The work performed in the REslag project is summarized below
WP2. Specifications and technical requirements of the process and of the final product: this activity was able to determine the exact conditions and relevant parameters of the real scenarios for each particular application.
WP3. Characterization and manufacturing of the slag pebbles: a complete characterization of the raw slag was carried out to determine its properties. With this data and the parameters released from WP2 and WP4, the specifications of the pebbles to fill Pilots 2 and 3 were fixed. Two different manufacturing routes were selected: mechanical conformation (Pilot 2) and sintering (Pilot 3). This WP was finalized with the manufacturing of 7 and 10 tons to fill Pilot 2 and 3, respectively.
WP4. Modelling and optimization of the processes and pebbles sizes for Pilot 2, 3 and 4. For Pilots 2 and 3, computational fluid dynamics and finite element analysis tools were implemented. In addition, modelling of the slag pebbles manufacturing processes was carried out to determine the optimized process parameters. Furthermore, HSC-Chemistry software and Thermo-Calc program were used to estimate compositions and mixing rules of the refractory bricks containing slag in its composition.
WP5. Design and construction of prototypes:
-Pilot 1: a pilot plant based on simulated moving bed technology was constructed at CEA laboratories in Grenoble (France) to demonstrate the recovery of high added value metals from slag.
-Pilot 2: a pilot plant was constructed at ArcelorMittal steelworks in Sestao (Spain) to demonstrate the potential of the steel slag as TES material for waste heat recovery applications.
-Pilot 3: two pilot plants were constructed to demonstrate the potential of steel slag as TES material for CSP applications. One of them was built at DLR facilities in Stuttgart (Germany) using air as heat transfer fluid (HTF) (Pilot 3a), while the second one was constructed at ENEA laboratories in Casaccia (Italy) using molten salts as HTF (Pilot 3b).
-Pilot 4: a pilot plant for the manufacturing of refractory bricks using steel slag as aggregate was constructed at Renotech laboratories in Turku (Finland).
WP6. Test and validation of prototypes:
-Pilot 1: a multistep process combining physical and chemical treatment was tested and optimized. It was proven to be highly efficient in rare earth recovery, achieving both high yield and purity in the recovered products.
-Pilot 2: the experimental campaign permitted the demonstration of the good thermal and mechanical properties of the slag particles over heating and cooling cycles. Furthermore, the heat exchanger design was identified as the key component for heat recovery applications from the electric arc furnace.
-Pilot 3a: the principle viability of using slag as a TES material for CSP applications using air as HTF was confirmed. Cyclic thermal and mechanical tests were performed to determine the resistance of the slag and inner insulation options on the one hand, and to determine the design of the TES on the other.
-Pilot 3b: the performed tests allowed to confirm that the sintered slag pebbles are compatible with the solar salt. Therefore, the sintered slags were proved to be suitable TES material for packed-bed TES systems in CSP plants using molten salts as HTF.
-Pilot 4: a valuable property data bank about slag containing refractory castables properties against commercial refractory materials were provided with the activities carried out in this pilot. The developed recipe formulas contain 80% slag (100% aggregates are slag based) with comparable properties to commercial reference.
WP7. Techno-economic viability and Environmental Impact. Replicability and up-scale: the life cycle assessment (LCA) and life cycle costing (LCC) analyses showed that the environmental benefit of REslag technologies can be summarized in 4 areas: reduction of waste generation, savings of primary raw materials, reduction in emissions and primary energy use and, reduction of EU energy dependence. Furthermore, a techno-economic analysis for the CSP technologies was also carried out for molten salt and air central receiver system using a thermocline hybrid energy storage system versus conventional two-tank storage. Finally, a business model for steel slag valorisation was also developed, through the launch of an ICT tool (www.reslag-market.eu) for mapping steel industries and doing a market screening for the different slag applications.
