Numerical simulation of the electromagnetic field and the heat and mass transfer processes during microwave-induced pyrolysis of a wood block

A detailed two-dimensional mathematical model is proposed for the microwave-induced pyrolysis of a wood block, based on a close combination of the propagation and absorption of electromagnetic waves into the lignocellulosic material and heat/mass transfer with chemical reactions. Owing to characteristic times shorter by several orders of magnitude, a quasi-steady approximation is used for the electromagnetic field. In agreement with experimental observation, predicted field variables show a conversion process controlled by volumetric heating with a reaction zone that rapidly enlarges from the most internal region towards the external surface. Good quantitative agreement is also obtained between the measured and predicted weight loss characteristics.