Browsing by Author "Hughes, Robin W."

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    The effect of HCl and steam on cyclic CO2 capture performance in calcium looping systems
    (Elsevier, 2017-08-14) Symonds, Robert T.; Lu, Dennis Y.; Macchi, Arturo; Hughes, Robin W.; Anthony, Edward J.
    Calcium looping is CO2 capture technology that is considered to be technically feasible at an industrial scale using a variety of fuels such as natural gas, coals, biomass, refuse derived fuels, and biofuels. Unfortunately, many of these fuels contain significant quantities of chlorine which principally converts to gaseous HCl during combustion or gasification. To date, very few studies have examined the effect of HCl on sorbent CO2 capture performance using calcium-based sorbents under realistic carbonation and calcination conditions. In this work, experiments were conducted using thermogravimetric analysis and fixed bed reactor testing to determine the effect of HCl addition during carbonation and calcination over repeated cycles using a Canadian limestone. The presence of HCl was found to increase sorbent reactivity towards CO2 capture when steam was injected during calcination. The resulting decomposition of CaCl2 to CaO during calcination caused changes in the particle morphology, which in turn decreased the CO2 diffusional resistance during carbonation. Fixed bed test results provided confirmation of full sorbent dechlorination under typical oxy-fuel calcination conditions. It was shown that both particle surface area and pore volume were higher during tests where HCl was present during carbonation and that greater than 99% HCl capture could be achieved without adversely affecting sorbent CO2 capture performance when steam was present during both carbonation and calcination.
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    Scale-up challenges and opportunities for carbon capture by oxy-fuel fluidized beds
    (Elsevier, 2018-10-09) Seddighi, Sadegh; Clough, Peter T.; Anthony, Edward J.; Hughes, Robin W.; Lu, Ping
    Oxy-fuel combustion is a promising technology for carbon capture and storage (CCS) from large point sources. In particular, fluidized bed (FB) boilers represent one of the power generation technologies capable of utilizing the oxy-fuel concept. This paper reviews the published material on the key aspects of oxy-fuel circulating FB, including the boiler heat balance, heat transfer mechanisms, furnace hydrodynamics, and the mechanical and chemical mechanisms of the process. In particular, it demonstrates the challenges of utilizing high inlet O2 concentrations in the oxy-fuel process in fluidized beds. This requires significantly more efficient gas-particle clean-up technology (especially for Cl with perhaps 19% retention and Hg with 2.15 μg/m3 in flue gases), high circulating solids flux and, hence, significant heat extraction outside the furnace (up to 60% of the boiler’s total heat extraction). Scale-up of oxy-fuel CFB technology can partially compensate for the energy penalty from air separation by furnace downsizing when operating at high inlet O2 concentrations. Critically, while there are numerous measurement campaigns and corresponding models from the pilot and, to a lesser extent, industrial scale, the paper endeavors to answer the questions about what information taken from such experimental campaigns is reliable, useful for future design, and for scale-up.