A method and device for coupling treatment of bauxite to co-produce potassium and silicon fertilizers

Abstract

The application discloses a method and device for producing bauxite coupled potassium-silicon fertilizer by potassium-calcium coupling treatment, and particularly relates to the field of clean production of alumina, which comprises the following steps: mixing calcium compounds, biomass, bauxite and potassium meta-aluminate circulating mother liquor in a vortex type ore slurry tank to obtain ore slurry; dissolving the ore slurry in a high-pressure dissolution reactor; under the potassium-calcium and biomass coupling effect, the aluminum potassium occurrence phase in the balanced solid phase is converted into calcium-potassium composite silicate, and the iron occurrence phase is converted into magnetic iron phase; the reaction temperature is controlled to be 140 DEG C-290 DEG C, and the reaction time is controlled to be 30-90 minutes; the dissolved ore slurry is preheated by a preheater to cool the cold ore slurry, and then is subjected to solid-liquid separation in a vortex type rapid settling tank to obtain a dissolution liquid and magnetic red mud; the dissolution liquid is decomposed to obtain aluminum hydroxide, and the aluminum hydroxide is calcined to obtain alumina; and (5) the magnetic red mud is subjected to magnetic separation to remove iron to obtain iron powder, and the residue is rich in 3-10% potassium oxide and can be used as magnetic potassium-silicon long-acting fertilizer.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of clean production of alumina, and particularly relates to a method and device for co-production of potash and silicon fertilizer by coupling treatment of bauxite with potassium and calcium. BACKGROUND

[0002] The bauxite resources in China are relatively scarce, with a basic reserve of about 1 billion tons, accounting for about 3% of the total global amount. Meanwhile, more than 98% of the bauxite in China is mainly of diaspore type, with complex mineral phase composition, and more than 70% of the total amount is of medium and low grade (aluminum-silicon ratio < 7), with high content of harmful impurities such as silicon, sulfur and iron.

[0003] At present, more than 90% of the alumina in the world is produced by the Bayer process. Red mud is a solid waste containing alkali generated in the process of producing alumina from bauxite by the Bayer process. With the rapid development of the alumina industry in China, the cumulative stockpiling amount of red mud has exceeded 1.3 billion tons, and is increasing by about 100 million tons per year, and dam stockpiling is the main treatment method for red mud at present. The discharge of a large amount of red mud not only causes the loss of sodium oxide and alumina, but also seriously wastes land resources and poses a serious threat to the environment. Therefore, the discharge of a large amount of red mud containing alkali has become a worldwide problem restricting the sustainable development of the alumina industry.

[0004] In view of the current situation of bauxite resources in China, a large amount of research work has been carried out by domestic alumina-related enterprises. Patent 202111242450.8 discloses a method for removing impurities and upgrading gibbsite-type high-iron bauxite in the original place, which pre-classifies gibbsite-type high-iron bauxite according to a pre-set classification particle size in a dry manner to obtain coarse-grained bauxite and fine-grained bauxite; crushes the coarse-grained bauxite, and then dry grinds to obtain dry-ground bauxite; first magnetic separates the dry-ground bauxite to obtain first aluminum concentrate and high-iron tailings; mixes the high-iron tailings and the fine-grained bauxite, and then wet grinds to obtain wet-ground bauxite; second magnetic separates the wet-ground bauxite to obtain wet aluminum concentrate and wet total tailings; settles, pressure filters and air dries the wet aluminum concentrate to obtain second aluminum concentrate; and mixes the first aluminum concentrate and the second aluminum concentrate to obtain product aluminum concentrate. The above method recovers iron in the crushed mineral by direct separation, but because the iron in the bauxite mainly exists in the form of weakly magnetic minerals such as goethite or hematite, the direct magnetic separation recovery efficiency is low, and it is difficult to achieve efficient recovery of multiple components.

[0005] Patent CN201310130769.0 discloses a method for producing alumina from low-grade bauxite by using KOH solution, comprising the steps of: 1) adding bauxite into potassium hydroxide solution for dissolution reaction, and filtering to obtain a dissolution solution containing potassium aluminate and red mud; 2) crystallizing the dissolution solution containing potassium aluminate in step 1), and filtering to obtain coarse potassium aluminate hydrate and a crystallization mother liquor; dissolving the coarse potassium aluminate hydrate with dilute alkali solution, and obtaining aluminum hydroxide after desiliconization and seeding, and obtaining alumina product after calcination; 3) mixing the red mud in step 1) with lime, and adding into dilute potassium hydroxide solution for reaction to recover alumina and potassium oxide, and obtaining filtrate and final red mud after liquid-solid separation of the reaction slurry; further comprising recycling the crystallization mother liquor in step 2) for the dissolution reaction of bauxite in step 1); further comprising recycling the filtrate in step 3) for dissolving the coarse potassium aluminate hydrate in step 2); the actual dissolution rate of alumina is above 90%, and the final red mud can be directly used as raw material for preparing building material products. However, the patent does not involve adding lime and biomass reducing agent, so that the low-grade bauxite resources cannot be utilized, the iron in the red mud cannot be effectively utilized, and the utilization way of potassium in the red mud is not proposed, so that the clean production of alumina without residue and the comprehensive utilization of aluminum, silicon, iron, potassium and other elements cannot be realized. SUMMARY

[0006] In view of the problems in the prior art, the application discloses a method and device for producing potassium-silicon fertilizer by coupling potassium and calcium to treat bauxite.

[0007] The method for producing potassium-silicon fertilizer by coupling potassium and calcium to treat bauxite comprises the following specific steps:

[0008] (1) mixing a circulating potassium aluminate mother liquor, a calcium compound, biomass and bauxite to obtain a slurry;

[0009] (2) conveying the slurry to a high-pressure dissolution reactor for dissolution reaction to obtain a dissolution slurry;

[0010] (3) preheating the slurry in step (1) by a heat exchanger, adding a flocculant for solid-liquid separation to obtain a dissolution solution and magnetic red mud;

[0011] (4) removing iron from the magnetic red mud in step (3) by magnetic separation to obtain a magnetic iron concentrate powder and a magnetic separation residue;

[0012] (5) decomposing the dissolution solution in step (3) in a seeding tank to obtain aluminum hydroxide, and calcining the aluminum hydroxide to obtain an alumina product.

[0013] The concentration of K2O in the circulating potassium aluminate mother liquor in step (1) is 200-400 g / L, and the molar ratio of K2O to Al2O3 in the circulating potassium aluminate mother liquor is (1-10):1;

[0014] The calcareous compound in step (1) includes one or more of CaO, lime, and carbide slag;

[0015] The biomass in step (1) includes one or more of cassava powder, potato powder, corn starch, bagasse, wheat bran, and rice straw, and the biomass is added in an amount of 0.4-2% of the solid mass in the ore slurry;

[0016] The bauxite in step (1) is one or more of gibbsite, diaspore, and boehmite;

[0017] The mass ratio of the calcareous compound to silicon oxide in the bauxite in step (1) is (0.5-3):1;

[0018] The liquid-solid ratio in the ore slurry in step (1) is (2-6):1;

[0019] The mixing in step (1) is carried out in a vortex ore slurrying tank;

[0020] The vortex stirring shaft is used in the vortex ore slurrying tank in step (1), and the solid-liquid mixing speed is increased by 60-300%;

[0021] The high-pressure leaching reactor in step (2) is one of a pipe-type reaction device, an external-stirring pipe-type reaction kettle, and an internal-stirring pipe-type reaction kettle, the working temperature of the high-pressure leaching reactor is not higher than 350°C, the stirring speed is 0-1000 r / min, and the working pressure is 0-60 MPa;

[0022] The leaching reaction temperature in step (2) is 140-290°C, and the reaction time is 30-120 min;

[0023] The solid phase in the leaching ore slurry in step (2) is potassium aluminosilicate and aluminum-silicon-calcium coexisting phase, and the mass ratio of Al2O3 to SiO2 in the solid phase of the leaching ore slurry is 0.85-1;

[0024] The preheating in step (3) is from room temperature to 100-140°C;

[0025] The solid-liquid separation in step (3) is carried out by using a vortex rapid sedimentation tank;

[0026] The magnetic separation intensity for removing iron in step (4) is 0.1-1 T;

[0027] The TFe of the magnetic iron concentrate powder in step (4) is >60%, and the iron recovery rate is >80%;

[0028] The mass fraction of K2O in the magnetic separation residue in step (4) is 5-30%, and the residue is ground and granulated to produce potassium silicate fertilizer.

[0029] The device for bauxite co-production of potassium and silicon fertilizer by potassium-calcium coupling treatment is a vortex rapid settling tank;

[0030] The vortex rapid settling tank comprises a stirring shaft, a slurry feeding pipeline, a settling tank body, a clear liquid overflow tank, a spiral flow guide bucket, a magnetic induction coil, a rake, and a underflow outlet; the slurry feeding pipeline is arranged at the top of the settling tank body, and the slurry feeding pipeline is horizontally connected with the spiral flow guide bucket in a tangent direction; the spiral flow guide bucket is arranged in the settling tank body and is fixed to the upper portion of the settling tank body, and the spiral flow guide bucket is internally provided with spiral downward lines; the magnetic induction coil is additionally arranged outside the spiral flow guide bucket; the stirring shaft is deeply arranged in the settling tank body, the stirring shaft is connected with the rake through a connecting rod at the bottom, the magnetic red mud is discharged from the underflow outlet of the settling tank body, and the leaching solution is discharged from the top of the settling tank body through the clear liquid overflow tank.

[0031] Compared with the prior art, the vortex rapid settling tank has the following beneficial effects:

[0032] (1) Potassium alkali is used to replace sodium alkali, the mass ratio of Al2O3 to SiO2 in the transformed slag is 0.85-1, and the leaching efficiency of alumina is increased by 5%-10% compared with the sodium alkali solution or sodium alkali circulating mother liquor used in the Bayer process. After iron is selected, the red mud residue obtained is rich in potassium oxide in a range of 5%-30%, and can be used as magnetic potassium-silicon long-acting fertilizer, thereby avoiding the worldwide problem that the sodium alkali red mud obtained by using the sodium alkali solution or sodium alkali circulating mother liquor in the traditional Bayer process is difficult to treat, realizing clean production of alumina without slag, and comprehensive utilization of elements such as aluminum, silicon, iron and potassium.

[0033] (2) The transformed calciumized biomass can convert the iron oxide in the red mud into magnetite in the bauxite leaching process, can make the inhibiting iron phase combine with the alumina and potassium alkali, and the leaching efficiency of alumina is increased by more than 5% compared with the case without adding the biomass; the calcium oxide reacts with the aluminum-silicon-potassium occurrence phase to be converted into the aluminum-silicon-calcium occurrence phase, so as to adjust the content of potassium oxide in the leaching solid phase; the obtained magnetic red mud is subjected to magnetic separation to obtain magnetite concentrate powder with TFe>60% and iron yield>80%. After the ingredients are adjusted, the alkaline pellets containing less than 0.5% of sodium alkali are prepared, the total iron content is not lower than that of conventional alkaline pellets, and the alkaline pellets can be directly prepared or used as sintering ore, so that the iron in the bauxite is efficiently recovered by magnetic separation;

[0034] (3) The vortex type slurry tank is provided with a vortex stirrer to form a vortex in a downward direction, so that the biomass and other materials are quickly sucked, the rapid and uniform mixing of the slurry is realized, and the solid-liquid mixing speed is increased by 60%-300%; the vortex rapid settling tank is provided with a rotating magnetic mechanism at the top, which can drive the magnetic iron-containing phase in the transformed slag to rotate, form a vortex to improve the sedimentation effect, simultaneously suck in the flocculating agent required for sedimentation, increase the sedimentation speed by about 60-300%, and inhibit the secondary reaction of the slurry. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 Process flow diagram of the present application;

[0036] Figure 2 Vortex type slurry tank diagram;

[0037] Reference numerals: 1, belt conveyor, 2, solid feeding pipe, 3, liquid feeding pipe, 4, vortex stirring shaft, 5, tank body, 6, slurry discharging pipe;

[0038] Figure 3 Vortex type rapid settling tank diagram;

[0039] Reference numerals: 1, stirring shaft, 2, slurry feeding pipe, 3, settling tank body, 4, clear liquid overflow tank, 5, spiral flow guide bucket, 6, magnetic induction coil, 7, rake, 8, underflow outlet.

[0040] Specific implementation

[0041] The bauxite composition used in the embodiments of the present application is as follows in terms of mass percentage: Al2O3-51.52%, SiO2-6.08%, Fe2O3-25.17%, and the balance is water, TiO2 and other impurities. The production method described in the present application is not limited to this type of bauxite, and any raw material mainly composed of aluminum oxide and iron oxide can be treated by the method.

[0042] The calcium compound composition used in the embodiments of the present application is as follows in terms of mass percentage: CaO-82.44%, SiO2-1.02%, Al2O3-2.14%, Fe-0.31%, and the balance is combined water and other impurities.

[0043] A method for coupling treatment of bauxite by potassium and calcium to co-produce potassium-silicon fertilizer, comprising the following steps:

[0044] (1) mixing the circulating potassium aluminate mother liquor, calcium compound, biomass and bauxite to obtain a slurry;

[0045] (2) delivering the slurry to a high-pressure leaching reactor for leaching reaction to obtain a leached slurry;

[0046] (3) preheating the slurry in step (1) by a heat exchanger, adding a flocculating agent for solid-liquid separation to obtain a leaching solution and magnetic red mud;

[0047] (4) removing iron from the magnetic red mud by magnetic separation to obtain a magnetic iron concentrate powder and a magnetic separation residue;

[0048] (5) decomposing the leaching solution in step (3) in a seed separation tank to obtain aluminum hydroxide, and roasting the aluminum hydroxide to obtain an aluminum oxide product.

[0049] The potassium-calcium-biomass coupling in step (2) is that in the dissolution process, the aluminum-silicon phase in the bauxite reacts with potassium alkali to generate potassium aluminosilicate, the biomass precipitates free hydrogen in the alkaline solution, the iron-containing phase in the mineral is converted into the magnetic iron phase, the aluminum-silicon potassium occurrence phase reacts with calcium oxide to be converted into the aluminum-silicon calcium occurrence phase, the content of potassium oxide in the dissolution solid phase is adjusted, and the above transformation processes are completed synchronously; the biomass converts the occurrence phase of iron in the bauxite into the magnetic iron phase and inhibits the generation of the iron-aluminum-potassium composite silicate phase;

[0050] Example 1

[0051] The vortex type slurry tank is composed of a belt conveyor 1, a solid feeding pipe 2, a liquid feeding pipe 3, a vortex stirring shaft 4, a tank body 5 and a slurry discharge pipe 6. The belt conveyor 1 conveys the solid raw material into the tank body 5 through the solid feeding pipe 2. The inclination angle between the solid feeding pipe 2 and the tank body 5 is 45-60°. The circulating mother liquor is conveyed into the tank body 5 through the liquid feeding pipe 3. The solid-liquid mixing is completed in the tank body 5. After uniform mixing, the slurry is sent to the high-pressure dissolution reactor of step (2) through the slurry discharge pipe 6. As shown in Figure 2

[0052] Example 2

[0053] The vortex rapid settling tank comprises a stirring shaft 1, a slurry feeding pipe 2, a settling tank body 3, a clear liquid overflow tank 4, a spiral guide bucket 5, a magnetic induction coil 6, a rake 7 and a underflow outlet 8. The slurry feeding pipe 2 is arranged at the top of the settling tank body 3 and is connected to the spiral guide bucket 5 in the tangential direction. The spiral guide bucket 5 is arranged in the settling tank body 3 and is fixed to the upper part of the settling tank body 3. The spiral guide bucket 5 has spiral downward lines inside. The magnetic induction coil 6 is arranged outside the spiral guide bucket 5. The stirring shaft 1 is deep into the settling tank body 3. The stirring shaft 1 is connected to the rake 7 through a connecting rod at the bottom. The magnetic red mud leaves the settling tank body 3 through the underflow outlet 8. The dissolution liquid is discharged from the top of the settling tank body 3 through the clear liquid overflow tank 4. As shown in Figure 3

[0054] Example 3

[0055] The flow chart is shown in Figure 1 ​​The bauxite is mixed with the potassium meta-aluminate circulating mother liquor with an alkali concentration of 240 g / L in a vortex slurry tank, the molar ratio of K2O to Al2O3 in the solution is 3:1, the reaction temperature is 280°C, the mass ratio of CaO in lime to SiO2 in bauxite is 0.8:1, the liquid volume to solid mass ratio in the mixed slurry is 5:1, the percentage of rice straw in the solid mass in the slurry is 1.0% by mass ratio, and the reaction time in the high-pressure leaching reactor is 60 min. After the reaction, centrifugal filtration, washing and drying are performed, and then analysis is performed. The leached slurry is preheated by a preheater to cool the slurry, is subjected to solid-liquid separation in a vortex rapid settling tank, and leached liquid and magnetic red mud are obtained; the leached liquid is decomposed in a low-power consumption stirring seed separation tank, and aluminum hydroxide is obtained, and the aluminum hydroxide is calcined to obtain aluminum oxide. The mass percentage of potassium oxide in the tailings is 4.52%, the aluminum dissolution rate is 63.4%, the primary enrichment of iron has a total iron grade of 42.68%, the secondary enrichment after magnetic separation has a total iron grade of 56.73%, and the recovery rate is 65.28%.

[0056] Example 4

[0057] The bauxite is mixed with the potassium meta-aluminate circulating mother liquor with an alkali concentration of 280 g / L in a vortex slurry tank, the molar ratio of K2O to Al2O3 in the solution is 2.5:1, the reaction temperature is 240°C, the mass ratio of CaO in lime to SiO2 in bauxite is 1:1. The liquid volume to solid mass ratio in the mixed slurry is 6:1, the percentage of wheat bran in the solid mass in the slurry is 1.0% by mass ratio, and the reaction time in the high-pressure leaching reactor is 70 min. After the reaction, centrifugal filtration, washing and drying are performed, and then analysis is performed. The leached slurry is preheated by a preheater to cool the slurry, is subjected to solid-liquid separation in a vortex rapid settling tank, and leached liquid and magnetic red mud are obtained; the leached liquid is decomposed in a low-power consumption stirring seed separation tank, and aluminum hydroxide is obtained, and the aluminum hydroxide is calcined to obtain aluminum oxide. The mass percentage of potassium oxide in the tailings is 7.52%, the aluminum dissolution rate is 67.4%, the primary enrichment of iron has a total iron grade of 43.68%, the secondary enrichment after magnetic separation has a total iron grade of 55.56%, and the recovery rate is 66.10%.

[0058] Example 5

[0059] Bauxite and potassium aluminate solution with alkali concentration of 180g / L were mixed in a vortex slurry tank, the molar ratio of K2O to Al2O3 in the solution was 2:1, the reaction temperature was 270℃, the mass ratio of CaO in lime to SiO2 in bauxite was 1.2:1. The liquid to solid ratio in the mixed slurry was 6:1, the percentage of flour in the solid mass of the slurry was 1.0% by mass ratio, and the reaction time in the high-pressure leaching reactor was 40min. After the reaction, the slurry was analyzed after centrifugal filtration, washing and drying. The leached slurry was preheated by a preheater to cool the slurry, and then separated by a vortex rapid settling tank to obtain leaching solution and magnetic red mud. The leaching solution was decomposed in a low-power stirring seed tank to obtain aluminum hydroxide, and the aluminum hydroxide was calcined to obtain alumina. The mass percentage of potassium oxide in the tailings was 8.36%, the aluminum dissolution rate was 60.4%, the primary enrichment of iron was 41.35% in terms of total iron grade, the secondary enrichment of iron after magnetic separation was 57.71% in terms of total iron grade, and the recovery rate was 63.23%.

[0060] Example 6

[0061] Bauxite and potassium aluminate solution with alkali concentration of 300g / L were mixed in a vortex slurry tank, the molar ratio of K2O to Al2O3 in the solution was 3:1, the reaction temperature was 220℃, the mass ratio of CaO in lime to SiO2 in bauxite was 0.7:1. The liquid to solid ratio in the mixed slurry was 8:1, the percentage of bagasse in the solid mass of the slurry was 1.0% by mass ratio, and the reaction time in the high-pressure leaching reactor was 50min. After the reaction, the slurry was analyzed after centrifugal filtration, washing and drying. The leached slurry was preheated by a preheater to cool the slurry, and then separated by a vortex rapid settling tank to obtain leaching solution and magnetic red mud. The leaching solution was decomposed in a low-power stirring seed tank to obtain aluminum hydroxide, and the aluminum hydroxide was calcined to obtain alumina. The mass percentage of potassium oxide in the tailings was 6.38%, the aluminum dissolution rate was 67.35%, the primary enrichment of iron was 42.57% in terms of total iron grade, the secondary enrichment of iron after magnetic separation was 57.12% in terms of total iron grade, and the recovery rate was 62.18%.

[0062] Example 7

[0063] ​bauxite ore and potassium aluminate solution with a concentration of 320 g / L of alkali were mixed rapidly in a vortex slurry tank, the molar ratio of K2O to Al2O3 in the solution was 3.5:1, the reaction temperature was 290℃, the mass ratio of CaO in lime to SiO2 in bauxite was 1.4:1, the liquid to solid ratio in the mixed slurry was 7:1, the percentage of rice husk in the solid mass of the slurry was 1.0% by mass ratio, and the reaction time in the high-pressure leaching reactor was 80 min. After the reaction, the slurry was analyzed after centrifugal filtration, washing and drying. The leached slurry was preheated by a preheater to cool the slurry, and then solid-liquid separation was performed in a vortex rapid settling tank to obtain leaching solution and magnetic red mud. The leaching solution was decomposed in a low-power stirring seed tank to obtain aluminum hydroxide, and the aluminum hydroxide was calcined to obtain alumina. The mass percentage of potassium oxide in the tailings was 9.38%, the aluminum dissolution rate was 69.28%, the primary enrichment of iron had a total iron grade of 44.38%, the secondary enrichment after magnetic separation had a total iron grade of 58.56%, and the recovery rate was 62.18%.

[0064] Example 8

[0065] bauxite ore and potassium aluminate solution with a concentration of 320 g / L of alkali were mixed rapidly in a vortex slurry tank, the molar ratio of K2O to Al2O3 in the solution was 3.5:1, the reaction temperature was 290℃, the mass ratio of CaO in lime to SiO2 in bauxite was 1.4:1, the liquid to solid ratio in the mixed slurry was 7:1, the percentage of rice husk in the solid mass of the slurry was 1.0% by mass ratio, and the reaction time in the high-pressure leaching reactor was 80 min. After the reaction, the slurry was analyzed after centrifugal filtration, washing and drying. The leached slurry was preheated by a preheater to cool the slurry, and then solid-liquid separation was performed in a vortex rapid settling tank to obtain leaching solution and magnetic red mud. The leaching solution was decomposed in a low-power stirring seed tank to obtain aluminum hydroxide, and the aluminum hydroxide was calcined to obtain alumina. The mass percentage of potassium oxide in the tailings was 9.38%, the aluminum dissolution rate was 69.28%, the primary enrichment of iron had a total iron grade of 44.38%, the secondary enrichment after magnetic separation had a total iron grade of 58.56%, and the recovery rate was 62.18%.

[0064] Example 8

[0065] bauxite ore and potassium aluminate solution with a concentration of 320 g / L of alkali were mixed rapidly in a vortex slurry tank, the molar ratio of K2O to Al2O3 in the solution was 3.5:1, the reaction temperature was 290℃, the mass ratio of CaO in lime to SiO2 in bauxite was 1.4:1, the liquid to solid ratio in the mixed slurry was 7:1, the percentage of rice husk in the solid mass of the slurry was 1.0% by mass ratio, and the reaction time in the high-pressure leaching reactor was 80 min. After the reaction, the slurry was analyzed after centrifugal filtration, washing and drying. The leached slurry was preheated by a preheater to cool the slurry, and then solid-liquid separation was performed in a vortex rapid settling tank to obtain leaching solution and magnetic red mud. The leaching solution was decomposed in a low-power stirring seed tank to obtain aluminum hydroxide, and the aluminum hydroxide was calcined to obtain alumina. The mass percentage of potassium oxide in the tailings was 9.38%, the aluminum dissolution rate was 69.28%, the primary enrichment of iron had a total iron grade of 44.38%, the secondary enrichment after magnetic separation had a total iron grade of 58.56%, and the recovery rate was 62.18%.

Claims

1. A method for co-producing potassium-silicon fertilizer from bauxite through potassium-calcium coupling treatment, characterized in that, Specifically, the steps include the following: (1) Mix the circulating potassium aluminate mother liquor, calcium compounds, biomass and bauxite to obtain a slurry; (2) The slurry is transported to a high-pressure leaching reactor for leaching reaction to obtain leached slurry; (3) The leached slurry is preheated in step (1) by a heat exchanger, and a flocculant is added for solid-liquid separation to obtain leached liquid and magnetic red mud. (4) The magnetic red mud is subjected to magnetic separation to remove iron, and magnetic concentrate powder and magnetic separation residue are obtained. (5) Decompose the leaching solution in step (3) in a seed tank to obtain aluminum hydroxide, and calcine the aluminum hydroxide to obtain alumina product.

2. The method for co-producing potassium-silicon fertilizer from bauxite through potassium-calcium coupling treatment according to claim 1, characterized in that, The concentration of K2O in the circulating potassium aluminate mother liquor in step (1) is 200-400 g / L, and the molar ratio of K2O to Al2O3 in the circulating potassium aluminate mother liquor is (1-10):

1.

3. The method for co-producing potassium-silicon fertilizer from bauxite through potassium-calcium coupling treatment according to claim 1, characterized in that, The calcium compound mentioned in step (1) includes one or more of CaO, lime, and carbide slag; the biomass includes one or more of crude cassava flour, potato flour, corn starch, bagasse, wheat bran, and rice straw, and the amount of biomass added accounts for 0.4% to 2% of the solid mass in the slurry; the bauxite is one or more of trihydrate bauxite, monohydrate gibbsite, and monohydrate boehmite.

4. The method for co-producing potassium-silicon fertilizer from bauxite through potassium-calcium coupling treatment according to claim 1, characterized in that, The liquid-to-solid ratio in the slurry in step (1) is (2-6):1; the mass ratio of the calcium compound to the silica in the bauxite is (0.5-3):1; the mixing is carried out in a vortex slurry mixing tank.

5. The method for potassium-calcium coupled treatment of bauxite to co-produce potassium-silicon fertilizer according to claim 4, characterized in that, The vortex slurry mixing tank described in step (1) increases the liquid-solid mixing rate in the slurry by 60-300%.

6. The method for co-producing potassium-silicon fertilizer from bauxite through potassium-calcium coupling treatment according to claim 1, characterized in that, The high-pressure leaching reactor mentioned in step (2) is one of a pipelined reaction device, an externally stirred tube reactor, or an internally stirred tube reactor. The working temperature of the high-pressure leaching reactor is not higher than 350℃, the stirring speed is 0~1000r / min, and the working pressure is 0~60MPa. The leaching reaction temperature is 140~290℃, and the reaction time is 30~120min.

7. The method for co-producing potassium-silicon fertilizer from bauxite through potassium-calcium coupling treatment according to claim 1, characterized in that, In step (2), the solid phase in the leaching slurry is potassium aluminosilicate and aluminum-silicon-calcium coexisting phase, and the mass ratio of Al2O3 to SiO2 in the solid phase of the leaching slurry is 0.85 to 1.

8. The method for co-producing potassium-silicon fertilizer from bauxite through potassium-calcium coupling treatment according to claim 1, characterized in that, The preheating mentioned in step (3) is from room temperature to 100-140℃; the solid-liquid separation is carried out using a vortex rapid settling tank.

9. A device for the co-processing of bauxite with potassium and calcium to produce potassium-silicon fertilizer, characterized in that, The device described is a rapid eddy current settling tank; The aforementioned vortex rapid settling tank includes a stirring shaft, a slurry feed pipe, a settling tank body, a clear liquid overflow tank, a spiral guide barrel, a magnetic induction coil, a sludge scraper, and an underflow outlet. The slurry feed pipe is located at the top of the settling tank body, and its inlet is horizontally connected tangentially to the spiral guide barrel. The spiral guide barrel is located within the settling tank body and fixed to its upper part; the interior of the spiral guide barrel has a downward spiral pattern. A magnetic induction coil is installed on the exterior of the spiral guide barrel. The stirring shaft extends deep into the settling tank body, and its bottom is connected to the sludge scraper via a connecting rod. Magnetic red mud exits the settling tank body from the underflow outlet. The dissolved liquid is discharged from the top of the settling tank body through the clear liquid overflow tank.

10. The method for co-producing potassium-silicon fertilizer from bauxite through potassium-calcium coupling treatment according to claim 1, characterized in that, The magnetic separation intensity for removing iron in step (4) is 0.1 to 1 T; the TFe content of the magnetite concentrate powder is >60% and the iron yield in the bauxite is >80%; the mass fraction of K2O in the magnetic separation residue is 5 to 30%, which is then ground and granulated to produce silicon-potassium fertilizer.

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