Abstract
Chemical looping with oxygen uncoupling (CLOU) is an innovative alternative to conventional combustion. CuO/ZrO2 oxygen carriers were tested in this system for their effectiveness and resilience. Cupric oxide (CuO) was demonstrated to be a reliable oxygen carrier for oxygen-uncoupling with consistent recyclability even after 50 redox cycles in a thermogravimetric analyzer (TGA). The reduction of CuO to generate Cu2O and oxygen was observed to be improved markedly for experiments operated at higher temperatures; however, the oxidation of Cu2O by air to generate CuO was hindered for experiments carried out at elevated temperatures. The reduction rate of fabricated CuO/ZrO2 particles containing 40% CuO was enhanced with increasing temperature and decreased with increasing particle size for experiments operated in a fixed bed reactor. The geometrical contraction and Avrami-Erofe’ev models were demonstrated to be appropriate for describing the reduction and oxidation of CuO/ZrO2, respectively. The activation energies for the reduction and oxidation were determined to be 250.6 kJ/mol and 57.6 kJ/mol, respectively, based on experimental results in the temperature range between 850 and 1000 °C.
Highlights
Chemical looping combustion (CLC) is a novel and effective combustion technique developed to achieve high purity CO2 in flue gas
Regardless of this reduction in oxidization efficiency, Cupric oxide (CuO) exhibited excellent oxygen uncoupling even after a 50-cycle operation, corresponding to the results reported by previous researchers [10]
While the size of particles varied between figures, the pore size and structure seemed to be rather constant, indicating that CuO is feasible as an oxygen carrier for chemical looping with oxygen uncoupling (CLOU) operations because of its stability and recyclability
Summary
Chemical looping combustion (CLC) is a novel and effective combustion technique developed to achieve high purity CO2 in flue gas. The overall energy balance of reactions involved for CLC process is exothermic, and the heat released could be utilized for various applications [1]. For chemical looping combustion of solid fuels, such as coal and petroleum coke, solid fuel gasification is frequently believed to be the rate-limiting step. A chemical looping with oxygen uncoupling (CLOU) process was subsequently suggested to be an alternative to skip solid fuel gasification. Oxygen molecules are uncoupled from metal oxides for experiments conducted in an oxygen-free atmosphere at high temperatures [4], as illustrated by Equation (1). The released oxygen is subsequently combusted with fuels, as described by Equation (2)
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