Case Studies in Thermal Engineering (Dec 2021)
Modelling analysis of pyrolysis process with thermal effects by using Comsol Multiphysics
Abstract
Numerical modelling of biomass pyrolysis in a packed bed reactor conducted with heating rate 1073 K/h was performed in this study. The devised modelling is a very effective way to analyse and evaluate physical phenomena for designing and optimizing pyrolysis process. As the shape of wood used was in the form of powder, the multi-phase flow was simulated using the heat transfer in porous medium and fluid flow. It was coupled to describe the pyrolysis process of woody biomass in a packed bed. Due to thermal effect being the most crucial matter in the designing of reactor, this work investigated the temperature and velocity distribution during the process. Besides, this study made predictions in other biomass feedstocks; bamboo and bark. The experimental data were obtained by means of a laboratory-scale real pilot plant in the packed bed furnace. The pyrolysis process lasted for 120 min. The temperature variations for investigating the thermal effects in pyrolysis process took place from 523 K to 923 K with heat source on the furnace wall. The numerical modelling indicated a good agreement between the experimental and calculated results in their validation. The pyrolysis temperature had the greatest effect on the heat and mass distribution during the process influencing the product yield and the direction of experimental heat transfers in the biomass packed bed were confirmed well by surface contour temperature with the calculated numerical model. However, there were slight differences due to water evaporation and heat reaction strongly influencing the heat transfers in the packed bed, affecting the absorption of heat energy in the pyrolysis process. In addition, the chemical properties of wood components greatly affected their physical properties, mostly influencing the heat transfers in the packed bed which dominantly occurred as thermal conduction. This had an impact on the amount of heat capacity of each feedstocks. Among the biomass feedstocks, the calculated results shows that the distribution temperature of bamboo was the highest in the study due to its properties.
