Local temperature measurements in a full-scale utility boiler with overfire air

Gas temperature and effluent NOx measurements were obtained in a full-scale (160 MWe) pulverized coal corner-fired utility boiler with separate overfire air. The measurements are the first of this kind in a full-scale boiler operated with overfire air and low-NOx burners. A test matrix of seven operating conditions was used to compare temperature and NOx with changes in overfire air, coal type, load and burner tilt. Peak temperatures were 1500-1600 degrees C and occurred just above the top burner. The measurements detailed the profile of temperature through a traverse of a coal burner, close-coupled overfire air port and separate overfire port. The data in the near-burner and overfire air regions showed evidence of reduced swirl as overfire air was increased. Little difference was seen in the temperatures for two coals with volatile fractions of 28 and 36 wt%. Temperature changes were quantified in the overfire air region for changes in burner tilt and load. Temperature was approximately the same in the overfire air region as load was decreased, but increased in this region as the burners were tilted from +5 degrees to -5 degrees. (C) 1997 Elsevier-Science Ltd.