Reconciling Mass And Energy Balances In An Ethylene Complex


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Emerson's Patrick Truesdale presents steps to improve energy efficiency in ethylene production processes.

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  • Most produced organic compound in the World. Steam cracking is the single most energy consuming processes in the chemical industry  ca. 30% of the sector’s total final energy use and ca. 180 millions tons of CO2 in 2004 Another reason for innovation over 35% of European crackers are over 25 years old
  • Pyrolysis section is the most energy consuming section in a steam cracker (65% of total energy use) Also energy consuming: Refrigeration and C2 separation (20%) Fractionation and compression (15%) Plenty of room for energy savings is possible in steam cracking Catalytic olefin technologies can lead to energy saving (up to 20%) on energy use by state-of-the-art steam cracking
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  • Sigmafine's data reconciliation engine is based on the statistical least-squares method, which cross-checks measurement errors on all meter and gauge readings (based on a tolerance assigned to each measurement). Sigmafine generates a matrix of equations which are solved simultaneously resulting in consistent results from balance point to balance point within the model. Error Detection – Sigmafine offers a comprehensive error analysis routine for gross errors (broken meters, mis-entered data, digit swapping, missed data), bias (the meter consistently reads too high or too low); random errors (the value varies at a random frequency). Mass Balance – In minus Out plus inventory changes equals zero. This identifies plant losses, measurement errors, and weaknesses in the measurement system. Component Balance – Mass or volume balance that includes individual components making up a flow (i.e. – a fuel gas system will include all of the components (ethylene, propylene …) in the component stream. Energy Balance – Mass and energy balance of many sources of energy (heat and steam). Currently does not handle state transformation (going from freezing to boiling). Unmeasured flow calculation – Sigmafine calculates unmeasured flows based on the surrounding measurements in the system. Yield Accounting – This is a business requirement of reporting receipts and shipments, inventories, production data on a daily, monthly and year to date basis. This is useful for fenceline companies that pass products between plants to identify losses due to measurement errors. Composition Tracking – Calculates and tracks the makeup of all materials in a tank. For example, in a 100K crude tank, Sigmafine can keep track of the various feedstocks of crude that exist in the tank (mixed or unmixed). Loss Analysis – Sigmafine uses the Institute of Petroleum (IP) loss analysis methodology to calculate known (flare, fugative emissions), unknown losses (things that you can’t manually isolate) within a facility. Using the mass balance, Sigmafine statistically resolves the unknown loss to zero. Coming: Stoichiometric balances (reactions), Constrained balances (The user can define constraints for an acceptable solution - “only calculate if the value is positive”). Sigmafine can perform a site-wide balance taking into account information for the entire plant. The result is a consistent site and unit-by-unit balance, removing any underlying data conflict. Sigmafine's reconciliation algorithm is highly automated, stable, and based on rigorous statistics.
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  • Reconciling Mass And Energy Balances In An Ethylene Complex

    1. 1. Reconciling Mass and Energy Balances in an Ethylene Complex Patrick Truesdale Senior Consultant Industry Solution Group Emerson Process Management November 11, 2009 Nashville, TN
    2. 2. Presentation Objectives <ul><li>Background and Business Challenge </li></ul><ul><li>Business Opportunities </li></ul><ul><li>How to Achieve? </li></ul><ul><li>Case Examples </li></ul><ul><li>Summary </li></ul>
    3. 3. Introduction <ul><li>Accurate measurements are an essential part of a refinery or petrochemical complex </li></ul><ul><li>Measurement technology has dramatically improved in past 25 years </li></ul><ul><li>Environmental and governmental regulations have increased necessitating accurate measurements </li></ul><ul><li>Changing demographics </li></ul><ul><li>Benefits can be significant! </li></ul>
    4. 4. Ethylene Plants: Configuration and Complexity Ref: T. Ren, University of Utrecht and BASF 2000
    5. 5. Ethylene Plants: Estimated Capacities – 1 Jan. 2009 Ref: OGJ 30 July 2009
    6. 6. Ethylene Plants: Global Distribution and Age In 1980’s Plants were typically ca 300kta Now Mega Crackers > 1,000kta Predominantly Greenfield Predominantly Brownfield
    7. 7. Hydrocarbon/Measurement Timeline
    8. 8. Challenges to achieve benefits <ul><li>Measurement systems for Mass are relatively new for old Plants </li></ul><ul><li>Belief that errors are mostly due to fuel gas/oil production/consumption over/under statement (ie. Little need to coordinate energy usage with losses) </li></ul><ul><li>Prices have escalated rapidly in past few years; currently many plants are spending significant capital to met new specs, increase capacity, regulatory compliance, process cheaper feed stocks. Staff is stretched. </li></ul><ul><li>Business function and organization requires addressing NOT just software tools; but the new operator and engineer in plant. </li></ul>
    9. 9. Typical Plant Demographics Operations Engineering Maintenance Small decline due to automation Downsized by 70 - 90% Downsized by 5% per year for past 10 years. Typical Plant w/ 3,308 workers <ul><li>Operators now responsible </li></ul><ul><li>for optimization efforts </li></ul><ul><li>75+% experienced operators </li></ul><ul><li>slated to retire by 2015 </li></ul><ul><li>Skilled labor pool falling </li></ul>0-20 21-34 35-44 45-54 55-65 65+ Age
    10. 10. Meet the New Engineers and Operators! We may dress funny but we’re computer geeks!
    11. 11. Key Performance Indexes <ul><li>Asset Utilization </li></ul><ul><li>Plant Reliability </li></ul><ul><li>Operating Efficiency </li></ul><ul><li>Margin </li></ul><ul><li>Energy Efficiency </li></ul><ul><li>Loss Opportunities </li></ul><ul><li>Environmental </li></ul><ul><li>Safety </li></ul>
    12. 12. Where are losses? Why Important? Open Inventory + Receipts – Shipments – Closing Inventory = Gain/Loss Gain/Loss = Accountable + Unaccountable Leaks Theft Flare Coke Fuel Produced Fuel Consumed
    13. 13. Energy Efficiency
    14. 14. Step 1: Define Process Boundaries C2 Hydrogenation Cold Box C3 Hydrogenation Cracked Gas Compressor Quench Tower Cracking Furnaces Hydrogen 1%-9% Methane 6%-28% (fuel) Ethylene 23%-76% Ethane 3%-20% (recycle) Propylene 3%-16% Propane 2%-10% C4s 2%-9% Gasoline <1%-35% Steam & Waste Heat Steam Steam Feeds (60%) Ethane (C2) Propane (C3) Butane (C4) Naphtha (C5 – C12) Gas Oil (C10 – C15) Fuel Gas Drying and Chilling Ethylene and Propylene Refrigeration Systems Steam (40%) Quench Water Circuit Oil / Tar Fractionator Fuel Oil Tar C2 Splitter Depropanizer C3 Splitter Debutanizer Deethanizer Demethanizer 800-900 ° C 1.5 bar 350 ° C 1.5 bar 30 ° C 1.5 bar 10 ° C 1.5 bar -100 ° C 32 bar 20 ° C 5 bar 50 ° C 2 bar -10 ° C 30 bar 10 ° C 10 bar -10 ° C 30 bar 75 ° C 30 bar 70 ° C 8 bar 90 ° C 5 bar 45 ° C 5 bar 45 ° C 16 bar 35 ° C 16 bar -20 ° C 20 bar -30 ° C 20 bar -6 ° C 20 bar 80 ° C 1.5 bar Fired Heater Distillation Cryogenic Distillation Hydrogenation Reactor Turbo Compressor
    15. 15. Shore Ship Consumers Raw Material Production & Supply Ethylene Complex Load Port Logistics Unload Port Ship Shore Shore Ship Transportation Loss Load Port Transportation Loss Shore Unload Port Ship $ “The Cash Register” Step 2: Identify Custody Transfer Boundaries? BOL BOL
    16. 16. Step 3: Design Mass and Energy Balances Receipts Shipments Intercompany Inventories Tank-to-tank transfers Unit-to-tank transfers Process Nodes Tank-to-unit transfers Losses Consumption
    17. 17. Step 4: Survey Measurement Systems <ul><li>With poor instrumentation and procedures: </li></ul><ul><ul><li>= 1.5 - 2.5% Mass losses </li></ul></ul><ul><li>With average instrumentation and procedures: </li></ul><ul><ul><li>= 0.7 – 1.5% Mass losses </li></ul></ul><ul><li>With good instrumentation and procedures: </li></ul><ul><ul><li>= < 0.5% Mass losses </li></ul></ul><ul><li>Pacesetter = <0.2% </li></ul><ul><li>Pacesetter look at Solomon KPI; </li></ul><ul><li>Others such Shell Global Services, Juran, etc. </li></ul>
    18. 18. Select Technology Required Pressure Drop Accuracy Low Maintenance Slurry Flows Viscosity Independent Flow meter Type Non- Conductive Fluids Non- Intrusive Turbine Positive Displacement Coriolis Magmeter Differential Pressure Vortex Good Marginal Poor Ultrasonic
    19. 19. Coriolis Measurement Capabilities <ul><li>Direct MASS flow measurement </li></ul><ul><li>Rangeability: (100:1 non custody), (20:1 custody) </li></ul><ul><li>Accuracy (@20:1 turndown) </li></ul><ul><ul><li>Mass Flow Rate: ± 0.10 % </li></ul></ul><ul><ul><li>Volume Flow Rate: ± 0.13% </li></ul></ul><ul><li>Unaffected by most fluid variations </li></ul><ul><ul><li>P,T,density,viscosity, conductivity </li></ul></ul><ul><ul><li>Velocity profile independent </li></ul></ul><ul><li>Bi-Directional </li></ul><ul><li>Multi-variable outputs available </li></ul><ul><ul><li>Qm, Qv, T, Density, % Solids, Viscosity </li></ul></ul>
    20. 20. Tank Gauge Measurement Capabilities 1 API ± 3/16&quot; (4 mm) 2 PTB, Germany 3 NMi, Netherlands 4 OIML, International 5 TankRadar
    21. 21. Flow meters or ATG’s ? <ul><li>Influence of batch size: </li></ul><ul><ul><li>At large transfer volumes ATG’s have potential to have better performance. Systematic error on a meter will have a large influence. </li></ul></ul><ul><ul><li>At small transfer volumes meters have potential to have better performance. Resolution may not be sufficient on an ATG. </li></ul></ul>
    22. 22. Do errors always get even out? Think again! NO: Statistical sum of several measurement errors equals: Square Root of the sum of Square of the errors When adding several errors, sum can not be zero!
    23. 23. Step 6: Develop Mass & Energy Balance Models <ul><li>Validation, Detection and Correction: Gross and Bias Errors </li></ul><ul><li>Reconciles for Random Errors </li></ul><ul><ul><li>Mass and Volume balancing </li></ul></ul><ul><ul><ul><li>Flows, inventories, material transfers </li></ul></ul></ul><ul><ul><li>Component balancing (Simple and Multi-phase) </li></ul></ul><ul><ul><ul><li>Flows, inventories </li></ul></ul></ul><ul><ul><li>Energy balancing </li></ul></ul><ul><ul><ul><li>Enthalpy, power, heat exchanger balance, steam </li></ul></ul></ul><ul><ul><li>Simultaneous Solution of all equations </li></ul></ul>
    24. 24. Example Heat Balance Envelope 100 Kg 9.242 MJ 91423.7 J/Kg 100 Kg 1.068 MJ 10683.6 J/Kg 100 Kg 4.217 MJ 42170 J/Kg 100 Kg 12.291 MJ 122.9 KJ/Kg 100 Kg 3.871 MJ 38706 J/Kg 100 Kg 11.944 MJ 11944.6 J/Kg
    25. 25. Example Heat Balance Envelope 100 Kg 9.242 MJ 91423.7 J/Kg 100 Kg 1.068 MJ 10683.6 J/Kg 100 Kg 4.217 MJ 42170 J/Kg 100 Kg 12.291 MJ 122.9 KJ/Kg 100 Kg 3.871 MJ 38706 J/Kg 100 Kg 11.944 MJ 11944.6 J/Kg
    26. 26. Step 5: Define Business Process Period End Cutoff Data Gross Error Detection and Diagnostics Trial Balancing Resolution or Reconciliation Checking Modifications Adjustments Complex Configuration Models Measurements Movements Lab Data Meter Tickets Surveyor Documents Tank Inventories Utilities Results Generation Manual Input Automatic Data Collection Reconciled Balances, Yield, Loss and Inventory Reporting Production Management Data Base Integrate with Other Systems (SCM, SAP, LP, etc)
    27. 27. Step 7: Identify KPI Reporting
    28. 28. KPI Dashboard
    29. 29. Step 8: Implement Continuous Improvement <ul><li>Where did it happen? </li></ul><ul><li>Models </li></ul><ul><li>Process </li></ul><ul><li>Data Quality </li></ul>Time (Weeks) <ul><li>Capacity </li></ul><ul><li>Utilization </li></ul><ul><li>Production rate </li></ul><ul><li>Quality </li></ul><ul><li>Energy </li></ul><ul><li>Yield </li></ul><ul><li>Margin </li></ul><ul><li>Reliability </li></ul><ul><li>Environmental </li></ul>What went wrong?? What went right?? Before (Monthly) Plan/Schedule 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Actual Operation After (Daily)
    30. 30. Get Benefits: Operational Excellence Impact Up to 7.9% Operational Improvement by Impacting… +3% +2.4% -1.3% -1% -0.2%
    31. 31. Measurement Losses: What is it worth? Assume 0.2% Loss Reduction 93% 1150$/t 500$/t
    32. 32. Measurement Losses: What is it worth? Assume 0.2% Loss Reduction <ul><li>Product </li></ul><ul><li>Capacity </li></ul><ul><li>Price </li></ul><ul><li>Margin </li></ul><ul><li>Utilization factor </li></ul><ul><li>Amount </li></ul><ul><li>Ethylene </li></ul><ul><li>900 kMT/yr </li></ul><ul><li>1 150 $/t </li></ul><ul><li>500 $/t </li></ul><ul><li>93% </li></ul><ul><li>47 774 $/hr </li></ul><ul><li>Propylene </li></ul><ul><li>450 kMT/yr </li></ul><ul><li>1 150 $/t </li></ul><ul><li>500 $/t </li></ul><ul><li>93% </li></ul><ul><li>23 887 $/hr </li></ul><ul><li>$71 661 </li></ul><ul><li>0.2% </li></ul><ul><li>$143/hr </li></ul><ul><li>1 hr </li></ul><ul><li>1 yr </li></ul><ul><li>$1 255 500 </li></ul>
    33. 33. Case 1: Losses Analysis (%Mass) Range <ul><li>Custody transfer (receipt and shipments) </li></ul><ul><li>Fuel and H2 consumption (understated, not real losses) </li></ul><ul><li>Flare, in effluent, evaporation, stack loss, vents and leaks, coke </li></ul>0.35 to 0.55 0.85 to 1.05 0.45 to 0.65 TOTAL 1.65 to 2.25 Estimate 0.45 0.95 0.55 1.95
    34. 34. Case 1: Benefit Calculation <ul><li>Estimate loss = 1.95% </li></ul><ul><ul><li>Custody Transfer Loss = 0.45% </li></ul></ul><ul><ul><li>Flare, Coke, Other Loss = 0.55% </li></ul></ul><ul><ul><li>Apparent (understated fuel/H2 consumption) = 0.95% </li></ul></ul><ul><li>Improvement </li></ul><ul><ul><li>Achievable Goal = 0.4% </li></ul></ul><ul><ul><ul><li>Delta = (0.45%+0.55%-0.4% = 0.6%) </li></ul></ul></ul><ul><ul><ul><li>0.6% x 12MM T/yr x 210US$/T = $15,120,000/yr </li></ul></ul></ul><ul><li>Supply chain optimization </li></ul><ul><ul><li>0.25 $/T x 12MM T/yr = $3,000,000/yr </li></ul></ul>
    35. 35. Case 2: Measurement Errors vs Economic Losses Control Variable Objective Function (e.g. Profit) Operating Region Deviations are often corrected with high-cost sub-optimum correction ! Potential lost profit from inaccurate measurements.
    36. 36. Trading Benefits A Gulf Coast refiner switched a cargo of crude with just one-and-a-half hours of supply left in inventory . Without very close coordination between trading and operations, the $8 million profit opportunity would have been lost. Hydrocarbon Processing
    37. 37. Trading Example Trader Gulf Coast Complex Okay, if you can agree with the shipper to deliver 8 hours earlier, then we will have a four hour safety margin and the trade is agreed. Hold on while we check:: - Current inventory - Maintenance Plan - Agreed Receipts and Shipments and rerun the schedule to check the impact on stocks and cash flow. Delivery 8 hours earlier is agreed. We make $3,000,000 and we extend our credit line by 3 days. GREAT, is there anything I can do to help with a backup strategy? We have an excellent opportunity to purchase a cargo of feed stock. Can we take it?
    38. 38. Key Takeaways <ul><li>Ethylene plants have large incentives to reduce losses and optimize energy usage. These two KPI are interrelated. </li></ul><ul><li>With the sharp increase in feedstock prices and accessibility, the industry has a compelling need for improving the timeliness and accuracy of production data. </li></ul><ul><li>Specifications and governmental regulations continue to tighten - accurate measurements are essential to mitigate compliance </li></ul><ul><li>Since late 1950 there has been and continues to be significant technological improvement in measurement systems </li></ul><ul><li>Smart Instruments and Wireless technology opens additional benefits for the future! </li></ul><ul><li>Improved accuracy of Production Data (Mass and Energy Balance Reconciliation) impacts many KPI’s . The solution approach, therefore, “ is Green ” (provides significant benefits). </li></ul>
    39. 39. Wrap-up <ul><li>Questions? Comments? </li></ul><ul><li>Where to get more information? </li></ul><ul><ul><li>White Papers </li></ul></ul><ul><ul><li>Presentations </li></ul></ul><ul><ul><li>Specific requirements? </li></ul></ul><ul><ul><li>Contact: </li></ul></ul><ul><ul><ul><li>Patrick Truesdale ( [email_address] ) </li></ul></ul></ul>
    40. 40. Thank You