Integration of a fluidised bed Ca–Cu chemical looping process in a steel mill

Abstract

An integrated full system to decarbonise a steelworks plant is discussed, using high temperature Ca–Cu chemical looping reactions. A H2-enriched gas is produced through sorption enhanced water-gas-shift (SEWGS) of blast furnace gas (BFG) using a CaO-based CO2 sorbent. The resulting CaCO3 is regenerated with heat from CuO reduction with N2-free steel mill off-gases. The high temperature operation allows for an effective integration of a power steam cycle that replaces the steel mill power plant. The proposed fluidised-bed process facilitates a solids segregation step to separate the O2 solid carrier from the CO2 sorbent. The CaO-rich stream separated could be used in the steelmaking process thereby removing the lime plant. Balances of a steel mill integrated with the Ca–Cu process are solved and compared with those obtained for a reference steelworks plant with post-combustion CO2 capture through amine absorption. Using exclusively steel mill off-gases in the Ca–Cu process can reduce CO2 emissions by 30%. Moreover, the H2-gas could produce about 10% of additional iron through a Direct Reduced Iron process. In contrast, by adding natural gas for CuO reduction, almost all the BFG can be decarbonised and an overall CO2 capture efficiency in the steel plant of 92% can be achieved.