Method for producing high-white aluminum hydroxide by low-carbon sintering of bayer process red mud

Abstract

The present application relates to a kind of Bayer red mud low carbon sintering production high white aluminium hydroxide method, belong to industrial solid waste processing field, comprising the following steps: (1) adding industrial sodium aluminate solution in Bayer red mud, mixed to make raw material pellet;(2) after drying, dry sintering and cooling are carried out to pellet;(3) adding lye to clinker and carrying out wet grinding leaching, and leaching slurry is carried out liquid-solid separation;(4) leaching solution is carried out atmospheric desiliconization and carbonation decomposition, and high white aluminium hydroxide is obtained;(5) the solution produced by carbonation decomposition is carried out evaporation crystallization to obtain industrial sodium carbonate, and after washing separation, tailings of extracting aluminium is used to prepare cementing material.The method of the present application is more simple and flexible using two components distribution, realizes the efficient recovery of Al2O3 in red mud, CO2 emission is substantially reduced compared with traditional sintering method, and the alumina in sodium aluminate solution can improve raw material aluminium-silicon ratio, and then improve the sintering, leaching and settling performance of clinker, achieve the high value and full utilization of red mud.

Description

Technical Field

[0001] This invention belongs to the field of industrial solid waste treatment, and in particular relates to a method for producing high-whiteness aluminum hydroxide by low-carbon sintering of Bayer red mud. Background Technology

[0002] my country possesses abundant reserves of low-grade monohydrate gibbsite-type bauxite, but the aluminum-to-silicon ratio is generally below 4. This type of bauxite requires high-temperature, high-pressure treatment and the addition of large amounts of lime during the Bayer process for alumina production. Therefore, the resulting Bayer process red mud is characterized by high aluminum, high alkali, and high calcium content, typically with Al₂O₃ content reaching 20-30%, Na₂O content reaching 10-15%, and CaO content reaching 15-25%. Currently, the soda-lime sintering method is the main method for large-scale industrial treatment of red mud, used to recover valuable metals such as aluminum and sodium. However, this method also has some drawbacks. For example, the use of wet spraying into the kiln increases sintering energy consumption due to the 35-40% moisture content in the raw slurry; the traditional sintering method uses soda ash as the alkali source and requires the addition of large amounts of limestone, leading to significant carbon dioxide emissions during sintering; and the low aluminum-to-silicon ratio of Bayer process red mud results in a narrow sintering range and a tendency for clinker to form rings in the kiln. In the field of industrial solid waste treatment, it is imperative to develop new methods for the efficient, economical, green, and low-carbon full utilization of Bayer process red mud.

[0003] While the alumina production processes and raw material substitution methods proposed in patents [CN109704374B] and [CN109516484B] can overcome the problems of high production costs and poor product performance associated with traditional sintering methods, they all employ multi-component batching, which reduces the precision of batching. Furthermore, the addition of limestone or calcium carbide sludge increases the amount of calcium required, thereby reducing the alumina content of the clinker and significantly increasing the amount of tailings. These methods still rely on a batching system using soda ash as the alkali source, and Na2CO3 reacts during sintering to generate large amounts of carbon dioxide gas, causing greenhouse effects and other hazards.

[0004] The methods for producing alumina through liquid alkali sintering proposed in patents such as [CN114940506A] can expand the alkali sources in the sintering section of the series production process and increase production diversity. However, they still suffer from a series of problems, including large amounts of calcium added to the clinker, large amounts of tailings, and difficulties in efficiently recovering alkali from the tailings due to secondary reactions. Furthermore, the metallurgical-grade alumina produced by these methods currently faces overcapacity, promoting the development of fine alumina products such as high-whiteness aluminum hydroxide.

[0005] The sintering method for removing organic matter from alumina mother liquor proposed in patents [CN108793213B] solves the problems of high consumption costs and difficult operation associated with existing methods for removing organic matter from mother liquor. However, the wet slurry spraying method used in this method has disadvantages such as poor sintering uniformity and high sintering energy consumption compared to the dry pellet sintering method. Similarly, the alumina clinker sintering process proposed in patents [CN109704373B] also suffers from problems such as the direct injection of raw slurry into the rotary kiln, increasing clinker sintering energy consumption and alumina production costs. Summary of the Invention

[0006] To address the aforementioned issues, this invention employs a two-component solid-liquid batching method that is simpler, more flexible, and easier to control. By reverse-compensating the alkali in the Bayer process to the sintering process, carbon emissions are significantly reduced, batching accuracy is improved, and various properties of the clinker are enhanced. This method also addresses the problem of high organic content and difficulty in removing organic matter from sodium aluminate solutions in the Bayer process, effectively reducing sintering energy consumption. The production of high-whiteness aluminum hydroxide and the co-preparation of cementitious materials realize the value-added and full-scale utilization of red mud.

[0007] This invention proposes a method for producing high-whiteness aluminum hydroxide by low-carbon sintering of Bayer red mud, specifically comprising the following steps:

[0008] (1) Add industrial sodium aluminate solution to the Bayer process red mud produced by high-pressure leaching of gibbsite-type bauxite to obtain raw material, mix evenly and pelletize to obtain raw material pellets;

[0009] (2) The raw material pellets are dried outside the kiln or air-dried naturally to remove excess moisture and obtain dried raw material;

[0010] (3) The dried raw material is sintered by dry sintering and then cooled to obtain sintered clinker;

[0011] (4) A dilute alkaline solution is added to the sintered clinker for wet milling and leaching to obtain a leaching slurry;

[0012] (5) The leaching slurry is subjected to liquid-solid separation, and the liquid phase obtained is leaching liquid, and the solid phase is aluminum extraction tailings;

[0013] (6) The leachate undergoes a period of atmospheric pressure desilication and carbonation decomposition to obtain high white aluminum hydroxide, wherein the whiteness of the high white aluminum hydroxide is 98-99% and the average particle size is ≤45μm.

[0014] In step (1) above, the Bayer process red mud is red mud produced by high-pressure leaching of low-grade gibbsite-type bauxite, and by mass percentage, it contains 20-30% Al2O3, 15-25% CaO, 15-25% SiO2, 5-15% Fe2O3, 3-8% TiO2, and 8-15% Na2O; the portion of the Bayer process red mud with a particle size ≤55μm accounts for ≥90% of the total mass; the industrial sodium aluminate solution is one or more of the ore leaching liquid, evaporation mother liquor, and circulating mother liquor from the Bayer process, and by mass concentration, it contains 200-300g / L NaOH (as Na2O), 10-30g / L Na2CO3 (as Na2O), 100-200g / L Al2O3, and 5-25g / L total organic matter (as organic carbon).

[0015] In step (1) above, the raw material is added at a rate of 0.2–1.0 m³ per ton of dry red mud. 3 Industrial sodium aluminate solution; the raw material is prepared without additional lime, and the alkali-silicon ratio is adjusted by adding industrial sodium aluminate solution to achieve a balanced batching system; the raw material is mixed using a mixer for 2-3 hours; the pelletizing is done using a pelletizing machine, and the resulting raw material pellets have a particle size of 2-3 cm and a moisture content of 15-20%.

[0016] In step (2) above, the kiln drying is carried out by a dryer, the drying temperature is 100-150°C, the drying time is 10-20h, and the heat source is the tail gas generated by dry sintering in step (3).

[0017] In step (3) above, the dry sintering adopts a rotary kiln, the sintering temperature is 1000-1200°C, and the sintering time is 0.5-2h; the cooling adopts a cooler, and the cooling temperature is 80-200°C.

[0018] In step (3) above, the main components of the sintered clinker are sodium aluminate, low-calcium calcium silicate, calcium titanate and sodium ferrite.

[0019] In step (4) above, the wet milling leaching is performed using a ball mill, the leaching reaction temperature is 70-80°C, and the leaching reaction time is 5-30 min; the wet milling leaching uses a dilute alkaline solution or red mud washing solution, which, by mass concentration, contains 10-30 g / L NaOH (calculated as Na2O) and 10-40 g / L Al2O3, with a molecular ratio of 1.1-1.4, and the liquid-solid ratio of the alkaline solution to the clinker is 3-5. The recovery rate of Al2O3 after leaching the clinker reaches 85-90%.

[0020] In step (5) above, the liquid-solid separation is performed using a settling tank, a filter, or a filter press.

[0021] In step (6) above, the first-stage atmospheric desilication temperature is 90-180°C, the desilication time is 1-4h, the CaO addition amount is 7-13g / L, and the silicon content index reaches 800 or above; the carbonation decomposition temperature is 40-60°C, the decomposition time is 4-6h, the CO2 gas concentration is 20-25%, the gas flow rate is 3-5L / min, no aluminum hydroxide seed crystals are added, and the decomposition rate reaches 90% or above.

[0022] Furthermore, the aluminum extraction tailings from step (5) are washed and separated, and then used to prepare a cementitious material. The particle size of the aluminum extraction tailings is ≤45μm, and the specific surface area is ≥550m². 2 / kg, by mass percentage, the proportion of aluminum extraction tailings in the cementitious material is ≥70%.

[0023] Further, the solution produced after carbonation decomposition in step (6) is evaporated and crystallized to obtain industrial sodium carbonate product; the solution produced after carbonation decomposition contains 90-150 g / L of Na2CO3 (calculated as Na2O) by mass concentration, the evaporation and crystallization temperature is 80-100°C, and the condensate recovered by evaporation and condensation is used for the production of fine alumina.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) The batching system consists only of Bayer red mud and industrial sodium aluminate solution after the dissolution of monohydrate gibbsite. Compared with the traditional sintering method which uses multiple batches of red mud, soda ash solution, limestone, coal powder or silica slag, the two batches are simpler, more flexible and easier to control. Since no lime is added, the problem of insufficient calcium leading to difficult sintering can be solved by adjusting the amount of alkali added, thereby increasing the alumina content of the clinker and reducing the alumina production cost.

[0026] (2) Replacing the soda ash solution in the traditional sintering method with industrial sodium aluminate solution can effectively solve the problem of large carbon emissions of soda ash in the sintering process, reducing carbon emissions by more than 80%. The alumina in the sodium aluminate solution can also increase the aluminum-silicon ratio of the raw material from 1.20 to more than 1.40, thereby improving the sintering, leaching and settling performance of the clinker.

[0027] (3) Industrial sodium aluminate solution can significantly reduce the organic content during sintering, thus effectively addressing a series of difficult-to-handle economic problems caused by organic matter in the Bayer process, such as decreased alumina product quality, increased alkali consumption, and equipment scaling.

[0028] (4) The batching system does not add lime, which reduces the amount of tailings by 20-30%, thus weakening the secondary reaction and enhancing the stability of low-calcium calcium silicate in the clinker. The desilication process of the leachate can be achieved by using a single-stage atmospheric pressure desilication process.

[0029] (5) The use of dry pellet sintering can effectively solve the problem of poor sintering uniformity caused by wet spraying into the kiln, and the sintering energy consumption is significantly reduced by more than 30%.

[0030] (6) Compared with metallurgical grade alumina, the high white aluminum hydroxide and other fine alumina produced can be widely used in fields such as high-purity nano-grade alumina powder and flame-retardant aluminum hydroxide to address multiple issues such as alumina overcapacity, poor bauxite resources, and environmental protection, and realize the high-value and full-scale utilization of red mud. Attached Figure Description

[0031] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0032] The present invention is further illustrated below with specific embodiments. It should be understood that these embodiments are for illustrative purposes only and do not limit the scope of application of the present invention.

[0033] In this embodiment of the invention, the Bayer process red mud is red mud obtained after high-pressure leaching of low-grade monohydrate gibbsite-type bauxite, and the industrial sodium aluminate solution is one or more of the ore leaching liquid, evaporation mother liquor, and circulating mother liquor from the Bayer process.

[0034] In the embodiments of the present invention, the concentration of caustic soda (N) K ) represents the mass-volume concentration of NaOH (calculated as Na₂O), and the carbon-base concentration (N₂O). C ) represents the mass-volume concentration of Na2CO3 (calculated as Na2O), and the alumina concentration (C). AO ) represents the mass-volume concentration of alumina, and the molecular ratio (α) K The ratio of the molar concentrations of sodium oxide to aluminum oxide is given by (L / S), and the liquid-to-solid ratio is given by (L / S) as the ratio of the volume of the leaching alkaline solution to the mass of the clinker.

[0035] In this embodiment of the invention, a mixing machine is used for raw material mixing, a briquetting machine is used for briquetting, and a dryer is used for drying.

[0036] In this embodiment of the invention, dry sintering is performed using a rotary kiln, and cooling is performed using a cooler.

[0037] In this embodiment of the invention, a ball mill is used for wet grinding and leaching, and a settling tank is used for liquid-solid separation.

[0038] Example 1

[0039] A method for producing high-whiteness aluminum hydroxide by low-carbon sintering of Bayer red mud, such as... Figure 1 As shown, it includes the following steps:

[0040] (1) Add industrial sodium aluminate solution to the Bayer process red mud produced by high-pressure leaching of gibbsite-type bauxite to obtain raw material, mix evenly and pelletize to obtain raw material pellets;

[0041] The main chemical components of Bayer red mud (by mass percentage) are: Al2O3 21.82%, CaO 23.18%, SiO2 17.89%, Fe2O3 10.07%, TiO2 3.89%, Na2O 14.83%, with an aluminum-silicon ratio of 1.2.

[0042] Industrial sodium aluminate solution is used as a circulating mother liquor. Its main chemical components (by mass concentration) are: N K 260g / L, N C 21g / L, C AO 154 g / L, total organic carbon 10 g / L, α K It is 2.8;

[0043] Add 0.4m per ton of dry red mud. 3 Industrial sodium aluminate solution, without the addition of lime, with a raw material pellet moisture content of 16.5%;

[0044] (2) The raw material pellets are dried outside the kiln at a temperature of 110°C for 10 hours to remove excess moisture and obtain dried raw material;

[0045] (3) The dried raw material is heated to 1175°C for dry sintering for 1.0 h; after sintering, it is cooled by a cooler at 100°C to obtain sintered clinker;

[0046] (4) Add a dilute alkaline solution to the sintered clinker and perform wet milling and leaching to obtain a leaching slurry;

[0047] The main chemical components of the dilute alkaline solution (by mass concentration): N K 20g / L, C AO 25g / L, α K It is 1.3;

[0048] Wet milling leaching ensures that the clinker and alkaline solution are fully mixed and reacted. The leaching temperature is controlled at 80°C, the leaching time is 20 min, and the liquid-to-solid ratio is 4.

[0049] (5) The leaching slurry is subjected to liquid-solid separation, and the liquid phase obtained is the leaching liquid and the solid phase is the aluminum extraction tailings.

[0050] (6) The leachate is subjected to a first-stage atmospheric pressure desilication and carbonation decomposition. The desilication temperature is 90°C, the desilication time is 4h, the CaO addition amount is 10g / L, and the silicon content index reaches 800 or above. The carbonation decomposition temperature is 60°C, the decomposition time is 4h, the CO2 gas concentration is 20%, the aeration rate is 3L / min, and no aluminum hydroxide seed crystals are added.

[0051] The obtained high-whiteness aluminum hydroxide has a whiteness of 98% and an average particle size of 45 μm.

[0052] The recovery rate of Al2O3 in Bayer red mud after clinker leaching was 89%.

[0053] The solution produced after carbonation decomposition in step (6) is evaporated and crystallized to obtain industrial sodium carbonate product; the solution produced after carbonation decomposition contains 120 g / L of Na2CO3 (calculated as Na2O) by mass concentration, the evaporation and crystallization temperature is 90°C, and the condensate recovered by evaporation and condensation is used for the production of fine alumina.

[0054] The aluminum extraction tailings from step (5) are washed and separated, and then used to prepare a cementitious material. The aluminum extraction tailings have a particle size of 40 μm and a specific surface area of ​​550 m². 2 / kg, by mass percentage, the aluminum extraction tailings component accounts for more than 70% of the cementitious material.

[0055] Example 2

[0056] The method is the same as in Example 1, except that:

[0057] (1) The main chemical components of Bayer red mud (by mass percentage): Al2O3 24.65%, CaO 17.93%, SiO2 20.96%, Fe2O3 12.18%, TiO2 4.27%, Na2O 13.63%, with an aluminum-silicon ratio of 1.2;

[0058] (2) The industrial sodium aluminate solution is the circulating mother liquor, and its main chemical components (by mass concentration) are: N K 290g / L, N C 27g / L, C AO 177 g / L, total organic carbon 9 g / L, α K It is 2.7;

[0059] (3) Add 0.8m per ton of dry red mud 3 Industrial sodium aluminate solution, without the addition of lime, with a raw material pellet moisture content of 18.5%;

[0060] (4) The raw material pellets are heated to 1200°C for sintering reaction, and the sintering time is 1.0h;

[0061] (5) The recovery rate of Al2O3 in Bayer red mud is 88%.

[0062] Example 3

[0063] The method is the same as in Example 1, except that:

[0064] (1) The main chemical components of Bayer red mud (by mass percentage): Al2O3 22.32%, CaO 20.93%, SiO2 15.94%, Fe2O3 7.63%, TiO2 4.99%, Na2O 9.75%, with an aluminum-silicon ratio of 1.4;

[0065] (2) The industrial sodium aluminate solution is the mother liquor from evaporation. Its main chemical components (by mass concentration) are: N K 252g / L, N C 19g / L, C AO 138 g / L, total organic carbon 7 g / L, α K It is 3.0;

[0066] (3) Add 0.5m per ton of dry red mud 3 Industrial sodium aluminate solution, without lime addition, with a raw material pellet moisture content of 17%;

[0067] (4) The raw material pellets are heated to 1175°C for sintering reaction, and the sintering time is 1.5h;

[0068] (5) The recovery rate of Al2O3 in Bayer red mud is 87%.

[0069] Example 4

[0070] The method is the same as in Example 1, except that:

[0071] (1) The main chemical components of Bayer red mud (by mass percentage): Al2O3 29.54%, CaO 23.11%, SiO2 21.88%, Fe2O3 6.97%, TiO2 3.32%, Na2O 11.55%, with an aluminum-silicon ratio of 1.4;

[0072] (2) The industrial sodium aluminate solution is the mother liquor from evaporation. Its main chemical components (by mass concentration) are: N K 239g / L, N C 18g / L, C AO 131 g / L, total organic carbon 7 g / L, α K It is 3.0;

[0073] (3) Add 0.3m per ton of dry red mud. 3 Industrial sodium aluminate solution, without lime addition, with a raw material pellet moisture content of 16%;

[0074] (4) The raw material pellets are heated to 1200°C for sintering reaction, and the sintering time is 1.0h;

[0075] (5) The recovery rate of Al2O3 in Bayer red mud is 87%.

[0076] Example 5

[0077] The method is the same as in Example 1, except that:

[0078] (1) The main chemical components of Bayer red mud (by mass percentage): Al2O3 27.37%, CaO 15.91%, SiO2 21.05%, Fe2O3 14.51%, TiO2 3.01%, Na2O 10.76%, with an aluminum-silicon ratio of 1.3;

[0079] (2) Industrial sodium aluminate solution is an ore leaching solution, and its main chemical components (by mass concentration) are: N K 206g / L, N C 20g / L, C AO 226 g / L, total organic carbon 9 g / L, α K It is 1.5;

[0080] (3) Add 0.7m per ton of dry red mud. 3 Industrial sodium aluminate solution, without lime addition, with a raw material pellet moisture content of 18%;

[0081] (4) The raw material pellets are heated to 1150°C for sintering reaction, and the sintering time is 1.0h;

[0082] (5) The recovery rate of Al2O3 in Bayer red mud is 86%.

[0083] Example 6

[0084] The method is the same as in Example 1, except that:

[0085] (1) The main chemical components of Bayer red mud (by mass percentage): Al2O3 21.82%, CaO 23.18%, SiO2 17.89%, Fe2O3 10.07%, TiO2 3.89%, Na2O 14.83%, with an aluminum-silicon ratio of 1.2;

[0086] (2) Industrial sodium aluminate solution is an ore leaching solution, and its main chemical components (by mass concentration) are: N K 199g / L, N C 19g / L, C AO 234 g / L, total organic carbon 8 g / L, α K It is 1.4;

[0087] (3) Add 0.9m per ton of dry red mud. 3 Industrial sodium aluminate solution, without lime addition, with a raw material pellet moisture content of 19%;

[0088] (4) The raw material pellets are heated to 1200°C for sintering reaction, and the sintering time is 1.0h;

[0089] (5) The recovery rate of Al2O3 in Bayer red mud is 87%.

Claims

1. A method for producing high-whiteness aluminum hydroxide by low-carbon sintering of Bayer red mud, characterized in that, Specifically, the following steps are included: (1) Add industrial sodium aluminate solution to the Bayer process red mud produced by high-pressure leaching of gibbsite-type bauxite to obtain raw material, mix evenly and pelletize to obtain raw material pellets; (2) The raw material pellets are dried outside the kiln or air-dried naturally to remove excess moisture and obtain dried raw material; (3) The dried raw material is sintered by dry sintering and then cooled to obtain sintered clinker; (4) A dilute alkaline solution is added to the sintered clinker for wet milling and leaching to obtain a leaching slurry; (5) The leaching slurry is subjected to liquid-solid separation, and the liquid phase obtained is leaching liquid, and the solid phase is aluminum extraction tailings; (6) The leachate undergoes a stage of atmospheric pressure desilication and carbonation decomposition to obtain high white aluminum hydroxide, wherein the whiteness of the high white aluminum hydroxide is 98-99% and the average particle size is ≤45μm; The Bayer red mud mentioned in step (1) is red mud produced by high-pressure leaching of low-grade gibbsite-type bauxite. By mass percentage, it contains 20-30% Al2O3, 15-25% CaO, 15-25% SiO2, 5-15% Fe2O3, 3-8% TiO2, and 8-15% Na2O. The portion of the Bayer red mud with a particle size ≤55μm accounts for ≥90% of the total mass. The industrial sodium aluminate solution is one or more of the ore leaching liquid, evaporation mother liquor, and circulating mother liquor from the Bayer process. By mass concentration, it contains 200-300g / L NaOH, 10-30g / L Na2CO3, 100-200g / L Al2O3, and 5-25g / L total organic matter. The raw material mentioned in step (1) is added at a rate of 0.2–1.0 m³ per ton of dry red mud. 3 Industrial sodium aluminate solution; the raw material is prepared without additional lime, and the alkali-silicon ratio is adjusted by adding industrial sodium aluminate solution to achieve a balanced batching system.

2. The method for producing high-whiteness aluminum hydroxide by low-carbon sintering of Bayer red mud according to claim 1, characterized in that, The raw material mixing in step (1) is carried out using a mixer for 2-3 hours; the pelletizing is carried out using a pelletizing machine, and the resulting raw material pellets have a particle size of 2-3 cm and a moisture content of 15-20%.

3. The method for producing high-whiteness aluminum hydroxide by low-carbon sintering of Bayer red mud according to claim 1, characterized in that, The kiln drying in step (2) uses a dryer with a drying temperature of 100-150°C and a drying time of 10-20 hours. The heat source is the tail gas generated by dry sintering in step (3).

4. The method for producing high-whiteness aluminum hydroxide by low-carbon sintering of Bayer red mud according to claim 1, characterized in that, The dry sintering in step (3) uses a rotary kiln with a sintering temperature of 1000-1200°C and a sintering time of 0.5-2h; the cooling uses a cooler with a cooling temperature of 80-200°C.

5. The method for producing high-whiteness aluminum hydroxide by low-carbon sintering of Bayer red mud according to claim 1, characterized in that, The main components of the sintered clinker mentioned in step (3) are sodium aluminate, low-calcium calcium silicate, calcium titanate and sodium ferrite.

6. The method for producing high-whiteness aluminum hydroxide by low-carbon sintering of Bayer red mud according to claim 1, characterized in that, The wet milling leaching in step (4) is performed using a ball mill, with a leaching reaction temperature of 70-80°C and a leaching reaction time of 5-30 min. The wet milling leaching uses a dilute alkaline solution or red mud washing solution, which, by mass concentration, contains 10-30 g / L NaOH and 10-40 g / L Al2O3, with a molecular ratio of 1.1-1.

4. The liquid-solid ratio of the alkaline solution to the clinker is 3-5, and the recovery rate of Al2O3 after leaching the clinker reaches 85-90%.

7. The method for producing high-whiteness aluminum hydroxide by low-carbon sintering of Bayer red mud according to claim 1, characterized in that, In step (6), the first-stage atmospheric desilication temperature is 90–180°C, the desilication time is 1–4 h, the CaO addition amount is 7–13 g / L, and the silicon content index reaches 800 or above; the carbonation decomposition temperature is 40–60°C, the decomposition time is 4–6 h, the CO2 gas concentration is 20–25%, the gas flow rate is 3–5 L / min, no aluminum hydroxide seed crystals are added, and the decomposition rate reaches 90% or above.

8. The method for producing high-whiteness aluminum hydroxide by low-carbon sintering of Bayer red mud according to claim 1, characterized in that, The aluminum extraction tailings from step (5) are washed and separated, and then used to prepare a cementitious material. The particle size of the aluminum extraction tailings is ≤45μm, and the specific surface area is ≥550m². 2 / kg, by mass percentage, the proportion of aluminum extraction tailings in the cementitious material is ≥70%.

9. The method for producing high-whiteness aluminum hydroxide by low-carbon sintering of Bayer red mud according to claim 1, characterized in that, The solution produced after carbonation decomposition in step (6) is evaporated and crystallized to obtain industrial sodium carbonate product; the solution produced after carbonation decomposition contains 90-150 g / L of Na2CO3 by mass concentration, the evaporation and crystallization temperature is 80-100°C, and the condensate recovered by evaporation and condensation is used for the production of fine alumina.

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