Effect of Flue Gas Recirculation on the Technical and Environmental Performance of a Boiler

Abstract

The results of studying the effect of flue gas recirculation on the amount of nitrogen oxides (NO_x) formed in a TP-101 steam boiler are presented. In firing oil shale, the recirculation of flue gas to the mills makes it possible to inject the portion of the primary air replaced by this gas to the furnace above the oil-shale burners, thus providing staged firing. This measure allows reaching a NO_x concentration limit of about 170 – 190 mg/m³. During co-firing of oil shale and retort gas (60:40 of total heat input), the recirculation of flue gas to the burners reduces the NO_x concentration at the boiler outlet from 500 to 230 – 240 mg/m³.