Effect of Temperature and Residence Time on Torrefaction Characteristics of African Birch (Anogeissus leiocarpa)

Abstract

In this study, the effect of temperature and residence time on African birch (Anogeissus leiocarpa) torrefaction characteristics was investigated. African birch trunk was procured from Aanu-Oluwapo Sawmill in Ogbomoso, SouthWestern Nigeria. The trunk was sawn into pieces. The pieces were machined into cylindrical samples of 40 mm diameter and 65 mm length using a wood lathe machine (Powermatic 3520B). Prepared samples were torrefied, one at a time, in an electrically heated fixed bed reactor at different torrefaction temperatures (200, 230, 260, and 290 oC) and residence times (10, 20, 30, and 40 min). The proximate analysis of both the raw sample and solid torrefaction products was done according to the ASTM D3174-76 standard. The mass and energy yields, Higher Heating Value (HHV), and water absorption characteristic of the solid torrefaction products were then determined. Findings revealed mass and energy yields of the torrefied solid products decreased with an increase in both temperature and residence time. HHV increased with temperature but did not show any consistent pattern with residence time. The water affinity of the torrefied biomass decreased with both temperature and residence time. Torrefaction inhibits biomass moisture uptake during storage while increasing its heating value