Matching of kinetics of CaCO3 decomposition and CuO reduction with CH4 in Ca–Cu chemical looping

Abstract

Ca-Cu chemical looping (CaL-CLC) based on calcium looping is a novel and promising process for CO 2 capture. The concept utilizes the heat released from the exothermic reduction of CuO to support the endothermic regeneration of CaO-based sorbents. Therefore, it is important for the two major reactions to have matching kinetics. This work assesses kinetics of the two reactions in a calciner under the conditions of interest for CaL-CLC. The reaction rates of the decomposition of CaCO 3 and reduction of CuO-based material with CH 4 were measured in a TGA by varying the temperature and gas atmosphere, and two gas-solid reaction models were utilized for the determination of the kinetic parameters. On the basis of these results, a dynamic model was developed to investigate the simultaneous reduction of CuO and decomposition of CaCO 3 in an adiabatic fixed-bed reactor operating at 1 atm. The simulation resultsshowed that the reduction of CuO completed extremely fast under all test conditions, and it could lead to hot spots in the calciner. It was found that addition of steam into the reducing gas could enhance the reaction rate of CaCO 3 decomposition and help it match the fast rate of CuO reduction, then reduce the formation of hot spots. Also, steam could be used to control the movement of reaction front. Although CO 2 could be used to control the reaction front as well, the higher CO 2 partial pressure in CH 4 was found to slow down the decomposition of CaCO 3 leading to incomplete reaction.

Cyclic Oxygen Release Characteristics of Bifunctional Copper Oxide/Calcium Oxide Composites

“…A wide range of oxygen carriers has been proposed and tested by numerous researchers, as summarized elsewhere . In recent years a new process, integrated chemical looping combustion and calcium looping combustion, has been proposed . In this process, the use of CuO/CaO composites is suggested to provide two functions: transporting oxygen and capturing CO 2 .…”

Combined Calcium Looping and Chemical Looping Combustion for Post‐Combustion Carbon Dioxide Capture: Process Simulation and Sensitivity Analysis

“…The combustion of a solid fuel in a CLC scenario is possible, but natural gas has been chosen to avoid the presence of sulfur and ash because both affect the sorbent performance negatively . The reduction of copper oxide by methane in composite CaL–CLC pellets has also been investigated by multiple authors and fast reaction kinetics were observed; this was also positive for the process because it favored the complete reduction of copper, and thus, the complete release of the required heat for calcination.…”

“…This process has previously been simulated for steam–methane reforming in a fixed‐bed configuration . Although fixed beds are easier to operate, fluidized‐bed reactors were chosen in this work due to the mitigated risk of hot spots and the continuous need for fresh sorbent addition. Moreover, the operation of fluidized beds generates a continuous feed of CO 2 to the compression train, whereas fixed beds would require the installation of multiple units to achieve such an operation.…”

CO2 capture from the calcination of CaCO3 using iron oxide as heat carrier

“…Extensive literature has been published in recent years about the application of the CLC concept at different pilot scales (Lyngfelt and Thunman, 2005;Linderholm et al, 2008;Forero et al, 2009;Kolbitsch et al, 2010;Lyngfelt, 2011;Fan et al, 2012). The use of a CueCuO chemical loop to carry out the calcination of CaCO3 on the basis of the unmixed combustion process (Lyon and Cole, 2000) has been also recently proposed, showing promising results in terms of low costs and high energy efficiency (Abanades et al, 2010;Kierzkoska and Müller, 2012;Martínez et al, 2014, Qin et al, 2015. Most CLC configurations consist of interconnected fluidized-bed reactors, which facilitate the transport of the oxidized carrier to the fuel reactor and its subsequent regeneration in the air reactor (Lyngfelt et al, 2001;Ishida et al, 2002).…”