Acs Lng Chemistry

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Acs Lng Chemistry

  1. 1. Gas Turbine Fuel Flexibility LNG, DME, MeOH, and Synthesis Gas
  2. 2. Introduction Fuel Types and Properties
  3. 3. Fuel Flexibility <ul><li>High level of concern raised by customers over gas interchangeability and fuel flexibility in general </li></ul><ul><ul><li>Driven by imported LNG, and declining US natural Gas production </li></ul></ul><ul><ul><li>Key products offerings could be </li></ul></ul><ul><ul><ul><li>Monitoring and fuel system retrofits to existing SPG gas turbines </li></ul></ul></ul><ul><ul><ul><li>Modifications to competitors equipment </li></ul></ul></ul><ul><ul><li>Products need to accept wider range of gas fuel quality </li></ul></ul>
  4. 4. Fuel Spectrum
  5. 5. Fuel Type and Temperature
  6. 6. Fuel Type and Delivery
  7. 7. Fuel Flexibility <ul><li>Stranded gas off-shore must be delivered to markets in a convenient form for shipping. </li></ul><ul><ul><li>Non-cryogenic liquid (Gas-to-Liquids), Fischer-Tropsch </li></ul></ul><ul><ul><li>Pressured gas (CNG or Dimethyl Ether, DME) </li></ul></ul><ul><ul><ul><li>DME for China and Indian diesel and home markets </li></ul></ul></ul><ul><ul><ul><ul><li>GE spent $20 million in R&D, BP continues to develop, as do the Japanese </li></ul></ul></ul></ul><ul><ul><li>Methanol </li></ul></ul><ul><ul><li>LNG </li></ul></ul>
  8. 8. Key Terminology <ul><li>Wobbe Index </li></ul><ul><ul><li>Based on fuel gas heating value and gas density (specific gravity) </li></ul></ul><ul><ul><ul><li>Widely used interchangeability parameter </li></ul></ul></ul><ul><li>Dew Point </li></ul><ul><ul><li>Boundary on a temperature/pressure map defining the region where condensation of complex mixtures of hydrocarbons occurs </li></ul></ul><ul><li>Higher Hydrocarbons </li></ul>
  9. 9. Gas Turbine Power Industry
  10. 10. Technology Progression Significant Impact of Gas Turbine Since the 1960’s. Technology shift to PreMixed Combustion in the 1990’s.
  11. 11. Industry Statistics
  12. 12. GT Industry Statistics <ul><li>210,000 MWe installed in power generation (US) </li></ul><ul><ul><li>Rapid construction/installation times. </li></ul></ul><ul><li>4,000+ gas turbines installed in pipeline and refinery operations. </li></ul><ul><li>16,000+ gas turbines installed worldwide </li></ul><ul><ul><li>50% in Oil and Gas Operation </li></ul></ul>
  13. 13. Industry Statistics <ul><li>22% of all US natural gas consumption is now used to generate electricity (both for consumers and industrial applications) </li></ul><ul><li>Most efficient package utility plants in the world are combined cycle (gas turbine+steam turbine) </li></ul><ul><li>Gas turbine power plants comprise less than 2% of all emissions in power generation sector . </li></ul>
  14. 14. August 2003 Blackout
  15. 15. Environmental Impact: NO x
  16. 16. Energy Resource Base
  17. 17. Off-Shore Gas Reserves <ul><li>Four methods of moving plentiful off-shore supplies to the end-user. </li></ul><ul><ul><li>LNG </li></ul></ul><ul><ul><ul><li>Extensive investment in LNG underway. However, wide variability of off-shore supply compositions greatly complicates the usability in DLN gas turbines. </li></ul></ul></ul><ul><ul><li>Non-cryogenic liquid (Gas-to-Liquids), Fischer-Tropsch </li></ul></ul><ul><ul><li>Pressured gas (CNG or Dimethyl Ether, DME) </li></ul></ul><ul><ul><li>Methanol </li></ul></ul>
  18. 18. Global Gas Supply Base World energy reserves of hydrocarbons are approximately even divided between natural gas, oil, and coal. But if methane hydrates are added to the resource base, the global reserves in gas could represent more than 80% of the hydrocarbon resources. EU Proposed Range US Historical
  19. 19. <ul><li>Domestic natural gas supply differs significantly from some off-shore natural gas resources. </li></ul><ul><ul><li>Based on Heating value (Btu), Wobbe Index, and/or chemical composition </li></ul></ul><ul><li>LNG’s cryogenic processing will remove virtually all components heavier than Butane. </li></ul><ul><ul><li>But high Btu components can still be present in the final delivered gas supply, especially if they were present at the source. </li></ul></ul>US and Offshore Supplies
  20. 20. Gas Supply Industry <ul><li>Regulated by the Federal Energy Regulatory Commission (FERC) </li></ul><ul><li>De-regulated the natural gas supply industry </li></ul><ul><ul><li>Transporters move the gas </li></ul></ul><ul><ul><ul><li>But don’t own the molecules </li></ul></ul></ul><ul><ul><li>Suppliers supply the gas </li></ul></ul><ul><ul><li>LDC’s distribute gas to end-users </li></ul></ul><ul><ul><ul><li>Probably not same molecules that supplier provided. </li></ul></ul></ul><ul><li>Contracts, with FERC approval, govern the exchange between each party. </li></ul>
  21. 21. Gas Quality <ul><li>Two key issues recently raised by the Federal Energy Regulatory Commission over pipeline tariff requirements. </li></ul><ul><ul><li>Hydrocarbon Dew Point </li></ul></ul><ul><ul><li>Interchangeability </li></ul></ul><ul><li>Each handled separately, despite obvious common features between the two. </li></ul>
  22. 22. Domestic Gas Composition C1 - Methane C2 - Ethane C3 - Propane C4 - Butane - LNG C5 - Pentane - Liquid formation occurs C6+-Hexane and Greater Plus diluents (oxygen, carbon dioxide)
  23. 24. Hydrocarbon Dropout <ul><li>When thermal value is greater than product value some producers may opt to reduce or cease processing </li></ul><ul><li>Rains within the pipeline – “liquid fall out” </li></ul><ul><li>Condensate can be a nuisance to the transporter and catastrophic to end-user </li></ul>
  24. 25. Condensate In Pipeline
  25. 26. Dew Point Curve LNG will not drop hydrocarbon liquids
  26. 27. Pipeline Dew Point (95/96)
  27. 28. Pipeline Control Measures <ul><li>Blending </li></ul><ul><ul><li>Coincidental – Open Access </li></ul></ul><ul><ul><li>Contractual - Within the Control of Shippers </li></ul></ul><ul><li>Heating </li></ul><ul><ul><li>Heat of Compression </li></ul></ul><ul><ul><li>Installation of Heaters </li></ul></ul><ul><li>Processing </li></ul>
  28. 29. Dew Point and LNG <ul><li>If LNG is high quality gas, and very dry, why the parallel concern over hydrocarbon dew point? </li></ul><ul><ul><li>Because of the draw down on US supplies, gas suppliers were putting anything into the pipeline to increase heating value. This appears to have caused significant issues to some downstream users. </li></ul></ul>
  29. 30. Interchangeabiliy <ul><li>FERC elected to treat gas interchangeability as a separate issue from Hydrocarbon Dew Point </li></ul><ul><li>Typical contract (tariff) parameters </li></ul><ul><ul><li>Heating Value </li></ul></ul><ul><ul><li>Wobbe Index </li></ul></ul><ul><ul><li>Inert content </li></ul></ul><ul><li>Gas turbine equipment manufacturer specifications turned out to be a limiting factor on interchangeability. </li></ul>
  30. 31. US Wobbe Data
  31. 32. Power Sector Turbine Technology
  32. 33. Combined Cycle Power Plant
  33. 34. <ul><li>The gas turbine has unique fuel flexibility characteristics </li></ul><ul><ul><li>Insensitive to parameters such as octane or cetane rating, which affects compression engines. </li></ul></ul><ul><ul><li>Corrosion is a factor, but usually only with heavy oils or liquid fuel, or with ingestion of corrosive material (e.g. seawater) </li></ul></ul><ul><ul><li>Concerns over domestic supply have usually focused on gas pre-treatment to meet equipment requirements </li></ul></ul><ul><ul><ul><li>Superheat fuel (keep it in the gas phase) </li></ul></ul></ul><ul><ul><ul><li>Removal of liquids and condensate </li></ul></ul></ul><ul><li>Offshore LNG introduces new complexities. </li></ul>Gas Turbine Design
  34. 35. Combustion Systems <ul><li>Fuel flexibility is directly tied to combustor design. </li></ul><ul><li>Two combustor designs in use today : </li></ul><ul><ul><li>Diffusion flame combustor design </li></ul></ul><ul><ul><ul><li>Highest degree of fuel flexibility. </li></ul></ul></ul><ul><ul><ul><li>Probably the “safest” combustion design system for continuous burners </li></ul></ul></ul><ul><ul><ul><ul><li>All aircraft gas turbines are based on diffusion combustor design. </li></ul></ul></ul></ul><ul><ul><li>Premixed design </li></ul></ul><ul><ul><ul><li>Newest designs (DLN and DLE introduced in 1990’s) </li></ul></ul></ul><ul><ul><ul><li>Premix fuel and air introduced tighter requirements on fuel quality. These were necessary to control basic combustion process conditions: </li></ul></ul></ul><ul><ul><ul><ul><ul><li>Flashback, blowoff, combustion instabilities, emissions, etc </li></ul></ul></ul></ul></ul>
  35. 36. <ul><li>Still in wide use, although in limited production within the US. </li></ul><ul><ul><li>Steam or water injection for NO x emissions. </li></ul></ul><ul><ul><ul><li>Water/steam operating costs are not insignificant; </li></ul></ul></ul><ul><ul><ul><ul><li>Additional combustor wear associated with stress on hot parts was a key factor in prompting the industry to develop other technologies </li></ul></ul></ul></ul><ul><ul><li>Diffusion combustor is usually the design-of-choice if low quality fuels (gas or liquid) are the primary fuel </li></ul></ul><ul><ul><ul><li>Design choice for landfill gases, heavy and medium grade oils, residual fuel oil, blast furnace gas, refinery gas, IGCC, crude oil—and even coal. </li></ul></ul></ul>Diffusion Combustor
  36. 37. <ul><li>Required extensive research and development by both industry and government. </li></ul><ul><ul><li>Eliminated the need to inject a diluent for control of NO x </li></ul></ul><ul><ul><ul><li>Combustor design and controls are more complex </li></ul></ul></ul><ul><ul><li>Introduced additional requirements on fuel quality requirements </li></ul></ul><ul><ul><ul><li>Wobbe Index variability requirements are typically much narrower (15% vs. 5%) </li></ul></ul></ul><ul><ul><ul><li>Limits on higher hydrocarbons to mitigate the risk of flashback in premixed systems. </li></ul></ul></ul><ul><ul><li>Premixed designs are predominantly natural gas </li></ul></ul><ul><ul><ul><li>Much harder to design “premixed” system with other fuels </li></ul></ul></ul>Premixed Combustor
  37. 38. Flame Types (Gas) Photos by Dr. F. Dinkelacker, Erlangen, 2005 Butane/Air Exit diameter 18 mm Fuel flow rate is hold constant Diffusion Flame Fully Premixed Flame Partial Premix Flame
  38. 39. DLN Cross Section
  39. 40. DLN-3D
  40. 41. Annular Combustor Combustion Chamber Compressor 24 Hybrid Burners
  41. 42. Silo (External) Combustor Wide variety of fuel applications Large, walk-in combustor chamber Low NOx Hybrid Burners
  42. 43. Interchangeability
  43. 44. Gas Interchangeability <ul><li>For many end users interchangeability with gas has primarily been the concern of equipment operability. </li></ul><ul><li>Emissions requirements introduced new complexity in fuel choice. </li></ul><ul><ul><li>These requirements are site (and project) specific, reflecting unique aspects of each site, equipment selection, and operating characteristics. </li></ul></ul><ul><ul><li>Nearly every facility has specific contract language for emissions and fuel requirements. </li></ul></ul>
  44. 45. Interchangeability: Geography Depending upon location on the pipeline grid, some users may experience more rapid shifts from domestic pipeline natural gas to imported LNG
  45. 46. Interchangeability: Geography Florida: 95%+ natural gas consumption is power generation, mostly gas turbines. Depending upon location on the pipeline grid, some users may experience more rapid shifts from domestic pipeline natural gas to imported LNG
  46. 47. <ul><li>Wobbe Index </li></ul><ul><ul><li>Modified Wobbe and/or Temperature Corrected </li></ul></ul><ul><li>Gas Composition—(Ethane, Propane Butane) </li></ul><ul><ul><li>Which definition of natural gas is controlling? </li></ul></ul><ul><ul><ul><li>EPA’s, Tariff, Fuel Specification? </li></ul></ul></ul><ul><li>Heating value limits </li></ul><ul><li>Dew point </li></ul><ul><ul><li>Many pipeline tariffs do not have dew point limits, yet the formation of condensates in the fuel supply can have severe consequences to equipment downstream. </li></ul></ul><ul><li>Temperature </li></ul>Interchangeability Parameters
  47. 48. Combustion Tests Simulating LNG
  48. 49. NO x -Thermal NO x At lower combustion temperatures, less NO x is generated. But there is a limit to the minimum temperature. Combustion instabilities (dynamics) become important in lean combustion systems.
  49. 50. NO x -Thermal NO x Pressure Effect on NO x and CO Emissions in Industrial Gas Turbines Anuj Bhargava . , Donald W. Kendrick, Kent H. Casleton and Daniel J. Maloney U.S. Department of Energy Federal Energy Technology Center Meredith B. Colket, William A. Sowa United Technologies Research Center East Hartford, CT Source: ASME 2000-GT-97 (with permission)
  50. 51. NO x -Combustor Tests Wobbe Index variation, as well as combustor design can affect emissions. Chart shows the response of two different combustor systems to changes in gas composition.
  51. 52. Full Scale Engine Evaluation Heating Value Reduced Dynamics Increased Minor changes to the gas composition was coincident with a step change in the combustor dynamic pressure. INFLUENCE OF VARIATIONS IN THE NATURAL GAS PROPERTIES ON THE COMBUSTION PROCESS IN TERMS OF EMISSIONS AND PULSATIONS FOR A HEAVY-DUTY GAS TURBINE Lars Nord and Helmer Anderson IJPGC2003-40188 (with permission)
  52. 53. Fuel Effects-NO x Minor increase in NO x emissions with increase of Wobbe Index from 1335 to 1400, a range that would account for addition of LNG from offshore supplies. Full scale engine testing confirms rig testing that, without burner modifications or engine control enhancements, increasing Wobbe Index can result in increased NO x .
  53. 54. Fuel Effects-CO CO (and unburned hydrocarbon) emissions are affected as well, although not in the same manner as NO x .
  54. 55. Diffusion Combustor Model Calculated for diffusion combustion system. Water Injection for NO x control, and fixed firing temperature. Differences in NO x due to fuel quality changes (Wobbe Index) are indicated. . Based on: A Model for the Prediction of Thermal, Prompt and Fuel NO x from Combustion Turbines J. L. Toof Journal of Engineering for Gas Turbines and Power , Vol. 108, No. 4, 1986, pp. 340-347
  55. 56. Supply Comparison US Domestic gas index has varied by only +/-2%, or 1315 to 1369. Requirements that are too broad could be difficult to manage without special equipment modifications to adapt to changes. Requirements too narrow could leave a significant amount of gas unacceptable to US markets . Industry fuel specifications vary from +/-2% to +/-10%, depending upon design features and equipment capabilities.
  56. 57. LNG Source and Impact US Domestic gas index has varied by only by +/-2%, or 1315 to 1369. Requirements that are too broad could be difficult to manage without special equipment modifications to adapt to changes. Requirements too narrow could leave a significant amount of gas unacceptable to US markets . Industry fuel specifications vary from +/-2% to +/-10%. Tolerance requirements for fuel quality are related to combustor design, emissions, and contract requirements. Proposed EU Range
  57. 58. NO x Variation and Design Variability in NO x emissions of equipment in service can differ significantly among different gas turbine designs. Even within a specific engine model, significant variation is evident. Emissions for three different gas turbine models in power generation service, reported through EDR network.
  58. 59. Other Technical Issues
  59. 60. NO 2 Plume (Yellow Plume) <ul><li>Observed at some installations in Europe and Asia </li></ul><ul><ul><li>The plume issue appears to strongly relate to combustion systems using LNG. </li></ul></ul><ul><ul><li>Units on West Coast have reported plumes (AWMA 2004) </li></ul></ul><ul><ul><ul><li>Stack geometry, location, viewing position, and total exhaust plume diameter affect the plume visibility. </li></ul></ul></ul><ul><li>NO 2 emissions appear to be related to the presence of higher hydrocarbons in the exhaust gas. </li></ul><ul><ul><li>NO 2 plume was and is a problem for some gas turbines operating in countries that use LNG as the primary fuel. </li></ul></ul><ul><ul><li>Plume formation is not predictable from current models for fuel interchangeability. </li></ul></ul>
  60. 61. LNG and Plume NO 2 production strongly dependent upon presence of specific hydrocarbons for reaction pathway. An Experimental and Kinetic Evaluation of the Promotion Effect of Hydrocarbons on the NO-NO 2 Conversion in a Flow Reactor Proceedings of the Combustion Institute, Volume 27. Hori, M., Matsunaga, N., Marinov, N., Pitz, W. and Westbrook, C., Proc. Combust.Inst. 27 (1998) 389-396
  61. 62. Conclusions
  62. 63. Diffusion Combustor Design <ul><li>Older power plants, and pipeline applications, use this design. </li></ul><ul><li>Most robust design </li></ul><ul><li>Greatest fuel flexibility (Low/High HV gases, liquids, etc). </li></ul><ul><li>Increasing higher hydrocarbon content could increase NO x , unless some control is used to mitigate against increased flame temperature. </li></ul>
  63. 64. <ul><li>Response to changes in gas composition may be more complex. </li></ul><ul><ul><li>Range of combustor configurations may respond differently </li></ul></ul><ul><ul><ul><li>Annular </li></ul></ul></ul><ul><ul><ul><li>Can-annular </li></ul></ul></ul><ul><ul><ul><li>Silo </li></ul></ul></ul><ul><ul><ul><li>Dual-fuel </li></ul></ul></ul><ul><ul><li>System response complicated by many different designs that are connected on same distribution network. </li></ul></ul><ul><ul><li>Different OEM fuel specifications reflect unique requirements for each gas turbine DLN design, and each gas turbine model (or frame) </li></ul></ul>Premixed Designs
  64. 65. Finally….. <ul><li>Offshore LNG destined for domestic users could differ substantially from historical norms based on the source of the gas. </li></ul><ul><li>Response of installed gas turbine fleet will be difficult to gage. </li></ul><ul><ul><li>Increasing the allowable range of chemical properties will have some impacts. </li></ul></ul><ul><ul><ul><li>But not all equipment is likely to respond the same way. </li></ul></ul></ul><ul><ul><li>Additional research on interchangeability is needed </li></ul></ul><ul><ul><ul><li>What parameters make sense today? </li></ul></ul></ul><ul><li>Equipment modifications can be made available to adapt the existing fleet of gas turbines. </li></ul><ul><ul><li>It will take time. </li></ul></ul>
  65. 66. Research Opportunities <ul><li>Full scale testing needed. </li></ul><ul><ul><li>More empirical evaluations similar to what has been carried out. </li></ul></ul><ul><li>Model studies on system response. </li></ul><ul><li>Review and update of interchangeability parameters </li></ul><ul><ul><li>No one office or agency acts as repository. </li></ul></ul><ul><li>Current energy budget has provisions for research funding spelled out. </li></ul>

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