Numerical simulations of a reburning process have been done. The calculations were conducted using a homemade complex chemical kinetics program for reactions between reburning fuel and flue gas from coal combustion. As the reburning gases, syngas and pyrolysis gas were tested, both obtained from wood. The aim of the simulations was the estimation of the influence of syngas on NO reduction. The results show a dependence of the relative amount of NO on temperature, air excess ratio and reaction time.