Evaluation of Kinetic Parameters for Rapid Coal Pyrolysis by Analyzing Two-dimensional Images of Releasing Volatile Matter

Abstract

Rapid pyrolysis behavior of a single coal particle in a spot heater apparatus was investigated under various conditions, such as pressure (N₂ atmosphere), temperature, heating rate and type of coal. During the heating, temperature-time histo-ry of coal sample was measured directly by a thin thermocouple and recorded automati-cally by a logger, and releasing images of volatile matter from a single coal particle were obtained by a CCD camera. Total weight loss of coal sample by pyrolysis was also meas-ured. Both the total weight loss and images showed that pyrolysis yield of coal depends on pressure, heating rate and temperature. Pressure had a significant impact on coal pyrolysis, which is attributed to secondary reactions and the resistance of volatile trans-fer in the coal particle. At higher temperature and higher heating rate, the amount of releasing volatiles from a coal particle increased, and a large releasing rate of the volatiles may reduce the opportunity for secondary cracking reactions and carbon depo-sition. Based on the analysis of image data, kinetic parameters for coal pyrolysis, such as apparent activation energy and frequency factor were estimated by using a first order reaction model.