The AmmLeach® process has the potential significantly to reduce costs at the mine site for a wide variety of copper projects. Absolute operating costs are dependent upon several variables, but a significant portion of the operating costs of any acid leaching operation is the cost of the sulphuric acid consumed.

For the AmmLeach® process nearly all the ammonia reagent is recycled, with reagent consumption typically ~3kg/t of ore processed, an order of magnitude lower than even the most efficient acid leaching operations. The higher the acid consumption of the ore, the bigger the cost differential compared to the lower cost AmmLeach® process. This is largely determined by the order of magnitude difference in reagent consumption – for typically high acid consuming ores sulphuric acid consumption per tonne of ore is over 40kg, compared to average ammonia consumption of only ~3kg/t.

Processing plant capital costs for AmmLeach® are similar to acid heap leach operations of similar size as essentially the same equipment is used for both processes. Capital costs associated with the handling and supply of the reagent are dependent upon the mine location and the form of generation/supply.

For many acid users, especially in remote locations, the safe supply of sulphuric acid is logistically difficult and prohibitively expensive. For example, the transport costs of sulphuric acid can be as much again as the delivered cost of acid to a port. In many instances, economics will dictate that the mine will have to build a sulphur burning sulphuric acid plant for the supply of acid, which is a significant capital cost. In addition, to regulate supply variations, acid storage tanks for around one month’s consumption, whether the mine makes its own or buys in acid, will be required; significantly adding to the capital cost.

For AmmLeach® , the supply of ammonia can be either from ammonia gas where circumstances are favourable or, as is more likely for more remote locations, by using urea, which is available safely and readily in dry granular form as a fertiliser. In fact, this is the preferred way to transport ammonia fertilizer around the world. At the mine site a thermal hydrolysis plant that converts urea into ammonia would be built, the main operating cost for such a plant being electricity. Capital costs for a sulphur burning acid plant for an average acid consuming (~35kg/t of ore) copper oxide ore mine producing circa 50,000tpa copper are some four times those of a urea hydrolysis ammonia plant.