Product Composition and Kinetics of Lignite Pyrolysis

Abstract

Yields, compositions, and selected elemental analyses have been determined for products from the pyrolysis of pulverized Montana lignite in a batch reactor. Heating rate, peak temperature, and residence time at the peak temperature were independently varied in the ranges 100-104 °C/s, 150-1100 °C, and 0-10 s. Yields of all volatile products increased monotonically with temperature at 1000 °C/s and 1 atm of helium, approaching the following asymptotes at 1000 °C: 16.5% water (including 6.8% moisture), 9.5% carbon dioxide, 9.4% carbon monoxide, 5.4% tar, 1.3% methane, 0.6% ethylene, 0.5% hydrogen, and 0.9% ethane, propylene, propane, benzene, plus trace hydrocarbons. Pyrolysis at 1000 °C volatilized about 70% of the sulfur and 25% of the nitrogen. The kinetics of production of major volatile species was modeled with one to three independent parallel first-order reactions. The frequency distribution of the derived activation energies agrees well with a Gaussian distribution previously obtained from weight loss data for the same lignite. © 1978, American Chemical Society. All rights reserved.