The schematic represents the HBI briquetting process.
Direct Reduced Iron is discharged hot from the reduction furnace and screw-fed into the nip between two counter rotating rollers. Pockets in the synchronously rotating rollers form the briquettes. This process occurs at high temperatures (typically approx. 700 °C) and high pressing forces. The continuous string of briquettes leaving the rollers is guided by a heavy chute and is separated into mostly single briquettes, for example by a rotor with impact bars.
Briquettes from fine material, produced in fluidised bed processes, may also be separated in a rotating tumbling drum.
The HBI production plant (Figure 2) typically consists of the following sections:
Figure 2: Briquetting line for pellet/lump-based HBI (left) and fines-based HBI with separating drum (right)
The key component in hot briquetting is a specially designed roller press. Figure 3 shows the assembly bay of Maschinenfabrik KÖPPERN (IIMA member) featuring modern machines for the production of HBI. Figure 4 shows an example of the arrangement of several briquetting presses for the annual production of 2 million tonnes.
The layout of the hot briquetting plant, which usually includes several lines to suit volume requirements, is designed to maximise plant availability, for example during scheduled maintenance on the machines and the system. Innovation and development are key to optimum production of HBI: for example, alternative concepts for briquette cooling are under consideration and larger machines are being designed for more effective handling of the higher output of future direct reduction plants.
The video links below show the two most modern HBI plants, Metalloinvest's Lebedinsky GOK at Gubkin, Russia and voestalpine Texas at Corpus Christi, Texas, USA.