In this blog post, we will look at the concept and principles of supercritical fluids and introduce their applications and advantages in various industries such as food, medicine, and the environment.
Solid, liquid, and gas are familiar concepts that classify the state of matter according to the arrangement of molecules. However, today’s engineers have discovered a fourth state of matter called supercritical state, which is being used in various fields such as food processing. To understand what supercritical fluids are, imagine ice water. At first, the ice floats on the water due to its low density, and the boundary between the ice and water is clearly visible.
However, as time passes and the ice gradually melts, the boundary between the ice and water disappears, and the two phases mix to create a new state called sherbet. The same is true for systems in which liquids and gases coexist. Initially, the lighter gas exists in the upper layer, and the boundary between the two phases can be clearly distinguished. However, as the pressure and temperature are gradually increased, the density difference between the liquid and gas decreases, the boundary disappears, and the liquid and gas mix. The temperature and pressure at the point where the boundary disappears are called the critical point, and the fluid at the point where the liquid and gas cannot be distinguished after the critical point is called a supercritical fluid.
The supercritical fluid created in this way was difficult to commercialize due to the high energy consumption required for the high temperatures and pressures needed to create the supercritical state in the early stages of research. However, with the discovery that carbon dioxide exists in a supercritical state at a temperature close to room temperature (31°C), supercritical fluids began to be used in extraction and separation processes and are now widely used in food engineering. Representative processes include the extraction of caffeine from coffee to reduce its caffeine content, the extraction of active ingredients from hops to produce beer, the extraction of saponin from red ginseng, and the extraction of sesame oil. However, other applications are expanding, such as non-heat sterilization of food and dry cleaning.
Furthermore, supercritical fluids are becoming increasingly useful in various industries, such as pharmaceuticals, cosmetics, and environmental engineering. For example, supercritical fluids are used in the pharmaceutical industry to extract and purify the active ingredients of drugs, and in the cosmetics industry to extract and purify natural ingredients. In environmental engineering, this technology is being applied to waste treatment and soil contamination remediation. These various applications highlight the importance and potential of supercritical fluids.
So, what are the advantages of supercritical fluids in these extraction and separation processes? The first thing to note is the excellent physical properties of supercritical fluids. Like sherbet, supercritical fluids have both liquid and gaseous properties. The solubility unique to liquids enables the separation of products in separation and extraction processes, and the high permeability of gases increases the efficiency of the separation process. In other words, when using supercritical fluids, the permeability is higher than that of conventional organic solvents, allowing them to reach the interior of the separator and completely dissolve the components to be extracted.
In addition, supercritical fluids offer cost savings in two ways. When using conventional liquid organic solvents, after the extraction process in which the substance to be extracted dissolves into the solvent, a final separation process is required to separate the solvent from the extracted components in order to produce the final product. However, in the case of supercritical fluids, changing the pressure and temperature to cause a phase change to a gaseous state causes the solubility to disappear, automatically separating the gas and the extracted components, thereby reducing the installation and operating costs of the separation process for producing the final product. In addition, supercritical fluids are easier to reuse than conventional organic solvents, enabling a reduction in raw material costs in operating costs.
Finally, supercritical fluids are widely used in extraction and separation processes because they are safe for humans and the environment. When organic solvents are used, there is a possibility that the unique flavors and nutrients of food may be destroyed during the separation process, or that toxic intermediate products may be generated through reactions. Even if only trace amounts of organic solvents are included, they can be toxic to humans, raising safety concerns. However, carbon dioxide used as a supercritical fluid has no effect on the human body, as it is used in carbonated beverages, so even if the final food product contains carbon dioxide, there are no safety concerns. In addition, it preserves the unique flavors and nutritional components of food and does not produce highly toxic intermediate products during the reaction process, reducing the risk of accidents and making it environmentally friendly.
Ultimately, due to its excellent physical properties, energy savings, stability, and environmental friendliness, supercritical fluid is used as a supercritical solvent in various industries, and its importance is growing. This suggests that there is unlimited potential for the use of supercritical fluids in various fields in the future, and through continuous research and development, it will become an even more efficient and safer process.
