The term ‘hot briquetting’ is used when the temperature of the feed material requires the use of highly heat-resistant roller presses that incorporate special arrangements for cooling. Temperatures at which hot briquetting takes place range between 250 and 750 °C.
Materials are briquettable under hot conditions if binding characteristics are activated at high temperatures. The most common application is the production of hot briquetted iron (HBI) from direct reduced iron (DRI), whereby the feed is charged to the roller press while still hot as it leaves the reactor. Alternatively, materials can be reheated, as for example in the hot briquetting of converter dust.
Hot-briquetted iron (HBI) is a densified form of direct-reduced iron (DRI).
It is produced at high temperature and pressure in the form of briquettes in order to make handling, storage and transport safer and economically more attractive. The originally highly reactive DRI is passivated sufficiently. This technique is the only passivation method accepted by the International Maritime Organization (IMO) to allow overseas shipment of direct reduced iron in a similar manner as practised for scrap. Additional advantages result from the consistent quality (clean iron units) and the choice of uniform product size and shape.
Roller presses and auxiliary equipment (e.g. briquette string separators, hot screens, hot fines recycle systems) are specially engineered and designed by Köppern to cope with the high temperatures. This involves the use of high-temperature resistant steel, the water-cooling of various machine parts as well as inertisation of housings to prevent re-oxidation.
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