CN106517246B - Method for continuously producing sodium fluoride - Google Patents

Abstract

The invention discloses a method for continuously producing sodium fluoride. The sodium fluorosilicate solution with a mass fraction of 20-30% and the soda ash solution with a mass fraction of 20-30% are sequentially and continuously added to a tubular reactor to control the reaction. The temperature is 60-100°C, and the metathesis reaction is carried out to generate sodium fluoride and silica slurry, which are continuously entered into the multi-stage flotation device for flotation. After flotation, the slurry containing sodium fluoride and the slurry containing silica are obtained respectively. The silicon slurry is centrifuged, washed and dried to obtain sodium fluoride product and silicon dioxide product; the solutions obtained by each centrifugation are combined and used as mother liquor for recycling. In the present invention, a large excess of soda ash is added in the reaction process, so that the sodium fluorosilicate is fully reacted, and the conversion rate reaches 100%. The purity of sodium fluoride produced by the method of the invention is above 98.5%, and the purity of silicon dioxide is above 98.0%. The method of the invention has less investment in production scale, can realize automatic control, reduces the labor intensity of employees, has excellent product quality and low raw material consumption.

Description

A method for continuous production of sodium fluoride

technical field

The invention relates to the technical field of chemical industry, in particular to a method for continuously producing sodium fluoride.

Background technique

The traditional method of producing sodium fluoride and silicon dioxide using sodium fluorosilicate and soda ash as raw materials is a batch method, which has small production scale, high labor intensity, high consumption and poor product quality. The specific realization process is: (1) put the mother liquor or water into the dissolving tank, put in solid soda ash under stirring, after heating and dissolving, transfer it to the high level tank with a concentration of 20-22% soda ash solution; (2) put the mother liquor or water into the preparation Put solid sodium fluorosilicate into the slurry tank under stirring to prepare sodium fluorosilicate slurry with a solid content of 20-30%, and transfer it to the reactor; (3) start the reactor agitator and heat to 60- 80°C, add the soda ash solution step by step, control the pH 7.5-8 as the end point (control the molar ratio 1:2), put it into the washing basin and rinse it with the mother liquor; (4) then manually remove the sodium fluoride in the washing basin Shovel it into a centrifuge for centrifugation, and dry to obtain a sodium fluoride product; (5) send the rinsed silicon dioxide to a centrifuge for centrifugation to separate the silicon dioxide, and obtain a silicon dioxide product after drying.

The block diagram of the traditional production process of sodium fluoride is shown in Figure 1. Chemical reaction equation:

2Na ₂ CO ₃ +Na ₂ SiF ₆ +nH ₂ 0＝6NaF↓+SiO ₂ .nH ₂ 0+2CO ₂ ↑

The sodium fluoride produced by the traditional method contains high silicon dioxide, poor quality, and intermittent operation, which is labor-intensive. At the same time, because sodium fluoride is washed by rinsing, the washing water containing solid silicon dioxide is finely fluorinated. There is a lot of sodium, and the silica solids separated by centrifugation contain a lot of fine sodium fluoride, resulting in material loss and increased consumption, and the quality of the produced silica products is poor.

The present invention aims at the disadvantages of poor quality sodium fluoride and silicon dioxide products, intermittent operation, high labor intensity and high raw material consumption in the traditional method for producing sodium fluoride products.

Contents of the invention

In view of this, the purpose of the present invention is to propose a method for continuous production of sodium fluoride, which has low production scale investment, and can realize automatic control, reduce labor intensity of employees, excellent product quality, and low raw material consumption.

Based on the above purpose, a method for continuously producing sodium fluoride provided by the present invention, the sodium fluorosilicate solution with a mass fraction of 20-30% and the soda ash solution with a mass fraction of 20-30% are successively and continuously added to the tubular reactor In the process, the reaction temperature is controlled at 60-100°C, and the metathesis reaction is carried out to generate sodium fluoride and silica slurry, which are continuously entered into the multi-stage flotation device for flotation, and the slurry containing sodium fluoride is respectively obtained after flotation and the slurry containing silicon dioxide are centrifuged, washed and dried respectively to obtain sodium fluoride product and silicon dioxide product; the solutions obtained by each centrifugation are combined and used as mother liquor for recycling.

In the present invention, preferably, the molar ratio of sodium fluorosilicate to soda ash is 1:2.2-4; the time of metathesis reaction is 1-5 minutes; more preferably, the molar ratio of sodium fluorosilicate to soda ash is 1: 2.5-3.

The invention realizes the continuous production of sodium fluoride by adopting a tubular reactor with a spiral agitator and a multistage flotation device.

In the present invention, preferably, the tubular reactor is a tubular reactor with a helical stirrer.

The production of sodium fluoride by sodium fluorosilicate soda ash method has the phenomenon of co-precipitation of sodium fluoride and silicon dioxide (white carbon black), which is easy to form "peritectic", which increases the difficulty of separating sodium fluoride and white carbon black. It also affects the quality of the product. In the present invention, the molar ratio of sodium fluorosilicate to soda ash is 1:2.2-4, and the soda ash is kept in excess to react, and the optimum molar ratio is 1:2.5-3, so that the pH is greater than 12, and the sodium fluorosilicate is fully reacted , and at the same time avoid the peritectic phenomenon of sodium fluoride generated by the reaction under high-speed stirring, and the purity is high.

The invention adopts a large excess of soda ash, the sodium fluorosilicate is fully reacted in the reaction process, the conversion rate reaches 100%, and there is no peritectic phenomenon, which improves the product quality. Excess soda ash is recycled.

In the present invention, it is preferred to put solid soda ash into the silo, use a screw conveyor to add the dissolving tank, add the mother liquor continuously in the dissolving tank, and heat it to 60°C-100°C with steam under stirring to dissolve the soda ash and keep The mass fraction of the dissolved soda ash solution is 20-30%, and it is continuously pumped out by a pump and sent into a tubular reactor. During this process, the amount of mother liquor entering and the amount of soda ash added are controlled to maintain the concentration of the dissolved soda ash solution.

In the present invention, it is further preferred that the speed of the screw conveyor is 1000kg/h, the flow rate of the mother liquor is 3600-4000kg/h, heated to 75°C-78°C with steam, and the mass fraction of the dissolved soda ash solution is 20 -twenty two%.

In the present invention, it is preferred to put the solid sodium fluorosilicate into the silo, put it into the pulping tank with a screw conveyor, continuously add the mother liquor in the pulping tank, and heat it to 60°C-100°C with steam under stirring , keep the mass fraction of the dissolved sodium fluorosilicate solution at 20-30%, and pump it out continuously and send it into the tubular reactor. During this process, the amount of mother liquor entering and the amount of sodium fluorosilicate added are controlled to maintain the concentration of the dissolved sodium fluorosilicate solution.

In the present invention, it is further preferred that the water content of the solid sodium fluorosilicate is 6%, the speed of the screw conveyor is 900kg/h, the flow rate of the mother liquor is 2400-2600kg/h, and it is heated to 75°C-78°C with steam. °C, the mass fraction of the dissolved sodium fluorosilicate solution is 25-27%.

In the present invention, preferably, the concrete steps of described flotation are as follows:

(1) Put the sodium fluoride and silicon dioxide slurry into the 1# flotation device continuously, rely on its own reaction solution to enter the flotation, obtain the slurry A containing sodium fluoride from the lower part of the flotation device, and obtain the slurry A from the upper part Silica-containing slurry a;

(2) Send the slurry A containing sodium fluoride into the 2# flotation device, carry out flotation with the mother liquor, float the fine silica, and obtain the slurry containing sodium fluoride from the lower part of the flotation device B, obtain the slurry b containing silicon dioxide from the top;

(3) Slurry B containing sodium fluoride is sent in 3# flotation device, carries out flotation and washing with soft water or industrial water, obtains the slurry C containing sodium fluoride from the bottom of 3# flotation device, Obtain the slurry c containing silicon dioxide and soda ash from the top;

(4) send in the 4# flotation device after the slurry a, slurry b that will contain silicon dioxide are merged, the slurry c that contains silicon dioxide and soda ash is used as the flotation liquid of 4# flotation device; Flotation After the fine sodium fluoride is combined with the slurry C containing sodium fluoride obtained in the lower part of the 3# flotation device, it is sent to the centrifuge for centrifugation, and the sodium fluoride product is obtained after drying;

(5) The silica-containing slurry d coming out from the upper part of the 4# flotation device is sent to the centrifuge for centrifugation, and then sent to the centrifuge for centrifugation after slurrying with hot water, and the silica product is obtained after drying.

In the present invention, the solutions obtained by each centrifugation in the flotation step are combined and used as the mother liquor for the previous process sodium fluorosilicate pulping, the dissolution of soda ash, the flotation liquid of the flotation device, etc., and the mother liquor is recycled; Comprise centrifugation three times, be respectively the fine sodium fluoride after the flotation in the step (4) and 3# flotation device lower part obtain the slurry C containing sodium fluoride to merge and send in the centrifuge for centrifugation, in the step (5) from 4 # The silica-containing slurry d from the upper part of the flotation device is sent to the centrifuge for centrifugation, and then sent to the centrifuge for centrifugation after making slurry with hot water.

In the present invention, preferably, the amount of mother liquor added in step (2) is 2000-3000 kg/h; the amount of soft water or industrial water added in step (3) is 300-500 kg/h.

In the present invention, preferably, step (5) the silica-containing slurry d coming out from the upper part of the 4# flotation device is sent to the centrifuge for centrifugation, and after slurrying with hot water at 70-100°C, steam Heating, keeping the temperature at 80°C, sending it to a centrifuge for centrifugation, and drying at 120°C to obtain a silica product.

Sodium fluoride product acquisition: The reacted slurry is continuously put into the 1# flotation device, and the flotation is carried out by its own reaction liquid, and the slurry containing sodium fluoride is obtained from the lower part, and the slurry containing silicon dioxide is obtained from the upper part. The slurry containing sodium fluoride enters the 2# flotation device again, carries out flotation with the mother liquor, further separates the silicon dioxide, and then enters the 3# flotation device with soft water for flotation and washing, and then centrifuges and drying to obtain sodium fluoride product. The purity of sodium fluoride is more than 98.5%, the content of silicon dioxide is less than 0.4%, and the content of soda ash is less than 0.2%, reaching the first-grade product standard.

Obtaining silica products: combine the silica-containing slurry obtained from the upper part of the 1# flotation unit with the silica-containing slurry from the 2# flotation unit and enter the 4# flotation unit, and use the liquid from the upper part of the 3# flotation unit After flotation, the silica-containing slurry is obtained from the upper part, sent to a centrifuge for centrifugation, and then heated with hot water at 70-100°C to further reduce the soda ash and sodium fluoride entrained in the silica. Then centrifuge and dry to obtain the silica product. The purity of silicon dioxide is above 98.0%, the content of sodium fluoride is less than 0.8%, and the content of soda ash is less than 1.0%.

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

(1) The present invention has realized the continuous production of sodium fluoride by adopting a tubular reactor with a spiral agitator and a multistage flotation device. In the present invention, a large excess of soda ash is added in the reaction process, so that the sodium fluorosilicate is fully reacted, and the conversion rate reaches 100%. The multi-stage flotation device performs flotation on the generated sodium fluoride and silica slurry, which improves the purity and quality of the product. The purity of sodium fluoride produced by the method of the invention is above 98.5%, and the purity of silicon dioxide is above 98.0%.

(2) The method of the present invention has less investment in production scale, and can realize automatic control, reduce the labor intensity of employees, have excellent product quality and low raw material consumption. In addition, in the method for continuously producing sodium fluoride of the present invention, the mother liquor can be recycled, further reducing the production cost.

Description of drawings

The accompanying drawings illustrate the process trend in detail in conjunction with the specific process implementation.

Fig. 1 is a block diagram of a traditional production process of sodium fluoride;

Fig. 2 is a block diagram of the process flow for continuous production of sodium fluoride in the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

Example 1

The block diagram of the technological process of continuous production of sodium fluoride in the present embodiment is as shown in Figure 2, and concrete steps are as follows:

(1) Put the solid soda ash into the silo, put it into the dissolving tank at a speed of 1000kg/h with a screw conveyor, continuously add the mother liquor of the subsequent process into the dissolving tank, add the flow rate of 3600-4000kg/h, and heat it with steam under stirring Dissolve the soda ash at 75°C-78°C, keep the concentration (mass fraction) of the dissolved soda ash solution at 20-22%, and pump it continuously into the tubular reactor;

(2) Put solid sodium fluorosilicate (water content 6%) into the silo, add it into the pulping tank at a speed of 900kg/h with a screw conveyor, continuously add the mother liquor of the subsequent process in the pulping tank, and add the flow rate 2400-2600kg/h, heat to 75°C-78°C with steam under stirring, keep the solid-liquid ratio (mass fraction of sodium fluorosilicate) in the sodium fluorosilicate slurry at 25-27%, and pump it out continuously into the tubular reactor;

(3) Start the spiral agitator in the tubular reactor, control the reaction temperature at 80-85° C., soda ash solution and sodium fluorosilicate solution carry out double decomposition reaction, generate sodium fluoride and silicon dioxide slurry, control the material (fluorine The molar ratio of sodium silicate to soda ash) is 1:2.2-4 (pH greater than 12), and the reaction time is 1-5 minutes;

(4) sodium fluoride after reaction and silica slurry enter in 1# flotation device, rely on the reaction liquid of self to enter flotation, obtain the slurry A containing sodium fluoride from the bottom of flotation device, from The upper part obtains the slurry a containing silicon dioxide;

(5) Send the slurry A containing sodium fluoride into the 2# flotation device, carry out flotation with the centrifuged mother liquor of the subsequent process, the addition of mother liquor is 2000kg/h, and the fine silica is floated out by flotation, Obtain slurry B containing sodium fluoride from the lower part of the flotation device, and obtain slurry B containing silicon dioxide from the top;

(6) Send the slurry B containing sodium fluoride into the 3# flotation device, carry out flotation and washing with soft water or industrial water, the addition of soft water or industrial water is 300kg/h, and obtain the slurry containing Slurry C of sodium fluoride, slurry C containing silicon dioxide, soda ash, etc. is obtained from the top;

(7) Slurry a, slurry b containing silicon dioxide are merged and sent in 4# flotation device, and the slurry c containing silicon dioxide and soda ash etc. is used as the flotation liquid of 4# flotation device; Flotation The final fine sodium fluoride is combined with the slurry C containing sodium fluoride obtained from the lower part of the 3# flotation device, and then sent to the centrifuge for centrifugation. After drying, the sodium fluoride product is obtained, with a weight of 1120kg. The purity of the sodium fluoride in it is analyzed to be 98.5 %, the content of silicon dioxide is less than 0.4%, the content of soda ash is less than 0.2%, reaching the first-grade product standard;

(8) The silica-containing slurry d from the upper part of the 4# flotation device is sent to the centrifuge for centrifugation, and then slurried with hot water at 70-100 ° C, heated with steam, and the temperature is maintained at 80 ° C, and then sent to the centrifuge Centrifuge in the machine, dry at 120°C to obtain silica (silica) product, weight 450kg (including bound water), silica purity above 98.0%, sodium fluoride content less than 0.8%, soda ash content less than 1.0%;

(9) The solutions obtained by each centrifugation (one centrifugation in step (7), two centrifugations in step (8)) are combined as mother liquor for pre-process step (2) sodium fluorosilicate pulping, step (1 ) the dissolving of soda ash, the flotation liquid etc. of step (5) 2# flotation device, mother liquor realizes recycling.

Example 2

The block diagram of the technological process of continuous production of sodium fluoride in the present embodiment is as shown in Figure 2, and concrete steps are as follows:

(1) Put the solid soda ash into the silo, put it into the dissolving tank at a speed of 1000kg/h with a screw conveyor, continuously add the mother liquor of the subsequent process into the dissolving tank, add the flow rate of 3600-4000kg/h, and heat it with steam under stirring Dissolve the soda ash at 80°C-85°C, keep the concentration (mass fraction) of the dissolved soda ash solution at 26-28%, and pump it continuously into the tubular reactor;

(2) Put solid sodium fluorosilicate (water content 6%) into the silo, add it into the pulping tank at a speed of 900kg/h with a screw conveyor, continuously add the mother liquor of the subsequent process in the pulping tank, and add the flow rate 2400-2600kg/h, heat it with steam to 80°C-85°C under stirring, keep the solid-liquid ratio (mass fraction of sodium fluorosilicate) in the sodium fluorosilicate slurry at 22-25%, and pump it out continuously into the tubular reactor;

(3) Start the helical agitator in the tubular reactor, control the reaction temperature at 88-90°C, the soda ash solution and the sodium fluorosilicate solution carry out the metathesis reaction, generate sodium fluoride and silicon dioxide slurry, control the material (fluorine The molar ratio of sodium silicate to soda ash) is 1:2.5-3 (pH greater than 12), and the reaction time is 1-5 minutes;

(4) sodium fluoride after reaction and silica slurry enter in 1# flotation device, rely on the reaction liquid of self to enter flotation, obtain the slurry A containing sodium fluoride from the bottom of flotation device, from The upper part obtains the slurry a containing silicon dioxide;

(5) Send the slurry A containing sodium fluoride into the 2# flotation device, carry out flotation with the centrifugal mother liquor of the subsequent process, the addition of mother liquor is 3000kg/h, and the fine silica is floated out by flotation, Obtain slurry B containing sodium fluoride from the lower part of the flotation device, and obtain slurry B containing silicon dioxide from the top;

(6) Send the slurry B containing sodium fluoride into the 3# flotation device, carry out flotation and washing with soft water or industrial water, the addition of soft water or industrial water is 500kg/h, and obtain the slurry containing Slurry C of sodium fluoride, slurry C containing silicon dioxide, soda ash, etc. is obtained from the top;

(7) Slurry a, slurry b containing silicon dioxide are merged and sent in 4# flotation device, and the slurry c containing silicon dioxide and soda ash etc. is used as the flotation liquid of 4# flotation device; Flotation The final fine sodium fluoride is combined with the slurry C containing sodium fluoride obtained from the lower part of the 3# flotation device and then sent to the centrifuge for centrifugation. After drying, the sodium fluoride product is obtained. %, the content of silicon dioxide is less than 0.3%, the content of soda ash is less than 0.2%, reaching the first-grade product standard;

(8) The silica-containing slurry d from the upper part of the 4# flotation device is sent to the centrifuge for centrifugation, and then slurried with hot water at 70-100 ° C, heated with steam, and the temperature is maintained at 80 ° C, and then sent to the centrifuge Centrifuge in the machine and dry at 120°C to obtain a silica (white carbon black) product with a weight of 430kg (including bound water), a silica purity of over 98.1%, a sodium fluoride content of less than 0.7%, and a soda ash content of less than 1.0%;

(9) The solutions obtained by each centrifugation (one centrifugation in step (7), two centrifugations in step (8)) are combined as mother liquor for pre-process step (2) sodium fluorosilicate pulping, step (1 ) the dissolving of soda ash, the flotation liquid etc. of step (5) 2# flotation device, mother liquor realizes recycling.

Example 3

The block diagram of the technological process of continuous production of sodium fluoride in the present embodiment is as shown in Figure 2, and concrete steps are as follows:

(1) Put the solid soda ash into the silo, put it into the dissolving tank at a speed of 1000kg/h with a screw conveyor, continuously add the mother liquor of the subsequent process into the dissolving tank, add the flow rate of 3600-4000kg/h, and heat it with steam under stirring Dissolve the soda ash at 60°C-65°C, keep the concentration (mass fraction) of the dissolved soda ash solution at 23-25%, and pump it continuously into the tubular reactor;

(2) Put solid sodium fluorosilicate (water content 6%) into the silo, add it into the pulping tank at a speed of 900kg/h with a screw conveyor, continuously add the mother liquor of the subsequent process in the pulping tank, and add the flow rate 2400-2600kg/h, heat to 60°C-65°C with steam under stirring, keep the solid-liquid ratio (mass fraction of sodium fluorosilicate) in the sodium fluorosilicate slurry at 28-30%, and pump it out continuously into the tubular reactor;

(3) Start the spiral agitator in the tubular reactor, control the reaction temperature at 68-70°C, the soda ash solution and the sodium fluorosilicate solution carry out the metathesis reaction, generate sodium fluoride and silicon dioxide slurry, control the material (fluorine The molar ratio of sodium silicate to soda ash) is 1:3-4 (pH greater than 12), and the reaction time is 1-5 minutes;

(4) sodium fluoride after reaction and silica slurry enter in 1# flotation device, rely on the reaction liquid of self to enter flotation, obtain the slurry A containing sodium fluoride from the bottom of flotation device, from The upper part obtains the slurry a containing silicon dioxide;

(5) Send the slurry A containing sodium fluoride into the 2# flotation device, carry out flotation with the centrifugal mother liquor of the subsequent process, the mother liquor addition is 2500kg/h, and the fine silica is floated out by flotation, Obtain slurry B containing sodium fluoride from the lower part of the flotation device, and obtain slurry B containing silicon dioxide from the top;

(6) Send the slurry B containing sodium fluoride into the 3# flotation device, carry out flotation and washing with soft water or industrial water, the addition of soft water or industrial water is 400kg/h, and obtain the slurry containing Slurry C of sodium fluoride, slurry C containing silicon dioxide, soda ash, etc. is obtained from the top;

(7) Slurry a, slurry b containing silicon dioxide are merged and sent in 4# flotation device, and the slurry c containing silicon dioxide and soda ash etc. is used as the flotation liquid of 4# flotation device; Flotation The final fine sodium fluoride is combined with the slurry C containing sodium fluoride obtained from the lower part of the 3# flotation device, and then sent to the centrifuge for centrifugation. After drying, the sodium fluoride product is obtained, with a weight of 1130kg. The purity of sodium fluoride in it is analyzed to be 98.7 %, the content of silicon dioxide is less than 0.4%, the content of soda ash is less than 0.2%, reaching the first-grade product standard;

(8) The silica-containing slurry d from the upper part of the 4# flotation device is sent to the centrifuge for centrifugation, and then slurried with hot water at 70-100 ° C, heated with steam, and the temperature is maintained at 80 ° C, and then sent to the centrifuge Centrifuge in the machine, dry at 120°C to obtain silica (silica) product, weight 460kg (including bound water), silica purity above 98.3%, sodium fluoride content less than 0.8%, soda ash content less than 1.0%;

(9) The solutions obtained by each centrifugation (one centrifugation in step (7), two centrifugations in step (8)) are combined as mother liquor for pre-process step (2) sodium fluorosilicate pulping, step (1 ) the dissolving of soda ash, the flotation liquid etc. of step (5) 2# flotation device, mother liquor realizes recycling.

Comparative example 1

This comparative example produces sodium fluoride technological process block diagram as shown in Figure 1, and concrete steps are as follows:

(1) mother liquor or water is dropped in the dissolving tank, drop into solid soda ash under stirring, after heating and dissolving, transfer to the high level tank, concentration 20-22% soda ash solution;

(2) Put the mother liquor or water into the pulping tank and put in solid sodium fluorosilicate (water content 6%) under stirring to prepare a sodium fluorosilicate slurry with a solid content of 20-30%, and transfer it to the reaction kettle middle;

(3) Start the reactor agitator, heat to 60-80°C, gradually add the soda ash solution, control the pH 7.5-8 as the end point (control the molar ratio 1:2), put it into the washing basin and rinse with the mother liquor;

(4) Manually shovel the sodium fluoride in the washbasin into a centrifuge for centrifugation, and dry to obtain a sodium fluoride product with a weight of 1000 kg. The purity of the sodium fluoride in the analysis is 95.0%, and the silicon dioxide content is less than 2.0%. The content of soda ash is less than 1.0%;

(5) Send the silicon dioxide rinsed out to a centrifuge for centrifugation to separate the silicon dioxide, and obtain a silicon dioxide (white carbon black) product after drying, with a weight of 400kg (containing bound water), and a purity of silicon dioxide of 85.0%. Above, the sodium fluoride content is less than 1.8%, and the soda ash content is less than 1.5%.

This comparative example is the same as the input amount of solid sodium fluorosilicate (water content 6%) and solid soda ash of embodiment 1-3.

As can be seen from the comparative results of Examples 1-3 and Comparative Example 1, the present invention has realized the continuous production and operation of sodium fluoride by adopting a tubular reactor with a spiral agitator and a multistage flotation device, and the production process Mother liquor can be recycled, further reducing production cost; And sodium fluorosilicate has obtained sufficient reaction, conversion rate reaches 100%, is far higher than the conversion rate (90%) of sodium fluorosilicate in comparative example 1; Carry out simultaneously The sodium fluoride purity of example 1-3 is more than 98.5%, and the silicon dioxide purity is more than 98.0%, which is also far higher than the purity of sodium fluoride and silicon dioxide in Comparative Example 1. Therefore, the method for the continuous production of sodium fluoride of the present invention is superior to the method in Comparative Example 1 no matter from the production process, or the conversion rate of raw materials, and the purity of the product.

In summary, the present invention realizes the continuous production of sodium fluoride by adopting a tubular reactor with a spiral agitator and a multistage flotation device. In the present invention, a large excess of soda ash is added in the reaction process, so that the sodium fluorosilicate is fully reacted, and the conversion rate reaches 100%. The multi-stage flotation device performs flotation on the generated sodium fluoride and silica slurry, which improves the purity and quality of the product. The purity of sodium fluoride produced by the method of the invention is above 98.5%, and the purity of silicon dioxide is above 98.0%. The method of the invention has less investment in production scale, can realize automatic control, reduces the labor intensity of employees, has excellent product quality and low raw material consumption. In addition, in the method for continuously producing sodium fluoride of the present invention, the mother liquor can be recycled, further reducing the production cost.

Those of ordinary skill in the art should understand that: the discussion of any of the above embodiments is exemplary only, and is not intended to imply that the scope of the present disclosure (including claims) is limited to these examples; under the idea of the present invention, the above embodiments or Combinations between technical features in different embodiments are also possible, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity. Therefore, any omissions, modifications, equivalent replacements, improvements, etc. within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (9)

1. A method for continuous production of sodium fluoride, characterized in that, the sodium fluorosilicate solution of 20-30% and the soda ash solution of 20-30% by massfraction are continuously added in the tubular reactor successively, Control the reaction temperature at 60-100°C, carry out the metathesis reaction to generate sodium fluoride and silica slurry, and continuously enter the multi-stage flotation device for flotation, and obtain the slurry containing sodium fluoride and the slurry containing Silica slurry is centrifuged, washed, and dried to obtain sodium fluoride products and silica products; the solutions obtained by each centrifugation are combined and used as mother liquor for recycling; The concrete steps of described flotation are as follows: (1) Put the sodium fluoride and silicon dioxide slurry into the 1# flotation device continuously, rely on its own reaction solution to enter the flotation, obtain the slurry A containing sodium fluoride from the lower part of the flotation device, and obtain the slurry A from the upper part Silica-containing slurry a; (2) Send the slurry A containing sodium fluoride into the 2# flotation device, carry out flotation with the mother liquor, float the fine silica, and obtain the slurry containing sodium fluoride from the lower part of the flotation device B, obtain the slurry b containing silicon dioxide from the top; (3) Slurry B containing sodium fluoride is sent in 3# flotation device, carries out flotation and washing with soft water or industrial water, obtains the slurry C containing sodium fluoride from the bottom of 3# flotation device, Obtain the slurry c containing silicon dioxide and soda ash from the top; (4) send in the 4# flotation device after the slurry a, slurry b that will contain silicon dioxide are merged, the slurry c that contains silicon dioxide and soda ash is used as the flotation liquid of 4# flotation device; Flotation After the fine sodium fluoride is combined with the slurry C containing sodium fluoride obtained in the lower part of the 3# flotation device, it is sent to the centrifuge for centrifugation, and the sodium fluoride product is obtained after drying; (5) The silica-containing slurry d coming out from the upper part of the 4# flotation device is sent to the centrifuge for centrifugation, and then sent to the centrifuge for centrifugation after slurrying with hot water, and the silica product is obtained after drying. 2. the method for continuously producing sodium fluoride according to claim 1 is characterized in that, the mol ratio of sodium fluorosilicate and soda ash is 1: 2.2-4; The time of metathesis reaction is 1-5 minute; The reactor is a tubular reactor with a helical stirrer. 3. The method for continuously producing sodium fluoride according to claim 2, characterized in that the molar ratio of sodium fluorosilicate to soda ash is 1:2.5-3. 4. the method for continuously producing sodium fluoride according to claim 1 is characterized in that, solid soda ash is dropped in the silo, adds dissolving tank with screw conveyor, adds mother liquor continuously in dissolving tank, under agitation with steam Heat to 60°C-100°C to dissolve the soda ash, keep the mass fraction of the dissolved soda ash solution at 20-30%, and pump it out continuously and send it into the tubular reactor. 5. The method for continuously producing sodium fluoride according to claim 4, characterized in that, the speed of the screw conveyor is 1000kg/h, and the flow rate of the mother liquor is 3600-4000kg/h, heated to 75°C-78°C with steam °C, the mass fraction of the dissolved soda ash solution is 20-22%. 6. The method for continuous production of sodium fluoride according to claim 1, characterized in that solid sodium fluorosilicate is dropped into the feed bin, added in the pulping tank with a screw conveyor, and the mother liquor is continuously added in the pulping tank , heated to 60°C-100°C with steam under stirring, keeping the mass fraction of the dissolved sodium fluorosilicate solution at 20-30%, and pumping it continuously into the tubular reactor. 7. the method for continuous production sodium fluoride according to claim 6 is characterized in that, the water content of solid sodium fluorosilicate is 6%, and the speed of screw conveyor is 900kg/h, and the adding flow of mother liquor is 2400- 2600kg/h, heated to 75°C-78°C with steam, the mass fraction of the dissolved sodium fluorosilicate solution is 25-27%. 8. the method for continuously producing sodium fluoride according to claim 1 is characterized in that, in the step (2), the mother liquor add-on is 2000-3000kg/h; Soft water or industrial water add-on is 300-300kg/h in the step (3). 500kg/h. 9. the method for continuous production sodium fluoride according to claim 1, is characterized in that, the slurry d containing silicon dioxide that step (5) comes out from 4# flotation device top sends centrifugal in the centrifuge, and then uses After slurrying with hot water at 70-100°C, heat it with steam, keep the temperature at 80°C, send it to a centrifuge for centrifugation, and dry it at 120°C to obtain a silica product.