Pyrolysis of white pine

Pyrolysis of white pine wood has been studied in thin samples (1.6 mm thick slabs) exposed in an oven at 199–365°C and in thick samples (8–50 mm diam branch segments) exposed in a wind tunnel at 365–525°C and 3–18 m/s wind speed. In the limit case of sufficiently low temperatures and thin samples, the mass-loss rate is kinetically controlled. The kinetics is effectively first order. Mass-loss histories of thin samples above 150–200°C are divided into a short initial period with high rate coefficient, a long middle period with medium rate coefficient, and a final indefinitely long period with very low rate coefficient. Energies of activation $\text{E}\text{R}\text{= 13.3}\text{kK}$ at 93–200°C and 16.3 kK at 200–365°C are inferred. Evidence is given that in thick samples at low temperatures pyrolysis and heat transfer are not very strongly coupled, mass loss being fairly well predicted by first calculating temperature fields as in the case of no chemcial reaction and then computing pyrolysis rates from the kinetic results with due allowance for temperature variation.