Life cycle and economic assessment of multi-stage blast furnace slag waste heat recovery system

In order to utilize the waste heat of blast furnace slag more effectively, the multi-stage slag waste heat recovery system was proposed. This study employed the life cycle assessment to evaluate the environmental performance of the proposed system. Meanwhile, the economic feasibility of the system was analyzed in terms of capital cost and return analysis. Based on the current status of the environment, CO2 tax was also referred in the net explicit profit and net implicit profit calculation of the system. The energy consumption and resource consumption of the system were 268.84 kg coal-eq/tslag and 1213.60 kg/tslag, respectively. The main environmental impact came from the slag production process. Under the consideration of CO2 tax, the net explicit profit and net implicit profit of the proposed method were 13.40 $/tslag and 135.14 $/tslag when the CO2 tax were 33.00 $ per ton. In this process, the evaluations of the proposed system were done in comparison with the conventional water quenching method-open circuit process and latest dry slag granulation method by the main energy, environmental and economic indicators. As results suggested, the multi-stage slag waste heat recovery system had a good application potential in the aspect of energy conservation and emission reduction for iron and steel industry.