ASTM D1946-90(2011)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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: D1946 − 90(Reapproved 2011)
Standard Practice for
Analysis of Reformed Gas by Gas Chromatography
This standard is issued under the fixed designation D1946; 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 characteristics, products of combustion, toxicity, and inter-
changeability with other fuel gases may also be inferred from
1.1 This practice covers the determination of the chemical
the chemical composition.
composition of reformed gases and similar gaseous mixtures
containing the following components: hydrogen, oxygen,
5. Apparatus
nitrogen, carbon monoxide, carbon dioxide, methane, ethane,
and ethylene.
5.1 Detector—The detector shall be a thermal conductivity
type or its equivalent in stability and sensitivity. The thermal
1.2 The values stated in SI units are to be regarded as
conductivity detector must be sufficiently sensitive to produce
standard. No other units of measurement are included in this
a signal of at least 0.5 mV for 1 mol% methane in a 0.5-mL
standard.
sample.
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the 5.2 Recording Instruments—Either strip chart recorders or
responsibility of the user of this standard to establish appro- electronicintegrators,orboth,areusedtodisplaytheseparated
priate safety and health practices and determine the applica- components. Although a strip chart recorder is not required
bility of regulatory limitations prior to use. when using electronic integration, it is highly desirable for
evaluation of instrument performance.
2. Referenced Documents
5.2.1 Therecorder,whenused,shallbeastripchartrecorder
with a full-range scale of 5 mV or less (1 mV preferred). The
2.1 ASTM Standards:
width of the chart shall be not less than 150 mm.Amaximum
E260Practice for Packed Column Gas Chromatography
pen response time of2s(1s preferred) and a minimum chart
3. Summary of Practice
speed of 10 mm/min shall be required. Faster speeds up to 100
mm/min are desirable if the chromatogram is to be interpreted
3.1 Components in a sample of reformed gas are physically
using manual methods to obtain areas.
separatedbygaschromatographyandcomparedtocorrespond-
5.2.2 Electronic or Computing Integrators—Proof of sepa-
ing components of a reference standard separated under
ration and response equivalent to that for the recorder is
identical operating conditions, using a reference standard
required for displays other than by chart recorder.
mixture of known composition. The composition of the re-
formed gas is calculated by comparison of either the peak
5.3 Attenuator—If manual methods are used to interpret the
height or area response of each component with the corre-
chromatogram, an attenuator must be used with the detector
sponding value of that component in the reference standard.
output signal to keep the peak maxima within the range of the
recorderchart.Theattenuatormustbeaccuratetowithin0.5%
4. Significance and Use
between the attenuator range steps.
4.1 The information about the chemical composition can be
5.4 Sample Inlet System:
usedtocalculatephysicalpropertiesofthegas,suchasheating
5.4.1 The sample inlet system must be constructed of
(calorific) value and relative density. Combustion
materials that are inert and nonadsorptive with respect to the
components in the sample. The preferred material of construc-
This practice is under the jurisdiction of ASTM Committee D03 on Gaseous tion is stainless steel. Copper and copper-bearing alloys are
Fuels and is the direct responsibility of Subcommittee D03.07 on Analysis of
unacceptable.
Chemical Composition of Gaseous Fuels.
5.4.2 Provision must be made to introduce into the carrier
Current edition approved Nov. 1, 2011. Published December 2011. Originally
gasaheadoftheanalyzingcolumnagas-phasesamplethathas
approved in 1962. Last previous edition approved in 2006 as D1946–90 (2006).
DOI: 10.1520/D1946-90R11.
beenentrappedineitherafixedvolumelooportubularsection.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Theinjectedvolumemustbereproduciblesuchthatsuccessive
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
runsofthesamesampleagreewithinthelimitsofrepeatability
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. for the concentration range as specified in 11.1.1.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D1946 − 90 (2011)
5.4.3 If the instrument is calibrated with pure components, 5.8.1 The columns shall be constructed of materials that are
theinletsystemshallbeequippedtointroduceasampleatless inert and nonadsorptive with respect to the components in the
than atmospheric pressure. The pressure-sensing device must sample. The preferred material of construction is stainless
be accurate to 0.1 kPa (1 mm Hg). steel. Copper and copper-bearing alloys are unacceptable.
5.8.2 Either an adsorption-type column or a partition-type
5.5 Column Temperature Control:
column, or both, may be used to make the analysis.
5.5.1 Isothermal—When isothermal operation is used, the
analytical columns shall be maintained at a temperature con- NOTE 1—See Practice E260 for general gas chromatography proce-
dures.
stant to 0.3°C during the course of the sample run and the
corresponding reference run.
5.8.2.1 Adsorption Column—This column must completely
5.5.2 Temperature Programming—Temperature program- separate hydrogen, oxygen, nitrogen, methane, and carbon
ming may be used, as feasible.The oven temperature shall not
monoxide.Ifarecorderisused,therecorderpenmustreturnto
exceedtherecommendedtemperaturelimitforthematerialsin thebaselinebetweeneachsuccessivepeak.Equivalentproofof
the column.
separationisrequiredfordisplaysotherthanbychartrecorder.
Fig. 1 is an example chromatogram obtained with an adsorp-
5.6 Detector Temperature Control—The detector tempera-
tion column.
ture shall be maintained at a temperature constant to 0.3°C
(1)Because of similarities in thermal conductivities, he-
during the course of the sample run and the corresponding
lium should not be used as the carrier gas for hydrogen when
reference run. The detector temperature shall be equal to, or
hydrogen is less than 1% of the sample. Either argon or
greater than, the maximum column temperature.
nitrogen carrier gas is suitable for both percent and parts per
5.7 Carrier Gas—The instrument shall be equipped with
million quantities of hydrogen.
suitable facilities to provide flow of carrier gas through the
(2)The use of a carrier gas mixture of 8.5% hydrogen and
analyzer and detector at a flow rate that is constant to 1%
91.5%heliumwillavoidtheproblemofreversingpolaritiesof
throughout the analysis of the sample and the reference
hydrogen responses as the concentration of hydrogen in the
standard. The purity of the carrier gas may be improved by
sample is increased.
flowing the carrier gas through selective filters before its entry
(3)The precision of measurement of hydrogen can be
into the chromatograph.
increased by using a separate injection for hydrogen, using
5.8 Columns: either argon or nitrogen for the carrier gas.
Column: 2-m by 6-mm inside diameter Type 13× Flow rate: 60-mL helium/min
molecular sieves, 14 to 30 mesh Sample size: 0.5 mL
Temperature: 35°C
FIG. 1 Chromatogram of Reformed Gas on Molecular Sieve Column
D1946 − 90 (2011)
(4)Another technique for isolating the hydrogen in a 6. Reference Standards
sample is to use a palladium transfer tube at the end of the
6.1 Moisture-free mixtures of known composition are re-
adsorption column; this will permit only hydrogen to be
quired for comparison with the test sample.They must contain
transferred to a stream of argon or nitrogen carrier gas for
known percentages of the components, except oxygen (Note
analysis in a second thermal conductivity detector.
2), that are to be determined in the unknown sample. All
5.8.2.2 Partition Column—This column must separate
componentsinthereferencestandardmustbehomogeneousin
ethane, carbon dioxide, and ethylene. If a recorder is used, the
the vapor state at the time of use.The fraction of a component
recorder pen must return to the baseline between each succes- in the reference standard should not be less than one half of,
sive peak. Equivalent proof of separation is required for nor differ by more than 10 mol% from, the fraction of the
correspondingcomponentintheunknown.Thecompositionof
displays other than by chart recorder. Fig. 2 is an example
thereferencestandardmustbeknowntowithin0.01mol%for
chromatogram obtained with a partition column.
any component.
5.8.3 General—Those column materials, operated either
isothermally or with temperature programming, or both, may
NOTE 2—Unless the reference standard is stored in a container that has
be used if they provide satisfactory separation of components. beentestedandprovedforinertnesstooxygen,itispreferabletocalibrate
Column: 1.2 m by 6.35 mm Temperature: 40°C
Porapak Q, 50 to 80 mesh Flow rate: 50-mL helium/min
Current setting: 225 mA Sample size: 0.5 mL
FIG. 2 Chromatogram of Reformed Gas on Porapak Q Column
D1946 − 90 (2011)
for oxygen by an alternative method.
oxygen is approximately equal to that of the oxygen in the
mixture be
...