UNIFYING ASPECTS OF CHEMICAL SEPARATION
Abstract
This work covers analogies between various methods of separation and discussed ideal separation means and ways of approaching these. It is divided into four parts. Part I proves the existence of characteristic directions or paths in equilibrium space, under certain assumptions. Deductions are then made about the legitimacy of proposed equilibrium relationships. Part 2 concerns predicting behavior under various operating systems: countercurrent, fixed-bed, and staged alternating flow. An extension of the Kremser equation is presented for coupled equilibrium. The eigenvalues of the Jacobian of equilibrium play a key role in determining the location of the pinch point. Next, the Underwood equations are extended to cover countercurrent multicomponent Langmuir adsorption, and solutions are found for when some (phi)'s are complex or when one (phi) is degenerate. This extends Martin's results to many components. The role of the "h transformation" is discussed for countercurrent mode. Part 3 explores the potentials of ideal separation schemes. These produce no entropy and are reversible. With ideal multicomponent extraction, products are formed whose solute concentrations equal those of the feed, but uncoupled equilibrium is required. If the equilibrium is not linear, two-dimensional cross-flow regimes are required. Ideal distillation is then developed, for minimizing work input. A novel method of calculating flows in the distillation and extraction schemes is based on topological treatment of the schemes as two-dimensional flow fields. Part 4 discusses applications. An inverse relationship between initial cost and entropy generation is developed for non-adiabatic binary distillation. Then adiabatic distillation schemes which imitate ideal schemes are considered. Unconventional schemes are found to be better in some cases. Two-dimensional distillation is proposed as an energy saving method, especially suited for complex mistures. Finally, simulation results are presented for a new method of solute concentration called thermal extraction. A nine-fold concentration was obtained with a tiny fraction of evaporation energy costs.
Degree
Ph.D.
Subject Area
Chemical engineering
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