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Understanding Membrane Distillation and Osmotic Distillation von Johnson, Robert A. (eBook)

  • Erscheinungsdatum: 16.03.2017
  • Verlag: Wiley
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Understanding Membrane Distillation and Osmotic Distillation

This book addresses principles and practical applications of membrane distillation and osmotic distillation, separation technologies which are gaining increasing attention due to their advantages over conventional concentration processes. - Addresses membrane and osmotic distillation, two closely related and novel processes that offer several advantages over conventional concentration processes - Has a widespread impact and application of the technology in industries such as food, environment, and nuclear clean-up / containment - Covers theoretical aspects of both processes, the properties of hydrophobic membranes, process economics, integrated processes and future prospects. - Caters the presentation caters for the diversity of readership with respect to links with membrane technologies. ROBERT A. JOHNSON, BSC, MSC, PHD (UQ) is a lecturer in Physical Chemistry and Chemical Technology at Queensland University of Technology. Prior to entering academia he was a Research Director at Syrinx Research Institute where he oversaw the development of Osmotic Distillation from a laboratory novelty to the pilot plant stage. MINH H. NGUYEN, BE, GRAD DIP, MSC (UNSW), PHD (UTS) is a Conjoint Associate Professor at the University of Newcastle and an Adjunct Associate Professor at Western Sydney University. He has a lifetime of experience in scientific research and development in industry, research laboratories and university. He was among the pioneers in research and development in membrane technology, in particular membrane distillation and osmotic distillation.


    Format: ePUB
    Kopierschutz: AdobeDRM
    Seitenzahl: 288
    Erscheinungsdatum: 16.03.2017
    Sprache: Englisch
    ISBN: 9781118880395
    Verlag: Wiley
    Größe: 4742 kBytes
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Understanding Membrane Distillation and Osmotic Distillation

Chapter 1
General Introduction

1.1 Overview of Distillation Processes

The term "distillation" refers to any process that facilitates the separation of solution components using their different volatilities. Distillation processes are categorized according to the number and nature of the components being separated as shown in Figure 1.1 . At a primary level, distillation processes can be categorized as simple distillation or fractional distillation. Simple distillation utilizes a still to effect the separation of two miscible liquids or a single liquid and its nonvolatile solutes in a single vaporization-condensation process. Fractional distillation refers to the separation of two or more liquids using repeated vaporization-condensation steps in a single column.

Figure 1.1 Overview of distillation processes.

Simple distillation of a mixture of two liquids facilitates enrichment of the distillate (vaporized fraction) with the most volatile component with a corresponding enrichment of the residue with the second component. The distillate is the desired component in typical industrial applications. The degree of enrichment depends on the relative volatilities of the liquids. In some applications, the distillate is subjected to a second simple distillation step in a separate still to obtain the required separation. In simple distillation involving a liquid and its nonvolatile solutes, a high degree of separation can be achieved by prolonged boiling of the liquid. Here, the distillate is free of solutes other than trace amounts transferred by the entrainment of liquid droplets in the vapor. In many cases, distillation is carried out progressively through a series of simple distillation steps in a continuous process. Removal of the liquid from its nonvolatile solutes defines this process as a stripping operation. Furthermore, the still or series of stills in which stripping occurs is referred to as an evaporator. Fractional distillation results in a high degree of liquid-liquid separation due to repetitive distillation steps. This process is referred to as rectification when used for the separation of just two liquids. Examples highlighting the importance and widespread use of simple distillation and fractional distillation processes in society are discussed below.

The production of whisky and brandy are examples of simple distillation involving two liquids, water with a boiling point of 100 °C and ethanol with a boiling point of 78 °C. Whisky is distilled from grain mash that has been fermented to an ethanol concentration of 5-7% v/v, while brandy is distilled from wine having an ethanol concentration of 8-12% v/v. These low-alcohol solutions are boiled in a pot still to produce a distillate with an ethanol concentration of 20-35% v/v. The distillate is then subjected to simple distillation in a second pot still to produce a spirit with an ethanol concentration of about 70% v/v. The volatile organic aroma components of the base material are transferred and condensed with the vapor in both steps of the process. Finally, the spirit is subjected to maturation in accordance with product identification requirements.

Simple distillation involving a single liquid and its nonvolatile solutes is a widely used form of industrial distillation. An important example in which the distillate is the desired product is the desalination of seawater or brackish water. Water is evaporated from the salty solution for subsequent condensation and consumption. This stripping process is generally carried out using multistage flash distillation (MSF), multiple-effect distillation (MED), or vapor compression distillation (VCD). These simple distillation processes owe their success to internal energy recovery mechanisms as discussed in Section 1.5 . With an estimated one billion people currently without access to safe drinking wat

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