The Evolution of Electric-Fused Brick Technology for Fully Electric and High-Crush-Ratio Glass Melting

The glass industry is at a historic turning point. Decarbonization goals, rising cullet recycling rates, and the widespread adoption of all-electric melting furnaces are fundamentally transforming glass melting technology. These changes also present new challenges to the relatively stable system of electric-fused AZS (alumina-zirconia-sapphire) bricks that has been in use for decades.

Trend 1: The Reshaping of the Thermal Environment Brought About by All-Electric Melting Furnaces

In furnaces primarily heated by electrodes, heat is generated by Joule heating within the molten glass, leading to two changes that directly affect the erosion behavior of electric-melting bricks:

First, the thermal load on the tank bottom and walls has significantly increased. In traditional furnaces, the tank bottom temperature was relatively low, resulting in slow bottom erosion. In electric-melting furnaces, the self-generated heat within the molten glass maintains the tank bottom at a very high temperature, subjecting the bottom AZS bricks to more intense upward heat flux and chemical erosion. While 33# bricks were sufficient for the tank bottom lining in the past, 36# bricks—and even 41# bricks in some areas—may become standard in the future.

Second, thermal cycling has become more frequent. Electric melting furnaces often operate to balance peak and off-peak electricity prices, resulting in periodic fluctuations in power output and intensified temperature fluctuations within the furnace. The repeated softening and solidification of the glass matrix in fused zirconia-alumina bricks can lead to the accumulation of microcracks, imposing higher standards on the bricks’ thermal shock resistance and residual stress control.

Trend 2: Chemical Challenges Posed by the Rising Proportion of Cullet

The extensive use of cullet (exceeding 90% in some kilns) has created a chemical “time bomb” for electric-fused refractories.

First is the variability in redox conditions. Crushed glass comes from complex sources, significantly increasing the likelihood of containing organic contaminants and metallic impurities, which can alter the local redox potential of the glass melt. For example, aluminum metal may undergo an exothermic reaction in molten glass, generating localized high temperatures and consuming oxygen, resulting in a morphology similar to reductive erosion on the surface of electric-fused bricks and accelerating interfacial reactions.

Second is the synergistic wear caused by metal impurities. Residual metals such as iron and lead, which have different melting points than glass, form a sediment layer at the bottom of the tank. These impurities may seep into the brick joints to directly corrode the brick matrix, alter the electrical conductivity of the tank bottom, and interfere with the uniform heating of the electric melting system.

To address the high-recycled-glass environment, the glass phase composition of electric-fused AZS bricks must be specially designed to possess a broader redox tolerance and higher chemical inertness.

Trend 3: Specialized Requirements for Electrode Bricks and Bubble Systems

As electric melting power density increases, electrode hole bricks and bubble plug bricks are subjected to the combined effects of high temperatures, high current density, and intense convective erosion. Common challenges include: ordinary fused zirconia-alumina bricks exhibit some electrical conductivity at high temperatures; if the ionic conductivity of the glass phase is too high, current may be diverted through the hole bricks to the furnace’s steel structure, creating safety hazards; Joule heating at the electrode tips causes the surrounding glass melt temperature to be 100–200°C higher than the furnace average, forming an accelerated erosion ring around the electrode holes.

To address this, ChaoYu has begun developing low-conductivity formulations, controlling high-temperature resistivity by adjusting the ratio of alkali and alkaline earth metals in the glass phase, and adopting shrinkage-free directional casting technology as the standard process for this area.

Trend 4: Moving Toward “Near-Zero Carbon” Electrically Fused Refractories

In the future, we may see zero-carbon kilns that rely entirely on hydrogen combustion or fully electric melting. The industry’s cutting edge is currently experimenting with carbon-free binders and induction melting technologies to reduce product carbon content to near-undetectable levels, thereby adapting to the high water vapor partial pressure environment generated by hydrogen combustion.

Chaoyu’s Technical Roadmap

In response to these changes, Chaoyu is building technical capabilities along three main lines: Microstructural Customization—designing differentiated glass phase compositions and grain sizes tailored to specific glass varieties and melting methods; Digital Quality Archives—establishing digital twin archives for each batch of critical bricks, including casting curves, X-ray flaw detection, ultrasonic C-scan data, and isothermal erosion rates; Full-Lifecycle Support—from selection consulting, zoning plans, and pre-assembly verification to mid-furnace online monitoring and residual thickness assessment, transforming from an electric-fused brick supplier into a refractory partner for long-term furnace management.

Fully electric melting and high-recycled glass are not merely changes in process flow; they represent an entirely new philosophy of melting. On the path toward a greener, more circular glass industry, the development of fused zirconia-alumina bricks is far from over; it is undergoing a profound transformation to adapt to new demands.