Project Title:An economic analysis of coal desulphurization by froth flotation to prevent acid rock drainage (ARD)
Supervisors: Prof Sue Harrison, Prof J-P Franzidis
Following from the work of Christian Kazadi Mbamba (above), who established the technical feasibility of the two-stage froth flotation process to separate the sulphides responsible for ARD formation from coal ultrafines, producing a salable coal product and low-sulphur tailings, this project examined the economic feasibility of the process. For a plant treating 100 t/h of ultrafine tailings, with a clean coal product of 80 t/h, a sulphide-rich concentrate of 8 t/h and a sulphide lean concentrate (benign) of 12 t/h, the model showed a positive NPV and IRR of 19%, reflecting process viability for the specific assumptions made. A sensitivity analysis showed that the NPV was very sensitive to coal price, reagent costs, operating costs and coal yield, but not to capital costs. The process might be especially viable in the case of abandoned mines where capital to finance ARD remediation is not easily accessible. An economic review on dry capping cover systems and ARD treatment processes (e.g., chemical neutralisation, ion exchange and reverse osmosis) showed that these remediation methods either have high costs and/or require long-term monitoring or continual funding. Further work to optimise flotation reagents (and thereby reduce the cost) was recommended.