Welcome to the final blog by Maria Erans of Cranfield University, on the UKCCSRC Call 2 project, UK Demonstration of Enhanced Calcium Looping and first Global Demonstration of Advanced Doping Techniques. (PI:Edward Anthony)
This UKCCSRC Call 2 project, called “UK Demonstration of Enhanced Calcium Looping and first Global Demonstration of Advanced Doping Techniques”, has focussed on the demonstration of advanced doping techniques through experimental investigations, as well evaluating the use of calcium looping cycles for different industrial processes. Additionally, spent sorbent was successfully used to produce cement, supporting the idea that this technology could also help to decarbonize the cement industry.
Carbonate looping cycles are a second generation CO2 capture technology, based on the reversible carbonation of lime-based sorbents. As such, they have been the subject of intense research efforts, due to the low cost of the sorbent and the low energy penalty. However, there are several challenges to move this technology forward. Namely, the sorbent reactivity decays over time, primarily due to sintering, and scale-up issues remain. This project focused on both of these challenges.
As a start point, we tested limestone on our 50 kWth CFB system (with two interconnected circulating fluidised beds) in order to make spent sorbent for cement making. The cement making was a success as the cement produced from this work showed comparable behaviour to commercial cements. Subsequently, we redesigned and reconstructed a 25 kWth CBF-BFB (with a circulating fluidised bed carbonator and a bubbling circulating fluidised bed calciner) in order to achieve higher capture. Another important feature of this work was that the gas burners that used to feed the two reactors were removed and two gas preheating lines were fitted in order to be able to feed both reactors with a desired mixture of gases. As a result, we were able to test flue gas compositions that are typical of different industries, most notably the steel and cement industries.
Once the reactor redesign was finished, we started with experimental campaigns, first, to commission the rig and then to explore the effect of different gas composition and enhancement methods. We adjusted the HBr-doping technique to produce around 40 kg of material and tested the modified sorbent in different experimental runs. The results showed the benefits of doping CaO-based sorbents, and the work demonstrated significantly higher capture efficiencies and lower attrition. Finally, we tested calcium aluminate pellets, which also showed more stable behaviour due to the presence of a mesoporous alumina phase that stabilised the structure delaying sintering.
During the project, it was a pleasure to work with several researchers like Dr Michal Jeremias, Dr Lunbo Duan, and with Prof Ben Anthony who made this investigation possible. Also, big thanks to our collaborators from Imperial College, especially to Dr Liya Zheng and Prof Paul Fennell for all the support and helpful insight that made the successful completion of this project possible.