Rate Analysis of Chemical-Looping with Oxygen Uncoupling (CLOU) for Solid Fuels

Abstract

Chemical-looping with oxygen uncoupling (CLOU) offers a promise to reduce energy penalty by facilitating the capture of CO2 emitted from power plants. It has a potential to lower the oxygen carrier inventory of the fuel reactor in contrast to chemical-looping combustion (CLC). The primary mechanism in CLOU for the combustion of solid fuels is their reaction with gaseous oxygen released by the decomposition of a metal oxide, which differs from CLC of solid fuels where the solid fuel has to be gasified first. The slower gasification reaction in CLC is subsequently followed by combustion of the fuel with a circulating oxygen carrier. The present study is concerned with the rate analysis from reported batch fluidized bed CLOU experimental data of Mexican petcoke particles by a CuO/ZrO2 oxygen carrier. The methodology to determine the kinetic parameters for CuO decomposition and solid fuel oxidation during the fuel reactor stage and for Cu2O oxidation in the air reactor stage have been discussed. The results of the study are expected to help in the development of a process model for CLOU, furthering the development of a pilot scale process.

Materials for Chemical-Looping with Oxygen Uncoupling

“…Eyring et al [77] investigated the rate of decomposition of fine CuO in a TGA in the temperature range of 750-950 ∘ C, found that the decomposition could be explained by an Arrhenius type of expression, and calculated an activation energy of 327 kJ/mol for the decomposition reaction, which was very similar to that found previously by Chadda et al [126]. A somewhat smaller activation energy of 281 kJ/mol was obtained by Sahir et al [127] for the decomposition reaction of a freeze-granulated CuO/ZrO 2 oxygen carrier.…”

Kinetic analysis of a Cu-based oxygen carrier: Relevance of temperature and oxygen partial pressure on reduction and oxidation reactions rates in Chemical Looping with Oxygen Uncoupling (CLOU)

“…(18), including nucleation mechanism [18,21,22] or first order chemical reaction [14,16]. The Langmuir-Hinshelwood mechanism is a surface reaction model widely used for gassolid catalytic reactions.…”

“…Most of the works were focused on the evaluation of the effect of temperature on reaction rate, thus calculating the activation energy of the process. Two types of reaction rate equations have been used to represent the CuO oxygen uncoupling and Cu 2 O oxidation reaction for the CLOU process [14,15]:…”

“…(7). Thus, the following values for the kinetic activation energy has been reported: 58 kJ/mol [15] for CuO/TiO 2 , and 67 kJ/mol [15] or 20 kJ/mol [14] for CuO/ZrO 2 .…”

“…However, only experiments far from the O 2 equilibrium were considered to obtain a reaction order of 1. Sahir et al [14] calculated the reaction order with respect to CuO and obtained a value of 0.…”