Pyrolytic Behavior and Products of Some Wood Varieties

Thick wood cylinders have been pyrolyzed with applied radiation intensities in the range 28-80 kW/m2, to investigate the role of wood variety on the degradation characteristics (temperature and weight loss dynamics), product (char, gas, and liquid) yields, and gas composition. Two hardwoods (beech, chestnut) and three softwoods (Douglas fir, redwood, and pine) have been examined. Apart from the higher minimum heat flux needed for softwood pyrolysis, all the varieties present the same qualitative behavior, and the process dynamics tend to become the same for applied heat fluxes above 40 kW/m2, when internal heat transfer is the controlling mechanism. However, quantitative differences remain large in terms of pyrolysis temperature (maximum values of 600-650 K), product yields (minimum char yields of 21-33%, maximum liquid yields of 47-57%), and average devolatilization rate, as a consequence of variations in the chemical composition.