System for deacidification of fumed silica

Abstract

The present application belongs to the technical field of inorganic nanometer material production equipment, and specifically discloses a gaseous silicon dioxide deacidification system, which comprises a deacidifier, a deacidification fluidization chamber, an exhaust chamber and a tower bottom discharge chamber, a feed inlet and a gaseous phase outlet are arranged at the top of the exhaust chamber, a discharge port is arranged at the bottom of the tower bottom discharge chamber, a waste gas cooler is connected with the gaseous phase outlet of the deacidifier through a pipeline, a pressure regulating valve is arranged on the pipeline between the waste gas cooler and the deacidifier, a tower bottom heater is connected with the waste gas cooler through a pipeline, a hot air circulating valve is arranged on the pipeline between the tower bottom heater and the waste gas cooler, and the exhaust end of the tower bottom heater is communicated with the deacidifier; the vertical reverse fluidization structure is matched with a bottom dispersion cone cap, airflow is uniformly distributed, there is no local short circuit and no powder accumulation and agglomeration; the powder is fully contacted with hot and humid medium, the content of finished product hydrogen chloride is stable, the pH of the suspension meets the standard, the specific surface area retention rate is better than the national standard bottom line, and the acid value batch fluctuation is small.

Description

Technical Field

[0001] This invention belongs to the technical field of inorganic nanomaterial production equipment, specifically relating to a fumed silica deacidification system. Background Technology

[0002] Fumed silica is prepared by high-temperature hydrolysis of halosilanes. Its native particle size is 10–40 nm, with a large specific surface area and rich silanol groups on the surface. It is widely used in industries such as silicone rubber, coatings, adhesives, pharmaceuticals, and food. After the hydrolysis reaction, the powder adsorbs a large amount of free hydrogen chloride acid, resulting in a low pH in the finished product. Acidic impurities can damage the stability of downstream products, necessitating a deacidification process to ensure that the specifications meet the mandatory standard GB / T20020-2025 "Fumed Silica".

[0003] National Standard Core Constraint Indicators: Hydrogen chloride content: hydrophilic type ≤0.1% (high specific surface area ≤0.15%), hydrophobic type ≤0.1%; Suspension pH: hydrophilic 3.5–6.5, hydrophobic 3.0–8.0; The silica purity is ≥99.8%, and no impurities are introduced during the deacidification process; The specific surface area retention rate is ≥95%, avoiding high-temperature agglomeration that degrades powder performance.

[0004] Existing industrial deacidification equipment falls into two categories: One type is the fluidized bed deacidification device: hot air at the bottom fluidizes the powder, which is then neutralized with steam / alkaline gas; uneven fluidization, severe local overheating, and particle agglomeration can easily lead to a decrease in the specific surface area of ​​the product and impaired performance.

[0005] Another type is moving bed / rotary kiln deacidification: the powder moves slowly and comes into contact with the hot air in the opposite direction, resulting in uniform heating, but the residence time is long, the equipment occupies a large area, the energy consumption per unit capacity is high, the deacidification is incomplete, and the acid value of the finished product fluctuates greatly.

[0006] In addition, existing deacidification furnaces generally have drawbacks such as high waste gas treatment load, acidic gas corrosion of equipment, high product temperature after deacidification requiring additional cooling, and inability to recover and utilize heat.

[0007] Therefore, it is necessary to design a fumed silica deacidification system to solve the above problems. Summary of the Invention

[0008] The purpose of this invention is to provide a fumed silica deacidification system to solve the problems mentioned in the background art.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a fumed silica deacidification system, comprising: A deacidifier includes a deacidification fluidization chamber, an exhaust chamber, and a bottom discharge chamber. The top of the exhaust chamber is provided with a feed inlet and a gas phase outlet, and the bottom discharge chamber is provided with a discharge outlet. The exhaust gas cooler is connected to the gas phase outlet of the deacidifier via a pipeline, and a pressure regulating valve is installed on the pipeline between the exhaust gas cooler and the deacidifier. The bottom heater is connected to the exhaust gas cooler via a pipe, and a hot air circulation valve is installed on the pipe between the bottom heater and the exhaust gas cooler. The outlet of the bottom heater is connected to the deacidifier.

[0010] To reduce the temperature of the exhaust gas and ensure its safe discharge into the exhaust gas system, while also generating hot compressed air to maximize energy utilization and reduce system energy consumption, the exhaust gas cooler preferably employs a shell-and-tube heat exchanger. Compressed air is used as the refrigerant to cool the high-temperature exhaust gas discharged from the desulfurization unit. The cooled exhaust gas is then discharged into the exhaust gas system. A portion of the heated compressed air is sent to the bottom heater of the tower, and the remainder is used as process purging hot air.

[0011] By employing a single-point air intake and gas distribution structure design, the problems of airflow collision and fluidization disorder that are easily caused by multi-point air intake are avoided. The overall airflow velocity is set to 1.2 to 3 times the minimum fluidization velocity of fumed silica, which ensures sufficient fluidization and dispersion of particles while avoiding excessive airflow velocity that would cause a large number of particles to be carried out, thus reducing material loss. Preferably, the mixture of hot air heated by the bottom heater and water vapor is used as the deacidification medium, wherein the water vapor accounts for 20% to 60% of the mass. The deacidification medium is sent into the deacidification fluidization chamber through the single-point air intake of the deacidifier, flows uniformly upward through the deacidification reaction section through the dispersion structure, and forms a counter-contact with the downward-moving fumed silica particles. The water vapor reacts with the free hydrogen chloride on the particle surface, and the gaseous acid is carried out of the reaction system by the hot air.

[0012] The electric heating rod bundle plate is used to stabilize and reinforce the electric heating tubes. The electric heating precisely controls the temperature to ensure that the internal temperature of the deacidification reaction section is stably maintained within the set range of 400-650℃, with temperature fluctuations controlled within ±10℃. Preferably, multiple sets of electric heating tubes are vertically arranged inside the deacidification fluidization chamber. The upper end of the exhaust chamber is provided with the electric heating rod bundle plate. The exhaust chamber is provided with an enlarged section. The upper part of the exhaust chamber is connected to an explosion-proof junction box. A conical wind cap is installed inside the bottom discharge chamber of the tower.

[0013] In order to pre-disperse the deacidification medium entering the deacidifier, and at the same time, the fumed silica is blown loose by the rising airflow when it flows downward around the dispersion cap, which can effectively prevent the agglomeration of fumed silica particles and ensure that the particles are in full contact with the deacidification medium, preferably, the bottom of the deacidifier is designed as a conical structure, the discharge port is located at the bottom center of the cone, and multiple thermometers are arranged in the deacidification fluidization chamber, with the insertion depth able to enter the internal fluidization chamber.

[0014] To ensure a stable and controllable feed flow rate, preferably, the feed inlet is at the same height as the gas phase outlet, and the powdered fumed silica raw material is quantitatively fed into the deacidification fluidization chamber from the feed inlet through a rotary feed valve or a discharge regulating valve.

[0015] To ensure good pre-dispersion effect, preferably, the bottom circle diameter of the conical wind cap is 30-100cm, and the included angle on both sides is 90-140 degrees.

[0016] To reduce the risk of acid gas leakage, preferably, the pressure regulating valve connected to the gas phase outlet controls the pressure range inside the deacidifier to remain stable between -10 and 0 mbar, ensuring that the entire deacidification process is under a slightly negative pressure.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. The vertical reverse fluidization structure, combined with the bottom dispersion cone, ensures uniform airflow distribution, eliminates local short circuits and powder agglomeration; the powder is in full contact with the hot and humid medium, resulting in stable hydrogen chloride content in the finished product and pH compliance of the suspension; the specific surface area retention rate is better than the national standard minimum, and the acid value fluctuates little from batch to batch.

[0018] 2. By using a waste heat recovery structure, the high-temperature exhaust gas discharged from the top of the tower is used to preheat the compressed air. The preheated compressed air is then used as the bottom deacidification medium to enter the system. Compared with traditional deacidification furnaces without waste heat recovery, the energy consumption per unit product is reduced, and the cost advantage under large-scale production is obvious.

[0019] 3. The overall structure is a vertical single-stage tower, which is simpler in structure and occupies less space compared to multi-stage deacidification equipment and horizontal rotary kilns. All easily corroded parts are made of corrosion-resistant alloy materials and are treated with anti-corrosion measures. The core components adopt a high-temperature corrosion-resistant explosion-welded composite structure, resulting in a low equipment failure rate and lower daily maintenance workload and costs compared to traditional equipment.

[0020] 4. The design of single-point deacidification medium feeding combined with continuous feeding and discharging can be directly connected to the existing synthesis process of fumed silica production without the need for large-scale modification of the existing production line. It has strong adaptability and can be used for new production lines or for upgrading and replacing existing deacidification equipment. The adjustable power and temperature range covers the deacidification needs of different types of fumed silica, making it more adaptable. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall front section structure of the deacidifier of the present invention; Figure 2 This is a schematic diagram of the deacidification system of the present invention; In the diagram: 1. Feed inlet; 2. Electric heating rod bundle plate; 3. Explosion-proof junction box; 4. Gas phase outlet; 5. Expansion section; 6. Deacidification fluidization chamber; 7. Electric heating tube; 8. Exhaust chamber; 9. Conical wind cap; 10. Bottom discharge chamber; 11. Discharge port. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example: Please refer to Figures 1 to 2 The present invention provides a technical solution: the fumed silica deacidification system consists of a deacidifier, a waste gas cooler, a pressure regulating valve, a bottom heater, a hot air circulation valve, supporting pipelines and automatic control components; the deacidifier is a vertical single-stage counter-current fluidized tower, which is divided into three sections from top to bottom: exhaust chamber 8, deacidification fluidization chamber 6, and bottom discharge chamber 10.

[0024] Exhaust chamber 8: An enlarged section 5 is set at the top to reduce the exhaust gas flow velocity and reduce powder entrainment; the top is arranged with the feed inlet 1 and the gas phase outlet 4 at the same height; the upper end of the exhaust chamber is equipped with an electric heating rod bundle tube plate 2, and the outer side is equipped with an explosion-proof junction box 3; the feed inlet 1 is equipped with a feeding regulating valve to realize quantitative feeding.

[0025] Deacidification fluidization chamber 6: 42 electric heating tubes 7 are vertically arranged inside, and the material is Inconel 600 seamless steel pipe; 5 thermometers are installed in deacidification fluidization chamber 6, and the temperature probes are inserted into the interior of deacidification fluidization chamber 6 to determine the material level in the tower by temperature distribution; the volume of deacidification fluidization chamber 6 ensures that the material stays for 45 minutes.

[0026] The bottom discharge chamber 10 is tapered downwards, with a discharge port 11 at the center of the bottom of the cone. A conical wind cap 9 is installed at the top of the cone, with a diameter of 50cm and a cone angle of 100°. The inner wall of the entire deacidifier in contact with the high-temperature acidic medium adopts a 310S explosion-welded composite corrosion-resistant alloy structure.

[0027] Exhaust gas cooler: shell and tube heat exchanger, using ambient temperature compressed air as the refrigerant.

[0028] Pressure regulating valve: installed between the gas phase outlet 4 of the deacidifier and the waste gas cooler, to regulate the pressure inside the deacidifier to stabilize at -5mbar.

[0029] Bottom heater: Receives hot compressed air after heat exchange from the exhaust gas cooler, mixes it with deionized water vapor to form a deacidification medium, the water vapor content of the medium is 40%, and the preheating temperature is 120℃; the medium is sent into the fluidization chamber from a single point at the bottom of the tower, and the airflow velocity is twice the minimum fluidization velocity of silica.

[0030] Hot air circulation valve: It splits the hot compressed air after heat exchange, one path is sent to the bottom heater of the tower to prepare the deacidification medium, and the other path is sent out as process purging hot air.

[0031] The process flow of this invention: Step 1: Feeding The initial crude fumed silica produced in the synthesis process is quantitatively conveyed through the feed inlet 1 and the feed flow rate is stably controlled by the pressure difference before and after the valve. The feed inlet 1 and the gas phase outlet 4 are arranged at the same height to avoid the feed airflow from directly short-circuiting into the gas phase outlet 4 and causing powder loss.

[0032] Step 2: Deacidification medium Ambient temperature compressed air is sent into the shell side of the exhaust gas cooler, where it exchanges heat with the high temperature acidic exhaust gas in the tube side and is heated to 120°C. A portion of the hot air is sent to the bottom heater of the tower through the hot air circulation valve and mixed with a certain amount of deionized water vapor to prepare a standard deacidification medium. The medium enters the tower from a single point at the bottom of the deacidifier tower, and is first pre-dispersed by a 50cm diameter conical wind cap 9 to eliminate the problems of single-point air inlet flow deviation and airflow collision, and then passes evenly upward through the entire deacidification fluidization chamber 6.

[0033] Step 3: Reverse fluidized bed deacidification reaction The powder slowly settles downwards from the feed inlet 1, while the hot and humid deacidification medium flows counter-currently from bottom to top. The particles are loosened and fluidized by the airflow, without accumulation or local agglomeration. Under a constant temperature environment of 480℃, the free hydrogen chloride adsorbed on the surface of the powder undergoes a displacement reaction with water vapor to generate gaseous hydrogen chloride, which enters the exhaust chamber at the top of the tower with the rising airflow. The entire process operates under slight negative pressure to avoid leakage of acidic gases that could contaminate the equipment and the environment.

[0034] Step 4: Waste heat recovery and heat exchange The high-temperature exhaust gas carrying acidic gases first undergoes pre-heat exchange with the newly introduced low-temperature powder in the expansion section 5 to initially reduce the exhaust gas temperature. Subsequently, the exhaust gas enters the shell-and-tube exhaust gas cooler to exchange heat with compressed air. After the exhaust gas is cooled down, it is sent to the downstream exhaust gas treatment system. The compressed air that has been heated up after heat exchange is recycled to reduce the energy consumption of the bottom heater. The electric heating tube 7 dynamically adjusts the heating power based on the multi-point temperature measurement data of the deacidification fluidization chamber 6 to compensate for the heat loss of the system and stabilize the reaction temperature range.

[0035] Step 5: Discharge The deacidified silica powder falls into the conical cavity at the bottom of the tower. The system monitors the internal material level in real time through the tower pressure difference and automatically adjusts the discharge port regulating valve to ensure that the discharge rate matches the feed rate and that the material is discharged continuously and stably.

[0036] Finished product testing: Hydrogen chloride content 0.038%, suspension pH=4.2 conforms to GB / T20020-2025 hydrophilic Class A product standard; specific surface area retention rate 98.7%, higher than the national standard minimum requirement of 95%; unit product energy consumption is reduced by 31% compared with traditional rotary kilns without waste heat recovery; the entire set of equipment has been running continuously for 12 months, and there are no obvious corrosion or leakage phenomena in the tower body, electric heating tubes, and conical wind caps.

[0037] As can be seen from the above description, the present invention has the following beneficial effects: compressed air is preheated by recovering the waste heat of high-temperature waste gas through the waste gas cooler, and mixed with water vapor to form a wet heat deacidification medium. The medium is introduced from a single point at the bottom of the tower and evenly distributed through the conical wind cap 9 before flowing upward; the raw material powder falls continuously from the equal-height feed port at the top of the tower, and the two are in full contact in opposite directions to complete the deacidification reaction; the high-temperature waste gas containing hydrogen chloride enters the waste gas cooler to recover heat and is then sent to the waste gas system for treatment; the qualified deacidified powder is continuously discharged from the conical discharge port 11 at the bottom of the tower; the system achieves fully automatic continuous and stable operation through micro negative pressure control, multi-point temperature measurement, and tower pressure difference material level monitoring, and simultaneously solves the defects of traditional equipment such as agglomeration, uneven deacidification, high energy consumption, and severe corrosion.

[0038] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0039] The above description is only used to illustrate the technical solution of the present invention and is not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention, as long as they do not depart from the spirit and scope of the technical solution of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A fumed silica deacidification system, characterized in that: include: Deacidifier; It includes a deacidification fluidization chamber (6), an exhaust chamber (8) and a bottom discharge chamber (10). The top of the exhaust chamber (8) is provided with a feed inlet (1) and a gas phase outlet (4), and the bottom discharge chamber (10) is provided with a discharge outlet (11). The exhaust gas cooler is connected to the gas phase outlet (4) of the deacidifier via a pipe, and a pressure regulating valve is installed on the pipe between the exhaust gas cooler and the deacidifier. The bottom heater is connected to the exhaust gas cooler via a pipe, and a hot air circulation valve is installed on the pipe between the bottom heater and the exhaust gas cooler. The outlet of the bottom heater is connected to the deacidifier.

2. The fumed silica deacidification system according to claim 1, characterized in that: The exhaust gas cooler adopts a shell-and-tube heat exchanger, using compressed air as the refrigerant to cool the high-temperature exhaust gas discharged from the deacidifier. The cooled exhaust gas is discharged to the exhaust gas system. Part of the heated compressed air after heat exchange is sent to the bottom heater of the tower, and the remainder is used as process purging hot air.

3. The fumed silica deacidification system according to claim 1, characterized in that: The mixture of hot air and water vapor heated by the bottom heater of the tower is used as the deacidification medium, wherein the water vapor accounts for 20-60% of the mass. The deacidification medium is sent into the deacidification fluidization chamber (6) through the single-point air inlet of the deacidifier, flows uniformly upward through the deacidification reaction section through the dispersion structure, and forms a counter-contact with the downward moving gaseous silica particles. The water vapor reacts with the free hydrogen chloride on the particle surface, and the gaseous acid is carried out of the reaction system by the hot air.

4. The fumed silica deacidification system according to claim 1, characterized in that: The deacidification fluidization chamber (6) is vertically arranged with multiple sets of electric heating tubes (7), the upper end of the exhaust chamber (8) is provided with an electric heating rod bundle plate (2), the exhaust chamber (8) is provided with an enlarged section (5), the upper part of the exhaust chamber (8) is connected to an explosion-proof junction box (3), and the bottom discharge chamber (10) is equipped with a conical wind cap (9).

5. The fumed silica deacidification system according to claim 1, characterized in that: The bottom of the deacidifier is designed as a cone structure, and the discharge port (11) is located at the bottom center of the cone. Multiple thermometers are arranged in the deacidification fluidization chamber (6), and the insertion depth can reach the internal fluidization chamber.

6. The fumed silica deacidification system according to claim 1, characterized in that: The feed inlet (1) is at the same height as the gas phase outlet (4). Powdered gas phase silica raw material is quantitatively fed into the deacidification fluidization chamber (6) from the feed inlet (1) through a rotary feed valve or a discharge regulating valve.

7. The fumed silica deacidification system according to claim 1, characterized in that: The bottom circle diameter of the conical wind cap (9) is 30-100cm, and the included angle between the two sides is 70-140 degrees.

8. The fumed silica deacidification system according to claim 1, characterized in that: The pressure regulating valve connected to the gas phase outlet (4) controls the pressure range inside the deacidifier to be stable between -10 and 0 mbar, ensuring that the entire deacidification process is in a slightly negative pressure state.

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