Large-size high-uniformity synthetic quartz glass ingot deposition furnace and preparation method

Abstract

The present application relates to a kind of large size high uniformity synthetic quartz glass ingot deposition furnace and preparation method, deposition furnace includes furnace body and furnace top, the furnace top is equipped with injection burner, its characterized in that in the middle part of furnace cavity corresponding injection burner is equipped with separate rotary lifting crucible, the outer periphery of separate rotary crucible is provided with annular flue below furnace cavity, corresponding annular flue is provided with air outlet along the circumference of furnace body.The rotating lifting disc-shaped bottom and cylindrical wall of separate rotary lifting crucible during deposition independently run, which not only can keep the constant distance between deposition target surface and injection burner, so that deposition state always remains stable, but also can make deposition target surface always slightly higher or flush with the top of cylindrical wall, exhaust gas and dust can be smoothly discharged from air outlet after passing through annular flue cavity, and will not be upwardly rolled, so that injection deposition gas flow and dust flow are smooth, solve the problem of air flow turbulence and dust local deposition caused by side wall obstruction of fixed crucible, effectively improve the uniformity of deposition.

Description

Technical Field

[0001] This invention belongs to the field of quartz glass ingot preparation technology, and particularly relates to a deposition furnace and preparation method for large-size, highly uniform synthetic quartz glass ingots. Background Technology

[0002] Due to its excellent properties, synthetic quartz glass has a large demand and application in fields such as semiconductors, optics, and aerospace, and large-size, highly uniform synthetic quartz glass is a key basic material.

[0003] Currently, the main method for preparing large-size synthetic quartz glass is vertical deposition furnace chemical vapor deposition (CVD). This method involves introducing volatile liquid silicon compounds into a burner under the influence of a carrier gas. In the burner flame, these compounds undergo hydrolysis or oxidation to generate amorphous silica, which is then deposited onto a high-temperature rotating target to form quartz glass. In traditional vertical CVD, the centrifugal force of rotation and the gravity of the quartz glass itself cause the quartz glass at the central feeding point to diffuse and flow across the entire target surface, while the glass at the edges cools and solidifies, providing support for the longitudinal growth of the quartz glass. This growth pattern inevitably results in a significant temperature gradient between the center and the edges, leading to a substantial gradient in the internal structure and hydroxyl composition of the quartz glass ingot. This not only increases the stress and striations in the quartz glass but also directly causes uneven distribution of properties such as density and refractive index. This gradient becomes even more pronounced during the preparation of large-size quartz ingots. Under this process technology, to produce large-size, highly uniform synthetic quartz glass products, it is necessary to select the central area of ​​the quartz ingot with better quality and perform heat treatment to reshape it. However, due to the large gradient change from the center to the edge, the effective area that can be selected is small, the utilization rate is low, and the product quality is difficult to guarantee.

[0004] To address the above issues, a vertical crucible chemical vapor deposition method was developed, an improvement upon the traditional vertical deposition method. In this method, the target material is placed within a concave crucible deposition tank. Due to the support of the crucible walls, the quartz ingot does not require careful shaping, thus the edge temperature does not need to be too low. The glass undergoes a relatively long period of diffusion and mixing within the crucible, resulting in good consistency between the central feeding area and the edges. However, in actual production, the waste gas and dust generated during deposition can be drawn upwards by the crucible, creating turbulence. This not only disrupts the airflow within the furnace but also causes a large amount of drawn-back dust to accumulate at the furnace top and burner walls, forming deposits. When these deposits reach a certain level, they fall into the quartz glass under the influence of gravity and airflow disturbance, forming defects such as bubbles. Meanwhile, to ensure stable target surface temperature, this process requires the crucible and target surface to be moved downwards as a whole at a certain rate during deposition. This moving speed needs to match the growth rate of the quartz glass ingot to maintain a constant distance between the target surface and the burner. This descent process causes the distance between the exhaust port and the crucible edge to change continuously, resulting in constant fluctuations in the airflow within the furnace. When preparing smaller quartz ingots, these problems can be solved through process control. However, when preparing larger quartz ingots (diameter exceeding 800mm, height exceeding 200mm), the longer production cycle makes it difficult to avoid these problems. Furthermore, to ensure consistent deposition surface temperature, a multi-burner process is typically used in the preparation of large quartz glass ingots. The flames and airflow from each burner can interfere with each other, further exacerbating the problems and ultimately affecting the preparation and quality of the quartz glass ingot. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a large-size, highly uniform synthetic quartz glass ingot deposition furnace and preparation method that addresses the shortcomings of the prior art. It has a uniform temperature distribution in the thermal field, stable airflow in the furnace, and good deposition quality.

[0006] The deposition furnace technology solution adopted by this invention to solve the above-mentioned problems is as follows:

[0007] The furnace includes a furnace body and a furnace top, wherein a jet burner is installed on the furnace top. The furnace top is characterized by having a separate rotating and lifting crucible installed in the middle of the furnace cavity corresponding to the jet burner, and an annular flue is provided on the outer periphery of the separate rotating crucible below the furnace cavity, with an air outlet provided along the circumference of the furnace body corresponding to the annular flue.

[0008] According to the above scheme, the detachable rotating crucible includes a disc-shaped crucible bottom and a cylindrical crucible wall, the disc-shaped crucible bottom and the cylindrical crucible wall are separate, and the disc-shaped crucible bottom is connected to the rotating lifting base to form a rotating lifting disc-shaped crucible bottom.

[0009] According to the above scheme, the cylindrical crucible wall is connected to the rotating platform to form a rotating cylindrical crucible wall.

[0010] According to the above scheme, the outer periphery of the rotating lifting disc-shaped crucible bottom is configured with the inner hole (periphery) of the rotating cylindrical crucible wall, and the rotating lifting disc-shaped crucible bottom can rotate and rise relative to the rotating cylindrical crucible wall.

[0011] According to the above scheme, the gap between the outer periphery of the rotating lifting disc-shaped crucible bottom and the inner hole of the rotating cylindrical crucible wall is 3-8mm.

[0012] According to the above scheme, the annular flue includes an annular furnace bottom, an inner wall of the furnace cavity, and an outer periphery of a cylindrical crucible wall. The upper end of the annular flue has an annular opening that communicates with the deposition chamber of the furnace cavity. The air outlet is located circumferentially below the furnace body and communicates with the bottom of the annular flue.

[0013] According to the above scheme, the air outlet is connected to the exhaust control system to control the exhaust volume of the annular flue and the furnace pressure.

[0014] According to the above scheme, 4 to 8 air outlets are set on the outer wall of the furnace body, and the exhaust control system is equipped with air volume regulating valves connected in series with each air outlet, and pressure and temperature monitoring devices are set at the air outlets.

[0015] According to the above scheme, the bottom of the furnace body is provided with an air inlet that is connected to the annular flue, the air inlet is connected to the make-up air chamber provided outside the bottom of the furnace body, and the make-up air chamber is connected to the air intake control system.

[0016] According to the above scheme, the air inlet is set along the bottom of the furnace body near the outer periphery of the cylindrical crucible wall, and the air inlet is connected to the inner side of the make-up air chamber.

[0017] According to the above scheme, the air intake control system is equipped with a gas heating temperature control device, thus forming an air intake control system with heating and temperature control functions.

[0018] The technical solution of the preparation method of the above-mentioned deposition furnace in this invention is as follows:

[0019] Quartz glass ingots are prepared by chemical vapor deposition (CVD). The deposition target is placed at the bottom of a rotating, lifting disc-shaped crucible. The target position is adjusted to be slightly higher than or flush with the top of the cylindrical crucible wall by a lifting and rotating base. The rotating base is then activated, causing the crucible bottom and the deposition target to rotate uniformly. The jet burner is ignited. Once the furnace temperature reaches the preset value, the raw material, propelled by the carrier gas, is injected onto the deposition target through the jet burner located on the furnace top. A chemical reaction occurs in the oxyhydrogen flame environment, generating silica particles which are deposited on the high-temperature target. As the deposition process progresses... The process begins with molten glass spreading across the entire deposition target. The deposited molten glass then serves as a new collection target surface. The lifting function of the rotating and lifting base is activated, causing the bottom of the disc-shaped crucible and the target surface to descend continuously and uniformly. The descent speed is balanced with the rising speed of the target surface to maintain a constant distance between the target surface and the jet burner. The target surface is always slightly higher or flush with the top of the cylindrical crucible wall. Dust in the furnace cavity is drawn out of the furnace cavity through the annular flue with the airflow, maintaining stable furnace cavity temperature and pressure. The jet burner's injection and the rotating and lifting disc-shaped crucible bottom continue to descend until the deposition height of the synthetic quartz glass ingot is reached.

[0020] According to the above scheme, under the action of the exhaust control system, a gradually decreasing pressure distribution and a gradually decreasing height distribution are formed on the deposition target surface, the annular flue cavity and the air outlet. A negative pressure zone P1 is formed at the air outlet, and a positive pressure zone P3 is formed on the deposition target surface due to the injection of combustion gas. The air intake at the air inlet of the annular flue cavity is controlled by adjusting the air supply cavity to maintain the pressure P2 at the annular flue cavity, so that P1 < P2 < P3, and the relative pressure (relative atmospheric pressure) of P2 is -50Pa to -200Pa.

[0021] According to the above scheme, the ratio of the negative pressure zone pressure P1 to the pressure P2 at the annular flue cavity is P1 / P2 > 2, and the height h1 of the air outlet is less than the height h2 of the annular flue cavity, h1 / h2 < 0.5, and the total area S1 of the air outlet is greater than the cross-sectional area S2 of the annular flue cavity, S1 / S2 > 1.2.

[0022] According to the above scheme, the height of the target surface above the top of the cylindrical crucible wall is 3 to 10 mm.

[0023] According to the above scheme, the rotation speed of the disc-shaped crucible bottom is 1-50 r / min, and the descent speed is 1-20 mm / h.

[0024] According to the above scheme, the temperature of the annular flue cavity is controlled between 1000℃ and 1700℃.

[0025] According to the above scheme, during the deposition process, the temperature of the annular flue cavity is controlled at 1300℃~1400℃. The temperature of the deposited quartz glass ingot decreases and the viscosity increases. At this time, the edge of the quartz glass ingot does not contact the cylindrical crucible wall, and the quartz ingot achieves longitudinal vertical growth, which is used to prepare quartz glass ingots with large diameter and high height.

[0026] According to the above scheme, during the deposition process, the temperature of the annular flue cavity is controlled at 1600℃~1700℃. The temperature of the deposited quartz glass ingot increases and the viscosity decreases. The molten glass comes into contact with the wall of the cylindrical crucible. At this time, the rotating stage is turned on, and the wall of the cylindrical crucible and the bottom of the disc crucible rotate synchronously to prepare quartz glass ingots with good uniformity.

[0027] According to the above scheme, after the deposition is completed, heat preservation treatment is carried out, the raw material supply to the jet burner is stopped, the hydrogen and oxygen ratio is adjusted, the flame of the jet burner is kept burning, the descent function of the rotating disc bottom is stopped, the rotation motion is continued, the temperature of the annular flue cavity is controlled at 1000℃~1400℃, and the heat preservation time is 2~12h (hours).

[0028] According to the above scheme, the material of the detachable rotating crucible is a refractory material, and the refractory material is zirconium oxide, alumina, or silicon carbide.

[0029] According to the above scheme, four or more jet burners are provided, the angle between the jet burner and the vertical line is 0° to 15°, and the distance between the jet burner and the target surface during deposition is 300 to 450 mm.

[0030] According to the above scheme, the jet burner is made of quartz glass, metal or metal alloy; the raw material is SiCl4 or an organic compound of silicon.

[0031] According to the above scheme, the air intake control system controls the air intake volume and air intake temperature of the make-up air chamber, with an air intake volume of 100 to 1000 L / min and a temperature of 25℃ to 500℃.

[0032] The beneficial effects of this invention are as follows: 1. By setting up a separate rotary lifting crucible as a deposition tank, the rotating and lifting disc-shaped bottom and cylindrical wall of the separate rotary lifting crucible operate independently during deposition. This not only maintains a constant distance between the deposition target surface and the jet burner, ensuring a stable deposition state, but also ensures that the deposition target surface is always slightly higher or flush with the top of the cylindrical crucible wall. Exhaust gas and dust will be smoothly discharged from the furnace through the annular flue cavity and the exhaust port, without being rolled upwards. This allows for smooth flow of jet deposition airflow and dust, solving the problems of airflow turbulence and localized dust deposition caused by the sidewall obstruction of the fixed crucible, effectively improving the uniformity and stability of deposition. 2. Crucibles are ceramic parts, especially the bottom, which is easily damaged and requires frequent replacement. The separate rotary lifting crucible only requires replacement of the bottom, which can greatly reduce equipment maintenance costs. 3. Throughout the deposition process, the relative positions of the target surface, the jet burner, and the exhaust vents remain constant. The atmosphere and environment inside the furnace do not change as the deposition process progresses. Through a combination of supplementary air intake and exhaust, the temperature and pressure of the annular flue cavity are controlled to remain relatively stable. The annular flue encloses the entire deposition tank, maintaining a stable temperature for the quartz glass ingot during deposition. It also insulates the edges of the quartz glass ingot, reducing the temperature difference between the edges and the center, and improving overall temperature uniformity. By controlling the edge temperature of the quartz glass ingot, the preparation process is stable and uniform, enabling the production of large-size, highly uniform synthetic quartz glass with an effective diameter greater than 800 mm and a height greater than 200 mm. 4. After the deposition process is complete, a flame continues to be supplied to insulate the quartz glass ingot. High-temperature gas, passing through the annular flue cavity, maintains the entire deposition tank in a relatively stable high-temperature environment, allowing for sufficient diffusion and mixing of particles within the quartz glass. This further improves the overall uniformity of the quartz glass ingot and effectively reduces and eliminates defects such as stress and striations formed during deposition. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the front sectional view of an embodiment of the present invention.

[0034] Figure 2 for Figure 1 Cross-sectional view of the central annular flue and air outlet. Specific implementation methods

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0036] Example 1: This example provides a large-size, highly uniform quartz glass ingot deposition furnace and deposition preparation method. The deposition furnace structure is as follows: Figure 1 , Figure 2As shown, the furnace includes a furnace body 12 and a furnace top 14. Six spaced-apart jet burners 1 are installed on the furnace top. A detachable rotating and lifting crucible is installed in the center of the furnace cavity, corresponding to the jet burners. The detachable rotating crucible includes a disc-shaped bottom 4 and a cylindrical wall 5, which are separate. The disc-shaped bottom is connected to a rotating and lifting base 7, which includes a rotating base and a lifting device connected to the rotating base, thus forming a rotating and lifting disc-shaped crucible bottom. The cylindrical crucible wall is connected to the rotating platform 6 to form a rotating cylindrical crucible wall. During deposition, depending on the deposition conditions, the cylindrical crucible wall can rotate synchronously with the disc-shaped crucible bottom or not rotate. The outer circumference of the rotating lifting disc-shaped crucible bottom is configured with the inner hole (circumference) of the rotating cylindrical crucible wall. The rotating lifting disc-shaped crucible bottom can rotate and rise relative to the rotating cylindrical crucible wall. The diameter of the rotating lifting disc-shaped crucible bottom is 800mm, and the gap between its outer circumference and the inner hole of the rotating cylindrical crucible wall is 5mm. The height of the cylindrical crucible wall is 420mm. An annular flue 10 is provided around the outer periphery of a separate rotating crucible at the bottom of the furnace cavity. The annular flue includes an annular furnace bottom, an inner wall of the furnace cavity, and the outer periphery of a cylindrical crucible wall. The upper end of the annular flue has an annular opening communicating with the deposition chamber 13 of the furnace cavity. The radial width of the annular flue is 200 mm. Corresponding to the annular flue, air outlets 11 are provided along the circumference of the furnace body. Eight air outlets are evenly distributed circumferentially below the furnace body, with a height of 100 mm and the bottom of the air outlets flush with the bottom of the annular flue. The air outlets are connected to a draft control system, which is equipped with a corresponding airflow regulating valve connected in series with each air outlet to control the draft volume of the annular flue and the furnace cavity pressure. Pressure and temperature monitoring devices are also installed at the air outlets. The furnace body has an air inlet 8 at the bottom that is connected to the annular flue. The air inlet is located at the bottom of the furnace body near the outer periphery of the cylindrical crucible wall. The air inlet can be an annular slit air inlet. The air inlet is connected to the make-up air chamber 9 located outside the bottom of the furnace body. The make-up air chamber is connected to the air intake control system. The air intake control system is equipped with a gas heating temperature control device and an air volume regulating valve, which constitutes an air intake control system with heating temperature control function.

[0037] The preparation process in this embodiment is as follows: Quartz glass ingots are prepared by chemical vapor deposition (CVD). The deposition target 3 is placed at the bottom of a rotating and lifting disc-shaped crucible 4. The target surface position is adjusted to be slightly higher than the top of the cylindrical crucible wall 5 by adjusting the lifting and rotating base. The rotating and lifting base is then turned on, causing the disc-shaped crucible bottom and the deposition target to rotate at a uniform speed of 10 r / min. The jet burners are ignited. After the furnace temperature rises to the preset temperature value, the silicon tetrachloride raw material passes through the evaporation system and, driven by the carrier gas, undergoes a chemical reaction in the combustion environment of an oxyhydrogen flame through the six jet burners 1 at the top of the furnace, generating silicon dioxide particles which are deposited on the high-temperature target. As the deposition process proceeds, the molten glass covers the entire deposition target. The deposited molten glass serves as a new collection target surface. The lifting function of the rotating and lifting base is then activated to drive the process. The bottom of the disc-shaped crucible and the target surface descend together at a constant speed, with the descent speed balancing the rise speed of the target surface to maintain a constant distance between the target surface and the jet burner. The target surface is always slightly higher than the top of the cylindrical crucible wall by 5 mm. During the deposition process, the exhaust system maintains a negative pressure of -600 Pa to -1200 Pa in the main exhaust pipe and -200 Pa to -300 Pa at the air outlet 11. The dust and exhaust gas inside the furnace are discharged from the furnace through the annular flue chamber 10 and multiple air outlets. The air supply volume in the make-up air chamber 9 is 100 L / min to 500 L / min. During the process, the air supply volume is adjusted to control the pressure at the annular flue chamber between -50 Pa and -100 Pa, maintaining the stability of the furnace temperature and pressure. The jet burner sprays and the rotating and descending disc-shaped crucible continues until the deposition height of the synthetic quartz glass ingot is reached.

[0038] In this embodiment, the distance between the jet burner and the target surface is 350mm, and the angle between the burner and the vertical is 15°. The gas flow rate, exhaust volume, and make-up air volume of the burner are adjusted to control the overall furnace temperature at 1500℃, the annular flue temperature at 1300℃~1400℃, and the distance between the edge of the quartz ingot and the cylindrical crucible wall is maintained at 5~10mm. Feeding is stopped when the quartz ingot height reaches 400mm. The gas flow rate of each burner is reduced, the exhaust pressure at the duct is reduced, and the air intake volume of the make-up air chamber is adjusted. The annular flue temperature is maintained at no less than 1200℃. The furnace is then shut down after holding the temperature for 6 hours. The resulting quartz glass blank ingot 2 has a diameter of 800mm and a height of 400mm. The quartz ingot is free of macroscopic defects such as bubbles and streaks. The optical uniformity is less than 3×10⁻⁶. -6 Stress less than 3×10 -6 .

[0039] Example 2: The difference from the previous example is that the diameter of the rotating lifting disc-shaped crucible bottom is 1600mm, the gap between its outer circumference and the inner hole of the rotating cylindrical crucible wall is 5mm, and the height of the cylindrical crucible wall is 220mm. Eight spaced-apart jet burners 1 are installed on the furnace top. The annular flue chamber 10 is controlled at 1600℃~1700℃. The cylindrical crucible wall and the rotating lifting disc-shaped crucible bottom rotate synchronously at a speed of 10r / min. Feeding is stopped after the quartz ingot height reaches 220mm. The gas volume of each burner is reduced, the exhaust pressure at the vent is reduced, and the air intake of the make-up air chamber is adjusted to maintain the temperature of the annular flue chamber 10 at no less than 1300℃. The furnace is shut down after maintaining this temperature for 6 hours. The resulting quartz glass blank ingot has a diameter of 1600mm and a height of 200mm. The optical uniformity of the quartz ingot product is less than 5×10⁻⁶. -6 Stress less than 5×10 -6 .

Claims

1. A large-size, highly uniform synthetic quartz glass ingot deposition furnace, comprising a furnace body and a furnace top, wherein a jet burner is installed on the furnace top, characterized in that... A separate rotating and lifting crucible is installed in the middle of the furnace cavity corresponding to the jet burner. An annular flue is set on the outer periphery of the separate rotating crucible at the bottom of the furnace cavity, and an air outlet is set along the circumference of the furnace body corresponding to the annular flue. The separate rotating crucible includes a disc-shaped crucible bottom and a cylindrical crucible wall. The disc-shaped crucible bottom and the cylindrical crucible wall are separate. The disc-shaped crucible bottom is connected to the rotating and lifting base to form a rotating and lifting disc-shaped crucible bottom.

2. The large-size, highly uniform synthetic quartz glass ingot deposition furnace according to claim 1, characterized in that... The cylindrical crucible wall is connected to the rotating platform to form a rotating cylindrical crucible wall.

3. The large-size, highly uniform synthetic quartz glass ingot deposition furnace according to claim 1 or 2, characterized in that... The annular flue includes an annular furnace bottom, an inner wall of the furnace cavity, and an outer periphery of a cylindrical crucible wall. The upper end of the annular flue has an annular opening that communicates with the deposition chamber of the furnace cavity. The air outlet is located circumferentially below the furnace body and communicates with the bottom of the annular flue.

4. The large-size, highly uniform synthetic quartz glass ingot deposition furnace according to claim 1 or 2, characterized in that... The air outlet is connected to the exhaust control system to control the exhaust volume of the annular flue and the furnace chamber pressure. There are 4 to 8 air outlets on the outer wall of the furnace body. The exhaust control system is equipped with an air volume regulating valve connected in series with each air outlet, and pressure and temperature monitoring devices are installed at the air outlets.

5. The large-size, highly uniform synthetic quartz glass ingot deposition furnace according to claim 3, characterized in that... The furnace body has an air inlet at the bottom that is connected to the annular flue. The air inlet is connected to a make-up air chamber located outside the bottom of the furnace body. The make-up air chamber is connected to the air intake control system.

6. The large-size, highly uniform synthetic quartz glass ingot deposition furnace according to claim 5, characterized in that... The air inlet is located near the bottom of the furnace body, close to the outer periphery of the cylindrical crucible wall, and is connected to the inner side of the make-up air chamber; the air intake control system is equipped with a gas heating temperature control device, thus forming an air intake control system with heating temperature control function.

7. A method for preparing large-size, highly uniform synthetic quartz glass ingots, characterized in that... Using any of the deposition furnaces described in claims 1-6, quartz glass ingots are prepared by chemical vapor deposition. The deposition target is placed at the bottom of a rotating and lifting disc-shaped crucible. The target surface is adjusted to be slightly higher than or flush with the top of the cylindrical crucible wall by adjusting the rotating and lifting base. The rotating and lifting base is opened, causing the disc-shaped crucible bottom and the deposition target to rotate together at a uniform speed. The jet burner is ignited. After the furnace temperature rises to the preset temperature value, the raw material is injected onto the deposition target by the jet burner placed on the furnace top, driven by the carrier gas. A chemical reaction occurs in the combustion environment of an oxyhydrogen flame, generating silica particles which are deposited on the high-temperature target. As the deposition process proceeds, the molten glass spreads across the entire deposition target. The deposited molten glass serves as a new collection target surface. The lifting function of the rotating lifting base is activated, causing the bottom of the disc-shaped crucible and the target surface to descend continuously and uniformly. The descent speed is balanced with the rising speed of the target surface to maintain a constant distance between the target surface and the jet burner. The target surface is always slightly higher or level with the top of the cylindrical crucible wall. Dust in the furnace cavity is drawn out of the furnace cavity through the annular flue cavity with the airflow, maintaining the stability of the furnace cavity temperature and pressure. The jet burner's injection and the rotating lifting disc-shaped crucible bottom continue to descend until the deposition height of the synthetic quartz glass ingot is reached.

8. The method for preparing large-size, highly uniform synthetic quartz glass ingots according to claim 7, characterized in that... Under the action of the exhaust control system, a progressively decreasing pressure distribution and a progressively decreasing height distribution are formed on the deposition target surface, the annular flue cavity, and the air outlet. A negative pressure zone P1 is formed at the air outlet, and a positive pressure zone P3 is formed on the deposition target surface due to the injection of combustion gas. By adjusting the air supply cavity, the air intake at the air inlet of the annular flue cavity is controlled to maintain the pressure P2 at the annular flue cavity, so that P1 < P2 < P3, and the relative pressure of P2 is -50 Pa to -200 Pa.

9. The method for preparing large-size, highly uniform synthetic quartz glass ingots according to claim 7 or 8, characterized in that... The temperature of the annular flue cavity is controlled between 1000℃ and 1700℃.

10. The method for preparing large-size, highly uniform synthetic quartz glass ingots according to claim 7 or 8, characterized in that... After deposition is complete, heat preservation treatment is carried out. The raw material supply to the jet burner is stopped, the hydrogen and oxygen ratio is adjusted, the flame of the jet burner is kept burning, the descent function of the rotating disc bottom is stopped, the rotation is continued, the temperature of the annular flue cavity is controlled at 1000℃~1400℃, and the heat preservation time is 2~12h.

11. The method for preparing large-size, highly uniform synthetic quartz glass ingots according to claim 7 or 8, characterized in that... The air intake control system controls the air intake volume and temperature of the make-up air chamber. The air intake volume is 100~1000 L / min and the temperature is 25℃~500℃.

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