Modelling and Simulation of Biomass Pyrolysis in Thermally Thin Regime
Authors: Okekunle PO, Itabiyi OE, Ogunwobi DO
Economic and environmental considerations regarding the use of fossil fuels have brought about the need for renewable energy sources like biomass through pyrolysis. However, thermal regimes (thin, thick and thermal wave) have been lumped up while studying biomass pyrolysis, causing ambiguity in results interpretation and process optimization. This work simulated biomass pyrolysis in thermally thin regime and investigated the effect of process parameters on products evolution and total yields over a wide range of reactor temperatures and heating rates. A chemical kinetic model was adopted, resulting in the development of five ordinary differential equations. Arrhenius rate equation of the first order was used to estimate the reaction rate constants for all the species. All equations were coupled and solved simultaneously using Euler numerical method with a time step of 0.001 s to simulate products evolution. Total yields of product species were obtained by trapezoidal rule. Tar evolution increased with heating rate but declined after reaching its peak until the end of the process. Gas evolution at low and high reactor temperatures increased with heating rate while increase in reactor temperature did not significantly influence gas evolution from 5 to 20 K/s. Char yield decreased with increase in both reactor temperature and heating rate. Maximum tar, gas and char yields were 70.536 (at 1 K/s and 673 K), 31.944 (at 20 K/s and 773 K) and 19.508% (at 1 K/s and 373 K), respectively. The conditions that will optimize the yields of product species in this thermal regime are presented.
Affiliations: Department of Mechanical Engineering, Faculty of Engineering and Technology, Ladoke Akintola University of Technology, PMB 4000, Ogbomoso, Oyo State, Nigeria
Keywords: Biomass, Pyrolysis, Kinetic Model, Thermally Thin Regime, Heating Rate, Temperature
Published date: 2019/12/30