The main process factors affecting glass melting extend beyond the melting stage itself, as they are influenced by pre-melting conditions such as raw material quality, cullet treatment and control, fuel properties, furnace refractory materials, furnace pressure, atmosphere, and the selection of fining agents. Below is a detailed analysis of these factors:
Ⅰ. Raw Material Preparation and Quality Control
1. Chemical Composition of Batch
SiO₂ and Refractory Compounds: The content of SiO₂, Al₂O₃, ZrO₂, and other refractory compounds directly affects the melting rate. Higher content increases the required melting temperature and energy consumption.
Alkali Metal Oxides (e.g., Na₂O, Li₂O): Reduce melting temperature. Li₂O, due to its small ionic radius and high electronegativity, is particularly effective and can improve the physical properties of glass.
2. Batch Pre-Treatment
Moisture Control:
Optimal Moisture (3%~5%): Enhances wetting and reaction, reduces dust and segregation;
Excessive Moisture: Causes weighing errors and prolongs fining time.
Particle Size Distribution:
Excessive Coarse Particles: Reduces reaction contact area, prolongs melting time;
Excessive Fine Particles: Leads to agglomeration and electrostatic adsorption, hindering uniform melting.
3. Cullet Management
Cullet must be clean, free of impurities, and match the particle size of fresh raw materials to avoid introducing bubbles or unmelted residues.
Ⅱ. Furnace Design and Fuel Properties
1. Refractory Material Selection
High-temperature erosion resistance: high zirconium bricks and electrofused zirconium corundum bricks (AZS) should be used in the area of the pool wall, furnace bottom and other areas that come into contact with the glass liquid, so as to minimize stone defects caused by chemical erosion and scouring.
Thermal stability: Resist temperature fluctuation and avoid refractory spalling due to thermal shock.
2. Fuel and Combustion Efficiency
Fuel calorific value and combustion atmosphere (oxidizing/reducing) must match the glass composition. For example:
Natural Gas/Heavy Oil: Requires precise air-fuel ratio control to avoid sulfide residues;
Electric Melting: Suitable for high-precision melting (e.g., optical glass) but consumes more energy.
Ⅲ. Melting Process Parameter Optimization
1. Temperature Control
Melting Temperature (1450~1500℃): A 1℃ increase in temperature can raise the melting rate by 1%, but refractory erosion doubles. A balance between efficiency and equipment lifespan is necessary.
Temperature Distribution: Gradient control in different furnace zones (melting, fining, cooling) is essential to avoid local overheating or unmelted residues.
2. Atmosphere and Pressure
Oxidizing Atmosphere: Promotes organic decomposition but may intensify sulfide oxidation;
Reducing Atmosphere: Suppresses Fe³+ coloration (for colorless glass) but requires avoiding carbon deposition;
Furnace Pressure Stability: Slight positive pressure (+2~5 Pa) prevents cold air intake and ensures bubble removal.
3.Fining Agents and Fluxes
Fluorides (e.g., CaF₂): Reduce melt viscosity and accelerate bubble removal;
Nitrates (e.g., NaNO₃): Release oxygen to promote oxidative fining;
Composite Fluxes**: e.g., Li₂CO₃ + Na₂CO₃, synergistically lower melting temperature.
Ⅳ. Dynamic Monitoring of the Melting Process
1. Melt Viscosity and Fluidity
Real-time monitoring using rotational viscometers to adjust temperature or flux ratios for optimal forming conditions.
2. Bubble Removal Efficiency
Observation of bubble distribution using X-ray or imaging techniques to optimize fining agent dosage and furnace pressure.
Ⅴ. Common Issues and Improvement Strategies
| Problems | Root Cause | The Solution |
| Glass Stones (Unmelted Particles) | Coarse particles or poor mixing | Optimize particle size, enhance pre-mixing |
| Residual Bubbles | Insufficient fining agent or pressure fluctuations | Increase fluoride dosage, stabilize furnace pressure |
| Severe Refractory Erosion | Excessive temperature or mismatched materials | Use high-zirconia bricks, reduce temperature gradients |
| Streaks and Defects | Inadequate homogenization | Extend homogenization time, optimize stirring |
Conclusion
Glass melting is a result of the synergy between raw materials, equipment, and process parameters. It requires meticulous management of chemical composition design, particle size optimization, refractory material upgrades, and dynamic process parameter control. By scientifically adjusting fluxes, stabilizing the melting environment (temperature/pressure/atmosphere), and employing efficient fining techniques, melting efficiency and glass quality can be significantly improved, while energy consumption and production costs are reduced.
Post time: Mar-14-2025
