The main mineral constituent in lime is called “Calcite” with the chemical formula CaCo3. Carbonate calcium is the equivalent. Limestone or carbonate calcium is rarely found in the form of pure lime in the nature. This stone is mostly seen in the form of Clay-line, sand-lime, and dolomite.
The important impurities in Limestone include: magnesium, silicon dioxide, aluminum, and manganese. Limestone is burnt in the kiln under suitable temperature with a specific chemical composition. Pure Limestone and clay-Limestone or dolomite are being calcined under 1000°C and 1300°C, respectively. Hydrated lime is also called “quick lime” or CaO. This kind of lime is not stable in air and humidity and cannot be maintained for a long time. Carbonate calcium in the Limestone has to be more than 90% and he relevant SiO2+Fe2O3+Al2O3 content must be less than 4% for the production of CaO. Limestone is being burnt in horizontal or vertical kilns. Steel industry: before 1960, lime used to be applied in open kilns in steelmaking process along with other matters. Amount of consumed lime for the production of one ton steel is around 12kg. From 1960 till date and upon introducing Basic Oxygen Furnace (BOF) methods, only lime is being used as the consumed amount is increased to 50-100kg/t. amount of consumed lime for the steel industry has increased from 1.4 million tons in 1961 to 8.1 million tons in 1979. Carbonate rocks: A mixture of calcium and non-carbonated base is considered to be the major carbonated rocks maker. This composition is appeared in the form of different minerals. The main contents include calcite (CaCo3), dolomite (Ca, Mg, CO3), and other types like siderite and ankerite. Additionally, Azar Sepeed Sepahan Co. has guaranteed calcination of the company both quantitatively and qualitatively upon owning one of the best Limestone mines 25km far from the factory.
