A critical appraisal of the present status of smelting reduction - Part 2 Potential commercial smelting reduction processes

摘要

The classical blast furnace will continue to be the dominant method of making iron globally in the years ahead. Several developments in blast furnace technology have been responsible for its unchallenged superiority even today as far as bulk production of hot metal is concerned. However, alternative methods of making molten iron have recently come into the fray under the generic name of smelting reduction. The aim of all SR processes is to produce hot metal, predominantly for use in EAF steelmaking in mini-mills by reducing iron ore (preferably fine, low-grade material) using non-coking coal. Though the concept was mooted in the late 1930s, the SR story really began in Sweden in the early 70s after direct reduction had failed to live up to its early promise. Many SR processes have since been suggested but only very few have gone beyond laboratory scale / demonstration plant tests to actual commercialisation. The problems have mainly been centred around handling/ processing of hot (and sometimes liquid) wustite prior to the production of hot metal. It has also been difficult to development issues - these include Corex (operating in three places and a fourth announced in China), HIsmelt (soon to begin operation in Australia), Fastmelt (the first part of which ie Fastmet has operated successfully in two large units in Japan), Finex (beginning commercial operation in a well known steel company ie Posco by the end of 2006) and ITmk3 (being commercialised by the end of 2006 by Kobe Steel, a company, which through its subsidiary, Midrex, is the world's leading supplier of shaft furnace DRI technology). None of these are single-stage SR processes and comprise at least two steps - reduction followed by melting. Romelt is the only single-stage SR process that has been on the verge of commercialisation - alas for far too long and despite many positive attributes, its future still remains uncertain. Two-stage SR is foreseen as becoming a vital cog for small-scale ironmaking thereby helping in the dissipation of steel production centres into different regions (particularly in the developing world - Asia, South America). This will assist the steel industry to flourish in the coming years and grow from a crude steel output of 1050Mt in 2004 to 1500Mt by 2015. It can be expected that smelting reduction would account for around 50Mt of hot metal production by then, at least 20Mt out of which would be in countries (like India) having access to high grade iron ore but not possessing adequate reserves of coking coal and requiring large volumes of steel to keep pace with their expected high GDP growth rates. Use of natural gas is now passe in direct reduction -this 'green reductant' could also find a place in SR. Another definite area of application of SR would be in extracting iron from steel plant wastes generated in existing steel units, particularly large scale integrated steel plants.