Desiliconizing agent and its application in Bayer process crude liquor

Abstract

The invention belongs to the technical field of hydrometallurgy, and discloses a desiliconizing agent and its application in desiliconizing in Bayer process crude liquor. At least one of opal, kaolinite and sodium silicate is added to sodium aluminate solution A, and at least one of NaCl, Na2SO4 and Na2CO3 is added. After a period of reaction, the reaction slurry is subjected to solid-liquid separation to obtain a synthetic sodium-based desiliconizing agent. Lime milk is added to sodium aluminate solution B for reaction, and the reaction slurry is subjected to solid-liquid separation to obtain a synthetic calcium-based desiliconizing agent. First, a synthetic sodium-based desiliconizing agent is added to Bayer process crude liquor to perform a first-stage desiliconization. After the first-stage desiliconization is completed, the solid-liquid separation is performed, and a synthetic calcium-based desiliconizing agent is added to the obtained first-stage desiliconized liquid to perform a second-stage desiliconization, thereby achieving deep desiliconization of Bayer process crude liquor and simultaneous removal of impurities such as fluorine, vanadium, sulfur and organic matter; or a synthetic sodium-based desiliconizing agent and a synthetic calcium-based desiliconizing agent are added to Bayer process crude liquor at the same time to achieve rapid desiliconization of Bayer process crude liquor and simultaneous removal of impurities such as fluorine, vanadium, sulfur and organic matter.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrometallurgy, and in particular relates to a method for removing and purifying silicon in a sodium aluminate solution during an alumina production process. Background Art

[0002] In the Bayer process of producing alumina, silicon in sodium aluminate solution is the most harmful impurity. Generally, silicon in sodium aluminate solution usually precipitates in the form of sodium silicon slag. If it precipitates during the separation of sodium aluminate solution, it will affect the quality of alumina products; if it precipitates in other production processes, it is easy to cause scarring on pipelines and equipment walls, which is difficult to handle and seriously affects the normal operation of production. Therefore, an effective desiliconization process must be adopted before the separation of sodium aluminate solution. For situations with higher requirements for alumina products, the sodium aluminate solution needs to be deeply desiliconized. The current desiliconization methods are as follows:

[0003] (1) Dilution desiliconization

[0004] The Bayer dissolution temperature of domestic diaspore ore is above 260℃. During the dissolution process, lime equivalent to about 10% of the ore amount is generally added to eliminate the blocking effect of titanium minerals on aluminum dissolution and reduce alkali consumption. In addition, excess lime can promote the dilution desiliconization process after the dissolution is completed. The dilution desiliconization process is to add the primary red mud washing water to the dissolution slurry to adjust the caustic soda concentration to a medium level, and then keep it at a certain temperature for a period of time to precipitate sodium silicate slag. In fact, dilution desiliconization mainly uses the decrease in the equilibrium concentration of silica after the caustic soda concentration and aluminum concentration of the solution are reduced, and the supersaturated silica is easy to precipitate to achieve desiliconization; at the same time, the sodium silicate slag and calcium silicate slag (i.e., hydrated garnet) formed during the high-temperature dissolution process can act as desiliconization seeds to promote the precipitation of silica. But at the same time, all the desiliconization products formed during the dilution desiliconization process will enter the red mud, resulting in increased alumina loss and increased alkali content in the red mud, which is not conducive to the subsequent comprehensive utilization of red mud.

[0005] The production of alumina using gibbsite ore generally adopts the low-temperature Bayer process, with a dissolution temperature of about 150°C and no lime added during the dissolution process. The dilution desiliconization process is difficult to meet the desiliconization requirements.

[0006] (2) Adding seed crystals and lime for desiliconization

[0007] Adding seed crystals can avoid the difficulty of forming hydrated sodium aluminosilicate (sodium silicate slag) nuclei and increase the crystal surface area, thereby increasing the speed and depth of desiliconization. Regarding the mechanism of action of seed crystals, it is generally believed that it is based on the principle of crystallography. Seed crystals can provide active points to promote the precipitation of silicate ions in the supersaturated solution of silicon dioxide, thereby transferring the silicon in the solution from the liquid phase to the solid phase for removal. After part of the silicon dioxide is precipitated as hydrated sodium aluminosilicate, the desiliconization process of continuing to add lime (or lime milk) to the solution, the following main reactions occur: 3Ca(OH)2+ 2NaAl(OH)4+ aq → 3CaO•Al2O3•6H2O + 2NaOH + aq. During or after the formation of hydrated calcium aluminate, it can absorb silicate in the solid solution to form hydrated garnet: 3CaO•Al2O3•6H2O + xNa2SiO3+ aq → 3CaO•Al2O3•xSiO2•(6-2x)H2O +2xNaOH + aq. Compared with sodium silicate slag, hydrated garnet has lower equilibrium solubility in sodium aluminate solution and better stability. The formation of hydrated garnet reduces the silicon concentration in the solution. With the increase of lime addition, the silicon content index of desiliconized semen can reach 1000~1200 or more.

[0008] When adding seeds for desiliconization, due to the high equilibrium solubility of sodium silicate slag (about 0.2~0.3g / L), the silicon content index of the semen is low (about 200~300) for the desiliconization process of adding seeds to form sodium silicate slag. When adding lime for desiliconization, although the solubility of the generated hydrated garnet is small, which can further improve the silicon content index of the semen, there are disadvantages such as large amount of lime added and large loss of alumina. Therefore, in production, the two methods are often combined for two-stage desiliconization, that is, the first stage allows as much silicon dioxide as possible to precipitate and separate as sodium silicate slag, and the second stage allows the remaining silicon dioxide to precipitate as hydrated garnet to further increase the desiliconization depth.

[0009] In addition to silicon dioxide impurities, the Bayer process crude liquor also contains a variety of other impurities that are not conducive to production or affect the quality of alumina products, such as fluorine, sulfur, vanadium and organic matter. Under calcium-free dissolution technology, the impurity fluorine will accumulate and precipitate NaF to cause scarring; the impurity sulfur will accelerate the corrosion of steel equipment and pipelines, increase alkali consumption, and make it difficult for red mud to settle after dissolution; the impurity vanadium will affect the decomposition of crystal seeds and the subsequent electrolytic aluminum production process; organic impurities will cause a large amount of foam in the slurry, resulting in a reduction in the effective volume of the equipment, and at the same time affect the decomposition of crystal seeds and product quality. Removing or partially removing these impurities while desiliconizing is conducive to further improving the quality of alumina products or reducing the burden of the production process, which is of great significance to my country's alumina industry. Summary of the invention

[0010] In view of the problems existing in the prior art, the present invention takes a different approach and provides a desiliconizing agent in the alumina production process and its application in desiliconizing in Bayer process crude liquor.

[0011] To achieve the above object, the present invention first provides a desiliconizing agent, namely a synthetic sodium-based desiliconizing agent, which is prepared by the following method:

[0012] At least one of opal, kaolinite and sodium silicate is added to sodium aluminate solution A, and at least one of NaCl, Na2SO4 and Na2CO3 is added. After a period of reaction, the reaction slurry is separated into solid and liquid, and the solid phase is a synthetic sodium-based desiliconizing agent.

[0013] Furthermore, in some preferred embodiments of the present invention, the caustic ratio of the sodium aluminate solution A is 1.35-4.0, and the caustic concentration is 140-300 g / L.

[0014] Further, in some preferred embodiments of the present invention, the solid-to-liquid ratio of the added amount of at least one of opal, kaolinite and sodium silicate to the sodium aluminate solution A is 5-30 g / 100 mL.

[0015] Furthermore, in some preferred embodiments of the present invention, the solid-to-liquid ratio of the added amount of at least one of NaCl, Na2SO4, and Na2CO3 (calculated as Na2O) to the sodium aluminate solution A is 0.5-3 g / 100 mL.

[0016] Furthermore, in some preferred embodiments of the present invention, the reaction temperature is 90-160° C., and the reaction time is 2-12 h.

[0017] The present invention also provides another desiliconizing agent, a synthetic calcium-based desiliconizing agent, which is prepared by the following method:

[0018] Lime milk is added to the sodium aluminate solution B for reaction, and the reaction slurry is subjected to solid-liquid separation, and the obtained solid phase is the synthetic calcium-based desiliconizing agent.

[0019] Furthermore, in some preferred embodiments of the present invention, the solid content of the lime milk is 100-300 g / L.

[0020] Furthermore, in some preferred embodiments of the present invention, the caustic ratio of the sodium aluminate solution B is 1.35-2.0, the alumina concentration is 70-150 g / L, and the concentration of Na2CO3 and / or Na2SO4 is 0-30 g / L in terms of Na2O.

[0021] Furthermore, the volume ratio of the lime milk to the sodium aluminate solution B is 1:1 to 1:4.

[0022] Furthermore, in some preferred embodiments of the present invention, the reaction temperature is 50-110° C., and the reaction time is 20-100 min.

[0023] Based on the same inventive concept, the present invention provides the use of the above-mentioned synthetic sodium-based desiliconizing agent and synthetic calcium-based desiliconizing agent in desiliconization in Bayer process crude liquor.

[0024] Specifically, the present invention provides a method for desiliconizing a Bayer process crude liquor, comprising a two-stage desiliconization process: first, the above-mentioned synthetic sodium-based desiliconizing agent is added to the Bayer process crude liquor to perform a first-stage desiliconization; after the first-stage desiliconization is completed, the above-mentioned synthetic calcium-based desiliconizing agent is added to the desiliconized fine liquor obtained by solid-liquid separation to perform a second-stage desiliconization.

[0025] Furthermore, in some preferred embodiments of the present invention, the reaction temperature of the first stage desiliconization is 80-160°C.

[0026] Furthermore, in some preferred embodiments of the present invention, in the first stage of desiliconization, the amount of synthetic sodium desiliconizer added is: 10-100 g of synthetic sodium desiliconizer is added to 1 L of Bayer process crude liquor. It is further preferred that the particle size of the synthetic sodium desiliconizer is 100-600 mesh.

[0027] Furthermore, in some preferred embodiments of the present invention, the desiliconization period is 2 to 10 hours.

[0028] Furthermore, in some preferred embodiments of the present invention, after the first stage of desiliconization is completed, the solid phase obtained by solid-liquid separation can be used as a desiliconization agent after grinding.

[0029] Furthermore, in some preferred embodiments of the present invention, the temperature of the second-stage desiliconization is 90-160°C.

[0030] Furthermore, in some preferred embodiments of the present invention, in the second-stage desiliconization, the amount of synthetic calcium-based desiliconizing agent added is: based on the CaO content, the amount of CaO added to each 1L of desiliconized semen is 2-20 g.

[0031] Furthermore, in some preferred embodiments of the present invention, the time of the second stage desiliconization is 1 to 8 hours.

[0032] In addition, in terms of the application of the above-mentioned synthetic sodium-based desiliconizing agent and the synthetic calcium-based desiliconizing agent in the desiliconization of Bayer process crude liquor, the present invention also provides another rapid desiliconization method for Bayer process crude liquor, comprising the following steps: simultaneously adding the above-mentioned synthetic sodium-based desiliconizing agent and the calcium-based desiliconizing agent to the Bayer process crude liquor for a rapid desiliconization reaction.

[0033] Furthermore, in some preferred embodiments of the present invention, the temperature of the desiliconization reaction is 90-160°C.

[0034] Further, in some preferred embodiments of the present invention, the amount of the synthetic sodium desiliconizing agent added is: 10-100 g of the synthetic sodium desiliconizing agent is added to 1 L of Bayer process crude liquor. It is further preferred that the particle size of the synthetic sodium desiliconizing agent is 100-600 mesh.

[0035] Furthermore, in some preferred embodiments of the present invention, the amount of the synthetic calcium-based desiliconizing agent added is: based on the CaO content, the amount of CaO added to each 1L of Bayer process crude liquor is 2-20 g.

[0036] Furthermore, in some preferred embodiments of the present invention, the desiliconization reaction time is 1 to 8 hours.

[0037] Furthermore, in some preferred embodiments of the present invention, after the desiliconization reaction is completed, the slag phase obtained by solid-liquid separation can be used as a desiliconization agent after grinding.

[0038] Compared with the prior art, the present invention has the following obvious beneficial technical effects:

[0039] (1) The synthetic sodium-based desiliconizing agent of the present invention has strong activity, a large specific surface area, and a good desiliconizing effect;

[0040] (2) The synthetic calcium-based desiliconizing agent of the present invention is a metastable substance with extremely strong desiliconization activity. Compared with adding lime desiliconizing agent, the desiliconization process consumes more free silica in the solution per unit mass of CaO, and the generated desiliconized product is more stable. Desiliconization using the synthetic calcium-based desiliconizing agent of the present invention can save the amount of lime used and reduce the loss of alumina caused by the generation of desiliconized products, and the desiliconization depth is greater than desiliconization using lime;

[0041] (3) The synthetic calcium-based desiliconizing agent of the present invention can remove part of the impurities such as fluorine, vanadium, sulfur and organic matter in the solution while efficiently removing silicon dioxide from the Bayer process crude liquor;

[0042] (4) The two-stage desiliconization process provided by the present invention can achieve ultra-deep desiliconization, and the silicon content index of the desiliconized solution can exceed 2000 under certain conditions;

[0043] (5) By adopting the two-stage desiliconization process provided by the present invention, a desiliconization product can be obtained separately in the desiliconization process, and aluminum and sodium can be recovered from the desiliconization product;

[0044] (6) The desiliconization process provided by the present invention of adding a synthetic sodium-based desiliconization agent and a synthetic calcium-based desiliconization agent simultaneously can rapidly reduce the silicon dioxide in the Bayer process crude liquor (crude sodium aluminate solution) to a relatively low level, thereby achieving rapid desiliconization. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1The present invention is a two-stage desiliconization process flow chart of Bayer process crude liquor.

[0046] Figure 2 The present invention is a process flow chart of the first stage desiliconization of Bayer process crude liquor. DETAILED DESCRIPTION

[0047] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the present invention, but the protection scope of the present invention is not limited to the following specific embodiments.

[0048] Unless otherwise defined, all the professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0049] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0050] The invention provides two desiliconizing agents and application of the two desiliconizing agents in desiliconizing Bayer process crude liquor.

[0051] The first desiliconizer, a synthetic sodium desiliconizer, is prepared by the following method:

[0052] At least one of opal, kaolinite and sodium silicate is added to sodium aluminate solution A, and at least one of NaCl, Na2SO4 and Na2CO3 is added. After a period of reaction, the reaction slurry is separated into solid and liquid, and the solid phase is a synthetic sodium-based desiliconizing agent.

[0053] In a specific embodiment, the caustic ratio of the sodium aluminate solution A is 1.35-4.0, preferably 1.5-3.5, and more preferably 2.0-3.5; the caustic concentration is 140-300 g / L, preferably 160-250 g / L.

[0054] In a specific embodiment, the solid-to-liquid ratio of at least one of opal, kaolinite and sodium silicate to the sodium aluminate solution A is 5-30 g / 100 mL, preferably 5-20 g / 100 mL, and more preferably 10-20 g / 100 mL.

[0055] In a specific embodiment, the solid-liquid ratio of the added amount of at least one of NaCl, Na2SO4, and Na2CO3 (calculated as Na2O) to the sodium aluminate solution A is 0.5-3 g / 100 mL, preferably 1-2 g / 100 mL.

[0056] In a specific embodiment, the synthesis reaction temperature is 90-160° C., preferably 100-130° C.; the synthesis reaction time is 2-12 h, preferably 6-12 h.

[0057] The present invention also provides another desiliconizing agent, a synthetic calcium-based desiliconizing agent, which is prepared by the following method:

[0058] Lime milk is added to the sodium aluminate solution B for reaction, and the reaction slurry is subjected to solid-liquid separation, and the obtained solid phase is the synthetic calcium-based desiliconizing agent.

[0059] In a specific implementation manner, the solid content of the lime milk is 100-300 g / L, preferably 150-250 g / L, and more preferably 200-250 g / L.

[0060] In a specific embodiment, the caustic ratio of the sodium aluminate solution B is 1.35-2.0, the aluminum oxide concentration is 70-150 g / L, and the concentration of Na2CO3 and / or Na2SO4 is 0-30 g / L in terms of Na2O.

[0061] In a specific implementation manner, the volume ratio of the lime milk to the sodium aluminate solution B is 1:1 to 1:4.

[0062] In a specific embodiment, the reaction temperature is 50-110° C., preferably 70-100° C.; the reaction time is 20-100 min, preferably 50-80 min.

[0063] The synthetic sodium-based desiliconizing agent and the synthetic calcium-based desiliconizing agent are applied to the desiliconization of Bayer process crude liquor, and a two-stage desiliconization process or a one-stage desiliconization process can be adopted.

[0064] In the two-stage desiliconization process of Bayer process crude liquor, the above-mentioned synthetic sodium-based desiliconizing agent is first added to the Bayer process crude liquor to carry out the first-stage desiliconization; after the first-stage desiliconization is completed, the above-mentioned synthetic calcium-based desiliconizing agent is added to the desiliconized fine liquor obtained by solid-liquid separation to carry out the second-stage desiliconization.

[0065] In a specific embodiment, the reaction temperature of the first stage desiliconization is 80-160°C, preferably 100-130°C.

[0066] In a specific embodiment, in the first stage of desiliconization, the amount of synthetic sodium desiliconizer added is: 10-100 g of synthetic sodium desiliconizer is added to 1 L of Bayer process crude liquor, preferably 40-70 g. It is further preferred that the particle size of the synthetic sodium desiliconizer is 100-600 mesh.

[0067] In a specific embodiment, the desiliconization time is 2 to 10 hours, preferably 2 to 8 hours, and more preferably 4 to 8 hours.

[0068] After the first stage of desiliconization is completed, the solid phase obtained by solid-liquid separation is ground to meet the particle size requirements and can be used as a desiliconization agent.

[0069] In a specific embodiment, the temperature of the second stage desiliconization is 90-160°C, preferably 100-130°C.

[0070] In a specific embodiment, in the second-stage desiliconization, the amount of synthetic calcium-based desiliconizing agent added is: based on the CaO content, the amount of CaO added to each 1L of desiliconized semen is 2-20g, preferably 8-16g.

[0071] In a specific embodiment, the second stage desiliconization time is 1 to 8 hours, preferably 3 to 8 hours.

[0072] In the first stage desiliconization process of the Bayer process crude liquor, the above-mentioned synthetic sodium-based desiliconizing agent and calcium-based desiliconizing agent are simultaneously added to the Bayer process crude liquor to carry out desiliconization reaction.

[0073] In a specific embodiment, the temperature of the desiliconization reaction is 90-160°C, preferably 100-150°C.

[0074] In a specific embodiment, the amount of the synthetic sodium desiliconizing agent added is: 10-100 g of the synthetic sodium desiliconizing agent is added to 1 L of Bayer process crude liquor, preferably 30-70 g. It is further preferred that the particle size of the synthetic sodium desiliconizing agent is 100-600 mesh.

[0075] In a specific embodiment, the amount of the synthetic calcium-based desiliconizing agent added is: based on the content of CaO, the amount of CaO added to each 1L of Bayer process crude liquor is 2-20g, preferably 6-15g.

[0076] In a specific embodiment, the desiliconization reaction time is 1 to 8 hours, preferably 4 to 8 hours.

[0077] After the desiliconization reaction is completed, the slag phase obtained by solid-liquid separation can be used as a desiliconization agent after grinding and treatment, and a synthetic calcium-based desiliconization agent can be added according to actual conditions.

[0078] The technical concept of the present invention is further described below through specific embodiments.

[0079] Example 1

[0080] Sodium aluminate solution A: caustic ratio is 3.5, caustic concentration is 220g / L;

[0081] Sodium aluminate solution B: caustic ratio is 1.7, alumina concentration is 105g / L;

[0082] Bayer process crude liquor: caustic ratio is 1.5, caustic concentration is 160g / L, SiO2 concentration is 1.12g / L, fluorine (F- The concentration of sulfur (SO4 2- The concentration of vanadium (V2O5) was 5.03 g / L, the concentration of vanadium (V2O5) was 0.37 g / L, and the concentration of organic matter (TOC) was 0.44 g / L;

[0083] Lime milk: solid content is 180g / L.

[0084] (1) Synthetic sodium desiliconizer

[0085] Add 15g opal to 100mL sodium aluminate solution A, then add 3.42g NaCl and 3.77g Na2CO3, stir and react at 120℃ for 7h, with a stirring rate of 300rpm. After the reaction is completed, filter the slurry to obtain a liquid phase and a solid phase. The solid phase is the synthetic sodium-based desiliconizing agent.

[0086] (2) Synthetic calcium desiliconizer

[0087] The volume ratio of lime milk to sodium aluminate solution B is 1:2, and the reaction is stirred at 80°C for 40 minutes at a stirring rate of 300 rpm. After the reaction is completed, the slurry is filtered to obtain a liquid phase and a solid phase. The solid phase is the synthetic calcium-based desiliconizing agent.

[0088] (3) Two-stage desiliconization of Bayer process crude liquor

[0089] 30g of synthetic sodium desiliconizer was added to each 1L of Bayer process crude liquor, and the particle size of the desiliconizer was less than 150 meshes; the reaction was stirred at 110°C for 5h, and the stirring reaction rate was 500rpm. After the reaction was completed, the slurry was filtered to obtain a slag phase and desiliconized fine liquor.

[0090] After grinding, the slag phase is returned to the Bayer process crude liquor desiliconization step and used as a desiliconization agent.

[0091] Add 6g of synthetic calcium-based desiliconizing agent (calculated as CaO) to every 1L of desiliconized semen, stir and react for 3h at 120℃, with a stirring rate of 600rpm. After the reaction is completed, filter the slurry, the liquid phase is the mother liquor after deep desiliconization, and the slag phase is discharged or partially recycled as a desiliconizing agent.

[0092] The silicon content index of the mother liquor after deep desiliconization is 2073, and the fluorine (F - The concentration of sulfur (SO4 2- The concentration of natural gas (calculated) was 3.77 g / L, the concentration of vanadium (calculated as V2O5) was 0.21 g / L, and the concentration of organic matter (TOC) was 0.23 g / L.

[0093] Example 2

[0094] Sodium aluminate solution A: caustic ratio is 3.2, caustic concentration is 230g / L;

[0095] Sodium aluminate solution B: caustic ratio is 1.55, alumina concentration is 90g / L, Na2CO3 concentration is 27.35g / L;

[0096] Bayer process crude liquor: caustic ratio is 1.5, caustic concentration is 150g / L, SiO2 concentration is 1.51g / L, fluorine (F - The concentration of sulfur (SO4 2- The concentration of vanadium (V2O5) was 6.36 g / L, the concentration of vanadium (V2O5) was 0.34 g / L, and the concentration of organic matter (TOC) was 0.79 g / L;

[0097] Lime milk: solid content is 220g / L.

[0098] (1) Synthetic sodium desiliconizer

[0099] Add 20g sodium silicate to 100mL sodium aluminate solution A, then add 2.56g Na2CO3 and 3.44g Na2SO4, stir and react at 130℃ for 8h, with a stirring rate of 300rpm. After the reaction is completed, filter the slurry to obtain a liquid phase and a solid phase. The solid phase is the synthetic sodium-based desiliconizing agent.

[0100] (2) Synthetic calcium desiliconizer

[0101] The volume ratio of lime milk to sodium aluminate solution B is 1:3, and the reaction is stirred at 75°C for 55 minutes at a stirring rate of 300 rpm. After the reaction is completed, the slurry is filtered to obtain a liquid phase and a solid phase. The solid phase is the synthetic calcium-based desiliconizing agent.

[0102] (3) Two-stage desiliconization of Bayer process crude liquor

[0103] 40g of synthetic sodium desiliconizer was added to each 1L of Bayer process crude liquor, and the particle size of the desiliconizer was less than 325 meshes; the reaction was stirred at 150°C for 4h, and the stirring reaction rate was 500rpm. After the reaction was completed, the slurry was filtered to obtain a slag phase and desiliconized fine liquor.

[0104] After grinding, the slag phase is returned to the Bayer process crude liquor desiliconization step and used as a desiliconization agent.

[0105] Add 8g of synthetic calcium-based desiliconizing agent (calculated as CaO) to every 1L of desiliconized semen, stir and react at 140℃ for 4h, with a stirring rate of 500rpm. After the reaction is completed, filter the slurry, the liquid phase is the mother liquor after deep desiliconization, and the slag phase is discharged or partially recycled as a desiliconizing agent.

[0106] The silicon content index of the mother liquor after deep desiliconization is 4188, and the fluorine (F - The concentration of sulfur (SO4 2-The concentration of natural gas (calculated) was 5.21 g / L, the concentration of vanadium (calculated as V2O5) was 0.18 g / L, and the concentration of organic matter (TOC) was 0.31 g / L.

[0107] Example 3

[0108] Sodium aluminate solution A: caustic ratio is 2.5, caustic concentration is 190g / L;

[0109] Sodium aluminate solution B: caustic ratio is 1.6, alumina concentration is 100g / L, Na2SO4 concentration is 22.91g / L;

[0110] Bayer process crude liquor: caustic ratio is 1.5, caustic concentration is 150g / L, SiO2 concentration is 1.43g / L, fluorine (F - The concentration of sulfur (SO4 2- The concentration of vanadium (V2O5) was 6.10 g / L, the concentration of vanadium (V2O5) was 0.31 g / L, and the concentration of organic matter (TOC) was 0.55 g / L;

[0111] Lime milk: solid content is 250g / L.

[0112] (1) Synthetic sodium desiliconizer

[0113] Add 10g of kaolinite to 100mL of sodium aluminate solution A, then add 2.26g of NaCl, 2.05g of Na2CO3 and 2.75g of Na2SO4, and stir at 140°C for 8h at a stirring rate of 400rpm. After the reaction is completed, filter the slurry to obtain a liquid phase and a solid phase. The solid phase is the synthetic sodium-based desiliconizing agent.

[0114] (2) Synthetic calcium desiliconizer

[0115] The volume ratio of lime milk to sodium aluminate solution B is 1:2, and the reaction is stirred at 70°C for 65 minutes at a stirring rate of 200 rpm. After the reaction is completed, the slurry is filtered to obtain a liquid phase and a solid phase. The solid phase is the synthetic calcium-based desiliconizing agent.

[0116] (3) Primary desiliconization of Bayer process crude liquor

[0117] Add 50g of synthetic sodium desiliconizer and 6g of synthetic calcium desiliconizer (calculated as CaO) to every 1L of Bayer process crude liquor. The particle size of the synthetic sodium desiliconizer is less than 100 mesh.

[0118] The reaction was stirred at 120° C. for 4 h at a stirring reaction rate of 500 rpm. After the reaction was completed, the slurry was filtered to obtain a slag phase and desiliconized semen.

[0119] After grinding, the slag phase is returned to the Bayer process crude liquor desiliconization step and used as a desiliconization agent.

[0120] The silicon content index of desiliconized semen is 419, and the fluorine (F - The concentration of sulfur (SO4 2- The concentration of natural gas (calculated) was 4.89 g / L, the concentration of vanadium (calculated as V2O5) was 0.18 g / L, and the concentration of organic matter (TOC) was 0.27 g / L.

[0121] Example 4

[0122] Sodium aluminate solution A: caustic ratio is 3.0, caustic concentration is 170g / L;

[0123] Sodium aluminate solution B: caustic ratio is 1.5, alumina concentration is 95g / L;

[0124] Bayer process crude liquor: caustic ratio is 1.5, caustic concentration is 145g / L, SiO2 concentration is 1.39g / L, fluorine (F - The concentration of sulfur (SO4 2- The concentration of carbon dioxide (calculated) was 7.77 g / L, the concentration of vanadium (calculated as V2O5) was 0.41 g / L, and the concentration of organic matter (TOC) was 0.49 g / L;

[0125] Lime milk: solid content is 150g / L.

[0126] (1) Synthetic sodium desiliconizer

[0127] Add 20g sodium silicate to 100mL sodium aluminate solution A, then add 4.27g Na2CO3 and 5.73g Na2SO4, stir and react at 110℃ for 10h, with a stirring rate of 400rpm. After the reaction is completed, filter the slurry to obtain a liquid phase and a solid phase. The solid phase is the synthetic sodium-based desiliconizing agent.

[0128] (2) Synthetic calcium desiliconizer

[0129] The volume ratio of lime milk to sodium aluminate solution B is 1:1, and the reaction is stirred at 80°C for 45 minutes at a stirring rate of 250 rpm. After the reaction is completed, the slurry is filtered to obtain a liquid phase and a solid phase. The solid phase is the synthetic calcium-based desiliconizing agent.

[0130] (3) Primary desiliconization of Bayer process crude liquor

[0131] 70g of synthetic sodium desiliconizer and 5g of synthetic calcium desiliconizer (calculated as CaO) are added to each 1L of Bayer process crude liquor. The particle size of the synthetic sodium desiliconizer is less than 325 mesh.

[0132] The reaction was stirred at 130° C. for 5 h at a stirring reaction rate of 500 rpm. After the reaction was completed, the slurry was filtered to obtain a slag phase and desiliconized semen.

[0133] After grinding, the slag phase is returned to the Bayer process crude liquor desiliconization step and used as a desiliconization agent.

[0134] The silicon content index of desiliconized semen is 393, and the fluorine (F - The concentration of sulfur (SO4 2- The concentration of natural gas (calculated) was 6.01 g / L, the concentration of vanadium (calculated as V2O5) was 0.19 g / L, and the concentration of organic matter (TOC) was 0.24 g / L.

[0135] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A synthetic sodium desiliconizing agent, characterized in that: Prepared by the following method: Add at least one of opal, kaolinite and sodium silicate, and at least one of NaCl, Na2SO4 and Na2CO3 to sodium aluminate solution A, react for a period of time, separate the reaction slurry into solid and liquid, and the solid phase is a synthetic sodium-based desiliconizing agent; The caustic ratio of the sodium aluminate solution A is 1.35-4.0, and the caustic concentration is 140-300 g / L; the solid-liquid ratio of the added amount of at least one of opal, kaolinite, and sodium silicate to the sodium aluminate solution A is 5-30 g / 100 mL; in terms of Na2O, the solid-liquid ratio of the added amount of at least one of NaCl, Na2SO4, and Na2CO3 to the sodium aluminate solution A is 0.5-3 g / 100 mL.

2. The synthetic sodium-based desiliconizing agent according to claim 1, characterized in that: The reaction temperature is 90-160° C., and the reaction time is 2-12 hours.

3. A method for desiliconizing a Bayer process crude liquor, characterized in that: The method comprises a two-stage desiliconization process: firstly, adding the synthetic sodium-based desiliconization agent described in any one of claims 1 to 2 to the Bayer process crude liquor to carry out a first-stage desiliconization; after the first-stage desiliconization is completed, adding the synthetic calcium-based desiliconization agent to the desiliconized fine liquor obtained by solid-liquid separation to carry out a second-stage desiliconization; The synthetic calcium-based desiliconizing agent is prepared by the following method: adding lime milk to a sodium aluminate solution B for reaction, subjecting the reaction slurry to solid-liquid separation, and obtaining a solid phase, which is the synthetic calcium-based desiliconizing agent.

4. The method for desiliconizing Bayer process crude liquor according to claim 3, characterized in that: The reaction temperature of the one-stage desiliconization is 80-160°C; in the one-stage desiliconization, the amount of synthetic sodium-based desiliconization agent added is: 10-100g of synthetic sodium-based desiliconization agent is added to every 1L of Bayer process crude liquor; the time of the one-stage desiliconization is 2-10h.

5. The method for desiliconizing Bayer process crude liquor according to claim 3, characterized in that: The temperature of the second stage desiliconization is 90-160°C; in the second stage desiliconization, the amount of synthetic calcium-based desiliconization agent added is: based on the content of CaO, the amount of CaO added to each 1L of desiliconized semen is 2-20g; the time of the second stage desiliconization is 1-8h.

6. The method for desiliconizing Bayer process crude liquor according to any one of claims 3 to 5, characterized in that: When preparing a synthetic calcium-based desiliconizing agent, the solid content of the lime milk is 100-300 g / L; the caustic ratio of the sodium aluminate solution B is 1.35-2.0, the alumina concentration is 70-150 g / L, and the concentration of Na2CO3 and / or Na2SO4 is 0-30 g / L in terms of Na2O; the volume ratio of the lime milk to the sodium aluminate solution B is 1:1-1:

4.

7. The method for desiliconizing Bayer process crude liquor according to claim 6, characterized in that: When preparing the synthetic calcium-based desiliconizing agent, the reaction temperature is 50-110° C. and the reaction time is 20-100 min.

8. A method for rapid desiliconization of Bayer process crude liquor, characterized in that: Adding the synthetic sodium-based desiliconizing agent and the synthetic calcium-based desiliconizing agent described in any one of claims 1 to 2 simultaneously to the Bayer process crude liquor to carry out a desiliconization reaction; The synthetic calcium-based desiliconizing agent is prepared by the following method: adding lime milk to a sodium aluminate solution B for reaction, subjecting the reaction slurry to solid-liquid separation, and obtaining a solid phase, which is the synthetic calcium-based desiliconizing agent.

9. The method for rapid desiliconization of Bayer process crude liquor according to claim 8, characterized in that: When preparing a synthetic calcium-based desiliconizing agent, the solid content of the lime milk is 100-300 g / L; the caustic ratio of the sodium aluminate solution B is 1.35-2.0, the alumina concentration is 70-150 g / L, and the concentration of Na2CO3 and / or Na2SO4 is 0-30 g / L in terms of Na2O; the volume ratio of the lime milk to the sodium aluminate solution B is 1:1-1:

4.

10. The method for rapid desiliconization of Bayer process crude liquor according to claim 9, characterized in that: When preparing the synthetic calcium-based desiliconizing agent, the reaction temperature is 50-110° C. and the reaction time is 20-100 min.

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