Calcium looping process for post-combustion CO2 capture – concept, trend of research, future perspective and ongoing research work in Niigata University, Japan

Carbon Capture and Storage (CCS) technologies have been extensively investigated worldwide to suppress the increase in CO2 concentration in the atmosphere. One of post-combustion CO2 capture technologies is Calcium Looping (CaL) process, which is a dry absorption/desorption process using dual-fluidized bed solid circulation system. The CaL process includes two reactors, as portrayed in Figure 1-(a). Capture of CO2 by CaO is conducted in one reactor (called the carbonator) at approximately 873 K, and a decomposition reaction of CaCO3 to CaO and CO2 is conducted in another reactor (called the regenerator) at approximately 1223 K. The heat to decompose CaCO3 is supplied by burning fuel with pure oxygen (Oxyfuel combustion) in the regenerator so that the flue gas consists only of CO2 and H2O. This process has attracted a great deal of attention as an energy- and cost-efficient post-combustion CO2 capture process.
In this seminar, the concept of CaL process is firstly introduced, including material and heat balance, heat recovery (steam quality, heat transfer tube arrangement and power generation), chemical kinetics of CO2 capture by CaO, and design of fluidized bed reactor. Then the recent trend of research towards the development of CaL process, from development and evaluation of sorbent to plant operation studies are summarized. Finally, the perspective of the future work is discussed and ongoing research work in Niigata University is introduced. Especially the experimental works on associated problems with coal combustion in regenerator are discussed in detail, as illustrated in Fig.1-(b). The combustion phenomena in the regenerator is basically similar to oxyfuel fluidized bed combustion which use O2-CO2 mixture, but the regenerator of CaL process has different characteristics from oxyfuel FBCs.