South Africa's mining sector is a major consumer of electricity, accounting for up to 14.3% of national electricity consumption. Furthermore, research on infrastructure modification to reduce electricity consumption in deep-level platinum mine drainage systems is limited and focuses on individual sub-systems within the drainage system. Therefore, there is a demand for infrastructure reconfiguration to combine individual sub-systems to reduce the electricity consumption of water discharge systems.
The main objective of this study was to reduce electricity consumption and costs on the dewatering system of a deep level platinum mine. To address the study objective, a five-step methodology was developed to modify the dewatering infrastructure of deep-level platinum mines to achieve electricity cost savings. The simulation results showed that two potential solutions can be implemented by modifying the dewatering infrastructure, namely load shifting on the dewatering pumps and underground water recirculation.
Underground water recirculation reduced annual electricity consumption by 1 033 MWh and provided a cost saving of R1.23 million per year. A further saving of R300 000 per annum could be achieved through load shifting ie. to run the drainage pumps outside Eskom's peak load periods.
WATER IN DEEP-LEVEL MINES
Introduction
- Platinum mining in South Africa
- Electricity usage in the mining sector
The mining industry consumed approximately 14.3% of the total electricity produced in the country, of which approximately 33% was consumed by the platinum mining sector [6], [7]. Deep-level mines are usually at depths between 500 m and 2 000 m below the earth's surface [8]. Therefore, there is an opportunity to improve these systems and make their use more effective.
Several major platinum mining companies in South Africa have been extremely successful in recent years. However, in past years, these companies have not been as successful and have experienced financial pressure. This financial pressure is mainly driven by increased operational costs such as labor and electricity costs.
This electricity price increase above inflation poses a major threat to mine companies' profitability if not mitigated properly.
Deep-level mine water reticulation system
- The use of water in deep-level mining
- Water reticulation system layout and sub-systems
After the water has been cooled on the surface using cooling towers and refrigeration plants, it is pumped. As water under high pressure can become dangerous, it is necessary to reduce the pressure before the water is supplied to the work areas. Breakwater dams reduce the pressure of the water by exposing it to ambient conditions [29].
A series of pumps pump water from the shaft into the warm water that keeps the dams afloat. Circulation of mine water can alter water quality due to mixing of fractured water with water used in actual mining operations. Brominators can be used to disinfect sanitary water by cleaning the water from algae.
The cold service water flows down into level ponds where the water will be used. From the work areas the water flows by gravity to the settlers where it is filtered.
![Figure 5: A rock drill operator using a pneumatic drill [18]](https://thumb-ap.123doks.com/thumbv2/pubpdfnet/10395667.0/17.892.111.788.92.545/figure-rock-drill-operator-using-pneumatic-drill-18.webp)
Potential for dewatering improvements
- Energy management initiatives
- DSM initiatives
- Previous studies conducted on DSM initiatives on dewatering systems
Reducing the amount of water used in a mine will reduce the electricity consumption of the dewatering pumps. This study was mainly aimed at reducing the amount of water sent underground and thereby reducing the electricity consumption of dewatering pumps through the use of control valves. Additional research needs to be done to reduce the electricity consumption of dewatering systems in platinum mines.
However, the study did not focus on the effect of infrastructure modification on the electricity consumption of water drainage systems. Alternative methods for reducing the electricity consumption of water discharge systems should be investigated focusing on infrastructure modifications. Research should be done to find additional methods for reducing electricity consumption in platinum mine water systems.
However, the study mentioned increasing groundwater recycling to reduce the electricity consumption of the water discharge system. Thus, additional methods for reducing electricity consumption in wastewater systems should be investigated by focusing on infrastructure modifications.
Need and objectives of the study
- Need for the study
- Problem statement and objectives of the study
Green blocks indicate that the author did research the associated aspects, while orange blocks indicate that the author did not. After water is used, it flows through numerous subsystems to large underground holding ponds. The water is then recirculated for use by mine personnel and equipment.
Service water is unnecessarily pumped to the surface and TOU periods are ignored when dewatering pumps are used. Therefore, the main objective of this study is to reduce the electricity consumption and the cost of the water removal system in a deep platinum mine.
Study overview
DEVELOPMENT OF AN INFRASTRUCTURE MODIFICATION
- Introduction
- Data acquisition of mine water reticulation systems
- SCADA
- Data quality
- Analysis of the dewatering network and infrastructure
- Electric power consumption of a pump
- Pump power
- Fixed variables
- Water flow management
- Underground recirculation
- Verifying solution through simulation
- Analyse the dewatering simulation
- Construct the simulation model
- Calibrate the simulation model
- Development of an electricity consumption profile
- Implementation of solution
- Conclusion
The five steps are discussed in detail and the chapter provides a universal solution for reducing the energy consumption of a deep level platinum mine's dewatering system.
IMPLEMENTATION OF THE INFRASTRUCTURE MODIFICATION
Introduction
Data acquisition of the water reticulation system
- Layout drawings
- SCADA
- Audit
Analysis of dewatering system
- Power consumption
- Displacement height
Verification through simulation
- Analysing the dewatering simulation
- Constructing the simulation model
- Calibrating the simulation model
- Constructing the electricity consumption baseline for the simulation model
- Testing possible solution on the simulation model
Construction of the actual electricity consumption baseline
Validation through actual implementation
- Implement solution on case study shaft
- Compare baseline and actual consumption
Conclusion
CONCLUSION
Summary
WRSs are large consumers of electricity, with dewatering pumps being the component that consumes the most electricity. Numerous methods exist to reduce the electricity consumption and cost of mine dewatering pumps. Unnecessary tap water is pumped to the surface and TOU periods are not taken into account in dewatering pump running schedules.
The main objective of this study was to reduce the electricity and other operating costs of the dewatering system in a deep-level platinum mine. In this step, data was collected regarding the mine's WRS in order to identify possible problems in the dewatering system. Problems in the drainage system were identified using the data collected in step 1 and possible solutions were formulated.
Simulation software was used to build a simulation model based on the data obtained in Step 1. The baseline was used to determine the impact of the proposed solutions on the electricity consumption of the water discharge system. The baseline was developed using the average electricity consumption of the water discharge pumps over a certain time.
The baseline was divided into working, Saturday and Sunday profiles to measure the actual effect on the dewatering pumps. The proposed solution was implemented on the case study shaft and the results were compared to the baseline developed in step 4. Groundwater recirculation reduced the current electricity consumption of the dewatering pumps by 118.0 kW or 1,033 MWh per year, a reduction of 16 % in energy consumption.
The secondary objectives of identifying a problem with WRS, formulating a possible solution, verifying through the use of simulation, and validating through actual results were also met.
Recommendations for future work
By further improving the control philosophy, more water can be recirculated, resulting in more electricity savings for the 21.5L dewatering pumps. Although load shifting was suggested in this study with positive results, it was not implemented by the shaft due to concerns about flooding the 21.5 L dams. Further study is required to convince the case study to implement load shifting on the 21.5 L pumps.
Conclusion
Available: http://www.angloamericanplatinum.com/~/media/Files/A/Anglo-American-Platinum/presentations-and-speeches/standardbankconference-anglo-. Groenewald, “Development of a Compressed Air Management Framework in the South African Platinum Group Metals Mining Industry,” MBA dissertation North-West University, Potchefstroom, 2019. Zietsman, “Identification Model for Cost Savings of electricity in a mine cooling system," Master's Dissertation, North-West University, Potchefstroom, 2018.
Tilgængelig: https://www.eurostoneusa.com/blog/pneumatic-vs-hydraulic-drills- the-differences-and-benefits (tilgået 30. maj 2021). Van Jaarsveld, "A control system for the efficient operation of bulk air coolers on a mine," Masters Dissertation, North-West University, Potchefstroom, 2015. Vosloo, "A new minimum cost model for water reticulation systems on deep mines," PhD. Afhandling, North-West University, Potchefstroom, 2008.
Meyer, “Improved control of an underground clean water pumping system for demand-side management in an interconnected South African gold mine,” MA thesis, North-West University, Potchefstroom, 2016. Venter, “Reconfiguration of deep mine drainage systems for increased water volumes,” Master's thesis, North-West University, Potchefstroom, 2020. Stols, “Quantifying the effects of system constraint improvements on the electricity costs of dewatering pumps,” Master's thesis, North-West University, Potchefstroom, 2016.
Du Plessis, “Investigating the dewatering energy saving potential of an opencast mine”, Master's thesis, North-West University, Potchefstroom, 2020. Schoeman, "The integrated effect of DSM on mine-cooled water systems", Master's thesis, North-West University, Potchefstroom, 2014. Pascoe, “Improved control processes to save electricity costs on a mine water reticulation system”, Masters Dissertation, North-West University, Potchefstroom, 2018.
Deysel, “DSM strategies to reduce electricity costs on platinum mines”, Masters Dissertation, North-West University, Potchefstroom, 2015. Available: http://www.ee.co.za/article/case-study-of-ingula-and -lima-pumped-storage-schemes.html (accessed January 6, 2021). De Jager, “Using Simulation to Prioritize Compressed Air Efficiency Solutions Implementation in Platinum Mines”, Masters Dissertation, North-West University, Potchefstroom, 2020.
![Figure 3: Electricity distribution in a typical platinum mine (adapted from [7])](https://thumb-ap.123doks.com/thumbv2/pubpdfnet/10395667.0/15.892.112.785.94.492/figure-3-electricity-distribution-typical-platinum-adapted-7.webp)
![Figure 11: Characteristic curve of a series pumping configuration (adapted from [38]) Settlers](https://thumb-ap.123doks.com/thumbv2/pubpdfnet/10395667.0/27.892.110.784.88.506/figure-characteristic-curve-series-pumping-configuration-adapted-settlers.webp)
![Figure 14: Relationship between water pressure and flow (adapted from [28])](https://thumb-ap.123doks.com/thumbv2/pubpdfnet/10395667.0/34.892.110.787.87.487/figure-14-relationship-water-pressure-flow-adapted-28.webp)
