A device and method for comprehensive utilization of monazite type rare earth concentrate

Abstract

A device and method for comprehensive utilization of monazite type rare earth concentrate belong to the field of rare earth comprehensive utilization and recovery, the device comprises a continuous packed bed, a two-stage multi-chamber furnace reactor and a condenser, an aluminum oxide chlorination reaction occurs in the lower part of the middle feeding port of the multi-chamber furnace, the generated aluminum chloride is used as raw material for the chlorination reaction of the rare earth concentrate in the upper part of the middle feeding port of the multi-chamber furnace, the cost of obtaining aluminum chloride is reduced, and the heat utilization efficiency is improved. The solid phase and the gas phase complete the reaction in the multi-chamber furnace in a countercurrent manner, compared with conventional gas-solid reactors, the heat utilization rate of the system reaches more than 80%, and the chlorine utilization efficiency reaches more than 99%. The continuous packed bed is used for carbon and carbon dioxide reaction to obtain carbon monoxide raw material as the heat source and carbon source of the chlorination reaction, after the carbon thermal chlorination reaction is completed, the carbon dioxide returns to the continuous packed bed for recycling, and the whole process does not produce waste gas and waste residue.

Description

Technical Field

[0001] This invention belongs to the field of rare earth comprehensive utilization and recycling, specifically relating to an apparatus and method for the comprehensive utilization of monazite-type rare earth concentrate. Background Technology

[0002] Rare earth resources have significant utilization value and are currently widely used in industry, military, medical, energy, and environmental fields. my country is the world's richest country in rare earth elements. Among them, fluorocarbon cerium-type rare earth, monazite-type rare earth, and fluorocarbon cerium-monazite mixed ores are the most common occurrence forms of rare earth minerals. These minerals contain approximately 40% to 60% rare earth elements, along with iron, calcium, silicon, fluorine, and other elements, resulting in complex compositions and therefore relatively complex rare earth extraction processes.

[0003] Common methods for extracting rare earth elements from monazite ore include high-pressure sulfuric acid leaching, sulfuric acid roasting, and biomass decomposition. Sulfuric acid decomposition and alkaline decomposition methods are complex processes that generate large amounts of waste gas, waste liquid, and waste residue, posing significant environmental hazards. Furthermore, the separation of residue and liquid is difficult, resulting in a high rare earth loss rate.

[0004] CN115818694A proposes a method for treating monazite rare earth ore by high-pressure acid leaching with concentrated sulfuric acid. This method decomposes monazite with high-concentration sulfuric acid under high temperature and high pressure. Although this process further reduces the decomposition temperature of monazite, it still cannot completely avoid the emission of waste gas, waste liquid and waste residue during the reaction process, and still poses certain hazards to the environment.

[0005] CN115992310A proposes a method for treating monazite rare earth ore using sulfuric acid roasting. This method involves mixing and granulating monazite fluorite concentrate with iron concentrate, then reacting it with sulfuric acid at high temperature to form a decomposition solution, followed by water leaching to obtain a rare earth solution. While this method achieves a high rare earth leaching rate, the purity of the obtained rare earth is low, and the reaction process generates waste residue and wastewater, harming the environment.

[0006] CN114231740A proposes a method for decomposing monazite using composite microorganisms. This method involves uniformly mixing a composite phosphorus-solubilizing microbial solution with monazite concentrate powder and then leaching it in two steps to obtain a rare earth solution and phosphate fertilizer product. This method has low production costs and minimal environmental impact, but the biological method has disadvantages such as high environmental requirements and a long microbial culture cycle.

[0007] In conclusion, existing methods for recycling monazite rare earth minerals cannot solve environmental problems, and they do not achieve comprehensive recovery of other metals in the ore. Summary of the Invention

[0008] The present invention aims to provide an apparatus and method for the comprehensive utilization of monazite-type rare earth concentrate.

[0009] A device for the comprehensive utilization of monazite-type rare earth concentrate includes a continuous packed bed, a two-stage multi-hearth furnace reactor and a condenser. The two-stage multi-hearth furnace reactor consists of a furnace body, a feed inlet, an air inlet, a material platform, a central shaft, a rake, a discharge outlet, an air outlet and a gas distributor. The furnace features internal airlocks at the inlet / outlet to ensure continuous unidirectional solid feeding or discharging. The inlet is installed at the top and middle of the furnace body, symmetrically distributed along the central axis. The inlet in the middle of the furnace body divides the multi-hearth furnace into upper and lower sections. The outlet is installed at the bottom of the furnace body, symmetrically distributed along the central axis. The air inlet / outlet is installed at the top and bottom of the furnace body, symmetrically distributed along the central axis. The inlet / outlet and air inlet / outlet are connected to the furnace body via sealing flanges. The material platform is located inside the furnace body and bolted to the inner wall, with the connection angle continuously adjustable within the range of 0° to 5°. The distance between material platforms is 20–30 mm. The central axis is located at the center of the furnace body, and the rake is bolted to the central axis, with the connection angle set at the rake arm angle. The angle is continuously adjustable within the range of 0° to 5°. The number of rake arms in the rake machine is equal to the number of material platforms. Rake teeth are evenly distributed on the rake arms, and the length of the rake teeth gradually increases. When the angle between the rake arm and the central shaft of the rake machine is 5°, all rake teeth are on the same plane. The rake machine rotates under the drive of the central shaft to move the material layer. The material enters the two-stage multi-hearth furnace reactor from the feed port at the top of the furnace body. Under the action of the rotating multi-hearth furnace rake machine and the downwardly inclined multi-layer material platform, the material moves from the upper material platform to the lower material platform. After the reaction is completed, the product is discharged from the discharge port at the bottom of the furnace body. The gas distributor is installed at the bottom of the multi-hearth furnace and is connected to the two bottom air inlets respectively. The purpose is to mix the gas entering the multi-hearth furnace. In the two-stage multi-hearth furnace, the solid phase and the gas phase react in a countercurrent manner during the heat exchange process.

[0010] The specific operating method is as follows:

[0011] (1) Carbon-containing raw materials and carbon dioxide are added to a continuous packed bed. The carbon-containing raw materials react with the carbon dioxide gas to generate carbon monoxide. The resulting high-temperature carbon monoxide flue gas enters through one of the inlets at the bottom of a two-stage multi-hearth furnace, serving as both a heat source and a carbon source. The other inlet is connected to chlorine gas. The gases introduced through both inlets are mixed by a bottom gas distributor before being introduced into the two-stage multi-hearth furnace. The reaction temperature in the continuous packed bed is 700–1100℃, and the reaction time is 10–90 min. The mass ratio of carbon in the carbon-containing raw materials to the total mass of alumina and rare earth concentrate is (2–10):1. The stoichiometric formula for the reaction between the carbon-containing raw materials and carbon dioxide in the continuous packed bed is:

[0012] CO2(g) + C = 2CO(g)

[0013] The carbon-containing raw materials are one or more of coking coal, petroleum coke, biochar, coal gangue, coal gasification slag, and fly ash, wherein the mass fraction of carbon in coal gangue, coal gasification slag, and fly ash is greater than 5%, and the diameter of the material after crushing and grinding is less than 0.15 mm.

[0014] After coal gangue, coal gasification slag, and fly ash are reacted in a continuous packed bed, they can be used as raw materials for silicon-potassium fertilizer or kaolin.

[0015] (2) Alumina raw material is added at the middle feed inlet of the two-section multi-hearth furnace, and monazite-type rare earth concentrate is added at the top feed inlet. The mass ratio of alumina to rare earth concentrate is (0.1~1):1. The carbothermic chlorination reaction mainly occurs at the lower part of the middle feed inlet of the two-section multi-hearth furnace, where alumina reacts with excess chlorine and carbon monoxide at a temperature of 500~1000℃ for 5~60 min. The reaction yields a mixed gas containing aluminum chloride, carbon dioxide, and excess carbon monoxide. The stoichiometric formula is:

[0016] xAl2O3(s)+(3x+n)CO(g)+(3x+m)Cl2(g)=2xAlCl3(g)+3xCO2+n CO(g)+m Cl2(g)

[0017] (3) Chlorination of monazite-type rare earth concentrate occurs above the feed inlet in the middle of the two-stage multi-hearth furnace: the rare earth concentrate reacts with the mixed gas obtained from the reaction in the lower part of the multi-hearth furnace, and the chlorination reaction temperature is 600-1200℃, with a reaction time of 30-120 min. The rare earth chlorides, aluminum phosphate, calcium chloride, and magnesium chloride generated by the chlorination reaction remain in the chlorination slag in solid form, while titanium tetrachloride, silicon tetrachloride, and ferric chloride leave the two-stage multi-hearth furnace in gaseous form. The reaction stoichiometry is as follows:

[0018] 1) For monazite-type rare earth elements:

[0019] CePO4(s)+AlCl3(s)=CeCl3(s,l)+AlPO4(s)

[0020] 2) For calcium fluoride:

[0021] 3 / 2CaF2(s)+AlCl3(s)=3 / 2CaCl2(s,l)+AlF3(s)

[0022] 3) For silicon dioxide:

[0023] 3SiO2(s)+4AlCl3(g)=2Al2O3(s)+3SiCl4(g)

[0024] SiO2(s)+2CO(g)+2Cl2(g)=SiCl4(g)+2CO2(g)

[0025] (4) The gaseous chlorination products are discharged from the outlet of the two-stage multi-hearth furnace and condensed and recovered in the condenser. The remaining tail gas, mainly carbon dioxide, is returned to the continuous packed bed as a raw material for reaction with carbon-containing raw materials. The solid products are discharged from the outlet of the two-stage multi-hearth furnace and separated by water leaching to obtain a mixed solution of aluminum fluoride solid, rare earth chloride, calcium chloride, and magnesium chloride. The mixed solution is then separated by extraction to obtain a single rare earth chloride with a mass fraction greater than 99.9%.

[0026] The apparatus and method for comprehensive utilization of monazite-type rare earth concentrate of the present invention have the following advantages compared with the prior art:

[0027] (1) The multi-hearth furnace described in this invention has a two-stage structure. The alumina chlorination reaction occurs in the lower part of the feed inlet in the middle of the multi-hearth furnace, and the resulting aluminum chloride is used as the raw material for the chlorination reaction of rare earth concentrate in the upper part of the feed inlet in the middle of the multi-hearth furnace, thereby reducing the cost of obtaining aluminum chloride and improving the heat utilization efficiency. The solid phase and gas phase complete the reaction in the multi-hearth furnace in a countercurrent manner. Compared with conventional gas-solid reactors, the system heat utilization rate reaches more than 80%, and the chlorine utilization efficiency reaches more than 99%.

[0028] (2) This invention utilizes a continuous packed bed to react carbon and carbon dioxide to obtain carbon monoxide as a heat source and carbon source for the chlorination reaction. After the carbothermic chlorination reaction is completed, the carbon dioxide is returned to the continuous packed bed for recycling. The entire process does not generate waste gas and there is no waste residue discharged. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of an apparatus for the comprehensive utilization of monazite-type rare earth concentrate. In the diagram, 1-feed inlet, 2-air outlet, 3-rake machine, 4-material platform, 5-air inlet, 6-discharge outlet, 7-central shaft, 8-furnace body, 9-gas distributor;

[0030] Figure 2 This is a process flow diagram for the comprehensive utilization of monazite-type rare earth concentrate. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to the embodiments.

[0032] The monazite used in the embodiments of the present invention contains more than 60% REO, more than 15% P2O5, and more than 6% ThO2.

[0033] A device for the comprehensive utilization of monazite-type rare earth concentrate includes a continuous packed bed, a two-stage multi-hearth furnace reactor, and a condenser, wherein, for example... Figure 1As shown, the two-section multi-hearth furnace reactor consists of a furnace body 8, a feed inlet 1, an air inlet 5, a material platform 4, a central shaft 7, a rake 3, a discharge outlet 6, an air outlet 2, and a gas distributor 9. The feed inlet 1 and discharge outlet 6 are equipped with airlocks to achieve continuous unidirectional feeding or discharging of solids. The feed inlet 1 is installed at the top and middle of the furnace body 8, symmetrically distributed on both sides of the central axis. The feed inlet in the middle of the furnace body divides the multi-hearth furnace into upper and lower sections. The discharge outlet 6 is installed at the bottom of the furnace body 8, symmetrically distributed on both sides of the central axis. The air inlet 5 and air outlet 2 are respectively installed at the top and bottom of the furnace body 8, symmetrically distributed on both sides of the central axis. The feed inlet 1 / discharge outlet 6 and the air inlet 5 / exhaust outlet 2 are connected to the furnace body 8. They are connected by sealing flanges respectively; the material platform 4 is set inside the furnace body 8 and is bolted to the inner wall of the furnace body 8. The connection angle is continuously adjustable within the range of 0° to 5°, and the distance between the material platforms is 20 to 30 mm; the central shaft 7 is placed in the center of the furnace body 8, and the rake machine 3 is bolted to the central shaft 7. The connection angle is continuously adjustable within the range of 0° to 5°. The number of rake arms in the rake machine 3 is equal to the number of material platforms 4, and all of them can be disassembled and increased or decreased according to the feeding situation. The rake teeth are evenly distributed on the rake arm, and the length of the rake teeth gradually increases. When the angle between the rake arm of the rake machine 3 and the central shaft 7 is 5°, all the rake teeth are on the same plane. The rake machine 3 rotates under the drive of the central shaft 7 to move the material layer. The material enters the multi-hearth furnace reactor from the top feed port 1 of the furnace body 8. Under the action of the rotating multi-hearth furnace rake machine 3 and the downwardly inclined multi-layer material platform 4, the material moves from the upper material platform to the lower material platform. After the reaction is completed, the product is discharged from the bottom discharge port 6 of the furnace body. The gas distributor 9 is installed at the bottom of the multi-hearth furnace and is connected to the two bottom air inlets respectively. Its purpose is to mix the gas entering the multi-hearth furnace. The solid phase and the gas phase in the multi-hearth furnace react in a countercurrent manner during the heat exchange process.

[0034] Example 1

[0035] An apparatus for the comprehensive utilization of monazite-type rare earth concentrate as described above, wherein the two-stage multi-hearth furnace reactor specifically houses eight material platforms, with five platforms located above the feed inlet in the middle of the furnace body and three platforms located below, and the distance between the material platforms is 30 mm.

[0036] A method for comprehensive utilization of monazite-type rare earth concentrate, implemented using the aforementioned apparatus, such as... Figure 2 As shown, the specific steps are as follows:

[0037] (1) Coal gangue and carbon dioxide are added to the continuous packed bed. The coal gangue reacts with carbon dioxide gas to generate carbon monoxide. The resulting high-temperature carbon monoxide flue gas enters through one of the inlets at the bottom of the two-stage multi-hearth furnace as a heat source and carbon source. The other inlet is connected to chlorine gas. The gases introduced through the two inlets are mixed by the bottom gas distributor 9 and then introduced into the two-stage multi-hearth furnace. The reaction temperature in the continuous packed bed is 1100℃ and the reaction time is 90min. The ratio of the mass of carbon in the coal gangue to the total mass of alumina and rare earth concentrate is 2:1.

[0038] (2) Alumina raw material is added to the middle feed port of the two-section multi-hearth furnace and monazite-type rare earth concentrate is added to the top feed port of the two-section multi-hearth furnace. The mass ratio of alumina to rare earth concentrate is 0.8:1. The carbothermic chlorination reaction of alumina with excess chlorine and carbon monoxide mainly occurs at the lower part of the middle feed port of the two-section multi-hearth furnace. The reaction temperature is 1000℃ and the reaction time is 60min. The reaction produces a mixed gas containing aluminum chloride gas, carbon dioxide gas and excess carbon monoxide gas.

[0039] (3) The chlorination reaction of monazite-type rare earth concentrate occurs above the feed inlet in the middle of the two-stage multi-hearth furnace. The rare earth concentrate reacts with the mixed gas obtained from the reaction in the lower part of the multi-hearth furnace, and the chlorination reaction temperature is 1200℃, and the reaction time is 60min. The rare earth chlorides, aluminum phosphate, calcium chloride, and magnesium chloride generated by the chlorination reaction remain in the chlorination slag in solid form, while titanium tetrachloride, silicon tetrachloride, and ferric chloride leave the two-stage multi-hearth furnace in gaseous form.

[0040] (4) The gaseous chlorination products are discharged from the outlet of the two-stage multi-hearth furnace and condensed and recovered in the condenser. The remaining tail gas, mainly carbon dioxide, is returned to the continuous packed bed as a raw material for reaction with carbon-containing raw materials. The solid products are discharged from the outlet of the two-stage multi-hearth furnace and separated by water leaching to obtain a mixed solution of aluminum fluoride solid, rare earth chloride, calcium chloride, and magnesium chloride. The mixed solution is then separated by extraction to obtain a single rare earth chloride with a mass fraction greater than 99.9%.

[0041] Using the aforementioned apparatus, the carbon reaction efficiency in a continuous packed bed is 97%, the alumina chlorination efficiency in a two-stage multi-hearth furnace is 98%, and the rare earth element chlorination efficiency in rare earth concentrate is 98%.

[0042] Example 2

[0043] A device for the comprehensive utilization of monazite-type rare earth concentrate as described above, wherein 10 material platforms are specifically placed in the two-stage multi-hearth furnace reactor, with 6 platforms set at the upper part and 4 platforms set at the lower part of the feed inlet in the middle of the furnace body, and the distance between the material platforms is 25mm.

[0044] A method for comprehensive utilization of monazite-type rare earth concentrate, implemented using the aforementioned device, includes the following specific operating steps:

[0045] (1) Fly ash and carbon dioxide are added to the continuous packed bed. The fly ash reacts with carbon dioxide gas to generate carbon monoxide in the continuous packed bed. The resulting high-temperature carbon monoxide flue gas enters the multi-hearth furnace reactor through one of the inlets at the bottom of the multi-hearth furnace as a heat source and carbon source. The other inlet is connected to chlorine gas. The gas introduced through the two inlets is mixed by the bottom gas distributor and then introduced into the two-stage multi-hearth furnace. The reaction temperature in the continuous packed bed is 700℃ and the reaction time is 90min. The ratio of the mass of carbon in the fly ash to the total mass of alumina and rare earth concentrate is 8:1.

[0046] (2) Alumina raw material is added to the middle feed port of the two-section multi-hearth furnace and monazite-type rare earth concentrate is added to the top feed port of the two-section multi-hearth furnace. The mass ratio of alumina to rare earth concentrate is 1:1. The carbothermic chlorination reaction of alumina with excess chlorine and carbon monoxide mainly occurs at the lower part of the middle feed port of the two-section multi-hearth furnace. The reaction temperature is 1000℃ and the reaction time is 5min. The reaction produces a mixed gas containing aluminum chloride gas, carbon dioxide gas and excess carbon monoxide gas.

[0047] (3) The chlorination reaction of monazite-type rare earth concentrate occurs above the feed inlet in the middle of the two-stage multi-hearth furnace. The rare earth concentrate reacts with the mixed gas obtained from the reaction in the lower part of the multi-hearth furnace, and the chlorination reaction temperature is 1200℃, and the reaction time is 30min. The rare earth chlorides, aluminum phosphate, calcium chloride, and magnesium chloride generated by the chlorination reaction remain in the chlorination slag in solid form, while titanium tetrachloride, silicon tetrachloride, and ferric chloride leave the two-stage multi-hearth furnace in gaseous form.

[0048] (4) The gaseous chlorination products are discharged from the outlet of the two-stage multi-hearth furnace and condensed and recovered in the condenser. The remaining tail gas, mainly carbon dioxide, is returned to the continuous packed bed as a raw material for reaction with carbon-containing raw materials. The solid products are discharged from the outlet of the two-stage multi-hearth furnace and separated by water leaching to obtain a mixed solution of aluminum fluoride solid, rare earth chloride, calcium chloride, and magnesium chloride. The mixed solution is then separated by extraction to obtain a single rare earth chloride with a mass fraction greater than 99.9%.

[0049] Using the aforementioned apparatus, the carbon reaction efficiency in a continuous packed bed is 97%, the alumina chlorination efficiency in a two-stage multi-hearth furnace is 95%, and the rare earth element chlorination efficiency in rare earth concentrate is 94%.

[0050] Example 3

[0051] A device for the comprehensive utilization of monazite-type rare earth concentrate as described above, wherein 12 material platforms are specifically placed in the two-stage multi-hearth furnace reactor, with 7 platforms set at the upper part of the feed inlet in the middle of the furnace body and 5 platforms set at the lower part, and the distance between the material platforms is 20mm.

[0052] A method for comprehensive utilization of monazite-type rare earth concentrate, implemented using the aforementioned device, includes the following specific operating steps:

[0053] (1) Coal gasification slag and carbon dioxide are added to the continuous packed bed. The coal gasification slag reacts with carbon dioxide gas in the continuous packed bed to generate carbon monoxide. The resulting high-temperature carbon monoxide flue gas enters the multi-hearth furnace reactor through one of the gas inlets at the bottom of the multi-hearth furnace as a heat source and carbon source. The other gas inlet is connected to chlorine gas. The gas introduced through the two gas inlets is mixed by the bottom gas distributor and then introduced into the two-stage multi-hearth furnace. The reaction temperature in the continuous packed bed is 1000℃ and the reaction time is 20min. The ratio of the mass of carbon in the coal gasification slag to the total mass of alumina and rare earth concentrate is 2:1.

[0054] (2) Alumina raw material is added to the middle feed port of the two-section multi-hearth furnace and monazite-type rare earth concentrate is added to the top feed port of the two-section multi-hearth furnace. The mass ratio of alumina to rare earth concentrate is 0.1:1. The carbothermic chlorination reaction of alumina with excess chlorine and carbon monoxide mainly occurs at the lower part of the middle feed port of the two-section multi-hearth furnace. The reaction temperature is 500℃ and the reaction time is 60min. The reaction produces a mixed gas containing aluminum chloride gas, carbon dioxide gas and excess carbon monoxide gas.

[0055] (3) The chlorination reaction of monazite-type rare earth concentrate occurs above the feed inlet in the middle of the two-stage multi-hearth furnace. The rare earth concentrate reacts with the mixed gas obtained from the reaction in the lower part of the multi-hearth furnace, and the chlorination reaction temperature is 600℃ and the reaction time is 120min. The rare earth chlorides, aluminum phosphate, calcium chloride and magnesium chloride generated by the chlorination reaction remain in the chlorination slag in solid form, while titanium tetrachloride, silicon tetrachloride and ferric chloride leave the two-stage multi-hearth furnace in gaseous form.

[0056] (4) The gaseous chlorination products are discharged from the outlet of the two-stage multi-hearth furnace and condensed and recovered in the condenser. The remaining tail gas, mainly carbon dioxide, is returned to the continuous packed bed as a raw material for reaction with carbon-containing raw materials. The solid products are discharged from the outlet of the two-stage multi-hearth furnace and separated by water leaching to obtain a mixed solution of aluminum fluoride solid, rare earth chloride, calcium chloride, and magnesium chloride. The mixed solution is then separated by extraction to obtain a single rare earth chloride with a mass fraction greater than 99.9%.

[0057] Using the aforementioned device, the carbon reaction efficiency in a continuous packed bed is 99%, the alumina chlorination efficiency in a two-stage multi-hearth furnace is 97%, and the rare earth element chlorination efficiency in rare earth concentrate is 96%.

[0058] Example 4

[0059] A device for the comprehensive utilization of monazite-type rare earth concentrate as described above, wherein 10 material platforms are specifically placed in the two-stage multi-hearth furnace reactor, with 6 platforms set at the upper part and 4 platforms set at the lower part of the feed inlet in the middle of the furnace body, and the distance between the material platforms is 25mm.

[0060] A method for comprehensive utilization of monazite-type rare earth concentrate, implemented using the aforementioned apparatus, includes the following specific operating steps:

[0061] (1) Coal gangue and carbon dioxide are added to the continuous packed bed. The coal gangue reacts with carbon dioxide gas to generate carbon monoxide. The resulting high-temperature carbon monoxide flue gas enters the multi-hearth furnace reactor through one of the inlets at the bottom of the multi-hearth furnace as a heat source and carbon source. The other inlet is connected to chlorine gas. The gases introduced through the two inlets are mixed by the bottom gas distributor and then introduced into the two-stage multi-hearth furnace. The reaction temperature in the continuous packed bed is 1100℃ and the reaction time is 30min. The ratio of the mass of carbon in the coal gangue to the total mass of alumina and rare earth concentrate is 8:1.

[0062] (2) Alumina raw material is added to the middle feed port of the two-section multi-hearth furnace and monazite-type rare earth concentrate is added to the top feed port of the two-section multi-hearth furnace. The mass ratio of alumina to rare earth concentrate is 0.5:1. The carbothermic chlorination reaction of alumina with excess chlorine and carbon monoxide mainly occurs at the lower part of the middle feed port of the two-section multi-hearth furnace. The reaction temperature is 600℃ and the reaction time is 5min. The reaction produces a mixed gas containing aluminum chloride gas, carbon dioxide gas and excess carbon monoxide gas.

[0063] (3) The chlorination reaction of monazite-type rare earth concentrate occurs above the feed inlet in the middle of the two-stage multi-hearth furnace: the rare earth concentrate reacts with the mixed gas obtained from the reaction in the lower part of the multi-hearth furnace, and the chlorination reaction temperature is 1000℃, and the reaction time is 30min. The rare earth chlorides, aluminum phosphate, calcium chloride, and magnesium chloride generated by the chlorination reaction remain in the chlorination slag in solid form, while titanium tetrachloride, silicon tetrachloride, and ferric chloride leave the two-stage multi-hearth furnace in gaseous form.

[0064] (4) The gaseous chlorination products are discharged from the outlet of the two-stage multi-hearth furnace and condensed and recovered in the condenser. The remaining tail gas, mainly carbon dioxide, is returned to the continuous packed bed as a raw material for reaction with carbon-containing raw materials. The solid products are discharged from the outlet of the two-stage multi-hearth furnace and separated by water leaching to obtain a mixed solution of aluminum fluoride solid, rare earth chloride, calcium chloride, and magnesium chloride. The mixed solution is then separated by extraction to obtain a single rare earth chloride with a mass fraction greater than 99.9%.

[0065] Using the aforementioned device, the carbon reaction efficiency in a continuous packed bed is 98%, the alumina chlorination efficiency in a two-stage multi-hearth furnace is 96%, and the rare earth element chlorination efficiency in rare earth concentrate is 95%.

Claims

1. A method for comprehensive utilization of monazite-type rare earth concentrate, characterized in that, Includes the following steps: (1) Carbon-containing raw materials and carbon dioxide are added to the continuous packed bed. The carbon raw materials react with carbon dioxide gas to generate carbon monoxide in the continuous packed bed. The resulting high-temperature carbon monoxide flue gas enters through one of the inlets at the bottom of the two-section multi-hearth furnace as a heat source and carbon source. The other inlet is connected to chlorine gas. The gas introduced through the two inlets is mixed by the bottom gas distributor and then introduced into the two-section multi-hearth furnace. (2) Alumina raw material is added at the middle feed inlet of the two-section multi-hearth furnace, and monazite-type rare earth concentrate is added at the top feed inlet of the two-section multi-hearth furnace; the carbothermic chlorination reaction mainly occurs at the lower part of the middle feed inlet of the two-section multi-hearth furnace, where alumina reacts with excess chlorine and carbon monoxide to produce a mixed gas containing aluminum chloride gas, carbon dioxide gas, and excess carbon monoxide gas; the reaction stoichiometric formula is: xAl2O3(s) + (3x+n) CO(g) + (3x+m) Cl2(g)=2xAlCl3(g)+3xCO2+ n CO(g)+m Cl2(g); (3) The chlorination reaction of monazite-type rare earth concentrate occurs at the upper part of the feed inlet in the middle of the two-section multi-hearth furnace: the mixed gas obtained by the reaction of rare earth concentrate and the lower part of the multi-hearth furnace undergoes chlorination reaction. The rare earth chloride, aluminum phosphate, calcium chloride and magnesium chloride generated by the chlorination reaction remain in the chlorination slag in solid form, while titanium tetrachloride, silicon tetrachloride and ferric chloride leave the two-section multi-hearth furnace in gaseous form. (4) The gaseous chlorination product is discharged from the outlet of the two-stage multi-hearth furnace and enters the condenser for condensation and recovery. The remaining tail gas is mainly carbon dioxide, which is returned to the continuous packed bed as a raw material for reaction with carbon-containing raw materials. The solid product is discharged from the outlet of the two-stage multi-hearth furnace and is separated by water leaching to obtain a mixed solution of aluminum fluoride solid and rare earth chloride, calcium chloride and magnesium chloride. The mixed solution is separated by extraction to obtain a single rare earth chloride.

2. The method for comprehensive utilization of monazite-type rare earth concentrate according to claim 1, characterized in that, In step (1), the reaction temperature in the continuous packed bed is 700~1100℃, the reaction time is 10~90min, and the ratio of the mass of carbon in the carbon-containing raw material to the total mass of alumina and rare earth concentrate is (2~10):

1.

3. The method for comprehensive utilization of monazite-type rare earth concentrate according to claim 1, characterized in that, In step (1), the carbon-containing raw material is one or more of coking coal, petroleum coke, biochar, coal gangue, coal gasification slag, and fly ash, wherein the mass fraction of carbon in coal gangue, coal gasification slag, and fly ash is greater than 5%, and the diameter of the material after crushing and grinding is less than 0.15 mm.

4. The method for comprehensive utilization of monazite-type rare earth concentrate according to claim 1, characterized in that, In step (2), monazite-type rare earth concentrate is added to the top feed port of the two-section multi-hearth furnace, with an alumina:rare earth concentrate ratio of (0.1 ~ 1):1 by mass. The lower part of the middle feed port of the two-section multi-hearth furnace mainly undergoes carbothermic chlorination reaction between alumina and excess chlorine and carbon monoxide, with a reaction temperature of 500~1000℃ and a reaction time of 5~60min.

5. The method for comprehensive utilization of monazite-type rare earth concentrate according to claim 1, characterized in that, In step (3), the chlorination reaction temperature is 600~1200℃ and the reaction time is 30~120min.

6. The method for comprehensive utilization of monazite-type rare earth concentrate according to claim 1, characterized in that, The apparatus used includes: a continuous packed bed, a two-section multi-hearth furnace reactor and a condenser; wherein, the two-section multi-hearth furnace reactor consists of a furnace body (8), a feed inlet (1), an air inlet (5), a material platform (4), a central shaft (7), a rake (3), a discharge outlet (6), an air outlet (2), and a gas distributor (9); wherein, airlocks are installed inside the feed inlet (1) and the discharge outlet (6) to achieve continuous unidirectional feeding or discharging of solids; the feed inlet (1) is installed at the top and middle of the furnace body (8), distributed symmetrically on both sides of the central axis, and the feed inlet in the middle of the furnace body divides the multi-hearth furnace into upper and lower sections; the discharge outlet (6) is installed at the bottom of the furnace body (8), distributed symmetrically on the central axis; the air inlet (5) and the air outlet (2) are respectively installed at the top and bottom of the furnace body (8), distributed symmetrically on both sides of the central axis; the feed inlet (1), the discharge outlet (6), the air inlet (5) and the air outlet (2) The material platform (4) is located inside the furnace body (8) and is connected to the inner wall of the furnace body (8) by bolts. The central shaft (7) is located in the center of the furnace body (8). The rake (3) is connected to the central shaft (7) by bolts. Rake teeth are evenly distributed on the rake arm. The length of the rake teeth gradually increases. The rake (3) rotates and moves the material layer under the drive of the central shaft (7). The material enters the multi-hearth furnace reactor from the feed port (1) at the top of the furnace body (8). Under the action of the rotating multi-hearth furnace rake (3) and the downward tilting multi-layer material platform (4), the material moves from the upper material platform to the lower material platform. After the reaction is completed, the product is discharged from the discharge port (6) at the bottom of the furnace body. The gas distributor (9) is installed at the bottom of the multi-hearth furnace and is connected to the two bottom air inlets respectively. The purpose is to mix the gas entering the multi-hearth furnace. The solid phase and the gas phase in the multi-hearth furnace react in a countercurrent manner during the heat exchange process.

7. The method for comprehensive utilization of monazite-type rare earth concentrate according to claim 6, characterized in that, The material platform (4) is set inside the furnace body (8) and is connected to the inner wall of the furnace body (8) by bolts. The connection angle is continuously adjustable within the range of 0°~5° and the distance between material platforms is 20~30mm.

8. The method for comprehensive utilization of monazite-type rare earth concentrate according to claim 6, characterized in that, The rake (3) and the central shaft (7) are connected by bolts. The connection angle is continuously adjustable within the range of 0° to 5°. The number of rake arms in the rake (3) is equal to the number of material platforms (4), and they can all be disassembled and increased or decreased according to the feeding situation. When the angle between the rake arm of the rake (3) and the central shaft (7) is 5°, all rake teeth are on the same plane.

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