PUMPS
underwater gold mining uses pumps to suck material to the surface and separate it through sluice boxes. Although somewhat effective, the method has drawbacks including restrictions on production because of lack of pump power and capabilities, lack of versatility, and environmental impact concerns.
The lack of pump power and capabilities largely stems from the type of pumps used. Most operations use centrifugal pumps deployed in an ejectorjet setup, which allows the pumping system to move large solids without clogging and destroying the pump. A conventional centrifugal pump has a small tolerance between the impeller and the volute, limiting what can pass through the pump without getting clogged at the impeller.
Additionally, the constant bombardment of abrasive solids on the impeller affects the tolerances. As a result, the pump suction significantly decreases. In many operations, the equipment is pumping at a rate of about 5 to 10 % solids versus water, and the heavier gold will often fall out of suspension because of lack of suction power.
Another option does not involve a centrifugal, positive displacement or vortex design, but instead an EDDY Pump hydrodynamic pump that uses fluid dynamics. Undersea gold extraction operations are greatly dependent on weather conditions. Wave conditions often make it too dangerous for divers to be in the water or for excavators and dredges to operate. Also, there are large restrictions on the depth of dredging— mainly 10 m or less.
Eddy Pump says its Subdredge“ state of the art dredging system, is unique to the market and is changing how companies mine for gold and perform sediment removal. The dredge pumps that power this unit are also available for slurry transport dredge projects.”
The Subdredge is a remote operated submersible dredge that can be powered hydraulically or electrically with pump sizes ranging from 4 in up to 10 in with production of 306 m 3 / h. The Subdredge can be equipped with an umbilical that allows for it to operate remotely at distances of up to 305 m or greater from the operator. The Subdredge is“ ideal for dredging applications that call for great depths, precision dredging, and unmanned operation.”
All Eddy dredges use its industrial pumps, which are non-clog pumps designed for high solids pumping applications. It says its“ patented pump technology outperforms all centrifugal, vortex and positive displacement pumps in a variety of the most difficult pumping applications.”
Eddy Pump technology uses the principles of a tornado to create a synchronised eddy current, which it says is“ the most highly efficient high solids and high specific gravity pump on the market. This translates to the ability to pump higher percent solids of material and capture the heavy specific gravity gold.”
The submersible dredge uses high-definition cameras and acoustic positioning integrated into a real-time kinematic GPS that allows it to operate virtually blind. The equipment also offers more mining time in all weather conditions. IM