Simultaneous Reduction of NOx Emission and SOx Emission Aided by Improved Efficiency of a Once-Through Benson Type Coal Boiler

Abstract

This paper presents a comprehensive approach for improved efficiency of a once-through Benson type coal boiler in a coal-fired power plant. In the method, petrographic properties, ultimate analysis and proximate analysis of coal feedstock is firstly determined. In addition, operational parameters, like O2 concentration, coal mass flow, air/fuel ratio and load were varied to establish their impact on both SO2 concentration and NOx reduction. The coal samples are led by inertinite in the range of 34.4 – 47.8 vol% afterward total vitrinite content in the range of 20.3 – 24.4 vol%. Liptinite content occurs in minor proportions of 1.8 – 4.3 vol% range. The optimum conditions for simultaneous reduction of NOx emission and SOx are achieved when the O2 concentration is 3.58% and coal mass flow of 288 tonnes/hr. Reducing coal mass flow from 331 to 288 Tonnes/hr caused high SO2 concentration to reduce from 3862 mg/Nm3 to 2232 mg/Nm3. Moreover, NOx concentration reduced from 350 mg/Nm3 to 310 mg/Nm3 when the air/fuel ratio varied from the lean side to the rich side. The optimum air/fuel ratio of 7.24 resulted in NOx reduction. The highest boiler efficiency of 90.97% was achieved at full load and the O2 concentration of 3.58%.