Dolomite – Its Processing and Application in Iron and Steel Industry Jun28

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

Dolomite – Its Processing and Application in Iron and Steel Industry Dolomite is an anhydrous carbonate mineral. It is a double carbonate of calcium and magnesium (CaCO3.MgCO3). It is one of the important raw materials used in production of iron and steel. Dolomite contains theoretically 54.35 % of CaCO3 and 45.65 % of MgCO3 or 30.41 % of CaO, 21.86 % of MgO, and 47.73 % of CO2. However, in nature, dolomite is not available in this exact proportion. Hence generally the rock containing in the range of 40 % to 45 % of MgCO3 is usually called dolomite. The main uses of dolomite in iron and steel industry are (i) as a fluxing material (ii) for protection of refractory lining, and (iii) as a refractory raw material. Dolomite in iron and steel industry is normally used in three forms. These are (i) raw dolomite which is also the natural form of dolomite, (ii) calcined dolomite, and (iii) sintered dolomite. When dolomite is used as a fluxing material then it is used as either raw dolomite or calcined dolomite. When dolomite is used for the protection of refractories, it is used in calcined form and when dolomite is being used as a refractory raw material, it is used in the form of sintered dolomite. The uses and form of dolomite in iron and steel industry is shown in Fig 1. Fig 1 Uses and form of dolomite in iron and steel industry Processing of dolomite Dolomite after its mining has to undergo several processing before it can be used in various processes. The basic processes in the production of dolomite are (i) quarrying of raw dolomite, (ii) preparing mined dolomite for its use by crushing and sizing, (iii) calcining of raw dolomite, (iv) processing...

Iron ore pellets

Iron ore pellets Iron ore pellet is a type of agglomerated iron ore fines which has better tumbler index when compared with that of parent iron ore and can be used as a substitute of lump ore for the production of direct reduced iron (DRI) and in blast furnaces for the production of hot metal. The term iron ore pellets refers to the thermally agglomerated substance formed by heating a variable mixture of iron ore, limestone, olivine, bentonite, dolomite and miscellaneous iron bearing materials in the range of 1250 deg C to 1350 deg C. Iron ore pellets are normally produced in two types of grades namely DRI grade and BF grade. BF grade pellets have higher basicity than the DRI grade. The general identification details of iron ore pellets are given Tab 1. Tab 1 Identification details of Iron ore pellets Chemical name Iron ores, agglomerates Other names Iron ore pellets, iron oxide pellets CAS No. 65996-65-8 EINECS No. 265-996-3 Molecular formula Fe2O3 Molecular weight (gram/mole) 159.7 Synonyms Di iron trioxide Mineral of identical or similar composition Hematite Other identity code: Related CAS No. Hematite (Fe2O3) 1317-60-8 REACH (Registration, Evaluation, Authorization, and restriction of Chemicals) registration No. 01- 2119474335-36-0013 DRI pellets donot contain CaO while BF grade pellets are fluxing pellets containing CaO. For BF grade pellets reducibility and swelling index are important properties while for DRI grade disintegration is an important property. The properties of pallets are given in Tab 2. Tab 2 Properties of pellets Size 8-20 mm Appearance Granular Colour Dark grey Odour Odourless pH (40 gm/L,20Deg C; slurry in water) 5.0 – 8.0 Melting point 1500-1600 deg C Bulk density 2.0 -2.2 t/Cum Water solubility Insoluble Oil solubility Insoluble Tumbler index (+6.3 mm) 93-94 % Abrasion index (-0.5 mm) 5-6...

Limestone and dolomite flux and their use in iron and steel plant...

Limestone and dolomite flux and their use in iron and steel plant Limestone is a naturally occurring mineral. The term limestone is applied to any calcareous sedimentary rock consisting essentially of carbonates.  The ore is widely available geographically all over the world. Earth’s crust contains more than 4 % of calcium carbonate. Limestone is basically calcite which is theoretically composed of exclusively calcium carbonate (CaCO3). When limestone contains a certain portion of magnesium, it is called dolomite or dolomitic limestone (CaCO3.MgCO3). Dolomite theoretically contains CaCO3 54.35 % and MgCO3 45.65 % or CaO 30.4 %, MgO 21.9 % and CO2 47.7 %. However, in nature, dolomite is not available in this exact proportion. Hence generally the rock containing 40-45 % MgCO3 is usually called dolomite. When MgCO3 is less than 40 % but more than 20 % then the limestone is called dolomitic limestone. The chemical composition of limestone and dolomite varies greatly from region to region as well as between different deposits in the same region. Therefore, the end product from each natural deposit is different.  Typically limestone and dolomite are composed of calcium carbonate (CaCO3), magnesium carbonate (MgCO3), silica (SiO2), alumina (Al2O3), iron (Fe), sulphur (S) and other trace elements. These minerals are shown in Fig 1 Fig 1 Limestone and dolomite The limestone from the various deposits differs in physical chemical properties and can be classified according to their chemical composition, texture and geological formation. Limestones from different sources differ considerably in chemical compositions and physical structures. The chemical reactivity of various limestones also shows a large variation due to the difference in crystalline structure and the nature of impurities such as silica, alumina and iron etc. The varying properties of the limestone have a big influence on the processing method....