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Case study: BHP Billiton iron ore heavy mining vehicle wash and oil water treatment

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article image Servicing the ES220 oil water separator

Ultraspin Technology supplied a complete solution for oily water separation at a BHP Billiton Iron Ore site for their 220 m³/hour heavy vehicle wash system.

The customer sought to reuse the water from the light and heavy vehicle wash and the trench flushing system. The system needed to recycle the wash water in the heavy vehicle wash area to reduce the amount of fresh bore water.

Ultraspin Technology supplied an ES220 oily water separator; ES220 heavy solids separator; electrical control panel; automated back-flushing system; automated recycle; level control systems; back-up strainer; S2 skimmer and S2 skimmer hose; aeration pump; ozone generator; 20 kL oil collection tank; and 5 kL waste oil tank. Ultraspin also provided testing and commissioning support to the installation contractor and operators on site.

The oily water and site conditions used in the design include a light vehicle wash application; a heavy vehicle wash application; and an MEM trench flushing system.

Water from these sources enters the oily water pond. Oily water effluent is drawn through an Ultraspin S2 stainless steel floating skimmer. The Ultraspin oil skimmer is an automatic self-adjusting, free floating type. A manifold is provided to allow bottom withdrawal for the balance of the flow.

The feed flows to a high capacity back-up debris strainer on the separator skid where large debris and particles are removed to protect downstream equipment. The back-up strainer inlet and outlet pressure is monitored.

Additional features have been incorporated as standard in this design to improve overall pumping system performance and reliability. The pump pressure switch is included to shut down the Ultraspin feed pump if it detects an abnormal state, either high or low pressure. The system will run in response to level or process controls.

The pump feed pressure drives the high performance separators by creating a strong vortex, which in turn creates a centrifugal force that separates the oil droplets from the water. The oily wet solids will also be affected by the vortex. Separated oil and smaller oil wet solids will go out with the reject stream while treated water will go through a second de-sanding treatment stage.

The solid underflow is returned to the HV wedge pits. The treated water is then aerated and treated with ozone in the 400 kL re-use tank, following which it is recycled back to the collection pit during low level activities, reducing the stagnant smell, keeping the water moving and preventing anaerobic build up. Make up bore water can be used from time to time to top up. The treated water will be re-used by the water cannons.

The separated oil (with some water) is sent to the 20kL Oil Collection and Decant Tank for further processing. The concentrated oil rises to the top of the tank due to its lower SG in comparison with that of water. The remaining water is decanted from the bottom of the collection tank and returned to the start for re-processing. The accumulated oil in this tank overflows to a 5000-litre oil collection tank.

The Ultraspin separators are protected by automated back flushing and operate at a frequency of two hours for duration of ten seconds. The first stage of the back flush operation (which lasts for five seconds) is a sweep flush, which sweeps the excess oil out of the reject chamber. The second stage of the back flush operation (which also lasts for five seconds) is the back flush of the reject orifices in each liner. Each back flushing stage occurs progressively.

Manual back flushing also allows the operator to initiate a back flush at any time by pressing the manual back flush button on the electrical control panel. 

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