GPA STD 2100-2000 Tentative Method for the Qualitative Determination of Carbonyl Sulfide in Propane《丙烷中硫化羰的定性测定暂行方法》.pdf

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1、STD-GPA 2100-ENGL 2000 W 382Yb99 002Ub38 b57 GPA Siandard 21 00-00 Tentative Method for the Qualitative Determination of Carbonyl Sulfide in Propane Adopted 2000 Gas Processors Association 6526 East 601h Street Tulsa, Oklahoma 741 45 STD.GPA 2100-ENGL 2000 382qb99 0020b39 595 = GPA publications nece

2、ssarily 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 sh

3、ould 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 publica

4、tion and hereby expressly disclaims any liability or responsibility for loss or damage resulting om 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 me

5、thod so covered. “Copyright 2000 by Gas Processors Association. All rights reserved. No part of this Report may be reproduced without the written consent of the Gas Processors Association. STD-GPA 2100-ENGL 2000 = 382Lib77 0020b40 207 GPA 2100-00 TENTATIVE METHOD FOR THE QUALITATIVE DETERMINATION OF

6、 CARBONYL SULFIDE IN PROPANE 1. SCOPE 1.1 This method is intended as a qualitative method to detect carbonyl sulfide in liquid propane at the ppm level. The data obtained during the development of this method do not indicate that it provides an accurate determination and this method should not be us

7、ed for certification purposes. A chromatographic method is recommended to obtain the most precise and accurate determination of carbonyl sulfide in propane. CAUTION: This test procedure requires the release of combustible LP-gas vapors. The user is warned to take proper safety precautions to prevent

8、 ignition. This procedure should never be performed in an en.closed building. Liquid propane evaporates rapidly, and can freeze flesh. Avoid skin contact. 2. SUMMARY OF METHOD 2.1 A sample of liquid propane is vaporized into a container, insuring the container is completely purged with the sample an

9、d the pressure in the container is at or near ambient pressure. A sample is then passed through a detector tube made specifically for the detection of carbonyl sulfide by specially prepared chemicals. The length of stain (or color change) produced in the detector tube when exposed to a measured volu

10、me of sample is directly proportional to the amount of carbonyl sulfide in the sample being tested. 2.2 A bellows or piston type pump is used to draw a measured volume of sample through the tube at a controlled rate of flow. The length of stain produced is converted to volume by comparison with a ca

11、libration scale supplied by the manufacturer with each box of detector tubes. The apparatus is easily portable and is completely suitable for making spot checks for carbonyl sulfide in LP-gas under field conditions. 3. APPARATUS 3.1 Piston or Bellows Pump-The pump is hand-operated and must be capabl

12、e of drawing a minimum of 100 mL per stroke of sample through the detector tube with an accuracy of 2.0 mL. 3.2 Detector Tube System - The tubes must be made of glass with break-off tips sized to fit the orifice of the pump used. (Tubes and pumps from different manufacturers should not be interchang

13、ed.) The chemicals sealed in the tubes must be specific for carbonyl sulfide and produce a distinct color change when exposed to a sample of LPG containing carbonyl sulfide. A calibration scale or other markings referenced to a scale should be etched directly on the detector tubes to provide for eas

14、y indication of carbonyl sulfide content. Shelf life of the detector tubes must be a minimum of two years when stored according to the manufacturers recommendations. Note 1 - Some detector tube systems will consist of two tubes, a primary tube and an analyzer tube. The primary tube is used to conver

15、t the COS to an analyte that can be quantified using the analyzer tube. 3.3 Gas Sampling Container- Any container that provides for access of the detector tube into a uniform flow of sample gas at atmospheric pressure and isolated from the surrounding atmosphere. 1 STD*GPA 2100-ENGL 2000 W 3.3.1 A s

16、uitable container may be devised from a one-pint polyethylene bottle. A 1/4-inch OD polyethylene tubing sealed into the bottle and discharging near the bottom provides for flow of sample gas into the bottle. A U2 inch hole cut into the cap of the bottle provides both access for the detector tube and

17、 a vent for gas flow. (Figure 1 . Note 2 -All nmterials used in obtaining a sample of LPG should be non-reuctive. Note 3 - Mylur gas collection bugs with a minimiim capucty of two liters are ai? acceptable suhtitute fr rhe bottle described in 3.3.1. 3.4 Needle Vclve and Tuhing - Any stainless steel

18、needle valve, which can be ,idiusted to conlrol the flow of gas from source pressure into the gas sampling Container, can be usd Polyethylene or Teflon tubing may be used to connect the gas sainpling container to the xieedle valve outlet. .Yote 4 -A pressure regulator may he used to control flow of

19、the sample gas in lieu c?fu needle ValLe. 4. SAMPLING 4.1 Before sampling, all sampling quipinent should be thoroughly cleaned and dricd. 4.1.1 Select a sampling point that affords accr:ss to a representative sample of LPG to be tes I ed. 4.1.2 Open source valve (Valve A, Figure 1 ) dnd blow dn vigo

20、rously to clear foreign materials froin source valve and connecting nipple. Close source valve. 4.1.3 Install control valve (Valve B, Figure l), or pressure regulator, on outlet of source valve. Connect outlet of control valve (Valve B) using the shortest length practicable of polyethylene or other

21、suitable tubing. 4.1.4 Open source valve (Valve A) and crack control valve (Vdve B) to obtain positive flow of gas (not liquid) through gas sample container venting to atmosphere through tube access and vent (Vent C, Figure 1). Note 5 -If liquid heginc, to collect at the bottorn of the gas sample co

22、ntuinel; the flow through the source vulve is toofast, or the sowce valvr has been left open too long. Stop the procedure, allow the gas sample container to wurrn hack to ambient temperature, unti resturt the procedure. 4.1 .S Purge gas sample container until all air is displaced. A minimum purge ti

23、me of three minutes is recommended. Note 6 - When using gas collection hags the same procedure i.) folloivtd. The bag is.filled once, disconnected and deflated. The bag ib jillrd a second time and is theri reudy,fi)r the unaLysis. 5. PROCEDURE 5.1 Irnrnediatcly, before euch series of measurements, t

24、est thc pump for tightness by inserting an unopened tube and operating the pump. A loss in vacuum on the pump within 60 seconds indicates a leak. 5.1.1 Select the tube range that includes the expected amount of carbonyl sulfide present in the sample. Reading accuracy is improved when the stain exten

25、ds at lcast SO 5% of the tube length. 5.1.2 Break off lips and insert the outlet end snugly into the pump head. If the detector “tube” being used conskis of a primary tube and an analyLer tubc, the analyzer tube is connccted directly to the pump head and the primary tubc is 2 STD-GPA 2100-ENGL 2000

26、382Lib79 0020b42 OBT connected to the analyzer tube using a short section of rubber tubing. Again, with the outlet of each tube pointing toward the pump. The temperature of tube must remain in the 0-40“C (32-104“ F ) range throughout the test period. Correction factors may need to be applied in case

27、s where the temperature of the detector tube (not the LPG) deviates significantly from 20C. These factors, if applicable, can be found in the manufacturers data sheets for the detector tubes. 5.1.3 Place open end of the detector tube system well into gas sampling container through the tube access an

28、d vent (Vent C). Note 7 - Gas sample container must be completely purged of air and with control valve (Valve B) adjusted to maintain a positive flow of gas leaving the tube access and vent (Vent C) for the duration of the test. 5.1.4 Operate the pump to draw a measured volume of gas through the det

29、ector tube. Only a single pump stroke is recommended. The use of multiple strokes may invalidate the test results. 6. CALCULATIONS 6.1 Remove the tube from the pump and follow the manufacturers instructions, if further handling of the tube is necessary. 6.1.1 Immediately read the concentration of ca

30、rbonyl sulfide from graduations on the detector tube or charts supplied with the tubes. The scale reading even with the end of the stain is the approximate carbonyl sulfide concentration in ppm/volume. 7. INTERPRETATION 7.1 The results obtained using a number of different formulations of stain tubes

31、 have varied greatly. The results obtained using this method should only be used to indicate that COS is present in the sample being tested. Current (1999) testing indicated some stain tubes might read 25 to 50% low compared to the true concentration. 7.2 The gas tubes are typically calibrated in pa

32、rts per million gas volume: gas volume units of COS per 1,O,O gas volume units of sample. Since the number of gas molecules for a given temperature/pressure/volume condition is nominally constant regardless of the type of molecule, parts per million (ppm) gas volume is equivalent to ppm mole. Parts

33、per million gas volume is often written as ppmv; this is not be confused with the ppm expression of concentration of a liquid solution which is CLg/mL. LPG are frequently written as ppmw or parts per million weight: weight units of COS per 1,000,000 weight units of sample. To convert from ppmv (gas

34、volume) to ppmw, multiply by the molecular weight of COS (60.070) and divide by the molecular weight of the product (Propane = 44.097). To convert from ppmw to ppmv (gas volume), multiply by the molecular weight of the product (Propane = 44.097) and divide by the molecular weight of the COS (60.070)

35、. 7.3 Product specifications for COS in 8. INTERFERENCES 8.1 The manufacturers literature should be consulted for possible interfering substances. Any substances known to interfere must be listed in instructions accompanying the tubes. 8.2 Under some conditions a condition may occur which results in

36、 the detector tube turning dark, rather than the expected whitening. This most usually occurs when more than one pump stroke is used in analyzing the sample. 3 STDOGPA 2LOO-ENGL 2000 W 3824b99 002Db43 TLb 8.3 If darkening occurs, or the detector Y. OTHER RECOGNIZED METHODS tube system does not behav

37、e as described in the rnmufacturers literature, then the test is invalid arid the results should be discarded. A second attempt can be inade using a fresh set of detector tubcs. If these second tests also do not behave as expectcd, the sample may contain an interferent and cannot be tested for carbo

38、nyl sulfide using this method. 9.1 The determination of carbonyl sulfide can be accomplished with a high degree of accuracy and precision using gas chromatography with a sulfur selective detector. Reference methods include GPA Technical Standard 2199- 99, ASTM D5504-94, and ASTM D6228-98. ip Source

39、Valve A - Source Valve B - Pump nibe Access & u GasVent C U Figure 1 4 Table 1. Representative Results from Round Robin Testing of COS Method 2,18* 2,12* 2,12* 1.5, 2.5* 1,2* 1,20* 2.40* 1,20* 2,25* Tester A 6 20 1 7,12* 20 2 7 16 2.5 8,42* 31 2 6 50* 3 5 20 3 8 28 2 7 22 2 6 30 2 B C D E F G St Dev

40、 Average RSD COS (SCD) EtSH (SCD) 63024 19 15 12.5* 20 20 15 15 12.5* 30* 17 15 12.5* 20 18 12.5* 11 10 10* 3.4 16 21% 38 60534 I 63004 I 59355 I 63021 2,2* 15 I 15 12 I I I 3 I 18 I 48 14 1 i 10 I I 1, NC 1,8* 1,18* 1,4* 1,8* I All values in table are ppm volume. Values for 63024 that have an * are

41、 from a half stroke measurement. They are obtained by multiplying the reading by 2.5. Values in the table with * are measurements where the stain tube did not lighten, but rather darkened. In cases where two strokes were puiled, the data are reported as x, y. Where x is the stain tube reading after the first stroke and y is the reading after the second stroke.