George Matthew Harriott

Convective Approximation of Adsorption Processes

In many adsorption processes, convection of at least one species is slow by design and this feature may be exploited to gain understanding and simplify calculations. Without convection, species balances integrate exactly to yield algebraic conservation laws and the dynamic evolution to periodicity is hastened by elimination of the slowest waves. Thermal convection, for example, is typically weak in bulk pressure swing adsorption processes and the expedient of dropping thermal convection leads to a conservation law in which equilibrium adiabats (not isotherms) govern adsorbent performance. Numerical computations of a simple process with and without thermal convection confirm that weak convection can considerably prolong dynamic evolution to the periodic state. Without thermal convection however calculations yield a rough representation of the full solution as weak convection has significant (singular) effect near boundaries and within the column over long times. Computations directed to resolve spatial boundary layers and multiple scales in time are proposed to achieve fast and consistent dynamic simulation of adsorption processes to their periodic states.

Fluid Mechanics of Distillation Trays (I): Depth-Averaged Theory and One-Dimensional Flows

Abstract Rigorous design of a distillation column requires a better fundamental understanding of the fluid mechanics of bubble formation and global flows on trays than that currently available. To progress beyond the empirical-or correlation-based state of understanding that currently exists, a theoretical and computational framework is described here that is based on reducing the governing set of three-dimensional conservation equations to a two-dimensional set by averaging them across the depth of the fluid film flowing across the tray. In contrast to related previous works, realistic boundary conditions to the flow problem are provided in this paper by solving simultaneously for the flow on the tray and its inlet and outlet downcomers. In this first of a series of papers, attention is focused on situations in which the flow is invariant in the direction perpendicular to the main flow direction. By means of such a set of one-dimensional, depth-averaged equations, predictions are made in several interest...