Heating process characteristics and kinetics of rice straw in different atmospheres

Rice growing engenders large quantities of straw, which is usually burnt in the open field, a practice implying a public health risk. There are, however, several ways of making use of this material, including its conversion into a valuable fuel. The aims of this research are to describe the thermal characteristics of the heating processes of rice straw in different atmospheres of air and nitrogen and to fit the heating profiles to two mathematical models proposed. This research was followed by thermogravimetric analysis, visual observation of the heating profiles revealing three stages in the rice straw heating process: drying, devolatilization and burning. The models described were found to adequately describe the weight loss of rice straw. The approximate integral method (AIM) is less complex than the direct method (DM), but the latter shows the order of reaction. A better fit is obtained for the heating atmospheres with a lesser proportion of oxygen. The presence of oxygen increases the activation energy and decreases the final temperature of each stage considered.