Small but powerful calcium carbonate: how far can it be used?

In this blog post, we take an interesting look at how small but powerful 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. Making chalk white and soft, smoothing newspaper surfaces for better printing, and polishing teeth—all these are the roles of calcium carbonate. Although calcium carbonate is present in many products we encounter daily, its importance is often overlooked. Calcium carbonate does more than just improve product properties; it also helps reduce production costs and increase production efficiency. In this way, calcium carbonate can be considered a hidden helper in many aspects of our lives. Calcium carbonate, also known as limestone, has a history dating back 1 billion years to the ancient Earth when shellfish flourished.
Over time, the shells of countless shellfish accumulated on the ocean floor, were buried underground due to tectonic movements, and transformed into limestone under the influence of geothermal heat and pressure. This limestone, created by the natural forces of time and pressure, has become an essential resource for us today. Limestone is widely available in its natural state, making it easy to obtain and cost-effective. This is one of the reasons why limestone is used in various applications across industries.
Calcium carbonate is the primary raw material for cement, a basic construction material, and is widely used in steel, agriculture, and chemical industries. When used as a raw material for cement, it enhances the durability of architectural structures through its strong bonding properties. In the steel industry, it plays a crucial role in refining iron ore and removing impurities. In agriculture, it regulates soil acidity to promote crop growth. With such diverse applications, calcium carbonate is an essential element of modern industry.
It also serves as a filler and reinforcing agent to strengthen rubber and plastics. When added to rubber and plastic products, it enhances their strength and durability while contributing to cost reduction in production. Since it is used in various fields, it is important to have manufacturing methods that can produce calcium carbonate in its natural state to suit the needs of each industry. For this reason, calcium carbonate manufacturing processes have been developed and applied in an optimized manner for each industry. Next, we will explain the calcium carbonate manufacturing process.
The calcium carbonate manufacturing process is broadly divided into physical grinding and chemical synthesis. First, physical grinding methods involve applying impact to large limestone particles to crush them. However, simply applying force does not necessarily result in complete fragmentation. When impact energy is applied to calcium carbonate particles using a grinder, part of this energy is converted into kinetic energy, causing the particles to move backward. The remaining impact energy is absorbed into the particles, acting as crushing energy to fracture them. Since the goal is to crush calcium carbonate, the kinetic energy used is actually useless. As the particles become smaller through continued crushing, the proportion of impact energy converted into kinetic energy increases, and eventually, when 100% of the impact energy is converted into kinetic energy, the crushing process reaches its limit and no further crushing occurs.
There are various methods of physical grinding, including dry grinding, where calcium carbonate is ground in air, and wet grinding, where it is ground in water. In dry grinding, the particle size can only be reduced to 1–46 microns due to the grinding limit. However, in the calcium carbonate industry, there are times when smaller particles are required. This led to the development of the wet grinding method. When calcium carbonate is dissolved in water and ground, the resistance of the water reduces the degree to which the particles soften. This results in a lower ratio of impact energy converted into kinetic energy. Therefore, much smaller particles, ranging from 0.35 to 1.2 microns, can be obtained. Precision wet grinding is approximately 2 to 3 times more expensive than dry grinding. The particles obtained through this physical grinding method are called heavy calcium carbonate.
Next, the principle of the chemical synthesis method can be easily understood through the molecular formula of calcium carbonate. When lime and carbon dioxide react, calcium carbonate is formed. Since natural lime does not react well with carbon dioxide, lime is dissolved in water to form calcium hydroxide, which is then reacted with carbon dioxide. After the reaction, calcium carbonate and water are obtained, and the water is used again to dissolve the lime. You may have seen stalactites resembling icicles in limestone caves.
The chemical synthesis method utilizes the recrystallization of calcium carbonate particles in this manner. The first advantage of the chemical synthesis method is the ability to freely control the particle size. When the calcium carbonate particles are recrystallizing one molecule at a time, adding an inhibitor stops the crystallization once particles of the desired size are formed. This allows for the creation of particles as fine as 0.03 to 0.08 microns, which is more than 10 times smaller than particles produced by physical grinding.
Calcium carbonate produced by the chemical synthesis method has a particle size of 0.03 to 0.08 microns, which is more than 10 times smaller than that produced by physical grinding. Hard calcium carbonate can also be produced, with a particle size of approximately 0.08 to 3 microns.
The second advantage of the chemical synthesis method is that it allows for the shaping of particles into desired forms. Calcium carbonate particles produced by physical grinding have been subjected to physical impact from all directions, resulting in a shape that is nearly spherical with no sharp edges. However, the chemical synthesis method allows for the formation of needle-shaped, hexagonal, or plate-like structures depending on the direction in which the calcium carbonate is layered, making it applicable in various industrial applications. For example, needle-shaped calcium carbonate is used as a filler in lightweight paper. Spherical calcium carbonate produced by physical grinding is compact when aggregated, but needle-shaped calcium carbonate is loose when aggregated. Therefore, even with the same volume, needle-shaped calcium carbonate is much lighter, making it suitable for use in lightweight paper.
However, the chemical synthesis method is costly due to its intricate process. Hard calcium carbonate is more than 10 times more expensive than dry grinding, and colloidal calcium carbonate requires much more precise work, resulting in a cost difference of over 20 times. Therefore, the physical grinding method is used for medium-density calcium carbonate in general industries where cost is a priority.
When specific shapes or ultra-fine particles are required, chemical synthesis methods are used despite the high costs. Calcium carbonate has been one of the most widely used raw materials on Earth for the past 5,000 years. Although we may not notice it, calcium carbonate plays a crucial role as a key material in numerous everyday products such as paper, toothpaste, rubber, and plastic.
Additionally, chemical synthesis methods can capture carbon dioxide emitted from other processes to produce calcium carbonate, thereby reducing carbon dioxide emissions and offering environmentally friendly benefits. Recently, as climate change and environmental issues have become global concerns, calcium carbonate manufacturing methods as a carbon dioxide reduction technology have garnered attention. Calcium carbonate is likely to play a significant role in future environmental industries.

 

About the author

Writer

I'm a "Cat Detective" I help reunite lost cats with their families.
I recharge over a cup of café latte, enjoy walking and traveling, and expand my thoughts through writing. By observing the world closely and following my intellectual curiosity as a blog writer, I hope my words can offer help and comfort to others.