Experimental Investigation of the Effect of Reactor Temperature on Soft and Hardwood Pyrolysis Characteristics in a Fixed-Bed Reactor

Abstract

In this work, product yield distribution at varying reactor temperatures during wood pyrolysis was investigated. Hard and soft wood samples (Mahogany- Khaya senegalensis and Gmelina- Gmelina arborea, respectively) were procured from Pakiotan sawmill in Ogbomoso, Oyo State, South-Western Nigeria. The samples were cut into cuboid shape, each with an average weight of 20 g. The samples were then pyrolyzed in a fixed bed reactor. Experiments were performed at five temperature level (350, 450, 550, 650 and 750 ^oC) at a fixed holding time of fifteen 15 mins and at vacuum pressure. The weight of char, tar and gas produced in each experiment were then measured, recorded and expressed in percentage of initial weight of the pyrolyzed sample. Results showed that Mahogany (Khaya senegalensis) gave maximum char, tar and gas yield of 39.43% at 350 ^oC, 42.53% at 350 ^oC and 53.93% at 750 ^oC, respectively, while for Gmelina (Gmelina arborea), the maximum yields were 28.35% at 350 ^oC for char, 24.81% at 350 ^oC for tar and 68.11% at 750 ^oC for gas. The minimum yield of Mahogany (Khaya senegalensis) for char, tar and gas were 28.35% at 750 ^oC, 17.72% at 750 ^oC and 18.04% at 350 ^oC, respectively and for Gmelina (Gmelina arborea), 17.72% at 750 ^oC, 14.18% at 750 ^oC and 46.84% at 350 ^oC, respectively. This study showed that char and tar yields decreased while gas yield increased as pyrolysis temperature increased. At all temperatures considered, gas yields were higher than tar and char yields for softwood while for hardwood, tar yield declined with increase in temperature with accompanying increase in gas yield.

Keywords: Biomass, hardwood, softwood, energy, reactor temperature, pyrolysis