Numerical simulations of coal combustion in the furnace of Unit 7 boiler of Thermal Power Plant (TPP) Kakanj, Bosnia and Herzegovina, have been performed in order to capture the processes occurring within. Proximate and ultimate analyses of coals are regularly performed, and the results have been used in the simulations to define lower heating value and pseudovolatile molecules. However, combustion kinetic parameters of Bosnian coals used for electricity production in TPPs have never been determined. Kinetic parameters for devolatilization, volatile combustion, char and CO oxidation, defined in the form of the Arrhenius equation, govern the speed of reactions, such having an impact on temperature and gas composition distribution within the furnace. In order to assess the impact on the results of computation, a new simulation with significantly different kinetic parameters has been done, keeping the initial and boundary conditions, as well as all other model parameters, the same. Comparison of the results showed the area of the furnace where the differences are largest and which computed variables are most influenced when combustion kinetic parameters are changed.