N.C.S.R. "Demokritos"

Research

Department of Materials Science

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Microwave processing for reduced environmental impact and energy use in industry

Drying and firing are the most energy-intensive processes during production of many products, such as ceramics etc. In large-scale industries, heating is nearly always carried out by the combustion of a fossil fuel such as gas or oil. For drying, forced hot air is used and the drying process can extend up to 5 days or more in a carefully controlled process. Firing is similar and the temperatures involved can reach 1600oC. In all such external heating processes, the main limiting factor deciding the effectiveness (and responsible for the high energy consumption and long duration) is the diffusion of heat from the surface to the centre of the material. To reduce both total energy consumption and process duration, we have developed Microwave short-pulse heating, applied during the drying or firing stages. Microwaves are able to penetrate non-metallic materials and by resonant coupling can heat up almost instantaneously polar molecules, such as water, in the body of the material. This leads to the heat and the contained water rapidly diffusing from the centre outwards where it is removed and, in industrial applications, it is possible to reduce energy consumption as well as duration by up to 75%. The technology has been spun-off to a new spin-off company “Advanced Industrial Technologies SA” which has successfully applied it to industrial drying chambers of volume greater than 100m3. Recent developments of our MW drying technology include continuous drying of clay masses and stone slabs, biological sewage sludge, lignite and other materials.The picture shows Roof tiles being loaded in an industrial MW-drying chamber in a plant in Northern Greece, made by AIT SA.

Department of Materials Science, N.C.S.R. "Demokritos", 153 10 Aghia Paraskevi, Attiki, phone: +30 210 6503381, fax: +30 210 6519430
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