Numerical simulation of a simplified, transient, 2D, non-reactive heat transfer model of a lab-scale fixed-bed pyrolysis reactor

Abstract

Pyrolysis of agro-industrial residues can be used to produce alternative liquid fuels to reduce consumption of fossil fuels. To study these biomass pyrolysis processes, experimentation and numerical simulations are commonly compared. For the latter, thermophysical properties of biomasses and proper thermal models of pyrolysis reactors are required in numerical simulations. This paper presents values for the specific heat capacity, density, and thermal conductivity of Colombian Coffee Husk, as well as a simplified non-reactive heat transfer model of a lab-scale, fixed-bed pyrolysis reactor. The thermal conductivity was determined by combining the axial rod method with transient temperature measurements and an inverse problem solution. CH properties values determined were 1.62 kJ/kg K, 1390 kg/m3, and 0.19 W/mK. To test the validity of the reactor’s thermal model simulation, temperature profiles results were compared with results from an experimental study employing a pyrolysis reactor with the same characteristics. Variations of temperature profiles in time were compared and good agreement between numerical and experimental results was observed for temperatures lower than pyrolysis temperatures (300–400 °C), validating the simplified model. Temperature differences above 300–400 °C were expected as chemical reactions were not included in the numerical model.