Parallel sampling device and sampling method for metal elements in natural gas

Abstract

The invention belongs to the technical field of natural gas extraction, processing and environmental protection, and discloses a parallel sampling device and a sampling method for metal elements in natural gas. The device comprises an air inlet shunting device, an absorbing device and a drying device which are communicated in sequence, a first gas inlet pipe of the gas inlet shunting device is connected with a natural gas pipeline; n branch outlets which are opposite pairwise and are used for parallel sampling are uniformly distributed on the horizontal plane of the same height of the air inlet shunting device, and the branch outlets are connected with a second air inlet pipe of the absorption device through a first air outlet pipe; valve bodies are arranged on the first air inlet pipe and the first air outlet pipe; sampling absorption liquid is contained in the absorption device, and absorbed gas is conveyed to the drying device through a second gas outlet pipe to be dried and is discharged through a third gas outlet pipe; and a flow meter is arranged on the third air outlet pipe. By means of the gas inlet flow dividing device with the controllable flow speed, parallel sampling of metal elements in natural gas can be achieved, and the accuracy of detection of the content of the metal elements in the natural gas is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of natural gas exploitation, processing and environmental protection, and in particular relates to a parallel sampling device and a sampling method for metal elements in natural gas. Background Art

[0002] The main components of natural gas are hydrocarbons, followed by non-hydrocarbon components including trace metal elements and non-metallic elements. In the field of natural gas exploration, trace metal elements are an important inorganic indicator, which can be used to determine the hydrocarbon source of natural gas reservoirs, the formation process of natural gas reservoirs, and the migration path of oil and gas, providing a basis for oil and gas exploration. In the process of natural gas processing and utilization, trace metal elements will adhere to or penetrate the surface of equipment and facilities, causing corrosion, scaling, blockage and other hazards, shortening the service life of equipment, and deactivating catalysts in the downstream processing of natural gas. At the same time, after natural gas combustion or process escape, heavy metal elements will be carried into the atmosphere and gradually accumulated, polluting the environment and endangering human health. In such cases, it is necessary to detect the metal elements in natural gas in order to extend the life of equipment, improve process effects, protect the environment, and even provide accurate data support for natural gas exploration and promote the high-quality development of the natural gas industry.

[0003] The existing standard GB / T 14099.4-2010 "Gas Turbine Procurement Part 4: Fuel and Environment" clearly puts forward the requirement for quantitative detection of corrosive components in natural gas: sodium (Na), potassium (K), vanadium (V), lead (Pb) and other metal elements. However, the concentration of metal elements in natural gas is small (micro or even trace levels), and there are various forms. Therefore, the sampling method of metal elements in natural gas is the key to accurate quantification. In the prior art, the sampling methods of metal elements in gas mainly include filter membrane adsorption method and solution absorption method (such as standards HJ 657 and HJ 543). Regardless of the sampling method, there is a lot of room for improvement in its scope of application, enrichment efficiency and other aspects.

[0004] The filter membrane adsorption method is to enrich metal elements on the filter membrane, and then detect the metal elements after the filter membrane is digested. This method is mainly suitable for sampling metal elements in air and exhaust gas, and there are many problems such as large blank error, complex operation process, and large deviation of experimental results. Patent document CN2343585Y discloses a natural gas trace metal sampler, which uses a two-layer filter membrane method to adsorb colloidal trace metals in natural gas. This method uses a mass flow meter. It is not mentioned whether the flow control accuracy meets the requirements during specific use. In addition, a special adsorption layer such as polyethylene pyridine oxide needs to be impregnated on the filter membrane. There is no data support for how to control the impregnation thickness and the interception effect of the adsorbent composition on colloidal metals. Whether it can intercept non-colloidal metal elements is also not explained in detail.

[0005] The solution absorption method of the standard (HJ 543-2009) is to absorb the metal elements with the absorption liquid and then detect the metal elements in the absorption liquid. This method is mainly suitable for sampling waste gas from fixed pollution sources. Since this method limits the sampling time to 5min-30min and the gas flow rate to 0.3L / min, whether it is suitable for natural gas sampling in the oil and gas extraction industry has not been explained in detail, and there is no research report. At the same time, this standard method does not involve the problems of how to conduct quality control, how to improve the absorption efficiency, and how to prevent the absorption liquid from freezing in winter.

[0006] The literature "Preliminary Study and Application of Trace Element Capture and Detection Technology in Natural Gas" (Wu Sheng: Natural Gas Geoscience, 2015, 26(11)) and "Research on Enrichment of Trace Copper Elements in Natural Gas" (Chen Shida, Petroleum and Natural Gas Chemical Engineering, 2015, 44(6)) reported the pretreatment method of enriching trace metal elements in natural gas using nitric acid solution, but the experimental device was only briefly explained in the form of a schematic diagram, and there was no introduction to the microbubble cutter.

[0007] Patent document CN105987857A discloses an absorption device, method and content detection method for metal elements in natural gas. In order to solve the problem of low absorption efficiency of metal elements in natural gas, the patented technology intends to use a three-layer sieve plate to solve the problem of low solution absorption efficiency. The three-layer sieve plate itself has inherent deficiencies such as difficulty in cleaning and processing, and the patented technology has not yet involved the quality control of metal element detection in natural gas and the problem of solution freezing in winter.

[0008] In terms of quality control of metal element sampling in natural gas, since it is impossible to add standard metal samples to the gas and there are no quality control samples of metal elements in the gas, the quality control of metal element detection in the gas can only adopt the parallel sampling method. How to collect homologous gas samples using different solution absorption devices at the same time is the key to quality control, and improvements are needed in the design of diversion devices and small flow metering devices.

[0009] In summary, the existing technology has technical difficulties such as difficulty in parallel sampling of metal elements in natural gas, low absorption efficiency of absorption liquid, freezing of absorption liquid in winter, and the question of whether the sampling method is applicable to special areas of natural gas extraction. Summary of the invention

[0010] The present invention aims to address the technical difficulties in preparing parallel samples caused by high pressure, unstable flow rate and unstable natural gas source composition during natural gas sampling, and to provide a parallel sampling device and a sampling method for metal elements in natural gas. The parallel sampling of metal elements in natural gas is achieved through an air intake diversion device with controllable flow rate, thereby improving the accuracy of detecting the metal element content in natural gas.

[0011] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0012] A parallel sampling device for metal elements in natural gas, comprising an air intake splitter, an absorption device and a drying device connected in sequence;

[0013] The first air inlet pipe of the air inlet splitter device is connected to the natural gas pipeline; the air inlet splitter device is evenly distributed with n branch outlets for sampling in pairs and in parallel on a horizontal plane at the same height, and each branch outlet is connected to the second air inlet pipe of the absorption device through a first air outlet pipe; at the same time, valve bodies are provided on the first air inlet pipe and the first air outlet pipe;

[0014] The absorption device contains a sampling absorption liquid, the liquid level of which is higher than the end of the second air inlet pipe, and is used to absorb metal elements in the natural gas;

[0015] The second air outlet pipe of the absorption device is connected to the third air inlet pipe of the drying device, and is used to transport the sampled and absorbed natural gas to the drying device for drying, and discharge it through the third air outlet pipe of the drying device; a flow meter is provided on the third air outlet pipe.

[0016] Further, the air intake splitter device comprises a splitter bottle, a first air intake pipe and a first air outlet pipe;

[0017] The lower end of the first air inlet pipe of the split bottle is a glass straight tube with a stopper, and the glass straight tube with a stopper is inserted into the bottom of the split bottle;

[0018] The diversion bottle is evenly distributed with n branch outlets for sampling in parallel in pairs on a horizontal plane at the same height, 2≤n≤8; each branch outlet is sintered with a threaded joint for connecting to the first air outlet pipe.

[0019] Furthermore, the diversion bottle is a spherical container; the end of the stoppered straight glass tube is 3-5 mm away from the bottom of the bottle.

[0020] Furthermore, the first air inlet pipe and the n first air outlet pipes are each provided with a flow regulating valve.

[0021] Furthermore, a flow regulating valve is provided on the first air inlet pipe;

[0022] Among the n first air outlet pipes, n-1 first air outlet pipes are each provided with a flow regulating valve, and the remaining first air outlet pipe is provided with a three-way valve.

[0023] Furthermore, the absorption device is an insertable absorption device or a variable diameter absorption device with a spoiler ball.

[0024] Furthermore, the insertable absorption device comprises an absorption bottle, a second air inlet pipe, a sample absorption liquid, a sand core and a second air outlet pipe;

[0025] The absorption bottle contains a sample absorption liquid; the end of the second air inlet pipe extends downward into the bottom of the absorption bottle and is immersed in the sample absorption liquid;

[0026] The end of the second air inlet pipe is a bell mouth, and the bell mouth port is provided with the sand core.

[0027] Furthermore, the sand core is composed of two layers of G1 sand core and G2 sand core;

[0028] The G2 sand core is sintered on the bell mouth, and the G1 sand core is placed above the G2 sand core and is not sintered with the bell mouth.

[0029] Furthermore, the pore size of the G1 sand core is 20-30 μm, and the thickness is 2-5 mm; the pore size of the G2 sand core 204 is 10-15 μm, and the thickness is 2-5 mm.

[0030] Furthermore, the liquid level of the sampling absorption liquid is 3-3.5 times the distance between the G2 sand core and the bottom of the bottle.

[0031] Furthermore, the variable diameter absorption device with spoiler ball comprises an absorption bottle, a second air inlet pipe, a sampling absorption liquid, a G2 sand core, a spoiler ball and a second air outlet pipe;

[0032] A second air inlet is provided on one side of the bottom of the absorption bottle, and the second air inlet is connected to the second air inlet pipe; the top of the absorption bottle is connected to the second air outlet pipe;

[0033] The G2 sand core is sintered in the absorption bottle at the upper end of the second air inlet; the spoiler ball is placed at the upper end of the G2 sand core;

[0034] The absorption bottle contains sampling absorption liquid; the liquid level of the sampling absorption liquid is lower than the upper end surface of the G2 sand core when there is no airflow circulation, and is higher than the upper end surface of the G2 sand core and more than half of the height of the spoiler ball when airflow disturbance occurs.

[0035] Furthermore, a bubble-shaped buffer tube is provided on the second air inlet pipe.

[0036] Furthermore, the pore size of the G2 sand core is 10-15 μm; the G2 sand core is 30-35 mm away from the bottom of the absorption bottle;

[0037] The spoiler ball is made of borosilicate glass, and a plurality of micro-pits are melted on the surface of the spoiler ball, with a pit depth of 1-2 mm.

[0038] Further, the drying device comprises a drying bottle, a third air inlet pipe and a third air outlet pipe;

[0039] A color-changing silica gel desiccant is placed in the drying bottle, and the color-changing silica gel desiccant covers the air inlet end of the third air inlet pipe.

[0040] Furthermore, the flow meter is a wet flow meter or a gas mass flow meter with a graduation value of 0.01L and an indication error of ±1.5%.

[0041] Further, the sampling absorption liquid includes an acid component and an alcohol component;

[0042] In the sampling absorption liquid, the volume concentration of the acid component is 3-10%, and the volume concentration of the alcohol component is 0.2-10%.

[0043] Furthermore, the acid component is one or more of sulfuric acid, nitric acid, hydrochloric acid, and hydrogen peroxide;

[0044] The alcohol component is one or more of ethanol, ethylene glycol and glycerol.

[0045] Furthermore, the gas inlet splitter device and the container portion of the absorption device are both made of borosilicate glass or quartz glass;

[0046] The first air inlet pipe, the first air outlet pipe and the second air inlet pipe are all made of polytetrafluoroethylene rubber tubes;

[0047] The valve bodies on the first air inlet pipe and the first air outlet pipe are both made of polytetrafluoroethylene.

[0048] Furthermore, it also includes a bracket, which is used to fix the air intake diversion device, the absorption device, the drying device and the flow meter.

[0049] At the same time, the present invention also provides a parallel sampling method for metal elements in natural gas, which is implemented by using the parallel sampling device as described in any one of the above items, and the method specifically comprises the following steps:

[0050] Step S1: Before sampling, the air intake splitter device and the container part of the absorption device, the first air intake pipe, the first air outlet pipe and the second air intake pipe are soaked in a nitric acid solution with a volume concentration of 20% for more than 12 hours in advance, and then cleaned with ultrapure water;

[0051] Step S2: injecting a sample absorption liquid into the absorption device after cleaning, and adding an alcohol component antifreeze agent into the sample absorption liquid;

[0052] Step S3: The natural gas is transported from the first air inlet pipe to the air inlet flow dividing device, and is divided into several symmetrical branches according to the parallel sampling requirements. After the flow is adjusted by the valve body, it is transported to the absorption device for absorption by the sampling absorption liquid. The absorbed gas is output through the third air outlet pipe of the drying device, and the volume V of the output natural gas under standard conditions is measured by the flow meter set on the third air outlet pipe. 天然气 ;

[0053] Step S4: dilute the sample absorption liquid by a factor of f 稀释倍数 , detect the metal element concentration C in the sample absorption liquid 测 and the blank sample concentration C O ;

[0054] Step S5: Calculate the concentration of metal elements in natural gas based on experimental test data:

[0055] C 浓度 =(C 测 -C O )×V 吸收液 / V 天然气 ×f 稀释倍数

[0056] In the above formula: C 浓度 is the concentration of metal elements in natural gas, μg / m 3 ; C 测 is the concentration of metal elements in the sample absorption liquid to be detected, μg / L; C O is the concentration of metal elements in the blank sample of the whole process, μg / L; V 吸收液 V is the volume of the sample absorption liquid, mL; 天然气 is the volume of natural gas passing through the absorption bottle, L; f 稀释倍数 It is the times of dilution of the sample absorption solution before detection.

[0057] Furthermore, the step S2 specifically includes:

[0058] After cleaning, inject the sampling absorption liquid into the insertable absorption bottle, add alcohol component antifreeze to the sampling absorption liquid, and the liquid level of the sampling absorption liquid is 3-3.5 times the distance between the G2 sand core and the bottom of the bottle;

[0059] Alternatively, after cleaning, inject sampling absorption liquid into the variable diameter absorption bottle with a spoiler ball, add alcohol component to the sampling absorption liquid, and adjust the inlet gas flow rate of the absorption bottle by adjusting the valve opening during the absorption process so that the liquid level of the sampling absorption liquid is higher than the upper end surface of the G2 sand core and is more than half of the height of the spoiler ball during the gas flow disturbance.

[0060] Furthermore, in step S4, the metal element concentration C in the sampled absorption liquid is 测 , Blank sample concentration C O Measured by trace or trace metal element detection equipment.

[0061] Compared with the prior art, the beneficial effects of the present invention are:

[0062] (1) Since the content of metal elements in natural gas is related to different processing processes and different gas sources, and there are no standard samples of metal elements in natural gas, parallel sampling must be carried out at the same time and under the same gas source conditions. The parallel sampling device provided by the present invention can realize the simultaneous collection of homologous gas samples by different absorption devices through a gas inlet diversion device with controllable flow rate, thereby avoiding the influence of large changes in gas source composition and unstable flow rate on the preparation of parallel samples, meeting the requirements of quality control of the detection process, achieving the purpose of preparing laboratory detection comparison samples, and improving the quality of natural gas quality inspection data.

[0063] (2) Since most metal elements in natural gas are in colloidal granular form, the reaction rate with the sampling absorption liquid is affected by many factors. In the prior art, a three-layer fixed glass sieve plate is used to solve the absorption efficiency problem; while the parallel sampling device provided by the present invention uses an insert-type absorption device or a variable diameter absorption device with a spoiler ball to solve the absorption efficiency problem:

[0064] When the insertion absorption device is used, the sand core is composed of two layers of G1 sand core and G2 sand core. The G1 sand core is placed above the G2 sand core. The G1 sand core is a suspended large-aperture porous plate. When the gas passes through, due to the resistance and the buoyancy of the acid, the G1 sand core will show a slight vibration state, which is conducive to the absorption of metal elements in the gas.

[0065] When a variable diameter absorption device with a spoiler ball is used, the gas flows from bottom to top. There are micro-pits on the surface of the spoiler ball. The gas forms an asymmetric pressure difference on the surface of the spoiler ball. At high flow rates, the spoiler ball is slightly trembling or even rotating, forming micro-vortices, which increases the contact time between the gas and the acid liquid and is beneficial to the absorption of metal elements.

[0066] (3) The parallel sampling device provided by the present invention controls a relatively low flow rate during sampling, utilizes the cutting effect of the sand core with a micron-sized aperture on the natural gas, and combines the affinity between the alcohols in the sampling absorption liquid and the natural gas to achieve efficient enrichment of metal elements in the natural gas.

[0067] (4) The parallel sampling device and sampling method provided by the present invention have a sampling absorption liquid in which an alcohol component is added to a conventional acidic sampling absorption liquid. The alcohol component is used as an antifreeze agent, and the freezing point of the sampling absorption liquid can be reduced to below -20°C, making it difficult to freeze in winter. This not only meets the sampling needs in extremely cold weather and expands the application scenarios of the detection method, but also, alcohol solutions have a high affinity for natural gas. The low interfacial tension of the alcohol solution can improve the resistance of bubbles to pass through the micropores of the sand core, which is beneficial to the continuous generation of microbubbles and the full progress of the enrichment reaction.

[0068] (5) The present invention aims at the technical difficulties such as difficulty in preparing parallel samples, low sampling absorption efficiency, and difficulty in sampling in winter caused by high pressure, unstable flow rate, and unstable gas source composition during natural gas sampling. The present invention provides a parallel sampling device and sampling method for metal elements in natural gas. Parallel sampling of metal elements in natural gas is achieved through an air intake diversion device with controllable flow rate. Through the special structural design of the absorption device and the addition of an alcohol component antifreeze sampling absorption liquid, efficient enrichment and winter detection can be achieved, and the accuracy of metal element content detection in natural gas can be improved. The present invention can be used to monitor changes in metal content in natural gas extraction, natural gas processing and transportation, so as to guide natural gas product quality inspection, natural gas processing technology optimization, environmental risk assessment, or provide reference for natural gas exploration. The present invention has good versatility, high practicality and high guiding value. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 This is a schematic diagram of the structure of a parallel sampling device according to an embodiment of the present invention;

[0070] Figure 2 It is a schematic diagram of the top view structure of the splitter bottle in the parallel sampling device according to an embodiment of the present invention;

[0071] Figure 3 It is a schematic structural diagram of a variable diameter absorption device with a spoiler ball according to an embodiment of the present invention. DETAILED DESCRIPTION

[0072] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0073] In the description of the present invention, it is necessary to understand that the terms "coaxial", "bottom", "one end", "top", "middle", "the other end", "upper", "one side", "top", "inside", "front", "center", "both ends" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0074] Combination Figure 1-3 As shown, an embodiment of the present invention provides a parallel sampling device for metal elements in natural gas, comprising an air intake splitting device, an absorption device and a drying device connected in sequence.

[0075] like Figure 1As shown, the first air inlet pipe 101 of the air inlet diversion device is connected to the natural gas pipeline; the air inlet diversion device is evenly distributed with n (2≤n≤8) branch outlets 103 that are opposite to each other and sampled in parallel on a horizontal plane at the same height, and each branch outlet 103 is connected to the second air inlet pipe 201 of the absorption device through a first air outlet pipe 102; at the same time, valve bodies are provided on both the first air inlet pipe 101 and the first air outlet pipe 102.

[0076] The absorption device contains a sample absorption liquid 202, the liquid level of which is higher than the end of the second air inlet pipe 201, and is used to absorb metal elements in natural gas;

[0077] The second gas outlet pipe 205 of the absorption device is connected to the third gas inlet pipe 301 of the drying device, and is used to transport the sampled and absorbed natural gas to the drying device for drying and discharge it through the third gas outlet pipe 303 of the drying device; the third gas outlet pipe 303 is provided with a flow meter 4.

[0078] Specifically, the air inlet splitter device comprises a splitter bottle 1, a first air inlet pipe 101 and a first air outlet pipe 102. The splitter bottle 1 is made of borosilicate glass or quartz glass and adopts a 1-in n-out structure (2≤n≤8). Figure 2 The diagram shows a schematic top view of the split bottle 1 when n=6. The six branch outlets 103 are evenly distributed on the same horizontal plane. Each branch outlet 103 is sintered with a threaded connector 104 for quick connection with the second gas outlet pipe 102 .

[0079] The diverter bottle 1 is spherical, and the lower end of the first air inlet pipe 101 of the diverter bottle 1 is a stoppered glass straight tube. The stoppered glass straight tube is inserted into the bottom of the diverter bottle and is 3-5mm away from the bottom of the bottle. After the gas enters the diverter bottle 1, it can be selected to be absorbed and sampled in parallel at several symmetrical branch outlets at the same time.

[0080] Through the large-volume spherical structure design of the diverter bottle 1 and the insertion depth design of the stoppered glass straight tube, the natural gas entering the diverter bottle 1 is deflected upward from the bottom and fully mixed, and then flows out in parallel from the symmetrical branch outlets at the same height, so as not to form local "gas channeling", play a good buffering role, and can reduce the impact of unstable flow rate caused by pressure fluctuations in the gas supply line.

[0081] The first air inlet pipe 101 and the six first air outlet pipes 102 of the diverter bottle 1 are each provided with a flow regulating valve 105. The flow rate at the branch outlet of the diverter bottle 1 is achieved by adjusting the opening of the flow regulating valve. The purpose is to adjust the gas flow at each branch outlet to meet the requirement that different absorption devices simultaneously absorb parallel samples of the same gas.

[0082] During sampling, natural gas first enters through the first air inlet pipe 101, then enters the diverter bottle 1 after being decompressed by the flow regulating valve 105; the diverter bottle 1 divides the gas into several branches according to the sampling requirements, and enters the absorption device after speed adjustment by the flow regulating valve 105 to meet the requirements of parallel sampling of the gas.

[0083] The absorption device may be Figure 1 The insertable absorbent device shown can also be Figure 3 The variable diameter absorption device with a spoiler ball is shown.

[0084] See also Figure 1 The insertable absorption device includes an absorption bottle 2, a second air inlet pipe 201, a sampling absorption liquid 202, a sand core (203 / 204) and a second air outlet pipe 205.

[0085] The absorption bottle 2 is made of borosilicate glass or quartz glass, and is filled with sampling absorption liquid 202; the end of the second air inlet pipe 201 extends downward into the bottom of the bottle body of the absorption bottle 2 and is immersed in the sampling absorption liquid 202; the end of the second air inlet pipe 201 is a bell mouth, and the bell mouth port is provided with the sand core.

[0086] The sand core is composed of two layers of G1 sand core 203 and G2 sand core 204. The G2 sand core 204 is sintered on the bell mouth, and the G1 sand core 203 is placed above the G2 sand core 204 and is not sintered with the bell mouth. The aperture of the G1 sand core is 20-30 μm and the thickness is 2-5 mm; the aperture of the G2 sand core 204 is 10-15 μm and the thickness is 2-5 mm; the liquid level of the sampling absorption liquid 202 is 3-3.5 times the distance between the G2 sand core 204 and the bottom of the bottle.

[0087] like Figure 3 As shown, the variable diameter absorption device with spoiler ball includes an absorption bottle 2, a second air inlet pipe 201, a sample absorption liquid 202, a G2 sand core 204, a spoiler ball 206 and a second air outlet pipe 205.

[0088] A second air inlet 207 is arranged on one side of the bottom of the absorption bottle 2, and the second air inlet 207 is connected to the second air inlet pipe 201, and a bubble buffer tube 208 is arranged on the second air inlet pipe to prevent liquid back suction; the top air outlet of the absorption bottle 2 is connected to the second air outlet pipe 205; the absorption bottle 2 is made of borosilicate glass or quartz glass, with an inner diameter of 28 mm and a height (with outlet connector) of 350 mm.

[0089] The G2 sand core 204 is sintered in the absorption bottle 2 at the upper end of the second air inlet 207, and is 32 mm away from the bottom of the bottle. The pore size of the G2 sand core is 10-15 μm; the spoiler ball 206 is placed on the upper end of the G2 sand core 204. The spoiler ball 206 is made of borosilicate glass, with a diameter of 20 mm, and 8-16 micro-pits are relatively evenly melted on the surface, with a pit depth of 1-2 mm.

[0090] The absorption bottle 2 contains a sampling absorption liquid 202; the liquid level of the sampling absorption liquid 202 is lower than the upper end surface of the G2 sand core when there is no airflow circulation, and is 12-14mm higher than the upper end surface of the G2 sand core and covers more than half of the spoiler ball when airflow disturbance occurs.

[0091] Since most of the metal elements in natural gas are in colloidal particles, the reaction rate with the sampling absorption liquid is affected by many factors. In the prior art, three layers of fixed glass sieve plates are used to solve the absorption efficiency problem. The present invention provides a parallel sampling device for metal elements in natural gas, which uses an insert-type absorption device or a variable diameter absorption device with a spoiler ball to solve the absorption efficiency problem:

[0092] When the insertion absorption device is used, the sand core is composed of two layers of G1 sand core and G2 sand core. The G1 sand core is placed above the G2 sand core. The G1 sand core is a suspended large-aperture porous plate. When the gas passes through, due to the resistance and the buoyancy of the acid, the G1 sand core will show a slight vibration state, which is conducive to the absorption of metal elements in the gas.

[0093] When a variable diameter absorption device with a spoiler ball is used, the gas flows from bottom to top. There are micro-pits on the surface of the spoiler ball. The gas forms an asymmetric pressure difference on the surface of the spoiler ball. At high flow rates, the spoiler ball is slightly trembling or even rotating, forming micro-vortices, which increases the contact time between the gas and the acid liquid and is beneficial to the absorption of metal elements.

[0094] In some other embodiments, the aperture of the sand core in the subsequent absorption device of the split bottle 1 is not completely consistent, resulting in different air flow resistances, and it is difficult to achieve completely consistent flow rates at the six branch outlets. Therefore, the valve body on one of the first air outlet pipes 102 of the split bottle 1 can be designed as a three-way valve to have a pressure relief control function as the main means of balancing the flow rates of other branch outlets. For example, Figure 2 In the 1-inlet-6-outlet splitter bottle 1 shown, the flow rates of 5 branch outlets are adjusted to 0.2 L / min (average flow rate) by a flow regulating valve. Due to the principle of pressure division, the flow rate of the 6th branch outlet is difficult to adjust to 0.2 L / min. The 6th branch outlet can only be used as a pressure relief port (similar to the splitter valve of a gas chromatograph) when the total flow rate of the first inlet is increased, so that the flow rate of each branch outlet can be controlled to the same value (average value).

[0095] Continue to see Figure 1 As shown, the drying device includes a drying bottle 3, a third air inlet pipe 301 and a third air outlet pipe 303; the drying bottle 3 can be vertical, horizontal or U-shaped, and a color-changing silica gel desiccant 302 is placed in the drying bottle 3, and the color-changing silica gel desiccant 302 just slightly submerges the air inlet end of the third air inlet pipe 301. The color-changing silica gel desiccant 302 is used to dry natural gas and is replaced in time after changing color; the dried natural gas enters the third air outlet pipe 303 through the air outlet of the drying bottle 3.

[0096] The third gas outlet pipe 303 is provided with a flow meter 4; the flow meter 4 can be a wet flow meter or a gas mass flow meter with a graduation value of 0.01L and an indication error of ±1.5%. The flow meter 4 is used to accurately measure the flow of the output natural gas under standard conditions on the corresponding branch.

[0097] In addition, the parallel sampling device further comprises a bracket 5, and the bracket 5 is used to fix the diversion bottle 1, the absorption bottle 2, the drying bottle 3 and the flow meter 4; the material and shape of the bracket 5 are not limited.

[0098] In order to prevent the equipment pipeline from contaminating the natural gas sample or the sampling absorption liquid and interfering with the collection results, the connecting pipelines before the outlet of the absorption bottle 2 (including the first air inlet pipe 101, the first air outlet pipe 102 and the second air inlet pipe 201) are all acid- and alkali-resistant polytetrafluoroethylene rubber tubes, and their lengths are such that the connected components do not produce obvious tension; the valve bodies (flow regulating valves or three-way valves) arranged on the first air inlet pipe 101 and the first air outlet pipe 102 of the diversion bottle 1 are also non-metallic regulating valves made of acid- and alkali-resistant polytetrafluoroethylene.

[0099] The sampling absorption liquid 202 in the absorption bottle 2 includes an acid component and an alcohol component. In the sampling absorption liquid 202, the volume concentration of the acid component is 3-10%, and the volume concentration of the alcohol component is 0.2-10%. Meanwhile, the concentration of the alcohol component is adjusted according to the ambient temperature.

[0100] The acid component is one or more of sulfuric acid, nitric acid, hydrochloric acid, and hydrogen peroxide; the alcohol component is one or more of ethanol, ethylene glycol, and glycerol.

[0101] The present invention adds an alcohol component to a conventional acid sampling absorption liquid, and uses the alcohol component as an antifreeze agent to reduce the freezing point of the sampling absorption liquid to below -20°C, which can solve the problem that the conventional acid sampling absorption liquid is easy to freeze in winter and meet the sampling needs in extremely cold weather; at the same time, the sand core porous channel at the end of the second air inlet pipe 201 of the absorption bottle 2 is used as a "microreactor" for gas-liquid reaction, so that the metal elements in the natural gas are digested, absorbed and enriched in the sampling absorption liquid, and the low interfacial tension of the alcohol solution is used to improve the resistance of the bubbles passing through the micropores, which is conducive to the continuous generation of microbubbles and the full progress of the enrichment reaction.

[0102] A method for parallel sampling of metal elements in natural gas is implemented by using the above parallel sampling device, and the method specifically comprises the following steps:

[0103] Step S1: Before sampling, the splitter bottle 1, the absorption bottle 2, the first air inlet pipe 101, the first air outlet pipe 102 and the second air inlet pipe 201 are soaked in a nitric acid solution with a volume concentration of 20% for more than 12 hours in advance, and then washed with ultrapure water;

[0104] Step S2: After cleaning, inject the sampling absorption liquid 202 into the insertable absorption bottle 2 (see Figure 1 ), the amount of alcohol component antifreeze added to the sampling absorption liquid 202 is flexibly adjusted according to the temperature, and the liquid level of the sampling absorption liquid 202 is 3-3.5 times the distance between the G2 sand core 204 and the bottom of the bottle;

[0105] Alternatively, after cleaning, inject the sampling absorption liquid into the variable diameter absorption bottle 2 with a spoiler ball (see Figure 3 ), the amount of alcohol component antifreeze added to the sample absorption liquid is flexibly adjusted according to the ambient temperature, and the intake gas flow rate of the absorption bottle 2 is adjusted by the valve body opening during the absorption process, so that during the gas flow disturbance process, the liquid level of the sample absorption liquid is 12-14mm higher than the upper end surface of the G2 sand core, and more than half of the spoiler ball is not covered;

[0106] Step S3: The natural gas is delivered to the diversion bottle 1 from the first gas inlet pipe 101, and is divided into a number of symmetrical branches (such as 2, 4, 6 or 8 branches) according to the parallel sampling requirements. After the flow rate is adjusted by the valve body, it is delivered to the absorption bottle 2 for absorption by the sampling absorption liquid. The absorbed gas is output through the third gas outlet pipe 303 of the drying bottle 3, and the volume V of the output natural gas under standard conditions is measured by the flow meter 4 set on the third gas outlet pipe 303. 天然气 ;

[0107] Step S4: dilute the sample absorption liquid by a factor of f 稀释倍数 , detect the metal element concentration C in the sample absorption liquid 测 and the blank sample concentration C O ;

[0108] The concentration of metal elements in the sample absorption liquid C 测 It is measured by inductively coupled plasma emission spectrometer ICP, inductively coupled plasma mass spectrometer ICP-MS and other trace metal element detection equipment, and the blank sample concentration C of the whole process is detected at the same time. O (The whole process blank sample means: during the whole process of testing in the laboratory, the reagents, solvents and sample preparation steps used are exactly the same as those of the test sample, but the sample is not added with the substance to be tested).

[0109] Step S5: Calculate the concentration of metal elements in natural gas based on experimental test data:

[0110] C 浓度 =(C 测 -C O )×V 吸收液 / V 天然气 ×f 稀释倍数

[0111] In the above formula: C 浓度 is the concentration of metal elements in natural gas, μg / m 3 ; C 测 is the concentration of metal elements in the sample absorption liquid to be detected, μg / L; C O is the concentration of metal elements in the blank sample of the whole process, μg / L; V 吸收液 V is the volume of the sample absorption liquid, mL; 天然气 is the volume of natural gas passing through the absorption bottle, L; f 稀释倍数 It is the dilution multiple of the sample absorption solution before detection.

[0112] Since the content of metal elements in natural gas is related to different processing processes and different gas sources, and there are no standard samples of metal elements in natural gas, parallel sampling must be carried out at the same time and under the same gas source conditions; the present invention adopts an air inlet splitter bottle device with controllable flow rate to solve the above-mentioned parallel sampling problem.

[0113] At the same time, the sampling and absorption liquid for metal elements in natural gas provided by the present invention is compounded with an acid solution and an alcohol solvent, which can meet the needs of natural gas sampling and absorption liquid absorption sampling in extremely cold weather; the sampling and absorption liquid provided by the present invention is not easy to freeze in winter, and the freezing point can be reduced to below minus 20°C, which can achieve the beneficial effect of expanding the application scenarios of the detection method; at the same time, the alcohol liquid antifreeze in the sampling and absorption liquid of the present invention has a high affinity with natural gas, and can achieve efficient enrichment of metal elements in natural gas.

[0114] Example 1

[0115] The embodiment of the present invention provides a parallel sampling device for metal elements in natural gas, such as Figure 1The thickness of the G1 sand core 203 and the G2 sand core 204 are both 3 mm, the average pore size of the G1 sand core 203 is 30 μm, and the average pore size of the G2 sand core 204 is 12 μm.

[0116] The natural gas transmission main pipeline is connected to the diverter bottle 1 through the first air inlet pipe 101, and the first air inlet pipe 101 is provided with a flow regulating valve 105; the six branch outlets of the diverter bottle 1 are connected to the second air inlet pipes 201 of the six plug-in absorption bottles 2 through the first air outlet pipe 102, wherein the first air outlet pipes 102 corresponding to the five branch outlets are all provided with flow regulating valves, and the first air outlet pipe 102 corresponding to the sixth branch outlet is provided with a three-way valve.

[0117] 100 mL of sampling absorption liquid was added to each of the six absorption bottles 2, the composition of which was 5% by volume nitric acid + 0.2% by volume ethanol; the liquid level of the sampling absorption liquid was 3 times the distance between the G2 sand core 204 and the bottom of the bottle.

[0118] The six absorption bottles 2 are connected to the third air inlet pipe 301 of the drying bottle 3 through the second air outlet pipe 205 respectively; the third air outlet pipe 303 of the drying bottle 3 is provided with a flow meter 4 for detecting the gas flow rate on the corresponding branch.

[0119] Open the flow regulating valve on the first air inlet pipe 101 to let in air, open the flow regulating valves on the first air outlet pipe 102 corresponding to the five branch outlets in turn, and slowly control the opening of the flow rate regulating valves on the five first air outlet pipes 102 to make the corresponding five absorption bottles 2 have an inlet flow rate of 0.3L / min; at this time, observe the inlet flow rate of the absorption bottle 2 corresponding to the sixth branch outlet, which is 1.6L / min, and then slowly open the three-way valve corresponding to the sixth branch outlet to make the flow rate displayed on the flowmeter 4 about 0.3L / min, after which sampling can officially begin.

[0120] The gas pressure of the natural gas transmission main pipeline is 1.3MPa, the gas temperature is 16.5℃, and the sampling absorption time is 4h.

[0121] The six experimental results of the parallel sampling device are shown in Table 1 below:

[0122] Table 1 Concentrations of 9 metal elements by parallel sampling method (μg / m 3 )

[0123] Group No. Na K Ca Mg Pb Ba Ni Mn Cu 1 17041.7 1056.7 3093.7 5847.9 1498.6 294.2 437.7 150.3 28 2 16915.8 1011.6 3175.5 5863.6 1505.3 278.3 412.5 129.4 18.6 3 16537.4 1123.1 3098.0 5865.8 1336.7 269.5 436.5 139.6 21.3 4 17103.2 984.8 3155.4 5726.8 1483.5 288.8 394.3 142.7 23.1 5 17005.5 976.5 2986.9 5735.4 1477.7 300.4 378.6 130.6 17.9 6 16964.6 1202.4 2897.6 5788.6 1490.0 310.2 425.6 160.1 20.5 average 16928.0 1059.2 18407.1 5804.7 1465.3 290.2 414.2 142.1 21.6

[0124] From the data in Table 1, we can see that the detected concentrations of the nine metal elements vary greatly, which means that the requirements for parallel sampling are high. From the gas detection results of different outlets of the same gas source, the parallelism between the groups is relatively good. For low-concentration Cu elements, the maximum relative average deviation is 29.6%; for high-concentration Na elements, the maximum relative average deviation is -2.3%, which can represent parallel samples for quality control.

[0125] Example 2

[0126] The embodiment of the present invention is intended to illustrate the influence of the flow-turbulating ball of the variable diameter absorption device on the flow of gas in the sample absorption liquid.

[0127] According to the flow rate adjustment method of Example 1, Figure 1 The absorption device shown is changed to Figure 3 The variable diameter absorption device with a spoiler ball is shown, and the absorption device in GB / T11060.1-2010 is used as a comparative experimental device.

[0128] The average pore size of the G2 sand core 204 is 12 μm and the thickness is 3 mm; 16 micro-pits are melted on the surface of the spoiler ball.

[0129] Conventional sampling absorption liquid containing 5% nitric acid was added to the four absorption bottles 2. Other conditions remained unchanged. Air was used as the gas source. The inlet gas flow rate of the absorption bottle 2 was adjusted to 0.5 L / min and 1.2 L / min respectively through the flow rate regulating valve and the three-way valve. The vibration state of the spoiler ball and the change in bubble size after the gas passed through the G2 sand core were observed. The experimental results are shown in Table 2 below.

[0130] Table 2 Effect of different absorption devices on the flow state of microbubbles

[0131] Absorption device Average flow rate Spoiler ball trembling state Microbubble morphology GB / T11060.1 Absorption device 0.5L / min / Small GB / T11060.1 Absorption device 1.2L / min / big Variable diameter absorption device with spoiler ball 0.5L / min Micro-tremor Small Variable diameter absorption device with spoiler ball 1.2L / min Severe shaking Small

[0132] From the data in Table 2, it can be seen that, obviously, no matter under the experimental conditions of high flow rate or low flow rate, the microbubble morphology of the variable diameter absorption device with a spoiler ball is small, which can effectively increase the reaction contact area and reaction time between the gas and the sample absorption liquid, and improve the absorption effect. The reason is: the smaller the bubble, the greater the contact area between the acid and the bubble, and the more complete the reaction; at the same time, the smaller the bubble, the easier it is for the solution to fit with the micro-pits on the surface of the spoiler ball to form a vortex state, the more bubble migration routes there are, and the longer the reaction time.

[0133] Example 3

[0134] The embodiments of the present invention are intended to illustrate the effectiveness of the antifreeze performance of the sample absorption liquid.

[0135] Extremely cold weather was chosen to carry out the antifreeze performance evaluation experiment of the sampling absorption liquid. The temperature in extremely cold weather was -22℃ to -13℃.

[0136] Take 5 mL of high-grade pure nitric acid, add it to an absorption bottle containing 85 mL of ultrapure water, stir evenly, let it stand for 5 minutes, and then add 10 mL of high-grade pure ethanol to obtain the sampling absorption solution.

[0137] Experimental verification has shown that the sampling absorption liquid with ethanol (antifreeze additive) added does not freeze when left at rest, and can meet the needs of absorption sampling of metal element solutions in natural gas in extremely cold weather.

[0138] Further, according to the test conditions of Example 1, 4 groups of comparative experiments were carried out simultaneously at an indoor room temperature of 26° C. to examine the flow state and pressure change of microbubbles through the sand core with and without the addition of an alcohol component antifreeze.

[0139] With air as the gas source, the six diversion bottles 1 only use four symmetrical branch outlets, first add 90 mL of 5% nitric acid solution into the four absorption bottles 2, adjust the flow rate through the valve body, make the reading of the flow meter 4 corresponding to the four branch outlets be 0.3 L / min, keep the opening of the valve body corresponding to each branch unchanged, then add 10 mL of 5% nitric acid, 10 mL of high-grade pure ethanol, 10 mL of high-grade pure ethylene glycol, and 10 mL of high-grade pure propylene glycol into the four absorption bottles 2 respectively, so that the total volume of the sampled absorption liquid added is 100 mL, and the volume concentration of the alcohol components is 10%.

[0140] Start the experiment, and see the experimental results in Table 3 below:

[0141] Table 3 Effect of different sampling absorption liquids on the flow state of microbubbles

[0142] Sampling absorption liquid Bubble size Flow rate variation Average flow rate 5% nitric acid solution (conventional) big big 0.3L / min 5% nitric acid solution + 10% ethanol solution middle Small 0.28L / min 5% nitric acid solution + 10% ethylene glycol solution Small Small 0.25L / min 5% nitric acid solution + 10% glycerin solution Small Small 0.25L / min

[0143] It can be seen from the data in Table 2 that the alcohol component antifreeze can reduce the flow resistance of microbubbles and make the gas pass through the micropores relatively evenly.

[0144] Example 4

[0145] The embodiments of the present invention are intended to illustrate the influence of the change of the acid components in the sampled absorption liquid on the absorption effect.

[0146] The variable diameter absorption device of Example 2 was used, and the average pore diameter of the sample G2 sand core 204 was 12 μm and the thickness was 3 mm; 16 micro-pits were ablated on the surface of the spoiler ball.

[0147] Using gas from a natural gas processing station as the gas source, 100 mL of sampling absorption liquid with different acid components was added to each of the six absorption bottles 2, namely: (1) 10% HCl; (2) 10% HNO3; (3) 10% H2SO4; (4) 10% H2O2; (5) 5% HCl + 5% HNO3; (6) 5% H2O2 + 5% HNO3. Each sampling absorption liquid contained 0.2% of ethanol component.

[0148] After the pipelines were connected, the flow rate was adjusted in the same manner as in Example 1, and the experiment was started when the gas flow rate in the six absorption bottles 2 was stabilized at 0.12 L / min.

[0149] The experimental temperature was 28°C, the natural gas pipeline pressure was 1.5 MPa, and the sampling time was 4 h.

[0150] After sampling, collect the sample absorption liquids and test the mass concentration of metal elements in natural gas on a machine. The experimental results are shown in Table 4 below:

[0151] Table 4 Concentrations of 9 metal elements in different acid absorption solutions (μg / m 3 )

[0152]

[0153]

[0154] It can be seen from the data in Table 4 that sampling absorption liquids with different acid components can effectively absorb trace metal elements in natural gas. Sampling absorption liquids with different acid components can be flexibly selected according to detection needs.

[0155] Example 5

[0156] The embodiment of the present invention takes the insertion type sampling device of embodiment 1 and the alcohol-containing sampling absorption liquid in embodiment 3 as examples, and takes the device of patent document CN105987857A as a comparative example to compare the sampling effects.

[0157] The formula of the alcohol-containing sampling absorption solution is: 5% nitric acid solution, 10% ethanol solution, and the balance is ultrapure water.

[0158] The ambient temperature is about -16°C. To prevent the absorption liquid from freezing, a foam insulation box is added to the outside of the absorption bottle and connecting pipelines of the patented device (CN105987857A).

[0159] The detection limit of the embodiments of the present invention (the lowest concentration value of the measured substance that can be detected, generally calculated as 3 times the blank standard deviation) is as low as 0.01-5.38 μg / L, and the relative standard deviation is 6.2%-15.0%; the detection limit measured in the comparative example is 0.1-31.4 μg / L, and the relative standard deviation is 44%-175%.

[0160] It can be seen that the absorption efficiency of the two devices is comparable, but the method of the embodiment of the present invention has a low detection limit and controllable quality.

[0161] At the same time, the sampling device of the embodiment of the present invention is assembled from different modules, which can be freely disassembled, and is easier to assemble, disassemble and clean. When cleaning, the sampling device of the embodiment of the present invention only needs to take out the sand core of the absorption device, soak it in nitric acid for more than 12 hours, then take it out, rinse it with ultrapure water, and dry it naturally; while the device of patent document CN105987857A has the following problems:

[0162] 1) The entire absorption device is a whole, which is bulky. Except for the connecting pipeline, the main part of the absorption bottle cannot be freely disassembled, which makes assembly and cleaning inconvenient;

[0163] 2) The three-layer sieve plate needs to be fixed at a specific position of the absorption bottle and is not suitable for processing. If a sieve plate has a problem, the entire device will be scrapped;

[0164] 3) It is not easy to dump the absorption liquid after absorption. Due to the barrier of the three-layer sieve plate, there will be a small amount of residual liquid in the absorption bottle. In order to clean the absorption bottle, it is necessary to use external pressure and repeatedly rinse it, which is easy to cause secondary contamination. In addition, the micropores of the three-layer sieve plate retain droplets, which are not easy to dry thoroughly.

[0165] In addition, the sampling absorption liquid in the embodiment of the present invention is an antifreeze formula, and there is no need to add an additional insulation box for sampling in winter, which makes the operation easier.

[0166] The above description is only an embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement and improvement made within the application scope of the present invention shall be included in the protection scope of the present invention.

Claims

1. A parallel sampling device for metal elements in natural gas, characterized in that: It includes an air intake splitter, an absorption device and a drying device which are connected in sequence; The first air inlet pipe of the air inlet splitter device is connected to the natural gas pipeline; the air inlet splitter device is evenly distributed with n branch outlets for sampling in pairs and in parallel on a horizontal plane at the same height, and each branch outlet is connected to the second air inlet pipe of the absorption device through a first air outlet pipe; at the same time, valve bodies are provided on the first air inlet pipe and the first air outlet pipe; The absorption device contains a sampling absorption liquid, the liquid level of which is higher than the end of the second air inlet pipe, and is used to absorb metal elements in the natural gas; The second air outlet pipe of the absorption device is connected to the third air inlet pipe of the drying device, and is used to transport the sampled and absorbed natural gas to the drying device for drying, and discharge it through the third air outlet pipe of the drying device; a flow meter is provided on the third air outlet pipe.

2. The device according to claim 1, characterized in that The air inlet flow splitter device comprises a flow splitter bottle, a first air inlet pipe and a first air outlet pipe; The lower end of the first air inlet pipe of the split bottle is a glass straight tube with a stopper, and the glass straight tube with a stopper is inserted into the bottom of the split bottle; The diversion bottle is evenly distributed with n branch outlets for sampling in parallel in pairs on a horizontal plane at the same height, 2≤n≤8; each branch outlet is sintered with a threaded joint for connecting to the first air outlet pipe.

3. The device according to claim 2, characterized in that The diversion bottle is a spherical container; the end of the stoppered glass straight tube is 3-5 mm away from the bottom of the bottle.

4. The device according to claim 1, characterized in that The first air inlet pipe and the n first air outlet pipes are both provided with flow regulating valves.

5. The device according to claim 1, characterized in that The first air inlet pipe is provided with a flow regulating valve; Among the n first air outlet pipes, n-1 first air outlet pipes are each provided with a flow regulating valve, and the remaining first air outlet pipe is provided with a three-way valve.

6. The device according to claim 1, characterized in that The absorption device is an insertable absorption device or a variable diameter absorption device with a spoiler ball.

7. The device according to claim 6, characterized in that The insertable absorption device comprises an absorption bottle, a second air inlet pipe, a sampling absorption liquid, a sand core, and a second air outlet pipe; The absorption bottle contains a sample absorption liquid; the end of the second air inlet pipe extends downward into the bottom of the absorption bottle and is immersed in the sample absorption liquid; The end of the second air inlet pipe is a bell mouth, and the bell mouth port is provided with the sand core.

8. The device according to claim 7, characterized in that The sand core is composed of two layers of G1 sand core and G2 sand core; The G2 sand core is sintered on the bell mouth, and the G1 sand core is placed above the G2 sand core and is not sintered with the bell mouth.

9. The device according to claim 8, characterized in that The pore size of the G1 sand core is 20-30 μm, and the thickness is 2-5 mm; the pore size of the G2 sand core 204 is 10-15 μm, and the thickness is 2-5 mm.

10. The device according to claim 8, characterized in that The liquid level of the sampling absorption liquid is 3-3.5 times the distance between the G2 sand core and the bottom of the bottle.

11. The device according to claim 6, characterized in that The variable diameter absorption device with a spoiler ball comprises an absorption bottle, a second air inlet pipe, a sampling absorption liquid, a G2 sand core, a spoiler ball and a second air outlet pipe; A second air inlet is provided on one side of the bottom of the absorption bottle, and the second air inlet is connected to the second air inlet pipe; the top of the absorption bottle is connected to the second air outlet pipe; The G2 sand core is sintered in the absorption bottle at the upper end of the second air inlet; the spoiler ball is placed at the upper end of the G2 sand core; The absorption bottle contains sampling absorption liquid; the liquid level of the sampling absorption liquid is lower than the upper end surface of the G2 sand core when there is no airflow circulation, and is higher than the upper end surface of the G2 sand core and more than half of the height of the spoiler ball when airflow disturbance occurs.

12. The device according to claim 11, characterized in that The second air inlet pipe is provided with a bubble buffer tube.

13. The device according to claim 12, characterized in that The pore size of the G2 sand core is 10-15 μm; the G2 sand core is 30-35 mm away from the bottom of the absorption bottle; The spoiler ball is made of borosilicate glass, and a plurality of micro-pits are melted on the surface of the spoiler ball, with a pit depth of 1-2 mm.

14. The device according to claim 1, characterized in that The drying device comprises a drying bottle, a third air inlet pipe and a third air outlet pipe; A color-changing silica gel desiccant is placed in the drying bottle, and the color-changing silica gel desiccant covers the air inlet end of the third air inlet pipe.

15. The device according to claim 1, characterized in that The flow meter is a wet flow meter or a gas mass flow meter with a graduation value of 0.01L and an indication error of ±1.5%.

16. The device according to claim 1, characterized in that The sampling absorption liquid comprises an acid component and an alcohol component; In the sampling absorption liquid, the volume concentration of the acid component is 3-10%, and the volume concentration of the alcohol component is 0.2-10%.

17. The device according to claim 16, characterized in that The acid component is one or more of sulfuric acid, nitric acid, hydrochloric acid, and hydrogen peroxide; The alcohol component is one or more of ethanol, ethylene glycol and glycerol.

18. The device according to any one of claims 1 to 17, characterized in that The gas inlet flow splitter and the container portion of the absorption device are both made of borosilicate glass or quartz glass; The first air inlet pipe, the first air outlet pipe and the second air inlet pipe are all made of polytetrafluoroethylene rubber tubes; The valve bodies on the first air inlet pipe and the first air outlet pipe are both made of polytetrafluoroethylene.

19. The device according to claim 18, characterized in that It also includes a bracket, which is used to fix the air intake diversion device, the absorption device, the drying device and the flow meter.

20. A method for parallel sampling of metal elements in natural gas, implemented using the parallel sampling device according to any one of claims 1 to 19, the method specifically comprising the following steps: Step S1: Before sampling, the air intake splitter device and the container part of the absorption device, the first air intake pipe, the first air outlet pipe and the second air intake pipe are soaked in a nitric acid solution with a volume concentration of 20% for more than 12 hours in advance, and then cleaned with ultrapure water; Step S2: injecting a sample absorption liquid into the absorption device after cleaning, and adding an alcohol component antifreeze agent into the sample absorption liquid; Step S3: The natural gas is transported from the first air inlet pipe to the air inlet flow dividing device, and is divided into several symmetrical branches according to the parallel sampling requirements. After the flow is adjusted by the valve body, it is transported to the absorption device for absorption by the sampling absorption liquid. The absorbed gas is output through the third air outlet pipe of the drying device, and the volume V of the output natural gas under standard conditions is measured by the flow meter set on the third air outlet pipe. 天然气 ; Step S4: dilute the sample absorption liquid by a factor of f 稀释倍数 , detect the metal element concentration C in the sample absorption liquid 测 and the blank sample concentration C O ; Step S5: Calculate the concentration of metal elements in natural gas based on experimental test data: C 浓度 =(C 测 -C O )×V 吸收液 / V 天然气 ×f 稀释倍数 In the above formula: C 浓度 is the concentration of metal elements in natural gas, μg / m 3 ; C 测 is the concentration of metal elements in the sample absorption liquid to be detected, μg / L; C O is the concentration of metal elements in the blank sample of the whole process, μg / L; V 吸收液 V is the volume of the sample absorption liquid, mL; 天然气 is the volume of natural gas passing through the absorption bottle, L; f 稀释倍数 It is the times of dilution of the sample absorption solution before detection.

21. The method according to claim 20, characterized in that The step S2 specifically includes: After cleaning, inject the sampling absorption liquid into the insertable absorption bottle, add alcohol component antifreeze to the sampling absorption liquid, and the liquid level of the sampling absorption liquid is 3-3.5 times the distance between the G2 sand core and the bottom of the bottle; Alternatively, after cleaning, inject sampling absorption liquid into the variable diameter absorption bottle with a spoiler ball, add alcohol component to the sampling absorption liquid, and adjust the inlet gas flow rate of the absorption bottle by adjusting the valve opening during the absorption process so that the liquid level of the sampling absorption liquid is higher than the upper end surface of the G2 sand core and is more than half of the height of the spoiler ball during the gas flow disturbance.

22. The method according to claim 21, characterized in that In step S4, the metal element concentration C in the sampled absorption liquid is 测 , Blank sample concentration C O Measured by trace or trace metal element detection equipment.

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