WHAT IS CALCITE? WHAT ARE ITS USES?
Properties Calcite; chemical formula CaCO3, crystal grain size between 1 mm-10 cm, is a mineral that is the building block of limestone. According to the Mohs hardness chart, its hardness is 3, specific gravity is 2.7 gr/cm3 at 20 °C and solubility is 0.0015 gr/cm3 H2O at 25 °C and it has beautiful cleavages according to its surfaces (1011). It breaks easily, has a glassy luster, is found in nature as translucent and matte. In the variety called Islanda Spati, it is optically negative, thin sections are colorless. It dissolves in acid and produces CO2 bubbles. Its double refraction is an important feature. Therefore, it shows the writings as double. The pure ones may contain 56% CaO, 44% CO2 and, depending on the rocks and minerals it is found with, a small amount of Mg, Fe, Mn, Zn, Sr, Cu, Pb, Co, Ba, Cr and As. It does not melt in the blower, but its color changes and becomes white or dull (Şahin, 1978). Its impurities are MgO, SiO2, Al2O3, Na2O, TiO2 and P2O2 as oxides, which negatively affect the quality depending on the industry in which it is used.
Limestone (Calcareous):
A massive, white monomineralic rock consisting of calcite crystals of various grain sizes. Its side minerals are pyrite, galena, rutile, zircon, gypsum, barite and feldspar.
Marble:
It is a metamorphosed limestone or limestone consisting of calcite with a crystal grain size larger than 0.1 mm. Its side minerals are silicate, feldspar, mica, iron oxide and fluorite.
Micronized Calcite:
It is the commercial name of calcite ground to 1-100 mm. It is generally used in the filling and coating industry.
Chalk:
Quality Determination Terms
Abrasion Value:
It is the weight loss in mg of 100 gr dry CaCO3 dispersed in 3.2 lt pure water in the abrasion device after 6000 cycles, and it is an important value in the paper industry.
Dispersion Speed:
It is the dispersion of CaCO3 grains in the environment where they are used. It is important in the filling industry.
Dispersion Speed:
It is the coating of grains with various aliphatics in order to reduce and decrease the gap between CaCO3 grains.
Whiteness Degree:
It is a value obtained as a result of comparison with standard MgO whiteness and is the percentage of the light reflectivity of the material. This value should be 96-100% for calcite, 96% for marble and 93-96% for chalk. It is a sought-after feature in paper and industries where whiteness is important.
Specific Surface:
It is the value of the total surface of 1 gr CaCO3 in cm2. It is sought in the coating and plastic industry.
Preparation and Enrichment:
Before calcite is used industrially, it is subjected to crushing, grinding, classification, magnetic separation and flotation processes depending on the structure of the material. Thus, calcite becomes homogeneous both in terms of material and chemically.
Crushing:
Jaw, impact, hammer crushers and rollers are used in crushing. The crusher is selected according to the material feature, hardness, plant capacity and product size. Jaw crushers give flat and long products, impact crushers give cubic or round products.
Grinding:
Rod and ball mills, vertical mills, ring mills, rotary mills and pulverizers are used.
Mills, ring mills and vertical mills are used with a classifier. A special classifier is used in wet grinding, and an air separator or filter is used in dry grinding. When using dry ball mills and ring mills, they are used with a cyclone or dust collector fan. Vertical mills are a new technology and their advantages over other mills are as follows:
1) Low installation cost
2) Cheap operation and low energy consumption
3) Quiet operation
4) Takes up little space
5) Few moving parts
6) Low excessive grinding and idleness
7) High internal volume capacity usage.
Sieving and Classification:
Sieving can be done wet to classify the material and wash and remove sand, clay, etc. that may be present with the material. Flat, conical, vibrating, shaking and rotary sieves are used for sifting. Air separators or cyclones are used for material with a grain size smaller than 147 microns.
Flotation:
Before the process, the sludge of the material classified below 74 microns is removed with a centrifuge or cyclone. Calcite is floated with fatty acids and soap at pH 8.5-9. Sericite, quartz and other silicates are suppressed with tannic acid, quebracho or chalcone. Na2CO3 and Na2SiO3 are used as control reagents. Reagents can be fed directly to the flotation cell or from the conditioner to the 20% solids density medium. NaOH is also used to increase efficiency. Flotation time can be 10-12 minutes.
Areas of Use
Important Areas of Use
Paper
Paint
Rubber
Plastic
Animal Feed
Agriculture
Medicine
Coal Mine
Glass
Glass Putty
Sugar
Cosmotics
Explosives
Carbide
Water Treatment
Ceramics
Joint Material
Other Areas of Use
1- Retention and emulsion of gases such as organic sulfur, SO2 and CS2 in petroleum refining,
2- As a saponifier in auto lubricating oil,
3- Protection of hot wire against oxidation in wire manufacturing,
4- Production of ink, glue, glycerin, vinegar and chewing gum, matches, linoleum, welding rods,
5- Saponification and fluidization of oils,
6- Removal of animal hair in leatherworking and as a disinfectant in insecticides, poison absorbent as,
7- It is used in the manufacture of soda, soap, cleaning powder, toothpaste and soft abrasives,
8- It is used in flotation and drilling mud.