Method for producing silicon dioxide and production system

Abstract

The application discloses a preparation method and a preparation system of silicon dioxide, and the method comprises the following steps: 1) mixing a gas containing chlorosilane with an aqueous solution, and performing a hydrolysis reaction on the chlorosilane to obtain a mixture; 2) filtering the mixture to obtain a filtrate, performing granulation on the filtrate, and heating to obtain the silicon dioxide. The preparation method of the silicon dioxide and the preparation system used in the application can effectively reduce the chlorine content in high-purity silicon dioxide, recover part of the chlorosilane generated in the polysilicon production process, reduce the chlorosilane content in waste gas, reduce the difficulty of subsequent reprocessing, and has convenience in industrialization.

Description

Technical Field

[0001] The present invention belongs to the technical field of quartz products, and in particular relates to a method and system for preparing silicon dioxide. Background Art

[0002] High-purity silica production methods are generally categorized into two types: natural and synthetic. The natural method uses natural quartz ore as raw material. Through a series of processes, including grinding, color sorting, and impurity removal, the ore is refined to improve its purity by removing impurities. Currently, leading companies producing high-purity silica using this process are concentrated abroad, while domestic companies face issues with low and inconsistent product quality. The synthetic method uses non-natural quartz ore as a silicon source. By selecting the silicon source and combining it with appropriate production processes, the desired high-purity silica can be produced, although there are certain differences in its morphology and intrinsic quality.

[0003] With the development of high-tech in my country, the demand for high-purity silica and its quality are both higher. Natural production methods are limited by raw materials, and their production process is significantly affected by the raw materials. Purity is difficult to exceed 5N5, and product stability also fluctuates due to the influence of raw material quality. Synthetic methods can use chemical technology to standardize raw materials and stabilize raw material quality. The high-purity silica produced by these methods has the advantages of high product purity and stable quality, making it more suitable for high-quality development needs.

[0004] The disclosed method for producing high-purity silica primarily uses high-purity silicon tetrachloride and / or alkoxysilane as raw materials. Through processes such as hydrolysis, gel formation, drying, pulverization, screening, and high-temperature treatment, amorphous silica is obtained. High-purity silica produced using silicon tetrachloride as raw material suffers from a high chlorine content.

[0005] At present, in the polysilicon production process, multiple processes generate waste gas rich in chlorosilanes. Usually, alkaline solution is used for leaching and absorption to convert chlorosilanes into silicates. However, in the actual operation process, the waste gas cannot be completely absorbed and cannot meet the emission standards. A large amount of silicate precipitates are generated during the conversion process, resulting in excessive equipment load and blockage. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art and provide a method and system for preparing silicon dioxide, thereby solving the problems in the prior art of using silicon tetrachloride as a raw material to produce high-purity silicon dioxide, such as high chlorine content and inefficient utilization of chlorosilane in the production process of polysilicon.

[0007] The technical solution adopted to solve the technical problem of the present invention is to provide a method for preparing silicon dioxide, comprising the following steps:

[0008] 1) mixing a gas containing chlorosilane with an aqueous solution, causing the chlorosilane to undergo a hydrolysis reaction to obtain a mixture;

[0009] 2) The mixture is filtered to obtain a filtrate, and the filtrate is granulated and heated to obtain silicon dioxide.

[0010] Preferably, the pH value of the hydrolysis reaction in step 1) is 2-6.

[0011] Preferably, the pH value of the aqueous solution in step 1) is 3-9.

[0012] Preferably, in step 1), the pH value of the hydrolysis reaction is adjusted by using a gas containing ammonia or an ammonia solution, and the mass proportion of ammonia in the gas containing ammonia or the ammonia solution does not exceed 10%.

[0013] Preferably, the heating temperature in step 2) is 1000-1300°C.

[0014] Preferably, in the step 2), when the content of the silicon dioxide polymer in the filtrate is 10 to 35 mas%, the filtrate is granulated.

[0015] Preferably, in step 2), the pH value of the filtrate is adjusted by using a gas containing ammonia or an ammonia solution, and the mass proportion of ammonia in the gas containing ammonia or the ammonia solution does not exceed 10%.

[0016] Preferably, the pH value of the filtrate after adjustment in step 2) is 6 to 9.5.

[0017] Preferably, the particle size of the granules obtained by granulation is 600 to 75 μm, and D50 is 280 to 350 μm.

[0018] More preferably, the particle size of the granules obtained by granulation is 500 to 150 μm, and D50 is 290 to 330 μm.

[0019] Preferably, the method for preparing silicon dioxide further comprises the following steps:

[0020] Before the filtrate is granulated, the filtrate is allowed to stand for at least 4 hours.

[0021] The present invention also provides a silicon dioxide preparation system used in the above-mentioned silicon dioxide preparation method, comprising:

[0022] A reactor for mixing the gas containing chlorosilane with the aqueous solution, causing the chlorosilane to undergo hydrolysis reaction to obtain a mixture;

[0023] A filtration unit is connected to the reactor and is used to filter the mixture to obtain a filtrate;

[0024] A granulation tower is connected to the filtration unit and is used to granulate the filtrate;

[0025] The heating furnace is connected to the granulation tower and is used to heat the granules obtained by granulation to obtain silicon dioxide.

[0026] Preferably, the silicon dioxide preparation system used in the silicon dioxide preparation method further comprises:

[0027] The first input mechanism includes: a storage tank, a first input pipeline connected to the storage tank, and a first atomizer connected to the first input pipeline, the first input pipeline is connected to the reactor, the first atomizer is disposed in the reactor, and the storage tank is used to store the aqueous solution;

[0028] The second input mechanism includes: a second input pipeline and a first nozzle connected to the second input pipeline, the second input pipeline is connected to the reactor, the first nozzle is arranged in the reactor, the first nozzle is arranged below the first atomizer, and the second input pipeline is used to input the gas containing chlorosilane;

[0029] The third input mechanism includes: a third input pipeline, a first input part connected to the third input pipeline, the first input part is a second atomizer or a second nozzle, the third input pipeline is connected to the reactor, the first input part is arranged in the reactor, and the first input part is arranged below the first nozzle. The third input pipeline is used to input ammonia gas or ammonia solution. When the third input pipeline inputs ammonia gas, the first input part is the second nozzle; when the third input pipeline inputs ammonia solution, the first input part is the second atomizer.

[0030] Preferably, the filtration unit comprises:

[0031] The first filter is connected to the reactor and is used to filter the mixture to obtain a first filtrate; the pore size of the filter element of the first filter is 20-60 μm.

[0032] a first filtrate storage tank, connected to the first filter, for storing the first filtrate, and further connected to the first input pipeline for inputting the first filtrate into the reactor;

[0033] The second filter is connected to the first filtrate storage tank and is used to filter the first filtrate to obtain a second filtrate. The pore size of the filter element of the second filter is smaller than that of the filter element of the first filter; the pore size of the filter element of the second filter is 2-10μm.

[0034] The second filtrate storage tank is connected to the second filter and is used to store the second filtrate.

[0035] Preferably, the silicon dioxide preparation system used in the silicon dioxide preparation method further comprises:

[0036] A solid silo is connected to the filter unit and is used to receive the filter residue obtained by filtering the filter unit; the solid silo is connected to the first filter and the second filter respectively and is used to receive the filter residue from the first filter and the second filter respectively;

[0037] An exhaust fan, connected to the reactor, is used to discharge the gas in the reactor into the chimney;

[0038] Chimney, connected to the exhaust fan, the chimney is used for exhausting air;

[0039] a fourth input mechanism comprising: a fourth input pipeline, a second input portion connected to the fourth input pipeline, the second input portion being a third atomizer or a third nozzle, the fourth input pipeline being connected to the granulation tower, the second input portion being disposed within the granulation tower, the fourth input pipeline being used to input ammonia gas or an ammonia solution, when the fourth input pipeline inputs ammonia gas, the second input portion being the third nozzle; and when the fourth input pipeline inputs an ammonia solution, the second input portion being the third atomizer;

[0040] The induced draft fan is connected to the granulation tower and introduces air into the granulation tower;

[0041] The separator is connected to the induced draft fan and the heating furnace respectively. The granules obtained by granulation are separated from the air through the separator and the granules are sent to the heating furnace;

[0042] Blower, used for blowing air;

[0043] The air inlet heater is connected to the blower and the granulation tower respectively, and is used to heat the blown air.

[0044] The silicon dioxide preparation method and the preparation system used therein of the present invention effectively reduce the chlorine content in high-purity silicon dioxide, and at the same time can recover part of the chlorosilanes generated during the polysilicon production process, reduce the chlorosilane content in the waste gas, and reduce the difficulty of subsequent reprocessing. At the same time, the solution is convenient in terms of industrial scale-up. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 Schematic diagram of the structure of the silicon dioxide preparation system in Example 2 of the present invention.

[0046] In the figure: V01-storage tank; T01-reactor; C01-exhaust fan; T02-chimney; S01-first filter; V02-first filtrate storage tank; S02-second filter; V03-second filtrate storage tank; V04-solids silo; T03-granulation tower; E01-inlet heater; C03-blower; C02-induced draft fan; S03-separator; F01-heating furnace; V05-finished product silo;

[0047] 1-first input pipeline; 2-first atomizer; 3-second input pipeline; 4-first nozzle;

[0048] 5-third input pipeline; 6-first input part; 7-fourth input pipeline; 8-second input part. DETAILED DESCRIPTION

[0049] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0050] 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.

[0051] Example 1

[0052] This embodiment provides a method for preparing silicon dioxide, comprising the following steps:

[0053] 1) mixing a gas containing chlorosilane with an aqueous solution, causing the chlorosilane to undergo a hydrolysis reaction to obtain a mixture;

[0054] 2) The mixture is filtered to obtain a filtrate, and the filtrate is granulated and heated to obtain silicon dioxide.

[0055] This embodiment also provides a silicon dioxide preparation system used in the above-mentioned silicon dioxide preparation method, comprising:

[0056] A reactor for mixing the gas containing chlorosilane with the aqueous solution, causing the chlorosilane to undergo hydrolysis reaction to obtain a mixture;

[0057] A filtration unit is connected to the reactor and is used to filter the mixture to obtain a filtrate;

[0058] A granulation tower is connected to the filtration unit and is used to granulate the filtrate;

[0059] The heating furnace is connected to the granulation tower and is used to heat the granules obtained by granulation to obtain silicon dioxide.

[0060] The silicon dioxide preparation method and preparation system in this embodiment effectively reduce the chlorine content in high-purity silicon dioxide, and at the same time can recover part of the chlorosilanes produced during the polysilicon production process, reduce the chlorosilane content in the waste gas, and reduce the difficulty of subsequent reprocessing. At the same time, this solution is convenient in terms of industrial scale-up.

[0061] Example 2

[0062] like Figure 1 As shown, this embodiment also provides a silicon dioxide preparation system, comprising:

[0063] Reactor T01 is used to mix the gas containing chlorosilane with the aqueous solution, and the chlorosilane undergoes a hydrolysis reaction to obtain a mixture, which includes silica polymers and silica precipitates;

[0064] A filtration unit connected to the reactor T01 is used to filter the mixture to obtain a filtrate;

[0065] Granulation tower T03, connected to the filtration unit, is used to granulate the filtrate;

[0066] The heating furnace F01 is connected to the granulation tower T03. The heating furnace F01 is used to heat the granules obtained by granulation to obtain silicon dioxide.

[0067] Preferably, the silicon dioxide preparation system used in the silicon dioxide preparation method further comprises:

[0068] The first input mechanism includes: a storage tank V01, a first input pipeline 1 connected to the storage tank V01, and a first atomizer 2 connected to the first input pipeline 1, wherein the first input pipeline 1 is connected to the reactor T01, the first atomizer 2 is disposed in the reactor T01, and the storage tank V01 is used to store the aqueous solution;

[0069] The second input mechanism includes: a second input pipeline 3 and a first nozzle 4 connected to the second input pipeline 3, the second input pipeline 3 is connected to the reactor T01, the first nozzle 4 is disposed in the reactor T01, and the first nozzle 4 is disposed below the first atomizer 2. The second input pipeline 3 is used to input the gas containing chlorosilane;

[0070] The third input mechanism includes: a third input pipeline 5, a first input part 6 connected to the third input pipeline 5, the first input part 6 is a second atomizer or a second nozzle, the third input pipeline 5 is connected to the reactor T01, the first input part 6 is arranged in the reactor T01, and the first input part 6 is arranged below the first nozzle 4. The third input pipeline 5 is used to input ammonia-containing gas or an ammonia solution. When the third input pipeline 5 inputs ammonia-containing gas, the first input part 6 is the second nozzle; when the third input pipeline 5 inputs an ammonia solution, the first input part 6 is the second atomizer.

[0071] Preferably, the filtration unit comprises:

[0072] The first filter S01 is connected to the reactor T01 and is used to filter the mixture to obtain a first filtrate; the pore size of the filter element of the first filter is 20-60 μm.

[0073] The first filtrate storage tank V02 is connected to the first filter S01 and is used to store the first filtrate. The first filtrate storage tank V02 is also connected to the first input pipeline 1 to input the first filtrate into the reactor T01;

[0074] The second filter S02 is connected to the first filtrate storage tank V02. The second filter S02 is used to filter the first filtrate to obtain a second filtrate. The pore size of the filter element of the second filter S02 is smaller than that of the filter element of the first filter S01; the pore size of the filter element of the second filter is 2-10 μm.

[0075] A second filtrate storage tank V03, connected to the second filter S02, and used to store the second filtrate;

[0076] Specifically, the silicon dioxide preparation system used in the silicon dioxide preparation method of this embodiment further includes:

[0077] The solid silo V04 is connected to the filter unit and is used to receive the filter residue obtained by the filter unit. The solid silo V04 is connected to the first filter S01 and the second filter S02 respectively and is used to receive the filter residue from the first filter S01 and the second filter S02 respectively.

[0078] Exhaust fan C01, connected to reactor T01, used to discharge the gas in reactor T01 into chimney T02;

[0079] Chimney T02 is connected to exhaust fan C01 and is used for exhausting air.

[0080] Preferably, the silicon dioxide preparation system used in the silicon dioxide preparation method further comprises:

[0081] The fourth input mechanism includes: a fourth input pipeline 7, a second input part 8 connected to the fourth input pipeline 7, the second input part 8 is a third atomizer or a third nozzle, the fourth input pipeline 7 is connected to the prilling tower T03, the second input part 8 is arranged in the prilling tower T03, the fourth input pipeline 7 is used to input ammonia-containing gas or an ammonia solution. When the fourth input pipeline 7 inputs ammonia-containing gas, the second input part 8 is a third nozzle; when the fourth input pipeline 7 inputs an ammonia solution, the second input part 8 is a third atomizer;

[0082] The induced draft fan C02 is connected to the granulation tower T03, and the induced draft fan C02 induces air to the granulation tower T03;

[0083] The separator S03 is connected to the induced draft fan C02 and the heating furnace F01 respectively. The granules obtained by granulation are separated from the air through the separator S03 and the granules are sent to the heating furnace F01.

[0084] Blower C03, used for blowing air;

[0085] The air inlet heater E01 is connected to the blower C03 and the granulation tower T03 respectively. The air inlet heater E01 is used to heat the blown air.

[0086] Specifically, the silicon dioxide preparation system used in the silicon dioxide preparation method of this embodiment further includes:

[0087] The finished product silo V05 is connected to the heating furnace F01 and is used to receive the prepared silicon dioxide.

[0088] This embodiment provides a method for preparing silicon dioxide using the above-mentioned silicon dioxide preparation system, comprising the following steps:

[0089] (1) Using chlorosilane-containing gas as a raw material, the chlorosilane-containing gas is transported to the first nozzle 4 in the reactor T01 through the second input pipeline 3;

[0090] (2) The aqueous solution is sprayed into the reactor T01 from the top of the reactor T01 using the first atomizer 2;

[0091] (3) spraying the ammonia solution into the reactor T01 using a second atomizer or the gas containing ammonia using a second nozzle;

[0092] (4) An exhaust fan C01 is connected to the top of the reactor T01 to discharge the gas, smoke or other gases generated by the reaction out of the reactor T01;

[0093] (5) A first pH online detector is provided at the bottom of the reactor T01 for regulating and controlling the reaction. The mixture at the bottom of the reactor T01 is transported to the first filter S01 for filtration, and the filtrate is sprayed back into the reactor T01 through the first atomizer 2;

[0094] (6) After a period of reaction, the silica polymer content of the solution at the bottom of reactor T01 is detected. The reaction is stopped when the pH value and silica polymer content meet the requirements;

[0095] (7) The solution in the reactor T01 was transferred to the first filter S01, and the filtrate was collected in the first filtrate storage tank V02. After standing for a period of time, the solution was filtered again through the second filter S02 and stored in the second filtrate storage tank V03. The pH value and silica polymer content of the secondary filtrate were measured;

[0096] (8) The filtrate in the second filtrate storage tank V03 is pumped into the spray granulation tower T03, and the ammonia solution is sent to the granulation using a third atomizer or the gas containing ammonia is sent to the granulation using a third nozzle to adjust the pH value, and the filtrate is granulated. The conveying pipeline between the second filtrate storage tank V03 and the granulation tower T03 is equipped with a micro-feeder, a strong mixer, and a second pH online detector;

[0097] (9) The granules obtained after drying are collected and subjected to high-temperature treatment in a heating furnace F01 to obtain high-purity silica particles.

[0098] Wherein, the gas containing chlorosilane in step (1) refers to the gas in which chlorosilane occupies a certain proportion. Specifically, in this embodiment, chlorosilane ≥ 60mas%, hydrogen chloride ≤ 5mas%, and the remainder is hydrogen. Preferably, the gas obtained by vaporizing pure chlorosilane through a vaporizer is used; if waste gas containing chlorosilane in a polysilicon production system is used, waste gas with a low hydrogen chloride content is preferably used to avoid consuming a large amount of gas containing ammonia due to excessively high hydrogen chloride content, which leads to an increase in the cost of the gas containing ammonia;

[0099] In step (1), the first nozzle 4 is located in the middle and lower part of the reactor T01 and is disc-shaped. A certain number of nozzles are evenly arranged on the first nozzle 4 so that the gas containing chlorosilane can be evenly distributed in the reactor T01.

[0100] In step (2), the aqueous solution is sprayed into the reactor T01 from the first atomizer 2 on the top of the reactor T01, so that the chlorosilane and water undergo a hydrolysis reaction;

[0101] The aqueous solution in step (2) has a certain pH value, and can also be the aqueous solution at the bottom of the reactor T01, but it needs to meet the pH value requirements, preferably an aqueous solution with a pH value of 3 to 9;

[0102] In step (3), the ammonia solution is sprayed into the reactor T01 through a second atomizer or the gas containing ammonia is sprayed through a second nozzle. Preferably, the second atomizer or the second nozzle is positioned at a location where the aqueous solution and the chlorosilane gas are in uniform contact. Preferably, the mass proportion of ammonia in the gas containing ammonia does not exceed 10%, which can be adjusted according to the content of the chlorosilane gas. Specifically, ammonia is mixed in nitrogen and sprayed into the reactor T01 through the second nozzle.

[0103] In step (4), the top of the reactor T01 is connected to an exhaust fan C01, which is mainly used to promptly discharge the gas, smoke and other gases generated by the reaction from the reactor T01 to reduce the content of hydrogen chloride or chloride in the reactor T01;

[0104] In step (5), a first pH online detector is provided at the bottom of the reactor T01 to facilitate monitoring and adjusting whether the aqueous solution meets the pH value requirements. If the pH value is too high or too low, the injection amount of the ammonia solution or the gas containing ammonia and the chlorosilane gas is adjusted in time;

[0105] In step (6), after a period of reaction, the pH value and the content of silica polymer in the solution at the bottom of the reactor T01 are detected. When the pH value and the content of silica polymer in the solution at the bottom of the reactor T01 reach a certain standard, the mixture at the bottom of the reactor T01 is transported to the first filter S01 for filtration.

[0106] Wherein, in step (6), the pH value of the solution at the bottom of the reactor T01 is 2-6, and the content of the silica polymer is 10-35 mas%, preferably the pH value of the solution at the bottom of the reactor T01 is 2.5-4, and the silica content is 15-25 mas%;

[0107] In step (7), the collected filtrate is stored in the first filtrate storage tank V02 and allowed to stand for ≥4 hours, preferably for 12 hours;

[0108] In step (7), the filtrate after standing is filtered again and stored in a second filtrate storage tank V03, and the pH value and the content of silica polymer in the filtrate after the second filtration are measured;

[0109] In step (8), a certain amount of ammonia solution is prepared according to the pH value of the filtrate in the second filtrate storage tank V03 and the content of the silica polymer, and the mass proportion of ammonia gas in the ammonia solution does not exceed 10%. The ammonia solution is fed through a micro-feeder, a strong mixer, and a second pH online detector to control the feeding amount of the ammonia solution and force mixing.

[0110] Wherein, in step (8), the pH value of the mixed solution is controlled to be 6 to 9.5, preferably 7 to 8.5;

[0111] Wherein, step (8) controls the system parameters of the granulation tower T03 to granulate the required particles, with a particle size range of 600-75 μm and a D50 of 280-350 μm, preferably a particle size range of 500-150 μm and a D50 of 290-330 μm;

[0112] In step (9), the collected particles are fed into the high-temperature equipment heating furnace F01 at a certain speed through a feeder;

[0113] Among them, the temperature range of the heating furnace F01 of the high-temperature treatment equipment in step (9) is from room temperature to 1300°C, and the preferred temperature range is from room temperature to 1220°C.

[0114] Specifically, in this embodiment, chlorosilane is usually transported into the reactor using nitrogen.

[0115] Specifically, in this embodiment, the chloride ions generated after hydrolysis are promptly removed from the material system or converted into ammonium chloride by reaction and promptly removed from the material system. At the same time, the ammonium chloride in part of the material system is removed from the material system by high temperature. In the entire process of this patent, the chloride ions are converted and removed, so the chloride ion content can be controlled, so that the chlorine content in the product is low.

[0116] Finished high-purity silica particles were collected and tested to find that the chloride ion content in the high-purity silica particles was 60-140 ppm, the carbon content was undetectable, the hydroxyl content was 20-50 ppm, and the total metal impurity content was 0.48-1.2 ppm.

[0117] The method for preparing silicon dioxide and the preparation system used therein in this embodiment effectively reduce the chlorine content in high-purity silicon dioxide, while being able to recover part of the chlorosilanes produced during the polysilicon production process, thereby reducing the chlorosilane content in the waste gas and reducing the difficulty of subsequent reprocessing. At the same time, this solution is convenient in terms of industrial scale-up.

[0118] Example 3

[0119] This embodiment provides a method for preparing silicon dioxide using the silicon dioxide preparation system of embodiment 2, comprising the following steps:

[0120] (1) Using refined silicon tetrachloride as a raw material, the gasified refined silicon tetrachloride is mixed with nitrogen, with a volume ratio of refined silicon tetrachloride to nitrogen being 1:1, and transported to the first nozzle of the reactor through a second input pipeline, and evenly sprayed into the reactor;

[0121] (2) spraying a pre-prepared hydrochloric acid solution with a pH value of 5 into the reactor through the first atomizer from the top of the reactor;

[0122] (3) After mixing ammonia and nitrogen, the ammonia gas accounts for 4% by mass in the gas containing ammonia, and is transported to the second nozzle of the reactor through a third input pipeline and evenly sprayed into the reactor;

[0123] (4) Before introducing the gas, turn on the exhaust fan connected to the top of the reactor so that the smoke and excess nitrogen generated by the reaction can be discharged from the reactor in time after the gas is introduced;

[0124] (5) The pH value of the solution at the bottom of the reactor is controlled between 3 and 5 by a first online pH detector that detects the pH at the bottom of the reactor in real time. After the operation is stable, the mixture at the bottom of the reactor is gradually discharged into the first filter. The filtrate is collected and transported to the top of the reactor and sprayed out by the first atomizer;

[0125] (6) After a period of reaction, the pH value of the solution at the bottom of the reactor is detected to be 3 and the silica polymer content is 20 mas%, and the introduction of refined silicon tetrachloride and ammonia-containing gas is stopped;

[0126] (7) The bottom solution of the reactor was completely discharged into the first filter for filtration. The filtrate was collected into the first filtrate storage tank and allowed to stand for 12 hours. The filtrate was filtered again through the second filter and collected into the second filtrate storage tank. The pH value of the secondary filtrate was measured to be 3.5 and the silica polymer content was 18.5 mas%.

[0127] (8) The secondary filtrate is pumped into a spray granulation tower for granulation, and a prepared ammonia solution is added during the transportation process, wherein the mass proportion of ammonia gas in the ammonia solution is 4%, and the pH value of the solution is adjusted to 8. The granulated particles are collected, and the particle size is 450-150 μm, and D50 is 310 μm;

[0128] (9) The particles are evenly added to a high-temperature equipment heating furnace through a feeder for high-temperature treatment. The maximum operating temperature is 1220°C and maintained for 12 hours. The high-temperature treatment is stopped and the temperature is lowered. The finished high-purity silica particles after treatment are collected. The chloride ion content in the high-purity silica particles is detected to be 85 ppm, the carbon content is not detected, the hydroxyl content is 30 ppm, and the total metal impurity content is 0.48 ppm.

[0129] Example 4

[0130] This embodiment provides a method for preparing silicon dioxide using the silicon dioxide preparation system of embodiment 2, comprising the following steps:

[0131] (1) Using chlorosilane-containing gas (chlorosilane accounts for 60mas%, hydrogen accounts for 35mas%, and hydrogen chloride accounts for 5mas%) as a raw material, the chlorosilane-containing gas is mixed with nitrogen, and the volume ratio of the chlorosilane-containing gas to the nitrogen is 3:1, and the mixture is transported to the first nozzle of the reactor through a second input pipeline and evenly sprayed into the reactor;

[0132] (2) spraying a pre-prepared ammonia solution with a pH value of 9 into the reactor through the first atomizer from the top of the reactor;

[0133] (3) After mixing ammonia and nitrogen, the ammonia gas accounts for 8% by mass in the gas containing ammonia, and is transported to the second nozzle of the reactor through the third input pipeline and evenly sprayed into the reactor;

[0134] (4) Before introducing the gas, turn on the exhaust fan connected to the top of the reactor so that the smoke and excess nitrogen generated by the reaction can be discharged from the reactor in time after the gas is introduced;

[0135] (5) The pH value of the solution at the bottom of the reactor is controlled between 4 and 6 by a first online pH detector that detects the pH at the bottom of the reactor in real time. After the operation is stable, the mixture at the bottom of the reactor is gradually discharged into the first filter. The filtrate is collected and transported to the top of the reactor and sprayed out by the first atomizer;

[0136] (6) After a period of reaction, the pH value of the solution at the bottom of the reactor is detected to be 3 and the silica polymer content is 20 mas%, and the introduction of the gas containing chlorosilane and the gas containing ammonia is stopped;

[0137] (7) The bottom solution of the reactor was completely discharged into the first filter for filtration. The filtrate was collected and placed in the first filtrate storage tank for 12 hours. The filtrate was filtered again through the second filter and collected in the second filtrate storage tank. The pH value of the secondary filtrate was measured to be 3.8 and the silica polymer content was 18 mas%.

[0138] (8) The secondary filtrate is pumped into a spray granulation tower for granulation, and a prepared ammonia solution is added during the transportation process, the mass proportion of ammonia gas in the ammonia solution is 8%, and the pH value of the solution is adjusted to 8. The granulated particles are collected, and the particle size is 400-120 μm, and D50 is 290 μm;

[0139] (9) The particles are evenly added to a high-temperature equipment heating furnace through a feeder for high-temperature treatment. The maximum operating temperature is 1220°C and maintained for 12 hours. The high-temperature treatment is stopped and the temperature is lowered. The finished high-purity silica particles after treatment are collected. The chloride ion content in the high-purity silica particles is detected to be 140 ppm, the carbon content is not detected, the hydroxyl content is 50 ppm, and the total metal impurity content is 1.2 ppm.

[0140] Example 5

[0141] This embodiment provides a method for preparing silicon dioxide using the silicon dioxide preparation system of embodiment 2, comprising the following steps:

[0142] (1) Using refined chlorosilane (silicon tetrachloride accounts for 75mas%, trichlorosilane accounts for 20mas%, and dichlorosilane accounts for 5mas%) as a raw material, the gasified refined chlorosilane is mixed with nitrogen, the volume ratio of refined chlorosilane to nitrogen is 1:3, and the mixture is transported to the first nozzle of the reactor through a second input pipeline and evenly sprayed into the reactor;

[0143] (2) spraying a pre-prepared hydrochloric acid solution with a pH value of 6 into the reactor through the first atomizer from the top of the reactor;

[0144] (3) The ammonia solution prepared in advance, wherein the mass proportion of ammonia gas in the ammonia solution is 10%, is delivered to the second nozzle of the reactor through the third input pipeline and evenly sprayed into the reactor;

[0145] (4) Before introducing the gas, turn on the exhaust fan connected to the top of the reactor so that the hydrogen, smoke and excess nitrogen generated by the reaction can be discharged from the reactor in time after the gas is introduced;

[0146] (5) The pH of the solution at the bottom of the reactor is controlled between 3 and 5 by a first online pH detector that detects the pH at the bottom of the reactor in real time. After the operation is stable, the mixture at the bottom of the reactor is gradually discharged into the first filter. The filtrate is collected and transported to the top of the reactor and sprayed out by the first atomizer;

[0147] (6) After a period of reaction, the pH value of the solution at the bottom of the reactor is detected to be 3 and the silica polymer content is 18 mas%, and the introduction of refined chlorosilane and ammonia solution is stopped;

[0148] (7) The bottom solution of the reactor was completely discharged into the first filter for filtration. The filtrate was collected and placed in the first filtrate storage tank for 12 hours. The filtrate was filtered again through the second filter and collected in the second filtrate storage tank. The pH value of the secondary filtrate was measured to be 3.6 and the silica polymer content was 17 mas%.

[0149] (8) The secondary filtrate is pumped into a spray granulation tower for granulation, and a prepared ammonia solution is added during the transportation process, the mass proportion of ammonia gas in the ammonia solution is 10%, and the pH value of the solution is adjusted to 8. The granules after granulation are collected, and the particle size is 380-100 μm, and D50 is 260 μm;

[0150] (9) The particles are evenly added to a high-temperature equipment heating furnace through a feeder for high-temperature treatment. The maximum operating temperature is 1220°C and maintained for 12 hours. The high-temperature treatment is stopped and the temperature is lowered. The finished high-purity silica particles after treatment are collected. The chloride ion content in the high-purity silica particles is detected to be 60 ppm, the carbon content is not detected, the hydroxyl content is 43 ppm, and the total metal impurity content is 0.67 ppm.

[0151] Example 6

[0152] This embodiment provides a method for preparing silicon dioxide using the silicon dioxide preparation system of embodiment 2, comprising the following steps:

[0153] (1) Using chlorosilane-containing gas (chlorosilane accounts for 80mas%, hydrogen accounts for 18mas%, and hydrogen chloride accounts for 2mas%) as a raw material, the chlorosilane-containing gas is mixed with nitrogen, and the volume ratio of the chlorosilane-containing gas to the nitrogen is 1:4, and the mixture is transported to the first nozzle of the reactor through a second input pipeline and evenly sprayed into the reactor;

[0154] (2) spraying a pre-prepared ammonia solution with a pH value of 8 into the reactor from the top through the first atomizer;

[0155] (3) After mixing ammonia and nitrogen, the ammonia gas accounts for 5% by mass in the gas containing ammonia, and is transported to the second nozzle of the reactor through the third input pipeline and evenly sprayed into the reactor;

[0156] (4) Before introducing the gas, turn on the exhaust fan connected to the top of the reactor so that the smoke and excess nitrogen generated by the reaction can be discharged from the reactor in time after the gas is introduced;

[0157] (5) The pH value of the solution at the bottom of the reactor is controlled between 4 and 6 by a first online pH detector that detects the pH at the bottom of the reactor in real time. After the operation is stable, the mixture at the bottom of the reactor is gradually discharged into the first filter. The filtrate is collected and transported to the top of the reactor and sprayed out by the first atomizer;

[0158] (6) After a period of reaction, the pH value of the solution at the bottom of the reactor is detected to be 3 and the silica polymer content is 17 mas%, and the introduction of the chlorosilane-containing gas and ammonia solution is stopped;

[0159] (7) The bottom solution of the reactor was completely discharged into the first filter for filtration. The filtrate was collected and placed in the first filtrate storage tank for 12 hours. The filtrate was filtered again through the second filter and collected in the second filtrate storage tank. The pH value of the secondary filtrate was measured to be 3.8 and the silica polymer content was 16.5 mas%.

[0160] (8) The secondary filtrate is pumped into a spray granulation tower for granulation. During the transportation process, a mixture of ammonia and nitrogen is added to achieve the desired effect. The mass proportion of ammonia in the gas containing ammonia is 10%. The pH value of the solution is adjusted to 8. The granulated particles are collected. The particle size is 500-150 μm and the D50 is 300 μm.

[0161] (9) The particles are evenly added to a high-temperature equipment heating furnace through a feeder for high-temperature treatment. The maximum operating temperature is 1220°C and maintained for 12 hours. The high-temperature treatment is stopped and the temperature is lowered. The finished high-purity silica particles after treatment are collected. The chloride ion content in the high-purity silica particles is detected to be 98 ppm, the carbon content is not detected, the hydroxyl content is 48 ppm, and the total metal impurity content is 0.95 ppm.

[0162]

[0163] Table 1

[0164] Table 1 shows the impurity content in the finished high-purity silicon dioxide particles in Examples 3 to 6.

[0165] The following differences exist between Example 3 and Example 4: ① The raw materials are different. Example 3 uses purified silicon tetrachloride, which is more suitable for the hydrolysis reaction; ② The reaction solutions are different. Example 3 uses an acidic aqueous solution to control the hydrolysis rate due to the use of purified silicon tetrachloride, while Example 4 uses an alkaline aqueous solution due to the use of chlorosilane gas, which contains some hydrogen chloride gas and needs to be neutralized. The subsequent process parameters are different.

[0166] The following differences exist between Example 5 and Example 6: ① The raw materials are different. Example 5 uses refined chlorosilane, which is relatively suitable for the hydrolysis reaction. ② The reaction solutions are different. Example 5 uses refined chlorosilane, which makes trichlorosilane and dichlorodihydrosilane more susceptible to hydrolysis and requires more controlled hydrolysis rate, so an acidic aqueous solution is used. Example 6 uses chlorosilane gas, which contains some hydrogen chloride gas and needs to be neutralized, so an alkaline aqueous solution is used. The subsequent process parameters differ.

[0167] Comparative analysis of Example 3 and Example 5 shows that the purified silicon tetrachloride is easier to control the reaction and obtains a better product; Example 4 and Example 6 have different material compositions and different reaction controls, and the process preference is more inclined towards materials with lower hydrogen chloride content.

[0168] Example 7

[0169] This embodiment provides a method for preparing silicon dioxide using the silicon dioxide preparation system of embodiment 2, comprising the following steps:

[0170] (1) Using refined trichlorosilane as a raw material, the gasified refined trichlorosilane is mixed with nitrogen, with a volume ratio of refined trichlorosilane to nitrogen being 1:4, and transported to the first nozzle of the reactor through a second input pipeline, and evenly sprayed into the reactor;

[0171] (2) spraying a pre-prepared hydrochloric acid solution with a pH value of 3 into the reactor through the first atomizer from the top of the reactor;

[0172] (3) delivering the ammonia solution to the second atomizer of the reactor through a third input pipeline, wherein the mass proportion of ammonia gas in the ammonia solution is 5%, and the solution is evenly sprayed into the reactor;

[0173] (4) Before introducing the gas, turn on the exhaust fan connected to the top of the reactor so that the smoke and excess nitrogen generated by the reaction can be discharged from the reactor in time after the gas is introduced;

[0174] (5) The pH value of the solution at the bottom of the reactor is controlled between 2 and 6 by a first online pH detector that detects the pH at the bottom of the reactor in real time. After the operation is stable, the mixture at the bottom of the reactor is gradually discharged into the first filter. The filtrate is collected and transported to the top of the reactor and sprayed out by the first atomizer;

[0175] (6) After a period of reaction, the pH value of the solution at the bottom of the reactor is detected to be 4 and the silica polymer content is 10 mas%, and the introduction of purified trichlorosilane and ammonia-containing gas is stopped;

[0176] (7) The bottom solution of the reactor was completely discharged into the first filter for filtration. The filtrate was collected and placed in the first filtrate storage tank for 20 h. The filtrate was filtered again through the second filter and collected in the second filtrate storage tank. The pH value of the secondary filtrate was measured to be 4.7 and the silica polymer content was 9 mas%.

[0177] (8) The secondary filtrate is pumped into a spray granulation tower for granulation. During the transportation process, a mixture of ammonia and nitrogen is added to achieve the desired effect. The mass proportion of ammonia in the gas containing ammonia is 5%. The pH value of the solution is adjusted to 6. The granulated particles are collected. The particle size is 400-75 μm and the D50 is 280 μm.

[0178] (9) The particles are evenly added to a high-temperature equipment heating furnace through a feeder for high-temperature treatment. The maximum operating temperature is 1000°C and maintained for 15 hours. The high-temperature treatment is stopped and the temperature is lowered. The finished high-purity silica particles after treatment are collected. The chloride ion content in the high-purity silica particles is detected to be 110 ppm, the carbon content is not detected, the hydroxyl content is 80 ppm, and the total metal impurity content is 0.53 ppm.

[0179] Example 8

[0180] This embodiment provides a method for preparing silicon dioxide using the silicon dioxide preparation system of embodiment 2, comprising the following steps:

[0181] (1) Using refined chlorosilane (silicon tetrachloride accounts for 55mas%, trichlorosilane accounts for 30mas%, and dichlorosilane accounts for 15mas%) as a raw material, the gasified refined chlorosilane is mixed with nitrogen, the volume ratio of refined chlorosilane to nitrogen is 1:10, and the mixture is transported to the first nozzle of the reactor through a second input pipeline and evenly sprayed into the reactor;

[0182] (2) spraying a pre-prepared hydrochloric acid solution with a pH value of 9 into the reactor through the first atomizer from the top of the reactor;

[0183] (3) The ammonia solution prepared in advance, wherein the mass proportion of ammonia gas in the ammonia solution is 2%, is transported to the second nozzle of the reactor through the third input pipeline and evenly sprayed into the reactor;

[0184] (4) Before introducing the gas, turn on the exhaust fan connected to the top of the reactor so that the hydrogen, smoke and excess nitrogen generated by the reaction can be discharged from the reactor in time after the gas is introduced;

[0185] (5) The pH of the solution at the bottom of the reactor is controlled between 2 and 5 by a first online pH detector that detects the pH at the bottom of the reactor in real time. After the operation is stable, the mixture at the bottom of the reactor is gradually discharged into the first filter. The filtrate is collected and transported to the top of the reactor and sprayed out by the first atomizer;

[0186] (6) After a period of reaction, the pH value of the solution at the bottom of the reactor is detected to be 3 and the silica polymer content is 30 mas%, and the introduction of refined chlorosilane and ammonia solution is stopped;

[0187] (7) The bottom solution of the reactor was completely discharged into the first filter for filtration. The filtrate was collected and placed in the first filtrate storage tank for 15 h. The filtrate was filtered again through the second filter and collected in the second filtrate storage tank. The pH value of the secondary filtrate was measured to be 3.8 and the silica polymer content was 28 mas%.

[0188] (8) The secondary filtrate is pumped into a spray granulation tower for granulation, and a mixture of ammonia and nitrogen is added during the transportation process, with the mass proportion of ammonia in the gas containing ammonia being 2%, and the pH value of the solution is adjusted to 9.5. The granulated particles are collected, and the particle size is 300-600 μm, and D50 is 350 μm;

[0189] (9) The particles are evenly added to a high-temperature equipment heating furnace through a feeder for high-temperature treatment. The maximum operating temperature is 1300°C and maintained for 15 hours. The high-temperature treatment is stopped and the temperature is lowered. The finished high-purity silica particles after treatment are collected. The chloride ion content in the high-purity silica particles is detected to be 124 ppm, the carbon content is not detected, the hydroxyl content is 20 ppm, and the total metal impurity content is 1.06 ppm.

[0190] It will be understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present invention, and the present invention is not limited thereto. Those skilled in the art will appreciate that various modifications and improvements can be made without departing from the spirit and substance of the present invention, and such modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing silicon dioxide, characterized in that: The following steps are involved: 1) mixing a gas containing chlorosilane with an aqueous solution, wherein the pH value of the aqueous solution is 3 to 9, and during the mixing, the aqueous solution flows from the top to the gas containing chlorosilane below, causing a hydrolysis reaction of the chlorosilane, wherein the pH value of the hydrolysis reaction is 2 to 6, and adjusting the pH value of the hydrolysis reaction by using a gas containing ammonia or an ammonia aqueous solution to obtain a mixture, and discharging the gas after the hydrolysis reaction; 2) Filtering the mixture to obtain a filtrate, and when the content of the silica polymer in the filtrate is 10-35 mas%, granulating the filtrate and heating it to obtain silica, wherein the particle size of the granulated particles is 600-75 μm and D50 is 280-350 μm.

2. The method for preparing silicon dioxide according to claim 1, wherein In the step 1), the mass proportion of ammonia in the ammonia-containing gas or ammonia solution does not exceed 10%.

3. The method for preparing silicon dioxide according to claim 1, wherein The heating temperature in step 2) is 1000-1300°C.

4. The method for preparing silicon dioxide according to claim 1, wherein In the step 2), the pH value of the filtrate is adjusted by using a gas containing ammonia or an ammonia solution, and the mass proportion of ammonia in the gas containing ammonia or the ammonia solution does not exceed 10%.

5. The method for preparing silicon dioxide according to claim 4, wherein The pH value of the filtrate after adjustment in the step 2) is 6 to 9.

5.

6. The method for preparing silicon dioxide according to claim 1, wherein The following steps are also included: Before the filtrate is granulated, the filtrate is allowed to stand for at least 4 hours.

7. A silicon dioxide preparation system used in the method for preparing silicon dioxide according to any one of claims 1 to 6, characterized in that: include: A reactor for mixing the gas containing chlorosilane with the aqueous solution, causing the chlorosilane to undergo hydrolysis reaction to obtain a mixture; An exhaust fan, connected to the reactor, is used to discharge the gas in the reactor into the chimney; Chimney, connected to the exhaust fan, the chimney is used for exhausting air; A filtration unit is connected to the reactor and is used to filter the mixture to obtain a filtrate; A granulation tower is connected to the filtration unit and is used to granulate the filtrate; The heating furnace is connected to the granulation tower and is used to heat the granules obtained by granulation to obtain silicon dioxide.

8. The silicon dioxide preparation system used in the method for preparing silicon dioxide according to claim 7, characterized in that: The method for preparing silicon dioxide according to claim 4 further comprises: The first input mechanism includes: a storage tank, a first input pipeline connected to the storage tank, and a first atomizer connected to the first input pipeline, the first input pipeline is connected to the reactor, the first atomizer is disposed in the reactor, and the storage tank is used to store the aqueous solution; The second input mechanism includes: a second input pipeline and a first nozzle connected to the second input pipeline, the second input pipeline is connected to the reactor, the first nozzle is arranged in the reactor, the first nozzle is arranged below the first atomizer, and the second input pipeline is used to input the gas containing chlorosilane; The third input mechanism includes: a third input pipeline, a first input part connected to the third input pipeline, the first input part is a second atomizer or a second nozzle, the third input pipeline is connected to the reactor, the first input part is arranged in the reactor, and the first input part is arranged below the first nozzle. The third input pipeline is used to input ammonia gas or ammonia solution. When the third input pipeline inputs ammonia gas, the first input part is the second nozzle; when the third input pipeline inputs ammonia solution, the first input part is the second atomizer.

9. The silicon dioxide preparation system used in the method for preparing silicon dioxide according to claim 7, characterized in that: The filter unit includes: a first filter connected to the reactor, and used to filter the mixture to obtain a first filtrate; a first filtrate storage tank, connected to the first filter, for storing the first filtrate, and further connected to the first input pipeline for inputting the first filtrate into the reactor; a second filter connected to the first filtrate storage tank, the second filter being used to filter the first filtrate to obtain a second filtrate, the pore size of the filter element of the second filter being smaller than the pore size of the filter element of the first filter; The second filtrate storage tank is connected to the second filter and is used to store the second filtrate.

10. The silicon dioxide preparation system used in the method for preparing silicon dioxide according to claim 7, characterized in that: The method for preparing silicon dioxide according to claim 8 further comprises: A solid silo is connected to the filter unit and is used to receive the filter residue obtained by filtering the filter unit; the solid silo is connected to the first filter and the second filter respectively and is used to receive the filter residue from the first filter and the second filter respectively; a fourth input mechanism comprising: a fourth input pipeline, a second input portion connected to the fourth input pipeline, the second input portion being a third atomizer or a third nozzle, the fourth input pipeline being connected to the granulation tower, the second input portion being disposed within the granulation tower, the fourth input pipeline being used to input ammonia gas or an ammonia solution, when the fourth input pipeline inputs ammonia gas, the second input portion being the third nozzle; and when the fourth input pipeline inputs an ammonia solution, the second input portion being the third atomizer; The induced draft fan is connected to the granulation tower and introduces air into the granulation tower; The separator is connected to the induced draft fan and the heating furnace respectively. The granules obtained by granulation are separated from the air through the separator and the granules are sent to the heating furnace; Blower, used for blowing air; The air inlet heater is connected to the blower and the granulation tower respectively, and is used to heat the blown air.

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