Numerical simulation of the pyrolysis zone in a downdraft gasification process

Models of the gasification process are mostly based on lumped analysis with distinct zones of the process treated as one entity. The study presented here was conducted to develop a more useful model specifically for the pyrolysis zone of the reactor of a downdraft gasifier based on finite computation method. Applying principles of energy and mass conservation, governing equations formed were solved by implicit finite difference method on the node of 100 throughout the length of the considered pyrolysis range (20 cm). Heat transfer considered convection, conduction, and the influence of solid radiation components. Chemical kinetics concept was also adopted to simultaneously solve the temperature profile and feedstock consumption rate on the pyrolysis zone. The convergence criteria were set at 10⁻⁶ and simulation used Fortran Power Station 4.0. Validation experiments were also conducted resulting in maximum deviation of 24 °C and 0.37 kg/h for temperature and feedstock feed rate, respectively.