In Situ Measurements of Flyash Formation from Pulverized Coal

Abstract

Optical methods for particle size distribution measurements in practical high temperature environments have achieved feasibility and offer significant advantages over conventional sampling methods. The present paper describes a mobile electro-optical system which has been designed for general use in a wide range of research and industrial environments. The instrument has demonstrated capability for measuring individual particles in the size range 0.25-100 microns at number densities up to 10¹²/m³.- The system incorporates an in situ alignment procedure that is easy to set up and use in a wide variety of research and industrial environments. In addition to demonstration of the system's wide dynamic range, we show the utility of the in situ alignment method in hot (1100 K) turbulent flows where beam steering can be a problem. A major focus of the work described here is the application of the particle sizing technique to measurements of flyash formation in laboratory reactors. Number and mass frequency distribution measurements of flyash and pulverized coal obtained in a turbulent and a laminar flow reactor show that the raw pulverized coal contains large numbers of submicron particles similar to the flyash formed after combustion. These results suggest another source for much of the submicron flyash formed in pulverized combustion, with significant implications for control of fine particle emissions.

Notes

† Research conducted at the Combustion Research Facility, sponsored by the United States Department of Energy through the Pittsburgh Energy Technology Center's Direct Utilization Advanced Research and Technology Centers.