EXPERIMENTAL CHARACTERIZATION OF AN INDUSTRIAL PULVERIZED COAL-FIRED FURNACE UNDER DEEP STAGING CONDITIONS

Abstract

Abstract Measurements have been performed in a 300 MWe, front-wall-fired, pulverized-coal, utility boiler. This boiler was retrofitted with boosted over fire air injectors that allowed the operation of the furnace under deeper staging conditions. New data are reported for local mean gas species concentration of O2, CO, CO2, NOx, gas temperatures and char burnout measured at several ports in the boiler including those in the main combustion and staged air regions. Comparisons of the present data with our previous measurements in this boiler, prior to the retrofitting with the new over fire system, show lower O2 and higher CO concentrations for the new situation as a consequence of the lower stoichiometry in the main combustion zone associated with the present boiler operating condition. Consistently, the measured mean NOx concentrations in the main combustion zone are now lower than those obtained previously, yielding emissions below 500 mg/Nm3@6%O2. Finally, the measured values of particle burnout at the furnace exit are acceptable being those measured in the main combustion zone comparable with those obtained with the conventional over fire system. Keywords: Deep air stagingLow NOx systemsParticle burnoutPulverized coal This work is part of a project carried out between the power plant owners (EDP-Energias de Portugal) and Instituto Superior Técnico. Financial support for this work was partially provided by the CEC/ECSC Research Programme of the European Commission under the contract number RFC-CR-03004 and is acknowledged with gratitude. The authors would like to thank the personnel of the Sines power plant for their valuable assistance during all the stages of the experiments, particularly, Mr. Luís Matos. The authors wish also to thank Dr. Zhao Hui Liu and Engineer André Ribeirete, undergraduate students Ricardo Ferreira, Ricardo Trindade, Rui Carreiro and Onésimo Silva and technician Manuel Pratas who assisted them in conducting the work presented here. Notes ∗Values for coal mixture in rows 2 to 5; row 1 had a slightly different coal mixture, see Costa et al. (Citation2003). ∗Values measured at the inlet of the regenerative air heaters. ∗∗Values measured at the chimney inlet.