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Uses of Steam Distillation in the O&G Industry
May 14, 2019 Welcome
Steam distillation (also known as steam stripping) is an old technique for fluid separation, originally invented during the 9th century. Today, the process has been optimized for use in lab-scale and industrial applications for recovering useful compounds from chemical solutions, purifying process streams, and in the treatment of industrial wastewater.
This article will explain the process of steam distillation with a special focus on its applications in the oil and gas industry.
What Is Steam Distillation?
Steam distillation is the process of separating organic compounds or volatile organic compounds (VOCs) from water or water-based process fluids. It is a continuous distillation process particularly useful for removing temperature-sensitive solutes such as natural aromatic compounds.
Advantages of Steam Distillation
A key advantage of steam distillation over other solvent recovery systems is that it prevents the decomposition of volatile compounds by distilling them at temperatures below their boiling points.
Under ideal conditions, steam stripper systems can achieve up to 99.9% removal efficiency in removing organic/volatile compounds. At this rate, industrial operators can ensure compliance with important environmental regulatory provisions such as the EPA’s Maximum Achievable Control Technology (MACT) standards.
How Does Steam Distillation Work?
The working principle of steam stripping is that separation of organic/volatile compounds which are immiscible with water occurs in phases under heated conditions, as each liquid exerts its own vapor pressure as though the other is not present.
This means when two solvents with different vapor pressures exist as a mixture, the vapor pressure of the overall mixture is the sum of the partial pressures contributed by both substances. With the introduction of steam, the partial pressures of the compounds are lowered, allowing them to distill out of the mixture at temperatures lower than their normal boiling points.
Steam distillation is an effective separation method for several organic compounds which have vapor pressures higher than water. It can be carried out on a lab or industrial scale, depending on the particulars of the application.
Industrial Applications of Steam Distillation
Steam distillation is a fairly popular technique employed in a wide range of industrial settings. Some important applications include:
Natural Oils Extraction
Distillation with steam is used extensively to extract natural products from parts of plants, e.g., in the production of Lemongrass oil and Eucalyptus oil. In this case, a lab-scale distillation apparatus may be used.
Water Purification
Steam stripping can help to reduce the biological oxygen demand (BOD) level and other indicators of water contamination in produced water prior to disposal into a receiving environment or recirculation.
Organic compounds such as Benzene, Toluene, and Xylene found in effluent have carcinogenic effects in humans. Steam distillation can be used to remove these Benzene-type compounds from process or wastewater prior to safe disposal to prevent the contamination of public water supplies.
At high concentrations, ammonia commonly found in water close to or emanating from industrial sites causes chronic toxicity in humans and aquatic life. For this reason, the EPA recommends reducing the ammonia concentration in surface water. Steam distillation helps to break down dissolved ammonia into water vapor and nitrogen.
Uses of Steam Distillation in Oil & Gas
In petrochemical refining, an important purpose of steam distillation to separate the individual components of products obtained from the chemical synthesis of crude oil. Other important compounds that can be separated by steam stripping includes hydroxyl group (–OH) alcohols, aliphatic components, acetate esters, ketones, and chlorinated hydrocarbons.
What is the Steam Distillation Process?
A standard steam stripper for industrial-scale separation consists of a supply pump with a heat exchanger, a stripping tower with distinct columns or “stages” for collecting the distillates, a condenser, and a decanter. The steam used in the distillation process is saturated (reboiled) steam. A temperature range of 90–120 °C (194–248 °F) and pressure range of 1–2 bar is maintained for efficient operation.
How Steam Distillation Works
Steam stripping typically involves the following steps:
- The feed mixture (effluent) is introduced into the distillation unit.
- Heated steam is passed through a tank containing aromatic compounds, vaporizing the various solutes at temperatures lower than their normal boiling points.
- The vaporized substance passes into a condenser which lowers the temperature, converting it back into liquid form.
- The condensed liquid flows into a decanter which removes any insoluble organic particles.
- The recovered components can be recirculated into the system until the desired degree of purity is attained.
Limitations of Steam Stripping
Steam stripping is overall a complex process to manage and is not easily automated. Industrial-scale steam strippers utilize electricity which may also increase the cost of operation.
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