Effect of Extended Surfaces on Temperature Distribution Inside a Fixed-Bed Biofuel Pyrolysis Batch Reactor

Abstract

This paper investigates the improvements in the temperature distribution of biomass in an alternative design of fixed-bed biofuel batch reactor while undergoing fast pyrolysis, compared to the conventional design. The reactor furnace temperature was selected based on optimum pyrolysis temperature and appropriate convective heat transfer coefficient was computed and used with corresponding boundary conditions for transient thermal analysis using ANSYS software. For the 3-D model, about eighty-one thousand and sixty-eight thousand elements were used for the conventional design and alternative design, respectively; while for the 2-D model, about three thousand elements were used for both the conventional and alternative designs in the transient ANSYS heat transfer analysis. The results show that the alternative design, which includes the use of extended surfaces, improves the temperature distribution in the reactor by making it more uniform during the fast pyrolysis process. The implications of this are that the alternative design gives a greater yield of bio-oil per batch run, and steady-state conditions are reached within 40% of the time taken for the conventional design, which translates to a shorter process time and reduction in overall energy input, thereby making it a more efficient system.