Thermal Degradation of Rice Husks in an Oxygen Atmosphere

Abstract

Of the various energy conversion options of rice husk, thermochemical conversion processes such as pyrolysis, combustion, and gasification offer the most efficient way to use rice husk. However, a knowledge of the thermal characteristics of rice husks is essential for the optimal design of these systems and for ensuring stringent emissions as well as high conversion efficiency. Thermogravimetric analysis is used to profile weight loss due to physical and chemical phenomena taking place in the sample while being subjected to high temperatures. This technique presents an ideal system to study thermal properties of carbonaceous materials. Evaluation of the thermogravimetric behavior of four rice husk varieties (Lemont, ROK 14, CP 4, and Pa Potho) at three heating rates (10, 20, and 50 C min) in an oxygen atmosphere is described. The thermal degradation rates, the initial degradation temperature, and the residual weight at 700 C were deter mined. These thermal degradation indices of rice husks are a function of tempera ture, heating rate, and the composition of the rice husks. The initial degradation temperature decreased while both the thermal degradation rate and the residual weight at 700 C increased when the heating rate was increased. The higher the cellulosic content of the rice husk, the higher the thermal degradation rate and the initial degradation temperature. Also, higher ash content in the rice husk resulted in higher residual weight at 700 C. Rice husk could be degraded to the extent of 73-80 %.