Development and Performance of CaO/La₂O₃Sorbents during Calcium Looping Cycles for CO₂Capture

Abstract

The calcium looping cycles method has been identified as an attractive method for CO2 capture during coal combustion and gasification processes. However, it is well-known that the capture capacity of CaO undergoes a rapid decrease after mutiple cycles. In order to improve the stability of CO2 capture capacity in CaO, this paper focuses on the development and performance of the synthetic CaO/La2O3 sorbents for calcium looping cycles.The sorbents were synthesized by three different methods: dry physical mixing, wet chemistry, and sol−gel combustion synthesis (SGCS). Their multicyclic CO2 capture capacity and the effect of the additive La2O3 were investigated in a fixed bed reactor system. The results indicate that the additive of La2O3 plays a positive role in the carbonation/calcination reactions, and the SGCS-made synthetic sorbent is composed of ultrafine well-dispersed hollow structured particles which are beneficial to the gas-phase diffusion on the surface area and can prevent small CaO particles from agglomeration effectively. As a result, the novel synthetic sorbent with the molar ratio of Ca to La of 10:1 made by the SGCS method provides the best performance of a carbonation conversion of 72% under mild calcination conditions and a carbonation conversion of 36% under severe calcination conditions (high temperature and high CO2 concentration) after 20 cycles.