| A comprehensive mathematical model has been developed to describe in detail the mechanisms involved in the multicomponent, nonisothermal, nonequilibrium adsorption/regeneration processes for the separation of gas mixtures.Mass, energy, and momentum balance equations for a fixed-bed adsorber were formulated. Four mass transfer mechanisms were considered for the development of mass balance equations: gas-film mass transfer, particle pore diffusion, particle surface diffusion, and adsorption of molecules in the pores onto the particle surface. Thermal effects caused by the release or consumption of energy resulting from adsorption and desorption were considered for the energy balance equations. The Ergun equation was used for the momentum balance equation. Concentrations and temperature of the gas and adsorbed phases, gas superficial velocity, adsorber wall temperature, and bed pressure are the variables calculated in the model. The ideal gas law was used to calculate concentrations.Linear, Langmuir, and Redlich-Peterson relationships were used to represent single component isotherms. Ideal adsorption solution theory and the vacancy solution model were used for the calculation of multicomponent equilibria, incorporating pure component isotherm parameters.The dynamic behavior of fixed-bed adsorbers subject to step changes in concentration and temperature at the inlet were studied. Parametric analyses were made for both temperature swing adsorption and pressure swing adsorption processes. The general model can be implemented in either mainframe or workstation computers.A simplified model, based on the general model, has been developed so that breakthrough calculations can be implemented on a personal computer. The simplified model has the advantage of a reduced set of equations to be solved while still maintaining a comprehensive consideration of factors that affect the performance of an adsorber. |
