The mining industry relies heavily on compressed air due to its versatility and the ease with which the compressed air system network can be expanded.
Cooling is crucial to avoid the excessive temperature increases that result from the compression of air in mines. Water is used for the cooling of the bulk air compressors. Watercare Mining is a specialist in compressor cooling water treatment.
A typical mine compressed air system consists of one or more compressors on the surface and an extensive piping network to transport the air to its various points of use.
Some of these pipe sections span up to 40km in a typical deep-level South African mine.
The compressed air is used to drive a variety of pneumatic equipment in mining operations. Some of the equipment used underground includes pneumatic cylinders, pneumatic rock drills, loaders, venturi blowers, pneumatic water pumps, saws and loading boxes.
Compressed air is also important in many mines for ventilation and cooling. Some shafts consume about 100 000 m3/h of compressed air during peak production periods.
A holistic solution to compressor cooling water treatment
Our approach differs from our competitors in that we look beyond just the treatment of a water system, making a holistic appraisal of all plant conditions surrounding the water system.
In this case, we looked at monitoring the performance of the six compressors that were being cooled by the water treated by Watercare Mining.
We found alternative ways to monitor the effectiveness of our water treatment programme, one of them being the cooling tower efficiency.
This led to an all-encompassing solution that included tailor-made, engineered plant and IT solutions that supported the application of the best-suited chemical programme.
Before Watercare Mining’s interventions
Before Watercare Mining took over the management of the compressor cooling system, it was found that:
- The cooling towers were not operating at ideal design specifications. The cooling operation was utilising 7.6% more make-up water, and the blowdown rate was 43% higher than ideal. The cycles of concentration were 75% optimal.
- The conductivity probes were providing incorrect readings to the controllers raising the concern that the probes were not accurately calibrated, or were faulty. The system was not blowing down correctly.
- Blowdown water was continuously running to waste.
- The pre-existing biocide dosing system was faulty as pipes were not properly connected. The cooling towers had biofilm and algae growing on the surfaces.
- The shaft’s safety audits were compromised as the chemical dosing station was non-compliant with the mine’s safety requirements.
When Watercare Mining took over the management of the cooling system, we mostly replaced and correctly calibrated the control equipment relating to the operation of the cooling tower.
After Watercare Mining’s interventions
A cost-effective chemical treatment programme was implemented. The efficacy of the programme was monitored by weekly analyses on the make-up and system water.
Remote monitoring with an early warning system, integrated with Watercare’s WaterBizz IT platform, was installed and commissioned.
The system enables remote monitoring of key operational parameters at Watercare Mining’s control room, or from the mine engineer’s PC. The cooling tower make-up and blowdown volumes, as well as heat rejection, are consistently monitored.
Thermal imaging of the cooling system was a further innovative visual monitoring tool that was used to evaluate the efficacy of the water management programme.
Since taking over the management of the cooling system, improved control of the make-up and bleed off has reduced water wastage through the bleed-off pipe. The cycles of concentration have increased from 4.2 to 5.5 (31%).
The cooling tower fill, louvres and other surfaces are free of deposit resulting in the delta T across the tower increasing from 8.5 to 11 (30,5%).
The compressors are now chilled by cooler water, improving the efficiencies of the compressors, and reducing the energy demand required to generate the required volume of compressed air.
The site is passing its safety audits, and the site engineer is able to monitor the condition of the system on his computer from his office.
Through our understanding of the system, we have identified a further continuous improvement initiative that treats blowdown water to a quality fit to return to the make-up line. This will conserve more water for the plant.
What sets us apart from our competitors?
- Our focus is on water conservation, not only by optimising the cooling towers but by replacing faulty hardware and controllers
- The quality of our dosing station and control panels, ensuring compliance with the site’s health and safety requirements
- Our understanding of the entire compressor system, and the value obtained from monitoring alternative performance data that indicate the successful implementation of the compressor cooling water treatment chemical treatment programme, data such as delta T across the cooling tower, and energy efficiency of the compressors
- Remote monitoring of the cooling system control parameters and central storage of the analytical data
- Our focus is on continuous improvement projects such as the water reconditioning system