API MPMS 14.5:2009 pdf download

API MPMS 14.5:2009 pdf download.Calculation of Gross Heating Value, Relative Density, Compressibility and Theoretical Hydrocarbon Liquid Content for Natural Gas Mixtures for Custody Transfer.
relative density
Relative density is the ratio of the mass density of the gas at the measurement temperature and pressure to the mass density of dry air (the assumed composition of air appears in Table A.1) at the same temperature and pressure. In the hypothetical ideal gas state, the relative density becomes the molar mass ratio.
3.12
saturated gas at base conditions
Saturated gas at base conditions contains the equilibrium amount of water vapor at base pressure and temperature. In the U.S., the quantity normally is expressed as pounds of water per MMSCF of delivered gas.
3.13
saturated gas at flowing conditions
Saturated gas at flowing conditions contains the equilibrium amount of water vapor at flowing pressure and temperature and is normally calculated by means of an algorithm. In the U.S., the quantity normally is expressed as pounds of water per MMSCF of delivered gas.
3.14
spectator water
Spectator water is water carried by the gas or air that feeds the combustion reaction. Spectator water does not contribute to the gross heating value.
3.15
theoretical hydrocarbon liquid content
The theoretical hydrocarbon liquid content is the amount of liquid theoretically condensable per unit volume of gas at base conditions. In the U.S., the term GPM (gallons of liquid hydrocarbon per thousand cubic feet of gas) is used.
3.16
wet gas
Gas that contains water, however, for practical purposes contracting parties often define wet as greater than 7 lb of water per million standard cubic feet of gas, i.e. gas that is either partially or completely water saturated.
examples because their application beyond the use as intermediate steps in the analysis calculation can lead to misapplication and subsequent errors.
The calculations in the following examples use the physical properties for the components from
GPA 2145-09.
Application Notes and Cautions
All calculations shall use the physical properties from the latest version of GPA 2145. If a component in the calculation is not present in CPA 2145, refer to CPA TP-17 for its properties.
A typical natural gas analysis determines the individual quantity of components lighter than hexanes, and groups the hexanes and heavier components into a single quantity. Characterization of the physical constants for hexanes and heavier components, commonly referred to as C6+, should use the most representative data available for the sample. Similar methodology can be used to group on a different component such as heptanes and heavier (C7+). This characterization may be:
• based upon the composition of the C6+ fraction determined in an extended chromatographic analysis performed in accordance with CPA 2286 or other equivalent method; (preferred method);
• generalized through an engineering evaluation; and
• as agreed upon among parties involved.
Table B.10 in Annex B provides example calculations for two commonly used characterizations.
While some chromatographs may detect water vapor in the analysis, there is no practical way to quantify the amount of water vapor. Other chromatographs may not be capable of detecting water vapor. The analysis report should include the method used to determine the water vapor content and calculation parameters, if applicable.
Be aware that excluding water vapor from the analysis of a wet gas stream causes inaccuracy in the relative density, compressibility at base conditions and LC (GPM).
Total energy results from multiplying a volume of gas by the heating value per unit volume, both being at the same conditions of pressure, temperature and water content. The base temperature and the base pressure must be the same for both the gas volume and the heating value. When the flowing stream is water saturated, the total energy delivered can be determined by compensating for water vapor in the analysis and subsequent heating value or by volumetrically quantifying the water vapor in the flowing stream, but not both. For example, a gas volume containing water vapor (wet volume) must be multiplied by a wet heating value.