This blog post calmly examines the journey of crude oil from deep underground, transformed through the refining process into gas and fuel, becoming the energy that powers modern society.
The morning sun peeks out, signaling the start of the day. You turn on the lights, take a warm shower, then heat up soup on the gas stove for breakfast. Changing into clean clothes and stepping outside, cars are packed tightly along the black roads. It’s the familiar morning scene we encounter daily. Yet, if just one thing were to disappear from this scene, all this routine would instantly sink into darkness. That one thing is oil.
Oil is like the lifeblood of modern society. It fuels power plants, breathing life into cities, while also forming the asphalt that builds the roads connecting them. What was once merely a dark, viscous liquid has transformed into light gases and clear oils, now flowing through every corner of the city. How did that foul liquid, buried deep underground, become the lifeblood supplying energy to modern society? It is the ‘heart’ of the crude oil refining process that makes this possible.
Crude oil, petroleum in its natural state, is a mixed liquid containing various hydrocarbon compounds with different molecular weights. The process of processing this crude oil into the various petroleum products we use is the crude oil refining process. The refining process can be broadly divided into three parts.
The first is the Topping process. This is the starting point and foundation of the entire refining process, separating crude oil into its various components through distillation. The core equipment for this process is the atmospheric distillation tower. This tower performs distillation under atmospheric pressure conditions and contains multiple plates, or trays, installed internally to allow the fluid to pass through. Crude oil entering the tower flows downward along these plates, while high-temperature gas passes upward between them. The gas transfers heat to the liquid components, causing some to condense and liquefy. Conversely, liquid components with lower boiling points that have absorbed heat vaporize and rise upward, while those with higher boiling points flow back down the plates. Through this repeated process, the lowest-boiling LPG gas accumulates at the top of the distillation tower. As one moves downward, lighter oils like gasoline, kerosene, and diesel are sequentially separated. The heaviest, highest-boiling residual oil remains at the bottom of the tower.
The second stage is the Hydro-skimming process. The products separated in the preceding Topping process contain large amounts of impurities like sulfur and nitrogen, resulting in low quality and low price. Therefore, an additional refining process is necessary to remove these impurities and improve fuel quality. This is called the Hydro-skimming process, or the hydrogen treatment process. The core of this process is hydro-treating, or the hydrogen treatment reaction. This involves introducing a catalyst and hydrogen gas into hydrocarbon compounds to remove impurity elements like sulfur and nitrogen that were bonded between carbon molecules. In modern refining processes, cobalt-molybdenum or nickel-molybdenum series catalysts are primarily used. These catalysts play a crucial role in enhancing impurity removal efficiency and improving the environmental suitability of the fuel.
The final stage is the cracking process. The heavy oil obtained from the bottom of the topping process constitutes a significant portion, accounting for approximately 40-60% of the total product. However, this heavy oil has an extremely high molecular weight and an excessively high boiling point, making further distillation difficult under atmospheric pressure conditions. Its impurity concentration is also high, resulting in an economic value lower than that of crude oil. Therefore, a process is needed to reprocess this heavy oil and produce additional light oil. This is called the cracking unit, or the upgrading process. Light oil consists of the same elements as heavy oil but differs in having a simpler molecular structure and a smaller molecular weight. In other words, breaking down the large heavy oil molecules into smaller fragments produces light oil. This is the core principle of the upgrading process, and the representative reaction enabling it is hydrocracking. When a catalyst and hydrogen gas are supplied to a polymeric hydrocarbon compound under high temperature and pressure, hydrogen atoms penetrate between carbon atoms and break the bonds. During this process, the long carbon chains break down, and the heavy crude oil mass separates into lighter components. These lighter components are then separated again in a distillation column, and the residual components left behind are ultimately used as the primary raw material for asphalt.
Beyond this, various auxiliary processes exist within the refining operation. These include the HMU process, which produces the hydrogen gas required for reactions; the BTX process, which manufactures aromatic compounds serving as base materials for petrochemical products; and the ALK process, which produces raw materials for oil additives and lubricants. These diverse processes are organically integrated to form a single, massive refinery. The entity responsible for designing, operating, and managing this entire complex and vast system is the chemical engineer. Chemical engineers not only design the plant’s structure and oversee daily operations but also conduct research to improve efficiency and perform continuous inspection and maintenance. Refineries can operate without interruption precisely because chemical engineers exist, enabling modern society to breathe continuously. For this reason, the refining process cannot stop even for a single moment. Thus, chemical engineers keep the lights of the refining process burning brightly at this very moment, silently illuminating the present and future of human society.
