Numerical Investigation of Nickel–Copper Oxygen Carriers in Chemical-Looping Combustion Process with Zero Emission of CO and H₂

Abstract

The chemical-looping combustion (CLC) technique with an intrinsic feature for carbon capture is playing a critical role in the industrial process planning. As the key technology in CLC, the behaviors of oxygen carriers with different weight ratios of NiO/CuO are investigated using the two-fluid model in this work. The kinetic theory of granular flow is employed for the description of particle motion, while the EMMS model is used to clarify the effect of mesoscale structure on gas–solid interaction in the fuel reactor. With the coexistence of Ni and Cu in the oxygen carriers, a zero emission of H2 and CO is observed at the outlet of the fuel reactor, while the intermediate products of H2 and CO arise in the system with Ni-based oxygen carriers. The complete conversion of CH4 is observed in the fuel reactor with various components of Ni–Cu oxygen carriers. The reactivity of CuO and NiO with gas fuel is analyzed, and the equilibrium state in the CLC system with different weight ratios of NiO/CuO is computed and compared. Moreover, different behaviors of oxygen carriers with mechanical mixing of nickel oxide and copper oxide are explored in the fuel reactor compared with that of Ni–Cu oxygen carriers. In addition, the bubble disturbance leads to the nonuniform distribution of reaction rate in the FR. The simulation results indicate that the Ni4Cu12 oxygen carriers have the most vigorous interaction with gas fuel, whereas the oxygen carriers with mechanical mixing of metal oxides are not recommended in the CLC process. The study assists in providing new insight into the understanding of oxygen carriers in the CLC system.

Numerical Investigation of a Syngas-Fueled Chemical Looping Combustion System

“…The grid independence test has been conducted in our previous work. 32 The detailed properties of the CLC system and parameters adopted in the current simulation are summarized in Table 3.…”

“…and solid bulk viscosity λ s . An EMMS-based drag model considering the effects of the mesoscale structure in the CLC system is employed, which has been proved to be reasonable by many researchers , and our previous work. , The expression of interphase momentum exchange coefficient is given by eq , where Re and ω­(ε g ) are the Reynolds number and correction factor.…”

“…Furthermore, each case in the current study is simulated with a total physical time of 80 s. The computational domain is uniformly divided into 122 × 448 cells in the horizontal and vertical directions, respectively. The grid independence test has been conducted in our previous work . The detailed properties of the CLC system and parameters adopted in the current simulation are summarized in Table .…”