GPA STD 8173-2017 Standard for Converting Mass of Natural Gas Liquids and Vapors to Equivalent Liquid Volumes.pdf

1、 Standard for Converting Mass of Natural Gas Liquids and Vapors to Equivalent Liquid Volumes GPA Midstream Standard 817317 API Manual of Petroleum Measurement Standards Chapter 14.4 Adopted as a Standard 1976 Revised 2017 GPA Midstream Association Sixty Sixty American Plaza, Suite 700 Tulsa, Oklahom

2、a 74135 GPA Midstream Standard 8173-17 American Petroleum Institute 1220 L Street, NW Washington, DC 20005 2 DISCLAIMER GPA Midstream Association publications necessarily address problems of a general nature and may be used by anyone desiring to do so. Every effort has been made by GPA Midstream to

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9、thout the written consent of the GPA Midstream Association. Contents Page 1 Scope .1 2 Summary of Method .1 2.1 General .1 3 Normative References .1 4 Terms, Definitions, Abbreviations, and Symbols 2 4.1 Definitions .2 4.2 Acronyms, Abbreviations, and Symbols 2 5 Limitations of the Standard.3 5.1 Ge

10、neral .3 6 Calculations 3 6.1 General .3 6.2 Component Volume from Mole Percent 3 6.3 Component Volume from Volume Percent .4 6.4 Component Volume from Mass Percent .5 7 Example CalculationsComponent Volume from Mole Percent (USC) 60 F.7 8 Example CalculationsComponent Volume from Volume Percent (US

11、C) 60 F8 9 Example CalculationsComponent Volume from Mass Percent (USC) 60 F 9 10 Example CalculationsComponent Volume from Mole Percent (SI) 15 C . 10 11 Example CalculationsComponent Volume from Volume Percent (SI) 15 C 11 12 Example CalculationsComponent Volume from Mass Percent (SI) 15 C . 12 13

12、 Example CalculationsComponent Volume from Mole Percent (SI) 20 C . 13 14 Example CalculationsComponent Volume from Volume Percent (SI) 20 C 14 15 Example CalculationsComponent Volume from Mass Percent (SI) 20 C . 15 1 Standard for Converting Mass of Natural Gas Liquids or Vapors to Equivalent Liqui

13、d Volumes 1 Scope This standard prescribes a method for calculating liquid volumes at equilibrium pressures and at temperatures of 60 F, 15 C, and 20 C from the mass of a natural gas fluid (liquid or vapor) measured at operating conditions, in conjunction with a representative compositional analysis

14、 and published values for each components molar mass and absolute density. 2 Summary of Method 2.1 General 2.1.1 The total mass of a natural gas liquid or natural gas vapor is determined at operating pressure and temperature using a mass measurement system. The total mass is converted to individual

15、component volumes using a representative component analysis. 2.1.2 The absolute density of pure hydrocarbons in pounds mass per gallon and in kilograms per cubic meter at 60 F and 15 C, respectively, as stated in GPA 2145, Table of Physical Properties for Hydrocarbons and Other Compounds of Interest

16、 to Natural Gas and Natural Gas Liquids Industries, shall be used. The absolute density of pure hydrocarbons in kilograms per cubic meter at 20 C, as generated from REFPROP, NIST Standard Reference Database 23, shall be used until such time as GPA 2145 includes this data set. An exception is made fo

17、r methane, which has a critical temperature of -82.59 C (190.56 K). The absolute density of 270 kg/m 3for methane at 20 C has been extrapolated from GPA 2145-09 and shall be used for methane at 20 C until GPA 2145 is updated to include a dataset of absolute densities at 20 C. Absolute densities at c

18、onditions other than those stated in GPA 2145 should be generated from REFPROP, NIST Standard Database 23, or other source(s) as agreed upon by interested parties. 2.1.3 The examples in this publication illustrate typical components. In actual practice, all the components detected that are represent

19、ative of the measured product stream should be included in the conversion to equivalent liquid volumes. 3 Normative References GPA 2145, Table of Physical Properties for Hydrocarbons and Other Compounds of Interest to the Natural Gas Industry REFPROP, Reference Fluid Thermodynamic and Transport Prop

20、erties, NIST Standard Reference Database 23 2 4 Terms, Definitions, Abbreviations, and Symbols 4.1 Definitions 4.1.1 absolute density The mass of a substance per unit of volume at a specified temperature and pressure. 4.1.2 Equilibrium Vapor Pressure (EVP) The pressure at which a liquid and its vapo

21、r are in equilibrium at a given temperature. 4.1.3 molar mass (M) The mass of a substance divided by its amount of substance. 4.1.4 mole The amount of substance of a system that contains as many elementary entities as there are atoms in 0.012 kilograms of carbon 12. 4.1.5 mole fraction The amount of

22、 a constituent divided by the total amount of all constituents in a mixture. 4.1.6 mole percent Mole fraction multiplied by 100. 4.1.7 natural gas liquids Those hydrocarbons liquefied at the surface in field facilities or in gas processing plants. Natural gas liquids include ethane, propane, butanes

23、 and natural gasoline. 4.2 Acronyms, Abbreviations, and Symbols For the purposes of this document, the following abbreviations and symbols apply. EVP equilibrium vapor pressure lbm pound mass; 1 lbm = 453.59237 grams (exact) M component molar mass; formerly molecular weight M icomponent mass per mol

24、e of mixture M tota ltotal mass per mole of mixture m total measured mass m icomponent mass from total measured mass m vicomponent mass of mixture m v tota ltotal mass of mixture 3 NGL natural gas liquid ab scomponent absolute density SI international system of units (Systeme Internationale) USC U.S

25、 customary units of measurement V icomponent volume at base temperature and a reference base pressure of 14.696 psia (101.325 kPa). When the substance is not in the liquid phase at 14.696 psia (101.325 kPa), the reference base pressure is then the equilibrium vapor pressure at base temperature. v i

26、component volume fraction of mixture w icomponent mass fraction of mixture; formerly weight fraction x icomponent mole fraction of mixture i (subscript) ith component number of components in the mixture 5 Limitations of the Standard 5.1 General 5.1.1 Methods for determining total measured mass are n

27、ot covered by this standard. 5.1.2 Methods for obtaining representative samples and subsequent compositional analyses are not covered by this standard. 6 Calculations 6.1 General 6.1.1 Three methods of calculation are presented, one for each fluid composition unit of measure: mole percent, volume pe

28、rcent, and mass percent. The method to use shall correspond with the calibration basis of the instrument used to analyze the fluid. For example, if a chromatograph is calibrated based on volume percent, the method to calculate component volume from volume percent (6.5) shall be used. 6.1.2 In order

29、to maintain consistent calculation results for accounting purposes, the arithmetic precision of calculations may imply an accuracy exceeding that of the analytical and measurement instruments. It should be noted that intermediate calculations may not represent the actual precision of the results. 6.

30、1.3 A normalization procedure is applied to certain calculations where the summation may differ from the sum of column values for the displayed precision. 6.2 Component Volume from Mole Percent Given the fluid composition as mole percent and the fluid total measured mass, calculate the component vol

31、umes at base temperature and EVP. 4 6.2.1 For each component, convert component mole percent values to component mole fraction of mixture (x i ) values by multiplying each component mole percent value by 0.01. 6.2.2 For each component, calculate component mass per mole of mixture (M i ) to six decim

32、al places by multiplying each component mole fraction (x i ) value by its molar mass (M): = Eq. (1) 6.2.3 Calculate total mass per mole for the mixture (M tota l ) by summing the component mass per mole (M i ) values: = = 1Eq. (2) 6.2.4 For each component, calculate component mass fraction of the mi

33、xture (w i ) value rounded to six decimal places by dividing each component mass per mole (M i ) value by the total mass per mole (M tota l ): = Eq. (3) 6.2.5 Normalize the component mass fraction ( ) values to total exactly 1.000000. If the sum of the component mass fractions ( = 1 ) does not equal

34、 1.000000 exactly, adjust the largest component mass fraction so that the sum of the component mass fractions equals 1.000000 exactly. If multiple component mass fractions share the largest component mass fraction value, adjust the largest component mass fraction having the least number of carbon at

35、oms. 6.2.6 Calculate component mass from total measured mass ( ) values by multiplying each component mass fraction ( ) value by the total measured mass ( ): 6.2.7 Normalize the component mass ( ) values to total exactly the total measured mass (m). If the sum of component mass values ( = 1 ) does n

36、ot equal the total measured mass ( ) exactly, adjust the largest component mass ( ) so that the sum equals the total measured mass ( ) exactly. If the largest component mass ( ) value is not unique, adjust the component having the least number of carbon atoms. 6.2.8 Calculate component volume ( ) va

37、lues for the mixture by dividing component mass ( ) values by component absolute density values ( ): = Eq. (5) 6.3 Component Volume from Volume Percent Given the fluid composition as volume percent and the fluid total measured mass, calculate the component volumes at base temperature and EVP. = Eq.

38、4) 5 6.3.1 For each component, convert component volume percent values to component volume fraction of mixture (v i ) values by multiplying each component volume percent value by 0.01. 6.3.2 For each component, calculate the component mass of the mixture (m vi ) rounded to six decimal places by mul

39、tiplying each component volume fraction (v i ) value by its absolute density ( ab s ): = Eq. (6) 6.3.3 Calculate the total mass of the mixture (m v tota l ) by summing the component mass of mixture (m vi ) values: = = 1Eq. (7) 6.3.4 For each component, calculate the component mass fraction of the mi

40、xture (w i ) value rounded to six decimal places by dividing each component mass (m vi ) value by the total mass of the mixture (m v tota l ): = Eq. (8) 6.3.5 Normalize the component mass fraction (w i ) values to total exactly 1.000000. If the sum of the component mass fractions ( w i n i = 1 ) doe

41、s not equal 1.000000 exactly, adjust the largest component mass fraction such that the sum of the component mass fractions equals 1.000000 exactly. If multiple component mass fractions share the largest component mass fraction value, adjust the largest component mass fraction having the least number

42、 of carbon atoms. 6.3.6 Calculate component mass from total measured mass (m i ) values by multiplying each component mass fraction (w i ) value by the total measured mass (m): = Eq. (9) 6.3.7 Normalize the component mass (m i ) values to total exactly the total measured mass (m). If the sum of comp

43、onent mass values ( m i n i = 1 ) does not equal the total measured mass (m) exactly, adjust the largest component mass (m i ) so that the sum equals the total measured mass (m) exactly. If the largest component mass (m i ) value is not unique, adjust the component having the least number of carbon

44、atoms. 6.3.8 Calculate component volume (V) values for the mixture by dividing component mass ( ) values by component absolute density values ( ): = Eq. (10) 6.4 Component Volume from Mass Percent Given the fluid composition as mass percent and the fluid total measured mass, calculate the component

45、volumes at base temperature and EVP. 6.4.1 For each component, convert component mass percent values to component mass fraction (w i ) values by multiplying each component mole percent value by 0.01. 6.4.2 For each component, calculate component mass from total measured mass (m i ) values by multipl

46、ying each component mass fraction (w i ) value by the total measured mass (m): = Eq. (11) 6 6.4.3 Normalize the component mass (m i ) values to total exactly the total measured mass (m). If the sum of the component mass values ( = 1 ) does not equal the total measured mass ( ) exactly, adjust the la

47、rgest component mass ( ) such that the sum equals the total measured mass ( ) exactly. If the largest component mass ( ) value is not unique, adjust the component that has the least number of carbon atoms. 6.4.4 Calculate component volume (V) values for the mixture by dividing component mass (m i ) values by component absolute density values ( ab s ): = Eq. (12) 7 7 Example CalculationsComponent Volume from M