A Simulation Based Parametric Study of CLOU Chemical Looping Reactor Performance

Authors: Zachary Reinking ^a, Kevin J.Whitty ^a, and JoAnn S.Lightyb ^b
a Department of Chemical Engineering, University of Utah, 50 S. Central Campus Drive, Room 3290, Salt Lake City, UT 84112, USA
^b Department of Mechanical and Biomedical Engineering, Boise State University, 1910 University Dr., Boise, ID 83725, USA

Source: This paper was published in 2021, Volume 215 of Fuel Processing Technology.

Abstract: Chemical looping with oxygen uncoupling (CLOU) is a variant on chemical looping combustion in which the oxygen carrier releases gaseous O₂ in the fuel reactor, making it well-suited for solid fuels, since the released gaseous O₂ readily reacts with solid char. This study presents several computational fluid dynamic (CFD) simulations of copper-based CLOU in a dual fluidized bed system, each with different operating conditions. The modeling predicted that coal particle sizes as large as 1000 μm did not significantly affect performance. Increased oxygen carrier copper loading resulted in an excess of gaseous oxygen in the product gas stream. Decreasing the oxygen carrier bed mass as well as reducing the air reactor fluidizing velocity did not supply enough oxygen to the fuel reactor to complete combustion of the coal. This generated a failure state in which the temperature continued to decrease in the fuel reactor from the lack of combustion, which in turn reduced the O₂ equilibrium partial pressure, further lowering the amount of combustion possible. Sufficient O₂ can be maintained in the fuel reactor by ensuring a high enough air reactor velocity and a large enough supply of oxygen carrier inventory to handle the chosen coal feed rate.