LNG measurement uncertainty,

review and progressKianoosh Hadidi

LNG workshop, Aberdeen 25th Oktober 2018

Workshop and Training 2018

The content of this presentation has been taken from the work carriedout by the partners in EMPR JRP, ENG03 LNG & ENG60 LNG II.

The related sources have been mentioned at the footnotes.

introduction

Start point ENG03 2009: Real estimation of measurement uncertainty of LNG energy, 1% Equivalent economic value of a reduction of 0.5 % in the energy

uncertainty was predeicted to be 150M€/year

𝐸 = 𝑉𝐿𝑁𝐺 ∙ 𝐷𝐿𝑁𝐺 ∙ 𝐺𝐶𝑉𝐿𝑁𝐺 + 𝐸𝐺𝐴𝑆 𝐷𝐼𝑆𝑃𝐿𝐴𝐶𝐸𝐷 ± 𝐸𝐺𝐴𝑆 𝑡𝑜 𝐸𝑅

These values can be either agreed on a certain value or determind, negligablecontrinution in many cases

The main contribution to theenergy uncertainty

MassLNG

The energy content in the tranfered LNG

LNG performance: Methane Number, an indication of theknocking behavier of a LNG

These two quantities have direct economic impact on LNG trade

introduction

Traceability

Development of calibration standards

Produce Reference data

Uncertainty evaluation

Measurement function

Clear estimation of the uncertainty sources

Uncertainty budget

Modification and developelment

New measurement methods/devices

Calculation methods

Uncertaintyreduction

Content

Mass flow measurement

Small scale mass flow standard

Volume flow measurement

Uncertainty evaluation of tank gauging systems

(LDV) based standard, and mid scale flowmeter calibration standard

Density measurement/calculations

State-of-the-art primary density standard

Development of a speed of sound (SOS) sensor

Development of a new fandamental equation of state

Gas calorific value, model calculation and uncertainty estimation

Energy uncertainty budget in large scales

The effect of small composition variation on the uncertainty of the LNG density and calorific value

The effect of temperature changes on the uncertainty of the LNG density

Methane number

Mass flow measurementSmall scale mass flow standard

A primary LNG mass flow standard at Rotterdam for small scale test and calibration facility Based onweighing method

Start point in development traceability

Measurement model of the reference mass

𝜑𝑀 𝑢𝑇 =𝑚𝑀𝑢𝑇 −𝑚𝑟𝑒𝑓

𝑚𝑟𝑒𝑓× 100

𝑚𝑟𝑒𝑓 = ∆𝑚𝑠𝑐𝑎𝑙𝑒 +𝑚𝑣𝑎𝑝𝑜𝑢𝑟 + 𝐶𝑖𝑛𝑐𝑙𝑖𝑛𝑎𝑡𝑖𝑜𝑛 + 𝐶𝑙𝑖𝑛𝑒𝑝𝑎𝑐𝑘

𝑚𝑣𝑎𝑝𝑜𝑢𝑟= total vapour mass flowing out of the weighing tank during calibration time window

∆𝑚𝑠𝑐𝑎𝑙𝑒 = accumulated cryogenic liquid in the weighing tank during the test time window

𝐶𝑙𝑖𝑛𝑒𝑝𝑎𝑐𝑘= correction due to change in trapped liquid mass between MuT and weighing tank,

𝐶𝑖𝑛𝑐𝑙𝑖𝑛𝑎𝑡𝑖𝑜𝑛= correction due to non-constantinclination of the calance

Results of the evaluation and preliminary validation of a primary LNG mass flow standard Metrologia 51 (2014) 539–551 doi:10.1088/0026-1394/51/5/539

Mass flow measurementSmall scale mass flow standard

The targeted uncertainty of the standard, 0.05%

The reached value of uncertainty 0.12% - 0.15%,

The main contributions to the irreproducibility are related to nonreversible parasitic forces in the weighing system

Potential improvement to reduce the CMC down to 0.1%

Results of the evaluation and preliminary validation of a primary LNG mass flow standard Metrologia51 (2014) 539–551 doi:10.1088/0026-1394/51/5/539

Volume flow measurement

Uncertainty evaluation of tank gauging systems

Ship tank volume measurement model.

Applicable for Membrane tank and a Moss tank

This work was fully in accordance with GUM and included real shipment data

Model measurement function

𝑉 = 𝑉𝑡𝑎𝑏𝑙𝑒 + 𝑐𝑉 𝐶𝑡𝑎𝑛𝑘,𝑡 𝑇 𝐶𝑡𝑎𝑛𝑘,𝑝 𝑝∆𝑉𝑇𝐴𝐵𝐿𝐸

∆ℎℎ − 𝑇𝑟𝑢𝑛𝑐(ℎ)

h = ℎ𝑖𝑛𝑑 𝐶𝑔𝑎𝑢𝑔𝑒,𝑇 𝑇𝑔𝑎𝑢𝑔𝑒 𝐶𝑔𝑎𝑢𝑔𝑒,𝑝 𝑝𝑔𝑎𝑢𝑔𝑒 + ∆ℎ𝑡𝑟𝑖𝑚 + ∆ℎ𝑙𝑖𝑠𝑡 + ∆ℎ𝜌 +

∆ℎ𝑐𝑜𝑚𝑝 + ∆ℎ𝑐𝑎𝑙 + ∆ℎ𝑑𝑟𝑖𝑓𝑡

Trim expressed in metres or fractions of a metre, according to the difference in bow and stern drafts

List represented by the angle α in degrees to port. In this illustrative case, the correction will be negative

Evaluation uncertainty in transferred LNG, https://lngmetrology.info/publications/project-reports/

Moss type Membrane type

Volume flow measurementUncertainty evaluation of tank gauging systems

An overview of relevant input quantities is given. Red color indicates that they may significantly influence the measurement of transferred volume.

Tank

Calibration

Drift/stabilit

Resolution

Temp. dim. structure

Hydrostaticpressure

Sagging/ Hogging

Temp. sensors

Inclinometer

Calibration

Drift/stabilit

Resolution

Disper. in readings

Sagging/ Hogging

Pressure gauge

CalibrationDrift

Float level gauge

Tape temp.

Liquid densityBoyancy

Calibration Location

Drift

Disper. in readings

Calibration

Drift/stabilit

Disper. in readings

Radar level gauge

Calibration

Mount. position

Temp.

Drift

Disper. readings

Surface detection

Measurand Value Uncertainty

Distribution

Standard uncertainty

Rel. Uncertaint

ySensitivity Contributio

n

hind,stop [m] 4,000 0,0075 normal 0,00 0,09 % 1 0,0038Dhcal [m] 0,000 0,002 normal 0,00 NA 1 0,0010Dhdrift [m] 0,000 0,01 normal 0,01 NA 1 0,0050

Dhtrim,stop[m] -0,009 0,000 rectangular 0,00 0,10 % 1 0,0000Trim [m] 0,033 0,01 rectangular 0,01 15,38 % -0,038 -0,0002

cTrim,loc,cal [m] 0,200 0,1 normal 0,05 25,00 % -0,038 -0,0019Dhlist,stop[m] -0,013 0,002 rectangular 0,00 -7,50 % 1 0,0010

List [°] 0,019 0,01 rectangular 0,01 26,32 % -0,007 0,0000cList,loc,cal [m] 2,000 0,5 standard 0,50 25,00 % -0,007 -0,0033Ttank,start [°C] -150,000 5 rectangular 2,50 -1,67 % 4,00E-06 0,0000Tref,tank [°C] -160,000 2 standard 2,00 -1,25 % -4,00E-06 0,0000

Tgauge,start [°C] -130,000 5 standard 5,00 -3,85 % -4,00E-06 0,0000Tref,gauge [°C] 20,000 0,5 standard 0,50 2,50 % 4,00E-06 0,0000

a 1,000E-06 standard

0,000,00 % 40 0,0000

b 1,000E-06 standard

0,000,00 % -600 0,0000

hstop 3,978 uh,empty 0,0075

Uh,empty 0,0149

Uh,empty* 0,38 %

Evaluation uncertainty in transferred LNG, https://lngmetrology.info/publications/project-reports/

Volume flow measurementUncertainty evaluation of tank gauging systems

Uncertainty budget of Moss type tank

Volume measurementUncertainty evaluation of tank gauging systems

• 𝐔𝑽=0.21%, GIIGL third edition 2010

• 𝐔𝑽=0.20 % to 0.55 % (k = 2) GIIGL fifth edition 2017

Measurand Value Uncertainty Distribution Standard uncertainty

Rel. st. uncertainty Sensitivity Contributi

onVtable (Trunc(hstart)) 34000 70,00 normal 35,000 0,10 % 1 35,00

hstart 22,84943 0,03774 standard 0,03774 0,17 % -1273,062204 -48,05DVSaggingHogging,start 0,000 70,000 rectangular 35,000 NA 1 35,00DVHydrostatic,start 0,000 70,000 rectangular 35,000 NA 1 35,00DVTable,drift,start 0,000 0,000 rectangular 0,000 NA 1 0,00

rectangular 0,000 NA 0,00Vtable (Trunc(hstop)) 1600 3,20 rectangular 1,600 0,10 % 1 1,60

hstop 0,15000 0,00786 standard 0,00786 5,24 % -19,05461974 -0,15DVSaggingHogging,stop 0,000 3,500 rectangular 1,750 NA 1 1,75DVHydrostatic,stop 0,000 3,500 rectangular 1,750 NA 1 1,75DVTable,drift,stop 0,000 0,800 rectangular 0,400 NA 1 0,4Ttank,start (°C) 20 20,0 rectangular 10,000 50,00 % 1,1E+00 11,22Ttank.stop (°C) 20 20,0 rectangular 10,00 50,00 % 5,3E-02 0,53Ttank,ref (°C) 20,00 2 rectangular 1,00 5,00 % -1,1E+00 -1,12

a 1,10E-05 1,1E-06 rectangular 0,00 5,00 % 0 0,0Vtank unloaded 33242,13 uVloaded 87.97

UV,loaded 175.95

UV,loaded* 0.53%

Evaluation uncertainty in transferred LNG, https://lngmetrology.info/publications/project-reports/

Uncertainty budget of membrane type tank

• Larger than twice the uncertainty mentioned in third edition of GIIGNL 2010

• Better agreement in GIIGNL 2017

Volume flow measurement(LDV) based standard, and mid-scale flowmeter calibration standard

Uncertainty budget flow rate measurements in LNG by Laser Doppler Velocimetry https://lngmetrology.info/publications/project-reports/

A new Laser Doppler Velocimetry (LDV) based standard

Mid-scale flow meter calibration has been built at Rotherdam

It is presently under testing

The master flow meter calibrated based on weighing method in the first LNG project

When operational this facility will enabletreacible calibration with an establisheduncertainty

Developed in ENG03 LNG and ENG60 LNG II

Further modification in LNG III to be validated in croyogrnic canditions and defined as primary reerence standard for LNGstandard

LDV standard can be a great support to cross valide this novel and traceable calibration standards facility

Measurement function:

Uncertainty budget flow rate measurements in, LNG by Laser Doppler Velocimetry https://lngmetrology.info/publications/project-reports/

Volume flow measurement(LDV) based standard, and mid-scale flowmeter calibration standard

𝑄𝑣 =𝑣𝑎𝑥𝑖𝑠 ∙ 𝜋 ∙ 𝑑

2

4(𝑎 + 𝑏 ∙ 𝑙𝑛(𝜌 ∙ 𝑣𝑎𝑥𝑖𝑠∙ 𝑑

𝜇 + 𝜖)

𝑄𝑣 Volumetric flowrate obtained from the LDV system

𝑣𝑎𝑥𝑖𝑠 Measured axial velocity using the LDV system

d Internal diameter of the LDV convergent throat

𝑎 Intercept of the model function

b Slope of the model function

𝜌 Density of LNG at local conditions of pressure and temperature

𝜇 Viscosity of LNG at local conditions of pressure and

𝜖 Model function error

A full uncertainty budget has been defined for LNG measurements. Field data was not acceible to apply. A randomly measurement data of liquid nitrogen at laboratory conditions shows a relative uncertainty of 0.63%.

A new Laser Doppler Velocimetry (LDV) based standard

Density measurementState-of-the-art primary density standard

Results of the LNG density measurements including uncertainty, https://lngmetrology.info/publications/project-reports/

Density measurement Single-Sinker Densimeter for cryogenic liquid mixtures

A special single-sinker densimeter

T-range: 90 K to 300 K

p-range: 0.05 MPa to 12 MPa