Exergy accounting applied to metallurgical systems: The case of nickel processing

Abstract

Exergy accounting of energy and material flows for the two main routes of nickel production (from laterites and sulphides ores) is performed so as to identify the main losses which take place in the overall chain. Accordingly, the chemical exergy of the different raw materials and utilities involved in the production of nickel is calculated. The results show that nickel processing has higher efficiencies when it is produced from sulphides than from laterites. Sulphide ore processing has efficiencies fluctuating from 0.67 to 0.79, depending on the specific technologies utilised. The higher efficiencies are reached when leaching technologies are used and on the contrary if nickel is produced from laterites, the efficiencies achieved are lower on average (0.38) due to the cost-intensive processing. The strengths and weakness of the methodology applied are discussed and compared with the exergoecology approach. If the analysis is carried out with the exergoecology methodology, the cost effectiveness of sulphides against laterites is not so evident.