Extractive and Azeotropic Distillation

Instead of modifying the heat exchange in columns, a reduction in energy is possible by altering the physical properties of the mixtures. For mixtures that are difficult to distil, a solvent may be added to increase the relative volatility of the mixture. If a suitable solvent can be found with a relatively low volatility, then the separation process is known as extractive distillation. A typical extraction distillation column arrangement is illustrated in Figure 8. This process is economical to use when a small amount of inert solvent can permit an easier (less expensive) separation of the original products. An additional tower is required to remove the solvent from the heavier product.

Solvent

Figure 8 Extractive distillation configuration.

Solvent

Figure 8 Extractive distillation configuration.

If the addition of a light component can alter an azeotrope, then the process is termed azeotropic distillation. The entrainer often forms a new low boiling azeotrope that is relatively easy to separate from the heavier product. The entrainer is separated from the lighter product with an additional column and/or condensed to two liquid phases that are separated in a settling drum. Azeotropes are common in the specialty chemicals industry and most configurations are proprietary.

Extractive or azeotropic distillation should be considered a last resort option. Finding a suitable solvent or entrainer that is inexpensive and relatively inert is the key to a practical design.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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