Browsing by Author "Lu, Dennis Y."

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    Combined calcium looping and chemical looping combustion for post‐combustion carbon dioxide capture: process simulation and sensitivity analysis
    (Wiley, 2016-05-24) Duhoux, Benoit; Mehrani, Poupak; Lu, Dennis Y.; Symonds, Robert T.; Anthony, Edward J.; Macchi, Arturo
    In this work, a combined calcium looping and chemical looping combustion (CaL--CLC) technology is simulated at thermodynamic equilibrium conditions and the results in terms of efficiency, power production, and solids circulation rates are compared with the case of using CaL alone. In addition, a new solids looping configuration in the CaL--CLC process is proposed with the purpose of mitigating the loss of calcium oxide conversion after high cycle numbers. Simulations show an improved process efficiency of the CaL--CLC method compared with CaL alone (34.2 vs. 31.2 % higher heat value) and an increased power output (136 vs. 110 MWe additional power) due to the higher energy requirement to preheat the reactants. A sensitivity analysis of the process operating parameters highlights the particular importance of the temperature difference between reactors, which has a strong impact on the required mass of solids circulating in the loops. Finally, partial carbon dioxide capture scenarios are considered and indicate that lower capture levels are suitable to match regulation targets.
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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.