Microwave heating of oil shale based on multiphysics field coupling: Positioning of the waveguide

Abstract

Microwave heating has proven widespread applications in oil shale pyrolysis; however, the impact of waveguide port positioning on the microwave reactor's thermal performance remains underexplored. This work establishes a 3D coupled model that incorporates electromagnetic, thermochemical, and fluid dynamics effects employing multiphysics modeling methodology. The thermochemical characteristics of an oil shale sample under microwave irradiation are quantified for a broad range of waveguide port positions, specified via Latin hypercube sampling, which ensures the randomness of the port coordinates. The cavity field strength exhibits markedly high sensitivity to the waveguide positioning: the standard deviation of the cavity-averaged electromagnetic intensities for all considered positions is found to be 30.42% greater compare to the associated mean. The best port position yields a temperature rising rate an order of magnitude higher than the worst positioning, for which kerogen pyrolysis does not appear to be even activated in the same initial stage. The ranking of waveguide positions identified based on the temperature rising rate aligns well with the analysis of microwave utilization efficiency. The study offers insights for optimized microwave reactor design with enhanced oil shale thermal treatment.