Method for recycling fumed silica by-product tail gas

Abstract

The invention discloses a method for recycling fumed silica by-product tail gas, which relates to the technical field of co-production of polycrystalline silicon and fumed silica, and comprises the following steps: after being subjected to bag dust removal and cooling treatment, tail gas enters a first material mixer containing a silicon-based high-boiling residue and a flocculating agent through bubbling at the middle lower part; a flocculating agent and an oxygen-containing high-boiling residue enter a first material mixer from the top, in the first mixer, water vapor in the tail gas reacts with the silicon-based high-boiling residue to generate silicon dioxide particles and hydrogen chloride, moisture in the tail gas is removed, and meanwhile hydrogen chloride and chlorine are absorbed by the silicon-based high-boiling residue in a first material mixing tank. Compared with the adsorption technology, the application of the absorption and adsorption technology effectively reduces the concentration of hydrogen chloride and chlorine in the vented tail gas, greatly prolongs the service life of the adsorbent, and widens the application scene of the silicon-based high-boiling residue; introduction of an aqueous solution in the system is reduced, and corrosion of strong acid to equipment is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of co-production of polysilicon and fumed silicon dioxide, and in particular to a method for recycling tail gas produced as a by-product of fumed silicon dioxide. Background Art

[0002] Due to its small particle size and large specific surface area, fumed silica is widely used in additives, reinforcing agents, fillers, and thickeners. Known as "industrial MSG," it possesses extremely high economic value. It is generally produced through the dry combustion of silicon tetrachloride (SiCl4). This process primarily involves burning silicon tetrachloride (SiCl4) in an oxyhydrogen flame, undergoing high-temperature vapor-phase hydrolysis. Fumed silica is then refined through coagulation, separation, deacidification, and screening to produce the final product. Compared to precipitated silica, fumed silica exhibits significant performance advantages, such as improved dispersibility, thixotropy, and thickening properties, as well as reinforcement in the rubber industry and insulation properties in the electronics industry. The tail gas from the dry-process production of silica from silicon tetrachloride primarily consists of hydrogen chloride, chlorine, water, and silica dust. Hydrogen chloride and chlorine are highly corrosive and cannot be discharged directly. Chlorine and hydrogen chloride are also important chlorine sources for the production of silicon tetrachloride, trichlorosilane, and organosilicon. Their recycling is a key approach to achieving clean silica production.

[0003] A search revealed that Chinese patent publication number CN112678775B discloses a method and apparatus for purifying and recovering silica tail gas. The method comprises filtering the silica tail gas to remove solid impurities, adsorbing hydrogen chloride and chlorine in the tail gas, thereby purifying the silica tail gas; desorbing the adsorbed hydrogen chloride and chlorine, and then converting the hydrogen chloride into chlorine to recover the chlorine. This method not only purifies the silica tail gas and reduces harmful gas emissions, but also recovers chlorine as a product with high economic value.

[0004] Existing technologies similar to the aforementioned recovery methods suffer from the following main problems: 1. Unfiltered nano-silica particles easily clog subsequent pipelines and the pores of the adsorbent and catalyst, shortening the equipment system's operating cycle and the service life of the adsorbent and catalyst; 2. The catalytic reaction must be carried out under high-temperature conditions, and the chlorine and hydrogen chloride in the exhaust gas easily corrode the equipment; 3. The application of adsorption technology to remove hydrogen chloride from exhaust gas is limited by the saturation capacity of the adsorbent. Therefore, there is room for improvement. Summary of the Invention

[0005] The present invention aims to address the shortcomings of existing technologies by proposing a method for recycling tail gas produced as a byproduct of fumed silica. Compared to adsorption technology, the absorption-adsorption method effectively reduces the concentrations of hydrogen chloride and chlorine in the exhaust gas, significantly extending the life of the adsorbent and broadening the application of silicon-based high-boiling materials. It also reduces the introduction of aqueous solutions into the system, which helps mitigate strong acid corrosion on equipment.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for recycling tail gas produced as a by-product of fumed silica comprises the following steps:

[0008] Step 1: After the tail gas is bagged and cooled, it is bubbled from the middle and lower part into the first material mixer containing silicon-based high-boiling substances and flocculants. The flocculants and oxygen-containing high-boiling substances enter the first material mixer from the top. In the first mixer, the water vapor in the tail gas reacts with the silicon-based high-boiling substances to produce silicon dioxide particles and hydrogen chloride, thereby removing water from the tail gas. At the same time, hydrogen chloride and chlorine are absorbed by the silicon-based high-boiling substances in the first material mixing tank.

[0009] Step 2: stirring to fully mix the flocculant and silica solid particles in the first mixer, and allowing to settle;

[0010] Step 3: The tail gas after being absorbed by the silicon-based high-boiling substance is further fed into the adsorption column to remove the residual hydrogen chloride and chlorine;

[0011] Step 4: The tail gas is absorbed by the sodium hypochlorite solution and then discharged;

[0012] Step 5: After the first material mixer is saturated with the tail gas from step 1, switch to another set of material mixers, transfer the supernatant from the first material mixer to a silicon-based high-boiling-point material storage tank, centrifuge the mixture using a centrifuge to further precipitate the nano- and submicron-sized particles in the solution, and then heat the mixture using a second heat exchanger to desorb the absorbed hydrogen chloride and chlorine. The desorbed gas enters the hydrogen chloride and chlorine storage tanks for recycling, and the silicon-based high-boiling-point material enters the storage tank.

[0013] Step 6: The material in the lower part of the first mixer enters the slag receiving tank, and after filter pressing, the solid slag is sent out, and the silicon-based high-boiling products enter the storage tank for recycling;

[0014] Step 7: After the adsorption column is saturated, it is purged with hot hydrogen and the tail gas enters the hydrogen system for recycling and reuse.

[0015] The present invention is further configured such that, in step one, the exhaust gas needs to be pre-dusted before entering the first material mixer, and the temperature needs to be reduced to below 50°C. The lower part of the first material mixer is a cone, and the inner wall is treated with corrosion-resistant ceramic thermal spraying.

[0016] The present invention is further configured such that the corrosion-resistant ceramic is one of silicon nitride or zirconium oxide, and the silicon-based high-boiling substance is a mixture of polychlorosilane and polychlorosiloxane having a boiling point higher than that of trichlorosilane and silicon tetrachloride, including tetrachlorodisiloxane, pentachlorodisiloxane, pentachlorodisiloxane, hexachlorodisiloxane and hexachlorodisiloxane.

[0017] The present invention is further configured such that the flocculant is one of chitosan, mannitol, polyaluminum chloride, polyferric chloride and clay, has a particle size of 18 to 106 μm, is added in an amount of 500 to 8000 ppm of silicon-based high boiling substances, and has an absorption temperature of -20 to 50°C.

[0018] The present invention is further configured such that, in the step 2, the settling time is 30 to 300 minutes, and after stirring, the solid silicon dioxide and the flocculant settle in the lower cone portion of the mixture.

[0019] The present invention is further configured as follows: in step three, the adsorbent is a mixture of modified activated carbon and silica gel, with a mass ratio of 1:3 to 5:1, the modified method of the activated carbon is sodium hydroxide solution impregnation and heat treatment, the impregnation solution concentration is 1 to 5 mol / l, the heat treatment temperature is 300 to 800°C, and the adsorption temperature is -20 to 50°C.

[0020] The present invention is further configured such that, in step five, the desorption temperature of the absorption liquid is 80-120°C.

[0021] The present invention is further configured such that, in step seven, the temperature of the hot hydrogen is 120-150°C.

[0022] The present invention is further configured such that the cooler has a tail gas waste heat recovery system, and the tail gas waste heat recovery system can recover waste heat for the analysis of chlorine and hydrogen chloride.

[0023] The beneficial effects of the present invention are:

[0024] 1. The silicon-based high-boiling substances produced as by-products in the production of trichlorosilane are reacted with water vapor to replace concentrated hydrochloric acid, concentrated sulfuric acid and other water-soluble strong acids to dry the tail gas, reducing the introduction of aqueous solutions into the system and helping to reduce the corrosion of strong acids on equipment;

[0025] 2. Silicon-based high-boiling substances react with water vapor to generate silicon dioxide particles and hydrogen chloride, thereby increasing the density of silicon dioxide particles in the silicon-based high-boiling substance system, which is conducive to the agglomeration and sedimentation of silicon dioxide particles;

[0026] 3. The addition of flocculants is beneficial to increase the nucleation points for the agglomeration of nano-silica particles, thereby effectively promoting the sedimentation of silica particles and greatly reducing the blockage of subsequent pipeline equipment and adsorbent channels;

[0027] 4. Compared with adsorption technology, the application of absorption plus adsorption technology effectively reduces the concentration of hydrogen chloride and chlorine in the exhaust gas, significantly extends the service life of the adsorbent, and broadens the application scenarios of silicon-based high-boiling substances;

[0028] 5. The purity of hydrogen, chlorine and hydrogen chloride in the desorption tail gas is high and can be directly used in the preparation of chlorosilane;

[0029] 6. The integrated application of liquid absorption drying, enhanced sedimentation, adsorption and desorption technologies provides new ideas for the effective separation of silica particles, water, hydrogen chloride and chlorine, as well as the recycling of chlorine sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the workflow of a method for recycling tail gas produced as a by-product of fumed silica proposed in the present invention. DETAILED DESCRIPTION

[0031] The technical solution of this patent is further described in detail below in conjunction with specific implementation methods.

[0032] The following describes in detail embodiments of the present invention, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0033] This patent discloses a method for recycling the by-product tail gas of fumed silica, which integrates liquid phase absorption, enhanced sedimentation, adsorption and desorption technologies to achieve the effective separation of silica particles, water, hydrogen chloride and chlorine and the recycling of chlorine source, and can effectively treat silica tail gas.

[0034] Compared with the existing technology, the advantages of this patented technology are as follows: (1) the use of silicon-based high-boiling substances, which are by-products generated during the production of trichlorosilane, to dry the tail gas instead of concentrated hydrochloric acid, concentrated sulfuric acid and other water-soluble strong acids is beneficial to reducing the corrosion of strong acids on equipment; (2) the silicon-based high-boiling substances react with water vapor to generate silicon dioxide particles and hydrogen chloride, thereby increasing the density of silicon dioxide particles in the silicon-based high-boiling substance system, which is beneficial to the agglomeration and sedimentation of silicon dioxide particles; (3) the addition of flocculants is beneficial to increasing the nucleation points for the agglomeration of nano-silica particles, thereby effectively promoting the sedimentation of silicon dioxide particles and greatly reducing the blockage of subsequent pipeline equipment and adsorbent pores; (4) the application of absorption + adsorption technology effectively reduces the concentration of hydrogen chloride and chlorine in the exhaust gas, greatly prolongs the service life of the adsorbent, and broadens the application scenarios of silicon-based high-boiling substances; (5) the purity of hydrogen, chlorine and hydrogen chloride in the desorbed tail gas is relatively high and can be directly used in the preparation of chlorosilane.

[0035] According to a specific embodiment, the recycling of the by-product tail gas of fumed silica mainly consists of 7 steps. Before entering the first material mixer, the tail gas is pre-dusted and the temperature needs to be reduced to below 50°C. The lower part of the first material mixer is a cone, and the inner wall is treated with corrosion-resistant ceramic thermal spraying. The corrosion-resistant ceramic is a kind of silicon nitride or zirconium oxide. The silicon-based high boiling point is a mixture of polychlorosilane and polychlorosiloxane with a boiling point higher than trichlorosilane and silicon tetrachloride, such as tetrachlorodisiloxane (H2Si2OCl4), pentachlorodisiloxane (HSi2OCl5), pentachlorodisiloxane (HSi2Cl5), hexachlorodisiloxane. (Si2OCl6) and hexachlorodisilane (Si2Cl6), etc., with a particle size of 18 to 106 μm, an addition amount of 500 to 50,000 ppm of silicon-based high-boiling substances, and an absorption temperature of -20 to 50°C; the adsorbent is a mixture of modified activated carbon and silica gel, with a mass ratio of 1:3 to 5:1, and the modification method of the activated carbon is sodium hydroxide solution impregnation and heat treatment, the impregnation solution concentration is 1 to 5 mol / l, the heat treatment temperature is 300 to 800°C, and the adsorption temperature is -20 to 50°C; the desorption temperature of the absorption liquid is 80 to 120°C; the temperature of the hot hydrogen is 120 to 150°C.

[0036] The present application will be further described below through some specific embodiments.

[0037] The fumed silica tail gas used in the comparative example and its components before and after dry recovery are shown in Table 1. The components of the high-boiling-point raw materials described in the following examples are shown in Table 1; the high-boiling-point raw materials include: tetrachlorodisiloxane, pentachlorodisiloxane, hexachlorodisiloxane, pentachlorodisiloxane, and hexachlorodisiloxane; the polychlorosiloxane includes: tetrachlorodisiloxane, pentachlorodisiloxane, and hexachlorodisiloxane, and their compositions are shown in Table 2.

[0038] Example 1:

[0039] Reference Figure 1 A method for recycling tail gas produced as a by-product of fumed silica comprises the following steps:

[0040] S1: After being bagged for dust removal (components are shown in Table 1) and cooled, the silica tail gas is bubbled from the middle and lower portion into the first material mixer 1-1 containing a silicon-based high-boiling substance (components are shown in Table 2) and a flocculant. In the first mixer, water vapor in the tail gas reacts with the silicon-based high-boiling substance to generate silicon dioxide particles and hydrogen chloride, thereby removing moisture from the tail gas. Simultaneously, hydrogen chloride and chlorine are absorbed by the silicon-based high-boiling substance in the first material mixing tank. After cooling, the tail gas temperature is 42°C. The lower portion of the first material mixer is conical, and the inner wall is sprayed with a silicon nitride corrosion-resistant coating. The flocculant is clay with a particle size of 53-106 μm, and the addition amount is 1000 ppm of the silicon-based high-boiling substance. The absorption liquid temperature is 45°C.

[0041] S2: stirring to fully mix the flocculant and silica solid particles in the first mixer 1-1, and letting them settle for 45 minutes;

[0042] S3: The tail gas after the absorption of silicon-based high-boiling substances further enters adsorption columns 1 to 4 to remove residual hydrogen chloride and chlorine by adsorption. The adsorbent is modified activated carbon and modified silica gel in a mass ratio of 1:1. The concentration of sodium hydroxide modified by impregnation of activated carbon is 1.5 mol / L. The heat treatment temperature is 450°C and the adsorption temperature is 30°C.

[0043] S4: The tail gas is absorbed by the sodium hypochlorite solution and then discharged;

[0044] S5: After the tail gas in step S1 is absorbed and saturated in the first material mixer 1-1, the mixer is switched to another set of material mixers 2-2, and the supernatant in 1-1 is transferred to a silicon-based high-boiling-point material storage tank 4. The supernatant is centrifuged using a centrifugal device 5 to further precipitate the nano- and submicron-sized particles in the solution. The supernatant is then heated using a second heat exchanger to desorb the absorbed hydrogen chloride and chlorine. The desorbed gas enters the hydrogen chloride and chlorine storage tanks for recycling and reuse, and the silicon-based high-boiling-point material enters the storage tank. The desorption temperature of the absorption liquid is 100°C.

[0045] S6: The material in the lower part of the first mixer enters the slag receiving tanks 1 to 3. After filter pressing, the solid slag is sent out and the silicon-based high-boiling products enter the storage tank for recycling.

[0046] S7: After the adsorption column is saturated, it is purged with hot hydrogen, and the tail gas enters the hydrogen system for recycling and reuse. The temperature of the hot hydrogen is 125°C.

[0047] After the above treatment, the exhaust gas composition after 10 hours of operation is shown in Table 1, that is, after the integrated treatment of dehydration, forced sedimentation of solid particles, absorption, adsorption and desorption technology, the concentrations of water, solid content, chlorine and hydrogen chloride in the exhaust gas are greatly reduced.

[0048] Example 2:

[0049] In this embodiment, the fumed silica tail gas treatment steps S1 to S4 are the same as in Example 1. In step S1, the flocculant is polyaluminum chloride, and the particle size range and addition amount are the same as in Example 1.

[0050] After being treated by S1 to S4 in Example 2 and running for 10 hours, the tail gas composition is shown in Table 1. Compared with clay, polyaluminum chloride further enhances the flocculation and sedimentation ability of solid particles.

[0051] Example 3:

[0052] In this embodiment, the fumed silica tail gas treatment steps S1 to S4 are the same as in Example 1. In step S1, the flocculant is chitosan, and the particle size range and addition amount are the same as in Example 1.

[0053] After treatment with S1 to S4 in Example 3 and operation for 10 hours, the tail gas composition is shown in Table 1. Compared with clay and polyaluminium chloride, chitosan further enhances the flocculation and sedimentation ability of solid particles.

[0054] Example 4:

[0055] In this embodiment, the fumed silica tail gas treatment steps S1 to S4 are the same as in Example 1. In step S1, the flocculant is chitosan with a particle size range of 18 to 53 μm. In step S2, the sedimentation time is 240 min, and the addition amount is the same as in Example 1.

[0056] After treatment with S1 to S4 in Example 4 and operation for 10 hours, the tail gas composition is shown in Table 1. By reducing the particle size of the flocculant and extending the settling time, the flocculant's flocculation and settling ability on the solid particles is further enhanced.

[0057] Example 5:

[0058] In this embodiment, the fumed silica tail gas treatment steps S1 to S4 are the same as in Example 4. In step S1, the flocculant is chitosan with a particle size range of 18 to 53 μm, the settling time is 240 min, and the flocculant addition amount is 7000 ppm.

[0059] After the treatment of S1 to S4 in Example 5 and operation for 10 hours, the tail gas composition is shown in Table 1. The amount of flocculant additive has no significant effect on the particle settling effect.

[0060] Based on Examples 1-5, the chemical composition, dosage, particle size, and settling time of the flocculant significantly affect the settling of solid particles, but have little effect on the removal rate of hydrogen chloride and chlorine in the tail gas. Considering the overall cost, the optimal dosage of the flocculant is 1000ppm of the silicon-based high-boiling substances.

[0061] Example 6:

[0062] In this embodiment, the fumed silica tail gas treatment steps S1 to S4 are the same as in Example 4. In step S1, the absorption liquid temperature is 0°C. After the treatment of S1 to S4 in Example 6 and operation for 10 hours, the tail gas composition is shown in Table 1. The lower the absorption liquid temperature, the more conducive it is to the absorption of chlorine and hydrogen chloride in the tail gas, and the effect on the sedimentation effect of the solid particles is not significant.

[0063] Example 7:

[0064] In this embodiment, the fumed silica tail gas treatment steps S1 to S4 are the same as in Example 4. In step S1, the absorption liquid temperature is 15°C. After the treatment of S1 to S4 in Example 7 and 10 hours of operation, the tail gas composition is shown in Table 1. The lower the absorption liquid temperature, the more conducive it is to the absorption of chlorine and hydrogen chloride in the tail gas. However, when the temperature is below 0°C, the effect is no longer significant.

[0065] Example 8:

[0066] In this embodiment, steps S1 to S4 of the fumed silica tail gas treatment are the same as those in Example 6. In step S3, the modified activated carbon impregnation solution is 3.5 mol / l sodium hydroxide, and the heat treatment temperature is 650°C. After the treatments of S1 to S4 in Example 8 and operation for 10 hours, the tail gas composition is shown in Table 1. After the sodium hydroxide solution impregnation and high-temperature heat treatment, the system's ability to remove chlorine and hydrogen chloride in the tail gas is significantly enhanced, especially chlorine.

[0067] Example 9:

[0068] In this example, steps S1 to S4 of the fumed silica tail gas treatment were the same as in Example 6. In step S3, the modified activated carbon impregnation solution was 4.5 mol / L sodium hydroxide, and the heat treatment temperature was 750°C. After treatment in steps S1 to S4 of Example 8 and 10 hours of operation, the tail gas composition is shown in Table 1. The sodium hydroxide solution impregnation and high-temperature heat treatment significantly enhanced the system's ability to remove chlorine and hydrogen chloride from the tail gas, particularly chlorine. When the impregnation solution concentration exceeded 3.5 mol / L and the heat treatment temperature exceeded 650°C, there was no significant increase in the removal of chlorine and hydrogen chloride from the tail gas.

[0069] Comparative Example 1:

[0070] In this embodiment, steps S1 to S2 are the same as those in Example 6, and then step S3 is not processed. The tail gas is discharged after being absorbed by the sodium hypochlorite solution. After running for 10 hours, the composition of the tail gas is shown in Table 1. Compared with the flocculation-enhanced sedimentation + absorption technology, the flocculation-enhanced sedimentation + absorption + adsorption integrated technology has no obvious effect on the solid content in the tail gas, but significantly enhances the removal capacity of chlorine and hydrogen chloride in the tail gas.

[0071] Comparative Example 2:

[0072] In this embodiment, steps S1 to S4 are the same as those in Example 6. The difference from Example 6 is that no flocculant is added in step S1. The exhaust gas components are shown in Table 1. Compared with the absorption + adsorption technology, the flocculation enhanced sedimentation + absorption + adsorption integrated technology significantly enhances the removal capacity of solid content, chlorine and hydrogen chloride in the exhaust gas.

[0073] Comparative Example 3:

[0074] In this example, step S3 was used to treat the tail gas, using the same technical parameters as in Example 6. After 10 hours of operation, the adsorption column reached saturation, and the tail gas composition is shown in Table 1. When using a single adsorption technique, the adsorbent quickly becomes saturated, and at the same time, the adsorbent pores become clogged by the fumed silica. Consequently, the ability to treat chlorine and hydrogen chloride in the tail gas rapidly decreases. Chlorine and water vapor react in the adsorption column, causing the concentration to decrease.

[0075] Table 1 Composition of fumed silica tail gas before and after dry recovery

[0076]

[0077]

[0078] Table 2 Composition of silicon-based high boiling point materials in Examples and Comparative Examples

[0079]

[0080] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for recycling tail gas produced as a by-product of fumed silica, characterized in that: The following steps are involved: Step 1: After the tail gas is bagged and cooled, it is bubbled from the middle and lower part into the first material mixer containing silicon-based high-boiling substances and flocculants. The flocculants and oxygen-containing high-boiling substances enter the first material mixer from the top. In the first mixer, the water vapor in the tail gas reacts with the silicon-based high-boiling substances to produce silicon dioxide particles and hydrogen chloride, thereby removing water from the tail gas. At the same time, hydrogen chloride and chlorine are absorbed by the silicon-based high-boiling substances in the first material mixing tank. Step 2: stirring to fully mix the flocculant and silica solid particles in the first mixer, and allowing to settle; Step 3: The tail gas after being absorbed by the silicon-based high-boiling substance is further fed into the adsorption column to remove the residual hydrogen chloride and chlorine; Step 4: The tail gas is absorbed by the sodium hypochlorite solution and then discharged; Step 5: After the first material mixer is saturated with the tail gas from step 1, switch to another set of material mixers, transfer the supernatant from the first material mixer to a silicon-based high-boiling-point material storage tank, centrifuge the mixture using a centrifuge to further precipitate the nano- and submicron-sized particles in the solution, and then heat the mixture using a second heat exchanger to desorb the absorbed hydrogen chloride and chlorine. The desorbed gas enters the hydrogen chloride and chlorine storage tanks for recycling, and the silicon-based high-boiling-point material enters the storage tank. Step 6: The material in the lower part of the first mixer enters the slag receiving tank, and after filter pressing, the solid slag is sent out, and the silicon-based high-boiling products enter the storage tank for recycling; Step 7: After the adsorption column is saturated, it is purged with hot hydrogen and the tail gas enters the hydrogen system for recycling and reuse.

2. The method for recycling the tail gas produced as a by-product of fumed silica according to claim 1, wherein: In the step 1, before entering the first material mixer, the tail gas needs to be pre-dusted and the temperature needs to be reduced to below 50° C. The lower part of the first material mixer is a cone, and the inner wall is treated with corrosion-resistant ceramic thermal spraying.

3. The method for recycling the tail gas produced as a by-product of fumed silica according to claim 2, wherein: The corrosion-resistant ceramic is one of silicon nitride or zirconium oxide, and the silicon-based high-boiling substance is a mixture of polychlorosilane and polychlorosiloxane with a boiling point higher than trichlorosilane and silicon tetrachloride, including tetrachlorodisiloxane, pentachlorodisiloxane, pentachlorodisiloxane, hexachlorodisiloxane and hexachlorodisiloxane.

4. The method for recycling the tail gas produced as a by-product of fumed silica according to claim 3, wherein: The flocculant is one of chitosan, mannitol, polyaluminum chloride, polyferric chloride and clay, with a particle size of 18 to 106 μm, an addition amount of 500 to 8000 ppm of silicon-based high boiling substances, and an absorption temperature of -20 to 50°C.

5. The method for recycling the tail gas produced as a by-product of fumed silica according to claim 1, wherein: The sedimentation time in the step 2 is 30 to 300 minutes. After stirring, the solid silicon dioxide and the flocculant are settled in the lower cone part of the mixture.

6. The method for recycling the tail gas produced as a by-product of fumed silica according to claim 1, characterized in that: In step three, the adsorbent is a mixture of modified activated carbon and silica gel in a mass ratio of 1:3 to 5:

1. The modified activated carbon is impregnated with a sodium hydroxide solution and heat treated. The impregnation solution concentration is 1 to 5 mol / l, the heat treatment temperature is 300 to 800°C, and the adsorption temperature is -20 to 50°C.

7. The method for recycling the tail gas produced as a by-product of fumed silica according to claim 1, characterized in that: The desorption temperature of the absorption liquid in step 5 is 80-120°C.

8. The method for recycling the tail gas produced as a by-product of fumed silica according to claim 7, wherein: The temperature of the hot hydrogen in step seven is 120-150°C.

9. The method for recycling the tail gas produced as a by-product of fumed silica according to claim 8, characterized in that: The cooler is provided with a tail gas waste heat recovery system, which can recover waste heat for the analysis of chlorine and hydrogen chloride.

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