Device for preparing precipitated silica

Abstract

The utility model relates to a device for preparing precipitation method silicon dioxide, which comprises a reaction kettle (1) and a bypass section comprising a static mixer (5), a pipeline (7), an optional process gas metering point (6) and / or a pump (8), and wherein the static mixer is configured to circulate back to the reaction vessel via a line.

Description

Technical Field

[0001] This utility model relates to an apparatus for preparing silicon dioxide, particularly precipitated silicon dioxide, the apparatus comprising a static mixer. Background Technology

[0002] The method for producing silica by precipitation in the liquid phase is well known in the art.

[0003] In recent years, there has been a growing interest in using emission process gases in chemical production processes to support environmental conversion and recycling. In the precipitation process for silica production, carbon dioxide-containing process gases are reacted with alkali metal silicates.

[0004] The methods and means of dispersing process gases into alkali metal silicate solutions may differ in each process, and those skilled in the art are seeking to achieve increased carbon dioxide / alkali metal silicate interactions. Enhanced interactions are achieved by increasing the carbon dioxide concentration in the reaction medium via purification of the process gases, or by better dispersing the gases into the solution using an air distributor, which subsequently leads to increased silica production yields and / or controlled silica particle sizes.

[0005] US 2006225615 (A1) discloses a method for preparing precipitated silica, wherein gas is directly injected into a precipitation container after silica precipitation.

[0006] CN 212356558 (A) discloses an apparatus for producing precipitated silica by carbon dioxide dispersion, wherein carbon dioxide is dispersed in a reaction liquid by dispersion blades, and the dispersion blades are all disposed inside a reaction vessel.

[0007] CN 104418332 (B) discloses a method for preparing silica by directly dispersing a process gas containing carbon dioxide into a reactor via an air distributor. The CO2 concentration is increased by purifying the process gas before it is introduced into the reaction medium, which requires additional process steps and involves controlling the particle size distribution using reaction blades.

[0008] All known methods in this art directly distribute the process gas into the liquid solution in the reactor, with or without prior gas purification. They attempt to better distribute CO2 using mixers, vane reactors, or by using nozzles, air distributors, or pumps. However, none of these methods provides the desired distribution of carbon dioxide gas into the alkaline solution.

[0009] Furthermore, conventional reactors cannot be properly used for silica production while using process gases, and special reactor designs are required.

[0010] Process gases typically have low CO2 concentrations, and the CO2 gas is unevenly dispersed in the silicate solution, resulting in an uneven particle size distribution (large aggregates or fine powder). Therefore, powerful pumps or air distributors are required to uniformly disperse the CO2 gas in the silicate solution. In some cases, gas purification is necessary to increase the reaction rate.

[0011] Therefore, there is a need for a method that can improve the yield of silica production processes while still using process gases, without requiring further process gas purification steps or the use of air distributors that directly distribute the gases into the solution in the reactor medium. Utility Model Content

[0012] The purpose of this invention is to provide a specific apparatus for better dispersing CO2 into a sodium silicate solution during the production of silica by precipitation, thereby improving silica yield by timely increasing the reaction rate and shortening the precipitation time.

[0013] Overview of this utility model

[0014] This invention provides an apparatus for preparing silica (silica), comprising a reaction vessel (1), a bypass section including a static mixer (5) and a pipeline (7), wherein the bypass section is located outside the reaction vessel and connected to the vessel via the pipeline, and wherein the static mixer is configured to circulate the reaction medium back to the reaction vessel via the pipeline. The apparatus of this invention solves the problem of uneven particle size distribution without using an air distributor or similar device, and solves the problem of low yield by increasing the reaction rate without further gas purification.

[0015] Surprisingly, it has been found that when process gas containing carbon dioxide is dispersed into the reaction medium via a bypass section containing a static mixer located outside the reactor and subsequently recycled back to the reactor vessel, no further gas purification steps or further arrangements within the reactor vessel, such as the use of nozzles / pumps or air distributors, are required to achieve uniform dispersion / distribution of CO2 into the liquid phase. This results in increased CO2 yields over the same process time compared to standard precipitation reactors employing direct gas injection.

[0016] The increased reaction rate is achieved through better interaction between CO2 and alkali metal silicates when precipitated silica is formed. Higher space-time yields of silica production can also be obtained because CO2 is used more efficiently to react with the same amount of silicate solution.

[0017] The method for preparing silica using the specific apparatus described above can be carried out in conventional reactors known in the art without requiring further arrangements within the reactor. By using a bypass section, the need for a special reactor design for silica production while using process gases is thus overcome.

[0018] The method for preparing precipitated silica includes the following steps:

[0019] (a) An alkali metal silicate solution is provided in the reactor (1);

[0020] (b) Transfer the alkali metal silicate solution from the reactor (1) to a bypass section comprising a static mixer (5) and a pipeline (7), wherein the bypass section is located outside the reactor (1) and connected to the reactor via a pipeline;

[0021] (c) Disperse the process gas containing carbon dioxide into the alkali metal silicate solution in the static mixer (5);

[0022] (d) Return the alkali metal silicate solution after reacting with the process gas to the reactor;

[0023] (e) Silica is precipitated, then filtered, washed and dried to obtain precipitated silica.

[0024] Preferably, the process gas contains carbon dioxide at a concentration of more than 10%, preferably 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% by volume.

[0025] Process gases can enter the static mixer in the form of bubbles through the process gas metering point.

[0026] Preferably, in step (a), the alkali metal silicate solution is mixed with water to obtain a solution with a pH higher than 8, preferably 9, preferably at a temperature between 50-95°C.

[0027] According to this invention, a further alkali metal silicate solution can be added to the reaction vessel to maintain the pH in the range of 8 to 10.5.

[0028] Preferably, the process gas is metered in the pipeline before the static mixer, preferably near the static mixer, or in the static mixer.

[0029] Alkali metal silicate solution can be metered from the reactor tank into the static mixer via pipeline, and the process gas is preferably metered into the static mixer simultaneously with the alkali metal silicate solution.

[0030] The alkali metal silicate solution mixture can be recycled back to the reactor at least once via a bypass section. Preferably, the alkali metal silicate solution mixture carried in step (d) after reacting with the process gas and being transferred to the reactor via pipeline is recycled more than once.

[0031] According to a preferred embodiment of the method, the alkali metal silicate solution is a sodium silicate solution.

[0032] The filtered silica in step (e) is preferably dried under conditions of the addition of an inorganic acid, such as sulfuric acid, or with CO2 or a process gas containing CO2, to adjust the pH value to between 4 and 9, preferably between 6 and 8.2.

[0033] This utility model relates to an apparatus for preparing precipitated silica materials.

[0034] The apparatus includes a reactor (1), a bypass section containing a static mixer (5) and a pipeline (7), wherein the bypass section is located outside the reactor and connected to the reactor via a pipeline, and wherein the static mixer is configured to circulate back to the reactor via the pipeline.

[0035] Preferably, the bypass section further includes a process gas metering point (6) to meter process gas into the static mixer, and the process gas metering point (6) is located before the static mixer in the flow direction, preferably near the static mixer, or on the static mixer.

[0036] Preferably, the process gas metering point is located on the pipeline before the static mixer in the flow direction, and more preferably near the static mixer.

[0037] The bypass section may contain more than one static mixer, preferably located one after another on the pipeline.

[0038] Preferably, the reactor includes a water metering point (3) and a silicate solution metering point (4), which are preferably located at the top or side of the reactor.

[0039] Preferably, the reactor includes an outlet (or suspension outlet) (9) preferably located at the bottom of the reactor to release the solution from the reactor.

[0040] The reactor may further include dispersing blades or agitators.

[0041] By using this device setup, there is no need for spray nozzles, gas distributors, or special high-pressure pumps to directly disperse process gases in the reactor. Attached Figure Description

[0042] Figure 1 This shows the overall production unit for silica production, which includes a reaction vessel and a static mixer. Detailed Implementation

[0043] Detailed Description of this Utility Model

[0044] This utility model relates to an apparatus for preparing precipitated silica, which can be used in an improved method for silica production, comprising the following steps:

[0045] (a) Provide an alkali metal silicate solution to the reactor (1);

[0046] (b) Transfer the alkali metal silicate solution from the reactor (1) to a bypass section comprising a static mixer (5) and a pipeline (7), wherein the bypass section is located outside the reactor (1) and connected to the reactor via a pipeline;

[0047] (c) Disperse the process gas containing carbon dioxide into the alkali metal silicate solution in the static mixer (5);

[0048] (d) Return the alkali metal silicate solution after reaction with the process gas to the reactor; and

[0049] (e) Silica is precipitated, then filtered, washed and dried to obtain precipitated silica.

[0050] This utility model relates to an apparatus for preparing precipitated silica, the apparatus comprising a reactor (a), a bypass section including a static mixer (5) and a pipeline (7), wherein the bypass section is located outside the reactor and connected to the reactor via the pipeline, and the static mixer is configured to circulate back to the reactor via the pipeline.

[0051] The term "reaction vessel" refers to a reaction cup or container that facilitates the conduction of the entire process. Terms such as reaction vessel, reaction container, or reactor are used interchangeably.

[0052] The reactor preferably includes a water metering point (3) and a silicate solution metering point (4). The water and silicate solution metering points are preferably located at the top or side of the reactor.

[0053] The reactor may further include dispersing blades or agitators, a pH sensor, and a temperature sensor. Heating can be achieved via direct steam injection or a heating jacket. The dispersing blades, pH sensor, and temperature sensor can be located inside the reactor.

[0054] The mixer and agitator can be located inside the reactor. The apparatus may also include dispersing blades to disperse the reacted liquid within the silicate solution in the reactor.

[0055] The dispersing blades or mixers may be equipped with vents that communicate with the internal components of the reactor and also with a gas source to deliver process gases directly into the reactor via these vents.

[0056] In a preferred embodiment of this invention, the reaction vessel can be a gas-liquid phase reactor, which can be a stirred tank reactor or a liquid / liquid phase reactor.

[0057] The bypass section according to this invention includes a static mixer (5) and a pipeline (7). The bypass section is located outside the reactor (1) and connected to the reactor via a pipeline. Preferably, the pipeline extends from the lower part of the reactor to the upper part of the reactor, more preferably from the bottom of the reactor to the top of the reactor, or from the bottom of the reactor to the middle or above the reactor.

[0058] The bypass section is connected to the reactor via pipeline, and is referred to as / used as a bypass system in silica production.

[0059] The bypass section preferably includes a process gas metering point (6).

[0060] Preferably, the process gas metering point is located on the pipeline before the static mixer in the flow direction, and more preferably near the static mixer.

[0061] Alternatively, the process gas metering point may be located on a static mixer.

[0062] The process gas metering point may be formed by at least one vent, and the diameter of the process gas metering point may vary depending on the reactor size, the length of the static mixer, and all other flow parameters.

[0063] Optionally, the bypass section may include a pump to pump the alkali metal silicate solution through the bypass section via a pipeline. Preferably, the pump is positioned between the bottom of the reactor and the static mixer.

[0064] The reactor (1) is connected to one end of the bypass section via a pipeline, and the pipeline extends back to the reactor from the other end of the bypass section to circulate the alkali metal silicate solution.

[0065] Preferably, the process gas flows / pressurizes over the silicate solution at a process gas metering point very close to the static mixer.

[0066] Preferably, the process gas mass rate (kg / h) is [value] for a 2 m [unit]. 3 400 g / min to 160 m³ for reactor vessels 3 The reactor vessel has a flow rate of 32,700 g / min. The mass rate depends on the final reactor size.

[0067] The bypass section of the device may contain more than one static mixer. In this case, the process gas is metered into the alkali metal silicate solution before the first static mixer, and then the mixture is moved from the first static mixer to a further static mixer for further reaction and mixing, and to achieve thorough mixing of CO2 gas with the alkali metal silicate solution and better CO2 distribution.

[0068] The length of the static mixer will also depend on the reactor size and the pipeline diameter. The larger the reactor, the longer the pipeline must be to connect all the structures. Generally, the pipeline should not be longer than required.

[0069] A static mixer is a device used for continuously mixing fluid materials without moving components. Typically, the fluid to be mixed is a liquid, but static mixers can also be used to mix gas streams, disperse gases into liquids, or blend immiscible liquids. The energy required for mixing comes from the pressure loss as the fluid flows through the static mixer, or from the insert that guides the flow of liquid / gas in a turbulent manner as it flows through. Static mixers are known in the art for various applications in chemical processing.

[0070] In this invention, different types of static mixer designs can be used, such as plate mixers or device types consisting of mixer elements contained in cylindrical (tube) or square housings. Horizontal or vertical static mixers can be used. Static mixers from Sulzer are universal and can be effectively used in this invention, regardless of any specific model or source.

[0071] Any known construction material for static mixer components can be used, including stainless steel, polypropylene, Teflon, PVDF, PVC, CPVC, and glass-lined steel, preferably PVDF or stainless steel.

[0072] By using process gases containing carbon dioxide instead of other known inorganic acids such as sulfuric acid, the environmental impact of acid consumption is reduced, and the amount of CO2 released via process gases is also reduced because it is recycled back into the silica production process. Both of these beneficial effects directly support sustainable silica production methods.

[0073] Furthermore, by using a bypass section containing a static mixer, further purification of the process gas is eliminated because CO2 is uniformly distributed into the solution via the static mixer in the bypass section. This also increases the yield of silica production in a shorter time with a uniform particle size distribution. The static mixer in the bypass section allows CO2 gas to be very well dispersed in the silicate solution, which is then recycled back to the reactor to mix with the alkali metal silicate solution.

[0074] By using this device setup, there is no need for spray nozzles, gas distributors, or special high-pressure pumps to directly disperse process gases in the reactor, although these may be used or present in the reactor.

[0075] Alkali metal silicate solutions are well known in the art and are combinations of alkali metal oxides (e.g., Na2O), silicon dioxide, and water, or combinations of alkali metal silicates and water.

[0076] Although other alkali metals, such as lithium or potassium, can be used, alkali metal silicate solutions are preferably sodium silicate solutions, also known as water glass. Sodium silicate solutions can be produced in a wide range of compositions and are distinguished by the ratio of silicon dioxide to alkali metal, with the general formula (Na₂O). x (SiO2) y (H2O) z , where x, y, z are molar ratios.

[0077] Preferably, in step (a), water and an alkali metal silicate solution are added to the reactor to bring the pH above 8, more preferably above 9. Preferably, the pH is maintained below 10.5. During the circulation of the alkali metal silicate solution through the pipeline section, the pH range is kept constant by adding additional alkali metal silicate solution.

[0078] Preferably, the alkali metal silicate solution is sucked from the bottom of the reactor and delivered to the static mixer (5) via a pipeline (7), optionally by means of a pump (8) arranged on the surface of the pipeline located between the bottom of the reactor and the static mixer (5).

[0079] The reaction between the alkali metal silicate solution and CO2 gas primarily occurs in a static mixer, and the alkali metal silicate solution, containing carbon dioxide as a process gas dispersion, is circulated back to the reactor via pipeline. Therefore, no additional process gas or CO2 gas is pumped / fed into the reactor itself.

[0080] Dispersing process gases containing carbon dioxide through a bypass section eliminates the need for an air distributor or pump inside the reactor to distribute other process gases.

[0081] The alkaline solution mixture should be held in the static mixer for the time required for the reaction to occur. If the gas is introduced into the mixer in the form of bubbles, the goal is to minimize the bubble size in the static mixer as much as possible. When the alkaline solution mixture is released from the static mixer, the goal is to have very small bubbles or no bubbles at all. Needless to say, the longer the static mixer, the longer the alkaline solution mixture will reside in it.

[0082] CO2 is primarily converted to carbonic acid in the static mixer and then piped into the reaction vessel for continuous precipitation. It is possible that some precipitation may also occur in the static mixer or pipeline.

[0083] In a preferred embodiment, the alkali metal silicate solution reacts with CO2 in a static mixer located outside the reactor as part of a bypass section, and the dispersed solution is then recycled back to the reactor at least once or more.

[0084] This new dispersion method and apparatus allows for more uniform dispersion of CO2 in the liquid phase, resulting in better reaction with sodium silicate to form precipitated silica. Therefore, it enables higher space-time yields for CO2-precipitated silica.

[0085] Process gases can be any waste gas containing carbon dioxide. This can be exhaust gas, tail gas, or waste gas from biomass containing carbon dioxide. Process gases can also be, for example, carbon dioxide captured during calcination or wastewater recycling processes.

[0086] The process gas may contain at least 10% carbon dioxide by volume. Preferably, the process gas contains more than 10% carbon dioxide by volume, preferably more than 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90%. The process gas may further contain carbon monoxide, hydrogen, nitrogen, oxygen, sulfur, or oxides thereof.

[0087] In a preferred embodiment, a process gas containing carbon dioxide is pressurized from a process gas metering point and uniformly dispersed in the form of microbubbles into an alkali metal silicate solution.

[0088] The gas pressure at the process gas metering point is preferably 2.5 to 4.5 bar.

[0089] Preferably, the alkali metal silicate solution is metered from the reactor tank into the static mixer via a pipeline, and the process gas is preferably metered into the static mixer simultaneously with the alkali metal silicate solution to keep the pH or alkaline number (the type of which depends on the formulation) constant.

[0090] The precipitation reaction temperature is typically between 50°C and 95°C, and the reaction time for precipitating silica is between 40 minutes and 150 minutes at atmospheric pressure, depending on the specific composition.

[0091] Heating can be achieved through direct steam injection or by heating the jacket.

[0092] By using this type of static mixer and optionally allowing the process gas to flow over the silicate solution via a process gas metering point in this mixer section, and then circulating it back to the reactor, the process gas and silicate solution can be thoroughly mixed and reacted, thereby preventing further reaction in the reactor, which increases the reaction rate and the yield of silica production.

[0093] The reaction of an alkali metal silicate solution with CO2 in a process gas is terminated by re-acidifying the solution with CO2, preferably a CO2-containing process gas, to precipitate the silica, followed by filtration to obtain filtered silica.

[0094] In one embodiment, the filtered silica is then dried by rotary flash drying with the addition of an inorganic acid, such as sulfuric acid, to achieve a final pH of 6.5.

[0095] In one embodiment, during the drying step, a silica slurry is obtained by mixing the resulting filtered silica with water and adding sulfuric acid to achieve a pH of 6.5, which is then fed into a spray dryer. Any drying method known in the art, such as spray drying and / or rotary flash drying and / or rotary dryer, may also be used.

[0096] In a preferred embodiment, the alkali metal silicate solution is circulated from the reactor back to the reactor at least once via a static mixer.

[0097] In a preferred embodiment, in step (e), additional CO2 or a process gas containing CO2 is added to the solution to precipitate silica at a pH above 8.

[0098] In a preferred embodiment, the solution is re-acidified after precipitation using CO2 or a process gas containing CO2 and by adding acid during the drying step.

[0099] In a preferred embodiment, the filtered silica in step (e) is dried under the addition of an inorganic acid, such as sulfuric acid, to adjust the pH value to between 4 and 9, preferably between 6 and 8.2, wherein the concentration of sulfuric acid is 50% or higher.

[0100] The dried silica particles can then be granulated or ground.

[0101] Once the alkali metal silicate solution is moved to the static mixer, the process gases required for silica production are metered into the static mixer. In this way, CO2 is already dispersed in the solution before entering the reactor. The reaction between the alkali metal silicate solution and the CO2 gas occurs in the static mixer, where almost all of the gas is dispersed within the alkali metal silicate solution mixture. It is expected that a small amount of unreacted CO2 gas may be carried into the reactor through piping.

[0102] By sending the alkali metal silicate solution back to the reactor in which CO2 is already dispersed via pipeline, there is no need for spray nozzles, gas distributors or special high-pressure pumps to directly deliver CO2 into the reactor.

[0103] When needed, the dispersed carbon dioxide can be recycled and uniformly dispersed in the reaction liquid, which is beneficial for the production of silica.

[0104] The silica produced by the apparatus according to this invention can be used in any suitable application, including rubber products such as tires, industrial belts, hoses, gaskets, rubber sheets, threshing rollers for grain processing, rubber shoes, and other rubber industrial products.

[0105] Measurement methods

[0106] CO2 yield calculation:

[0107] The required CO2 yield was determined based on the stoichiometry of the reaction. Theoretical calculations indicate that 421 grams of CO2 are needed per kilogram of SiO2 for complete neutralization. This calculation is based on the Na2O neutralization reaction. To assess CO2 consumption, the CO2 bottle was weighed before and after the reaction, taking into account the CO2 delivered to the reactor and any remaining unreacted CO2. Alternatively, a CO2 mass flow meter can be used to measure CO2 consumption.

[0108] Use a pH meter to measure pH.

[0109] abbreviation

[0110] WGL / WG = Water glass or sodium silicate

[0111] Example

[0112] The present invention will be further illustrated in detail below with reference to the embodiments and comparative examples.

[0113] Standard water glass contains approximately 8% Na₂O and 27% SiO₂ – thus having a modulus of 3.45, meaning the SiO₂ / Na₂O weight ratio in solid sodium silicate is approximately 3.45. Assuming a 100% CO₂ yield (meaning CO₂ consumed / used in the reaction, using all calculated CO₂), then for such a WGL, 113.6 g / min of CO₂ should be metered in for a WGL of 1 kg / min. If CO₂ consumption is less than 100%, a higher metered CO₂ addition may be needed to maintain a constant pH. The water glass source can also vary, and the range can differ accordingly. For example, for water glass containing approximately 21% SiO₂ and 6.3% Na₂O (modulus 3.45), the CO₂ metered addition needs to be adjusted accordingly to achieve a higher yield.

[0114] The same standard water glass containing approximately 8% Na2O and 27% SiO2 was used in all the comparative embodiments disclosed in this invention and the embodiments according to this invention, as shown below.

[0115] After the precipitation of silica, the same filtration and drying steps as described in Comparative Example 1 are followed for the remaining embodiments. In the embodiments of this invention, CO2 can be used instead of sulfuric acid during the drying step.

[0116] In the comparative embodiments, a conventional reactor is used, wherein a conventional reactor can refer to any known type of reactor suitable for silica precipitation and known in the art. The conventional reactor arrangement does not include pipeline sections with static mixers as described in this invention.

[0117] Example 1 – Comparison

[0118] A sodium silicate solution (solid sodium silicate and water) is metered and added to a 2 m³ reactor containing a turbine and agitator, equipped with a metering nozzle. 3 In a conventional reactor.

[0119] The reaction was carried out with a stirrer at 80 rpm while water was added to the alkali metal silicate solution to achieve pH 9. The solution volume reached 1400 L, and the temperature was maintained at approximately 82°C.

[0120] Precipitation of silica:

[0121] CO2 was metered into the sodium silicate solution at a pressure of 4 bar (measured in the pipeline) at a mass addition rate / flow rate of 316 g / min. Additional sodium silicate was metered in at a rate of 4 kg / min, for a total addition of 500 kg.

[0122] A metering nozzle is present inside the reactor, and CO2 is metered in using the first and / or second metering nozzle tubes within the reactor. The end of the metering nozzle tube is located above the reactor turbine and meters the CO2 onto it.

[0123] Reacidification was then initiated by stopping the metered addition of sodium silicate and continuing the metered addition of CO2. The CO2 pressure was maintained at 4 bar, and the CO2 metered addition rate remained at 316 g / min.

[0124] When pH 8 is reached, re-acidification is stopped. The total reaction time, including the re-acidification step, is approximately 240 minutes.

[0125] The resulting suspension was then pumped to a filter press for washing (to remove residual salt) and dehydration. After filtering out the precipitate using the filter press and washing, a clear, impurity-free liquid sodium silicate was obtained.

[0126] The resulting filtered silica was then dried using a rotary flash dryer. During the drying step, sulfuric acid was metered onto the filtered silica to achieve a final pH of approximately 6.5. The powder was then optionally granulated using conventional methods.

[0127] For the remaining embodiments, the same filtration, drying, and optional granulation steps are followed.

[0128] The calculated total CO2 yield of 75% means that 75% of the CO2 calculated and fed into the reaction is consumed / used during precipitation, while the remaining 25% of CO2 is either released into the environment or is not accurately distributed and reacted within the reaction medium. This implies that the method will require the addition of more CO2 and may even require increasing the precipitation time for total silicate conversion to increase the amount of SiO2 precipitated.

[0129] CO2 consumption was calculated using stoichiometry. Theoretically, 421 g CO2 / kg SiO2 is required for neutralization. The yield calculation is based on the neutralization reaction of Na2O. CO2 consumption was determined by weighing the CO2 bottle before and after the reaction, taking into account the CO2 delivered to the reactor and the remaining / unreacted CO2. Alternatively, CO2 consumption can also be determined using a CO2 mass flow meter. The same calculations were used for the remaining examples.

[0130] Example 2 – Comparison

[0131] A sodium silicate solution (solid sodium silicate and water) is metered and added to a 2 m³ reactor containing a turbine and agitator, equipped with a metering nozzle. 3 In a conventional reactor.

[0132] The reaction was carried out with a stirrer at 80 rpm while water was added to the alkali metal silicate solution to achieve pH 9. The solution volume reached 1400 L, and the temperature was maintained at approximately 75°C.

[0133] Precipitation of silica:

[0134] CO2 was metered into the sodium silicate solution at a pressure of 4 bar (measured in the pipeline) at a mass addition rate / flow rate of 324 g / min. Additional sodium silicate was metered in at a rate of 4 kg / min, for a total addition of 500 kg.

[0135] As described above, CO2 is metered and added using either the first or second metering nozzle inside the reactor. The end of the metering nozzle is located above the reactor turbine and meters the CO2 onto it.

[0136] Reacidification was then initiated by stopping the metered addition of sodium silicate and continuing the metered addition of CO2. The CO2 pressure was maintained at 4 bar, and the CO2 metered addition rate remained at 324 g / min.

[0137] When pH 8 is reached, re-acidification is stopped. The total reaction time, including the re-acidification step, is approximately 240 minutes.

[0138] The calculated total CO2 yield of 82% means that 82% of the calculated and fed CO2 in the reaction is consumed / used during precipitation, while the remaining 18% of CO2 is either released into the environment or is not accurately distributed and reacted within the reaction medium. This implies that the method will require the addition of more CO2 and may even require increasing the precipitation time for total silicate conversion to increase the amount of SiO2 precipitated.

[0139] Example 3 – This utility model

[0140] A sodium silicate solution (solid sodium silicate and water) is metered and added to the volume specified in this invention. Figure 1 The diagram shows a 2 m diameter outlet (referred to here as the suspension outlet) at the bottom of the reactor. 3 In the reactor.

[0141] A circulation pump is present on the pipeline, which pumps the suspension through the pipeline (with a pipe diameter of 84.3 mm) past a static mixer. The static mixer is 250 mm long and has a PVDF insert. The pipeline returns the suspension to the reactor at a position below the liquid surface in the middle of the reactor.

[0142] The reaction was carried out at a stirrer speed of 95 rpm while water was added to the alkali metal silicate solution to achieve pH 9, the solution volume was 1400 L, and the temperature was maintained at approximately 75°C.

[0143] Precipitation of silica:

[0144] CO2 is added via a metering point, which is located before the static mixer and has a diameter of 10 mm.

[0145] CO2 was metered into the sodium silicate solution at a pressure of 4 bar (measured in the pipeline) at a mass addition rate / flow rate of 325 g / min. Additional sodium silicate was metered in at a rate of 4 kg / min, for a total addition of 500 kg.

[0146] The suspension circulation pump attached to the pipeline section has a pump speed of 2800 rpm.

[0147] Then, reacidification is initiated by stopping the additional WGL metering and continuing the CO2 metering.

[0148] The CO2 pressure is 4 bar, and the CO2 metering rate remains at 325 g / min.

[0149] Reacidification was stopped when pH 8 was reached. The total reaction time, including the reacidification step, was approximately 189 minutes.

[0150] The total CO2 yield was calculated to be 92%, meaning that 92% of the CO2 calculated and fed into the reaction was consumed / used during precipitation, with only 8% of the remaining CO2 either released into the environment or not accurately distributed and reacted within the reaction medium. CO2 consumption was again calculated stoichiometrically. This was determined by weighing the CO2 bottles before and after the reaction, taking into account the CO2 delivered to the reactor and the remaining / unreacted CO2.

[0151] Example 4 - This utility model

[0152] A sodium silicate solution (solid sodium silicate and water) is metered and added to the volume specified in this invention. Figure 1 The diagram shows a 2000 mL reactor with an outlet (here referred to as suspension outlet 9) at the bottom of the reactor.

[0153] A circulation pump is present on the pipeline, which pumps the suspension through the pipeline (with a pipe diameter of 12 mm) past the static mixer.

[0154] In this setup, two static mixers are used in close succession. Each static mixer is 1 m long, thus using a total static mixer length of 2 m, which includes stainless steel inserts. This line returns the suspension to the reactor from the top, below the liquid surface.

[0155] The reaction was carried out at a stirrer speed of 300 rpm while water was added to the alkali metal silicate solution to achieve pH 9, resulting in a solution of 1205 mL containing 11 g WGL, while the temperature was maintained at approximately 70°C.

[0156] Precipitation of silica:

[0157] The CO2 metering point is located before the static mixer and has a diameter of 5 mm.

[0158] CO2 was metered into the sodium silicate solution at a pressure of 2.5 bar (measured in the pipeline), at a CO2 metering rate / flow rate of 0.42 g / min. Additional sodium silicate was metered in at a rate of 6 g / min, for a total addition of 555 g.

[0159] The suspension circulation pump attached to the pipeline section has a suspension flow rate of 667 mL / min.

[0160] Then, reacidification is initiated by stopping the additional WGL metering and continuing the CO2 metering.

[0161] The CO2 pressure is 2.5 bar, and the CO2 metering rate remains at 0.42 g / min.

[0162] Reacidification was stopped when pH 8 was reached. The total reaction time, including the reacidification step, was approximately 115 minutes.

[0163] The total CO2 yield was calculated to be 100%, meaning that all CO2 calculated and fed into the reaction was consumed / used during the precipitation process. CO2 consumption was again calculated stoichiometrically. This was determined by weighing the CO2 bottles before and after the reaction, taking into account the CO2 fed into the reactor and the remaining / unreacted CO2.

[0164] Example 5 – This utility model

[0165] A sodium silicate solution (solid sodium silicate and water) is metered and added to the volume specified in this invention. Figure 1 The diagram shows a 2000 mL reactor with an outlet (here referred to as suspension outlet 9) at the bottom of the reactor.

[0166] A circulation pump is present on the pipeline, which pumps the suspension through the pipeline (with a pipe diameter of 12 mm) past the static mixer.

[0167] In this setup, two static mixers are used in close succession. Each static mixer is 1 m long, thus using a total static mixer length of 2 m, which includes stainless steel inserts. This line returns the suspension to the reactor from the top, below the liquid surface.

[0168] The reaction was carried out at a stirrer speed of 300 rpm while water was added to an alkali metal silicate solution to achieve pH 9, resulting in a solution volume of 1200 mL containing 11 g WGL, while the temperature was maintained at approximately 70°C.

[0169] Precipitation of silica:

[0170] The CO2 metering point is located before the static mixer and has a diameter of 5 mm.

[0171] CO2 was metered into the sodium silicate solution at a pressure of 2.5 bar (measured in the pipeline) at a mass addition rate / flow rate of 0.6 g / min. Additional sodium silicate was metered in at a rate of 8.3 g / min, for a total addition of 555 g.

[0172] The suspension circulation pump attached to the pipeline section has a suspension flow rate of 667 mL / min.

[0173] Then, reacidification is initiated by stopping the additional WGL metering and continuing the CO2 metering.

[0174] The CO2 pressure is 2.5 bar, and the CO2 metering rate remains at 0.6 g / min.

[0175] When pH 8 is reached, re-acidification is stopped. The total reaction time, including the re-acidification step, is approximately 90 minutes.

[0176] The total CO2 yield was calculated to be 100%, meaning that all CO2 calculated and fed into the reaction was consumed / used during the precipitation process. CO2 consumption was again calculated stoichiometrically. This was determined by weighing the CO2 bottles before and after the reaction, taking into account the CO2 fed into the reactor and the remaining / unreacted CO2.

[0177] Example 6 – This utility model

[0178] A sodium silicate solution (solid sodium silicate and water) is metered and added to the volume specified in this invention. Figure 1 The diagram shows a 2000 mL reactor with an outlet (here referred to as suspension outlet 9) at the bottom of the reactor.

[0179] A circulation pump is present on the pipeline, which pumps the suspension through the pipeline (with a pipe diameter of 12 mm) past the static mixer.

[0180] In this setup, two static mixers are used in close succession. Each static mixer is 1 m long, thus using a total static mixer length of 2 m, which includes stainless steel inserts. This line returns the suspension to the reactor from the top, below the liquid surface.

[0181] The reaction was carried out at a stirrer speed of 300 rpm while water was added to an alkali metal silicate solution to achieve pH 9, resulting in a solution volume of 1200 mL containing 11 g WGL, while the temperature was maintained at approximately 67°C.

[0182] Precipitation of silica:

[0183] The CO2 metering point is located before the static mixer and has a diameter of 5 mm.

[0184] CO2 was metered into the sodium silicate solution at a pressure of 2.5 bar (measured in the pipeline) at a mass addition rate / flow rate of 0.3 g / min. Additional sodium silicate was then metered in at a rate of 4.1 g / min, for a total addition of 500 g.

[0185] The suspension circulation pump attached to the pipeline section has a suspension flow rate of 667 mL / min.

[0186] Then, reacidification is initiated by stopping the additional WGL metering and continuing the CO2 metering.

[0187] The CO2 pressure is 2.5 bar, and the CO2 metering rate remains at 0.3 g / min.

[0188] Reacidification was stopped when pH 8 was reached. The total reaction time, including the reacidification step, was approximately 147 minutes.

[0189] The total CO2 yield was calculated to be 100%, meaning that all CO2 calculated and fed into the reaction was consumed / used during the precipitation process. CO2 consumption was again calculated stoichiometrically. This was determined by weighing the CO2 bottles before and after the reaction, taking into account the CO2 fed into the reactor and the remaining / unreacted CO2.

[0190] Table 1

[0191]

[0192] result

[0193] The last column in Table 1 reflects the CO2 yield, which refers to the total utilization rate of CO2 for acidification.

[0194] Therefore, Table 1 reflects the improvement in CO2 consumption at the reduced precipitation temperature, while the third column reflects the higher solid SiO2 content obtained after precipitation.

[0195] When compared with Comparative Example 1 or 2, and Example 3 of this invention, the apparatus of this invention enables an upgrade of existing silica precipitation reactors. The apparatus of this invention can achieve higher air / hour yields using CO2 as an acidifying agent. The conventional reactors of Comparative Examples 1 and 2, with CO2 metering devices inside the reactor, exhibit longer precipitation times (240 / 214 vs. 189 minutes) at the same SiO2 solid content g / L, compared to methods using reactors with bypass sections (where a static mixer is mounted externally).

[0196] The CO2 yield is significantly increased, meaning that the embodiments of this invention utilize almost all the CO2 fed in, with little release into the external environment or any unreacted CO2 left in the reaction medium. In particular, embodiments 4-6 of this invention exhibit excellent CO2 yields, where all CO2 is reacted.

[0197] As shown in Table 1, higher SiO2 solid / precipitated silica ratios were obtained at shorter reaction times (including precipitation and re-acidification). This increased yield is attributed to the use of up to 100% CO2 in the reaction medium, which enabled higher silica conversion from silicate materials.

[0198] By using this new method and reaction setup with the apparatus, it is not necessary to meter the addition of higher amounts of CO2, or to purify the gas mixture to obtain higher amounts of CO2. Example 3 of this invention is provided as a comparative example to show that even when the metered amount of CO2 added is comparable to Comparative Examples 1 and 2, a higher amount of CO2 is consumed.

Claims

1. An apparatus for preparing precipitated silica, comprising a reactor (1), a bypass section including a static mixer (5) and a pipeline (7), wherein the bypass section is located outside the reactor and connected to the reactor via the pipeline, and wherein the static mixer is configured to circulate a reaction medium back to the reactor via the pipeline.

2. The apparatus for preparing precipitated silica according to claim 1, wherein the bypass section further includes a process gas metering point (6) for metering process gas into the static mixer, and the process gas metering point (6) is located on a pipeline preceding the static mixer in the flow direction, or on the static mixer.

3. The apparatus for preparing precipitated silica according to claim 2, wherein the process gas metering point is located on the pipeline before the static mixer and near the static mixer in the flow direction.

4. The apparatus for preparing precipitated silica according to any one of claims 1 to 3, characterized in that... The bypass section contains more than one static mixer (5).

5. The apparatus for making precipitated silica according to claim 4, characterized in that The more than one static mixer (5) is located one after another on the pipeline.

6. The apparatus for making precipitated silica according to any one of claims 1 to 3, characterized in that The reactor includes a water metering point (3) and a silicate solution metering point (4).

7. The apparatus for making precipitated silica according to claim 6, characterized in that The water metering point (3) and the silicate solution metering point (4) are located on the top or side of the reactor.

8. The apparatus for making precipitated silica according to any one of claims 1 to 3, characterized in that The reactor includes an outlet (9) for releasing an alkali metal silicate solution from the reactor.

9. The apparatus for making precipitated silica according to claim 8, characterized in that The outlet (9) is located at the bottom of the reactor.

10. The apparatus for preparing precipitated silica according to any one of claims 1 to 3, characterized in that... The reactor contains dispersing blades.

11. The apparatus for making precipitated silica according to any one of claims 1 to 3, characterized in that The reactor includes a stirrer.

12. The apparatus for making precipitated silica according to any one of claims 1-3, characterized in that The bypass section includes a pump (8) arranged on the pipeline.

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