A new study published in Engineering has reported the successful demonstration of a 5‑MW_th chemical looping combustion (CLC) unit fueled by lignite, developed under the Sino‑European CHEERS project co‑funded by China’s Ministry of Science and Technology and the European Union’s Horizon 2020 program. As the largest CLC pilot unit worldwide, the facility features a Chinese configuration in which the air reactor operates as a transport bed and the fuel reactor functions as a bubbling/turbulent fluidized bed, with solid circulation regulated by an overflow method and oxygen carriers from the air reactor cyclone returning to the fuel reactor riser.

From June to September 2024, the demonstration unit was operated continuously with a thermal input ranging from 3.5 to 5.0 MW_th, using Norwegian ilmenite as the oxygen carrier and Indonesian lignite as fuel. The entire system achieved auto‑thermal CLC operation without external electric or other heating, relying entirely on heat released from the oxidation of oxygen carriers inside the air reactor; the unit was heated up within 48 hours, and the switch to CLC mode was completed in less than one hour. During stable operation, temperatures in the air reactor and fuel reactor remained steady at 1000–1040 °C and 940–980 °C, respectively.

Operational data show that the maximum CO₂ capture efficiency of the lignite‑fed CLC unit exceeded 97%, while the minimum oxygen demand for unburnt gases at the fuel reactor outlet reached 2.45%. The flue gas from the fuel reactor was dominated by CO₂, with only small amounts of carbon monoxide, hydrogen, and methane; the carbon dioxide concentration at the air reactor outlet remained mostly below 2% due to limited char carryover. Solid carbon conversion and char conversion both reached levels above 99.48%, reflecting nearly complete conversion of lignite fed into the dense bed of the fuel reactor. Concentrations of sulfur dioxide and nitrogen oxides emitted from the fuel reactor were measured at 332–815 ppm and 0–101 ppm (dry basis), respectively.

The research team observed that the primary air ratio in the air reactor and the bed inventory in the fuel reactor both influenced the oxygen demand of unburnt gases, while higher bed inventory generally improved combustible gas conversion. This long‑term auto‑thermal operation with high carbon capture efficiency and low oxygen demand fills the gap between laboratory‑scale research and industrial applications for solid‑fuel CLC systems, supporting the technical advancement of chemical looping combustion toward integration within industrial carbon capture, utilization, and storage chains.

The paper “Demonstration of a 5-MW_th Chemical Looping Combustion Unit Fueled by Lignite,” is authored by Zhenshan Li, Yang Wang, Weicheng Li, Geng Wei, Xinglei Liu, Shanhu Lin, Jiaye Li, Dan Li, Qingsong Meng, Li Nie, Vincent Gouraud, Shuting Wei, Patrice Font, Nils Erland L. Haugen, Øyvind Langørgen, Yngve Larring, Zuoan Li, Ningsheng Cai. Full text of the open access paper: https://doi.org/10.1016/j.eng.2025.07.017. For more information about Engineering, visit the website at https://www.sciencedirect.com/journal/engineering.