This blog post will explain how small but strong calcium carbonate is used in everyday life and industry.
What do chalk, newspaper, and toothpaste have in common? They are all made from calcium carbonate. Calcium carbonate is used to make chalk white and soft, to make the surface of newspaper smooth and easy to print on, and to polish teeth. Although calcium carbonate is contained in many products that we use in our daily lives, we often overlook its importance. Calcium carbonate not only improves the properties of products, but also helps reduce the production cost and increase the production efficiency of such products. In this way, calcium carbonate can be said to be a hidden helper in our lives.
Calcium carbonate, also called limestone, has a history that dates back to the time when shellfish thrived on the ancient Earth 1 billion years ago. Numerous shells that were under the sea were deposited over a long period of time, and then they were buried underground due to tectonic shifts and became limestone under the pressure of geothermal heat. Limestone, which was created by the time and power of nature, has become an essential resource for us today. Limestone is widely found in nature, making it easy to obtain and affordable. This is one of the reasons why limestone is used for various purposes across industries.
Calcium carbonate is the main ingredient in cement, which is the basis of construction materials, and is widely used in steel, agriculture, and chemical raw materials. When used as the main ingredient in cement, it improves the durability of building structures through its strong binding power, and in the steel industry, it plays an important role in refining iron ore and removing impurities. In agriculture, calcium carbonate is used to regulate the acidity of the soil to promote the growth of crops. It is an essential element of modern industry.
It also acts as a filler and reinforcing agent to make rubber and plastic stronger. Calcium carbonate is added to rubber and plastic products to increase their strength and durability, while also contributing to reducing production costs. Because it is used in various fields, it is important to develop a manufacturing method that can produce calcium carbonate in a natural state that is suitable for the industry that needs it. For this reason, manufacturing processes for calcium carbonate are being developed and applied in an optimized manner for each industry. I will now explain the manufacturing method for calcium carbonate.
The manufacturing process for calcium carbonate is largely divided into physical crushing and chemical synthesis. First, the physical crushing method involves applying impact to large limestone particles to break them down. However, applying force does not always break them down. When the calcium carbonate particles are impacted by the crusher, some of the impact energy is used as kinetic energy, causing the particles to move backward. The remaining impact energy is absorbed into the particles, causing the particles to split as crushing energy. Since the purpose is to crush the calcium carbonate, the kinetic energy is actually useless. As the particle size decreases due to continued grinding, the proportion of impact energy used as kinetic energy increases, and eventually, when 100% of the energy is used as kinetic energy, the limit of grinding is reached at which no further grinding occurs.
There are also various methods of physical crushing, and the method of crushing calcium carbonate in air is called “dry crushing,” while the method of crushing it in water is called “wet crushing.” In the case of dry crushing, the particle size can only be divided into 1 to 46 microns due to the crushing limit. However, in the calcium carbonate industry, smaller particles are sometimes needed. So, the wet grinding method was developed. When calcium carbonate is dissolved in water and ground, the resistance of the water reduces the degree to which the particles recede. The ratio of impact energy to kinetic energy is reduced. Therefore, much smaller particles of 0.35 to 1.2 microns can be obtained. High-precision wet grinding costs two to three times more than dry grinding. The particles obtained by this physical grinding method are called heavy calcium carbonate.
Next, the principle of the chemical synthesis method is easy to understand through the molecular formula of calcium carbonate. When quicklime and carbon dioxide react, they become calcium carbonate. Since quicklime in its natural state does not react well with carbon dioxide, quicklime is dissolved in water to make calcium hydroxide, which then reacts with carbon dioxide. After the reaction, calcium carbonate and water are obtained, and the water is used to dissolve the quicklime again. You may have seen stalactites that look like icicles in limestone caves. The chemical synthesis method uses the recrystallization of calcium carbonate particles.
The first advantage of the chemical synthesis method is that the size of the particles can be freely controlled. When the calcium carbonate particles are recrystallized one molecule at a time, the crystals are stopped when an inhibitor is added when the required size of the particles is created. Therefore, it is possible to create very fine units. The size of the colloidal calcium carbonate, which is made by a chemical synthesis method, is 0.03 to 0.08 microns, which is 10 times smaller than the physical grinding. In addition, hard calcium carbonate is also produced, which is about 0.08 to 3 microns.
The second advantage of the chemical synthesis method is that it can induce the desired particle shape. The calcium carbonate particles that have undergone physical crushing have no sharp edges because they have been physically impacted from all directions, and thus they only have a near-spherical shape. However, the chemical synthesis method can be used in industry because it can produce needle-shaped, cuboid, and flaky structures depending on the direction in which the calcium carbonate is stacked. For example, needle-shaped calcium carbonate is used as a filler in lightweight paper. Spherical calcium carbonate, which is made by physical crushing, is dense when it is gathered together, but needle-shaped calcium carbonate is loose when it is gathered together. Therefore, needle-shaped calcium carbonate is used in lightweight paper because it is much lighter even at the same volume.
However, chemical synthesis methods are expensive due to the detailed process. In the case of light calcium carbonate, it is more than 10 times more expensive than dry grinding, and in the case of colloidal calcium carbonate, the cost difference is more than 20 times because it is a much more sophisticated process. Therefore, heavy calcium carbonate using physical grinding is used in general industries that value price. If a specific shape is required or if ultra-fine particles are required, a chemical synthesis method is used even if it costs a lot of money.
Calcium carbonate has been the most popular raw material on the planet for the past 5,000 years. Although we may not notice it, calcium carbonate has become an important material industry in many products that are closely related to our daily lives, including paper, toothpaste, rubber, and plastic. In addition, the chemical synthesis method can capture carbon dioxide emitted from other processes to produce calcium carbonate, which has an eco-friendly effect of reducing carbon dioxide emissions. Recently, as climate change and environmental issues have become global topics, the calcium carbonate manufacturing method as a carbon dioxide reduction technology has been drawing attention. Calcium carbonate is likely to play an important role in the environmental industry of the future.
