Cold bonded ore–coal composite pellets for sponge ironmaking Part 1 Laboratory scale development

Abstract

carbonaceous material with iron ore during agglomeration has definite advantages. The reduction kinetics is expected There is a need for the development of efficient to be enhanced owing to the presence of reductants in situ, industrial processes to use iron ore fines of high leading to shorter diffusion distances of the reductant, and grade. Attention is particularly drawn to rotary kiln also because a large number of reaction sites are available sponge ironmaking technology using lump iron ore, simultaneously. These agglomerates must be cold bonded where productivity is low and energy consumption since the carbonaceous material is to be retained for reduction. high compared with gas based processes.Any attempt to heat harden would result in premature Fundamental studies carried out elsewhere indicate consumption of in situ reductants. that the reduction of lump iron is accelerated if aThe reduction of iron oxides mixed with carbonaceous limited amount of carbonaceous material is material has been an interesting area of research for many incorporated in the agglomerate of iron ore fines.years. Most investigations have been of a fundamental Based on these considerations, cold bonded nature, studying the kinetics and reaction mechanisms of ore-coal composite pellets have been developed carbothermic reduction.3-8 These studies have been confor sponge ironmaking in a rotary kiln. These ducted on either single particles or handmade agglomerates. composite pellets were tested in the laboratory andIn a few cases, a commercial process has been developed to found to reduce very quickly, compared with lump produce ore-coal agglomerates, with subsequent reduction iron ore. Composite pellets were also tested in an studies. In a programme started at Michigan Technological 8 t/day rotary kiln sponge iron plant giving University (MTU) in 1966, a cold bonded pelletisation enhanced productivity and lower coal consumption, process termed 'MTU Pelletech' was developed,1 but low and these results will be presented in Part 2 of this temperature, high pressure autoclaving was needed to paper (next issue).I&S/1494a harden the green pellets. Another process termed 'Inmetco' produced green pellets without any heat hardening step2At the time the work was carried out, Dr Agrawal and Dr Prasad but the pellets were so weak that they had to be charged were at the R&D Centre for Iron and Steel, Steel

Use of Iron Ore Fines in Cold-Bonded Self-Reducing Composite Pellets

“…The dry strength of the composite pellets increased with an increase in binder quantity, but decreased with an increase in coke quantity from 15-20 % of the raw pellet mix. The decrease in dry strength with an increase in carbonaceous materials was also observed by Agrawal et al (10). This decrease in the dry strength of the pellets with an increase in coke quantity could be attributed to the increase in hydrophobic material (carbon) in the raw pellet mix.…”

“…For a given pellet mixture design, the compression strength was the average of compression strength of twenty pellets of the same pellet design. A minimum strength of 300 N/pellet was required (10,26). The objective was therefore to identify a binder and pellet design mixture that produced composite pellets with a minimum dry strength of 300 N/pellet.…”

The Microstructure of the Pig Iron Nuggets

“…Also, the internal gas generation, and small diffusion distances in the sample enhances the solid-gas reduction reactions, reducing gas regeneration, slag forming and carburization reactions. [10][11][12][13][14][15] iv. Impurity (Gangue) Separation with Formation of Fusible Slag For the blast furnace process and pig iron nugget process, the impurities are separated from the metal by the formation of slag.…”

Development of Cold Bonded Chromite Pellets for Ferrochrome Production in Submerged Arc Furnace

“…Dextrin was tried by other workers and found superior compared to bentonite, sodium silicate, molasses, slaked lime and oil slush as a cold setting binder for the production of coal based DRI. 13) But the limitations of the most of the organic binders are their high cost and loss of strength at lower temperatures due to the burn off. When the dextrin burns off at 250-300°C temperature, there will not be any bonding between ore particles and hence another supporting inorganic binder is required to hold the particles till they develop required bonding.…”