Sample introduction method of volatile liquid

Abstract

The invention provides a sample introduction method of volatile liquid, which uses an inverted U-shaped tubular sample introduction needle as a main liquid transfer tool, can realize sample introduction of the volatile liquid in a completely closed state, liquid components are not distorted, an introduced sample is not leaked, and an error between an actual sample introduction amount and a measured value can be obviously reduced. In addition, the sample introduction method provided by the invention is safe to operate, simple and convenient to maintain, small in environmental pollution, controllable in sample introduction amount, capable of realizing normal-temperature operation and continuous operation, and good in practicability.

Description

Technical Field

[0001] The invention relates to the analysis field of coal chemical industry and petrochemical industry, and in particular to a sampling method for volatile liquid. Background Art

[0002] Volatile materials are common in coal chemical and petrochemical industries, among which the moisture content of materials is one of the key control indicators. At present, the main methods used to determine the moisture content in such materials are: SH / T0246-1992 Determination of water content in light petroleum products (coulometric method) and GB / T 6283-2008 Determination of moisture content in chemical products Karl Fischer method (general method). The above two standards belong to the general methods for determining the moisture content of chemical liquid products, and both are syringe sampling and analysis.

[0003] However, when measuring samples that are volatile at room temperature, such as industrial isopentane and mixed carbon five, there are certain limitations in sampling with a syringe. This is because volatile liquids have a low boiling point at room temperature and pressure and are extremely volatile, while the syringe needle is only sealed with a rubber pad, which is not very tight. When sampling directly with a syringe, the sample is very easy to be lost due to volatilization and cannot be accurately weighed, resulting in a large gap between the analysis result and the true value. The analysis result obtained is also difficult to use to guide the continuous and stable production of the process.

[0004] It can be seen that there is an urgent need to develop a new type of volatile liquid injection method to replace the general syringe method, to facilitate the analysis of the moisture content of volatile liquids, and to ensure the accuracy and reliability of the analysis results. Summary of the invention

[0005] In order to make up for the deficiencies in the prior art, the purpose of the present invention is to provide a method for injecting volatile liquids, by which the volatile liquids can be sealed and not leaked during the entire injection process, and the sample composition is not distorted, thereby ensuring the accuracy and reliability of subsequent analysis results.

[0006] The method for injecting volatile liquid provided by the present invention comprises the following steps:

[0007] S1: Weigh the weight of the closed container storing the volatile liquid;

[0008] S2: using an inverted U-shaped tubular injection needle, first connecting the outlet end of the injection needle to the destination container to be injected, and then connecting the inlet end of the injection needle to the closed container, where it is in contact with the volatile liquid, and injecting dry gas into the closed container to promote the transfer of the volatile liquid to the destination container;

[0009] S3: when the injection is finished, the inlet end of the injection needle is first disconnected from the volatile liquid, and the dry gas is continuously injected to transfer all the volatile liquid remaining in the injection needle to the destination container, and then the outlet end of the injection needle is disconnected from the destination container; and

[0010] S4: After the injection is completed, the closed container is weighed, and the injection volume is obtained by the weight difference.

[0011] The injection method provided by the present invention uses an inverted U-shaped tubular injection needle as a main transfer tool for volatile liquids. When the injection starts, the outlet end of the injection needle is first connected to a destination container to be injected, and then the inlet end of the injection needle is contacted with the volatile liquid. At this time, the volatilized liquid directly flows into the destination container and will not volatilize into the air to cause loss. During the injection, dry gas is injected into the sealed container and the volatile liquid is pushed to be transferred to the destination container by the pressure difference, so that long-term and continuous injection can be achieved. When the injection is about to end, the inlet end of the injection needle is first disconnected from the volatile liquid, and the dry gas is continuously injected to transfer all the residual volatile liquid to the destination container. Since the volatile liquid is very volatile at room temperature, this operation will not cause the liquid in the destination container to be sucked back, and a trace amount of gas can completely transfer the residual liquid in the injection needle to the destination container without causing retention. The instantaneous sample loss during the operation is extremely small. Finally, the injection amount is obtained by calculating the weight difference of the sealed container before and after the injection.

[0012] Through the above operation method, the volatile liquid to be sampled can be continuously sampled, and the sample transfer in a completely closed state can be truly realized. Moreover, the loss caused by the volatilization of the liquid can be reduced, and the influence of moisture in the air can be eliminated, so that the sampled volatile liquid is closer to its real composition. In addition, the above sampling method can also be operated at room temperature, which is also conducive to avoiding the distortion of the composition of the volatile liquid. This is because the moisture in the air will condense into the liquid and the utensils during refrigeration, causing the moisture content to increase. Taking isopentane as an example, the refrigeration method can cause the actual moisture content of the sample to be about 3-5ppm higher.

[0013] The sampling method provided by the present invention is applicable to the detection of volatile liquids in the fields of coal chemical industry and petrochemical industry. In some preferred embodiments, the volatile liquid can be C4 hydrocarbons, C5 hydrocarbons or C4-C5 mixed hydrocarbons, for example, it can be isopentane with a very low boiling point. In other preferred embodiments, the target container to be sampled can be a titration cell of Karl Fischer titration method, which is used to detect the water content in the volatile liquid.

[0014] In the injection method provided by the present invention, the injection needle can be made of metal, either a single metal material (such as copper) or an alloy material, with good rigidity and sufficient sharpness, and will not produce chemical reactions with volatile liquids.

[0015] In the injection method provided by the present invention, the inlet end and the outlet end of the injection needle can be respectively provided with a detachable conical tip. The design of the conical tip makes it easier to pierce the septum of the container and prevent the debris of the septum from clogging the pinhole, and the detachable structure is also conducive to timely cleaning. In some preferred embodiments, a filter plate can also be provided between the conical tip and the tube body of the injection needle. The provision of the filter plate can further prevent impurities and septum debris from clogging the injection needle pinhole, and the material of the filter plate can be polytetrafluoroethylene.

[0016] In the injection method provided by the present invention, two layers of suction holes can be vertically distributed on the tube body at the inlet end of the injection needle, and the number of suction holes in each layer can be 2 to 4 (for example, 2, 3 or 4), which are evenly distributed along the tube body. In some preferred embodiments, the number of suction holes in each layer is 2, and the angle between the suction holes of the two layers is 90°. The special structure of the 90° holes can realize the simultaneous suction of liquid samples in four horizontal directions, and the samples are uniform and representative. It can also avoid the blockage of the injection needle caused by impurities, debris, etc. due to direct suction. The structure of the two groups of symmetrical holes can also better realize the dredging of the needle when it is blocked, compared with the design of single hole and asymmetric hole, and the dredging operation is relatively simple.

[0017] In the injection method provided by the present invention, three layers of release holes can be vertically distributed on the tube body at the outlet end of the injection needle, and the number of holes in each layer can be 3 to 6 (for example, 2, 3, 4, 5 or 6), which are evenly distributed along the tube body. Compared with the single outlet direct injection method of the syringe, the structural design of the three-layer release hole can release the liquid sample in multiple directions horizontally at the same time, thereby effectively enhancing the dissolution efficiency of the sample in the destination container, and realizing rapid absorption and reaction with the solution in the destination container (for example, the detection reagent solution), and the outlet direction of the liquid is in the same plane as the stirring direction, which is also very conducive to the dissolution and absorption of the liquid. If it is designed as 2 layers, similar to the suction hole at the inlet end, the slow sample discharge is not conducive to dissolution and absorption. If the number of layers is too large, it is easy to exceed the liquid surface, which is also not conducive to the dissolution and absorption of the liquid. In some preferred embodiments, the number of holes in the three-layer release hole can be 4, 3 and 4 respectively, and the release holes of each layer are evenly distributed along the tube body.

[0018] In the injection method provided by the present invention, the inlet end and the outlet end of the injection needle can be respectively provided with a slidable protective sleeve at a position close to the conical tip. The protective sleeve can slide along the tube body of the injection needle but will not fall off the tube body. The protective sleeve is used to prevent the operator from being accidentally stabbed by the exposed tip, and also helps the operator to hold and operate during injection, which can reduce the operator's fatigue and the risk of misoperation during use. The protective sleeve does not fall off the tube body, which can prevent the sleeve from sliding to the needle tip and contaminating or damaging the needle tip when not in use.

[0019] In the injection method provided by the present invention, the injection needle can be used once or repeatedly. The disposable design can reduce cleaning and maintenance and reduce the risk of cross contamination, while the reusable design can be more environmentally friendly and economical. In some preferred embodiments, the injection needle of the present invention can be used repeatedly on the basis of ensuring that good performance and safety can be maintained after multiple uses.

[0020] In the sampling method provided by the present invention, the closed container is also connected to a gas injection device for injecting dry gas therein. The gas injection device can be a common device in the art, such as a syringe. A gas drying device (such as a drying tube) can be further arranged between the closed container and the gas injection device to ensure that the injected gas is as dry as possible.

[0021] In the sampling method provided by the present invention, the drying gas can be selected from dry air or inert gas. In some preferred embodiments, the drying gas can be selected from dry air or nitrogen.

[0022] In the sampling method provided by the present invention, the sealed container can be arranged in a fixing frame, and the sealed container can be fixed by means of a card slot and a spring clip in the fixing frame, thereby making the operation process more stable and simple, ensuring a smooth and stable sampling process, and also greatly reducing the workload of the operator.

[0023] In the injection method provided by the present invention, the injection needle may also be connected to an electronic flow control device or a high-precision micro pump, through which the accuracy of the injection amount can be improved and controlled, the flow rate can be monitored in real time, and the injection amount can be more accurately obtained by using a high-precision instrument to participate in the calculation, and the injection process can also be better controlled. Among them, the electronic flow control device or the high-precision micro pump can be detached for use.

[0024] The technical solution provided by the present invention has the following advantages:

[0025] (1) The injection method provided by the present invention can realize the injection of volatile liquids in a completely closed state, without distortion of liquid composition and leakage of injected samples. The error between the actual injection volume and the measured value is significantly reduced, thus providing a guarantee for the accuracy of subsequent analysis and detection.

[0026] (2) The injection method provided by the present invention is safe to operate, easy to maintain, has little environmental pollution, and has a controllable injection volume. It can also be operated at room temperature and continuously, and has higher practicality.

[0027] (3) The injection method provided by the present invention uses an inverted U-shaped injection needle, which can conveniently realize the transfer of volatile liquids between different containers, thereby alleviating the difficulty of operation and reducing the workload of the operator.

[0028] (4) The injection needle provided by the present invention is easy to disassemble and assemble, and is easy to clean and maintain, thereby ensuring a good injection effect and achieving multiple and repeated uses, which can significantly reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a schematic diagram of the structure of the device used in the sampling method of the present invention; wherein: 1. titration cell; 2. sampling needle; 3. gas syringe; 4. sample bottle; 5. sample fixing rack; 6. sampling needle inlet end; 7. sampling needle outlet end; 8. protective sleeve; 9. electronic flow controller. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments.

[0031] Unless otherwise specified, the raw materials or reagents used in the examples of the present invention are commercially available products.

[0032] Example Injection of isopentane

[0033] Isopentane is a colorless, transparent, and highly volatile liquid at room temperature, with a boiling point of 27.8°C. When an ordinary syringe is used for sampling, isopentane exposed to the air easily absorbs moisture in the air, and isopentane is volatile, so the moisture content in the isopentane sample will change, and it cannot truly reflect the original properties of the sample, and the measurement accuracy is low and the repeatability is poor.

[0034] like Figure 1 As shown, the sample injection device used in this embodiment is as follows:

[0035] 1. Select the common Karl Fischer titration cell size for water determination. Titration cell 1 has a vertical sample injection port and no other special requirements.

[0036] 2. The setting of the inverted U-shaped injection needle 2: a hollow injection needle with a length of about 300 mm and an outer diameter of about 1.5 mm, made of copper. The injection needle inlet end 6 is provided with two layers of suction holes, two holes in each layer, and the angle between the suction holes in each layer is 90°, that is, the four suction holes in the two layers are distributed in a "four-point four-direction" manner, the vertical hole spacing of the two layers is 3 mm, and the aperture is about 0.3 mm, which can achieve balanced liquid flat suction in multiple directions, and avoid the impurities at the bottom of the bottle from clogging the needle hole in the direct suction mode. The injection needle outlet end 7 is a horizontal outlet mode of 4 / 3 / 4 three layers with a total of 11 holes (the first layer and the third layer each have 4 holes, which are evenly distributed along the tube body, that is, "four points and four directions", and the middle layer has 3 holes, which are also evenly distributed along the tube body), with an aperture of about 0.3 mm. This setting can increase the dissolution efficiency of the outlet sample, realize the rapid absorption reaction of the solution, and at the same time improve the rigidity of the needle. The inlet and outlet ends of the injection needle are also provided with a detachable conical tip, which can prevent impurities at the bottom of the bottle and septum debris from clogging the injection needle hole. The inner wire diameter of the detachable conical tip (i.e., the needle hole diameter) is 1.1 mm, the inner wire length is 4 mm, and the exposed tip length is 10 mm. A filter sheet made of polytetrafluoroethylene is also provided between the conical tip and the tube body of the injection needle. The filter sheet is a circular sheet containing micropores, which can further prevent impurities and septum debris from clogging the injection needle hole.

[0037] 3. Gas syringe 3: volume is 5.00mL, graduation is 0.10mL.

[0038] The above-mentioned injection needle 2 with a total length of about 300 mm and an outer diameter of 1.5 mm is used to connect the sealed sample bottle 4 containing isopentane and the Karl Fischer titration cell 1. The injection needle 2 pierces the sample bottle sealing septum and the Karl Fischer injection port septum to connect the sample bottle 4 and the titration cell 1. In the titration cell 1, the injection needle 2 and the indicator electrode need to be kept at a certain distance, and it is necessary to ensure that the sample bottle 4 can be placed horizontally (it can be placed in a sample fixing rack 5 with a fixing function), otherwise the length of the injection needle 2 can be appropriately lengthened, but it cannot exceed 360 mm. The length of the injection needle 2 can also be appropriately reduced according to the site conditions, but it must ensure that the connection function is achieved, at least 270 mm, to ensure matching connection, not compact, and the injection needle 2 enters the titration cell 1 below the liquid level by 10 mm.

[0039] The injection process is as follows:

[0040] First, the outer wall of the sealed sample bottle 4 containing isopentane is purged clean with nitrogen to ensure that there is no stain or other volatile substances on the bottle. The sample bottle is weighed and the initial mass is recorded as m. 1Next, the injection needle outlet end 7 is first passed into the titration cell 1 and penetrated to 10 mm below the liquid surface, and then passed into the sample bottle 4 with a 5.00 mL syringe 3, and then the injection needle inlet end 6 is passed into the sample bottle 4 10 mm below the liquid surface. At this time, the isopentane sample in the sample bottle directly flows into the titration cell 1 due to its own volatility and will not evaporate into the air. The sample amount transferred by the injection needle can be calculated or monitored according to the flow rate and time displayed by the electronic flow controller 9.

[0041] At the beginning of the injection, the sample is volatilized by the sample itself. Then, the syringe 3 is kept to slowly fill the sample bottle 4 with dry gas to continuously push the liquid sample to the titration cell 1 for transfer. At the same time, it is necessary to ensure that the liquid released from the outlet cannot break through the vortex and directly overflow the liquid surface. When the injection volume reaches the required amount, the injection needle inlet end 6 is first lifted to above the liquid surface of the sample bottle 4. At this time, the remaining sample in the injection needle is also pushed by the syringe 3 to achieve full transfer into the titration cell. When no bubbles are generated below the liquid surface of the titration cell, continue to pass dry gas for 2 to 3 seconds. After all the samples in the injection needle are completely in the titration cell 1, the injection needle 2 is finally pulled out from the titration cell 1, and the syringe 3 in the sample bottle 4 is pulled out. Through the above process, the closed transfer of volatile liquid samples is achieved. It can be seen that in this process, the volatile liquid sample basically does not contact the external water, and the volatilized part also enters the titration cell 1 together, and will not cause loss.

[0042] Since volatile liquids are very easy to evaporate at room temperature, the inlet end of the injection needle is pulled out first, and then the outlet end is pulled out. This operation will not cause the Karl Fischer reagent in the titration cell to be sucked back, and the gas introduced into the micro-syringe can completely transfer the residual sample in the injection needle to the titration cell without any sample retention. The loss of sample at the moment of operation is extremely small and can be ignored.

[0043] After the injection is completed, weigh the remaining mass m of the sample bottle again 2 , m 1 -m 2 The difference obtained is the amount of sample actually entering the Karl Fischer titration cell.

[0044] The above operation process requires wearing rubber gloves to prevent oil and moisture on the hands from affecting the quality of the sample.

[0045] The moisture content result of the first measurement was discarded, and the above process was repeated at least 3 times to determine the average moisture content of the isopentane sample.

[0046] Using the injection method of the above embodiment, the sample amount error of the volatile liquid is about 0.0010g, while when the same sample is injected using a syringe, the sample amount error is about 0.0100g. It can be seen that compared with the existing syringe method, the injection method provided by the present invention can greatly reduce the error and improve the accuracy of the injection amount.

[0047] Unless otherwise defined, the terms used in the present invention have the meanings commonly understood by those skilled in the art.

[0048] The embodiments described in the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Those skilled in the art may make various other substitutions, changes and improvements within the scope of the present invention. Therefore, the present invention is not limited to the above embodiments, but is only limited by the claims.

Claims

1. A method for injecting a volatile liquid, characterized in that: The following steps are involved: S1: Weigh the weight of the closed container storing the volatile liquid; S2: using an inverted U-shaped tubular injection needle, first connecting the outlet end of the injection needle to the destination container to be injected, and then connecting the inlet end of the injection needle to the closed container, where it is in contact with the volatile liquid, and injecting dry gas into the closed container to promote the transfer of the volatile liquid to the destination container; S3: when the injection is finished, the inlet end of the injection needle is first disconnected from the volatile liquid, and the dry gas is continuously injected to transfer all the volatile liquid remaining in the injection needle to the destination container, and then the outlet end of the injection needle is disconnected from the destination container; and S4: After the injection is completed, the closed container is weighed, and the injection volume is obtained by the weight difference.

2. The sampling method according to claim 1, characterized in that: The volatile liquid is C4 hydrocarbons, C5 hydrocarbons or C4-C5 mixed hydrocarbons.

3. The sampling method according to claim 1 or 2, wherein the destination container is a titration cell for Karl Fischer titration for detecting water content.

4. The sampling method according to any one of claims 1 to 3, characterized in that: The inlet end and the outlet end of the injection needle are respectively provided with a detachable conical tip, and a filter sheet is optionally provided between the conical tip and the tube body of the injection needle.

5. The sampling method according to any one of claims 1 to 4, characterized in that: Two layers of suction holes are vertically distributed on the tube body at the inlet end of the injection needle, and the number of suction holes in each layer is 2, 3 or 4, which are evenly distributed along the tube body; preferably, the number of suction holes in each layer is 2, and the angle between the suction holes in the two layers is 90°.

6. The sampling method according to any one of claims 1 to 5, characterized in that: Three layers of release holes are vertically distributed on the tube body at the outlet end of the injection needle, and the number of holes in each layer is 3 to 6, which are evenly distributed along the tube body; preferably, the number of holes in the three layers of release holes are 4, 3 and 4 respectively.

7. The sampling method according to any one of claims 4 to 6, characterized in that: The inlet end and the outlet end of the injection needle are respectively provided with slidable protective sleeves at positions close to the conical tip.

8. The sampling method according to any one of claims 1 to 7, characterized in that: The sealed container is also connected to a gas injection device for injecting dry gas therein.

9. The sampling method according to any one of claims 1 to 8, characterized in that: The drying gas is selected from dry air or an inert gas, preferably selected from dry air or nitrogen.

10. The sampling method according to any one of claims 1 to 9, characterized in that: The injection needle is also connected to an electronic flow control device or a high-precision micro pump.

Images