Modern Mining November 2017

DIAMONDS

several months. Put simply, it consists of a Dragflow 60 kW submersible pump complete with high depth compensators accommodated on a pontoon structure. The pump boasts a nominal flow rate of 200 m 3 /h, with up to 60 mm-sized particles pumped through a 150 NB pipe. The pump is suspended from a rotatable crane structure, which also serves as the lifting equipment for maintenance tasks. The Dragflow submersible dredge pump has been supplied by Tsurumi Pumps Africa who are the sole agents for Dragflow pumps and Dragflow dredging equipment. The position of the iDredge on the river is controlled via an onboard control panel through four winches mounted inside the pontoons. The winch cables are fed through the four corners of the dredge and anchored to the river bank. The depth of the Dragflow pump is also controlled from the central panel and depth readings pro- vided for logging of pumping operations. The pump is driven electrically and fed via a cable from the river bank and space has been created in the pontoons to house two diesel gensets as a more mobile option. The material from the dredging operation will be fed through a sizing screen on the river bank, which will remove the undersize and oversize fractions. At this stage, sorting will be by hand although, as mentioned, the intention is to install a customised solution incorporating a suitable sorter. Prinsloo notes that the iDredge is collaps- ible for transport. This is an important feature as getting it to site in the DRC is likely to be a demanding task, given the fact that it will have to be taken by road all the way from the port of Matadi (via Kinshasa) to the Tshikapa area. This is a distance of around 1 200 km over a road network that in many parts is in a state of disrepair. The dredge and associated equip- ment needed will be transported in two 40 ft containers and two 20 ft containers. Although not ordered by Africa Resources, an optional extra for the iDredge is a 3D Sonar scanner and monitor, which would enable viewing of the suction area. Another option available is the protection of the pontoon hulls against rock damage via the addition of Ultra High Molecular Weight Polyethylene. The effectiveness of the iDredge as a dia- mond mining tool is obviously still to be evaluated but Häggkvist is confident that it will deliver production rates well in excess of those currently been achieved. “The pumps being used by existing dredging operations have only a fraction of the capacity of our Dragflow pump,” he observes. “We are expecting

will augment the much less effective dredging methods currently being used to mine the allu- vial diamonds of the Tshikapa River. Africa Resources, established in 2014, is the 75 %-holder of a licence (Permit 674), which is 36 km 2 in size and includes a stretch of the Tshikapa River around 20 km north of the border with Angola. The remaining 25 % is held by a DRC national, Clement ‘Papa’ Leta, and related parties. Leta has operated in the area since the early 1990s and has huge local expertise. Leta is also the holder of an adjacent licence (Permit 665). Africa Resources and Leta are partnering on the development of both con- cessions, which between them have an inferred resource of approximately 3,4 million carats. According to Thomas Häggkvist, CEO of Africa Resources, the Tshikapa River project offers excellent potential. “The river origi- nates in the diamond-rich areas of Lunda Norte Province in northern Angola and has been a source of diamonds for many decades,” he says. “What has generally been lacking is modern mining techniques and sorting technology and this is what we intend providing, starting with the iDredge, which will be the most advanced dredge yet to have been deployed in Kasai.” He adds that existing dredges in use on the river are relatively unsophisticated. “Basically, what you have is barges from which div- ers equipped with suction hoses operate,” he explains. “It’s a simple, relatively low-cost approach but production is slow and the div- ers can’t get down to the river bed in some of the deeper potholes that occur. One pothole in Clement’s concession could be more than 40 m deep and this is where we will probably deploy the iDredge first.” Development of the iDredge has taken just

Pictured here (left to right) are Jaco Prinsloo of Imilingo, Clement Leta, Sven-Erik Zachrisson and Thomas Häggkvist, both of Africa Resources, and Bona Leta (Clement’s son).

“The pumps being used by

existing dredging operations have only a fraction of the capacity of our Dragflow pump.”

32  MODERN MINING  November 2017