ASTM D4784-93(2003)

Standard for LNG Density Calculation Models

ABSTRACT
This specification covers LNG density calculation models for use in the calculation or prediction of the densities of saturated liquefied natural gas (LNG) mixtures at a specified temperature range given the pressure, temperature, and composition of the mixture. Composition restrictions for the LNGs are given for methane, nitrogen, n-butane, i-butane, and pentanes. It is assumed that hydrocarbons with carbon numbers of six or greater are not present in the LNG solution. The mathematical models presented here are the extended corresponding states model, hard sphere model, revised Klosek and McKinley model, and the cell model.
SCOPE
1.1 This standard covers LNG density calculation models  for use in the calculation or prediction of the densities of saturated LNG mixtures from 90 to 120K to within 0.1% of true values given the pressure, temperature, and composition of the mixture.
1.2  This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 09-May-2003
• ICS: 75.060 - Natural gas
• Technical Committee: D03 - Gaseous Fuels
• Drafting Committee: D03.08 - Thermophysical Properties

Relations

• Replaces: ASTM D4784-93(1998) - Standard for LNG Density Calculation Models
• Effective Date: 10-May-2003
• Replaced By: ASTM D4784-93(2010) - Standard for LNG Density Calculation Models
• Effective Date: 01-May-2010
• Referred By: ASTM D7551-10(2015) - Standard Test Method for Determination of Total Volatile Sulfur in Gaseous Hydrocarbons and Liquefied Petroleum Gases and Natural Gas by Ultraviolet Fluorescence
• Effective Date: 10-May-2003

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information.
Designation: D4784 – 93 (Reapproved 2003)
Standard Specification for
1
LNG Density Calculation Models
This standard is issued under the fixed designation D4784; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
This standard is a description of four mathematical models of the equation of state for LNG-like
mixtures that were adopted in 1988.The four models include an extended corresponding states model,
a cell model, a hard sphere model, and a revised Klosek and McKinley model. Each of the models has
been optimized to the same experimental data set which included data for pure nitrogen, methane,
ethane, propane, iso and normal butane, iso and normal pentane, and mixtures thereof. For LNG-like
mixtures(mixturesoftheorthobaricliquidstateattemperaturesof120Korlessandcontainingatleast
60 % methane, less than 4 % nitrogen, less than 4 % each of iso and normal butane, and less than 2 %
total of iso and normal pentane), all of the models are estimated to predict densities to within 0.1 %
of the true value.These models were developed by the National Institute of Standards andTechnology
(formerly the Bureau of Standards) upon culmination of seven years of effort in acquiring physical
properties data, performing extensive experimental measurements using specially developed equip-
ment, and in using these data to develop predictive models for use in density calculations.
1. Scope tions is 60.1 %. The restrictions on composition of the
2
liquefied natural gas are:
1.1 This standard covers LNG density calculation models
methane 60 % or greater
for use in the calculation or prediction of the densities of
nitrogen less than 4 %
saturated LNG mixtures from 90 to 120K to within 0.1 % of
n-butane less than 4 %
truevaluesgiventhepressure,temperature,andcompositionof
i-butane less than 4 %
pentanes less than 2 %
the mixture.
1.2 This standard does not purport to address all of the
It is assumed that hydrocarbons with carbon numbers of six
safety concerns, if any, associated with its use. It is the
or greater are not present in the LNG solution.
responsibility of the user of this standard to establish appro-
3. Models
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
3.1 Extended Corresponding States—The extended corre-
sponding states method is defined by the following equations:
2. Significance and Use
Z @P,T] 5 Z @Ph /f , T/f # (1)
i o ii,o ii,o ii,o
2.1 The models in this standard can be used to calculate the
G P,T] 5 f G Ph /f , T/f 2 RT ln h (2)
@ @ # ~ !
i ii,o o ii,o ii,o ii,o ii,o
density of saturated liquid natural gas in the temperature range
90 to 120K. The estimated uncertainty for the density calcula-
where:
Z = compressibility factor,
1 G = Gibbs free energy,
This standard is under the jurisdiction of ASTM Committee D03 on Gaseous
P = pressure,
Fuels and is the direct responsibility of Subcommittee D03.08 on Thermophysical
Properties. T = temperature,
Current edition approved May 10, 2003. Published May 2003. Originally
o = reference fluid, and
approved in 1988. Last previous edition approved in 1998 as D4784 – 93 (1998).
i = fluid for which properties are to be obtained via the
DOI: 10.1520/D4784-93R03.
2 equation of state for the reference fluid and the
The formulation of the models and the supporting work was done by the
National Bureau of Standards under the sponsorship of British Gas Corp., Chicago transformationfunctionsf andh areintroducedto
ii,o ii,o
BridgeandIronCo.,ColumbiaGasServiceCorp.,DistrigasCorp.,EascoGasLNG,
allow extension of the method to mixtures.
Inc., El Paso Natural Gas, Gaz de France, Marathon Oil Co., Mobil Oil Corp.,
The two defining Eq 1 and Eq 2 are necessary since there are
Natural Gas Pipeline Co., Phillips Petroleum Co., Shell International Gas, Ltd.,
two transformation functions. In this case, an equation of state
Sonatrach, Southern California Gas Co., Tennessee Gas Pipeline, Texas Eastern
Transmission Co., Tokyo Gas Co., Ltd., and Transcontinental Gas Pipe Line Corp.,
for methane was chosen for the reference fluid. During the
through a grant administered by the American Gas Association, Inc.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D4784 – 93 (2003)
course of the study it was necessary to modify the equation of
a 5 a xx (12)
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state to give a realistic vapor liquid phase boundary down to a
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