Acknowledgements

of heat recovery by using hot gases from downstream in the process for drying and for feeding

The pre-heating zone is divided into two steps: tempered pre-heating zone and pre-heating zone, where maximum temperatures may reach between 1000 and 1100�C. Pellets need to gain some mechanical strength during pre-heating to withstand the tumbling inside the rotating

The firing in the rotating kiln generates pellets with more uniform properties. The movement of the kiln causes pellets to mix during the firing treatment and the temperature is more even among different pellets. The furnace is heated with a flame on the discharge side. The use of fuel is more flexible in this case in comparison to the straight grate. Besides gaseous and liquid fuels, solid fuels such as coal may also be used. This is of particular interest in regions with

Therefore, pellets undergo more charging and discharging operations during the grate-kiln process than in the straight grate. This causes a greater generation of fines during the process. However, the final pellet properties are more uniform, and fines generation during transport for final use is therefore expected to be lower for pellets produced in the grate-kiln process.

The worldwide pelletizing capacity is divided into 60% for the straight grate process and 40% for the grate-kiln. Both systems are used to produce quality blast furnace and direct reduction

The properties of iron ore depend much on its genesis. Different ores have distinct characteristics and varying performances in the mining and in the metallurgical processes. Ore particle shape, size, texture and capability of water retention, capillarity and cohesive strength among different particles determine the velocity of pellet growth during balling and pellet porosity. Ore characteristics also influence on the required amount of binder to produce pellets with satisfactorily quality. The use of iron ores with smaller crystal size and less dense structure usually results in pellets with better reducibility, impacting the performance of ironmaking reactors. Therefore, different iron ores should be valued in function of the benefit from their

The influence of ore characteristics on beneficiation, concentration, and pelletizing are important for process optimization, improving product quality, and consequently, more efficient use of natural resources and energy. Hence, as described by Moraes and Ribeiro [31], the growing

Mining companies work toward obtaining pellets with customized properties for each type of ironmaking process and also to meet specific requirements of different iron- and steelmaking

the burners is also present. However, a rotary kiln is used for the firing step.

After firing, pellets are discharged in a pallet car for the cooling stages.

7. Challenges and innovations in iron ore pelletizing

importance of this topic that is referred to as geometallurgy is evident.

kiln where firing is performed.

56 Iron Ores and Iron Oxide Materials

availability of cheap solid fuels.

pellets.

use [3].

The authors would like to thank assistant researcher Dafne Pereira da Silva and interns (mining engineering students) Milton Candido Torres da Silva and Lucas Shin Takyia for helping find and organize figures and references.
