African Mining February 2021 | Page 25

OPERATIONS •

More basic approaches involve calculation methodologies which quantify various inputs to estimate and expected energy saving . While this method quick and straightforward , it does not consider more complex compressed air systems .

Single compressor simulation models provide a more in-depth , yet still limited view . This simulation simplifies the network to a single supply process and outflow to each level . Condensing compressed air systems to a single flow model limits accuracy . As demonstrated in one study which had a 10 -25 % variance when estimated savings were compared to implemented results .

For a more detailed understanding of the potential improvements , an integrated approach should be applied to compressed air models . A structured process investigating the current system , utilising data to develop and verify a simulation model , and testing scenarios to prioritise and quantify results is shown to produce the most accurate improvement strategy .

Air is connected to the chamber via the main air lines and filtered to manufacturing specifications and mine safety guidelines .

A recent case study , involving refuge bays in a South African mine used the third simulation method to demonstrate the potential savings of effective compressed air management to refuge chambers . Results showed a potential energy saving of 22MWh , the equivalent of R6.3-million per annum .

Compressed air management for refuge chambers Air is supplied to refuge chambers for two reasons : to keep occupants breathing clean air and to prevent gaseous hazards from entering . In a mine , networks of air lines can be extensive , with multiple equipment , machinery , and chambers connected . Typically , refuge stations are set to run at a 50 % flow rate to maintain an operational standard . If left unmanaged , refuge chambers can add a considerable strain on compressed air usage .

In contrast , MineARC ’ s Compressed Air Management System ( CAMS ) prevents unnecessary air consumption . With CAMS installed , once the refuge chamber reaches the required internal positive pressure , the shut-off valve is activated . If the pressure sensor detects a drop below 200Pa , the valve opens and emits bursts of compressed air to maintain the positive pressure and to reduce the risk of over pressurisation . Without CAMS , air will continually flow through the chamber .

Removing the free flow of compressed air to the refuge reduces wastage and strain on the system while ensuring critical operational equipment remains optimised . For example , savings can be equivalent to turning off a 75kw compressor at 10bar .

Efficient use of compressed air can save sites significant energy , resulting in financial and environmental benefits . Investigating a practical approach will establish new performance benchmarks for on-site compressed air networks . There are multiple tools available to companies , from simulations to more accurately identify a strategy , to management systems to execute best practice . Proactive management is critical to strategic operations and accommodates changing circumstances surrounding energy . •

A recent case study involving refuge bays in a South African mine used the third simulation method to demonstrate the potential savings of effective compressed air management to refuge chambers . Results showed a potential energy saving of 22MWh , the equivalent of R6.3- million per annum .