Low-Temperature Pyrolysis of Woody Biomass in the Thermally Thick Regime

Abstract

Pyrolysis of biomass is a thermal degradation process in the absence of oxygen, producing gas, tar, and char. The product distribution depends on pyrolysis conditions (heating rate, peak temperature, particle size). In this work, the decomposition of dried poplar wood cylinders of 1.9 cm diameter is investigated under conditions favoring production of "biochar" for soil amendment, that is, in the thermally thick regime with maximum temperature <450 °C. The intraparticle temperature history was measured using a thin sheathed thermocouple. Time-resolved mole fractions of light pyrolysis species, CO, CO2, CH4, HCHO, CH3OH, HCOOH, and CH3COOH, were measured by FTIR analyzer. Tar was collected and identified by GC/MS, and yields of gas, tar, and char are reported. The experiments were compared to the predictions of a one-dimensional model proposed by Park, W. C.; Atreya, A.; and Baum, H. R. (2010) and implemented in Comsol Multiphysics commercial software. Sensitivity to model parameters was determined. The timing of gas production relative to temperature changes supports the view that exothermic processes are caused by decomposition of an intermediate solid, after the main volatiles release.