Sintering Ore Mineral Composition
Sintering, also known as agglomeration, is the process of compacting and forming a mass of material into a porous and uniform product by heating and pressing. This technique is widely used in the manufacture of iron and steel ore concentrates from the unprocessed ore. This process takes place at a sinter plant when iron ore, limestone and other raw materials are heated to a sufficient temperature for them to form materials that can then be easily formed into a uniform, porous and relatively tough mass.
In a sinter plant, two types of ore pellets are formed, namely fine-grained ore pellets and coarse-grained ore pellets. These two types of pellets are produced through different heating and pressing processes. The fine-grained pellets are used in the initial stages of sintering while the coarse-grained pellet is used to provide the uniform and strong mass required in the final stages.
In sintering, the mineral composition of the ore feed is the key factor influencing the properties of the sinter produced. The percentage of various ores used in the process can vary depending on the grade and composition of the ore feed. Generally, the ore feed used for sintering usually consists of equal amounts of hematite, magnetite and quartz. However, the percentage of different minerals used can vary based on the grade of the ore feed. The types of minerals which can be used in sintering are:
• Hematite: It is an iron oxide, containing approximately 70% iron, most commonly found in sedimentary rocks. This mineral makes it possible for the ore feed to attain a high level of strength without having an overly high carbon content.
• Magnetite: This is a black magnetic mineral, with a particularly high iron content – between 70 and 72%. It is a crucial constituent of the ore feed, providing the necessary strength and other properties.
• Quartz: Quartz is a major component of the ore feed which contributes to the high level of strength associated with the mass produced. This mineral is composed of silicon and oxygen atoms and is found in igneous, metamorphic and sedimentary rocks.
• Clay: Clay is a general term used to describe a variety of different minerals which result in a product with a low permeability and considerable strength.
• Dolomite: Dolomite is widely found throughout the ore feed, usually present in a range between 45 and 60% of the total weight. It consists of calcium and magnesium, and contributes to the overall strength of the ore feed.
• Limestone: Limestone is used to provide an additional source of lime and aids in controlling the chemical composition of the ore feed.
Once the ore feed has been prepared, the ore blend is heated and some of the minerals undergo chemical reactions. These reactions create more complex mineral compounds, which give the mass its strength. After sintering, the ore particles are fused together according to their original mineral composition, resulting in the formation of a strong, uniform and porous mass which is suitable for further processing. The mineral composition of the ore feed is an important factor in determining the characteristics and consistency of the sinter produced, and thereby determines the efficiency of production.
