Kiyoshi Narato

Laser ignition of pulverized coals

Abstract 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 are 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.

A study of gas composition profiles for low NOx pulverized coal combustion and burner scale-up

A turbulent diffusion flame of pulverized coal was investigated to clarify the relationship between flame structure and NOx emissions. NO was formed in the initial flame zone and was reduced in the fuel-rich, post-flame regions, where HCN and NH 3 were produced probably by the oxidation of coal by H 2 O and CO 2 . Burner scale-up also was examined by conducting parallel experiments in a small-scale combustor and a facility with a 25-fold larger coal feedrate. The performance and the profiles of gas species in the flame of the large-scale furnace were well simulated by the data obtained in a laboratory-scale burner where combustion air inlets were remotely located from the central fuel jet to surpress the transverse mixing of air and coal.