THERMOGRAVIMETRIC STUDIES ON THE KINETICS OF RICE HULL PYROLYSIS AND THE INFLUENCE OF WATER-TREATMENT

Rice hulls were pyrolyzed in a thermogravimetric analyzer in a helium atmosphere to determine the kinetic parameters of devolatilization rea ctions. The pyrolysis experiments were conducted by heating rice hulls from room temperature to 1173 K at constant heating rates of 3, 10, 3 0, 60, and 100 K/min. The global mass loss during rice hull pyrolysis was successfully simulated by a combination of four independent parall el reactions, the decompositions of four major components in rice hull s: moisture, hemicellulose, cellulose, and lignin. The activation ener gy for the decomposition of the nonmoisture components was in the orde r cellulose > hemicellulose > lignin. It was also found in the present study that the pyrolytic behaviors were significantly influenced by w ater wash prior to pyrolysis. The water wash elevates the peak tempera ture and the activation energy for the decomposition of each component of rice hulls. The volatile yields resulting from cellulose and hemic ellulose decompositions during rice hull pyrolysis increase due to the water treatment, whereas those from lignin decomposition and the char yield decrease.