Limestone – Its Processing and Application in Iron and Steel Industry Jul07

Limestone – Its Processing and Application in Iron and Steel Industry...

Limestone – Its Processing and Application in Iron and Steel Industry Limestone is a naturally occurring and abundant sedimentary rock consisting of high levels of calcium carbonate (CaCO3) in the form of the mineral calcite. Some limestones may contain small percentage of magnesium carbonate (MgCO3). These limestones are known as dolomitic limestones. Limestone is also a very important industrial mineral. Its chemical properties make it a valuable mineral for a wide range of industrial/manufacturing uses. Limestone is also one of the vital raw materials used in production of iron and steel. Limestone, by definition, is a rock that contains at least 50 % of CaCO3 in the form of calcite by weight. There can be small particles of quartz (silica), feldspar (alumino-silicates), clay minerals, pyrite (iron sulphide), siderite (iron carbonate), and other minerals associated with the limestone. All limestones contain at least a few percent other materials. The Impurities in limestone can consists of silica (SiO2), alumina (Al2O3), iron oxide (Fe2O3), sulphur (as sulphides or sulphates), phosphorus (P2O5), potash (K2O), and soda (Na2O). Silica and alumina are the main impurities of limestone. The limestone which is used in ironmaking is required to contain at least 85 % of calcium carbonate and a low percentage of alumina. Similarly limestone which is used for steelmaking is required to contain at least 92 % of calcium carbonate and a very low percent of impurities especially the silica percentage. The main uses of limestone in iron and steel industry are (i) as a fluxing material, and (ii) other usage which consists of desulphurizing agent, coating of moulds of pig casting machine, neutralizing of acidic water, water treatment, waste water(effluent) treatment, flue gas treatment, and sludge and sewage treatment. It is also a component of synthetic slag. Limestone is...

Dolomite – A Useful Mineral...

Dolomite – A Useful Mineral Dolomite is also known as dolostone and dolomite rock.  It is a sedimentary rock which primarily consists of the mineral dolomite. It is found in sedimentary basins worldwide. Dolomite rock is similar to limestone rock. Both dolomite and limestone rocks share the same colour ranges of white-to-gray and white-to-light brown (although other colours such as red, green, and black are also possible). Both the rocks have approximately the same hardness, and they are both soluble in dilute hydrochloric (HCl) acid. The original mineral name ‘dolomie’ was given by NT Saussare, in 1792, in honor of the French geologist Deodat Guy de Dolomieu (1750–1801). Dolomite, the rock, contains a large proportion of dolomite the mineral. Ideal dolomite has a crystal lattice consisting of alternating layers of Ca and Mg, separated by layers of CO3 and is typically represented by a stoichiometric chemical composition of CaMg(CO3)2, where calcium and magnesium are present in equal proportions. Dolomite originates in the same sedimentary environments as limestone i.e. in warm, shallow, marine environments where calcium carbonate (CaCO3) mud accumulates in the form of shell debris, fecal material, coral fragments, and carbonate precipitates. Dolomite is thought to form when the calcite in carbonate mud or limestone is modified by magnesium-rich groundwater. The available magnesium facilitates the conversion of calcite into dolomite. This chemical change is known as dolomitization. Dolomitization can completely alter a limestone into a dolomite, or it can partially alter the rock to form a dolomitic limestone. Dolomite is a complex mineral. It is relatively a soft mineral which can be easily crushed to a soft powder. The mineral is an anhydrous carbonate mineral consisting of a double carbonate of calcium (Ca) and magnesium (Mg). It is chemically represented by CaMg(CO3)2 or CaCO3.MgCO3. It theoretically contains...