eLITHE demonstrates 100% electric ceramic frit melting at temperatures approaching 1,500 °C
The demonstrator, developed within the European project eLITHE, has produced its first drops of frit without using natural gas, paving the way for the design of an industrial furnace ten times larger.
CIRCE – the Technology Centre has coordinated the design and construction of an electric furnace for ceramic frit melting that has successfully completed its first operational tests. This milestone is the result of the joint work of several eLITHE partners on top of CIRCE coordination: Plustherm Point AG for the development of the inductive heating system at the furnace outlet, Glass Service, a.s. for the design support of the electric smelter, Insertec Furnaces & Refractories for the design and supply of refractory materials and CSIC – Instituto de Cerámica y Vidrio (ICV) for the formulation and characterisation of the frits suitable for electric melting.
What is frit and why does it matter?
Frit is a glassy material produced by melting raw materials — mainly silica, alumina and boron oxide — at around 1,500 °C and rapidly quenching the melt in water to form vitreous granules. Once milled, these granules are applied onto tiles, sanitaryware and other ceramic products, where they melt again during firing to form the glaze that provides the final colour, finish and abrasion resistance. Frit melting is one of the most gas-intensive stages in the entire ceramic value chain.
A process historically dependent on natural gas
Frit melting is one of the most demanding processes in the ceramic sector, with operating temperatures reaching up to 1,500 °C. Until now, this stage relied almost exclusively on natural gas. The new furnace demonstrates that these temperatures can be reached and maintained using electricity alone, by integrating two complementary technologies.
Two electric systems working in series
The first technology is an electrode-based heating system that exploits the Joule effect. Two molybdenum electrodes pass current directly through the molten frit; the electrical losses within the material itself generate the heat required to keep it liquid, with no flame and no combustion.
The second is an induction system located at the furnace outlet, a particularly critical point of the process. A molybdenum tube heated by induction ensures the flowability of the frit at the moment of discharge: a temperature drop in this area would cause the material to solidify and block the furnace. The system also makes it possible to regulate the outlet flow rate, and even to stop and restart it on demand — a level of operational flexibility that is difficult to achieve with conventional gas burners.
Results of the first tests
During the recent trials, the furnace operated as expected. The electrodes and the induction system maintained stable frit production without using natural gas during the continuous operation. The target productivity of the pilot was 25 kg/h, a figure that has been reached and occasionally exceeded, with operation validated at close to 40 kg/h.
Next steps
Following the validation of the current demonstrator, eLITHE partners will move on to the design of an industrial-scale furnace with a production capacity ten times higher. The aim is to generate the technical and economic data needed to de-risk investment and facilitate the replication of the technology in commercial plants.
Picture courtesy of Miguel Zarzuela