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Mathematical modelling of heat and mass transfer in a fixed biomass fuel bed. Part 1, Drying

Gemechu B., Atreya A., Blasiak W.

Archives of Thermodynamics

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1999

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Vol. 20, no 3/4

49-61

EN

A one-dimensional quasi-steady state mathematical model of heat and mass transfer in a fixed bed of biomass fuel during drying is presented. Heat is transferred from the pyrolysing fuel bed to the drying fuel above it by conduction and convection. The gas flow rate is determined by mass flux flowing through the bed. The drying rate curve is analyzed theoretically and the best drying curve formula is chosen. As a result, a one-dimensional quasi-steady state mass and temperaturedistributions in the bed are determined. @eng

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Mathematical modelling of heat and mass transfer in a fixed biomass fuel bed. Part 2, Pyrolysis

Gemechu B., Atreya A., Blasiak W.

Archives of Thermodynamics

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1999

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Vol. 20, no 3/4

63-72

EN

Heat and mass transfer in a fixed bed of biomass during thermal degradation of biomass in a hot inert gas (pyrolysis) is modeled. Biomass fuel decomposes to give gas, tar and char as a result of hot gas flowing through it upwards from a combustion char below. The main heating mode at this stage is conduction and convection. The fuel bed is assumed to be a porous homogenous layer composedof uniformely distributed coarse particles that are randomly oriented. The mathematical model formulates the basic equations and solves them numerically to describe the temperature and solid fuel degradation to tar, gas and char. Thermal non-equilibrium between the gas phase and the solid particle surfaces is assumed, conseqently the use of separate equations for gas and solid phase equations is necessary

3

Mathematical modelling of heat and mass transfer in a fixed biomass fuel bed. Part 3, Char Combustion

Gemechu B., Atreya A., Blasiak W.

Archives of Thermodynamics

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1999

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Vol. 20, no 3/4

73-88

EN

One-dimensional propagation of a combustion front in a solid fuel bed of char is modelling by making the solid fuel as stationary with gas flowing through it upwards. The main means of heat transfer considered are conduction, convection and radiation. The fuel bed is assumed to be a porous homogenous layer composed of uniformly distributed coarse particles that are randomly oriented. The bed is thermally thick rendering a time-dependent, non-uniform temperature distribution between the top and the bottom. The mathematical model formulates the basic equations and solves them numerically to describe the temperature and species distribution in the region. Thermal non-equilibrium between the gas phase and the solid particle syrfaces is assumed, cosequently the use of separate equations for gas and solid phase equations is necessary. The method of solution is more complicated due to the fact that the partial differential equations of heat transfer are simultaneous non-linear partial differential equations. Numerical methods are used applaying Mathematica and Fortran ODE codes. Both methods show good results compared with previous works.