1、 AGA Report No. 8 Thermodynamic Properties of Natural Gas and Related Gases DETAIL and GROSS Equations of State Third Edition April 2017 (A revision of AGA Report No. 8, 2nd edition, 1994) Prepared by Transmission Measurement Committee Part 1 AGA Report No. 8 Part 1 Thermodynamic Properties of Natur
2、al Gas and Related Gases DETAIL and GROSS Equations of State Prepared by Transmission Measurement Committee Third Edition April 2017 (A revision of AGA Report No. 8, 2nd edition,1994) Copyright 2017 American Gas Association All Rights Reserved Catalog No. XQ1704-1 ii iii DISCLAIMER AND COPYRIGHT The
3、 American Gas Associations (AGA) Operations and Engineering Section provides a forum for industry experts to bring their collective knowledge together to improve the state of the art in the areas of operating, engineering and technological aspects of producing, gathering, transporting, storing, dist
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5、ngineering Section technical committee. While AGA may administer the process, neither AGA nor the technical committee independently tests, evaluates or verifies the accuracy of any information or the soundness of any judgments contained therein. AGA disclaims liability for any personal injury, prope
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13、o urge action that is not in compliance with applicable laws, and its publications may not be construed as doing so. Information concerning safety risks, proper installation or use, performance or fitness or suitability for any purpose with respect to particular products or materials should be obtai
14、ned from the manufacturer or supplier of the material used. Changes to this document may become necessary from time to time. If changes are believed appropriate by any person or entity, such suggested changes should be communicated to AGA in writing and sent to: Operations full name of the document;
15、 suggested revisions to the text of the document; the rationale for the suggested revisions; and permission to use the suggested revisions in an amended publication of the document. Copyright 2017, American Gas Association, All Rights Reserved. iv v FOREWORD AGA Report No. 8, Part 1, is designated a
16、s the third edition of the revised 1994 second edition of AGA Report No. 8. As in the second edition, the third edition provides the technical information necessary to compute thermodynamic properties including compressibility factors and densities of natural gas and related gases for states in the
17、gas phase only. Additionally, equations for calculating speeds of sound and other thermodynamic properties are given. Historical information on this document is given in Section 1.2, Background. Analyses of the calculation of uncertainties are provided for various gas temperatures, pressures, and co
18、mpositions. It is based on research managed and sponsored by the then Gas Research Institute (GRI) in cooperation with AGA and the Groupe Europeen de Recherches Gazieres (GERG). Because the equations of state contained within International Standards Organization documents ISO 12213: Natural Gas Calc
19、ulation of Compression Factor, Part 2: Calculation Using Molar-Composition Analysis, 2006 edition, and ISO 20765: Natural Gas Calculation of Thermodynamic Properties, Part 1: Gas Phase Properties for Transmission and Distribution Applications, 2005 edition, are based on the same equations in this re
20、vision, calculated properties should have the same values. This revised edition, now designated as AGA Report No. 8, Part 1, uses the same DETAIL and GROSS equations of state as in the 1994 edition of AGA Report No. 8. However, the temperature, pressure, and gas composition limits have been modified
21、 in this edition; and therefore, it will be necessary to ensure that the temperature, pressure, and gas composition fall within the new limits for the desired uncertainty. The users are advised to verify the applicability/acceptability of the program for the new limits based on the 1994 edition of A
22、GA 8. The documentation of programs for calculating properties from the methods described in this document is available as supplementary material in Appendix C. Examples are available in Fortran, VB, and C+ code. The supplementary material also contains a Microsoft Excel spreadsheet for property cal
23、culations. This can be used to determine if, for a particular temperature, pressure, and composition, the property values calculated from the equations in Part 1 are within the desired uncertainty (by comparing with those in Part 2) even though one or more of these inputs may be outside the ranges g
24、iven in Part 1. A file containing calculated points at different compositions (not necessarily related to typical natural gas) is included, which can be used to verify that programs or equipment have been implemented or upgraded correctly to produce values that are in agreement with the equations in
25、 this document. The user is encouraged to compare property values obtained through the use of the software provided in this edition with those obtained from the users existing software and determine if the differences are within the uncertainty limits of their respective calculation methods. The Exc
26、el spreadsheet provided in the supplementary material can be used to determine if property values are within the acceptable uncertainty limits even though the state point may be outside the ranges given in this revision. If the property values are not within the uncertainty limits, the user should c
27、onsider implementing AGA Report No. 8, Part 2, noted below. AGA Report No. 8, Part 2, published separately, is based on the GERG-2008 equation of state, and is applicable for temperature, pressure, and composition ranges outside those in Part 1, with uncertainties in density, compressibility factor,
28、 and speed of sound still within 0.1 %. Part 2 can also be used for operating conditions and compositions that are applicable for Part 1, with differences in the calculated values within the uncertainty limits of each equation, where uncertainties are given with a 95 % level of confidence (k=2). Whi
29、le adoption of the equations in Part 2 is encouraged, the decisions to upgrade existing installations to use AGA Report No. 8, Part 2, are left to the discretion of the parties involved. Some material described in Part 1 also applies to Part 2, and vice versa, and is not repeated in both parts. For
30、example, Part 1 describes an algorithm for obtaining densities through an iterative procedure that can also be used with the equations in Part 2 (and which is applied for this purpose to the GROSS, DETAIL, and GERG-2008 equations of state in the programs in the supplementary material). Similarly, Pa
31、rt 2 outlines the method for reporting calculated results and uncertainties from the equations in both parts, and also describes the experimental vi database available for natural gas mixtures (both binary and multicomponent systems), much of which was used in the development of the equations in Par
32、t 1. Some information, however, is repeated in both parts, such as the material in Sections 2 and 3. The combination of Parts 1 density at 60 F, 14.73 psia) and in SI units are (15 C, 0.101325 MPa; density at 0 C, 0.101325 MPa). The upper limit for the mole percent of CO2 is reduced under the follow
33、ing conditions: xCO2,max = 20 % when xN2 7 % xCO2,max = 5 % when xC3 2 % xCO2,max = 10 % when xN2 15 % xCO2,max = 10 % when xiC4 0.1 % xCO2,max = 7 % when xC3 1 % xCO2,max = 10 % when xnC4 0.3 % See the discussion in Section 1.3.1 for further information. 6 1.3.2 GROSS Equation of State The GROSS eq
34、uation of state was developed for dry, sweet natural gas to calculate compressibility factors. The limits for this method are listed in Table 2. For some gases at the upper limits of the allowed compositions, with temperatures below 80 F (27 C) or at pressures above 800 psia (5.5 MPa), the uncertain
35、ty of the GROSS equation of state can exceed 0.1 %. The maximum composition limits were therefore significantly reduced from the 1994 edition of AGA 8 so as to meet the 0.1 % uncertainty level. When exceeding the bounds listed in Table 2, the procedure given at the end of Section 1.3.1 for validatin
36、g the uncertainty of a particular state should be followed. Section 5 and Appendix A present information for this equation of state. Optimally, natural gas property calculations from the GROSS equation require the gas composition, i.e., the mole fractions of the components in the mixture. When this
37、information is not available, methods given in Appendix A can be used as a substitute to obtain the molar ideal gross heating value HCH of the mixture of hydrocarbon components present in the natural gas along with the compositions of nitrogen and carbon dioxide in the mixture. Table 2 Ranges for Te
38、mperature, Pressure, Heating Value, and Relative Density with Uncertainties Less than 0.1 % in Compressibility Factors of Natural Gas Calculated with the GROSS Equation of State Quantity Range 1 Range 2 Temperature 25 F to 143 F (4 C to 62 C) 17 F to 143 F (8 C to 62 C) Maximum pressure 1500 psia (1
39、0.3 MPa) 600 psia (4.1 MPa) Relative density 0.554 to 0.63 0.554 to 0.89 Gross heating value 930 to 1040 Btu/scf 665 to 1100 Btu/scf 34.7 to 38.7 MJ/m3 24.8 to 41 MJ/m3 Upper composition limits (mole percent) Nitrogen 7 20 Carbon dioxide 3 25 Ethane 2 8 Propane 0.5 4 Total butanes 0.3 0.5 Total pent
40、anes 0.2 0.3 Hexanes plus 0.04 0.08 Hydrogen 0.2 2 Oxygen 0.2 0.5 Carbon monoxide 0.4 1 Water 0.03 0.2 Hydrogen sulfide 0.08 0.2 Helium 0.05 0.3 Argon 0.1 0.2 Values are based on a methane lower composition limit of 60 mole percent. Reference conditions in U.S. customary units are (60 F, 14.73 psia;
41、 density at 60 F, 14.73 psia) and in SI units are (15 C, 0.101325 MPa; density at 0 C, 0.101325 MPa). The nonhydrocarbon species listed in this table (except nitrogen and CO2) are considered here as impurities for use in the GROSS equation of state, and should be added to the equivalent hydrocarbon
42、mole fraction as explained in Section 5.2. The SGERG-88 equation contains additional parameters for hydrogen and carbon monoxide, and Reference 3, ISO 12213:3, or GERG TM 5 (1991) should be consulted when the mixture contains these fluids. 7 1.4 Uncertainty The uncertainties of compressibility facto
43、rs or densities (relative deviations calculated in terms of Z or in terms of d are nearly identical but with an opposite sign) calculated with either the DETAIL equation of state or the GROSS equation of state depend upon the natural gas composition and the operating temperature and pressure conditi
44、ons. Evaluations of the uncertainties of calculated compressibility factors for natural gas were made by comparing to the GRI and GERG compressibility factor reference databases. The reference databases have similar natural gas physical characteristics as those listed in Table 1. Comparisons were al
45、so made with data for pure fluids and binary mixtures. Lastly, comparisons were made with experimental speed-of-sound data to access derived thermodynamic property capabilities of the DETAIL equation of state. Uncertainty analyses are available in Appendix B. 1.4.1 DETAIL Equation of State Uncertain
46、ty The GRI and GERG compressibility factor reference databases and comparisons with the GERG-2008 equation of state have verified the expected uncertainties given in Table 1 and within Region 1 and parts of Regions 2, 3, and 4 of Figure 1. The boundaries in Table 1 can often be exceeded at lower tem
47、peratures or higher pressures than those given. The last paragraph of Section 1.3.1 explains the procedure that can be used to determine if a particular gas or operating condition still resides within the 0.1 % uncertainty limit. 1.4.2 GROSS Equation of State Uncertainty In general, the expected unc
48、ertainty in density of the GROSS equation of state is 0.1 % for natural gas having compositions and operating conditions identified in Table 2. The GRI and GERG compressibility factor reference databases and comparisons with the GERG-2008 equation of state have verified the expected uncertainties gi
49、ven in Table 2. The equation was not designed for and should not be used outside of these limits, unless comparisons as described in the last paragraph of Section 1.3.1 have been made. 1.5 Recommendations Two different equations for the compressibility factor, the DETAIL equation of state and the GROSS equation of state, are provided in Part 1. The choice of a particular equation of state depends on the natural gas composition and operating conditions, and the uncertainty expectation. See Part 2 for liquid phase and vapor-liquid equilibrium ph
