Pressure- and vacuum-swing adsorption processes are challenging to model and difficult to solve
rapidly because the system response is a nonlinear function of both the axial and temporal
domains with periodic boundary conditions. Extensive computing power is required to solve the
conservation equations that describe the temperature, composition, and pressure profiles during
operation of an adsorption process. Furthermore, the physics of the source/sink terms in the
conservation equations of mass and energy, which relates to the ad/desorption of absorbable
species, is not always easily described. These rigorous numerical models are useful for furthering
our understanding of these complex processes and are the only methods available for the design
of industrial units. However, such complicated numerical simulators for model-based control
schemes are not feasible at the current level of computing resources. Simplification of the
conservation equations is required to derive a practical mechanistic model for predictive control
purposes. In a previous study, Beh and Webley (Adsorpt. Sci. Technol. 2003, in press) have
demonstrated that much of the complexity of these processes can be captured through the use
of a simple model consisting of a series of coupled tanks which approximates the bulk flows and
pressures to a satisfactory degree. In this paper, an extension is made to this model to incorporate
the time-varying composition variable. The limitations of this method will be discussed in relation
to field operation.