Simulation study of chemical looping with oxygen uncoupling of municipal solid waste tar model compounds by ReaxFF molecular dynamics

Abstract

Context

The chemical looping with oxygen uncoupling (CLOU) technology offers a low-carbon approach for municipal solid waste (MSW) management. However, tar generated from MSW pyrolytic-gasification can impair the cyclic reactivity of oxygen carriers (OCs). This study uses reactive force field molecular dynamics (ReaxFF MD) simulations to examine the interactions between three tar model compounds (toluene, phenol, and naphthalene) and CuO OCs during CLOU. The results indicate that tar initially undergoes thermal cracking, while CuO releases small amounts of O radicals that facilitate the reaction. The oxygen release rate and capacity of CuO are strongly influenced by temperature. All three tar compounds produce intermediate C₂H₂, which is further oxidized to C₂O₂ in the cases of phenol and naphthalene. CuO can nearly completely oxidize these tar compounds to CO₂ and H₂O at stoichiometric ratio, with only minor CO and H₂ byproducts. The research provides guidance for promoting CLOU technology in the efficient and clean energy utilization of MSW.

Methods

The models of MSW tar compounds and CuO are constructed using Materials Studio (MS) and are preliminarily optimized with the Forcite module. ReaxFF MD calculations are conducted using the ReaxFF module within the Amsterdam Modeling Suite (AMS) computational platform, employing force field parameters of C/H/O/N/S/Mg/P/Na/Cu/Cl. The temperature control is maintained using the Nose–Hoover chain (NHC) thermostat. The first-order Arrhenius equation is utilized to calculate the activation energy of the reaction process.