Energy Efficiency and Carbon Management in Mineral Processing Plants

Sammanfattning: Copper processing plants involved in smelting, electro-refining and electro-winning are heat-intensive undertakings that provide extensive challenges for attainment of high energy efficiency. Literature has shown that most of these plants, especially smelters, operate at low overall energy efficiency due to the seemingly complex energy scenario where heat and electricity as forms of energy are treated distinctively from each other. Many copper processing plants have not yet explored both available and emerging waste heat recovery technologies hence remain operating at lower energy efficiencies. In the copper processing plants under study in particular the Nchanga tailings leach plant (TLP), plant operators hinted that some of the processes that ought to operate in heated environments operate at ambient temperatures because of lack of a heating mechanism. The project discusses possible heating mechanisms from available local resources and applicable technologies. As the competing options for providing the required heat at the Nchanga TLP present different carbon emission scenarios, the carbon emissions associated to the recommended installations shall be quantified against a suitable baseline. Flue gas waste heat from the nearby Nchanga smelter has been taken as the available local energy source on which the applicable heating scenarios at TLP are analyzed. The project analyzed waste heat scenarios for three furnaces at Nchanga smelter where it has been established that flue gases from the furnaces contain 37.31 MW of waste heat. Analysis for channeling the waste heat into heat recovery steam generators gave the steam turbine power generation potential of 7.06 MW. The project also demonstrated how energy efficiency undertakings can be used as a driver for carbon emission reduction measures and for participation to the available carbon trading mechanisms such as CDM. Selection of suitable baseline scenarios revealed a lot of potential for carbon finance undertakings in the three case study plants. At the Nchanga smelter, the 7.06 MW power generation capacity has an associated potential of 61,820 tCO2/year emission reductions that can be monetized through the available carbon trading markets. The research established that Nchanga TLP has a heating demand of 10.87MW. If this heating demand was to be met by using the smelter waste heat, the undertaking can be taken as CDM activity or other carbon trading platform with an associated potential of 95,183 tCO2/year.