LASER IGNITION OF PULVERIZED COALS

We present a novel experiment to study the ignition of pulverized coal. A dilute stream of particles is dropped into a laminar, upward-flow wind tunnel with a quartz test section. The gas stream is not preheated. A single pulse from a Nd:YAG laser is focused through the tunnel and ignites the fuel. The transparent test section and cool walls allow for optical detection of the ignition process. In this article we describe the experiment and demonstrate its capabilities by observing the ignition behavior of spherical, amorphous-carbon particles and two coals: an anthracite and a high-volatile bituminous coal. The ignition behaviors of the carbon spheres and the anthracite are as expected for heterogeneous ignition, while the mechanism of the bituminous coal is uncertain. Calculations are also presented to describe the physical behavior of a laser-heated particle, and the heat transfer and chemistry of heterogeneous ignition.