Kinetics of lignite pyrolysis in fixed bed and entrained flow reactors. Technical report No. 17 [electronic resource].
- Washington, D.C. : United States. Dept. of Energy, 1979.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
- Physical Description:
- Pages: 112 : digital, PDF file
- Additional Creators:
- United States. Department of Energy
United States. Department of Energy. Office of Scientific and Technical Information
- A laminar flow isothermal furnace has been constructed and used to study lignite pyrolysis in nitrogen at temperatures between 700/sup 0/ and 1000/sup 0/C. Particles of a Texas lignite (Darco Seam) between 41 and 201 microns in mean diameter, are found to flow down the furnace tube with velocities approximated by the summation of the gas plug-flow velocity and particle free-fall velocities. Some particle shrinkage and density changes occur during pyrolysis. Pyrolysis rate is particle size independent and increases with increase in temperature over the range of operating conditions. Ultimate yield of volatiles in the isothermal furnace, which is calculated from the linear relationship between weight loss and change in proximate volatile matter, is 66% of the original dry-ash-free coal and is particle size independent and relatively temperature independent. Ultimate yields of volatiles from fixed beds of pulverized coal are smaller than for dispersed particles of the same size. Proximate volatile matter for the lignite is, for example, 51% of the original dry-ash-free coal. Heating rates drop from about 10,000/sup 0/C/s in the isothermal furnace to about 20/sup 0/C/s in the proximate volatile matter test. Pyrolysis rates decrease and display particle size dependency in fixed beds. This implication of physical rate control is attributed to heat transfer limitations. It is proposed that pyrolysis rate and therefore residence time of volatiles in the fixed bed are important parameters affecting the preponderance of secondary char forming reactions.Also important is the total particle external surface area in the bed. Secondary char formation is considered responsible for yields of volatiles lower than the true volatile content of the lignite as measured in the isothermal furnace.
- Published through SciTech Connect.
Walker, Jr., P. L.; Scaroni, A. W.
Pennsylvania State Univ., University Park (USA). Coal Research Section
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