Dielectric property measurements in design of industrial scale hybrid kiln

It has been appreciated for some years now that the dielectric properties of a material need to be considered if microwave processing is to progress from an empirical basis. The present paper describes the evaluation of materials for use in a pilot plant scale hybrid kiln. Previous kilns at Staffordshire University using microwaves as the only source of energy operated at 2·45 GHz but a new pilot plant scale hybrid kiln for operation at 896 MHz with 75 kW of microwave power is under development with improved, more complex, insulation and firing arrangements. For this reason a range of new refractory and insulation materials has been assessed, e.g. support tubes for heating elements and previously used products and materials measured at only 2·45 GHz have been remeasured at 911 MHz. The results of dielectric property measurements are presented for a range of refractory materials together with an assessment of their likely interactions with the microwave environment.