AKINETIC STUDY OF LOW-TEMPERATURE LIGNITE CARBONIZATION

Abstract

Abstract Seyilömer and Tunçbilck lignite samples have been carbonized in a fixed-bed reactor under various temperature and time conditions in a nitrogen atmosphere. The total conversion, tar and gas yields have been calculated as functions of temperature and time. The results were grouped as those obtained in the constant-heating-rate regime and those obtained at the constant stable temperature. Different kinetic models were applied to these “increasing” and “constant” temperature regimes. In the increasing temperature regime the degree of the reaction was deduced through the proposed kinetic model. In the constant temperature regime the reaction degree was presumed at the beginning and the gaseous products were identified as primary and secondary. Various models have been examined for lignite carbonization process for comparison of experimental findings. Parameter estimating analysis were carried out on the results and the rate constants have been found. Then, multiple linear regression analysis were used to deduce activation energies and frequency factors. The kinetic rate constants (k1=0.00002 and k2=0.00106 min−1 at 600°C) that were found for tar and primary gas are lower with respect to the corresponding values in the constant temperature region. The secondary gas decomposition rate is observed to be higher than production rate.