Comparison of experimental results from three dual fluidized bed test facilities capturing CO2 with CaO

Postcombustion CO2 capture technologies using CaO as a regenerable solid sorbent have emerged as a promising route to reduce the electricity penalty and the cost of CO2 capture from flue gases of both new and existing fossil fu elled power plants. Rapid progress is taking place in the understanding of these processes at different levels. However, experimental information, validating the concept under continuous operating conditions similar to those expected for large-scale application, remain scarce. We present here a comparative analysis of the results obtained in three laboratory-scale dual fluidized bed (DFB) test facilities in Spain, Germany and Canada. The test facilities range from 10 to 75 kW th with riser heights between 4.5 and 12.4 m. They have been operated to capture CO2 with CaO from simulated flue gases in the bubbling, turbulent and fast fluidization fluid-dynamic regimes. The carbonator reactors are interconnected with regenerators, where the CaCO3 decomposition has been conducted continuously and semi-continuously, operated in both air-combustion and oxy-combustion modes. Many stationary and non stationary states have been achieved at different combinations of the key operating parameters (e.g. calcium looping ratio). All DFB test facilities showed a carbon balance closure of high quality in most tests. The trends of CO2 capture efficiency with respect to operating conditions and sorbent characteristics are compared and a discussion is made on the most appropriate methodology to conduct future tests under a joint new FP7 project (CaOling) that aims at the rapid scaling up of the calcium looping technology.