Understanding the liquefaction mechanism of Beypazarı lignite in tetralin with ultraviolet irradiation using discrete time models

Abstract

This study has proposed four different liquefaction models consisting of both reversible and irreversible reaction steps with three lumped parameters, asphaltenes, preasphaltenes, and oils, for the liquefaction of Turkish lignite (Beypazarı-Çayırhan). The coal had been liquefied in tetralin using a solvent/coal ratio of 5/1 at four different ultraviolet irradiation light sources of 90, 120, 150, and 180 W. The validity of the proposed models is specified by first order linear discrete-time models with the experimental data. Furthermore, the reaction rates of the proposed liquefaction models are determined using a Matlab program with the use of Kalman filter. The validation of proposed models for the liquefaction of Beypazarı lignite is defined using the sum of the squared differences of the models and experimental data. The results demonstrate that models which consist of reversible steps provide a better fit with experimental data compared to models consisting of irreversible steps. While the liquefaction step from reactive coal to oils demonstrates a maximum reaction rate constant of 2*10−2 h−1, the other steps from reactive coal to either preasphaltenes or asphaltenes show lower reaction rate constants, about 1*10−2 h−1. In addition to the fact that the formation of preasphaltenes and asphaltenes from reactive coal takes place slowly, a major proportion of the oils are formed directly from reactive coal.