HomeEnergyAutomatic energy optimisation saves millions

Automatic energy optimisation saves millions

AEL (African Explosives Ltd.) Intelligent Blasting’s nitric acid plant in Johannesburg, South Africa has saved a massive R3.6 million on annual energy operating costs, thanks to an upgrade from direct-on-line operation to Danfoss’ VLT drive control of electric pumps and motors.

This article first appeared in Mining Review Africa Issue 5, 2020
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The 720 Mtpd nitric acid plant supplies other AEL divisions serving mining operations with chemicals and explosives, nationally and internationally. The plant has improved its reliability by upgrading the process water cooling system, and reduced energy consumption by 500 kWh hourly, in the process.

For many years, motors and pumps in the process cooling water (PCW) system operated direct-on-line.

With the upgrade, AEL Intelligent Blasting aimed to improve efficiency and reliability by introducing AC drive motor control.

They chose VLT AQUA Drive FC 202 and VLT HVAC Drive FC 102 drives from Danfoss, based on their ability to ensure stable operation despite unreliable mains power supply.

These drives offer automatic energy optimisation and kinetic back-up features to support highly efficient and reliable plant operation.

During the upgrade, there was no disruption of operations as pre-installation of all equipment was performed with wires run to and from the MCC.

The final connections were made during a planned shutdown for a catalyst change out.

Fast payback time

Since the upgrade, AEL Mining Services has been able to reduce the electricity consumption from the two fans by 200 kWh combined and by another 300 kWh on the motors.

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“Because we linked everything to our distributed control system (DCS) we were able to use the drives to reach a nice sweet spot of running the pumps and fans on the cooling system so as not to drop efficiency or negatively impacting on plant production or quality but still maintaining an energy saving of around 360 kWh. The resultant payback period was about 18 months,” adds Eben Jacobs, AEL process and control engineer.

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The total savings on operating costs based on an average electricity charge of 85 c/kWh, are roughly (200 + 300) x 8560 hr x 0.85 = R3.6 million. The remarkable payback time of only 18 months reflects the vast improvement in process cooling water efficiency enjoyed by AEL Intelligent Blasting.

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