Pyrolysis of Potassium-Doped Wood at the Centimeter and Submillimeter Scales

The effect of potassium additives on pyrolysis of poplar was investigated at 427 °C, both at the submillimeter scale, through thermogravimetric analysis (TGA), and at the centimeter scale, through pyrolysis of wood cylinders in a turbulent reactor. Internal temperatures and time-resolved rates of production of gases and light volatiles were measured in the centimeter-scale study. The potassium level in the samples was varied through vacuum treatment with distilled water or solutions of KCl or K 2 CO 3, resulting in potassium levels of approximately 100, 4500, and 7000 ppm (dry, mass basis). At the centimeter scale, potassium addition had a dramatic effect on conversion time and on the magnitude of exothermic temperature excursions, as well as a significant effect on the yields of gases and light volatiles. Consistent with the literature, submillimeter-scale TGA experiments with external temperature control also indicated a catalytic effect of the potassium additives, with K 2 CO 3 more effective than KCl in promoting pyrolysis and char formation.