The Python An Underground Processing Plant

The Python – An Underground Processing Plant for Narrow Vein Mining
T R Hughes1 and N J Grigg2
ABSTRACT
Gekko Systems has developed an underground pre-concentration plant (Python) to reduce mine operating costs. Many ores liberate favourably using either high pressure grinding rolls (HPGR) or vertical shaft impactors (VSI). Using this comminution circuits for mineral liberation; rather thanfor the final recovery process and by utilising a high mass pull, high recovery process route (gravity/flotation), a narrow, low head, compact processing plant was developed that can sensibly be operated underground. The Python underground processing plant can provide a number of advantages for narrow vein mines including lower haulage costs, improved mine call factor and lower operating costs. Thefocus on fine crushing reduces the power requirement of the plant to approximately 8 kWh/tonne. The Python underground processing plant has been designed to be towed down the decline or lowered down a shaft, and is capable of being installed in sloping, non-linear drives for placement close to the working face. The overall benefit to mining companies of this concept has been estimated to be asaving in mining costs and a significantly smaller environmental footprint.

methods. The valuable component is then the only material removed from underground to the surface while the non-valuable tailings remain underground for backfilling (see Figure 1). Gekko Systems has built a prototype processing plant (Python) to demonstrate the concept and successfully commissioned the unit on surface inSeptember 2007.

PYTHON PROCESSING PLANT
The principle of the Python processing plant involves size reduction, screening, gravity and flotation pre-concentration underground and as close to the working face as possible. In order to achieve this, a low tonnage Gekko Modular unit has been designed to be installed in drives at each of the working stopes, such that as the ore is blasted it is removedby a LHD or similar unit and delivered directly into the Python’s grizzly feed hopper. The limited handling minimises the possibility of fines losses into footwall cracks and the operating costs of internal haulage. The ore is then crushed and ground to minimum economic liberation size for gravity and flotation pre-concentration. The liberation size is determined by testing the ore and byinterpreting typical gravity yield recovery curves for different type ores. A typical yield recovery curve for a Witwatersrand ore is presented in Figure 2. These curves represent the un-optimised single pass gravity recovery. A rougher/scavenger type application has been recently commercialised, which increases the recovery achievable in practice. The addition of a flash flotation module furtherincreases the recoveries of the fine (-150 µm) fractions. Gekko are proposing that only the pre-concentration step be performed underground. The conventional understanding of gravity concentration is the utilisation of extremely high grade, very low mass pull equipment (eg centrifugal concentrators); however the Python exploits the use of a mass pull of ten to 35 per cent using inline pressure jigsresulting in very high recoveries, typically in the +90 per cent region. This results in

BACKGROUND TO PROJECT
During 2004/2005 Gekko Systems was awarded an AusIndustry research grant to both investigate and commercialise the idea of underground processing of primarily gold bearing ores. The key concept of the project is to fine crush and pre-concentrate the ore underground and as close to theworking face as possible with a combination of gravity and flotation
1. FAusIMM, Research and Development Manager, Gekko Systems Pty Ltd, 321 Learmonth Road, Ballarat Vic 3350. Email: timh@gekkos.com MAusIMM, Sales Manager, Gekko Systems Pty Ltd, 321 Learmonth Road, Ballarat Vic 3350. Email: nigelg@gekkos.com

2.

FIG 1 - Conceptual underground processing plant layout.

Narrow Vein Mining...