Grate-KilnTM System for Iron Ore Pelletizing
Downdraft drying Green balls Downdraft drying Downdraft drying Tempered preheat Preheat zone Rotary kiln Zone 1 Zone 2 Zone 3 Zone 4
Travelling grate Annular cooler
Pellets Stack Modern Grate-Kiln System flowsheet.
Histor ory Hist or y
The first Grate-Kiln System pellet plant was installed in 1960. The plant took iron ore concentrate and produced superior iron ore pellets for blast furnace and direct reduced iron feed. Since then, Grate-Kiln Systems have been used for over 50 plants, on both magnetite and hematite ores, with an installed capacity of over 115 million tpy. TM
In a Grate-Kiln System, the traveling grate is used to dry and preheat the pellets. A refractory lined rotary kiln is used for induration. In a straight grate, the grate cars have to go through the drying and induration zones. So, a deep bed of pellets with a hearth layer is required. What this means is that a modern Grate-Kiln System will have a power requirement of less than 20 kwh/ton, while a straight grate system will use over 35 kwh/ton. Another part of the Grate Kiln System process flexibility is because there is only one burner. The kiln burner can use liquid gas, or solid (coal or wood) fuels separately or in combination. One burner reduces maintenance costs and improves fuel efficiency. In the Grate Kiln System, 95% of the air used for combustion is +1,000 C air from the cooler. A straight grate, with up to 50 burners, cannot match this level of energy recovery. Green pellets Grate castings Grate-Kiln Green pellets Fired pellets hearth layer Grate bars 127 – 230 mm
There are two main processes for producing iron ore pellets: The Grate-Kiln System and the straight grate system. In the straight grate system, a continuous parade of grate cars moves at the same speed though the drying, induration and cooling zones. Any change in one section...