Gpa 2286-95.pdf 141b

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G P A STD*(<228b 95

3824b99 00LiLbA 214 GPA Standard 2286-95

Tentative Method of Extended Analysis for Natural Gas and Similar Gaseous Mixtures by Temperature Programmed Gas Chromatography

Adopted as Tentative Standard 1986 Reprinted 1989, 1991, 1995 Revised 1995

Gas Processors Association 6526 East 60th Street Tulsa, Oklahoma 74145

COPYRIGHT Gas Processors Association (GPA) Licensed by Information Handling Services

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DISCLAIMER GPA publications necessarily address problems of a general nature and may be used by anyone desiring to do so. Every effort has been made by GPA to assure accuracy and reliability of the information contained in its publications. With respect to particular circumstances, local, state, and federal laws and regulations should be reviewed. It is not the intent of GPA to assume the duties of employers, manufacturers, or suppliers to warn and properly train employees, or others exposed, concerning health and safety risks or precautions. GPA makes no representation, warranty, or guarantee in connection with this publication and hereby expressly disclaims any liability or responsibility for loss or damage resulting from its use or for the violation of any federal, state, or municipal regulation with which this publication may conflict, or for any infringement of letters of patent regarding apparatus, equipment, or method so covered.

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COPYRIGHT Gas Processors Association (GPA) Licensed by Information Handling Services

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G P A STDa2286 95

3824677 0017170 772

Tentative Method of Extended Analysis for Natural Gas and Similar Gaseous Mixtures by Temperature Programmed Gas Chromatography sections. The first section separating oxygen, nitrogen and methane is tied mathematically to the second section which separates methane through normal pentane. The third section which separates the components eluting from iso-pentane through tetradecane (listed in Table I) are in turn tied to the second section by the common components is0 and normal pentanes. Components in section one are separated under isothermal conditions on an adsorption type column and detected by thermal conductivity. The second section of the analysis is taken from a new sample charged to a partition-type column held isothermally for six minutes and then finished by a temperature program. This column effluent es through a splitter which permits carbon dioxide and hydrogen sulfide to be detected by thermal conductivity and the methane through pentane by hydrogen flame ionization methods. At the same time as section two components are ing through the partition column a third column system is charged with a fresh sample using the same temperature program to yield a breakdown of the components from iso-pentane to the tetradecanes with detection on a second flame ionization unit. (See suggested flow system in Figure 1 .) Twelve programmable open collector transistor switch closures are required to perform the necessary valve operations in this method.

1. SCOPE 1.1 This method covers the determination of the chemical composition of natural gas and similar gaseous mixtures within the ranges listed in Table I. In cases where peaks are known to contain one or more components, groupings are shown in Table I and also again in Figure 4. Improved results for Btu content over those obtained using GPA 2261 will not necessarily be achieved. This method is intended for use with rich gas systems and i n situations where the heptanes plus compositional breakdown is desired. 1.2 Components sometimes associated with natural gases, ie., helium, carbon monoxide and hydrogen are excluded from the main body of the method. These components are determined and made a part of the complete compositional data by following special techniques outlined in Appendix B.

NOTE 1-Hydrogen suljïde is eluted in a well defined peak between ethane and propane on the suggested partition column described in 3.1.4. For further discussion of the hydrogen sulfide content in natural gases see Appendix B. 2. SUMMARY OF METHOD

2.1 Components to be determined in a gaseous sample are physically separated by Gas Chromatography and compared to calibration data obtained under identical operating conditions. Set volumes of sample in the gaseous phase are charged by gas sample valves at designated times to three different packed column systems, effectively splitting the analysis into three

r------I I I

NOTE 2-The TCD and FID may be run in series $desired instead of using an efluent splitter. N O T E 3-The times listed in this method are f o r informational purposes only and may vary with changes in operating parameters.

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Gas Sample Loop

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side A

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Hdiun in

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-

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Gas Sample Oui

L - - - - - - - -- - - - -

Gas Sample In Vacuum Saum

Figure 1 - Suggested Flow System Using an Effluent Splitter.

COPYRIGHT Gas Processors Association (GPA) Licensed by Information Handling Services

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G P A STD*228b 95

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Table I Natural Gas Components and Range of Components Covered Peak Number

1 2 3 4

5 6

7 8

9 10 11 12 13 14 15

Component Oxygen Nitrogen Carbon Dioxide Methane Ethane Hydrogen Sulfide Propane Iso-Butane n-Butane iso-Pentane n-Pentane 2,Z-Dimethylbutane 2-Methylpentane 23-Dimethylbutane 3-Methylpentane Cyclopentane n-Hexane Methylcyclopentane 2.2-Dimethylpentane 2,CDimethylpentane 2.2.3-Trimethylbutane Benzene 3.3-Dimethylpentane Cyclohexane ZMethylhexane 2,3-Dimethylpentane 3-Methylhexane 1,l-Dimthylcyclopentane 1t,3-Dimethylcyclopentane 1c,3-Dimethylcyclopentane 1t, 2-Dimethylcyclopentane 3-Ethylpentane n-Heptane Methylcyclohexane 2,2-Dimethylhexane 1,1,3-Trimethylcyclopentane Ethylcyclopentane 2,CDimethylhexane 2,5-Dimethylhexane

Conc. Range Mol %

Peak Number

0.005 - 20 0.005 - 100 0.005 - 100 0.001 - 100 0.001 - 100 0.10 - loo 0.001 - 100 0.001 - 10 0.001 - 10 0.001 - 5 0.001 - 5 0.001 - 5

16 17 18 19 20

0.001 - 5

21

0.001 - 5 22 0.001 - 5 23 0.001 - 2

24

25 0.001 - 2

26

0.001 - 2 0.001 - 2

27

0.001 - 2 28

0.001 - 2

29 30 31 32 33 34 35

0.001 - 2 0.001 - 2 0.001 - 2

Component 1c,2t,4-Trimethylcyclopentane lc,2t,3-Trimethylcyclopentane 2,3,4-Trimethylpentane Toluene 2,3-Dimethylhexane 2-Methylheptane CMethylheptane 3-Methylheptane 3,4-Dimethylhexane 1c,2c,4-Trimethylcyclopentane 1c,3-Dimethylcyclohexane 1t,4-Dimethylcyclohexane 1.1-Dimethylcyclohexane 1-Methyl-cis-3-ethylcyclopentane 1-Methyl-trans-2-ethylcyclopentane 1-Methyl- 1-ethylcyclopentane n-Octane 1t,2-Dimethylcyclohexane 1c,2c,3-Trimethylcyclopentane 1c,2-Dimethylcyclohexane 2,s-Dimethylheptane 3,s-Dimethylheptane Ethylbenzene 1,3-Dimethylbenzene 1,CDimethylbenzene 2,3-Dimethylheptane 3,4-Dimethylheptane 2-Methyloctane 3-Methyloctane 1,2-Dimethylbenzene n-Nonane Decanes Undecanes Dodecanes Tridecanes Tetradecanes

Conc. Range Mol % 0.001 - 2 0.001 - 2 0.001 - 2 0.001 - 2 0.001 - 2

0.001 - 2 0.001 - 2 0.001 - 2 0.001 - 2 0.001 - 2 0.001 - 2

0.001 - 2 0.001 - 2 0.001 - 2 0.001 - 2 0.001 - 1 0.001 - 1 0.001 -1 0.001 - 1 0.001 - 1

CAUTION: Peak identification and component groupings are based on the spec@ column arrangement and operating conditions used in the development of this method. volumes up to 0.5 ml will normally be required. The sample volume should be reproducible such that successive runs agree to HIS% of the counts on each component peak.

2.2 An equally acceptable method using a packed column/ capillary system is described in Appendix A. Use of a capillary column provides a more detailed characterization of the hexanes plus fraction identifying more individual components than packed columns. 3.

NOTE &The sample size limitation of 0.5 ml or smaller is selected with the linearity of detector response and ejjìciency of the column separation in mind. Larger samples may occasionally be used to improve measurement accuracy in low concentration components.

APPARATUS

3.1 Chromatograph-Any gas chromatograph may be used which has the following specifications:

3.1.3 Adsorption Column (Column 1)-This column must completely separate oxygen, nitrogen and methane by returning to the baseline after each peak. Figure 2 shows an example chromatogram obtained using an acceptable adsorption column.

3.1.1 Detectors-The instrument should be equipped with thermal conductivity detection and dual flame ionization with dual electrometers. 3.1.2 Sample Valves-Valves

capable of introducing gas

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3.1.5 Extended Analysis Packed Column (Column 3)-This column must separate hydrocarbons, pentane through tetradecane. Principal components separated are shown in Table I. The column packing must be capable of withstanding temperature programming to 170 "C. Figure 4 shows an example chromatogram obtained using a suitable extended analysis column to separate these components.

Column - 12 ft. 13X Mol Sieve Temperature - 60°C Inlet Pressure - 25 psig Sample Size - 0.25 cc Type Detector - Thermal Conductivity Carrier Gas - Helium W

e c

5

NOTE 7-The preparation of a suitable exfended analysis packed column to perform this separation is described in Appendix C-3.

P

3.1.6 Attenuator-The chromatograph should be equipped with an attenuator to control the signal manually, if needed. However most modern computing integrators have the ability to program the attenuation of the signal automatically and this procedure is strongly recommended.

s

.ze c= o

O

A

Figure 2 - Separation of Oxygen, Nitrogen and Methane.

NOTE 5-The preparation of a suitable adsorption column to perform this separation is described in Appendix C.1.

3.1.4 Partition Column (Column 2)-This column must separate the hydrocarbons methane through pentanes, and nonhydrocarbons nitrogen andor air, carbon dioxide and hydrogen sulfide. All peaks must be completely resolved with a return to baseline following each peak. Figure 3 shows an example chromatogram obtained using a suitable partition column to separate these components. NOTE &The preparation of a suitable partition column to perform this separation is described in Appendix C.2.

3.1.7 Temperature Control-During the iso-thermal part of the method the analyzer columns shall be maintained at a temperature within +0.2"C of the required temperature. The temperature rise versus time must be checked periodically to determine that the program is repeatable. Care should be taken that the upper limit of the program never exceeds the maximum recommended temperature limit of the materials used in the column packings.

3.2 Carrier Gas-Pressure reducing and flow control devices shall provide a flow of helium or other suitable carrier gas to through the chromatographic columns at rates not varying more than +0.5% during the sample and reference standard runs while in the isothermal mode.

3.3 Recording Instruments-Either strip-chart recorders or electronic integrators with printer-plotters should be used to display and measure the peaks as they through the detectors. A chromatogram provides an evaluation of instrument performance during the course of the run.

-

Column Silicone Composite Temperature - Programmed 60°C - 170°C Inlet Pressure 50 psig Sample Size - 0.25 cc Type Detector See Fig. 3 Carrier Gas - Helium

-

)c-

TCD Signal Plot

COPYRIGHT Gas Processors Association (GPA) Licensed by Information Handling Services

FID Sional Plot

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Column - 15 ít. UCL-45 Temperature - Programmed 60°C - 170°C Inlet Pressure - 80 psig Sample Size - 0.25 cc Type Detector - Flame Ionization Carrier Gas - Helium

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I

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w Figure 4.

4. LINEARITY CHECK PROCEDURE

3.3.1 .Recorders-Recorders shall be strip-chart types with a full range scale of 1 mv and a response time of 1 second. Minimum chart speed is recommended to be 1 cm/min and maximum speed 10 c d m i n and minimum chart width IO cm.

4. 1 For any specific chromatograph, the linear range of the major components of interest must be determined on their respective detectors. The linear range should be established for any new chromatograph and re-established whenever the instrument has undergone a major change (i.e., replaced detectors, increased sample size, switched column size, or dramatically modified run parameters).

3.3.2 Integrator/Computers-Wide range, 0-1 volt/O-IO volt, with both printing and plotting capabilities, baseline tracking and tangent skim peak detection. Integratorkomputers should have sufficient memory to handle the large number of components and have a minimum of 12 programmable external event relays.

In order to determine the range of linearity it is necessary to construct response curves. These may be obtained by charging varying amounts of sample of each pure component to the chromatograph and then plotting all the response counts versus the appropriate partial pressures. Tables II and III show the range of partial pressures used for the various components.

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3.4 Manometer-May be either U-tube type or well type equipped with an accurately graduated and easily read scale covering the range O to 900 mm (36 in.) of mercury or larger. The U-tube type is useful with the GPA Gas Standard, since it permits filling the sample loop with up to two atmospheres of sample pressure, thus extending the range of all components. The well type inherently offers better precision and is preferred when calibrating with pure components. Samples can be entered up to one atmosphere of pressure. With either manometer, the mm scale can be read more accurately than the inch scale. Caution should be used in handling mercury because of its toxic nature. Avoid with the skin. Wash thoroughly after any .

NOTE 9-To generate pure component data necessary to construct linearity plots, it is suggested that mini-programs be written to run just long enough to charge the GC with the component of interest, elute it from the TCD, and return the sample value to the load position. This will avoid waiting for the instrument to proceed through the complete cycle of 35 minutes before another data point can be determined.

NOTE 10-Dry air can be used f o r the calibration of oxygen and nitrogen, using composition values of 21.87 mol 96 for oxygen (includes argon which is eluted with oxygen on a molecular sieve column at these conditions) and 78.08 mol % for nitrogen.

NOTE 8-A suggested mangold arrangement for entering samples to the chromatograph under vacuum is shown in Figure 5.

3.5 Vacuum Pump-Must have the capability of producing a vacuum of 1 mm of mercury absolute or less. COPYRIGHT Gas Processors Association (GPA) Licensed by Information Handling Services

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4

G P A STD*228b 95

= 3824699 001717Y

Table II Range of Partial Pressures Used to Determine Pure Component Linearity Response Data on Partition Column (Column 2) by Thermal Conductivity Detection Component Nitrogen Methane Carbon Dioxide Ethane Hydrogen Sulfide*

TO

-

VACLILIM ...- -..

PUMP r;\

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Methane

Carbon Monoxide

n

n

50 - Atmosphere 50 - Atmosphere 50 - Atmosphere 50 - Atmosphere 50 - Atmosphere U

W I

4.3.3 Record exact partial pressure, operate appropriate gas sample valve to place sample on Column 1,

Partial Pressure Range mm of Mercury 50 - Atmoshpere 50 - Atmoshpere 50 - Atmoshpere 20 - 200

Helium

II

Figure 5 - Suggested Manifold Arrangement for Entering Vacuum Samples.

Table III Range of Partial Pressures Used to Determine Pure Component Linearity Response Data on Adsorption Column (Column 1) by Thermal Conductivity Detection

Oxygen Nitrogen

VAIVF

Partial Pressure Range m m of Mercury

T A UTION: Exercise appropriate handling procedures when using pure hydrogen sulfide. See Appendix B-3.

Component

518

4.3.4 Repeat steps 4.3.2 and 4.3.3 above at partial pressures of 100,200, 300,400,500,600,700 and atmospheric pressure in mm of mercury absolute (4.0, 8.0, 12.0, 15.5, 19.5, 23.5, 27.5 and atmospheric pressure in inches of Hg).

NOTE 12-Dry air can be used f o r the calibration of oxygen and nitrogen in lieu of the pure components due to the hazard of handling pure oxygen. The procedure for air is exactly the same as for pure components (4.3) except that the partial pressure recorded f o r a i r is allocated proportionately 21.87 mol % to oxygen and 78.08 mol % to nitrogen. Thus, air sampled at 100 mm mercury absolute yields a point for the oxygen curve at 21.9 mm of mercury absolute and a point on the nitrogen curve at 78.1 mm of mercury absolute. Thus, a complete calibration curve using air to atmospheric pressure results in a linearig curve for oxygen over the range O to 21.9 mol % and a linearig curve for nitrogen over the range O to 78.1 mol %.

20- 100

NOTE II-Procedures for the calibration and analysis of helium and carbon monoxidefound by test to meet requirements of this method are described in Appendix B. 4.2 For each of the components nitrogen, methane, carbon dioxide, ethane and hydrogen sulfide proceed as follows: 4.2.1 Connect sample source to gas sampling part of chromatograph. Evacuate manifold system, including sample loop and check for leaks. (See Figure 5 for suggested manifold arrangement.) Total system must be vacuum tight.

4.4 From experimental data developed in accordance with 4.2, 4.3, response curves shall be prepared in the following manner:

4.2.2 Carefully open metering valve to it pure component up to approximately 50 mm mercury absolute (2 in. Hg).

4.4.1 Determine area counts of all peaks of interest.

4.2.3 Record exact partial pressure, operate appropriate gas sample valve to place sample onto Column 2.

4.4.2 Tabulate peak area counts opposite the appropriate partial pressure used for each calibration run.

4.2.4 Repeat steps 4.2.2 and 4.2.3 above at partial pressures of 100, 200, 300, 400, 500,600, 700 and atmospheric pressure in mm of mercury (4.0, 8.0, 12.0, 15.5, 19.5,23.5, 27.5 and atmospheric pressure in inches of Hg).

4.4.3 Plot the data in 4.4.2. Use rectangular coordinate paper, the y-axis being partial pressure, the x-axis being peak area counts. Draw smooth lines through the points plotted for peak area count and extend down to zero. The linear range will be that portion from zero to the point at which the plot departs from a straight line.

4.3 For each of the compounds oxygen, nitrogen and methane separated on the adsoption column (Column 1) proceed as follows:

5. CALIBRATION PROCEDURE 4.3.1 Connect sample source to gas sampling valve of chromatograph. Evacuate manifold system, including sample loop and check for leaks.

5.1 The routine method of calibration is to use the response factor from a gas reference standard of known composition. This method may be used for those components in an unknown that lie within the proven linear range for a specific chromatographic instrument.

4.3.2 Carefully open metering valve to it pure component up to approximately 50 mm absolute (2 in. of Hg). COPYRIGHT Gas Processors Association (GPA) Licensed by Information Handling Services

5

suggested that a temperature of 60°C be used in conjunction with thermal conductivity detection for this section of the analysis. In about three minutes, methane will have eluted from side A of the TC cell and the program should rotate the eight port routing valve (V3) so causing Column 1 to be placed in the back flush mode. The remaining components will now exit from the system through side B. This now places Column 2 in series with side A of the TC cell. At the same time as valve (V3) is rotated, both V1 and V2 sampling valves should automatically be moved to the sample "load" position. (A schematic flow diagram of this procedure is shown in Figure 6.)

5.1.1 Connect reference standard gas to gas sampling part of chromatograph. Evacuate manifold system, including sample loop and check for leaks.

5.1.2 Carefully open metering valve to it reference standard gas up to pressure decided upon for all runs. (See analytical procedure.) 5.1.3 Record atmospheric pressure and start program to actuate sample valve to place sample on Column 2.

5.1.4 Determine peak area counts from the TCD and FID for all components of interest. These data shall be used to calculate response factors in accordance with section 7.

Evacuate V1 and V2 and then fill with fresh sample using the manifold arrangement shown in Figure 5. This pari of the procedure must be carried out in approximately four minutes which is the period of time needed to complete the back-flushing of Column 1. The program has now reached an elapsed time of seven minutes. At this point V1 is rotated and a sample now es into Column 2. Meanwhile the oven temperature still

6. ANALYTICAL PROCEDURE 6.1 General-The full range analysis of a gaseous sample first requires a run on an adsorption column (Column 1) at isothermal conditions to determine oxygen, nitrogen and methane. It is Molecular Sieve Column

Silicone Comoosite Column TCIFID Split Effluent Part isothermal - part temperature programmed TCD (Coi. 2)

TC-Isothermal

FID (Coi. 2)

TCD (Col. I) Oxygen Nitrogen Methane

Nitrogen (Air Free) Methane Carbon Dioxide

t Briged in Mol Yo t

c Briged in Mol % c

-

Ethane

-

Hydrogen Sulfide

UCL-45 Column

FID (Col. 3)

Weight Percent

Methane -

Propane ¡so-Butane n-Butane ¡so-Pentane n-Pentane

-

¡so-Pentane n-Pentane 2,2-Dimethylbutane 2-Methylpentane 2.3-Dimethylbutane 3-Methylpentane Cyclopentane n-Hexane Methylcyclopentane 2,P-Dimethylpentane 2,4-Dimethylpentane 2.2,3-Trimethylbutane Benzene 3,3-Dimethylpentane Cyclohexane 2-Methylhexane 2,3-Dimethylpentane 3-Methylhexane 1,I -Dimethylcyclopentane 1t,3-Dimethylcyclopentane 1c,3-Dimethylcyclopentane 1t,2-Dimethylcyclopentane 3-Ethylpentane n-Heptane Methylcyclohexane 2.2-Dimethylhexane 1,I ,3-Tnmethylcyclopentane Ethylcyclopentane 2.4-Dimethylhexane 2,5-Dimethylhexane 1c,2t,4-Trimethylcyclopentane 1c,2t,3-Tnmethylcyclopentane 2,3,4-Tnmethylpentane Toluene - 2.3-Dimethylhexane

-

In Weight Percent Converted to Mol Relationship

+ Briged in Weight % + YCL-45 Column

FID (Col. 3)

Weight Percent -

2-Methylheptane 4-Methylheptane 3-Methylheptane 3,4-Dimethylhexane 1~,2~,4-Trimethylcyclopentane 1c,3-Dimethylcyclohexane 1t,4-Dimethylcyclohexane 1,l -Dimethylcyclohexane 1-Methyl-cis-3-ethylcyclopentane 1-Methyl-trans-2-ethylcyclopentane 1-Methyl-1-ethylcyclopentane n-Octane 1t,2-Dimethylcyclohexane 1c,2~,3-Trimethylcyclopentane Ic,2-Dimethylcyclohexane 2,5-Dimethylheptane 3.5-Dimethylheptane Ethylbenzene 1,3-Dimethylbenzene 1,4-Dimethylbenzene 2,3-Dirnethylheptane 3.4-Dimethylheptane 2-Methyloctane 3-Methyloctane 1,2-Dimethylbenzene n-Nonane Decanes Undecanes Dodecanes Tridecanes Tetradecanes

Figure 6 - Calculation Procedure.

NOTE 13-Bridge 2 al). (See 7.2)

FID (Col. 3) in weight % to FID (Col. 2). Convert both data columns to moles and then bridge to TCD (Col.

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G P A S T D W 2 8 b 95 M 3824699 OOl17l175 454

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G P A STD*228b 95

3824699 00LïLïb 390 higher than any expected sampling temperature. This includes any gas filter that may be in use in the charging line to the GC and also any tubing and connections that may be inside the chromatograph but not inside the oven. The purpose of this is to ensure îhat the gas shall not be allowed to drop below its dew point and shall be representative of the gas that was sampled.

remains at 60°C isothermal. Components leave Column 2 in the following order - inerts, methane, carbon dioxide, ethane and hydrogen sulfide, as shown in Figure 3, and through the effluent splitter. Suggested split ratio is one part to the hydrogen flame detector, three parts to the themal conductivity detector. At an elapsed time of 11 minutes, or after four minutes in Column 2, V2 is automatically rotated and a sample is charged to Column 3 that separates the components iso-pentane through tetra-decanes. At 14 minutes elapsed time the hydrogen sulfide will have cleared the TC cell and been integrated, and the TC detection part of the analysis is completed.

NOTE 14-To be sure of representative samples in the field, select appropriate sampling method from GPA Publication 2166. Table IV Example of Response Factors Determined from Reference Síandard and Pure Components by Thermal Conductivity

At this time the oven temperature heating program commences and adds heat at approximately 2û°C per minute, reaching the final temperamre of 170°C at approximately 20 minutes elapsed time. Meanwhile, Column 3 is analyzing the heavy ends of the sample and detecting components on the second hydrogen flame detector (FID 2) and yielding a chromatogram as shown in Figure 4. At 23 minutes elapsed time the propane, iso- and normal butanes and iso- and normal pentanes have eluted from Column 2 and have been detected on FID 1 (Figure 3). At this point the program causes V3 to rotate so back-flushing the hexanes plus to the atmosphere via the TC cell, and also returns both V1 and V2 to the sample "load" position. After two more minutes (25 minutes elapsed time) tetradecane has cleared FiD 2 and the oven is switched to the "cool down" mode. Ten more minutes (35 minutes of elapsed time) and the system is now equiiibriated at 6O"C, ail valves are back to the starting position of the cycle and a new sample may be charged to the system.

component

Mol %

Response Factor

oxrsen

2.73 17795

=

0.W1534

Nitrogen

29.282 252925

=

o.Ooo1158

Methane (Mol Sieve)

69.97 498116

= 0.0001405

Methane ( S i i i iComposite)

52.42 1337500

= 0.00003919

Carbon Dioxide

7.37 280215

= 0.00OûZ630

Hydrogen Culide

2.5 -

=

I

6.2.1 Evacuate charging system, including sample loop, back to the valve on sample cylinder to 1 mm of mercury absolute or less. Close valve to vacuum source and carefully meter gas from sample cylinder into charging system until sample loop is filled at the selected pressure as indicated on the manometer. The chromatograph is now ready to start the analysis procedure outlined in Section 6.1.

Response factors from natural gas reference standards used in conjunction with response curves derived from pure components as discussed in Sections 4 and 5 of this method are essential to accurately determine the composition of an unknown gas sample. Care must be maintained to ensure that identical instrument operating conditions exist during the running of the gas standard and the unknown. As long as this stipulation is met numerous samples can be analyzed using a single gas reference standard run. If the sample volumes are measured at atmospheric pressure the operator is at the mercy of the day-to-day variations in barometric pressure resulting in poor, unnormalized totals (see Note 15-Calculations). It is suggested that the operator always charge a consistent partiai pressure of 400 mm pressure to the sample loop using the manifold arrangement discussed earlier-Figure 5 . This procedure will remove the effect of fluctuating barometric pressure and make sure that the GC receives a representative sample, particularly when the gas is rich in heavy ends and has been sampled from a high temperature source. If a component concentration falls outside the established linear range of that component, reduce the sample volume so that all components stay in the linear range. One response factor can then be used for all concentrations of that component.

7.

CALCULATIONS

7.1 Response factors are calculated for each component from nitrogen through normal pentane using the peak area counts of the reference standard. The appropriate moi or weight percent of each component is used depending upon whether the peak is taken from the TC cell or the FID.(Examples are shown in Tables IV and V.) The response factors are calculated by the following formula: Table V Example of Response Factors Determined from Reference Standard by FID Compooent Methane

Ethane

6.2 Preparation and Introduction of Sample-If field data indicate the gas sample was taken at a temperature greater than that of the laboratory, the sample must be heated to at least 20°F above the sampling temperature. It is recommended that ail lines connecting the sample to the GC be made of stainless steel and that these lines should be permanenrly heated to a tempemure

Weight %

47.69 6926850

11.89 1670658

Responce Factor

=

0.00000688

=

0.00000712

ProPane

11.32 1547536

=

0.00000732

Ico-BUtane

7.46 919943

=

0.00000810

=

0.00000806

=

0.00000893

n-8utane iso-Pentane

Mentane

7.28 902966

3.04 340424 3.06

340528

7 COPYRIGHT Gas Processors Association (GPA) Licensed by Information Handling Services

0.00002857

87500

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= 0.00000899

by TC from the following formula:

M (or W) P K - Response factor on either mol or weight basis M - Mol percent of component in reference standard W - Weight percent of component in reference standard P - Integrator area counts of component in reference standard Where K =

M=PxK Where

M -Mol percent of component in unknown P - Peak area counts of each component in unknown K - Molar response factor as determined in 7.1 Table VI Example of Relative Sensitivity Values Determined from Liquid Blend by Flame Ionization Detector (as Described in 7.2)

NOTE 15-Some integrators determine a response factor

Be sure to use the approach that is consistent with your integration equipment.

Component

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¡soPentane n-Pentane 2,2-Dirnethylbutane 2-Methylpntane 2,3-Dimethylbutane 3-Methylpentane Cyclopntane n-Hexane Methylcyclopentane 2,2-Dmethylpentane 2,4-Dmthylpentane 2,2,3-Tnmethylbutane Benzene 3,3-Dimethylpentane Cyclohexane 2-Methylhexane 2.3-Dimethylpentane 3-Methylhexane 1.l-Dimethylcyclopentane 11,3-Dimethylcyclopentane 1c,3-Dimethylcyclopentane 1t ,2-Dimethylcyclopentane 3-Ethylpentane n-Heptane Methylcyclohexane 2,2-Dimethylhexane 1,1,3-Trimethylcyclopentane Ethylcyclopentane 2.4-Dimethylhexane 2.5-Dimethylhexane 1c,21,4-Trimethylcyclopentane 1c,21,3-Trimethylcyclopentane 2.3.4-Trimethylpentane Toluene 2.3-Dimethylhexane 2-Methylheptane 4-Methylheptane 3-Methylheptane 3,4-Dimethylhexane 1~,2~,4-Trimethylcyclopentane 1c.3-Dimethylcyclohexane 1t.4-Dimethylcyclohexane 1.1-Dimethylcyclohexane 1-Methyl-cis-3-ethylcyclopentane 1-Methyl-trans-2-ethyIcyclopentane 1-Methyl-14hylcyclopentane n-Octane 11.2-Dimethylcyclohexane 1c.2c.3-Trimethylcyclopentane 1c,2-Dimethylcyclohexe 2,5-Dimethylheptane 3,5-Dimethylheptane Ethylbenzene 1,3-Dirnethylbenzene 1,4-Dimethylbenzene 2,3-Dimethylheptane 3,4-Dimethylheptane 2-Methyloctane 3-Methyloctane 1,2-Dimethylbenzene n-Nonane Decanes Undecanes Dodecanes Tridecanes Tetradecanes

7.2 Response factors for a flame ionization detector from C5 to C, can be determined relative to the response of pentane by analyzing a liquid blend of aliphatic, aromatic, and naphthenic hydrocarbons from C5 to C,. (Examples of relative sensitivity values for the FID are shown in Table VI.) Weight sensitivities relative to i-Cs and n-Cs for the above components are very close to 1.o0so making peak area percent almost equal to weight percent.l Each area count is divided by the relative sensitivity for that particular component to convert to the true weight distribution in counts. This distribution is then connected to the Cl through Cs unnormalized weight percent distribution by the bridge components iCs and nCs and an unnormalized weight percent for the components C6 to C, may then be calculated. Both of these parts of the analysis may then be converted to a mole relationship by dividing by the molecular weight. The non-hydrocarbons oxygen, nitrogen, carbon dioxide and hydrogen sulfide which have been analyzed on the TC side of the system are then added to the rest of the analysis using the bridge component methane. (See Figure 6.) The unnormalized total of all the components analyzed should be within fl.O% of 100.00%.Any air is now removed from the analysis based on the oxygen percent and the results may be normalized to an air free basis. (See Table VIL) 7.2.1 Response factors for the liquid blend C5 to C, are calculated by the following formula: W K= P Where

K - Weight response factor W -Weight percent of component in liquid blend P - Peak area counts of component in liquid blend 7.2.2 Calculate the weight concentration of all the components in unknown determined by FID in 7.1 and 7.2 by the following formula: W=PxK Where W - Weight percent of component in unknown P - Peak area counts of component in unknown K - Weight response factor as determined in 7.1 or 7.2.1

0.94

0.97 0.93 0.93 0.97 0.97 0.93 1.o2 0.93 0.93 0.93 0.93 0.93 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.93 0.97 0.97 0.97 0.93 0.93 0.99 0.98 0.98 0.94 0.94 0.94 0.94

0.98 0.94 0.95 0.94 0.95 0.95 0.95

NOTE Z6-Each area count is divided by the relative sensitivity vahe to get the true area count.1

7.2.3 Calculate the moi % of oxygen, nitrogen, methane, carbon dioxide and hydrogen sulfide in unknown as determined 8 COPYRIGHT Gas Processors Association (GPA) Licensed by Information Handling Services

Relative Sensitivity 1.o0 1.o0 0.99 0.99 0.98 0.98 0.98 0.99 0.97 0.98 0.98 0.98 1.O7 0.96 0.97 0.96 0.96 0.96 0.97 0.97 0.97 0.97 0.96 0.96 0.97 0.93

~

~~

3824699 O O L ï L ï 8 L b 3

G P A STD*<228b 95

Table VI1 Calculation of Unknown Sample using Response Factors

-

Adsorption Column Thermal Conductivity Detection

Comoonent

Counts

Oxygen Nitrogen Methane

210 237928 378759

Response Factor

für Containing Unnormalized Mol %

0.0001534 0.0001 158 0.0001405

0.032 27.545 53.21 5

Air Containing Air Free Air Free Mol % Corrected Mol % Corrected Mol Yo (Unnormalized) Wnnormalized) (Normalized) 0.032 27.545 53.21 5

-

27.429 53.215

27.435 53.225

Composite Silicone Column Thermal Conductivity Detection Component

counts

Response Factor

Methane Carbon Dioxide Hydrogen Sulfide

1351682 240863 98732

0.00003919 0.00002630 0.00002857

Unnormalized Mol % 52.972 6.335 2.821

Air Containing Corrected Mol YO (Unnormalized) 53.21 5 6.364 2.834

-

Air Free Air Free Corrected Mol Yo Mol % (Unnormalized) (Normalized) 53.21 5 6.364 2.834

6.365 2.835

Composite Silicone Column Flame ionization Detection Component

Counts

Response Factor

Methane Ethane Propane iso-Butane n-Butane iso-Pentane n-Pentane

5322628 849288 596340 228233 286869 135164 104274

0.00000688 0.00000712 0.00000732 0.00000810 0.00000806 0.00000893 0.00000899

Unnormalized Weight % Mol wt. 36.620' 6.047' 4.365' 1.849' 2.312' 1.207 0.937'

Mdes

Air Containing Corrected Mol % (Unnormalized)

2.28304 0.201 10 0.09900 0.031 81 0.03978 0.01673 0.01299

16.04 30.07 44.09 58.12 58.12 72.15 7215

53.215 4.687 2.308 0.742 0.927 0.390 0.303

Air Free Corrected Mol Yo (Unnormalized) 53.215 4.687 2.308 0.742 0.927 0.390 0.303

Air Free MOI% (Normalized] 4.688 2.309 0.742 0.927 0.390 0.303

-

Silicone UCL-45 Column Flame ionization Detection Relative Corrected Unnormalized Sensitivitv Counts Weipht % Mol Wt.

Air Containing Air Free Air Free Corrected Mol % Corrected Moi Yo Mol % Moles (Unnormalized) (Unnormalized) (Normalized

Component

Counts

iso-Pentane n-Pentane 2,2-Dimethyibutane

332181 268065 18200

1.o0 1.o0 0.99

332181 268065 18384

1.207 0.937 0.066*

86.1 8

0.00077

0.01 8

0.01 8

0.018

2-Methylpentane 2,3-Dimethylbutane

93830

0.99

94778

0.339'

86.18

0.00393

0.092

0.092

0.092

3-Methylpentane Cyclopentane

64900

0.98

66224

0.237'

78.16

0.00303

0.071

0.071

0.071

145200

0.99

146667

0.524'

86.18

0.00608

O. 142

0.142

0.142

Methylcyclopentane 2,2-Dimethyipentane 2,4-dimethyl pentane 2.2.3-Trimethylbutane

33916

0.98

34608

0.124'

85.76

0.00145

0.034

0.034

0.034

Benzene 3,SDimethyipentane

20550

1.O6

19387

0.069'

80.31

0.00086

0.020

0.020

0.020

Cyclohexane

11352

0.97

11703

0.042'

84.16

0.00050

0.01 2

0.012

0.012

2-Methylhexane 2,3-Dirnethylpentane

16190

0.96

16865

0.060'

100.20

0.00060

0.014

0.014

0.014

3-Methylhexane 1,l -Dimethylcyclopentane

8250

0.96

8594

0.031'

99.76

0.00031

0.007

0.007

0.007

1t,3-Dimethylcyclopentane 1c,3-Dimethyicyclopentane 1t,2-Dimethylcyclopentane 3-Ethylpentane

15110

0.97

15577

0.056'

98.19

0.00057

0.013

0.013

0.013

101176

0.96

105392

0.376'

100.20

0.00375

0.087

0.087

0.087

21448

0.96

22342

0.080'

99.78

0.00080

0.01 9

0.019

0.019

Ethyicyclopentane 2,4-Dimethylhexane 2,BDimethyl hexane

7982

0.94

8492

0.030'

110.22

0.00027

0.006

0.006

0.006

1c,2t,4-Tnmethylcyclopentane

4940

0.97

5093

0.018'

112.22

0.0001 6

0.004

0.004

0.004

N-Hexane

n-Heptane Methyicyclohexane 2,2-Dimethyl hexane 1.1,3-Tnrnethylcyclopentane

9 COPYRIGHT Gas Processors Association (GPA) Licensed by Information Handling Services

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G P A STDa228b 95

m 3824699 OOL7L79

OTT

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Table VI1 - Continued

-

Silicone UCL-45 Column Flame Ionization Detection

Component

Counts

lc,2t,3-Trimethyicyclopentane

5420

2,3,4-Trimethylpentane

Relative Corrected Unnormalized Sensitivity Counts Weight % Mol Wt.

Moles

Air Free Air Containing Air Free Corrected Mol % Corrected Mol % Mol % (Unnormalized) . .(Unnormalized) (Normalized)

0.97

5588

0.020'

113.22

0.00018

0.004

0.004

0.004

Toluene

34318

1.o2

33645

o. 120*

92.1 3

0.00130

0.030

0.030

0.030

2,3-Dimethylhexane 2-Methylheptane 4-Methylheptane

15722

0.93

16905

0.060*

114.23

0.00053

0.012

0.012

0.012

5249

0.93

5644

0.020*

114.23

0.00018

0.004

0.004

0.004

10651

0.97

10980

0.039'

112.21

0.00035

0.008

0.008

0.008

0.97

2322

0.008'

112.21

0.00007

0.002

0.002

0.002

43566

0.93

46845

0.167'

114.23

0.00146

0.034

0.034

0.034

1c,2~,3-Trimethylcyclopentane

1453

0.97

1498

0.005'

112.21

0.00005

0.001

0.001

0.001

1c,2-Dimethylcyclohexane

2251

0.97

2321

0.008'

112.21

0.00007

0.002

0.002

0.002

2,5-Dimethylheptane 3,5-Dimethylheptane

10519

0.93

11311

0.040"

128.25

0.00031

0.007

0.007

0.007

Ethylbenzene 1,3-Dimethylbenzene 1,4-Dirnethylbenzene 2,3-Dimethylheptane 3P-Dimethylheptane

35740

0.96

37229

0.133'

117.23

0.001 14

0.027

0.027

0.027

2-Methyloctane 3-Methyloctane

15482

0.94

16470

0.059"

128.25

0.00046

0.01 1

0.01 1

0.01 1

1,2-Dimethylbenzene

10251

0.98

10460

0.037*

106.16

0.00035

0.008

0.008

0.008

n-Nonane

30120

0.94

32043

0.1 15'

128.25

0.00090

0.021

0.021

0.021

Decanes

63980

0.95

67347

0.241'

142.28

0.00169

0.039

0.039

0.039

Undecanes plus

56871

0.94

60501

0.216'

156.30

0.00138

3-Meth ylheptane 3,4-Dimethylhexane 1c,2~,4-Trimethylcyclopentane 1c,3-Dimethylcyclohexane 1t,4--Dimethylcyclohexane

1-1-Dimethylcyclohexane 1-Methyl-cis-3-ethylcyclopentane 1-Methvl-Trans-2-ethvlcvclo~entane 2252 1-Meth;l-l -ethylcyclopentane I

I

.

n-Octane 1t,2-Dimethylcyclohexane

'

0.032

0.032

0.032

100.128'

99.980

100.000

*NOTE 17-if all components are measured, the unnomlized total should not vary more than & 1.00%from 100.00%. APPENDIX A Supplementary Procedures A. 1 Extended Analysis by Capillary Gas Chromatography

Table A-I GPA Standard 2261

A.l.l Scope-This method covers the determination of the chemical composition of natural gas by combining the analysis described in GPA Standard 2261 with an extended analysis of the hexanes and heavier components using capillary gas chromatography. Table A-I and Table A-II name the individual or grouping of components for GPA Standard 2261 and Extended Analysis respectively.

1. Hexanes and heavier 2. Nitrogen 3. Methane 4. Carbon Dioxide 5. Ethane 6. Propane 7. Ico-butane 8. nButane 9. Iso-pentane 10. n-Pentane

A.1.2 Summary of Method-An analysis of a gaseous mixture is made according to GPA Standard 2261 except results are reported to three places to the right of the decimal for more accurate normalization of the combined data. On the same gaseous mixture, an analysis is made on the iso-pentane and heavier fraction by capillary gas chromatography. The latter analysis provides essentially an individual component char-

The two analyses are combined into a simple report using the common peaks iso-pentane and normal pentane in each analysis as the bridge to correctly adjust the peak areas of the 10

COPYRIGHT Gas Processors Association (GPA) Licensed by Information Handling Services

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acterization of this fraction as shown in Figure A-I. For convenience of calculation, some peak groupings are made according to hydrocarbon type to produce Table A-II for calculating the physical properties of gaseous mixtures.

G P A STD*228b 95

3 8 2 4 b 9 9 O O L 7 L B O 811 A.2.4 Capillary Column-A 60 meter x 0.26 mm ID fused silica capillary coated with a 1.O micron film thickness of DB- 1 has been found by experiment to be suitable for this analysis.

components shown in Table A-II to the same sample size as the components of Table A-I. The peak areas of Table A-II are then converted to molar response using response factors (if needed) and molecular weight factors relative to pentane. These converted areas are calculated to mol percent relative to the total mol percent of pentanes determined by GPA Standard 2261. Peaks 2 through 10 in Table A-I are summed with peaks 1 1 through 33 in Table A-II and normalized to 1OO.ooO%.

A.2.5 Integratorkomputer-Wide range, O- 1 VIO-10 V, with both printing and plotting capabilities, baseline tracking, and tangent skim peak detection. A.2.6 Carrier Gas-The sensitive flame ionization detector requires hydrocarbon free carrier gas. Chromatographic grade helium (99.998% pure) has proven satisfactory for this analysis.

Table A-II Capillary Extended Analysis 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22.

23. 24.

25. 26.

27. 28. 29.

30. 31. 32. 33.

Iso-pentane n-Pentane Neohexane 2-Methylpentane 3-Methylpentane n-Hexane Methylcyclopentane Benzene Cyclohexane 2-Methylhexane 3-Methylhexane Dimethylcyclopentanes n-Heptane Methylcyclohexane Tnmethylcyclopentanes Toluene 2-Methylheptane 3-Methylheptane Dimethylcyclohexanes n-Octane C, Aromatics C, Naphthenes C, Paraffins n-Nonane Decanes and heavier

A.2.7 Pressure Reducing a n d Flow Control Devices-Upstream restrictions such as flow controllers are not permitted when using inlet sample splitters. Column inlet pressures should remain constant during splitting and the period of analysis. A.3 Preliminary Preparations A.3.1 Hydrocarbon Test Blend-Prepare a gravimetric standard of n-hexane, n-octane, n-decane and n-dodecane using >98% purity of the pure hydrocarbons. Weigh accurately approximately 1 gram of each hydrocarbon into a narrow mouth 4 ounce bottle followed by approximately 96 grams of hexanefree n-pentane. Cap the bottle tight and keep refrigerated except during use. From the recorded weights calculate the exact concentration of the hydrocarbons in the blend. A.3.2 Instrument Conditions-The capillary instrument should be installed according to the manufacturer's instructions, including installation of the capillary column and inlet splitter system. Parameters to be recorded for the operation file include: Hydrogen Press., psig Air Press., psig Carrier Gas Press., psig Initial Temperature Temperature Program Final Hold Inlet Splitter Temp. Detector Temperature Split Ratio

A.2 Apparatus A.2.1 Apparatus description includes only that additional apparatus required for a capillary gas chromatography system. Reference should be made to GPA Standard 2261 for information on apparatus requirements. A.2.2 Chromatograph-The chromatograph must be equipped with flame ionization detector, temperature programming that includes settable initial and final constant temperature periods, and settable temperature programming rates over the range of 2 - 10°C per minute; inlet splitter in heated zone; small volume capillary connectors at inlet splitter and detector inlet to allow proper location of capillary column ends in inlet splitter and detector inlet, and provision for makeup gas at detector inlet if detector manifold design requires such gas.

NOTE A-2-Before the capillary column is inserted into the detector inlet, the carrier gas flow through this column should be measured at 30"C, using a soap bubble meter or similar technique to measure flow as a function of time. A t 30"C, establish a flow of 1.8-2.0 cc/minute by adjusting the column inlet pressure up or down until the desiredflow rate is achieved.

A.2.3 Sample Inlet System-A gas sampling valve must be provided to introduce about 2 cc of sample gas into the inlet splitter. The gas sampling valve should be mounted in its own temperature controlled oven capable of being maintained at 2050°F above the highest expected field sampling temperature.

A.3.3 Setting Split Ratio-Connect a reference gas to the sample inlet system and with splitter set near 1 :200. inject a 2 cc sample of gas and record the ¡so- and normal pentane peaks on scale. Repeat the above step at a ratio of 1:300, record the pentane peaks and observe whether the resolution has improved. Repeat this step and increase the split ratios until no visual resolution differences are observed for these two peaks. Select the smallest split ratio that exhibits the best resolution for this operating parameter.

NOTE A-1-A vacuum sample entry system, such a s described in GPA Standard 2261, can be used to avoid heating the sample valve. For example, a 5 cc sample loop filled to 300 mm partial pressure would provide the approximate 2 cc of gas for analysis. The 300 mrn partial pressure would greatly reduce the possibility of condensation of heavier sample components, 11 COPYRIGHT Gas Processors Association (GPA) Licensed by Information Handling Services

(15-30) (Nominal Range) (40-60) (Nominal Range) (40-60) (Nominal Range) 30°C for 3.0 min. 6"C/min. for 20.0 min. 150°C for 1 min. 175°C 175°C 1:400 (nominal)

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3824694 O O L 7 L 8 L 758 A.3.4 Sample Discrimination Check-Using a microliter syringe, inject 1.0 microliter of the blend prepared in A.3.1, using the split ratio parameter determined in A.3.3 and the temperature program parameters detailed in A.3.2. Record the peak retention times and peak areas. For the blend components used, the flame ionization detector responds relative to mass (weight), therefore since the same mass of each of the four components was injected, the area under the individual peaks should be very close to the same value. If not, adjust inlet splitter temperature upward and repeat test until the four peak areas agree to within f l % relative.

A S Calculations A.5.1 Assemble Peak Areas for Table A-II by appropriately grouping like hydrocarbon types of the same molecular weight into a single area for inclusion in Table A-II. Figure A-I has every peak labeled with its corresponding location in Table A-II. A.5.2 GPA Standard 2261 above 120' C-Areas in Table A-

Ii heavier than n-pentane are normalized to 100%. The normalized area percent of each Table A-II component is multiplied by the total area of hexanes and heavier from GPA Standard 2261 (Table A-I). This correctly distributes the total hexanes and heavier area of GPA Standard 2261 (Table A-I) according to the components named in Table A-II. Next the areas in Table A-II are calculated to mol percent as follows:

NOTE A-3-This blend can be used f o r guidance in adjusting instrumentparameters for optimum analysis time since n-decane is usually the last significant component in natural gas.

AcxMsxRn) C n = ( (As x Mc) Where

A.4 Analysis Procedure A.4.1 Make an analysis on the unknown gas according to GPA Standard 2261. If this analysis is made at 120'C or above, record the unnormalized mol percent values for nitrogen through n-butane, the peak areas and unnormalized mol percent for isoand normal pentane, and the peak area for hexanes and heavier. For an analysis made below 120'C, do not record the peak area for hexanes and heavier.

Cn = Mol percent of component n Ac = Peak area of component n As = Peak area of iso- and normal pentane Cs = Mol percent of iso- and normal pentane Mc = Molecular weight of component n Ms = Molecular weight of iso- and normal pentane Rn = Flame ionization response factor for component n (if needed)

NOTE A-4-At temperatures above 120"C, the GPA Standard 2261 is expected to measure all of the hexanes and heavier components. This may not be the case for lower column temperatures.

NOTE A-5-Flame ionization response factors are significant for benzene and toluene. These are also significant components in natural gas residues. For this method the response factor (multiplying factor) for benzene is assumed to be 0.928 and for toluene 0.972. All remaining components in Table A-I have assumed response factors relative to iso-and normal pentane having responsefactors of 1.000. (Refer to Table VI, main text.)

A.4.2 Connect the unknown gas to the sample inlet system of the capillary gas chromatograph and inject about 2 cc of gas. Record the peak areas, beginning with iso- and normal pentane, of the heavier peaks in the sample. A typical chromatogram of a capillary column separation is shown in Figure A-I.

-+\

Time - Minutes Figure A-I - Natural Gas Residue by Capillary Gas Chromatography.

12 COPYRIGHT Gas Processors Association (GPA) Licensed by Information Handling Services

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G P A STD*:228b 95

~

3824699 0017182 b 9 4

Table A-III Example Calculations (above 120°C)

Table A-IV Example Calculations (below 120°C)

TABLE A-I

TABLE A4

Area 1. 4400 2. 3. 4. 5. 6. 7. 8. 9. 5500 10. 5000

Unnorm. Mol %

Norm. Mol %

4.031 71.456 1.O62 9.843 5.462 2.998 3.014 1.012 ,921

4.012 71.129 1.O57 9.797 5.437 2.984 3.000 1.O07 .SI 7

Area -

600 18500 14250 21350 15600

9500

17890 6500 6450 7540 11840 22. 10560 23. 1200 24. 4560 25. 1100 26. 905 27. 1360 28. 826 29. 425 30. 100 31. 100 32. 75 33. 50 151281

Norm.

4.031 71.456 1.O62 9.843 5.462 2.998 3.01 4 1.012 .921

4.012 71.129 1.O57 9.797 5.437 2.984 3.000 1.O07 .917

3. 4.

5. 6. 7. 8. 9. 5500 10. 5000

Mol %

TABLE A-Il Nom. x Area(1) Apportioned Area (1) Area %

x A-I (9)(10) Adjusted for A-Il (9)(10) Sample Size

crl -

.o03 .o05 .O03 .o01 c.001 <.o01 c.001 <.o01

9. 186700 10. 167900 11. 600 12. 18500 13. 14250 14. 21350 15. 15600 16. 9500 17. 17890 18. 6500 6450 19. 20. 7540 21. 11840 22. 10560 23. 1200 24. 4560 25. 1100 26. 905 27. 1360 826 28. 29. 425 100 30. 31. 100 75 32. 33. 50

100.000

151281

9. 1o. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21.

Unnorm. Mol %

1. 2.

TABLE A-Il Area -

~

.397 12.229 9.41 9 14.113 10.312 6.280 11.826 4.297 4.263 4.984 7.826 6.980 .793 3.014 .727 .598

.a99 ,546 .281 .O66 .O66 .O49 .O33 100.000

4400

17.468 538.076 414.436 620.972 453.728 276.320 520.344 189.068 187.572 219.296

344.344

.O03 .O83 .O64 .O96 .O72 .O42 .O82 .O25 .O25 .O29 .o45 .O41 .O04 .O18 .O04

307.120 34.892 132.616 31.988 26.316 .O03 .O05 39.556 .O03 24.024 12.364 .o01 <.o01 2.904 2.904 c.001 2.156 c.001 1.452 c.001 ___4400.000 100.450

.O03 .o83

.o64 .O96 .O72 .O42

.O82 .O25 .O25 .O29 .O45 .O41

.o04 .O18

.o04

A.5.3 The mol percent from the individual components from A.5.2 are summed with the n-pentane and lighter components from GPA Standard 2261 (Table A-I) and normalized to 100.000%.An example calculation is shown in Table A-III.

.O2961

17.766 547.785 421.942 632.1 74 461.816 281.295 529.723 192.465 190.984 223.259 350.582 312.682 35.532 135.022 32.571 26.970 40.269 24.458 12.584 2.961 2.961 2.221 1.480

.O03 .o01 <.o01 <.o01 <.o01 <.o01

.042 .004 .o18 .004 .003 .005 .003 ,001 <.001 <.001 c.001 c.001

4479.502

100.455

100.000

.O03 .O84 .O65 .O97 .O73 .O43 .O84 .O25 .O25 .O30 .O47 .O42 .O04 .O18 .O04 .O03

.O05

.003 .084 .065 .097 .073 .o43 .o84 .025 .025 .O30 ,047

APPENDIX B

B. 1 Determination of Carbon Monoxide-This component is encountered in association with oxygen, nitrogen, carbon dioxide and the conventional hydrocarbons in the effluent streams from combustion processes such as insitu combustion, manufactured gas, and many varied types of stack gas. A 10 ft. molecular sieve 5A column, 100/120 mesh substituted for the adsorption column shown in 3.1.3 of the main text, will determine carbon monoxide since it elutes shortly after methane. If a calibration gas is available containing carbon monoxide, obtain a response factor as for methane on the molecular sieve column. However, should a gas blend not be available, a calibration curve should be developed using pure carbon monoxide to determine the extent of the nonlinearity, if present.

A.5.4 GPA Standard 2261 below 120°C- The summed areas of is0 and normal pentane in Table A-II are divided into the summed areas of is0 and normal pentane of Table A-I to produce a multiplying factor to convert the component areas of Table A-II to the same sample size as used in GPA Standard 2261 (Table A-I). These adjusted areas are calcula-ted to mol % in exactly the same manner as described in A.5.2. These mol % data are summed into the n-pentane and lighter data from GPA Standard 2261 and the combined data is normalized to lOO.ooO%. An example calculation is shown in Table A-IV.

B.2 Determination of Hydrogen and Helium-If hydrogen is to be separated from helium, a 40 ft. molecular sieve 13X column

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crl

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GPA STDx2286 95 M 3824699 QOLïL83 520 M

30# nitrogen carrier 40°C even 1/2 cc. loop 250 m.a. 40-foot mol sieve 13X (1/8- inch col.) Thermal conductivitydetection

c œ O

-5

z I

I

O

1

2

3 Tima, minules

4

5

~~

using nitrogen or argon as a carrier gas may be used (Figure B-1). Low temperature, 40°C or less, is necessary to effect this separation.

The Maximum Allowable Concentration to which a person may be exposed without approved respiratory protection equipment is 10 ppm for an eight hour working period. Concentrations as low as 15.0 ppm may cause severe initation to the eyes and respiratory tract if the exposure lasts through the working day. Exposure of 800 to 1,ooO ppm may be fatal in a few minutes. The nose cannot be depended upon to detect the pressure of hydrogen sulfide, as 2- 15 minutes of exposure will cause the loss of sense of smell.

When helium is used as a carrier gas and hydrogen is present, hydrogen will elute on the standard molecular sieve column just before oxygen. It will also be noted that a low percentage recovery is obtained in the case where helium is present in the unknown gas indicating the need for a separate helium determination on the long 40 ft. (12 meters) molecular sieve 13X column. If a calibration gas blend is available containing hydrogen and helium, it should be used to obtain response factors. However, this not being the case, the pure components, hydrogen and helium, may be used to develop response curves in the manner set forth in section 4.3, main text.

APPENDIX C Preparation of Equipment C.1 Linde Molecular Sieve Column-Clean a 12 ft. (3.6 meter) length of 1/8 in. (3.18 mm) stainless steel tubing with acetone and dry with a stream of clean, dry air or inert gas. Plug one end of the tubing with about 1/2 in. of glass wool.

B.3 Determination of Hydrogen Sulfide

Attach a small funnel to the other end and fill the tubing with Type 13X, 100/120 mesh, dry Linde Molecular Sieve. Continuously vibrate the tubing while filling by moving an electric vibrator up and down the length of the tubing. When completely full, remove about 1/2 in. (10-15 mm) of the packing and replace with glass wool.

As indicated earlier in this text, to determine the hydrogen sulfide content of a gas accurately, analyses should be made at the sample source. However, in the case where a field analysis has not been made and although corrosion of the sample bottle may have resulted in some loss of hydrogen sulfide, an analysis of the in-place component may be made by gas chromatography. It is necessary to charge a sample of pure hydrogen sulfide to the column prior to charging the unknown gas. As soon as the pure hydrogen sulfide has cleared the column, the unknown gas should be charged. (All calibrations should be done the same way, that is, each partial pressure charge of pure hydrogen sulfide must be preceded by a full sample loop of pure hydrogen sulfide.)

Shape the finished column to mount conveniently in the chromatograph. Condition new column at 300°C overnight with carrier flow and disconnected from TC cell. This column will separate hydrogen, oxygen, nitrogen and methane. About 25 psig of carrier gas pressure at the inlet will give a suitable flow rate.

A column that has proved satisfactory for this type of analysis is the Silicone 200-500 column. It is most convenient since this is the recommended column for analyzing the hydrocarbons in natural gas. Hydrogen sulfide elutes between ethane and propane with good resolution. Extreme care must be taken when working with hydrogen sulfide due to the very toxic nature of the gas. The best ventilation possible must be maintained in the laboratory.

C.2 Silicone 200-500 Composite Column-A suitable partition column to resolve the components nitrogen and/or air, methane and all hydrocarbons and non-hydrocarbons through normal pentane (as discussed in 3.1.4 and shown in Figure 3 main text) can be made as follows: Clean a 20 ft., 2 ft., and 1 1/2 ft. (6, 0.6, and 0.4 meter) length of 1/8 in. (3.2 mm) stainless steel column tubing with

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Figure B-1-Separation of Helium and Hydrogen.

95

= 3824b99

chloroethane followed by acetone, and then dry with a stream of clean, dry air or inert gas. Bend into a U-shape for filling. Dilute 30 grams of Silicone 200-500 with about 300 grams of ethyl ether in a filter flask and add 80 grams of 100/120 mesh Chromosorb P or equivalent material. Shake the flask gently to disperse the solvent. Connect a vacuum line to the flask and evaporate the solvent. Swirl the flask gently several times while removing the solvent, to avoid concentration of the silicone in the upper layer. Pour the dry packing into both ends of the 20 ft. length of tubing using a small funnel and electric vibrator to completely fill the column. Plug each end with 1/2 in. (10-15 mm) of glass wool. Shape the finished column to mount conveniently in the chromatograph. Pour some 80/100 mesh Chromosorb 102 into the 2 ft. length of tubing using a funnel and electric vibrator to completely fill the column. Plug each end with 112 in. (10-15 mm) of glass wool. Repeat above procedure with Porapak T and the 1 1/2 ft. length of tubing. Using two 1/8 in. (3.2 mm) stainless steel unions the 2 ft. length of Chromosorb 102 and the 1 1/2 ft. length of Porapak T to the 20 ft. length of Silicone 200-500 in that order. Condition column at 200°C (maximum) overnight before using. Caution: temperatures in excess of 200°C will harm this column. This column will separate air, methane, carbon dioxide ethane, hydrogen sulfide, propane, iso-butane, n-butane, isopentane, n-pentane and other natural gas hydrocarbons as described in the method procedure. C.3 UCL-45 Column-A suitable packed column to resolve the components iso-pentane through tetradecane (as discussed in 3.1.5 and shown in Figure 4 main text) can be made as follows: Clean a 15 ft. (4.5 m) length of 1/8 in. (3.2mm) stainless steel tubing (0.021 in. wall) with chloroethane followed by acetone, and then dry with a stream of clean, dry air or inert gas. Bend into a U-shape for filling. Weigh approximately 1.4 grams Silicone UCL-45 (methyl) in a clean beaker and add 60 cc of chloroform. Allow several hours for mixture to become completely homogeneous, stirring during this time at regular intervals. Weigh 10.6 grams Gas Chrom QI1 or Supelcoport (100/120 mesh) in a side-arm flask and add dissolved liquid phase. With the flask gently rotating pull a vacuum on the side-arm of flask and apply mild heat. Continue until material is dry and can be poured satisfactorily into a bottle. Place open bottle and material in oven at 120°F for one hour. Pack column in U-shape using a vibrator. Do not use a vacuum pump on the column during the packing process. Plug each end with 1/2 in. (10-15 mm) glass wool, and bend finished column to required shape for installation in the chromatograph. Condition column at 200°C overnight with carrier gas flow before using.

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0037384 467

C.4 Preparation of a Reference Standard by Weigh?-Materials required: a. Five gallon cylinder. b. 2,000 gram balance, sensitivity I O mg. c. 100 ml pressure cylinder. d. Pure components, methane through n-pentane, and carbon dioxide. All materials except methane, carbon dioxide and possibly ethane, will be added as a liquid. The pure components should be 99+% pure. Run chromatogram on each component to check on given composition. Evacuate the five gallon cylinder for several hours. Evacuate the 100 ml cylinder and obtain its true weight. Connect the 100 ml cylinder to a source of pure n-pentane with a metal connection of calculated length to contain approximately the amount of n-pentane to be added. Flush the connection with the n-pentane by loosening the fitting at the 100 ml cylinder valve. Tighten the fitting. Close the n-pentane valve and open the 100 ml cylinder valve to it the n-pentane from the connection and then close. Disconnect and weigh the 100 ml cylinder to obtain the weight of n-pentane added. Similarly, using connections of suitable length for each component, add iso-pentane, n-butane, iso-butane, propane, ethane and carbon dioxide as desired to include in the reference standard. Weigh the 100 ml cylinder after each addition to obtain weight of component added. Connect the 100 ml cylinder to the five gallon cylinder using as short a connection as possible. Open valves on both cylinders to transfer the sample. Disconnect and weigh the 100 ml cylinder to obtain weight of sample not transferred. Analyze the material remaining in the 100 ml cylinder and calculate the weight of all components transferred into the five gallon cylinder. Weigh a one quart cylinder containing pure methane at about 1500 pounds pressure. Transfer the methane to the five gallon cylinder until the pressure equalizes. Weigh the quart cylinder to determine the weight of methane transferred. Thoroughly mix the contents of the five gallon cylinder by heating at the bottom by convenient means such as hot water or heat lamp and leaving in vertical position for six hours or longer. From the weights and purities of all components added, calculate the composition and convert the weight percent to mol percent.

NOTE C-1-Maintain the GPA Reference Standard at 21°C or above, which is safely above the hydrocarbon dew point. Ifit should be exposed to lower temperature, heat the bottom of the cylinder for several hours before using. REFERENCE Dietz. W. A., J of GC, February, 1967, Pages 68-71.

NIOSH No. MX1225000.

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GPA STD*228b

G P A STD*228b 95

= 3824bïï

0017185 3T3

Appendix D Calculations Performed in Association with Gas Analyses PREFACE All physical constants used in these calculations should come from the most recent edition of GPA 2145. The constants used in the examples that follow are from GPA 2145-95. The following physical constants not listed in GPA 2145 have been used in some of the calculations: 0.25636 = vapor pressure of H,O (psia) @ 60°F (reference: U.S. Bureau of Standards) 1230 = vapor pressure of CO, (psia) @ 100°F

5000 = vapor pressure of N, (psia) @ 100°F -

R = Gas Constant = 1545.3504 ft. - lbplb - mol OR Cu.ft./lb - mol of any gas at 14.696 psia and 60°F = 1 n

=E P

(1545,3504)(459.67+ 60) (144)(14.696)

= 379.48357 Constant values for hexanes plus ((2,)' or heptanes plus (C,') mutually agreed upon by all concerned parties.

if not actually determined by extended analysis should be

For ease of hand calculations in the examples shown the number of significant figures does not match those shown in GPA2145. Precision of numbers in computer generated calculations should match that of GPA-2145. Rounding of numbers can cause some differences in final results. Computer generated calculations should only round those final numbers displayed on analyses, not numbers generated in intermediate calculations. For those calculations that are pressure dependent, the mathematics should be carried out using the constants at a pressure base of 14.696 and the final result converted to the desired pressure base after all other mathematical functions are completed. Conversion of the physical constants to equivalent values at other pressure bases or the use of generated secondary factors prior to performing calculations is not recommended. I t is further recommended that computer software be written to follow these methods and recommendations and that hardbound documentation of the software programs be maintained and available at all times.

For use in these calculations, moi fraction shall be equal to: mo1%/100.

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~

~

G P A STD*2'28b 95 W 3824699 001718b 23T

Calculation of Physical Properties from Mol Fraction D.1

Calculation of Heating Value (Btu), Relative Density (Specific Gravity) and Compressibility Factor (Z). The reader is referred to GPA 2172 for the proper method of calculation for these properties.

0.2

Calculation of GPM (Liquid Volume Equivalent Expressed as Gallons per 1000 CU. fi. of Gas) of Natural Gas. Column 1 Mol Fraction

Component Nitrogen Methane Carbon Dioxide Ethane Propane Iso-Butane N-Butane Iso-Pentane N-Pentane Hexanes Plus

0.0068 0.7987 0.0056 O. 1034 0.0523 0.0074 0.0138 0.0040 0.0035 0.0045

Totals

1.o000

Column 2 Cu. Ft./Gallon d 14.696 psia GPA-2145 91.413 59.135 58.807 37.476 36.375 30.639 31.791 27.380 27.673 23.235*

Column 3 GPM Q 14.696 Dsia (Col. 1 x 1ooo)/col. 2

Column 4 GPM Q 14.650 psia Col. 3 x 14.650 14.696

2.759 1.438 0.242 0.434 0.146 O. 126 0.1 94

2.7504 1.4335 0.2412 0.4326 0.1 455 0.1 256 0.1934

C +, GPM = C+ , GPM = IC5+ GPM =

5.339 2.580 0.466

5.3222 2.5718 0.4645

* Arbitrarily assumed value (used if average value not determined).

Note: It is recommended that this calculation be carried out using cu.ft./gallon constants at a pressure base of 14.696 psia until the final calculation at which time GPM can be converted to any desired pressure base as shown. Conversion of or manipulation of constants prior to performing the calculation is not recommended. 0.3

Calculation of 26-70 Gasoline Content of Natural Gas. Column 1 Mol Fraction

Column 2 Vapor Pressure

Column 3 Partial Pressure

GPA-2145

Col. 1 x Col. 2

20.450 15.580 3.683*

0.0818 0.0545 0.01 66

Component Iso-Pentane N-Pentane Hexanes Plus Total

0.0040 0.0035 0.0045

B = 0.1529

A = 0.0120

* Arbitrarily assumed value (used if average value not determined).

Note: The reader is directed to the GPSA Engineering Data Book, Vol. I, Section 6 (Storage), Figure 6-4for conversion of Reid Vapor Pressure to True Vapor Pressure.

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= 3824699 0037387 176 m ~

G P A STDx2286 95

Mol Fraction of NC, Required to Produce 26 PSI Gasoline: [(27.5 x A) - B ] t 24.22 = mol fraction of NC, required [(27.5 x 0.012) - 0.1529 ] + 24.22 = 0.0073 Where:

27.5

=

24.22 = A

=

B =

True Vapor Pressure (psia) required to obtain an ASTM Reid Vapor Pressure of 26 psi.

NC, Vapor Pressure (51.72) - required pressure (27.5) Sum of mol fractions of C,+ components. Sum of Partial Pressures of C,+ components.

Column 1 Mol Fraction

Column 2 Cu. Ft./Gallon

Column 3 GPM Q 14.696 psia

GPA-2145

Col. 1 x 1000 Col. 2

31.791 27.380 27.673 23.235*

0.2296 0.1461 0.1265 0.1937

Component N-Butane Iso-Pentane N-Penatane Hexanes Plus

0.0073 0.0040 0.0035 0.0045

Total 26 psi Reid V.P. Gasoline GPM = 0.6959 * Arbitrarily assumed value (used if average value not determined).

D.4

Calculation of 14 psi Reid Vapor Pressure Gasoline Content of Natural Gas. 14 psi Reid Vapor Pressure Gasoline content is calculated in exactly the same manner as 26 psi Gasoline with the following two changes: (1) 15.25 is used in place of 27.5 as the required True Vapor Pressure to obtain a correct reading of 14 psi Reid. (2) 36.47 is used in place of 24.22 as the difference between NC4 True Vapor Pressure and required pressure.

D. 5

Calculation of Actual Btu (Based on Field Determined H 2 0 Content) of Natural Gas.

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Actual Btdcu. ft. = Dry Btu @ PB x

Where:

(21.0649 CU. ft.Ab x 14.696PB)I

PB = Pressure Base (psia) of Dry Btu Pounds = Field determined H,O Content in pounds per MMcf 21.0649 = 379.48357 (CU. ft. per mol H,O) 18.015 (mol wt. H,O)

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~

G P A S T D t 2 2 8 b 95

0.6.

m 3824699 0017188

002

m

Calculation of Btu per pound of Natural Gas.

D.6a

Calculation of Weight Fraction.

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Column 1 Mol Fraction

Column 2 Molecular Wt. GPA-2145

Column 3 Comp. Pounds Col. 1 x Col. 2

Column 4 WeinM Fraction Col. 3 Sample Mol. Wt.

Nitrogen Methane Carbon Dioxide Ethane Propane Iso-Butane N-Butane Iso-Pentane N-Pentane Hexanes Plus

0.0068 0.7987 0.0056 0.1 o34 0.0523 0.0074 0.01 38 O.Oo40 0.0035 0.0045

28.01 3 16.043 44.01 o 30.070 44.097 58.123 58.123 72.1 50 72.1 50 92.489*

O. 1905 12.8135 0.2465 3.1 092 2.3063 0.4301 0.8021 0.2886 0.2525 0.41 62

0.0091 0.61 44 0.01 18 0.1491 0.1106 0.0206 0.0385 0.01 38 0.0121 0.0200

Totals

1.oOOo

Sample mol wt. = 20.8555

1.moo

Component

* Arbitrarily assumed value (used 1 average value not determined).

D.6b

Calculation of Bhúlb. Column 1 Weight F r a c t x

Component Nitrogen Methane Carbon Dioxide Ethane Propane Iso-Butane N-Butane IsoPentane N-Pentane Hexanes Plus

0.0091 0.61 44 0.01 18 0.1491 0.1 106 0.0206 0.0385 0.01 38 0.0121 0.0200

Total

1.o000

Column 2 BtuAb. Mass

Column 3 Comp. Btu/lb.

GPA-2145

Col. 1 x Col. 2

-

O 14679 O 3330 2395 437 820 290 255 41 8

23891

-

22333 21653 21232 21300 21o43 21085 20899'

BtuAb. mass = 22624

Arbitrarily assumed value (used if average value not determined).

Notes: 1. Bhúlb. mass constantsporn GPA-2145 are fuel as ideal gas. 2. Since mass is not pressure dependent the final sample Btdlb. mass should not be adjusted for any pressure base corrections.

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95 W 3824699 0037189 T 4 9 W

GPA STD*228b

Conversion of Known Btu Value to Btu Value at Different Condition.

0-7.

Btu Conversion Factors Conditions 14.650 psia

of

14.696 psia

-Dry . . - Sat D r y - p

Known

Required Btu Conditions 14.730 psia

Sat

Dry

Btu

14.735 psia

15.025 psia

Sat

Dry

Sat

Dry

Sat

1.0081 1.O261

Multiply By:

14.650 mia

Dry Sat

1.000 1.O178

0.9825 1.O000

1.0031 1.O21O

0.9856 1.O032

1.0055 1.O234

0.9880 1.O056

1.0058 1.O237

0.9883 1.O059

1.0256 1.O439

14.696 psia

Dry Sat

0.9969 1.0146

0.9794 0.9968

1.0000 1.0178

0.9826 1.0000

1.0023 1.0201

0.9849 1.0024

1.0027 1.0205

0.9852 1.0027

1.0224 1.0049 1.0405 1.0228

14.730 psia

Dry Sat

0.9946 1.O122

0.9772 0.9945

0.9977 1.O154

0.9803 0.9977

1.0000 1.O177

0.9826 1.O000

1.0003 1.O181

0.9829 1.O003

1.0200 1.0026 1.O381 1.O204

14.735 psia

Dry Sat

0.9942 1.O118

0.9768 0.9941

0.9974 1.O150

0.9800 0.9973

0.9997 1.O174

0.9823 0.9997

1.0000 1.O177

0.9826 1.O000

1.0197 1.0023 1.O377 1.O200

15.025 psia

Dry Sat

0.9750 0.9920

0.9580 0.9746

0.9781 0.9951

0.9610 0.9777

0.9804 0.9974

0.9633 0.9800

0.9807 0.9977

0.9636 0.9804

1.0000 0.9829 1.0174 1.0000

Note: Sat (saturation) assumes that the gas contains all of the water vapor it can hold at 60°F and the indicated pressure base.

Formulas Used to Derive Btu Conversion Factors

1. Dry to Dry:

PB Required Known Dry Btu PB

Known Dry Btu

2. Dry to Sat: PB Required - 0.25636

Known Dry Btu

Known Dry Btu PB 3. Sat to Dry:

4.

Sat to Sat:

Where:

PB Required x Known Sat Btu Known Sat Btu PB - 0.25636 PB Required - 0.25636 Known Sat Btu PB - 0.25636

Known Sat Btu

PB = pressure base (psia)

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