A hybrid kinetics model for the bond cleavage of low rank coals

The amounts (N-B,N-t) and rates of bond cleavage of coal are essential for the development and optimization of pyrolysis and direct liquefaction processes. A hybrid first order kinetics model is developed in this work to suit the complex and diverse properties of covalent bonds in coal, and the NB, t of four low rank coals at 380-440 degrees C are fitted to determine the kinetics parameters. In specific, the hybrid model includes the single-temperature linear regression (STLR) and the multi-temperature nonlinear regression (MTNLR). The STLR method yields the maximum amounts of cleavable bonds N-B,N-0 at different temperatures, which are then incorporated into the MTNLR model to yield the kinetics parameters, Ea and A. The hybrid model significantly improves the fitting accuracy in comparison with the single STLR or MTNLR model. The lnA similar to E-a relations in the three models for four coals' bond cleavage kinetics follow a similar compensation effect but differ from those for the mass change kinetics.