CN101306820A - A method for continuous production of sodium fluorosilicate - Google Patents

Abstract

The invention discloses a method for continuously producing sodium fluorosilicate. The present invention can adopt a multi-compartment synthesis tank, and openings are arranged on the partitions or partition walls of the multi-compartment synthesis tanks to communicate with each other, and there is no opening or communication between the first grid and the last grid. The raw materials fluosilicic acid and brine are metered into the first grid at the same time, and the stirring reaction is carried out. Under the action of stirring, the reaction slurry enters the second grid, and in this grid, fluorosilicic acid or/and brine can be added for further reaction and crystal growth, and then the reaction slurry enters the third grid in turn until the last grid. Crystal growth. The present invention can also adopt a single-cell synthesis tank and set multiple crystal growth tanks at the same time, and discharge materials at the cone bottom positions of the single-cell synthesis tank and each crystal growth tank. The raw materials fluosilicic acid and brine are metered into the single-cell synthesis tank at the same time, and the stirring reaction is carried out. Then enter the first crystal growth tank, which can be supplemented with fluosilicic acid or/and brine for further reaction and crystal growth. Then, the reaction slurry enters the second crystal growth tank sequentially until the last crystal growth tank for crystal growth.

Description

A method for continuous production of sodium fluorosilicate

technical field

The present invention relates to the production method of sodium fluorosilicate, more specifically, the present invention relates to a kind of method of continuous production sodium fluorosilicate.

Description of drawings

In view of the fact that the description of the present invention is more concise and clear with reference to the accompanying drawings, therefore, the content of the accompanying drawings is briefly described first.

Fig. 1 is a schematic flow chart of "intermittent production of sodium fluorosilicate process";

Fig. 2 is a schematic flow sheet of "continuous production of sodium fluorosilicate process" in the prior art;

Fig. 3 is the multi-grid synthesis tank adopted in "continuous production of sodium fluorosilicate-multi-grid synthesis tank technology" of the present invention-preferably positive cylindrical grid shape and regular (rectangular) cube grid combined shape (preferably 4 grid, 3 grid, 2 grid) plan view;

Fig. 4 is a schematic flow sheet of the present invention "continuous production of sodium fluorosilicate-multi-compartment synthesis tank technology" (taking the three-compartment tank as an example);

Fig. 5 is a schematic flow chart of "continuous production of sodium fluorosilicate-crystal growth tank process" of the present invention (taking two crystal growth tanks as an example).

Background technique

When using fluosilicic acid (H ₂ SiF ₆ ) and industrial sodium chloride, brine (NaCl solution) or Glauber’s salt (Na ₂ SO ₄ ) as raw materials to produce sodium fluosilicate, in the synthesis tank, H ₂ SiF ₆ and NaCl solution (or Na ₂ SO ₄ solution) to react to generate sodium fluorosilicate precipitation crystals and dilute hydrochloric acid (or dilute sulfuric acid) mother liquor, the chemical reaction formula is as follows:

H ₂ SiF ₆ +2NaCl====Na ₂ SiF ₆ ↓+2HCl

H ₂ SiF ₆ +Na ₂ SO ₄ ====Na ₂ SiF ₆ ↓+H ₂ SO ₄

In the prior art, the production of sodium fluorosilicate has been a batch production process for a long time, that is, in the single-cell synthesis tank, the metered H ₂ SiF ₆ is added first, and then the NaCl solution or Na ₂ SO ₄ is metered. Solution, stirring and reacting for a certain period of time, after growing the crystal for a certain period of time, stop stirring, clarify in the single-cell synthesis tank, separate the upper layer mother liquor, then add water to wash the precipitate for 2 to 3 times (clarify after each washing, separate the upper layer for washing liquid). After washing, the sodium fluorosilicate precipitate is obtained, which is transferred to a centrifuge to dry, and then dried to obtain the sodium fluorosilicate product. The single-cell synthesis tank repeats the synthesis reaction and washing operation, and the mother liquor and washing liquid are discharged after being neutralized. The process flow of "intermittent production of sodium fluorosilicate process" is shown in Figure 1.

The method of intermittently producing sodium fluorosilicate has the advantages of stable control of synthesis reaction time and crystal growth time, consistent product crystallization life, large and uniform crystal grain size, and good product quality. But its shortcomings are: backward technology, low production efficiency, high labor intensity, only suitable for small-scale, workshop-style production, not suitable for modern large-scale production.

In the past two years, individual sodium fluorosilicate production devices have appeared, and continuous production processes have been adopted. That is, in the single-cell synthesis tank, fluosilicic acid and brine are metered at the same time, stirred and reacted, and after staying for a certain period of time, the reaction slurry comes out of the synthesis tank and enters the first-stage thickener for sedimentation. The upper layer mother liquor is separated, and the first-stage The underflow slurry of the thickener is pumped into the pulping tank, mixed with water, washed, and then enters the secondary thickener for sedimentation, and the upper washing liquid is separated, and the underflow slurry of the secondary thickener enters the continuous centrifuge dried, and then sent to air dryer for drying to obtain sodium fluorosilicate product. The mother liquor and lotion are discharged after being neutralized. The flow chart of the "continuous production of sodium fluorosilicate process" in the prior art is shown in Figure 2.

As shown in Figure 2, compared with the "continuous production of sodium fluorosilicate process" in the prior art and the "intermittent production of sodium fluorosilicate process", the degree of automation is higher, the process is more advanced, the production efficiency is improved, and the device capacity is large. , the operation is relatively simple. However, since the single-cell synthesis tank is still used for continuous production, in the same space of the single-cell synthesis tank, it is necessary to realize the addition of raw materials H ₂ SiF ₆ , NaCl solution (or Na ₂ SO ₄ solution), and To achieve the formation and growth of Na ₂ SiF ₆ precipitated crystals, and to realize the removal of reaction products, this method cannot avoid a large number of newly formed fine crystals short-circuiting and mixed into the reaction products removed from the synthesis tank. The finely divided Na ₂ SiF ₆ crystals removed from the synthesis tank enter the subsequent process, and it is difficult to settle in the thickener and dry in the centrifuge, which reduces the production capacity of the device and also affects the liquid-solid separation and washing process, which is easy to cause If the free acid of the product exceeds the standard, it is easy to cause more Na ₂ SiF ₆ products to be entrained in the mother liquor and lotion in the upper layer of the thickener, resulting in lower yield, higher consumption, and easy pollution of the environment. Too finely divided Na ₂ SiF ₆ crystals are likely to cause high content of fine dust in the drying tail gas when drying by airflow dryer, making it difficult to collect and remove dust, resulting in a decrease in efficiency, resulting in product loss and environmental pollution. Moreover, finely divided crystals are difficult to meet the requirements of users (especially users in the European market) for Na ₂ SiF ₆ products "the particle size should not be too fine, and there is a lower limit index limit". Caking easily. These deficiencies urgently need to be overcome and improved.

Contents of the invention

The purpose of the present invention is to overcome the shortcoming in the prior art, provide a kind of new method of continuous production sodium fluorosilicate.

The purpose of the present invention is achieved through the following technical solutions.

* Unless otherwise specified, the percentage concentrations used in the present invention are mass percentage concentrations.

The invention provides a method for continuous production of sodium fluorosilicate, which adopts "continuous production of sodium fluorosilicate - multi-cell synthesis tank process" or "continuous production of sodium fluorosilicate - crystal growth tank process" "Both technical solutions can be realized.

1. When adopting "continuous production of sodium fluorosilicate - multi-cell synthesis tank process", the following steps are included:

(1) The sodium fluorosilicate synthesis tank adopts a multi-grid synthesis tank. The multi-grid synthesis tank is composed of any shape and any number of single cells, preferably a positive cylindrical grid shape and a regular (cuboid) cube Combination shapes of grids, preferably 2, 3 or 4 grids. The size of the cells after division can be different (that is, the unequal structure) or the same (that is, the equal structure), and the unequal structure is preferred. In the unequal structure, since the feeding and synthesis reaction must be completed in the first cell, the volume of this cell is designed to be larger, so the optimal solution for the volume of each cell is that the volume of the first cell is large, and the volume of the other cells is small and the same.

Two compartments: the volume of the first compartment accounts for 55% to 70% of the total volume (preferably 55% to 65%); three compartments: the volume of the first compartment accounts for 35% to 60% of the total volume (preferably 45% to 55%) ); four compartments: the volume of the first compartment accounts for 28% to 45% of the total volume (preferably 30% to 40%). According to the different design capabilities of the device, the total volume of the multi-cell synthesis tank (the sum of the volumes of each cell) is different, generally in the range of 2M ³ to 70M ³ , and the total effective volume (the sum of the effective volume of each cell) is generally in the range of 1.6M ³ to 56M ^3. Preferably, the total effective volume is 2M ³ -40M ³ .

(2) The multi-grid composite tank is a steel tank or a concrete tank with anti-corrosion treatment. The grids of the multi-grid synthesis tank are connected in series. On the dividing plate or partition wall of each grid of the multi-grid synthetic tank, open an opening of any shape (preferably a square opening, a rectangular opening and a circular opening) at a position of 0-0.5m (preferably 0-0.2m) from the bottom of the tank, Depending on the design capacity of the device and the total effective volume of the synthesis tank, the opening cross-sectional area varies, generally ranging from 0.04M ² to 1.50M ² , preferably 0.06M ² to 1.00M ² . There is no opening or connection between the first grid and the last grid. The opening near the bottom of the tank is to ensure that the crystals entering the next compartment are large-sized crystals.

(3) The raw materials fluosilicic acid and brine are metered into the first grid at the same time, and the reaction is carried out under stirring. The reaction slurry enters the second grid under the action of stirring. In this grid, fluosilicic acid or/and brine can be added, Eliminate the supersaturation of SiF ₆ ^2- or Na ⁺ , carry out further reaction and crystal growth, then, the reaction slurry enters the third compartment in turn, until the last compartment for digestion and crystal growth. 1/6 to 2/5 (preferably 1/5 to 1/3) of the total amount of reaction slurry from the last grid is used as the return slurry (seed crystal), which is sent back to the first grid by a circulating pump, and the remaining 5/6 ~3/5 (preferably 4/5 ~ 2/3) of the slurry enters the next process.

The production method determined by the "continuous production of sodium fluorosilicate-multi-cell synthesis tank process" adopted by the present invention, the rest is the same as the "continuous production of sodium fluorosilicate process" in the prior art of Fig. 2 .

The process of "continuous production of sodium fluorosilicate-multi-compartment synthesis tank process" adopted by the present invention is shown in Figure 4 (taking three-compartment tank as an example).

2. When using "continuous sodium fluorosilicate production - crystal growth tank process", the following steps are included:

(1) The sodium fluorosilicate synthesis tank adopts a single-cell synthesis tank, and multiple single-cell crystal growth tanks (referred to as crystal growth tanks, the same below) are set at the same time. The single-cell synthesis tank has any shape, preferably a right cylinder with a conical bottom and a regular (cuboid) parallelepiped with a quadrangular pyramid bottom. The crystal growth tanks provided are of any shape and any number, preferably the shape of a right cylinder with a conical bottom and a regular (cuboid) parallelepiped with a quadrangular pyramid bottom. Preferably, the number of crystal growth tanks is 1, 2 or 3. Since feeding and synthesis reactions are to be completed in the single-cell synthesis tank, the optimal solution for the volume of the single-cell synthesis tank and crystal growth tank is: the volume of the single-cell synthesis tank is large, and the volume of each crystal growth tank is small and the same.

When the number of crystal growth tanks is 1, the volume of the single cell synthesis tank accounts for 55% to 70% of the total volume (preferably 55% to 65%); when the number of crystal growth tanks is 2: the volume of the single cell synthesis tank accounts for 35% to 35% of the total volume 60% (preferably 45%-55%); when the number of crystal growth tanks is 3: the volume of the single cell synthesis tank accounts for 28%-45% (preferably 30%-40%) of the total volume. According to the different design capabilities of the device, the sum of the volume of the single cell synthesis tank and multiple crystal growth tanks is generally 2M ³ ~ 70M ³ , the sum of the effective volume is generally 1.6M ³ ~ 56M ³ , and the sum of the effective volume is preferably 2M ³ ~ ^40M3 .

(2) The single cell synthesis tank and the crystal growth tank are both steel tanks or concrete tanks with anti-corrosion treatment. There is a serial relationship between the single cell synthesis tank and each crystal growth tank. The material is discharged at the cone bottom position of the single-cell synthesis tank and each crystal growth tank. The purpose of opening the discharge at the cone bottom of the tank is to ensure that the crystals entering the next tank are large-sized crystals and facilitate discharge.

(3) The raw materials fluosilicic acid and brine are metered into the single-cell synthesis tank at the same time, and the reaction is carried out under stirring. The reaction slurry is discharged from the outlet of the conical bottom of the tank and enters the first crystal growth tank. In this tank, fluorosilicic acid or/and brine can be added to eliminate the supersaturation of SiF ₆ ^2- or Na ⁺ for further reaction and growth. crystal. Then, the reaction slurry is discharged from the outlet of the cone bottom of the tank, and then enters the second and last crystal growth tanks for digestion and crystal growth. 1/6～2/5 (preferably 1/5～1/3) of the total amount of reaction slurry coming out of the last crystal growth tank is used as return slurry (seed), and is sent back to the single cell synthesis tank with a circulation pump, and the rest 5/6～3/5 (preferably 4/5～2/3) of the slurry enters the next process.

The production method determined by the "continuous production of sodium fluorosilicate-crystal growth tank process" adopted by the present invention, the rest is the same as the "continuous production of sodium fluorosilicate process" in the prior art of Fig. 2 .

The process of "continuously producing sodium fluorosilicate-crystal growth tank process" adopted by the present invention is shown in Figure 5 (taking two crystal growth tanks as an example).

Compared with the prior art, the present invention has the following beneficial effects:

1. The present invention aims at the problems existing in the "continuous production of sodium fluorosilicate process" in the prior art, and two improvements are made to the production method to form "continuous production of sodium fluorosilicate-multi-cell synthesis tank process" and " Continuous production of sodium fluorosilicate - crystal growth tank process" can achieve good results.

2. Taking the "continuous production of sodium fluorosilicate - crystal growth tank process" in Figure 5 as an example (two crystal growth tanks are set), in the single cell synthesis tank, the raw materials H ₂ SiF ₆ , NaCl solution ( or Na ₂ SO ₄ solution) to carry out the synthesis reaction, that is, SiF ₆ ^2- combines with Na ⁺ to form Na ₂ SiF ₆ crystals, and under the condition of returning slurry (seed crystal), it can effectively avoid the formation of too many new crystal nuclei , effectively reducing the number and proportion of finely divided crystals. In the first crystal growth tank, a small amount of brine or/and fluorosilicic acid can be supplemented as needed to carry out digestion and crystal growth to eliminate the supersaturation of SiF ₆ ^2- or/and Na ⁺ . In the second crystal growth tank, the crystal growth process is mainly completed, the supersaturation of SiF ₆ ^2- or/and Na ⁺ is further eliminated, the yield is increased, and coarse Na ₂ SiF ₆ product crystals are formed. At the same time, the independent setting of the two crystal growth tanks can effectively isolate and prevent small crystals from entering the next tank, so as to ensure that the crystallization of the product coming out of the last crystal growth tank and entering the next process is coarse and uniform.

3. Compared with the products produced by the prior art, in the products produced by the present invention: the ratio of +150um particles is increased from 10% to 30% to 50% to 70%; the ratio of +100um particles is increased from 30% to 50% increased to 80% to 90%; the proportion of -45um particles decreased from 30% to 50% to less than 8%; the fluorine yield increased from 75% to 85% to more than 90%; the fluorine per ton of sodium fluorosilicate products The consumption of silicic acid (100% H ₂ SiF ₆ ) drops from 0.901 to 1.021 tons to less than 0.851 tons, which fundamentally solves the shortcomings of the "continuous production of sodium fluorosilicate" in the prior art.

Detailed ways

Example 1

Adopting the "continuous production of sodium fluorosilicate-crystal growth tank process" of the present invention, the process is provided with one single cell synthesis tank and two crystal growth tanks. The single-cell synthetic tank is a cylindrical (φ2.6×2.3m) steel tank with a conical bottom (cone height 1.4m) with anti-corrosion treatment, its volume is 16.3M ³ , and its effective volume is 13.0M ³ . The two crystal growth tanks are of the same size and are both cylindrical (φ2.1×1.8m) steel tanks with conical bottoms (cone height 1.1m) with anti-corrosion treatment. Their volumes are both 8.15M ³ , and their effective volumes are ^6.5M3 . The total volume of the single synthesis tank and the two crystal growth tanks is 32.6M ³ , and the total effective volume is 26.0M ³ .

The sodium fluorosilicate production capacity of the device is 5.190t/h, the fluorine yield is 90%, and the addition amount of 100% fluorosilicate is 4.417t/h, and all fluorosilicates are added to the single-cell synthesis tank. Based on the amount of fluosilicic acid added, calculate the theoretical amount of brine added according to the reaction formula. The actual addition of brine is based on 120% of the theoretical addition (wherein 110% is added in the single cell synthesis tank, and 10% is added in the first crystal growth tank).

All of the fluosilicic acid and 110% of the theoretical amount of brine were simultaneously metered into the single-cell reaction tank. The concentration of fluosilicic acid is 11.0%, the density is 1.106g/cm ³ , and the dosage is 36.31M ³ /h; the concentration of brine is 24.5%, the density is 1.216g/cm ³ , and the dosage of brine in the single cell synthesis tank is 13.241M ³ /h; The amount of slurry returned from the second crystal growth tank and sent back to the single cell synthesis tank by the circulation pump is 12.0M ³ /h. The above materials are stirred and reacted in the single-cell synthesis tank, and the formed reaction slurry enters the first crystal growth tank through the outlet of the cone bottom of the tank.

In the reaction slurry of the first crystal growth tank, the amount of brine metered is 10% of the theoretical amount, that is, 1.201M ³ /h, and the stirring reaction is carried out, and the SiF ₆ ^2- supersaturation is further eliminated through reaction and digestion, and Carry out crystal growth, increase the crystallization, and the formed reaction slurry enters the second crystal growth tank through the outlet of the cone bottom of the tank.

The reaction slurry is stirred and reacted in the second crystal growth tank, through reaction, digestion, and crystal growth, the SiF ₆ ^2- supersaturation is further eliminated, and the crystallization is increased, and then the returned slurry is discharged through the circulation pump set at the outlet of the cone bottom of the tank. (Seed crystal) was sent back to the single-cell synthesis tank, and the amount of returned slurry was 12.0M ³ /h. The remaining reaction slurry is sent to the first-stage thickener for settling, and the upper mother liquor is separated, and the underflow slurry of the first-stage thickener is pumped into the slurry tank, and water is added to adjust the slurry, washed, and then enters the second-stage thickener for sedimentation , to separate the upper lotion, the underflow slurry of the secondary thickener enters the continuous centrifuge to dry, and then sends it to the air dryer for drying to obtain the sodium fluorosilicate product. The mother liquor and lotion are sent to the neutralization tank, and discharged after neutralization.

Among the obtained products, the proportion of +150um particles reached 69%; the proportion of +100um particles reached 88%; the proportion of -45um particles decreased to 5%; the fluorine yield reached 91.2%; The consumption of fluosilicic acid (100% H ₂ SiF ₆ ) was reduced to 0.840 tons.

Example 2

Adopt the "continuous production of sodium fluorosilicate - multi-cell synthesis tank process" of the present invention. The multi-grid synthetic tank for anti-corrosion treatment is a cylindrical φ3.6×3.2m steel tank, divided into three grids, with a total volume of 32.6M ³ and a total effective volume of 26.0M ³ . The volume of the first grid is 16.3M ³ , and its effective volume is 13.0M ³ . The volumes of the second and third grids are both 8.15M ³ , and their effective volumes are both 6.5M ³ .

The sodium fluorosilicate production capacity of the device is 5.190t/h, the fluorine yield is 90%, and the addition amount of 100% fluosilicic acid is 4.417t/h. According to the reaction formula, the theoretical addition of brine is calculated. The actual addition of brine is based on 120% of the theoretical addition (wherein 110% is added in the 1st grid, and 10% is added into the 2nd grid).

The entirety of the fluosilicic acid and 110% of the theoretical amount of brine are simultaneously metered into compartment 1. The concentration of fluosilicic acid is 11.0%, the density is 1.106g/cm ³ , and the addition amount is 36.31M ³ /h; the brine concentration is 24.5%, the density is 1.216g/cm ³ , and the addition amount of brine in the first cell is 13.241M ³ /h; The amount of slurry returned to the first grid from the third grid is 12.0M ³ /h through the circulation pump. The above materials are stirred and reacted in the first grid, and the formed reaction slurry enters the second grid through a square hole (0.4m×0.4m) at a position 0m away from the bottom surface of the tank on the dividing plate.

In the reaction slurry in the second grid, the amount of brine metered is 10% of the theoretical amount, that is, 1.201M ³ /h, and the stirring reaction is carried out, and the SiF ₆ ^2- supersaturation is further eliminated through reaction and digestion, and the culture is carried out. crystallization, increase the crystallization, and the formed reaction slurry enters the third cell through the square hole (0.4m×0.4m) at the position of 0m from the bottom of the tank on the partition.

The reaction slurry is stirred and reacted in the third cell, and the SiF ₆ ^2- supersaturation is further eliminated through reaction, digestion, and crystal growth, and the crystallization is increased, and then the return slurry (seed crystal) is sent back to the first cell by a circulating pump , The amount of returned slurry is 12.0M ³ /h. The remaining reaction slurry is sent to the first-stage thickener for settling, and the upper mother liquor is separated, and the underflow slurry of the first-stage thickener is pumped into the slurry tank, and water is added to adjust the slurry, washed, and then enters the second-stage thickener for sedimentation , to separate the upper lotion, the underflow slurry of the secondary thickener enters the continuous centrifuge to dry, and then sends it to the air dryer for drying to obtain the sodium fluorosilicate product. The mother liquor and lotion are discharged after being neutralized.

Among the obtained products, the proportion of +150um particles reached 67%; the proportion of +100um particles reached 86%; the proportion of -45um particles decreased to 6%; the fluorine yield reached 91.0%; The consumption of fluosilicic acid (100% H ₂ SiF ₆ ) was reduced to 0.842 tons.

Claims (10)

1. A method for continuously producing sodium fluorosilicate, characterized in that: the sodium fluorosilicate synthesis tank adopts a multi-grid synthesis tank, and the multi-grid synthesis tank is composed of any shape and any number of single cells , the grids of the multi-grid synthesis tank are connected in series; on the partition or partition wall of each grid of the multi-grid synthesis tank, an opening of any shape is opened at a position 0-0.5m away from the bottom of the tank to connect, the first grid and the last There is no opening or connection between the 1 compartments; the raw materials fluosilicic acid and brine are metered into the first compartment of the multi-compartment synthesis tank at the same time, and the stirring reaction is carried out. Under the action of stirring, the reaction slurry enters the second compartment for further reaction and Digestion, crystal growth, and then the reaction slurry enters the third cell in turn, until the last cell for digestion, crystal growth, and then enters the next step. 2. The method for continuous production of sodium fluorosilicate according to claim 1, characterized in that: 1/6 to 2/5 of the total amount of slurry discharged from the last cell is used as the return slurry seed crystal, and the cycle is used to Pump back to the first cell, and the remaining 5/6-3/5 of the slurry enters the next process. 3. The method for continuously producing sodium fluorosilicate according to claim 1, characterized in that: supplement brine or/and fluorosilicic acid in the second cell of the multi-cell synthesis tank to eliminate SiF ₆ ^2- or/ and Na ⁺ supersaturation. 4. The method for continuously producing sodium fluorosilicate according to claim 1, characterized in that: when two compartments are used for the multi-compartment synthesis tank, the volume of the first compartment accounts for 55% to 70% of the total volume; When three compartments are used, the volume of the first compartment accounts for 35% to 60% of the total volume; when four compartments are used, the volume of the first compartment accounts for 28% to 45% of the total volume; the total volume of multi-compartment tanks is 2M ³ ~ 70M ³ , the total effective volume is 1.6M ³ -56M ³ ; the cross-sectional area of the opening on the partition or partition wall is 0.04M ² -1.50M ² . 5. The method for continuously producing sodium fluorosilicate according to claim 1, characterized in that: the multi-grid synthesis tank adopts a steel tank or a concrete tank for anti-corrosion treatment. 6. A method for continuously producing sodium fluorosilicate. The sodium fluorosilicate synthesis tank adopts a single-cell synthesis tank, which is characterized in that: a plurality of single-cell crystal growth tanks are set at the same time, and the single-cell synthesis tank is connected with each The crystal growth tanks are connected in series; the single-cell synthesis tank and each crystal growth tank are opened at the bottom of the cone; the raw materials fluosilicic acid and brine are simultaneously metered into the single-cell synthesis tank for stirring reaction, and the single-cell synthesis tank cone The reaction slurry discharged from the bottom outlet enters the first crystal growth tank for further reaction, digestion and crystal growth, and the slurry discharged from the cone bottom outlet of the first crystal growth tank enters the second crystal growth tank in turn until the last crystal growth tank After the crystal tank is digested and grown, it enters the next process. 7. The method for continuously producing sodium fluorosilicate according to claim 6, characterized in that: 1/6 to 2/5 of the slurry from the last crystal growth tank is used as return slurry and sent back to the unit by circulating pump grid synthesis tank, and the remaining 5/6 to 3/5 of the slurry enters the next process. 8. The method for continuously producing sodium fluorosilicate according to claim 6, characterized in that: supplement brine or/and fluorosilicic acid in the first crystal growth tank to eliminate SiF ₆ ^2- or/and Na ⁺ of supersaturation. 9. The method for continuously producing sodium fluorosilicate according to claim 6, characterized in that: the crystal growth tanks are of any shape and any number; when the number of crystal growth tanks is 1, the volume of the single cell synthesis tank Accounting for 55% to 70% of the total volume; when the number of crystal growth tanks is 2, the volume of single synthesis tanks accounts for 35% to 60% of the total volume; when the number of crystal growth tanks is 3, the volume of single synthesis tanks accounts for 30% of the total volume 28% to 45%; the sum of the volume of the single-cell synthesis tank and multiple crystal growth tanks is 2M ³ -70M ³ , and the sum of the effective volume is 1.6M ³ -56M ³ . 10. The method for continuously producing sodium fluorosilicate according to claim 6, characterized in that: the single-cell synthesis tank and the crystal growth tank are all in the shape of a right cylinder with a conical bottom or a square pyramid with a bottom Cube or cuboid; the synthesis tank and the crystal growth tank are both steel tanks or concrete tanks with anti-corrosion treatment.

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