A silicon dioxide particle size control process

Abstract

The present invention discloses a method for controlling the particle size of silicon dioxide, wherein the silicon dioxide particles are formed by drying silicon dioxide slurry through a pressure spray drying tower; the pressure spray drying tower comprises a nozzle and a spray plate arranged at the nozzle discharge port, and the spray plate is provided with a spray plate through hole; the particle size control of the silicon dioxide particles is mainly achieved by adjusting the aperture of the spray plate through hole, the spray pressure of the pressure spray drying tower, the solid content of the silicon dioxide slurry, and the viscosity of the silicon dioxide slurry. The technical solution of the present invention adjusts the solid content of the slurry, the viscosity and temperature of the slurry, the aperture of the spray plate, the spray pressure and other factors during the pressure drying spray stage of silicon dioxide, and at the same time adds a fluidized bed secondary drying process, so as to realize the controllable particle size distribution of the final product particles, and can produce products with a variety of particle size ranges to meet the various customer needs in different industries.

Description

Technical Field

[0001] The invention relates to the technical field of silicon dioxide production, in particular to a silicon dioxide particle size control process. Background Art

[0002] With the continuous expansion of the silica application industry, the requirements for products are getting higher and higher, and different users have different performance requirements for silica particles. Some users require the material particles to be as small and uniform as possible; some users require the powder to have as many large particles as possible and uniform. This requires manufacturers to be proficient in silica particle size distribution control technology and be able to produce products with different particle size distribution ranges to meet different industry needs and customer requirements.

[0003] At present, in the production process of pressure spray-dried silica, the particle size distribution of the obtained material is not ideal, the particle size polarization is obvious, sometimes the particles are too large, and sometimes a large amount of fine powder is produced. The particle size distribution is very wide, and the particle size and hardness are uneven, which cannot meet the needs of high-end users. Particles that are too large are prone to produce a large amount of waste, increasing production costs; and too much fine powder in the product is prone to cause dust flying, which cannot meet the environmental protection requirements of customers. Summary of the invention

[0004] The present invention aims at solving the deficiencies in the prior art and provides a silicon dioxide particle size control process.

[0005] The object of the present invention is achieved in the following manner:

[0006] A method for controlling the particle size of silicon dioxide, wherein the silicon dioxide particles are formed by drying silicon dioxide slurry through a pressure spray drying tower; the pressure spray drying tower comprises a nozzle and a spray plate arranged at the nozzle outlet, and the spray plate is provided with a spray plate through hole; the particle size control of the silicon dioxide particles is mainly achieved by adjusting the aperture of the spray plate through hole, the spray pressure of the pressure spray drying tower, the solid content of the silicon dioxide slurry, and the viscosity of the silicon dioxide slurry.

[0007] As an optional solution of the technical solution of the present invention, the pressure-type spray drying tower includes a tower body, a nozzle, a high-pressure feed pump, a hot air distributor, a bag dust collector and an induced draft fan. The pressure of the high-pressure feed pump forms fine droplets of the silica material through the nozzle, which are then quickly dried through sufficient heat exchange with the hot air to obtain the silica particles.

[0008] As an optional scheme of the technical solution of the present invention, the water content of the silicon dioxide particles after being dried in the pressure spray drying tower is 11.4% to 12.6%. After the silicon dioxide particles are secondary dried in a fluidized bed, the water content is reduced to 5.2% to 5.9% and then discharged from the discharge port of the fluidized bed.

[0009] As an optional scheme of the technical solution of the present invention, the fluidized bed includes a bed, a sieve plate, a heater, and a blower; the silica particles after pressure spray drying enter the fluidized bed through the feed port of the fluidized bed, and the filtered clean air is heated by the heater and then sent to the bottom of the fluidized bed by the blower, and contacts with the silica particles through the sieve plate to form a fluidized state to achieve gas-solid heat and mass exchange to achieve the purpose of drying.

[0010] As an optional scheme of the technical solution of the present invention, when the particle size of the silica is 20-60 mesh, the aperture of the spray plate through hole is 2.6-3.0 mm, the spray pressure of the pressure spray drying tower is 1.2-1.5 MPa, the solid content of the silica slurry is 25-30%, the viscosity of the silica slurry is <500 CPs, and the temperature in the fluidized bed is 32-36°C.

[0011] As an optional scheme of the technical solution of the present invention, when the silica particle size is 40-80 mesh, the aperture of the spray plate through hole is 2.1-2.5 mm, the spray pressure of the pressure spray drying tower is 1.7-2.2 MPa, the solid content of the silica slurry is 22-25%, the viscosity of the silica slurry is 500-1000 CPs, and the temperature in the fluidized bed is 32-36°C.

[0012] As an optional scheme of the technical solution of the present invention, when the silica particle size is 60-150 mesh, the aperture of the spray plate through hole is 1.6-2.0 mm, the spray pressure of the pressure spray drying tower is 2.5-3.5 MPa, the solid content of the silica slurry is 10-20%, the viscosity of the silica slurry is 1000-2000 CPs, and the temperature in the fluidized bed is 52-56°C.

[0013] The beneficial effects of the present invention are:

[0014] The technical solution of the present invention adjusts factors such as the solid content of the slurry, the slurry viscosity and temperature, the aperture of the spray plate, the spray pressure, etc. during the pressure drying and spraying stage of silicon dioxide, and at the same time adds a fluidized bed secondary drying process, so that the particle size distribution of the final product can be controlled, and products with a variety of particle size ranges can be produced to meet the various customer needs in different industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0016] Figure 1 Schematic diagram of the nozzle structure in an embodiment of the present invention.

[0017] Figure 2 Schematic diagram of the structure of the fluidized bed in an embodiment of the present invention.

[0018] Reference numerals:

[0019] 10-nozzle seat; 11-swirl plate; 12-spray plate; 13-housing; 14-blocking plate; 15-nozzle chamber; 20-fluidized bed; 21-bed; 22-sieve plate; 23-discharge port; 24-air inlet; 25-feed port. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0021] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0022] In the description of the embodiments, unless otherwise clearly specified and limited, the terms "disposed", "connected" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or it can be connected through an intermediate medium, or it can be a communication between the two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0023] Pressure spray drying tower is a commonly used equipment for synthetic silicon dioxide to complete drying and granulation at the same time. The whole drying system consists of drying tower, nozzle, high-pressure feed pump, hot air distributor, bag dust collector, induced draft fan, etc. The working process is to use the pressure of the high-pressure feed pump to atomize the silicon dioxide slurry into fine droplets through the nozzle. The droplets are quickly dried for more than ten seconds to tens of seconds after sufficient heat exchange with the hot air, so as to obtain fine granular silicon dioxide products. Spray drying directly affects the forming performance, particle size, particle uniformity, particle strength, etc. of silicon dioxide particles, so this process is crucial in the production process of silicon dioxide.

[0024] like Figure 1 As shown, the nozzle mainly includes a nozzle seat 10, a swirl plate 11, a shell 13, a baffle 14 and a nozzle cavity 15 surrounded by the shell. The nozzle is arranged on a pressure spray drying tower through the nozzle seat 10. A spray plate 12 is placed at the discharge port of the nozzle. A spray plate through hole is opened in the middle of the spray plate 12. During actual operation, the spray plate 12 with different apertures of the spray plate through hole can be replaced according to actual needs.

[0025] The invention controls the particle size distribution by adjusting the relevant parameters of the slurry itself, adjusting the aperture of the spray plate through hole and the spray pressure, and removing fine powder through the fluidized bed technology.

[0026] 1. Technical solutions

[0027] 1) Regulate the particle size distribution and particle strength by adjusting the slurry parameters

[0028] ①Slurry solid content: According to the test, when the aperture of the spray piece and the spray pressure remain unchanged, the solid content of the slurry increases, the particles obtained by spraying become larger, the proportion of particles above 60 mesh increases, the proportion of fine powder below 100 mesh decreases, the particle size distribution becomes narrower, the product particle size is overall coarse, and at the same time, the strength of the particles is improved. It is suitable for the production of products with coarse particle size and high output.

[0029] ② Slurry viscosity: Under the premise that the solid content of the slurry, the aperture of the spray piece and the spray pressure remain unchanged, the viscosity of the slurry is adjusted by adding different types of surface modifiers to the slurry. It is found that the slurry with higher viscosity has larger particle size after spray drying, narrower particle size distribution, and coarser product particle size as a whole, which is suitable for the production of medium-coarse particle size products. Thickening surface modifiers can be polyacrylamide or sodium hydroxide solution to increase the viscosity of the slurry; viscosity-reducing surface modifiers can be sodium metasilicate or acetic acid solution to reduce the viscosity of the slurry.

[0030] ③ Slurry temperature: The slurry is heated during the ongoing spraying process. When the temperature rises from 35°C to 55°C and stabilizes, the resulting dry product is finer overall, with an increased proportion of fine powder below 100 mesh, but the particle size distribution does not change significantly, making it suitable for the production of products with medium to fine particle sizes.

[0031] 2) Control particle size distribution by adjusting the nozzle aperture and spray pressure:

[0032] ① When other process and equipment parameters are constant, the aperture of the spray piece increases, the droplet diameter is large, the particles after drying are coarse, and the particle size distribution is narrow; the aperture of the spray piece decreases, the droplet diameter is small, the particles after drying are fine, and the particle size distribution is wide. In production, according to the different uses of silica, spray pieces with different apertures can be used in combination to obtain the ideal particle size distribution.

[0033] ② When other process and equipment parameters are constant, the greater the spray pressure, the greater the proportion of fine particles in the silica material, and the wider the particle size distribution; the smaller the spray pressure, the greater the proportion of coarse particles in the material, and the narrower the particle size distribution. However, if the pressure is too low, the production capacity of the spray drying tower will decrease and the cost will increase significantly. If the spray pressure is too high, the life of the spray piece will be significantly reduced, and the particle size distribution range will drift.

[0034] Although adjusting the aperture of the spray piece and the spray pressure is the most convenient measure to control the particle size, it has certain limitations. Changing the physical and chemical properties of the slurry is more likely to solve the problem fundamentally.

[0035] 3) Control particle size distribution using fluidized bed technology:

[0036] The fluidized bed is a device that uses hot air to blow into the bed layer where wet materials are placed to fluidize the particles, thereby increasing the heat transfer coefficient and drying the materials. The fluidized bed 20 includes a bed 21, a sieve plate 22, a heater, and a blower; the silica particles after pressure spray drying enter the fluidized bed through the feed port 25 of the fluidized bed, and the filtered clean air is heated by the heater and sent to the bottom of the fluidized bed by the blower through the air inlet 24, and contacts the silica particles through the sieve plate to form a fluidized state to achieve gas-solid heat and mass exchange to achieve the purpose of drying. The material is discharged from the discharge port 23 after being dried again. The purpose of using fluidized technology is to perform secondary drying of silica particles. Under an adjustable negative pressure state, according to the different requirements of different customers for the particle size distribution of the product, the fine powder in the silica microbeads is selectively removed to make the particle size more uniform and the distribution narrower; at the same time, the obtained silica fine powder can be targetedly sold as a derivative special particle size product to increase added value.

[0037] 2. Technical Effect

[0038] 1) By using a larger spray plate aperture (2.6-3.0 mm), a lower spray pressure (1.2-1.5 MPa), a higher slurry solid content (25-30%), and a lower slurry viscosity (<500 CPS), a core particle size of 20-60 mesh can be obtained. This range accounts for more than 80% of the particle size distribution, which is a narrow particle size distribution. The commercially available product accounts for about 60% of this range. This solution can produce large-particle silica, which is used as an environmentally friendly reinforcing agent for rubber products, especially high-performance tires.

[0039] 2) Selecting a medium-coarse spray plate aperture (2.1-2.5 mm), a moderate spray pressure (1.7-2.2 MPa), a normal slurry solid content (22-25%), and a normal slurry viscosity (<1000 CPS) can obtain a core particle size of 40-80 mesh. This range accounts for more than 80% of the particle size distribution, which is a narrow particle size distribution. The commercially available product accounts for less than 70% of this range. This solution can produce medium-sized silica particles, which are used as adsorption carriers for oily items such as rubber additives, vitamins, and acidulants.

[0040] 3) By selecting a smaller spray plate aperture (1.6-2.0 mm), a higher spray pressure (2.5-3.5 MPa), a lower slurry solid content (18-20%), and a higher slurry viscosity (1000-2000 CPS), a core particle size of 60-150 mesh can be obtained. This range accounts for more than 85% of the particle size distribution, which is a relatively wide particle size distribution. The commercially available products account for less than 65% of this range. This solution can produce small-particle silicon dioxide with a wide particle size distribution, which can be used as a carrier diluent for liquid feed additives such as choline chloride, ethoxyquin, and allicin.

[0041] The effects of the present invention are specifically described below through several embodiments.

[0042] Embodiment 1,

[0043] The solid content of silicon dioxide slurry is 27.0%, the aperture of the spray plate is 3.0mm, the spray pressure is 1.5MPa, the slurry viscosity is 500CPS, the slurry temperature is 35℃, and the particle size distribution of the product is measured as follows:

[0044] Above 20 mesh: 2.1%;

[0045] 20-40 mesh: 35.3%;

[0046] 40-60 mesh: 46.8%;

[0047] Below 60 mesh: 15.8%.

[0048] Embodiment 2,

[0049] The solid content of silicon dioxide slurry is 23.6.0%, the aperture of the spray plate is 2.4mm, the spray pressure is 2.0MPa, the slurry viscosity is 880CPS, the slurry temperature is 35℃, and the particle size distribution of the product is measured as follows:

[0050] Above 40 mesh: 7.6%;

[0051] 40-60 mesh: 40.5%;

[0052] 60-80 mesh: 41.7%;

[0053] Below 80 mesh: 10.82.

[0054] Embodiment 3,

[0055] The solid content of silicon dioxide slurry is 19.2%, the aperture of the spray plate is 1.8mm, the spray pressure is 3.5MPa, the slurry viscosity is 1600CPS, the slurry temperature is 55℃, and the particle size distribution of the product is measured as follows:

[0056] Above 60 mesh: 3.8%;

[0057] 60-100 mesh: 47.7%;

[0058] 100-150 mesh: 40.9%;

[0059] Below 150 mesh: 7.6%.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in the field to implement; when the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

Claims

1. A method for controlling silicon dioxide particle size, characterized in that: The silicon dioxide particles are formed by drying silicon dioxide slurry in a pressure spray drying tower; the pressure spray drying tower comprises a nozzle and a spray plate arranged at the nozzle outlet, and the spray plate is provided with a spray plate through hole; The particle size control of the silicon dioxide particles is achieved by adjusting the aperture of the spray plate through hole, the spray pressure of the pressure spray drying tower, the solid content of the silicon dioxide slurry and the viscosity of the silicon dioxide slurry; The pressure spray drying tower comprises a tower body, a nozzle, a high-pressure feed pump, a hot air distributor, a bag dust collector and an induced draft fan. The pressure of the high-pressure feed pump forms fine droplets of the silica material through the nozzle, and then the droplets are rapidly dried by sufficient heat exchange with the hot air, thereby obtaining the silica particles. The moisture content of the silicon dioxide particles after being dried in the pressure spray drying tower is 11.4% to 12.6%. The silicon dioxide particles are secondary dried in a fluidized bed to reduce the moisture content to 5.2% to 5.9% and then discharged from the discharge port of the fluidized bed; When the particle size of the silicon dioxide is 20-60 mesh, the aperture of the spray plate through hole is 2.6-3.0 mm, the spray pressure of the pressure spray drying tower is 1.2-1.5 MPa, the solid content of the silicon dioxide slurry is 25-30%, the viscosity of the silicon dioxide slurry is less than 500 CPs, and the temperature in the fluidized bed is 32-36°C; When the silica particle size is 40-80 mesh, the aperture of the spray plate through hole is 2.1-2.5 mm, the spray pressure of the pressure spray drying tower is 1.7-2.2 MPa, the solid content of the silica slurry is 22-25%, the viscosity of the silica slurry is 500-1000 CPs, and the temperature in the fluidized bed is 32-36°C; When the silica particle size is 60-150 mesh, the aperture of the spray plate through hole is 1.6-2.0 mm, the spray pressure of the pressure spray drying tower is 2.5-3.5 MPa, the solid content of the silica slurry is 10-20%, the viscosity of the silica slurry is 1000-2000 CPs, and the temperature in the fluidized bed is 52-56°C; The fluidized bed includes a bed, a sieve plate, a heater, and a blower; the silica particles after pressure spray drying enter the fluidized bed through the feed port of the fluidized bed, and the filtered clean air is heated by the heater and then sent to the bottom of the fluidized bed by the blower, and contacts the silica particles through the sieve plate to form a fluidized state to achieve gas-solid heat and mass exchange to achieve the purpose of drying.

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