sCO2 waste heat recovery system optimization for electric arc furnaces exhaust stream

Decarbonization of power generation, transportation, and energy-intensive industries (i.e., steel and iron, cement, aluminum, glass, food and beverage, paper, etc.) is necessary to reduce CO2 emissions considering the continually growing world population and related increasing energy consumption. CO2 emissions from energy-intensive industries can be reduced through several different approaches (i.e., direct - alternative fuel or energy source and Carbon capture systems; indirect - utilization of waste heat for the plant’s own consumption), where waste heat recovery represents a low-cost, zero-emissions power generation option with near-term deployment opportunities. In this paper, the steelmaking process is investigated as a potential source of waste heat to reduce the plant’s own consumption. The steelmaking process has three sources of waste heat in three different steps where the waste heat can be utilized. The exhaust gas stream is only approximately 10 % of the available waste heat. However, the temperatures are between 473 and 1573 K based on the process step and type of furnace (i.e., Blast furnace, Basic oxygen furnace, Electric arc furnace). Due to the large temperature range, potential retrofitting, and limited footprint, a sCO2 waste heat recovery system can be an ideal candidate for utilizing waste heat streams in the steelmaking processes. The paper is focused on the optimization of potential waste heat recovery systems based on sCO2 power cycle for a steel plant with several electric arc furnaces (EAF). Several different sCO2 cycle layouts (i.e., Simple, Recuperated, Intercooling, Recompression, Reheating, Split expansion cycle) have been investigated to meet the requirements. Results show higher performance of the sCO2 cycle and potential retrofitting into the current steel plants. The sCO2 power cycles can reach cycle efficiencies above 40 % and provide approximately 800 kWel from the waste heat stream. Part of the work is cost analysis which provided additional parameter/decision value for cycle layout selection.