A Fast Method for the Prediction of Breakthrough Curves of Non-Isothermal Fixed-Bed Reactors

A model and a computer program have been developed for the prediction of breakthrough curves of a non-isothermal adsorption column, packed with porous spherical particles. At time zero, a step change in the concentration of an adsorbable component is introduced to the flowing stream. Together with this concentration step, the temperature of the flowing stream may be changed. The adsorption column is subjected to axial dispersion, external film diffusion resistance, pore diffusion resistance, heat effects of the adsorption process, axial heat transfer resistance of the solid and the fluid phase, external film heat transfer resistance and heat transfer from the fluid and the solid phase to the wall. Radial gradients, the pressure drop across the bed, mass accumulation in the pores and the heat capacity of the fluid in the pores are neglected. Other assumptions are: plug flow takes place in the bed: heat capacities, densities and the adsorption heat are constant with respect to concentrations, temperatures and time; and the wall temperature is uniform and constant. At the solid surface, the fluid phase and solid phase are assumed to be in equilibrium. This equilibrium must be represented by an isotherm that is linear with respect to concentration and temperature, because for the method of solution, this isotherm must be Laplace transformed. The model equations are solved by Laplace transformation, both with respect to time and place. The inverse Laplace transform with respect to place is calculated analytical by complex integration. The inverse Laplace transform with respect to time is calculated numerically by applying the Fast Fourier Transform. As a result, the computer program calculates concentration and temperature breakthrough curves in a few minutes on a Personal Computer with a 8086 processor and a 8087 mathematical coprocessor. The model describes quantitative the existence of different breakthrough regimes and temperature plateaus. The effects of variations of the process parameters, such as diffusion coefficients and heat transfer resistances are described qualitative. In order to make the program useful for a more general set of fixed-bed processes, future developments should be directed towards a more general adsorption isotherm and the radial components of the model equations. Especially the possibility of non-linear isotherms would make the program very powerful.Chemical Reactor EngineeringDelftChemTechApplied Science

Voorstudie G-opdracht 1988-I GOfiner - Esso Rotterdam

Document(en) uit de collectie Chemische Procestechnologie.DelftChemTechApplied Science

Fast calculation of breakthrough curves in nonisothermal fixed-bed adsorbers

Applied Science

Fast simulation of non-steady state emission problems in energy conversion

Application of the Fast Fourier Transform (FFT) to the inversion of Laplace transforms is a recent development in the solution of the equations describing the behavior of chemical reactors. Chen and Hsu (1987) used the Fast Fourier Transform for the prediction of breakthrough curves of an isothermal fixed bed adsorber. The Fast Fourier Transform method has been further developed for the calculation of breakthrough curves in non-isothermal adsorbers (Mees et al., 1989). The purpose of this work is the application of this method to a practical engineering problem involving parameter estimation.Applied Science

Ontwerp Gofiner

Document(en) uit de collectie Chemische Procestechnologie.DelftChemTechApplied Science