Improved Long-Term Conversion of Limestone-Derived Sorbents for In Situ Capture of CO₂ in a Fluidized Bed Combustor

Abstract

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.

The calcium looping cycle for CO2 capture from power generation, cement manufacture and hydrogen production

“…calcium acetate, calcium ethanoate (Lu et al, 2006;Lu, H. et al, 2008;Liu et al, 2010a) with particular success using a MgO support (Liu et al, 2010b) to similarly enhance the reactive surface area; dispersal of CaO within an inert porous matrix such as mayenite (Li et al, 2005;Li et al, 2006;Pacciani et al, 2008a) to improve mechanical stability; and use of cementitious binders (Manovic and Anthony, 2009a; to improve mechanical stability. Sorbent reactivity can be periodically improved by hydration of calcined sorbent, though this is often at the expense of mechanical strength of the sorbent (Hughes et al, 2004;Fennell et al 2007b;Manovic and Anthony, 2007;Manovic and Anthony., 2008a;Sun et al, 2008;Zeman, 2008). Thermal preactivation / pre-treatment, by treating sorbent at high temperature under N2, has been found to improve long-term reactivity of sorbents (Manovic and Anthony, 2008b;.…”

CO2 capture by calcium aluminate pellets in a small fluidized bed

“…The most simple precursor is Ca(OH)2 [6]; however, numerous other precursors have been investigated, such as calcium acetate, calcium formate, calcium nitrate [7], amongst others. These precursors have been shown to give a CaO of a very high porosity and surface area [8,9].…”

Investigation on SO2 emission from 410t/h circulating fluidized bed boiler burning petroleum coke and coal

“…The calcium content and size distribution are generally the most important index for power plant to select limestone, while the microstructure [15,16] as another important index is always neglected. From Tables 3 and 4, the two selected limestones have similar calcium content and size distribution, but their sulfur retention abilities are quite different.…”