277047 Kinetic Modeling & Simulation of Thermo-Chemical Conversion of Jatropha De-Oiled Cake
Biomass from agricultural residues is one of the most viable renewable energy sources. Towering prices and limited supply of fossil fuels make the biomass as an important alternate energy source for most developing countries. Biochemical and thermo-chemical processes are widely used for the recovery of value added products and energy from biomass (Sheth and Babu, 2010). The thermo-chemical conversion of biomass, via pyrolysis, gasification, and combustion, is one of the promising routes among the renewable energy options of future energy (Sheth and Babu, 2009). Pyrolysis of biomass has been proposed as an alternate solution due to the increasing energy demand and environmental awareness. In the present study, the de-oiled cake of Jatropha is considered as a biomass. Jatropha plant has the potential as a renewable energy crop as its oil is upgraded via transesterification to the conventional biodiesel. Extraction of Jatropha oil results in residue cake which needs to be disposed. Generally, collection and disposal of residues are becoming more difficult and expensive and may create environmental problems if not properly done (Sricharoenchaikul and Atong, 2009).
Kinetics of thermal decomposition of biomass material is complicated, as it involves a large number of reactions in parallel and series. Different classes of mechanisms are reported for the pyrolysis of wood and other ligno-cellulosic materials. The models are classified into three categories: one-step global models; one-stage multi-reaction models; and two-stage semi-global models. The second category of models discuss those mechanisms, which consider simultaneous and competing first order reactions in which virgin biomass decomposes into different constitutes of pyrolysis products, namely, tar, char, and volatile gases. The third class of models consider pyrolysis to be a two-stage reaction, in which the products of the first stage break up further in the presence of each other to produce secondary pyrolysis products (Babu, 2008). These reported kinetic studies are limited to use for certain species of biomass only for which kinetic data are available. In this work, the pyrolysis process is described by the independent parallel first order reactions model.
In the present study, a kinetic model is developed to represent the pyrolysis process that is described by independent parallel first order reactions. The kinetic model is simulated using finite forward difference method to predict the pyrolysis rate. The corresponding kinetic parameters of the model are estimated by minimizing the square of the error between the experimental data of thermo-gravimetry and simulated model predicted values of residual weight fraction using Differential Evolution (Price and Storn, 1997, Gujrathi and Babu, 2011), a population based search algorithm. Thermo-gravimetric experimental runs are carried out using Thermo-gravimetric analyzer (TGA 4000, Perkin Elmer) of Jatropha cake waste. TGA study is performed in a nitrogen atmosphere under non-isothermal conditions at different heating rates and the thermal decomposition profiles are used to find the kinetic parameters.
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