ASTM D4891-89(2006)
(Test Method)Standard Test Method for Heating Value of Gases in Natural Gas Range by Stoichiometric Combustion
Standard Test Method for Heating Value of Gases in Natural Gas Range by Stoichiometric Combustion
SIGNIFICANCE AND USE
This test method provides an accurate and reliable procedure to measure the total heating value of a fuel gas, on a continuous basis, which is used for regulatory compliance, custody transfer, and process control.
Some instruments which conform to the requirements set forth in this test method can have response times on the order of 1 min or less and can be used for on-line measurement and control.
The method is sensitive to the presence of oxygen and nonparaffin fuels. For components not listed and composition ranges that fall outside those in Table 1, modifications in the method may be required to obtain correct results.
SCOPE
1.1 This test method covers the determination of the heating value of natural gases and similar gaseous mixtures within the range of composition shown in Table 1.
1.2 This standard involves combustible gases. It is not the purpose of this standard to address the safety concerns, if any, associated with their 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.
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Designation: D4891 − 89 (Reapproved2006)
Standard Test Method for
Heating Value of Gases in Natural Gas Range by
Stoichiometric Combustion
This standard is issued under the fixed designation D4891; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3.2.4 critical combustion ratio— for a specific burned gas
parameter, the combustion ratio at which a plot of burned gas
1.1 Thistestmethodcoversthedeterminationoftheheating
parameter versus combustion ratio has either maximum value
value of natural gases and similar gaseous mixtures within the
or maximum slope.
range of composition shown in Table 1.
4. Summary of Test Method
1.2 This standard involves combustible gases. It is not the
purpose of this standard to address the safety concerns, if any,
4.1 Air is mixed with the gaseous fuel to be tested. The
associated with their use. It is the responsibility of the user of
mixture is burned and the air-fuel ratio is adjusted so that
this standard to establish appropriate safety and health prac-
essentially a stoichiometric proportion of air is present. More
tices and determine the applicability of regulatory limitations
exactly, the adjustment is made so that the air-fuel ratio is in a
prior to use.
constant proportion to the stoichiometric ratio which is a
relative measure of the heating value. To set this ratio, a
2. Referenced Documents
characteristic property of the burned gas is measured, such as
temperature or oxygen concentration.
2.1 ASTM Standards:
D1826TestMethodforCalorific(Heating)ValueofGasesin
5. Significance and Use
Natural Gas Range by Continuous Recording Calorimeter
E691Practice for Conducting an Interlaboratory Study to 5.1 This test method provides an accurate and reliable
Determine the Precision of a Test Method procedure to measure the total heating value of a fuel gas, on
a continuous basis, which is used for regulatory compliance,
3. Terminology custody transfer, and process control.
5.2 Some instruments which conform to the requirements
3.1 All of the terms defined in Test Method D1826 are
set forth in this test method can have response times on the
included by reference.
orderof1minorlessandcanbeusedforon-linemeasurement
3.2 Definitions of Terms Specific to This Standard:
and control.
3.2.1 combustion ratio—the ratio of combustion air to
5.3 The method is sensitive to the presence of oxygen and
gaseous fuel.
nonparaffin fuels. For components not listed and composition
3.2.2 stoichiometric ratio—the combustion ratio when the
ranges that fall outside those in Table 1, modifications in the
quantityofcombustionairisjustsufficienttoconvertallofthe
method may be required to obtain correct results.
combustibles in the fuel to water and carbon dioxide.
6. Apparatus
3.2.3 burned gas parameter—a property of the burned gas
after combustion which is a function of the combustion ratio.
6.1 A suitable apparatus for carrying out the stoichiometric
combustion method will have at least the following four
components: flow meter or regulator, or both; combustion
chamber; burned gas sensor; and electronics. The requirement
ThistestmethodisunderthejurisdictionofASTMCommitteeD03onGaseous
for each of these components is discussed below. The detailed
Fuels and is the direct responsibility of Subcommittee D03.03 on Determination of
Heating Value and Relative Density of Gaseous Fuels.
design of each of these components can vary. Two different
Current edition approved June 1, 2006. Published June 2006. Originally
apparatus are shown in Fig. 1 and Fig. 2. In each figure the
approved in 1989. Last previous edition approved in 2001 as D4891–89(2001).
equivalent of the four necessary components are enclosed in
DOI: 10.1520/D4891-89R06.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or dashed lines.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
6.2 Overview—Airandfuelentertheapparatusandtheflow
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. of each is measured. Alternatively, only one gas flow need be
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4891 − 89 (2006)
TABLE 1 Natural Gas Components and Range of Composition
6.3 Flow Meter and/or Regulator—The flow measurement
Covered
part of the apparatus should have an accuracy and precision of
Compound Concentration Range, mole, %
the order of 0.1%. Likewise, if the flow is to be kept constant,
Helium 0.01 to 5
the flow regulator should maintain this constant value within
Nitrogen 0.01 to 20
0.1%.Themeterorregulatorfornaturalgasmustmaintainthis
Carbon dioxide 0.01 to 10
precision and accuracy over the density and viscosity ranges
Methane 50 to 100
Ethane 0.01 to 20
consistent with the composition range in Table 1.
Propane 0.01 to 20
n-butane 0.01 to 10
6.4 Combustion Chamber:
isobutane 0.01 to 10
6.4.1 There are two different types of combustion chambers
n-pentane 0.01 to 2
thatmaybeused.Inthefirsttypetheairandfuelaremixedand
Isopentane 0.01 to 2
Hexanes and heavier 0.01 to 2
burned in a single burner. The apparatus shown in Fig. 1 has
this type of combustion chamber.
6.4.2 In the second type of combustion chamber, the air and
fuel are each divided into two streams, and combustion takes
place simultaneously in two burners. The division of air flow
must be such that the proportion of air going to each burner
always remains the same. Likewise the division of fuel flow
must always remain the same even through fuel composition
changes.Anotherrequirementisthattheflowdivisionsbesuch
thatoneburnerhasamixturewithaslightlyhighercombustion
ratiothantheother.TheapparatusshowninFig.2hasthistype
of combustion chamber.
6.5 Burned Gas Sensor:
6.5.1 The burned gas sensor must measure a characteristic
of the burned gas which is a function of the combustion ratio
and for which there is a critical combustion ratio related to the
stoichiometric ratio. A combustion chamber of the first type
FIG. 1 Gas Btu Transmitter (Functional Overview)
(Fig.1)wouldhaveonesensorintheburnedgasanditsoutput
signalwouldconstitutethedesiredmeasurement.Inacombus-
tion chamber of the second type (Fig. 2) there would be a
sensor in the burned gas from each burner. The difference
between the two output signals would constitute the desired
measurement.
6.5.2 There are several properties of the burned gas which
are related uniquely to the combustion ratio. A burned gas
sensormaybeselectedwhichprovidesameasureofanyoneof
these, for example, either temperature or oxygen partial pres-
sure.
6.6 Electronics—Electronics are used to receive the signals
from the components described above to control the flow of
gases into the combustion chamber in response to the signal
from the burned gas sensor and to provide a digital or analog
output signal, or both, which is proportional to the heating
value of the gaseous fuel.
FIG. 2 Stoichiometric Combustion Apparatus
6.7 Temperature Stability and Operating Environment—The
method is capable of operating over a range of temperatures
limited only by the specific apparatus used to realize the
measured if the flow of the other is kept the same during
method. It is desirable to equilibrate the air and fuel tempera-
measurement and calibration.This is illustrated in Fig. 2. Next
tures before the gases are measured. The electronics should
there is a combustion chamber in which the air and fuel are
also be stabilized against temperature changes and the burned
mixedandburned.Thiscanbeassimpleasabunsenormeeker
gas sensor should be insensitive to changes in the ambient
burner, but precautions should be taken that subsequent mea-
conditions.
surements of burned gas characteristics are not influenced by
ambient conditions. Finally, there is a sensor in the burned gas
7. Reagents and Materials
which m
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