1.2 Raw materials and its preparation for iron making.pptx

just for undarstanding

1. Raw materials for Iron making Raw material required for iron making are: Iron ore, including sinter , pellet etc. Coking coal or coke Pulverized coal ( by tuyere) Limestone Air Iron ore Iron constitutes about 4.6 % of earth crust. Most widely distributed and abundant element in nature It is not generally found in native state.

2. Classification of Iron Ores Iron ores are classified in terms of their appearance, nature of gangue content associate with it and based on texture. In terms of appearance: Hematite Red ore Magnetite Black ore Limonite Brown ore Carbonate Grey or whitish ore In terms of gangue content associate with ore: Siliceous ore predominantly silica Aluminous Largely alumina calcarious predominantly lime Bituminoius large amount of coaly matter Titaniferous large amount of Ilmenite ( FeO.TiO 2 )

3. Types of Iron Ores Magnetite Ores : These ores are broadly classified into three categories- sedimentary metamorphic, contact metamorphic and magmatic. Sedimentary metamorphic : usually fine-grained and texture may be banded. Ores of this generally contains iron carbonates and silicates. Gangue is mostly quartz and S, P are generally low. Contact metasomatic : occurs in grains of different sizes and the amount of sulphides of iron, cu and Zn can be high. considerable amount of CaO is present with siliceous gangue. Magmatic : differs widely in grain size and composition. P content is also generally high.

4. Hematite ores : These are usually of the sedimentary-metamorphic type. Due to the differences in condition of formation of the metamorphic processes the granulometry, structure and the iron content of these ores very considerably. The S and P contents of hematite ores are usually low. The gangue mainly contains SiO 2 but Al 2 O 3 can also be appreciable. Siderites (Spathic ores) : These are carbonate type of ores Siderites are prone to oxidation and the ore often contains hydroxides, these ores bodies are covered by siderite-limonite-hematite cap.

5. Titanomagnetitites : These are complex ores. The main ore mineral is magnetite with titanium present as ilmenite. The composition varies considerably and may contain 60-70 % magnetite and 20-27 % ilmenite. Lateritites : contains 50-60 % iron in the form o f hydroxides and a high proportion of Al 2 O 3 . Contains impurities like Cr, Ni, CO etc. These ores are difficult to process and hence still largely remain unused.

6. Structure and texture of Iron ores The presence or distribution of mineral content in the ore depends on geological ( area ), metamorphic ( transformation due to heat and pressure ) and geochemical (  chemical composition of the earth ) influences which the ore body has undergone. T he pattern of the mineral content in the ore, will have a bearing on the course which ore preparation should follow and on the behavior of the ore in the blast furnace.

7. Classification of ores based on texture Oolitic ores: contains (45 - 49 % Fe), Oolitic iron ores are a distinctive subset of iron ore deposits, and are characterized by their spherical grains composed of concentric layers containing goethite, limonite and quartz and a minor amount of hematite along with impurity elements such as S i and P. BSE image of oolitic iron ores

8. Lateritic ores: These are formed by surface action at the expense of underlying rock rich in iron and consist of iron hydroxides, alumina hydroxides and other minerals.   Forms in hot and wet tropical areas Powdery ores: These can not be charged as such in the furnace. It must be agglomerated before charging

9. Banded ores : These are characterized by alternate bands usually a few mm thick to several cms. In this some bands may have predominance of iron minerals while other may have predominance of quartz and silicates. All banded ores are easy to beneficiate. These ores are exists in different types based on thickness of banding, grain size, degree of liberation, constituent minerals.

10. Hard massive ores : It consist mainly of hematite (> 80 %) with minor amounts of goethite and limonite. The constituents are intergrown into a homogeneous mass showing no preferential direction except occasionally very slight banding. It is a fine grained material and offers high resistance to crushing and abrasion. These ores are difficult to reduce in the blast furnace. Soft ores: The ore minerals consist mainly of goethite and limonite together with minor amount of hematite. These can be massive but the crystals are more loosely joined together to somehow a banded structure. These are more porous and are liable to produce more fines during handling.

11. Valuation of Iron ores Value of an iron ore deposits depends upon several factors: Richness – Fe content Location- geographical & geological Composition of gangue- P, Al 2 O 3 , S, alkali content Treatment and preparation needed for smelting- Dense ore ( crushing or breaking ) Fine ores ( agglomeration ) End use ( Produce in the form of liquid or DRI)