Telestack has recently installed a custom design mobile truck unloading, stockpiling, reclaiming and barge loading facility in Sierra Leone (Fig. 1). Installation commenced towards the end of 2011 and has been completely commissioned and signed over in early 2012. The turnkey solution was delivered as part of London Mining Company’s (LMC) Phase 1 investment. LMC choose a logistic system which sees material coming from their Outetec beneficiation plant (8000 t/d), being trucked 40 km from the mine site in Marampa into the barge loading facility in Thofeyim on the river Loko. From this point, the material is loaded onto 8000 t barges at 1500 t/h. The barges then form part of a transhipping process, where they are unloaded via grab cranes onto Handymax vessels ranging from 37 000-55 000 dwt. The project consists of various stages, which ensure maximum operational flexibility for the operator.
1 Truck unloading
From the beneficiation plant, truck and dog units are loaded with 2 x 40 t of iron ore fines with typical FE content of 65 % +. The trucks then travel to LMC‘s purpose built road to the stockpiling and barge loading site. On arrival the trucks pass over a wheel wash before driving over the Telestack grid hopper where each trailer is unloaded (Fig. 2). The unloading hopper has a capacity of 150 t (54 m3) and is fully lined with low friction liners. The trailers are bottom discharge and can unload their 80 t cargo in less than 5 minutes. The unloading hopper regulates the feed at between 800-1000 t/h from the surge by means of a robust apron belt feeder with a variable height gate outlet, all custom designed and manufactured by Telestack for this project. The heavy duty apron belt feeder module is 1200 mm wide and incorporates a 800 kN chain. The apron belt feeder incorporates all the strength of a normal apron pan feeder but has much better sealing properties as it can be sealed like a traditional belt feeder, therefore optimising both spillage prevention and robust feeder characteristics all to cater for the heavy surge of iron ore at 2.8 t/m3 (Fig. 3 and Fig. 4).
From the hopper the material is transferred onto a Telestack 20 m link conveyor which weighs the material by means of a dual idler belt weigher. This is used to keep records of daily, weekly, monthly and annual capacities and to monitor stocks of iron ore in the stockpile. The 20 m link conveyor discharges into the feed-boot of the Telestack 850, a mobile radial and telescopic stockpiling conveyor all in one chasis which can peak at 1000 t/h and has a total length of 51.2 m. The TS 850 has been positioned on an 8 m high plinth which utilizes the natural topography of the site and therefore allows a total stockpile height of 25 m to be achieved. This gives LMC approx 350 000 t of material within a 180 ° radial axis. Material is stacked at approximately 8000-10 000 t/d which means the stockpile has maximum between 35-44 days complete production without any shipments. All maintenance is carried out via access walkways and all transfer points are lined and incorporate high valley angles to minimise blockage potential especially in the rainy season (Fig. 5).
The operator cabin is located at the optimum point to allow best viewing points for truck unloading and stacking. Also, strategically placed metal halite flood lights allow for 24 hour operation.
From the stockpile a WA 600 Komatsu wheel loader reclaims material from the pile and feeds a Telestack track mobile hopper feeder with an 18 m3 apron belt feeder. The apron belt feeder (50 t) regulates the feed of the heavy surge from the 28 t dump (10 m3) bucket of the WA 600. Both apron belt feeders are designed to be started under full load condition.
The reclaim hopper is located in the centre line of the stockpile to minimise the load and carry distance. The single WA 600 can comfortably deliver between 1200-1500 t/h. The feeder then transfers the material onto a Telestack 27.5 m link conveyor which weighs the material and also takes a sample using a certified ISO 308 standard sampling unit. The ESSA sampler is a reverse spoon type design and takes a cut from the falling stream as per iron ore best practice sampling procedure. Sampling can be done manually, by setting intervals on a timing basis or by setting intervals on a tonnage basis (Fig. 6 and Fig. 7).
From the link conveyor the iron ore is transported to a Telestack TS 1550, a mobile radial telescopic shiploading conveyor operating at 1500 t/h. The TS 1550 has an operating cabin located at the end of the outer conveyor to ensure maximum visibility when loading of the barge. The operator trims the barge by means of the TS 1550 barge loaders radial telescopic and luffing capabilities. This technology ensures they can trim the entire barge from one feed-in position to enhance production rates and limit down-time in comparison to other designs. The range of discharge points allow the 8000 tonne barge to be loaded without having to move the barge in any way (Figs. 8, 9 and 10).
Loading is carried out in linear heaps which give optimum efficiency further down the logistic chain when grabs pick up material and transfer onto the handymax vessels via the transhipping process.
This fully customised system shows Telestack’s commitment to the customer base, in designing, manufacturing and installing heavy duty mining specification units to meet the needs of the application. This system can be utilised for all mining companies in existing mines or new mines that are opening up, especially in remote locations for typical phase one of installations globally to start the mining process. The main advantages over large fixed stackers/reclaimers and fixed installations include:
• Less capital investment
• Limited civil works required on site
• Lead time as quick as 4-8 months from order to installation
• No planning permission needed
• Full dust/spillage control and elimination
• Capacities up to 3000 t/h
In 3-5 years time when the production is increased and fixed conveyor systems installed, equipment can still be used as emergency back-up system if fixed system fails and planned maintenance. Furthermore there is an optimised stockyard area where stacker/reclaiming units cannot reach.
The sell-on potential of this equipment is vast, as all units can be packed into 40 ft containers for shipping globally and can be used in a range of industries including quarrying, powerstation, steel mills, ports, inland terminals, rail wagon loading and many more (Fig. 11). To see a video of the entire system in operation, please visit: http://www.telestack.com/videos/telestack-london-mining-stockpiling-reclaiming-and-bargeloading-system-1732.