Computational Modelling of Retrofitting a Coal Fired Boiler Type OP-230 for Predicting NOX Reduction
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This study focuses on a CFD modelling of biomass-derived syngas co-firing with coal in an older mid-sized PC-fired boiler of type OP-230 with low-emission burners on the front wall. The simulations were performed to determine whether the boiler can be retrofitted for the fulfilment of the prospective environmental protection regulations relating to levels of NOX emissions. The improvement of the air staging via the dual-fuel technique was based on the indirect co-firing technology. The impact of two arrangements of dedicated syngas nozzles (below and above the existing coal burners), two syngas compositions and two heat replacements (5% and 15%) on the course of thermal processes in a furnace was tested. The reductions in NOX emissions were predicted relative to the baseline when only coal is combusted. The highest reduction of about 38% was achieved with the syngas nozzles below the existing coal burners and 15% heat replacement. This arrangement of nozzles offers the residence time sufficient to co-fire coal with waste derived syngas. A lower reduction in NOX emissions was obtained with the nozzles above the burners as the enlargement of local fuel rich zone near syngas injection becomes significant for 15% heat replacement. Results provide for the decreasing impact of methane content along with the increase of syngas heat input. The avoided CO2 emissions through the syngas indirect co-firing with coal in the boiler are linear function of heat replacements.
Keywordsboiler modelling co-firing biomass derived syngas NOX emission retrofitting
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Research have been carried out in the framework of 3190/23/P and S/WZ/1/2015 works financed by Ministry of Science and Higher Education of Poland from the funds for science.
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