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

The effect of potassium additives on pyrolysis of poplar was investigated at 427 degrees 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 K2CO3, 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 K2CO3 more effective than KCl in promoting pyrolysis and char formation.