Online detection device for content of hydrogen dissolved in water

Abstract

The utility model relates to the technical field of gas detection, in particular to an on-line water dissolved hydrogen content detection device, which is characterized in that a sample of a to-be-detected dissolved hydrogen water pipeline is received by using a hollow cavity internally provided with an air bag, and the to-be-detected dissolved hydrogen is subjected to energy dissipation to normal pressure, so that the interference of pressure fluctuation of the to-be-detected water pipeline on the detection process is avoided; the dissolved hydrogen is blown off by the air pump, the hydrogen content in the gas phase is detected by the thermal conductivity sensor, the concentration of the dissolved hydrogen in the to-be-detected water is further determined, and the detection device is simple in structure, is not influenced by the water pressure of the to-be-detected pipeline, and can be used for on-line detection of more than 0.1 ppm of the dissolved hydrogen in the water.

Description

Technical Field

[0001] The invention relates to the technical field of gas detection, and in particular to an online device for detecting dissolved hydrogen content in water. Background Art

[0002] Aqueous solutions rich in hydrogen molecules are increasingly used in drinking, bathing, agricultural irrigation, breeding, etc. The existing methods for detecting dissolved hydrogen concentration mainly include OPR method, reagent titration method, headspace gas chromatography, etc. Among them, OPR method detection is only suitable for pure water systems, reagent titration method is time-consuming and labor-intensive, and online detection cannot be achieved, while gas chromatography equipment is complex and expensive. In addition, for online detection devices, another difficulty is that the water pressure range of the pipeline to be tested is large, and the pressure will greatly affect the detection accuracy and reproducibility of the thermal conductivity detector.

[0003] In view of this, the present invention provides an online detection device for the content of dissolved hydrogen in water. The device uses a hollow cavity with an air bag inside to receive samples of a water pipeline to be tested for dissolved hydrogen, and uses the air bag to connect to the atmosphere to dissipate the energy of the dissolved hydrogen to be tested to normal pressure, so as to avoid interference of pressure fluctuations in the water pipeline to be tested on the detection process, and then uses an air pump to blow off the dissolved hydrogen to achieve gas-liquid equilibrium. The thermal conductivity sensor detects the hydrogen content in the gas phase, and then determines the concentration of dissolved hydrogen in the water to be tested. The detection device has a simple structure, is not affected by the water pressure of the pipeline to be tested, and can detect dissolved hydrogen above 0.1ppm in water online. Summary of the invention

[0004] The object of the present invention is to provide an online device for detecting dissolved hydrogen content in water to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] An online device for detecting dissolved hydrogen content in water, characterized in that it comprises a hollow cavity, an air bag, a water inlet pipeline, a drainage pipeline, an exhaust pipeline and a circulation pipeline;

[0007] The airbag is installed in the hollow cavity, and the airbag is provided with an airbag interface. The airbag is connected to the outside of the airbag through and only through the airbag interface; the airbag interface is connected to the atmosphere through an exhaust pipeline, and an exhaust solenoid valve is provided on the exhaust pipeline;

[0008] Among them, the bottom of the hollow cavity is provided with a bottom interface, and the side wall is provided with a side wall interface. The hollow cavity is connected to the outside of the hollow cavity through and only through the bottom interface and the side wall interface; the side wall interface is connected to the bottom interface through a circulation pipeline, and the side wall interface is also installed with a pressure sensor; the bottom interface of the hollow cavity is connected to the water inlet pipeline, and is connected to the dissolved hydrogen water pipeline to be tested through the water inlet interface at the end of the water inlet pipeline. The bottom interface of the hollow cavity is also connected to the drainage pipeline, and is connected to the wastewater pipeline through the drainage interface at the end of the drainage pipeline; the water inlet solenoid valve and the drainage solenoid valve are respectively provided on the water inlet pipeline and the drainage pipeline;

[0009] Among them, an air pump is arranged on the circulation pipeline, and a front-pump solenoid valve and a rear-pump solenoid valve are arranged before and after the air pump respectively; the front-end circulation pipeline of the air pump and the rear-end circulation pipeline of the air pump are respectively connected to the detection cavity through the detection pipeline, the detection cavity is sealed with the circuit board, and the thermal conductivity detection module welded to the circuit board is located in the detection cavity;

[0010] Furthermore, the detection pipelines connected to the front-end circulation pipeline of the air pump and the rear-end circulation pipeline of the air pump are both provided with hydrophobic microporous filter membranes with a pore size of 0.1 μm-1 μm;

[0011] Furthermore, the circulation pipeline at the rear end of the air pump can also be connected to the exhaust pipeline through a boost pipeline, and a boost solenoid valve is also provided on the boost pipeline;

[0012] Furthermore, the front-end circulation pipeline of the air pump is connected to the side wall interface of the hollow cavity through a parallel pipeline, a buffer tank is arranged on the parallel pipeline, and a front-tank solenoid valve and a rear-tank solenoid valve are arranged on the front and rear pipelines of the buffer tank respectively.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: the device utilizes a hollow cavity with an air bag inside to receive samples of a water pipeline for dissolved hydrogen to be tested, utilizes the air bag to communicate with the atmosphere, dissipates energy of the dissolved hydrogen to be tested to normal pressure, avoids interference of pressure fluctuation of the water pipeline to be tested on the detection process, and then utilizes an air pump to blow off the dissolved hydrogen to achieve gas-liquid equilibrium, and detects the hydrogen content in the gas phase through a thermal conductivity sensor, thereby determining the concentration of dissolved hydrogen in the water to be tested. The detection device has a simple structure, is not affected by the water pressure of the pipeline to be tested, and can detect dissolved hydrogen above 0.1ppm in water online. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the process of the present invention.

[0015] Figure 2 This is the dissolved hydrogen concentration and analog signal calibration curve of the present invention.

[0016] Serial numbers in the figure: 1 hollow cavity, 2 airbag, 3 airbag interface, 4 bottom interface, 5 water inlet interface, 6 drainage interface, 7 water inlet solenoid valve, 8 drainage solenoid valve, 9 pressure sensor, 10 tank front solenoid valve, 11 pump rear solenoid valve, 12 boost pipeline, 13 exhaust solenoid valve, 14 air pump, 15 pump front solenoid valve, 17 water inlet pipeline, 18 drainage pipeline, 19 exhaust pipeline, 20 circulation pipeline, 21 boost solenoid valve, 22 side wall interface, 23 tank rear solenoid valve, 24 parallel pipeline, 25 buffer tank, 1601 microporous filter membrane, 1602 microporous filter membrane, 1603 detection cavity, 1604 thermal conductivity detection module, 1605 circuit board, 1606 detection pipeline. DETAILED DESCRIPTION

[0017] 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.

[0018] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" 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, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0019] In the description of this patent, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "set" should be understood in a broad sense. For example, it can be fixedly connected or set, or it can be detachably connected or set, or connected or set in one piece. For ordinary technicians in this field, the specific meanings of the above terms in this patent can be understood according to specific circumstances. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically limited.

[0020] See also Figure 1-Figure 2 As shown, an online device for detecting dissolved hydrogen content in water provided by the present invention is Embodiment 1:

[0021] The hollow cavity 1 is a cylindrical cavity with elliptical sealing plates at both ends, with an inner diameter of 6 cm, a total internal height of about 25 cm, and an internal volume of 600 ml; the airbag has an outer diameter of 5.5 cm, a total height of 22 cm, and a volume of 500 ml. The buffer tank is a cylindrical cavity with an inner diameter of 3 cm, a height of 10 cm, and an internal volume of 50 ml.

[0022] A bottom interface 4 is provided at the bottom of the hollow cavity 1, which is connected to the dissolved hydrogen water pipeline to be tested (not shown) through the water inlet pipeline 17, the water inlet solenoid valve 7 and the water inlet interface 5 in sequence; the bottom interface 4 at the bottom of the hollow cavity 1 is also connected to the wastewater pipeline (the wastewater pipeline is an open discharge pipeline, not shown) through the drainage pipeline 18, the drainage solenoid valve 8 and the drainage interface 6 in sequence.

[0023] A side wall interface 22 is provided on the side wall of the hollow cavity 1, which is connected to a pressure sensor 9. The side wall interface 22 is also connected to the bottom interface 4 through a circulation pipeline 20, and a front-pump solenoid valve 15, an air pump 14 and a rear-pump solenoid valve 11 are sequentially installed on the circulation pipeline 20 along the direction from the side wall interface 22 to the bottom interface 4; the circulation pipeline 20 at the front end of the air pump 14 and the rear end of the air pump 14 are connected through a 1606 detection pipeline, and a microporous filter membrane 1601 with a pore size of 0.45 μm, a detection cavity 1603 and a 1602 microporous filter membrane are sequentially connected on the 1606 detection pipeline; wherein, the detection cavity 1603 is sealed and connected to a circuit board 1605, and a thermal conductivity detection module 1604 is welded on the circuit board 1605.

[0024] The boost pipeline 12 is connected to the circulation pipeline 20 and the exhaust pipeline 19 , and the boost pipeline 12 is also provided with a boost solenoid valve 21 .

[0025] An airbag interface 3 is provided on the top of the airbag 2, which is connected to the atmosphere through an exhaust pipe 19, and an exhaust solenoid valve 13 is also provided on the exhaust pipe 19.

[0026] The front circulation pipeline 20 of the air pump is connected to the side wall interface 22 of the hollow cavity 1 through a parallel pipeline 24. A buffer tank 25 is arranged on the parallel pipeline. A front solenoid valve 10 and a rear solenoid valve 23 are arranged on the front and rear pipelines of the buffer tank respectively.

[0027] The entire system is powered and controlled by a main control board (not shown).

[0028] The device can use manual sampling or timed sampling mode to perform online detection of the dissolved hydrogen water in the dissolved hydrogen water pipeline to be tested; when detection is required, all solenoid valves are in a closed state, the water inlet solenoid valve 7 is opened, and the water to be tested enters the hollow cavity 1 through the water inlet interface 5, the water inlet pipeline 17, the water inlet solenoid valve 7 and the bottom interface 4 in sequence. When the reading of the pressure sensor 9 no longer changes, the surface hollow cavity 1, the airbag 2 and the dissolved hydrogen water pipeline to be tested reach pressure balance. At this time, the pressure sensor 9 reads 3 bar (gauge pressure), indicating that the pressure of the dissolved hydrogen water pipeline to be tested is 3 bar (gauge pressure). Close the water inlet solenoid valve 7.

[0029] Since the volume V in the hollow cavity 1 is T0 600ml, including 2 air bags with volume V B0 500ml is the volume V0 of the space between the hollow cavity 1 and the airbag 2, and 100ml is the volume V0 of the space between the hollow cavity 1 and the airbag 2. When the dissolved hydrogen water to be tested is not filled, the pressure inside the hollow cavity 1 and the airbag 2 is normal pressure, that is, the absolute pressure is 1 bar, and the volume occupied by the original air is V A = V0; after filling with dissolved hydrogen water to be tested, the pressure becomes 4 bar (absolute pressure), V B0 Reduce to 125ml, V A reduced to 25ml, V0 increased to 475ml, and

[0030] V0=V A +V G0 +V L ;(1)1

[0031] V G0 =V H0 +V N0 (2)

[0032] Among them, V L is the total volume of the liquid to be measured in the V0 space after the water inlet solenoid valve 7 is closed, V G0 is the total volume of dissolved gas released from the liquid to be tested in the space V0 after the water inlet solenoid valve 7 is closed, which is equal to the original volume of dissolved hydrogen released from the liquid to be tested in the space V0 after the water inlet solenoid valve 7 is closed. H0 After the water inlet solenoid valve 7 is closed, the volume V of the original dissolved non-hydrogen gas released from the liquid to be tested in the space V0 is N0 The sum of the two;

[0033] For hydrogen dissolved water under normal conditions, the dissolved gases other than hydrogen in the water are mostly nitrogen and oxygen (carbon dioxide is negligible, and excessive carbon dioxide will interfere with the detection process of this device). The saturated gas content of the gas under 4 bar (absolute pressure) does not exceed 12%. At the same time, when the hydrogen dissolved water to be tested is injected into the V0 space, the maximum pressure difference is the initial pressure difference, that is, 3 bar, and the duration is very short. Even if all the dissolved gases are released, their value will not exceed 9% of the liquid volume. At 4 bar (absolute pressure), their volume will not exceed 2.25% of the liquid volume, that is, V G0 <2.25%*V L， Actual measurements show that V G0 <1%V L，

[0034] Therefore, equation 1 can be simplified (also applicable under other pressure conditions) as follows:

[0035] V0=V A +V L (3)

[0036] That is V L It is 450ml.

[0037] Open the exhaust solenoid valve 13, the airbag 2 is connected to the atmosphere, and the compressed gas in the airbag 2 is discharged into the atmosphere through the airbag interface 3, the exhaust pipeline and the exhaust solenoid valve 13 in sequence. Due to the pressure in V0, the airbag 2 is further compressed until the pressure in V0 is balanced with the atmospheric pressure. This value depends only on the atmospheric pressure and the elastic modulus of the airbag 2. For a very soft silicone airbag, it can be approximately equal to the atmospheric pressure. Therefore, it can be ensured that each time the gas concentration is detected, the pressure of the gas to be tested is at normal pressure, avoiding the interference of pressure changes on the thermal conductivity detector.

[0038] When the pressure sensor 9 drops to atmospheric pressure, the front-pump solenoid valve 15, the air pump 14 and the rear-pump solenoid valve 11 are opened, and the air pump 14 extracts the gas at the top between the hollow cavity 1 and the airbag 2 through the side wall interface 22, and passes through the circulation pipeline 20 to the bottom interface 4, and returns to below the liquid level of the dissolved hydrogen water to be tested between the hollow cavity 1 and the airbag 2. The above-mentioned "aeration" process is used to achieve full mixing of gas and liquid, and the hydrogen dissolved in the dissolved hydrogen water to be tested is continuously released into the gas at the top between the hollow cavity 1 and the airbag 2. Since the airbag 2 is connected to the atmosphere, the pressure in V0 always remains at atmospheric pressure during this process.

[0039] There is a pressure difference before and after the air pump 14, and because the gas resistance of the microporous filter membrane 1601 and the microporous filter membrane 1602 is relatively large, only a small amount of gas in the circulation pipeline 20 passes through the microporous filter membrane 1602 into the detection cavity 1603, and then returns to the circulation pipeline 20 through the microporous filter membrane 1601. The weak gas flow can achieve gas balance in the detection cavity 1603 and the circulation pipeline 20; the thermal conductivity detection module 1604 located in the detection cavity 1603 converts the thermal conductivity value of the gas into an analog signal corresponding to the gas phase hydrogen concentration and transmits it to the circuit board 1605. When the signal is stable, it can be considered that the gas-liquid two phases in the hollow cavity 1 and the airbag 2 are balanced. The circuit board 1605 transmits the signal to the main control board, and the main control converts it into a dissolved hydrogen concentration value according to the calculation formula:

[0040] When the mV signal value measured by the thermal conductivity detection module 1604 is stable at -300 mV, according to the calibration curve mv value = -22.38*hydrogen content%-4.4245, it is converted into the gas phase hydrogen volume concentration C in V0. HG1 13.2%:

[0041] C HG1 =V HG1 / (V HG1 +V NG1 +V A )(4)

[0042] That is, 13.2% = V HG1 / (V HG1 +V NG1 +100)(5)

[0043] Among them, V HG1 is the volume of hydrogen released from the dissolved hydrogen water sample to be tested and enters the V0 gas phase, V NG It is the volume of non-hydrogen gas released from the dissolved hydrogen water sample to be tested and enters the V0 gas phase.

[0044] At the same time, under this equilibrium condition, the volume content of hydrogen in the gas phase V HG1 and the volume of hydrogen dissolved in water V HL1 The content should satisfy Henry's law, that is

[0045] V HL1 =k*P HG1 *V L (6)

[0046] P HG1 =C HG1 (7)

[0047] V HT =V HG1 +V HL1(8)

[0048] Among them, V HT is the total volume of gas phase and dissolved hydrogen in V0, k is the hydrogen solubility constant, P HG1 is the gas phase partial pressure of hydrogen in V0. Since the solubility of hydrogen is 17.7 ml / L, V L is 0.45L, so equations (6), (7) and (8) can be combined and rewritten as:

[0049] V HG1 =V HT -8*C HG1 (9)

[0050] Substituting formula (9) into formula (5), we can obtain:

[0051] C HG1 =(V HT -8*C HG1 ) / (V HT -8*C HG1 +V NG1 +V A )(10)

[0052] The C HG1 Afterwards, the front solenoid valve 15 of the pump is closed, and the front solenoid valve 10 of the tank and the rear solenoid valve 23 of the tank are opened, so that the buffer tank 25 is connected with the hollow cavity 1 through the parallel pipeline 24 and the side wall interface 22 in sequence.

[0053] As above, when the mV signal value measured by the thermal conductivity detection module 1604 is stable at -197mV, according to the calibration curve mv value = 22.38*hydrogen content%-4.4245, it is converted into the gas phase hydrogen volume concentration C in V0. HG2 8.8%:

[0054] C HG2 =V HG2 / (V HG2 +V NG2 +V A +V D )(11)

[0055] C HG2 =(V HT -8*C HG2 ) / (V HT -8*C HG2 +V NG2 +V A +V D )(13)

[0056] Among them, V D The volume of the buffer tank is 50 ml. To simplify the calculation, VNG1 and V NG2 Equal (in actual testing, it was found that the numerical error obtained by this method is small). Equations (10) and (13) are combined into a linear equation system, and V is obtained by solving HT It is 13.1ml, that is, the dissolved hydrogen content in the water to be tested is 2.62mg / L, and the signal is transmitted to the terminal device through the main electronic control board.

[0057] After completing the current detection, close the solenoid valve 10 in front of the tank, the solenoid valve 11 in the back of the pump and the air pump 14, open the drain solenoid valve 8, and the dissolved hydrogen water in the hollow cavity 1 is discharged into the wastewater pipeline through the drain pipe 18, the drain solenoid valve 8 and the drain interface 6 in turn. After 10 seconds, the drainage is completed, open the solenoid valve 10 in front of the tank, the solenoid valve 23 in the back of the tank, the solenoid valve 15 in front of the pump, the air pump 14, the boost solenoid valve 21 and the exhaust solenoid valve 13, and the atmosphere in the open wastewater pipeline enters the hollow cavity 1 through the drain pipe 18, and then is discharged through the circulation pipe 20 and the parallel pipe 24, the boost pipe 12, and the exhaust pipe 19, thereby completing the replacement of hydrogen in the above-mentioned pipes and the hollow cavity.

[0058] After completing the above operations, all solenoid valves are closed and wait for the next test.

[0059] Compared with the prior art, the beneficial effects of the present invention are as follows: the device utilizes a hollow cavity with an air bag inside to receive samples of a water pipeline for dissolved hydrogen to be tested, utilizes the air bag to communicate with the atmosphere, dissipates energy of the dissolved hydrogen to be tested to normal pressure, avoids interference of pressure fluctuation of the water pipeline to be tested on the detection process, and then utilizes an air pump to blow off the dissolved hydrogen to achieve gas-liquid equilibrium, and detects the hydrogen content in the gas phase through a thermal conductivity sensor, thereby determining the concentration of dissolved hydrogen in the water to be tested. The detection device has a simple structure, is not affected by the water pressure of the pipeline to be tested, and can detect dissolved hydrogen above 0.1ppm in water online.

[0060] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. An online device for detecting dissolved hydrogen content in water, characterized in that: It includes a hollow cavity, an air bag, a water inlet pipeline, a drainage pipeline, an exhaust pipeline and a circulation pipeline; The airbag is installed in the hollow cavity, and the airbag is provided with an airbag interface. The airbag is connected to the outside of the airbag through and only through the airbag interface; the airbag interface is connected to the atmosphere through an exhaust pipeline, and an exhaust solenoid valve is provided on the exhaust pipeline; Among them, the bottom of the hollow cavity is provided with a bottom interface, and the side wall is provided with a side wall interface. The hollow cavity is connected to the outside of the hollow cavity through and only through the bottom interface and the side wall interface; the side wall interface is connected to the bottom interface through a circulation pipeline, and the side wall interface is also installed with a pressure sensor; the bottom interface of the hollow cavity is connected to the water inlet pipeline, and is connected to the dissolved hydrogen water pipeline to be tested through the water inlet interface at the end of the water inlet pipeline. The bottom interface of the hollow cavity is also connected to the drainage pipeline, and is connected to the wastewater pipeline through the drainage interface at the end of the drainage pipeline; the water inlet solenoid valve and the drainage solenoid valve are respectively provided on the water inlet pipeline and the drainage pipeline; Among them, an air pump is provided on the circulation pipeline, and a front-pump solenoid valve and a rear-pump solenoid valve are respectively provided before and after the air pump; the circulation pipeline at the front end of the air pump and the circulation pipeline at the rear end of the air pump are respectively connected to the detection cavity through the detection pipeline, the detection cavity is sealed with the circuit board, and the thermal conductivity detection module welded to the circuit board is located in the detection cavity.

2. The online device for detecting dissolved hydrogen content in water according to claim 1, characterized in that: The detection pipelines connected to the front-end circulation pipeline of the air pump and the rear-end circulation pipeline of the air pump are both provided with hydrophobic microporous filter membranes with a pore size of 0.1 μm-1 μm.

3. The online device for detecting dissolved hydrogen content in water according to claim 1, characterized in that: The circulation pipeline at the rear end of the air pump can also be connected to the exhaust pipeline through a boost pipeline, and a boost solenoid valve is also provided on the boost pipeline.

4. The online device for detecting dissolved hydrogen content in water according to claim 1, characterized in that: The front circulation pipeline of the air pump is connected to the side wall interface of the hollow cavity through a parallel pipeline. A buffer tank is arranged on the parallel pipeline. A front solenoid valve and a rear solenoid valve are arranged on the front and rear pipelines of the buffer tank respectively.

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