Abstract
Microwave directional heating can rapidly increase the temperature of coal and promote the desorption of coalbed methane. The temperature field of coal subjected to microwave directional heating was simulated by using COMSOL software. By coupling the energy conservation equation for an electromagnetic field with the heat conduction equation for solids, a heat conduction equation for the microwave directional heating of coal was established. The effects of the microwave heating time, power, frequency, incident distance and cross-sectional area of the waveguide on the temperature field of coal were studied via simulation. The results revealed that the increasing rate of temperature was high in the early stages of microwave heating. Moreover, higher microwave power corresponded to a higher coal sample temperature, a larger temperature gradient for the coal sample, and less energy being required to achieve the desired coal sample temperature. Additionally, it was found that there is an optimal microwave frequency that maximises the temperature of the coal sample. A larger microwave incident distance resulted in a lower average coal sample temperature. The waveguide was also found to have an optimal cross-sectional area that maximises the maximum temperature of the coal sample.
Highlights
China has abundant coalbed methane resources; most of them exhibit low permeabilities
The simulated results were used to investigate the effects of microwave heating duration, power, frequency, incident distance and waveguide cross-sectional area on the temperature field of the coal sample
The results show that the temperature change in the coal samples with increasing heating time was complicated
Summary
China has abundant coalbed methane resources; most of them exhibit low permeabilities. Microwave heating of coal can effectively promote the development of pores and fractures and increase the permeability of coal seams. Microwave heating of coal promotes the desorption of coalbed methane from coal; the process is highly sensitive to the excitation frequency, and higher powers cause greater thermal heterogeneity [11]. C. Su et al.: Numerical Simulation of the Temperature Field of Coal Subjected to Microwave Directional Heating influence of coal compaction, thermal expansion, thermally induced gas desorption, and sorption-induced coal deformation on the coalbed methane extraction [12]. The simulated results are discussed to describe the effects of the microwave heating duration, power, frequency, incident distance, and cross-sectional area of the waveguide on the temperature field of the coal sample. The fifth section summarizes the paper and discusses future research directions
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