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Research Papers: Fuel Combustion

Numerical Simulation Comparison of Two Reactor Configurations for Chemical Looping Combustion and Chemical Looping With Oxygen Uncoupling

[+] Author and Article Information
Matthew A. Hamilton

The University of Utah,
50 South Central Campus Drive, Room 3290,
Salt Lake City, UT 84112-9203
e-mail: Matthew.a.hamilton@utah.edu

Kevin J. Whitty

The University of Utah,
50 South Central Campus Drive, Room 3290,
Salt Lake City, UT 84112-9203
e-mail: Kevin.Whitty@utah.edu

JoAnn S. Lighty

The University of Utah,
50 South Central Campus Drive, Room 3290,
Salt Lake City, UT 84112-9203
e-mail: jlighty@utah.edu

Contributed by the Advanced Energy Systems Division of ASME for publication in the JOURNAL OF ENERGY RESOURCES TECHNOLOGY. Manuscript received November 2, 2015; final manuscript received March 17, 2016; published online April 19, 2016. Assoc. Editor: Ashwani K. Gupta.

J. Energy Resour. Technol 138(4), 042213 (Apr 19, 2016) (9 pages) Paper No: JERT-15-1423; doi: 10.1115/1.4033108 History: Received November 02, 2015; Revised March 17, 2016

Chemical looping with oxygen uncoupling (CLOU) is a carbon capture technology that utilizes a metal oxide as an oxygen carrier to selectively separate oxygen from air and release gaseous O2 into a reactor where fuel, such as coal, is combusted. Previous research has addressed reactor design for CLOU systems, but little direct comparison between different reactor designs has been performed. This study utilizes Barracuda-VR® for comparison of two system configurations, one uses circulating fluidized beds (CFB) for both the air reactor (AR) and fuel reactor (FR) and another uses bubbling fluidized beds for both reactors. Initial validation of experimental and computational fluid dynamic (CFD) simulations was performed to show that basic trends are captured with the CFD code. The CFD simulations were then used to perform comparison of key performance parameters such as solids circulation rate and reactor residence time, pressure profiles in the reactors and loopseals, and particle velocities in different locations of the reactor as functions of total solids inventory and reactor gas flows. Using these simulation results, it was determined that the dual CFB system had larger range for solids circulation rate before choked flow was obtained. Both systems had similar particle velocities for the bottom 80% of particle mass, but the bubbling bed (BB) obtained higher particle velocities as compared to the circulating fluidized-bed FR, due to the transport riser. As a system, the results showed that the dual CFB configuration allowed better control over the range of parameters tested.

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References

Figures

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Fig. 1

Chemical looping with oxygen uncoupling diagram

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Fig. 2

Solid fraction profile versus dimensionless height for different fluidization regimes. Figure adapted from Ref. [13].

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Fig. 3

Schematic of the cold-flow unit, a dual CFB system, used in the simulation

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Fig. 4

Particle size distribution

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Fig. 5

Schematic of the bench-scale unit: (1) AR, (2) cyclone, (3) upper loopseal, (4) FR, and (5) lower loopseal. System is a dual BB and numbers indicate flow pattern.

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Fig. 6

Dual CFB circulation rate versus volumetric flow rate with an FR fluidizing velocity of 2.22 m/s

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Fig. 7

Dual CFB bed mass and residence time fluidizing velocity for (a) AR and (b) FR

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Fig. 8

Dual BB reactor global circulation rate versus AR volumetric flow rate

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Fig. 9

Dual BB reactor bed mass and residence time versus AR fluidizing velocity for (a) AR and (b) FR

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Fig. 10

Circulation rate comparison versus AR volumetric flow rate normalized with reactor diameter

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Fig. 11

Reactor residence time versus AR volumetric flow rate normalized by reactor diameter: (a) AR and (b) FR

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Fig. 12

Particle cumulative percentage versus particle velocity

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