Optimizing Flare System Performance at the Valero Sunray Refinery

© 2010 Aspen Technology, Inc. All rights reserved

April 28, 2011

Optimizing Flare System Performance at the Valero Sunray Refinery

Presented by: James Holoboff Process Ecology

Outline

• Background

• Application 1: Options for reducing backpressure • Application 2: Addition of a Flare Gas Recovery Unit • Demo

• Improving the Workflow: Automatic transfer of

data to Aspen Flare System Analyzer (Flarenet)

Who are we?

• Valero

– Fortune 500 company based in San Antonio

– North America’s largest independent petroleum refiner and marketer

– 14 refineries and 10 ethanol plants

• Process Ecology

– Engineering Consulting Company – Founded 2003 in Calgary, Alberta

– Team’s experience in engineering consulting, engineering

Benefits

• Flarenet can be used to quickly identify the best alternatives for reducing backpressure

• Flarenet can be used to review the impact of adding an FGRU

• FGRU represents a significant opportunity to recover fuel gas

• Automatic Transfer of data to Flarenet is possible and saves time

Background

• Process Ecology developed a Flarenet model for Valero as part of a refinery flare system upgrade

– Main objectives: verify seal drum levels,

determine crossover sizes/locations, review various scenarios

• Initially a “high-level” model was developed, and later expanded as needed

Applications of Flarenet

• Application 1: Options for reducing backpressure

• Application 2: Addition of a Flare Gas Recovery Unit

• Improving the Workflow: Automatic transfer of data to Aspen Flare System Analyzer

Application 1: Options for addressing

excessive backpressure

• Options for addressing excessive backpressure • Simulation

Using Flarenet to review options for

reducing backpressure (1)

• PSV Selection: check backpressure; impact of valve type on backpressure

For conventional valve, backpressure should not exceed 10% of set pressure; consider balanced or pilot valves if backpressure excessive

Using Flarenet to review options for

reducing backpressure (2)

Using Flarenet to review options for

Reducing backpressure (2)

Using Flarenet to review options for

Reducing backpressure (3)

• Line size changes: for existing flare systems, this might mean replacing pipes, or running a parallel flare line

• Moving loads: There may be options for moving a load to a different part of the flare system; if there are

Simulation –

Scenario Management

• Managing scenarios which incorporate

different proposals for reducing backpressure

• Flarenet Scenarios can accommodate PSV changes (flow, conditions) but not differences in line size / structure / ignored pipes / etc.

• Two options:

1. Keep separate cases, or

2. Track changes in a spreadsheet (possibly for import).

Case Header Size Jumpover?

Option 1 8" No Option 2 8" Yes Option 3 10" No

Simulation –

– After significant changes, clear estimates (in

Scenario Editor)

– Make modifications to flare model in steps

– Check for convergence to reasonable

tolerances (not always obvious)

– Check tolerances

Results

• How simulation helped quantify the impact of

different scenarios and determine the best course of action

Back Pressure (psig)

PSV Mass Rate (lb/hr) Set Pres. (psig) MABP (psig)

Base Case Case #1 Case #2 Case #3 Case #4

PSV #1 8,000 250 25 57.1 106.0 61.6 50.3 70.9 PSV #2 8,000 250 25 57.1 106.0 61.6 50.3 70.9 PSV #3 8,000 250 25 56.3 105.6 60.9 49.5 70.3 PSV #4 19,783 150 105 78.7 119.5 82.6 74.8 87.6 PSV #5 19,783 150 105 80.3 120.6 84.2 76.4 89.1 PSV #6 130,965 235 117.5 82.3 121.1 85.5 78.2 78.6 PSV #7 20,860 270 135 76.5 117.4 79.9 71.1 72.4 PSV #8 759 365 182.5 75.6 116.8 79.0 70.1 71.4 PSV #9 7,220 265 132.5 77.4 117.9 80.7 72.0 73.3 PSV #10 132,165 180 90 44.0 55.9 55.9 44.4 55.9 PSV #11 39,158 280 140 44.1 56.0 56.0 44.5 56.0 • Change PSV #1 / PSV #2 / PSV #3 to balanced PSV

Application 2: Addition of a Flare Gas

Recovery Unit

What is an FGRU?

• FGRU = Flare Gas Recovery Unit

• Usually a liquid ring / vane compressor

– Liquid used to mitigate explosivity risk

• Recovers gas in flare system due to ‘everyday’ releases (purges, vents, leaking valves, tank vents, etc.)

• Vacuum on flare system can affect seals – design must take this into account.

What are the benefits of an FGRU?

• Economic savings

– Benefit from recovering and reprocessing blanket

gas, other light gases

• Less flaring – less wear on flare equipment, less visible flare to surrounding neighbors • Regulatory

– Many jurisdictions requiring FGRUs to reduce

How do you simulate an FGRU? (1)

• Compressors

– Flarenet will not model compressor directly, use a

‘flare tip’ with a defined inlet pressure (e.g. Compressor suction pressure)

• Seal Drums

– “Flow Bleed” with fixed pressure drop used during

How do you simulate an FGRU? (2)

• What to do in model with flares during routine venting

– Not a typical ‘flare scenario’

– Manually Turn off flares, run model with FGRU On

– Check Seal Drums to see if DP of seal exceeded,

How do you simulate an FGRU? (3)

• What scenarios do we need to run?

– Challenge to ensure ‘normal venting’ and all major

flare scenarios are defined.

– Especially challenging when multiple flares are

Results

• Simulation helped design of compressor

suction piping & determine seal drum levels

– Identified excessive losses in compressor suction

piping, suggested alternative sizing.

– Identified where the biggest savings in pressure

loss were to be had, allowing only essential piping to be upsized.

– Identified losses in piping so that seal drum levels

could be adjusted and minimum DP in seals maintained during normal operation.

Improving the Workflow

• Benefits of the Valero “Connector Application” • Using Connector Application

Plant Pressure Management / Documentation Tool

Aspen Flare System Analyzer

Transfer PSV / Scenario Data

Benefits of the Connector Application

• Enables automatic transfer of data from plant pressure protection management /

documentation tool (Siemens PPM)

– PPM used for refinery flare system / PSV

management

• As information changes in PPM, the Flarenet model can be automatically updated

Using the Connector Application

1. Select PPM File Location and Flarenet File

2. Mapping: PPM Source / Scenario to Flarenet Source / Scenario 3. Compare Flarenet to PPM Data

4. Export Flarenet input file

5. Save Connector Application File

1 2

3

4

Using the Connector Application

• Comparing Flarenet to PPM Values

Using the Connector Application

Quantifying the Benefits

• Flarenet can be used to quickly identify the best alternatives for reducing backpressure

– Appropriate decisions can be made quicker using a flare analysis tool – hundreds of hours over the course of

supporting flare operations

• Flarenet can be used to review the impact of adding an FGRU

– Associated decisions such as inlet pipe sizing and seal drum heights can be made; e.g., allowing only essential piping to be upsized

– Cost savings associated with correct pipe sizing could be in range of $tens of thousands

Quantifying the Benefits

• FGRU represents a significant opportunity to recover fuel gas

Source: John Zink Based on $2/MMBTU

Quantifying the Benefits

• Automatic Transfer of data to Flarenet is possible

– “Connector Application” provides significant

time/cost savings; reduced manual data entry and associated entry errors

• Manually transferring data (Flow, MW, conditions) for 50 PSVs would take several hours

• With Connector Application this would take a few minutes with no errors in data transfer

• For a few scenarios it would easily represent significant time savings (10-30 hours)

Concluding Remarks

• Flarenet is an effective application for analyzing flare system modifications

• Flarenet can be successfully used to review the impact of flare gas recovery unit

• Workflow can be improved by automating the transfer of data to Flarenet

Thank you!

• Valero

• Alan Swiedom and Laura Chutny • AspenTech

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Contact Information

James Holoboff Process Ecology

Email: [email protected]

Glenn Dissinger

AspenTech (Aspen HYSYS family product manager) Email: [email protected]

Ken Dooley

AspenTech (industry marketing) Email: [email protected]