Limestone is a sedimentary rock composed mainly of calcite (calcium carbonate CaCO3). It is usually formed in marine or lake environments and is precipitated through biological and chemical processes. The characteristics and types of limestone are as follows:

Color: generally gray, white, yellow, brown, etc., depending on the impurities contained.

Texture: The texture is uniform and fine, but there are also cases of fossils or other rock fragments.

Structure: It can be granular, mud crystal, bioclast and other structures.

Hardness: Mohs hardness is about 3, relatively soft.

Solubility: It is easily soluble in acid and will produce carbon dioxide bubbles.

According to different standards, limestone can be processed to obtain a variety of products, which are widely used in different industries. The following are several main products and their applications after limestone processing:

1. Portland cement

After the limestone is crushed, ground and mixed with clay and other auxiliary materials, the mixed materials are crushed, screened, and further ground to an appropriate particle size. The powdered material is sent to a rotary kiln and calcined at a high temperature (about 1450°C) to form cement clinker. After adding an appropriate amount of gypsum, the clinker is ground into a very fine powder again, which is the finished cement.

2. Building stone

Used as the basic material of buildings, such as foundations, walls, etc., especially for civil buildings, cheap limestone can enhance structural stability and reduce costs.

3. Glass

When making glass, limestone is mixed with soda ash (Na2CO3) and quartz (SiO2) in proportion and melted at high temperature to react to form calcium silicate (CaSiO3) and carbon dioxide (CO2), thereby making ordinary glass.

4. Iron ore smelting aid

Limestone is used as a desulfurizer in the iron ore process to help remove silicon dioxide (SiO2) from iron ore and form low-melting calcium silicate (CaSiO3), which is convenient for removing impurities from molten iron.

5. Quicklime (CaO)

Limestone is calcined and decomposed at high temperature (900°C - 1300°C) to form calcium oxide (CaO), i.e. quicklime. This process is usually completed in a vertical furnace or a rotary kiln. It can be used as a building material, desiccant, silent explosive, and dehydrating agent in food, medicine and other fields.

6. Calcium hydroxide (Ca(OH)2)

Calcium hydroxide (Ca(OH)2), also known as slaked lime or hydrated lime, is produced by the digestion of quicklime with water. This step can be carried out in a specially designed digester to control temperature and humidity conditions. It is used to make Bordeaux mixture for pesticides, improve acidic soils, and treat acidic wastewater.

7. Heavy calcium carbonate (GCC)

Limestone mined from the mine is initially crushed, and the crushed limestone is further ground into fine powder by a ball mill or other type of grinding equipment. The powder is graded using an air separator to ensure that the desired particle size distribution is achieved. Due to its high chemical purity, inertness and thermal stability, it is suitable for use as a filler in industries such as papermaking, plastics, rubber, and coatings.

8. Light calcium carbonate (PCC)

Chemical preparation: Use high-purity limestone as the starting material, calcine limestone to obtain quicklime, digest quicklime to obtain calcium hydroxide slurry, precipitate calcium hydroxide into calcium carbonate crystals under carbon dioxide atmosphere, and finally filter, wash, dry and other processes to make light calcium carbonate products (PCC).

Due to its fine particles and large surface area, it is suitable for use in rubber, plastics, papermaking, building materials, inks, daily chemicals and other fields.

9. Pharmaceutical grade calcium carbonate

Food-grade and pharmaceutical-grade calcium carbonate that meets strict standards is used as a nutrient additive in calcium supplement tablets and multivitamin tablets, as well as a fortifier in the food industry.

10. Food-grade calcium carbonate

High-purity limestone that meets food safety standards is selected as the raw material, and a series of strict quality control measures such as ultra-fine grinding, purification, and disinfection are carried out to ensure the safety and purity of the product. It is widely used in the calcium supplement nutrition and health food industry in modern life, such as dairy products, beverages, cakes, etc., to increase the calcium content of the product and improve the taste.

The above lists the main types of products after limestone ore processing. Each product plays an important role in its respective application field due to its unique properties and functions. With the advancement of science and technology, the deep processing technology of limestone has been continuously improved, making its derivatives more diversified and meeting more diversified market needs.

In order to improve the value and quality of limestone, pre-sorting limestone through mineral processing equipment and throwing out impurities in it will help improve the purity and quality of the final product, thereby meeting a wider range of application needs.

Among them, photoelectric mineral processing equipment such as ore color sorter or artificial intelligence sorter.

Color sorter: The color sorter mainly distinguishes the target substance and impurities by detecting the color difference of the material through optical sensors. When the limestone passes through the machine, the sensor will identify particles with a color different from pure limestone and blow these impurities out of the production line through compressed air or other means. This method is very effective for removing impurities with significantly different colors.

Artificial intelligence sorter: Compared with traditional color sorters, artificial intelligence sorters use more advanced technologies, including but not limited to machine vision, deep learning algorithms, etc. It can not only classify by color, but also accurately identify and separate impurities based on multi-dimensional features such as shape, texture, luster, gloss, etc. The AI system is trained to recognize small and complex differences, which allows it to more effectively handle impurities that are similar in color to limestone but different in composition.

When choosing suitable equipment, mining companies need to consider the following factors:

The type of impurities in the limestone raw material and their physical properties (such as color, shape, density, etc.); the speed and throughput requirements of the production line; the investment budget and technical maintenance capabilities

In addition, based on actual conditions, it may be necessary to pre-treat the limestone (such as crushing and screening) to ensure the best sorting effect. Finally, it is also very important to regularly calibrate and maintain the sorting equipment to ensure its long-term stable operation and maintain efficient working performance.