G. Rincon, E. La Motta Civil & Environmental Engineering Kinetics of the Electrocoagulation of Oil and Grease Guillermo J. Rincon, Ph.D. Student Enrique.

G. Rincon, E. La Motta Civil & Environmental Engineering

Kinetics of the Electrocoagulation of Oil and

Grease

Guillermo J. Rincon, Ph.D. StudentEnrique J. La Motta, Ph.D., P.E.

THE SOUTHEAST SYMPOSIUM ON CONTEMPORARY ENGINEERING

TOPICS (SSCET)

New Orleans, October 26, 2012

Civil & Environmental Engineering

Disclaimer

All the laboratory equipment and instruments, including the proprietary bench-scale reactor, utilized in this research, are property of the University of New Orleans and where purchased by this institution prior to the conception of this research. It is not the authors’ intention to support, advertise, criticize or disqualify the design, performance and/or use of any of these equipment and instruments.

G. Rincon, E. La Motta

Civil & Environmental Engineering

Outline

Tracer tests on a bench-scale reactor

Electrocoagulation of oil and grease

Kinetics of electrocoagulation (reaction order and rate coefficient)

Reactor modeling and models comparison

G. Rincon, E. La Motta

Civil & Environmental Engineering

Background

Electrocoagulation

Generation of coagulants in-situ by dissolving aluminum or iron electrodes.

Contaminants in wastewater react chemically and/or attach to colloidal particles generated at the anode.

Flocs are removed by flotation, sedimentation and/or filtration.

G. Rincon, E. La Motta

Civil & Environmental Engineering

Background

Electrocoagulation (EC) was first proposed in England in 1889.

EC with iron and aluminum electrodes was patented in the U.S. in 1909.

Applied in large scale in the U.S for the first time in 1946.

Electrochemical wastewater treatment technologies have regained importance in the past two decades.

G. Rincon, E. La Motta

Civil & Environmental Engineering

Background

No information on the kinetics of EC process was available.

Research on EC of oil and grease is taking place at the University of New Orleans.

Experimentation has been done using a proprietary bench-scale EC reactor.

Removal of Hexane Extractable Materials (HEM) by EC with Al and/or Fe electrodes has been proved highly effective (>95%).

Deficient reactor performance indicated possible design flaws.

G. Rincon, E. La Motta

Civil & Environmental Engineering

Objectives

To identify design flaws in the EC reactor.

To generate Residence Time Distribution (RTD) data for the EC reactor.

To establish the kinetics of the EC process.

To propose a model for the EC reactor.

RTD data + Kinetics + Model = Performance Prediction

G. Rincon, E. La Motta

Civil & Environmental Engineering

Experimental Plan

Perform tracer tests using different reactor configurations and fluid velocities to obtain RTD data.

Conduct EC experiments using synthetic oily wastewater

Perform reactor modeling using both the dispersion model and the TIS model.

Data analysis and interpretation of results.

G. Rincon, E. La Motta

Civil & Environmental Engineering

Laboratory Equipment

EC Reactor

Reactor Cell

G. Rincon, E. La Motta

Civil & Environmental Engineering

Experimental Set-Up

Rotation of electrode plates changes the fluid’s path of flow through the reactor.

G. Rincon, E. La Motta

Civil & Environmental Engineering

Experimental Set-Up

Tracer test set-up

EC experiments set-up

G. Rincon, E. La Motta

Civil & Environmental Engineering

Data Acquisition

Step-Input tracer test output

G. Rincon, E. La Motta

Civil & Environmental Engineering

Data Acquisition

EC experiment output

G. Rincon, E. La Motta

Civil & Environmental Engineering

Results

Effect of slot orientation on RTD in an 8-cell reactor with Q=0.5 L/min

Effect of slot orientation on RTD in an 8-cell reactor with Q=1.0 L/min

G. Rincon, E. La Motta

Civil & Environmental Engineering

Results

Effect of fluid velocity on RTD in an 8-cell reactor with horizontal slots.

Effect of fluid velocity on RTD in an 8-cell reactor with vertical slots.

G. Rincon, E. La Motta

Civil & Environmental Engineering

Results

Summary of RTD data

G. Rincon, E. La Motta

Civil & Environmental Engineering

Results

Data points fitting by linear regression using ideal PFR first-order kinetics

G. Rincon, E. La Motta

Civil & Environmental Engineering

Results

k’= 0.0441 s-1

R2=0.974

Fraction remaining vs. k’t curve using the dispersion model

G. Rincon, E. La Motta

Civil & Environmental Engineering

Results

Fraction remaining vs. k’t curve using the TIS model

n = 8.1

k’= 0.0443 s-1

R2=0.970

G. Rincon, E. La Motta

Civil & Environmental Engineering

Results

Comparison of fraction remaining curves for different models

G. Rincon, E. La Motta

Civil & Environmental Engineering

Conclusions

Electrocoagulation with aluminum electrodes is highly effective for HEM removal from stable emulsions and follows first-order reaction kinetics.

Electrocoagulation of oil and grease follows first order reaction kinetics. Therefore, PFR is the best type.

The reactor configuration used in this research allows easily changing the contact time.

Both the dispersion model and the tanks-in-series model correlate the experimental data very well (R2 = 0.970).

The TIS model offers a simpler approach to modeling this type of reactors.

G. Rincon, E. La Motta

Civil & Environmental Engineering

Conclusions

Ninety-degree rotation of the electrode plates has a significant effect on the reactor’s performance.

Stagnant water, and pockets of hydrogen gas are the main operating problem with horizontal slots.

These problems increased when the flow-through velocity decreased below 0.032 m s-1.

Changing slot orientation increases the reactor average detention time by 50% and the HEM removal efficiency by 14%.

G. Rincon, E. La Motta

Civil & Environmental Engineering

Recommendations

More research on the kinetics of the electrocoagulation of HEM is needed.

Performing experiments under different operational conditions (wider range of flow rates and HEM concentrations, different current intensities, and electrode materials).

This reactor must be operated with fluid velocity higher than 0.032 m s-1 and following a horizontal path (slots oriented vertically).

For any reactor design and operational conditions, tracer tests must be performed in order to identify potential anomalies in flow pattern behavior .

G. Rincon, E. La Motta

Questions?