Lime, sometimes referred to as quicklime, is a term commonly applied to a number of related materials. Pure lime is calcium oxide (CaO) formed by “burning” a form of calcium carbonate such as limestone or marble (CaCO3). Carbon dioxide gas (CO2) is released and leaves lime behind. Dolomite, a calcium magnesium carbonate (CaMg(CO3)2) can also be calcined to form dolomitic lime, which has different reactivity due to the presence of MgO.
Lime can be mixed with water to form hydrated lime (Ca(OH)2), which some also call lime. To further muddy the waters, in agriculture adding lime to the soil is not done with true lime but with limestone.
Uses for Lime
Many applications for lime exploit the alkalinity that is created when the lime is formed. Lime is a strong base, so reacts with, and neutralizes, acids. In this capacity, it is used to treat wastewater, drinking water and other industrial acid streams. Lime is widely used to desulfurize stack emissions in coal- and oil-fired power plants. The lime reacts with sulfur in the coal or oil to form calcium sulfate (gypsum). In the past, this material would have been sent to landfills. However, as environmental regulations have become more pervasive, the gypsum produced from desulfurization is now used as a raw material to create wallboard.
Lime enjoys its most extensive use as a flux in purifying steel in the both electric arc furnaces (EAF) and basic oxygen furnaces (BOF). It is particularly effective in removing phosphorus, sulfur, and silica, and to a lesser extent, manganese. Lime also has important uses in the secondary refining of steel and in the manufacture of steel products.
Lime is one of the world’s oldest components in cements and mortars for building purposes. Hydrated lime mortars were used in Roman times and are still performing as designed after all these years. Hydrated lime is widely used in asphalt, masonry, stuccos, cements and in soil stabilization.
Finally, lime is widely used in the manufacture of precipitated calcium carbonate (PCC). Carbon dioxide gas is introduced into a lime slurry and CaCO3 is precipitated out of solution. Precipitated calcium carbonates are produced in large quantities for paper, plastics, sealants, food and pharmaceuticals. Click on the link below to learn more about precipitated calcium carbonates.
Specialty Minerals Lime Products
Specialty Minerals manufactures lime at its Adams, Massachusetts plant— both for internal use in precipitated calcium carbonate manufacture, and for merchant sales. A fluo-solid type kiln is used, which yields a granular quicklime of high reactivity that is dust-free and free-flowing.
Two types of lime are produced: metallurgical grade and chemical grade. The high-calcium metallurgical grade’s high reactivity and low impurity levels make it suitable for many steel desulfurization applications. The chemical grade quicklime is used in many industrial applications.