Industrial & Engineering Chemistry Research, Vol.58, No.8, 2801-2811, 2019
110th Anniversary: Kinetic Model for Syngas Chemical Looping Combustion Using a Nickel-Based Highly Performing Fluidizable Oxygen Carrier
The study reports a kinetic model for a nickel based highly performing oxygen carrier (HPOC). This HPOC is free of nickel aluminates and can perform very efficiently at lower temperatures (i.e., 550-650 degrees C). In this study, a kinetic model is proposed to predict syngas chemical looping combustion (CLC) using an HPOC. The syngas used in this study emulates the syngas that can be derived from biomass gasification containing H-2, CO, CH4, and CO2. To establish the kinetic model, isothermal runs are developed in the CREC riser simulator, which is a mini-batch fluidized bed reactor. The operating conditions are varied between 2 and 40 s reaction times and 550-650 degrees C, with the H-2/CO ratio being 2.5 and 1.33 and with the psi parameter (fuel stoichiometric oxygen to HPOC oxygen ratio) being 0.5 and 1. For the 2.5 and 1.33 H-2/CO ratios, a 92% CO2 yield with 90% CO, 95% H-2, and 91% CH4 conversions are achieved. In addition, the HPOC shows an oxygen transport capacity ranging between 1.84 and 3.0 wt % (gO(2)/gOC) with a 40-70% oxygen carrier oxygen conversion. The solid-state kinetics considered uses of a nucleation and nuclei growth model. The proposed kinetics leads to a model with 10 independent intrinsic kinetic parameters. The various kinetic parameters are determined via numerical regression within a 95% confidence interval and small cross correlation coefficients. According to the frequency factors obtained, the reactivity of the species with a HPOC can be expressed following the H-2 > CO > CH4 order. Given that the HPOC shows high performance and stability, it is anticipated that the developed kinetic model could contribute to establishing large-scale reactor CLC for syngas combustion.