Alumina and its Role in Iron and Steelmaking...

Alumina and its Role in Iron and Steelmaking Alumina is a chemical compound of aluminum (Al) and oxygen (O2) with the chemical formula aluminum oxide (Al2O3). It is the most commonly occurring of several aluminum oxides. It is significant in its use to produce aluminum metal. It is being used as an abrasive material because of its hardness. It is also being used as a refractory material owing to its high melting point. Aluminum oxide is an amphoteric substance. It can react with both acids and bases, acting as an acid with a base and a base with an acid, neutralizing the other and producing a salt.  It is insoluble in water. Aluminum oxide has a white solid appearance and is odorless. The molar mass of aluminum oxide is 101.96 grams per mole. Specific gravity of alumina is 3.986. It is insoluble in water. Melting point of aluminum oxide is 2072 deg C while the boiling point is 2977 deg C. Alumina affects the processes of producing iron and steel during the production of iron and steel. Besides alumina is a very important refractory material for the lining of furnaces and vessels in iron and steel plants. Role of alumina in ironmaking Alumina during ironmaking enters the process through impurities in the input materials mainly iron ore. Alumina affects the sintering of iron ore. The most harmful effect of alumina is to worsen the RDI (reduction degradation index) value of sinter. RDI value increases as the alumina content rises. It is seen that within a 10 % to 10.5 % CaO content range, an increase of 0.1 % in the alumina content raises the RDI by 2 points. The strength and quality of sinter deteriorate as the alumina content rises. Alumina promotes the formation of SFCA (silico ferrite of calcium and aluminum), which is beneficial for sinter strength, but the strength of the ore components is lower, since a...

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 Agglomeration Processes and their Historical Development Dec28

Iron Ore Agglomeration Processes and their Historical Development...

Iron Ore Agglomeration Processes and their Historical Development There are four types of agglomerating processes which have been developed (Fig 1). They are (i) briquetting, (ii) nodulizing, (iii) sintering, and (iv) pelletizing. Fig 1 Agglomeration processes Briquetting is the simplest and earliest applied process. Fine grained iron ores are pressed in to pillow shaped briquettes with the addition of some water or some other binder under high mechanical compressive pressure. In the nodulizing process, fines or concentrate along with carbonaceous material are passed through inclined rotary kiln heated by gas or oil. The temperature inside the kiln is sufficient to soften but not high enough to fuse the ore. The nodules vary considerably in composition and are too dense, slaggy, lack required porosity and hence this process could not find great favour. Briquetting and nodulizing are cold binding processes and mostly used for the recycling of recovered iron ore wastes in the steel plant. Sintering and pelletizing are the processes of major importance for the iron production. During 2014, as per World Steel Association, the production of blast furnace iron and direct reduced iron were 1183 million tons and 73 million tons respectively. Most of this production has come from iron ore in the form of sinter and pellet. While the preferred feedstock for blast furnace iron is sinter and/or pellets, that of direct reduced iron is pellets only. Though accurate production data for sinter and pellets are not compiled, but world production of sinter and pellets together can be safely estimated to be well over 1300 million tons per year to support the iron production of 1256 million tons. Historically, the feedstock for the world?s blast furnaces was naturally occurring lump ores. During the mining of iron ores, large amounts were getting generated....

Lime and Calcined Dolomite for Use in Steel Plant...

Lime and Calcined Dolomite for Use in Steel Plant Lime is a versatile compound.  Various forms of lime are used in environmental, metallurgical, construction, and chemical/industrial applications etc.  The largest single use of lime is in steel manufacturing, where it serves as a  flux for removing impurities (silica, phosphorus, and sulphur) during refining of steel. The fastest growing use of lime is in environmental applications, where lime is used for treatment of flue gases, wastewater, solid waste, and drinking water. Lime is a white crystalline solid with a melting point of 2572 deg C. It is a basic oxide and is used to react with the acidic oxides (e.g. silica) in various smelting operations. With water it makes milk of lime used for neutralizing acidic waste water. It is also being known as quick lime, lime flux, unslaked lime, and fluxing lime. Lime having some percentage of MgO (usually 2 % to 4 %) is also known as dolomitic lime. Lime is a hygroscopic material and absorbs moisture from the air. With the absorption of moisture it loses its reactivity and gets hydrated. Lime is calcium oxide (CaO) produced on heating (calcination) of limestone (CaCO3) to a temperature of 900 deg C and above (usually 1100 deg C). CaCO3(s) + heat = CaO(s)  +CO2(g) This reaction is reversible. Calcium oxide reacts with carbon dioxide to form calcium carbonate. The reaction is driven to the right by flushing of carbon dioxide from the mixture as it is released. Hydrated lime [Ca(OH)2] is formed by reaction of lime with water (slaking). CaO + H2O = Ca(OH)2 + heat Hydrated lime is also known as slaked lime. It is in the form of a dry white powder. Hydrated lime is an alkali and used for neutralizing acidic solutions. In...