NL2028533A - Method and online circulation system for collecting light hydrocarbon in natural gas - Google Patents
Method and online circulation system for collecting light hydrocarbon in natural gas Download PDFInfo
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Abstract
This disclosure relates to gas geochemical analysis, and more particularly to a method and an online circulation system for collecting light hydrocarbons in natural gas. The method including: allowing the natural gas to flow through a pipeline 5 equipped with a molecular sieve in a vacuum circulation system repeatedly so as to enrich the light hydrocarbons in the natural gas on the molecular sieve; and heating the molecular sieve enriched with the light hydrocarbons in the vacuum circulation system to collect the light hydrocarbons released 10 from the molecular sieve. The light hydrocarbons are selected from the group consisting of C5 hydrocarbons, C6 hydrocarbons, C7 hydrocarbons, C8 hydrocarbons and a combination thereof. Pure CE,—C8 light hydrocarbons can be obtained from natural gas with low light hydrocarbon in content by constructing the 15 circulation system with the molecular sieve 5Â. The method of this application has simple operation, low cost and high efficiency.
Description
TECHNICAL FIELD This application relates to gas geochemical analysis, and more particularly to a method and an online circulation system for collecting light hydrocarbons in natural gas.
BACKGROUND Light hydrocarbons (Cs-Cs) are important components of natural gas, which reveal extremely important and abundant geochemical information. The geochemical indicator of light hydrocarbons can not only be used to determine the maturity of natural gas, determine whether gas reservoirs suffer from water washing or biodegradation and trace the source of natural gas, but also be used to classify the genetic type of natural gas.
A large amount of volatile light hydrocarbon is contained in crude oil samples, which can be analyzed by gas chromatography or high performance liquid chromatography. However, the content of light hydrocarbon in natural gas is extremely low, especially in “dry gas”, in which the methane content reaches 95% or more, and other hydrocarbon components are very low in the content. Therefore, only a few primary components such as methane and ethane can be detected by gas chromatography, and the light hydrocarbon ({Cs-Cs) ingredients with a content below the detection limit cannot be detected.
Due to the limitation of analysis approaches, the research on the light hydrocarbon composition in natural gas is far behind that on the light hydrocarbon composition in crude oil and source rocks, which hinders the progress of gas-oil-source comparison work in geological sciences. Therefore, how to accurately and conveniently analyze trace light hydrocarbons in natural gas by GC has been a key point in the improvement of analysis techniques.
Considering the extremely low content in natural gas, the light hydrocarbons must be enriched in advance. Currently, the gas extraction method, thermal evaporation method, rock closed extraction method, rock low-boiling point light hydrocarbon extraction method and adsorption-acidolysis hydrocarbon analysis method are only applicable to crude oil and source rock samples with relatively high light hydrocarbon content. Xu Lian (1990) designed a pressurized sampling method, which was only suitable for the analysis of natural gas with high humidity, and the natural gas cylinder needed to be heated to 120°C, posing a great safety hazard. Zhang Juhe et al. (1994) disclosed a quartz tube enrichment method, by which the amount of the collected natural gas was limited, and it was prone to error due to the use of a six-way valve, failing to accurately determine the light hydrocarbon components. Recently, solid phase micro-extraction (SPME) technique has been applied to the analysis of light hydrocarbons in natural gas (Li, Z. , Wang, X. , Li, L. , Zhang, M. , Tao, M. , & Xing, L. , et al. (2014). Development of new method of &13C measurement for trace hydrocarbons in natural gas using solid phase micro-extraction coupled to gas chromatography isotope ratio mass spectrometry. Journal of Chromatography A, 1372, 228-235), but it still fails to enable the detection of light hydrocarbon components in natural gas. Wang Shunyu et al. disclosed a new method for concentrating and analyzing C3-Cs hydrocarbons in natural gas, in which a self-made C:3-°Cs hydrocarbon concentrator was used to directly collect natural gas enrichment samples on site at the wellhead. However, it is still necessary to remove the methane, ethane and other impurity gases in the concentrator by elution.
SUMMARY To realize an efficient, simple, convenient, safe and accurate analysis of trace light hydrocarbon components in natural gas and provide more reliable experimental data for geochemical research to promote the research progress of the light hydrocarbon geochemical indicators in natural gas and the gas-oil-source comparison in geological sciences, this application provides a method and device for cyclic enrichment of light hydrocarbons in a fixed volume of natural gas, where the device can also collect the enriched light hydrocarbon components online and transfer them to gas chromatography instrument for analysis. The device and method can achieve the simple, convenient, safe, accurate and efficient enrichment of trace light hydrocarbon components in natural gas.
Technical solutions of this application are described as follows.
In a first aspect, this application provides a method for collecting light hydrocarbons in natural gas, comprising: allowing the natural gas to flow through a pipeline equipped with a molecular sieve in a vacuum circulation system repeatedly so as to enrich the light hydrocarbons in the natural gas on the molecular sieve; and heating the molecular sieve enriched with the light hydrocarbons in the vacuum circulation system to collect the light hydrocarbons released from the molecular sieve; wherein the light hydrocarbons are selected from the group consisting of Cs hydrocarbons, Cs hydrocarbons, Cs hydrocarbons, Cs hydrocarbons and a combination thereof.
In some embodiments, the vacuum circulation system is a vacuum pipeline connected with the molecular sieve in series; and an air pump and a vacuum pump are provided on the vacuum pipeline.
In some embodiments, the pipeline equipped with the molecular sieve is a U-shaped pipeline or other pipeline which is capable of increasing a contact area between the natural gas and the molecular sieve and allowing the natural gas to flow through.
In some embodiments, the molecular sieve is a 5A molecular sieve.
In some embodiments, the vacuum pump is arranged at one end of the vacuum pipeline, and a valve is provided on a pipeline connecting the vacuum pump with the vacuum pipeline.
In some embodiments, to visually observe a vacuum environment inside the vacuum pipeline, a vacuum gauge is arranged at the other end of the vacuum pipeline to indicate the vacuum environment of the vacuum pipeline.
In some embodiments, the air pump is arranged at an end of the vacuum pipeline close to the vacuum gauge. When the vacuum pipeline forms a circulation loop, the air pump is turned on, and the airflow in the vacuum pipeline undergoes a directional circulation flow under the action of the air pressure difference of the air pump, so as to realize the circulation flow of the natural gas.
In some embodiments, the pipeline equipped with the molecular sieve is arranged in a middle section of the vacuum pipeline. The natural gas flows slowly into the pipeline equipped with molecular sieve, and then the filtered natural gas slowly flows into the natural gas storage unit.
In some embodiments, a gas collection port is provided at one end of the pipeline equipped with the molecular sieve to collect the gas desorbed from the molecular sieve.
In some embodiments, a first valve is provided at the other end of the pipeline equipped with the molecular sieve for controlling flow in the molecular sieve; a second valve is provided at the end of the pipeline equipped with the molecular sieve where the gas collection port is provided for controlling flow at the gas collection port; and the gas collection port is provided between the second valve and the molecular sieve.
In a second aspect, this application provides an online circulation system for collecting light hydrocarbons in natural gas, comprising: a natural gas storage unit; a light hydrocarbon adsorption unit with a molecular sieve inside; a light hydrocarbon collection unit; and a circulating power unit arranged between the light hydrocarbon adsorption unit and the natural gas storage unit; wherein the natural gas storage unit, the circulating power unit, the light hydrocarbon adsorption unit and the light hydrocarbon collection unit are sequentially connected in series to form a vacuum pipeline of the online circulation system.
In some embodiments, the vacuum pipeline is provided with 5 an air pump, a vacuum pump and a plurality of valves for controlling an air flow.
In some embodiments, the natural gas storage unit is a commercially available high-pressure steel cylinder with a straight-through valve respectively at both ends.
In some embodiments, the light hydrocarbon adsorption unit is a U-shaped stainless steel pipeline with the molecular sieve inside, or other stainless steel pipeline which is capable of increasing a contact area between the natural gas and the molecular sieve and allowing gas to flow through.
In some embodiments, the molecular sieve is a 5A molecular sieve.
Only the 5A molecular sieve is used herein to absorb the light hydrocarbons in natural gas, allowing for low cost and simple operation.
In some embodiments, the light hydrocarbon collection unit comprises: a heating device arranged around the light hydrocarbon adsorption unit; and a gas collection port arranged on a pipeline adjacent to the light hydrocarbon adsorption unit.
In some embodiments, the heating device is a commercially avallable high-temperature furnace that is capable of being arranged on a stainless steel pipeline, and has a temperature control function or an intelligent adjustment function.
In this application, the light hydrocarbons adsorbed in the adsorption unit can be desorbed by turning on the heating device, simplifying the operation.
In this application, the gas collection port is sealed with a silicone pad.
For the quantitative sampling of light hydrocarbons, the existing quantitative sampling equipment is inserted into the silicone pad to extract the light hydrocarbons, or an external export device is used to quantitatively export the light hydrocarbons in the circulating system.
In some embodiments, the light hydrocarbon collection unit is connected to a detection system through an existing quantitative sampling equipment.
In some embodiments, the detection system is a gas chromatographic instrument or other light hydrocarbon analysis device.
In a third aspect, this application provides a use of the method mentioned above for gas geochemical analysis.
The light hydrocarbons collected by this method have less impurities and high content, which can meet the requirement of gas geochemical analysis.
In a fourth aspect, this application provides a chemical composition analysis device for light hydrocarbons in natural gas, comprising: the online circulation system mentioned above.
This application has the following beneficial effects.
This application constructs a circulation system equipped with a 5A molecular sieve, which can obtain pure Cs-Ce light hydrocarbons from natural gas with very low light hydrocarbon content for the geochemical analysis. The method of this application has simple operation, low cost, high efficiency and stable test result.
BRIEF DESCRIPTION OF THE DRAWINGS Fig. lisaschematic diagramof an online circulation system for collecting light hydrocarbons in natural gas according to Embodiment 1 of the disclosure.
Fig. 2 is a line chart of the adsorption amount of several components on the molecular sieve in the online circulation system according to Embodiment 1 of the disclosure versus adsorption time.
Fig. 3 is a line chart of the adsorption amount of methane, ethane, isobutane and isopentane on the molecular sieve in the online circulation system according to Embodiment 1 of the disclosure versus the adsorption time.
: Fig. 4 shows relationship between the desorption amount of several components and desorption temperature at an adsorption time of 30 min in the online circulation system according to Embodiment 2 of the disclosure.
Fig. 5 schematically shows a content of gas components desorbed respectively at eight desorption temperatures for 30 min in the online circulation system according to Embodiment 2 of the disclosure; where 1, methane; 2, ethane; 3, propane; 4, isobutane; 5, n-butane; 6, isopentane; 7, n-pentane; 3, 2,2-dimethylbutane; 9, cyclopentane and 2, 3-dimethylbutane; 10, Z-methylpentane; 11, 3-methylpentane; 12, n-hexane; and 13, methylcyclopentane.
In the drawings, 1, natural gas storage unit; 11, high-pressure steel cylinder; 12, first connector; 2, light hydrocarbon adsorption unit; 21, molecular sieve; 3, light hydrocarbon collection unit; 31, heating device; 32, gas collection port; 321, second connector; 322, silicone pad; 4, circulation power unit; 5, vacuum pipeline; 51, vacuum gauge; 52, vacuum pump; 53, first valve; 54, second valve; and 55, third valve.
DETAILED DESCRIPTION OF EMBODIMENTS The disclosure will be further described below in detail with reference to the accompanying drawings and the embodiments. It should be understood that these embodiments are merely illustrative of the present disclosure, and are not intended to limit the scope of the present disclosure. Unless otherwise specified, the experiments in the following embodiments are conducted under conventional conditions or the conditions recommended by the manufacturer.
Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art, and the reagents and products used are commercially available. The processes and methods that are not described in detail are conventional methods well known in the art. The source of the reagents used, the trade name, and those whose components are necessary to be listed are all specified when they first appear, and unless otherwise specified, the information of the same reagents used thereafter is the same as that specified for the first time. Embodiment 1 Online circulation system for collecting light hydrocarbons in natural gas As shown in Fig. 1, an online circulation system for collecting light hydrocarbons in natural gas in this application includes a natural gas storage unit 1, a light hydrocarbon adsorption unit 2, a light hydrocarbon collection unit 3, a circulation power unit 4 and a vacuum pipeline 5.
In some embodiments, the natural gas storage unit 1 includes a high-pressure steel cylinder 11 for storing the natural gas anda first connector 12 for connecting the high-pressure steel cylinder 11 to a vacuum pipeline.
In some embodiments, the high-pressure steel cylinder 11 for storing the natural gas is a high-pressure steel cylinder conventionally used in the field with through valves 13 at both ends, such as the LPG stainless steel sampling cylinder sold by Jiangsu Wheatstone Electromechanical Technology Co., Ltd., etc.
In some embodiments, the first connector 12 is a commercially available connectable stainless steel sealing joint.
In some embodiments, the light hydrocarbon adsorption unit 2 is a U-shaped tube eduipped with the molecular sieve 21.
In some embodiments, the molecular sieve is a commercially available 5A molecular sieve.
In some embodiments, the light hydrocarbon collection unit 3 includes a heating device 31 arranged around the light hydrocarbon adsorption unit 2 and a gas collection port 32 arranged on a pipeline adjacent to the light hydrocarbon adsorption unit 2.
In some embodiments, the gas collection port 32 is connected to the online circulation system through a second connector
321.
In some embodiments, the gas collection port 32 can be closed by using the silicone pad 322.
In some embodiments, the heating device 31 is a commercially available device capable of heating a U-shaped tube, such as a high-temperature furnace, or a commercially available high-temperature furnace capable of temperature control. The second connector 321 is a commercially available connectable stainless steel sealing joint.
In some embodiments, the circulation power unit 4 is a commercially available micro air pump. This application utilizes the pressure difference generated at both ends of the micro air pump to cause the airflow to generate a directional circulating flow in the system.
In some embodiments, the vacuum pipeline 5 connects the natural gas storage unit 1, the circulation power unit 4, the light hydrocarbon adsorption unit 2 and the light hydrocarbon collection unit 3 in series to form a circulation system, and the circulation power unit 4 circulates the natural gas in one direction in the natural gas storage unit 1 and the light hydrocarbon adsorption unit 2.
In some embodiments, the vacuum pipeline 5 is provided with a vacuum gauge 51, a vacuum pump 52, a first valve 53 arranged between the circulation power unit 4 and the light hydrocarbon adsorption unit 2, and a second valve 54 and a third valve 55 arranged on the pipeline between the gas collection port 32 and the natural gas storage unit 1 in sequence.
In some embodiments, the vacuum gauge 51 is configured to indicate the vacuum degree of the circulation system, and the vacuum pump 52 is configured to construct the vacuum environment in the circulation system and discharge impurity gases. The third valve 55 is configured to control the opening and closing of the vacuum pump, the first valve 53 and the second valve 54 are configured to open and close the gas flow at both ends of the light hydrocarbon adsorption unit 2.
In some embodiments, the vacuum pipelines used in this application are all commercially available stainless steel pipelines. In an embodiment, a 1/4 inch stainless steel pipeline made by Swagelok is used as the vacuum pipe. The above-mentioned structure adopted by this application is simple and low in cost. In particular, the adsorption carrier in the light hydrocarbon adsorption unit 2 only needs 5A molecular sieves, which has a single composition and low cost, and is convenient to replace. Embodiment 2 Method for collecting light hydrocarbons in natural gas by using the online circulation system The method for collecting light hydrocarbons in natural gas by using the online circulation system provided in Embodiment 1 was described as follows.
1. Installation and connection of natural gas storage device The connecting piece 12 was configured to connect the high-pressure steel cylinder 11 for collecting natural gas to the circulation adsorption system according to the structural connection provided in Embodiment 1. At this time, the through valves 13 at both ends of the high-pressure steel cylinder were closed.
2. Air tightness inspection The gas collection port was closed, and leak detection was performed on the circulation adsorption system connected to the high-pressure steel cylinder 11. Whether the air tightness of each part of the system is good was checked, and the leak detection method adopted a conventional method in the field. The third valve 55 was closed to observe whether there was any change in the vacuum gauge 51. If the reading of the vacuum gauge 51 does not change much, it is judged that the air tightness of the circulation system is good, and if the reading of the vacuum gauge becomes large, it means that the air tightness of the system is poor.
3. Build a vacuum circulation system The vacuum pump 52 was turned on, and the first valve 53, the second valve 54 and the third valve 55 were opened. When the vacuum gauge displayed 1.0x10-2 mbAr, the third valve 55 was closed. At this time, the air in the system was pumped out. Then the through valves 13 at both ends of the high-pressure steel cylinder were slowly opened, and the micro air pump 4 was opened at the same time. The natural gas in the system underwent a directional circulation flow due to the pressure difference between the two ends of the air pump.
4. Adsorption of light hydrocarbons in natural gas The natural gas flowed out from one end of the high-pressure steel cylinder 11 under the action of the micro air pump 4 and flowed through the 5A molecular sieve in the U-shaped tube 2 along the vacuum pipeline 5. The light hydrocarbons in the natural gas were absorbed by the 5A molecular sieve, and the remaining natural gas was returned back to the high-pressure steel cylinder 11. The natural gas continuously flowed out from the high-pressure steel cylinder and flowed through the U-shaped tube 2, and then continuously flowed back to the high-pressure steel cylinder 11. The natural gas repeatedly contacted the 5A molecular sieve, and the light hydrocarbons in the natural gas were continuously enriched in the 5á molecular sieve.
5. Collection of light hydrocarbons in natural gas When the adsorption of light hydrocarbons was completed, the third valve 55 was opened first, and the vacuum pump 52 was turned on to discharge the impurity gas. Then the first valve 53 and the second valve 54 were closed, and the heating device 31 was turned on to heat the U-shaped tube to desorb the light hydrocarbons adsorbed by the molecular sieve. Existing quantitative sampling equipment was used to collect the light hydrocarbons from the gas collection port 32 after heating for a period of time. For example, an external device with a fixed volume of saturated saline water was used to connect the gas collection port 32 to duantitatively take light hydrocarbons. The purity of the light hydrocarbons adopted by the method of this application was high, so that the light hydrocarbons collected from the gas collection port 32 can be directly used for gas chromatographic detection, thereby performing gas geochemical analysis.
Application embodiment A high-pressure steel cylinder with a capacity of 1 L is connected to the circulation adsorption system of Embodiment
1. 3 g of the 5A molecular sieve is loaded in the U-shaped pipe of the circulation system, and then the adsorption and collection of light hydrocarbons are performed according to the method provided in Embodiment 2.
Specifically, the adsorption time was 30-60 min; the discharge time of the impurity gas was 30 s; the heating temperature was less than 300°C; and the heating time was 2 min.
The impurity gas is tested to contain methane, ethane, propane, isobutane and n-butane. The gas taken from the gas collection port 32 contains isopentane, n-pentane, 2,2-dimethylbutane, cyclopentane and 2,3-dimethylbutane, 2-methylpentane, 3-methylpentane, n-hexane and methylcyclopentane.
It can be seen that the online circulation system of this application can efficiently and accurately collect the trace light hydrocarbons in natural gas. Experimental Example 1 Effect of adsorption time on adsorption of components In order to further study the adsorption of the 5Ä molecular sieve in the circulation system on the light hydrocarbons in natural gas, the test was performed under different adsorption times (5 min, 10 min, 30 min, 60 min, 150 min and 300 min) and different desorption temperatures (150°C, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C and 500°C). An injection volume of the chromatographic detection was 0.5 mL. In order to avoid various accidental errors, the sample collectedin each adsorption time period was repeatedly tested multiple times (n is more than or equal to 5), and the obtained test results were averaged. The total amount of light hydrocarbons absorbed by the molecular sieve was the sum of the gas components desorbed at individual temperature points under different adsorption times.
The experimental data was shown in Table 1, Fig. 2 and Fig.
3. Table 1 Adsorption amount of each component on the molecular sieve under different adsorption times min. 10 min. 30 min. 60 min. 150mm. 300 min. Methane 392151 25382 4624.2 1364399 2334331 407072 Ethane 2051097 437596.7 1680621 1108818 1522885 25596335 Propane 1091479 1317281 2847380 2733148 1593390 2540289 Isobutane 162483 99.6 5819.5 7752.6 252229 3294.2 n-butane 737933.8 806853.9 1299619 1345036 389919.1 108302.6 Isopentane 454768 24555 589904 301919 48809.7 6600.8 n-pentane 119972.8 104296.8 137682.3 198738.2 318547 7393.4
2.2-Dimethylbutane 635.7 321.5 652.6 395.1 324.6 62.3 Cyclopentane and 2 3-dimethylbutane 1211.7 642.5 1309.1 1091.7 478.5 71.6 2-Methylpentane 9923.5 4208 121273 10094 8 3946.9 446.4 3-Methylpentane 4049.8 1868.3 4930.8 4513.8 1437.4 194.2 n-hexane 4473.9 3811.3 4851.9 7781 1146.7 93.6 Methylcyclopentane 1328.6 571 2140.4 2327 491.1 - > 4476003 2705388 6060749 5586329 3853340 677160.7 5 Note: the amount of the component was expressed by the area of the chromatographic peak (mV*s); and the data in the table were the sum of the amount of each component desorbed at the six temperature points of 150°C, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C and 500°C.
It can be seen from Table 1 and Fig. 1 that the adsorption amount of propane, n-butane, n-pentane, 2,2-dimethylbutane, cyclopentane and 2,3-dimethylbutane, 2-methylpentane, 3-methylpentane, n-hexane and methylcyclopentane on the molecular sieve increased with time before 60 min, reached a maximum between 30-60 min, and then decreased with the increase of the adsorption time. It indicated that the adsorption capacity of molecular sieve for these components presented a unimodal distribution over time. As shown in Fig. 2, the adsorption capacity of the molecular sieve for methane, ethane, isobutane and isopentane altered greatly over time, and the molecular sieve exhibited the maximum adsorption capacity within an adsorption time of 30-60 min.
After 60 min, the adsorption capacity began to decrease, which was explained by that the adsorption of gas components on the molecular sieve has reached the equilibrium, and the gas began to diffuse.
It can also be seen from Fig. 2 that the adsorption of methane was the least at 30 min, and the other components basically reached the maximum adsorption at 30 min.
Therefore, adsorption for 30 min can effectively filter out the main component (CH) in natural gas, so as to concentrate the light hydrocarbons.
Through the above analysis, it can be concluded that the optimal adsorption time was 30 min.
Experimental Example 2 Content of each component desorbed at different desorption temperatures According to the analysis result of Experimental Example 1, the light hydrocarbons adsorbed by the molecular sieve were desorbed at eight temperatures (150°C, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C and 500°C). The temperature error was controlled within +10°C.
The resulting component data was shown in Table 2 and Fig. 4.
Table 2 Content of each component desorbed at different desorption temperatures 150°C 200°C 250°C 300°C 350°C 400°C 450°C 500°C
Methane 3303.1 309 314.3 53.6 80.8 477 124.1 191.6 Ethane 481739.5 503744.5 495931.1 1140942 58925.4 13038.6 7174.1 5974 Propane 163297 2854306 5482538 993649.8 638870.2 121707.9 54071.4 40099.6 Isobutane 4700.5 740.1 300.8 - - 34.1 22 22 n-butane 13607 25000.5 141505.9 397352.8 445325.9 142669.6 76681.6 574754 Isopentane 238127 13637.5 9630.4 44737 4544.1 1376.9 805.8 709.3 n-pentane 874 1243.3 6703.5 26361.7 477857 23163 4 178737 13677 2,2-Dimethylbutane 141.8 136 155.5 73.6 66.4 34 23.4 21.9 Cyclopentane and 2,3-dimethy butane 175.2 234.6 317.8 185.5 169.7 98.1 67.2 61 2-Methylpentane 1844.9 1786.6 2794.6 1890.7 1754.3 872.1 047.6 536.5 3-Methylpentane 619.8 650.2 1116.8 814.8 764.2 398.2 312 254.8 n-hexane 100.8 87.2 225 308.6 1134.8 804.9 1160.8 829.8 Methyleyclopentane 179 171.6 4239 366.7 371 226.2 220 182 Y 6943953 8333717 1207673 1541826 1199793 3044717 159183.7 1200349
Note: the data in the Table was the peak area of each component in the chromatogram (mV*s).
According to Table 2 and Fig. 4, it can be seen that the total amount of light hydrocarbons desorbed from the molecular sieve was the largest when the desorption temperature was 300°C. The amount of light hydrocarbons desorbed below 300°C gradually increased, and the amount of light hydrocarbons desorbed from the molecular sieve decreased sharply after the desorption temperature exceeded 300°C. It indicated that most of the light hydrocarbon components adsorbed by the molecular sieve can be desorbed at 300°C.
Fig. 5 schematically showed a content of gas components desorbed respectively at eight desorption temperatures, it can be seen that the desorption amount of methane, ethane, isopentane, 2,2-dimethylbutane, etc., decreased with the increase of the desorption temperature, and isobutane had been almost completely desorbed below 300°C, indicating that these components can be desorbed from the molecular sieve at a lower desorption temperature. The maximum desorption of propane, n-butane, n-pentane, n-hexane and other components were realized at 300°C. The methane content in the adsorbed gas was significantly reduced, indicating that the 5A molecular sieve also had the function of filtering out methane and concentrating light hydrocarbons.
It can also be seen from Fig. 5 that methane and ethane had the lowest content in the gas desorbed at 300°C and 350°C.
The content of the components after isopentane in the desorbed gas gradually increased with the increase in temperature, and the higher the carbon number of the component, the content thereof increased more obviously with the increase of the temperature. Since the thermodynamic properties of the higher carbon number hydrocarbon molecule determined that it requires a higher desorption temperature to be desorbed from the molecular sieve. The concentration of Cst components was significantly increased in the sample after SAmolecular sieve adsorption compared to the original sample composition.
Experimental Example 3 Reproducibility of the enrichment effect of 5A molecular sieve
The reproducibility of the enrichment effect of BSA molecular sieve was performed (repetition number n=7), and the gas was desorbed at 300°C for 30 min.
The chromatographic detection conditions were unchanged.
The data was shown in Table 3. The standard deviation of all light hydrocarbon components was less than 0.4. Table 3 Reproducibility of the enrichment effect of GSA molecular sieve 1 2 3 4 5 6 7 SD Methane 0.01 0.01 0.01 0.005 0.008 0.008 0.003 0002 Ethane 4.91 4.45 4.44 4.29 4.33 414 4.12 0.267 Propane 53.25 5262 5309 33,34 5356 53.36 5380 0372 Isobutane - - - - - - - - n-butane 37.12 37.88 37.66 37.64 37.64 37.99 37.83 0.283 Isopentane 0,38 0.44 0.43 0.45 0.29 0.28 0.27 0.081 n-pentane 3.98 4.24 4.04 3.95 3.87 3.90 3.66 0.173 2,2-DimethyTbutane 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.001 Cyclopentane and 2 3-dimethylbutane 0.01 0.01 0.02 0.01 0.02 0.02 0.02 0.002 2-Methylpentane 0.15 0.16 0.15 0.14 0.13 0.13 0.13 0.010 3-Methylpentane 0.06 0.07 0.06 0.06 0.06 0.06 0.06 0.004 n-hexane 0.09 0.10 0.09 0.08 0.08 0.09 0.08 0.007 Methylcyclopentane 0.03 0.02 0.02 0.02 0.02 0.02 0.02 0.005 Note: the data in the Table were the percentage concentration (3) of the components tested by the gas chromatography.
The above are only the preferred embodiments of the present disclosure, and are not intended to limit the scope of the present disclosure.
Any changes, modifications and improvements made by those skilled in the art without departing from the spirit of the present disclosure shall fall within the scope of the present disclosure.
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