The glass melting furnace is the heart of a float glass production line. Its service life mainly depends on the degree of erosion and wear of the sidewalls, crown, and regenerators. Proper furnace operation, together with maintenance of critical areas, is fundamental to extending furnace campaign life, prolonging the service life of the entire production line, and improving economic efficiency.
Based on the case of a solar ultra-clear float glass furnace (hereinafter referred to as Furnace A), this paper introduces maintenance and operational practices adopted during the late stage of furnace service. After more than eight years of operation, severe wear had occurred in the furnace bottom, sidewalls, crown, and checkerwork. Different technical measures were taken for different areas, which improved the erosion condition, extended the service life of the furnace, and provided valuable experience for enterprises seeking to prolong furnace campaign life.
In China, one of the main reasons for cold repair of glass furnaces is severe sidewall wear. Therefore, proper maintenance of the furnace sidewalls is the key to extending furnace life.
Furnace A was designed for a service life of eight years. By May 2019, it had been in operation for 7 years and 9 months, approaching its design life. The thickness of the sidewalls from the charging end to the back wall was measured, and it was found that the sidewalls at burners No. 3 to No. 5 on both sides had suffered severe erosion, with the thinnest point measuring only 34 mm.
The sidewalls of Furnace A had previously undergone patching twice, and a third sidewall patching was therefore planned. Based on the available patching blocks, the patch thickness was set at 75 mm and the height at 700 mm, consisting of 400 mm + 300 mm in two layers (upper and lower), supported by 140 mm channel steel, leaving room for a possible fourth layer of patching in the future. The specific arrangement is shown in Figure 1.
After the sidewall patching, the furnace continued operating for more than six months beyond its design life, and no sidewall hot spots or redness were observed. It was estimated that, with enhanced air cooling, the furnace could safely continue running for another year before the fourth sidewall patching would be required, while still ensuring safe operation of the tank sidewalls.
Ceramic materials used for hot repair can bond to damaged refractory areas. During the melting process, an exothermic reaction is generated, with the temperature reaching as high as 2200°C. Therefore, ceramic materials can be used to repair refractory materials such as silica, alumina, AZS, and magnesia. Ceramic welding can be carried out without shutting down the furnace and has relatively little impact on production.
Furnace A regularly invited specialized ceramic welding contractors to inspect heavily eroded refractory areas, including the L-shaped doghouse wall, crown, breast walls, and regenerators, and to perform ceramic welding repairs.
After ceramic welding, the eroded areas were restored and “rat holes” were effectively repaired. Photos before and after the repair are shown in Figures 2 and 3.
In the later stage of furnace operation, slag accumulation in the checker passages accelerates, blockage becomes severe, and partial collapse may occur. This not only affects flame control stability, but may also worsen rapidly if handled improperly, leading to premature cold repair.
A combination of high-temperature melting and manual cleaning was adopted to clear the checkerwork and ensure smooth airflow through the regenerator in the late campaign stage.
During the late operation period of Furnace A, severely blocked checkerwork in the regenerators had to be cleaned approximately every six months. Reflections of the checkerwork before and after cleaning are shown in Figure 4.
In addition to strengthening inspections and promptly repairing “rat holes” in the crown and burned-through crown debris areas, it is also necessary to establish a reasonable schedule and method for regenerator cleaning in order to ensure safe and normal regenerator operation.
During the later stage of furnace operation, nine surveillance cameras were installed successively at the following positions:
These cameras were used to monitor safety hazards such as glass leakage from the furnace bottom, crown burn-through, and sidewall glass leakage. Operators on shift could observe the crown, furnace bottom, burner sidewalls, and other critical areas from the central control room, allowing hidden risks to be identified at an early stage.
A total of 18 resistance temperature detectors (RTDs) were installed on the sidewalls at the six pairs of burners in the melting end, the refining section, the neck, and the cooling section. Alarm temperature limits were set, enabling central control room personnel to promptly go to the site and verify sidewall operating conditions whenever abnormal temperature changes occurred.
A total of 11 infrared thermometers were installed on the furnace bottom in the No. 1 burner refining section for real-time temperature monitoring. By comparing temperature curves, operators could track refractory erosion trends and take maintenance measures in advance.
When Furnace A had been operating for 8 years and 4 months, a slight glass leakage occurred at the corner block of the neck in the refining section sidewall. The RTD monitoring system triggered an alarm immediately, and the operators on duty promptly handled the leakage area, preventing the incident from deteriorating and buying valuable time for emergency repair.
Due to long-term operation, the inner walls of the bubbler pipes had suffered severe corrosion. The return water temperature of some bubbler pipes exceeded the allowable limit. Simply reducing the circulating water temperature of the cooling tower could not fundamentally eliminate the risk of bubbler pipe burn-through.
When Furnace A had been operating for 8 years and 6 months, the No. 3 bubbler pipe burned through. During the attempt to withdraw the pipe downward, a small amount of glass flowed out along the bubbler block. The operation was immediately stopped, and the bubbler pipe was reinserted into the bubbler block.
It was concluded that because Furnace A had long been producing ultra-clear glass, the furnace bottom had suffered severe erosion, and the remaining thickness of the bottom blocks could not be determined before shutdown. Therefore, for safety reasons, an additional air-cooling system for the bubbler was installed to prevent glass outflow and potential safety accidents.
Furnace maintenance measures must be determined according to the furnace type and the degree of damage in different areas. In this case, the ultra-clear float glass furnace achieved safe operation beyond its design life through measures such as sidewall block patching, ceramic welding repair, regenerator checkerwork cleaning, installation of safety monitoring equipment, and addition of a bubbler cooling system. These measures ensured safe operation of the furnace beyond its design campaign life and helped the company reduce costs.
