Chemical-Looping With Oxygen Uncoupling of Coal in a Spouted Bed

The objective of this study is to explore the potential of chemical-looping with oxygen uncoupling (CLOU) for coal. Theoretical models for chemical-looping combustion and unique experimental facilities are utilized for this proof-of-concept study.  Chemical-looping refers to indirect combustion and reforming processes for power generation and/or hydrogen production taking place in two reactors (a Reducer and an Oxidizer) with inherent CO₂ separation. Combustion is accomplished in the Reducer reactor using an oxygen carrier (metal oxide) instead of air in traditional combustion. The exhaust stream of the Reducer consists mainly of CO₂ and H₂O; therefore, upon condensation of steam, CO₂ is captured without requiring an expensive CO₂ separation unit. The metal oxides are re-oxidized with air in the Oxidizer reactor. Of particular interest to the combustion of solid fuels is chemical-looping with oxygen uncoupling, which enables O₂ to be dissociated from Cu oxides, thereby overcoming the slow solid-solid reduction reactions in chemical-looping combustion. To achieve excellent mixing of coal with oxygen carrier and subsequent fly ash/oxygen carrier separation via entrainment, a conical spouted-bed (Figure 1) reactor is explored. The experimental setup includes a bench-scale spouted bed reactor connected to a Flourier transform infrared (FTIR) spectrometer and an Agilent 5975C mass selective detector for gas product composition analysis in real time. The hydrodynamics of the spouted-bed are modeled following the basic principles of the Kunii and Levenspiel [1,2] 3-phase model modified for application to spouted-beds.

The focus of this poster is to provide a proof-of-concept of coal chemical-looping, accomplished by optimal design of a spouted-bed reactor, and simulate and analyze the experimental results of chemical-looping reduction in spouted-bed reactors.  The potential of in-situ ash separation via entrainment is explored and showcased in the bench-scale setup.

Figure 1: Spouted-bed chemical-looping setup used in this work.

Acknowledgement: This material is based upon work supported by the National Science Foundation under Grant No. 1054718.

[1]      D. Kunii, O. Levenspiel, Bubbling bed model: model for the flow of gas through a fluidized bed, I & EC Fundamentals. 7 (1968) 446¨C452.

[2]      D. Kunii, O. Levenspiel, Bubbling bed model for kinetic processes in fluidized beds: Gas-Solid Mass and Heat Transfer and Catalytic Reactions, I & EC Process Design and Development. 7 (1968) 481¨C492.