Near-Zero Flare for Chemical Process Industry via Plant-wide Optimization and Simulation

Qiang Xu, Kuyen Li, and John L. Gossage

Department of Chemical EngineeringLamar University, Beaumont, TX 77710

TERC SAC MeetingHouston, TX

February 21-22, 2008

Flare Minimization, Why It Is Important?Texas Air Quality Challenges

Ozone Non-Attainment• Dallas/Fort Worth• Houston/Galveston• Beaumont/Port Arthur• El Paso

Ozone Near Non-Attainment• Austin/San Antonio• Corpus Christi/Victoria• Tyler/Longview/Marshall

Ref: http://www.tceq.state.tx.us/implementation/air/sip/siptexas.html

Emission from Chemical Plant Turnaround Operations

C, CO, CO2

VOCNOx

Example: Emissions during the Startup of an Ethylene Plant

• An ethylene plant with a capacity of 1.2 billion pounds of ethylene production per year

• About 5 million pounds of ethylene for flaring during an ordinary startup

• About 98% flaring efficiency

NOx = 7.5K lbsCO = 40.0K lbsHC = 15.1K lbs

HRVOC = 100.0K lbs

Emissions:

Economical & Environmental Challenges

Environmental Burden:• Air pollution• Influence on regional environmental quality and

sustainability

Economical Burden:• Raw material lavished• Productivity reduced• Additional environmental penalties

Current Studies on Flare Minimization

Qualitative Ways (Major efforts):• Depend on the experienced operators/engineers/

administration and well plant planning/scheduling/training• Reduce the number of instances when the plant has to flare

and the quantity of the materials to be flared

Quantitative Methods:• Dynamic simulation for operational feasibility test• Virtual run for process risk analysis• Cost-effective way

How does It Work for Turnaround Operations?

• Industrial expertise integrated process modification

• Industrial expertise integrated operation scheduling

• Dynamic simulation for feasibility, operability, and safety test

modificationschedulingsimulation

operation

Project Objectives

• Develop a systematic methodology for significant emission reduction from chemical process industry

• Provide the source of emission with details for point (industry) sources, which “have never been compiled previously and are expected to help explain many of the monitoring observations.”

• Demonstrate the benefits will accrue not only for the environment and society, but also for economics and sustainability

MethodologyFramework

for Near-zero Flaring

Off-spec products should be either recycled for online reuse, or stored somewhere temporarily for future reprocessing.

The off-spec products will be reused instead of being flared.

Process Design and Modification

Superstructure for Conceptual Design

Logic-based Mixed-integer Dynamic Optimization for Design and Scheduling

OperationalScheduling

IndustrialExpertise

DesignSuperstructure

Logic-basedMIDO

Dynamics Logic

Binary

SolutionIdentification

Dynamic Simulation Task

Build steady state flowsheet in Aspen Plus

Prepare flowsheet for dynamic simulationAdd Dynamic data

Export simulation

Simulation inAspen Dynamics

Change control system, testing procedures

Test Bed: An Ethylene Plant Startup

C1

C2, C3C4

Achievements from Previous Activities

• The flaring was reduced to less than 3.5 hours

Huntsman Petrochemical Ethylene Plant:

• The flaring was reduced by 75% comparing to the earlier startupLyondell Chemicals Olefin Plant:

• Avoid runaway reactions during the startupLyondell PDGlycol Plant:

• The flaring was reduced by 50% comparing to the earlier startupBASF-TOTAL Ethylene Complex:

Technology Transfer

• Submit the report with the detailed methodology and project data

• Generate papers and give presentations based on the developed methodologies and technologies

• Develop educational website to disseminate concepts of near-zero flare, methodology framework, and selected models and results

• Offer flare minimization workshop at Lamar University through continuing education and provide consultation for chemical plant turnaround operations

Concluding Remarks

• Near-zero flare is a fundamental solution for emission source reduction in chemical process industry

• Integration of process modification, operational scheduling, and dynamic simulation can help chemical plants identify near-zero flaring opportunities

• Our previous research activities and industrial collaborations provide solid foundations for the project

Concluding Remarks (Cont’d)

Research Institute Industrial Partners

Government & Supporting Agency

Near-zero Flare

• Improve Air Quality in Texas

• Provide Point Source Emission

• Cost-effective Control Strategy

• Profitable Pollution Prevention Way

Publications and Presentations

1. “Flare Minimization for Chemical Plant Turnaround Operation via Plant-wide Dynamic Simulation,” accepted and to be appear in Proceedings of FOCAPO 2008.

2. “Flare Minimization during Plant Startup via Dynamic Simulation”, 2007 PSE ASIA, Xi’an, China, August 15 - 18.

3. “Flare minimization toward zero discharge for chemical plant turnaround operation via dynamic simulation”, AIChE Annual Meeting, Salt Lake City, Utah, November 4 - 9 in 2007.

4. “Flare Minimization via Dynamic Simulation,” Int. J. Environment and Pollution, 29, 19, 2007.

5. “Better Plant Startup via Simulation” presentation in the AIChE National Meeting, San Francisco, CA, November 12 - 17, 2006.

6. “Flare Minimization via Dynamic Simulation”, Conference Proceedings in the AIChE National Meeting, New Orleans, FL, April 25 - 29, 2004.

7. EPA Region 6 - P2 Roundtable Meeting, March 11, 2004.8. Beaumont-Port Arthur Emission Events Meeting, TX, June 9, 2004.9. La Porte Emission Events Meeting, June 8, 2004.10. Six master theses and one doctoral dissertation were generated.