Numerical modelling of retrofitting an industrial boiler type OP-230 for predicting NOx reduction

摘要

This study focuses on the indirect co-firing CFD simulations of reductions in NOx emissions relative to the coal combustion. For the given biomass-derived syngas composition and 15% syngas heat input, two arrangements of nozzles dedicated to the syngas injection into the furnace of an older PC-fired boiler of type OP-230 with low-emission burners on the front wall were chosen to investigate the impact of their location on the reduction in NOx emissions. It was shown that the highest reduction achieved by means of the improvement of the air staging via the dual-fuel technique can reach up to 40% (Case 1: nozzles at the elevation of the bottom row of burners) and up to 32% (Case 2: nozzles above the upper level of the burners). The modelling results also showed that one can meet the requirements for co-firing of coal with waste derived syngas. The boiler can be retrofitted for the fulfilment of the prospective environmental protection regulations relating to levels of NOx emissions by combining the described technology with SNCR methods. It is also very important that the indirect co-firing enables reduction of carbon dioxide emissions proportionally to the syngas heat input.