A method for preparing white carbon black from fluorine-containing silicon slag

Abstract

The present application belongs to the technical field of fluorine-containing silicon slag recycling, and specifically discloses a method for preparing white carbon black from fluorine-containing silicon slag. The fluorine-containing silicon slag is first dried and calcined at high temperature to make fluorine escape in the form of silicon tetrafluoride; the tail gas is absorbed by multi-stage water circulation to obtain an acidic solution. The calcined residue is reacted with calcium hydroxide to generate calcium silicate, which is then acid-dissolved by sulfuric acid and separated from calcium sulfate by water washing. The silicon dioxide is dried and dehydrated by n-butanol to obtain white carbon black. The present application can efficiently treat the fluorine-containing silicon slag generated in the production of anhydrous hydrogen fluoride by fluorosilicic acid method, realize the recycling of fluorine and silicon components, convert fluorine into an acidic solution, and convert silicon into high-value-added white carbon black, thus achieving both environmental and economic benefits.

Description

Technical Field

[0001] This invention relates to the field of fluorinated silica slag recycling technology, and in particular to a method for preparing silica from fluorinated silica slag. Background Technology

[0002] Fluorosilica slag is a large amount of silica gel produced during the hydrolysis of silicon tetrafluoride in the process of producing hydrogen fluoride from fluorosilicic acid by reacting it with concentrated sulfuric acid. Its fluorine content is relatively high, typically between 5% and 15%. Existing methods for treating fluorosilica slag suffer from high costs and unstable product quality. For example, traditional high-temperature calcination severely damages the microstructure of silica, resulting in products with low adsorption performance and little economic value. Currently, the main uses of fluorosilica slag are for preparing defluorinating agents, water glass, silica, industrial silicon, silicon carbide, cement additives, and refractory bricks. As an important solid waste, fluorosilica slag faces problems such as environmental pollution, resource waste, high treatment costs, and low added value in practical applications. Therefore, developing efficient and environmentally friendly resource utilization technologies is of great significance for achieving the harmless treatment and resource utilization of fluorosilica slag. Summary of the Invention

[0003] This invention discloses a method for preparing silica from fluorinated silica slag as raw material. It can efficiently treat the fluorinated silica slag generated during the production of anhydrous hydrogen fluoride by the fluorosilicic acid method, convert the fluorine resources into an acidic solution, and convert the silicon resources into silica through reaction, thereby realizing the resource recovery and utilization of fluorine and silicon components.

[0004] The technical implementation scheme of the present invention is as follows:

[0005] A method for preparing silica from fluorinated silica slag includes the following steps:

[0006] S1. Pretreatment and dehydration: Dry the fluorinated silicon slag to remove most of the moisture, and then transfer it to a muffle furnace for high-temperature calcination, so that the fluorine in the fluorinated silicon slag will escape in the form of silicon tetrafluoride gas.

[0007] S2, exhaust gas absorption: The gas obtained in step S1 is passed into a multi-stage water circulation absorption system to obtain an acidic solution;

[0008] S3, Alkali conversion: Mix the calcined residue with calcium hydroxide and heat it to react the two to produce calcium silicate;

[0009] S4. Acid hydrolysis purification: The generated calcium silicate is heated and reacted with sulfuric acid. The reacted material is placed in water, ground and crushed, and washed multiple times to separate silicon dioxide and calcium sulfate. Finally, the silicon dioxide is placed in n-butanol to dry and dehydrate to obtain silica.

[0010] As a further description of the above technical solution, in step S1, the moisture content of the fluorinated silicon slag is 50%-75%, the moisture content after drying is 0.5%-4%, and the moisture content after calcination is 0.01%-0.3%.

[0011] As a further description of the above technical solution, in step S1, during the drying process of the fluorosilicone slag, the drying temperature is 100℃-120℃, the calcination temperature in the muffle furnace is 800℃-1000℃, and the calcination time is 30min-180min.

[0012] As a further description of the above technical solution, in step S3, the calcium hydroxide content is 80%-95%, and the mass ratio of residue to calcium hydroxide is (100-140):(90-100).

[0013] As a further description of the above technical solution, in step S3, the reaction temperature is 600℃-800℃ and the reaction time is 10min-90min.

[0014] As a further description of the above technical solution, in step S4, calcium mesosinate is first added to water to separate it from other substances before reacting.

[0015] As a further description of the above technical solution, in step S1, the fluorinated silicon slag is dried and graded using a drying system. The drying system includes a first fixed frame, a second fixed frame, a crushing and drying mechanism, and a cyclone separation mechanism. The crushing and drying mechanism is installed inside the first fixed frame and is connected to the cyclone separation mechanism to heat and crush the fluorinated silicon slag. The crushing and drying mechanism includes a drying chamber, a crushing disc, a rotating shaft, a first feeding pipe, and a hot air inlet mechanism. The chamber is fixedly installed inside the first fixed frame, and the rotating shaft and crushing disc are installed inside the chamber. The rotating shaft is connected to the output shaft of the first drive motor via a transmission chain. One end of the drying chamber has a feed inlet connected to the feeding pipe. The first feeding pipe has a first spiral guide rod installed inside, and a second drive motor is installed at the other end of the first spiral guide rod. A feed hopper is installed at the top of the first feeding pipe, and the first feeding pipe is connected to the first fixed frame via a support rod at the bottom. A hot air inlet mechanism is installed at the bottom of the drying chamber.

[0016] As a further description of the above technical solution, the hot air introduction mechanism includes an air guide box, a heat source pump, a protective cover, and an air inlet pipe. The air guide box is installed on the outside of the drying chamber and extends into the interior of the drying chamber through the air inlet pipe. One end of the drying chamber is connected to the heat source pump, and a protective cover is installed on the outside of the heat source pump.

[0017] As a further description of the above technical solution, the cyclone separation mechanism includes a cyclone dust collector, a third drive motor, an axial fan, a ventilation duct, and an air passage duct. The cyclone dust collector has a ventilation duct inside, and an axial fan connected to the output shaft of the third drive motor is installed inside the ventilation duct. The cyclone dust collector has an air inlet and an air outlet. The air inlet of the cyclone dust collector is connected to the top outlet of the drying chamber through a first material guide pipe, and the air outlet of the cyclone dust collector is connected to the dust removal mechanism through a second material guide pipe. The bottom of the cyclone dust collector has a second feeding pipe, and a second spiral guide rod is installed inside the second feeding pipe. One end of the second spiral guide rod is connected to the fifth drive motor.

[0018] As a further description of the above technical solution, the dust removal mechanism includes a dust removal box, a fixing plate, a dust removal bag and a discharge port. The dust removal box is provided with a fixing plate inside, and the upper part of the fixing plate is provided with multiple through holes, and a dust removal bag is provided at the through holes. The bottom of the dust removal box is provided with a discharge port that communicates with the internal chamber.

[0019] The present invention has the following advantages:

[0020] Fluorine-containing silicon slag is calcined at high temperature, and the generated gas is absorbed through a multi-stage water circulation system. The fluorine resources contained therein are converted into an acidic solution, which can be used for the production of quick-setting agents, thus solving the problem of wasted fluorine resources in fluorine-containing silicon slag. After defluorination, the silicon slag reacts with calcium hydroxide to produce calcium silicate. The calcium silicate in the mixture is filtered and separated, and then added to water in a certain proportion. Sulfuric acid is slowly added dropwise to the calcium silicate aqueous solution until the pH value is neutral. The reacted substances are placed in water, ground and crushed, and washed multiple times to separate silicon dioxide and calcium sulfate. Finally, the silicon dioxide is dried and dehydrated in n-butanol to obtain precipitated silica. This method can transform fluorine-containing silicon slag into high-purity precipitated silica products. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of the present invention.

[0022] Figure 2 This is the test report for Embodiment 1 of the present invention.

[0023] Figure 3 This is a schematic diagram of the drying system of the present invention.

[0024] Figure 4 This is a front view of the drying system of the present invention.

[0025] Figure 5 This is a cross-sectional view of the drying system of the present invention.

[0026] Figure 6 This is a schematic diagram of the hot air inlet mechanism of the present invention.

[0027] The meanings of the reference numerals in the figure are as follows: 1-First fixed frame, 2-Second fixed frame, 3-Crushing and drying mechanism, 301-Drying chamber, 302-Pulverizing disc, 303-Rotating shaft, 304-First drive motor, 305-Transmission chain, 306-Support rod, 307-Feeding pipe, 308-Feeding hopper, 309-First spiral guide rod, 310-Second drive motor, 311-First guide pipe, 4-Cyclone separation mechanism, 401 - Cyclone dust collector, 402- Ventilation duct, 403- Axial flow fan, 404- Third drive motor, 405- Second feeding duct, 406- Fifth drive motor, 407- Fifth drive motor, 5- Dust removal mechanism, 501- Dust collector body, 502- Fixing plate, 503- Dust collector bag, 504- Discharge port, 6- Hot air inlet mechanism, 601- Heat source pump, 602- Protective cover, 603- Air guide box, 604- Air inlet duct. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. It is hereby declared that the directional terms such as up, down, left, right, front, back, inside, and outside used in this text are based solely on the accompanying drawings and are not intended to specifically limit the invention.

[0029] Example 1:

[0030] like Figure 1 As shown, a method for preparing silica from fluorinated silica slag includes the following steps:

[0031] The first step is to dry the fluorinated silicon slag to remove most of the moisture, and then transfer it to a muffle furnace for high-temperature calcination, causing the fluorine in the fluorinated silicon slag to escape in the form of silicon tetrafluoride gas. The moisture content of the fluorinated silicon slag is 68.73%, the moisture content after drying is 2.16%, and the moisture content after calcination is 0.25%. During the drying process, the drying temperature is 105℃, the calcination temperature is 850℃, and the calcination time is 60 minutes.

[0032] The second step involves passing the gas generated in the first step into a multi-stage water circulation absorption system to obtain an acidic solution.

[0033] The third step involves mixing the residue from the second step with calcium hydroxide and heating it to react and form calcium silicate. In this process, the calcium hydroxide content is 95%, and the mass ratio of the residue to calcium hydroxide is 125:100. The reaction temperature in this step is 800℃, and the reaction time is 30 minutes.

[0034] The fourth step involves reacting the calcium silicate generated in the third step with sulfuric acid under heat. The reacted material is then placed in water, ground and crushed, and repeatedly washed to separate the silica and calcium sulfate. Finally, the silica is dried in n-butanol to obtain fumed silica. In this process, the calcium silicate is first added to water to separate it from other substances before reacting. During this process, the sulfuric acid content is 40%, and the mass ratio of sulfuric acid to calcium silicate is 100:120. The reaction temperature is 80℃, and the reaction time is 60 minutes. The washing process involves washing six times with distilled water. The amount of n-butanol added is 400% of the mass of the solid phase.

[0035] It should be noted that this invention uses fluorinated silica slag as raw material to prepare silica, realizing the resource utilization of solid waste, reducing production costs and mitigating environmental risks; high-temperature calcination defluorination combined with multi-stage water absorption can efficiently recover fluorine elements and avoid waste gas pollution; the process of calcification into salt followed by acid hydrolysis separation is mild and easy to control, resulting in high silica purity; combined with n-butanol drying and dehydration, it can effectively prevent particle agglomeration, and the resulting silica has good dispersibility and stable quality. The process is simple and suitable for industrial production.

[0036] Example 2:

[0037] A method for preparing silica from fluorinated silica slag includes the following steps:

[0038] The first step is to dry the fluorinated silicon slag to remove most of the moisture, and then transfer it to a muffle furnace for high-temperature calcination, causing the fluorine in the fluorinated silicon slag to escape in the form of silicon tetrafluoride gas. The moisture content of the fluorinated silicon slag is 68.65%, the moisture content after drying is 2.34%, and the moisture content after calcination is 0.23%. In this process, the drying temperature is 110℃, the calcination temperature is 800℃, and the calcination time is 60 minutes.

[0039] The second step involves passing the gas generated in the first step into a multi-stage water circulation absorption system to obtain an acidic solution.

[0040] The third step involves mixing the residue from the second step with calcium hydroxide and heating the mixture to react and generate calcium silicate. The calcium hydroxide content is 95%, and the mass ratio of the residue to calcium hydroxide is 120:90. During this process, the reaction temperature is 850°C and the reaction time is 40 minutes.

[0041] In the fourth step, the generated calcium silicate reacts with sulfuric acid under heat. The reacted material is then placed in water, ground and crushed, and washed multiple times to separate silicon dioxide and calcium sulfate. Finally, the silicon dioxide is dried and dehydrated in n-butanol to obtain silica. In this step, calcium silicate is first added to water to separate it from other substances before reacting. The sulfuric acid content is 35%, and the mass ratio of sulfuric acid to calcium silicate is 100:90. The reaction temperature is 90℃, the reaction time is 70 min, and the washing process involves washing with distilled water 6 times. The amount of n-butanol added is 400% of the mass of the solid phase.

[0042] Comparing the two examples, the process in Example 1 yielded the best results in preparing silica. Specific test reports are attached. Figure 2 As shown.

[0043] like Figures 3-5 As shown, the drying system includes a first fixed frame 1, a second fixed frame 2, a crushing and drying mechanism 3, and a cyclone separation mechanism 4. The crushing and drying mechanism 3 is installed inside the first fixed frame 1 and is connected to the cyclone separation mechanism 4 to heat and crush the fluorosilicon slag. The crushing and drying mechanism 3 includes a drying chamber 301, a crushing disc 302, a rotating shaft 303, a first feeding pipe 307, and a hot air inlet mechanism 6. The chamber 301 is fixedly installed inside the first fixed frame 1, and the chamber 301 contains a rotating shaft 303 and a crushing disc 302. 303 is connected to the output shaft of the first drive motor 304 via a transmission chain 305; one end of the drying chamber 301 is provided with a feed inlet, which is connected to a feeding pipe 307; a first spiral guide rod 309 is provided inside the first feeding pipe 307, and a second drive motor 310 is provided on the other end of the first spiral guide rod 309; a feeding hopper 308 is provided at the upper part of the first feeding pipe 307, and the first feeding pipe 307 is connected to the first fixed frame 1 via a support rod 306 at the bottom; a hot air inlet mechanism 6 is provided at the bottom of the drying chamber 301.

[0044] It should be noted that in step S1, the drying operation for the fluorosilicone slag is carried out by a drying system. The entire structure is divided into a crushing and drying mechanism 3, a cyclone separation mechanism 4, and a hot air introduction mechanism 6. The crushing and drying mechanism 3 is used for crushing and drying the fluorosilicone slag, the cyclone separation mechanism 4 is used for separating and removing impurities from the dried fluorosilicone powder, and the hot air introduction mechanism 6 can assist the crushing and drying mechanism 3 in introducing hot air during the crushing process, and simultaneously achieve drying.

[0045] It should be further explained that in the crushing and drying mechanism 3, the drying chamber 301 is located inside the first fixed frame 1, and the drying chamber 301 is equipped with a rotating shaft 303 and a first feeding pipe 307. Driven by the first drive motor 304, the fluorinated silicon slag introduced by the first feeding pipe 307 is rapidly crushed. At the same time, the hot air introduction mechanism 6 is used to introduce hot air into it, and the hot air lifts the dried fluorinated silicon slag upwards. It is connected to the top discharge port of the drying chamber 301 through the first guide pipe 311 to realize the discharge of the material. The material that is not completely dried will settle again and be crushed and dried again.

[0046] like Figures 3-5 As shown, the hot air introduction mechanism 6 includes an air guide box 603, a heat source pump 601, a protective cover 602, and an air inlet pipe 604. The air guide box 603 is installed on the outside of the drying chamber 301, and the air guide box 603 extends into the interior of the drying chamber 301 through the air inlet pipe 604. One end of the drying chamber 301 is connected to the heat source pump 601, and the heat source pump 601 is provided with a protective cover 602.

[0047] It should be noted that the heat source pump 601 is located on the upper part of the first fixed frame 1, and the hot air generated by the heat source pump 601 enters the air guide box 603. The air guide box 603 is installed on the outside of the drying box 301. The hot air is then introduced into the interior of the air guide box 603 through the air inlet pipe 604 to realize the introduction of hot air and achieve integrated crushing and drying.

[0048] like Figures 3-5 As shown, the cyclone separation mechanism 4 includes a cyclone dust collector 401, a third drive motor 404, an axial fan 403, a ventilation duct 402, and an air passage duct 406. The cyclone dust collector 401 is equipped with a ventilation duct 402, and the axial fan 403, which is connected to the output shaft of the third drive motor 404, is installed inside the ventilation duct 402. The cyclone dust collector 401 is equipped with an air inlet and an air outlet. The air inlet of the cyclone dust collector 401 is connected to the top outlet of the drying chamber 301 through a first material guide pipe 311, and the air outlet of the cyclone dust collector 401 is connected to the dust removal mechanism 5 through a second material guide pipe 406. The bottom of the cyclone dust collector 401 is equipped with a second feeding pipe 405, and a second spiral guide rod is installed inside the second feeding pipe 405. One end of the second spiral guide rod is connected to the fifth drive motor 407.

[0049] It should be noted that the cyclone dust collector 401 is located inside the second fixed frame 2, and the cyclone dust collector 401 is equipped with a ventilation duct 402, which contains an axial flow fan 403 connected to the third drive motor 404. When the axial flow fan 403 rotates, it can cyclone the introduced dust. Heavier dust falls to the bottom of the cyclone dust collector 401 and is discharged through the second feeding pipe 405, while lighter dust enters the dust collector through the second guiding pipe 406, thus achieving dust removal. Dust collection; the purpose of this design is that cyclone separators can only separate heavier dry particles and cannot collect very light ultrafine fluorosilicone slag dust. Direct discharge would cause material loss, fan wear, and exceed environmental standards. Therefore, it must be used in conjunction with a bag filter to form a two-stage dust collection system. First, the cyclone separator recovers most of the finished powder, and then the bag filter captures the remaining ultrafine dust. This not only improves the material recovery rate and protects the fan equipment, but also ensures that the exhaust gas meets emission standards, so that the entire drying system can operate stably, environmentally friendly, and efficiently.

[0050] like Figures 3-5 As shown, the dust removal mechanism 5 includes a dust removal box 501, a fixing plate 502, a dust removal bag 503, and a discharge port 504. The dust removal box 501 is provided with a fixing plate 502 inside, and the upper part of the fixing plate 502 is provided with multiple through holes, and a dust removal bag 503 is provided at the through holes. The bottom of the dust removal box 501 is provided with a discharge port 504 that communicates with the internal chamber.

[0051] It should be further noted that the dust collector 501 has a fixed plate 502 inside, and a dust collector bag 503 is installed in the through hole of the plate to facilitate the collection of the discharged ultrafine dust and prevent the waste of ultrafine dust.

[0052] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for preparing silica from fluorinated silica slag, characterized in that, Includes the following steps: S1. Pretreatment and dehydration: Dry the fluorinated silicon slag to remove most of the moisture, and then transfer it to a muffle furnace for high-temperature calcination, so that the fluorine in the fluorinated silicon slag will escape in the form of silicon tetrafluoride gas. S2, exhaust gas absorption: The gas obtained in step S1 is passed into a multi-stage water circulation absorption system to obtain an acidic solution; S3, Alkali conversion: Mix the calcined residue with calcium hydroxide and heat it to react the two to produce calcium silicate; S4. Acid hydrolysis purification: The generated calcium silicate is heated and reacted with sulfuric acid. The reacted material is placed in water, ground and crushed, and washed multiple times to separate silicon dioxide and calcium sulfate. Finally, the silicon dioxide is placed in n-butanol to dry and dehydrate to obtain silica.

2. The method for preparing silica from fluorinated silica slag as a raw material according to claim 1, characterized in that, In step S1, the moisture content of the fluorinated silicon slag is 50%-75%, the moisture content after drying is 0.5%-4%, and the moisture content after calcination is 0.01%-0.3%.

3. A method for preparing silica from fluorinated silica slag as a raw material according to claim 1, characterized in that, In step S1, during the drying process of the fluorosilicone slag, the drying temperature is 100℃-120℃, the calcination temperature in the muffle furnace is 800℃-1000℃, and the calcination time is 30min-180min.

4. A method for preparing silica from fluorinated silica slag as a raw material according to claim 1, characterized in that, In step S3, the calcium hydroxide content is 80%-95%, and the mass ratio of residue to calcium hydroxide is (100-140):(90-100).

5. A method for preparing silica from fluorinated silica slag as a raw material according to claim 1, characterized in that, In step S3, the reaction temperature is 600℃-800℃ and the reaction time is 10min-90min.

6. A method for preparing silica from fluorinated silica slag as a raw material according to claim 1, characterized in that, In step S4, calcium mesosilicate is first added to water to separate it from other substances before reacting.

7. A method for preparing silica from fluorinated silica slag as a raw material according to claim 1, characterized in that, In step S1, the fluorinated silicon slag is dried and graded using a drying system. The drying system includes a first fixed frame (1), a second fixed frame (2), a crushing and drying mechanism (3), and a cyclone separation mechanism (4). The crushing and drying mechanism (3) is installed inside the first fixed frame (1), and the crushing and drying mechanism (3) is connected to the cyclone separation mechanism (4) to heat and crush the fluorinated silicon slag. The crushing and drying mechanism (3) includes a drying box (301), a crushing disc (302), a rotating shaft (303), a first feeding pipe (307), and a hot air inlet mechanism (6). The box (301) is fixedly installed inside the first fixed frame (1), and the rotating shaft (303) and the crushing disc (302) are installed inside the box (301). The rotating shaft (303) is connected to the output shaft of the first drive motor (304) through a transmission chain (305). The drying chamber (301) has a feed inlet at one end, and the feed inlet is connected to the feeding pipe (307). The first feeding pipe (307) has a first spiral guide rod (309) inside, and a second drive motor (310) is provided on the other end of the first spiral guide rod (309). The upper part of the first feeding pipe (307) is provided with a feeding hopper (308), and the first feeding pipe (307) is connected to the first fixed frame (1) through the support rod (306) at the bottom; The bottom of the drying chamber (301) is provided with a hot air inlet mechanism (6).

8. A method for preparing silica from fluorinated silica slag as a raw material according to claim 7, characterized in that, The hot air introduction mechanism (6) includes an air guide box (603), a heat source pump (601), a protective cover (602), and an air inlet pipe (604). The air guide box (603) is installed on the outside of the drying chamber (301), and the air guide box (603) extends into the interior of the drying chamber (301) through the air inlet pipe (604). One end of the drying chamber (301) is connected to the heat source pump (601), and the heat source pump (601) is provided with a protective cover (602).

9. A method for preparing silica from fluorinated silica slag as a raw material according to claim 8, characterized in that, The cyclone separation mechanism (4) includes a cyclone dust collector (401), a third drive motor (404), an axial fan (403), a ventilation duct (402), and an air passage duct (406). The cyclone dust collector (401) is equipped with a ventilation duct (402), and the ventilation duct (402) is equipped with an axial fan (403) that is connected to the output shaft of the third drive motor (404). The cyclone dust collector (401) is provided with an air inlet and an air outlet. The air inlet of the cyclone dust collector (401) is connected to the top outlet of the drying box (301) through the first material guide pipe (311), and the air outlet of the cyclone dust collector (401) is connected to the dust removal mechanism (5) through the second material guide pipe (406). The bottom of the cyclone dust collector (401) is provided with a second feeding pipe (405), and the inside of the second feeding pipe (405) is provided with a second spiral guide rod. One end of the second spiral guide rod is connected to the fifth drive motor (407).

10. A method for preparing silica from fluorinated silica slag as a raw material according to claim 9, characterized in that, The dust removal mechanism (5) includes a dust removal box (501), a fixing plate (502), a dust removal bag (503) and a discharge port (504). The dust removal box (501) is provided with a fixing plate (502) inside, and the upper part of the fixing plate (502) is provided with multiple through holes, and a dust removal bag (503) is provided at the through holes. The bottom of the dust collector (501) is provided with a discharge port (504) that communicates with the internal chamber.

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