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The New ISO 10723 Advances and new concepts in the performance evaluation and benchmarking of on line natural gas analysers. Dr Paul Holland BD Director, EffecTech Group Natural gas quality measurement composition (content) of natural gas

  1. The New ISO 10723 Advances and new concepts in the performance evaluation and benchmarking of on ‐ line natural gas analysers. Dr Paul Holland BD Director, EffecTech Group

  2. Natural gas quality measurement composition (content) of natural gas • inert gases  nitrogen, carbon dioxide, helium, (argon & hydrogen) • hydrocarbons  methane, ethane, propane, iso ‐ butane, n ‐ butane, pentanes, hexanes + ...... properties (characteristics) of natural gas • calorific value, Wobbe number, standard density (ISO 6976) • compression factor, line density (ISO 12213) • hydrocarbon dew point (ISO 23874) • emission factors

  3. Energy determination

  4. Risks in energy metering Annual Value / € 4,500,000 Typical gas fired power station 4,000,000 Power output : 500 MW Energy Price : €60 / MWh 3,500,000 3,000,000 2,500,000 2,000,000 1,500,000 Typical 1,000,000 500,000 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 U(Energy) / %

  5. Gas quality measurement instruments

  6. Legal / commercial legislation requirements • customer protection (example in UK law) Public Gas Transporters (PGTs) shall carry out performance evaluations of gas quality metering instruments in accordance with ISO 10723 following installation or maintenance. Provided that the results of the procedure show that the error on the calculated calorific value of transmission gas will not exceed 0.10 MJ.m ‐ 3 for gas compositions allowed in the system, the PGT may then use that instrument for the determination of calorific values for the purposes of section 12 of the Gas Act 1986.” • control of GHG emissions (example in EU directive) commercial gas contracts • sales gas agreements / contracts (end ‐ users) • allocation agreements (upstream)

  8. Revision of ISO 10723 : 1995 revision to existing standard required for • inclusion of measurement uncertainties  instrument precision, instrumental errors  working calibration gas • compliance with GUM • more rigorous assessment of errors and uncertainties of measurement of  composition (gas content amount fraction)  gas properties (calculated from composition) revision by • ISO/TC193/WG15 (with liaison from ISO/TC158) • Drafting by G Squire (EffecTech, UK) and D Lander (NGG, UK)

  9. ISO/DIS 10723 : 2011 ‐ Scope Determine E(x), E(P) Determine a range of and U(x), U(P) over a compositions for each pre ‐ defined range of specified component compositions for each which satisfy pre ‐ specified component defined maximums in E(x), E(P) and U(x), U(P) using a specified calibration gas composition and uncertainty calibration gas redesign composition and uncertainty

  10. Instrument errors response / (peak area) y=F ass (x) x cal 0 1 2 3 4 5 6 7 8 9 10 content / (% mol/mol)

  11. Instrument errors response / (peak area) y=F ass (x) y=F true (x) x cal 0 1 2 3 4 5 6 7 8 9 10 content / (% mol/mol)

  12. Instrument errors response / (peak area) y=F ass (x) y=F true (x) x cal 0 1 2 3 4 5 6 7 8 9 10 content / (% mol/mol)

  13. Instrument errors response / (peak area) y=F ass (x) y=F true (x) x cal 0 1 2 3 4 5 6 7 8 9 10 content / (% mol/mol)

  14. Challenge measurement of TRUE (actual) response functions for the instrument for all components (i=1..q) • calibration functions  y = F i,true (x) • analysis functions  x = G i,true (y) function types for F & G • polynomials of order 1, 2 or 3 2 + a 3 x i  y i = F i,true (x i ) = a 0 + a 1 x i + a 1 x i 3 2 + b 3 y i  x i = G i,true (y i ) = b 0 + b 1 y i + b 2 y i 3

  15. Design of reference gases a series of reference gases is measured by the instrument being calibrated components included in reference gases • depends on application range of composition • equal or greater than that expected to be measured by the instrument (no extrapolation) number of mixtures • dependent upon expected order of F and G  3 (1 st order), 5 (2 nd order), 7 (3 rd order) • approximately equally spaced within the range

  16. ISO 10723 ‐ Performance evaluations of on ‐ line analytical systems • ISO 17025 accredited calibration gases • well established reference values & uncertainties • 7 ‐ 10 cylinders each containing 10,11 or 12 components • wide range natural gas compositions

  17. Experimental replicate measurements design reference gases Batch ‐ wise calibration  simplest / manual / most practical ( p gas changes)  temporal drift has more significance

  18. Experimental replicate measurements design reference gases Drift compensation calibration  compensates for temporal drift (due to sample size effects)  automation required

  19. Drift correction Samples are injected at (or with reference to) ambient pressure. response � effective sample size � ambient pressure Batch ‐ wise calibration Drift compensation calibration measure ambient pressure at time of sample injection (P ijk ) y ijk = y’ ijk . P ref / P ijk

  20. Gas fired power station

  21. Gas fired power station

  22. Witnessed factory evaluation

  23. LNG receiving terminal

  24. Custody transfer border station

  25. Drift compensation calibration (automated)

  26. Offshore allocation / sales gas

  27. Regression analysis parameters F and G are calculated using GLS • maximum liklihood functions relationships (MLFR) • uncertainties in both variables (amount and response) • procedure identical to that prescribed in ISO 6143 response functions validated for each component and in each domain F and G using ISO 6143

  28. Calibration results

  29. Errors content / amount fraction & properties x  G ( y ) • assumed i i , ass i y  F ( x ) • true i i , true i • measured amount following calibration (where functions coincide) G ( F ( x ))  * i , ass i , true i , true x x . i , meas i , cal G ( F ( x )) i , ass i , true i , cal • normalise * x  i , meas x  i , meas * x i , meas • errors    x x x i , meas i , meas i , true    P P P meas meas true

  30. Uncertainties in errors contributions from u x • calibration gas ( ) i , cal • instrument precision u ( y ) & u ( y ) i , cal i , meas properties • any property / characteristic calculated from composition P  f ( x , x ,..., x , w , w ,..., w ) 1 2 n 1 2 m 2 2       n m f f         2 2 2 u P u x u w ( ) ( ) ( )     c  i  i  x   w    i 1 i 1 i i

  31. Off ‐ line model produce a off ‐ line model of instrument • errors as a function of amount fraction • repeatability as a function of amount fraction • uncertainties as a function of amount fraction use Monte Carlo simulation • generate 10,000 different gas compositions • for each composition calculate  errors in physical properties  uncertainties in physical properties

  32. Errors and uncertainties on errors E(CV SUP ) / MJ.m -3 0.15 0.10 0.05 0.00 -0.05 -0.10 -0.15 78 80 82 84 86 88 90 92 94 96 98 methane content / (% mol/mol)

  33. Error distribution E(CV SUP ) / MJ.m -3 0.15 0.10 0.05 0.00 -0.05 -0.10 -0.15 78 80 82 84 86 88 90 92 94 96 98 methane content / (% mol/mol)

  34. Mean error (bias) E(CV SUP ) / MJ.m -3 0.16 0.14 0.12 0.10 0.08 0.06 0.04 0.02 Maximum Permissible 0.00 Bias (MPB) mean error = bias ‐ B(P) -0.02  P  MPB -0.04 -0.06 -0.08 -0.10 -0.12 -0.14 -0.16 78 83 88 93 98 methane content / (%mol/mol)

  35. Uncertainty on mean error E(CV SUP ) / MJ.m -3 0.16 0.14 0.12 0.10 0.08 0.06 0.04 0.02 Maximum Permissible 0.00 Error (MPE) uncertainty on the mean error   MPE ≈ uncertainty on bias ‐ U(B(P)) -0.02     P U P c -0.04 -0.06 -0.08 -0.10 -0.12 -0.14 -0.16 78 83 88 93 98 methane content / (%mol/mol)

  36. Errors and uncertainties ‐ summary

  37. Example – design of calibration gas

  38. Example – design of calibration gas x C1,cal = 0.88 mean E(CV) = 0.001 ± 0.061 MJ.m ‐ 3

  39. Example – design of calibration gas x C1,cal = 0.88 mean E(CV) = 0.001 ± 0.061 MJ.m ‐ 3 x C1,cal = 0.81 mean E(CV) = 0.000 ± 0.028 MJ.m ‐ 3

  40. Analysis function correction ‐ superior CV

  41. Instrument errors response / (peak area) y=F ass (x) y=F true (x) x cal 0 1 2 3 4 5 6 7 8 9 10 content / (% mol/mol)

  42. Dove House Dove Fields Uttoxeter Staffordshire ST14 8HU United Kingdom tel : +44 (0)1889 569229 e ‐ mail : paul.holland@effectech.co.uk web ‐ site : www.effectech.co.uk I SO9 0 0 1 :2 0 0 8 FS 5 5 4 5 3 9

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