The wet processing of iron ore involves washing and beneficiation of iron ore fines and lumps. Moisture remains in the processed iron ore to an extent of 3-4% in lumps (size 10 mm to 40 mm) and 7-8% in fines (size 0.15 mm to 10 mm) and increases to 12-15% in rainy seasons. The processed ore is transferred via conveyors and stored as stockpiles in bunkers or in a few cases it passes through a temporary storage unit called surge piles (Figure 1) before being stored in bunkers (Figure 2). From the bunkers, the ore is conveyed to the dispatch section and loaded onto railway wagons, and transported out.
High moisture content is an opportunity lost to load more ore per wagon due to underloading. In addition, over-freight charges may be imposed in case the load exceeds because of high moisture content. High moisture content also causes problems in the unloading of iron ore at the unloading stations due to reduced flowability. Few attempts to reduce moisture, such as the use of dispersants, stacking of ore for drainage and drying, and use of hot air blowers, were made in the past to reduce the moisture content in the dispatched ore. However, these approaches did not yield promising results.
Approximately 18 million tons/year of iron ore undergoes wet processing. The reduction of moisture content in the ores will result in significant savings. Therefore, a solution is required for reducing the moisture in the dispatched iron ores so that we can avoid instances of underloading (to reduce the penalty to the customers) or overloading (to reduce the penalty to Indian railways) of railway wagons as well as achieve improved flowability of iron ores. The proposed solution should be cost-effective and should enable a reduction in moisture content either during the storage of materials or at the point of dispatch.