Iron ore processing is one of the most important processes in the chain of steel production. Iron ore is divided into two categories according to the product: granulated iron ore and iron ore concentrate. In ore deposits (rock masses containing valuable minerals at a cost that is reasonably extractable) the average grade of iron ore is low and the amount of trace elements is acceptable. For this reason, concentrates are produced to accelerate the use of more advanced methods and more sophisticated circuits. The processing circuit is generally composed of crushing units – grind – Purify and dewatering.
Alongside these units, transport units, water supply, installations, etc. are listed as ancillary units.
Steps of Iron Ore Concentrate Production:
The first step, Crushing:
The first step in the process begins with the entry of the ore into the crusher. In this section, pieces between 20 and 25 cm to 100cm dimensions crushing into smaller than 20 – 25 cm.
Actually, at the entrance of the Grizzly Fixed Crusher, the apertures are equal to the dimensions of the crusher output. In this way, smaller dimensions do not enter the crusher so they not crush.
The crushed minerals then enter the next step of crushing and screening. In this section, depending on the dimensions and properties of the minerals, it may consist of two steps of dry crushing, the cone crusher is used and the dimensions of the minerals are reduced by 30 mm.
It should be noted that multi-step crushing is done to control aggregation and prevent over-crushing of ore.
Step Two, Grinding:
Then these minerals of less than 30 mm dimension enter the grinding step to further crushing. At this point, the materials are made by mill by semi-self-destructive or roller-pressed grinding 0.5 to 1 mm.
This material, with the dimensions of 0.5 to 1mm, is then moved to the next step, where it is further crushed by bullet mills.
In these areas where crushing is carried out in the environment, the crushing dimensions are controlled by hydrocyclones and the pumping of materials that are floating in water to form slurry is performed by the pumps.
Step Three, Purifying:
The particles have reached the finer dimensions after crossing the mills step and need to enter the next step in order to separate valuable materials from the intracellular tailings compounds. The slider is driven by the pump to the magnetic separation step. More magnetic separators are generally drum type separators. Magnets pass through these drums that have magnetic properties. The iron minerals attach to the drum and are collected at the end of the drum by a blade from the drum. Other minerals in the slurry are also mined.
These magnetic separators have a variety of low intensity, medium intensity, high intensity and high gradient that are selected based on the properties of the minerals and the processing tests previously performed on the mineral, while elements such as phosphorus and sulfur in the If the concentrate is present, the flotation method is used to separate the intruder from the concentrate.
This method uses the physical properties of the material’s surface chemistry to separate them from each other. The precious mineral surface is reabsorbed by the collector. To adjust the hydration of the valuable mineral surfaces, the environmental properties, including the pH of the aquatic environment, are carefully adjusted. The mineral is placed in the aquatic environment where air bubbles are created. As the surface of the ore is hydrated, it adheres easily to the air bubble and floats on the fluid surface. Substances called foaming agents are used to stabilize the air bubble and prevent them from bursting and to prevent the air bubbles from joining together.
The fourth stage, Dewatering:
High-grade iron ore contains quantities of water that must be dehydrated and dried to reach a moisture content of 9–۱۰%. For this purpose, the filters are used to separate the obtained concentrate water, then the dehydrated concentrate is transferred to the product warehouse and stored there.
The tailings are also directed to equipment called the ticker for dewatering. There, the solids settle and the water drains off the top of the tuner. The precipitated solid particles are also directed to the center by the picker floor pickup arm and pumped to the tailings dam. Polymeric chemicals called flocculants are used to increase the settling rate of these materials, which binds the tailings particles together and increases their rate of collapse. The output of the above steps forms the iron ore concentrate.