1、GPA Standard 21 99-99 The Determination of Specific Sulfur Compounds by Capillary Gas Chromatography and Sulfur Chemiluminescence Detection Gas Processors Association 6526 East 60th Street Tulsa, Oklahoma 741 45 STDOGPA 2L77-ENGL 1777 3824b77 0020938 877 DISCLAIMER GPA publications necessarily addre
2、ss 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 revie
3、wed. 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 here
4、by 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 cov
5、ered. “Copyright 1999 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 2199-ENGL 1999 W 3824b99 0020437 723 m The Determination of Specific Sulfur Compounds by Capillary Gas 1. Scope 1
6、.1 This method provides for the determination of individual sulfur compounds normally found in natural gas and natural gas liquid streams. The method is applicable to natural gas, liquefied petroleum gases, and natural gasolines with a final boiling point of 260C (500F). The detection range for sulf
7、ur compounds, reported as ppmv S, is 0.1 to 4000 based upon the analysis of a 1 cc sample size for gases and 0.1 to 5000 ng S for liquids using a 1 p1 sample size. 1.2 This test method may not identify all individual sulfur compounds. The detector response to sulfur is equimolar for all sulfur compo
8、unds within the scope (1.1) of this method, so unknown sulfur compounds are determined with equal precision to that of known compounds. Total sulfur content of samples is calculated from the total of the individual sulfur compounds determined. 1.3 The method determines, in a single analysis, the ind
9、ividual sulfur compounds occurring naturally, or added odorants, in natural gas and natural gas liquids including hydrogen sulfide, carbonyl sulfide and carbon disulfide. The method does not address procedures for determining other oxides of sulfur or any other hetero- atom sulfur compounds that may
10、, through chemical reaction, be present in refinery and or chemical plant streams. 1.4 It is assumed that the user of this method has the responsibility to establish appropriate safety and health procedures consistent with good laboratory practice. 2. Referenced Documents 2.1 GPA Standards 2377 2 16
11、6 2265 2261 2174 2177 The Determination of H,S and CO, using Length of Stain Tubes. Method for Obtaining Natural Gas Samples for Analysis by Gas Chromatography . Standard for Determination of Hydrogen Sulfide and Mercaptan Sulfur in Natural Gas (Cadmium Sulfate- Iodometric Titration Method). Standar
12、d of Analysis for Natural Gas and Similar Gaseous Mixtures by Gas Chromatography. Obtaining Liquid Hydrocarbon Samples for Analysis by Gas Chromatography. Analysis of Demethanized Hydrocarbon Mixtures Containing Nitrogen and Carbon Dioxide by Gas Chromatography. 3. Terminology 3.1 Table 1 is a list
13、of sulfur compounds analyzed by this method. The list is in order of elution on the specified column and shows the abbreviated letters for each compound as well as other information that may be used in calculations for calibration and analysis 4. Summary of Method 4.1 Sulfur species to be determined
14、 in natural gases and natural gas liquids are physically separated by gas chromatography using a wall-coated open tubular (WCOT) column and temperature programming. The sulfur compounds are detected using a sulfur chemiluminescence detector (SCD) and detector response is compared to calibration data
15、 obtained under identical operating conditions. The reactivity of many sulfur compounds requires careful attention to sample handling, from collection through analysis, to insure reliable results. Analysis is ideally performed on-site to eliminate the potential of sample deterioration. Sample contai
16、ners must be specially conditioned for transporting sulfur samples to the laboratory. This sample container conditioning may be simple passivation with H2S or special inert linings such as fused silica or epoxy type materials. Tedlar bags have proven to be non-reactive over limited time periods and
17、can be used for sampling. The elapsed time from sample collection through analysis should be minimal to insure more accurate results. Provided the instrument set up demonstrates good repeatability, this method will generate precise sulfur specie data on the collected samples, but due to the reactivi
18、ty of sulfur compounds, may not accurately reflect the true sulfur concentrations at the sample source. For those samples normally liquid at atmospheric pressure and ambient temperature, sample injection can be with a microliter syringe, calibration is with dimethyldisulfide, a reasonably stable com
19、pound over the operating temperature range of this method. For those samples normally gas at 30“C, calibration is with carbonyl sulfide, a reasonably stable compound when the diluent gas, such as methane or helium, is dry. For analysis of liquefied petroleum products and full boiling range natural g
20、asolines, the preferred method of calibration is a prepared calibration standard of carbonyl sulfide and dimethyldisulfide in a sulfur free hydrocarbon, such as butane. 4.4 Sulfur Chemiluminescence Detection- (2) less than 0.1 mgkg sensitivity; (3) greater than 1 x lo6 selectivity for sulfur compoun
21、ds over hydrocarbons; (4) linear and equimolar response to sulfur concentration. As sulfur compounds elute from the WCOT column they are combusted and reduced in a hydrogen/oxygen atmosphere. The resulting products are transported by vacuum into the reaction chamber of the SCD. In the reaction chamb
22、er, ozone, supplied from an ozone generator, reacts with sulfur monoxide to form the excited state of sulfur dioxide as denoted in the following reactions: Sulfur compounds + HdO, -+ SO where hv = chemiluminescent light energy SO + 03- SO,*+ SO, + hv The schematic of the SCD configuration is shown i
23、n Figure 1. Combustion furnace - The furnace is mounted in one of the detector positions on the chromatograph. This allows the furnace inlet to penetrate into the chromatograph oven and permits a direct connection of the WCOT column to the furnace inlet. There is an optional configuration that yield
24、s quantitative data for both the hydrocarbons on the FID and the sulfur species on the SCD if the two detectors are coupled via a post column split. To maintain 6.1.4.2 optimal performance of both detectors, the preferred SCD configuration includes one that provides its own combustion and reduction
25、gases, rather than one that relies solely on the FID for combustion. Operating parameters for this furnace are shown in Table 2. 6.1.4.3 Vacuum pump - A heavy duty vacuum pump is supplied as an integral part of the SCD. The pump must have a displacement capacity of 1 cubic feet per minute and capabl
26、e of achieving less 10 Torr with zero through flow. It may be either an oil-less or an oil- sealed pump. If an oil-sealed pump is used, water must be removed via a coalescer. The SCD is equipped with an ozone scrubber to prevent any release of ozone into the vacuum pump or the laboratory. 6.2 Column
27、 - A 60 M x 0.32 mm ID fused silica WCOT column is used containing a 4 pm film thickness of 100% bonded methyl silicone liquid phase. The column shall provide retention and column characteristics as listed in Table 1 and illustrated in Figure 2. The column must also exhibit a sufficiently low liquid
28、 phase bleeding at high temperature such that no loss of sulfur sensitivity occurs at a maximum temperature of 225C. 6.3 Electronic Integrator - The use of an electronic integrator or computer is recommended to digitize the analog signal from the SCD. 6.3.1 The device and software must have the foll
29、owing capabilities: Graphic presentation of the chromatogram Digital display of the chomatographic peak areas and identification of peaks by absolute retention times. Calculation and use of response factors. External standard and normalization methods of calculation and data presentation. Table 2 Ty
30、pical Instrument Operating Parameters Column: Column Oven: Initial Temp. 30C Initial Hold 4.0 min. 60 M x 0.32 mm.1 D. fiwed silca with 4 pn film thickness of 100% methylsilicone; Helium carrier gas 30psig Rate 8“C/mh Final Temp. 225C Final Hold 10 min. Flame Ionization Detector: 300C H2 Air 300-400
31、 cdmin Make-up Gas None Split ratio: 50 to 1 (Mounted on an FID) 30-40 e I o U ce Q U. L c) n !E a v) .- E E pi P x - - e Ei e .- E 10 15 I 15 Minutes I 20 I 25 I 30 1 a STD-GPA 2199-ENGL 1999 E 3824b99 0020447 BTT E Figure 3 Chromatogram of Demethanized NGL; 30 M x 0.32 I.D., 4pm Film Thickness, Fu
32、sed Silica SPB-l Column, Initial Hold 40C for 3 min., Temp. Prog. 40-200C lO“C/min. I MeSH - . EtSY -%-. +- DMS iPrSH 1 c nPrSH tBuSH MES sBuSH ; c - DES nBuSH DMDS 3-AmSH n-AmSH Di(iso-propyl) sulfide Di(n-propyl) sulfide DEDS 9 Figure 4 Linearity of SCD 5000000 25000000 E J- 10000000 E m E Figure
33、5(a) Constant Volume Sampling from Cylinders. Carrier Gas to LSV - Carrier Gas to Column r Figure 5(b) Constant Volume Sampling with a Syringe. 5 cc Syringe with Luer-Lok Fitting _ 16 Gauge 2 in. Luer-lok Needle Fitted to 1/16 Maie Vaico Zero Deadvolume Fitting Camer Gas to UV - 3 Carrier Gas to Column r 10
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