Industrial Separation Processes

Fundamentals

André B. de Haan,H. Burak Eral,Boelo Schuur

• Publisher: De Gruyter
• Year: 2020
• ISBN:
  9783110654912
• Edition: 2
• Topic: Biowissenschaften
• Subtopic: Biotechnologie

Separation processes on an industrial scale account for well over half of the capital and operating costs in the chemical industry. Knowledge of these processes is key for every student of chemical or process engineering. This book is ideally suited to university teaching, thanks to its wealth of exercises and solutions. The second edition boasts an even greater number of applied examples and case studies as well as references for further reading.

Chapter 1 Characteristics of Separation Processes

1.1 Significance of separations

When ethanol is placed in water, it dissolves and tends to form a solution of uniform composition. There is no simple way to separate the ethanol and the water again. This tendency of substances to form a mixture is a spontaneous, natural process that is accompanied by an increase in entropy or randomness. In order to separate the obtained mixture into its original species, a device, system or process must be used that supplies the equivalent of thermodynamic work to induce the desired separation. The fact that naturally occurring processes are inherently mixing processes makes the reverse procedure of “unmixing” or separation processes one of the most challenging categories of engineering problems. We can now define separation processes as

Those Operations that Transform a Mixture of Substances into Two or More Products that Differ from Each Other in Composition

The separation of mixtures, including enrichment, concentration, purification, refining and isolation are of extreme importance to chemists and chemical engineers. Separation technology has been practiced for millennia in the food, material processing, chemical and petrochemical industry. In the food, material processing and petrochemical industry, most processes do not involve a reaction step but are merely used for the recovery and purification of products from natural resources. Examples are oil refining (Figure 1.1), metal recovery from ores and the isolation and purification of sugar from sugar beets or sugar cane schematically shown in Figure 1.2. In this process a combination of separation techniques (washing, extraction, pressing, drying, clarification, evaporation, crystallization and filtration) are used to isolate the desired product, sugar, in its right form and purity.

Figure 1.1: Very simple schematic of a refinery for converting crude oil into products.

Figure 1.2: Processing sequence for producing sugar from sugar beets.

Within the chemical industry, separation technology is mostly used in conjunction with chemical reactors. One of the main characteristics of all these chemical processes is that many more separation steps are used compared to the amount of chemical reaction steps. An illustrative example is the oxidation of ethylene to ethylene oxide shown in Figure 1.3. After the reaction, several absorption, desorption and distillation steps are required to obtain the ethylene oxide as a pure product.

Figure 1.3: Ethylene oxide production by oxygen oxidation.

The above examples serve to illustrate the importance of separation operations in the majority of industrial chemical processes. Looking at the flow sheets in Figures 1.2 and 1.3 it should not be surprising that separation processes account for 40–90% of capital and operating costs in industry and their proper application can significantly reduce costs and increase profits. As illustrated by Figure 1.4, separation operations are employed to serve a variety of functions:

Figure 1.4: Schematic of the functions of separations in manufacturing.

• Removal of impurities from raw materials and feed mixtures
• Recycling of solvents and unconverted reactants
• Isolation of ...