1、Designation: D 7164 05Standard Practice forOn-line/At-line Heating Value Determination of GaseousFuels by Gas Chromatography1This standard is issued under the fixed designation D 7164; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision
2、, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice is for the determination of heating value inhigh methane content gaseous fuels such as na
3、tural gas usingan on-line/at-line gas chromatograph.1.2 The values stated in SI units are standard. Values statedin other units are for information only.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of th
4、is standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1070 Test Methods for Relative Density of Gaseous FuelsD 1945 Test Method for Analysis of Natural Gas by GasChromatog
5、raphyD 1946 Practice for Analysis of Reformed Gas by GasChromatographyD 3588 Practice for Calculating Heat Value, Compressibil-ity Factor, and Relative Density of Gaseous FuelsD 3764 Practice for Validation of Process Stream AnalyzerSystemsD 4626 Practice for Calculation of Gas ChromatographicRespon
6、se FactorsD 5287 Practice for Automatic Sampling of Gaseous FuelsD 5503 Practice for Natural Gas Sample-Handling andConditioning Systems for Pipeline InstrumentationD 6122 Practice for Validation of Multivariate Process In-frared SpectrophotometersD 6299 Practice for Applying Statistical Quality Ass
7、uranceTechniques to Evaluate Analytical Measurement SystemPerformanceD 6621 Practice for Performance Testing of Process Ana-lyzers for Aromatic Hydrocarbon MaterialsE 260 Practice for Packed Column Gas ChromatographyE 594 Practice for Testing Flame Ionization Detectors Usedin Gas or Supercritical Fl
8、uid ChromatographyE 1510 Practice for Installing Fused Silica Open TubularCapillary Columns in Gas Chromatographs3. Terminology3.1 Definitions:3.1.1 direct samplingsampling where there is no directconnection between the medium to be sampled and theanalytical unit.3.1.2 in-line instrumentinstrument w
9、ith an active elementinstalled in a pipeline, which is used to measure pipelinecontents or conditions.3.1.3 on-line instrumentinstrument that samples gas di-rectly from a pipeline, but is installed externally.3.1.4 at-line instrumentinstrumentation requiring opera-tor interaction that samples gas di
10、rectly from the pipeline.3.1.5 continuous fuel monitorinstrument that samples gasdirectly from the pipeline on a continuous or semi-continuousbasis.3.1.6 heating valuein general terms, the heating value isthe total energy per volume transferred as heat from thecomplete, ideal combustion of the gas a
11、t a specified tempera-ture and pressure. The heating value can be reported on a netor gross basis for a gaseous stream that is assumed to be fullywater vapor saturated.3.1.7 gross heating value(also called higher heatingvalue)the amount of energy per volume transferred as heatfrom the complete, idea
12、l combustion of the gas at standardtemperature in which all the water formed by the reactioncondenses to liquid.3.1.8 net heating value(also called lower heatingvalue)the amount of energy per volume transferred as heatfrom the complete, ideal combustion of the gas at standardtemperature in which all
13、 the water formed by the reactionremains in the vapor state.4. Summary of Practice4.1 Arepresentative sample of the Gaseous Fuel is extractedfrom a process pipe or a pipeline and is transferred in a timelymanner to an analyzer sampling system. After appropriate1This practice is under the jurisdictio
14、n of ASTM Committee D03 on GaseousFuels and is the direct responsibility of Subcommittee D03.12 on On-Line/At-LineAnalysis of Gaseous Fuels.Current edition approved June 15, 2005. Published June 2005.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Servic
15、e at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.conditioning steps that maintain the sample in
16、tegrity arecompleted, a precise volume of sample is injected onto anappropriate gas chromatographic column. Excess extractedprocess or pipeline sample is vented to atmosphere, a flareheader, or is returned to the process in accordance withapplicable economic and environmental requirements andregulat
17、ions.4.2 Sample constituents are separated in the column to eluteindividually for identification and quantification by the detectorand its data handling system. The heating value is calculatedusing the results of the compositional analysis using anappropriate algorithm.4.3 Calibration, maintenance,
18、and performance protocolsprovide a means to validate the analyzer operation.5. Significance and Use5.1 On-line, at-line, in-line and other near-real time moni-toring systems that measure fuel gas characteristics such as theheating value are prevalent in the natural gas and fuel gasindustries. The in
19、stallation and operation of particular systemsvary on the specific objectives, process type, regulatory re-quirements, and internal performance requirements needed bythe user. This protocol is intended to provide guidelines forstandardized start-up procedures, operating procedures, andquality assura
20、nce practices for on-line, at-line, in-line and othernear-real time heating value monitoring systems.6. Apparatus6.1 InstrumentAny instrument of standard manufacture,with hardware necessary for interfacing to a natural gas orother fuel gas pipeline and containing all the features necessaryfor the in
21、tended application(s) can be used.6.1.1 Chromatographic-based SystemsThe chromato-graphic parameters employed generally should be capable ofobtaining a relative retention time repeatability of 0.05 min (3s) for duplicate measurements. Instrumentation should satisfyor exceed other chromatographic and
22、 analytic performancecharacteristics for accuracy and precision for the intendedapplication without encountering unacceptable interference orbias. In addition, components in contact with sample streamssuch as tubing and valving must be constructed of suitable inertmaterials to ensure constituents in
23、 the fuel stream do notdegrade these components or alter the composition of thesampled gas. Additional information related to analyzinggaseous fuels using gas chromatography can be found in TestMethod D 1945 and Practice D 1946.6.2 Sample Probes/Sample ExtractionThe location andorientation of sampli
24、ng components are critical for ensuringthat a representative sample is analyzed. The locations andorientation of sampling components should be selected basedupon sound analytic and engineering considerations. Samplingpractices for gaseous fuels can be found in Practice D 5287.6.3 Sample Inlet System
25、The siting and installation of anat-line or on-line monitor is critical for collecting representa-tive information on heating value content. Factors that shouldbe considered in siting an instrument include ease of calibra-tion, ease of access for repair or maintenance, sample unifor-mity at the samp
26、ling point, appropriateness of samples from asampling location, ambient conditions, and of course safetyissues. An automated gas sampling valve is required in manyapplications. All sampling system components in contact withthe fuel stream must be constructed of inert or passivatedmaterials. Care sho
27、uld be taken to ensure that the extractedsample is maintained in a single clean gaseous phase. Theaddition of heat at the point of pressure reduction or along thesample line to the analyzer may be required to ensure that thesample is maintained in the gas phase. The need for heattracing and the exte
28、nt to which it is required will be sitespecific. In general, considerations impacting heat tracingdecisions include sample compositions and the expected varia-tions, ambient temperature fluctuations, operating pressures,and anticipated pressure differentials in sample system com-ponents. Sample filt
29、ration should be utilized as required toremove particulate matter from the extracted sample. Thesampling frequency relative to the process bandwidth is criticalto ensuring that the reported analytical results adequatelyrepresent the process being monitored. The Nyquist-Shannonsampling criterion of a
30、 sampling frequency that exceeds twicethe process bandwidth can be used to establish a minimumanalytical cycle time. Sample handling and conditioning sys-tem practices can be found in Practice D 55036.3.1 Carrier and Detector Gas ControlConstant flowcontrol of carrier and detector gases is critical
31、for optimum andconsistent analytical performance. Control is achieved by useof pressure regulators and fixed flow restrictors. Temperaturecontrol is generally vital for ensuring consistent operation ofthese devices. The gas flow is measured by appropriate meansand adjusted as necessary. Mass flow co
32、ntrollers, capable ofmaintaining gas flow constant to 61 % at the flow ratesnecessary for optimal instrument performance are generallyused.6.3.2 DetectorsA thermal conductivity detector (TCD) iscommonly used. Other detectors, such as the flame ionizationdetector (FID), Practice E 594, can be used bu
33、t should at leastmeet TCD linearity, sensitivity, and selectivity in the selectedapplication.6.4 ColumnsA variety of columns, ranging from packedcolumns to open tubular capillary columns, can be used in thedetermination of the Heating Value of a gaseous fuel. Packedcolumns and open tubular capillary
34、 columns are covered inPractices E 260 and E 1510 respectively. Columns should beconditioned in accordance with the manufacturers recommen-dations. The selected column must provide retention andresolution characteristics that satisfy the intended application.The column must be inert towards gaseous
35、fuel components. Ifthe selected column utilizes a liquid phase, bleeding at hightemperatures must be sufficiently low so as to avoid the loss ofinstrument response during high temperature operation.6.5 Data AcquisitionData acquisition and storage can beaccomplished using a number of devices and medi
36、a. Followingare some examples.6.5.1 RecorderA 0 to 1 mV range recording potentiom-eter or equivalent, with a full-scale response time of2sorlesscan be used.6.5.2 IntegratorAn electronic integrating device or com-puter can be used. For GC-based systems, it is suggested thatthe device and software hav
37、e the following capabilities:D71640526.5.2.1 Graphic presentation of chromatograms.6.5.2.2 Digital display of chromatographic peak areas.6.5.2.3 Identification of peaks by retention time or relativeretention time, or both.6.5.2.4 Calculation and use of response factors.6.5.2.5 External standard calc
38、ulation and data presentation.6.5.2.6 Site-appropriate archives up to one month of allruns. Archives could include raw data, derived componentvalues or heating value results or both. Hourly, daily, andmonthly averages are included as required.6.5.3 Communications SystemsEfficient communicationsbetwe
39、en the analyzer and the host depend on resolving any andall interface issues. Signals to and from the host are typicallyoptically isolated from each other.7. Reagents and MaterialsNOTE 1Warning: Compressed gas standards should only be handledin well ventilated locations away from sparks and flames.
40、Improperhandling of compressed gas cylinders containing calibration standards, air,nitrogen, hydrogen, argon or helium can result in explosion. Rapid releaseof nitrogen or helium can result in asphyxiation. Compressed air supportscombustion.7.1 StandardsThe components in the reference standardshould
41、 be representative of the monitored gas. Concentrationsof major components are typically selected between one halfand twice their expected concentration in the monitored gas.Standards must be maintained as close as practicable to aconstant temperature within the temperature range specified bythe man
42、ufacturer to ensure accuracy and stability.8. Equipment Siting and Installation8.1 Asample inlet system capable of operating continuouslyat or above the maximum column operating temperature isnecessary. The location of the sample inlet to the analyzerrelative to the sample extraction point is critic
43、al to obtainingtimely analytical results. Ideally, the analyzer is close coupledto the sample extraction point and there is an insignificantsampling lag time. Normally, the analyzer is mounted at somedistance away from the sample extraction point. This increaseddistance represents increased lag time
44、 between when a sampleis extracted from a process and when an analytical result isreported. The maximum allowable lag time depends on thespecifics of the sampling location relative to the process beingsampled. A fast loop sweep can be used to minimize the lagtime by creating a bypass loop that flows
45、 sample from theprocess to the analyzer and is then returned to the process or isvented.8.2 The sample should flow continuously without impedi-ment through the instrument sampling system. The samplingsystem should be capable of delivering a sample to thedetection system within the cycle time of the
46、analyzer. Shortertimes may be required to meet the intended need.8.3 A monitoring system pretest of both sampling andanalysis functions is critical to determining monitoring systemcharacteristics, identify unforeseen factors affecting measure-ment and to determine optimal operating conditions for th
47、eintended use. This pretest is performed before the system isplaced in continuous service and may be performed in a varietyof ways including a comparison of results to another instru-ment already in service, analysis of a known gaseous sampleetc.9. Performance Tests9.1 The following performance test
48、s are suggested as part ofa overall QA program. This list is not all-inclusive. The userslocal, regional, state and federal regulations as well as theusers judgement and the manufacturers recommendations aswell as the application, may stipulate use of some or all ofthese performance tests as well as
49、 test not listed.9.2 7-Day Calibration Error TestPeriodically evaluate thesystem performance over seven consecutive days. The calibra-tion drift should not exceed 10 percent of the full-scale range.Alternatively, it is possible to specify an appropriate percent-age of detector response for each calibrant component, such asa maximum 10 % change in the calibrant response during thecourse of one week.9.3 Maintain a current Standard Operating Procedure (SOP)and maintenance log.9.4 A daily calibration check using a gas standard can beperformed as follows:9.4.1 Per
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