A raw material melting method for melting quartz glass by a gas refining method

Abstract

The application discloses a raw material melting method for smelting quartz glass by air refining method, and comprises the following steps: S1, raw material pretreatment; S2, hydrogen-oxygen burner design; S3, preheating treatment; S4, quartz sand discharging; and S5, bubble elimination treatment. Thus, the quartz sand raw material before melting is subjected to impurity removal treatment, the adverse effect of trace impurities generated during the melting of the quartz sand on the quartz glass ingot can be reduced, high-temperature flue gas is discharged in time, and the forming quality of the quartz glass ingot is avoided from being affected. Meanwhile, the combustion temperature of the hydrogen-oxygen burner and the discharging process of the quartz sand are accurately controlled, and the melt during the melting of the quartz sand and the bottom ingot is subjected to defoaming treatment, so that the quartz glass ingot is avoided from containing bubbles during forming, the corrugation generated when the temperature is too high is avoided, and the forming quality and the production efficiency of the quartz glass ingot are improved.

Description

Technical Field

[0001] This invention relates to the field of quartz glass gas refining technology, and in particular to a method for melting raw materials for gas refining quartz glass. Background Technology

[0002] Currently, the main methods for melting quartz glass ingots are electrofusion and gas melting. The gas melting method involves first melting quartz sand in a high-temperature oxyhydrogen flame. Under these conditions, the molten quartz sand fuses with a base ingot. Then, by controlling the temperature and cooling rate, the ingot is gradually cooled and shaped into a quartz glass ingot. Currently, the gas melting method typically uses a quartz gas furnace. This furnace, with its lower open section, heats the base ingot using an oxyhydrogen burner and feeds it with quartz sand. The quartz sand melts and deposits onto the base ingot, while the base ingot descends to form a cylindrical quartz glass ingot.

[0003] In the actual production of quartz glass using the gas refining process, the temperature required to melt quartz sand is above 1750℃, and the temperature at the center of the oxyhydrogen flame is above 2000℃ to ensure the melting effect of the quartz sand raw material and its smooth fusion with the ingot. However, during the heating and melting process of the quartz sand raw material, trace impurities generated during the melting process will be deposited on the molten surface of the quartz glass under the influence of the high-temperature flue gas flow, thereby reducing the forming quality of the quartz glass ingot. At the same time, if the temperature of the oxyhydrogen burner is not high enough when the quartz sand raw material is melted, the quartz glass ingot will contain air bubbles during forming, reducing the forming quality of the quartz glass ingot. If the temperature of the oxyhydrogen burner is too high, although there will be fewer air bubbles in the quartz glass ingot after the quartz sand is melted, the excessively high temperature will cause ripples on the outside of the quartz glass ingot during the forming process, reducing the forming quality of the quartz glass ingot and resulting in low production efficiency. Summary of the Invention

[0004] To address the technical problems in existing technologies, such as the deposition of trace impurities generated during the melting of quartz sand on the molten surface of quartz glass under the influence of high-temperature flue gas flow, and the significant impact of the temperature of the hydrogen-oxygen burner on the melting of quartz sand raw materials, which reduces the molding quality of quartz glass ingots, the present invention provides the following technical solution.

[0005] This invention discloses a method for melting raw materials for gas refining to produce quartz glass, comprising the following steps: S1: Raw material pretreatment: Select quartz sand raw material with SiO2 content ≥99.9% and quartz sand particle size of 100-200 mesh. Clean and dry the quartz sand and remove impurities and adsorbed water from the surface of the quartz sand. S2: Hydrogen-oxygen burner design: The hydrogen-oxygen burner adopts a multi-nozzle ring array (24 to 48 nozzles), and the flame diameter can cover the quartz sand feeding path; S3: Preheating treatment: Preheating the furnace chamber and the bottom ingot on the support platform of the quartz gas refining furnace; S4: Quartz sand feeding: When the temperature inside the furnace reaches above 1750℃ and the bottom ingot gradually melts, start spraying quartz sand raw material onto the bottom ingot. The initial feeding rate is 10-12g / min. When it is observed from the viewing window that the quartz sand raw material has melted and fused with the bottom ingot, raise the furnace temperature and increase the feeding rate to 30-40g / min. During this process, maintain a slight positive pressure state inside the furnace and promptly discharge the high-temperature flue gas. S5: Bubble elimination treatment: Apply a 20kHz ultrasonic field to the molten area between the quartz sand and the bottom ingot to cause microbubbles in the melt to coalesce and float to the surface, thus eliminating the bubbles.

[0006] As a further technical solution, in step S1, when removing impurities from the surface of the quartz sand, the quartz sand is placed in a microwave plasma reactor and NF3 gas is introduced to etch the contamination layer on the surface of the quartz sand.

[0007] As a further technical solution, in step S2, the number of hydrogen-oxygen burners is 1-6.

[0008] As a further technical solution, in step S3, hydrogen and oxygen are first introduced into the hydrogen-oxygen burner to preheat the furnace and bottom ingot. The temperature is first rapidly increased to 800°C, and then the furnace is preheated to 1400°C at a heating rate of 10-20°C per hour. When the furnace temperature reaches 1400°C, the temperature is rapidly increased to make the furnace temperature finally stabilize and be controlled above 1750°C.

[0009] As a further technical solution, in step S4, when it is observed from the viewing window that the quartz sand raw material is melting and melting with the bottom ingot, the furnace temperature is increased and the feed rate is increased at a rate of 1-2 g / min until it is increased to 30-40 g / min.

[0010] As a further technical solution, in step S4, a dual protective gas is used when feeding the quartz sand. The outer layer of the quartz sand is isolated from oxygen by high-purity Ar gas, and the inner layer of the quartz sand is circulated with hydrogen gas to maintain a reducing environment.

[0011] As a further technical solution, in step S4, the flow rate of high-purity Ar gas is 3-5 m³ / h, and the flow rate of hydrogen gas is 1-2 m³ / h.

[0012] As a further technical solution, in step S4, the ratio of hydrogen to oxygen introduced into the hydrogen-oxygen burner is 2:1 or 2:0.9.

[0013] As a further technical solution, in step S4, the hydrogen pressure is 0.6-0.8 MPa and the flow rate is 20-30 m³ / h, and the oxygen pressure is 0.7-0.9 MPa and the flow rate is 10-16 m³ / h.

[0014] As a further technical solution, in step S4, the temperature at the center point of the hydrogen-oxygen flame is maintained at 2000-2300℃.

[0015] The beneficial effects of this invention are as follows: The invention removes impurities from the quartz sand raw material before melting, reducing the adverse effects of trace impurities generated during quartz sand melting on quartz glass ingots. It also ensures timely removal of high-temperature flue gas, preventing it from affecting the molding quality of the quartz glass ingots. Simultaneously, it precisely controls the combustion temperature of the hydrogen-oxygen burner and the quartz sand feeding process, and defoams the melt during the melting of quartz sand and the ingot, preventing air bubbles in the quartz glass ingots during molding and avoiding ripples caused by excessively high temperatures, thereby improving the molding quality and production efficiency of the quartz glass ingots. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0017] In the description of this invention, it should be understood that the terms "upper" and "lower," referring to orientation or positional relationships, are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0018] This invention discloses a method for melting raw materials for gas refining to produce quartz glass, comprising the following steps: S1: Raw material pretreatment: Select quartz sand raw material with SiO2 content ≥99.9% and quartz sand particle size of 100-200 mesh. Clean and dry the quartz sand and remove impurities and adsorbed water from the surface of the quartz sand.

[0019] In step S1, the preferred particle size of the quartz sand is 100-150 mesh. A vacuum drying method is used, employing heating at 90℃–150℃ in a vacuum environment (low pressure) to effectively remove moisture from the micropores and prevent high-temperature oxidation or agglomeration. Subsequently, to remove surface impurities from the quartz sand, it is placed in a microwave plasma reactor, and NF3 gas is introduced to etch the surface contaminant layer, increasing the specific surface area by 30%. After pretreatment, the metallic impurities on the quartz sand surface are reduced to the 0.3 ppm level. This removes trace amounts of adsorbed water and impurities from the quartz sand raw material, reducing the adverse effects of trace impurities generated during quartz sand melting on quartz glass ingots.

[0020] S2: Hydrogen-oxygen burner design: The hydrogen-oxygen burner adopts a multi-nozzle ring array (24 to 48 nozzles), and the flame diameter can cover the quartz sand feeding path.

[0021] In step S2, the number of hydrogen-oxygen burners is 1-6, and the nozzles of the hydrogen-oxygen burners are arranged around the feed pipe of the quartz sand, so that the quartz sand is always in the hydrogen-oxygen flame during the feeding process.

[0022] S3: Preheating treatment: Preheating the furnace chamber and the bottom ingot on the support platform of the quartz gas refining furnace.

[0023] In step S3, hydrogen and oxygen are first introduced into the hydrogen-oxygen burner to preheat the furnace and bottom ingot. The temperature is first rapidly increased to 800°C, and then the furnace is preheated to 1400°C at a rate of 10-20°C per hour. When the furnace temperature reaches 1400°C, the temperature is rapidly increased to stabilize the furnace temperature and control it above 1750°C.

[0024] S4: Quartz Sand Feeding: When the temperature inside the furnace reaches above 1750℃ and the bottom ingot gradually melts, start spraying quartz sand raw material onto the bottom ingot. Initially, the feeding rate is 10-12g / min. When it is observed from the viewing window that the quartz sand raw material has melted and fused with the bottom ingot, increase the furnace temperature and increase the feeding rate at a rate of 1-2g / min until the feeding rate is 30-40g / min. During this process, maintain a slight positive pressure in the furnace and promptly discharge the high-temperature flue gas.

[0025] In step S4, when the hydrogen-oxygen burner is working, the hydrogen pressure is 0.6-0.8 MPa and the flow rate is 20-30 m / h, the oxygen pressure is 0.7-0.9 MPa and the flow rate is 10-16 m / h, and the temperature at the center of the hydrogen-oxygen flame is maintained at 2000-2300℃.

[0026] S5: Bubble elimination treatment: A 20kHz ultrasonic field is applied to the molten area between the quartz sand and the bottom ingot to cause microbubbles in the melt to coalesce and float to the surface, thus eliminating the bubbles. The bubble density of the quartz glass ingot after molding is <0.005 bubbles / cm³.

[0027] After the quartz sand and the base ingot are melted, a supporting platform is driven to slowly rotate and lower the quartz glass ingot. The melt then cools and forms a cylindrical quartz glass ingot as it descends with the base ingot and the supporting platform. The rotation speed is 4–10 r / min, and the descent speed is 0.6–0.7 mm / min. Since this invention uses an existing quartz gas furnace and quartz glass cutting structure, and only improves the quartz sand melting method, the subsequent cooling, shaping, and length-cutting processes of the quartz glass ingot are not described in detail.

[0028] The present invention will be further described below with reference to specific embodiments. Unless otherwise specified, the raw materials and operating steps used in the following embodiments are all commercially available conventional materials and conventional steps for gas refining of quartz glass known to those skilled in the art.

[0029] Example 1: First, quartz sand raw material with a particle size of 100-200 mesh and a SiO2 content ≥99.9% is selected. Under vacuum (low pressure), it is heated at 90℃–150℃ to remove moisture from the micropores of the quartz sand. Then, the quartz sand is placed in a microwave plasma reactor, and NF3 gas is introduced to etch the surface contaminant layer, increasing the specific surface area by 30%. After pretreatment, the metallic impurities on the quartz sand surface are reduced to 0.3ppm. Next, the quartz sand is placed into a feeding system equipped with high-purity Ar and hydrogen gas. A dual protective gas system is used during quartz sand feeding: high-purity Ar gas is used to isolate oxygen from the outer layer of the quartz sand, while hydrogen gas is introduced into the inner layer to maintain a reducing environment. The high-purity Ar gas flow rate is 3 m³ / h, and the hydrogen gas flow rate is 1 m³ / h.

[0030] The feeding system and oxyhydrogen burner are connected to the quartz gas refining furnace, driving the support platform to rise and elevate the bottom ingot to the upper end of the forming channel. Preheating then begins on the furnace chamber and the bottom ingot on the support platform. During oxyhydrogen burner operation, the hydrogen pressure is 0.6 MPa and the flow rate is 20 m³ / h, while the oxygen pressure is 0.7 MPa and the flow rate is 10 m³ / h. The temperature at the center of the oxyhydrogen flame is maintained at 2000-2300℃. The furnace temperature is first rapidly increased to 800℃, then preheated to 1400℃ at a rate of 10-20℃ per hour. Once the furnace temperature reaches 1400℃, it is rapidly increased again to stabilize and control the furnace temperature above 1750℃.

[0031] When the temperature inside the furnace reaches above 1750℃ and the bottom ingot gradually melts, quartz sand raw material is sprayed onto the bottom ingot. The initial feed rate is 10g / min. When the quartz sand raw material is observed to melt and fused with the bottom ingot through the viewing window, the furnace temperature is increased and the feed rate is increased at a rate of 1g / min until the feed rate reaches 30g / min. During this process, a slight positive pressure is maintained inside the furnace.

[0032] A 20kHz ultrasonic field is applied to the molten area between the quartz sand and the ingot to cause microbubbles in the melt to coalesce and float to the surface, thus eliminating the bubbles. The quartz glass ingot is then slowly rotated and lowered at a uniform rotation speed of 4–10 r / min and a descent speed of 0.6–0.7 mm / min. Subsequent cooling, shaping, and length-determined cutting processes are then performed on the quartz glass ingot.

[0033] Example 2: First, quartz sand raw material with a particle size of 100-200 mesh and a SiO2 content ≥99.9% is selected. Under vacuum (low pressure), it is heated at 90℃–150℃ to remove moisture from the micropores of the quartz sand. Then, the quartz sand is placed in a microwave plasma reactor, and NF3 gas is introduced to etch the surface contaminant layer, increasing the specific surface area by 30%. After pretreatment, the metallic impurities on the quartz sand surface are reduced to 0.3ppm. Next, the quartz sand is placed into a feeding system equipped with high-purity Ar and hydrogen gas. A dual protective gas system is used during quartz sand feeding: high-purity Ar gas is used to isolate oxygen from the outer layer of the quartz sand, while hydrogen gas is introduced into the inner layer to maintain a reducing environment. The high-purity Ar gas flow rate is 4 m³ / h, and the hydrogen gas flow rate is 1.5 m³ / h.

[0034] The feeding system and oxyhydrogen burner are connected to the quartz gas refining furnace, driving the support platform to rise and raise the bottom ingot to the upper end of the forming channel. Preheating then begins on the furnace chamber and the bottom ingot on the support platform. During oxyhydrogen burner operation, the hydrogen pressure is 0.7 MPa and the flow rate is 25 m³ / h, while the oxygen pressure is 0.8 MPa and the flow rate is 12.5 m³ / h. The temperature at the center of the oxyhydrogen flame is maintained at 2000-2300℃. The furnace temperature is first rapidly increased to 800℃, then preheated to 1400℃ at a rate of 10-20℃ per hour. Once the furnace temperature reaches 1400℃, it is rapidly increased again to stabilize and control the furnace temperature above 1750℃.

[0035] When the temperature inside the furnace reaches above 1750℃ and the bottom ingot gradually melts, quartz sand raw material is sprayed onto the bottom ingot. The initial feed rate is 11g / min. When it is observed from the viewing window that the quartz sand raw material has melted and fused with the bottom ingot, the furnace temperature is increased and the feed rate is increased at a rate of 1.5g / min until the feed rate reaches 35g / min. During this process, a slight positive pressure is maintained inside the furnace.

[0036] A 20kHz ultrasonic field is applied to the molten area between the quartz sand and the ingot to cause microbubbles in the melt to coalesce and float to the surface, thus eliminating the bubbles. The quartz glass ingot is then slowly rotated and lowered at a uniform rotation speed of 4–10 r / min and a descent speed of 0.6–0.7 mm / min. Subsequent cooling, shaping, and length-determined cutting processes are then performed on the quartz glass ingot.

[0037] Example 3: First, quartz sand raw material with a particle size of 100-200 mesh and a SiO2 content ≥99.9% is selected. Under vacuum (low pressure), it is heated at 90℃–150℃ to remove moisture from the micropores of the quartz sand. Then, the quartz sand is placed in a microwave plasma reactor, and NF3 gas is introduced to etch the surface contaminant layer, increasing the specific surface area by 30%. After pretreatment, the metallic impurities on the quartz sand surface are reduced to 0.3ppm. Next, the quartz sand is placed into a feeding system equipped with high-purity Ar and hydrogen gas. A dual protective gas system is used during quartz sand feeding: high-purity Ar gas is used to isolate oxygen from the outer layer of the quartz sand, while hydrogen gas is introduced into the inner layer to maintain a reducing environment. The high-purity Ar gas flow rate is 5 m³ / h, and the hydrogen gas flow rate is 2 m³ / h.

[0038] The feeding system and oxyhydrogen burner are connected to the quartz gas refining furnace, driving the support platform to rise and raise the bottom ingot to the upper end of the forming channel. Preheating then begins on the furnace chamber and the bottom ingot on the support platform. During oxyhydrogen burner operation, the hydrogen pressure is 0.8 MPa and the flow rate is 30 m³ / h, while the oxygen pressure is 0.9 MPa and the flow rate is 16 m³ / h. The temperature at the center of the oxyhydrogen flame is maintained at 2000-2300℃. The furnace temperature is first rapidly increased to 800℃, then preheated to 1400℃ at a rate of 10-20℃ per hour. Once the furnace temperature reaches 1400℃, it is rapidly increased again to stabilize and control the furnace temperature above 1750℃.

[0039] When the temperature inside the furnace reaches above 1750℃ and the bottom ingot gradually melts, quartz sand raw material is sprayed onto the bottom ingot. The initial feed rate is 12g / min. When it is observed from the viewing window that the quartz sand raw material has melted and fused with the bottom ingot, the furnace temperature is increased and the feed rate is increased at a rate of 2g / min until the feed rate reaches 40g / min. During this process, a slight positive pressure is maintained inside the furnace.

[0040] A 20kHz ultrasonic field is applied to the molten area between the quartz sand and the ingot to cause microbubbles in the melt to coalesce and float to the surface, thus eliminating the bubbles. The quartz glass ingot is then slowly rotated and lowered at a uniform rotation speed of 4–10 r / min and a descent speed of 0.6–0.7 mm / min. Subsequent cooling, shaping, and length-determined cutting processes are then performed on the quartz glass ingot.

[0041] Comparative Example 1: First, quartz sand raw material with a particle size of 100-200 mesh and a SiO2 content of ≥99.9% is selected. The moisture inside the micropores of the quartz sand is removed by heating at 90℃–150℃ in a vacuum environment (low pressure). Then, the quartz sand is placed into the feeding system.

[0042] The feeding system and oxyhydrogen burner are connected to the quartz gas refining furnace, and the supporting platform is driven to rise, raising the bottom ingot to the upper end of the forming channel. Preheating then begins on the furnace chamber and the bottom ingot on the supporting platform. During oxyhydrogen burner operation, the hydrogen pressure is 0.6-0.8 MPa and the flow rate is 20-30 m³ / h, while the oxygen pressure is 0.7-0.9 MPa and the flow rate is 10-18 m³ / h. The temperature at the center of the oxyhydrogen flame is maintained at 2000-2300℃. The furnace temperature is first rapidly increased to 800℃, then preheated to 1400℃ at a rate of 10-20℃ per hour. Once the furnace temperature reaches 1400℃, the temperature is rapidly increased again to stabilize and control the furnace temperature above 1750℃.

[0043] When the temperature inside the furnace reaches above 1750℃ and the bottom ingot gradually melts, quartz sand raw material is sprayed onto the bottom ingot. The initial feed rate is 10g / min. When the quartz sand raw material is observed to melt and fused with the bottom ingot through the viewing window, the furnace temperature is increased and the feed rate is increased at a rate of 1-2g / min until the feed rate reaches 30g / min. During this process, a slight positive pressure is maintained inside the furnace.

[0044] A 20kHz ultrasonic field is applied to the molten area between the quartz sand and the ingot to cause microbubbles in the melt to coalesce and float to the surface, thus eliminating the bubbles. The quartz glass ingot is then slowly rotated and lowered at a uniform rotation speed of 4–10 r / min and a descent speed of 0.6–0.7 mm / min. Subsequent cooling, shaping, and length-determined cutting processes are then performed on the quartz glass ingot.

[0045] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 did not use a microwave plasma reactor to remove impurities from the quartz sand, and it did not use a double protective gas to protect the quartz sand. The quartz glass ingots produced by melting in Example 1 and Comparative Example 1 were tested separately. The tests showed that the quartz glass ingots melted in Comparative Example 1 contained trace impurities and occasional cracks, with a finished product qualification rate of approximately 55%. In contrast, the quartz glass ingots melted and molded in Example 1 had smooth, transparent surfaces, no bubbles, and no cracks, with a finished product qualification rate of approximately 75%.

[0046] Comparative Example 2: First, quartz sand raw material with a particle size of 100-200 mesh and a SiO2 content of ≥99.9% is selected. Under vacuum environment (low pressure), the moisture in the micropores of the quartz sand is removed by heating at 90℃–150℃. Then, the quartz sand is placed in a microwave plasma reactor and NF3 gas is introduced to etch the contamination layer on the surface of the quartz sand, thereby increasing the specific surface area by 30%. After pretreatment, the metal impurities on the surface of the quartz sand are reduced to the level of 0.3ppm.

[0047] The feeding system and oxyhydrogen burner are connected to the quartz gas refining furnace, and the supporting platform is driven to rise, raising the bottom ingot to the upper end of the forming channel. Preheating then begins on the furnace chamber and the bottom ingot on the supporting platform. During oxyhydrogen burner operation, the hydrogen pressure is 0.6-0.8 MPa and the flow rate is 20-30 m³ / h, while the oxygen pressure is 0.7-0.9 MPa and the flow rate is 10-18 m³ / h. The temperature at the center of the oxyhydrogen flame is maintained at 2000-2300℃. The furnace temperature is first rapidly increased to 800℃, then preheated to 1400℃ at a rate of 10-20℃ per hour. Once the furnace temperature reaches 1400℃, the temperature is rapidly increased again to stabilize and control the furnace temperature above 1750℃.

[0048] When the temperature inside the furnace reaches above 1750℃ and the bottom ingot gradually melts, the quartz sand raw material is sprayed onto the bottom ingot. The initial feed rate is 11g / min. When the quartz sand raw material is observed to melt and melt with the bottom ingot through the viewing window, the furnace temperature is increased and the feed rate is increased until the feed rate is 35g / min. During this process, a slight positive pressure is maintained inside the furnace.

[0049] A 20kHz ultrasonic field is applied to the molten area between the quartz sand and the ingot to cause microbubbles in the melt to coalesce and float to the surface, thus eliminating the bubbles. The quartz glass ingot is then slowly rotated and lowered at a uniform rotation speed of 4–10 r / min and a descent speed of 0.6–0.7 mm / min. Subsequent cooling, shaping, and length-determined cutting processes are then performed on the quartz glass ingot.

[0050] The difference between Comparative Example 2 and Example 2 is that Comparative Example 2 did not use a double protective gas to protect the quartz sand raw material, and it did not use a gradual feeding method with an increasing feed rate of 1-2 g / min. The quartz glass ingots produced by melting in Example 2 and Comparative Example 2 were tested. The tests showed that the quartz glass ingots melted in Comparative Example 2 contained trace impurities and occasionally showed incompletely melted quartz sand dots, with a finished product qualification rate of approximately 52%. In contrast, the quartz glass ingots melted and molded in Example 2 had a smooth and transparent surface, free of bubbles and cracks, with a finished product qualification rate of approximately 80%.

[0051] Comparative Example 3: First, quartz sand raw material with a particle size of 100-200 mesh and a SiO2 content ≥99.9% is selected. Under vacuum (low pressure), it is heated at 90℃–150℃ to remove moisture from the micropores of the quartz sand. Then, the quartz sand is placed in a microwave plasma reactor, and NF3 gas is introduced to etch the surface contaminant layer, increasing the specific surface area by 30%. After pretreatment, the metallic impurities on the quartz sand surface are reduced to 0.3ppm. Next, the quartz sand is placed into a feeding system equipped with high-purity Ar and hydrogen gas. A dual protective gas system is used during quartz sand feeding: high-purity Ar gas is used to isolate oxygen from the outer layer of the quartz sand, while hydrogen gas is introduced into the inner layer to maintain a reducing environment. The high-purity Ar gas flow rate is 3-5 m³ / h, and the hydrogen gas flow rate is 1-2 m³ / h.

[0052] The feeding system and oxyhydrogen burner are connected to the quartz gas refining furnace, and the supporting platform is driven to rise, raising the bottom ingot to the upper end of the forming channel. Preheating then begins on the furnace chamber and the bottom ingot on the supporting platform. During oxyhydrogen burner operation, the hydrogen pressure is 0.6-0.8 MPa and the flow rate is 20-30 m³ / h, while the oxygen pressure is 0.7-0.9 MPa and the flow rate is 10-18 m³ / h. The temperature at the center of the oxyhydrogen flame is maintained at 2000-2300℃. The furnace temperature is first rapidly increased to 800℃, then preheated to 1400℃ at a rate of 10-20℃ per hour. Once the furnace temperature reaches 1400℃, the temperature is rapidly increased again to stabilize and control the furnace temperature above 1750℃.

[0053] When the temperature inside the furnace reaches above 1750℃ and the bottom ingot gradually melts, quartz sand raw material is sprayed onto the bottom ingot. Initially, the feed rate is 10-12 g / min. When it is observed from the viewing window that the quartz sand raw material has melted and fused with the bottom ingot, the furnace temperature is increased and the feed rate is increased at a rate of 1-2 g / min until the feed rate is 30-40 g / min. During this process, a slight positive pressure is maintained inside the furnace.

[0054] The quartz glass ingot is then slowly rotated and lowered at a constant rotation speed of 4–10 r / min and a descent speed of 0.6–0.7 mm / min. Following this, the quartz glass ingot undergoes subsequent cooling, shaping, and length-cutting processes.

[0055] The difference between Comparative Example 3 and Example 3 is that Comparative Example 3 did not use an ultrasonic field to defoam the microbubbles in the melt. The quartz glass ingots produced by Example 3 and Comparative Example 3 were tested. The tests showed that the quartz glass ingots produced by Comparative Example 3 occasionally contained bubbles, with a finished product qualification rate of approximately 62%. In contrast, the quartz glass ingots produced by Example 3 had smooth, transparent surfaces, no bubbles or cracks, and a finished product qualification rate of approximately 78%.

[0056] As can be seen from the above, the raw material melting method for gas refining quartz glass of the present invention can remove impurities from the quartz sand raw material before melting, reduce the adverse effects of trace impurities generated during quartz sand melting on quartz glass ingots, can precisely control the combustion temperature of the hydrogen-oxygen burner and the quartz sand feeding process, and can defoam the melt when quartz sand and bottom ingot are melted, so as to avoid the presence of air bubbles in the quartz glass ingot during molding, avoid the ripples generated when the temperature is too high, and improve the molding quality and production efficiency of quartz glass ingots.

[0057] The preferred embodiments and examples of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments and examples. Within the scope of knowledge possessed by those skilled in the art, various changes or equivalent substitutions can be made without departing from the concept of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A method for melting raw materials in the gas refining process for producing quartz glass, characterized in that, Includes the following steps: S1: Raw material pretreatment: Select quartz sand raw material with SiO2 content ≥99.9% and quartz sand particle size of 100-200 mesh. Clean and dry the quartz sand and remove impurities and adsorbed water from the surface of the quartz sand. S2: Hydrogen-oxygen burner design: The hydrogen-oxygen burner adopts a multi-nozzle ring array (24 to 48 nozzles), and the flame diameter can cover the quartz sand feeding path; S3: Preheating treatment: Preheating the furnace chamber and the bottom ingot on the support platform of the quartz gas refining furnace; S4: Quartz sand feeding: When the temperature inside the furnace reaches above 1750℃ and the bottom ingot gradually melts, start spraying quartz sand raw material onto the bottom ingot. The initial feeding rate is 10-12g / min. When it is observed from the viewing window that the quartz sand raw material has melted and fused with the bottom ingot, raise the furnace temperature and increase the feeding rate to 30-40g / min. During this process, maintain a slight positive pressure state inside the furnace and promptly discharge the high-temperature flue gas. S5: Bubble elimination treatment: Apply a 20kHz ultrasonic field to the molten area between the quartz sand and the bottom ingot to cause microbubbles in the melt to coalesce and float to the surface, thus eliminating the bubbles.

2. The raw material melting method for gas refining quartz glass according to claim 1, characterized in that: In step S1, when removing impurities from the surface of the quartz sand, the quartz sand is placed in a microwave plasma reactor and NF3 gas is introduced to etch the contamination layer on the surface of the quartz sand.

3. The raw material melting method for gas refining quartz glass according to claim 1, characterized in that: In step S2, the number of hydrogen-oxygen burners is 1-6.

4. The raw material melting method for gas refining quartz glass according to claim 1, characterized in that: In step S3, hydrogen and oxygen are first introduced into the hydrogen-oxygen burner to preheat the furnace and bottom ingot. The temperature is first rapidly increased to 800°C, and then the furnace is preheated to 1400°C at a rate of 10-20°C per hour. When the furnace temperature reaches 1400°C, the temperature is rapidly increased to stabilize the furnace temperature and control it to above 1750°C.

5. The raw material melting method for gas refining quartz glass according to claim 1, characterized in that: In step S4, when the quartz sand raw material is observed to melt and melt with the bottom ingot through the viewing window, the furnace temperature is increased and the feed rate is increased at a rate of 1-2 g / min until it reaches 30-40 g / min.

6. The raw material melting method for gas refining quartz glass according to claim 1, characterized in that: In step S4, a dual protective gas is used when feeding the quartz sand. The outer layer of the quartz sand is isolated from oxygen by high-purity Ar gas, and the inner layer of the quartz sand is circulated with hydrogen gas to maintain a reducing environment.

7. The raw material melting method for gas refining quartz glass according to claim 6, characterized in that: In step S4, the flow rate of high-purity Ar gas is 3-5 m³ / h, and the flow rate of hydrogen gas is 1-2 m³ / h.

8. The raw material melting method for gas refining quartz glass according to claim 1, characterized in that: In step S4, the ratio of hydrogen to oxygen introduced into the hydrogen-oxygen burner is 2:1 or 2:0.

9.

9. The raw material melting method for gas refining quartz glass according to claim 1, characterized in that: In step S4, the hydrogen pressure is 0.6-0.8 MPa and the flow rate is 20-30 m³ / h, while the oxygen pressure is 0.7-0.9 MPa and the flow rate is 10-16 m³ / h.

10. The raw material melting method for gas refining quartz glass according to claim 1, characterized in that: In step S4, the temperature at the center of the oxyhydrogen flame is maintained at 2000-2300℃.