The Atacama Desert in northern Chile is believed to be the driest desert on Earth, with the exception of the Polar regions. In spite of its inhospitable nature, the desert and surrounding region is a focal point of activity. The reason for this is its enormous wealth of natural resources. The abundant lithium, copper, silver, gold and platinum deposits are extracted in numerous local mines and form an important pillar of the economy in this South American country. One of these mines is Quebrada Blanca located in northern Chile’s Tarapacá region near the Atacama Desert. At an altitude of 4,400 meters some 240 kilometers southeast of the town of Iquique, the mine produces copper cathodes by processing in an SX/EW plant.
An efficient duo: copper mine with a desalination plant
In order to exploit the remaining copper resources in this deposit, this mine is now being expanded to include a copper concentrator with a production capacity of 140,000 tons per day. In order to use the Pacific Ocean, which is only about 150 kilometers away, as a water source, the Quebrada Blanca Phase 2 (QB2) expansion project includes a 165-kilometer water supply pipeline from the company’s own port which includes a desalination plant.
The reverse osmosis process will be used in the desalination plant. This process filters the water through several semi-permeable membranes to remove the salt and other impurities. After this treatment, five pumping stations pump the water to the concentrator to an altitude of 4,300 m, where it is needed for the copper extraction process. The residual salt concentrate (referred to as brine) is returned to the ocean in an environmentally compatible way through diffusers at a depth of 40 meters and a distance of 750 meters from the coastline.
To use the Pacific Ocean, which is only about 150 kilometers away, as a water source, the Quebrada Blanca Phase 2 (QB2) expansion project includes a 165-kilometer water supply pipeline from the company’s own port which includes a desalination plant.
To implement this venture and comply with the related stringent environmental protection measures, the mine operator Teck with a majority holding in Quebrada Blanca awarded the order to one of the globally leading water treatment specialists – IDE. At the QB2 project, IDE is acting as EP (engineer and procurement supply) contractor. For this type of contract, the basic requirement is that key components for the desalination process – such as membranes, pumps and centrifuges – are only supplied by qualified companies with a healthy balance sheet and good financial standing. After a competitive bidding process, Andritz was awarded the order to manufacture and deliver the process pumps for seawater desalination and the centrifuges to treat the brine.
Key technologies
With a complete, high-quality pumps and centrifuge program, Andritz covers most of the processes in modern, smart desalination plants. In this case, the Quebrada Blanca Desal Plant will be equipped with 11 process pumps and two centrifuges.
The pumps program here comprises five vertical line shaft pumps for the pre-treatment process. There three of these hydraulic machines act as backwash pumps. They transport the filtered seawater into the filter system to backwash the filters in the pre-treatment process, while the other two pumps convey the backwashing liquid from the pre-treatment system to the centrifuges for dewatering.
In addition, five double-flow axial split-case pumps from the ASP series are provided as general booster pumps. As a part of the main process, they pump the filtered seawater to the high-pressure pumps. A single-stage centrifugal pump from the ACP series completes the pumps delivery. It conveys the filtered seawater to the so-called dissolved air flotation system (DAF) acting as DAF circulation pump. This is a water treatment process, which clarifies wastewater by removing suspended solids such as oil or other solid matter. All of these hydraulic machines fulfill the most stringent customer requirements in terms of efficiency, long lifetimes, ease of maintenance, and cost-effectiveness. Furthermore, the high efficiencies help to conserve valuable resources.
Due to its repeated contact with the aggressive seawater or salt water, the choice of material for the pump and also the centrifuge material is a crucial factor in an efficient desalination process. This is why Andritz is manufacturing the pumps from a special material: Duplex stainless steel. The structure of this steel is highly resistant to corrosion fatigue, energy absorption, erosion, and abrasion, as well as showing very little thermal expansion. However, the processing of duplex steel requires decades of experience and expertise. Duplex stainless steel. The structure of this steel is highly resistant to corrosion fatigue, energy absorption, erosion, and abrasion, as well as showing very little thermal expansion.
