Method for producing alumina material
By heating aluminum chloride hexahydrate at low temperature to form oxyhydroxychloride and heating and drying under controlled conditions, the problems of large particle size of aluminum oxide and high residual chloride in the prior art are solved, and high efficiency and low pollution bauxite production is achieved.
Patent Information
- Application Number
- CN202380045962.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-06-08
- Filing Date
- 2023-06-03
- Publication Date
- 2025-03-25
AI Technical Summary
The prior art has problems such as excessive particle size, high residual chloride, difficult to capture or recycle hydrogen chloride, and difficult to reduce pollutants when producing aluminum oxide or alumina, which affects the performance of the material and the efficiency of the process.
The aluminum oxyhydroxychloride crystals are heated by low temperature to form oxyhydroxychloride and heated under a controlled air flow, combined with at least partial vacuum drying, to produce aluminum oxyhydroxychloride and alpha alumina.
It achieves a smaller particle size, reduces the residual chloride level, improves the capture and recirculation efficiency of hydrogen chloride, and effectively reduces the content of pollutants, improves the purity of the material and the efficiency of the process.
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Figure CN119698394A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a process for producing aluminous materials. In particular, the present invention relates to a process for producing aluminum oxyhydroxychloride and alpha alumina. Background Art
[0002] There are several known processes for producing aluminum oxide or alumina. These processes are based on alkaline extraction processes, such as the Bayer process, or acid extraction processes. In particular, acid extraction processes have been used to extract aluminum from non-bauxite materials.
[0003] In 1927, the United States Bureau of Mines published a comparative study on the extraction of aluminum from non-bauxite materials (such as kaolin-type clays) using strong acids (such as sulfuric acid, nitric acid, and hydrochloric acid).
[0004] In 1946, the United States Bureau of Mines published a paper describing the development of the hydrochloric acid process for producing alumina from clay. This publication and subsequent publications described the basic process as follows:
[0005] Treating (e.g., by crushing, flotation, etc.) aluminous materials, such as kaolin-type materials, as necessary to reduce particle size and increase aluminum content;
[0006] · calcining (also known as calcining or thermal dehydroxylation) the kaolin-type material to produce metakaolin, which is more soluble in dilute acid than kaolin;
[0007] digesting (also known as leaching or acid dissolving) the alumina material with hydrochloric acid to form a slurry;
[0008] Filtering the slurry to separate a solid phase and a liquid phase, wherein the solid comprises insoluble siliceous material and the rich liquid comprises a solution containing aluminum and soluble impurities;
[0009] Precipitating (also known as crystallizing, recrystallizing or salting-out) aluminum chloride hexahydrate crystals by bubbling with hydrogen chloride gas and causing aluminum chloride hydrate to crystallize (aluminum chloride hexahydrate);
[0010] calcining (also known as ignition, heating, decomposition, pyrolysis or hydro-pyrolysis) aluminum chloride hexahydrate to obtain aluminum oxide, and
[0011] Capturing (also called recycling) hydrogen chloride for reuse as leaching acid, scrubbing liquid or gas for crystallization of aluminum chloride hexahydrate.
[0012] Subsequent research has focused largely on determining the range of conditions at various stages in the overall alumina manufacturing process in order to optimize the hydrochloric acid extraction of alumina from kaolin-type clays.
[0013] However, the prior art is fraught with problems. For example, the particle size of alumina produced using prior art methods may be too large for certain applications, which requires grinding the alumina to obtain the desired particle size. However, using a grinding process can increase the risk of introducing contaminants into the alumina that are difficult to remove from the final product, as well as requiring additional energy input into the system.
[0014] In addition, current processes can result in high residual chloride levels, which prevent materials, particularly aluminum chlorohexahydrate, from flowing easily through the reaction vessel and agglomerate into a coating on the reaction vessel surface, resulting in poor and uneven heating of the decomposed material. The release of gaseous hydrogen chloride during drying can also cause corrosion of the reaction vessel in which the pyrolysis occurs, requiring expensive maintenance or the purchase of custom drying equipment.
[0015] Additionally, hydrogen chloride gas is valuable as a recyclable chemical, however, in the production of aluminum oxide or alumina from clay, hydrogen chloride gas is difficult to capture or recycle, and existing methods (such as the method disclosed in JP2013-203598) occur at temperatures above the optimal temperature for capture.
[0016] Furthermore, the intermediate reaction product, aluminum chloride hexahydrate, is hygroscopic and unstable, cementitious, has very poor flow properties, and can release gaseous hydrogen chloride during storage, which is harmful to human health and highly corrosive.
[0017] Still further, prior art processes are unable to effectively reduce contaminants (e.g., chromium, magnesium, and phosphorus) that are commonly found in aluminum-containing feedstocks having sufficient aluminum content for the production of alumina to levels desired by users of high purity (>99.99% purity) alumina.
[0018] It is clearly understood that if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the general knowledge in the art in Australia or any other country. Summary of the invention
[0019] Embodiments of the present invention provide methods of producing aluminous materials that may at least partially address one or more of the above-mentioned problems or deficiencies, or may provide the public with a useful or commercial choice.
[0020] As used herein, the term "oxyhydroxychlorides" is intended to refer to intermediate products in the formation of alumina, which are formed by heating aluminum chlorohexahydrate crystals at low temperatures. Oxyhydroxychlorides contain a mixture of dehydrated aluminum oxychloride species and a low concentration of free chloride, which are generally chemically stable and have good flow properties.
[0021] As used herein, the term "at least partial vacuum" means that the pressure inside the container is reduced relative to the pressure outside the container. It will be understood that in general the term "at least partial vacuum" refers to a pressure below atmospheric pressure.
[0022] As used herein, the term "roasting" is intended to refer to a heating process that causes dehydroxylation of a mineral-containing raw material. It is also commonly referred to as calcining or thermal dehydroxylation.
[0023] As used herein, the term "digest" is intended to refer to a solvent extraction process that uses a strong acid or base to digest or leach minerals from a mineral-bearing raw material. It is also commonly referred to as leaching or acid dissolution.
[0024] As used herein, the term "precipitate" refers to the process of separating a solid material from a solution. It is also commonly referred to as crystallization, recrystallization or salting out.
[0025] As used herein, the term "calcination" is intended to refer to a high temperature heating process whereby a mineral-containing material is converted into its oxide form. It is also commonly referred to as ignite, heat, decompose, pyrolyze or hydrothermolyze.
[0026] As used herein, the term "recover" is intended to refer to the recovery of solvent for reuse. It is also commonly referred to as recycling.
[0027] According to a first aspect of the present invention, there is provided a method for producing an alumina material, the method comprising:
[0028] Provide aluminum-containing raw materials;
[0029] Separating the aluminum-containing raw material to obtain a rich solution;
[0030] Concentrating the rich solution to obtain a saturated aluminum solution;
[0031] The saturated aluminum solution is subjected to a crystallization process, the crystallization process comprising:
[0032] heating the saturated aluminum solution;
[0033] bubbling the saturated aluminum solution with gaseous hydrochloric acid to form a slurry of aluminum chloride hexahydrate crystals;
[0034] separating the aluminum chloride hexahydrate crystals from spent liquor; and
[0035] The aluminum chlorohexahydrate crystals are heated at a temperature between about 100°C and about 350°C under a controlled air flow to obtain a dehydrated aluminum oxychloride.
[0036] It will be understood that the term "dehydrated aluminum oxyhydroxy chloride" is intended to refer to an aluminum oxyhydroxy chloride from which at least a portion of the water associated therewith has been removed. Any suitable amount of water may be removed to form the dehydrated aluminum oxyhydroxy chloride. For example, in some embodiments of the present invention, at least 10% w / w of the water associated with the aluminum oxyhydroxy chloride is removed to form the dehydrated aluminum oxyhydroxy chloride. More preferably, at least 25% w / w of the water associated with the aluminum oxyhydroxy chloride is removed to form the dehydrated aluminum oxyhydroxy chloride. More preferably, at least 50% w / w of the water associated with the aluminum oxyhydroxy chloride is removed to form the dehydrated aluminum oxyhydroxy chloride. More preferably, at least 75% w / w of the water associated with the aluminum oxyhydroxy chloride is removed to form the dehydrated aluminum oxyhydroxy chloride. More preferably, at least 90% w / w of the water associated with the aluminoxochloride is removed to form the dehydrated aluminoxochloride. In some embodiments, substantially all of the water associated with the aluminoxochloride is removed to form the dehydrated aluminoxochloride.
[0037] As mentioned, an aluminum-containing raw material may be provided.
[0038] Any suitable type of aluminum-containing feedstock may be used.
[0039] In some embodiments, the aluminum-containing raw material may be a source of alumina, aluminum hydroxide, aluminum metal, aluminum chlorohexahydrate, red mud, fly ash, aluminosilicate, kaolin, zeolite, feldspar, and the like.
[0040] In some embodiments, the aluminum-containing raw material may be calcined. In this case, it will be understood that the aluminum-containing raw material may have been subjected to a heating process to reduce impurities or thermally dehydroxylate the aluminum-containing raw material.
[0041] In other embodiments, the aluminum-containing raw material may be formed by dispersing the aluminum-containing raw material in a solvent.
[0042] Any suitable solvent may be used. Typically, the solvent may be sufficient to leach aluminum from the aluminum-containing raw material. For example, the solvent may be a strong acid, such as hydrochloric acid, sulfuric acid, nitric acid, and the like.
[0043] The aluminum-containing raw material may be in any suitable pulp density. For example, the aluminum-containing raw material may be in a pulp density of about 10%, about 15%, about 20%, or about 25%.
[0044] In a preferred embodiment, the aluminum-containing raw material may be in a slurry concentration of about 20%.
[0045] In some embodiments, the aluminum-containing raw material may be kaolin, wherein the kaolin may be roasted to form metakaolin, and then leached with hydrochloric acid to form the aluminum-containing raw material.
[0046] In some embodiments, the aluminum-containing raw material may be mining tailings or aluminum-containing waste materials, which may be leached with hydrochloric acid to extract aluminum.
[0047] As described, the aluminum-containing raw material can be separated to obtain a pregnant liquor.
[0048] The aluminum-containing raw material may be separated using any suitable technique known in the art. Preferably, the separation technique may be sufficient to separate the aluminum-containing raw material into a rich liquid and a solid residue. For example, the separation technique may include: gravity settling clarifier, sedimentation, decanting, centrifugation, filtration, and the like.
[0049] In some embodiments, the pregnant solution may be polished.
[0050] The pregnant liquor may be polished or clarified using any suitable technique known in the art. Preferably, the polishing step may be sufficient to remove or reduce suspended solids, such as fine sediments, insoluble materials, etc. In some embodiments, the pregnant liquor may be polished or clarified using a filtration process and / or a flocculant.
[0051] As shown, the rich solution can be concentrated to obtain a saturated aluminum solution.
[0052] The rich solution may be concentrated using any suitable technique known in the art. Generally, the concentration technique may be sufficient to increase the aluminum in the rich solution to its saturation point without causing the aluminum to precipitate as aluminum chlorohexahydrate crystals. For example, the rich solution may be concentrated by heating the rich solution to its boiling point, evaporating the rich solution by heating it below its boiling point, and the like. The concentrated rich solution may be subjected to a finishing step to remove insoluble contaminants such as silica or other precipitates.
[0053] Preferably, the rich solution may be concentrated to its saturation point by evaporation.
[0054] The rich liquid may be concentrated by boiling the rich liquid at a temperature between about 75° C. and about 130° C., between about 85° C. and about 120° C., preferably between about 95° C. and about 110° C. In some embodiments, the rich liquid may be concentrated by boiling the rich liquid at a temperature between about 95° C. and about 110° C.
[0055] However, one skilled in the art will appreciate that the temperature may vary depending on a number of factors, including whether the concentration is performed under vacuum, the level and type of impurities, and the molarity of the hydrochloric acid.
[0056] In some embodiments, the pregnant solution may be concentrated to an aluminum concentration of about 60,000 ppm.
[0057] Advantageously, concentrating the rich solution can reduce the consumption of hydrogen chloride gas per unit of aluminum chloride hexahydrate precipitated during crystallization. Further, given the same gas flow rate, the seed nucleation phase can be reduced relative to the growth phase, reducing the overall introduction of impurities from the solution, which are more easily captured during the nucleation phase.
[0058] As described, the saturated solution may be subjected to a crystallization process.
[0059] Any suitable crystallization process may be used. Generally, the crystallization process may be sufficient to precipitate the aluminum chloride hexahydrate crystals and minimize precipitation of impurities.
[0060] Preferably, the crystallization process may include: heating the saturated aluminum solution and bubbling gaseous hydrochloric acid to the saturated aluminum solution, thereby forcing aluminum chlorohexahydrate crystals to crystallize and forming a slurry of aluminum chlorohexahydrate crystals.
[0061] Any suitable type of gaseous hydrochloric acid may be used. For example, the gaseous hydrochloric acid may be purified, enriched, etc.
[0062] The saturated aluminum solution may be added to a stirred reaction vessel. In some embodiments, the stirred reaction vessel may be heated.
[0063] The saturated aluminum solution may be preheated to any suitable temperature. For example, the saturated aluminum solution may be preheated at a temperature between about 30°C and about 100°C, between about 40°C and about 90°C, between about 50°C and about 80°C, or between about 60°C and about 70°C.
[0064] In some embodiments, the saturated aluminum solution may be preheated to a temperature between about 60°C and about 70°C.
[0065] The saturated aluminum solution may be bubbled with gaseous hydrochloric acid at a reaction temperature between about 40°C and about 120°C, between about 50°C and about 110°C, between about 60°C and about 100°C, preferably between about 70 and 90°C.
[0066] In some embodiments, gaseous hydrochloric acid may be bubbled through the saturated aluminum solution, maintaining the reaction temperature between about 60°C and about 70°C.
[0067] The saturated aluminum solution may be bubbled with gaseous hydrochloric acid until the hydrochloric acid concentration of the saturated aluminum solution reaches between about 20 wt % and about 45 wt %, between about 25 wt % and 40 wt %, preferably between about 30 wt % and 35 wt %.
[0068] In some embodiments, the saturated aluminum solution may be bubbled with gaseous hydrochloric acid until the hydrochloric acid concentration of the saturated aluminum solution reaches between about 30 wt % and 34 wt %.
[0069] Advantageously, preheating the saturated aluminum solution prior to bubbling with gaseous hydrochloric acid reduces the incorporation of contaminants (e.g., phosphorus and magnesium) into the precipitate by slowing down crystallization and reducing the rate of nucleation. In addition, preheating the saturated aluminum solution prior to bubbling with gaseous hydrochloric acid can increase the purity obtained during crystallization and reduce the number of recrystallization steps required.
[0070] In some embodiments, the slurry of aluminum chlorohexahydrate crystals may be subjected to one or more recrystallization steps. Generally, one skilled in the art will appreciate that crystals formed by a crystallization process may be recrystallized to reduce or remove any impurities from the crystallized compound.
[0071] In this case, it is envisaged that the slurry of aluminium chlorohexahydrate crystals obtained by crystallization from a saturated solution of aluminium chlorohexahydrate may be subjected to one or more recrystallization steps before being subjected to pyrolysis.
[0072] The slurry of aluminum chlorohexahydrate crystals may be recrystallized using any suitable technique known in the art. Generally, the recrystallization process may be sufficient to precipitate purified aluminum chlorohexahydrate crystals and minimize precipitation of impurities.
[0073] The recrystallization process may include separating and washing the precipitated crystals, and then dissolving the washed precipitated crystals in a solvent (such as ultrapure water, demineralised water, etc.) to form a feed solution. The feed solution may be subjected to a finishing step to remove insoluble contaminants such as silicon dioxide. The feed solution may then be heated and bubbled with gaseous hydrochloric acid to precipitate aluminum chloride hexahydrate crystals.
[0074] In some embodiments, the aluminum chlorohexahydrate crystal slurry may be cooled prior to separating the aluminum chlorohexahydrate crystals from the barren liquor. Preferably, the aluminum chlorohexahydrate solution may be cooled during the final crystallization and / or recrystallization step.
[0075] The aluminum chloride hexahydrate solution may be cooled using any suitable technique. For example, the aluminum chloride hexahydrate solution may be actively cooled, such as by refrigeration or the like. Alternatively, the aluminum chloride hexahydrate solution may be cooled by removing a heating source and allowing the aluminum chloride hexahydrate solution to cool to ambient temperature over a period of time. Advantageously, cooling the aluminum chloride hexahydrate solution improves hydrogen chloride recovery.
[0076] The aluminum chloride hexahydrate solution may be cooled to any suitable temperature. Generally, the aluminum chloride hexahydrate solution may be cooled to a temperature sufficient to crystallize relatively small aluminum chloride hexahydrate crystals without crystallizing impurities.
[0077] In some embodiments, the aluminum chloride hydroxide solution may be cooled to a temperature of less than about 0°C. More preferably, the aluminum chloride hydroxide solution may be cooled to a temperature of less than about -5°C. More preferably, the aluminum chloride hydroxide solution may be cooled to a temperature of less than about -10°C. Still more preferably, the aluminum chloride hydroxide solution may be cooled to a temperature of less than about -15°C. Still more preferably, the aluminum chloride hydroxide solution may be cooled to a temperature of less than about -20°C. Most preferably, the aluminum chloride hydroxide solution may be cooled to a temperature of less than about -25°C. The aluminum chloride hexahydrate solution may be agitated during cooling. In applications, it is contemplated that agitating the solution during cooling may help avoid the formation of agglomerates and help form smaller particles.
[0078] Advantageously, cooling the aluminum chloride hexahydrate solution to a sufficiently low temperature and agitating the solution during cooling produces crystals of smaller size than conventional practice (less than about 10 μm, versus an average particle size of about 20 μm to about 100 μm) and increases the nucleation rate rather than the crystal growth rate.
[0079] The precipitate may be separated using any suitable technique known in the art. Preferably, the separation technique may be sufficient to separate the precipitate from the barren solution. For example, the separation technique may include a gravity settling clarifier, sedimentation, decantation, centrifugation, filtration, and the like.
[0080] The precipitate may be washed to separate the aluminum chloride hexahydrate crystals from impurities in the precipitate.
[0081] Any suitable wash liquid may be used to wash the precipitate. Generally, the wash liquid may be sufficient to redissolve soluble contaminants from the crystals, etc. The wash liquid may also be sufficient to displace entrained contaminated supernatant and replace it with a less contaminated wash liquid.
[0082] In some embodiments, the washing liquid may be hydrochloric acid, lean solution, etc. The washing liquid used to wash the precipitate obtained from crystallization of a saturated solution may be the same as the washing liquid used to wash the precipitate obtained from recrystallization of a feed solution, or may be different therefrom.
[0083] Any suitable technique known in the art may be used to separate the aluminum chloride hexahydrate crystals from the excess hydrochloric acid. For example, the separation technique may include gravity settling, sedimentation, decantation, centrifugation, filtration, and the like.
[0084] As shown, the aluminum chlorohexahydrate crystals may be heated at a temperature between about 100°C and about 350°C under a controlled air flow to produce aluminum oxychlorohydroxide.
[0085] The aluminum chlorohexahydrate crystals may be heated using any suitable technique known in the art. Generally, the heating technique may be sufficient to provide a heating profile that dries the aluminum chlorohexahydrate and produces a dehydrated aluminum oxychloride.
[0086] Preferably, the aluminum chlorohexahydrate crystals may be heated under controlled air flow conditions. For example, the aluminum chlorohexahydrate crystals may be heated directly or indirectly. The heat source may include a forced air-drying oven, a flash dryer, a fluidized bed dryer, a microwave oven, a rotary kiln, a tunnel furnace, a fluidized bed reactor, far infrared rays, high frequency waves, etc. Those skilled in the art will appreciate that under controlled air flow conditions, air is introduced into the container so that it contacts the aluminum chlorohexahydrate crystals and helps remove water and hydrochloric acid vapor from the container.
[0087] In some embodiments, the container may be heated. Preferably, the aluminum chloride hexahydrate crystals may be heated under heat and / or under a flow of dry air in a heated container.
[0088] The aluminum chlorohexahydrate crystals may be heated at any suitable hold temperature. However, those skilled in the art will appreciate that the hold temperature may vary depending on a variety of factors, including hold time, gas flow conditions, the amount and type of liquid present in the crystals, and the desired final properties of the aluminum oxyhydroxychloride formed.
[0089] The aluminum chlorohexahydrate crystals may be heated at a holding temperature between about 100° C. and about 350° C., between about 150° C. and about 280° C., between about 170° C. and about 250° C., preferably between about 180° C. and about 230° C. Most preferably, the aluminum chlorohexahydrate crystals may be heated at a holding temperature of about 230° C.
[0090] Preferably, the aluminum chlorohexahydrate crystals are heated under a controlled air flow at a temperature between about 180°C and 230°C to obtain a dehydrated aluminum oxychloride.
[0091] In some embodiments, the aluminum chlorohexahydrate crystals may be heated at a holding temperature of less than about 230°C.
[0092] It is contemplated that by heating the aluminum chlorohexahydrate crystals at these relatively low drying temperatures, the hydrochloric gas vapour may be recovered from the drying process using any suitable technique. The recovery of the hydrochloric gas vapour may generate useful heat, thereby reducing energy input requirements, while also allowing the recovery of reagents for further use.
[0093] Furthermore, by drying the aluminum chlorohexahydrate crystals under a controlled air flow, recovery of the hydrochloric acid can be improved and condensation of the acid on reactor surfaces (thus causing corrosion) can be reduced or eliminated.
[0094] Any suitable ramp rate (rate of change of temperature over time) can be used to reach the holding temperature. For example, the ramp rate can be about 10°C / minute, about 20°C / minute, about 30°C / minute, about 40°C / minute, about 50°C / minute, about 75°C / minute, about 100°C / minute, or greater.
[0095] In use, it is envisaged that the ramp rate may be selected to reach the holding temperature as quickly as possible.
[0096] The aluminum chlorohexahydrate crystals may be heated at the holding temperature for any suitable time. However, those skilled in the art will appreciate that the holding time may vary depending on a variety of factors, including the holding temperature, gas flow conditions, and the amount and type of liquid present in the crystals.
[0097] For example, the aluminum chlorohexahydrate crystals can be heated at a holding temperature for a period of at least about 30 minutes, at least 60 minutes, at least about 90 minutes, at least about 2 hours, at least about 3 hours, at least about 4 hours, at least about 5 hours, at least about 6 hours, or more.
[0098] Preferably, the aluminum chlorohexahydrate crystals may be agitated while being heated under controlled air flow conditions. In use, it is envisioned that agitating the crystals while being heated may break up any agglomerates that form and assist in reducing the particle size of the crystals. Additionally, heating the aluminum chlorohexahydrate crystals under controlled air flow conditions may assist in deagglomeration and / or particle size reduction of the crystals by introducing high velocity air into the container. In other embodiments, the aluminum chlorohexahydrate crystals may be subjected to a particle size reduction process before, during, or after being heated under controlled air flow conditions.
[0099] In some embodiments, the aluminum oxychloride formed by heating the aluminum chlorohexahydrate crystals has a residual chloride level of from about 2 weight percent to about 10 weight percent of the aluminum oxychloride.
[0100] In some embodiments, the aluminum oxychloride comprises particles that can pass through a mesh aperture of up to about 10 μm, preferably up to about 5 μm, and more preferably up to about 2 μm.
[0101] Advantageously, heating the aluminum chlorohexahydrate crystals under controlled air flow conditions dislodges entrained liquid which may condense inside the heating device and cause agglomeration and formation of cementitious material, thereby causing uneven drying and decomposition of the aluminum chlorohexahydrate crystals.
[0102] Advantageously, decomposing aluminum chlorohexahydrate into dehydrated aluminum oxychloride results in a more stable alumina precursor, since aluminum chlorohexahydrate can be corrosive, hygroscopic, and release gaseous hydrogen chloride over time. Additionally, aluminum chlorohexahydrate readily absorbs ambient moisture, resulting in the formation of rock-like agglomerates that are significantly more difficult to heat and introduce uncontrollable changes since they can retain more chloride. Additionally, dehydrated aluminum oxychloride is a free-flowing material that can be easier to handle and stable when stored for long periods of time.
[0103] Preferably, the method for producing alumina material according to the first aspect of the present invention further comprises:
[0104] The aluminum chlorohexahydrate crystals are dried under at least partial vacuum at a temperature between about 50°C and 150°C before being heated at a temperature between about 100°C and about 350°C under a controlled air flow to obtain a dehydrated aluminum oxychloride.
[0105] The aluminum chloride hexahydrate crystals may be dried at any suitable pressure. Generally, the partial vacuum may be sufficient to assist in removing water by lowering its boiling point.
[0106] In some embodiments, the aluminum chlorohexahydrate crystals may be dried at a pressure of between about 50 mBar and about 1000 mBar, more preferably between about 100 mBar and about 900 mBar, more preferably between about 150 mBar and about 800 mBar, more preferably between about 200 mBar and about 700 mBar, still more preferably between about 250 mBar and about 600 mBar, still more preferably between about 300 mBar and about 500 mBar, and most preferably between about 350 mBar and about 400 mBar.
[0107] The aluminum chlorohexahydrate crystals may be dried at a temperature between about 50°C and about 150°C, between about 60°C and about 140°C, preferably between about 80°C and about 130°C.
[0108] Preferably, the aluminum chlorohexahydrate crystals may be dried at a temperature between about 80°C and 130°C under at least a partial vacuum.
[0109] In some embodiments, after drying the aluminum chlorohexahydrate crystals under at least a partial vacuum, the aluminum chlorohexahydrate crystals have a residual chloride level of about 30% to about 45% by weight of the aluminum chlorohexahydrate crystals.
[0110] In some embodiments, the aluminum chlorohexahydrate crystals contain substantially no or no residual moisture content.
[0111] Preferably, the step of drying the aluminum chlorohexahydrate crystals under at least partial vacuum at a temperature between about 50° C. and 150° C. occurs after the step of cooling the aluminum chlorohexahydrate crystal slurry and separating the aluminum chlorohexahydrate crystals from the barren liquor, and before the step of heating the aluminum chlorohexahydrate crystals under a controlled air flow at a temperature between about 100° C. and about 350° C. to obtain a dehydrated aluminum oxychloride.
[0112] In use, it is envisioned that low temperature heating of the aluminum chlorohexahydrate crystals under at least partial vacuum may help reduce liquid (including water) entrained within the crystals to provide stabilized dehydrated aluminum chlorohexahydrate. The stabilized dehydrated aluminum chlorohexahydrate may then be dried to provide aluminum oxychloride. In this case, it will be appreciated that low temperature heating of the aluminum chlorohexahydrate crystals provides a further pyrolysis step in the process of converting aluminum chlorohexahydrate to alpha alumina.
[0113] Advantageously, cryogenically drying the aluminum chlorohexahydrate crystals under partial vacuum to reduce entrained liquid prior to drying the crystals at a higher temperature can improve the energy efficiency of the drying stage compared to using a direct thermal drying process.
[0114] The aluminum chlorohexahydrate crystals may be heated using any suitable technique known in the art. Generally, the heating technique may be sufficient to provide a heating characteristic that helps reduce liquid entrained within the aluminum chlorohexahydrate crystals without decomposing the crystals. For example, the aluminum chlorohexahydrate crystals may be dried under vacuum using a vacuum dryer, a microwave dryer, a microwave-assisted vacuum dryer, or any other suitable indirect drying technique.
[0115] In some embodiments of the present invention, the aluminum chloride hexahydrate crystals may be heated using a rotary kiln, a tunnel furnace, a fluidized bed reactor, microwave vacuum assisted drying, far infrared rays, high frequency waves, and the like.
[0116] According to a second aspect of the present invention, there is provided a method for producing an alumina material, the method comprising:
[0117] Provide aluminum-containing raw materials;
[0118] Separating aluminum-containing raw materials to obtain rich liquid;
[0119] Concentrating the rich solution to obtain a saturated aluminum solution;
[0120] The saturated aluminum solution is subjected to a crystallization process, wherein the crystallization process comprises:
[0121] heating the saturated aluminum solution;
[0122] bubbling the saturated aluminum solution with gaseous hydrochloric acid to form a slurry of aluminum chloride hexahydrate crystals;
[0123] separating aluminum chloride hexahydrate crystals from the slurry of aluminum chloride hexahydrate crystals to produce a barren solution;
[0124] drying the aluminum chloride hexahydrate crystals at a temperature between about 50° C. and 150° C. under at least a partial vacuum, and
[0125] The aluminum chlorohexahydrate crystals are heated at a temperature between about 100°C and about 350°C under a controlled air flow to produce aluminum oxychlorohydroxide.
[0126] Preferably, the method for producing alumina material according to the first aspect or the second aspect of the present invention further comprises:
[0127] decomposing aluminum oxychloride at a temperature between about 800° C. and about 980° C. to form primarily amorphous aluminum oxide, and
[0128] The decomposed amorphous alumina is calcined at a temperature between about 1,100°C and about 1,300°C to obtain primarily alpha alumina.
[0129] As described, alumina materials containing aluminum oxyhydroxychloride may be decomposed at temperatures between about 800°C and about 980°C to primarily form amorphous alumina, and the amorphous alumina may be calcined at temperatures between about 1,100°C and about 1,300°C to primarily yield alpha alumina.
[0130] Alumina materials containing aluminum oxychlorides may be decomposed at high temperatures (eg, by a rotary kiln, fluidized bed, etc.) to transform aluminum oxide phases such as gamma alumina and amorphous alumina.
[0131] The aluminum oxychloride may be decomposed at any suitable temperature. Generally, the decomposition temperature may be sufficient to remove a majority of the remaining chloride. However, those skilled in the art will appreciate that the decomposition temperature may vary depending on a variety of factors, including the decomposition time, the heat transfer rate, the particle size of the aluminum chlorohexahydrate crystals, and whether the container is under agitation.
[0132] The aluminum oxychloride may be heated at a decomposition temperature between about 600°C and about 1,200°C, between about 700°C and about 1,100°C, between about 800°C and about 1,000°C.
[0133] In some embodiments, the aluminum oxychloride may be heated at a decomposition temperature of about 800°C.
[0134] The aluminum oxychloride may be heated at the decomposition temperature for any suitable period of time.
[0135] For example, the aluminum oxychloride may be heated at the decomposition temperature for a period of at least about 30 minutes, at least 60 minutes, at least about 90 minutes, at least about 2 hours, at least about 3 hours, at least about 4 hours, at least about 5 hours, at least about 6 hours, or more.
[0136] In some embodiments, the step of decomposing the alumina material comprising aluminum oxyhydroxy chloride may comprise controlling the humidity in the container. In use, it is contemplated that controlling the humidity in the container may help improve chloride removal prior to the calcining step.
[0137] In some embodiments, the amorphous alumina and gamma alumina formed by decomposing an aluminous material containing aluminum oxychloride has a residual chloride level of less than about 1.5 wt %, preferably less than about 1.0 wt %, and more preferably less than about 0.4 wt % of the amorphous alumina and gamma alumina.
[0138] Advantageously, reducing the residual chloride levels of the amorphous alumina and gamma alumina reduces the potential for causing corrosion of the vessel during calcination. This therefore allows for a wider selection of materials used in constructing the vessel, kiln, calciner, etc. in which pyrolysis occurs.
[0139] Advantageously, dividing the decomposition process into lower temperature heating and higher temperature decomposition stages effectively separates the process into two pieces of equipment, each of which can be designed for a tighter range of operating conditions, reducing the stress placed on each piece of equipment and thereby reducing potential equipment failure.
[0140] As mentioned, alumina may be obtained by calcining amorphous alumina and gamma alumina at high temperature (eg, by a rotary kiln, a fluidized bed, a calcining furnace, etc.) Preferably, the obtained alumina may mainly comprise alpha alumina.
[0141] The amorphous alumina and gamma alumina may be calcined at any suitable temperature. Generally, the calcination temperature may be sufficient to convert the amorphous alumina and gamma alumina into alpha alumina. However, those skilled in the art will appreciate that the calcination temperature may vary depending on a variety of factors, including residence time in the calciner, equipment capacity, and sintering temperature.
[0142] The amorphous alumina and gamma alumina may be heated at a calcination temperature between about 950°C and about 1,300°C, preferably between about 1,100°C and about 1,300°C.
[0143] In some embodiments, the amorphous alumina and gamma alumina may be heated at a calcination temperature between about 1,100°C and about 1,300°C.
[0144] The amorphous alumina and gamma alumina may be heated at the calcining temperature for any suitable period of time.
[0145] For example, amorphous alumina and gamma alumina can be heated at the calcining temperature for a period of at least about 30 minutes, at least 60 minutes, at least about 90 minutes, at least about 2 hours, at least about 3 hours, at least about 4 hours, or more.
[0146] In some embodiments, the step of calcining the amorphous alumina and gamma alumina may include controlling the humidity in the container.
[0147] Preferably, the rich solution may be concentrated to its saturation point by evaporation.
[0148] Preferably, the slurry of aluminum chloride hexahydrate crystals is subjected to one or more recrystallization processes.
[0149] Advantageously, the method of the present invention provides improved contamination control in the production of high purity alumina. In particular, the present invention provides improved control of impurities such as silica, phosphorus, chromium and magnesium.
[0150] In addition, the process of the present invention provides improved particle size control during the formation of aluminum chlorohexahydrate. Advantageously, improved particle size control reduces the need for post-calcination processing (such as grinding), which can introduce contaminants that are practically impossible to remove. In addition, reducing the need for post-calcination processing reduces the need for additional energy input into the system.
[0151] Any feature described herein may be combined in any manner with any other feature or features described within the scope of the present invention.
[0152] The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that the prior art forms part of the common general knowledge. BRIEF DESCRIPTION OF THE DRAWINGS
[0153] The preferred features, embodiments and variations of the present invention can be discerned from the following detailed description, which provides sufficient information for those skilled in the art to implement the present invention. The detailed description should not be considered to limit the scope of the above invention in any way. The detailed description will refer to the following multiple drawings:
[0154] Figure 1 A method for producing high purity alumina material according to an embodiment of the present invention is described;
[0155] Figure 2 A method for producing high purity alumina material according to an embodiment of the present invention is described;
[0156] Figure 3 A method for producing high purity alumina material according to a further embodiment of the present invention is described;
[0157] Figure 4 A method of producing a high purity alumina material according to an embodiment of the present invention is described. DETAILED DESCRIPTION
[0158] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
[0159] First describe in detail Figure 1 The method (100) for producing an alumina material. Preferably, the alumina material comprises aluminum oxyhydroxy chloride.
[0160] At step 10, an aluminum-containing raw material may be provided.
[0161] Any suitable type of aluminum-containing feedstock may be used.
[0162] In some embodiments, the aluminum-containing raw material may be a source of alumina, aluminum hydroxide, aluminum metal, aluminum chlorohexahydrate, red mud, fly ash, aluminosilicate, kaolin, zeolite, feldspar, and the like.
[0163] The aluminum-containing raw material may be formed by dispersing the aluminum-containing raw material in a solvent.
[0164] Any suitable solvent may be used. Generally, the solvent may be sufficient to leach aluminum from the aluminum-containing raw material. For example, the solvent may be a strong acid, such as hydrochloric acid, sulfuric acid, nitric acid, and the like.
[0165] In step 20, the aluminum-containing raw material may be separated to obtain a rich solution.
[0166] The aluminum-containing raw material may be separated using any suitable technique known in the art. Preferably, the separation technique may be sufficient to separate the aluminum-containing raw material into a rich liquid and a solid residue. For example, the separation technique may include a gravity settling clarifier, sedimentation, decantation, centrifugation, filtration, and the like.
[0167] In step 30, the rich solution may be concentrated to obtain a saturated aluminum solution.
[0168] The rich solution may be concentrated using any suitable technique known in the art. Generally, the concentration technique may be sufficient to increase the aluminum concentration in the rich solution to its saturation point without precipitating the aluminum as aluminum chloride hexahydrate crystals.
[0169] Preferably, the rich solution may be concentrated to its saturation point by evaporation.
[0170] In some embodiments, the rich liquor may be concentrated by boiling the rich liquor at a temperature between about 95°C and about 110°C.
[0171] In some embodiments, the pregnant solution may be concentrated to a concentration of about 60,000 ppm aluminum.
[0172] At step 40, the saturated solution may be subjected to a crystallization process.
[0173] Any suitable crystallization process may be used. Preferably, the crystallization process may include heating the saturated aluminum solution and bubbling gaseous hydrochloric acid through the saturated aluminum solution, thereby forcing aluminum chlorohexahydrate crystals to crystallize and form a slurry of aluminum chlorohexahydrate crystals.
[0174] In some embodiments, the saturated aluminum solution may be preheated to a temperature between about 60°C and about 70°C.
[0175] In some embodiments, gaseous hydrochloric acid may be used to bubble the saturated aluminum solution, with the reaction temperature maintained between about 60°C and about 70°C.
[0176] In some embodiments, the saturated aluminum solution may be bubbled with gaseous hydrochloric acid until the hydrochloric acid concentration of the saturated aluminum solution reaches between about 30 wt % and 34 wt %.
[0177] In some embodiments, the slurry of aluminum chlorohexahydrate crystals may be subjected to one or more recrystallization steps. In this example, it is contemplated that the slurry of aluminum chlorohexahydrate crystals obtained from crystallization of a saturated solution of aluminum chlorohexahydrate may be subjected to one or more recrystallization steps prior to being subjected to pyrolysis.
[0178] The slurry of aluminum chlorohexahydrate crystals may be recrystallized using any suitable technique known in the art. Preferably, the recrystallization process may comprise separating and washing the precipitated crystals, followed by dissolving the washed precipitated crystals in a solvent such as ultrapure water, demineralized water, etc. to form a feed solution. The feed solution may be subjected to a finishing step to remove insoluble contaminants such as silicon dioxide. The feed solution may then be heated and bubbled with gaseous hydrochloric acid to precipitate aluminum chlorohexahydrate crystals.
[0179] At step 50, the aluminum chlorohexahydrate crystal slurry may be cooled and the precipitated aluminum chlorohexahydrate crystals may be separated from the barren liquor.
[0180] The aluminum chlorohexahydrate crystal slurry may be cooled before separating the aluminum chlorohexahydrate crystals from the barren solution. Preferably, the aluminum chlorohexahydrate solution may be cooled during final crystallization and / or recrystallization.
[0181] The aluminum chloride hexahydrate solution may be cooled to any suitable temperature. Preferably, the aluminum chloride hexahydrate solution may be cooled to less than about -10°C.
[0182] The aluminium chloride hexahydrate solution may be agitated during cooling. In use, it is envisaged that agitating the solution during cooling may help avoid the formation of agglomerates and help form smaller particles.
[0183] Advantageously, cooling the aluminum chloride hexahydrate solution to a sufficiently low temperature and agitating the solution during cooling produces crystals of smaller particle size than conventional practice (less than about 10 μm, versus an average particle size of about 20 μm to about 100 μm) and increases the nucleation rate rather than the crystal growth rate.
[0184] The precipitate may be separated using any suitable technique known in the art. Preferably, the separation technique may be sufficient to separate the precipitate from the barren solution. For example, the separation technique may include: gravity settling clarifier, sedimentation, decantation, centrifugation, filtration, and the like.
[0185] The precipitate may be washed in order to separate the aluminum chloride hexahydrate crystals from impurities in the precipitate.
[0186] Any suitable wash liquid may be used to wash the precipitate. Generally, the wash liquid may be sufficient to redissolve soluble contaminants from the crystals, etc. The wash liquid may also be sufficient to displace entrained contaminated supernatant and replace it with a less contaminated wash liquid.
[0187] In some embodiments, the washing liquid may be hydrochloric acid, lean solution, etc. The washing liquid used to wash the precipitate obtained from crystallization of a saturated solution may be the same as the washing liquid used to wash the precipitate obtained from recrystallization of a feed solution, or may be different.
[0188] The aluminum chloride hexahydrate crystals can be separated from the excess hydrochloric acid using any suitable technique known in the art. For example, the separation technique may include: gravity settling clarifier, sedimentation, decantation, centrifugation, filtration, and the like.
[0189] At step 60, the aluminum chlorohexahydrate crystals may be heated at a temperature between about 100°C and about 350°C under a controlled air flow to obtain a dehydrated aluminum oxychloride.
[0190] Preferably, the aluminum chlorohexahydrate crystals may be heated under controlled air flow conditions. Preferably, the aluminum chlorohexahydrate crystals may be heated in a heated container under a heated and / or dry air flow.
[0191] The aluminum chlorohexahydrate crystals may be heated at any suitable holding temperature. Preferably, the aluminum chlorohexahydrate crystals are heated at a temperature between about 180°C and 230°C under a controlled air flow to obtain a dehydrated aluminum oxychloride.
[0192] The aluminum chlorohexahydrate crystals may be heated for any suitable period of time while maintaining the temperature. Preferably, the aluminum chlorohexahydrate crystals may be agitated while being heated under controlled air flow conditions.
[0193] In some embodiments, the dehydrated aluminum oxychloride formed by heating the aluminum chlorohexahydrate crystals has a residual chloride level of about 2% to about 10% by weight of the aluminum oxychloride.
[0194] In some embodiments, the aluminum oxychloride comprises particles that can pass through mesh openings of up to about 10 μm, preferably up to about 5 μm, and even more preferably up to about 2 μm.
[0195] The detailed description is as follows Figure 2The method for producing an alumina material (200) as described in claim 1. Preferably, the alumina material mainly comprises alpha alumina. Figure 2 The methods shown and described in the specification and Figure 1 The method is the same as shown in and described in the specification, except that the alumina material containing aluminum oxyhydroxy chloride is subjected to additional processing steps 80 and 90. Figure 2 The method shown in fully covers Figure 1 The method shown in . Figure 2 The intermediate product of aluminum oxyhydroxy chloride can be Figure 1 The final product is the same.
[0196] In this embodiment, it will be appreciated that the method (200) of the present invention provides a three-step pyrolysis to convert aluminum chlorohexahydrate into alpha alumina, wherein the three-step pyrolysis comprises steps 60, 80, and 90.
[0197] At step 80, the alumina material containing aluminum oxychloride may be decomposed at a temperature between about 800°C and about 980°C to form primarily amorphous aluminum oxide.
[0198] The aluminum oxychloride may be decomposed at any suitable temperature. Preferably, the aluminum oxychloride may be heated at a decomposition temperature between about 800°C and about 980°C.
[0199] In some embodiments, the step of decomposing the aluminous material comprising aluminum oxyhydroxy chloride may include controlling the humidity in the container.
[0200] In some embodiments, the amorphous alumina and gamma alumina formed by decomposing an aluminous material containing aluminum oxychloride has a residual chloride level of less than about 1.5 wt %, preferably less than about 1.0 wt %, and more preferably less than about 0.4 wt % of the amorphous alumina and gamma alumina.
[0201] At step 90, the amorphous alumina and gamma alumina may be calcined at a high temperature to obtain alumina. Preferably, the obtained alumina may comprise substantially alpha alumina.
[0202] The amorphous alumina and gamma alumina may be calcined at any suitable temperature. Preferably, the amorphous alumina and gamma alumina may be heated at a calcination temperature between about 1,100°C and about 1,300°C.
[0203] The detailed description is as follows Figure 3 The method (300) for producing an alumina material as shown in . Preferably, the alumina material comprises aluminum oxyhydroxy chloride. Figure 3 The methods shown and described in the specification, and Figure 1The method is the same as that shown in and described in the specification, except that an additional processing step 70 is used to produce an alumina material containing aluminum oxychloride.
[0204] Prior to the heating step 60, a drying step 70 is used.
[0205] At step 70, the aluminum chlorohexahydrate crystals may be dried under at least partial vacuum at a temperature between about 50°C and about 150°C before being heated at a temperature between about 100°C and about 350°C under a controlled air flow to obtain aluminum oxychloride.
[0206] Preferably, the aluminum chloride hexahydrate crystals may be dried at a pressure between about 50 mBar and about 1000 mBar.
[0207] Preferably, the aluminum chlorohexahydrate crystals may be dried at a temperature between about 80°C and about 130°C under at least a partial vacuum.
[0208] In some embodiments, after the step of drying the aluminum chlorohexahydrate crystals under at least a partial vacuum, the aluminum chlorohexahydrate crystals have a residual chloride level of about 30% to about 45% by weight of the aluminum chlorohexahydrate crystals.
[0209] In some embodiments, the aluminum chlorohexahydrate crystals contain substantially no residual moisture content.
[0210] In use, it is contemplated that low temperature heating of the aluminum chlorohexahydrate crystals under at least partial vacuum may help reduce liquid (including water) entrained within the crystals to provide stabilized dehydrated aluminum chlorohexahydrate, which is then dried to provide aluminum oxychloride. Advantageously, the low temperature drying stage under at least partial vacuum (step 70) reduces the time of drying the aluminum chlorohexahydrate crystals at high temperature (step 60) and provides improved energy efficiency compared to if a one-step drying process were used alone.
[0211] The detailed description is as follows Figure 4 The method (400) for producing an alumina material is shown in . Preferably, the alumina material mainly comprises alpha alumina. Figure 4 The methods shown and described in the specification and Figure 3 The method is the same as that shown in and described in the specification, except that the alumina material containing aluminum oxyhydroxy chloride is subjected to additional processing steps 80 and 90. Figure 4 The method shown in fully covers Figure 3 The method shown in . Figure 4 The intermediate product aluminum oxyhydroxy chloride can react with Figure 3 The final product is the same.
[0212] In this embodiment, it will be appreciated that the method (400) of the present invention provides a four-step pyrolysis to convert aluminum chlorohexahydrate to alpha alumina, wherein the four-step pyrolysis comprises steps 60, 70, 80, and 90.
[0213] like Figure 4 Steps 10, 20, 30, 40, 50, 60, and 70 of the method shown in correspondence to Figure 3 Steps 10, 20, 30, 40, 50, 60, and 70 of the method shown in .
[0214] At step 80, the alumina material containing aluminum oxychloride may be decomposed at a temperature between about 800°C and about 980°C to form primarily amorphous aluminum oxide.
[0215] In some embodiments, the step of decomposing the aluminous material comprising aluminum oxyhydroxy chloride may include controlling the humidity in the container.
[0216] In some embodiments, the amorphous alumina and gamma alumina formed by decomposing the aluminous material containing aluminum oxychloride has a residual chloride level of less than about 1.5 wt %, preferably less than about 1.0 wt %, and more preferably less than about 0.4 wt % of the amorphous alumina and gamma alumina.
[0217] At step 90, the amorphous alumina and gamma alumina may be calcined at a high temperature to obtain alumina. Preferably, the obtained alumina comprises substantially alpha alumina.
[0218] The amorphous alumina and gamma alumina may be calcined at any suitable temperature. Preferably, the amorphous alumina and gamma alumina may be heated at a calcination temperature between about 1,100°C and about 1,300°C.
[0219] The alpha alumina may be subjected to one or more further processing steps, such as pelletizing, sintering, grinding, etc., in order to produce a product having a particular density, particle size, and / or shape.
[0220] In the present specification and claims, the term "comprising" and its derivatives including "comprises" and "comprise", if any, include each stated integer / integers but do not exclude the inclusion of one or more additional integers / integers.
[0221] In this specification, "one embodiment" or "(one) embodiment" means that the specific features, structures or characteristics related to the embodiment are included in at least one embodiment of the present invention. Therefore, the expression "in one embodiment" or "in (one) embodiment" appearing in different places throughout the specification does not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics can be combined in one or more combinations in any appropriate manner.
[0222] In accordance with the statute, the invention has been described in language more or less specific to structural or methodological features. It will be understood that the invention is not limited to the specific features shown or described, as the means described herein comprise preferred forms of practicing the invention. Therefore, the invention is claimed for protection in any form or modification thereof within the proper scope of the appended claims (if any) as appropriately interpreted by those skilled in the art.
[0223] References
[0224] Tilley, GS; Millar, RW and Ralston, OC, "Acid Processes for the Extraction of Alumina" USBureau of Mines, No. 267, 1927.
[0225] Hoffman,JI,Leslie,RT,Caul,HJ,Clark,LJand Hoffman,JD, "Development of a Hydrochloric Acid Process for the Production of Alumina fromClay",Journal of Research of the National Bureau of Standards.1946,vol.37,pages409-428.
Claims
1. A method for producing alumina material, comprising: Provide aluminum-containing raw materials; Separating the aluminum-containing raw material to obtain a rich solution; Concentrating the rich solution to obtain a saturated aluminum solution; The saturated aluminum solution is subjected to a crystallization process, wherein the crystallization process comprises: heating the saturated aluminum solution; Bubbling the saturated aluminum solution with gaseous hydrochloric acid to form a slurry of aluminum chloride hexahydrate crystals; separating the aluminum chloride hexahydrate crystals from the aluminum chloride hexahydrate crystal slurry to form a barren solution; and The aluminum chlorohexahydrate crystals are heated under a controlled air flow at a temperature between about 100°C and about 350°C to obtain a dehydrated aluminum oxychloride.
2. The method for producing alumina material according to claim 1, further comprising: The aluminum chlorohexahydrate crystals are dried under at least a partial vacuum to a temperature between about 50°C and 150°C prior to drying the aluminum chlorohexahydrate crystals under a controlled air flow at a temperature between about 100°C and about 350°C to obtain a dehydrated aluminum oxychloride.
3. The method for producing alumina material according to claim 1 or claim 2, further comprising: decomposing the aluminum oxychloride at a temperature between about 800° C. and about 980° C. to form primarily amorphous aluminum oxide, and The amorphous alumina is calcined at a temperature between about 1,100°C and about 1,300°C to obtain primarily alpha alumina.
4. A method for producing an aluminous material as claimed in any one of the preceding claims, wherein drying the aluminium chlorohexahydrate crystals at a temperature between about 50°C and 150°C under at least partial vacuum is carried out using microwave vacuum assisted drying.
5. A method for producing aluminous material as claimed in any one of the preceding claims, wherein the rich solution is concentrated to its saturation point by evaporation.
6. A method for producing aluminous material as claimed in any one of the preceding claims, wherein the slurry of aluminium chloride hexahydrate crystals is subjected to one or more recrystallisation processes.
7. A method as described in any of the preceding claims, wherein the aluminum-containing feedstock comprises an aluminum-containing material including: aluminum hydroxide, aluminum metal, aluminum chlorohexahydrate, red mud, fly ash, a mineral processing waste stream, aluminosilicate, kaolin, zeolite, or feldspar.
8. A method as claimed in any one of the preceding claims, wherein the aluminium-containing feedstock is formed by dispersing the aluminium-containing material in a solvent.
9. The method of any one of the preceding claims, wherein the aluminum-containing raw material is separated using a gravity settling clarifier, settling, decantation, centrifugation, or filtration.
10. The method of any one of the preceding claims, wherein the aluminum-containing feedstock is separated into the rich liquid and a solid residue.
11. The method of any one of the preceding claims, wherein the saturated aluminum solution is obtained by concentrating the rich solution by boiling or evaporation.
12. The method of any one of the preceding claims, wherein the pregnant solution is concentrated such that the aluminum concentration of the saturated aluminum solution is between about 50,000 ppm and 70,000 ppm.
13. The method of any one of the preceding claims, wherein the saturated aluminum solution is preheated to between about 50°C and about 80°C.
14. The method of any one of the preceding claims, wherein the saturated aluminum solution may be bubbled with gaseous hydrochloric acid at a reaction temperature between about 60°C and about 100°C.
15. The method of any one of the preceding claims, wherein the saturated aluminum solution is bubbled with gaseous hydrochloric acid until a hydrochloric acid concentration of the saturated aluminum solution reaches between about 30% and 35% by weight.
16. A process as claimed in any one of the preceding claims, wherein the slurry of aluminium chlorohexahydrate crystals is subjected to one or more recrystallisation steps prior to pyrolysis.
17. The method of claim 16, wherein the one or more recrystallization steps are configured to precipitate purified aluminum chlorohexahydrate crystals from the slurry of aluminum chlorohexahydrate crystals.
18. The method of claim 17, wherein the purified aluminum chlorohexahydrate crystals are separated from a slurry of aluminum chlorohexahydrate crystals and dissolved to form a feed solution.
19. The method of claim 18, wherein the feed liquid is polished to remove insoluble contaminants.
20. The method of claim 19, wherein: After removing the insoluble contaminants, the feed solution is heated and bubbled with gaseous hydrochloric acid to precipitate aluminum chloride hexahydrate crystals.
21. The method of any one of the preceding claims, wherein the slurry of aluminum chlorohexahydrate crystals is cooled to a temperature of less than about -10°C prior to separating the aluminum chlorohexahydrate crystals from the barren liquor.
22. The method of any one of the preceding claims, wherein the slurry of aluminum chlorohexahydrate crystals is agitated during cooling to obtain aluminum chlorohexahydrate crystals having a particle size of less than about 10 μm.
23. The process of any one of the preceding claims, wherein the aluminum chloride hexahydrate crystals are heated in a forced air drying oven, a flash dryer, or a fluidized bed dryer.
24. The method of any one of the preceding claims, wherein the aluminum chlorohexahydrate crystals are heated at a ramp rate of at least about 75°C / minute to reach a temperature at which aluminum oxyhydroxychloride is obtained.
25. A process as claimed in any preceding claim wherein the aluminium chlorohexahydrate crystals are agitated during heating to assist in deagglomeration and / or particle size reduction of the crystals.
26. The method of any one of the preceding claims, wherein the aluminum oxychloride formed by heating the aluminum chlorohexahydrate crystals has a residual chloride level of from about 2% to about 12% by weight of the dehydrated aluminum oxychloride.
27. The method of claim 2, wherein the aluminum chlorohexahydrate crystals are dried at a pressure between about 250 mBar and about 600 mBar.
28. The method of claim 2 or claim 27, wherein after the step of drying the aluminum chlorohexahydrate crystals under at least a partial vacuum, the aluminum chlorohexahydrate crystals have a residual chloride level of about 30% to about 45% by weight of the aluminum chlorohexahydrate crystals.
29. The method of claim 3, wherein decomposing the aluminum oxychloride primarily forms the amorphous alumina and gamma alumina.
30. The method of claim 29, wherein the residual chloride level of the amorphous alumina and the gamma alumina is less than about 0.4 wt. %.
Citation Information
Patent Citations
Method of producing alumina powder
JP2013203598A