Measurement of soot and char in pulverized coal fly ash

The unburned carbon in the fly ash produced by low-NOx pulverized coal comb ustion has been shown by electron microscopy to be a mixture of porous coal char particles and aggregates of submicron particles, which are thought to be soot. The carbon is bimodally distributed with large soot aggregates mi xed with the char in the particles larger than 10 mu m and dispersed soot f ound with the submicron particles. A method fur determining the mass of soo t and char by liquid-suspension gravity separation was used with both labor atory-scale and power plant fly ash samples. For low-NOx, staged, pilot-sca le combustion of bituminous coal the soot in the furnace exit ash was estim ated to be 0.2-0.6% of the fuel carbon, which was about 35% of the total un burned carbon. (C) 2000 Elsevier Science Ltd. All rights reserved.