rus
increasing of the petrochemical industry based on petroleum refinery products, gas condensate, and associated, refinery and natural gas. Specifically, quality requirements grow to the feedstock and final products of petroleum and gas chemistry. Gas chromatography is one of the most popular methods of analysis in the oil and gas industry.
Теги: detector gas chromatograph natural gas газовая хроматография детектор кран-дозатор природный газ
Shimadzu Company offers several ready to use solutions for the oil and gas industry. These systems are based on the gas chromatography GC (Fig.1) for analysis of refinery gas, natural gas, gasoline, detailed hydrocarbon fuels analysis, fractional composition determination of crude oil, fuels, oils and others. All instruments confirm to ASTM and GPA standards.
We dwell particularly on the systems of natural gas analysis and on Shimadzu solutions for the fractional composition of oil determination.
Shimadzu solutions for natural gas analysis
The principle component of natural gas is methane, its structure includes also С2–С6 hydrocarbons, H2, O2, N2, CO, CO2 inorganic gases and hydrogen sulphide.
Shimadzu GC Systems present a flexible platform for complex characteristics determination of natural gas. Some models of analytical systems, which determine the chemical composition of natural gases, are given in Table 1 below. The digital flow controller was adapted for them, thereby improving the reliability and accuracy of analysis results.
So, three 10-port injection valves, two thermal conductivity detectors (TCD), three packed columns and three pre-columns are used in GC-2014NGA1 basic system.
GC-2014ENGA1 system (Fig.2, 3) is used for extended natural gas analysis. By using this system, it is possible to determine the hydrocarbon component up to С13, inclusive; and through the use of a flame ionization detector (FID) the detection sensitivity significantly increases up to several ppm. GC-2014ENGA2 system for extended fast analysis with two thermostats provides hydrocarbons determination up to С18.
GC-2014FNGA model with one TCD (or two if it is necessary to determine additionally helium and hydrogen) and with one FID is applied to speed up the analysis. The time of natural gas integrated analysis will be only 10 min. Chromatograms obtained with TCD-1 and FID detectors, when performing natural gas analysis by using
GC-2014ENGA1 system, are shown in Fig.4 and 5.
The basic principle of Shimadzu company in flow lines organization is easy maintenance. Whereas the diagrams of such systems at first sight may seem complicated (some of them contain up to 4 injection valves), their lines are designed in such a way that all flows are independent. Every single line has its own specific columns for chromatographic separation of certain compounds, which provides the analysis conditions choosing and maintenance performance independently of the other lines.
The high reproducibility of components peaks retention time is achieved by automatic flow controller AFC and automatic pressure controller APC (see. Fig.2). Back purging technique baffling carrier gas flow is applied in GC-systems to reduce the analysis time and protect the column and detector against contamination with heavy components.
Analysis duration and low sensitivity are the major disadvantages of the traditional system of natural gas analysis with TCD and FID. Shimadzu company presents the system capable to determine all components, including inorganic gases at ppm level; herewith the analysis time is five minutes only. This system uses FID and barrier discharge ionization detector BID – the unique development of Shimadzu company (Fig.6), information thereof can be found in our previous articles [1, 2]. This detector was awarded by the "The Analytical Scientist" magazine in the area of innovation for 2013 [3]. BID is a versatile detector, capable of detecting all components, except helium and neon, with the sensitivity 1.5–5 times higher than FID sensitivity and about 50–100 times higher than TCD one. Due to the unique technology of helium plasma obtaining, BID features excellent stability and reliability.
The combination of BID detector with reputable on the market Shimadzu GC-2010 Plus gas chromatograph is the Tracera system, whose name reflected the beginning of a new era in the analysis of trace amounts of compounds (Fig.7). The configuration of Tracera-UFNGA (Ultra Fast Natural Gas Analysis) system for natural gas analysis has two analytical lines, three injection valves and six columns (three principal columns and three pre-columns), its diagram is shown in Fig.8. Dosing is done automatically: the first 10-ports injection valve is used for CO2, C2H4, C2H6, C2H2 determination and for H2S, H2O and C3+ back purging. The second 10-ports injection valve – for H2, O2, N2, CH4 and CO, CO2, as well as H2O back purging. The third injection valve – to determine C1–C5 hydrocarbons and total content of C6 hydrocarbons and higher.
We present the results of natural gas analysis.
Analysis conditions:
Column 1....................... Porapak-N 1 m, 80/100 mesh
Column 2....................... Porapak-N 1 m, 80/100 mesh
Column 3............................. OV-1 1 m, 80/100 mesh
Columnа 4............. Rtx-MS-5A, 30 m × 0,53 mm × 50 μm
Column 5.............. Rt-Q PLOT, 30 m × 0,53 mm × 20 μm
Column 6..................... Rtx-1, 30 m × 0,32 mm × 5 μm
Column temperature
program ........... 65°C (1 min) – 10°C/min – 150°C (3 min)
Injection port temperature............................. 100°C
Injection mode.................................... Split (3 : 1)
Carrier gas........................... High purity helium gas
Carrier gas control
mode.................... Constant pressure, flow 10 ml/min
BID temperature........................................ 200°C
FID temperature........................................ 200°C
Non condensable gases and hydrocarbons up to С2 were separated by Rt-Q PLOT and Rt-MS-5A capillary columns, and were determined using BID. All hydrocarbon gases were separated by Rtx-1 column, and detected using FID, herewith the separation time of all components was less than five minutes! (Ref. chromatograms in Fig.9 and 10). The resulting peak areas had good reproducibility with the relative standard deviation RSD < 0.5% for six replications. The minimum detection limit was less than 10 ppm for all compounds except methane (see. Table 2).
The given example clearly demonstrates that Tracera system has high sensitivity of natural gas components determining, short analysis time, good reproducibility and can be effectively applied for qualitative and/or quantitative natural gas analysis. The software offered with the system automatically calculates the parameters of the test sample such as thermal characteristics, molecular weight, relative density and Wobbe index. Moreover, Shimadzu company can provide various configurations of natural gas analysis system, depending on customer requirements.
Shimadzu system for simulated distillation
Simulated distillation performance by using gas chromatography is widely used in the oil refinery industry to determine the fractional composition of the feedstock. Information on fractions distribution by boiling points is one of the most important, when performing quality control, regulatory compliance, as well as output products prediction. In most cases, the specialized software is required for peaks integration and for distillation curve plotting. Shimadzu company presents SimDist complementary program, fully integrated in LabSolutions basic software. Conditions for gas chromatographic analysis and SimDist parameters are stored in one procedural file, and the obtained chromatogram and the analysis results of simulated distillation are stored in one data file. Compared with the traditional method of distillation, the system provides quick, simple and cheap method for determining properties of hydrocarbon oil fractions and petroleum products.
Simulated distillation is performed using the gas chromatograph equipped with a non-polar column, where petroleum fractions (such as kerosene, diesel, and heavy oil) are distributed according to their boiling points. When analyzing the hydrocarbon mixture with known boiling points, the calibration curve of boiling temperature to components retention time is plotted. The total area below the chromatographic curve of an unknown sample is divided into equal time intervals, the area of each segment is calculated, which is proportional to the volume of the eluted fraction at a given time period. The volume ratio in % of fraction eluted during this time interval is equal to the ratio of the area of the selected segment to the total area below the chromatographic curve. Therefore, calculating the volume ratio of the fraction, using its retention time and the curve of boiling temperature to components retention time, the program creates the characteristic distillation curve. This method of total area is applicable in the case of all sample’s components eluting by the column.
Other methods are used for the analysis of crude oil and samples containing heavy non-eluted components: the internal standard method, adding the internal standard sample to a test sample, or the external standard method, which compares results of a test sample and of the external standard sample.
SimDist software supports official methods for fractional composition determination by using capillary gas chromatography (Table 3).
According to ASTM D6352, ASTM D7500, ASTM D7169, EN 15199-1, EN 15199-2, EN 15199-3 methods and others, it is necessary to determine fractions of heavy hydrocarbons up to С90 and more. By using SimDist system, it is possible to perform analysis of crude oil and oil products containing high-boiling hydrocarbon fractions up to С120 with boiling point of 750°С (Fig.11). High reproducibility of the analysis (see Fig.12 and Table 4) should be noted, which is achieved due to the reliability of the system’s instrumental performance. The relative standard deviation RSD is equal to only 0.096%. High reproducibility along with the daily system suitability test are guarantors of reliable results obtaining. The suitability test is done automatically by calculating the peak resolution, symmetry, relative standard deviation and comparing with standard values set in the program.
SimDist software completely automates the whole process of analysis performance by using simulated distillation method, moreover, functions of chromatographic parameters determination and calculation of oil products characteristics are set in it according to the ASTM requirements:
automatic determination of start and end points of the peaks (ASTM D3710, D7213, D7500);
calculation of relative sensitivity and content coefficients (%) of individual components (ASTM D3710, ASTM D7096);
calculation of damping factor (ASTM D7169);
calculation of the engine oil volatility (ASTM D6417);
calculation of cut points (ASTM D6417, ASTM D7500);
calculation of the flash point (ASTM D 7215);
calculation of Reid Vapor Pressure (ASTM STP 577).
Let us consider the example of diesel fuel analysis in conformity with ASTM D2887 method, using Shimadzu SimDist software. ASTM D2887 method is used to analyze oil products and fractions with the boiling point up to 538°С (corresponding to С44 hydrocarbons); it is most widely used for oil products analysis.
The analysis was performed by using Shimadzu GC-2010 Plus gas chromatograph, equipped with a flame ionization detector, direct input injector for wide capillary columns and AOC-20i automatic measurer of liquid samples. All components of the test sample are completely eluted from the chromatography column, so the method of total area was used.
Conditions for analysis performance:
Column................ BPX 1-Sim Dist 0,53 mm × 10 m, 0,9 μm
Column temperature............................... 35–15°С/min
.................................................... –350°С (5°С)
Carrier gas flow rate… 7 ml/min (helium) Injection port temperature 350°С
FID temperature.......................................... 380°С
Makeup gas flow rate................................ 30 ml/min
Hydrogen flow rate.................................. 40 ml/min
Air flow rate........................................ 400 ml/min
Injection volume......................................... 0,4 μl
Initially, two standard samples were analyzed, one of which contained the mixture of n-С1 – n-С10 hydrocarbons, and the second sample contained n-C10 – n-C44 mixture. Overlapping of obtained chromatograms is shown in Fig.13. Then the analysis of diesel oils comparison sample was performed (Fig.14), distillation characteristics were calculated and compared with attached values (Table 5). Corresponding distillation curves are presented in Fig.15. Using SimDist software, it is possible to perform comparison and to combine up to 16 fractional composition curves on the same graph, significantly facilitating the daily quality control and comparison with data obtained previously.
Fig.16 and Table 6 show the chromatogram and results of an unknown sample of diesel fuel analysis.
Presented data show that Shimadzu simulated distillation system is an accurate method for analysis of hydrocarbon fractions distribution.
The article presents only short overview of Shimadzu solutions for the oil and gas industry. Shimadzu company offers complete systems based on gas chromatography for a wide range of applications, including complete hydrocarbon analysis, determination of sulphur-containing compounds, aromatic compounds and oxygenates in the fuel, determination of gas impurities at ppm level, analysis of transformer oil, refinery gas, liquefied petroleum gas and many others. All systems are reliable and meet all modern quality standards.
We dwell particularly on the systems of natural gas analysis and on Shimadzu solutions for the fractional composition of oil determination.
Shimadzu solutions for natural gas analysis
The principle component of natural gas is methane, its structure includes also С2–С6 hydrocarbons, H2, O2, N2, CO, CO2 inorganic gases and hydrogen sulphide.
Shimadzu GC Systems present a flexible platform for complex characteristics determination of natural gas. Some models of analytical systems, which determine the chemical composition of natural gases, are given in Table 1 below. The digital flow controller was adapted for them, thereby improving the reliability and accuracy of analysis results.
So, three 10-port injection valves, two thermal conductivity detectors (TCD), three packed columns and three pre-columns are used in GC-2014NGA1 basic system.
GC-2014ENGA1 system (Fig.2, 3) is used for extended natural gas analysis. By using this system, it is possible to determine the hydrocarbon component up to С13, inclusive; and through the use of a flame ionization detector (FID) the detection sensitivity significantly increases up to several ppm. GC-2014ENGA2 system for extended fast analysis with two thermostats provides hydrocarbons determination up to С18.
GC-2014FNGA model with one TCD (or two if it is necessary to determine additionally helium and hydrogen) and with one FID is applied to speed up the analysis. The time of natural gas integrated analysis will be only 10 min. Chromatograms obtained with TCD-1 and FID detectors, when performing natural gas analysis by using
GC-2014ENGA1 system, are shown in Fig.4 and 5.
The basic principle of Shimadzu company in flow lines organization is easy maintenance. Whereas the diagrams of such systems at first sight may seem complicated (some of them contain up to 4 injection valves), their lines are designed in such a way that all flows are independent. Every single line has its own specific columns for chromatographic separation of certain compounds, which provides the analysis conditions choosing and maintenance performance independently of the other lines.
The high reproducibility of components peaks retention time is achieved by automatic flow controller AFC and automatic pressure controller APC (see. Fig.2). Back purging technique baffling carrier gas flow is applied in GC-systems to reduce the analysis time and protect the column and detector against contamination with heavy components.
Analysis duration and low sensitivity are the major disadvantages of the traditional system of natural gas analysis with TCD and FID. Shimadzu company presents the system capable to determine all components, including inorganic gases at ppm level; herewith the analysis time is five minutes only. This system uses FID and barrier discharge ionization detector BID – the unique development of Shimadzu company (Fig.6), information thereof can be found in our previous articles [1, 2]. This detector was awarded by the "The Analytical Scientist" magazine in the area of innovation for 2013 [3]. BID is a versatile detector, capable of detecting all components, except helium and neon, with the sensitivity 1.5–5 times higher than FID sensitivity and about 50–100 times higher than TCD one. Due to the unique technology of helium plasma obtaining, BID features excellent stability and reliability.
The combination of BID detector with reputable on the market Shimadzu GC-2010 Plus gas chromatograph is the Tracera system, whose name reflected the beginning of a new era in the analysis of trace amounts of compounds (Fig.7). The configuration of Tracera-UFNGA (Ultra Fast Natural Gas Analysis) system for natural gas analysis has two analytical lines, three injection valves and six columns (three principal columns and three pre-columns), its diagram is shown in Fig.8. Dosing is done automatically: the first 10-ports injection valve is used for CO2, C2H4, C2H6, C2H2 determination and for H2S, H2O and C3+ back purging. The second 10-ports injection valve – for H2, O2, N2, CH4 and CO, CO2, as well as H2O back purging. The third injection valve – to determine C1–C5 hydrocarbons and total content of C6 hydrocarbons and higher.
We present the results of natural gas analysis.
Analysis conditions:
Column 1....................... Porapak-N 1 m, 80/100 mesh
Column 2....................... Porapak-N 1 m, 80/100 mesh
Column 3............................. OV-1 1 m, 80/100 mesh
Columnа 4............. Rtx-MS-5A, 30 m × 0,53 mm × 50 μm
Column 5.............. Rt-Q PLOT, 30 m × 0,53 mm × 20 μm
Column 6..................... Rtx-1, 30 m × 0,32 mm × 5 μm
Column temperature
program ........... 65°C (1 min) – 10°C/min – 150°C (3 min)
Injection port temperature............................. 100°C
Injection mode.................................... Split (3 : 1)
Carrier gas........................... High purity helium gas
Carrier gas control
mode.................... Constant pressure, flow 10 ml/min
BID temperature........................................ 200°C
FID temperature........................................ 200°C
Non condensable gases and hydrocarbons up to С2 were separated by Rt-Q PLOT and Rt-MS-5A capillary columns, and were determined using BID. All hydrocarbon gases were separated by Rtx-1 column, and detected using FID, herewith the separation time of all components was less than five minutes! (Ref. chromatograms in Fig.9 and 10). The resulting peak areas had good reproducibility with the relative standard deviation RSD < 0.5% for six replications. The minimum detection limit was less than 10 ppm for all compounds except methane (see. Table 2).
The given example clearly demonstrates that Tracera system has high sensitivity of natural gas components determining, short analysis time, good reproducibility and can be effectively applied for qualitative and/or quantitative natural gas analysis. The software offered with the system automatically calculates the parameters of the test sample such as thermal characteristics, molecular weight, relative density and Wobbe index. Moreover, Shimadzu company can provide various configurations of natural gas analysis system, depending on customer requirements.
Shimadzu system for simulated distillation
Simulated distillation performance by using gas chromatography is widely used in the oil refinery industry to determine the fractional composition of the feedstock. Information on fractions distribution by boiling points is one of the most important, when performing quality control, regulatory compliance, as well as output products prediction. In most cases, the specialized software is required for peaks integration and for distillation curve plotting. Shimadzu company presents SimDist complementary program, fully integrated in LabSolutions basic software. Conditions for gas chromatographic analysis and SimDist parameters are stored in one procedural file, and the obtained chromatogram and the analysis results of simulated distillation are stored in one data file. Compared with the traditional method of distillation, the system provides quick, simple and cheap method for determining properties of hydrocarbon oil fractions and petroleum products.
Simulated distillation is performed using the gas chromatograph equipped with a non-polar column, where petroleum fractions (such as kerosene, diesel, and heavy oil) are distributed according to their boiling points. When analyzing the hydrocarbon mixture with known boiling points, the calibration curve of boiling temperature to components retention time is plotted. The total area below the chromatographic curve of an unknown sample is divided into equal time intervals, the area of each segment is calculated, which is proportional to the volume of the eluted fraction at a given time period. The volume ratio in % of fraction eluted during this time interval is equal to the ratio of the area of the selected segment to the total area below the chromatographic curve. Therefore, calculating the volume ratio of the fraction, using its retention time and the curve of boiling temperature to components retention time, the program creates the characteristic distillation curve. This method of total area is applicable in the case of all sample’s components eluting by the column.
Other methods are used for the analysis of crude oil and samples containing heavy non-eluted components: the internal standard method, adding the internal standard sample to a test sample, or the external standard method, which compares results of a test sample and of the external standard sample.
SimDist software supports official methods for fractional composition determination by using capillary gas chromatography (Table 3).
According to ASTM D6352, ASTM D7500, ASTM D7169, EN 15199-1, EN 15199-2, EN 15199-3 methods and others, it is necessary to determine fractions of heavy hydrocarbons up to С90 and more. By using SimDist system, it is possible to perform analysis of crude oil and oil products containing high-boiling hydrocarbon fractions up to С120 with boiling point of 750°С (Fig.11). High reproducibility of the analysis (see Fig.12 and Table 4) should be noted, which is achieved due to the reliability of the system’s instrumental performance. The relative standard deviation RSD is equal to only 0.096%. High reproducibility along with the daily system suitability test are guarantors of reliable results obtaining. The suitability test is done automatically by calculating the peak resolution, symmetry, relative standard deviation and comparing with standard values set in the program.
SimDist software completely automates the whole process of analysis performance by using simulated distillation method, moreover, functions of chromatographic parameters determination and calculation of oil products characteristics are set in it according to the ASTM requirements:
automatic determination of start and end points of the peaks (ASTM D3710, D7213, D7500);
calculation of relative sensitivity and content coefficients (%) of individual components (ASTM D3710, ASTM D7096);
calculation of damping factor (ASTM D7169);
calculation of the engine oil volatility (ASTM D6417);
calculation of cut points (ASTM D6417, ASTM D7500);
calculation of the flash point (ASTM D 7215);
calculation of Reid Vapor Pressure (ASTM STP 577).
Let us consider the example of diesel fuel analysis in conformity with ASTM D2887 method, using Shimadzu SimDist software. ASTM D2887 method is used to analyze oil products and fractions with the boiling point up to 538°С (corresponding to С44 hydrocarbons); it is most widely used for oil products analysis.
The analysis was performed by using Shimadzu GC-2010 Plus gas chromatograph, equipped with a flame ionization detector, direct input injector for wide capillary columns and AOC-20i automatic measurer of liquid samples. All components of the test sample are completely eluted from the chromatography column, so the method of total area was used.
Conditions for analysis performance:
Column................ BPX 1-Sim Dist 0,53 mm × 10 m, 0,9 μm
Column temperature............................... 35–15°С/min
.................................................... –350°С (5°С)
Carrier gas flow rate… 7 ml/min (helium) Injection port temperature 350°С
FID temperature.......................................... 380°С
Makeup gas flow rate................................ 30 ml/min
Hydrogen flow rate.................................. 40 ml/min
Air flow rate........................................ 400 ml/min
Injection volume......................................... 0,4 μl
Initially, two standard samples were analyzed, one of which contained the mixture of n-С1 – n-С10 hydrocarbons, and the second sample contained n-C10 – n-C44 mixture. Overlapping of obtained chromatograms is shown in Fig.13. Then the analysis of diesel oils comparison sample was performed (Fig.14), distillation characteristics were calculated and compared with attached values (Table 5). Corresponding distillation curves are presented in Fig.15. Using SimDist software, it is possible to perform comparison and to combine up to 16 fractional composition curves on the same graph, significantly facilitating the daily quality control and comparison with data obtained previously.
Fig.16 and Table 6 show the chromatogram and results of an unknown sample of diesel fuel analysis.
Presented data show that Shimadzu simulated distillation system is an accurate method for analysis of hydrocarbon fractions distribution.
The article presents only short overview of Shimadzu solutions for the oil and gas industry. Shimadzu company offers complete systems based on gas chromatography for a wide range of applications, including complete hydrocarbon analysis, determination of sulphur-containing compounds, aromatic compounds and oxygenates in the fuel, determination of gas impurities at ppm level, analysis of transformer oil, refinery gas, liquefied petroleum gas and many others. All systems are reliable and meet all modern quality standards.
Readers feedback
