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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-421-2

International Heat Transfer Conference 15
August, 10-15, 2014, Kyoto, Japan

Two Different Methods for Determination of Exothermic Reaction Enthalpies from Temperature Measurements in Beechwood Cylinders During Torrefaction

Get access (open in a dialog) DOI: 10.1615/IHTC15.tpp.008348
pages 8975-8988

Resumo

Torrefaction is a process for producing "bio coal" from lignocellulosic biomass via thermal treatment in an oxygen-free atmosphere. In order to achieve a stable and secure process, the exothermic reaction enthalpy has to be known. In this paper, two different approaches for determining the heat released in beechwood cylinders during torrefaction using temperature measurements at different radial positions are presented and compared. One approach is based on heat conduction within the cylinder, assuming quasi-stationary conditions at each point of time. The other is based on a heat balance at the cylinder's surface. The surface temperature, which cannot be measured with sheathed thermocouples, has to be known for both approaches. Therefore, it is extrapolated from the available measurement data and the impact of measurement uncertainties on this temperature is investigated. Exothermic reaction enthalpies at different reactor temperatures ranging from 230 to 290 °C are determined with both methods. Possible sources of uncertainties through non-ideal bore positions or imprecise temperature measurements are discussed. The highest temperatures measured in the cylinders exceed the reactor temperature by 4 to 46K, resulting in calculated exothermic reaction enthalpies ranging from -30 to -179 kJ/kgdry wood