The process of extracting and producing pure alumina from the hazardous aluminium dross industry

Abstract

Aluminum is one of the most widely used non-ferrous metals in the world, with numerous industrial applications. Recycling aluminum instead of extracting it from bauxite stone reduces energy consumption by 95%. The resulting byproduct, called dross, is harmful to the environment and requires neutralizing technology. However, recycling aluminum dross has led to the development of a third aluminum industry, with various applications such as construction materials, road paving, and inert composite fillers. Alumina, a compound of aluminum, is also widely used in industries due to its unique properties, including high compressive strength and resistance to chemical attack

Description

the process of extracting and producing pure alumina from the hazardous Aluminium dross industry

[0001] Aluminum is one of the most widely used non-ferrous metals in the world, with numerous industrial applications. Recycling aluminum instead of extracting it from bauxite stone reduces energy consumption by 95%. The resulting byproduct, called dross, is harmful to the environment and requires neutralizing technology. However, recycling aluminum dross has led to the development of a third aluminum industry, with various applications such as construction materials, road paving, and inert composite fillers. Alumina, a compound of aluminum, is also widely used in industries due to its unique properties, including high compressive strength and resistance to chemical attacks.

[0002] C21D 3 / 02

[0003] KR1020000020557 - METHOD FOR RECYCLING ALUMINUM DROSS

[0004] A method for recycling aluminum dross is provided which can prevent environmental pollution and by which cost for raw materials and equipment can be reduced and a hydrogen gas can be obtained during the process.

[0005] CONSTITUTION: An aluminum dross is recycled as follows: after cracking the aluminum dross into pieces, remelting a piece which is bigger than 1 mm to draw back an aluminum; dissolving aluminum component of the aluminum dross smaller than 1 mm in 10-20% of sodium hydroxide (which generates hydrogen gas), followed by filtering it and adding aluminum hydroxide seeds to it to hydrolyze it to obtain aluminum hydroxide. The filtered precipitates, mixed with an aggregate and an aluminum cement, is used to produce a castable fireproof material.

[0006] The invention above is also a method for recycling the Aluminum dross, but it uses hydrolyzing and leaching for this aim, while our invention is based on digesting the dross by acid and crystalizing method.

[0007] AU1993045501 - Extracting alumina from bauxiteA process for extracting alumina from bauxite comprising the steps of concentration a portion of spent caustic liquor (18), combining said concen- trated spent caustic liquor with a bauxite slurry (3) to provide a final aluminato caustic ratio (A / C) of greater than 0.7 in the slurry / liquor mixture, heatingthe mixture by means of a heat exchanger (5), subjecting the mixture to diges- tion in a tank (7) at a temperature below that at which reversion of dissolved gibbsite to boehmite may occur to thereby extract alumina from the gibbsite bauxite in the slurry, separating the high alumina pregnant liquor (9) from the boehmite containing residue in a pressure decanter (8), mixing the residue with the remaining portion of unconcentrated spent caustic liquor (18) and subject- ing the mixture to high temperature digestion in a tank (11) to extract the re- maining alumina from the residue, subjecting the digested mixture to flash cooling in flash tanks (13), and separating the alumina rich liquors from the high alumina pregnant liquor and from the digested mixture in an atmospheric separator (14) or a pressure decanter (17)

[0008] The invention above is also a method for extracting alumina, while our invention focuses on extracting this product from the aluminum dross and the mentioned invention extracts it from the bauxite stone, which is almost a rare stone in the world.

[0009] CN102180498 - Method for extracting alumina from bauxite

[0010] The invention discloses a method for extracting alumina from bauxite, which is suitable for extracting the alumina from various and different ore mineral types of bauxites. The method comprises the following steps: mixing and grinding the crushed bauxite and sodium carbonate according to a certain proportion, and then obtaining high-purity alumina through roasting, circular leaching, sedimentation-filtration, carbonization, additive recycling, washing, calcination, and the like. In the whole production process, the generated carbon dioxide and the used additive can be recovered and reused. Compared with the Bayer process and other methods for producing the alumina, the method has the advantages of low requirement on the grade of the alumina from the bauxite, low requirement on the aluminum-silicate (A / S) ratio, no limitation to the type of minerals, high extraction rate of the alumina, low energy consumption, more succinct process, no special requirements on the equipment, lower cost, and the like, thereby easily realizing industrialization.

[0011] The invention above differs from ours in its extraction method, as it uses roasting, cyclic leaching, precipitating and filtering, carbon separation, auxiliary agent and water recovery and ours do not use any of these methods and instead, uses acid and crystallization metho for this aim. Also, our invention do not extract alumina brom the bauxite stone, but from the harmful aluminum dross.

[0012] US4128618 - Process for extracting alumina from alumina-containing ores

[0013] In a process for extracting alumina from alumina-containing ores on a two-stream system by individually preheating a slurry of alumina-containing ores and an aqueous alkali solution each in preheaters of indirectly heating, mixing the preheated slurry with the preheated aqueous alkali solution, and extracting alumina from the ores in a digester of either the heating type involving the direct injection of live steam or the heat-insulated type, the alumina is extracted from the ores by preparing the slurry of alumina-containing ores with water or a diluted aqueous alkali solution, such as from the drain obtained by recovering steam from an evaporator for cooling the slurry resulting from extraction, and utilizing the recovered steam in preheating the slurry of the alumina-containing ores or decomposition solution or both, preheating the slurry of alumina-containing ores, and mixing the preheated slurry with an aqueous alkali solution preheated as another stream as the decomposition solution. Scale formation can be prevented completely or substantially on the inside surface of the preheater for the slurry of alumina-containing ores.

[0014] The invention above extracts alumina from the ores containing it, while ours extracts alumina from the harmful aluminum dross with a different method.

[0015] CA1049795 - PROCESS FOR EXTRACTING ALUMINA FROM ALUMINA-CONTAINING ORES

[0016] In a process for extracting alumina from alumina-containing ores by individually preheating a slurry of alumina-containing ores in alkali solution, and an alkali solution, and feeding the preheated slurry and tne preheated alkali solution to a digester maintained at a temperature of about 200° to about 300°C, thereby extracting alumina from the alumina- containing ore, the alumina extraction is carried out without any formation of scales on the inside surface of preheater with a considerably prolonged operating duration by preparing a slurry having a molar ratio of Na2O / Al2O3 of not more than 1 from the alumina- containing ores and an alkali solution, subjecting the slurry to preliminary desilication treatment, if necessary, then adding an alkali material to the slurry while preheating the slurry before the slurry reaches a temperature of forming scales originating from deposition of boehmite-type alumina from the slurry, thereby obtaining the slurry having an adjusted molar ratio of Na2O / Al2O3 of more than 1, further preheating the slurry having the adjusted molar ratio to a temperature higher than that of forming scales originating from deposition of boehmite- type alumina from the slurry before the adjustment of the molar ratio. and then extracting the alumina from the alumina-containing ores in the slurry admixed with a separately preheated alkali solution in the digester.

[0017] The invention above is about extracting alumina from ores containing it, while ours is about extracting that from the aluminum dross.

[0018] AU1993040620 - Process for the extraction of alumina

[0019] This invention relates to a process for the extraction of alumina from alumina-containing solid material, particularly the alumina-containing ores known as bauxite. The process comprises: a) providing the material in the form of a slurry (101) in an alkaline solution having a concentration of free caustic therein sufficient at the temperature reached in step (c) to dissolve alumina values, b) classifying (6) the slurry into a fine particle fraction and a coarse particle fraction, c) heating the fine particle fraction (105) to a temperature sufficient to dissolve at least some of the alumina values therein with consequential reduction in the free caustic concentration in the liquid phase of the fine fraction slurry, and d) combining the coarse particle fraction (109) from step (b) with the free caustic-depleted slurry liquid from step (c) at a temperature higher than that reached in the step (c) so as to dissolve at least some of the alumina values in the coarse particle fraction.

[0020] The mentioned invention is about extracting alumina, mostly from bauxite, while ours is about extracting it from aluminum dross.

[0021] WO2009063482 - EXTRACTION OF ALUMINA

[0022] A process for extraction of alumina from aluminum containing ores is disclosed. The process involves the following steps: determining the alumina and silica content in the ore; treating the ore with caustic, subjecting the reaction mass to electromagnetic radiation, leaching soluble intermediate product with water to separate insoluble red mud as residue and to obtain a filtrate containing aluminate, silicate and vanadate; separating silicate and other impurities as residue from the filtrate to obtain beneficiated aluminate liquor and extracting alumina from sodium aluminate by a conventional method.

[0023] The invention above is about extracting alumina and silica from the ores, while ours is about extracting it from aluminum dross.

[0024] A method for extracting Alumina (Al2O3) from aluminum dross using sulfuric acid, nitric acid, or hydrochloric acid for alumina digestion. The process involves acidic digestion, separation of Al ions, and various stages of neutralization and filtration to obtain Al(OH)3, which is then refined to obtain Al2O3.

[0025] aluminum is one of the most used non-ferrous metals in the world. It is used in industry for the production of different products and in the economy, it plays an important role. The universal production of Aluminium was 31.9 million tones in the year 2005 which makes it the second metal after iron with 837 million tones. The aluminum alloys have specific properties like high strength compared to their weight, good weldability, perfect forming, and high torsional resistance which makes them be used vastly in different constructions, Aviation, and marine industries, electricity transferring lines, transportation, etc. The primary aluminum is produced from electrolyte extraction of alumina. Bauxite is the main source of alumina, in a way that more than 96% of the alumina produced in the world is extracted from bauxite, which is a mineral material with alumina percentages between 40-60 percent the source is in Jamaica, Australia, Brazil, and Africa, India, and Russia.

[0026] Using recycled aluminum instead of extracting it from bauxite stone reduces 95 percent of the energy consumption. It is estimated that 30 cans are easily produced from about 450 grams of Aluminium waste, and the quality does not differ from the newly extracted Aluminium. Based on that, in recent decades, a new industry was formed that is called the Second Aluminium industry.

[0027] Plus, in the first Aluminium industry, while producing different alloys and performing billet-making and extruding, there were unwanted side products that most of it is Aluminium and oxides and different combinations of them which are called Wet / White Dross. This product is sold in some countries like America, Europe, and Russia by the same factory and in some countries by the smaller factories. During the process of grinding and sieving, the metal (6-8% of the whole dross) is separated and the rest of the product which is without metal (NMP) and is also called FB dross it is released in the environment.

[0028] The amount of the produced dross is estimated about 13 kilograms per a ton of production, which means about 300-500 thousands of tons of it is produced in the whole world. Maybe this amount is not significant but considering its harm to the environment, the United States Environmental Protection Agency (USEPA) in the year 1980 and the European Union (Council Resolution 1994), the dross’ soil is also considered harmful waste to the environment and depo-off or releasing them needs the best neutralizing technology for the environment. Once even a spontaneous combustion happened because of the aluminothermy process that exists in FB dross.

[0029] Processing and recycling Aluminium dross is also considered to be the third Aluminium industry. The industry is so busy producing the products that are favorable in the market.

[0030] Different applications are defined for this dross filler materials in construction, road paving, components of furnaces, inert composite fillers, absorbents, and mineral woods. Nevertheless, the most economical use for that is reported to be exploiting aluminum and the most valuable combination that is exploited from that is also alumina.

[0031] Alumina is a group of inorganic compounds with the chemical formula Al2O3. The features of alumina have made it useful in many industries including:

[0032] – high compressive strength

[0033] – high density

[0034] – high torsional resistance

[0035] – resistance to chemical attacks with a wide range of chemicals even in high temperatures

[0036] High heat conductivity

[0037] Resistance to the heat shock

[0038] High refractory

[0039] high dielectric strength

[0040] high electric resistance even in high temperatures

[0041] transparency against the microwave radiation frequencies

[0042] Gamma alumina is the basic catalyst in industries, as well as the HDS catalyst that has a vast application in the oil, gas, and petrochemistry industries. The average annual consumption of alumina-based catalysts in this industry is more than 650 thousand tons. In the ceramic section, one or a few grades of the alumina are used, due to the requiery. In this project, the aluminum factory dross that has gone under many levels of mechanical process, and most of its metallic aluminum is recycled was used. As mentioned before, this dross is graded as non-metallic dross and its elements include 30-32% Aluminum, silica 5.1%, iron 5.0%, calcium 5.5%, and magnesium 2.2%, sodium 3.1%, potassium 1.1%, chlorine 2.5% and fluor 3.5% that is considered a dangerous material for the environment. The European rules have categorized it under H12 waste material grades because in the presence of water and humidity, Spontaneous, and exothermic reactions may happen and they may cause the release of toxic compounds including hydrogen, ammonia, methane, and hydrogen sulfide. On the other hand, due to the existence of micrometer light particles that cause air pollution and dust.Solution of problem

[0043] Considering the percentage of the existing elements in the used dross which is shown in Table 1, the proper process for exploiting alumina from dross was chosen. The acidic solution could be used for digesting the alumina. As an example, sulfuric acid, nitric acid, or hydrochloric acid can be used. Acidic digestion can solve the aluminum ions and separate them from the dross sample. As an example, the amount of the used acids based on volume percentage could be 20%, 30%, 35%, 40%, 45%, 50%, 55%, 60% or 65%. The amount of soluble sample in this stage could be based on the weight-volume ratio of solid to liquid, as an example with the portion of 1:5, 1:4, 1:3, 1:2, or 1:1. The digestion temperature based on centigrade degrees could be 80, 90, 100 or 110. In the stage of digesting, the Aluminum ions Al3+transfer to the solution phase and can be separated from the solid amount that is not digested yet. To regain the Al3+ions that are solved in the solution phase, it is possible to use alkali , like NaOH, KOH, NH3OH, NH4HCO3, (NH4)2CO3, (NH4)Al(SO4)2, or a CO2 gas to neutralize it. The PH of the regaining stage of the Al3+ions could be equal to 4.0, 4.2, 4.4, 4.6, 4.8, or 5. The process could go on by separation with only one filter and the resulting product is Al(OH)3. If sulfuric acid is used for digestion, it is possible to separate the probable iron ions in the solution phase before the neutralizing level by complexing agents like EDTA or crystallization of the solution. If the crystallization method is used, the solution gained from the digestion level could be provided without changing the concentration or diluting it with the ratio of 1:2, 1:3, 1:4, or 1:5. The crystallization process could happen in low temperatures like 4, 5, 6 or 7 centigrade degrees for 24 hours and the process can continue, by growth with or without the primary core. the amount of the obtained crystal in this level is based on the ratio of the sample amount and the weight ratio could be 1:1 the percentage of the elements inside the crystal is shown in the table. 1.

[0044] The obtained crystal could be solved in water with the weight-volume ratio of 10%, 20%, 30%, 35%, 40%, 45%, or 50%, and the gained solution in the temperatures 40, 50, 60 or 70 centigrade degrees with alkali like NaOH, KOH, NH3OH, NH4HCO3, (NH4)2CO3 and (NH4)Al(SO4)2 or CO2 gas. The PH in this level could be set at 4.0, 4.2, 4.4, 4.6, 4.8, or 5. The process can go on with separation by a filter and result in the product Al(OH)3. The resulting Al(OH)3 could be used for more purifying in an alkaline solution, with for example NaOH, KOH, NH3OH, NH4HCO3, or (NH4)2CO3, at a temperature of 80, 90, 100, or 110 centigrade degrees and reflux it for 2, 3, 4, 5 or 6 hours. Then with filtration, Al(OH)3 with high purification percent is obtained. The EXD analysis of the resulting product is shown in Table 1. In this analysis, a little element F is seen that is the result of the combinations inside the dross and it is eliminated at a temperature of more than 200 centigrade degrees.

[0045] The images were taken with a scanning electron microscope SEM from the Al(OH)3 and the produced alumina shows that different morphologies like spherical particles, rod-like particles, hexagonal particles, and rice-shaped particles from Al(OH)3 are preparable with this method. The resulting Al(OH)3 could be calcinated at a temperature of 800 to 1200 centigrade degrees and turns into AL2O3.Advantage effects of the invention

[0046] – using harmful ingredients for the environment and changing it into a valuable material

[0047] – cheap used ingredients

[0048] – having local technical knowledge for exploiting valuable elements from metal industry waste

[0049] - Not needing expensive and developed equipment

[0050] - Cheap products in comparison to other similar products in the market

[0051] : demonstrates the whole process of alumina extraction from Aluminum dross

[0052] : the figure illustrates how the alumina is extracted from alumina dross, in different levels like digestion, filtration, and acid reflux.Examples

[0053] [Table. 1]: The amount of elements existing in the dross and the crystal obtained from it with the use of EDX analysis

[0054] [diagram.1]: the EDX analysis of aluminum oxide resulting from the Aluminum dross industry

[0055]

[0056] [ picture. 2]: the SEM picture from synthesized aluminum hydroxide from the aluminum dross industry with 2000 times magnifying

[0057]

[0058] [picture. 3]: the SEM picture from synthesized aluminum hydroxide from the aluminum dross industry with 2000 times magnifying

[0059]

[0060] [picture. 4]: the SEM picture from synthesized aluminum hydroxide from the aluminum dross industry with 8000 times magnifying

[0061]

[0062] [picture. 5]: the SEM picture from synthesized aluminum hydroxide from the aluminum dross industry with 25000 times magnifying

[0063]

[0064] [picture. 6]: the SEM picture from synthesized aluminum hydroxide from the aluminum dross industry with 50000 times magnifying

[0065]

[0066] [picture. 7]: the SEM picture from synthesized aluminum hydroxide from the aluminum dross industry with 10000 times magnifying

[0067]

[0068] Gama aluminum is considered a basic catalyst in industries, including HDS which has a vast application in the oil, gas, and petrochemistry industry. The annual consumption of the basic alumina catalyst in this industry is more than 650 thousand tons. In the ceramic section, considering the alumina needs, one or a few grades are used.

[0069] The Nanoalumina is used in different industries including ceramic production, composite, nanocomposite, plastic industry, rubber manufacturing, polymer industry, metal industry, Pulp and paper industry, automotive industries, Fuel cell, and battery energy, fuel industry and explosive material, Water and sewage treatment industries as catalyst in oil, gas and petrochemistry industry, Construction industry, hygiene industry, cosmetic industry, medical and biology industry, filtration, military and aerospace industry. The Gama phase of the Alumina nanoparticles with high contact area and high activity, can turn into a microporous spherical structure or a honeycomb structure catalysor. These structures are incredible containers of catalysts.

[0070] If used as an industrial catalyst, the basic material for oil refining, petrochemistry, and exhaust smoke refinery. These nanoparticles are used as abrasive material due to their hardness and they are also electrically conductive and have high heat conductivity. Categorically, Alumina is categorized in a ceramic category and the categories put this material among the catalysts and thermal-resistant composites as abrasive material, dielectric, and bioceramics.

Claims

A method for extracting Alumina(Al2O3) from harmful aluminum dross using Sulfuric acid, Nitric acid, or Hydrochloric acid for alumina digestion.]The method according to the claim.1, wherein the Al ion could be separated from the dross sample by acidic digestion.The method according to claim. 2, wherein the acid percentage is 20%, 30%, 35%, 40%, 45%, 50%, 55%, 60% or 65%, based on the volume percent.The method according to claim. 3, wherein the digestible sample in this stage could be 1:1, 1:2, 1:3, 1:4, or 1:5 based on the volume percent ratio.The method according to claim. 4, wherein the digestion process temperature could be 80, 90, 100, or 110.The method according to claim. 5, wherein the Al3+solves in the liquid at the digestion level and can be separated from the undigested amount with filtration.The method according to claim. 6, wherein the solved Al3+ions in the solution phase could be neutralized using alkali like NaOH, KOH, NH3OH, NH4HCO3,(NH4)2CO3, (NH4)Al(SO4)2, or CO2gas. The PH of the regaining stage of the Al3+ions can be 4.0, 4.2, 4.4, 4.6, 4.8 or 5.0.The method according to claim. 7, wherein if sulfuric acid is used, the probable Fe ions in the solution can be separated by a complexing agent like EDTA or by crystalizing the solution.The method according to claim. 8, if the solution crystallization method is used, the resulting solution from the digestion level can be used with the ratio of 1:2, 1:3, 1:4, and 1:5, without changing the concentration or dilution.The method according to claim. 9, wherein the crystallization can happen in low temperatures like 4, 5, 6, or 7 centigrade degrees for 24 hours, and the process can continue with the growth of the primary ore or without it.The method according to claim. 10, wherein the amount of the obtained crystal in this level based on the used sample amount according to the weight ratio could be 1:1The method according to claim. 11, the obtained crystal with a maximum 50% weight-volume ratio, is solved in the water.The method according to claim. 12, wherein the resulting solution is neutralized at a temperature of 40, 50, 60, or 70 centigrade degrees with an alkali like NaOH, KOH, NH3OH, NH4HCO3, (NH4)2CO3, (NH4)Al(SO4)2, or CO2gas.The method according to claim. 13, wherein the pH could be set to a maximum of 5.0.The method according to claim. 14, wherein the separation process can continue with a filter, and the Al(OH)3could be obtained.The method according to claim. 15, the resulting Al(OH)3, could be refluxed in an alkaline solution like NaOH, KOH, NH3OH, NH4HCO3, (NH4)2CO3, or (NH4)2CO3, in the maximum temperature of 110 centigrade degrees for maximum 6 hours, for more purification.The method according to claim. 16, wherein the resulting Al(OH)3could be obtained with filtration.The method according to claim. 17, wherein the Al(OH)3could be calcinated in a temperature of 800-1200 centigrade degrees and it turns into Al2O3.

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