Experimental study of microwave slow wave comb and ceramic applicators for soil treatment at frequency 2.45 GHZ

Abstract

[EN] In many cases in industry it is required to heat or treat surface layers of different material (soil, timber, concrete, plastics and so on) with microwaves (MW). Traditional MW irradiators (antennas) cannot provide heating only to the surface areas and energy penetrates deep into the material, where it decays exponentially due to normal attenuation. To reduce energy losses it was required to develop special MW applicators for surface treatment to increase process efficiency. To address this problem, a slow wave ("surface wave") comb and ceramic applicators were designed, built and studied. The main property of slow waves is that the energy concentration is very near impedance electrode – comb or ceramic plate surface. Comb and ceramic slab applicators for frequency 2.45 GHz operation were designed for the soil treatment and studied using soil with moisture content range 32-174% and density range 590-1070 kg/m3 . 30 kW MW plant was used for experiments.

Results of the experiments showed that a ceramic applicator provides better uniformity of energy distribution across the width of the applicator. It reduces overheating of the soil surface and energy losses. The depth of energy penetration provided by ceramic applicator is lower compared with the comb applicator. It means that the ceramic applicator provides better energy localization and more energy absorption in the soil surface layers compared with the comb applicator. The ceramic applicator is more effective for MW treatment of the soil surface areas and is recommended for practical use in machines for thermal treatment and sterilization of surface layers of the soil and other materials.