Method for co-producing high-modulus potash water glass and white carbon black based on silica fume

Abstract

The invention discloses a method for co-production of high-modulus potash water glass and white carbon black based on silica fume, and relates to the technical field of inorganic silicate material preparation, and the method specifically comprises the following steps: S1, synthesis of high-modulus potash water glass; and S2, synthesizing the white carbon black. According to the method, the synthesis of the high-modulus potash water glass is realized under the normal-pressure condition, the process flow is simple, the energy consumption is low, two high-added-value products are continuously produced by using the same raw material, the efficient resource utilization of the silica fume is realized, and the method has remarkable economic and environmental benefits.

Description

Technical Field

[0001] This invention relates to the field of inorganic silicate material preparation technology, specifically to a method for co-producing high-modulus potassium silicate and fumed silica based on microsilica powder. Background Technology

[0002] Microsilica powder is a powder produced by collecting and processing the fumes emitted during the high-temperature smelting of ferrosilicon alloys and industrial silicon in industrial electric furnaces using a special collection device. Depending on the densification method, it is classified into three types: undensed, semi-densed, and fully densified. Its main component is amorphous SiO2, with a content exceeding 90%, and it contains small amounts of other metal oxides and carbon impurities. Microsilica powder, with its extremely fine particle size, high SiO2 content, and high pozzolanic activity, is used to improve the performance of many products, including concrete and refractory materials. Patent CN113896474A discloses a method for preparing microsilica-modified permeable steel slag concrete, which, by adding microsilica powder with a relatively small average particle size to the raw materials, produces high-strength permeable steel slag concrete with performance meeting or exceeding the C30 standard. Based on the application characteristics of concrete and refractory materials, microsilica powder is added at only 5%-10%. However, considering the estimated industrial silicon production of approximately 4.8 million tons in 2025, the industrial silicon industry alone will generate 1.5 million tons of microsilica powder as a byproduct. Due to its extremely fine particle size, microsilica powder easily generates dust during storage and disposal, posing a threat to the environment and human health. The large-scale storage of microsilica powder not only occupies land resources but may also cause soil and water pollution. Traditional disposal methods such as landfilling not only waste resources but also increase disposal costs for enterprises. Therefore, developing resource utilization technologies for microsilica powder to turn waste into treasure has become an urgent need for the sustainable development of the industrial silicon industry. Currently, the technical routes for preparing high value-added products using microsilica powder mainly focus on the production of silica (precipitated silica) and water glass (sodium silicate).

[0003] Existing technologies for preparing precipitated silica from silica powder mostly employ an "alkali dissolution-precipitation" process. Typically, silica powder is first reacted with an alkaline solution (such as sodium hydroxide) under heating to generate a water glass solution, which is then reacted with an acid (such as sulfuric acid) or carbon dioxide to produce precipitated silica. Patent CN105347350A discloses a method for preparing precipitated silica from silica powder. The production process utilizes silica powder, a waste product from the manufacturing process, as raw material. Silica powder and caustic soda are mixed at a weight ratio of 1.2~3.0:1.0 and reacted at 80~180℃ and 1~10 atm for 2~5 hours to obtain a water glass solution, which is then precipitated with acid to obtain precipitated silica. Patent CN105... Patent 110353A discloses a method for carbonizing by-product soda ash for water treatment using microsilica powder as raw material. It uses microsilica powder, which is produced from high-temperature flue gas dust from a ferrosilicon thermal electric furnace, as raw material. Water glass is prepared by dissolving it in sodium hydroxide solution under heating conditions. Finally, carbon dioxide is introduced to react with the water glass to produce silica. Patent CN108017066A discloses a method for producing high-purity silica using industrial silicon by-product microsilica powder. After calcining the microsilica powder to remove organic impurities, it is reacted with caustic soda to obtain water glass mother liquor, which is then reacted with refined sulfuric acid to obtain high-purity silica.

[0004] Water glass preparation is another important way to utilize microsilica powder resources. Existing methods usually react microsilica powder with sodium hydroxide solution under heating conditions to produce sodium water glass. Patent CN118637631A discloses a method for preparing industrial high-modulus water glass using microsilica powder. First, the microsilica powder is calcined at 600-900℃ to remove carbon impurities. Then, it is mixed with hydrochloric acid solution. After acid leaching and activation, iron in the microsilica powder can be removed, so that the iron content in the water glass is below 50ppm. Finally, the acidified microsilica powder is mixed with sodium hydroxide solution in a certain proportion and reacted. The liquid after reaction is centrifuged to obtain water glass. Patent CN117534081A discloses a synthesis method for water glass from microsilica powder. The treated microsilica powder, alkali, additives, and water are added to a reaction vessel in a certain proportion and reacted at atmospheric pressure at a temperature ≤100℃. After a certain reaction time, it is transferred to a high-pressure reaction vessel and reacted at high pressure at a temperature ≥100℃. Finally, the resulting suspension is rapidly filtered with the help of a filter aid to obtain a water glass solution. Although existing technologies can achieve the resource utilization of microsilica, certain limitations remain. Resource utilization is not high, water glass preparation often requires high temperature and pressure conditions, resulting in significant energy consumption. Impurities in the microsilica can affect product quality, necessitating complex pretreatment and impurity removal steps. Current technologies primarily produce sodium water glass, with limited reports on the production of potassium water glass using microsilica.

[0005] Potassium silicate glass, due to its stable modulus and good weather resistance, has unique applications in specialty coatings, adhesives, and other fields. Traditional potassium silicate preparation processes are mainly divided into two categories: dry (solid-phase) and wet (liquid-phase) methods. The dry method involves uniformly mixing quartz sand and potassium silicate, then melting and reacting them in a high-temperature furnace (1300℃~1500℃) to produce molten potassium silicate. After cooling and crushing, a solid product is obtained, or it can be directly dissolved in water to produce liquid potassium silicate. This method is extremely energy-intensive. The wet method involves directly reacting quartz sand with a high-concentration potassium hydroxide (KOH) solution under pressure and heating (0.8MPa, 180℃) to produce liquid potassium silicate. This method has high requirements for the particle size and activity of the raw quartz sand, a slow reaction rate, and a long production cycle. It typically only produces products with a modulus ≤2.8 (low to medium modulus), making it difficult to economically produce high-modulus products.

[0006] Therefore, developing a process that can co-produce high-modulus potassium silicate and high-value-added silica from microsilica powder under mild conditions is of great significance for realizing the high-value utilization of microsilica powder, reducing production costs, and promoting clean production in the industrial silicon industry. Summary of the Invention

[0007] This invention addresses the aforementioned problems by providing a method for the co-production of high-modulus potassium silicate and precipitated silica based on microsilica powder. This method solves the problems of existing technologies using microsilica powder, such as limited product variety and low resource utilization, as well as the high energy consumption and difficulty in economically producing high-modulus potassium silicate using traditional methods. The method of this invention features a simple process flow, high resource utilization, and enables large-scale consumption and high-value utilization of microsilica powder. It reduces the accumulation of industrial solid waste and environmental pollution, while simultaneously meeting market demand for potassium silicate and precipitated silica, resulting in significant environmental and economic benefits. Furthermore, the potassium silicate produced using a potassium compound system may exhibit superior performance and broader application prospects compared to traditional sodium silicate.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a method for co-producing high-modulus potassium silicate and precipitated silica based on microsilica powder, specifically comprising the following steps: S1: Synthesis of high-modulus potassium silicate: Pre-add the base material to an atmospheric pressure reactor, start stirring and heating; pump microsilica powder, solvent, caustic soda, and additives into the atmospheric pressure reactor for atmospheric pressure reaction; heat the reaction system to 80-100℃, and stir the system at a constant temperature for 2-5 hours while it is boiling; after the reaction, adjust the potassium silicate concentration to 22%-28%, stop heating, and continue stirring to cool to 60-90℃; filter the resulting mixed suspension, repeatedly wash the filter cake, collect the filtrate, and obtain a high-modulus potassium silicate product with a modulus of 3.3-3.8; S2: Synthesis of silica: The high-modulus potassium silicate obtained in step S1 is mixed with water in a certain proportion to prepare a base solution, which is pumped into a synthesis reactor and heated to 60-70℃ and kept at that temperature. Then, acid solution is pumped in for pre-acidification to adjust the pH of the system to 9.0±0.1. Subsequently, potassium silicate solution and acid solution are added simultaneously in a co-current manner to control the pH of the reaction system to be stable at 9.0±0.1. The total reaction time is 50-70 min, and segmented temperature control is used in this process. After the co-current process is completed, post-acidification is performed to adjust the pH of the system to 4-5. After aging for 10-30 min, the reaction mixture is filtered, washed, pulped, dried, and granulated to obtain silica product.

[0009] Further, in step S1, the base material is one of water, filter cake wash water, or a 0.5% potassium silicate solution, and the amount of base material added is 10-20% of the total reaction mass; the atmospheric pressure reactor is a special reactor with an exhaust port, a manhole, an axial flow fan, and a steam recovery device; the heating method is jacketed heating or direct heating, and the heating medium is steam or electric heating.

[0010] Furthermore, in step S1, the microsilica powder is dust produced by industrial silicon smelting flue gas after desulfurization and dust removal, and then subjected to densification or non-densification and iron removal treatment; the mass fraction of SiO2 in the microsilica powder is 80%-95%, and the mass fraction of calcium oxide is 0.5%-3.0%.

[0011] Further, in step S1, the solvent is one or more of water, filter cake wash water, and steam condensate; the caustic alkali is a 32%-50% potassium hydroxide solution; and the auxiliary agent is a CO3-containing... 2- SiO3 2- One of the water-soluble potassium salts, or filter cake wash water can be used directly as an additive.

[0012] Further, in step S1, the mass ratio of the microsilica powder to the solvent is 1:1.5-1.8; the amount of caustic alkali added is based on the molar ratio of SiO2 to K2O: n(SiO2):n(K2O)=3.3-3.8; and the amount of the additive added is 0-1% of the mass of the microsilica powder.

[0013] Furthermore, in step S1, the filtration is carried out by direct filtration using a filter press, or by adding diatomaceous earth or 45μm unrefined 95% silica fine powder as a filter aid.

[0014] Further, in step S2, the concentration of potassium silicate added to the base solution is 22%-28%, and the mass ratio of potassium silicate to water is 1:1-1.5; the pre-acidification specifically involves adding sulfuric acid with a mass concentration of 10-30% at a temperature of 60-70℃ to adjust the pH value of the system to 9.0±0.1.

[0015] Further, in step S2, the mass fraction of the potassium silicate added in parallel is 22%-28%, and the mass fraction of the sulfuric acid is 10%-30%; the segmented temperature control is as follows: first react at 60-70℃ for 10-20 min, then raise the temperature to 75-85℃ within 10-15 min, and react at 75-85℃ for 30-50 min.

[0016] Further, in step S2, the post-acidification specifically involves: after the co-flow is completed, stopping the addition of potassium silicate, continuing to add acid until the pH of the reaction system reaches 4-5, aging for 10-30 minutes, and then performing pressure filtration, washing, pulping, drying, and granulation to obtain the silica product.

[0017] Furthermore, the acid solution is 10%-30% sulfuric acid.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention fully utilizes the high reactivity of amorphous SiO2 in microsilica powder. In an open, atmospheric-pressure reactor, by adding additives and ensuring the reaction is carried out under boiling conditions, high-modulus potassium silicate with a modulus of 3.3-3.8 was successfully prepared. This eliminates the high-temperature and high-pressure conditions required by traditional processes, significantly reducing equipment investment and energy consumption. Simultaneously, this invention achieves the co-production of potassium silicate and silica, improving the resource utilization efficiency and added value of microsilica powder, and solving the problem of single-product diversification in existing technologies. Furthermore, the filter cake wash water generated during the process can be recycled as solvents or additives, reducing wastewater discharge and conforming to green chemistry principles. The entire process is simple and safe to operate, providing a new technical approach for the high-value utilization of microsilica powder, offering both environmental and economic benefits. Detailed Implementation

[0019] To make the objectives and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0020] Unless otherwise specified, the instruments, reagents, and materials used in the following embodiments are all conventional instruments, reagents, and materials already available in the prior art and can be obtained through legitimate commercial channels. Unless otherwise specified, the experimental methods and detection methods used in the following embodiments are all conventional experimental methods and detection methods already available in the prior art.

[0021] The microsilica powder used in the following examples and comparative examples all came from Xinjiang Changji Jisheng New Building Materials Co., Ltd., and its specific parameters are shown in Table 1.

[0022] Table 1. Parameters of the microsilica powder used in the examples and comparative examples

[0023] Example 1 S1: Synthesis of high-modulus potassium silicate: at 2m 3 In an atmospheric pressure reactor equipped with a jacketed heating system, stirring device, vent, and steam recovery system, approximately 10% of the total reaction mass of filter cake wash water was added as a base material. Stirring (60 rpm) and steam heating were started. 200 kg of silica fume (95% SiO2 content), 300 kg of water, a 48% potassium hydroxide solution (calculated based on n(SiO2):n(K2O) = 3.6), and 1 kg of potassium carbonate (an additive, accounting for 0.5% of the silica fume mass) were pumped into the reactor. The reaction system was heated to boiling and stirred at 100°C for 3 hours. After the reaction, the concentration of potassium silicate in the reactor was adjusted to 26%, heating was stopped, and the mixture was stirred and cooled to 90°C. The resulting suspension was filtered using a plate and frame filter press. The filter cake was washed twice with 60°C hot water to obtain a clear potassium silicate product with a modulus of 3.6.

[0024] S2: Synthesis of precipitated silica: The potassium silicate solution obtained above was mixed with deionized water at a mass ratio of 1:1.5 to prepare a base solution, which was pumped into a precipitated silica synthesis reactor and heated to 60°C and maintained at that temperature. Stirring was started, and 20% sulfuric acid solution was slowly added for pre-acidification, adjusting the pH of the system to 9.0. Maintaining the temperature at 60°C, 26% potassium silicate solution and 10% sulfuric acid solution were added in a co-current flow, controlling the pH of the reaction system to remain stable at 9.0±0.1. After 20 minutes of co-current flow, the temperature was raised to 75°C within 10 minutes, and the co-current flow was maintained at this temperature for another 30 minutes (total co-current reaction time 60 minutes). After the co-current flow was completed, the addition of potassium silicate was stopped, and 10% sulfuric acid solution was slowly added for post-acidification until the pH of the system dropped to 4.5. Acid addition was then stopped, and the mixture was allowed to mature for 10 minutes. Finally, the reaction mixture was filtered, the filter cake was washed until neutral, and then pulped, spray-dried, and granulated to obtain the precipitated silica product.

[0025] Example 2 S1: Synthesis of high-modulus potassium silicate: at 4m 3In the reactor, approximately 12% (by total reaction mass) of 0.5% potassium silicate was added as a base material. Stirring and direct steam heating were initiated. 500 kg of silica powder (90% SiO2 content, densified), 900 kg of steam condensate, and a 50% potassium hydroxide solution (calculated based on n(SiO2):n(K2O) = 3.8) were pumped into the reactor. Simultaneously, 5 kg of potassium silicate solution (as an additive, accounting for 1% of the silica powder mass) was added and stirred at a constant temperature for 2 hours under vigorous boiling. After the reaction, some water was evaporated, the potassium silicate concentration was adjusted to 22%, heating was stopped, and the reactor was cooled to 75°C. A small amount of diatomaceous earth was added as a filter aid during filtration. After pressure filtration, the filter cake was thoroughly washed, and the filtrate was collected to obtain high-modulus potassium silicate with a modulus of 3.8.

[0026] S2: Synthesis of precipitated silica: Take the above-mentioned potassium silicate and mix it with wash water at a mass ratio of 1:1.3 to prepare a base solution. Pump this solution into the synthesis reactor and heat it to 65°C. Pre-acidify with 10% sulfuric acid to pH=8.9. Perform co-current feeding: potassium silicate concentration is 22%, sulfuric acid concentration is 20%. Control the reaction temperature: first react at 65°C for 15 minutes, then raise the temperature to 80°C within 15 minutes and continue reacting at 80°C for 40 minutes, for a total co-current time of 70 minutes, during which the pH remains stable at 9.0-9.1. After co-current feeding, acidify with 20% sulfuric acid to pH=4.0, and mature for 20 minutes. Subsequently, after pressure filtration, washing, pulping, spray drying, and granulation, the precipitated silica product is obtained.

[0027] Example 3 S1: Synthesis of high-modulus potassium silicate: at 6m 3 In the reactor, water, accounting for approximately 20% of the total reaction mass, was added as a base material. 800 kg of finely densified desulfurized silica powder (88% SiO2, 3.0% CaO), 1300 kg of filter cake wash water (0.8% silica), and a 32% potassium hydroxide solution calculated based on n(SiO2):n(K2O) = 3.3 were pumped into the reactor. The mixture was heated to 80°C and stirred at a constant temperature for 5 hours. After the reaction, the concentration was adjusted to 28%, and the mixture was cooled to 60°C. Undensed 95% silica fine powder was then added, filtered, and washed to obtain potassium silicate with a modulus of 3.3. This example demonstrates that even using low-grade silica powder, this method can still effectively produce qualified products.

[0028] S2: Synthesis of precipitated silica: Base solution preparation: The mass ratio of potassium silicate to water is 1:1.0; pre-acidification is carried out at 70℃, with the pH adjusted to 9.1 using 30% sulfuric acid. Co-current process: Potassium silicate concentration 28%, sulfuric acid concentration 30%. Temperature control: First react at 70℃ for 10 minutes, then increase to 85℃ within 15 minutes, reacting for 50 minutes. After acidification with 30% sulfuric acid solution to pH=5.0, and aging for 30 minutes, the product is filtered, washed, pulped, spray-dried, and granulated to obtain a precipitated silica product with a low specific surface area.

[0029] Comparative Example 1 S1: Potassium silicate synthesis: The raw material ratio and additives are the same as in Example 1, but the reaction is carried out in a closed reactor at 150°C and about 0.5 MPa for 3.5 hours. After the reaction is completed, the pressure is released and the mixture is cooled. Then, subsequent steps such as concentration adjustment and filtration are carried out.

[0030] S2: Synthesis of silica: Same as in Example 1.

[0031] Compared to the reaction at atmospheric pressure, the reaction rate is indeed faster, and the conversion rate of microsilica powder is comparable to or even slightly higher than that in Example 1. However, the high-pressure reaction places high demands on the equipment, significantly increasing investment and maintenance costs. More importantly, the trace metal impurities carried by the microsilica powder during the reaction process intensify the corrosion of the reactor under high temperature and pressure, which may shorten the equipment life and introduce new metal impurities to contaminate the product. In addition, it is impossible to remove volatile impurities in the boiling state, and the final water glass is yellowish in color.

[0032] This comparative example demonstrates that the present invention, employing an open-top atmospheric pressure reactor, reacts under boiling conditions. This allows some impurities, such as residual sulfides, chlorides, and volatile organic compounds, to escape with the steam, improving product quality. It represents an optimal balance between reaction efficiency, equipment investment, operational safety, product purity, and overall cost. While high-pressure reactions are feasible in terms of conversion rate, they reduce economic efficiency and safety, and hinder impurity removal, negatively impacting the quality of the water glass. This, in turn, proves the superiority and rationality of the atmospheric pressure process of the present invention.

[0033] Comparative Example 2 This comparative example aims to illustrate the importance of the "boiling state" reaction temperature for improving the reactivity and conversion rate of microsilica powder.

[0034] S1: Potassium silicate synthesis: The steps of Example 1 are followed, but the reaction temperature is controlled at 60°C (far below the boiling state), and the other conditions remain unchanged. Due to incomplete reaction, subsequent steps cannot proceed normally, so silica synthesis is not performed.

[0035] After reacting at 60°C for 3.5 hours, a large amount of unreacted silica fume remained suspended or precipitated in the reaction mixture, indicating that the system was far from homogeneous. Filtration revealed that the amount of filter cake was significantly greater than in Example 1. Chemical titration analysis showed that the potassium silicate modulus in the filtrate was only 2.2, while the effective conversion rate of SiO2 in the silica fume was approximately 40%, far lower than in Example 1 (>80%). The resulting filtrate had a low concentration and unstable modulus, making it unsuitable as a qualified product and unusable for the next stage of silica production.

[0036] This comparative example demonstrates that if the reaction is not carried out at the 80-100℃ (preferably boiling state) temperature specified in this invention, the reaction rate between the silica powder and the alkali is extremely slow, the conversion rate is low, and the goal of efficient industrial production cannot be achieved, thus proving the necessity of a specific reaction temperature range.

[0037] Comparative Example 3 This comparative example aims to illustrate the key role of "parallel addition" and "segmented temperature control" in controlling the product structure during silica synthesis.

[0038] S1: Potassium silicate synthesis: Qualified potassium silicate was prepared by following the steps in Example 1 exactly.

[0039] S2: Silica Synthesis: Modified Acidification Process: All potassium silicate used for co-current addition is added to the bottom solution at once, followed by a rapid addition of the calculated amount of dilute sulfuric acid to quickly adjust the pH to 4.5. The mixture is aged at 75°C for 60 minutes, followed by subsequent filtration, washing, and drying.

[0040] Due to the instantaneous and localized excessive concentration of acid and alkali, the reaction was too violent, causing the generated silica particles to rapidly agglomerate and form hard, difficult-to-disperse gel blocks. Subsequent filtration and washing became extremely difficult, resulting in low product yield; the dried silica product had large particles with a specific surface area of ​​only 90 m². 2 The oil absorption value was also significantly lower than that of the product in Example 1. Application tests in rubber showed that its reinforcing properties were far inferior to those of the product in Example 1.

[0041] This comparative example demonstrates that abandoning the unique "pre-acidification-co-current addition-segmented temperature control-post-acidification" fine control process of this invention, and instead adopting the traditional one-time feeding method, makes it impossible to prepare high-performance silica with high specific surface area and high reinforcing properties. This highlights the decisive influence of the process design of this invention on the performance of the final product.

[0042] The comparison between the above embodiments and comparative examples shows that the present invention, through specific reactor equipment, raw material ratios, reaction under boiling conditions, and the use of specific additives, significantly improves the reactivity and conversion rate of microsilica powder, ensuring the smooth synthesis and efficient filtration of high-modulus potassium silicate, thereby providing qualified raw materials for the production of high-quality silica. The entire process is reasonable, realizing the high-value-added comprehensive utilization of microsilica powder, and has significant industrial application value.

[0043] Experiment Example 1 Performance Testing The above-described embodiments and comparative products were tested using existing methods, and the results are shown in the table below.

[0044] Table 2 Test Results of Example and Comparative Product

[0045] As can be seen from the water glass test data of Examples 1-3 in Table 2, for microsilica powder with SiO2 content of 80%-95%, this method can obtain potassium water glass with high modulus, and the effective conversion rate of silicon dioxide in microsilica powder can reach more than 82%. From the precipitated silica test data of Examples 1-3, it can be seen that the potassium water glass prepared by this invention can prepare precipitated silica with different specific surface areas, which can meet most market needs.

[0046] Based on the test data from the examples and comparative examples, the potassium silicate and precipitated silica produced by the present invention are comparable to those prepared by conventional methods.

[0047] This invention uses industrial silicon waste microsilica powder as raw material to co-produce potassium silicate and precipitated silica. With a superior process, milder production conditions, safer equipment, and lower investment, it achieves large-scale disposal and high-value utilization of industrial silicon waste microsilica powder. While reducing the accumulation of industrial solid waste and environmental pollution, it meets the market demand for potassium silicate and precipitated silica, resulting in significant environmental and economic benefits and conforming to the current principles of green chemistry.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for co-producing high-modulus potassium silicate and precipitated silica based on microsilica powder, characterized in that: Specifically, it includes the following steps: S1: Synthesis of high-modulus potassium silicate: Pre-add the base material to an atmospheric pressure reactor, start stirring and heating; pump microsilica powder, solvent, caustic soda, and additives into the atmospheric pressure reactor for atmospheric pressure reaction; heat the reaction system to 80-100℃, and stir the system at a constant temperature for 2-5 hours while it is boiling; after the reaction, adjust the potassium silicate concentration to 22%-28%, stop heating, and continue stirring to cool to 60-90℃; filter the resulting mixed suspension, repeatedly wash the filter cake, collect the filtrate, and obtain a high-modulus potassium silicate product with a modulus of 3.3-3.8; S2: Synthesis of silica: The high-modulus potassium silicate obtained in step S1 is mixed with water in a certain proportion to prepare a base solution, which is pumped into a synthesis reactor and heated to 60-70℃ and kept at that temperature. Then, acid solution is pumped in for pre-acidification to adjust the pH of the system to 9.0±0.

1. Subsequently, potassium silicate solution and acid solution are added simultaneously in a co-current manner to control the pH of the reaction system to be stable at 9.0±0.

1. The total reaction time is 50-70 min, and segmented temperature control is used in this process. After the co-current process is completed, post-acidification is performed to adjust the pH of the system to 4-5. After aging for 10-30 min, the reaction mixture is filtered, washed, pulped, dried, and granulated to obtain silica product.

2. The method for co-producing high-modulus potassium silicate and precipitated silica based on microsilica powder according to claim 1, characterized in that: In step S1, the base material is one of water, filter cake wash water, or a 0.5% potassium silicate solution, and the amount of base material added is 10-20% of the total reaction mass; the atmospheric pressure reactor is a special reactor with an exhaust port, a manhole, an axial flow fan, and a steam recovery device; the heating method is jacketed heating or direct heating, and the heating medium is steam or electric heating.

3. The method for co-producing high-modulus potassium silicate and precipitated silica based on microsilica powder according to claim 1, characterized in that: In step S1, the microsilica powder is the dust produced by industrial silicon smelting flue gas after desulfurization and dust removal, and then subjected to densification or non-densification and iron removal treatment; the mass fraction of SiO2 in the microsilica powder is 80%-95%, and the mass fraction of calcium oxide is 0.5%-3.0%.

4. The method for co-producing high-modulus potassium silicate and precipitated silica based on microsilica powder according to claim 1, characterized in that: In step S1, the solvent is one or more of water, filter cake wash water, and steam condensate; the caustic alkali is a 32%-50% potassium hydroxide solution; and the auxiliary agent is a CO3-containing... 2- SiO3 2- One of the water-soluble potassium salts, or filter cake wash water can be used directly as an additive.

5. The method for co-producing high-modulus potassium silicate and precipitated silica based on microsilica powder according to claim 1, characterized in that: In step S1, the mass ratio of the microsilica powder to the solvent is 1:1.5-1.8; the amount of caustic alkali added is based on the molar ratio of SiO2 to K2O: n(SiO2):n(K2O)=3.3-3.8; and the amount of the additive added is 0-1% of the mass of the microsilica powder.

6. The method for co-producing high-modulus potassium silicate and precipitated silica based on microsilica powder according to claim 1, characterized in that: In step S1, the filtration is carried out by direct filtration using a filter press, or by adding diatomaceous earth or 45μm unrefined 95% silica fine powder as a filter aid.

7. The method for co-producing high-modulus potassium silicate and precipitated silica based on microsilica powder according to claim 1, characterized in that: In step S2, the concentration of potassium silicate added to the base solution is 22%-28%, and the mass ratio of potassium silicate to water is 1:1-1.5; the pre-acidification specifically involves adding sulfuric acid with a mass concentration of 10-30% at a temperature of 60-70℃ to adjust the pH value of the system to 9.0±0.

1.

8. The method for co-producing high-modulus potassium silicate and precipitated silica based on microsilica powder according to claim 1, characterized in that: In step S2, the mass fraction of potassium silicate added in parallel is 22%-28%, and the mass fraction of sulfuric acid is 10%-30%. The segmented temperature control is as follows: first react at 60-70℃ for 10-20 min, then raise the temperature to 75-85℃ within 10-15 min, and react at 75-85℃ for 30-50 min.

9. The method for co-producing high-modulus potassium silicate and precipitated silica based on microsilica powder according to claim 1, characterized in that: In step S2, the post-acidification specifically involves: after the co-flow is completed, stopping the addition of potassium silicate, continuing to add acid until the pH of the reaction system reaches 4-5, aging for 10-30 minutes, and then performing pressure filtration, washing, pulping, drying, and granulation to obtain the silica product.

10. A method for co-producing high-modulus potassium silicate and precipitated silica based on microsilica powder according to claim 9, characterized in that: The acid solution is 10%-30% sulfuric acid.

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