Last 31^st May and 1^st June, RETROFEED partners met again in person in Huelva (Spain), after more than 2 years of online meetings.

During the first day, partners explained their latest advances such as the development of the flame visualisation monitoring tools by CIRCE or the quality monitoring system for clinker by AIMEN, both systems to be working on SECIL in the coming weeks. Moreover, partners also defined the last inputs needed for the monitoring infrastructure and the control strategies for retrofitting.

Besides, the beta version of the DSS, the decision support system that will help operator plant to use the alternative feedstock using the Digital twins developed by CIRCE, IEN and CSM, was explained for the demo-sites to make the last adaptations.

Finally, workshops for each demo site were conducted, where involved partners explained the status of the developments and the planning for the following months:

• In TORRECID (ceramic sector, Spain), commissioning and installation of the control system, by-pass for combustion air pre-heating, visual camera, new sensors, etc. in the smelting furnace has already finished, and the real demonstration using the DSS is ongoing, with very good results.
• In SECIL (cement sector, Portugal), the last steps before the installation of the new RDF burner, new sensor, flame monitoring tool and the quality monitoring system for clinker has been performed, and the digital twin is going to be finished early.
• ASAS (aluminium sector, Turkey) has already installed the new O₂ injector, delacquering drum and burner heads designed and constructed by STEK. With the digital twin already finished, the DSS will be tested in the following weeks once the commissioning is finished.
• At FERRIERE NORD (steel sector, Italy) and TENARIS SILCOTUB (steel sector, Romania), the flexible burner, coal injectors and dried residues injectors have already designed and constructed by HTT. Moreover, the DSS is already being tested in FENO after the digital twin developed by CSM, and it is expected to be working soon in TENARIS SILCOTUB.
• Finally, in FERTIBERIA the pilot plant is working to obtain data for implementing the process in the real plant, where the purchased tubular reactor is wating to be installed. Moreover, this data will also help to adjust the current digital twin developed by CIRCE.

In the second day, all partners visited two plants that FERTIBERIA has in Palos de la Frontera and Huelva. They were able to gain a better understanding of the urea and ammonia manufacturing processes at the Palos de la Frontera plant and the innovative fertilizer produced in Huelva, as well as to observe the technology, equipment and installations needed.