A Multi-Scale Model for Nickel-Based Oxygen Carrier in Chemical-Looping Combustion

The selection of oxygen carrier (OC) particles is crucial for the development of chemical-looping combustion (CLC) technology. Common OC particle models often involve first-order chemical reactions with respect to the concentration of fuel gas, which may not be able to account for the complex reaction mechanisms taking place on the contacting surface between gas and solid reactants. In this work, we apply a multiscale modelling framework on NiO-based OC particle in order to explicitly consider and understand the effect of reaction kinetics. The proposed multiscale model consists of gas diffusion model and surface reaction. Continuum equations are used to describe the gas diffusion inside OC particles, whereas mean-field approximation and kinetic Monte Carlo methods are adopted to simulate the microscale events, such as molecule adsorption and elementary reaction, occurring on the contacting surface. These sub-models communicate through a boundary condition that defines the mass fluxes of both reactant and product gas species. Surface reaction mechanisms and the corresponding reaction rate constants considered in the present work are obtained from a systematic density functional theory (DFT) analysis. The qualititive comparison with experimental data available in the literature suggests that the kMC-based multiscale model is able to provide better results than the MFA-based counterpart. A sensitivity analysis on the rate constants of key elementary reactions, length of intra-particle pore, and particle porosity was conducted to assess the effect of reaction kinetics and mass transport on the overall reaction process and validate the proposed multiscale model. The simulation results show reasonable tendencies and responses to changes in these modelling parameters, which indicates that the proposed multiscale modelling scheme on OC particle is suitable. To the author's knowledge, this is the first implementation of a multiscale model in CLC technology

Recent advances on first-principles modeling for the design of materials in CO2 capture technologies

The final publication is available at Elsevier via https://doi.org/10.1016/j.cjche.2018.10.017� 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Novel technologies in consideration of industrial sustainability (IS) are in urgent need to satisfy the increasing demands from the society. IS realizes the production of materials and while maintaining environmental and resource sustainability. The chemical materials used in CO2 capture and storage (CCS) technologies play a significant role in the disposal of greenhouse gas emissions coming from large stationary fossil-fired power plants, which breaks the principle of IS and brings severe environmental problems. This study aims at providing a detailed review of first-principles modeling (density functional theory, DFT) of materials in CO2 capture technologies. DFT analysis provides insight into the atomic properties of the studied systems and builds an efficient guidance of the future design of the materials used in CO2 capture technologies. Major materials including oxygen carriers, metal organic frameworks, membranes, zeolites, ionic liquids and some other promising candidates are considered. The computational studies bring the outcomes of the adsorption behaviors, structural characteristics and accurate force fields of the studied materials in short turn-around times at low cost. This review can stimulate the design of novel materials with specific target of CO2 capture and promote the industrial sustainability of fossil fuel combustion technologies.Chinese Scholarship Counci

A Multi-scale model for CO2 capture: A Nickel-based oxygen carrier in Chemical-looping Combustion

In this work, we present a multi-scale modelling framework for the Ni-based oxygen carrier (OC) particle that can explicitly account for the complex reaction mechanism taking place on the contacting surface between gas and solid reactants in Chemical Looping Combustion (CLC). This multi-scale framework consists of a gas diffusion model and a surface reaction model. Continuum equations are used to describe the gas diffusion inside OC particles, whereas Mean-field approximation method is adopted to simulate the micro-scale events, such as molecule adsorption and elementary reaction, occurring on the contacting surface. A pure CO stream is employed as the fuel gas whereas the NiO is used as the metal oxide because it is one of the mostly used material in laboratory and pilot-scale plants. Rate constants for the micro-scale events considered in the present work were obtained from a systematic Density Functional Theory (DFT) analysis, which provides a reasonable elementary reaction kinetics and lays a solid foundation for multi-scale calculations. A sensitivity analysis on the size of intra-particle pore and the adsoprtion rate constant was conducted to assess the mass transport effects on the porous particle. The proposed multi-scale model shows reasonable tendencies and responses to changes in key modelling parameters