Green and energy-saving preparation method of high-purity anhydrous aluminum trichloride

Abstract

The invention belongs to the field of chemical production, and provides a green and energy-saving preparation method of high-purity anhydrous aluminum trichloride, which comprises the following steps: S1, weighing and mixing: weighing an aluminum oxide raw material and a carbon source according to a ratio, uniformly mixing to form a mixed raw material, and conveying the mixed raw material to a fluidized bed furnace; the purity of the aluminum oxide raw material meets the following conditions: Al2O3 is not less than 75%; the carbon source and the alumina raw material are consistent in particle size distribution; s2, gas preheating; s3, boiling reaction; s4, impurity removal: high-temperature flue gas at the top of the fluidized bed furnace is subjected to dust removal through a cyclone separator and then enters an impurity remover; the high-temperature flue gas after impurity removal is further cooled to 260-400 DEG C and then enters a high-temperature filter to be filtered; s5, crystallization: the flue gas filtered by the high-temperature filter enters a continuous crystallizer; s6, tail gas treatment: washing and drying the tail gas at the outlet of the continuous crystallizer and then combusting as a heat source of the heat exchanger in the step S2; and combusted tail gas enters an alkali liquor absorption tower to be absorbed and recycled. According to the method disclosed by the invention, the high-purity anhydrous aluminum trichloride can be prepared with low cost, low energy consumption and high yield.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical industry, and particularly relates to a green and energy-saving preparation method of high-purity anhydrous aluminum chloride. Background Art

[0002] Anhydrous aluminum chloride, with the chemical formula AlCl3, is an odorless, colorless, transparent hexagonal flaky crystalline solid. Industrial anhydrous aluminum chloride often appears light yellow, yellow or light gray due to the presence of impurities such as iron, free chlorine, and free aluminum. It has a strong smell of hydrochloric acid and its melting point and boiling point are very low. When aluminum chloride vapor or dissolved in non-polar solvents or in a molten state, it exists in the form of covalent dimer molecules (Al2Cl6).

[0003] Anhydrous aluminum chloride is an indispensable catalyst in organic synthesis reactions and is commonly used in synthetic resins, synthetic rubber, petroleum cracking, synthetic dyes, synthetic detergents, medicines, fragrances, pesticides, etc. In addition, anhydrous aluminum chloride can also be used to prepare aluminum-containing organic compounds, as a metal refining and lubricating oil processing, etc.

[0004] The existing domestic production processes for anhydrous aluminum chloride mainly include the aluminum ingot method and the alumina powder method.

[0005] Aluminum ingot method: also known as the metal aluminum method, which is to pass chlorine directly through molten metal aluminum, and the two directly contact and react to produce anhydrous aluminum chloride. It is the mainstream process for producing anhydrous aluminum chloride in China. The reaction equation is:

[0006] 2Al+3Cl2=2AlCl3

[0007] The reaction temperature of this reaction is generally controlled at about 800°C. The gas phase product anhydrous aluminum chloride enters the product collector at about 400°C, and is naturally condensed and crystallized to obtain anhydrous aluminum chloride product. The tail gas is washed and absorbed by dilute alkali and then discharged.

[0008] The aluminum ingot method for producing anhydrous aluminum chloride has the advantages of short process, less equipment, and simple operation. Normal production relies on reaction heat to maintain the process temperature, and no additional heat source is required. Overall, the aluminum ingot method is mature and stable. However, the aluminum source of this method is metallic aluminum, which leads to relatively high production costs. At the same time, it is easy to generate by-products such as aluminum monochloride and aluminum dichloride, reducing the purity of the product. In addition, in order to reduce the cost of raw materials, some impurities are often used as raw materials in production, but due to the complex composition of the impurity raw materials, there will be more impurities in the product.

[0009] Alumina method: The alumina method uses alumina as the aluminum source, chlorine as the chlorinating agent, and carbon as the reducing agent to produce anhydrous aluminum chloride by a chlorination reaction at high temperature. The reactor used can be a fixed bed or a fluidized bed. The reaction equation is:

[0010] Al2O3+(m+n)C+3Cl2=2AlCl3+mCO+nCO2

[0011] Compared with the aluminum ingot method, the alumina method has the obvious advantage of low raw material prices; however, it has problems such as complex process flow and multiple equipment.

[0012] In order to reduce the cost of raw materials, more and more existing technologies choose to use alumina method to prepare anhydrous aluminum chloride. However, there is an obvious problem of high impurity content of the product when preparing aluminum chloride by alumina method. The existing technology is mainly divided into two categories of technologies to solve the problem of high impurity content of the product: (1) using high-purity aluminum oxide as raw material and sacrificing the yield of high-purity aluminum chloride product to a certain extent to achieve the purpose of preparing high-purity aluminum chloride, such as the method disclosed in patent CN109942013A, by setting three-stage collection, the quality of aluminum chloride product is further subdivided to ensure the purity of aluminum chloride in the middle stage, and the remaining two stages are used as low-purity products. The cost advantage of raw materials in this way is not obvious, and the yield of high-purity products is low, and the production capacity is low; (2) using low-purity aluminum oxide as raw material and adding impurity removal process flow in the whole process flow, such as the method disclosed in patent CN111661861A, after preparing aluminum chloride product, continue to re-sublimate and purify the product, this method will undoubtedly increase the reaction process, increase equipment cost and product production fixed cost.

[0013] In summary, how to use the alumina method to prepare aluminum trichloride at low cost is an important issue that the industry needs to solve at present. In particular, how to use low-purity alumina as a raw material to prepare high-purity aluminum trichloride at low cost and high yield is a key issue to be solved in promoting the industrialization of the alumina method. Summary of the invention

[0014] The invention provides a green and energy-saving preparation method of high-purity anhydrous aluminum chloride, which can realize the preparation of high-purity anhydrous aluminum chloride with low cost, low energy consumption and high yield.

[0015] The present invention achieves the above object through the following technical solutions:

[0016] The present invention provides a green and energy-saving preparation method of high-purity anhydrous aluminum chloride, comprising the following steps:

[0017] A green and energy-saving preparation method of high-purity anhydrous aluminum chloride comprises the following steps:

[0018] S1 weighing and mixing: weighing alumina raw materials and carbon sources in proportion and uniformly mixing them to form a mixed raw material, and transporting the mixed raw material to a boiling furnace by pneumatic conveying; wherein the mass ratio of the alumina raw material and the carbon source satisfies m(Al2O3):m(C)=1:0.3-1; the purity of the alumina raw material satisfies: Al2O3≥75%;

[0019] The particle size distribution of the carbon source satisfies the following conditions by mass: 40-100 mesh accounts for 20%-25%; 100-250 mesh accounts for 40%-60%; 250-350 mesh accounts for 20-40%; the particle size distribution of the alumina raw material satisfies the following conditions by mass: 40-100 mesh accounts for 20%-25%; 100-250 mesh accounts for 40%-60%; 250-350 mesh accounts for 20-40%;

[0020] S2 gas preheating: liquid chlorine is gasified and preheated by the heat exchanger before entering the boiling furnace;

[0021] S3 boiling reaction: the mixed raw material in step S1 and the gas preheated in step S2 react in a boiling furnace, the generated high-temperature flue gas is discharged from the top of the boiling furnace, and the generated slag is regularly discharged from the slag discharge port at the bottom of the boiling furnace;

[0022] S4 impurity removal: the high-temperature flue gas at the top of the boiling furnace in step S3 is dusted by a cyclone separator and then enters a de-dusting device, where it is mixed with a reducing agent for impurity removal; the high-temperature flue gas after impurity removal is further cooled to 260-400°C and then enters a high-temperature filter for filtration;

[0023] S5 crystallization: the flue gas filtered by the high temperature filter in step S4 enters a continuous crystallizer, and the outlet temperature of the continuous crystallizer is controlled to be 150-170°C;

[0024] S6 Tail gas treatment: The tail gas at the outlet of the continuous crystallizer in step S5 is washed by a primary water washing tower and a primary alkali washing tower and then enters a dryer for drying and dehydration. The dehydrated tail gas is burned as a heat source for the heat exchanger in step S2; the burned tail gas enters an alkali liquid absorption tower for absorption and recovery.

[0025] Preferably, the alumina of the present invention can be industrial alumina, or gibbsite-type, boehmite-type, or diaspore-type alumina. The lower the purity of the alumina, the higher the efficiency of the entire system.

[0026] Preferably, the carbon source of the present invention is selected from calcined coke or biomass carbon, and more preferably, the carbon source of the present invention is calcined coke.

[0027] The present invention achieves the purpose of preparing anhydrous aluminum chloride by the alumina method by sequentially carrying out the steps of weighing and mixing, gas preheating, boiling reaction, impurity removal, crystallization and tail gas treatment. After the raw materials are weighed and mixed, they are put into the boiling furnace together with the preheated gas for reaction. After the reaction is finished, the high-temperature flue gas is heat exchanged and dusted by the cyclone dust collector and then enters the impurity remover. In the impurity remover, it is mixed with the reducing agent to react to remove unreacted chlorine and reduce the trivalent iron to divalent iron (ferrous chloride). Subsequently, the divalent iron and the unreacted reducing agent and other impurities are filtered and removed through a high-temperature filter. Subsequently, the high-temperature flue gas enters the continuous crystallizer for crystallization to prepare aluminum chloride solid. The main components of the tail gas coming out of the continuous crystallizer are CO and CO2. The tail gas is dried and dehydrated after primary water washing and primary alkali washing. The main component is CO, which is sent to the heat exchanger of step S2 for combustion to preheat the chlorine; and the generated CO2 enters the alkali washing tower for absorption to form carbonate, completing the whole process.

[0028] More importantly, the present invention achieves the purpose of preparing high-purity anhydrous aluminum chloride with energy saving and low consumption by using relatively low-purity aluminum oxide as a raw material through the process design in each step. Specifically: the present invention designs the particle size distribution of two raw materials, aluminum oxide raw material and carbon source, to ensure that both have appropriate particle size distribution on the one hand and consistent particle size distribution on the other hand.

[0029] First, the particle size distribution of the present invention adopts a ratio of 40-100 meshes accounting for 20%-25%; 100-250 meshes accounting for 40%-60%; 250-350 meshes accounting for 20%-40%, in order to: (1) enable the particles to form an optimal flow state after entering the boiling furnace, without obvious stratification between particles of different particle sizes, and without dead zones in the bed layer, so that the gas-solid phase can fully contact during the reaction; (2) a sufficient amount of 250-350 mesh fine particle size raw materials are provided, and after entering the boiling furnace, the fine particle size will stay in The upper layer is fully in contact with the chlorine in the upper layer and reacts quickly, which helps to consume the low concentration of chlorine in the upper bed layer and reduce the chlorine concentration in the tail gas; (3) If the proportion of fine particles in the raw material is too large, the residence time of the raw material as a whole in the boiling furnace is insufficient and it is easy to blow out. If the proportion of fine particles is too small, it will cause low reaction efficiency, less reaction heat, large heat loss, and higher demand for external heat source. Therefore, the present invention designs the above-mentioned reasonable particle size distribution to ensure that the fluctuation of the bed temperature is small enough without affecting the reaction efficiency and production capacity.

[0030] More importantly, in order to achieve the purpose of using low-purity alumina raw material as an aluminum source to prepare high-purity anhydrous aluminum chloride, the present invention maintains the consistency of the proportion of different particle sizes of two solid-phase reaction raw materials, alumina and carbon source, on the basis of maintaining the above-mentioned particle size distribution; in this way, the position distribution of alumina and carbon source of the same particle size in the boiling furnace will remain consistent, so that the two solid-phase raw materials of the same particle size can fully contact when entering the bed, and can quickly complete the reaction with the participation of chlorine after entering the bed; since the activity of alumina in the alumina raw material is much higher than that of impurity oxides (such as silicon oxide, calcium oxide, etc.), after the two solid-phase raw materials contact, the alumina in the alumina raw material quickly participates in the reaction, and after the reaction, the particle size becomes smaller and is directly blown out of the boiling furnace, so that other impurity oxides are directly blown out in the form of oxides before participating in the reaction, and these blown oxide solid phases will be filtered and retained in the subsequent high-temperature filter, so that the impurity oxides in the alumina raw material will not enter the final aluminum chloride product and affect the purity of the aluminum chloride.

[0031] Further preferably, step S2 of the present invention further includes preheating oxygen before entering the boiling furnace; in step S3, the mixed raw material of step S1 and the preheated chlorine and preheated oxygen of step S2 react together in the boiling furnace; the volume ratio of the chlorine and the oxygen satisfies: 1:0.35~1.

[0032] In order to further prevent other impurity oxides from participating in the carbonization and chlorination reaction in the fluidized bed furnace and entering the high-temperature flue gas, the present invention also adds oxygen to the fluidized bed furnace, so as to construct an oxidizing environment in the fluidized bed furnace through this operation to inhibit the carbonization and chlorination reaction of the impurity oxides. It should be noted that since the carbonization and chlorination reaction of metal oxides in the presence of a carbon source and chlorine is a reduction reaction, the presence of oxygen will to a certain extent construct an oxidizing environment and thus affect the reduction reaction. Therefore, the present invention controls the amount of oxygen to meet V chlorine: V oxygen = 1: 0.35 ~ 1. Under this amount, the reduction reaction of aluminum oxide with a higher content is not affected, while the reduction reaction of impurity oxides with a lower content is inhibited, further reducing the impurity content in the product and ensuring the purity of the product.

[0033] At the same time, the addition of oxygen into the boiling furnace will directly burn with the carbon source to generate heat, which supplements the heat required for material heating and equipment heat dissipation during equipment operation, greatly reducing the energy consumption and implementation difficulty of external heating (such as electric heating).

[0034] The top outlet of the fluidized bed furnace of the present invention is connected to the cyclone separator, and the mixed raw material in step S1 enters the fluidized bed furnace from the cyclone separator; in step S4, the high-temperature flue gas at the top of the fluidized bed furnace is mixed with the mixed raw material for heat exchange in the cyclone separator; solid materials with a particle size greater than S in the cyclone separator are collected and returned from the top of the fluidized bed furnace to the fluidized bed furnace; wherein S is 650-1100 mesh. In the present application, the temperature in the fluidized bed furnace is controlled to be 700-950°C, and the temperature of the mixed raw material and the high-temperature flue gas after heat exchange from the cyclone separator can reach 500-700°C.

[0035] In step S1, the weighed mixed material is pneumatically conveyed to the cyclone separator at the top of the boiling furnace by nitrogen. The high-temperature flue gas in the boiling furnace also enters the cyclone separator after being blown out of the boiling furnace. The mixed raw material and the high-temperature flue gas are in direct contact in the cyclone separator and in the pipeline between the cyclone separator and the boiling furnace, so that the mixed raw material is rapidly heated to a certain temperature (500-700°C) in a short time, and the high-temperature flue gas is rapidly cooled to a certain temperature (500-700°C) in a short time; through this operation, the heat utilization rate of the system can be greatly improved, saving the heat for preheating the raw materials and the circulating water required for cooling the high-temperature flue gas.

[0036] More importantly, when the mixed material enters the boiling furnace through the cyclone separator, the water and low-boiling-point substances entrained in the material will evaporate rapidly, especially when gibbsite, boehmite, diaspore alumina and calcined coke are used as raw materials, the low-boiling-point substances and water in the material will also evaporate rapidly in this process. In this process, since there is no chlorine gas or only a small amount of chlorine gas overflowing from the top of the boiling furnace, the probability of generating corrosive hydrogen chloride is greatly reduced, and the problem of equipment corrosion is effectively improved.

[0037] At the same time, by controlling the particle size of the dust collected by the cyclone separator, on the one hand, the impurity oxides that do not participate in the reaction (with extremely small particle size, less than 650-1100 mesh) can be discharged from the system in time, and on the other hand, the excess unreacted carbon source in the boiling furnace can be recycled, greatly improving the utilization rate of the raw materials.

[0038] Further preferably, in step S2, chlorine is preheated to 400-700°C and then enters the boiling furnace from the bottom of the boiling furnace; oxygen is preheated to 400-700°C and then enters the boiling furnace from the top of the boiling furnace.

[0039] Chlorine enters the boiling furnace from the bottom, and the raw materials with larger particles at the bottom participate in the reaction first. Oxygen enters the boiling furnace from the top, so that the reaction of the impurity oxides in the fine particles of the raw materials at the top is suppressed first. This ensures that both the promotion reaction (main reaction) and the inhibition reaction (side reaction) can proceed at the best time and in the best state, thereby improving the overall reaction rate and product purity.

[0040] After the reaction is completed, the high-temperature flue gas is cooled to 500-700°C after heat exchange with the mixed raw materials in the cyclone separator. The high-temperature flue gas of 500-700°C is passed into the impurity remover and first mixed with the reducing agent in the impurity remover. The reducing agent in step S4 is selected from aluminum powder, hydrogen or iron powder, preferably aluminum powder. The reducing agent will react with the free chlorine in the flue gas and reduce the trivalent iron ions in the flue gas to divalent iron and be intercepted after passing through the high-temperature filter to reduce the impurity content in the product. Specifically, the particle size of the aluminum powder used in the present invention is 200-300 mesh, and the amount of aluminum powder added is 50% to 100% of the sum of the free chlorine and iron ion contents to be reacted.

[0041] Specifically, the impurity remover of the present invention is of cyclone counterflow + pipeline baffle type, that is, high-temperature flue gas enters from the bottom of the pipeline, aluminum powder enters from the top of the pipeline, and multiple baffles are arranged inside the pipeline impurity remover, so that aluminum powder and high-temperature flue gas can be fully contacted, and the reaction and impurity removal are more complete.

[0042] In step S4, the temperature of the high-temperature flue gas coming out of the impurity remover is 450-650°C. The high-temperature flue gas is first cooled to 260-400°C by a U-type cooler, and then enters the adsorption drying device and then the high-temperature filter; in step S5, the tail gas at the outlet of the continuous crystallizer first enters the adsorption drying device and then enters the primary water washing tower. The adsorption drying device adsorbs the low-boiling point metal chlorides and other volatile substances generated during the cooling process to separate them from the product.

[0043] The high-temperature filter in step S4 of the present invention performs heat preservation filtration, and the temperature difference of the gas entering and leaving the filter does not exceed 10°C, and cannot be lower than 260°C, so as to ensure that the temperature change of the flue gas passing through the high-temperature filter is small, and thus low-boiling point metal chlorides and other impurities will not precipitate to affect the filtering effect of the filter; and the filtration accuracy of the high-temperature filter of the present invention is 5-10μm, which can remove the solid phase impurities generated in the above steps and the unreacted impurity oxides mixed in the high-temperature flue gas.

[0044] In particular, in step S5 of the present invention, the flue gas is subjected to gradient cooling crystallization in a continuous crystallizer, wherein the outlet temperature of the first stage crystallization is 220-240°C, the outlet temperature of the second stage crystallization is 160-200°C, and the outlet temperature of the third stage crystallization is 150-170°C; and in step S5, the pressure in the continuous crystallizer is controlled to be less than 10KPa.

[0045] Specifically, the continuous crystallizer of the present invention is a screw-propelled continuous crystallizer.

[0046] In the temperature range of the first crystallization, the impurities that were not condensed in the impurity removal step are further condensed and removed; in the temperature range of the second crystallization, aluminum chloride begins to crystallize in large quantities; in the temperature range of the third crystallization, it further crystallizes in large quantities to form products. Through step cooling, the appropriate crystallization rate is guaranteed, the grain size is appropriate, and the quality and output of the product are improved; at the same time, the temperature at the outlet of the continuous crystallizer is controlled to be no less than 150°C and the pressure is less than 10KPa (gauge pressure), which prevents low-boiling impurities such as oxides, chlorides and water from condensing into the product.

[0047] Preferably, in step S6, the exhaust gas after combustion enters an alkali liquid absorption tower, the alkali liquid in the alkali liquid absorption tower is 30-40% KOH, the temperature is 80-90°C, the gas stays in the tower for 12-15s, the CO2 absorption rate reaches 90%, and the absorption liquid is spray-dried to produce industrial potassium carbonate.

[0048] The beneficial effects of the present invention are:

[0049] 1. The present invention achieves the purpose of controlling the reaction rate and the degree of reaction by controlling the particle size distribution of the raw material solid phase, and ultimately achieves the purpose of improving the reaction efficiency, the yield and the purity of the product.

[0050] 2. The present invention forms an oxidizing environment in the fluidized bed furnace by adding oxygen in a volume ratio of 0.35-1:1 to chlorine to suppress the chlorination carbonization reaction of impurity oxides with low reaction activity, thereby further improving the purity of the product; at the same time, the addition of oxygen can also maintain the temperature in the fluidized bed furnace stable through combustion, reducing the demand for external heating.

[0051] 3. The present invention adds chlorine from the bottom of the boiling furnace and oxygen from the top of the boiling furnace. The migration path and distribution law of chlorine in the boiling furnace match the distribution law of raw materials with different particle sizes and the law of the reaction, which can effectively control the reaction process, improve the reaction efficiency and reduce the generation of impurities.

[0052] 4. The present invention mixes the raw materials, exchanges heat with high-temperature flue gas through a cyclone separator, and then adds them to a boiling furnace, which can effectively save the energy consumption of raw material preheating and can recover the carbon source that does not participate in the reaction to a certain extent; at the same time, by feeding from the cyclone separator, the risk of water in the raw materials forming hydrogen chloride to corrode equipment is greatly reduced.

[0053] 5. The present invention removes other metal impurities such as iron ions and free chlorine in the flue gas by adding a reducing agent, and removes unreacted solid powder through a high-temperature filter, further reducing the possibility of impurities entering the product, and the product purity is higher and the quality is better.

[0054] 6. The present invention achieves the purpose of further purifying the product and controlling the particle size of the product through step-by-step cooling crystallization.

[0055] 7. The present invention uses CO in the tail gas as a heat source for preheating chlorine and oxygen, greatly reducing external heating energy consumption.

[0056] 8. The present invention absorbs CO2 in the tail gas and CO2 generated after combustion through KOH to form an industrial potassium carbonate product, which greatly increases the added value of the product and reduces carbon emissions.

[0057] 9. The entire process of the present invention is simple, and no re-sublimation and desublimation process is added. Through the continuous design of each process step and the detailed design of each process step, the purity of the product is guaranteed while ensuring the product production capacity, which greatly reduces the investment in equipment and the energy consumption of the reaction process, and achieves the purpose of preparing high-purity products in an energy-saving and low-carbon manner.

[0058] 10. The present invention adopts boiling chlorination process, and the maximum production capacity of a single set can reach 50,000 tons / year, and the investment per ton of equipment and land cost are greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 This is a process flow chart of the green and energy-saving preparation method of high-purity anhydrous aluminum chloride in Example 1 of the present application. DETAILED DESCRIPTION

[0060] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the present invention is further described below in conjunction with specific embodiments. For those without specific conditions in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are followed. The exemplary embodiments can be implemented in various forms and should not be construed as being limited to the examples described herein; on the contrary, these embodiments are provided so that the present invention will be more comprehensive and complete, and the concept of the exemplary embodiments will be fully conveyed to those skilled in the art.

[0061] Example 1

[0062] This embodiment provides a green and energy-saving preparation method of high-purity anhydrous aluminum chloride, comprising the following steps:

[0063] S1 weighing and mixing: weighing industrial alumina (Al2O3 content 99.2%) and calcined coke (C content 91.5%) in proportion and uniformly mixing them to form a mixed raw material, and transporting the mixed raw material to the cyclone separator at the top of the boiling furnace by nitrogen pneumatic conveying; wherein the mass ratio of industrial alumina and calcined coke is converted into Al2O3 and C, satisfying m(Al2O3):m(C)=1:0.5;

[0064] The particle size distribution of calcined coke meets the following requirements by mass: 40-100 mesh accounts for 20%; 100-250 mesh accounts for 60%; 250-350 mesh accounts for 20%; the particle size distribution of industrial alumina meets the following requirements by mass: 40-100 mesh accounts for 20%; 100-250 mesh accounts for 60%; 250-350 mesh accounts for 20%.

[0065] S2 gas preheating: liquid chlorine is gasified and preheated to 700℃ by heat exchanger before entering the fluidized bed furnace from the bottom; oxygen is prepared by oxygen generator and preheated to 700℃ by heat exchanger before entering the fluidized bed furnace from the top; the volume ratio of chlorine and oxygen meets the requirement of 1:0.35.

[0066] S3 boiling reaction: after the mixed raw materials in step S1 are heat-exchanged with the high-temperature flue gas discharged from the top of the boiling furnace in the cyclone separator, the solid phase with a particle size larger than 650 mesh is collected and enters the boiling furnace from the top of the boiling furnace, and reacts with the chlorine gas and oxygen preheated in step S2 in the boiling furnace, the generated high-temperature flue gas is discharged from the top of the boiling furnace, and the generated slag is regularly discharged from the slag discharge port at the bottom of the boiling furnace;

[0067] Among them, the temperature of the solid phase collected by the cyclone separator is 670°C, and the temperature of the high-temperature flue gas coming out of the cyclone separator is 690°C; the chlorine gas velocity is 0.15m / s, and the gas velocity of chlorine and the gas velocity of oxygen meet: 1:0.5; the reaction temperature in the boiling furnace is 935°C.

[0068] S4 impurity removal: the high-temperature flue gas at the top of the boiling furnace in step S3 is cooled to 690°C after heat exchange and dust removal with the mixed raw materials in step S1 by the cyclone separator. The 690°C high-temperature flue gas enters from the bottom of the pipeline impurity remover and is fully mixed with the aluminum powder entering from the top of the pipeline impurity remover for impurity removal. The pipeline impurity remover is also evenly provided with baffles; the high-temperature flue gas after impurity removal is further cooled to 400°C by the U-type cooler and then enters the adsorption drying device to remove the liquid phase. The high-temperature flue gas coming out of the adsorption drying device enters the high-temperature filter for filtration; the high-temperature filter device is kept warm at 400°C, and the filtration accuracy of the high-temperature filter is 5μm;

[0069] S5 crystallization: the flue gas filtered by the high temperature filter in step S4 enters a screw-propelled continuous crystallizer for step-by-step cooling crystallization, wherein the first stage crystallization outlet temperature is 235°C, the second stage crystallization outlet temperature is 183°C, and the third stage crystallization outlet temperature is 170°C; and in step S5, the pressure in the continuous crystallizer is controlled to be less than 10KPa;

[0070] S6 tail gas treatment: the tail gas from the outlet of the continuous crystallizer in step S5 is washed by a primary water washing tower and a primary alkali washing tower respectively, and then enters a dryer for drying and dehydration. The dehydrated tail gas is burned as a heat source for the heat exchanger in step S2; the burned tail gas enters an alkali liquid absorption tower for absorption and recovery; the alkali liquid in the alkali liquid absorption tower is 40% KOH, the temperature is 80-90°C, the gas stays in the tower for 15s, and after the absorption is completed, the absorption liquid is spray dried to obtain industrial potassium carbonate.

[0071] After the system of this embodiment runs stably, the purity of aluminum trichloride prepared is 99.93%; the conversion rate (or yield) of aluminum oxide is 99.5%.

[0072] Example 2

[0073] This embodiment provides a green and energy-saving preparation method of high-purity anhydrous aluminum chloride, comprising the following steps:

[0074] S1 weighing and mixing: weighing industrial alumina (Al2O3 content 99.2%) and calcined coke (C content 91.5%) in proportion and uniformly mixing to form a mixed raw material, and transporting the mixed raw material to the cyclone separator at the top of the boiling furnace by nitrogen pneumatic conveying; wherein the mass ratio of industrial alumina and calcined coke is converted into Al2O3 and C, satisfying m(Al2O3):m(C)=1:0.59;

[0075] The particle size distribution of calcined coke meets the following requirements by mass: 40-100 mesh accounts for 20%; 100-250 mesh accounts for 60%; 250-350 mesh accounts for 20%; the particle size distribution of industrial alumina meets the following requirements by mass: 40-100 mesh accounts for 20%; 100-250 mesh accounts for 60%; 250-350 mesh accounts for 20%.

[0076] S2 gas preheating: liquid chlorine is gasified and preheated to 600℃ by heat exchanger before entering the fluidized bed furnace from the bottom; oxygen is prepared by oxygen generator and preheated to 600℃ by heat exchanger before entering the fluidized bed furnace from the top; the volume ratio of chlorine and oxygen meets the requirement of 1:0.5.

[0077] S3 boiling reaction: after the mixed raw materials in step S1 are heat-exchanged with the high-temperature flue gas discharged from the top of the boiling furnace in the cyclone separator, the solid phase with a particle size larger than 650 mesh is collected and enters the boiling furnace from the top of the boiling furnace, and reacts with the chlorine gas and oxygen preheated in step S2 in the boiling furnace, the generated high-temperature flue gas is discharged from the top of the boiling furnace, and the generated slag is regularly discharged from the slag discharge port at the bottom of the boiling furnace;

[0078] Among them, the temperature of the solid phase collected by the cyclone separator is 630°C, and the temperature of the high-temperature flue gas coming out of the cyclone separator is 650°C; the chlorine gas velocity is 0.15m / s, and the gas velocity of chlorine and the gas velocity of oxygen meet: 1:0.5; the reaction temperature in the boiling furnace is 900°C.

[0079] S4 impurity removal: the high-temperature flue gas at the top of the boiling furnace in step S3 is cooled to 630°C after heat exchange and dust removal with the mixed raw materials in step S1 by the cyclone separator. The 650°C high-temperature flue gas enters from the bottom of the pipeline impurity remover and is fully mixed with the aluminum powder entering from the top of the pipeline impurity remover for impurity removal. The pipeline impurity remover is also evenly provided with baffles; the high-temperature flue gas after impurity removal is further cooled to 400°C by the U-type cooler and then enters the adsorption drying device to remove the liquid phase. The high-temperature flue gas coming out of the adsorption drying device enters the high-temperature filter for filtration; the high-temperature filter device is kept warm at 400°C, and the filtration accuracy of the high-temperature filter is 5μm;

[0080] S5 crystallization: the flue gas filtered by the high temperature filter in step S4 enters a screw-propelled continuous crystallizer for step-by-step cooling crystallization, wherein the first stage crystallization outlet temperature is 235°C, the second stage crystallization outlet temperature is 180°C, and the third stage crystallization outlet temperature is 155°C; and in step S5, the pressure in the continuous crystallizer is controlled to be less than 10KPa;

[0081] S6 tail gas treatment: the tail gas from the outlet of the continuous crystallizer in step S5 is washed by a primary water washing tower and a primary alkali washing tower respectively, and then enters a dryer for drying and dehydration. The dehydrated tail gas is burned as a heat source for the heat exchanger in step S2; the burned tail gas enters an alkali liquid absorption tower for absorption and recovery; the alkali liquid in the alkali liquid absorption tower is 40% KOH, the temperature is 80-90°C, the gas stays in the tower for 15s, and after the absorption is completed, the absorption liquid is spray dried to obtain industrial potassium carbonate.

[0082] After the system of this embodiment runs stably, the purity of aluminum trichloride prepared is 99.89%; the conversion rate (or yield) of aluminum oxide is 99.4%.

[0083] Example 3

[0084] This embodiment provides a green and energy-saving preparation method of high-purity anhydrous aluminum chloride, comprising the following steps:

[0085] S1 weighing and mixing: weighing gibbsite alumina (Al2O3 content 75.2%) and calcined coke (C content 91.5%) in proportion and uniformly mixing to form a mixed raw material, and transporting the mixed raw material to the cyclone separator at the top of the boiling furnace by nitrogen pneumatic conveying; wherein the mass ratio of industrial alumina and calcined coke is converted into Al2O3 and C, satisfying m(Al2O3):m(C)=1:0.88;

[0086] The particle size distribution of calcined coke meets the following requirements by mass: 40-100 mesh accounts for 20%; 100-250 mesh accounts for 50%; 250-350 mesh accounts for 30%; the particle size distribution of industrial alumina meets the following requirements by mass: 40-100 mesh accounts for 20%; 100-250 mesh accounts for 50%; 250-350 mesh accounts for 30%.

[0087] S2 gas preheating: liquid chlorine is gasified and preheated to 500℃ by heat exchanger before entering the fluidized bed furnace from the bottom; oxygen is prepared by oxygen generator and preheated to 500℃ by heat exchanger before entering the fluidized bed furnace from the top; the volume ratio of chlorine and oxygen meets the requirement of 1:1.

[0088] S3 boiling reaction: after the mixed raw materials in step S1 are heat-exchanged with the high-temperature flue gas discharged from the top of the boiling furnace in the cyclone separator, the solid phase with a particle size larger than 1100 mesh is collected and enters the boiling furnace from the top of the boiling furnace, and reacts with the chlorine gas and the preheated oxygen preheated in step S2 in the boiling furnace, the generated high-temperature flue gas is discharged from the top of the boiling furnace, and the generated slag is regularly discharged from the slag discharge port at the bottom of the boiling furnace;

[0089] Among them, the temperature of the solid phase collected by the cyclone separator is 590°C, and the temperature of the high-temperature flue gas coming out of the cyclone separator is 620°C; the chlorine gas velocity is 0.12m / s, and the gas velocity of chlorine and the gas velocity of oxygen meet: 1:0.8; the reaction temperature in the boiling furnace is 880°C.

[0090] S4 impurity removal: the high-temperature flue gas at the top of the boiling furnace in step S3 is cooled to 620°C after heat exchange and dust removal with the mixed raw materials in step S1 by the cyclone separator. The 620°C high-temperature flue gas enters from the bottom of the pipeline impurity remover and is fully mixed with the aluminum powder entering from the top of the pipeline impurity remover for impurity removal. The pipeline impurity remover is also evenly provided with baffles; the high-temperature flue gas after impurity removal is further cooled to 300°C by the U-type cooler and then enters the adsorption drying device to remove the liquid phase. The high-temperature flue gas coming out of the adsorption drying device enters the high-temperature filter for filtration; the high-temperature filter device is kept warm at 300°C, and the filtration accuracy of the high-temperature filter is 10μm;

[0091] S5 crystallization: the flue gas filtered by the high temperature filter in step S4 enters a screw-propelled continuous crystallizer for step-by-step cooling crystallization, wherein the first stage crystallization outlet temperature is 220°C, the second stage crystallization outlet temperature is 180°C, and the third stage crystallization outlet temperature is 160°C; and in step S5, the pressure in the continuous crystallizer is controlled to be less than 10KPa;

[0092] S6 tail gas treatment: the tail gas from the outlet of the continuous crystallizer in step S5 is washed by a primary water washing tower and a primary alkali washing tower respectively, and then enters a dryer for drying and dehydration. The dehydrated tail gas is burned as a heat source for the heat exchanger in step S2; the burned tail gas enters an alkali liquid absorption tower for absorption and recovery; the alkali liquid in the alkali liquid absorption tower is 40% KOH, the temperature is 80-90°C, the gas stays in the tower for 15s, and after the absorption is completed, the absorption liquid is spray dried to obtain industrial potassium carbonate.

[0093] After the system of this embodiment runs stably, the purity of aluminum trichloride prepared is 99.76%; the conversion rate (or yield) of aluminum oxide is 98.7%.

[0094] Example 4

[0095] This embodiment provides a green and energy-saving preparation method of high-purity anhydrous aluminum chloride, comprising the following steps:

[0096] S1 weighing and mixing: weighing gibbsite alumina (Al2O3 content 75.2%) and calcined coke (C content 91.5%) in proportion and uniformly mixing to form a mixed raw material, and transporting the mixed raw material to the cyclone separator at the top of the boiling furnace by nitrogen pneumatic conveying; wherein the mass ratio of industrial alumina and calcined coke is converted into Al2O3 and C, satisfying m(Al2O3):m(C)=1:0.53;

[0097] The particle size distribution of calcined coke meets the following requirements by mass: 40-100 mesh accounts for 20%; 100-250 mesh accounts for 50%; 250-350 mesh accounts for 30%; the particle size distribution of industrial alumina meets the following requirements by mass: 40-100 mesh accounts for 20%; 100-250 mesh accounts for 50%; 250-350 mesh accounts for 30%.

[0098] S2 gas preheating: liquid chlorine is gasified and preheated to 550℃ by heat exchanger and then enters the boiling furnace from the bottom of the boiling furnace; oxygen is prepared by oxygen generator and preheated to 550℃ by heat exchanger and then enters the boiling furnace from the top of the boiling furnace; the volume ratio of chlorine and oxygen meets the requirement of 1:0.4.

[0099] S3 boiling reaction: after the mixed raw materials in step S1 are heat-exchanged with the high-temperature flue gas discharged from the top of the boiling furnace in the cyclone separator, the solid phase with a particle size larger than 1100 mesh is collected and enters the boiling furnace from the top of the boiling furnace, and reacts with the chlorine gas and the preheated oxygen preheated in step S2 in the boiling furnace, the generated high-temperature flue gas is discharged from the top of the boiling furnace, and the generated slag is regularly discharged from the slag discharge port at the bottom of the boiling furnace;

[0100] Among them, the temperature of the solid phase collected by the cyclone separator is 590°C, and the temperature of the high-temperature flue gas coming out of the cyclone separator is 620°C; the chlorine gas velocity is 0.12m / s, and the gas velocity of chlorine and the gas velocity of oxygen meet: 1:0.8; the reaction temperature in the boiling furnace is 920°C.

[0101] S4 impurity removal: the high-temperature flue gas at the top of the boiling furnace in step S3 is cooled to 620°C after heat exchange and dust removal with the mixed raw materials in step S1 by the cyclone separator. The 620°C high-temperature flue gas enters from the bottom of the pipeline impurity remover and is fully mixed with the aluminum powder entering from the top of the pipeline impurity remover for impurity removal. The pipeline impurity remover is also evenly provided with baffles; the high-temperature flue gas after impurity removal is further cooled to 300°C by the U-type cooler and then enters the adsorption drying device to remove the liquid phase. The high-temperature flue gas coming out of the adsorption drying device enters the high-temperature filter for filtration; the high-temperature filter device is kept warm at 300°C, and the filtration accuracy of the high-temperature filter is 10μm;

[0102] S5 crystallization: the flue gas filtered by the high temperature filter in step S4 enters a screw-propelled continuous crystallizer for step-by-step cooling crystallization, wherein the first stage crystallization outlet temperature is 225°C, the second stage crystallization outlet temperature is 180°C, and the third stage crystallization outlet temperature is 160°C; and in step S5, the pressure in the continuous crystallizer is controlled to be less than 10KPa;

[0103] S6 tail gas treatment: the tail gas from the outlet of the continuous crystallizer in step S5 is washed by a primary water washing tower and a primary alkali washing tower respectively, and then enters a dryer for drying and dehydration. The dehydrated tail gas is burned as a heat source for the heat exchanger in step S2; the burned tail gas enters an alkali liquid absorption tower for absorption and recovery; the alkali liquid in the alkali liquid absorption tower is 40% KOH, the temperature is 80-90°C, the gas stays in the tower for 15s, and after the absorption is completed, the absorption liquid is spray dried to obtain industrial potassium carbonate.

[0104] After the system of this embodiment runs stably, the purity of aluminum trichloride prepared is 99.72%; the conversion rate (or yield) of aluminum oxide is 98.9%.

[0105] Example 5

[0106] This embodiment provides a green and energy-saving preparation method of high-purity anhydrous aluminum chloride, comprising the following steps:

[0107] S1 weighing and mixing: Boehmite alumina (Al2O3 content 82%) and calcined coke (C content 91.5%) are weighed in proportion and uniformly mixed to form a mixed raw material, and the mixed raw material is transported to the cyclone separator on the top of the boiling furnace by nitrogen pneumatic conveying; wherein the mass ratio of industrial alumina and calcined coke is converted into Al2O3 and C, satisfying m(Al2O3):m(C)=1:0.735;

[0108] The particle size distribution of calcined coke meets the following requirements by mass: 40-100 mesh accounts for 25%; 100-250 mesh accounts for 45%; 250-350 mesh accounts for 30%; the particle size distribution of industrial alumina meets the following requirements by mass: 40-100 mesh accounts for 25%; 100-250 mesh accounts for 45%; 250-350 mesh accounts for 30%.

[0109] S2 gas preheating: liquid chlorine is gasified and preheated to 400℃ by heat exchanger before entering the fluidized bed furnace from the bottom; oxygen is prepared by oxygen generator and preheated to 400℃ by heat exchanger before entering the fluidized bed furnace from the top; the volume ratio of chlorine and oxygen meets the requirement of 1:0.75.

[0110] S3 boiling reaction: after the mixed raw materials in step S1 are heat-exchanged with the high-temperature flue gas discharged from the top of the boiling furnace in the cyclone separator, the solid phase with a particle size larger than 900 mesh is collected and enters the boiling furnace from the top of the boiling furnace, and reacts with the chlorine gas and the preheated oxygen preheated in step S2 in the boiling furnace, the generated high-temperature flue gas is discharged from the top of the boiling furnace, and the generated slag is regularly discharged from the slag discharge port at the bottom of the boiling furnace;

[0111] Among them, the temperature of the solid phase collected by the cyclone separator is 540°C, and the temperature of the high-temperature flue gas coming out of the cyclone separator is 580°C; the chlorine gas velocity is 0.10m / s, and the gas velocity of chlorine and the gas velocity of oxygen meet: 1:0.75; the reaction temperature in the boiling furnace is 800°C.

[0112] S4 impurity removal: the high-temperature flue gas at the top of the boiling furnace in step S3 is cooled to 580°C after heat exchange and dust removal with the mixed raw materials in step S1 by the cyclone separator. The 580°C high-temperature flue gas enters from the bottom of the pipeline impurity remover and is fully mixed with the aluminum powder entering from the top of the pipeline impurity remover for impurity removal. The pipeline impurity remover is also evenly provided with baffles; the high-temperature flue gas after impurity removal is further cooled to 300°C by the U-type cooler and then enters the adsorption drying device to remove the liquid phase. The high-temperature flue gas coming out of the adsorption drying device enters the high-temperature filter for filtration; the high-temperature filter device is kept warm at 300°C, and the filtration accuracy of the high-temperature filter is 7μm;

[0113] S5 crystallization: the flue gas filtered by the high temperature filter in step S4 enters a screw-propelled continuous crystallizer for step-by-step cooling crystallization, wherein the first stage crystallization outlet temperature is 220°C, the second stage crystallization outlet temperature is 183°C, and the third stage crystallization outlet temperature is 170°C; and in step S5, the pressure in the continuous crystallizer is controlled to be less than 10KPa;

[0114] S6 tail gas treatment: the tail gas from the outlet of the continuous crystallizer in step S5 is washed by a primary water washing tower and a primary alkali washing tower respectively, and then enters a dryer for drying and dehydration. The dehydrated tail gas is burned as a heat source for the heat exchanger in step S2; the burned tail gas enters an alkali liquid absorption tower for absorption and recovery; the alkali liquid in the alkali liquid absorption tower is 40% KOH, the temperature is 80-90°C, the gas stays in the tower for 12s, and after the absorption is completed, the absorption liquid is spray dried to obtain industrial potassium carbonate.

[0115] After the system of this embodiment runs stably, the purity of aluminum trichloride prepared is 99.86%; the conversion rate (or yield) of aluminum oxide is 96.4%.

[0116] In summary, it can be concluded that even when relatively low-purity alumina is used as raw material, the present invention can still produce a high-purity product, thereby ensuring high product purity while ensuring product production capacity. In addition, the entire process is simple, the equipment design is simple, and the process energy consumption is low, which greatly reduces the investment in equipment and the energy consumption of the reaction process, thereby achieving the purpose of preparing high-purity products in an energy-saving and low-carbon manner.

[0117] The present invention is not limited to the above-mentioned embodiments, and anyone should be aware that any structural changes made under the enlightenment of the present invention, and any technical solutions that are the same or similar to the present invention, fall within the protection scope of the present invention.

Claims

1. A green and energy-saving preparation method of high-purity anhydrous aluminum chloride, characterized in that: The steps include: S1 weighing and mixing: weighing alumina raw materials and carbon sources in proportion and uniformly mixing them to form a mixed raw material, and transporting the mixed raw material to a boiling furnace by pneumatic conveying; wherein the mass ratio of the alumina raw material and the carbon source satisfies m(Al2O3):m(C)=1:0.3-1; the purity of the alumina raw material satisfies: Al2O3≥75%; The particle size distribution of the carbon source satisfies the following conditions by mass: 40-100 mesh accounts for 20%-25%; 100-250 mesh accounts for 40%-60%; 250-350 mesh accounts for 20-40%; the particle size distribution of the alumina raw material satisfies the following conditions by mass: 40-100 mesh accounts for 20%-25%; 100-250 mesh accounts for 40%-60%; 250-350 mesh accounts for 20-40%; S2 gas preheating: liquid chlorine is gasified and preheated by the heat exchanger before entering the boiling furnace; S3 boiling reaction: the mixed raw material in step S1 and the gas preheated in step S2 react in a boiling furnace, the generated high-temperature flue gas is discharged from the top of the boiling furnace, and the generated slag is regularly discharged from the slag discharge port at the bottom of the boiling furnace; S4 impurity removal: the high-temperature flue gas at the top of the boiling furnace in step S3 is dusted by a cyclone separator and then enters a de-dusting device, where it is mixed with a reducing agent for impurity removal; the high-temperature flue gas after impurity removal is further cooled to 260-400°C and then enters a high-temperature filter for filtration; S5 crystallization: the flue gas filtered by the high temperature filter in step S4 enters a continuous crystallizer, and the outlet temperature of the continuous crystallizer is controlled to be 150-170°C; S6 Tail gas treatment: The tail gas at the outlet of the continuous crystallizer in step S5 is washed by a primary water washing tower and a primary alkali washing tower and then enters a dryer for drying and dehydration. The dehydrated tail gas is burned as a heat source for the heat exchanger in step S2; the burned tail gas enters an alkali liquid absorption tower for absorption and recovery.

2. The green and energy-saving preparation method of high-purity anhydrous aluminum chloride according to claim 1, characterized in that: The alumina raw material is selected from industrial alumina, gibbsite alumina, boehmite alumina or diaspore alumina.

3. The green and energy-saving preparation method of high-purity anhydrous aluminum chloride according to claim 1, characterized in that: In step S2, it also includes preheating the oxygen before entering the boiling furnace; in step S3, the mixed raw material of step S1 and the preheated chlorine and preheated oxygen in step S2 react together in the boiling furnace; the volume ratio of the chlorine and the oxygen satisfies: 1:0.35~1.

4. The green and energy-saving preparation method of high-purity anhydrous aluminum chloride according to claim 1, characterized in that: The top outlet of the fluidized bed furnace is connected to the cyclone separator, and the mixed raw material in step S1 enters the fluidized bed furnace from the cyclone separator; in step S4, the high-temperature flue gas at the top of the fluidized bed furnace is mixed with the mixed raw material for heat exchange in the cyclone separator; solid materials with a particle size greater than S in the cyclone separator are collected and returned from the upper part of the fluidized bed furnace to the fluidized bed furnace; wherein S is 650-1100 mesh.

5. The green and energy-saving preparation method of high-purity anhydrous aluminum chloride according to claim 3, characterized in that: In step S2, the chlorine gas is preheated to 400-700°C and then enters the boiling furnace from the bottom of the boiling furnace; the oxygen gas is preheated to 400-700°C and then enters the boiling furnace from the top of the boiling furnace.

6. The green and energy-saving preparation method of high-purity anhydrous aluminum chloride according to claim 1, characterized in that: The reducing agent in step S4 is selected from aluminum powder, hydrogen or iron powder.

7. The green and energy-saving preparation method of high-purity anhydrous aluminum chloride according to claim 1, characterized in that: In step S4, the high-temperature flue gas first enters the adsorption drying device before entering the high-temperature filter, and then enters the high-temperature filter; In step S5, the tail gas at the outlet of the continuous crystallizer first enters the adsorption drying device and then enters the primary water washing tower.

8. The green and energy-saving preparation method of high-purity anhydrous aluminum chloride according to claim 1, characterized in that: The high temperature filter in step S4 performs heat preservation filtration, the temperature difference of gas entering and leaving the high temperature filter does not exceed 10°C, and the gas temperature in the high temperature filter cannot be lower than 260°C; the filtration accuracy of the high temperature filter is 5-10μm.

9. The green and energy-saving preparation method of high-purity anhydrous aluminum chloride according to claim 1, characterized in that: In step S5, the flue gas is subjected to gradient cooling crystallization in the continuous crystallizer, wherein the outlet temperature of the first stage crystallization is 220-240°C, the outlet temperature of the second stage crystallization is 160-200°C, and the outlet temperature of the third stage crystallization is 150-170°C; and in step S5, the pressure in the continuous crystallizer is controlled to be less than 10KPa.

10. The green and energy-saving preparation method of high-purity anhydrous aluminum chloride according to claim 1, characterized in that: In step S6, the tail gas after combustion enters the alkali liquid absorption tower; the alkali liquid in the alkali liquid absorption tower is 30-40% KOH, the temperature is 80-90° C., the gas stays in the tower for 12-15 seconds, and the absorption liquid is spray-dried to obtain industrial potassium carbonate.

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