Electric Glass Furnace
Electric Melting Processes in the Glass Industry
Electric melting processes are becoming increasingly important in the glass industry, especially when it comes to high process stability, energy efficiency, and low emissions. The energy is introduced directly into the glass melt, which enables precise temperature control and uniform melting conditions.
In contrast, in the hot-top process, heating occurs via gas or oxyfuel burners above the glass melt.
An established electric process is the cold-top principle, which is primarily used in the production of special glasses and is characterized by stable process control and efficient energy utilization.
IWG Glasofenbau supplies fully electric glass melting tanks that are individually tailored to the glass type, production requirements, and furnace geometry.
Fully Electric Tank // IWG Glasofenbau
Fully Electric Cold Top Glass Furnace
The fully electric glass melting tank using the cold-top process represents a particularly energy-efficient and low-emission melting process. By completely eliminating fossil fuels, heating is exclusively electric and directly within the glass melt.
Characteristic of the cold-top principle is the closed batch blanket on the melt surface. This reduces heat losses, minimizes dust emissions, and ensures stable process control.
The uniform energy input enables precise temperature control and creates optimal conditions for high-quality glass – especially for special glasses.
Typical advantages include:
- High energy efficiency through direct electric heating
- Low emissions and reduced exhaust gas management
- Stable melting conditions due to a closed batch blanket
- Very good glass quality with high process control
Fully electric cold-top tanks are individually designed for melting capacity, glass type, and production requirements, offering a future-proof solution for modern glass production.
Technical Glass
C-Glass and Soda-Lime Silicate Glass
Tableware
Lead Crystal, Crystal Glass, Borosilicate Glass, Opal Glass, and Cold Soda-Lime Glass
Optical Glass
Optical Glass
Glass Containers
Opal and Soda-Lime Glass
Glass Conditions
Electric Forehearth
Hot Top Glass Furnace
The glass melting tank using the hot-top process is a proven melting concept for high throughputs and flexible applications. In contrast to the cold-top principle, heating occurs above the glass melt and is typically based on the use of gas or oxyfuel burners.
The open melt surface enables direct energy transfer and supports rapid melting of the batch. This makes the hot-top process particularly suitable for applications with high melting capacities and varying raw material compositions.
Through targeted control of flame guidance, air supply, and exhaust gas flow, the melting process can be precisely adjusted and operated stably.
Typical advantages include:
- High melting capacities with flexible process control
- Direct energy input via gas or oxyfuel burners
- Good adaptability to different batches and glass types
- Proven technology for continuous production processes
Hot-top glass melting tanks are individually designed for furnace geometry, heating concept, and production requirements, offering a robust solution for high-performance melting processes.
Technical Glass
Soda-Lime Silicate Glass
Tableware
Lead Crystal, Crystal Glass, Borosilicate Glass, Opal Glass, and Soda-Lime Glass
Optical Glass
Optical Glass
Glass Containers
Opal and Soda-Lime Glass
Glass Conditions
Electric Forehearth
Equipment for Hot Top
Operating a hot-top glass furnace requires a coordinated interplay of various plant components. Heating is provided by gas or oxyfuel burners in the upper furnace chamber and by electrodes in the melt.
Burner systems with appropriate gas and oxygen supply are used, as well as electrical components such as electrodes, transformers, thyristors, and control cabinets. Suitable cooling water and air cooling ensure safe and stable plant operation.
For charging, feeder systems such as plunger or screw feeders are used, which are individually adapted to the furnace type and process. Additionally, systems such as furnace pressure measurement and drainage contribute to process stability and operational safety.
After melting, further processing takes place via coordinated forehearth systems, which enable controlled temperature management up to shaping.
Equipment
E-Boosting as a holistic system concept
Equipment
Cooling water distribution station
Equipment
Cooling water treatment station
Equipment
Control cabinets
Equipment
Transformers, Thyristors
Equipment
Oxy-Fuel burners as a complete system
Equipment
Air cooling
Equipment
Charger
Equipment
Furnace pressure measurement
Equipment
Drainage system
Equipment for Cold Top
Cold-top glass furnaces operate with fully electric energy input, where the melt is heated directly via electrodes in the glass bath. This results in specific requirements for the plant technology used.
Central components include electrical systems such as electrodes, transformers, power electronics (thyristors), and control cabinets, which enable precise control of energy input. Reliable cooling water treatment and distribution are also required for safe operation.
Additionally, air cooling systems are used to specifically limit thermal loads. Batch feeding is carried out via adapted feeder systems, such as X/Y feeders, which ensure uniform and controlled charging.
Systems such as furnace pressure measurement and drainage concepts are integrated for process monitoring and safety. After the melting process, forehearths take over the targeted temperature control and conditioning of the melt for further processing.
Technical Glass
E-Boosting as a holistic system concept
Equipment
Cooling water distribution station
Equipment
Cooling water treatment station
Equipment
Control cabinets
Equipment
Transformers, Thyristors
Equipment
Air cooling
Equipment
X/Y Charger
Equipment
Furnace pressure measurement
Equipment
Drainage system
How Cold Top, Hot Top, and Hybrid Glass Furnaces Work
Modern glass melting furnaces differ primarily in the type of energy input and process control. While fully electric cold-top furnaces rely on direct electrical heating, energy input in hot-top furnaces occurs via gas or oxyfuel burners above the glass bath. Hybrid furnaces combine both technologies, allowing flexible adaptation to different production requirements.
Cold-Top Process (all-electric)
The Cold-Top glass furnace operates based on a fully electric melting process. Energy is introduced directly into the glass melt via electrodes, resulting in very precise and uniform heating.
Characteristic is the closed raw material blanket (\'batch\') on the melt surface. This acts as an insulator, reduces heat loss, and stabilizes the entire process. The melting, refining, and homogenization process occurs predominantly vertically, leading to a very homogeneous glass quality.
Depending on the type of glass, different electrodes are used:
- Molybdenum electrodes – high temperature resistance, ideal for special and high-performance glasses
- Tin oxide electrodes (SnO₂) – very good chemical resistance, often used for less aggressive glass types
- Platinum electrodes – for high-purity special applications with the highest quality requirements
The electrodes can be arranged as bottom, side, or top electrodes, allowing for targeted energy input into the melting process.
1. Molybdenum Electrodes
Properties: Molybdenum electrodes are ideal for the glass industry due to their high melting temperature (over 2600°C). They have high electrical conductivity and are corrosion-resistant.
Usage: Particularly suitable for the production of special glass and high-purity glass, e.g., for optics. They are often used in furnaces for borosilicate and aluminosilicate glasses.
Advantages: Long lifespan, high efficiency in aggressive environments.
Disadvantages: Susceptible to oxidation, especially in areas exposed to air.
Cold Top Suitability: These electrodes are ideal for the Cold-Top process, as they are used in fully electric melting furnaces that rely on electrical energy. They withstand high temperatures and aggressive glass components and are particularly well-suited for this process.
2. Tin Oxide Electrodes (SnO₂)
Properties: Tin oxide is a ceramic material that is very resistant to chemical corrosion by glass.
Usage: Tin oxide electrodes are often used in the production of container glass or in furnaces for less aggressive glass types.
Advantages: High chemical stability, particularly resistant to glass components that could cause corrosion.
Disadvantages: Not suitable for extremely high temperatures, limited electrical conductivity compared to metallic electrodes.
Cold Top Suitability: Tin oxide electrodes are also frequently used in the Cold-Top process because they are resistant to chemical corrosion and harmonize well with the requirements of fully electric melting processes.
3. Platinum Electrodes
Properties: Platinum has extremely high corrosion resistance and is ideal for high-purity melting processes.
Usage: Typically for the production of ultra-pure glass or optical glasses that tolerate no impurities.
Advantages: Excellent corrosion resistance, very stable in all environments.
Disadvantages: Very expensive, therefore mainly used for special applications with high purity requirements.
Cold Top Suitability: Platinum electrodes are rarely used in the Cold-Top process; they are primarily intended for high-purity and special glass manufacturing.
Other electrode materials such as graphite or silicon carbide (SiC) are generally available, but due to limited resistance and operational limits, they are rarely used in classic glass melting furnaces and are primarily found in special high-temperature applications.
Difference between Cold Top, Hot Top, and Hybrid Glass Furnaces
Modern glass melting furnaces differ primarily in the type of energy input and process control. Depending on the concept, heating is done fully electrically, via burner systems, or as a targeted combination of both energy forms.
Cold-Top Glass Furnaces (fully electric)
In the Cold-Top process, energy is introduced almost entirely electrically via electrodes directly into the glass melt. Characteristic is the closed batch blanket on the surface, which reduces heat losses and stabilizes the process. The electrical energy component here is typically almost 100%.
Hot-Top Glass Furnaces (open surface with combined heating)
In the Hot-Top process, energy is introduced both via electrodes in the melt and via gas or oxyfuel burners in the upper furnace space. The open melt surface allows for direct heat transfer and high melting capacities.
The proportion of electrical energy can vary depending on the design and contribute both supportively and significantly to the melting performance. Typically, the electrical proportion is often in the range of approximately 0–30%, but can exceed this depending on the plant concept.
Hybrid Glass Furnaces (targeted combined energy input)
Hybrid furnaces consciously combine electrical and fuel-based heating into an integrated energy concept. Electrical energy takes on a significant share of the melting performance and is specifically used for process stabilization and efficiency enhancement.
In practice, the electrical proportion is often in the range of approximately 30–80%, meaning both energy forms are process-determining.
Cold Top: almost entirely electric, maximum process control and low emissions
Hot Top: open process control with combined heating and variable energy distribution
Hybrid: targeted combination with significant electrical component and high flexibility
Is the Cold Top process CO2-free?
The Cold-Top process is almost CO₂-free because it is primarily powered by electrical energy and does not use fossil fuels. This eliminates direct emissions such as CO₂ that would arise from the combustion of gas, oil, or coal in conventional melting processes. Thus, there are no combustion emissions in the melting process itself.
However, the CO₂ balance of the Cold-Top process is highly dependent on the source of the electrical energy. If the electricity comes from renewable energies (e.g., wind, solar, hydropower), the process remains almost emission-free. However, if electricity from fossil sources such as coal or gas is used, indirect CO₂ emissions are generated.
Electric Heating Systems for Glass Furnaces from Ingenieurbüro Wagenbauer
Are you active in glass production and want to make your processes more environmentally friendly? Are you looking for an efficient and sustainable solution to modernize your existing glass furnace? We at Ingenieurbüro Wagenbauer offer comprehensive services for the planning and implementation of fully electric heating systems and other innovative technologies in glass furnace construction.
Whether it\'s a renovation or the new construction of an electric glass furnace – our experienced team will accompany you from the initial planning phase to final realization. Our customized solutions help you minimize the ecological footprint of your production and make your processes more energy-efficient. Together, we develop future-proof technologies for sustainable glass production.