In this blog post, we’ll examine the process by which crude oil extracted from the ground is separated into various components in a distillation tower based on differences in boiling points, thereby creating the raw materials for the diverse products we use in our daily lives.
How does crude oil become the raw material for various products?
Plastics, synthetic fibers, and gasoline—these are common items in our daily lives. PET bottles, a type of plastic, line the shelves of stores, filled with the water and beverages we buy. Synthetic fibers such as polyester and nylon are used in clothing, and gasoline fills the fuel tanks of cars driving on the roads. All of these are either substances obtained during the refining of crude oil or are made using those substances as raw materials.
We often hear the word “petroleum” in our daily lives; however, the oil that has just been drilled from the ground—that is, unrefined oil—is called crude oil. Crude oil is a mixture of various hydrocarbon compounds—composed of carbon and hydrogen—that come in a variety of lengths and structures. In other words, crude oil contains a blend of the substances needed to make the many chemical products and fuels we use. Therefore, it is necessary to separate the various components that make up crude oil. But how is this done?
How is crude oil separated in a distillation column?
Crude oil refining facilities contain massive tower-shaped structures, one of which is called a distillation column. A distillation column is a massive separation device consisting of multiple stages, where the various components of crude oil are separated based on their different boiling points. This process utilizes differences in boiling points to separate the mixture, a method known as fractional distillation. The principle is similar to the process of distilling alcohol to separate its ethanol content.
The first step involves heating the mixture to be separated. Just as a mixture is placed in a distillation apparatus and heated when distilling alcohol, crude oil is first heated and then fed into the distillation column. At this point, the crude oil is heated to a high temperature in the furnace, and part of it enters the distillation column in a vaporized state. In other words, the crude oil does not boil entirely and turn into a gas all at once after entering the distillation column; rather, it is heated before entering the column and flows in as a mixture of liquid and vapor.
Next is the process in which the components are separated as the vapor and liquid come into contact with each other. The gaseous components of the crude oil entering the distillation column rise upward through the column, while the liquid components flow downward. The distillation column is designed so that the lower section is relatively hotter, and the temperature decreases as one moves upward. Therefore, as the vapor rises, its temperature drops, and some of it condenses into liquid according to the boiling points of each component and the vapor-liquid equilibrium conditions. The components that have turned into liquid flow downward and come into contact with the rising vapor, further separating the components. As this process repeats across the distillation column’s multiple stages, components with lower boiling points are separated relatively higher up, while those with higher boiling points are separated relatively lower down.
Finally, the liquid components that have been separated are collected. Inside the distillation column, devices for extracting different components are installed at various heights. As mentioned earlier, this structure is designed to account for the fact that the degree of separation varies depending on the height within the column, since each component has a different boiling point and boiling range. The components of crude oil separated in this way are used as fuel or, after undergoing further refining and chemical processes, serve as raw materials for producing various petrochemical products.
How does a distillation column increase the value of crude oil?
Crude oil is a highly valuable resource, as nations around the world are striving to secure it. However, rather than being used in its raw form, crude oil must undergo a refining process to be transformed into substances suitable for various applications. In a distillation column, crude oil is heated to vaporize a portion of it, and this vapor is then condensed; this cycle is repeated to separate components with different boiling points. Some of the separated components are used directly as fuel or raw materials, while others undergo additional processing to be turned into fuels such as gasoline, jet fuel, and diesel, or into raw materials for various petrochemical products. Therefore, distillation columns play a crucial role in separating crude oil—a simple mixture—into its various useful components.
Furthermore, distillation columns are widely used not only in the crude oil refining process but also in other chemical processes to separate liquid mixtures based on differences in boiling point or volatility. In particular, crude oil refining utilizes not only atmospheric distillation, which takes place at atmospheric pressure, but also vacuum distillation to separate heavy components with high boiling points at lower temperatures. As such, distillation remains an important separation method in the chemical industry today, and thanks to distillation columns, necessary components can be efficiently separated and utilized from various mixtures, including crude oil.
