In the glass manufacturing industry, the glass furnace, as the core production equipment, accounts for over 75% of the total energy consumption of the entire plant, with some high-energy-consumption enterprises reaching as high as 85%. With the intensification of the global energy crisis, tightening environmental policies, and increasingly fierce market competition, energy conservation and consumption reduction in glass furnaces have become a critical issue for the sustainable development of the industry. In recent years, domestic glass enterprises have conducted extensive technological research and made significant progress in various areas, including optimization of glass batch compositions, upgrading of feeding systems, improvement of combustion systems, optimization of glass furnace structure, enhancement of glass furnace body insulation, waste heat recovery and utilization, and operational process control. The fuel consumption per unit of product for many enterprises has significantly decreased, with the operational levels of glass furnaces in some advanced enterprises reaching first-class or top-tier standards. However, compared to international advanced levels, there remains a 15%-20% gap in terms of energy efficiency, thermal utilization efficiency, and service life of refractory materials in domestic glass furnaces. Therefore, further exploring technological pathways for energy saving and consumption reduction in glass furnaces, combined with the application of high-performance refractory materials, to maximize energy utilization efficiency, holds significant practical importance for promoting the green and low-carbon development of the glass industry. This article will elaborate in detail on the core technological pathways for energy saving and consumption reduction in glass furnaces from multiple dimensions, with a particular focus on the selection, application, and optimization strategies of refractory materials, providing references for industry technological upgrades.

 

I. Increasing Glass Melt Temperature Without Raising Flame Temperature

 

The melting quality and efficiency of the glass melt directly determine the production efficiency and energy consumption level of the glass furnace. Without raising the flame temperature, increasing the glass melt temperature by optimizing heat transfer mechanisms and improving temperature field distribution can effectively accelerate the melting speed, shorten the melting cycle, thereby increasing output per unit time and reducing energy consumption per unit product. The core of this technological pathway lies in enhancing the heat transfer efficiency between the flame space and the glass melt, while optimizing the temperature uniformity of the glass melt within the glass furnace basin to avoid energy waste and product quality defects caused by localized excessive or insufficient temperatures.

 

1.1 Increasing Radiative Heat Transfer from the Flame Space to the Glass Melt

 

The absorption of radiant energy by the glass melt is highly selective; it can only effectively absorb short-wave radiant energy with wavelengths less than 3 micrometers. This type of radiant energy can penetrate the glass melt surface and transfer inward, thereby increasing the overall temperature of the glass melt. Key carriers capable of generating short-wave radiation in the flame space include carbon particles in the flame and the inner wall surfaces of the glass furnace. Therefore, increasing flame emissivity and maintaining high emissivity values of the glass furnace lining become core means to enhance radiative heat transfer. Simultaneously, the performance of refractory materials on the glass furnace inner wall directly affects radiative heat transfer efficiency and glass furnace heat loss, making their selection and maintenance crucial.

 

1.1.1 Optimizing Flame Emissivity and Glass furnace Lining Emissivity Control

 

Flame emissivity is a key indicator for measuring the radiation capacity of a flame. By employing oxygen-deficient combustion technology or carbon-enrichment measures, the concentration of carbon particles in the flame can be increased, significantly enhancing flame emissivity and short-wave radiation intensity. Oxygen-deficient combustion technology precisely controls the air-fuel ratio, allowing fuel to burn incompletely and generate more carbon particles. These particles not only enhance radiative heat transfer but also reduce nitrogen oxide generation, offering benefits in both energy conservation and environmental protection. Carbon-enrichment measures involve adding appropriate carbon-based additives to the fuel to further increase carbon particle content in the flame and optimize radiative heat transfer effects.

 

The emissivity value of the glass furnace lining is closely related to the surface roughness, temperature, and material of the lining. Different types of refractory materials exhibit significant differences in emissivity values under high-temperature environments, as detailed in the table below:


To maintain high emissivity values of the glass furnace lining, efforts must be made from three aspects: refractory material selection, construction quality control, and daily maintenance. During the selection stage, refractory materials with stable emissivity and excellent high-temperature performance should be reasonably chosen based on the working temperature, corrosive environment, and heat transfer requirements of different glass furnace parts. For example, the melting basin walls are in direct contact with high-temperature glass melt and require fused cast AZS refractory blocks or zircon bricks with strong corrosion resistance; the glass furnace crown should prioritize silica bricks with high-temperature strength and stable emissivity. During construction, the flatness and sealing of refractory brick laying should be ensured to reduce gaps between bricks, avoiding heat loss and decreased emissivity due to excessive gaps. During daily operation, regular inspections of the glass furnace lining surface condition are necessary. Surface deposits such as dust, slag, and glass melt adhesion layers should be cleaned promptly to maintain surface roughness and ensure stable emissivity. Additionally, drastic fluctuations in glass furnace body temperature should be avoided to prevent thermal shock damage to refractory materials, which could cause surface spalling and affect radiative heat transfer efficiency.

 

1.1.2 Clearing the "Cold Gas" Film Near the Melt Surface to Enhance Heat Transfer

 

A "cold gas" film easily forms near the melt surface in glass furnaces. This gas film, a mixture of air and combustion products with low thermal conductivity, severely impedes heat transfer from the flame to the glass melt, leading to lower surface temperature and affecting melting efficiency. To eliminate the adverse effects of the "cold gas" film, actions need to be taken from two aspects: equipment structure optimization and process improvement measures. In terms of equipment structure, the height between the burner block floor and the melt surface and the flame ejection angle should be designed rationally. If the burner block floor is too high above the melt surface, flame energy disperses; if too low, it may cause direct flame impingement on the melt surface, leading to splashing and slagging. Through numerical simulation and practical debugging, optimal height parameters (typically 1.2-1.8 meters, adjusted based on glass furnace capacity and fuel type) can be determined to allow the flame to uniformly cover the melt surface and effectively penetrate the "cold gas" film. Optimization of the flame ejection angle is equally critical, generally controlled between 15° and 30°, causing the flame to tilt downward and act directly above the melt surface, enhancing disturbance and disruption of the "cold gas" film, thereby improving heat transfer efficiency.

 

Employing oxygen boosting technology is an effective process measure to eliminate the "cold gas" film and enhance heat transfer. Foreign practices show that blowing oxygen at high speeds of 195-500 m/s near the melt surface can significantly accelerate the flame‘s combustion speed and heat transfer rate, raising the flame temperature near the melt surface by approximately 100°C, effectively breaking through the barrier of the "cold gas" film. The advantages of oxygen boosting technology include:
1) increasing flame temperature and emissivity, enhancing radiative heat transfer;

2) accelerating the removal of combustion products, reducing the formation of the "cold gas" film;

3) promoting convective stirring of the glass melt, improving temperature uniformity.

When applying this technology, attention must be paid to the injection position, angle, and flow rate of oxygen to avoid localized overheating leading to excessive glass melt volatilization and intensified refractory corrosion. Simultaneously, high-temperature resistant, corrosion-resistant oxygen lance materials, such as zirconia-based or alumina-based materials, should be selected to ensure the service life and operational safety of the lances.

 

The protection of refractory materials in the oxygen boosting area is crucial. The combined action of high-speed oxygen flow and high-temperature flame causes severe scouring and erosion on refractory materials at locations such as burner ports and glass furnace walls near the melt surface. Therefore, these areas should employ refractory materials with excellent scouring and corrosion resistance, such as zircon-alumina composite bricks or fused cast AZS refractory blocks. These materials possess extremely high high-temperature strength and chemical stability, effectively resisting erosion from oxygen flow and glass melt, extending glass furnace service life, and reducing energy consumption increases and production interruptions caused by refractory damage.

 

1.2 Increasing Temperature or Temperature Uniformity of Glass Melt within the Glass furnace Basin

 

The temperature level and uniformity of the glass melt within the glass furnace basin directly affect melting efficiency and product quality. The traditional view holds that the melt surface temperature should be increased to accelerate melting. However, practice shows that appropriately lowering the melt surface temperature can increase the temperature difference between the flame and the glass melt, thereby increasing the heat transfer rate from the flame to the glass melt. Simultaneously, lowering the melt surface temperature can reduce surface volatilization and slagging of the glass melt, improve temperature distribution in the depth direction, and enhance the overall temperature uniformity of the glass melt.

 

To achieve this goal, optimizing the structural design and temperature field control of the glass furnace basin is key. In terms of glass furnace basin structure, the depth-to-width ratio should be designed rationally, with depth generally controlled between 1.8 and 2.5 meters, ensuring sufficient convective space for the glass melt and promoting heat exchange between upper and lower layers. Employing a stepped bottom design can guide the glass melt to form orderly convective circulation, avoiding localized dead zones and temperature stratification. In terms of temperature field control, zoned heating technology divides the melting end into a hot spot zone, melting zone, and refining zone, controlling temperatures in different areas separately, maintaining the hot spot zone at 1500-1550°C, the melting zone at 1450-1500°C, and the refining zone at 1400-1450°C, forming a reasonable temperature gradient that ensures both melting efficiency and temperature uniformity.

 

The thermal conductivity and insulation properties of refractory materials have a significant impact on the temperature field distribution within the glass furnace basin. The glass furnace basin walls and bottom should employ refractory materials with moderate thermal conductivity and good insulation properties, such as high-alumina bricks, alumina bricks, or fused cast AZS refractory blocks. These materials can effectively reduce heat loss to the outside of the glass furnace, maintaining a high-temperature environment within the basin, while avoiding temperature non-uniformity caused by localized excessive heat dissipation. The selection of bottom refractory materials is particularly critical, requiring consideration of load-bearing capacity, corrosion resistance, and insulation properties. A multi-layer structure design is typically adopted: the bottom layer consists of insulating bricks (e.g., ceramic fiber bricks), the middle layer of high-alumina bricks, and the top layer of fused cast AZS refractory blocks, ensuring both insulation effect and improved corrosion resistance.

 

II. Optimization of Shallow Refining and Deep Withdrawal Technology and Refractory Material Application

 

The refining process of glass melt is a key step for removing bubbles and improving glass quality, while the rationality of the withdrawal process directly affects product quality and energy utilization. Shallow refining and deep withdrawal technology, by controlling the glass melt to flow in a single-channel straight-through direction, can significantly increase the temperature of the glass melt in the refining zone, reduce backflow, and select high-quality glass melt into the throat, thereby improving both glass product quality and output while reducing heat loss and energy waste caused by backflow. The core of this technology lies in optimizing glass furnace structural design, rationally setting dams and the throat, and matching with high-performance refractory materials to ensure structural stability and service life.

 

2.1 Technical Principles and Structural Optimization

 

The core principle of shallow refining is to reduce the depth of the refining basin, shorten the rising path of bubbles in the glass melt, accelerate bubble removal, and improve refining efficiency. Traditional refining basins are relatively deep (typically over 2.0 meters). With a long rising distance for bubbles, some bubbles can easily become entrapped in the glass melt and are difficult to remove, affecting refining effectiveness. After adopting shallow refining technology, the refining basin depth is controlled between 1.2 and 1.5 meters, reducing bubble rise time by 30%-40% and significantly improving refining efficiency. Simultaneously, shallow refining can make the temperature distribution of the glass melt in the refining zone more uniform, avoiding increased viscosity due to low temperature in deep layers, further promoting bubble removal.

 

Deep withdrawal involves sinking the throat near the glass furnace basin bottom (0.3-0.5 meters from the bottom) to select well-refined and homogenized bottom-layer glass melt into the forehearth. The bottom-layer glass melt has stable temperature, uniform viscosity, and extremely low impurity and bubble content, effectively improving forming quality. Additionally, deep withdrawal can reduce glass melt backflow. In traditional withdrawal methods, some glass melt forms backflow between the refining and melting zones, causing refined glass melt to mix back with unrefined glass melt, leading to heat loss and quality fluctuations. After adopting single-channel straight-through flow control, the backflow rate can be reduced by over 50%, significantly reducing energy waste.

 

To achieve shallow refining and deep withdrawal, it is necessary to set a wide and low dam in the glass furnace structural design. The main function of the dam is to separate the melting zone and refining zone, guide the glass melt to flow in the set direction, and control the depth of the refining basin. The dam height is typically 0.8-1.0 meters, and the width is 1.5-2.0 meters, with specific parameters adjusted based on glass furnace capacity, glass type, and production scale. A wide and low dam can effectively reduce the depth of the refining basin while avoiding excessive energy consumption increases due to high flow resistance. For melting dark-colored glass batches (such as amber glass, black glass), due to their strong heat absorption and relatively low viscosity, bubble removal is relatively easier. Based on actual conditions, a submerged throat may not be necessary, simplifying structural design.

 

2.2 Refractory Material Selection and Application

 

The dam and throat are key structural components in shallow refining and deep withdrawal technology. Their working environment is extremely harsh, requiring resistance to high-temperature glass melt scouring, erosion, and thermal shock. Therefore, the performance requirements for refractory materials are extremely high. Reasonable selection and application of refractory materials are important guarantees for the stable operation of this technology. As a key component separating the melting and refining zones, the dam is in direct contact with high-temperature glass melt, subjected to intense scouring and erosion, and must also possess sufficient high-temperature strength and thermal stability. Therefore, the dam should be constructed using refractory materials with strong corrosion resistance, high high-temperature strength, and excellent thermal shock resistance, such as fused cast AZS refractory blocks or zircon-alumina composite bricks. Fused cast AZS refractory blocks contain large amounts of ZrO₂ and Al₂O₃, offering extremely high chemical stability and resistance to glass melt erosion, effectively resisting erosion from alkali metal oxides (e.g., Na₂O, K₂O) in the glass melt, with a service life 3-5 times that of ordinary refractory blocks. Zircon-alumina composite blocks combine the corrosion resistance of zircon with the high-temperature strength of alumina, suitable for moderately corrosive environments, with relatively lower cost and significant cost-performance advantages. During dam construction, a staggered bond laying method should be used to ensure tight brick joints, reduce glass melt penetration, and simultaneously fill brick joints with high-temperature sealing materials (e.g., zircon-based mortar) to further improve sealing and structural stability.

 

The throat is the critical channel for glass melt to enter the forehearth from the refining zone. Its inner walls are in direct contact with high-speed flowing glass melt, subjected to intense scouring and wear, while requiring a smooth inner surface to avoid glass melt retention and slagging. Therefore, the inner walls of the throat should employ refractory materials with high density, smooth surfaces, and extremely strong scouring resistance, such as dense fused cast AZS refractory blocks or zirconia-based refractory materials. Dense fused cast AZS refractory blocks have porosity below 3% and surface roughness Ra ≤ 0.8 μm, effectively reducing glass melt adhesion and slagging, while their high-temperature strength can withstand the scouring pressure of the glass melt. For throats in large glass furnaces, monolithically cast refractories (e.g., alumina-based castables) can be used, reducing the number of brick joints, improving structural integrity and sealing, and further extending service life.

 

Refractory materials for the refining basin bottom and glass furnace basin bottom also require focused attention. The refining basin bottom withstands the static pressure and erosion of the glass melt and should employ refractory materials with strong corrosion resistance and high compressive strength, such as high-alumina bricks or fused cast AZS refractory blocks. The glass furnace basin bottom adopts a multi-layer structural design: the bottom layer consists of insulating bricks (e.g., ceramic fiber modules), the middle layer of fireclay bricks or high-alumina bricks, and the top layer of fused cast AZS refractory blocks, ensuring both insulation effect and improved corrosion resistance. Furthermore, glass furnace wall areas in the refining and withdrawal zones should employ high-temperature resistant, corrosion-resistant alumina bricks or zircon bricks to avoid glass melt contamination and increased energy consumption caused by refractory damage.

 

2.3 Operational Maintenance and Optimization Measures

 

To ensure the stable operation of shallow refining and deep withdrawal technology, daily operational maintenance and optimization adjustments must be strengthened. Regularly inspect the condition of refractory materials at key parts such as the dam and throat, promptly clean surface slag and glass melt adhesion layers to avoid channel blockage and increased flow resistance caused by excessive slagging. Simultaneously, monitor the flow state and temperature distribution of the glass melt, optimize glass melt flow velocity and temperature by adjusting combustion system parameters and throat opening, ensuring stable single-channel straight-through flow.

 

During production, adjust the dam height and throat position promptly based on changes in glass type and output to ensure refining effectiveness and withdrawal quality. For example, when producing high-viscosity glass, the dam height can be appropriately lowered to reduce flow resistance; when producing low-viscosity glass, the dam height can be appropriately raised to enhance refining effectiveness. Additionally, perform hot repairs on refractory materials regularly, using high-temperature spraying techniques (e.g., alumina-based spray materials) to repair damaged areas, extending refractory service life, reducing downtime for maintenance, and improving production efficiency.

 
III. Stable Feeding Technology and Refractory Material Matching Schemes

 

The stability of feeding is a prerequisite for ensuring glass forming quality and output, directly affecting product dimensional accuracy, surface quality, and production efficiency. Stable gob shape, size, and temperature need to be achieved by optimizing the structural design of the feeding system, strengthening insulation measures, and improving heating and cooling systems. Simultaneously, refractory material matching for various parts of the feeding system is crucial, as their performance directly affects operational stability, service life, and energy consumption level of the feeding system.

 

3.1 Feeding System Structure Optimization

 

The structural design of the feeding system is the foundation for achieving stable feeding, mainly including key parameters such as the separation method between the forehearth and working end, cross-sectional shape and dimensions of the forehearth, and the depth of the feeder bowl.

 

The degree of separation between the forehearth and the working end directly affects the operational stability of the forehearth. Full separation design allows the forehearth to maintain an independent operating regime, unaffected working end temperature fluctuations and airflow interference, ensuring stable glass melt temperature and flow rate within the forehearth. Some factories adopt non-fully separated designs, relying on heat from the melting end to heat the forehearth. Although this simplifies the structure, it easily causes forehearth temperature to be greatly affected by the melting end, with frequent fluctuations, affecting feeding stability; therefore, it is not recommended. Full separation design typically uses separation walls constructed from refractory materials. The separation wall should employ high-temperature resistant, corrosion-resistant alumina bricks or zircon bricks to ensure structural stability and sealing, avoiding heat transfer and airflow interference.

 

The cross-sectional shape and dimensions of the forehearth have a significant impact on the temperature uniformity and flow stability of the glass melt. A saddle-shaped bottom cross-section of the forehearth can reduce lateral temperature differences because the saddle shape can cause natural convection in the middle of the forehearth, promoting lateral heat exchange and avoiding the phenomenon of low temperature on both sides and high temperature in the middle. The cross-sectional dimensions of the forehearth should be determined based on flow rate and production scale. Typically, the width is 0.8-1.2 meters, and the height is 1.0-1.5 meters, ensuring sufficient flow space for the glass melt while avoiding excessive heat loss due to overly large cross-sections.

 

The depth design of the feeder bowl is also critical. Appropriately deepening the feeder bowl can increase the static head, making gob temperature more stable. The feeder bowl depth is generally controlled between 1.2-1.8 meters, adjusted based on forming process requirements. Deepening the feeder bowl increases the storage capacity of the glass melt, buffers flow rate fluctuations, and improves the static pressure stability of the gob, ensuring uniform gob shape and size. The material of the feeder bowl should employ refractory materials with strong corrosion resistance and high density, such as fused cast AZS refractory blocks or alumina-based castables, to avoid bowl deformation and leakage caused by glass melt erosion.

 

The length design of the forehearth needs to balance temperature regulation and flow rate adaptability. A slightly longer forehearth is beneficial for temperature regulation and can adapt to changes in flow rate within a larger range. Generally, forehearth length is controlled between 6-10 meters. An excessively long forehearth increases glass melt flow resistance and heat loss, while too short a forehearth cannot achieve sufficient temperature regulation. The forehearth length should be determined comprehensively based on flow rate, glass type, and forming speed to ensure stable feeding under different production conditions.

 

3.2 Feeding System Insulation Technology and Refractory Material Application

 

The forehearth has significant heat loss, especially at the feeder bowl, where heat loss accounts for over 60% of the total heat loss of the feeding system. Therefore, strengthening insulation measures for the feeding system to reduce heat loss is key to achieving stable feeding and energy saving. The insulation layer of the forehearth should adopt a multi-layer composite structure, from inside to outside: refractory castable layer, insulating brick layer, and ceramic fiber layer. The inner refractory castable layer should employ high-temperature resistant, corrosion-resistant alumina-based or high-alumina castables with a thickness of 100-150 mm to ensure direct resistance to the high temperature and erosion of the glass melt; the middle insulating brick layer uses aluminosilicate insulating bricks with a thickness of 150-200 mm, offering good insulation properties and mechanical strength; the outer ceramic fiber layer uses ceramic fiber modules with a thickness of 100-150 mm, with low thermal conductivity and excellent insulation effect. This composite insulation structure can effectively reduce heat loss, controlling glass melt temperature fluctuations within the forehearth within ±5°C.

 

Insulation at the feeder bowl is particularly important. Due to the large opening of the feeder bowl, heat loss is severe, requiring special insulation design. The sidewalls and bottom of the feeder bowl adopt the same composite insulation structure as the forehearth. The top of the feeder bowl is equipped with an insulation cover plate, made of ceramic fiber board or refractory castable, which can be opened or closed as needed for production to reduce heat loss. Simultaneously, install an insulation hood around the feeder bowl to further enhance the insulation effect.

 

The selection of refractory materials for the feeding system must be precisely matched according to the working environment of different parts. The forehearth sidewalls and bottom are in direct contact with the glass melt, subjected to high-temperature erosion and scouring, and should employ fused cast AZS refractory blocks, alumina-based castables, or zircon bricks; the forehearth top and insulation layer employ refractory materials with excellent insulation properties, such as ceramic fiber modules and aluminosilicate insulating bricks; the feeder bowl employs refractory materials with strong corrosion resistance and high density, such as fused cast AZS refractory blocks or alumina-based castables. Simultaneously, the construction quality of refractory materials is crucial. Ensure tight brick joints and dense vibration of castables to avoid heat loss and refractory damage caused by construction defects.

 

3.3 Ensuring Stable Operation of the Feeding System

 

To ensure stable operation of the feeding system, a comprehensive operation monitoring and maintenance system must be established. Set multiple temperature monitoring points within the forehearth and feeder bowl, use thermocouples to monitor glass melt temperature in real-time, and automatically adjust operating parameters of heating and cooling systems through the control system to ensure temperature stability. Simultaneously, monitor the flow state of the glass melt within the forehearth and the shape and size of the gob, promptly adjust flow rate and feeding speed to ensure forming quality.

 

During daily maintenance, regularly inspect the condition of refractory materials in the feeding system, promptly clean surface slag and glass melt adhesion layers, and repair damaged areas. For heating and cooling systems, regularly inspect the operating status of components such as nozzles, electrodes, and cooling water pipes, clean blockages, and replace damaged parts. Simultaneously, periodically conduct insulation performance tests on the feeding system, repair damaged insulation layers promptly upon discovery to ensure insulation effectiveness.

 

IV. Summary and Outlook

 

Energy saving and consumption reduction in glass furnaces is a systematic project involving multiple links such as glass batch composition, feeding system, combustion system, glass furnace structure, glass furnace body insulation, waste heat utilization, and operational control. This article has focused on elaborating core energy-saving technological pathways, including increasing glass melt temperature without raising flame temperature, shallow refining and deep withdrawal, and stable feeding, while integrating refractory material selection, application, and optimization strategies, emphasizing the synergistic role of refractory materials and energy-saving technologies.

 

Refractory materials, as key basic materials for glass furnaces, their performance directly affects the thermal efficiency, operational stability, and service life of the glass furnace. In the process of energy saving and consumption reduction for glass furnaces, high-performance refractory materials, such as fused cast AZS refractory blocks, zircon bricks, alumina-based castables, ceramic fiber modules, etc., should be precisely selected based on the working environment and technical requirements of different glass furnace parts. Simultaneously, construction quality control and daily maintenance of refractory materials should be strengthened to ensure their performance is fully utilized.

Henan SNR Refractory Co., Ltd. is dedicated to the manufacture, research and development of fused cast AZS refractory blocks and bonded refractory materials for the glass industry. Meanwhile, SNR can provide total solutions and services for glass furnace design, glass furnace construction, renovation, and upgrading. Please contact me if you have any requirements.

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