Microwave absorption characteristics of Dongsheng lignite and Yallourn lignite during pyrolysis process

Parameters S11 and ψS11 were obtained by measurement using a microwave network analyzer. Dongsheng lig- nite (DS) from Inner Mongolia and Yallourn lignite (YL) from Australia were examined by means of ANN computa- tion techniques, and their relative dielectric coefficients from room temperature to 800 ℃ pyrolysis process at 2 450 MHz microwave frequency were acquired. The coefficients are used to characterize the microwave absorption properties of the two lignite in the pyrolysis process. The analysis of the weight loss test data suggest that:Before the initial pyrolysis temperature,DS lignite and YL lignite behave very similarly in terms of ε′,ε″,and tan δ values,all at a low level and showing a very slight growth as the temperature increases. At the stage from the initial pyrolysis tem- perature to the pyrolysis end temperature,their characteristic parameters ε′,ε″,and tan δ increase dramatically with the temperature and reach a peak value in the neighborhood of the pyrolysis end temperature;however,the parameters of DS lignite grow both quicker and more appreciably than for YL lignite. All the wave absorption parameters dicline slightly after the pyrolysis end temperature. The experiments show that Dongsheng lignite has a better microwave ab- sorption capability than Yallourn lignite,and that capability can be obviously intensified by high temperature pyrolysis.