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...

Role of Slag in Converter Steelmaking Aug01

Role of Slag in Converter Steelmaking...

Role of Slag in Converter Steelmaking The oxygen converter process is the primary steelmaking process for the production of carbon and low-alloy steels. The process is essentially an oxidizing process of refining of the high carbon hot metal (HM) to low carbon liquid steel. The oxidizing process is carried out by blowing oxygen in the converter. This causes liquid iron and the other metallic and non-metallic impurities present in the liquid melt in the converter bath to form oxides that are lighter than the liquid steel and they float to the surface of the bath. The generic name of these oxides is ‘slag’. Some oxides are acidic in nature which can react with the basic refractories of the converter and hence a basic slag using lime and calcined dolomite is usually made for protecting the converter refractories. The oxygen can also react with carbon to create a gas that provides bubbles for foaming the liquid slag and for providing chemical energy needed during steelmaking. In steelmaking process, the slag is predominantly a mixture of oxides with small amounts of sulphides and phosphides. The oxides are either acidic or basic in nature. Slag is formed during refining of hot metal in which Si oxidizes to SiO2, Mn to MnO, Fe to FeO, and P to P2O5 etc., and addition of oxides such as CaO (lime), MgO (calcined dolomite), iron oxide, and others. The addition of oxides is done to obtain desired physico-chemical properties of slag like melting point, basicity, viscosity etc. There are four primary sources for the slag during the steelmaking process in the converter. These are (i) oxidation of metallic elements in the liquid steel (e.g. silicon, manganese, aluminum, titanium, chromium, and vanadium etc.), (ii) due to presence of non-metallics in the liquid...

Improved Designs  and Campaign Life of a Blast Furnace May23

Improved Designs and Campaign Life of a Blast Furnace...

Improved Designs  and Campaign Life of a Blast Furnace The cost of rebuilding or relining a blast furnace (BF) is very high. Hence techniques to extend BF campaign lives are important and need to be pursued very actively. Large BFs usually have a slightly higher campaign output per unit volume. This difference is because larger BFs generally are of more modern design and are well automated.  Since the viability of an integrated steel plant depends on a continuous supply of hot metal (HM), which, in a plant with a small number of large BFs, puts great importance on long campaign life. The techniques for prolongation of BF campaign life falls under the following three categories. Operational practices – The control of the BF process has a major effect on the campaign life. BF is to be operated not only for meeting the production needs but also to maximize its life. Hence it is necessary to modify operating practices as the campaign progresses and in response to the problem areas for the maximization of campaign life. Remedial measures – Once wear or damage that affects the life of the BF becomes evident, engineering repair techniques are to be used or developed to maximize campaign life. Improved designs – As improved materials and equipment are developed, these are to be incorporated into future rebuilds to extend the life of critical areas of the BF, where it is cost effective to do so. Improved designs of the BF for improving the campaign life are discussed in this article. The correct design of the furnace proper is fundamental to reliable operation, metallurgical performance, sustained high productivity, long campaign life and an availability of more than 98 %. BF design has had many improvements in recent decades and campaigns...