Principles and Modern Applications of Mass Transfer Operations

Jaime Benitez

• Éditeur: Wiley
• Année: 2016
• ISBN:
  9781119276944
• Édition: 3
• Sujet: Technology & Engineering
• Sous-sujet: Chemical & Biochemical Engineering

A staple in any chemical engineering curriculum

• New edition has a stronger emphasis on membrane separations, chromatography and other adsorptive processes, ion exchange
• Discusses many developing topics in more depth in mass transfer operations, especially in the biological engineering area
• Covers in more detail phase equilibrium since distillation calculations are completely dependent on this principle
• Integrates computational software and problems using Mathcad
• Features 25-30 problems per chapter

1
Fundamentals of Mass Transfer

1.1 INTRODUCTION

When a system contains two or more components whose concentrations vary from point to point, there is a natural tendency for mass to be transferred, minimizing the concentration differences within the system and moving it toward equilibrium. The transport of one component from a region of higher concentration to that of a lower concentration is called mass transfer.

Many of our daily experiences involve mass-transfer phenomena. The invigorating aroma of a cup of freshly brewed coffee and the sensuous scent of a delicate perfume both reach our nostrils from the source by diffusion through air. A lump of sugar added to the cup of coffee eventually dissolves and then diffuses uniformly throughout the beverage. Laundry hanging under the sun during a breezy day dries fast because the moisture evaporates and diffuses easily into the relatively dry moving air.

Mass transfer plays an important role in many industrial processes. A group of operations for separating the components of mixtures is based on the transfer of material from one homogeneous phase to another. These methods—covered by the term mass-transfer operations—include such techniques as distillation, gas absorption, humidification, liquid extraction, adsorption, membrane separations, and others. The driving force for transfer in these operations is a concentration gradient, much as a temperature gradient provides the driving force for heat transfer.

Distillation separates, by partial vaporization, a liquid mixture of miscible and volatile substances into individual components or, in some cases, into groups of components. The separation of a mixture of methanol and water into its components; of liquid air into oxygen, nitrogen, and argon; and of crude petroleum into gasoline, kerosene, fuel oil, and lubricating stock are examples of distillation.

In gas absorption, a soluble vapor is absorbed by means of a liquid in which the solute gas is more or less soluble, from its mixture with an inert gas. The washing of ammonia from a mixture of ammonia and air by means of liquid water is a typical example. The solute is subsequently recovered from the liquid by distillation, and the absorbing liquid can be either discarded or reused. When a solute is transferred from the solvent liquid to the gas phase, the operation is known as desorption or stripping.

In humidification or dehumidification (depending upon the direction of transfer), the liquid phase is a pure liquid containing but one compon...