Interaction of Mustard Husk with microwave radiation: A study on dielectric properties and its variation with frequency

Abstract

Microwave or dielectric heating is an efficient way of treating biomass thermally for energy related applications. Efficiency and effectiveness of microwave heating largely depends upon the dielectric properties of the material to be heat treated. Present study discusses the dielectric properties of Mustard Husk (MSH) in frequency window of 0.5–20.0 GHz at ambient temperature. Dielectric constant (ε’), dielectric loss (ε'') and penetration depth (Dp) decreased to 36%, 9% and 99% respectively on increasing the frequency from 0.5 GHz to 20.0 GHz, while within the same frequency range loss tangent (tan δ) increases to 41%. In this study, dielectric properties of MSH are analysed specifically at 900 MHz and 2450 MHz as well. Relaxation time and tan δ values at 900 MHz frequency are 49.514 ns & 0.082 and at frequency 2450 MHz these values change to 46.394 ns & 0.104 ns respectively. Decrease in dielectric loss, penetration depth, with increase in frequency suggest that MSH is a suitable material for the microwave heating and the lower frequencies of microwave heating are more favourable as compared to the higher frequencies.