Water vapor calibration device and method

Abstract

The present application belongs to the field of spectrum technology, and particularly relates to a water vapor calibration device and method. The device comprises a water vapor generating unit and an adjusting unit. The adjusting unit comprises: a cavity which is separated into a first part and a second part by a permeable membrane, the first part is connected to the water vapor generating unit and a calibration instrument, the permeable membrane only allows water molecules to pass through and has a through hole; a delivery pump connected to the second part, a sensor for obtaining the pressure in the second part; and a control module for adjusting the operation of the delivery pump so that the water vapor content C A meets the requirements. The present application has the advantages of automation and high precision, and is applied in the calibration of gas analysis instruments.

Description

Technical Field

[0001] This invention relates to the field of spectroscopy, and particularly to a water vapor calibration device and method. Background Technology

[0002] Products such as infrared gas analyzers require regular calibration of water vapor to ensure measurement accuracy. However, for some outdoor gas monitoring and analysis instruments, due to limitations, it is impossible to move the bulky and expensive dew point generators from the laboratory to the field for humidity calibration, and traditional dew point generators cannot obtain water vapor concentrations with dew point values ​​below 0°C.

[0003] Currently, some literature uses a bubbling method combined with gas mixing to solve this problem. This involves passing standard gas into water and bubbling it to obtain a high-humidity standard gas, which is then mixed with zero gas at different flow rates to obtain standard gases with different water vapor contents. The actual water vapor concentration is calculated from the dry and wet standard gas concentrations measured by the instrument, and this water vapor concentration is used to perform water vapor linearity calibration on the instrument. While this method can obtain standard gas with low water vapor concentrations, it also has the following problems:

[0004] 1. A small amount of the components in the standard gas will be absorbed by water, resulting in inaccurate standard gas concentration, which in turn leads to inaccurate calculated water vapor concentration;

[0005] 2. Bubbling can remove heat, causing temperature fluctuations, and there are also problems such as uneven bubble size distribution, which makes the water vapor concentration unstable and the linearity of water vapor concentration obtained by gas mixing is not high.

[0006] 3. The gas mixing method requires zero gas and a gas mixing instrument, which results in a large overall equipment size, complicated operation, and difficulty in portability. Summary of the Invention

[0007] To address the shortcomings of the existing technical solutions, the present invention provides a water vapor calibration device.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] A water vapor calibration device includes a water vapor generating unit; the water vapor calibration device further includes an adjustment unit, the adjustment unit comprising:

[0010] The cavity and the permeable membrane, wherein the interior of the cavity is separated into a first part and a second part by the permeable membrane, the first part is connected to the water vapor generating unit and the instrument to be calibrated, and the permeable membrane only allows water molecules to pass through and has through holes;

[0011] A delivery pump and a sensor, the delivery pump being connected to the second part, and the sensor being used to obtain the pressure within the second part;

[0012] The control module is used to adjust the operation of the delivery pump so that the water vapor content C delivered to the instrument to be calibrated is... A The requirements are met.

[0013] The present invention also aims to provide a water vapor calibration method, which is achieved through the following technical solution.

[0014] The water vapor calibration method includes the following steps:

[0015] A1. The water vapor generated by the water vapor generating unit enters the first part of the cavity, water molecules enter the second part of the cavity through the permeation membrane, and gas enters the second part through the through-holes of the permeation membrane.

[0016] A2. The delivery pump is turned on, the gas in the second section is discharged, and the pressure in the second section changes; the sensor obtains the pressure in the second section.

[0017] The water vapor content C sent from the first part to the instrument to be calibrated A The requirements are met.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] 1. A humidity inverse calculation method is used to achieve water vapor calibration without the need for a quantitative humidity value;

[0020] 2. The water vapor calibration process is divided into two stages, each of which can be controlled independently, allowing for better control of water vapor concentration;

[0021] In the first stage (corresponding to step A1 of the method), the water vapor concentration is reduced uniformly by increasing the mass transfer resistance of water molecules.

[0022] In the second stage (corresponding to step A2 of the method), the water vapor concentration decreases approximately linearly through precise pressure control.

[0023] 3. A longer water vapor descent time and a more uniform descent rate result in more fitting points and more accurate calibration.

[0024] 4. The entire device is highly integrated, relatively compact, and easy to use and carry. Attached Figure Description

[0025] The disclosure of this invention will become more readily understood with reference to the accompanying drawings. It will be readily understood by those skilled in the art that these drawings are merely illustrative of the technical solutions of this invention and are not intended to limit the scope of protection of this invention. In the drawings:

[0026] Figure 1 This is a schematic diagram of the water vapor calibration device of the present invention;

[0027] Figure 2 This is a schematic diagram of the cavity structure of the present invention;

[0028] Figure 3 This is a schematic diagram of the structure of the first part of the present invention;

[0029] Figure 4 This is a graph showing the change in water vapor concentration in Embodiment 2 of the present invention;

[0030] Figure 5 This is a graph showing the change in water vapor concentration in Embodiment 3 of the present invention;

[0031] Figure 6 This is a graph showing the change in water vapor concentration in Embodiment 4 of the present invention.

[0032] In the attached diagram, 1-container, 2-peristaltic pump, 3-water tank, 4-permeable membrane, 5-cavity, 6-first part, 7-second part, 8-sensor, 9-transfer pump, 10-insulation box, 11-insulation pipe, 12-instrument to be calibrated, 51-guide plate, 52-through hole, 53-first end, 54-second end. Detailed Implementation

[0033] Figures 1-6 The following description illustrates optional embodiments of the invention to teach those skilled in the art how to implement and reproduce the invention. Some conventional aspects have been simplified or omitted to teach the technical solutions of the invention. Those skilled in the art should understand that variations or substitutions derived from these embodiments will be within the scope of the invention. Those skilled in the art should understand that the following features can be combined in various ways to form multiple variations of the invention. Therefore, the invention is not limited to the optional embodiments described below, but is defined only by the claims and their equivalents.

[0034] Example 1.

[0035] This embodiment provides a water vapor calibration device, such as... Figure 1 As shown, the device includes:

[0036] Water vapor generation unit.

[0037] like Figure 2 As shown, the adjustment unit includes:

[0038] The cavity 5 is divided into a first part 6 and a second part 7 by a permeation membrane 4. The first part 6 is connected to the water vapor generating unit and the instrument to be calibrated 12. The permeation membrane 4 only allows water molecules to pass through and has through holes 52.

[0039] The delivery pump 9 is connected to the second part 7, and the sensor 8 is used to obtain the pressure within the second part 7.

[0040] The control module is used to adjust the operation of the delivery pump 9 so that the water vapor content C delivered to the instrument 12 to be calibrated is adjusted. A The requirements are met.

[0041] To accommodate instrument calibration, the requirement is further specified as a water vapor content C. A It decreases linearly, such as C A =K·e [mt / (mt-K)] .

[0042] Under the operation of the delivery pump 9, the output value P of the sensor 8 B satisfy:

[0043] P B =P A ·[1-SQRT(m·d 2 / (D·(Km·t)))],P A is the pressure within the first part 6, m is the absolute value of the derivative of the water vapor concentration with time t, d is the thickness of the permeation membrane, K is the water vapor concentration within the first part 6 at t=0, and D is the diffusion coefficient of the permeation membrane 4.

[0044] To further improve the accuracy of water vapor concentration control, such as... Figure 2 As shown, the water vapor generating unit and the delivery pump 9 are connected to the first end 53 of the cavity 5, and the instrument to be calibrated 12 is connected to the second end 54 of the cavity 5, which is opposite to the first end 53. The through hole 52 is adjacent to the second end 54.

[0045] To further improve the accuracy of water vapor concentration control, such as... Figure 3 As shown, multiple guide vanes 51 are provided in the first part 6, and the gas flows in an S-shape within the first part 6.

[0046] To provide water vapor, further, such as Figure 1 As shown, the water vapor generating unit includes:

[0047] The adsorbent material is filled in container 1 to adsorb moisture, but does not adsorb the detection gas of the instrument 12 to be calibrated.

[0048] The container 1 has a liquid water inlet, a standard gas inlet, and a water vapor outlet.

[0049] To further improve the accuracy of water vapor concentration control, the ratio of the flow rate sent to the instrument to be calibrated 12 to the flow rate at the through-hole 52 is 2.

[0050] The water vapor calibration method of this invention includes the following steps:

[0051] A1. The water vapor generated by the water vapor generating unit enters the first part 6 of the cavity 5, the water molecules enter the second part 7 of the cavity 5 through the permeation membrane 4, and the gas enters the second part 7 through the through hole 52 of the permeation membrane 4.

[0052] A2. When the delivery pump 9 is turned on, the gas in the second section 7 is discharged, and the pressure in the second section 7 changes; the sensor 8 obtains the pressure in the second section.

[0053] The water vapor content C sent from Part 1, 6 to instrument 12 to be calibrated. A The requirements are met.

[0054] To accommodate instrument calibration, the requirement is further specified as a water vapor content C. A It decreases linearly, such as C A =K·e [mt / (mt-K)] .

[0055] Under the operation of the delivery pump 9, the output value P of the sensor 8 B satisfy:

[0056] P B =P A ·[1-SQRT(m·d 2 / (D·(Km·t)))],P A Here, is the pressure within the first part 6 (in kPa), m is the absolute value of the derivative of the water vapor concentration with time t, d is the thickness of the permeable membrane 4 (in meters), K is the water vapor concentration within the first part 6 at t=0, and D is the diffusion coefficient of the permeable membrane 4 (in meters). 2 / s).

[0057] Example 2.

[0058] An application example of the water vapor calibration device and method in Embodiment 1 of the present invention.

[0059] In this application example, the analyzer measures a wide range of water vapor, and the water vapor needs to show an approximately decreasing trend over a wide humidity range.

[0060] As required, in the second stage of water vapor calibration, a relatively large initial concentration of 2% (20000ppm) is taken. That is, when the water vapor concentration drops to 2%, the delivery pump 9 (using a vacuum pump) is turned on for pressure regulation.

[0061] like Figure 1As shown, water tank 3 is connected to container 1 via peristaltic pump 2. A weakly polar porous material (such as resin) fills container 1, which has a certain adsorption capacity for water but no adsorption for the components measured by the analyzer (such as CO2, CH4, etc.). The liquid water inlet and water vapor outlet are located at the upper end of container 1, and the standard gas inlet is located at the lower end of container 1. The water vapor generation unit and adjustment unit are located inside the insulation box 10. The water vapor output from the adjustment unit is connected to the instrument to be calibrated 12 via insulation pipe 11.

[0062] like Figure 2 As shown, the water vapor generating unit and the delivery pump 9 are connected to the first end 53 of the cavity 5, and the instrument to be calibrated 12 is connected to the second end 54 of the cavity 5, which is opposite to the first end 53. The through hole 52 is adjacent to the second end 54.

[0063] like Figure 3 As shown, multiple guide vanes 51 are provided in the first part 6, and the gas flows in an S-shape within the first part 6.

[0064] P A =101.325 kPa, d=0.001 m, D=1×10⁻⁶ for membrane 4 -9 m 2 / s, the diameter of the through hole 52 is 0.1mm, K=20000ppm, m=3, that is, when the humidity is 5000ppm, the transfer pump 9 (adjustable speed vacuum pump) starts to work, and the humidity decrease slope is -3.

[0065] Part 2, Section 7: Internal Pressure P B =101.35·[1-SQRT(3000 / (10 -9 ·(20000-3t)))], that is, through the negative feedback of pressure sensor 8, the speed of delivery pump 9 is adjusted so that the pressure P of the second part is increased. B As time changes, it satisfies the above equation, such that:

[0066] Water vapor concentration C sent to instrument 12 to be calibrated A =20000·e [3t / (3t-20000)] The corresponding water vapor concentration curve is as follows: Figure 4 As shown, its linearity is relatively high over a larger range.

[0067] During operation, the ratio of the flow rate sent to the instrument to be calibrated 12 to the flow rate at the through-hole 52 is 2.

[0068] Example 3.

[0069] An application example of the water vapor calibration device and method in Embodiment 1 of the present invention.

[0070] In this application example, an outdoor analytical device requires water vapor calibration, and due to time constraints, the calibration needs to be completed in a shorter period of time. Based on this requirement, the water vapor descent rate (m) can be increased to allow the water vapor concentration to decrease more quickly.

[0071] like Figure 1 As shown, water tank 3 is connected to container 1 via peristaltic pump 2. A weakly polar porous material (such as resin) fills container 1, which has a certain adsorption capacity for water but no adsorption for the components measured by the analytical equipment. The liquid water inlet and water vapor outlet are located at the upper end of container 1, and the standard gas inlet is located at the lower end of container 1. The water vapor generation unit and adjustment unit are located inside the insulation box 10. The water vapor output from the adjustment unit is connected to the instrument to be calibrated 12 via insulation pipe 11.

[0072] like Figure 2 As shown, the water vapor generating unit and the delivery pump 9 are connected to the first end 53 of the cavity 5, and the instrument to be calibrated 12 is connected to the second end 54 of the cavity 5, which is opposite to the first end 53. The through hole 52 is adjacent to the second end 54.

[0073] like Figure 3 As shown, multiple guide vanes 51 are provided in the first part 6, and the gas flows in an S-shape within the first part 6.

[0074] P A =101.325kpa, d=0.001m, D=1×10 -9 m 2 / s, the aperture of through-hole 52 is 0.15mm, let K=20000ppm, m=10, then the rate of decrease of water vapor concentration at this time is:

[0075] C A =20000·e [t / (t-2000)] The corresponding water vapor concentration curve is as follows: Figure 5 As shown, under these conditions, the rate of water vapor descent is greatly accelerated, and the calibration time is greatly shortened.

[0076] Part 2, Section 7: Internal Pressure P B =101.35·[1-SQRT(1000 / (2000-t))].

[0077] During operation, the ratio of the flow rate sent to the instrument to be calibrated 12 to the flow rate at the through-hole 52 is 2.

[0078] Example 4.

[0079] An application example of the water vapor calibration device and method in Embodiment 1 of the present invention.

[0080] In this application example, a certain analyzer experiences significant interference from water vapor in other measured gases when the water vapor concentration is low. Therefore, it is desirable to achieve more accurate water vapor measurement and compensation results at low concentrations. Consequently, a slower water vapor descent rate is needed at lower water vapor concentrations to obtain a more precise fitting curve. Based on this requirement, the initial water vapor concentration K can be set relatively small, and the water vapor descent rate m can also be reduced.

[0081] like Figure 1 As shown, water tank 3 is connected to container 1 via peristaltic pump 2. A weakly polar porous material (such as resin) fills container 1, which has a certain adsorption capacity for water but no adsorption for the components measured by the analyzer. The liquid water inlet and water vapor outlet are located at the upper end of container 1, and the standard gas inlet is located at the lower end of container 1. The water vapor generation unit and adjustment unit are located inside the insulation box 10. The water vapor output from the adjustment unit is connected to the instrument to be calibrated 12 via insulation pipe 11.

[0082] like Figure 2 As shown, the water vapor generating unit and the delivery pump 9 are connected to the first end 53 of the cavity 5, and the instrument to be calibrated 12 is connected to the second end 54 of the cavity 5, which is opposite to the first end 53. The through hole 52 is adjacent to the second end 54.

[0083] like Figure 3 As shown, multiple guide vanes 51 are provided in the first part 6, and the gas flows in an S-shape within the first part 6.

[0084] P A =101.325kpa, d=0.001m, D=1×10 -9 m 2 / s, the aperture of through-hole 52 is 0.2mm, let K=2000ppm, m=0.2, then the rate of decrease of water vapor concentration at this time is:

[0085] C A =20000·e [t / (t-10000)] The corresponding water vapor concentration curve is as follows: Figure 6 As shown, the rate of descent is slower when the water vapor concentration is low.

[0086] Part 2, Section 7: Internal Pressure P B =101.35·[1-SQRT(10000 / (10000-t))].

[0087] During operation, the ratio of the flow rate sent to the instrument to be calibrated 12 to the flow rate at the through-hole 52 is 2.

Claims

1. A water vapor calibration device comprising a water vapor generating unit; characterized in that, The water vapor calibration device further comprises an adjusting unit, the adjusting unit comprises: a cavity and a permeable membrane, the inside of the cavity is separated into a first part and a second part by the permeable membrane, the first part is communicated with the water vapor generating unit and the instrument to be calibrated, the permeable membrane only allows water molecules to pass through and has a through hole; a delivery pump and a sensor, the delivery pump is communicated with the second part, and the sensor is used to obtain the pressure in the second part; - a control module for adjusting the operation of the delivery pump so that the water vapor content C delivered to the instrument to be calibrated A meets the requirements, which are a water vapor content C A decreases linearly; Under the operation of the delivery pump, the output value P of the sensor B satisfies: P B = P A · [1 - SQRT(m · d 2 / (D · (K - m · t)))], P A is the pressure in the first section, m is the absolute value of the derivative of the water vapor concentration with respect to time t, d is the thickness of the permeation membrane, K is the water vapor concentration in the first section at t = 0, and D is the diffusion coefficient of the permeation membrane.

2. The water vapor calibration device of claim 1, wherein, Water vapor content C A satisfies: C A =K·e [mt / (mt-K)] .

3. The water vapor calibration device of claim 1, wherein, the water vapor generating unit and the delivery pump are communicated with the first end of the cavity, the instrument to be calibrated is communicated with the second end of the cavity which is arranged opposite to the first end, and the through hole is adjacent to the second end.

4. The water vapor calibration device of claim 3, wherein, A plurality of flow guides are arranged in the first part, and the gas flows in an S shape in the first part.

5. The water vapor calibration device of claim 1, wherein, The water vapor generating unit comprises: a container and an adsorption material, the adsorption material is filled in the container and is used to adsorb water, and has no adsorption to the detection gas of the instrument to be calibrated; the container has a liquid water inlet, a standard gas inlet and a water vapor outlet.

6. The water vapor calibration device of claim 1, wherein, The ratio of the flow rate sent to the instrument to be calibrated to the flow rate at the through hole is 2.

7. The water vapor calibration method implemented by the water vapor calibration device according to claim 1, wherein, The method comprises the following steps: A1. The water vapor generated by the water vapor generating unit enters the first part of the cavity, the water molecules enter the second part of the cavity through the permeable membrane, and the gas enters the second part through the through hole of the permeable membrane; A2. The delivery pump is started, the gas in the second part is discharged, the pressure in the second part changes, and the sensor obtains the pressure in the second part; The water vapor content C from the first part is sent to the instrument to be calibrated A The requirement is met, the water vapor content C A Decreases linearly; Under the operation of the delivery pump, the output value P of the sensor B satisfies: P B = P A · [1 - SQRT(m · d 2 / (D · (K - m · t)))], P A is the pressure in the first section, m is the absolute value of the derivative of the water vapor concentration with respect to time t, d is the thickness of the permeation membrane, K is the water vapor concentration in the first section at t = 0, and D is the diffusion coefficient of the permeation membrane.

8. The water vapor calibration method of claim 7, wherein, Water vapor content C A satisfies: C A =K·e [mt / (mt-K)] .

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