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Optimal design and operation of a Draft Tube Spouted Bed Reactor for a photocatalytic process David Follansbee , John Paccione, Lealon Martin. Environmental Division Fundamentals of Environmental Systems Engineering . Tuesday, November 6, 2007. Outline . Motivation for process

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Optimal design and operation of a Draft Tube Spouted Bed Reactor for a photocatalytic process

David Follansbee, John Paccione, Lealon Martin

Environmental Division

Fundamentals of Environmental

Systems Engineering

Tuesday, November 6, 2007

outline
Outline

Motivation for process

Process Model

Parameters and Problem statement

Results

Conclusion and Future Work

traditional photocatalytic reactors
Traditional photocatalytic Reactors

Photocatalytic slurry reactors

Batch configuration

Photocatalyst particle separation

Photocatalyst loading limitations

Photocatalytic fixed bed reactors

Cross sectional area limitations

Longer reactor length for increase throughput

High pressure drops

Mass transfer and kinetics are coupled

Photocatalyst coating of reactor walls

Cross sectional and mass transfer limitations

motivation for dtsmb
Motivation for DTSMB

Decoupling of mass transfer from kinetics

Continual degradation of contaminant and regeneration of photocatalyst

Counter-current design

Photocatalyst immobilized on large, dense particles

UV

Jet flow

Draft tube

Clean water outlet

Dirty Water inlets

process block diagram
Process block diagram

Design

Parameters

Gp

.

xo

WUV

Gfd

Target

Parameters

Gfa

yo

Performance

variables

Gp

xi

εD

Key design

variables

DA

Dt

M

HA

εA

Gfd

Gp

.

xo

Gfa

yi

WPump

Photo Reactor

Draft tube

Packed bed

reactor

annular bed model
Annular bed Model

Assumptions:

Counter current contact

Constant fluid properties

Costant particle size and density

Langmuir adsorption:

Mass load :

Gp

Gp

Mass balance:

xi

xo

DA

GA

M

HA

yo

Log mean concentration difference:

H

HA

GA

Height:

yi

GA

yi

Gp

xi

GA

yo

Gp

xo

GA

yi

A.Y. Khan. Titanium dioxide coated activated carbon: Masters thesis, University of Florida, 2003.

V. Manousiouthakis and L. L. Martin. Computers & Chemical Engineering, 28(8):1237–1247, July 2004.

draft tube model
Draft tube model
  • Assumptions
  • Only non-accelerating portion of bed

Mass flowrate of fluid:

Mass flow rate of particles:

Fluid-particle interphase drag coefficient:

Slip velocity:

Pressure Drop

Gp

GfD

Dt

Ht

εD

Gp

GfD

Z.B. Grbavcic, R.V. Garic, D.V. Vukovic, D.E. Hadzismajlovic, H.Littman, M.H. Morgan, and S.D. Jovanovic. Powder Technology, 72(2):183–191, Oct. 1992.

uv model intensity power and kinetics
UV model (Intensity, Power, and Kinetics)

Modeled as a PFR

Pseudo first order reaction

No mass transfer limitations

.

WUV

Mass flow rate:

Rate equation:

I

Intensity (Lambert-Beer Law):

Adsorption coefficient:

Power required:

Gp

xo

DUV

HUV

Io

Gp

xi

operation limitations and specifications
Operation limitations and specifications
  • Mass flowrate can not exceed an upper limit where particles will not settle in annular bed
          • Gp<(1-mf)Aapva(max)
  • Voidage in the draft tube has to be above a critical collapsing voidage and below 1
          • vc< D<1
  • The fluid velocity has to be great enough to ensure transport of particles
          • u1.5vt
test system
Test System

Reactive Red degradation

2 mm catalyst particles

TiO2/AC photocatalyst composites

SiO2 substrate

model constants
Model Constants

Z.B. Grbavcic, R.V. Garic, D.V. Vukovic, D.E. Hadzismajlovic, H.Littman, M.H. Morgan, and S.D. Jovanovic. Hydrodynamic modeling of vertical liquid solids flow. Powder Technology, 72(2):183–191, Oct. 1992.

problem statement
Problem Statement

Given:

Adsorptive mass transfer rates

Contaminant degradation rates

The annular flowrate and inlet concentration

Target concentration

Minimize

schematic of algorithm
Schematic of Algorithm

Physical Properties

Design Parameters

Operation specs

Interval analysis

Math Model

Optimal design

and

operating conditions

Sensitivity

Analysis

Sensitivity

Analysis

Minimizing

objective function

conclusion
Conclusion

Height of annular bed is insensitive to change in mass flowrate.

Operating at a low mass flowrate (<0.1 kg/s) allows for the most robust performance.

For the test system of TiO2/AC UV cost is high

Motivates for optimization of catalyst properties

i.e. density, UV adsorption, and kinetics

Model must be experimentally validated

Specifically the kinetics and mass transfer models

acknowledgements
Acknowledgements

Dr. Howard Littman

Dr. Joel Plawsky

Dr. David Dziewulski (DOH and SUNY school of Public health)

Martin Research Group

RPI funding

Department of Defense