Thermal decomposition study on Jatropha curcas L. waste using TGA and fixed bed reactor

Pyrolysis experiments on Jatropho curcas L. (physic nut) waste were carried out using thermogravimetric analysis (TGA) and a fixed bed quartz reactor to determine suitable degradation model as well as investigate the effect of operating conditions on product distribution. It was found that the main thermal decomposition of physic nut waste generally occurred over the temperature range of 250-450 degrees C. The three-parallel reactions model was applied for simulating the degradation of this waste. The model agreed relatively well with the experimental data. From the model, the activation energy of hemicelluloses, cellulose and lignin was in the range of 41-68, 187-235, and 97-150 kJ/mol, respectively. Reaction orders of those fractions were in the range of 2.4-3.2. Results from pyrolysis process using fixed bed reactor indicated that increase in temperature and hold time lead to greater production of hydrogen, methane and light hydrocarbons with highest gas production detected at 900 degrees C. Tar decomposed at higher temperatures resulted in lower liquid yield while gas yield and total conversion increased. Liquid product consists of several fatty acids such as palmitic acid, stearic acid, and oleic acid in the range of 10-23%, 5-12%, and 35-42%, respectively. The amount of char residue decreased with increasing reactor temperature and hold time. Fixed carbon in char increased with temperature with the expense of volatile matter while there was little change on ash content. Generally, pyrolysis of this residue may be applied for the production of value-added products as well as fuels after some upgrading processes. (C) 2008 Elsevier B.V. All rights reserved.