Solar-thermal sintering of iron ore

Iron ore sintering is a thermal process to convert iron ore fines into larger agglomerates required for efficient blast furnace operation. Estimated to account for 13% of CO₂ emissions and 14% of energy consumption for integrated steel plants, it is an important target for decarbonisation efforts in this sector. This paper proposes a concentrating solar-thermal (CST) sintering process for iron ore. The concept is assessed via optical, thermal and techno-economic modelling. The optical system is a novel off-vertical-axis beam-down central tower system, with hyperbolic secondary on the tower and compound parabolic concentrator (CPC) at the focus. The thermal system is a moving-grate sinter kiln with a solar-irradiated aperture midway along. Heat recovery is achieved via gas flow-paths before and after the irradiated portion of the kiln. The major system design parameters are optimised via an integrated model, to minimise the levelised cost of sintering (LCOS), with the incident concentrated solar radiation fixed at 50 MW_rad. The optimal system reaches an LCOS of ∼60 USD/t of product. The annual optical efficiency is 43%, and the capacity factor is 14.7%. At design point, the thermal system reaches the target sintering temperature of 1350 °C with solar heating, net of losses, of 13.86 MW, and heat recovery of 48.87 MW. Although more expensive than conventional fossil-fired sintering (∼20 USD/t), this system would break even if a CO₂ emissions tax of ∼156 USD/tCO₂ is applied. Numerous options exist for further improvement to the concept.