Demonstration of a 5-MWth Chemical Looping Combustion Unit Fueled by Lignite

Abstract

A 5-MW_th chemical looping combustion (CLC) unit was designed, built, operated, and demonstrated in China as part of the Chinese–European Emission-Reducing Solutions (CHEERS) project, funded by China’s Ministry of Science and Technology (MOST) and the European Union (EU)’s Horizon 2020. In the configuration designed by the Chinese partners, the air reactor (AR) is a transport bed, while the fuel reactor (FR) is a bubbling/turbulent fluidized bed. The solid circulation between the FR and AR is regulated by the overflow method, and the oxygen carrier (OC) from the AR cyclone returns to the FR riser. From June to September 2024, the 5-MW_th demonstration unit was operated and tested more or less continuously, with a thermal input ranging from 3.5 to 5.0 MW_th. During the operation, all solid fuel was fed into the dense bed of the FR, while only air was introduced into the AR. No electric or other external heating was applied, meaning that the whole pilot unit was heated by the oxidation of the OC within the AR. Hence, auto-thermal CLC operation was successfully achieved. Heating the unit was completed in 48 h; furthermore, switching to CLC mode was straightforward and took less than 1 h. During the operation, the temperature of the entire loop was stable. The temperatures of the AR and FR were 1000–1040 °C and 940–980 °C, respectively. Based on the operational data, the maximum CO₂ capture efficiency of the lignite-fed CLC unit was greater than 97%, and the minimum oxygen demand for unburnt gases from the FR was 2.45%. This work bridges the gap between lab-scale research and industrial applications in the field of CLC.