Effect of Temperature, Pressure, Feed Particle Size, and Feed Particle Density on Structural Characteristics and Reactivity of Chars Generated during Gasification of Pittsburgh No.8 Coal in a High-Pressure, High-Temperature Flow Reactor

Abstract

The gasification behavior of coal under high-temperature and high-pressure conditions is important from the perspective of designing and optimizing high efficiency gasifiers and troubleshooting existing gasifiers. The effect of feed particle size, density, temperature, and pressure on char porous structure, morphology, reflectance, and reactivity under conditions relevant to entrained-flow gasification was investigated. The chars were generated over a range of temperatures (1100, 1300, and 1400 °C at 11.3 bar for the −150 + 106 µm fraction), pressures (3.4, 6.2, 11.3, 15.5, and 21.7 bar at 1300 °C for the −150 + 106 µm fraction), for various size fractions (−106 + 75, −150 + 106, −212 + 150, −420 + 212 µm at 1300 °C and 11.3 bar), and density fractions (<1.3, 1.3–1.6, >1.6g/cc for the −106 + 75 µm at 1300 °C and 11.3 bar) of Pittsburgh No.8 bituminous coal using a high-pressure, high-temperature flow reactor (HPHTFR) in a equimolar mixture of CO2 and N2. Chars were characterized for conversion, morphology, thermal swelling ratio, and reactivity using ash tracer technique, oil immersion microscopy, tap density technique, and a thermogravimetric analyzer, respectively, and the results were statistically analyzed to determine for effects by feed particle density, feed particle size, temperature, and pressure. The results showed that the conversion was most affected by temperature, followed by feed particle size, pressure, and feed particle density. In the case of structural characteristics (i.e., thermal swelling ratio and group-I char concentration), feed particle density affected group-I concentration, while both feed particle size and feed particle density affected thermal swelling ratio. Variation in vitrinite content and fragmentation affected the thermal swelling ratio and group-I char concentration. In the case of intrinsic reactivity, particle density showed the largest effect, followed by temperature, particle size, and pressure. An increase in reflectance and temperature was found to inversely affect intrinsic reactivity.