JP2005043002A - Burner for deposition, and manufacturing method of silica soot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a burner for deposition, and a manufacturing method of silica soot capable of synthesizing the silica soot (a deposit of silica particulates) mainly composed of silica obtained by combustion reaction of raw material gas containing a silicon compound at a high yield and deposition speed. <P>SOLUTION: In the burner for deposition having a raw material gas blowout opening, and gas blowout openings on both sides of the raw material gas blowout opening, the raw material gas blowout opening is like a slit with an aspect ratio of 20 or more, and a gas jetting angle θ<SB>1</SB>of a gas blowout opening with the largest gas linear speed of the gas blowout openings provided on both sides of the raw material gas blowout opening spreads outward at an angle of 0.5-20° with respect to a jetting direction of the raw material gas. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a deposition burner used in the production of an optical fiber preform, and in particular, a deposition burner excellent in the deposition rate and yield of a silica-based compound produced by a combustion reaction of a raw material gas containing a silicon compound. And a method for producing silica soot.

  In order to burn the source gas and deposit silica soot on the target surface efficiently, the silicon oxide powder generated in the flame needs to move toward and adhere to the target surface. It is said that the thermophoresis effect greatly affects this phenomenon. The thermophoresis effect refers to a phenomenon in which fine particles drifting in a space with a temperature gradient move to a low temperature side, and the effect increases as the temperature gradient increases.

In order to make the thermophoresis effect work effectively, it is necessary that a flame (hereinafter referred to as a raw material flame) containing silicon oxide powder generated by a combustion reaction of the raw material gas flows as thinly as possible on the target surface. The flame at this time is preferably a laminar flame.
As a burner suitable for this purpose, a concentric multi-tube burner is generally used. This burner has a structure in which a gas containing a raw material is ejected from a central gas outlet, and a combustion gas such as hydrogen or oxygen is ejected from an outer outlet.

When the above burner is used, a laminar raw material flame can be obtained relatively easily. However, it is difficult for the burner having this structure to flow a large amount of source gas due to the following problems.
That is, when the flow rate of the source gas is increased for the purpose of increasing the deposition rate, the Reynolds number increases because the gas linear velocity increases, and a turbulent flame tends to occur. On the other hand, if the gas linear velocity is decreased by increasing the diameter of the gas outlet, the thickness of the raw material flame on the target surface is increased, the deposition efficiency is lowered, and the yield is likely to be deteriorated.

  In order to solve this problem, it has been proposed to make the gas outlet of the burner elliptical or rectangular (see Patent Document 1). According to this proposal, since the spread of the raw material flame on the target surface can be controlled by the size of the short axis of the outlet, it is possible to flow a large amount of raw material gas, and the deposition rate and yield are improved. Yes. However, when the aspect ratio of the gas outlet is increased, there is a problem that the flame is easily disturbed and the performance of the burner cannot be exhibited sufficiently.

Japanese Patent Laid-Open No. 04-260616

  In view of the above problems, the present invention is for deposition capable of synthesizing silica soot (silica fine particle deposit) mainly composed of silica obtained by combustion reaction of a raw material gas containing a silicon compound at a high yield and a high deposition rate. It aims at providing the manufacturing method of a burner and a silica soot.

A first invention is a burner having a source gas outlet and gas outlets on both sides thereof, wherein the source gas outlet has a slit shape with an aspect ratio of 20 or more, and gas outlets provided on both sides of the burner. Among them, the gas injection angle θ ₁ of the gas outlet having the highest gas linear velocity is spread outward at an angle of 0.5 to 20 ° with respect to the injection direction of the raw material gas. It is.

A second invention is a burner having a source gas outlet and gas outlets on both sides thereof, the source gas outlet having a slit shape with an aspect ratio of 20 or more, and a gas injected from the source gas outlet The deposition burner is characterized in that the flow spreads at an angle θ ₂ of 0.5 to 20 ° in the longitudinal direction of the slit, and the gas introduction path of the raw material gas outlet is on the side in the longitudinal direction of the slit. A structure having a tapered portion substantially widened at an angle θ ₃ of 0.5 to 20 ° is preferable.

A third invention is a burner having a source gas outlet and gas outlets on both sides thereof, the source gas outlet having a slit shape with an aspect ratio of 20 or more, and a gas line at the center of the source gas outlet fast and V _O, deposition ratio V _O / V ₁ with gas linear velocity V ₁ at the 80% point towards the said center part in the longitudinal direction of the slit, characterized in that a 0.9 to 1.7 For burners.

  A fourth invention is a burner having a source gas outlet and gas outlets on both sides thereof, wherein the source gas outlet is in a slit shape with an aspect ratio of 20 or more, and a gas introduction path of the source gas outlet is provided. A deposition burner characterized by having a gas reservoir having a width wider than the slit width of the raw material gas outlet and a mesh rectifier having a mesh opening of 0.2 mm or less. The width of the gas reservoir is the same as that of the raw gas outlet. It is preferable that the width is not less than twice the slit width.

  The deposition burner according to the present invention is provided with a seal gas outlet having a slit length longer than that of the source gas outlet, adjacent to the source gas outlet, and a combustion gas outlet is provided adjacent to the seal gas outlet. The length of the slit constituting the seal gas outlet is longer by L than the slit length of the source gas outlet, and the two seal gas outlets provided such that L sandwiches the source gas outlet. It is good to set it as 2 times or more of the space | interval S of a mouth.

  The method for producing silica soot according to the present invention uses the above-described deposition burner to inject a carrier gas containing a support gas together with a source gas from a source gas outlet, and contains a support gas from the seal gas outlet. And a combustion gas containing a combustible gas is injected from a combustion gas outlet, and this is also characterized in that the combustible gas together with the raw material gas is injected from the raw material gas outlet. The carrier gas containing the gas is injected, the seal gas containing the combustible gas is injected from the seal gas outlet, and the combustion gas containing the combustion-supporting gas is injected from the combustion gas outlet. Also good. Note that the linear velocity of the seal gas injected from the seal gas outlet is preferably 5 to 10% of the linear velocity of the gas injected from the raw material gas outlet.

In the deposition burner of the present invention, a laminar flame can be obtained even when a large amount of source gas is supplied by making the aspect ratio of the source gas outlet to be 20 or more slits. In addition, among the gas outlets arranged around the raw material gas outlet, the injection angle θ ₁ of the gas outlet having the highest gas linear velocity is spread outwardly with respect to the injection direction of the raw material gas. The angle of 20 °, the gas introduction path of the raw material gas outlet, the side portion of the slit in the longitudinal direction has a structure with a taper portion having an angle θ ₃ of 0.5 to 20 °, A gas reservoir and a rectifying section are provided in the gas introduction path of the raw material gas outlet, and a stable flame flow is obtained by these, which is extremely excellent in improving the deposition rate and yield.

  In order to improve the yield of silica soot, it is necessary that the silica fine particles in the raw material flame adhere to the target surface efficiently. It is the thermophoresis effect that plays this role, but in order for the thermophoresis effect to work effectively, the raw material flame needs to flow as thinly as possible on the target surface. The flame at this time is preferably a laminar flame.

The Reynolds number is known as a parameter for determining the laminar flow or turbulent flow of the flame. The Reynolds number Re is a dimensionless number represented by the following formula 1. Further, it is known that a smaller Reynolds number is better for obtaining a laminar flame. In order to reduce the Reynolds number of the flame, it can be seen from Equation 1 that the linear velocity and / or representative dimension of the gas should be reduced.
Re = μL / ν (Formula 1)
(Μ: linear velocity of gas, L: representative dimension (for example, diameter), ν: kinematic viscosity of gas)

  On the other hand, in order to improve the deposition rate of silica soot, the injection amount of the raw material gas per unit time must be increased. For this reason, if the raw material gas injection speed is increased without changing the shape of the raw material gas outlet of the burner, the linear velocity of the raw material gas increases and the Reynolds number Re increases. As a result, a stable laminar flame cannot be obtained, leading to a decrease in yield.

  In addition, assuming that the laminar flame of the raw material spreads on the target surface (hereinafter referred to as a laminar flame region) hardly changes depending on the raw material gas injection speed, a large amount of raw material gas is injected over a certain area. Therefore, the raw material flame on the target surface cannot spread thinly, and it becomes difficult to make the thermophoresis effect work effectively.

  As a method in which the yield does not decrease even if the raw material gas injection speed is increased, it is conceivable that the linear velocity of the raw material gas is decreased by increasing the diameter of the raw material gas outlet and increasing the cross-sectional area. However, in this method, since the representative dimension L is large, the effect of reducing the Reynolds number is small, and the effect of expanding the laminar flame region is small, and the effect of improving the yield is small.

Therefore, the present inventors examined increasing the aspect ratio of the outlet as a method of enlarging the cross-sectional area of the source gas outlet. The following two points can be expected as merits of increasing the aspect ratio of the outlet.
(A) Reduction of Reynolds number (b) Expansion of laminar flame area

First, the effect of “reducing the Reynolds number” in FIG.
The representative dimension L of a conduit having a large aspect ratio can be expressed by the following equation (fluid engineering, Shiro Ito, Science and Technology Company).
L = 4 × cross-sectional area of pipe line / peripheral length of pipe cross-section (Equation 2)
From the above formulas 1 and 2, the Reynolds number when the aspect ratio of the gas outlet is changed with the same cross-sectional area is as shown in FIG.

From FIG. 1, when the aspect ratio of the gas outlet is increased, the Reynolds number can be substantially reduced even if the cross-sectional area is the same.
When the aspect ratio exceeds 20, it is possible to suppress the Reynolds number to half or less than that of a normal circular tube type gas outlet, and it is predicted that the effect of the slit type gas outlet is sufficiently exhibited. Further, when the aspect ratio is sufficiently increased, the representative dimension L converges to a value twice the slit width, and the slit length does not affect the representative dimension L.

In the case of a circular pipe, if the cross-sectional area is increased by increasing the diameter, the representative dimension L increases, so if the gas linear velocity is kept constant, the Reynolds number will increase, but in the case of a slit-shaped outlet Even if the slit length is extended to expand the cross-sectional area, the representative dimension L does not change, and the Reynolds number does not increase when the linear velocity is constant.
Thus, by adopting the slit-like gas outlet, the cross-sectional area can be effectively enlarged, and a laminar flame can be maintained even when a large amount of source gas is burned.

Next, the effect of “expansion of laminar flame region” in (b) will be described.
The state in which the raw material flame spreads on the target surface is shown in FIG. 2, and the region where the laminar flame spreads is shown in FIG. The raw material flame spreads along the target when it hits the target surface. Here, the flame spreads while maintaining a laminar flame up to a certain distance from the point of collision with the target (solid line in the figure). However, outside this region, laminar flow cannot be maintained and turbulent flames occur. The distance that the laminar flame can be maintained and spread (laminar flame distance) varies depending on the flame temperature and the material and shape of the target, but is difficult to change arbitrarily.

  Assuming that the silica fine particles generated in the raw material flame adhere to the target surface in the laminar flame region (contributes to silica soot formation), the yield can be improved by making the laminar flame region as large as possible. Is possible.

Then, the method of enlarging the laminar flame area was examined.
In the case of a burner having a circular outlet, the flame injected from the outlet is cylindrical. The laminar flame region obtained by the collision of the flame with the target surface is a circular region surrounded by a certain distance (laminar flame distance) from the point where the flame collides with the target. Here, even if the diameter of the outlet is doubled, the diameter of the laminar flame region cannot be doubled as shown by the broken line region in FIG.

On the other hand, in the case of a flame obtained from a slit-type outlet, as shown in FIG. 5, even in a flame having the same cross-sectional area as that of a flame from a circular outlet, the laminar flame region is enlarged only by increasing the slit length. It becomes possible.
As described above, adopting a slit-type outlet for the deposition burner from both sides of the “Reynolds number” in (a) and the “laminar flame region” in (b) is a high yield and high deposition rate. It turns out that it is very effective in aiming at.

However, when silica soot deposition is actually performed using a slit-type burner (hereinafter referred to as a slit burner), it has been found that it is difficult to obtain a high yield and a high deposition rate as expected.
As a result of examining this cause, the plate-like flame ejected from the slit-type outlet (hereinafter referred to as plate-like flame) is more susceptible to disturbance than the circular flame, and the laminar flow state is disturbed. It was found that it was easy to form a laminar flame area with a sufficient area on the target surface.

  Based on such knowledge, as a result of earnest investigation on a deposition burner that can form a laminar flame region with a stable laminar flow and a sufficient laminar flame region, the configuration described in the claims Was found to be effective, and the present invention was completed.

The deposition burner according to the first aspect of the present invention is characterized in that the injection angle θ ₁ of the gas outlet having the highest gas linear velocity among the gas outlets arranged around the source gas outlet is the injection direction of the source gas, in other words, As shown in FIG. 6, the angle is 0.5 to 20 ° spreading outward with respect to the line A parallel to the center line of the raw material gas introduction path, and the outer side is directed to the raw material outlet. It is a plus. FIG. 6 is a longitudinal sectional view of the deposition burner of the present invention cut perpendicularly to the longitudinal direction of the slit, showing the source gas outlet, the flame outlet with the highest linear velocity, and the injection direction.
This is a means for solving that the plate-like flame injected from the slit-type outlet is easily disturbed by the flame flow injected from another gas outlet of the same burner.

Of the flames injected from the same burner, the flame that tends to disturb the plate flame is the flame with the highest linear velocity. Therefore, as a result of investigating the relationship between the injection angle θ ₁ of the gas outlet for injecting such a flame and the yield of silica soot, the yield of silica soot was improved when θ ₁ was in the range of 0.5 to 20 °. It was also found that when θ ₁ is in the range of 2 to 10 °, the yield is further excellent and more desirable.

  In addition, it is considered that the reason why the yield decreases on the low angle side is the angle at which the flame with the highest linear velocity starts to directly affect the plate flame that is the raw material flame. Moreover, the cause of the decrease in yield on the high angle side may be a decrease in temperature due to diffusion of a flame having the largest linear velocity.

The deposition burner according to the second invention is such that the gas flow injected from the raw material gas outlet is expanded and injected at an angle θ ₂ of 0.5 to 20 ° in the longitudinal direction of the slit. Is a taper shape in which the side shape in the longitudinal direction of the slit is widened at an angle θ ₃ of 0.5 to 20 °.

  This measure optimizes the direction of the flame flow of the plate flame. The plate-shaped flame is likely to be disturbed unless the flame flow in the longitudinal direction of the slit is set optimally. For example, as shown in FIG. 7, when there is a flame flow flowing in the direction of the center line of the flame, a vortex is generated when the flame collides with the target, and the flame is disturbed.

In order to solve this phenomenon, as shown in FIG. 8, it is effective to direct the flame flow outward at an angle θ ₂ with respect to the flame center line. In order to realize such a flame flow, a gas introduction path forming a slit-type flame outlet is tapered outwardly at an angle θ ₃ as shown in FIGS. 9 (a) and 9 (b). It is good to form in a shape. 8 and 9, the outlets other than those for the raw material flame are not shown.

9 (b), the raw material gas gas inlet passage has a monotonically taper shape slit longitudinal sides thereof extends at an angle theta _3. Further, the gas introduction passage for the source gas may be expanded at an angle θ ₃ from the middle as shown in FIG. 9 (c), or may be substantially tapered with a curved portion as shown in FIG. 9 (d). . As a result, the gas can be injected at a blowing angle θ ₂ of 0.5 to 20 °. This angle θ ₂ is particularly preferably 2 to 10 °.
Similarly, the gas inlet gas introduction path is preferably tapered at an angle θ ₃ .

The deposition burner according to the third invention is a ratio V _O between the gas linear velocity V _O at the center of the raw material gas outlet and the gas linear velocity V ₁ at the 80% position from the center toward the longitudinal direction of the slit. / V ₁ is set to 0.9 to 1.7.
The measure for regulating the gas linear velocity is also intended to suppress the disturbance of the plate flame. The plate flame formed by the slit burner is difficult to stabilize in the longitudinal direction of the slit. As one of the causes, it has been found that the flame gas linear velocity distribution in the longitudinal direction of the slit is related.

When the linear velocity distribution of the flame gas is inappropriate, as shown in FIG. 10A, vortices are generated in the flame and the flame is disturbed. An appropriate flame gas linear velocity distribution that solves this problem is obtained by relatively increasing the linear velocity at the slit center as shown in FIG. _O / V ₁ is set to 0.9 to 1.7.
In the case of the oblique injection flame, the gas linear velocity is, as shown in FIGS. 11 (a) and 11 (b), the burner vertical direction (gas ejection direction) as the y-axis and the outlet longitudinal direction (slit longitudinal direction). Is defined as the size of the y-component vector where x is the x-axis. In FIG. 11, the outlets other than the source gas are not shown.

Further, the value of the gas linear velocity ratio V _O / V ₁ is more preferably in the range of 1.1 to 1.5. Here, the reason why the gas linear velocity is defined at the point of 80% is that the gas flow is not stable at the end (100% position) of the gas outlet and measurement is difficult.
In the above, the prescribed position of the gas linear velocity is the central portion and the left and right 80% points, but the linear velocity distribution between these is a gentle distribution on the left and right as shown in FIG. 11 (b). It is desirable to do.

A deposition burner according to a fourth aspect of the present invention is provided with a gas reservoir having a width wider than the slit width of the raw material gas outlet and a mesh rectifier having a mesh size of 0.2 mm or less in the gas introduction path of the raw material gas outlet. is there.
In the slit burner, it is desired to form a uniform gas flow in the slit-like gas introduction path. In order to form a uniform gas flow, the gas introduction path should be long enough. However, there are many cases where the flow path cannot be made sufficiently long due to restrictions on the dimensions of the burner, and as shown in FIGS. 12 (a) and 12 (b), the gas flow is disturbed.

In this case, there is a possibility that the above-described measures for obtaining the ideal plate flame cannot be sufficiently exhibited. In order to solve this problem, a gas reservoir having a width wider than that of the slit-like gas introduction path is provided near the gas pipe of the slit-like gas introduction path. In this method, at least one mesh-like rectifying plate having a mesh size of 0.2 mm or less is provided in an arbitrary place in the gas reservoir or the gas introduction path. By the above measures, the gas flow in the gas introduction path becomes uniform, and the yield can be greatly improved.
The width t of the gas reservoir may be at least twice the width of the slit-like gas introduction path, and is preferably at least four times. Two or more rectifying plates may be provided (see FIGS. 13 and 14).

  The deposition burner according to the present invention has the following countermeasures. That is, a seal gas outlet having a slit length longer than that of the source gas outlet is provided adjacent to the source gas outlet, and a combustion gas outlet is provided adjacent to the seal gas outlet. Thus, by making the sealing gas outlet longer than the source gas outlet, it is possible to reliably prevent the silicon oxide powder from adhering to the burner.

  Here, as shown in FIG. 15, the slit length of the seal gas outlet is longer than the slit length of the raw material gas outlet and more than twice the interval S between the two seal gas outlets. Further, in order to further ensure the effect of preventing the silicon oxide powder from adhering to the burner, the length is preferably at least four times the interval S. It should be noted that the blowout port for the seal gas does not need to be formed only by the slit, but may have a slit-shaped portion and the slit length may be longer than the slit length of the raw material gas blowout port.

  The combustion gas outlet is not necessarily slit-shaped, and a large number of circular outlets may be provided. Further, the combustion gas outlet may be for a diffusion flame in which a combustible gas and a combustion-supporting gas are separately arranged, or for a premixed flame in which a combustible gas and a combustion-supporting gas are mixed in advance. It may be. Further, the premixed flame outlet and the diffusion flame outlet may be arranged together.

  When the silica soot is produced using the slit burner having such a structure, when the carrier gas introduced together with the raw material gas includes a combustion-supporting gas, the seal gas injected from the seal gas blow-out port contains the combustion support gas. A gas containing a combustible gas is injected from the combustion gas outlet. On the other hand, when the carrier gas contains a combustible gas, the seal gas contains a combustible gas, and a gas containing a combustion-supporting gas is injected from the combustion gas outlet.

The selection of the gas to be supplied is a measure for quickly bringing the raw material gas into a high-temperature flame state to obtain a stable laminar plate flame. Normally, when a gas enters a flame state, the kinematic viscosity increases, and a stable laminar flow state is easily formed. This is explained by a decrease in the Reynolds number obtained from Equation 1 as the kinematic viscosity increases.
Therefore, in order to obtain a stable laminar flame, it means that it is important for the gas injected from the gas outlet to be in a flame state quickly.

In order for the source gas to quickly form a flame, a gas that easily forms a flame is mixed as a carrier gas. Examples of the gas that easily forms a flame include a combustion-supporting gas and a combustible gas.
When the combustion-supporting gas is mixed into the carrier gas together with the raw material gas, a combustion gas outlet for injecting a gas containing a combustible gas is provided as close as possible to the raw material gas outlet.

However, if a gas containing oxygen (for example, oxygen gas) is used as the combustion-supporting gas and a gas containing hydrogen (for example, hydrocarbon gas such as hydrogen gas or methane) is used as the combustible gas, the following problems occur. .
In other words, the water generated by the combustion reaction reacts quickly with the silicon compound (for example, silicon tetrachloride, methylchlorosilane, etc.) as a raw material, causing silicon oxide powder to deposit in the vicinity of the burner outlet, causing problems such as burner clogging. Arise.

  As a means for solving this problem, a seal gas outlet having a slit length longer than the source gas outlet is provided adjacent to the source gas outlet, and the seal gas outlet does not cause a combustion reaction with the source gas. Introduce seal gas. For the seal gas, if the carrier gas of the raw material contains a flammable gas, use a flammable gas. If the carrier gas contains a flammable gas, use a gas containing a flammable gas. desirable. Thus, the seal gas blocks water generated by the combustion of the combustion gas and performs a combustion reaction with the combustion gas to promote ignition of the raw material gas.

  Note that the linear velocity of the seal gas injected from the seal gas outlet is preferably 5 to 10% of the linear velocity of the gas injected from the raw material gas outlet. If it is smaller than this, the ability to prevent the silicon oxide powder produced by the flame reaction from adhering to the burner is lowered, and if it is larger than this, flame formation of the raw material gas is inhibited.

The gas injected from the combustion gas outlet closest to the source gas outlet must be properly used depending on the type of carrier gas supplied together with the source gas. That is, when the carrier gas contains a combustion-supporting gas, it is desirable to inject the combustible gas from the combustion gas outlet closest to the raw material gas outlet, and when the carrier gas contains a combustible gas, It is desirable to inject the combustion-supporting gas from the combustion gas outlet closest to the gas outlet.
This is an effective means for quickly generating a flame in the raw material gas while preventing the silicon oxide powder from adhering to the burner.

  The deposition burner of the present invention is excellent in the deposition rate and yield of a compound mainly composed of silica produced by a combustion reaction of a raw material gas containing a silicon compound, and is suitably used for producing an optical fiber preform.

It is a graph which shows the relationship between the aspect-ratio of a blower outlet, and Reynolds number. It is a schematic diagram which shows the spreading state of the raw material flame in the target surface. It is a figure which shows the spreading state of the laminar flame which looked at the flame flow front. It is a figure which shows the spreading state of the laminar flame when the diameter of a blower outlet is changed. It is a figure which compares and shows the laminar flow flame area | region of a circular flame and a plate-like flame with the flame of the same cross-sectional area. It is the longitudinal cross-sectional view which cut | disconnected the burning burner of this invention perpendicularly | vertically to the slit longitudinal direction. It is a figure which shows the disturbance of the flame of a slit burner. It is a figure explaining the flame disorder countermeasure of the slit burner of this invention. (A) is a front view which shows the source gas blowing outlet of the slit burner of this invention, (b), (c), (d) is sectional drawing along the slit thickness direction centerline of (a). These indicate gas introduction paths. (A), (b) is a figure which shows the relationship between the flame linear velocity distribution of a slit burner, and the disturbance of a flame. (A), (b) is a figure explaining the gas linear velocity distribution of the slit burner by this invention. It is a figure which shows the gas flow in the gas introduction path of a slit burner. It is a figure explaining the gas flow control method of the slit burner by this invention. It is a figure explaining the gas flow control method of the slit burner by this invention. It is a figure which shows the positional relationship of the sealing gas blower outlet and combustion gas blower outlet of the slit burner by this invention.

Claims (11)

A burner having a source gas outlet and gas outlets on both sides thereof, the source gas outlet having a slit shape with an aspect ratio of 20 or more, and the gas linear velocity among the gas outlets provided on both sides thereof A deposition burner characterized in that the gas injection angle θ ₁ of the large gas outlet widens outward at an angle of 0.5 to 20 ° with respect to the injection direction of the source gas. A burner having a source gas outlet and gas outlets on both sides thereof, wherein the source gas outlet has a slit shape with an aspect ratio of 20 or more, and the gas flow injected from the source gas outlet is in the longitudinal direction of the slit The deposition burner is characterized by spreading at an angle θ ₂ of 0.5 to 20 °. _3. The deposition burner according to claim 2, wherein the gas introduction path of the raw material gas outlet has a tapered portion substantially widened at an angle θ3 of 0.5 to 20 ° on a side portion in the longitudinal direction of the slit. . A burner having a source gas outlet and gas outlets on both sides thereof, wherein the source gas outlet has a slit shape with an aspect ratio of 20 or more, a gas linear velocity V _O at the center of the source gas outlet, A deposition burner characterized in that the ratio V _O / V ₁ to the gas linear velocity V ₁ at a point of 80% from the center to the longitudinal direction of the slit is 0.9 to 1.7. A burner having a source gas outlet and gas outlets on both sides thereof, wherein the source gas outlet is slit-shaped with an aspect ratio of 20 or more, and the source gas outlet is connected to a gas introduction path of the source gas outlet. A deposition burner comprising a gas reservoir having a width wider than a slit width and a mesh-like rectifying portion having a mesh size of 0.2 mm or less. 6. The deposition burner according to claim 5, wherein the width of the gas reservoir is at least twice the slit width of the raw material gas outlet. 7. A seal gas outlet having a slit length longer than that of the source gas outlet is provided adjacent to the source gas outlet, and a combustion gas outlet is provided adjacent to the seal gas outlet. The deposition burner according to any one of the above. The length of the slit constituting the seal gas outlet is longer than the slit length of the raw material gas outlet by L, and this L is the distance S between the two seal gas outlets provided so as to sandwich the raw gas outlet. The deposition burner according to any one of claims 1 to 7, wherein the burner is at least double. Using the deposition burner according to any one of claims 1 to 8, a carrier gas containing a combustible gas together with the raw material gas is injected from the raw material gas outlet, and the auxiliary gas is injected from the seal gas outlet. A method for producing silica soot, comprising the steps of injecting a sealing gas contained therein and injecting a combustion gas containing a combustible gas from a combustion gas outlet. Using the deposition burner according to any one of claims 1 to 8, a carrier gas containing a combustible gas together with a source gas is injected from a source gas outlet, and a combustible gas is contained from a seal gas outlet. A method for producing silica soot, comprising: injecting a sealing gas and injecting a combustion gas containing a combustion-supporting gas from a combustion gas outlet. The method for producing silica soot according to claim 9 or 10, wherein a linear velocity of the seal gas injected from the seal gas outlet is 5 to 10% of a linear velocity of the gas injected from the raw material gas outlet.

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