air, and the MgCl2 particles will be further dried to magnesium chloride dihydrate. The dried material is discharged from the discharge port. The wet gas is discharged from the air outlet above the primary fluidized bed 4 into the spray tower 7, and a 30% concentration MgCl2 solution is used as the spray liquid to spray the wet gas to dissolve the MgCl2 powder entrained in the wet gas. After spraying, the concentration of the MgCl2 solution is further increased and returned to the magnesium chloride evaporation device 3 for further evaporation and concentration for recycling.

[0027] The magnesium chloride dihydrate obtained by drying in the primary fluidized bed 4 is transported to the secondary fluidized bed 9 by the feeding device. The second heater 10 heats the HCl gas. The second heater 10 is an indirect heater with a double-layer hollow structure. The hollow part is for the HCl gas to pass through. The outer layer heats the HCl by hot air. The heated HCl gas enters the secondary fluidized bed 9 from the bottom of the secondary fluidized bed 9 through the air distribution plate. The temperature in the secondary fluidized bed 9 is maintained at 260-280°C during the drying process. The magnesium chloride dihydrate particles dried in the primary fluidized bed enter the secondary fluidized bed and are heated in the hot The HCl gas is dehydrated to anhydrous under the HCl gas atmosphere and discharged from the discharge port to enter the next process flow; the wet HCl gas is discharged from the exhaust port above the secondary fluidized bed 9 and enters the cyclone dust collector 11 to remove fine powder entrained in the gas, and then enters the dehumidification moving bed 12, the interior of the dehumidification moving bed 12 is filled with anhydrous MgCl2 particles or anhydrous CaCl2 particles to remove moisture in the wet HCl gas, and then enters the second heater 10 to recover the HCl gas for recycling. A gas supply pipeline is set at the front end of the second heater 10 to regularly replenish HCl gas to the system.

[0028] The above contents are only preferred embodiments of the present invention and cannot be used to limit the scope of implementation of the present invention. That is, any simple equivalent changes and modifications made according to the claims and description of the present invention are still within the scope of the present invention.

Claims

1. A system for preparing anhydrous magnesium chloride, characterized in that: The preparation system comprises a high-concentration magnesium chloride solution preparation system, a primary fluidized bed drying system and a secondary fluidized bed drying system which are sequentially connected. The primary fluidized bed drying system is provided with a spray feeding device which is connected to the high-concentration magnesium chloride solution preparation system via a pressurized pipeline. The secondary fluidized bed drying system is connected to an HCl gas heating and recycling system.

2. A system for preparing anhydrous magnesium chloride according to claim 1, characterized in that, The spray feeding device comprises a feeding pipe horizontally arranged at the feeding end of the primary fluidized bed, a plurality of nozzles are arranged on the feeding pipe, the feeding pipe is connected to a pressurized pipeline and a high-pressure gas source, and the nozzles of the nozzles are arranged upward.

3. A system for preparing anhydrous magnesium chloride according to claim 2, characterized in that, The air inlet end of the primary fluidized bed is connected to an air supply pipeline, and a first heater is arranged on the air supply pipeline.

4. A system for preparing anhydrous magnesium chloride according to claim 3, characterized in that, The air outlet end of the primary fluidized bed is connected to a spray tower and an induced draft fan in sequence through pipelines.

5. A system for preparing anhydrous magnesium chloride according to claim 4, characterized in that, A spray device is arranged at the upper part of the spray tower, a liquid inlet pipeline of the spray device is connected to a low-concentration magnesium chloride solution storage tank, and a liquid outlet pipeline at the bottom end of the spray tower is connected to a high-concentration magnesium chloride solution preparation system.

6. A system for preparing anhydrous magnesium chloride according to claim 1, characterized in that, The HCl gas heating and recycling system comprises a dust collector, a dehumidifying moving bed, a circulating fan and a second heater which are sequentially connected by pipelines, wherein an air inlet end of the dust collector is connected to an air outlet end of the secondary fluidized bed, and an air outlet end of the second heater is connected to an air inlet end of the secondary fluidized bed.

7. A system for preparing anhydrous magnesium chloride according to claim 5, characterized in that: The high-concentration magnesium chloride solution preparation system comprises a magnesium chloride refining device and a magnesium chloride evaporating device which are connected in sequence, and the magnesium chloride refining device is connected to a low-concentration magnesium chloride solution storage tank.

8. A system for preparing anhydrous magnesium chloride according to claim 6, characterized in that: The dust collector is a cyclone dust collector.

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