STUDY OF CO2 CAPTURE USING CO2 LOOPING COMBUSTION TECHNOLOGY

摘要

Absorption processes for CO2 separation employing solid sorbents such as limestone appear to be technically feasible and cost effective. At appropriate temperature and pressure, CO2 from flue gas stream is absorbed by CaO-based sorbent via the carbonation reaction, and the sorbent is then regenerated in a separate reactor and a nearly pure CO2 stream is produced suitable for industrial use or ultimate sequestration. This technology has now been demonstrated using the CANMET pilot-scale dual-fluidized bed system. Havelock limestone from eastern Canada, was used as the CO2 sorbent, while a synthesis gas mixture of air and CO2 (15%) was employed to represent combustion flue gas. Oxy-fuel combustion of biomass and coal was employed in the sorbent regenerating step, creating a high CO2 concentration off-gas stream suitable for sequestration. Pure O2 was mixed with recycled off-gas and this along with the excellent heat transfer characteristics of fluidized bed allowed us to use an O2 ratio of 40% in the combustion gas. In addition, samples were characterized for pore distribution (nitrogen adsorption/desorption: BET and BJH) and skeleton characterization (density by He pycnometry), as well as changes in sample volume during hydration (sample swelling). The results obtained showed successful hydration even for hydration periods as short as 15 min, and very favorable sample properties. Their pore surface area, pore volume distribution and swelling during hydration are very promising with regard to their use in additional CO2 capture cycles or SO2 retention.