Numerical research on the SNCR method in a grate boiler equipped with the innovative FJBS system

The paper describes numerical simulations of processes occurring in the combustion chamber of a stoker boiler. The main topic of CFD analysis presented in this paper is the process of reducing nitrogen oxides emission using the patented Furnace Jet Boiler System (FJBS) in combination with the selective non-catalytic reduction (SNCR) method (FJBS+). The presented method is characterized by introducing a compressed urea-air mixture into the furnace. The reagent is injected through supersonic nozzles, the operating conditions of which are shown on a separate CFD model. The developed model enabled optimization of the existing NO_x reduction system, especially in the case of a boiler operating at maximum load. The overall effect of the operation of FJBS + technology is a significant reduction of NO_x emissions, by approximately 57%. The results achieved are comparable to those obtained from measurements. It was also confirmed that the operation of FJBS + has a positive effect on the equalization of temperature distribution in the furnace and the concentration of flue gas components. Finally, a sensitivity analysis on the basis of two parameters, specific heat of the fuel and thermal conductivity is presented.