Modern Mining September 2015

MINING News

New technology pins down infrastructure location of the total sand mined. All the sand and associated mined minerals are transported to the processing plant. The heavy metal is separated and the residual sand then needs to be returned and rehabilitated which is why the positioning of the wet plant was so important.

Earlier this year profes- sional services provider WorleyParsons RSA was commissioned to undertake a scoping study for the position- ing of a new primary wet processing plant for Tronox’s KZN Sands operation. KZN Sands is one of two Tronox mining

the optimal costs over the lifespan of a mine. As the name implies, OptiMap also provides a visual representation on a map of the most optimal location of the infra- structure. The tool has the functionality to identify cost implications immediately if the position is changed. “We are exceptionally pleased with the development of OptiMap as the use of this tool gave the WorleyParsons team an edge. It is an optimisation model capable of handling the massive num- ber of possible configurations available,” says WorleyParsons RSA project manager Marthinus Odendaal. Consulting economic- geologist Vannessa Clark-Mostert adds that locat- ing infrastructure in terms of the cost impact it has on the mine is a common problem that OptiMap now addresses efficiently. The tool can be used in many locations and for any mining commodity, as the same theory and principles apply. Furthermore, OptiMap is also compat- ible with other existing WorleyParsons methodologies such as the EcoNomics™ Delt∆ tool to provide a truly unique value offering, especially in a discrete options evaluation environment. Odendaal and Clark-Mostert go on to explain that the mineral deposits found in the sand represent only a small percentage grade at the mine continues to improve as the more mineralised ore from within the resource model envelope is exposed. When run-of-mine feed grade reaches the planned grade, RHA expects that produc- tion targets will be achieved. RHA is able to produce grade at any percentage of contained WO 3 (tung- sten trioxide) from below 50 per cent to marginally in excess of 70 per cent. The company’s analysis indicates that at the current pricing levels of APT (ammonium paratungstate), the financial returns are potentially improved by targeting output at the lower grade as any penalty for any lower grade concentrate is more than off- set by the benefits of lower production costs and a greater tonnage of concentrate produced. George Roach, CEO, commented: “I am pleased to report that the RHA pro- cess plant modifications notified in our

“For the new Port Durnford site, we had to establish a position for the primary wet plant, and the position had a significant impact in terms of cost,” says Odendaal. “We first of all had to determine the eco- nomical mining pit based on the geological block model using Whittle Optimisation software. The mine is then scheduled over the life of the mine and mining blocks determined. We define all the mining and process ‘streams’ and express them as a cost relationship relative to the distance in rand/tonne/km. “The distance of the mining block to the process plant varies over time as min- ing progress. The total cost over the life of mine is minimised by determining the plant position using OptiMap. Here we did a lot of ground-breaking work for the client with the use of OptiMap. It was also pos- sible to advise the client on what mining method to use as the model made it pos- sible to determine the total incremental cost of mining and processing over the life of the mine.”  announcement published on 8 July 2015 have now been installed. This successful installation was completed simultaneously with a replacement of the tailings discharge system. The replacement of this element of the process plant became necessary due to design deficiencies only understood when production increased to the design throughput of the plant (of not less than 16 tons per hour of resource grade ore, a mean diluted feed grade target of 0,8 per cent contained WO 3 and target production of 5 800 metric ton units per month). “The modified plant now accepts the design tonnage into the recovery circuits. Fine tuning and optimisation is continu- ing, both as we explore the upper tonnage limits of the plant in excess of 16 tons per hour and seek to achieve consistent mate- rial flow through the recovery circuits. We expect that as and when concentrate pro- duction reaches the design output of the plant, RHA will operate profitably.” 

Marthinus Odendaal of WorleyParsons.

ventures in South Africa and concentrates on removing naturally occurring heavy minerals such as ilmenite and zircon from dune sand. The minerals are then either used as feedstock in their natural form or in an upgraded form such as synthetic rutile and titania slag which are produced through the secondary processing of ilmenite. The scoping study, completed by WorleyParsons over a five-month period, set out to establish the most economi- cally viable location for the proposed new processing plant at the Port Durnford greenfield site at KZN Sands. To identify the most optimal position for the new plant, WorleyParsons RSA developed an innova- tive methodology, dubbed ‘OptiMap’. Incorporating various cost relationships and value chain theory, OptiMap calculates

Modifications to tungsten plant now installed AIM-traded Premier African Minerals Limited, which operates and has a 49 % interest in the newly commissioned RHA tungsten project (RHA) in north-east Zimbabwe, says that previously announced process plant modifications have been installed and the operational benefits confirmed.

The modifications were designed to improve efficiency of the crushing circuits and allow better utilisation of the surplus capacity on the downstream concentration circuits. The immediate effect of the modi- fications was anticipated to be an increase in the percentage of higher grade fines con- centrate over the coarse concentrate, with a probable overall increase of total tonnage of concentrate produced. Prior to installation of the modifications, up to 40 per cent of feed ore was rejected as oversize and stockpiled. Premier African Minerals says that feed

10  MODERN MINING  September 2015