What is iron pelletizing?
Iron ore, which is categorised as high grade or low grade based on its Fe content, is the main raw material used in the iron and steel industry. The earth’s crust does not contain enough high-grade iron ores that can be used directly in a blast furnace to meet the demands of the iron and steel industries. Following enrichment, low-grade iron ores can be exploited. Significant levels of impurities, such as silica, alumina, calcium, and magnesium compounds, are present in low-grade iron ores.
Therefore, prior to using separation techniques, a concentration procedure based on crushing and grinding is necessary for sufficient release. The majority of liberation is possible at very tiny particle sizes. Because of this, the resulting concentrate cannot be charged straight into the direct reduction plant or blast furnace without first being transformed into agglomerates of the proper size.
Pelletizing is the most widely used agglomeration technology, which creates agglomerates (green or wet pellets) by rolling up a mixture of iron ore, water, and binder in a mechanical disc or drum.
How it works?
There are several different sub-processes, or process segments, that make up the pelletising process. The iron ore passes through the following primary process steps on its journey from the mine to a finished product:
Step 1: The iron ore is crushed, and the waste rock is removed. About 85 % of the particles should be less than 44 μm (in length, width, or height). It is then possible to extract the valuable mineral, which is magnetite
Step 2: Water is added to the magnetite to make magnetite slurry
Step 3: Additive material (dolomite or olivine, depending on the product) is added to the slurry
Step 4: Most of the water is then removed from the slurry by use of press filters. The water content after this filtering is about 9% of the weight.
Step 5: After the filtering, binder (bentonite or organic binder) is added
Step 6: Green pellets are made using balling drums. When leaving the drum, the pellets are screened, and all pellets with too small a diameter are fed back to go through the drum once more. Oversized pellets are crushed and recycled. The rest are the correctly sized pellets which form the drum’s output.
Step 7: The on-size pellets are transported on a conveyor to the drying process, where they are dried by hot air flowing through the bed.
Step 8: The pellets are fired (1250-1300°C) and then cooled down to about 200°C.
What are the benefits?
Iron ore pelletizing offers several significant benefits that enhance the efficiency and effectiveness of iron production processes. Here are the key advantages:
Improved Resource Utilization
Pelletizing allows for the efficient use of iron ore, especially as high-grade reserves deplete globally. This method minimizes waste and ensures that lower-grade ores can still be effectively processed into usable forms.
Enhanced Steel Production
Iron ore pellets can replace traditional lump ore and sinter in blast furnaces, improving the overall performance of steel production. Their uniform size and high porosity facilitate better permeability and reduction rates during processing.
Operational Efficiency
The uniformity in size and composition of pellets leads to stable operations in blast furnaces, which enhances productivity and reduces the need for frequent adjustments during steelmaking. The use of pellets can reduce coke rates in blast furnaces, leading to lower operational costs and improved environmental performance due to decreased emissions.
Economic Advantages
Iron ore pellets exhibit high cold crushing strength, which minimizes fines generation during handling. This results in lower overall production costs and increased campaign life for furnaces due to reduced maintenance needs.
Environmental Benefits
The pelletizing process contributes to more environmentally friendly steel production by lowering emissions associated with traditional iron ore processing methods. This aligns with global efforts to reduce carbon footprints in industrial processes.
In summary, pelletizing iron ore not only optimizes resource utilization but also enhances operational efficiency, reduces costs, and supports environmental sustainability in steel production.
