Analysis of Oxygen Carrier Reactivity and Fuel Conversion in Copper-Based Chemical Looping with Oxygen Uncoupling (CLOU) Systems

2015 AIChE Annual Meeting- "Chemical Looping Processes"

Performance of a 10 kW_th Dual Fluidized Bed Chemical Looping Combustion Reactor Operating in iG-CLC and CLOU Modes

Kirsten M. Merrett and Kevin J. Whitty

Dept. of Chemical Engineering, University of Utah, Salt Lake City, UT

ABSTRACT

Chemical looping combustion (CLC) is a technology to combust solid fuels while intrinsically separating the greenhouse gas CO₂. This eliminates the energy cost associated with gas separation, making CLC an attractive technology for CO₂ separation. CLC involves circulating a metal-based "oxygen carrier" between two reactors in which it is oxidized by air and then reduced by a fuel, in essence combusting the fuel. In the variant of CLC known as chemical looping with oxygen uncoupling (CLOU), the oxygen carrier releases gas-phase oxygen as O₂ once in the fuel reactors reducing environment, allowing for a gas-solid reaction to occur. Particles are then circulated to the air reactor and reoxidized. The natural mineral ilmenite presents a cost-effective oxygen carrier material with demonstrated strength and cyclability, while copper allows for the desired oxygen uncoupling behavior of the metal oxide during CLOU operation.

The University of Utah has developed a 10 kW_th bench scale dual fluidized bed chemical looping combustion system. The goal of the study presented here was to assess system performance and compare conventional chemical looping combustion, known as indirect gasification-CLC or iG-CLC, with CLOU chemical looping. In this study two different fuels, coal and coal char, were processed and the degree of fuel conversion, CO₂ capture efficiency and CO₂ purity were evaluated. Performance of the unit itself is also evaluated by changing variables such as temperature, flow rate, bed inventory, and circulation rate to determine optimal performance.