NOx Emissions From Combustion of High Sulfur Lignite in an ABFBC Test Rig

Abstract

NOx emissions from fluidized bed combustion of various coals have extensively been investigated and well documented. However, NOx emissions from combustion of Turkish lignites with high ash, volatile matter and sulfur contents have not drawn much attention to date. Recent trend in utilization of indigenous lignites in fluidized bed boilers necessitated investigation of pollutant emissions and adaptation of fluidized bed combustion technology to these lignites. In this study, experimental results of various runs pertaining to the formation and emission of NOx from METU 0.3 MWt Atmospheric Bubbling Fluidized Bed Combustor (ABFBC) test rig burning typical indigenous lignites; Aydin without limestone addition and Beypazari with and without limestone addition are presented. NOx profiles along the combustor show that concentrations are higher in bed compared to those in freeboard and that conditions leading to higher unburned volatiles in freeboard enhances NOx reduction in that region. Limestone addition results in higher concentrations of NOx in bed but lower concentrations in freeboard, albeit insignificantly.