Mercury Capture by Fly Ash Carbon Sorbent in a Fixed Bed

2-D Finite Element Computational Modeling

Brandie Markley & Onur Mustafaoglu

Project Motivation EPA’s Clean Air Mercury Rule

Passed March 15, 2005 Targets coal-fired power plants

Mercury Toxic Persistent Bioaccumulation

Activated Carbon Injection Using Fly Ash Promising technology 63% of fly ash produced is disposed in landfills Inherent properties of fly ash

Statement of the Problem

Governing Equations

)()()(

)(

zkyjxi

cuRcDtc

ts

• The Convection Diffusion Equations

0

)])(([)(

u

FuuIuutu T

• Incompressible Navier-Stokes Equation

Formulation

Results and Observations

Observations-2

Observations-3

Observations-4.1

Observations-4.2

Validation

00.10.20.30.40.50.60.70.80.9

1

0 2 4 6 8 10 12 14 16 18 20Hrs

Inlet abs

0

0.1

0.2

0.3Outlet abs

Sorbent bed inlet

Sorbent bed outlet

COMSOL breakthrough curve at center of sample tube outlet

COMSOL breakthrough curve along the side of the sample tube outlet

Actual experimental results

Parametric Study

COMSOL breakthrough curve with actual reaction rate

COMSOL breakthrough curve with reaction rate increased by 10000 times

-0.10

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000Secs

AAS response

Experimental data

Conclusion

Velocity develops and mercury breakthrough occurs most quickly at the center of the element

Adsorption through the element behaves as expected

COMSOL is an effective modeling tool for this application COMSOL data matches experimentally observed results

Further investigation is needed for accurate parameter identification (e.g., force velocity, dynamic viscosity, diffusion coefficient)

Works Cited

U.S. EPA. CLEAN AIR MERCURY RULE (online), March 15, 2005. Available at http://www.epa.gov/air/mercuryrule/.

American Coal Ash Association, 2003 COAL COMBUSTION PRODUCT PRODUCTION AND USE SURVEY (online), Available at http://www.acaa-usa.org/PDF/2003_CCP_Survey(10-1-04).pdf.

Iliuta I, Petre CF, Larachi F, CHEMICAL ENGINEERING SCIENCE 59 (4): 879-888 2004

Wu YX, Wang X, Ching CB, J. CHEMICAL ENGINEERING & TECHNOLOGY 27 (9): 955-961 2004

Etc…(the rest of reference list is in the final paper)

Questions?