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Funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Climate, Infrastructure and Environment Executive Agency. Neither the European Union nor the granting authority can be held responsible for them. Development of solar rotary kiln technology at the DLR for heating and treatment of particles 06 November 2025 | Stakeholders event | Zaragoza, Spain Juan Pablo Rincon Duarte, Megan Kirschmeier, Clarisse Lorreyte, Gkiokchan Moumin, Martin Roeb German Aerospace Center (DLR) –Institute of Future Fuels, Germany
www.pysolo.eu •Introduction: solar rotary kiln technology •Technology development at DLR •Challenges and main achievements •Further technological development in project PYSOLO •Outlook J. P. Rincon Duarte| PYSOLO | 06 Nov. 2025 2 Outline
www.pysolo.eu J. P. Rincon Duarte| PYSOLO | 06 Nov. 2025 3 Introduction Some interesting facts about conventional rotary kilns (RK) •A RK is a cylindrical vessel that rotates around the longitudinal axis •It is a device on the border between energy and process engineering •Suitable for drying, combustion, calcination, pyrolysis, or the thermochemical treatment of various materials. Device able to process diverse feedstock and control the residence time (tilt and rotation speed). •A RK is heated by gas (process burners), liquid, or solid fuel àusually high energy demand •Other aspects: dust generation, varying product quality, and tendency to lower thermal efficiency are barriers to the wider utilization of RK Source: 2022, Bojanovsky et. al., Rotary kiln, current state and perspectives Waste to energy Pyrolysis, gasification Sewage sludge treatment Solar energy 1990 2000 Development of main research areas in the past three decades Clinker and lime Waste incineration
www.pysolo.eu J. P. Rincon Duarte| PYSOLO | 06 Nov. 2025 4 Introduction Use of concentrated solar energy and solar rotary kilns 1980, G. Flamant et. al. Study on solar fluidized bed and solar rotary kiln: “Such reactors could find applications for conversion of concentrated solar energy, e.g. heating of gas by means of fluidized bed receiver, high temperature thermal storage with solid material, thermochemical storage involving gas-solid systems, preparative chemistry of carbonated materials, thermal treatment of ores, drying and dehydration” Direct solar radiation Use of solar heat for power or other applications Concentrator system, e.g. solar tower system Solar receiver / solar reactor Thermal energy
www.pysolo.eu J. P. Rincon Duarte| PYSOLO | 06 Nov. 2025 5 Solar rotary kiln description Example of DLR-rotary kiln with direct irradiation of treated material Screw feeder Aperture / Reactor window Crucible Motor Storage Gas Solid material Solar radiation Suction system for gases
www.pysolo.eu J. P. Rincon Duarte| PYSOLO | 06 Nov. 2025 6 Solar rotary kiln description Example of DLR-rotary kiln with direct irradiation of treated material Solar radiation Gas Solid particles
www.pysolo.eu J. P. Rincon Duarte| PYSOLO | 06 Nov. 2025 7 Research at DLR with solar rotary kilns Some of the processes that we have studied Thermal reduction of solid particles ~ 1000 °C Cobalt oxide, MnFeOx, SrFeOx Heating of solid particles 600 –1200 °C Aluminium oxide, bauxite, sand, olivine Heat storage (sensible / thermochemical heat) N2purification purposes Commodities CO2capture Metal recycling 700 –850 °C Thermochemical reactions with solid particles 650 –1000 °C Limestone, cement raw meal, lime, kaolin Aluminium Process Material Application
www.pysolo.eu J. P. Rincon Duarte| PYSOLO | 06 Nov. 2025 8 Research at DLR with solar rotary kilns Solar test facilities for technology development at DLR 25 kW Solar Furnace Solar Towers Solar Towers MW scale 20 kW Solar Simulator Synlight 300 kW Solar Simulator Cologne site Jülich site
www.pysolo.eu J. P. Rincon Duarte| PYSOLO | 06 Nov. 2025 9 Research at DLR with solar rotary kilns Batch-operated concepts Time SOLAM, 2015 Al smelting, 2000 SOLARTWINS, 2024 Solarization of the zeolite production: Calcination of kaolin as proof-of-concept https://doi.org/10.1016/j.jclepro.2023.137611 DÜSOL, 2019 https://elib.dlr.de/131236/ Design of a rotary kiln for a solar-powered air separation process Solar Aluminum Recycling in a Directly Heated Rotary Kiln https://elib.dlr.de/108902/
www.pysolo.eu J. P. Rincon Duarte| PYSOLO | 06 Nov. 2025 16 Further technological development in project PYSOLO Solar receiver design Ongoing solar receiver design and commissioning •15 kWtpower •Open and closed operation •System inclination up to 20° •To be tested at the solar simulator and solar furnace in Cologne
www.pysolo.eu J. P. Rincon Duarte| PYSOLO | 06 Nov. 2025 17 Further technological development in project PYSOLO Solar receiver design •Room temperature setup to understand: •How time of passage is affected by steep inclination angles •Increase in passage time possible with internal lifting structures •Results presented at SolarPACES 2025, publication in review process Particle Material Olivine (dp= 250 µm; 𝜌!≈ 1900 kg/m3) Inclination Angles 3-30° Rotational Speeds 1-8 RPM (For rolling regime) Mass Flow Rates 10-130 kg/hr Internal Lifting Structures
www.pysolo.eu J. P. Rincon Duarte| PYSOLO | 06 Nov. 2025 18 Further technological development in project PYSOLO Solar receiver design •Results deviate from correlation by 100% at 30° Θ!""#$%&'( =36° (for olivine) [2] 3 RPM •Maximum passage time àno particles flowing over the structures •10.4x increase in passage time at 30° Empty Kiln Internal Structures 𝜏 = 1.77 (𝐿"#$% 𝐷"#$% (Θ&''()*+," 𝛿"#$% (𝜔"#$% Inclination angle Rotation speed Angle of Repose * Derived using data for inclination angles of 1-6° Sullivan et al. (1927) Correlation [1]
www.pysolo.eu J. P. Rincon Duarte| PYSOLO | 06 Nov. 2025 19 Outlook PYSOLO Finalize commissioning of solar receiver Experimental testing at the solar simulator and solar furnace in Cologne scheduled for 2026 Support activities for the overall system analysis and scale up Validation of model for solar receiver (POLIMI-DLR) 20272026 Integration of internal structures
www.pysolo.eu J. P. Rincon Duarte| PYSOLO | 06 Nov. 2025 20 Outlook Sand sintering Copper recycling Bricks sintering Thermal processing of sewage sludge Colemanite processing MgCaCO3 Further development of the technology and expansion into other areas such as Research activities at DLR
www.pysolo.eu 21 www.pysolo.eu Thank you for your attention! [email protected] DLR – Institute of Future Fuels Department of Solar Chemical Process Development And special thanks to Stefania Tescari, Martina Neises-von Puttkamer, Lamark de Oliveira, Bruno Lachmann and the rest of our DLR-colleagues who have contributed to the development of solar rotary kiln technology at DLR This study is funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Climate, Infrastructure and Environment Executive Agency (CINEA). Neither the European Union nor the granting authority can be held responsible for them. The PYSOLO project receives funding from the Horizon Europe Framework Programme under grant agreement number 101118270.
