DISCLAIMER AND COPYRIGHT
ACKNOWLEDGEMENTS
FOREWORD
TABLE OF CONTENTS
1 SCOPE OF APPLICATION
1.1 General
1.2 Range Of Application
1.2.1 Inclusion Criteria for Fuel Gas Mixtures
1.3 Range of Gas Mixture Constituents
1.3.1 Concentration of Gas Constituents
1.3.2 Directly Supported Constituents
1.3.3 Other Constituents
1.3.4 Grouped Constituents
1.4 Other Composition-Dependent Gas Properties
1.5 Range of Contract Base Pressures and Contract Base
Temperatures
1.6 Compounds in the Liquid State
2 DEFINITIONS AND BACKGROUND
2.1 British Thermal Unit (Btu)
2.2 Calorie
2.3 Combustion
2.4 Combustion Reference Temperature
2.5 Contract Base Conditions
2.6 Dekatherm
2.7 Dry Gas
2.8 Higher Heating Value (HHV), also known as Gross Heating
Value (GHV)
2.9 Ideal Gas
2.10 Motor Octane Number (MON)
2.11 Methane Number (MN)
2.12 Natural Gas Energy Measurement
2.13 Lower Heating Value (LHV), also known as Net Heating
Value (NHV)
2.14 Real Gas
2.15 Relative Density and Specific Gravity
2.16 Sensible Heat
2.17 Therm
2.18 Water Dew Point
2.19 Water-Saturated and Partially Water-Saturated Gases
2.20 Wobbe Number (WN), also known as Wobbe Index (WI)
3 BASIS FOR CUSTODY TRANSFER
3.1 Specification of Energy
3.2 Specification of Heating Value
3.3 Higher (Gross) Versus Lower (Net) Heating Value
3.4 Dry Versus Saturated Heating Value
3.5 Energy Derived from Volumetric Measurements
3.6 Energy Derived from Mass Measurements
3.7 Sampling and Off-line Analysis
3.8 Compressibility Factor
3.9 Enthalpy
3.10 Accounting for the Presence of Water
4 UNCERTAINTY
4.1 Acceptance Criteria
5 HEATING VALUE DETERMINATION METHODS
5.1 Heating Value from Gas Composition
5.1.1 General Requirements
5.1.2 Gas Chromatography
5.1.3 Mass Spectrometry
5.2 Heating Value Measurement
5.2.1 General Requirements
5.2.2 Calorimeter
5.2.3 Fuel/Air Titration
5.3 Heating Value from Inferential (Correlative) Methods
6 REFERENCES
APPENDIX A
Pre-Calculated Tables of Ideal Gas Gross Heating Value
(Volumetric Basis)
Pre-Calculated Tables of Ideal Gas Gross Heating Value
(Mass Basis)
Example Calculation of Volumetric Heating Value (Imperial units)
Example Calculation of Volumetric Heating Value (SI Units)
Standard Enthalpies of Formation
Stoichiometric Coefficients
Balanced Combustion Reaction Equations for Common Hydrocarbons
Ideal Gas Molar Heating Values at 298.15 K
Enthalpy of Vaporization of Water
Enthalpy Adjustment
Equation Constants for the Ideal Gas Heat Capacity Correlation
Calculation of Summations Factors
Equation Constants for 2nd Virial Coefficients
Summation Factors at Common Reference Temperatures
Molar Masses
Table of H/C (Hydrogen to Carbon) Ratios
Example Process for Supporting Additional Compounds
Calculating Natural Gas Relative Density and the
Compressibility of Air
Estimation of Water Content from Dew Point Measurements
Dew Point Temperature Versus Water Content in Natural Gas
APPENDIX B
FORM FOR PROPOSALS ON AGA REPORT NO. 5, MARCH 2009