TY - JOUR
T1 - Microwave upgradation of Yunnan lignite
T2 - dielectric properties, drying pattern and kinetics
AU - Guo, Lei
AU - Liu, Chenhui
AU - Srinivasakannan, C.
AU - Jiyun, Gao
N1 - Funding Information:
The authors acknowledge the financial supports from the National Natural Science Foundation of China (CN) [Nos. 51964046, 51504217].
Publisher Copyright:
© 2021 International Microwave Power Institute.
PY - 2021
Y1 - 2021
N2 - The work attempts to investigate the dielectric properties and microwave drying characteristics of Yunnan lignite, so as to upgrade it. The effect of drying temperature, moisture content and microwave heating frequency on dielectric properties was measured using resonant cavity method. Results indicate that both the values of ε′ and ε″ presented two stage at the investigated temperatures. Bulk water was found to be the main factor contributing to an increase in the ε′ and ε″. Microwave drying kinetics of lignite were carried out. The Page model was the best model reflecting the drying kinetics, and the effective diffusion coefficient and active energy at different drying stages were obtained. In addition, the microwave drying mechanism has been proposed based on the study of dielectric and drying properties of lignite. The SEM images indicated that microchannels were formed within the lignite particle by the microwave pumping effect. FT-IR spectra showed that the oxygen-containing functional groups and hydrogen bonds between them were break by microwave drying. Based on the achieved results, the microwave treatment at 150 °C is helpful to upgrade the lignite.
AB - The work attempts to investigate the dielectric properties and microwave drying characteristics of Yunnan lignite, so as to upgrade it. The effect of drying temperature, moisture content and microwave heating frequency on dielectric properties was measured using resonant cavity method. Results indicate that both the values of ε′ and ε″ presented two stage at the investigated temperatures. Bulk water was found to be the main factor contributing to an increase in the ε′ and ε″. Microwave drying kinetics of lignite were carried out. The Page model was the best model reflecting the drying kinetics, and the effective diffusion coefficient and active energy at different drying stages were obtained. In addition, the microwave drying mechanism has been proposed based on the study of dielectric and drying properties of lignite. The SEM images indicated that microchannels were formed within the lignite particle by the microwave pumping effect. FT-IR spectra showed that the oxygen-containing functional groups and hydrogen bonds between them were break by microwave drying. Based on the achieved results, the microwave treatment at 150 °C is helpful to upgrade the lignite.
KW - apparent activation energy
KW - dielectric properties
KW - effective diffusion coefficient
KW - Lignite upgrading
KW - microwave drying kinetics
KW - microwave pumping effect
UR - http://www.scopus.com/inward/record.url?scp=85113389799&partnerID=8YFLogxK
U2 - 10.1080/08327823.2021.1952834
DO - 10.1080/08327823.2021.1952834
M3 - Article
AN - SCOPUS:85113389799
SN - 0832-7823
VL - 55
SP - 248
EP - 269
JO - Journal of Microwave Power and Electromagnetic Energy
JF - Journal of Microwave Power and Electromagnetic Energy
IS - 3
ER -