Modeling the impact of shrinkage on the pyrolysis of dry biomass

A new method for modeling shrinkage of a biomass particle is presented and validated in a detailed wood pyrolysis model. This model is applied to particle half-thicknesses ranging from to , temperatures from 800 to , and shrinkage factors of 1.0–0.4. Internal temperatures, pyrolysis rates, and yields of tar, light hydrocarbons and char are presented. Based on the results of the model, it is found that shrinkage has a negligible affect on pyrolysis in the thermally thin (Bi 10) shrinkage affects both the pyrolysis time and the pyrolysis products. Char shrinkage impacts the pyrolysis process in several ways. These include thinning the pyrolysis reaction region and increasing the pyrolysis temperatures, reducing the residence time of the gases within the particle, and cooling the char layer due to the higher mass flux rates of pyrolysis products. Within the thermal wave pyrolysis regime these effects significantly reduce the light hydrocarbon yield, increase the tar yield, and reduce the pyrolysis time. In the case of a large 2-cm half-thickness poplar particle, with a background temperature of and a shrinkage factor of 0.4, inclusion of shrinkage reduces the pyrolysis time by 43%, increases the tar yield from 7% to 13%, decreases the light hydrocarbon yield from 66% to 60%, and decreases the char yield slightly.

[1]  B. B. Krieger,et al.  Modelling and experimental verification of physical and chemical processes during pyrolysis of a large biomass particle , 1985 .

[2]  F. Berruti,et al.  A KINETIC MODEL FOR THE PRODUCTION OF LIQUIDS FROM THE FLASH PYROLYSIS OF BIOMASS , 1988 .

[3]  Robert H. White,et al.  Burning rate of solid wood measured in a heat release rate calorimeter , 1992 .

[4]  J. Lédé,et al.  A new model for thermal volatilization of solid particles undergoing fast pyrolysis , 1983 .

[5]  K. W. Ragland,et al.  Modeling thermally thick pyrolysis of wood , 2002 .

[6]  Edward J. Kansa,et al.  Mathematical model of wood pyrolysis including internal forced convection , 1977 .

[7]  M. C. Melaaen,et al.  Modelling and Simulation of Moist Wood Drying and Pyrolysis , 1997 .

[8]  N. Papayannakos,et al.  Modelling of the pyrolysis of biomass particles. Studies on kinetics, thermal and heat transfer effects , 1991 .

[9]  José L. Figueiredo,et al.  A model for pyrolysis of wet wood , 1989 .

[10]  Colomba Di Blasi.  Predictions of wind-opposed flame spread rates and energy feedback analysis for charring solids in a microgravity environment , 1995 .

[11]  Colomba Di Blasi,et al.  Heat, momentum and mass transport through a shrinking biomass particle exposed to thermal radiation , 1996 .

[12]  Colomba Di Blasi,et al.  Analysis of Convection and Secondary Reaction Effects Within Porous Solid Fuels Undergoing Pyrolysis , 1993 .

[13]  Colomba Di Blasi,et al.  Modeling and simulation of combustion processes of charring and non-charring solid fuels , 1993 .

[14]  John Finn Siau,et al.  Transport Processes in Wood , 1984, Springer Series in Wood Science.

[15]  R. Panton,et al.  Pyrolysis of a slab of porous material , 1971 .

[16]  K. W. Ragland,et al.  A model of chunkwood combustion , 1988 .

[17]  William A. Peters,et al.  Product compositions and kinetics in the rapid pyrolysis of sweet gum hardwood , 1985 .

[18]  Robert F. Chaiken,et al.  Charring pyrolysis of wood in fires by laser simulation , 1977 .

[19]  A. TenWolde,et al.  Thermal properties of wood and wood panel products for use in buildings , 1988 .

[20]  Anthony V. Bridgwater,et al.  Advances in Thermochemical Biomass Conversion , 1993 .

[21]  F. Thurner,et al.  Kinetic investigation of wood pyrolysis , 1981 .

[22]  Jaakko Saastamoinen,et al.  Model for Drying and Pyrolysis in an Updraft Biomass Gasifier , 1993 .