This technique which consists in reducing the iron oxide that is removing oxygen is commonly used by the steel manufacturing industry to obtain iron. Due to this deoxidation, the DRI shows a very porous structure, hence its name of sponge iron and tends to reoxidize very quickly. The handling and transport of raw DRI is very uneasy because of the risk of autoignition caused by reoxidation.
The hot briquetting process of DRI aims at eliminating this risk of autoignition by reducing the porosity and consequently the surface in contact with the air that would be likely to react with the moisture contained in the air. It consists in transforming the particles of DRI into briquettes (HBI) of a volume of about 100 cm3.
The DRI particles are compacted directly at the outlet of the reduction process by means of a double roll press.
This press is equipped with a force-feeder with one or two conical screws ; this feeding system enables to feed the DRI through the rolls and transform the particles into briquettes when running through the pocketed rolls.
At the press outlet, the strings of briquettes are conveyed towards a separator, made up mainly of a rotor fitted with impact bars dividing the chain of briquettes into separate briquettes.
The press and the separator are the key-equipment of a sponge iron hot briquetting plant. The removal and recycling of the fines generated during briquetting back to the press by means of a screen and elevator is a possibility.
The hot briquetting process is a reliable and recognized sponge iron passivation technique that enables to obtain a secure product, allowing easy handling, storage and transport.