Distillation is the processing of a liquid mixture to separate the components by alternating evaporation and condensation. Distillation may result in fundamentally complete separation, producing almost pure components, or it may be a partial separation that increases concentrations of certain components of the mixture. The distillation process leverages differences in the volatility of the mixture's components.

Applications

Widely used in commercial applications, distillation takes many forms.

• In oil and gas production, distillation is a major method for obtaining materials from crude oil for fuels and for chemical components and feed stocks.
• Gas and air separation can be undertaken industrially by distillation to separate air in to its components—nitrogen, oxygen, carbon dioxide, etc.
• Industrial chemistry operations, working with large ranges of crude liquid products of chemical synthesis, use distillation techniques to separate components from other products, from impurities, or from unreacted materials.
• Distillation of fermented products produces alcoholic beverages with high alcohol content. It also separates out other fermentation products that may have commercial value.

Specifications

Distillation can be done at laboratory scale through large industrial processing. The prime difference between laboratory and industrial is laboratory scale distillation is often performed in batches. During batch distillation, the composition of the materials in process change during the distillation. In batch distillation, a still is supplied with a batch of feed mixture. The distillation process separates it into component fractions that are collected consecutively from most volatile to least volatile, with the “bottoms” removed at the end. The still can then be re-filled and the process repeated. Industrial distillation quite often happens continuously. In continuous distillation, the source materials and the products are kept at a constant composition. This is accomplished by carefully replenishing the source material and removing both vapor and liquid from the system. Continuous distillation results in a better control of the separation process.

Solvent recovery systems are used extensively in recycling applications and to reduce manufacturing waste. A solvent recovery system, or solvent recover system, usually includes the use of a heating component and a condensation component to distill the liquid and separate the solvent from water. Solvent recovery equipment may also include a vacuum unit that enables the system to operate at temperatures that are typically lower than the solvent’s boiling point. Solvent recycling is accomplished by a distillation process that includes the following steps:

1. A distillation vessel processes waste solvent solution on either a batch or continuous basis.
2. A heated jacket injects heat into the waste solvent by conductive thermal transfer.
3. The vessel may be operated under vacuum, which lowers the boiling temperature of the solvent.
4. When the waste solvent reaches its boiling point, the solvent changes phase from liquid to a vapor.
5. The clean solvent vapor passes over a condenser containing both a condensing and a sub-cooling section. In the condenser, the solvent changes back to a liquid and is cooled back to ambient temperature.
6. The contaminants do not undergo a vapor phase, but stay behind to be discharged out of the drain port.

Features

Distillation equipment and solvent recovery systems are used for steam and wastewater stripping, chemical product purification, and solvent recovery. Distillation equipment and solvent recovery systems often consist of metal cylinders armed internally with perforated horizontal plates that are used to promote the separation of liquids that ascend as vapor. Distillation equipment and solvent recovery systems are used to perform steam stripping or distillation of wastewater for removal of hydrocarbons such as alcohols, ketones, and acetates. Distillation equipment and solvent recovery systems may contain several other functional components, including an adsorption column or bed, where molecules of solvent in liquid or gas form adhere to the surface of a solid material. An aeration column is used when treating wastewater and involves pumping the water through a series of columns to add oxygen to the wastewater. Aeration increases the surface area of the contaminated water allowing a waste solvent recovery system to remove any volatile compounds more easily. Telescoping columns are also available from some suppliers of distillation equipment and solvent recovery systems. Distillation equipment and solvent recovery systems are used to recycle and recover contaminants from the manufacturing of polymers, resins, and paints. A distillation system can mix waste products so they are discharged as a sludge, paste, or powder depending on the specific industry’s best disposal practices.

Manufacturing companies are realizing the benefits of solvent recovery systems not only from an environmental viewpoint but also from an economic perspective. Solvent distillation systems diminish the need for raw materials by using the recovered solvent in the production process as makeup or cleaning solvent. These systems provide an uncomplicated way for companies to recover spent liquid solvent in turn reducing wastes and disposal costs. Distillation equipment serves well as a key component in waste recovery systems, but also is a cornerstone in the chemical and food processing industries for production of everything from fuels and chemical feed stocks through fermented distilled beverages for public consumption.

Finally, desalination through distillation is one of mankind's earliest forms of water treatment, and it is still a popular treatment method used throughout the world today. In ancient times, people used this process on ships to convert sea water into drinking water. Today, desalination plants are creating drinking water from sea water on ships and in many desert regions worldwide. They treat polluted water that is fouled by natural and unnatural contaminants. Distillation is the water treatment technology that most completely eliminates a range of drinking water impurities.

Related Information

CR4 Community—Energy Consumption in a Crude Oil Refinery Distillation Process

CR4 Community—Low Pressure Water Distillation. Why Is it Not Used More?

CR4 Community—Thermal Processing Vs. Solvent-Based Processing

CR4 Community—Glass Distillation Column

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terry joyce / CC BY-SA 2.0

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