In this blog post, we explore why separation technology in chemical engineering is regarded as the core technology that dictates product quality and production costs.
This year’s rice harvest seems to be poor due to frequent rain. Nevertheless, when harvest time arrives, rural areas are filled with vitality. But imagine if, after a joyful harvest, every threshing machine nationwide broke down, making it impossible to separate the rice grains. Farmers would immediately worry about their livelihoods due to unsellable rice. What we value is the edible grain separated from the husk, not the grain still encased within it.
A similar situation occurs in the realm of chemical industry. If producing products from raw materials through chemical reactions defines the chemical industry, then initiating these reactions can be likened to farming, while separating only the desired substance from the resulting product resembles the threshing process. Just as threshing is essential for using rice as food, the process of separating the desired substance is equally vital. The material stream exiting a chemical reactor contains not only the desired product but also various other substances. Raw materials themselves contain impurities, and if unwanted reactions occur, their byproducts must also be removed. Additionally, raw materials that remain unreacted become impurities.
These impurities cause various adverse effects: they trigger unwanted reactions, degrade the product’s mechanical properties, or negatively impact human health and the environment. Therefore, it can be said that the resultant product generated through chemical reactions must undergo separation and purification to become a valuable product.
The most commonly used apparatus in separation processes is the distillation column. You may have wondered about the identity of the tall, towering structure that is the most noticeable feature in the appearance of a chemical plant. This structure, resembling a chimney but emitting no smoke, is the distillation column. Just as water boils at 100°C, every substance has its own boiling point. Distillation is the method of separating substances by utilizing the fact that boiling points differ for each substance.
Examples of distillation can easily be found in everyday life. For instance, distilled spirits like whiskey or soju are produced by concentrating alcohol through distillation. Alcohol boils at around 78°C. By maintaining a temperature between 78°C and 100°C, the alcohol component vaporizes more readily. Meanwhile, the water component remains liquid. Collecting the evaporated vapor yields a liquid with a high alcohol concentration. In chemical production, this distillation principle is applied on a much larger and more complex scale. Distillation columns used in chemical plants typically require purities exceeding 90%, making their size and complexity vastly different from those used for distilling alcohol. However, the fundamental principle remains the same.
As the size of distillation columns suggests, the cost of separation processes can be substantial, sometimes exceeding the cost of the chemical reaction itself. Particularly for products where purity is critical, it is not uncommon for separation process costs to account for over 50% of the final product price, including raw material, transportation, and storage expenses. For this reason, separation processes occupy a central position in chemical engineering; in extreme cases, separation is performed without any chemical reactions. The petroleum refining process is a prime example, where the primary goal is to separate the various components already present in crude oil. While chemical reactions are partially utilized in this process, it fundamentally centers on separation.
Furthermore, beyond distillation, various separation technologies are currently being researched. For instance, membrane separation technology selectively separates substances in gaseous or liquid states by passing them through extremely thin membranes. Compared to distillation, this technology consumes less energy and has a smaller environmental impact, making it a promising next-generation separation technology.
Meanwhile, adsorption technology separates substances by selectively adsorbing them onto a solid surface, primarily used to remove specific pollutants from air or water.
Separation processes are not only an essential part of chemical processes but also play a crucial role in other industries. For instance, in food processing, separation processes are applied to remove impurities from beverages or edible oils, or to concentrate specific components from raw materials. In the pharmaceutical industry, separation processes are essential for increasing the purity of compounds during new drug development. Thus, the necessity of separation processes is immense across diverse industries, ensuring the quality and safety of the products they produce.
In chemical engineering, separation processes are not merely one step in a sequence; they are critical factors determining the final product’s quality and cost. Without separation processes, substances generated through chemical reactions cannot be properly utilized. Incorrect separation can degrade product performance or negatively impact the environment. Separation processes will continue to be researched and developed as a core field of chemical engineering. The technology of separation processes is essential for making the diverse products humanity uses more efficient and safer. Through this, we can obtain better products and maintain a sustainable environment.
