WO2015165152A1 - Calcification-carbonization process-based method for producing aluminum oxide without evaporation - Google Patents

Abstract

Provided is a calcification-carbonization process-based method for producing aluminum oxide without evaporation. The method comprises: mixing monohydrallite and calcium aluminate with lime and a sodium aluminate primary circulation mother liquid, or mixing calcium aluminate with lime and the sodium aluminate primary circulation mother liquid, and then performing primary calcification transformation dissolution; refining and decomposing the dissolved mother liquid and then directly returning to a dissolution process to realize recycling; performing secondary low-temperature aluminum dissolution on calcified slag after carbonization transformation; performing, by using a calcium-containing material, aluminum precipitation on a sodium aluminate solution generated after secondary dissolution to obtain calcium aluminate; returning the calcium aluminate to the primary calcification transformation dissolution process so that the calcium aluminate is recycled as a calcium source. The method does not have an evaporation process, reduces energy consumption during the production process, and realizes harmless utilization of the tailings.

Description

 Method for producing alumina without evaporation based on calcification-carbonization method

 The present invention relates to the field of alumina production, and in particular to a method for producing alumina in a non-evaporation based on a calcification-carbonization process.

technical background

 Aluminum is a pillar industry in China's non-ferrous metallurgy industry. As of 2013, China's primary aluminum production capacity reached 18 million tons, and alumina production capacity was close to 40 million tons, ranking first in the world. Compared with China's high-speed development of aluminum industry, China's bauxite resources are not large, and most of them are high-alumina, high-silicon, low-aluminum-silicon ratio diaspore-type bauxite. The energy consumption of alumina production using diaspore-type bauxite is much higher than that of foreign gibbsite. The reason is:

 (1) The temperature required for the Bayer process of the diaspore (usually above 260 °C) and the caustic concentration (about 240 g/L) are higher, resulting in higher energy consumption in the dissolution process, which can account for alumina production. More than 30% of the process;

 (2) The sodium metaaluminate solution produced by the dissolution is difficult to decompose under high alkalinity. Therefore, the alkali concentration of the dissolved mother liquor should be diluted to 170 g/L or less after decomposition, and the relative concentration is low. The mother liquor also needs to be recycled to return to the Bayer process alumina production process, and the energy consumption of the evaporation process can account for about 40% of the production process.

 In addition, with the rapid development of China's alumina industry, the amount of red mud produced along with the production process has also increased year by year. Red mud is difficult to be used on a large scale due to high alkali content, so it is often treated by direct storage. In 2013, China's red mud emissions reached nearly 50 million tons.

 In recent years, China's aluminum industry has done a lot of research on how to reduce the energy consumption of alumina production process and the comprehensive utilization of Bayer process red mud, such as "a bauxite ore dressing" invented by Chen Xiangqing and others. Desiliconization method, application number: 201210262148 "Improve the aluminum-silicon ratio of bauxite by flotation desiliconization to reduce the energy consumption of the Bayer process. This method is to classify the rough bottom stream and grade it. After the coarse-grained product is ground, it is subjected to a roughing process for secondary rough desiliconization; the fine-grained product obtained by the classification is fed to a sweeping process for flotation desiliconization, and the recovery rate of the flotation alumina by the method is greater than 80%;

Li Yingchun of China Aluminum Corporation, invented, "An Alumina Baking Furnace Flue Gas Waste Heat Recovery The anti-scrapping method of the process, application number: 201010265999" is characterized in that the water system of the gas-liquid exchange tower of the recycling process adopts an independent self-circulation mode, and the produced hot water is then passed through indirect heat exchange equipment to perform water required by the production user. Heat exchange, the purpose of separating the water of the direct heat exchange system from the user water. The anti-crusting method of the flue gas waste heat recovery process of the alumina roaster, the process of directly recovering the waste heat from the flue gas of the alumina roaster , can greatly slow down the system's crusting speed, improve the recovery system operation rate and energy utilization efficiency, thus ensuring the normal operation of the recycling process;

 "A silo for preheating alumina, "Application No.: 201220035681" invented by Hunan Yutong Technology Group Co., Ltd. discloses a silo for preheating alumina, which is provided with materials inside A shelling device having a uniform discharge direction, and a flue gas recovery pipe is disposed between the shelling device and the inner wall of the silo. The solution makes the high-temperature gas in the flue gas recovery pipeline and the alumina raw material in the silo generate large-area heat exchange, thereby heating the alumina to achieve the purpose of energy saving and consumption reduction;

 Kunming University of Science and Technology Xia Feipei and other people invented "a kind of brick without red mud and magnesium slag as the main material, application number: 201110209460" with red mud and magnesium slag as raw materials, pre-treated, mixed, static pressure Brick making process such as molding, blanking, steam curing, etc., to obtain burn-free bricks.

 The above patented technologies all aim at energy saving and consumption reduction in the alumina production process and the harmless utilization of red mud, but they have not achieved the purpose of completely solving the alkali content in the red mud and greatly reducing the energy consumption in the production process.

Summary of the invention

 In order to solve the above problems, the present invention is a method for producing alumina by evaporation-free carbonization-based carbonization method, which utilizes the activation of calcium aluminate in a Bayer process to reduce the caustic alkali required for the Bayer process. The concentration allows the dissolution mother liquor to reach the decomposition requirement without dilution, thereby eliminating the evaporation process of the conventional alumina production process, achieving the purpose of greatly reducing the energy consumption of the production process, and solving the problem of high alkali aluminum content in the red mud.

 The technical solution for implementing the present invention is carried out as follows:

 (1) Calcification transformation dissolution

The crushed bauxite is mixed with calcium aluminate or calcium aluminate and lime and sodium aluminate primary circulation mother liquor, and the calcification transformation reaction is carried out at a temperature of 100-280 ° C, and the reaction time is 15 to 60 min; The dissolved slurry is separated by solid-liquid separation to obtain calcified slag and the molar ratio of sodium oxide to alumina is (1.5~2): 1 sodium aluminate is dissolved once, and the silicon-containing phase in bauxite is all converted into hydrated garnet. Into the calcification slag; wherein, the mass ratio of the calcium aluminate or calcium aluminate and lime to bauxite is (0.2 1.2): 1; the sodium aluminate primary circulation mother liquor concentration is sodium oxide content 100~170g /L, sodium oxide and alumina Molar ratio (2.5~3.5): 1;

 The sodium aluminate primary dissolution mother liquor is a sodium aluminate solution having a molar ratio of sodium oxide to alumina of (1.5~2):1;

 In the calcification transformation dissolution reaction, a part of the alumina in the mineral reacts with the sodium aluminate solution to form sodium metaaluminate, and the reaction is as follows:

(Al ₂ 0 ₃ )+2NaOH+3H ₂ 0=2NaAl(OH)4 ( 1 ) In the calcification transformation dissolution reaction, all the silicon-containing phases in the mineral are converted into hydrated garnet into the calcification slag, and the reaction is as follows:

3CaO-Al ₂ 0 ₃ -6H ₂ 0+ ( Si0 ₂ ) →3CaOAl ₂ 0 ₃ -xSi0 ₂ -(6-2x)H ₂ 0+aq (2) In this step, enter the dissolution mother liquor and enter the calcification slag. The proportion of alumina is related to the content of silica in the mineral. The higher the silica content, the more alumina enters the calcification slag;

 The calcium source used is a mixture of calcium aluminate or calcium aluminate and lime, and the degree of crystallization of the calcification product is different from that of the lime calcification process alone;

 (2) One-time dissolution mother liquor treatment

 The primary dissolution mother liquid obtained in the step (1) is decomposed by the lime milk and the aluminum oxide seed crystals are decomposed to precipitate aluminum hydroxide, and then the aluminum hydroxide and the decomposition mother liquid are respectively obtained, and the mother liquid is decomposed to have a sodium oxide content of 100 to 170 g/L. The molar ratio of sodium oxide to aluminum oxide is (2.5 3.5 ): 1 sodium aluminate solution, the decomposition mother liquor is returned to step (1) as a primary cycle mother liquor cycle; aluminum hydroxide is calcined to prepare an alumina product; :

NaAl(OH) ₄ →Al(OH) ₃ +NaOH (3 ) The calcination reaction is:

2Α1(ΟΗ) ₃ →Α1 ₂ 0 ₃ +3Η ₂ 0 (4) After decomposition, the content of sodium oxide in the mother liquor is 100-170g/L, and the molar ratio of sodium oxide to alumina is (2.5~3.5): 1 , that is, one cycle of mother liquor, can be directly returned to the dissolution reaction cycle, without going through the evaporation process;

 (3) Carbonization transformation

After mixing the clean water and calcified slag according to the liquid-solid ratio (3~15) _: l mL/g in a closed container, pass C0 ₂ into the closed container to make the partial pressure of C0 ₂ gas in the closed container reach 0.8~1.8MPa. Then, under the condition of 90~150 °C, the carbonization transformation reaction is 10~240min, and the obtained slurry is separated by liquid-solid. The solid phase is the carbonized slag of calcium silicate, calcium carbonate and aluminum hydroxide, and the liquid phase is water. ; The carbonization transformation response is as follows:

3CaOAl ₂ 0 ₃ 'xSi0 ₂ '(6-2x)H ₂ 0+(3-2x)C0 ₂ →xCa ₂ Si0 ₄ +(3-2x)CaC0 ₃ +2Al(OH) ₃ +(3-2x)H The carbonization transformation reaction described in ₂ 0 ( 5 ) is based on clear water as a medium of transformation, and clear water is recycled in the transformation reaction;

(4) Low temperature aluminum dissolution

The carbonized slag obtained in the step (3) is subjected to a secondary low-temperature molten aluminum mother liquor having a sodium hydroxide concentration of 50 to 150 g/L, and the carbonization transformation is carried out under the conditions of an aluminum melting temperature of 40 to 100 ° C and an aluminum melting time of 20 to 120 minutes. The liquid-solid ratio of aluminum hydroxide in the slag, the secondary low-temperature molten aluminum mother liquor and the carbonized slag is (4~15) _: lmL/g, and the obtained slurry is separated by liquid-solid separation, and the solid phase is mainly composed of calcium silicate and The new structure of calcium carbonate is red mud, and the liquid phase is a secondary low-temperature dissolution mother liquor containing sodium aluminate;

 The main reaction of aluminum dissolution is as follows:

Al(OH) ₃ + NaOH=NaAl(OH) ₄ (6) Step (3) carbonization transformation reaction and step (4) low temperature aluminum dissolution reaction may be carried out 1 to 5 times;

 (5) Shen Aluminum

 Step (4) The secondary low-temperature dissolution mother liquor is treated by using a calcium-containing material to precipitate aluminum, wherein the mass ratio of calcium oxide in the calcium-containing material to the mother liquor is (1.3~2.5): 1, at a precipitation temperature of 20-90 Calcium aluminate precipitation and sodium hydroxide solution were obtained under the reaction conditions of °C and precipitation time of l~60min;

 The calcium-containing material is a raw material containing calcium oxide, including lime, calcium aluminate, calcium carbide slag, etc.; the calcium aluminate obtained by the reaction is returned to step 1. The calcification transformation dissolution reaction is used as a calcium source, and the sodium hydroxide solution is used as a low-temperature solution. The aluminum mother liquor is returned to step 4 for use in the low temperature aluminum dissolution reaction cycle.

 Compared with the prior art, the features and benefits of the present invention are:

 (1) The present invention uses a low concentration of sodium hydroxide as a dissolution solution in the calcification transformation dissolution reaction of bauxite, and the whole process is mainly a wet process, thereby eliminating the high concentration dissolution solution of the conventional alumina production process. After dilution, the aluminum hydroxide is decomposed, and the dissolution solution is evaporated to a high concentration evaporation process, thereby greatly reducing the energy consumption of the production process and reducing the energy consumption by more than 20%;

 (2) The main purpose of the transformation process described in the present invention is to completely convert the silicon-containing phase in the low-grade aluminum-containing raw material into a hydrated garnet phase, that is, to achieve complete calcification transformation, thereby obtaining a low sodium alkali content once. Transformation slag

(3) The low-grade aluminum-containing raw material is processed by the production method of the present invention, and the overall yield of the alumina in the mineral can reach 90% to 100%, and the aluminum-silicon ratio of the dissolution slag can be reduced to 0.4 or less, and the sodium alkali content It can also be reduced to below 0.5%. The alumina extraction rate of minerals can be increased by more than 15% compared with the Bayer process. The production of one ton of alumina can be reduced. Reduce by about 20%;

 (4) The bauxite is treated by the production method of the present invention, and the main mineral phase of the obtained tailings is calcium silicate and calcium carbonate, which can be directly used as a raw material of the cement industry, and fundamentally solve the red mud occupation pollution. Environmental issues.

Detailed ways

The embodiment of the present invention uses a low-grade bauxite with an aluminum-to-silicon ratio of 3.29 as a raw material, and the bauxite composition is by mass percentage: Al ₂ 0 ₃ -54.14%, Si0 ₂ -16.55%, Fe ₂ 0 ₃ -7.16 %, the balance is reduced water, Ti0 ₂ and impurities;

 The low-grade bauxite is used in the embodiment of the present invention. The production content of the present invention is not limited to the use of such minerals, and any alumina-containing minerals include medium-high grade bauxite, nepheline, feldspar, and high. Lingshi, fly ash, alum, iron-aluminum symbiotic ore, etc. can be produced by this technology;

The CO ₂ gas used in the embodiment of the present invention is a CO ₂ exhaust gas produced by a lime burning process, but the production process described in the present invention is not limited to the use of such a gas, and any gas containing CO ₂ can be transformed as a carbonization. Process raw materials;

 The lime described in the present invention is calcined, but the calcified raw material used in the aluminum precipitation reaction is not limited to the calcined lime, and the raw material used may include any material containing calcium oxide as a main component.

Example 1

 The bauxite is crushed to -250 μm, mixed with calcium aluminate and one cycle mother liquor, and calcified slag and one dissolution mother liquor are obtained under calcification transformation dissolution conditions at 280 ° C and reaction for 15 min. Calcium aluminate during calcification transformation and dissolution. The mass ratio of bauxite is 1.2:1, the sodium oxide content in the primary circulating mother liquor is 170g/L, and the molar ratio of sodium oxide to alumina in the primary circulating mother liquor is 3.5:1;

 The molar ratio of sodium oxide to alumina obtained by dissolving the calcification transformation is 1.5:1, and the aluminum hydroxide is obtained by refining the molten mother liquor and decomposing and precipitating the aluminum hydroxide seed crystals, respectively, to obtain aluminum hydroxide and Aluminum hydroxide and sodium oxide content of 170g / L, sodium oxide and alumina molar ratio of 3.5: 1 primary decomposition mother liquor, primary decomposition mother liquor as a primary cycle mother liquor return to calcification transformation dissolution process recycling, aluminum hydroxide is obtained by roasting Alumina product;

The calcified slag undergoes a carbonization transformation reaction of 10 min in C0 ₂ gas partial pressure of 1.8 MPa, and a transformation temperature of 150 ° C in clear water. The liquid-solid ratio of clear water and calcified slag is 10: 1 mL/g, and the main components are calcium silicate and carbonic acid. Carbonization transition slag of calcium and aluminum hydroxide; clean water is recycled in the process;

The carbonization transformation slag uses a secondary low-temperature molten aluminum mother liquor with a sodium hydroxide concentration of 150g/L at a molten aluminum temperature of 100 The aluminum hydroxide was extracted under the condition of °C and aluminum melting time for 20 min. The liquid-solid ratio of the secondary low-temperature molten aluminum mother liquor to the carbonized slag was 10:1 mL/g, and the obtained slurry was separated by liquid-solid separation, and the solid phase was the main component. It is a new type of red mud of calcium silicate and calcium carbonate, and the liquid phase is a secondary low-temperature dissolution mother liquid containing sodium aluminate;

 Repeating the above carbonization transformation reaction and low temperature aluminum dissolution reaction three times;

 The secondary low-temperature dissolution mother liquor obtained by the reaction 3 times is treated by using lime-aluminum, wherein the mass ratio of calcium oxide in the lime to the alumina in the mother liquor is 1.3:1, under the reaction conditions of a precipitation temperature of 90 ° C and a precipitation time of 1 min. The calcium aluminate precipitate and the sodium hydroxide solution are obtained; the calcium aluminate obtained by the reaction is returned to the calcification transformation and the dissolution process is used as a calcium source, and the sodium hydroxide solution is recycled as a low-temperature molten aluminum mother liquor to return to the low-temperature aluminum dissolution process.

 The mass ratio of alumina to silica in the obtained tailings was 0.28: 1, and the content of sodium oxide was 0.5%. Example 2

 The bauxite is crushed to -250 μιη, mixed with calcium aluminate and one cycle mother liquor, and calcified slag and one dissolution mother liquor are obtained under calcification transformation dissolution conditions at 100 ° C and reaction for 60 min. Calcium aluminate during calcification transformation and dissolution. And the mass ratio of lime to bauxite is 0.2: 1, the sodium oxide content in the primary cycle mother liquor used is 100g / L, the molar ratio of sodium oxide to alumina in the primary cycle mother liquor is 2.5: 1;

 The molar ratio of sodium oxide to alumina in the primary dissolution mother liquor obtained by calcification transformation is 2:1, and the dissolution mother liquor is dehydrated by lime milk and decomposed by aluminum hydroxide seed crystals to precipitate aluminum hydroxide in the mother liquor, respectively, to obtain hydrogen hydroxide respectively. Aluminum and sodium oxide content of 100g / L and a molar ratio of sodium oxide to alumina of 2.5: 1 primary decomposition mother liquor, primary decomposition mother liquor as a primary cycle mother liquor return to calcification transformation dissolution process recycling, aluminum hydroxide is calcined to obtain alumina Product

Calcification slag C0 ₂ gas partial pressure 0.8Mpa, the transformation reaction Transformation water temperature of 90 ° C in 90min, water and calcification slag by liquid-solid ratio of 3: I mL / g, generates a main component calcium silicate, calcium carbonate , carbonization transformation slag of aluminum hydroxide; clean water is recycled in the process;

 The carbonization transition slag is extracted from the secondary low-temperature molten aluminum mother liquor with a sodium hydroxide concentration of 50g/L at a solution temperature of 40 ° C and an aluminum dissolution time of 120 min, and the secondary low-temperature molten aluminum mother liquor and carbonized slag are extracted. The liquid-solid ratio is 15: ImL/g, the slurry obtained by the reaction is separated by liquid-solid separation, the solid phase is a new structure red mud mainly composed of calcium silicate and calcium carbonate, and the liquid phase is a secondary low-temperature dissolution mother liquid containing sodium aluminate. ;

 The above carbonization transformation reaction and the aluminized reaction are repeated 5 times;

The secondary low-temperature dissolution mother liquor obtained by the reaction 5 times is treated by using lime-aluminum, wherein the mass ratio of calcium oxide in the lime to the alumina in the mother liquor is 2.5:1, the precipitation temperature is 20 ° C and the precipitation time is 60 min. Calcium aluminate precipitation and sodium hydroxide solution are obtained under the reaction conditions; the calcium aluminate obtained by the reaction returns to the calcification transformation and dissolution process as a calcium source, and the sodium hydroxide solution is recycled as a low-temperature molten aluminum mother liquor to return to the low-temperature aluminum dissolution process.

 The mass ratio of alumina to silica in the obtained tailings was 0.43 : 1, and the content of sodium oxide was 0.72%. Example 3

 After the bauxite is crushed to -250 μ m, it is mixed with calcium aluminate and one cycle mother liquor. Calcium slag and one dissolution mother liquor are obtained under the calcification transformation dissolution condition of 240 ° C and reaction for 45 min. Calcium aluminate during calcification transformation and dissolution. The mass ratio of bauxite to 0.5: 1, the primary cycle mother liquor used in the sodium oxide content of 160g / L, the primary cycle mother liquor in the molar ratio of sodium oxide to alumina is 3.0: 1;

 The molar ratio of sodium oxide to aluminum oxide in the primary mother liquor is 1.55: 1, and the dissolved mother liquor is refined by lime milk and aluminum hydroxide seed crystals are decomposed to precipitate aluminum hydroxide in the mother liquor, and then aluminum hydroxide and sodium oxide content are respectively obtained. It is a primary decomposition mother liquor of 160g/L and a molar ratio of sodium oxide to alumina of 3.0:1, and a primary decomposition mother liquor is used as a primary circulation mother liquor to return to the calcification transformation dissolution process, and the aluminum hydroxide is calcined to obtain an alumina product;

The calcification slag has a partial pressure of 1.2Mpa in C0 ₂ gas, and a transformation reaction occurs in clear water at a transition temperature of 120 °C for 240 minutes. The liquid-solid ratio of clear water and calcified slag is 15:1 mL/g, and the main components are calcium silicate and calcium carbonate. , carbonization transformation slag of aluminum hydroxide; clean water is recycled in the process;

 The carbonization transition slag is extracted from the secondary low-temperature molten aluminum mother liquor with a sodium hydroxide concentration of 100g/L at a solution temperature of 60 ° C and an aluminum dissolution time of 60 min, and the secondary low-temperature molten aluminum mother liquor and carbonized slag are extracted. The liquid-solid ratio is 4: lmL/g, the slurry obtained by the reaction is separated by liquid-solid separation, the solid phase is a new structure red mud mainly composed of calcium silicate and calcium carbonate, and the liquid phase is a secondary low-temperature dissolution mother liquid containing sodium aluminate. ;

 The secondary low-temperature dissolution mother liquor is treated by lime-aluminum precipitation, wherein the mass ratio of calcium oxide in the lime to the alumina in the mother liquor is 1.8: 1, and the calcium aluminate precipitate is obtained under the reaction conditions of a precipitation temperature of 60 ° C and a precipitation time of 15 min. Sodium hydroxide solution; the calcium aluminate obtained by the reaction returns to the calcification transformation and dissolution process as a calcium source for recycling, and the sodium hydroxide solution is recycled as a low-temperature molten aluminum mother liquor to return to the low-temperature aluminum dissolution process.

 The mass ratio of alumina to silica in the obtained tailings was 0.45 : 1, and the content of sodium oxide was 0.56%. Example 4

The bauxite is crushed to -250 μm, mixed with calcium aluminate and one cycle mother liquor, and calcified slag and one dissolution mother liquor are obtained under calcification transformation dissolution conditions at 220 ° C and reaction for 30 min. Calcium aluminate during calcification transformation and dissolution The mass ratio to bauxite is 0.5: 1. The sodium oxide content in the primary cycle mother liquor used is 150g / L, the molar ratio of sodium oxide to alumina in the primary cycle mother liquor is 3.1: 1.

 The molar ratio of sodium oxide to aluminum oxide in the primary mother liquor is 1.6:1, and the dissolved mother liquor is refined by lime milk and aluminum hydroxide seed crystals are decomposed to precipitate aluminum hydroxide in the mother liquor, and then aluminum hydroxide and sodium oxide content are respectively obtained. It is a primary decomposition mother liquor of 150g/L and a molar ratio of sodium oxide to alumina of 3.1:1, and a primary decomposition mother liquor is used as a primary circulation mother liquor to return to the calcification transformation and dissolution process, and the aluminum hydroxide is calcined to obtain an alumina product;

L .OMpa calcification slag in the partial pressure of C0 ₂ gas, water transformation reaction Transformation temperature 130 ° C in 65min, water and calcification slag by liquid-solid ratio of 7: 1 mL / g, mainly composed of calcium silicate generate carbonate Carbonization transition slag of calcium and aluminum hydroxide; clean water is recycled in the process;

 The carbonization transition slag is extracted from the secondary low-temperature molten aluminum mother liquor with a sodium hydroxide concentration of 80g/L at a solution temperature of 50V and an aluminum dissolution time of 120 minutes, and the liquid solidification of the secondary low-temperature molten aluminum mother liquor and the carbonized slag. The ratio is 6: lmL / g, the slurry obtained by the reaction is separated by liquid-solid separation, the solid phase is a new structure red mud mainly composed of calcium silicate and calcium carbonate, and the liquid phase is a secondary low-temperature dissolution mother liquid containing sodium aluminate;

 The secondary low-temperature dissolution mother liquor is treated by lime-aluminum precipitation, wherein the mass ratio of calcium oxide in the lime to the alumina in the mother liquor is 2.2:1, and the calcium aluminate precipitate is obtained under the reaction conditions of a precipitation temperature of 45 ° C and a precipitation time of 30 min. Sodium hydroxide solution; the calcium aluminate obtained by the reaction returns to the calcification transformation and dissolution process as a calcium source for recycling, and the sodium hydroxide solution is recycled as a low-temperature molten aluminum mother liquor to return to the low-temperature aluminum dissolution process.

 The mass ratio of alumina to silica in the obtained tailings was 0.36: 1, and the content of sodium oxide was 0.78%. Example 5

 The bauxite is crushed to -250 μιη, mixed with calcium aluminate and one cycle mother liquor, and calcified slag and one dissolution mother liquor are obtained under the calcification transformation dissolution condition of 160 ° C and reaction for 60 min, and calcium aluminate is formed during calcification transformation and dissolution. The mass ratio of bauxite to 0.8: 1, the primary cycle mother liquor used in the sodium oxide content is 130g / L, the molar ratio of sodium oxide to alumina in the primary cycle mother liquor is 2.8: 1;

 The molar ratio of sodium oxide to aluminum oxide in the primary mother liquor is 1.5:1, and the dissolved mother liquor is refined by lime milk and aluminum hydroxide seed crystals are decomposed to precipitate aluminum hydroxide in the mother liquor, and then aluminum hydroxide and sodium oxide content are respectively obtained. It is a primary decomposition mother liquor of 130g/L and a molar ratio of sodium oxide to alumina of 2.8:1, and a primary decomposition mother liquor is used as a primary circulation mother liquor to return to the calcification transformation and dissolution process, and the aluminum hydroxide is calcined to obtain an alumina product;

The calcified slag has a partial pressure of 1.4Mpa in C0 ₂ gas, and a transformation reaction in the clear water at a transformation temperature of 100 °C for 120 minutes. The liquid-solid ratio of clear water and calcified slag is 12: 1 mL/g, and the main components are calcium silicate and calcium carbonate. , Carbonization transition slag of aluminum hydroxide; clean water is recycled during the process;

 The carbonization transformation slag is extracted from the secondary low-temperature molten aluminum mother liquor with a sodium hydroxide concentration of 60g/L at a solution temperature of 60 ° C and an aluminum dissolution time of 50 min, and the secondary low-temperature molten aluminum mother liquor and carbonized slag are extracted. The liquid-solid ratio is 12: lmL/g, the slurry obtained by the reaction is separated by liquid-solid separation, the solid phase is a new structure red mud with main components of calcium silicate and calcium carbonate, and the liquid phase is a secondary low-temperature dissolution mother liquid containing sodium aluminate. ;

 The secondary low-temperature dissolution mother liquor is treated by lime-aluminum precipitation, wherein the mass ratio of calcium oxide in the lime to the alumina in the mother liquor is 2.0: 1, and the calcium aluminate precipitate is obtained under the reaction conditions of a precipitation temperature of 30 ° C and a precipitation time of 45 min. Sodium hydroxide solution; the calcium aluminate obtained by the reaction returns to the calcification transformation and dissolution process as a calcium source for recycling, and the sodium hydroxide solution is recycled as a low-temperature molten aluminum mother liquor to return to the low-temperature aluminum dissolution process.

 The mass ratio of alumina to silica in the obtained tailings was 0.47: 1, and the content of sodium oxide was 0.35%.

Claims

1. A method for producing alumina without evaporation based on the calcification-carbonization method, which is characterized by following the following steps: (1) Calcification transformation and dissolution Mix bauxite with calcium aluminate or calcium aluminate and lime and sodium aluminate primary circulation mother liquor, at temperature The calcification transformation dissolution reaction is carried out at 100~280°C. The reaction time is 15~60 minutes. After the reaction, the calcification slag whose main components are hydrated garnet and the sodium aluminate primary dissolution mother liquor are obtained; (2) Primary dissolution mother liquor treatment After the primary dissolution mother liquor is refined with lime milk and decomposed by adding aluminum hydroxide seeds and precipitating aluminum hydroxide, aluminum hydroxide and decomposed mother liquor are obtained respectively, and the aluminum hydroxide is roasted to prepare alumina products; (3) Carbonization transformation After mixing clean water and calcified slag in a closed container according to the liquid-to-solid ratio (3~15) _: 1 mL/g, introduce CO ₂ into the closed container so that the partial pressure of CO ₂ gas in the closed container reaches 0.8~1.8MPa , and then undergo a carbonization transformation reaction at 90~150°C for 10~240 minutes. The obtained slurry undergoes liquid-solid separation. The solid phase is carbonized slag whose main components are calcium silicate, calcium carbonate and aluminum hydroxide, and the liquid phase is clean water. ; (4) Low temperature melted aluminum Use a secondary low-temperature aluminum dissolving mother liquor with a sodium hydroxide concentration of 50~150g/L to extract the aluminum hydroxide from the carbonized transformation slag at an aluminum dissolving temperature of 40~100°C and an aluminum dissolving time of 20~120 minutes. The liquid-to-solid ratio of the secondary low-temperature aluminum-dissolving mother liquor and carbonized slag is (4~15) _: 1mL/g. The slurry obtained by the reaction is liquid-solid separated, and the solid phase is a new structure red mud whose main components are calcium silicate and calcium carbonate. , the liquid phase is a secondary low-temperature dissolution mother liquor containing sodium aluminate; Perform steps (3) and (4) 1 to 5 times; (5) Immersed aluminum Add calcium-containing materials to the secondary low-temperature dissolution mother liquor, and react to obtain calcium aluminate precipitation and sodium hydroxide solution. 2. A method for producing alumina without evaporation based on the calcification-carbonization method, characterized in that the mass ratio of calcium aluminate or calcium aluminate and lime to bauxite in step (1) is (0.2 1.2 ): 1; The primary circulating mother liquor of sodium aluminate is a sodium aluminate solution with a sodium oxide content of 100~170g/L and a molar ratio of sodium oxide to aluminum oxide (2.5 3.5): 1; the primary sodium aluminate The dissolution mother liquor is a sodium aluminate solution with a molar ratio of sodium oxide to aluminum oxide (1.5~2):1. 3. A method for producing alumina without evaporation based on the calcification-carbonization method, characterized in that the decomposition mother liquor in step (2) has a sodium oxide content of 100~170g/L, and a molar ratio of sodium oxide to alumina. (2.5 3.5): 1 sodium aluminate solution. 4. A method for producing alumina without evaporation based on the calcification-carbonization method, characterized in that the decomposition mother liquor in step (2) is returned to step (1) and the calcification transformation dissolution reaction is recycled as a primary circulation mother liquor. 5. A method for producing alumina without evaporation based on the calcification-carbonization method, characterized in that the clean water obtained in step (3) is recycled in the carbonization transformation reaction of this step. 6. A method for producing alumina without evaporation based on the calcification-carbonization method, characterized in that the calcium-containing material described in step (5) is a raw material containing calcium oxide, including lime, calcium aluminate, and carbide slag. 7. A method for producing alumina without evaporation based on the calcification-carbonization method, characterized in that the mass ratio of calcium oxide in the calcium-containing material described in step (5) to alumina in the secondary low-temperature dissolution mother liquor is (1.3 2.5 ): 1. 8. A method for producing alumina without evaporation based on the calcification-carbonization method, characterized in that the reaction conditions of the calcium-containing material described in step (5) and the secondary low-temperature dissolution mother liquor are: reaction temperature 20~90°C And the reaction time is 1~60min. 9. A method for producing alumina without evaporation based on the calcification-carbonization method, characterized in that the calcium aluminate obtained by the reaction in step (5) is returned to step (1) for calcification transformation dissolution reaction and is recycled as a calcium source. The sodium hydroxide solution returns to step (4) and the low-temperature aluminum-dissolving reaction is recycled as a low-temperature aluminum-dissolving mother liquor.