ASTM D4891-89(2001)
(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
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(Reapproved 2001)
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 (e) indicates an editorial change since the last revision or reapproval.
TABLE 1 Natural Gas Components and Range of Composition
1. Scope
Covered
1.1 Thistestmethodcoversthedeterminationoftheheating
Compound Concentration Range, mole, %
value of natural gases and similar gaseous mixtures within the
Helium 0.01 to 5
range of composition shown in Table 1.
Nitrogen 0.01 to 20
1.2 This standard involves combustible gases. It is not the
Carbon dioxide 0.01 to 10
purpose of this standard to address the safety concerns, if any, Methane 50 to 100
Ethane 0.01 to 20
associated with their use. It is the responsibility of the user of
Propane 0.01 to 20
this standard to establish appropriate safety and health prac-
n-butane 0.01 to 10
isobutane 0.01 to 10
tices and determine the applicability of regulatory limitations
n-pentane 0.01 to 2
prior to use.
Isopentane 0.01 to 2
Hexanes and heavier 0.01 to 2
2. Referenced Documents
2.1 ASTM Standards:
D1826 TestMethodforCalorificValueofGasesinNatural
Gas Range by Continuous Recording Calorimeter
essentially a stoichiometric proportion of air is present. More
E691 Practice for Conducting an Interlaboratory Study to
exactly, the adjustment is made so that the air-fuel ratio is in a
Determine the Precision of a Test Method
constant proportion to the stoichiometric ratio which is a
relative measure of the heating value. To set this ratio, a
3. Terminology
characteristic property of the burned gas is measured, such as
3.1 All of the terms defined in Test Method D1826 are
temperature or oxygen concentration.
included by reference.
5. Significance and Use
3.2 Descriptions of Terms:
3.2.1 combustion ratio—the ratio of combustion air to
5.1 This test method provides an accurate and reliable
gaseous fuel.
procedure to measure the total heating value of a fuel gas, on
3.2.2 stoichiometric ratio—the combustion ratio when the
a continuous basis, which is used for regulatory compliance,
quantityofcombustionairisjustsufficienttoconvertallofthe
custody transfer, and process control.
combustibles in the fuel to water and carbon dioxide.
5.2 Some instruments which conform to the requirements
3.2.3 burned gas parameter—a property of the burned gas
set forth in this test method can have response times on the
after combustion which is a function of the combustion ratio.
orderof1minorlessandcanbeusedforon-linemeasurement
3.2.4 critical combustion ratio—for a specific burned gas
and control.
parameter, the combustion ratio at which a plot of burned gas
5.3 The method is sensitive to the presence of oxygen and
parameter versus combustion ratio has either maximum value
nonparaffin fuels. For components not listed and composition
or maximum slope.
ranges that fall outside those in Table 1, modifications in the
method may be required to obtain correct results.
4. Summary of Test Method
6. Apparatus
4.1 Air is mixed with the gaseous fuel to be tested. The
mixture is burned and the air-fuel ratio is adjusted so that
6.1 Asuitable apparatus for carrying out the stoichiometric
combustion method will have at least the following four
1 components: flow meter or regulator, or both; combustion
ThistestmethodisunderthejurisdictionofASTMCommitteeD03onGaseous
Fuels and is the direct responsibility of Subcommittee D03.03 on Determination of chamber; burned gas sensor; and electronics. The requirement
Heating Value and Relative Density of Gaseous Fuels.
for each of these components is discussed below. The detailed
Current edition approved Jan. 27, 1989. Published March 1989.
design of each of these components can vary. Two different
Annual Book of ASTM Standards, Vol 05.05.
Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D4891–89 (2001)
apparatus are shown in Fig. 1 and Fig. 2. In each figure the
equivalent of the four necessary components are enclosed in
dashed lines.
6.2 Overview—Airandfuelentertheapparatusandtheflow
of each is measured. Alternatively, only one gas flow need be
measured if the flow of the other is kept the same during
measurement and calibration.This is illustrated in Fig. 2. Next
there is a combustion chamber in which the air and fuel are
mixedandburned.Thiscanbeassimpleasabunsenormeeker
burner, but precautions should be taken that subsequent mea-
surements of burned gas characteristics are not influenced by
ambient conditions. Finally, there is a sensor in the burned gas
which measures a property of this gas that is sensitive to the
combustion ratio and has a unique feature at the stoichiometric
ratio.Twosuchpropertiesaretemperatureandoxygenconcen-
trations, and either can be measured.
FIG. 2 Stoichiometric Combustion Apparatus
6.3 Flow Meter and/or Regulator—The flow measurement
part of the apparatus should have an accuracy and precision of
(Fig.1)wouldhaveonesensorintheburnedgasanditsoutput
the order of 0.1%. Likewise, if the flow is to be kept constant,
signalwouldconstitutethedesiredmeasurement.Inacombus-
the flow regulator should maintain this constant value within
tion chamber of the second type (Fig. 2) there would be a
0.1%.Themeterorregulatorfornaturalgasmustmaintainthis
sensor in the burned gas from each burner. The difference
precision and accuracy over the density and viscosity ranges
between the two output signals would constitute the desired
consistent with the composition range in Table 1.
measurement.
6.4 Combustion Chamber:
6.5.2 There are several properties of the burned gas which
6.4.1 There are two different types of combustion chambers
are related uniquely to the combustion ratio. A burned gas
thatmaybeused.Inthefirsttypetheairandfuelaremixedand
sensormaybeselectedwhichprovidesameasureofanyoneof
burned in a single burner. The apparatus shown in Fig. 1 has
these, for example, either temperature or oxygen partial pres-
this type of combustion chamber.
sure.
6.4.2 In the second type of combustion chamber, the air and
6.6 Electronics—Electronics are used to receive the signals
fuel are each divided into two streams, and combustion takes
from the components described above to control the flow of
place simultaneously in two burners. The division of air flow
gases into the combustion chamber in response to the signal
must be such that the proportion of air going to each burner
from the burned gas sensor and to provide a digital or analog
always remains the same. Likewise the division of fuel flow
output signal, or both, which is proportional to the heating
must always remain the same even through fuel composition
value of the gaseous fuel.
changes.Anotherrequirementisthattheflowdivisionsbesuch
6.7 Temperature Stability and Operating Environment—
thatoneburnerhasamixturewithaslightlyhighercombustion
The method is capable of operating over a range of tempera-
ratiothantheother.TheapparatusshowninFig.2hasthistype
tures limited only by the specific apparatus used to realize the
of combustion chamber.
method. It is desirable to equilibrate the air and fuel tempera-
6.5 Burned Gas Sensor:
tures before the gases are measured. The electronics should
6.5.1 The burned gas sensor must measure a characteristic
also be stabilized against temperature changes and the burned
of the burned gas which is a function of the combustion ratio
gas sensor should be insensitive to changes in the ambient
and for which there is a critical combustion ratio related to the
conditions.
stoichio
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