Pyrolysis of biomass: improved models for simultaneous kinetics and transport of heat, mass and momentum

Abstract Understanding the physical phenomena of pyrolysis and representing them with an appropriate mathematical model is essential in the design of pyrolysis reactors and biomass gasifiers. Description of the chemical processes of pyrolysis is coupled to an unsteady state, one dimensional, variable property model of transport phenomena, including heat convection, conduction and radiation, volatiles and gas transport by diffusion and convection and momentum transfer. In this study, a generalized reference model (Model I) incorporating all the above effects is proposed. This is further improved by proposing two simplified models (Models II and III) incorporating additional assumptions. A finite difference pure implicit scheme utilizing a Tri-Diagonal Matrix Algorithm (TDMA) is employed for solving the heat transfer and mass transfer model equations. A Runge–Kutta fourth order method is used for the chemical kinetics model equations. Simulations are performed considering different geometries of equivalent radius ranging from 0.0001 to 0.017 m and temperatures ranging from 303 to 2800 K. The results obtained using these improved models are in excellent agreement with the experimental data, much better than the agreement with earlier models reported in the literature. The improved validated model, which is best suited for wide ranges of operating conditions, is utilized to investigate the influence of particle size, particle shape, product distribution, conversion time and heat of reaction.

[1]  B. Babu,et al.  Modeling, simulation and estimation of optimum parameters in pyrolysis of biomass , 2003 .

[2]  B. Babu,et al.  Parametric study of thermal and thermodynamic properties on pyrolysis of biomass in thermally thick regime , 2004 .

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

[4]  C. Blasi.  Influences of physical properties on biomass devolatilization characteristics , 1997 .

[5]  Colomba Di Blasi,et al.  Physico-chemical processes occurring inside a degrading two-dimensional anisotropic porous medium , 1998 .

[6]  Ö. Onay,et al.  Fixed-bed pyrolysis of safflower seed: influence of pyrolysis parameters on product yields and compositions , 2002 .

[7]  C. Blasi.  Influences of model assumptions on the predictions of cellulose pyrolysis in the heat transfer controlled regime , 1996 .

[8]  H. A. Luther,et al.  Applied numerical methods , 1969 .

[9]  Kenneth M. Bryden,et al.  Modeling the impact of shrinkage on the pyrolysis of dry biomass , 2002 .

[10]  D. L. Pyle,et al.  Heat transfer and kinetics in the low temperature pyrolysis of solids , 1984 .

[11]  Jack B. Howard,et al.  Coal devolatilization and hydrogastification , 1976 .

[12]  B. Babu,et al.  Modeling for pyrolysis of solid particle: kinetics and heat transfer effects , 2003 .

[13]  D. H. Malan,et al.  The combustion of wood. Part I , 1946, Mathematical Proceedings of the Cambridge Philosophical Society.

[14]  C. Koufopanos,et al.  Kinetic modelling of the pyrolysis of biomass and biomass components , 1989 .

[15]  L. T. Fan,et al.  A mathematical model for pyrolysis of a solid particle: Effects of the lewis number , 1977 .

[16]  Olivier Boutin,et al.  Flash pyrolysis of cellulose pellets submitted to a concentrated radiation: experiments and modelling , 2002 .

[17]  V. K. Srivastava,et al.  Predictions of concentration in the pyrolysis of biomass materials—I , 1994 .

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

[19]  T. Liliedahl,et al.  Heat transfer controlled pyrolysis kinetics of a biomass slab, rod or sphere , 1998 .

[20]  Hsiang-Cheng Kung,et al.  A mathematical model of wood pyrolysis , 1972 .

[21]  V. K. Srivastava,et al.  Studies on pyrolysis of a single biomass cylindrical pellet—kinetic and heat transfer effects , 1999 .

[22]  L. Fan,et al.  A mathematical model for pyrolysis of a solid particle — effects of the heat of reaction , 1977 .

[23]  Fred Shafizadeh,et al.  Introduction to pyrolysis of biomass , 1982 .