411-306 Separation Processes 1

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Objectives:

Upon completion of this unit the students will:

• be familiar with the concepts of equilibrium stage and continuous contactor analysis applied to simple distillation, gas absorption and liquid extraction;

• be able to assess quantitatively the performance of simple, conventional distillation, gas absorption and liquid extraction equipment.

Content:

Introduction: Definition of separation processes, separating agents, separation factors, equilibrium and rate type processes, equilibrium stage, non-equilibrium performance.

Mass Transfer Rates: Mass transfer in a single phase and between phases, mass transfer coefficients for equimolar diffusion and bulk flow. Examples in separation processes.

Equilibrium stage processes:

Distillation: Concept of enthalpy as separating agent, relative volatility, enthalpy-concentration diagrams. Single-stage separations, equilibrium flash, differential distillation. Multistage separations, operating lines, reflux. Binary distillation, varying reflux ratio, minimum reflux, total reflux, optimum reflux, feed plate location, side stream, open steam. Tray efficiency via overall and Murphree efficiencies.

Liquid Extraction: Applications of liquid extraction, liquid-liquid equilibria, equilateral and right-triangular coordinates, solvent-free coordinates. Choice of solvent. Single-stage extraction, choice of solvent/feed ratio. Multistage cross-current extraction. Continuous counter-current multistage extraction, varying solvent/feed ratio, use of reflux, operation-line/equilibrium methods of analysis and simplifications.

Continuous Contact Operations:

Gas Absorption: Basic mass transfer mechanism (c. f. distillation), solubilities of gases, choice of solvent. Material balances, co-current and counter-current flow, limiting L/G ratio. Multistage absorption and the absorption factor method (also applicable to distillation). Continuous contact, transfer units, height of a transfer unit, calculation of number of transfer units (also applicable to distillation). Non-isothermal gas absorption.

Assessment: