“Smart mines” of the future need to address many challenges. These include safer mining, greener mining, increased ore recovery, reducing the impact of waste rock, issues surrounding the lack of specialised personnel, sustainable mining, and extreme remote mining.
A holistic approach to mine-to-mill operations is required to address these challenges and to optimise ore recovery and mineral extraction to maximise overall project profitability and shareholder value.
The role of effective solid liquid separation in the mining industry
The movement of broken ore from the point of blasting to the point of milling results in ore losses and dilution. Some of the ore and fines end up in the water which is utilised during in-situ blasting and mine drilling activities.
The mine process water is therefore a source of ore and should be considered in the holistic approach to managing ore losses. The removal of mineral-rich ore and fines from water is referred to as solid liquid separation.
There are several points in the mine’s water transfer system where advanced equipment technology can contribute to improving ore recovery through a more holistic approach.
What is the most efficient use of mine capital in the design of an optimum mine water transfer system?
There are two ways of managing run-of-mine water:
- Pumping it directly out of the mine using a slurry pump and then settling the water on the surface, or
- Settling the water underground to produce clear water and thickened mud, with separate pumping facilities for each of these two streams
Some of the drawbacks of pumping run-of-mine water directly out of the mine for surface settling are:
- Mine water contains grit that reduces the life of the dirty water-pumping equipment
- The maintenance requirements and costs are generally higher for slurry pumps than for clear water pumps on a cost-per-litre basis
- Capital cost is significantly higher
- Intermediate dams between levels tend to silt up due to the suspended solid loading of the water
- This mud-pumping system tends to be relatively power-intensive
The benefits of the second option of underground clarifying before pumping to the surface include increased pumping efficiency, reliability, and safety of water and mud transfer.
However, underground clarification and multi-stage clear water pumping arrangements have several drawbacks:
- The use of operating labour for the operation of the dirty water handling equipment
- The requirement for extra equipment
- Additional excavations for the underground settling
Clearwater pumping systems are more suited for very deep mines, wet mines with a high ingress of fissure water, and mines where the water is likely to be very clean. In other applications, the pumping of dirty water using mud pumps show more advantages.
Integrated Solid Liquid Separation Technologies for the Mine Water Transfer System
In keeping with the objectives of a “Smart Mine”, specifically, the objectives of safer mining, greener mining (increased water recovery and reuse), and optimal ore and mineral recovery, Watercare Innovations advocates a seamless equipment interface within a complete integrated mining system, that improves ore recovery and water efficiency.
The integrated solid liquid separation system may integrate into configurations for the pumping of either dirty water or clear water in the following ways:
- Underground de-gritting, pH correction, and surface clarifying, coupled with a dirty water pumping system
- Underground de-gritting, pH correction, and clarifying, coupled with mud- and clearwater pumping systems
The integrated solid liquid separation technology comprises the following equipment:
- High-flow de-grit plant: The modular, compact de-grit plant removes mineral-rich solids before the process water is treated in the clarifiers. The separated solids are mechanically handled with the mined ore. The removal of grit is critical for the optimal functioning of any clarifier, whether underground or on the surface. De-gritting is also required with the pumping of dirty water.
- High-rate clarifier: Effective removal of fine suspended solids ensures optimal clear water pumping efficiency with minimised pump maintenance downtime. The modular, compact, high-rate clarifier design has significantly higher rise rates than traditional clarifiers, effectively separating suspended solids to generate clear water overflow with a turbidity of less than 30mg/L and compact underflow SG of 1.05 to 1.3.
- Automatic flocculant dosing plant: The optimal agglomeration of suspended solids by the addition of polymer requires the correct hydration, mixing, and dosage of the polymer. The control philosophy of the automatic flocculant dosing plant is based on an automated batch preparation and transfer system, that is controlled via a Programmable Logic Controller (PLC) or Solid-State (SS) control panel.
- Automatic pH powder dosing plant: Automatic reagent mixing and dosing control the ratios of powder and water added into the mixing chamber where the reagent solution is made up. The concentration of the solution in the process is controlled by using a pH probe. Electric control and instrumentation coupled with remote monitoring ensure reliable reagent dosing in challenging conditions. Automated reagent dosing eliminates the need for large mixing dams with costly agitation systems.
- Dam agitator: In the water collection areas, the dam agitator controls sedimentation by keeping the solids suspended as a homogeneous slurry that is consistently and safely pumped by the transfer pumps. This source of mineral-rich solids is combined with the mine’s mud handling system, contributing to improved mineral recovery and reduced ore dilution.
The consideration of pump configuration and integrated solid liquid separation equipment technologies for the mine’s water transfer system is important in the holistic consideration of improved mine-to-mill ore and mineral recoveries.
The benefits of this holistic water-handling approach include:
- A single specialist contractor for the total integrated system, thus eliminating interfacing difficulties between individual sub-contractors
- Drastically reduced construction and installation cost, due to single-level, compact excavation required for the compact equipment design
- The equipment is modular and interchangeable leading to flexibility in equipment layout configuration to accommodate different pumping designs
- Flexible orientation of individual equipment based on the end users’ site requirements
- Minimal civil design and construction required
- Semi- or fully automatic control, enabling minimal operator intervention
Consideration of the mine’s water and mud-handling systems are important mine infrastructures to consider when addressing the challenge of ore loss and dilution resulting from the in-situ blasting and drilling mining activities.