Optimizing Flare System Performance at the Valero Sunray Refinery

Transcription

1 Engineering Excellence Webinar Series: Optimizing Flare System Performance at the Valero Sunray Refinery Presented by: James Holoboff Process Ecology April 28, Aspen Technology, Inc. All rights reserved

2 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) Concluding Remarks

3 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 software development and process simulation and optimization

4 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

5 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

6 Background - Scope of Flarenet Model

7 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 (Flarenet)

8 Application 1: Options for addressing excessive backpressure Options for addressing excessive backpressure Simulation Results

9 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

10 Using Flarenet to review options for Jumpovers: impact of jumpovers to relieve local backpressure reducing backpressure (2) High backpressure

11 Using Flarenet to review options for Reducing backpressure (2) Jumpovers: impact of jumpovers to relieve local backpressure Backpressure reduced New jumpover Backpressure reduced Increase in backpressure

12 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 multiple flares, moving to a different flare

13 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

14 Simulation Improving convergence / speed Tips for improving convergence and speed 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 Property Package, composition options

15 Results How simulation helped quantify the impact of different scenarios and determine the best course of action Back Pressure (psig) PSV Mass Rate Set Pres. MABP Base Case Case #1 Case #2 Case #3 Case #4 (lb/hr) (psig) (psig) PSV #1 8, PSV #2 8, PSV #3 8, PSV #4 19, PSV #5 19, PSV #6 130, PSV #7 20, PSV # PSV #9 7, PSV #10 132, PSV #11 39, Change PSV #1 / PSV #2 / PSV #3 to balanced PSV Make jumpover changes in Case #3 to reduce backpressures

16 Application 2: Addition of a Flare Gas Recovery Unit What is an FGRU? Benefits of an FGRU Simulation Results

17 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.

18 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 emissions

19 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 emergency release scenario

20 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, turn flare on if so.

21 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 involved, as cross scenarios are possible.

22 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.

23 Demonstration

24 Improving the Workflow Benefits of the Valero Connector Application Using Connector Application Plant Pressure Management / Documentation Tool Transfer PSV / Scenario Data Aspen Flare System Analyzer

25 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 Developed by Process Ecology

26 Using the Connector Application Select PPM File Location and Flarenet File Mapping: PPM Source / Scenario to Flarenet Source / Scenario Compare Flarenet to PPM Data Export Flarenet input file Save Connector Application File

27 Using the Connector Application Comparing Flarenet to PPM Values

28 Using the Connector Application Import data into Flarenet

29 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

30 Quantifying the Benefits FGRU represents a significant opportunity to recover fuel gas Source: John Zink Based on $2/MMBTU

31 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)

32 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

33 Thank you! Valero Alan Swiedom and Laura Chutny AspenTech

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36 Flare Network Design and Rating Training Flare Network Design and Rating: (EHY2511) May 2, 2011 Houston, TX May 13, 2011 Pune, India June 21, 2011 Virtual Americas July 14, 2011 Melbourne, Australia Perform equipment sizing, rating, and debottlenecking of flare systems using the reporting utilities of Aspen Flare System Analyzer Solve convergent, divergent and looped networks Reduce calculation time and improve accuracy using tips and best practices Take advantage of the two-phase modeling capabilities of Aspen Flare System Analyzer 2010 Aspen Technology, Inc. All rights reserved 36

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38 Questions

39 Contact Information James Holoboff Process Ecology Glenn Dissinger AspenTech (Aspen HYSYS family product manager) Ken Dooley AspenTech (industry marketing)

40 Thank you.