1、Measurement of Thermally Cracked GasAPI TECHNICAL REPORT 2575 FIRST EDITION, SEPTEMBER 2014Special NotesAPI publications necessarily address problems of a general nature. With respect to particular circumstances, local, state, and federal laws and regulations should be reviewed.Neither API nor any o
2、f APIs employees, subcontractors, consultants, committees, or other assignees make any warranty or representation, either express or implied, with respect to the accuracy, completeness, or usefulness of the information contained herein, or assume any liability or responsibility for any use, or the r
3、esults of such use, of any information or process disclosed in this publication. Neither API nor any of APIs employees, subcontractors, consultants, or other assignees represent that use of this publication would not infringe upon privately owned rights.API publications may be used by anyone desirin
4、g to do so. Every effort has been made by the Institute to assure the accuracy and reliability of the data contained in them; however, the Institute makes no representation, warranty, or guarantee in connection with this publication and hereby expressly disclaims any liability or responsibility for
5、loss or damage resulting from its use or for the violation of any authorities having jurisdiction with which this publication may conflict.API publications are published to facilitate the broad availability of proven, sound engineering and operating practices. These publications are not intended to
6、obviate the need for applying sound engineering judgment regarding when and where these publications should be utilized. The formulation and publication of API publications is not intended in any way to inhibit anyone from using any other practices.Any manufacturer marking equipment or materials in
7、conformance with the marking requirements of an API standard is solely responsible for complying with all the applicable requirements of that standard. API does not represent, warrant, or guarantee that such products do in fact conform to the applicable API standard.All rights reserved. No part of t
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9、05.Copyright 2014 American Petroleum InstituteForewordNothing contained in any API publication is to be construed as granting any right, by implication or otherwise, for the manufacture, sale, or use of any method, apparatus, or product covered by letters patent. Neither should anything contained in
10、 the publication be construed as insuring anyone against liability for infringement of letters patent.Suggested revisions are invited and should be submitted to the Standards Department, API, 1220 L Street, NW, Washington, DC 20005, standardsapi.org.iiiContentsPage1 Scope . . . . . . . . . . . . . .
11、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Normative References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
12、 Terms, Definitions, Abbreviations, and Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.1 Terms and Definitions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13、. . 13.2 Abbreviations and Symbols. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.3 Units and Conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14、 . . . . . . . . . . . . 24 Types of Gases Covered. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Operating Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15、. . . . . . . . . . . . . . . . . . . . . . . 36 TCG Calculation Method Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46.1 Overview of Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46.2 TCG Reference Mixture Data56.3 TCG Method Uncertainty57 General Equations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 Reference Conditio
17、ns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58.1 Mass Density at Contract Condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58.2
18、FpvReference Condition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68.3 Relative Density Reference Condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19、. . . . 69 TCG Method for Compressibility Factors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20、. . . . . . . . . . . . . . . 69.2 TCG Virial Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Annex A (informative) Example Computation Flow Diagram . . . . . . . . . . . . . . . . . . . . . . . .
21、 . . . . . . . . . . . . . . . . . 11Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Figures1 Targeted Uncertainty for Thermally Cracked Gas Mixture . . . . . . . . . . . .
22、. . . . . . . . . . . . . . . . . . . . . . . . . . . 4A.1 Example Flow Diagram for Computing Z Using the Virial Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Tables1 Units Conversions 32 Thermally Cracked Gas Characteristics . . . . . . . . . . . . . . . . . . . . . . . . .
23、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Illustrative Example Terms for Equation (7) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 Illustrative Example Terms for Equation (8) . . . . . . . . . . . . . . . . . . . . . . .
24、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9A.1 Example TCG Components and Mole Percents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13A.2 Example TCG T and P Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
25、 . . . . . . . . . . . . . . . . . . . . . . . . 13A.3 Illustrative Example CalculationB Terms ( 293.15 K) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14A.4 Illustrative example calculation - C terms ( 293.15 K) . . . . . . . . . . . . . . . . . . . . . . . . . . .
26、. . . . . . . . . . . . . 15vIntroductionThis document initiates improving thermally cracked gas (TCG) property calculation methods for measurement applications. It is a research report on TCG research work in progress. The methods presented here are for example illustration purposes only. They are
27、not for use at this stage in the development work. Modifications will occur to the methods presented here and to other industry methods commonly used for TCG measurement once the research work is completed. The goal is to reduce TCG custody transfer uncertainty. TCG is not a naturally occurring natu
28、ral gas mixture. It is produced as a by-product in the refining process of petroleum fluids. The principal flow measurement method used to measure TCG is orifice measurement as applied in API MPMS Ch. 14.3/AGA Report No. 3/GPA 8185. These documents reference the use of API MPMS Ch. 14.2/AGA Report N
29、o. 8/GPA 8185 for compressibility factor calculations. The assumption in the current application of API MPMS Ch. 14.3/AGA Report No. 3/GPA 8185 is that the fluid sampling, measurement, and calculations conditions are in the single gas phase region and that the fluid components are consistent with AP
30、I MPMS Ch. 14.2/AGA Report No. 8/GPA 8185. TCG mixtures contain significant quantities of olefins and hydrogen. These fluid mixtures are not natural gases and fall outside of natural gas measurement and operation practices.No reference or inference is made in API MPMS Ch. 14.2/AGA Report No. 8/GPA 8
31、185 to applying natural gas components as chemical analogs for olefinic compounds, or that high concentrations of hydrogen can be permitted in such mixtures. Nor do current industry measurement documents make statements regarding the uncertainty of such practices. Current orifice measurement standar
32、ds do not address the metering, operations, or physical properties of TCGs. Industry practice has been to substitute natural gas component analogs as a means to estimate TCG property values for custody transfer. This practice increases measurement uncertainties. In order to address the issues associ
33、ated with TCGs, API initiated a four-phase project on TCG measurement. Phase I evaluated current TCG measurement practices. The results suggested that component substitution methods produced mass density uncertainties of 0.3 % to 5 % for TCG mixtures. The uncertainty depends on operating conditions.
34、 Phase I identified experimental data gaps and the need for experimental reference data over custody transfer and common pipeline operating conditions. In order to initiate filling experimental data gaps for TCG mixture mixtures, a single gas mixture was prepared and measured during Phase II. The Ga
35、s Technology Institute (GTI) provided the experimental setup and measured data to support Phase II work. The experimental work measured gas phase measurements of density, sound speed, and capacitance for a synthetic TCG mixture over a narrow operating range. Measured data were compared to predicted
36、values from API MPMS Ch. 14.2/AGA Report No. 8/GPA 8185, NIST14-DDMIX, GERG 2004/GERG 2008, and the Soave-Redlich-Kwong equations of state. Subsequent analysis was also made using ISO 20765-2 for extended range applications. This report completes the Phase III work. The final phase, Phase IV, will o
37、btain data over a broad range of TCG operating conditions. Measured reference data for many key TCG mixtures are not available. The mixture data from the Phase IV lab work may be used to evaluate TCG mixture data and determine the applicability of various measurement equations to TCG mixtures.vii1Me
38、asurement of Thermally Cracked Gas1 ScopeThis technical report presents a method to compute the density, compressibility factor, and supercompressibility factor for thermally cracked gas (TCG) for custody transfer using orifice meters. It provides equations, parameters, computation flow diagrams, an
39、d example spreadsheet calculations. This technical report applies to TCG mixtures after treatment. See Table 2 for more information on the types of gases covered. It applies for temperature from 90 F to 120 F (305 K to 322 K) at pressures up to 300 psig (2 MPa). It is limited to a specific operating
40、 region. The method is for the single gas phase only. 2 Normative ReferencesThe following referenced documents are indispensable for the application of this document or provide additional information pertinent to mass measurement of natural gas liquids. For dated references, only the edition cited a
41、pplies. For undated references, the latest edition of the referenced document (including any amendments) applies.API Manual of Petroleum Measurement Standards (MPMS), Chapter 14.2, Compressibility Factors of Natural Gas and Other Related Hydrocarbon Gases (AGA Report No. 8 1) (GPA 8185 2)3 Terms, De
42、finitions, Abbreviations, and Symbols3.1 Terms and DefinitionsThe quantities used in the equations in this document are defined when they are used. 3.2 Abbreviations and SymbolsFor the purposes of this document, the following abbreviations and symbols apply.B second virial coefficientBmixmixture sec
43、ond virial coefficientbnconstant in Table 4C third virial coefficient Cmixmixture third virial coefficientcnconstant in Table 4d mass density (mass per unit volume)(T, P) molar density at reference condition T, PFpvsupercompressibility factorMr molar mass (molecular weight)Mr (air) molar mass of air
44、molar mass of i th component N number of components in gas mixturen number of moles of gas1American Gas Association, 400 N. Capitol Street, NW, Suite 450, Washington, DC 20001, www.aga.org.2Gas Processors Association, 6526 E. 60th Street, Tulsa, Oklahoma 74145, .Mri2 API TECHNICAL REPORT 2575P absol
45、ute pressure Pbabsolute pressure at base conditionsPdreference pressure for densityPgrreference pressure for relative densityR gas constantT absolute temperature of gasTbabsolute temperature at base conditionsTdreference temperature for densityTgrreference temperature for relative density (specific
46、gravity)V gas volumeximole fraction of component the i th in gas mixturexjmole fraction of component j in the gas mixturexkmole fraction of component j in the gas mixture molar density (mass per unit volume)(Tgr, Pgr) molar density of gas mixture at Tgr, Pgr(air, Tgr, Pgr) molar density of air at Tg
47、r, Pgrbmass density at contract reference base condition Tb, PbZ compressibility factorZbcompressibility factor at contract reference condition Tb, Pb3.3 Units and ConversionsThe units used in the basic formulation of the equations and in the associated computer subroutines are SI units.The subrouti
48、nes use the following units for the absolute temperature in kelvins (K), pressure in megapascals (MPa), and molar density in moles per cubic decimeter (mol/dm3). The value of the gas constant is 0.008314472 KJ/mol-K.Conversion factors are required for conversions to and from other units. Consistent
49、conversion factors for use with the TCG method are given in Table 1. When possible, the conversion factors given in Table 1 correspond to international standards (GPA 2172-2009 and ISO 6976). Any differences in values used in this program and later values are within the experimental uncertainty in the validation data. Hence any unit conversion changes are unlikely to affect the uncertainty of the calculations. It is recommended that any subsequent changes be ignored unless the agency promoting the change provides a detailed cost impact of the change on i
