1、Designation: D 7314 08Standard Practice forDetermination of the Heating Value of Gaseous Fuels usingCalorimetry and On-line/At-line Sampling1This standard is issued under the fixed designation D 7314; the number immediately following the designation indicates the year oforiginal adoption or, in the
2、case of revision, 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 the heatingvalue measurement of gaseous fuels
3、using a calorimeter.Heating value determination of sample gasses containing watervapor will require vapor phase moisture measurements of thepre-combustion sample gas as well as the non-condensedgasses exiting the calorimeter. Instruments equipped withappropriate conditioners and algorithms may provi
4、de heatingvalue results on a net or gross and dry or wet basis.1.2 This practice is applicable to at-line and in-line instru-ments that are operated from time to time on a continuousbasis.1.3 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for inf
5、ormationonly.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility 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.
6、 Referenced Documents2.1 ASTM Standards:2D 1070 Test Methods for Relative Density of Gaseous FuelsD 1826 Test Method for Calorific (Heating) Value of Gasesin Natural Gas Range by Continuous Recording Calorim-eterD 3588 Practice for Calculating Heat Value, Compressibil-ity Factor, and Relative Densit
7、y of Gaseous FuelsD 3764 Practice for Validation of the Performance of Pro-cess Stream Analyzer SystemsD 4150 Terminology Relating to Gaseous FuelsD 4891 Test Method for Heating Value of Gases in NaturalGas Range by Stoichiometric CombustionD 5287 Practice for Automatic Sampling of Gaseous FuelsD 55
8、03 Practice for Natural Gas Sample-Handling andConditioning Systems for Pipeline InstrumentationD 6122 Practice for Validation of the Performance of Mul-tivariate Process Infrared SpectrophotometersD 6299 Practice for Applying Statistical Quality Assuranceand Control Charting Techniques to Evaluate
9、AnalyticalMeasurement System PerformanceD 6621 Practice for Performance Testing of Process Ana-lyzers for Aromatic Hydrocarbon MaterialsD 7164 Practice for On-line/At-line Heating Value Determi-nation of Gaseous Fuels by Gas Chromatography2.2 ISO Standards:3ISO 14532 Natural gas VocabularyISO 7504 G
10、as analysis Vocabulary3. Terminology3.1 Definitions:3.1.1 at-line instrument, nSee Terminology D 4150, Sec-tion 3.3.1.2 auto-verification, nan automated means of introduc-ing Calibration Gas Mixtures or Reference Gas Mixtures intoan analyzer for the purposes of verifying the analyzer responsewithout
11、 making any adjustments to the calibration parametersof the analyzer.3.1.3 bypass line, nLine ultimately vented to the atmo-sphere that is used where it is impractical to provide a sufficientpressure differential.3.1.3.1 DiscussionThe flowrate and pressure loss in theopen-ended line needs to be cont
12、rolled so as to ensure that thesample accuracy is not affected from any cooling and conden-sation or both (reference ISO 14532 paragraph 2.3.2.9).3.1.4 calibration gas mixture, na certified gas mixturewith known composition used for the calibration of a measur-ing instrument or for the validation of
13、 a measurement or gasanalytical method.3.1.4.1 DiscussionCalibration Gas Mixtures are the ana-logues of measurement standards in physical metrology (ref-erence ISO 7504 paragraph 4.1)3.1.5 calorimeter, nSee Terminology D 4150, Section 3.1This practice is under the jurisdiction of ASTM Committee D03
14、on GaseousFuels and is the direct responsibility of Subcommittee D03.12 on On-Line/At-LineAnalysis of Gaseous Fuels.Current edition approved May 1, 2008. Published May 2008.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For A
15、nnual 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 Internatio
16、nal, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.6 continuous fuel monitor, nan instrument thatsamples gas directly from a source continuously and providesan analytical result on a continuous or semi-continuous basis.3.1.7 direct sampling, adjsampling wher
17、e there is a directconnection between the sample source and the analytical unit,that is, in-line or on-line instrument.3.1.8 dry gas, nSee Terminology D 4150, Section 3.3.1.9 fast loop/hot loop, nBypass loop that returnssampled gas to the process line in a closed configuration andused for environmen
18、tal and safety considerations.3.1.9.1 DiscussionThe loop requires a pressure differen-tial from the collection point to the discharge point so as toensure a constant and steady flowrate through the samplingequipment located in the loop (reference ISO 14532 paragraph2.3.2.8)3.1.10 gross heating value
19、 (also called higher heatingvalue), nSee Terminology D 4150, Section 3.3.1.11 heating value, nthe amount of energy per volumetransferred as heat from the complete, ideal combustion of thegas at standard temperature.3.1.12 in-line instrument, nSee Terminology D 4150,Section 3.3.1.13 net heating value
20、 (also called lower heating value),nSee Section 3 entitled Terminology, of D 4150.3.1.14 on-line instrument, nSee Terminology D 4150,Section 3.3.1.15 reference gas mixture, na certified gas mixturewith known composition used as a reference standard fromwhich other compositional data are derived.3.1.
21、15.1 Discussion Reference Gas Mixtures are the ana-logues of reference standards (ISO 7504 paragraph 4.1.1)3.1.16 wet gas, nSee Terminology D 4150, Section 3.3.2 Acronyms:3.2.1 SOP, nStandard Operating Procedure.3.2.2 QA, nQuality Assurance.4. Summary of Practice4.1 A representative sample of the ga
22、seous fuel is extractedfrom a process pipe, a pipeline, or other gaseous fuel streamand is transferred to an analyzer sampling system. Afterconditioning that maintains the sample integrity, the sample isintroduced into a calorimeter. Excess extracted process orsample gas is vented to the atmosphere,
23、 a flare header, or isreturned to the process in accordance with applicable economicand environmental requirements and regulations. Post-combustion gasses from the calorimeter are typically vented tothe atmosphere.4.2 The heating value is calculated based upon the instru-ments response to changes in
24、 the heating value of the samplegas using an algorithm.4.3 Calibration (7.1), maintenance (Section 10), and perfor-mance (Section 9) protocols provide a means to validate andassess operation of the analyzer.5. Significance and Use5.1 On-line, at-line, in-line and other near-real time moni-toring sys
25、tems that measure fuel gas characteristics such asheating value are prevalent in various gaseous fuel industriesand in industries either producing or using gaseous fuel in theirindustrial processes. The installation and operation of particu-lar systems vary depending on process type, regulatory requ
26、ire-ments, and the users objectives and performance require-ments. This practice is intended to provide guidance forstandardized start-up procedures, operating procedures, andquality assurance practices for calorimeter based on-line,at-line, in-line and other near-real time heating value monitor-ing
27、 systems. Users employing gas chromatographic basedinstrumentation for measurement of gaseous fuel heating valueare referred to Practice D 7164.6. Apparatus6.1 InstrumentAny instrument of standard manufacture,with hardware necessary for interfacing to a fuel gas pipelineand containing all the featur
28、es necessary for the intendedapplication(s) can be used.6.1.1 Combustion SystemOperating parameters employedmust be capable of converting all of the volatile combustiblechemical species in the sample into carbon dioxide, water,nitrogen, nitrogen dioxide, and/or sulfur dioxide, using a dry,hydrocarbo
29、n-free oxidant which is typically air. A change ofless than or equal to 1,000 ppm/wt in the moisture content ofinstrument air between calorimeter calibrations is acceptable tomaintain a statistically insignificant 6 0.1% heating valueaccuracy as denoted in Practice D 4891. The less than 1,000ppm/wt
30、moisture content control value is easily achieved usingdesiccant or refrigerant air dryers when the air dryers aremaintained according to the manufacturers recommendations.Instrumentation must satisfy or exceed analytic performancecharacteristics for accuracy and precision for the intendedapplicatio
31、n without encountering unacceptable interference orbias. In addition, components in contact with sample streamssuch as tubing and valving must be constructed of suitable inertor passivated materials to ensure that the composition of thesampled gas is not altered.6.2 Sample Probes/Sample ExtractionTh
32、e 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 analytic and engineering considerations. Samplingpractices for gaseous fuels can be found in Prac
33、tice D 5287.6.3 Sample Inlet SystemAn automated gas sampling valveis required in many applications. All sampling system compo-nents in contact with the fuel stream must be constructed ofinert or passivated materials. Care should be taken to ensurethat the extracted sample is maintained in a single c
34、leangaseous phase. The addition of heat at the point of pressurereduction or along the sample line to the analyzer may berequired to ensure that the sample is maintained in the gasphase. The need for heat tracing and the extent to which it isrequired will be site specific. In general, considerations
35、 im-pacting heat tracing decisions include sample compositions andthe expected variations, ambient temperature fluctuations,operating pressures, and anticipated pressure differentials insample system components. Sample filtration should be uti-lized as required to remove particulate matter from the
36、ex-tracted sample.6.3.1 Combustion Air, Sample, and Carrier Gas ControlConstant flow control of combustion air, sample gas, andD7314082carrier gas, if required by the measurement application, isnecessary for optimum and consistent analytical performance.Control is typically achieved by use of pressu
37、re regulators andfixed flow restrictors. Ambient, combustion air, sample, andcarrier gas temperature control is generally vital for ensuringconsistent operation of flow control devices. The gas flow ismeasured and verified by appropriate means and adjusted asnecessary.6.3.2 DetectorsCommon calorimet
38、ry heating value detec-tion systems include stoichiometric combustion (TestMethod 4891), continuous recording calorimeters (TestMethod D 1826), non-stoichiometric combustion, and residualoxygen detection calorimeters. Other detectors can be usedprovided they have appropriate linearity, accuracy, sen
39、sitivityand measurement range for the selected application. In select-ing a detector, the user should consider the linearity andsensitivity of a particular detection system prior to installation.The user should also consider potential sample compositionaleffects that may influence the reported heati
40、ng value.6.4 Data AcquisitionData acquisition and storage can beaccomplished using a number of devices and media. Followingare some examples:6.4.1 RecorderA 0 to 1 millivolt or a 4-20 milliamp rangerecording potentiometer or equivalent, with a full-scale re-sponse time of 2 s or less can be used mou
41、nted locally orremotely.6.4.2 Communications SystemsEfficient communicationsbetween the analyzer and the host depend on resolving any andall interface issues. Signals to and from the host are typicallyisolated from each other in an appropriate manner.7. Reagents and Materials7.1 WarningCompressed ga
42、s standards should only behandled in well ventilated locations away from sparks andflames. Improper handling of compressed gas cylinders con-taining calibration standards or air can result in explosion.Compressed air supports combustion.7.1.1 StandardsComponents in the Calibration Gas Mix-ture shoul
43、d be representative of the monitored gas. The heatingvalue is either determined instrumentally or is calculated usinga certified gas composition of the standard. Practice D 3588 orother methods as required for regulatory purposes can be usedto calculate the heating value of a gas mixture. Other heat
44、ingvalue calculational algorithms can be used so long as allinterested parties are advised of and are in agreement with thecalculational methodology employed, or both. Methods relatedto determining the relative density of gaseous fuels can befound in Practice D 1070. Mixtures of major components are
45、typically specified to achieve the desired heating value. Aminimum of major representative components is frequentlyused. The number of components used is frequently minimizedfor economical reasons and to reduce the probability of errorduring the preparation of the Calibration Gas Mixture. In orderto
46、 ensure their accuracy and stability by preventing condensa-tion and degradation, Calibration Gas Mixtures must be main-tained within the temperature range specified by the manufac-turer. If there is any doubt concerning the validity of theCalibration Gas Mixture, a Reference Gas Mixture should beus
47、ed to verify the validity of the Calibration Gas Mixture.8. Equipment Siting and Installation8.1 The siting and installation of an at-line or on-linemonitor is critical for collecting representative information onheating value content. Factors that should be considered insiting an instrument include
48、 hazardous area rating, ease ofcalibration, ease of access for repair or maintenance, sampleuniformity at the sampling point, appropriateness of samplesfrom a sampling location, ambient conditions, and of coursesafety issues. A sample inlet system capable of operatingcontinuously at or above the max
49、imum operating sampletemperature is necessary. The location of the sample inlet to theanalyzer relative to the sample extraction point is critical toobtaining timely analytical results. Ideally, the analyzer isclose-coupled to the sample extraction point and there is aninsignificant sampling lag time. Normally, the analyzer ismounted at some distance away from the sample extractionpoint. This increased distance will result in increased lag timebetween when a sample is extracted from a process and whenan analytical result is reported. The maximum
