The conveyor transports 2000 tph of iron ore material from the crushing plant at Kumaraswamy mine to an existing screening plant, at Donimalai, which is approximately 5.20 km away. The 4.7 km downhill conveyor was commissioned in September 2017 for the NMDC Steel plant in Kumaraswamy, India (Fig. 1).
NMDC Limited, a premier iron ore producer in the world and export house for high grade iron ore lumps and fines, is presently engaged in mining activities at Donimalai, located in the district of Bellary, Karnataka State, India.
NMDC proposed, in 2010, to develop the Kumaraswamy iron ore mines for a ROM (run of mine) capacity of 7 million tonnes per annum to produce calibrated lump sizes of -30 mm to +10 mm and fines of -10 mm. With this in mind a crushing plant was built which was 5.2 km from the existing screening plant. It was proposed to convey the material down the mountain from the new crushing plant to the screening plant via a series of conveyors which included a downhill conveyor Fig. 2).
The selection of the mechanical equipment and arrangement/location of critical equipment tested every bit of experience in the bulk materials handling industry. The conveyor is complex in every sense, being a regenerative conveyor, compromising of four horizontal curves, six vertical curves, belt turnover devices, horizontal gravity take-up with a counterweight tower and a brake control system. It is also equipped with a traveling trolley to do maintenance 60 m above ground. See Fig. 3 below showing the conveyor profile.
Design Features of the Downhill Conveyor
High Speed Conveying
The long downhill belt conveyor operates at a speed of 6.0 m/s and is transporting 2000 tph of iron ore. This results in cost effective transfer of ore as per the following criteria:
- using a narrow belt width of 1050 mm, instead of 1400 mm,
- four numbers of horizontal curves thus eliminating transfer towers,
- increased idler spacing, and
- compact triangular gantry design.
Due to the selection of high speed for the conveyor, a small belt will allow for the design of a lightweight technological structure, small curve radius and low material load on belt.
With reducing material load, the idler spacing can increase therefore minimizing the idler quantities and also idler-roll material cost. See Fig. 4 showing the material loading profile of the conveyor.