Synthetic oxygen carrier C28 compared to natural ores for chemical looping combustion with solid fuels in 80 kWth pilot plant experiments

Chemical Looping Combustion (CLC) is a highly efficient CO2 separation technology with no direct contact between combustion air and fuel. A metal oxide is used as oxygen carrier (OC) in a dual fluidized bed to generate clean CO2. The use of solid fuels, especially biomass, is the focus of current research, because of the possibility of negative CO2-emissions. The OC is a key component, because it must meet special requirements for solid fuels, which are different to gaseous fuels. Most frequently naturals ores or synthetic materials are used as OC. Synthetic OC are characterised by higher reactivity at the expense of higher costs. For this reason, so far not so many experiments have been conducted on a larger scale with synthetic OC on solid CLC. This work deals with the synthetic perovskite C28 and investigating the suitability as oxygen carrier in an 80 kWth pilot plant for chemical looping combustion with biogenic fuels. The experiments show a significantly increased combustion efficiency of 99.6 % compared to natural ores and a major influence of the solid circulation rate on general performance, whereby carbon capture rates up to 98.3 % were reached. Furthermore, the role of the fuel reactor's counter-current flow column and its impact on better gas conversion was investigated. C28 suffered no deactivation or degradation over the experimental time, but first traces of ash layer formation, phase shifting and attrition of fines could be detected. The focus of further research should lie on long-term stability and reactivity for their high impact on the economic scale up of C28.

Automated summary

Chemical Looping Combustion (CLC) is a CO2 separation technology that utilizes a metal oxide as oxygen carrier in a dual fluidized bed to generate clean CO2. Synthetic materials are used as an oxygen carrier, offering higher reactivity but at a higher cost. This study focuses on investigating the suitability of synthetic perovskite C28 as an oxygen carrier in an 80 kWth pilot plant for CLC with biogenic fuels. The experiments show significantly improved combustion efficiency compared to natural ores and emphasize the importance of solid circulation rate and the role of the fuel reactor's counter-current flow column in gas conversion. Further research should focus on the long-term stability and reactivity of C28 for scaling up purposes.