1. The utility model provides a regulation and control flame method synthetic silica particle size's device, its characterized in that includes that combustor (1) and cover establish guard shield (2) outside combustor (1), guard shield (2) include guard shield pipeline section (2.1) and connect in guard shield pipeline section (2.1) top, with guard shield pipeline section (2.1) inside communicating shrink pipeline section (2.2), the cross sectional area of shrink pipeline section (2.2) is followed supreme diminishing gradually down, and open at the top of shrink pipeline section (2.2) has collection mouth (2.3), it is equipped with updraft ventilator (3) outward to collect mouth (2.3).

2. Device for regulating the particle size of silica synthesized by flame method according to claim 1, characterized in that the cross section of the convergent pipe section (2.2) is circular with a diameter of 0.5cm to 50 cm.

3. Device for regulating the particle size of silica synthesized by flame method according to claim 1 or 2, characterized in that the convergent tube section (2.2) comprises a plurality of convergent tubes which are detachably connected.

4. Device for regulating the particle size of silica synthesized by flame method according to claim 1, characterized in that the constriction (2.2) is provided with a heating device (4).

5. Device for regulating the particle size of silica synthesized by flame method according to claim 4, characterized in that the heating device (4) is a heating wire arranged outside the convergent section (2.2).

6. A method for regulating the particle size of synthetic silica by flame method, characterized in that the apparatus according to any of claims 1 to 5 is used, comprising the steps of,

s1: introducing fuel, inorganic silicon-containing precursor and carrier gas into a combustor, and carrying out combustion reaction to generate silicon dioxide particles;

s2: the silica particles enter the contraction pipe section under the action of buoyancy and an exhaust fan, and are continuously collided and condensed to form silica particles with larger sizes.

7. The method for modulating the size of silica particles synthesized by the flame process of claim 6, wherein the fuel is one or more of hydrogen, methane, ethane, propane, and butane.

8. The method for regulating the size of silica particles synthesized by flame method according to claim 6, wherein the inorganic silicon-containing precursor is silicon tetrachloride and/or SiH₄。

9. The method of claim 6 or 8, wherein the inorganic silicon-containing precursor is fed to the burner at a flow rate of 2 to 4 slm.

10. The method for regulating the size of silica particles synthesized by flame method as claimed in claim 6, wherein the temperature of the outer wall surface of the contraction pipe section is 200-300 ℃.

Background

The high-purity silicon dioxide particles are basic materials of high and new technology industries such as semiconductors, photovoltaics, optical fiber communication, aerospace and the like, and are very important strategically. Among them, the semiconductor industry accounts for the largest proportion, but the productivity is insufficient in China at present, the gap is large, and the import is mainly relied on. The synthesis method of the high-purity silicon dioxide particles mainly comprises a flame method, a gel sol method, natural crystal processing, deep purification of quartz minerals and the like, wherein the flame method has great advantages in the aspects of raw materials, process, cost and quality, and domestic research institutions have accumulated certain technologies on the synthesis of the high-purity silicon dioxide particles by the flame method.

The synthesis of silica particles by flame method (or combustion method) refers to the process of reacting silicon-containing precursors (such as silicon tetrachloride, organosilicon, etc.) in high-temperature flame to generate silica particles. The particles synthesized by the flame method have the advantages of wide raw material source, simple process, high purity and high yield, and can realize batch production. However, the silica particles produced by the flame method have high-reactivity hydrophobic groups on the particle surfaces and small size and particle diameter, which seriously affect the wide application in the industries of semiconductors, optical fiber communication and the like. For example, CN102530962A describes a method for synthesizing hydrophobic nano silica particles by flame method, which uses organosilicon as precursor, and the surface of the synthesized silica particles is hydrophobic, and the particle size is less than 10 nm.

In summary, the silica particles synthesized by the existing flame method use organosilicon as a precursor, and the surface of the synthesized particles contains hydrophobic groups (mainly methyl groups CH)₃) (ii) a Meanwhile, the prior art adopts a particle collector to collect particles, and the collector only plays a role in collecting particles and cannot change and regulate the size of the particle size.

Disclosure of Invention

Aiming at the defects that hydrophobic groups exist on the surface of particles synthesized by the prior art and the synthesized particles are small in size and are not adjustable, the invention provides a device and a method for regulating and controlling the size of the particles of silicon dioxide synthesized by a flame method.

According to the technical scheme, the device for regulating and controlling the size of the silicon dioxide particles synthesized by the flame method comprises a combustor and a shield covered outside the combustor, wherein the shield comprises a shield pipe section and a contraction pipe section which is connected above the shield pipe section and communicated with the shield pipe section, the cross section area of the contraction pipe section is gradually reduced from bottom to top, a collection opening is formed in the top of the contraction pipe section, and an air draft device is arranged outside the collection opening.

Furthermore, the cross section of the contraction pipe section is a circle with the diameter of 0.5cm-50 cm.

In particular, the convergent section may be in the form of a flare or a taper.

Furthermore, the shrinkage pipe section comprises a plurality of shrinkage pipes which are detachably connected, and the final particle size can be controlled by disassembling the shrinkage pipes.

Furthermore, the number of the shrink tubes is 3-8. In the embodiment shown in FIG. 1, the number of the shrink tubes is 5, and the shrink tubes are A-E from bottom to top and respectively correspond to a first particle length area, a second particle length area, a third particle length area, a fourth particle length area and a fifth particle length area, and the corresponding length and the upper end section diameter of each shrink tube are respectively H₁And D₁，H₂And D₂，H₃And D₃，H₄And D₄，H₅And D₅The diameter of the section of the lower end of the A shrinkage pipe is D₀Wherein D is₀＞D₁＞D₂＞D₃＞D₄＞D₅。

Further, the length of the shrinkage pipe is increased from bottom to top in sequence.

Further, in order to avoid the deposition of particles in the shrink tubing section, the shrink tubing section is provided with a heating device.

Furthermore, the heating device is a heating wire arranged outside the contraction pipe section, and can heat the wall surface of the pipeline to keep the wall surface at a proper temperature.

Preferably, the air draft device is arranged right above the collecting opening.

Further, the air draft device is an exhaust fan.

In the device, the burner is wrapped by the shield pipe section, so that the influence of external air flow on flame can be avoided, and wall surface particles can be scattered into surrounding air. The principle that the size of the particles can be increased by the contraction pipe section is that the particles grow up by continuous collision and aggregation among the particles, the contraction pipe section is in a contraction shape, the diameter of the pipe section is reduced from large to small, the probability of collision among the particles is increased after the particles enter the pipe section with the small diameter from the pipe section with the large diameter, and the small particles can be combined into large particles; the smaller the diameter of the pipe section, the greater the concentration of particles in the pipe section, the higher the probability of collision coalescence and the larger the resultant size. The wall surface of the contraction pipe section is provided with the heating wires, so that the temperature gradient can be reduced, the thermophoretic deposition of particles is reduced, and the particles are effectively prevented from being deposited on the wall surface of the pipeline.

In another aspect of the present invention, there is provided a method for regulating the size of silica particles synthesized by flame method, which comprises the following steps,

s1: introducing fuel, inorganic silicon-containing precursor and carrier gas into a combustor, and carrying out combustion reaction to generate silicon dioxide particles;

s2: the silicon dioxide particles enter the contraction pipe section under the action of buoyancy and the air draft device, and are continuously collided and condensed to form larger silicon dioxide particles.

Further, the fuel is one or more of hydrogen, methane, ethane, propane, and butane.

Further, the inorganic silicon-containing precursor is silicon tetrachloride and/or SiH₄。

Further, the carrier gas is oxygen.

Further, the flow rate of the inorganic silicon-containing precursor introduced into the combustor is 2-4 slm.

Further, the flow rate of the fuel into the combustor is 600-1000mL/min, and the flow rate of the carrier gas into the combustor is 300-600 mL/min.

Further, the air exhaust pressure of the air exhaust device is 10-300 pa.

Further, the temperature of the outer wall surface of the contraction pipe section is 200-300 ℃.

Compared with the prior art, the technical scheme of the invention has the following advantages: the purity of the silica particles synthesized by the flame method is improved, the generation of hydrophobic groups on the surfaces of the particles is reduced, the size of the silica particles is increased, and the particle size is regulated according to actual requirements.

Drawings

FIG. 1 is a schematic structural diagram of the present invention.

Description of reference numerals: 1-burner, 2-shield, 2.1-shield pipe section, 2.2-contraction pipe section, 2.3-collection port, 3-air draft device and 4-heating device.

Detailed Description

The present invention is further described below in conjunction with the following figures and specific examples so that those skilled in the art may better understand the present invention and practice it, but the examples are not intended to limit the present invention.

As shown in figure 1, the device for regulating and controlling the size of silica particles synthesized by a flame method comprises a combustor 1 and a shield 2 covered outside the combustor 1, wherein the shield 2 comprises a shield pipe section 2.1 and a contraction pipe section 2.2 connected above the shield pipe section 2.1 and communicated with the inside of the shield pipe section 2.1, the cross section area of the contraction pipe section 2.2 is gradually reduced from bottom to top, a collection opening 2.3 is formed in the top of the contraction pipe section 2.2, an air draft device 3 is arranged outside the collection opening 2.3, and a heating device 4 is arranged at the position of the contraction pipe section 2.2.

Example 1: with hydrogen H₂As fuel, silicon tetrachloride SiCl₄As a precursor, oxygen O₂The flow rates of the carrier gas are 800mL/min of hydrogen, 2.0slm of silicon tetrachloride and 430mL/min of oxygen respectively. The contraction tube is provided with A, B, C three sections from bottom to top, corresponding to H₁＝20cm，H₂＝40cm，H₃＝60cm，D₀＝15cm，D₁＝12cm，D₂＝8cm，D₃The temperature of the outer wall surface of the contraction pipe section is 200 ℃ by a heating device (heating wire) under the air exhaust pressure of 60pa which is 4 cm.

At this time, the silica particles at the outlet had an average size of about 30 to 50 μm and a methyl group content of less than 1.0ppb on the surface of the particles.

Example 2: with hydrogen H₂As fuel, silicon tetrachloride SiCl₄As a precursor, oxygen O₂The flow rates of the carrier gas are 800mL/min of hydrogen, 2.0slm of silicon tetrachloride and 430mL/min of oxygen respectively. Shrink tube fromA, B, C three sections from bottom to top, corresponding to H₁＝10cm，H₂＝20cm，H₃＝30cm，D₀＝15cm，D₁＝12cm，D₂＝8cm，D₃4cm, the air exhaust pressure is 30pa, and the heating wire enables the temperature of the outer wall surface of the contraction pipe section to be 200 ℃.

At this time, the silica particles at the outlet had an average size of about 10 to 20 μm and a methyl group content of less than 1.0ppb on the surface of the particles.

Example 3: with hydrogen H₂As fuel, silicon tetrachloride SiCl₄As a precursor, oxygen O₂The flow rates of the carrier gas are 800mL/min of hydrogen, 2.0slm of silicon tetrachloride and 430mL/min of oxygen respectively. The contraction tube is provided with A, B, C, D four sections from bottom to top, corresponding to H₁＝20cm，H₂＝40cm，H₃＝60cm，H₄＝80cm，D₀＝15cm，D₁＝12cm，D₂＝8cm，D₃＝4cm，D₄The temperature of the outer wall surface of the contraction pipe section is 200 ℃ by a heating wire under the pumping pressure of 120pa which is 2 cm.

At this time, the silica particles at the outlet had an average size of about 60 to 80 μm and a methyl group content of less than 1.0ppb on the surface of the particles.

Example 4:

with hydrogen H₂As fuel, silicon tetrachloride SiCl₄As a precursor, oxygen O₂The flow rates of the carrier gas are 800mL/min for hydrogen, 2.0slm for silicon tetrachloride and 430mL/min for oxygen respectively. The shrink tube has A, B, C, D, E five sections (as shown in fig. 1) from bottom to top, corresponding to H₁＝20cm，H₂＝40cm，H₃＝60cm，H₄＝80cm，H₅＝80cm，D₀＝15cm，D₁＝12cm，D₂＝8cm，D₃＝4cm，D₄＝2cm，D₄The temperature of the outer wall surface of the contraction pipe section is 200 ℃ by a heating wire under the suction pressure of 150pa which is 1 cm.

At this time, the silica particles at the outlet had an average size of about 70 to 100 μm and a methyl group content of less than 1.0ppb on the surface of the particles.

Example 5: with hydrogen H₂As fuel, silicon tetrachlorideSiCl₄As a precursor, oxygen O₂The flow rates of the carrier gas are 800mL/min of hydrogen, 2.0slm of silicon tetrachloride and 430mL/min of oxygen respectively. The contraction tube is provided with A, B, C three sections from bottom to top, corresponding to H₁＝20cm，H₂＝40cm，H₃＝60cm，D₀＝15cm，D₁＝12cm，D₂＝8cm，D₃4cm, the air exhaust pressure is 60pa, and the heating wire enables the temperature of the outer wall surface of the contraction pipe section to be 300 ℃.

At this time, the silica particles at the outlet had an average size of about 40 to 60 μm and a methyl group content of less than 1.0ppb on the surface of the particles.

Example 6: with hydrogen H₂As fuel, silicon tetrachloride SiCl₄As a precursor, oxygen O₂The flow rates of the carrier gas are 800mL/min of hydrogen, 4.0slm of silicon tetrachloride and 430mL/min of oxygen respectively. The contraction tube is provided with A, B, C three sections from bottom to top, corresponding to H₁＝20cm，H₂＝40cm，H₃＝60cm，D₀＝15cm，D₁＝12cm，D₂＝8cm，D₃4cm, the air exhaust pressure is 60pa, and the heating wire enables the temperature of the outer wall surface of the contraction pipe section to be 300 ℃.

At this time, the silica particles at the outlet had an average size of about 50 to 80 μm and a methyl group content of less than 1.0ppb on the surface of the particles.

According to the embodiment, the size of the silicon dioxide particles can be adjusted by adjusting the flow of the silicon tetrachloride, the number of the shrinkage pipes and the temperature and the pumping pressure of the shrinkage pipe sections; meanwhile, it is conceivable that the size of the silica particles can be adjusted by adjusting the flow rates of the fuel gas and the carrier gas, the shape parameters of the shrinkage tube, and the like.

Examples 7 to 10

On the basis of example 1, hydrogen was replaced with methane, ethane, propane and butane, respectively.

Examples 11 to 12

The flow rates of hydrogen gas were adjusted to 600mL/min and 1000mL/min, respectively, based on example 1.

Examples 13 to 14

On the basis of example 1, carrier gas O₂The flow rates of (A) and (B) were adjusted to 300mL/min and 600mL/min, respectively.

Example 15

On the basis of example 1, silicon tetrachloride is replaced by SiH₄。

Examples 16 to 17

On the basis of example 1, the evacuation pressures were adjusted to 10pa and 300 pa.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of the invention may be made without departing from the spirit or scope of the invention.