Computation of turbulence and dispersion of cork in the NETL riser

Jiradilok, Veeraya; Gidaspow, Dimitri; Breault, Ronald W.; Guenther, Chris; Shi, Shaoping

doi:10.1016/j.ces.2008.01.019

Cited by 43 publications

(19 citation statements)

References 49 publications

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“…The dispersion coefficients for the bubbling bed at 25 atmospheres are much higher than at atmospheric pressure due to the high bed expansion with smaller bubbles. The computed dispersion coefficients are in reasonable agreement with the experimental measurements reported over the last half century and those measured at IIT and in the NETL riser in Morgantown (Jiradilok et al, 2007(Jiradilok et al, , 2008). …”

Section: Discussionsupporting

confidence: 79%

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Gasificaton Transport: A Multiphase CFD Approach & Measurements

Gidaspow¹,

Jiradilok²,

Kashyap³

et al. 2009

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OBJECTIVEThe objective of this project was to develop predictive theories for the dispersion and mass transfer coefficients and to measure them in the turbulent fluidization regime, using existing facilities. A second objective was to use our multiphase CFD tools to suggest optimized gasifier designs consistent with aims of Future Gen. CONCLUSIONSWe have shown that the kinetic theory based CFD codes correctly compute:(1) Dispersion coefficients (2) Mass transfer coefficients Hence, the kinetic theory based CFD codes can be used for fluidized bed reactor design without any such inputs.We have also suggested a new energy efficient method of gasifying coal and producing electricity using a molten carbonate fuel cell. The principal product of this new scheme is carbon dioxide which can be converted into useful products such as marble, as is done very slowly in nature. We believe this scheme is a lot better than the cancelled FutureGen, since the carbon dioxide is safely sequestered. OBJECTIVEThe objective of this project was to develop predictive theories for the dispersion and mass transfer coefficients and to measure them in the turbulent fluidization regime, using existing facilities. A second objective was to use our multiphase CFD tools to suggest optimized gasifier designs consistent with aims of Future Gen. SUMMARY OF ACCOMPLISHMENTS • Dispersion coefficientsThe dispersion coefficient is a measure of the quality of mixing. We have identified two types of solids dispersion coefficients: those due to random particle oscillations, "laminar" type, and those due to cluster or bubble motion, "turbulent" type. A literature review shows that dispersion coefficients in fluidized beds differ by more than five orders of magnitude. To understand the phenomena, two types of hydrodynamics models that compute turbulent and bubbling behavior were used to estimate radial and axial gas and solids dispersion coefficients. The 6 autocorrelation technique was used to compute the dispersion coefficients from the respective computed turbulent gas and particle velocities.The computations show that the gas and the solids dispersion coefficients are close to each other in agreement with measurements. The simulations show that the radial dispersion coefficients in the riser are two to three orders of magnitude lower that the axial dispersion coefficients, but less than an order of magnitude lower for the bubbling bed at atmospheric pressure. The dispersion coefficients for the bubbling bed at 25 atmospheres are much higher than at atmospheric pressure due to the high bed expansion with smaller bubbles. The computed dispersion coefficients are in reasonable agreement with the experimental measurements reported over the last half century and those measured at IIT and in the NETL riser in Morgantown (Jiradilok et al., 2007(Jiradilok et al., , 2008).• Optimized gasifier designs (Gasifier -fuel cell)For carbon capture fossil fuel electric power generation plants will have to be made more efficient. Department of Energy vision 21 c...

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Section: Discussionsupporting

confidence: 79%

“…We have shown that the kinetic theory based CFD codes correctly compute: We have recently shown that the particle and the gas axial and radial dispersion coefficients (Jiradilok et al, 2007(Jiradilok et al, , 2008, and the mass transfer coefficients …”

Section: Discussionmentioning

confidence: 99%

Gasificaton Transport: A Multiphase CFD Approach & Measurements

Gidaspow¹,

Jiradilok²,

Kashyap³

et al. 2009

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“…The kinetic theory of granular flow (KTGF), based on the molecular dynamics, proposed the definition of the granular temperature, which is used to describe the hydrodynamic character for the solid phase. By using the granular temperature, solid phase pressure and viscosity can be modeled [13,14], which express the physical properties of solid phase and close the N-S equations.…”

Section: Simulation Modelsmentioning

confidence: 99%

The simulation and experimental validation on gas-solid two phase flow in the riser of a dense fluidized bed

Wang

Jiang

et al. 2009

J. Therm. Sci.

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Gas-solid flow in dense CFB (circulating fluidized bed)) riser under the operating condition, superficial gas 15.5 m/s and solid flux 140 kg/m2s using Geldart B particles (sand) was investigated by experiments and CFD (computational fluid dynamics) simulation. The overall and local flow characteristics are determined using the axial pressure profiles and solid concentration profiles. The cold experimental results indicate that the axial solid concentration distribution contains a dilute region towards the up-middle zone and a dense region near the bottom and the top exit zones. The typical core-annulus structure and the back-mixing phenomenon near the wall of the riser can be observed. In addition, owing to the key role of the drag force of gas-solid phase, a revised drag force coefficient, based on the EMMS (energy-minimization multi-scale) model which can depict the heterogeneous character of gas-solid two phase flow, was proposed and coupled into the CFD control equations. In order to find an appropriate drag force model for the simulation of dense CFB riser, not only the revised drag force model but some other kinds of drag force model were used in the CFD. The flow structure, solid concentration, clusters phenomenon, fluctuation of two phases and axial pressure drop were analyzed. By comparing the experiment with the simulation, the results predicted by the EMMS drag model showed a better agreement with the experimental axial average pressure drop and apparent solid volume fraction, which proves that the revised drag force based on the EMMS model is an appropriate model for the dense CFB simulation.

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“…The results demonstrated that there are two types of particle clusters in a riser/downer, and the formation of clusters is affected by the operational conditions. Jiradilok et al (2008) numerically computed the solid volume fraction profiles for flow of cork particles in a NETL riser. They concluded that the axial and radial gas and solids dispersion coefficients in the risers operating in the turbulent flow regime can be computed using a multiphase computational dynamics model.…”

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confidence: 99%