ASTM D4784-93(2010)

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.
SIGNIFICANCE AND USE
The models in this specification can be used to calculate the density of saturated liquid natural gas in the temperature range 90 to 120K. The estimated uncertainty for the density calculations is ±0.1 %. The restrictions on composition of the liquefied natural gas are:
SCOPE
1.1 This specification 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 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 This standard does not purport to address all of the safety concerns, 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: 30-Apr-2010
• ICS: 75.060 - Natural gas
• Technical Committee: D03 - Gaseous Fuels
• Drafting Committee: D03.08 - Thermophysical Properties

Relations

• Replaces: ASTM D4784-93(2003) - 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: 01-May-2010

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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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 2010)
Standard Specification for
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
ThisspecificationisadescriptionoffourmathematicalmodelsoftheequationofstateforLNG-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
equipment, and in using these data to develop predictive models for use in density calculations.
1. Scope priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
1.1 This specification covers LNG density calculation mod-
els for use in the calculation or prediction of the densities of
2. Significance and Use
saturated LNG mixtures from 90 to 120K to within 0.1 % of
2.1 The models in this specification can be used to calculate
truevaluesgiventhepressure,temperature,andcompositionof
the density of saturated liquid natural gas in the temperature
the mixture.
range 90 to 120K. The estimated uncertainty for the density
1.2 The values stated in SI units are to be regarded as
calculations is 60.1 %. The restrictions on composition of the
standard. No other units of measurement are included in this
liquefied natural gas are:
standard.
methane 60 % or greater
nitrogen less than 4 %
1.3 This standard does not purport to address all of the
n-butane less than 4 %
safety concerns, if any, associated with its use. It is the
i-butane less than 4 %
responsibility of the user of this standard to establish appro- pentanes less than 2 %
It is assumed that hydrocarbons with carbon numbers of six
or greater are not present in the LNG solution.
This standard is under the jurisdiction of ASTM Committee D03 on Gaseous
3. Models
Fuels and is the direct responsibility of Subcommittee D03.08 on Thermophysical
Properties. 3.1 Extended Corresponding States—The extended corre-
CurrenteditionapprovedMay1,2010.PublishedJuly2010.Originallyapproved
sponding states method is defined by the following equations:
in 1988. Last previous edition approved in 2003 as D4784 – 93 (2003). DOI:
10.1520/D4784-93R10. Z P,T 5 Z Ph /f , T/f (1)
@ # @ #
i o ii,o ii,o ii,o
The formulation of the models and the supporting work was done by the
G @P,T# 5 f G @Ph /f , T/f # 2 RTln ~h ! (2)
i ii,o o ii,o ii,o ii,o ii,o
National Bureau of Standards under the sponsorship of British Gas Corp., Chicago
BridgeandIronCo.,ColumbiaGasServiceCorp.,DistrigasCorp.,EascoGasLNG,
where:
Inc., El Paso Natural Gas, Gaz de France, Marathon Oil Co., Mobil Oil Corp.,
Natural Gas Pipeline Co., Phillips Petroleum Co., Shell International Gas, Ltd., Z = compressibility factor,
Sonatrach, Southern California Gas Co., Tennessee Gas Pipeline, Texas Eastern
G = Gibbs free energy,
Transmission Co., Tokyo Gas Co., Ltd., and Transcontinental Gas Pipe Line Corp.,
P = pressure,
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
D4784−93 (2010)
PV 11y1y a
T = temperature,
5 c 2 (11)
RT ~1 2 y! RTV
o = reference fluid, and
i = fluid for which properties are to be obtained via the
where:
equation of state for the reference fluid and the
y = b/4V and a, b, and c are adjustable parameters,
transformation functions f and h are introduced to
ii,o ii,o
P = pressure,
allow extension of the method to mixtures.
V = specific volume,
The two defining Eq 1 and Eq 2 are necessary since there are
T = temperature, and
two transformation functions. In this case, an equation of state R = the gas constant.
for methane was chosen for the reference fluid. During the
The equation is applied to mixtures by assuming the one-
course of the study it was necessary to modify the equation of
fluid theory and applying the following combining rules.
state to give a realistic vapor liquid phase boundary down to a
a 5 a x x (12)
temperature of 43K. This modification was necessary to
m ( ( ij i j
i j
accommodatetheverylowreducedtemperaturesoftheheavier
b 5 b x x (13)
m ij i j
hydrocarbons and was accomplished without changing the ( (
i j
performance of the equation of state above the triple point of
c 5 c x x (14)
m ( ( ij i
...