LNG workshop. Flow Metering. Peter Lucas and Nikola Pelevic

Transcription

1 LNG workshop Flow Metering Peter Lucas and Nikola Pelevic

2 Physical Properties Page

3 Flow metering Contents of this module Flow meter technology Fluid properties and measurement Calibration methods Field comparison tests and calibration Regulation

4 Flow metering applications LNG allocation metering skid in Qatar LNG Floating Production Storage Offloading LNG custody transfer at regasification terminal LNG truck fuelling LNG buses LNG bunkering

5 Flow metering technologies Requirements flow meters Low pressure drop to avoid (local) boiling Minimal moving parts The ability to function in cryogenic conditions Proven performance Common technologies Coriolis flow meters (Clamp on) ultrasonic flow meter Other technologies Turbine Laser Doppler Velocimetry (Anemometry)

6 Coriolis Principle t Principle U bend excited at natural frequency Ω Coriolis effect: perpendicular deflection of moving parts Twist angle is a measure for mass flow rate Natural frequency is a measure for density sbofw Practice Two vibrating tubes Phase difference ( t) is a measure for mass flow rate Natural frequency is a measure for mass

7 Coriolis flow meter General considerations - Not sensitive to flow profile (although there are discussions with respect to sensitivity to Re) - Relative large pressure drop - Proper mounting and support required (internal stress impacts zero reading) - Zero procedure before calibration required - Water flow calibration reflects a lot of other liquids - Big and very heavy: limited available pipe sizes

8 Coriolis flow meter Application to LNG - Proven technology, already used for small and mid scale - Relative large pressure causing (local) boiling not really an issue - Avoid internal stresses (due to contraction) - Correct for contraction flow meter (density reading) - Correct for Young s elasticity modules (density and mass flow rate reading) - Meter factor based on calibration with LNG - Meter factor based on calibration with water and temperature (extrapolation) model

9 Ultrasonic flow meter Principle Principle Travelling sound wave is convected (transported) with flow Difference between upstream and downstream sound wave is measure for velocity Flow rate is velocity times surface area Practice Various paths to get a good average for the velocity

10 Ultrasonic flow meter General considerations - Low pressure drop - Sensitive to sound wave attenuation (damping), reflection and deflection (particles/ impurities, boiling) - Minimal pipe size (3 ~ 4 ) - Sensitive to flow profile - Enough upstream pipe length - Multi path flow meter - Flow conditioner - Calibration inclusive upstream piping

11 Ultrasonic flow meter Application to LNG - Becoming more common for large scale, however as of yet only to monitor the process - Not suitable for small scale LNG custody transfer (< 3 ~ 4 ) - Very sensitive to (local) boiling - Low pressure drop - Correct for contraction flow meter - Meter factor based on actual calibration - Meter factor based on calibration with water and temperature (extrapolation) model

12 Flow metering Contents of this module Flow meter technology Fluid properties and measurement Calibration methods Field comparison tests and calibration Regulation

13 Pressure Density Volume mass m V Density required for Mass to volume conversion (or vice versa) Line pack corrections 10 bar 500 kg/m kg/m kg/m 3 NG 20 o C ~ 100% / bar ~ 0.3% / o C Water at 20 o C ~ 0.1% / bar ~ 0.1% / o C 1 bar 100 K 120 K Temperature LNG at -165 o C (108 K) ~ 1% / bar ~ 0.4% / o C

14 Pressure and temperature The pressure and temperature are needed to - Determine the density (together with composition) - Determine the probability of no boiling, potential local boiling or boiling - Correct the flow meter reading in case of a significant dependency on pressure and/ or temperature

15 Temperature Elements - RTD (Pt-100) - Thermo well - Transmitter - Read out Challenges - Heat leakage - Slow process - Point measurement - Close to the flow meter Flow

16 Pressure Elements - Membrane (fast process) - Transmitter Challenges - Measure close to meter - No cryogenic membranes available - The pressure in a liquid column follows from: p g h - Correction required in case pressure sensor and tap point are not located at the same height - (Point measurement)

17 Flow metering Contents of this module Flow meter technology Fluid properties Calibration methods Field comparison tests and calibration Regulation

18 Calibration Prior considerations Type of flow meter (USM, CMF) Use of the flow meter in the field (ambient conditions, installation effects, insulation) What can we expect from the calibration facility Traceability required Required uncertainty

19 Calibration methods Methods Gravimetric Pipe prover method Master meter method Piston prover tank

20 Gravimetric method Principle

21 Gravimetric method Application to cryogenic fluids Open collection tank not possible: Fixed connection between scale and world (VSL, NL) No connection Fast and spill free decoupling mechanism (VSL) Road tanker (JV, NK) Tank within a tank (NIST/ CEESi, USA)

22 Gravimetric method Fixed connection Cooling down by depressurization Subcooling by pressurization MUT mmut m m scale scale Stabilizing mode Calibration mode

23 Gravimetric method Fixed connection - considerations Permanent set up Fixed connection causes additional forces on balance which are difficult to predict Steady and good control of flow conditions Continuous signal during calibration Small scale Q m = kg/s Uncertainty 0.15 ~ 0.2%

24 Gravimetric method Road tanker (no connection) 1 - Loading of LNG road tanker MUT mmut m m scale scale 3 - Unloading of LNG road tanker Unloading LNG road tanker 24 Weighing full empty LNG LNG road Test Coriolis flow tanker road tanker meters Storage tank LNG workshop - module 2C

25 Gravimetric method Road tanker - considerations Temporarily set up Mass changes road tanker difficult to predict Unsteady flow and no control of flow conditions Only start and end mass available Uncertainty on mass 0.2%

26 Gravimetric method Tank within tank - principle Load cell Calibration weights Weighing tank

27 Gravimetric method Tank within tank - considerations Permanent setup Steady and good control of flow conditions Buoyancy force difficult to predict Small scale Q m = kg/s Uncertainty 0.12 ~ 0.15%

28 Master meter method Principle

29 Master meter method Considerations Permanent set up Not a primary standard Bootstrapping can be used to get traceability for larger flow rates Good control of flow conditions Uncertainty follows from primary standard

30 LNG flow calibration standard (design schematics) Front view

31 Flow metering Contents of this module Flow meter technology Fluid properties Calibration methods Field comparison tests and calibration Regulation

32 Coriolis flow meter Flow metering accuracy small scale Right scale A B C D

33 Field applications Small scale custody transfer results - Good reproducibility - Good agreement From Mortensen and Kolbjørnsen, Field tests for the comparison of LNG static and dynamic mass measurement methods, JV, 2013

34 Field applications Large scale custody transfer set up Comparison volume USM and tank gauging 1 : Ship tank gauging based on GIIGNL Terminal tank gauging based on GIIGNL Volume measurement using an USM (dual path, 32 ) Part of Metrology for LNG Location: Enagás Terminal Cartagena Date: April 2011 to April 2013 Difference defined as: VUSM V V tank tank 1) Benito et al, presented at LNG conference, Delft, 2013

35 Field applications Large scale custody transfer results - Poor reproducibility - Significant deviation USM vs tank terminal USM vs tank ship

36 Flow metering Contents of this module Flow meter technology Fluid properties Calibration methods Field comparison tests and calibration Regulation

37 Legal requirements for Custody Transfer B2B or B2C Law states that all transactions based on mass (NAWI) or volume of liquids (MID) must be metered with approved meters B2B transactions regarding gaseous fuels which are not intended for residential, commercial or light industrial use do not require MID approved meters The definition for light industrial use differs from member state to member state E.g. in the Netherlands, limit is given by the condition that the amount delivered > m 3 (n)/year or a connection to the local grid > Qmax 40m 3 /h Page

38 Measuring system volume/mass of cryogenic liquids, EU Into the market: - The MPE on the complete metering system is 2,5% (incl. the flow meter MPE set at 1,5%) - The return gas flow should be seen as part of the metering system and as such should also fit within the 2,5% MPE In use: MPE for measuring system (National legislation): - 2,5% with exception of Denmark, Iceland, Romania, Slovakia, Slovenia and Switzerland. MPE > 2,5% Page LNG Custody Transfer Study P 38

39 LNG Custody Transfer related standards ISO '11 calibration and verification of automatic tank gauges ISO 10976'12 Procedure for custody transfer on board ships ISO 8943'07 the continuous and intermittent sampling of LNG Legend GAP/not ready LNG Metrology/ custody transfer NG Metrology/ custody transfer Large/Mid scale Applicable in general Small scale ISO '11 verification testing of automatic level gauges GIIGNL Int. Group importers of LNG custody transfer handbook EU Directive 23/2009/EG Class III type approved weighing instruments (non automatic weighing instruments: NAWI GERG 2008 Equations of State for NG / LNG AGA Report No.5 NG energy measurement ISO 6976:1995 Natural gas, Calculation of calorific values, density, etc. ISO 6974:2012 Natural gas, composition, gas chromato graphy. ISO /DIS Part 1-18 different issues, reqrmnts, Test methods, Safety issues, Temperature sensors etc OIML Int. Org. For Legal Metrology API 521 pressure-relieving and vapourdepressuring systems ISO 12991'12 construction requirements for refillable fuel tanks for LNG ISO/DIS designing LNG filling stations/ dispenser systems OIML R81 Dynamic measurement devices for cryogenic liquids However: No Massflow meters EU MID 2004/22/ec annex 1&5 European Legal Metrology Interpretation by NOBO OIML R117 Dynamic Measurement Systems Liquid other than Water ISO /DIS fuelling nozzles and receptacles constructed NFPA 57 design, installation, operation, maintenance of (LNG) engine fuel systems and dispensers MID certificate OIML testreports OIML R105 Massflow meters However non cryogenic Design metering systems, test protocols Combine R81,105,117&solve LNG Custody Transfer Study Page P 39 inconsistencies

40 VSL PO Box AR Delft The Netherlands T F E I info@vsl.nl Erik Peter Smits Lucas E fsmits@vsl.nl E plucas@vsl.nl Peter Lucas: nl.linkedin.com/in/lucaspeter VSL group: VSL Fluid Flow Metrology group: Questions?