Oxidising roasting behaviours of anthracite containing haematite pellets

Abstract

In this investigation, the roasting features of haematite pellets to which a small amount of anthracite was added and the effects of carbon on the induration behaviours of the pellets were studied. The results indicate that the suitable dosage of pulverised anthracite is 1?0-1?5%. During the roasting, part of the original haematite grains in the pellets are reduced to magnetite, and some original haematite grains are decomposed into magnetite. Then, the newborn magnetite is oxidised to secondary haematite, which is beneficial to the recrystallisation of Fe 2 O 3 in the fired pellets. Therefore, adding a certain proportion of anthracite is an effective way to improve the roasting strength of haematite pellets, as well as to reduce the roasting temperature and the total energy consumption of the pellet production. IntroductionOxidised pellets, possessing good mechanical and metallurgical properties, are high quality burdens for blast furnace ironmaking. 1,2 However, with the rapid development of the iron and steel industries, magnetite resources are becoming scarce. Thus, it is imperative to make good use of haematite resources to produce pellets. 3 Imported haematite concentrate is of high iron grade, low gangue content and fine granularity. 4 However, the high quality finished pellets from haematite concentrates require a higher roasting temperature and narrower firing temperature range (1300-1350uC), and the fired strength is relatively lower than that of magnetite pellets. 5,6 Hence, how to solve the problems of oxidised pellets prepared from haematite concentrates becomes very important. Much research has been conducted on oxidised pellets prepared from mixed haematite-magnetite concentrates, 4,6,7 where it has been shown that roasting temperature can be reduced and fired strength improved. However, to ensure adequate strength for blast furnace use, magnetite needs to exceed 20%. 7,8 Practical results for adding a certain proportion of solid fuel to haematite concentrates show that the pellet strength is increased, energy consumption is reduced and the pellet metallurgical properties are improved. 9,10 However, before the oil crisis of 1973, because of their low price and easy use, oil and natural gas were widely used as fuels, and the practice of adding solid fuel in haematite pellets had not been well developed. 9 Since the oil crisis, the price of oil has soared and far exceeds that of solid fuel, and much research on carbon containing pellet preparation has been conducted. 9,11,12 However, most of the research has focused on energy saving, and few studies have been designed to reveal the induration mechanisms of carbon containing haematite pellets.In the last 20 years, some investigations on carbon containing haematite pellets have been carried out in China; 13-17 however, most of the research was directed towards the preparation of reduced pellets for non-blast furnace ironmaking. 18 With the increasing requirement for Blast Furnace (BF) fuel economy, adding solid fuel to pellets as an energy saving measu...

Effects of Calcium Addition on Nonmetallic Inclusions in High‐Al Steel

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Phase and Microstructural Characterization of Iron Ore Pellet and their Relation with Cold Crushing Strength Test

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