Effects of Pressure on Coal Pyrolysis at High Heating Rates and Char Combustion Effects of Pressure on Coal Pyrolysis at High Heating Rates and Char Combustion
A flat-flame burner was used in a high pressure laminar flow facility to conduct high temperature, high heating rate pyrolysis and combustion experiments for four coals. The high-heating-rate (10000 K/s), high-temperature atmosphere can better simulate industrial conditions than the conventional drop tube facility. Pressure and heating rate have a significant impact on the total volatiles, char physical structure including morphology, and char internal surface areas. The high heating rate decreases the swelling ratios of chars at pressures from 2.5 to 15 atm. TGA char oxidation reactivities were measured at the same total pressure as the char preparation pressure. The general trend was that the TGA reactivity on a gram per gram available basis decreased with increasing char formation pressure. When the reactivity was normalized by either the N2 or CO2 surface area, the normalized reactivity was found to be relatively constant with increasing pressure.
Char burnout was measured at different pressures and O2 concentrations at high temperature in the pressurized flat flame burner facility. For a given pressure, the particle diameter ratio based on coal (d/dcoal,0) decreased with increasing O2 concentration. Two char kinetic models (CBK 8 and CBK/E) were used to fit the char burnout data, and the modeling results showed that the intrinsic char oxidation rate increased with increasing total pressure at constant oxygen partial pressure.
School:Brigham Young University
School Location:USA - Utah
Source Type:Master's Thesis
Keywords:combustion coal char pressure heating rate
Date of Publication:08/04/2005