Modeling of a strongly coupled Thermal, Hydraulic and Chemical problem: drying and low-temperature pyrolysis of chromated copper arsenate (CCA)-wood waste particles in a moving bed reactor

Low temperature thermal carbonization might be the ultimate solution to the growing disposal problem of chromated copper arsenate (CCA) - treated waste wood. This energy and material recuperating technology is currently in the process of upscaling to an industrial level. In the present study, a numerical reactor model is developed in COMSOL multiphysics that allows to investigate the temperature profiles, gas velocity, char and combustible gas yields and emissions of tars and arsenic during the thermal carbonization of CCA-wood in a moving bed reactor. Strong couplings exist between all equations due to the source terms, changes in gas density/velocity and other physical properties. The resulting system becomes very stiff and recourse has to be made to an iterative, sequential solving procedure to obtain the steady state solution making use of a MATLAB code.