HEAP AERATION

Air Requirements Air supplied to the GEOCOAT® heap serves three separate purposes:

• Provides oxygen for oxidation of the sulfide minerals
• Satisfies the oxygen requirements of the aerobic bacteria
• Removes heat by evaporating water, allowing heap temperatures to be controlled within the optimum range for biooxidation.

The flow rate of air required for heap temperature control is typically an order-ofmagnitude more than that required for the oxidation reactions and for the bacteria. The air supply and distribution system is therefore designed on the basis of the heap cooling requirements. The specific flow rate depends on the mineralogical and chemical composition of the concentrate, the coating ratio (or the quantity of sulfide per unit volume of heap), the rates of reaction of the sulfide minerals, and the ambient conditions at the project site.

Air Supply and Distribution

Air is supplied by low-pressure fans installed near the heap. The number and capacity of fans are selected to cover the required range of air flow rates for the concentrate being biooxidized, and the anticipated ambient conditions. The system can be designed to minimize energy consumption by equipping the fans with variable-speed drives.

The air distribution piping consists of parallel stringers, connected to large-diameter headers running the length of the pad. The headers may be collapsible fabric or rigid FRP mine ventilation ducting or large-diameter HDPE piping. The HDPE stringers are spaced 1.2-1.5m apart and are perforated to pass and uniformly distribute the maximum design air flow.