Temperature Rising Behaviors Under Microwave Radiation and Dielectric Properties of Diverse Rank Coals: Insights to Coalbed Methane (CBM) Production
摘要
Microwave (MW) radiation is competitive in promoting coalbed methane (CBM) desorption and meanwhile reforming reservoirs, thereby enhancing CBM recovery. The MW absorbing and resultant temperature rising capabilities associated with dielectric properties of coals determine the feasibility of MW energy in producing CBM. Thus, the temperature rising performance under MW radiation and dielectric properties of diverse rank coals were measured. Moreover, the implications for CBM production by using MW radiation were raised in this study. Results indicated that the MW radiation is functional in rapidly heating coal samples of different metamorphic grades. The increased temperature of coal samples with or without moisture positively correlates with coal rank. Overall, the temperature rising of the coal samples can be separated into fast and slow stages. The polarity and evaporation of H2O jointly affect the temperature of coals under MW radiation. The dielectric properties of the coal samples are positively related to aromaticity. Moreover, both pyrite and moisture benefit the dielectric response of the coals to MW energy. Furthermore, the response of dielectric parameters including ε′, ε″, and tanδ of the coals to temperature becomes inapparent with the increasing frequency. Eventually, 2450 MHz is chosen as the optimum frequency for all the coals. The optimum operating temperatures for MW radiation toward the low-rank TL coal are recommended at 80 °C; it is 220 °C for the medium- and high-rank LF, JC, and QX coals.