Power plants are prime candidates to apply CO2 capture for final storage as a mitigation option for climate change. Many CO2 capture concepts make use of a sorption−desorption cycle to separate CO2 from flue gas or O2 from air. These include commercial absorption processes, as well as processes using new sorbent formulations, adsorption, and high-temperature chemical looping cycles for CO2 and O2. All of these new processes must confront the large scale of carbon flows typical in a power plant. In this work, a common mass balance for all of these processes is used to define a parameter that highlights the minimum sorbent performance required to keep sorbent makeup costs at an acceptable level. A well-established reference system for which reliable commercial data exist (absorption with monoethanolamine, MEA) is used as a technoeconomic baseline to show that some of the sorbents being proposed in the open literature might need to be tested under laboratory conditions for tens of thousands of sorption−desorption cycles before they can be further considered as viable options for CO2 capture from power plants.

Cyclic carbonation and calcination reactions were investigated for capturing CO2 from combustion and gasification processes. Sorbent particles in the size range 600−1400 μm were subjected to multiple capture cycles at atmospheric pressure to obtain a surface mapping of conversion based on calcination and carbonation temperatures. Steam hydration of CaO was utilized to increase both pore area and pore volume to improve long-term conversion to CaCO3 over multiple cycles. The steam hydration improved the long-term performance of the sorbent, resulting in directly measured conversions as high as 52% and estimated conversions as high as 59% after up to 20 cycles. It is estimated that the increase in conversion has improved the economics of the proposed process to the point where commercialization is attractive. It has been shown that when carbonating in the temperature range from 700 to 740 °C, calcination temperatures from 700 to 900 °C can be used without seriously reducing the conversion of CaO for CO2 capture over multiple cycles. Processes based on this approach are expected to be able to reduce CO2 emissions from coal- and petroleum coke-fired fluidized bed combustors by up to 85%, while avoiding excessive sorbent replacement.