Adjustable diffusion cell for dynamic gas distribution by diffusion method

Abstract

The invention provides an adjustable diffusion cell for dynamic gas distribution through a diffusion method, and relates to the technical field of standard gas preparation, the adjustable diffusion cell comprises a liquid storage tank and at least two diffusion pipes communicated with a gas phase space of the liquid storage tank, the liquid storage tank is provided with a sample adding port, and the outlet end of the top of each diffusion pipe is provided with a sealing cover. The diffusion pipes on the liquid storage tank are configured to be different in length or inner diameter, and stepped diffusivity adjustment is achieved by opening different diffusion pipe combinations.

Description

Technical Field

[0001] The invention relates to the technical field of standard gas preparation, in particular to an adjustable diffusion pool used for dynamic gas distribution by a diffusion method. Background Art

[0002] As a method for generating dynamic gas standards, the diffusion method is widely used in fields such as gas detection and instrument calibration. The method utilizes a diffusion cell as its core component. Its basic structure is a liquid storage container with a capillary tube. The gas distribution principle is that the liquid stored in the liquid storage container vaporizes at a certain external temperature and flows out through a diffusion tube of appropriate size (length and diameter) at the top of the container. It is then carried by a constant flow of carrier gas and diluted to produce a gas standard containing a certain content of the liquid components in the liquid storage container.

[0003] The amount of liquid volatilized from the liquid storage container is quantitatively related to the external temperature and the length and diameter of the diffusion tube. Conventional diffusion cells are manufactured based on the concentration of the generated gas, with the length and diameter of the diffusion tube designed in advance. If you want to change the concentration of the generated gas, you need to recalculate and then reprocess it. On the one hand, this increases the experimental time. On the other hand, the diffusion rate of a fixed diffusion cell can be changed very little, which is inconvenient and not conducive to conducting experiments. In addition, for some special liquids with low saturated vapor pressure and high diffusion rates, a diffusion tube with only one diffusion outlet (one diffusion hole) cannot meet the needs of a larger diffusion rate. In order to meet the requirement of stable diffusion rate, the diameter of the diffusion tube needs to be controlled (0.1-2cm), which cannot be achieved simply by shortening the capillary length and increasing the diameter. Summary of the Invention

[0004] In order to overcome the problems in the background technology, the present invention has developed an adjustable diffusion cell for dynamic gas distribution by diffusion method, which solves the problems that the diffusion rate of traditional diffusion cells is fixed and the variable range is very small, making it difficult to dynamically adjust the diffusion rate according to the gas distribution needs, and the convenience is low and the adjustment time is long.

[0005] To achieve the above object, the present invention is implemented through the following technical solutions: An adjustable diffusion cell for dynamic gas distribution by diffusion method comprises a liquid storage tank and at least two diffusion tubes connected to the gas phase space of the liquid storage tank. The liquid storage tank is provided with a sample addition port, and the inner cavity outlets of the diffusion tubes are installed with detachable seals. Each diffusion tube on the liquid storage tank is configured to have an unequal length or inner diameter, and step-by-step diffusion rate adjustment is achieved by opening different combinations of diffusion tubes.

[0006] Furthermore, a plurality of connectors for fixing the diffusion tube are provided on the tank body of the liquid storage tank, and the diffusion tube is detachably mounted on the liquid storage tank via the connectors.

[0007] Furthermore, the outlet of the diffuser is a plurality of side holes connected to the inner cavity of the diffuser opened at different heights on the side wall of the diffuser, and seals are installed on the side holes. The effective length of the diffuser can be adjusted by opening the side holes at different heights on the diffuser.

[0008] Furthermore, the outlet of the diffuser is a vertical slot provided on the side wall of the diffuser, and the lower end of the vertical slot is connected to the inner cavity of the diffuser; an adjusting sleeve is rotatably installed on the outer wall of the diffuser to cover the vertical slot, and a spiral strip-shaped through hole is provided on the tube wall of the adjusting sleeve covering the vertical slot; the effective length of the diffuser is adjusted by rotating the opening position formed by the overlapping area of ​​the strip-shaped through hole of the adjusting sleeve and the vertical slot.

[0009] Furthermore, the distance between the two ends of the strip-shaped through hole is greater than the length of the vertical slot, and the rotation angle of the strip-shaped through hole set on the adjusting sleeve does not exceed degrees.

[0010] Furthermore, the connecting piece is tubular and integrally formed with the liquid storage tank. The inner diameters of the tube lumens of the connecting pieces are all the same and are connected to the internal space of the liquid storage tank. A limit platform is provided at the lower end of the inner wall of the tube lumen of each connecting piece. The outer diameters of the diffusion tubes are all the same. The diffusion tubes can be inserted into the tube lumen of the connecting piece and collide with the limit platform. A sealing rubber ring is provided on the outer wall of the tube section of the diffusion tube inserted into the connecting piece.

[0011] Furthermore, the sealing member includes a ferrule capable of engaging with the diffusion tube and a rubber plug fixed on the inner side of the ferrule and interference-fitted with the side hole.

[0012] Furthermore, the tank body of the liquid storage tank includes an upper cover and a liquid tank that are threadedly connected. The connecting piece is arranged on the upper cover, and the opening where the liquid tank is connected to the upper cover is a sample addition port.

[0013] Beneficial effects of the present invention: 1. The multi-diffusion tube design on the liquid storage tank can achieve significant adjustment of the diffusion rate by opening a single one or in groups. This not only increases the range of the diffusion rate, but also is easy to use and can dynamically adjust the diffusion rate according to different gas distribution requirements; 2. The side tube and sleeve structure design of the diffuser not only greatly increases the adjustable range and adjustable magnitude of the diffusion rate, but also realizes stepless adjustment of the diffusion rate within a certain range; it can achieve rapid and large-scale changes in the diffusion rate of the diffusion cell, thereby improving the adjustment efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the implementation structure of this application; Figure 2 This is a schematic diagram of the diffusion pool structure of this application Figure 1 ; Figure 3It is a schematic diagram of the diffusion tube structure of this application; Figure 4 This is the schematic diagram of the liquid storage tank structure of this application Figure 1 ; Figure 5 This is a schematic diagram of the diffusion pool structure of this application Figure 2 ; Figure 6 This is a schematic diagram of the diffusion pool structure of this application Figure 3 ; Figure 7 This is a schematic diagram of the side hole diffuser structure of the present application; Figure 8 This is a schematic structural diagram of the side hole type diffuser tube seal of the present application; Figure 9 This is a schematic diagram of the diffusion pool structure of this application Figure 4 ; Figure 10 This is a schematic diagram of the sleeve-type diffuser structure of this application Figure 1 ; Figure 11 This is a schematic diagram of the sleeve-type diffuser structure of this application Figure 2 ; Figure 12 This is a schematic diagram of the sleeve-type diffuser structure of this application Figure 3 ; Figure 13 This is the schematic diagram of the liquid storage tank structure of this application Figure 2 .

[0015] 1-liquid storage tank, 11-sample addition port, 12-connector, 13-limiting platform, 2-diffusion tube, 21-inner cavity, 22-sealing rubber ring, 23-base, 24-adjustment scale, 3-side hole, 4-seal, 41-ferrule, 42-rubber plug, 5-vertical slot, 6-adjustment sleeve, 61-strip through hole, 62-indicator. DETAILED DESCRIPTION

[0016] In order to make the objectives, technical solutions and beneficial effects of the present invention more clear, preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings to facilitate understanding by technicians.

[0017] See Figure 2 、 Figure 5 An adjustable diffusion cell for dynamic gas distribution by diffusion method comprises a liquid storage tank 1 and at least two diffusion tubes 2 connected to the gas phase space of the liquid storage tank 1, the liquid storage tank 1 is provided with a sample addition port 11, and the outlet of the inner cavity 21 of the diffusion tube 2 is installed with a detachable seal 4, each diffusion tube 2 on the liquid storage tank 1 is configured to have an unequal length or inner diameter, and step-by-step diffusion rate adjustment is achieved by opening different combinations of diffusion tubes 2.

[0018] See Figure 4 The tank body of the liquid storage tank 1 is provided with a plurality of connectors 12 for fixing the diffusion tube 2. The diffusion tube 2 is detachably mounted on the liquid storage tank 1 through the connectors 12, so that the diffusion tube 2 with different parameters can be easily replaced.

[0019] See Figure 6 、 Figure 7 The outlet of the diffuser 2 is a plurality of side holes 3 opened at different heights on the side wall of the diffuser 2 and connected to the inner cavity 21 of the diffuser 2. A seal 4 is installed on the side hole 3. By opening the side holes 3 at different heights on the diffuser 2, the effective length of the diffuser 2 can be adjusted, so that one diffuser 2 can adjust multiple diffusion rates.

[0020] See Figure 9 、 Figure 10 、 Figure 11 、 Figure 12 The outlet of the diffuser 2 is a vertical slot 5 opened on the side wall of the diffuser 2, and the lower end of the vertical slot 5 is connected to the inner cavity 21 of the diffuser 2; an adjusting sleeve 6 is rotatably installed on the outer wall of the diffuser 2 to cover the vertical slot 5, and a spiral strip-shaped through hole 61 is opened on the tube wall of the adjusting sleeve 6 covering the vertical slot 5; the effective length of the diffuser 2 can be adjusted by rotating the opening position formed by the overlapping area of ​​the strip-shaped through hole 61 of the adjusting sleeve 6 and the vertical slot 5, so that almost all diffusion rates within a certain range can be adjusted by one diffuser.

[0021] See Figure 10 、 Figure 11 The distance between the two ends of the strip-shaped through hole 61 is greater than the length of the vertical slot 5. The rotation angle of the strip-shaped through hole 61 on the adjusting sleeve 6 does not exceed 360°, which can avoid multiple overlapping areas between the strip-shaped through hole 61 and the vertical slot 5, ensuring that the opening formed by the overlapping area is unique; A base 23 is provided on the outer wall of the diffuser 2 below the vertical notch 5. A circle of adjustment scale 24 is marked on the base 23. The inner diameter of the adjustment sleeve 6 matches the outer diameter of the diffuser 2. An interference fit layer is provided on the inner wall of the adjustment sleeve 6 to enhance sealing and damping. This interference fit layer covers the entire inner wall of the adjustment sleeve 6 excluding the strip-shaped through-hole 61, such as the entire inner wall or the upper and lower ends. The interference fit layer can be made of a flexible material. An indicator 62 is provided at the lower end of the adjustment sleeve 6, which contacts the base 23 and can align with the adjustment scale 24. The adjustment scale 24 is determined based on the corresponding relationship between the effective length and the degree of rotation determined by Formula 1.

[0022] See Figure 3 、 Figure 4The connecting piece 12 is tubular and integrally formed with the liquid storage tank 1. The inner diameter of the tube cavity of the connecting piece 12 is the same and is connected to the internal space of the liquid storage tank 1. The lower end of the inner wall of the tube cavity of each connecting piece 12 is provided with a limit platform 13; the outer diameter of the diffuser tube 2 is the same, and the diffuser tube 2 can be inserted into the tube cavity of the connecting piece 12 and contact the limit platform 13. A sealing rubber ring 22 is provided on the outer wall of the tube section of the diffuser tube 2 inserted into the connecting piece 12, which can ensure the sealing performance of the connection of the diffuser tube 2.

[0023] See Figure 8 The sealing member 4 includes a ferrule 41 that can be engaged with the diffuser 2 and a rubber plug 42 fixed on the inner side of the ferrule and interference fit with the side hole 3, thereby ensuring the convenience of operation and the sealing of the side hole 3.

[0024] See Figure 13 The tank body of the liquid storage tank 1 includes a threaded upper cover and a liquid tank. The connecting piece 12 is arranged on the upper cover. The open opening where the liquid tank is connected to the upper cover is a sample addition port 11 for convenient sample addition.

[0025] The diffusion tube is based on the principle of capillary diffusion. The vapor generated by the target component liquid diffuses outward through the capillary tube. Under a certain temperature and pressure, the diffusion rate remains unchanged: See Figure 1 During dynamic gas distribution using the diffusion method, the diffusion cell A of this application is placed in a constant-temperature, enclosed thermostat B. The thermostat B has a carrier gas inlet C and a mixed gas outlet D. A stable flow of inert gas, supplied by an external gas source, enters the thermostat B through the carrier gas inlet C, carrying the target vapor from the capillary outlet of diffusion cell A out through the mixed gas outlet D. Subsequently, through dilution, a series of mixed gases containing different concentrations of the target component are obtained. Subsequent examples will be implemented based on this structure.

[0026] Example 1 See Figure 2 、 Figure 3 、 Figure 4 An adjustable diffusion cell for dynamic gas distribution by diffusion method includes a liquid storage tank 1 and five diffusion tubes 2 connected to the gas phase space of the liquid storage tank 1. The five diffusion tubes are numbered diffusion tube 1, diffusion tube 2, diffusion tube 3, diffusion tube 4, and diffusion tube 5 respectively. A detachable seal 4 is installed at the outlet of each diffusion tube 2. The five diffusion tubes 2 are configured to have unequal lengths. The five diffusion tubes 2 have the same inner diameter, and the outlets are all located at the top of the diffusion tube 2.

[0027] Taking water diffusion as an example, the above-mentioned diffusion cell is used to perform dynamic gas distribution by diffusion method, and by opening the outlets of different diffusion tubes 2, the diffusion tube combinations 1 to 5 of Example 1 can achieve a diffusion rate adjustment range as shown in Table 1.

[0028] Table 1 Diffusion rate adjustment range of Example 1 Example 2 See Figure 5 , an adjustable diffusion cell for dynamic gas distribution by diffusion method, comprising a liquid storage tank 1 and five diffusion tubes 2 connected to the gas phase space of the liquid storage tank 1. The structure of the liquid storage tank 1 is the same as that of Example 1. The five diffusion tubes are numbered as diffusion tube 1, diffusion tube 2, diffusion tube 3, diffusion tube 4, and diffusion tube 5 respectively. A detachable seal 4 is installed at the outlet of each diffusion tube 2. The five diffusion tubes 2 are configured to have unequal inner diameters, the five diffusion tubes 2 have the same length, and the outlets are all arranged at the top of the diffusion tube 2.

[0029] Taking water diffusion as an example, the above-mentioned diffusion cell is used to perform dynamic gas distribution by diffusion method, and by opening the sealing covers 21 of different diffusion tubes 2, the diffusion rate adjustment range of the diffusion tube combinations 1 to 5 of Example 2 can be achieved as shown in Table 2.

[0030] Table 2 Diffusion rate adjustment range of Example 2 From Table 1 and Table 2, the diffusion cell of the present technical solution achieves a relatively large diffusion rate adjustment range.

[0031] Example 3 See Figure 6 、 Figure 7 An adjustable diffusion cell for dynamic gas distribution by diffusion method includes a liquid storage tank 1 and two diffusion tubes 2 connected to the gas phase space of the liquid storage tank 1. The structure of the liquid storage tank 1 is the same as that of Example 1. The two diffusion tubes 2 are numbered diffusion tube 1 and diffusion tube 2 respectively. Diffusion tube 1 and diffusion tube 2 have different inner diameters. The outlets of diffusion tube 1 and diffusion tube 2 are a plurality of side holes 3 opened at different heights on the side wall to connect to the diffusion tube cavity 21. The side holes 3 are equipped with sealing members 4 for controlling the connection of the cavity 21 to the outside world. By opening the side holes 3 at different heights, the effective lengths of diffusion tube 1 and diffusion tube 2 can be finely adjusted. The opening positions of the side holes are determined according to the following formula 1: qm-diffusion rate g / min; D-diffusion coefficient m2 / s; S-capillary cross-sectional area m2; M-target molecular weight g / mol; l- capillary length m; ew-saturated vapor pressure Pa; R-gas constant J / (kg·K); T-diffusion cell temperature K.

[0032] Taking water diffusion as an example, the above-mentioned diffusion cell is used to perform dynamic gas distribution by diffusion method, and by opening the side holes 3 at different heights, the diffusion tube 1 and the diffusion tube 2 of Example 3 can achieve the diffusion rate adjustment range shown in Table 3 and Table 4.

[0033] Table 3 Example 3 diffusion tube diffusion rate adjustment range Table 4: Diffusion rate adjustment range of the second diffusion tube in Example 3 From Tables 3 and 4, the diffusion cell of the present technical solution achieves a relatively large diffusion rate adjustment range through a single tube, with a more precise control level and more efficient regulation.

[0034] Example 4 See Figure 9-12 An adjustable diffusion cell for dynamic gas distribution by diffusion method comprises a liquid storage tank 1 and a diffusion tube 2 having the same parameters as those in Example 3, except that the outlets on the first and second diffusion tubes are vertical slots 5 provided on the side walls of the diffusion tubes 2; The lower end of the vertical slot 5 is connected to the inner cavity 21 of the diffuser 2, and the cross-sectional area of ​​the vertical slot 5 is the same as the cross-sectional area of ​​the inner cavity 21 of the diffuser 2; An adjusting sleeve 6 is rotatably mounted on the outer wall of the diffuser 2 to cover the vertical slot 5. A spiral strip-shaped through hole 61 is opened on the tube wall of the adjusting sleeve 6 covering the vertical slot 5, wherein the spacing between the two ends of the strip-shaped through hole 61 is greater than the length of the vertical slot 5. The rotation angle of the strip-shaped through hole 61 set on the adjusting sleeve 6 does not exceed 360°, and the opening area formed by the overlapping area of ​​the strip-shaped through hole 61 and the vertical slot 5 is the same as the cross-sectional area of ​​the inner cavity 21 of the diffuser 2.

[0035] Taking water diffusion as an example, the above-mentioned diffusion cell is used for dynamic gas distribution by diffusion method. The effective length of the diffusion tube 2 is adjusted by rotating the opening position formed by the overlapping area of ​​the strip through hole 61 of the adjustment sleeve 6 and the vertical slot 5. The diffusion tube 1 and the diffusion tube 2 of Example 4 can achieve any diffusion rate between the endpoint values ​​shown in Table 3 and Table 4 of Example 3, that is, accurate control of any diffusion rate between 5.3530μg·min⁻¹-147.21μg·min⁻¹ and any combination of any two groups of diffusion rates between 5.3530μg·min⁻¹-29.441μg·min⁻¹ and 29.441μg·min⁻¹-147.21μg·min⁻¹. The control range and magnitude are more refined, and the adjustment is more efficient.

[0036] Example 5 See Figure 4 、 Figure 13, an adjustable diffusion cell for dynamic gas distribution by diffusion method, comprising a liquid storage tank 1 and a diffusion tube 2 connected to the gas phase space of the liquid storage tank 1. The volume of the liquid storage tank 1 is the same as that of Example 1. Five connecting pieces 12 for fixing the diffusion tube 2 are provided on the tank body. The connecting pieces 12 are tubular and integrally formed with the liquid storage tank 1. The inner diameters of the tube lumens of the connecting pieces 12 are all the same and are connected to the internal space of the liquid storage tank 1. The lower end of the inner wall of the tube lumen of each connecting piece 12 is provided with a limit platform 13; The diffusion tube 2 is detachably mounted on the liquid storage tank 1 through the connector 12. The diffusion tube 2 is any five diffusion tubes selected from Examples 1-4, and the outer diameter of the tube cavity of the connector 12 is set to match. The five diffusion tubes are inserted into the tube cavity of the connector 12 and contact the limit platform 13, and are sealed by the sealing rubber ring 23 set on the outer wall of the diffusion tube 2. The diffusion pool structure of Example 5 can flexibly adjust the diffusion tube 2 of the required specifications for installation according to the gas distribution requirements to achieve diffusion rate adjustment with different ranges and different degrees of precision.

[0037] Example 6 When preparing an ester compound with a boiling point of approximately 180°C, due to its high boiling point, its diffusion rate in a diffusion cell with an inner diameter of 20 mm and a length of 60 mm was calculated to be only approximately 2 μg / min, at a cell temperature of approximately 45°C. The target diffusion rate was 5 μg / min, and to maintain the performance of the diffusion tubes, increasing the inner diameter was no longer feasible. To achieve the target diffusion rate, any of the diffusion cells in Examples 1-4 was used, and the target diffusion rate was achieved by increasing the number of diffusion tubes 2 and adjusting the effective length of each diffusion tube 2, as shown in Table 5.

[0038] Table 5 Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. An adjustable diffusion cell for dynamic gas distribution by diffusion method, characterized by: The invention comprises a liquid storage tank (1) and at least two diffusion tubes (2) connected to the gas phase space of the liquid storage tank (1), wherein the liquid storage tank (1) is provided with a sample addition port (11), and an outlet of an inner cavity (21) of the diffusion tube (2) is provided with a detachable sealing member (4), and each diffusion tube (2) on the liquid storage tank (1) is configured to have an unequal length or inner diameter, and step-type diffusion rate adjustment is achieved by opening different combinations of the diffusion tubes (2).

2. The adjustable diffusion cell for dynamic gas distribution by diffusion method according to claim 1, characterized in that: The tank body of the liquid storage tank (1) is provided with a plurality of connecting pieces (12) for fixing the diffusion tube (2), and the diffusion tube (2) is detachably mounted on the liquid storage tank (1) via the connecting pieces (12).

3. The adjustable diffusion cell for dynamic gas distribution by diffusion method according to claim 1, characterized in that: The outlet of the diffusion tube (2) is a plurality of side holes (3) opened at different heights on the side wall of the diffusion tube (2) and communicating with the inner cavity (21) of the diffusion tube (2). A sealing member (4) is installed on the side hole (3). By opening the side holes (3) at different heights on the diffusion tube (2), the effective length of the diffusion tube (2) can be adjusted.

4. The adjustable diffusion cell for dynamic gas distribution by diffusion method according to claim 1, characterized in that: The outlet of the diffuser (2) is a vertical slot (5) provided on the side wall of the diffuser (2), and the lower end of the vertical slot (5) is communicated with the inner cavity (21) of the diffuser (2); an adjusting sleeve (6) is rotatably mounted on the outer wall of the diffuser (2) to cover the vertical slot (5), and a spiral strip-shaped through hole (61) is provided on the wall of the adjusting sleeve (6) covering the vertical slot (5); the effective length of the diffuser (2) is adjusted by rotating the opening position formed by the overlapping area of ​​the strip-shaped through hole (61) of the adjusting sleeve (6) and the vertical slot (5).

5. The adjustable diffusion cell for dynamic gas distribution by diffusion method according to claim 4, characterized in that: The distance between the two ends of the strip-shaped through hole (61) is greater than the length of the vertical notch (5), and the rotation angle of the strip-shaped through hole (61) on the adjustment sleeve (6) does not exceed 360°.

6. The adjustable diffusion cell for dynamic gas distribution by diffusion method according to claim 2, characterized in that: The connecting piece (12) is tubular and is integrally formed with the liquid storage tank (1). The inner diameters of the tube lumens of the connecting piece (12) are all the same and are communicated with the internal space of the liquid storage tank (1). The lower end of the inner wall of the tube lumen of each connecting piece (12) is provided with a limit platform (13); the outer diameters of the diffuser tubes (2) are all the same. The diffuser tubes (2) can be inserted into the tube lumen of the connecting piece (12) and abut against the limit platform (13). A sealing rubber ring (22) is provided on the outer wall of the tube section of the diffuser tube (2) inserted into the connecting piece (12).

7. The adjustable diffusion cell for dynamic gas distribution by diffusion method according to claim 3, characterized in that: The sealing member (4) comprises a ferrule (41) capable of engaging with the diffusion tube (2) and a rubber plug (42) fixed on the inner side of the ferrule and interference-fitted with the side hole (3).

8. The adjustable diffusion cell for dynamic gas distribution by diffusion method according to claim 2, characterized in that: The tank body of the liquid storage tank (1) comprises a threaded upper cover and a liquid tank, the connecting piece (12) is arranged on the upper cover, and the open opening where the liquid tank is connected to the upper cover is a sample addition port (11).

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