Date of Graduation
1994
Document Type
Dissertation/Thesis
Abstract
The measurement and prediction of the devolatilization temperature histories of bituminous coal particles (of size 106-125 {dollar}\\mu\\rm m){dollar} are carried out for a range of heating intensities. Single particles were isolated in an electrodynamic balance and their three-dimensional external surface areas, volumes, and densities were measured using rapid optical methods. The particles were then irradiated with a pulsed Nd:YAG laser beam of equal intensity from opposite sides. Devolatilization temperature transients during heating and cooling (after the laser pulse was terminated) were measured using a single-color pyrometer. Truncated pulse-widths were also employed to heat and cool some particles prior to devolatilization. Temporal power variations of individual laser pulses were followed using an ultra-fast uv light transmitter coupled to a laser monitor. Size changes were measured using a high-speed diode array imaging system. Dynamics of volatile evolution and particle swelling were recorded using high-speed cinematography. The assumptions of a spherical particle and literature density on the predicted temperature histories are assessed. It was found in general that the measured shape and density correction improved the fit. A sensitivity analysis on the thermal properties was performed and an excellent fit of the model to the data prior to devolatilization was found when the room temperature values of the heat capacity and thermal conductivity were incorporated into the model. Data from the high-speed motion pictures were used to incorporate a first-order Arrhenius type devolatilization kinetic model so that the mass loss is considered in the analysis. Two distinct heat capacity curves were assumed to best fit the temperature data during devolatilization: one for the parent coal with the room temperature value and a second for the lost volatile matter with the temperature-dependent values. The thermal conductivity of coal was assumed to remain at the room temperature value. An apparent heat of devolatilization of {dollar}-{dollar}250 cal/g was assumed. The significance of this work is the development of a detailed model which can predict accurately the temperature history of a single coal particle for heating, devolatilization, and cooling. Such a model would be useful for the more efficient design of advanced coal gasifiers, combustors, and liquefaction reactors.
Recommended Citation
Sampath, Ramanathan, "Measurement and prediction of temperature histories for single coal particles prior to and during devolatilization." (1994). Graduate Theses, Dissertations, and Problem Reports. 9706.
https://researchrepository.wvu.edu/etd/9706