Direct reduction

Over the last twenty years or so, four facts have become very striking in the field of direct reduction of iron ores, which is, as is well known, the accepted denomination for the reduction of iron ores to the solid state (which practically takes place below 1,000 to 1,100°C).

• First and foremost, there has been growth in capacity and worldwide production of solid reduced iron ores, i.e. DRI (Direct Reduced Iron) and HBI (Hot Briquetted Iron). Most of this expansion is taking place in developing countries, with industrialized countries playing a very limited role.

• Secondly, we note the predominant role of natural gas reduction processes, compared with coal reduction (although there are signs of a shift in this respect) and consequently, as mentioned above, the development of direct reduction in countries where natural gas is abundant and cheap, i.e. above all in developing countries.

• Then came the development of hot briquetting of reduced ores (to obtain HBIs) to facilitate transport, particularly by sea, with less risk of reoxidation, thus creating a global market for reduced ores.

• Finally, alongside the now classic processes based on natural gas and shaft furnaces (MIDREX and HYL), research and development activities are still ongoing, but more to improve existing processes than to create new ones.

These four points constitute the main parts of this article, which will be preceded by a review of the scientific basis for the reduction of iron ores to the solid state, and followed by a conclusion on the advantages, difficulties and future of direct reduction.