Evaluation of electric furnace waste heat recovery using organic Rankine cycle: A case study of Pt. Vale Indonesia TBK nickel smelter

Heat conversion technologies need to be developed to take advantage of the necessary increase in the supply renewable energy. Organic Rankine Cycle (ORC) is suited for these applications, mainly because of the ability to recover low-grade heat. Generating electricity by utilizing electric furnace #4 off-gas through Organic Rankine Cycle (ORC) system is the main topic of this paper. Heat and mass balance calculation shows a huge potential of sensible heat out from the furnace off-gas. The ORC heat recovery system appears to be feasible. Furnace off-gas would bypass the existing spray chamber and be routed through thermal heat exchanger. The hot thermal oil will be sent to the ORC system where at the end will generate electrical power. A major advantage of the ORC implementation is that the power generated can be tied into the internal smelter grid and the power generated can be used throughout the smelter and connected to the existing power distribution. Additionally, this option could be utilized on all four furnaces, and the ORC equipment could potentially be modularized to simplify expansion to the remaining three furnaces. The order of magnitude capital cost estimate for the furnace #4 ORC project totals $9,280,000. This option has the potential to save between $2,497,000 and $4,115,000 in electricity costs, based on an electricity cost range of $150 to $247.24 per MWh. This results in a simple Return on Investment (RoI) of 27% to 44% (2 to 3.7 years payback). Apart of cost savings, it reduces the carbon foot print of the plant and improves the company's reputation as being environmentally and socially responsible.