Substrate glass annealing furnace

Abstract

An upper air knife system, a middle air knife system and a lower air knife system are arranged on the furnace wall at intervals from top to bottom, each air knife system comprises two sets of air knife assemblies, and the two sets of air knife assemblies are symmetrically arranged on the two sides of substrate glass. An air curtain generated by each group of air knife components is obliquely downwards blown to the substrate glass; the upper air knife system is positioned between the shaping furnace and the annealing furnace and is used for isolating the shaping furnace from the annealing furnace; the medium-speed blade system is positioned in the middle of the annealing furnace; the lower air knife system is located above the transverse cutting machine and used for isolating the annealing furnace from the transverse cutting machine. The air curtains generated by the three groups of air knife systems in the annealing furnace can completely prevent low-temperature gas entering the furnace body from the lower part of the furnace body from rising, so that the environment temperature in the annealing furnace is stabilized, the dust environment in the furnace can be optimized, and the pollution degree of the glass surface is reduced.

Description

Technical Field

[0001] This invention specifically relates to an annealing furnace for substrate glass, belonging to the field of annealing technology for display substrate glass production equipment. Background Technology

[0002] Overflow pull-down method is currently the mainstream production technology for display substrate glass. Its basic production process involves molten glass overflowing from the top of an overflow tank, flowing down the outer surfaces of both sides of the tank, and converging at the bottom. The glass ribbon, in a natural hanging state, sequentially passes through a forming furnace, an annealing furnace for annealing and cooling, and then flows down through the furnace opening. During its descent, it is cut to the required dimensions by a cross-cutting machine. The annealing furnace is the core equipment in the forming process for annealing the glass substrate. Located below the forming zone's sizing furnace, its bottom is connected to the cross-cutting machine. Inside the annealing furnace, the temperature decreases from top to bottom, with lower air pressure in areas of higher temperature; the environmental pressure in the cutting zone is higher than in the forming zone. Due to these two factors, a "chimney effect" occurs inside the annealing furnace, where low-temperature, unclean air rises. The chimney effect has a significant impact on display glass production, causing issues such as unstable temperature fields, dust contamination on the glass surface, and increased energy consumption.

[0003] In existing technologies, multiple baffles (partitions) are typically installed inside the annealing furnace to divide the furnace into sections and block the upward flow of air, for example, with... Figure 3 A curved steel baffle 17 is used between the near and far ends of the furnace to mitigate the "chimney effect" and prevent the rising of low-temperature air. However, there is a certain space between the edge of the baffle and the pull-down glass. Because of this relatively large gap, some low-temperature gas still enters the annealing furnace, causing instability in the furnace's temperature field and significantly affecting precise temperature control. In addition, driven by the rising airflow, some glass dust (such as glass powder generated during cutting) adheres to the glass surface, affecting its cleanliness. Furthermore, glass breakage is inevitable during glass production. Since the partitions in the annealing furnace only have narrow gaps for the glass substrate to overflow and pull down, and the distance between the two side walls of the furnace remains constant, the cantilever of the partition on the furnace wall is long. When a glass plate breaks, it will clog the partitions in various sections of the furnace, accumulating more and more, making it difficult to clean. Cleaning glass fragments prolongs downtime for maintenance. Summary of the Invention

[0004] In view of the problems existing in the prior art, the present invention provides a substrate glass annealing furnace, which aims to alleviate or eliminate the chimney effect in the existing annealing furnace and solve at least one of the many problems such as unstable temperature field inside the furnace and difficulty in cleaning broken glass.

[0005] The technical solution of this invention is as follows: An annealing furnace for substrate glass has at least one set of air knife systems on the furnace wall. Each set of air knife systems includes two sets of air knife assemblies, which are symmetrically arranged on both sides of the substrate glass. The air curtain generated by each set of air knife assemblies blows obliquely downward toward the substrate glass.

[0006] Furthermore, each air knife assembly includes an air pipe through which clean compressed air is introduced. The part of the air pipe that passes through the furnace wall is the air knife. The end of the air knife is a downward-sloping duckbill-shaped outlet. The duckbill-shaped outlet is located inside the furnace and has a certain distance from the substrate glass. Its width matches the width of the substrate glass.

[0007] Furthermore, each air knife assembly also includes an air heating system, which preheats the air entering the furnace to bring its temperature up to the ambient temperature of the furnace space where the air knife is located.

[0008] Furthermore, the air heating system includes an air knife heater and an air knife thermocouple. The air knife heater is used to heat the air knife, and the air knife thermocouple is used to detect the outlet air temperature of the air knife.

[0009] Furthermore, a regulating valve, a pressure transmitter, and a flow meter are sequentially installed on the air pipe of the air knife assembly. The regulating valve is used to regulate the airflow of clean air into the furnace body to ensure that the air pressure on both sides of the substrate glass plate is the same, thus maintaining glass stability. The gas pressure transmitter is used to detect the gas pressure after the regulating valve and to provide pressure compensation for the vortex flow meter to measure the gas mass. The flow meter is used to detect the volumetric flow rate of clean air flowing into the furnace body, and its detection value is output to the DCS system to control the opening of the regulating valve.

[0010] Furthermore, a check valve is installed on the gas pipe downstream of the flow meter to prevent high-temperature gas from backflowing.

[0011] Furthermore, the regulating valve, pressure transmitter, flow meter, and check valve are all located on the outside of the annealing furnace body.

[0012] Furthermore, three sets of air knife systems are arranged at intervals from top to bottom on the furnace wall of the annealing furnace: an upper air knife system, a middle air knife system, and a lower air knife system. The upper air knife system is used to isolate the shaping furnace from the annealing furnace, and the lower air knife system is used to isolate the annealing furnace from the cross-cutting machine.

[0013] Furthermore, in-furnace heating systems are installed on the furnace wall between the upper and middle air knife systems, and on the furnace wall between the middle and lower air knife systems.

[0014] Beneficial effects: This invention, by setting up three sets of air knife systems (upper, middle, and lower) inside the substrate glass annealing furnace, allows clean compressed air to be symmetrically blown onto both sides of the glass through air curtains generated by the air knife systems, stabilizing the glass and dividing the annealing furnace into upper and lower temperature zones. The three air curtains can block the rise of low-temperature gases entering the furnace from the bottom, thereby mitigating or even eliminating the "chimney effect" within the annealing furnace. Simultaneously, the air curtains can also prevent dust from entering the annealing furnace and even the upper setting furnace, thus improving the cleanliness of the glass. The clean compressed air entering the furnace... After being heated, its temperature reaches the ambient temperature of the furnace space where the air knife is located, so it will not affect the temperature field inside the furnace. Clean compressed air enters the annealing furnace from the upper air knife and is discharged from the bottom of the furnace. This airflow circulation is equivalent to replacing the inside of the furnace with clean gas, optimizing the dust environment inside the furnace and reducing the degree of contamination on the glass surface. Finally, the formation of the air curtain allows for an increase in the distance between the air knife outlet and the substrate glass. Combined with the downward-sloping duckbill-shaped outlet design, the accumulation of broken glass on it is greatly reduced, significantly shortening the maintenance time. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall annealing furnace assembly.

[0016] Figure 2 This is a schematic diagram of the air knife and air curtain of the annealing furnace of the present invention (taking the middle air knife system as an example).

[0017] Figure 3 This is the original baffle design drawing for the annealing furnace in the existing design.

[0018] Figure descriptions: 0. Furnace wall, 1. Display glass, 2. Middle zone of annealing furnace, 3. Thermocouple in the middle of annealing furnace (referred to as TLD-1 in the text to measure temperature), 4. Heating wire inside the furnace, 5. Regulating valve, 6. Pressure transmitter, 7. Vortex flow meter, 8. Check valve, 9. Middle air knife heater, 10. Middle air knife, 11. Middle air knife thermocouple, 12. Lower air knife system, 13. Upper air knife system, 14. Middle air knife air curtain of annealing furnace, 15. Low-temperature gas rising from the bottom of the furnace, 16. Downward flow path of the air curtain after encountering the glass, 17. Original design baffle, 18. Gas pipe. Detailed Implementation

[0019] The present invention will now be described in further detail with reference to the accompanying drawings. The drawings are provided to further illustrate the present invention and are used in conjunction with the specific embodiments to explain the present invention, but do not constitute a limitation thereof.

[0020] like Figure 1-2As shown, a substrate glass annealing furnace has three air knife systems arranged from top to bottom on the furnace wall 0: an upper air knife system 13, a middle air knife system, and a lower air knife system 12. Each air knife system includes two sets of air knife components, which are symmetrically arranged on both sides of the substrate glass 1. The air curtain generated by each air knife component blows obliquely downwards towards the substrate glass. The upper air knife system 13 is located between the shaping furnace and the annealing furnace, and is used to isolate the two furnaces. The temperature fields of the shaping furnace and the annealing furnace are significantly different. The purpose of setting the air knife here is to block the upward flow of air from the annealing furnace and eliminate the influence of the air flow from the annealing furnace on the temperature field of the shaping furnace. The middle air knife system is located in the middle of the annealing furnace. The area above the middle air knife is a temperature precision control zone. The quality of the display glass product is closely related to the ambient temperature in this area. According to the production process requirements, the temperature in this area needs to be extremely stable. The air curtain generated by the air knife here can completely isolate the low-temperature airflow from the lower area. The lower air knife system 12 is located above the cross-cutting machine and is used to isolate the annealing furnace from the cross-cutting machine. The air curtain formed by this air knife has an airtight effect on the annealing furnace, completely preventing low-temperature gases carrying dust from entering the annealing furnace, thereby improving the cleanliness of the glass surface. The air curtain clamps the glass on both sides, reducing the amplitude of glass shaking caused by cutting and lowering the risk of glass breakage. The three sets of air knife systems divide the annealing furnace into upper and lower temperature zones. Furnace heating systems are installed on the furnace walls between the upper and middle air knife systems, and between the middle and lower air knife systems. The furnace heating systems include heating wires 4 and thermocouples 3. Thermocouples 3 are used to detect the temperature of the space where the annealing furnace is located to control the annealing temperature inside the furnace.

[0021] The following uses a central stromal knife system as an example to illustrate its structural composition and working principle. Figure 2As shown, the air knife assembly includes an air pipe 18, which is connected to clean compressed air or nitrogen. The air pipe 18 passes through the furnace wall of the annealing furnace. From the outside to the inside, the air pipe is sequentially equipped with a regulating valve 5, a pressure transmitter 6, a flow meter 7, a check valve 9, and an air knife 10. The regulating valve 5, pressure transmitter 6, flow meter 7, and check valve 9 are located outside the furnace, while the air knife 10 passes through the furnace wall. The end of the air knife is a downward-sloping duckbill-shaped outlet located inside the furnace, with a certain distance between it and the substrate glass 1. The width of this outlet matches the width of the substrate glass. The regulating valve is used to regulate the amount of clean air entering the furnace, ensuring equal air pressure on both sides of the glass plate and maintaining stable glass production. The gas pressure transmitter detects the gas pressure after the regulating valve, providing pressure compensation for the vortex flow meter's measurement of gas mass. The vortex flow meter detects the volumetric flow rate of clean air entering the furnace, and its detection value is output to the DCS distributed control system to control the opening of the regulating valve. An air heating system preheats the air entering the furnace to reach the ambient temperature of the furnace space where the air knife is located. A clean air heating system is also installed at the middle air knife 10 to preheat the air entering the furnace to reach the ambient temperature of the air knife area. This air heating system specifically includes a middle air knife heater 9 and a middle air knife thermocouple 11. The air knife heater is located around the middle air knife and within the furnace wall insulation layer to provide heating for the air knife. The air knife thermocouple is used to detect the outlet air temperature of the air knife assembly. As a detection element of the clean air heating system, the air knife thermocouple measures the temperature of the heated air. It is required that the heated air temperature be consistent with the furnace temperature to minimize the entry of gases with temperature differences into the furnace; otherwise, it will affect the furnace ambient temperature. Its value should be consistent with the thermocouple value in the corresponding area of ​​the annealing furnace. The check valve is used to prevent high-temperature gas from flowing back and blowing onto the regulating valve in case of equipment malfunction, thereby damaging the instruments and valves, thus providing protection.

[0022] The effects of the above-mentioned air knife system design are as follows: (1) The air knife end is designed with a downward-sloping duckbill shape to form an air curtain 14 at an acute angle to the glass. The air curtain can be adjusted by adjusting the air intake regulating valve; (2) After the air curtain is heated, it will not affect the temperature of the area. When it enters the annealing furnace, the air curtain is close to the downward flow path 16 of the glass and can completely block the low-temperature gas rising due to the "chimney effect"; (3) Clean compressed air enters the annealing furnace from the upper air knife and is discharged from the lower part. This airflow circulation is equivalent to clean replacement treatment of the gas inside the furnace, optimizing the dust environment inside the furnace and reducing the degree of pollution on the glass surface.

[0023] The principle and method of eliminating the "chimney effect" of the annealing furnace according to the present invention will be explained below.

[0024] The clean compressed gas selected in this invention is kept at a constant temperature of 20°C before entering the annealing furnace. First, the clean gas needs to be heated. The clean air entering the furnace must be heated; otherwise, the low-temperature gas entering the high-temperature furnace will severely affect the furnace's ambient temperature, and consequently, product quality. Heating is performed as the clean air passes through the furnace structure, with the target heating value being the ambient temperature of the corresponding zone. Taking the air curtain temperature in the middle zone as an example, its heated temperature should be equal to the ambient temperature inside the furnace in the middle zone. Based on this target value, according to the thermodynamic formula: , Where, P: the pressure value inside the pipeline, which is measured by the pressure transmitter; M ω The average molar mass of air is approximately 28.97 g / mol. V: Volumetric flow rate, measured by a vortex flow meter; C P Specific heat capacity at constant pressure (C) P =1.005kJ / (kg*K), at room temperature); T2: Temperature of clean air after heating (taking the central air blade curtain as an example, T2=TLD-1, where TLD-1 is the ambient temperature inside the furnace in the central zone of the annealing furnace). T1: Temperature of clean gas before heating, T1=20℃; R is the gas constant, 8.314 J / (mol·K); Q: Heating power.

[0025] The heating power required to heat clean air can be calculated from the above formula, providing a basis for selecting the specifications and model of the air knife heater.

[0026] The dynamic changes of clean air within the furnace are then discussed. Air knives form an air curtain within the furnace, blocking the rising low-temperature airflow due to the "chimney effect." Then, driven laterally by the air curtain, the low-temperature airflow converges towards the edge of the display glass. Simultaneously, the high-temperature air curtain also enhances the low-temperature airflow through heat transfer, reducing its impact on the glass surface. After converging on the glass surface, the clean gas moves downwards along the surface. This is because: 1. the air curtain's blowing angle is obliquely downwards; 2. airflow characteristics are related to boundary conditions, and in this invention, the "boundary condition" is the vertically downward-facing display glass. The following discussion uses fluid dynamics principles to demonstrate airflow.

[0027] The principle of continuity. Air, as a fluid, follows the continuity equation: when flow is obstructed, air cannot "accumulate" at the obstacle and must find a new path to continue flowing. The glass surface forces the airflow to change direction, forming a wall-hugging flow near the glass surface to maintain the overall conservation of mass.

[0028] Viscous Forces and Boundary Layer Effects. 1. Air has viscosity. When airflow impacts a glass surface, air molecules close to the surface are "adhered" to it due to viscosity, causing their velocity to drop sharply to zero (a condition known as "no-slip boundary condition"). 2. This low-velocity layer (boundary layer) affects the upper airflow: because the upper airflow is faster, it gradually deflects towards the glass surface under the influence of viscous forces, creating a tendency to flow along the wall.

[0029] Based on the above theoretical analysis, the airflow inside the furnace will run along the glass surface and be discharged at the bottom of the annealing furnace.

[0030] From the overall assembly of the annealing furnace Figure 1 As can be seen, a lower air knife system is installed between the bottom of the annealing furnace and the cross-cutting machine. The air curtain formed by this air knife also needs to be heated, with the target heating value referring to the glass cutting temperature requirements. The heated air curtain blows towards the glass, forming a windbreak that completely covers the glass outlet at the bottom of the annealing furnace. This windbreak acts as an air seal at the glass outlet, preventing dust-laden airflow from entering. Furthermore, the air knife system of this invention is symmetrically installed on both sides, with equal inlet pressure and flow rate. Therefore, the air curtain formed by this system can stably hold the glass in place on both sides, greatly reducing the swaying amplitude during glass production and thus lowering the probability of glass breakage.

[0031] Based on the above discussion of the dynamic changes of clean air inside the furnace and at the glass outlet, it can be seen that this invention has a significantly better effect on eliminating the "chimney effect" of annealing furnaces compared to the previous method of installing baffles inside the furnace. Furthermore, in traditional annealing furnaces, baffles are placed very close to the glass to block rising airflow, meaning the baffles extend a considerable distance from the furnace wall. When glass breaks, it easily falls onto the baffles and accumulates, making subsequent cleaning difficult. In contrast, this application utilizes an invisible air curtain to block rising airflow, with a larger distance between the air knife outlet and the glass, and the air knife outlet has a duckbill-shaped downward angle. When the glass breaks, the broken glass falls freely, rarely accumulating at the air knife outlet, requiring almost no cleaning and significantly improving maintenance efficiency.

[0032] In summary, the substrate glass annealing furnace device provided by the present invention can completely block the rise of low-temperature gas entering the furnace body from the bottom, stabilize the ambient temperature inside the annealing furnace, optimize the dust environment inside the furnace, and reduce the degree of contamination on the glass surface.

Claims

1. A substrate glass annealing furnace, characterized in that, At least one set of air knife system is installed on the furnace wall of the annealing furnace. Each set of air knife system includes two sets of air knife components, and the two sets of air knife components are symmetrically arranged on both sides of the substrate glass. The air curtain generated by each set of air knife components blows symmetrically and obliquely downward toward the substrate glass.

2. The substrate glass annealing furnace according to claim 1, characterized in that, Each air knife assembly includes an air pipe through which clean compressed gas is introduced. The part of the air pipe that passes through the furnace wall is the air knife. The end of the air knife is a downward-sloping duckbill-shaped outlet located inside the furnace and spaced a certain distance from the substrate glass. The width of the outlet matches the width of the substrate glass.

3. The substrate glass annealing furnace according to claim 2, characterized in that, Each air knife assembly also includes an air heating system, which preheats the air entering the furnace to the same temperature as the ambient temperature of the furnace space where the air knife is located.

4. The substrate glass annealing furnace according to claim 3, characterized in that, The air heating system includes an air knife heater and an air knife thermocouple. The air knife heater is used to heat the air knife, and the air knife thermocouple is used to detect the outlet air temperature of the air knife.

5. The substrate glass annealing furnace according to claim 2, characterized in that, A regulating valve, a pressure transmitter, and a flow meter are also sequentially installed on the air pipe of the air knife assembly.

6. The substrate glass annealing furnace according to claim 5, characterized in that, A check valve is also installed on the gas pipe downstream of the flow meter.

7. The substrate glass annealing furnace according to claim 6, characterized in that, The regulating valve, pressure transmitter, flow meter, and check valve are all located on the outside of the annealing furnace body.

8. The substrate glass annealing furnace according to claim 1, characterized in that, Three sets of air knife systems are arranged at intervals from top to bottom on the furnace wall of the annealing furnace: the upper air knife system, the middle air knife system, and the lower air knife system. The upper air knife system is used to isolate the shaping furnace from the annealing furnace, and the lower air knife system is used to isolate the annealing furnace from the cross-cutting machine.

9. The substrate glass annealing furnace according to claim 8, characterized in that, An in-furnace heating system is installed on the furnace wall between the upper and middle air knife systems, and on the furnace wall between the middle and lower air knife systems.

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