HPE > Mining Solutions > Energy recovery –
3 Chamber Pump System (3CPS)

Energy recovery –
3 Chamber Pump System (3CPS)

The purpose of a 3 Chamber Pump System, 3CPS, (also known as the      3 Chamber Pipe Feeder System) is to recover the gravitational potential or pressure energy of the water entering a mine and use it to pump water out of the mine. Unlike a Pelton wheel turbine energy recovery device, the 3CPS also pumps the water out of the mine allowing the conventional de-watering pumps to be switched off for most of the time. This translates into significant energy and maintenance savings.



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A 3CPS uses the incoming chilled water to displace the outgoing warm water. A booster pump is used to overcome friction in the U-tube formed by the high-pressure chilled water feed column, the 3CPS, and the out-going warm water delivery column. A filling pump fills the chambers with warm water. The three chambers are each fitted with valves at either end which are actuated in a sequence to achieve a continuous and steady flow in and out of the system. Typically, these valves are controlled by a PLC which incorporates start-up, operation and shut-down sequences and the necessary safety interlocks. This PLC and the instrumentation are connected via a fibre network to the mine’s SCADA system in the control room on surface. Full view of the status and performance of the entire system can be seen as well as remote controlled (start-up or shut-down) . At any one time, one chamber is pumping, one is being filled and one is ready for pressure equalization. Each chamber has 4 valves, two of which are controlled by the local PLC. A 3CPS does not replace the conventional de-watering pumps as these have to be available in the event of the following:

  • The 3CPS not being operational
  • A dissipator is always fitted in parallel with the 3CPS to break the high pressure of the underground cold water when the 3CPS is not available
  • More water needs to be pumped out the mine that what is fed into the mine

BENEFITS

  • Pumping costs dramatically reduced because incoming chilled water displaces outgoing warm water out of the mine
  • Additional savings or cooling benefits are incurred by the fact that energy recovered (from the hydrostatic pressure in the incoming water to pump water out of the system) means that energy is not dissipated resulting in minimal Joule-Thompson heating. Normally dissipation of the pressure energy results in the water temperature rising 2.34 deg C per 1000m depth. Avoiding this temperature rise by recovering the energy, translates either into a saving on the refrigeration load for a given cooling effect in the mine or better temperatures in the mine for a given refrigeration input on surface.
  • Can switch off conventional de-watering pumps
  • Unattended operation
  • Low maintenance

SAVINGS EXAMPLE

Examples of Actual Savings

Pump-out flow rate (litre/sec) 360
Design Pressure (MPa) 13.5
Rated power saving (MW) 5
Annual Energy Saving (MWh) 42 302
Annual Cost Savings* (ZAR) R 39.1 million

 

MORE INFORMATION

The 3CPS consists of three chambers (high pressure piping), valves, a PLC and typically two low-pressure pumps. It is connected to the high-pressure columns into and out of the mine and to the low-pressure piping to and from the dams as shown below.

 

A 3CPS uses the incoming chilled water to displace the outgoing warm water. A booster pump is used to overcome friction in the U-tube formed by the high-pressure chilled water feed column, the 3CPS, and the out-going warm water delivery column. A filling pump fills the chambers with warm water.

The three chambers are each fitted with valves at either end which are actuated in a sequence to achieve a continuous and steady flow in and out of the system.
Typically, these valves are controlled by a PLC which incorporates start-up, operation and shut-down sequences and the necessary safety interlocks. This PLC and the instrumentation are connected via a fibre network to the mine’s SCADA system in the control room on surface. Full view of the status and performance of the entire system can be seen as well as remote controlled (start-up or shut-down) .
At any one time, one chamber is pumping, one is being filled and one is ready for pressure equalization. Each chamber has 4 valves, two of which are controlled by the local PLC.

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