Ignition rate measurement of laser-ignited coals. Technical progress report, July 1--September 30, 1996

Abstract

Over the last several decades many experiments have been conceived to study the ignition of pulverized coal and other solid fuels. The authors are constructing a laser-based apparatus which offers several advantages over those currently in favor. Sieve-sized particles are dropped batch-wise into a laminar, upward-flow wind tunnel which is constructed 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 several particles. The transparent test section and cool walls allow for application of two-color pyrometry to measure the particles` temperature history during ignition and combustion. Coals ranging in rank from lignites to low-volatile bituminous, and chars derived from these coals, will be studied in this project. For each fuel type, measurements of the ignition temperature under various experimental conditions (particle size and free-stream oxygen concentration), combined with a detailed analysis of the ignition process, will permit the determination of kinetic rate constants of ignition. During the past reporting period, the authors have been working on the development of the high-speed data-acquisition system to be used with the two-color pyrometry system for particle temperature measurement. After several attempts and failures at implementing a PC-based data-acquisition board for this purpose, they have decided to purchase an off-the-shelf data-acquisition system. In addition, they have been preparing a manuscript based on data they obtained together with a new model developed to describe the ignition behavior of pulverized coals.