Improving efficiency of a mine compressed air system

Abstract

Eskom supplies electricity to South Africa, which experienced a capacity margin shortfall. Energy savings companies (ESCOs) implement demand side management (DSM) initiatives to reduce the power strain on the electricity grid. Mine compressed air is a large electricity consumer. The operating costs associated with using compressed air can be reduced by implementing energy efficiency initiatives. Most compressed air systems on mines are inefficient. A typical deep level mine consists of a standalone or ring feed network, containing several centrifugal compressors. Compressors deliver air to surface and underground users. These compressors can have inlet guide vane controls that are effective for controlling airflow. Control valves are also installed on surface or underground for pressure control. Some initiatives affect the inlet guide vane control of the compressors directly. Implementing these initiatives has proven to reduce the power consumption of a compressed air system. The initiatives with the greatest impact on improving energy efficiency of deep level mine compressed air systems were fixing leaks, adjusting delivery pressure set points and reducing pressure on some levels with control valves. A new efficient approach to leak auditing was developed. Control valves were used during the morning changeover period and different pressure control philosophies were developed. This dissertation discussed how the compressed air system improved when a large leak was fixed. The compressed air system was adjusted for improved cost savings. This study also investigated other initiatives available for improving the energy efficiency of a deep level mine compressed air system, such as replacing and selecting compressors, replacing compressor inlet air filters and offloading compressors. Control philosophies were developed to maximise the power savings associated with offloading a compressor. The control philosophies can be implemented to maximise the cost savings when offloading compressors. Implementation of the initiatives achieved a power reduction of 1.35 MW, which relates to an estimated annual electricity cost saving of R8 million. Leak auditing, adjusting delivery pressure set points, reducing pressure on some levels, developing control philosophies for control valves and offloading compressors are effective initiatives to implement on mine compressed air systems. It was proven that these initiatives reduce compressed air power consumption and operating costs