Modern Mining January 2017

TIN

The proposed mining method is Sub Level Caving (SLC) to remove the orebody in retreat fashion from the southern and northern limits of mineralisation back towards the centralised trucking ramp. Blasted ore will be loaded by 14-tonne capacity rubber-tyred LHDs dump- ing into 40-tonne articulated dump trucks and hauled to surface where it will be stockpiled ahead of processing for tin recovery. The process design is based on recovery of tin into concentrate through conventional – and simple – gravity separation methods. Mined ore will be crushed to 100 % passing 10 mm. The coarse material (10 mm to +1 mm) accounts for 75 % of the mass flow and the tin contained in this size fraction will be recov- ered in conventional jigs. The fine material (-1 mm) makes up the balance of the mate- rial and the tin contained in this stream will be recovered using spirals. The concentrates from both the jigs and spirals will be milled and subjected to flotation to remove sulphide material. The tin rich concentrate will be thickened, filtered and dispatched for trans- port to smelters for further refining. Comments Kamstra: “Our present plan is to truck the concentrate to a secure export ware- house – a tin terminal, if you like – in Goma using rough terrain vehicles. Once in Goma, it will be sold to tin traders. Our concentrate will grade at more than 60 % tin and will be unique inasmuch as it will contain no penalty elements such as bismuth or arsenic.” At this stage, Kamstra envisages that con- struction of Bisie – which will take place over 18 months – will start in 2017, which will mean first production can be expected by 2019. To build the mine, Alphamin has appointed DRA – responsible for building the process plant and other infrastructure at the Kibali gold mine in the north-east of the DRC – as its preferred EPCM contractor. In anticipation of the start of construction, there is currently a 60 m return airway adit being developed at the site. Kamstra describes this as an exercise in “getting some infrastruc- ture in and getting an understanding of the rock” while, at the same time, gauging the avail- ability and level of mining skills in the area. To take Bisie into implementation, Alpha­ min has put together what it believes is a highly experienced team. Kamstra himself is a civil engineer who started his career with Grinaker while the company’s COO is Trevor Farber, who played a major role in developing the Blue Ridge platinum project in South Africa and the Kinsenda copper project in the DRC.

plant, a tailings dam and associated facilities with a ROM process capacity of 360 kt/a. It esti- mates the project’s ungeared NPV 8 (real after tax) at US$262,7 million and the ungeared IRR (real after tax) at 48,4 %. The payback period from first tin production is put at 23 months. The mine would produce 10 750 tonnes of tin in concentrate on average per year (account- ing for approximately 3 % of world production) over an almost 12-year mine life, with cash costs being US$7 396 per tonne tin. DRA are running a Front End Engineering and Design programme to optimise the designs and processes of Bisie. The results of this pro- gramme will be available early in 2017.

Miners working on the return airway drive have all been recruited from the local community.

Top projects

Continued on page 45

36  MODERN MINING  January 2017