1、Designation: D7164 10Standard Practice forOn-line/At-line Heating Value Determination of GaseousFuels by Gas Chromatography1This standard is issued under the fixed designation D7164; 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 () 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 natur
3、al gas usingan on-line/at-line gas chromatograph.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibili
4、ty of the user of this 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:2D1070 Test Methods for Relative Density of Gaseous FuelsD1945 Test Method for Analysis of Natural G
5、as by GasChromatographyD1946 Practice for Analysis of Reformed Gas by GasChromatographyD3588 Practice for Calculating Heat Value, CompressibilityFactor, and Relative Density of Gaseous FuelsD3764 Practice for Validation of the Performance of Pro-cess Stream Analyzer SystemsD4626 Practice for Calcula
6、tion of Gas ChromatographicResponse FactorsD5287 Practice for Automatic Sampling of Gaseous FuelsD5503 Practice for Natural Gas Sample-Handling and Con-ditioning Systems for Pipeline InstrumentationD6122 Practice for Validation of the Performance of Mul-tivariate Process Infrared Spectrophotometer B
7、ased Ana-lyzer SystemsD6299 Practice for Applying Statistical Quality Assuranceand Control Charting Techniques to Evaluate AnalyticalMeasurement System PerformanceD6621 Practice for Performance Testing of Process Analyz-ers for Aromatic Hydrocarbon MaterialsE260 Practice for Packed Column Gas Chroma
8、tographyE594 Practice for Testing Flame Ionization Detectors Usedin Gas or Supercritical Fluid ChromatographyE1510 Practice for Installing Fused Silica Open TubularCapillary Columns in Gas Chromatographs2.2 ISO Standards3ISO 7504 Gas Analysis-Vocabulary3. Terminology3.1 Definitions:3.1.1 calibration
9、 gas mixture, na certified gas mixturewith known composition used for the calibration of a measur-ing instrument or for the validation of a measurement or gasanalytical method.3.1.1.1 DiscussionCalibration Gas Mixtures are the ana-logues of measurement standards in physical metrology (ref-erence ISO
10、 7504 paragraph 4.1).3.1.2 direct samplingsampling where there is no directconnection between the medium to be sampled and theanalytical unit.3.1.3 in-line instrumentinstrument with an active elementinstalled in a pipeline, which is used to measure pipelinecontents or conditions.3.1.4 on-line instru
11、mentinstrument that samples gas di-rectly from a pipeline, but is installed externally.3.1.5 at-line instrumentinstrumentation requiring opera-tor interaction that samples gas directly from the pipeline.3.1.6 continuous fuel monitorinstrument that samples gasdirectly from the pipeline on a continuou
12、s or semi-continuousbasis.3.1.7 heating valuein general terms, the heating value isthe total energy per volume transferred as heat from the1This practice is under the jurisdiction of ASTM Committee D03 on GaseousFuels and is the direct responsibility of Subcommittee D03.12 on On-Line/At-LineAnalysis
13、 of Gaseous Fuels.Current edition approved Jan. 1, 2010. Published February 2010. Originallyapproved in 2005. Last previous edition approved in 2005 as D716405. DOI:10.1520/D7164-10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.o
14、rg. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from International Organization for Standardization (ISO), 1, ch. dela Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http:/www.iso.ch.1Copyright ASTM I
15、nternational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United Splete, ideal combustion of the gas at 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.
16、8 gross heating value(also called higher heatingvalue)the amount of energy per volume transferred as heatfrom the complete, ideal combustion of the gas at standardtemperature in which all the water formed by the reactioncondenses to liquid.3.1.9 net heating value(also called lower heatingvalue)the a
17、mount of energy per volume transferred as heatfrom the complete, ideal combustion of the gas at standardtemperature in which all the water formed by the reactionremains in the vapor state.3.2 reference gas mixture, na certified gas mixture withknown composition used as a reference standard from whic
18、hother compositional data are derived.3.2.1 DiscussionReference Gas Mixtures are the ana-logues of measurement standards of reference standards (ref-erence ISO 7504 paragraph 4.1.1).4. Summary of Practice4.1 Arepresentative sample of the Gaseous Fuel is extractedfrom a process pipe or a pipeline and
19、 is transferred in a timelymanner to an analyzer sampling system. After appropriateconditioning steps that maintain the sample integrity arecompleted, a precise volume of sample is injected onto anappropriate gas chromatographic column. Excess extractedprocess or pipeline sample is vented to atmosph
20、ere, a flareheader, or is returned to the process in accordance withapplicable economic and environmental requirements andregulations.4.2 Sample constituents are separated in the column to eluteindividually for identification and quantification by the detectorand its data handling system. The heatin
21、g value is calculatedusing the results of the compositional analysis using anappropriate algorithm.4.3 Calibration, maintenance, 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 syste
22、ms that measure fuel gas characteristics such as theheating value are prevalent in the natural gas and fuel gasindustries. The installation and operation of particular systemsvary on the specific objectives, process type, regulatory re-quirements, and internal performance requirements needed bythe u
23、ser. This protocol is intended to provide guidelines forstandardized start-up procedures, operating procedures, andquality assurance 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
24、hardware necessary for interfacing to a natural gas orother fuel gas pipeline and containing all the features necessaryfor the intended application(s) can be used.6.1.1 Chromatographic-based SystemsThe chromato-graphic parameters employed generally should be capable ofobtaining a relative retention
25、time repeatability of 0.05 min (3s) for duplicate measurements. Instrumentation should satisfyor exceed other chromatographic and analytic performancecharacteristics for accuracy and precision for the intendedapplication without encountering unacceptable interference orbias. In addition, components
26、in contact with sample streamssuch as tubing and valving must be constructed of suitable inertmaterials to ensure constituents in the fuel stream do notdegrade these components or alter the composition of thesampled gas. Additional information related to analyzinggaseous fuels using gas chromatograp
27、hy can be found in TestMethod D1945 and Practice D1946.6.2 Sample Probes/Sample ExtractionThe location andorientation of sampling components are critical for ensuringthat a representative sample is analyzed. The locations andorientation of sampling components should be selected basedupon sound analy
28、tic and engineering considerations. Samplingpractices for gaseous fuels can be found in Practice D5287.6.3 Sample Inlet SystemThe 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
29、in siting an instrument include ease of calibra-tion, ease of access for repair or maintenance, sample unifor-mity at the sampling point, appropriateness of samples from asampling location, ambient conditions, and of course safetyissues. An automated gas sampling valve is required in manyapplication
30、s. All sampling system components in contact withthe fuel stream must be constructed of inert or passivatedmaterials. Care should 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
31、to the analyzer may be required to ensure that thesample is maintained in the gas phase. The need for heattracing and the extent to which it is required will be sitespecific. In general, considerations impacting heat tracingdecisions include sample compositions and the expected varia-tions, ambient
32、temperature fluctuations, operating pressures,and anticipated pressure differentials in sample system com-ponents. Sample filtration should be utilized as required toremove particulate matter from the extracted sample. Thesampling frequency relative to the process bandwidth is criticalto ensuring th
33、at the reported analytical results adequatelyrepresent the process being monitored. The Nyquist-Shannonsampling criterion of a 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
34、 found in Practice D5503.6.3.1 Carrier and Detector Gas ControlConstant flowcontrol of carrier and detector gases is critical for optimum andconsistent analytical performance. Control is achieved by useof pressure regulators and fixed flow restrictors. Temperaturecontrol is generally vital for ensur
35、ing consistent operation ofthese devices. The gas flow is measured by appropriate meansand adjusted as necessary. Mass flow controllers, capable ofmaintaining gas flow constant to 61 % at the flow ratesnecessary for optimal instrument performance are generallyused.D7164 1026.3.2 DetectorsA thermal c
36、onductivity detector (TCD) iscommonly used. Other detectors, such as the flame ionizationdetector (FID), Practice E594, can be used but should at leastmeet TCD linearity, sensitivity, and selectivity in the selectedapplication.6.4 ColumnsA variety of columns, ranging from packedcolumns to open tubul
37、ar capillary columns, can be used in thedetermination of the Heating Value of a gaseous fuel. Packedcolumns and open tubular capillary columns are covered inPractices E260 and E1510 respectively. Columns should beconditioned in accordance with the manufacturers recommen-dations. The selected column
38、must provide retention andresolution characteristics that satisfy the intended application.The column must be inert towards gaseous fuel components. Ifthe selected column utilizes a liquid phase, bleeding at hightemperatures must be sufficiently low so as to avoid the loss ofinstrument response duri
39、ng high temperature operation.6.5 Data AcquisitionData acquisition and storage can beaccomplished using a number of devices and media. 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 Integr
40、atorAn electronic integrating device or com-puter can be used. For GC-based systems, it is suggested thatthe device and software have the following capabilities:6.5.2.1 Graphic presentation of chromatograms.6.5.2.2 Digital display of chromatographic peak areas.6.5.2.3 Identification of peaks by rete
41、ntion time or relativeretention time, or both.6.5.2.4 Calculation and use of response factors.6.5.2.5 External standard calculation 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
42、 both. Hourly, daily, andmonthly averages are included as required.6.5.3 Communications SystemsEfficient communicationsbetween 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 Mater
43、ialsNOTE 1Warning: Compressed gas standards should only be handledin well ventilated locations away from sparks and flames. Improperhandling of compressed gas cylinders containing calibration standards, air,nitrogen, hydrogen, argon or helium can result in explosion. Rapid releaseof nitrogen or heli
44、um can result in asphyxiation. Compressed air supportscombustion.7.1 StandardsThe components in the reference standardshould be representative of the monitored gas. Concentrationsof major components are typically selected between one halfand twice their expected concentration in the monitored gas.St
45、andards must be maintained as close as practicable to aconstant temperature within the temperature range specified bythe manufacturer to ensure accuracy and stability.8. Equipment Siting and Installation8.1 Asample inlet system capable of operating continuouslyat or above the maximum column operatin
46、g temperature isnecessary. The location of the sample inlet to the analyzerrelative to the sample extraction point is critical to obtainingtimely analytical results. Ideally, the analyzer is close coupledto the sample extraction point and there is an insignificantsampling lag time. Normally, the ana
47、lyzer is mounted at somedistance away from the sample extraction point. This increaseddistance represents increased lag time 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 rela
48、tive to the process beingsampled. A fast loop sweep can be used to minimize the lagtime by creating a bypass loop that flows 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 sampl
49、ing system. The samplingsystem should be capable of delivering a sample to thedetection system within the cycle time of the 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 theintended use. This pretest is performed before the system isplaced in continuous service and may be performed in a varietyof wa
