In this blog post, we’ll examine what the key to success is for a chemical plant by looking at chemical processes and the role of reactors.
What are South Korea’s leading export items today? While many people think of semiconductors and cutting-edge IT products, petroleum products are also among the country’s leading exports. Although South Korea is a non-oil-producing nation that does not produce crude oil itself, it imports most of its crude, refines it, and processes it into high-value-added petrochemical products. Leveraging its outstanding technological capabilities, the country exports a variety of petroleum products—such as gasoline and diesel—to countries around the world.
As such, the process of refining crude oil takes place in chemical plants. Chemical plants are large-scale industrial facilities composed of various unit operations and processes, and they serve as the core infrastructure for producing the countless products needed in modern society. Therefore, designing processes more efficiently and developing new ones is of great importance. It can be said that South Korea’s ability to secure competitiveness in the petrochemical industry is due to such process development and continuous technological innovation. So, let’s take a closer look at what a process is.
Simply put, every process involves feeding in raw materials, undergoing a separation process, triggering a reaction, and then undergoing another separation process to obtain products and byproducts. This can be easily understood through the water purification process used to produce the tap water we use in our daily lives. In the water purification process, water sourced from a water source is first used as the raw material and undergoes a primary separation process to remove debris such as wood chips and trash. Next, chemicals are added to trigger reactions that eliminate odors and remove impurities. The precipitates formed during this process are removed through filtration, ultimately producing clean water.
In such processes, while the reactor—which converts reactants into products—accounts for a portion of the process equipment costs, separation devices often incur higher costs than the reactor. However, since the scale and cost of the subsequent separation equipment can vary significantly depending on the reactor’s performance, the reactor can be considered a key piece of equipment that determines the overall economic viability of the process. Therefore, designing the reactor rationally is one of the most important factors in process development.
Let’s look at a simple example to see how a reactor is designed. Various types of reactors are used in the crude oil refining process. The most common types are continuous stirred reactors and tubular reactors. A continuous stirred reactor is a stirred tank-type reactor in which reactants and products flow continuously; since the interior is thoroughly mixed, the composition remains constant throughout the reactor. In contrast, in a tubular reactor, the reaction proceeds as the reactants move along a long tube, so the composition continuously changes depending on the location within the reactor.
Both continuous stirred reactors and tubular reactors have their respective advantages and disadvantages. Because continuous stirred reactors are tank-shaped, they are relatively easy to clean, and since the interior is thoroughly mixed, composition and temperature are maintained consistently, making temperature control easy. In contrast, tubular reactors are structurally difficult to clean, and temperature can vary along the length of the reactor, making temperature control relatively challenging. However, continuous stirred reactors have the disadvantage of a lower conversion rate compared to tubular reactors.
The conversion rate is a value that indicates the extent to which a chemical reaction has proceeded; it is calculated by dividing the amount of product formed by the amount of reactant initially added. In other words, when the reaction is complete, the conversion rate is 1, and when no reaction occurs at all, it is 0. The reason the conversion rate decreases in a continuous stirred reactor is that complete mixing causes the reactants and products to blend together, thereby lowering the concentration of the reactants. Generally, chemical reactions occur more vigorously as the concentration of reactants increases; therefore, as the reactant concentration decreases, the conversion rate also decreases.
As with everything in life, to design a reactor most rationally, it must be engineered to achieve maximum effectiveness at minimum cost. This means keeping the reactor volume as small as possible while maximizing the conversion rate. So, what determines the conversion rate? As we saw earlier, the conversion rate varies depending on the type of reactor. In addition, the conversion rate can vary significantly depending on the size of the reactors and how identical reactors are arranged. This is similar to the positioning of players in soccer. While the individual abilities of players are important, the principle is the same as in soccer, where even with the same team of players, performance varies depending on which players are placed in which positions.
Therefore, determining the size and sequence of various types of reactors is a very important issue. In actual processes, after comprehensively considering various conditions, two continuous stirred reactors and one tubular reactor are sometimes arranged in appropriate sizes and sequences. Of course, this configuration does not apply to all processes; each process uses different types and sizes of reactors, as well as different arrangement methods, depending on its reaction characteristics and production objectives.
South Korea’s petrochemical plants are actually composed of much more complex processes, making it difficult to explain every detail. However, one thing is clear: today’s petrochemical plants are also built based on these process design principles. The reason South Korea—a country that does not produce crude oil—has achieved global competitiveness in the petrochemical industry lies in its efficient chemical processes and continuous process development. Even now, research and technological innovation aimed at developing more efficient and competitive processes are steadily ongoing in South Korea’s chemical industry.
