Thermal balance para hydrogen concentration measurement method and device based on specific enthalpy difference analysis

Abstract

The application discloses a kind of heat balance secondary hydrogen concentration measurement method and device based on specific enthalpy difference analysis, to solve the technical problems that existing measurement method is difficult to meet the whole process of low-temperature hydrogen energy industry chain Each link secondary hydrogen measurement measurement demand.The measurement method of the application is: 1) connect heating channel on the gas path to be measured;2) measure the mass flow, temperature and pressure of sample hydrogen at the inlet of heating channel;3) heat the sample hydrogen in the heating channel with known heat power;4) measure the temperature and pressure of sample hydrogen at the outlet of heating channel;5) based on the measurement results of 2) and 4), the concentration of secondary hydrogen in sample hydrogen is obtained by specific enthalpy difference analysis and heat balance calculation.The principle of the method is simple and reliable, easy to implement and operate, low in cost, high in feasibility, fast in response and wide in application, and can meet the requirements of continuous and accurate measurement of secondary hydrogen concentration under most working conditions of low-temperature hydrogen energy industry chain.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of low-temperature gas composition measurement, and particularly relates to a heat balance para-hydrogen concentration measurement method and device based on specific enthalpy difference analysis. BACKGROUND

[0002] Due to the difference in the spin direction of atomic nuclei, there are two forms of hydrogen molecules, i.e., ortho-hydrogen (with the same spin direction) and para-hydrogen (with opposite spin directions). At normal temperature, the para-hydrogen concentration of equilibrium hydrogen is about 25%, and such hydrogen is also called normal hydrogen. At low temperature, the para-hydrogen concentration of equilibrium hydrogen increases with the decrease of temperature, and when the temperature reaches the hydrogen liquefaction temperature, the para-hydrogen concentration of equilibrium hydrogen is about 99%. The spin isomerization reaction in hydrogen occurring with the change of temperature has a certain heat effect, and the conversion of ortho-para hydrogen releases heat, and the conversion of para-ortho hydrogen absorbs heat. Such heat effect makes the spin isomerization reaction of hydrogen an important factor that cannot be ignored in the process design of hydrogen liquefaction, liquid hydrogen storage and transportation and other key hydrogen energy industry chains. Therefore, it is necessary to measure the degree of hydrogen spin isomerization reaction by using a para-hydrogen concentration measurement device corresponding to the low-temperature hydrogen energy industry chain.

[0003] The difference in the spin direction leads to the difference in the physical properties of ortho-hydrogen and para-hydrogen, which provides a theoretical basis for the measurement of para-hydrogen concentration. At present, some public information proposes methods for measuring the para-hydrogen concentration based on the difference in the physical properties, such as:

[0004] The invention patent with the publication number CN 104792656 A discloses a method and system for measuring the para-hydrogen content in liquid hydrogen in real time. First, the temperature value, pressure value and corresponding density of the liquid hydrogen to be measured are measured. Then, the density of normal hydrogen and the density of para-hydrogen at the temperature and pressure are obtained according to the measured temperature value and pressure value. Finally, the para-hydrogen content is calculated by using the density of normal hydrogen, the density of para-hydrogen and the measured density.

[0005] The invention patent with the publication number CN 104730141 A discloses a method and system for measuring the para-hydrogen content in liquid hydrogen according to the difference in nuclear magnetic moment. First, at least two groups of temperature values T and the molar magnetic susceptibility χM at the corresponding temperature of the liquid hydrogen are measured, and a straight line equation of the molar magnetic susceptibility χM and 1 / T is established to obtain the intercept and slope. Then, the straight line equation is converted into a form containing the content of ortho-hydrogen molecules by considering that only ortho-hydrogen molecules can produce paramagnetic susceptibility in liquid hydrogen. The molar magnetic susceptibility and temperature value of the liquid hydrogen to be measured are obtained, and are substituted into the straight line equation to obtain the content of ortho-hydrogen molecules. Finally, the content of para-hydrogen is calculated according to the content of ortho-hydrogen molecules.

[0006] The invention patent with the publication number CN 113607769 A discloses a para-hydrogen content detection device and method using nuclear magnetic resonance. The nuclear magnetic resonance is used to quantitatively detect the para-hydrogen content of different proportions of gas.

[0007] Patent publication number CN 112834636 A discloses an analysis device and method for ortho-para hydrogen metastable components. The chromatographic column is connected to a ten-way valve, and the electronic gas pressure control module of the carrier gas distribution device is adjusted to balance the carrier gas paths. The chromatographic column is placed in a refrigeration unit and cooled to the required low-temperature environment. A hydrogen sample is introduced into the quantitative loop of the ten-way valve and repeatedly replaced until the second pipeline and the quantitative loop are completely replaced. The hydrogen sample injection flow rate is then set using a flow stabilization valve. Once the ortho-para hydrogen metastable component analysis device is preheated, measurement of the ortho-para hydrogen metastable components can begin.

[0008] In summary, the existing measurement methods can all achieve the measurement of parahydrogen content to varying degrees, but the existing measurement methods all require the use of some specific experimental equipment. They are difficult to implement, costly, and complex to operate, making it difficult to meet the parahydrogen measurement needs of all links in the entire process of the low-temperature hydrogen energy industry chain. Summary of the Invention

[0009] In order to solve the technical problem that existing measurement methods are difficult to meet the parahydrogen measurement requirements of all links in the entire process of the low-temperature hydrogen energy industry chain, the present invention provides a thermal equilibrium parahydrogen concentration measurement method and device based on specific enthalpy difference analysis.

[0010] To achieve the above objectives, the technical solutions of the present invention are as follows:

[0011] A method for measuring parahydrogen concentration in thermal equilibrium based on specific enthalpy difference analysis is characterized in that it comprises the following steps:

[0012] Step 1: Connect the heating channel to the gas path to be tested;

[0013] Step 2] Measure the mass flow rate, temperature, and pressure of the sample hydrogen at the air inlet of the heating channel to obtain the specific enthalpy values ​​of orthohydrogen and parahydrogen in the sample hydrogen at the air inlet of the heating channel;

[0014] Step 3] Heating the sample hydrogen in the heating channel with a known thermal power;

[0015] Step 4] Measure the temperature and pressure of the sample hydrogen at the outlet of the heating channel to obtain the specific enthalpy values ​​of orthohydrogen and parahydrogen in the sample hydrogen at the outlet of the heating channel;

[0016] Step 5] Based on the measurement results of step 2] and step 4], the parahydrogen concentration in the sample hydrogen is obtained by specific enthalpy difference analysis and heat balance calculation.

[0017] Furthermore, in step 5], the calculation formula for the parahydrogen concentration x in the sample hydrogen is:

[0018]

[0019] wherein, W is the heat power of the sample hydrogen heating process, m is the mass flow of the sample hydrogen, ΔH o is the specific enthalpy difference of the ortho-hydrogen in the sample hydrogen at the inlet and outlet, ΔH p is the specific enthalpy difference of the para-hydrogen in the sample hydrogen at the inlet and outlet of the heating channel.

[0020] Further, in step 2, the sample hydrogen is hydrogen in liquefaction process or liquid hydrogen in liquid hydrogen storage tank or evaporated hydrogen.

[0021] Further, the sample hydrogen includes all hydrogen sources in low-temperature hydrogen energy industry chain, wherein, the temperature span of the sample hydrogen is 20-300K; and the span of the para-hydrogen concentration in the sample hydrogen is 25-100%.

[0022] Further, the heating in step 3 adopts electric heating to ensure the stability, uniformity and adjustability of the heating process, and the heating power can be adjusted according to the conditions of the inlet working condition and the requirements of the outlet working condition, so as to ensure that the temperature of the sample hydrogen at the outlet is above 150K, and the measurement accuracy is improved.

[0023] In addition, the present application also provides a heat balance para-hydrogen concentration measuring device based on specific enthalpy difference analysis, which is used to realize the heat balance para-hydrogen concentration measuring method based on specific enthalpy difference analysis, and the special features are that the device comprises a heating unit and a measuring unit.

[0024] The heating unit comprises a heating channel and a heating layer arranged on the outer surface of the heating channel; one end of the heating channel is an inlet, and the other end is an outlet, wherein the inlet end is connected with a gas path to be measured;

[0025] The measuring unit comprises an inlet measuring assembly and an outlet measuring assembly; the inlet measuring assembly comprises a first temperature sensor, a first pressure sensor and a mass flow sensor arranged at the inlet; and the outlet measuring assembly comprises a second temperature sensor and a second pressure sensor arranged at the outlet.

[0026] Further, the heating unit further comprises an insulation layer, which is arranged on the outer surface of the heating layer, so as to ensure the heating effect.

[0027] Further, the heating channel is a round pipe channel or a plate-fin channel, and a turbulence device is further arranged in the heating channel to enhance the heat exchange efficiency of the heating channel.

[0028] Further, in order to improve the measurement accuracy and ensure the accuracy of the temperature and pressure measurement data of the sample hydrogen at the gas inlet and the gas outlet, the measurement accuracy of the first temperature sensor and the second temperature sensor is not less than ±0.05K; the measurement accuracy of the first pressure sensor and the second pressure sensor is not less than ±0.05%; and the measurement accuracy of the mass flow sensor is not less than ±0.05%.

[0029] Further, the heating layer is an electric heating layer, and the heat preservation layer is an adiabatic heat preservation layer, which adopts a vacuum multilayer adiabatic mode for heat preservation, thereby reducing the influence of heat leakage on the measurement result.

[0030] The present application has the following advantages:

[0031] 1. Based on the significant specific enthalpy difference of primary and secondary hydrogen under low-temperature working conditions, the sample hydrogen is heated at a certain power, the temperature and pressure states of the sample hydrogen before and after heating are measured, and the secondary hydrogen concentration of the sample hydrogen is obtained by combining specific enthalpy difference analysis and heat balance calculation. The method is simple, reliable, convenient to implement and highly feasible, and can meet the secondary hydrogen measurement requirements of each link in the whole process of the low-temperature hydrogen energy industry chain.

[0032] 2. The measurement method can continuously and accurately measure the secondary hydrogen concentration under various working conditions, has a fast reaction speed and a wide application range.

[0033] 3. The measurement device provided by the present application has a simple structure, a low manufacturing cost and high universality.

[0034] 4. The heating channel is heated by an electric heating mode, thereby ensuring the heating effect, uniformity and adjustability.

[0035] 5. The heating channel is provided with a turbulence device, thereby further strengthening the heat exchange efficiency of the heating channel. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 FIG. 1 is a structural schematic view of an embodiment of a heat balance secondary hydrogen concentration measurement device based on specific enthalpy difference analysis of the present application;

[0037] Figure 2 FIG. 4 is a comparison diagram of the specific enthalpy difference of primary and secondary hydrogen in an embodiment of a heat balance secondary hydrogen concentration measurement method of the present application.

[0038] The reference signs are as follows:

[0039] 1-gas inlet; 11-first temperature sensor; 12-first pressure sensor; 13-mass flow sensor; 2-heat preservation layer; 3-heating layer; 4-heating channel; 5-gas outlet; 51-second temperature sensor; 52-second pressure sensor. DETAILED DESCRIPTION

[0040] The design principle of the present application is that among a plurality of physical properties, the specific enthalpy value difference of ortho-para hydrogen in a low temperature process is obvious. Data shows that taking 0.1 MPa and 20 K as the specific enthalpy value reference point of ortho-para hydrogen, the specific enthalpy difference of ortho-para hydrogen (relative to the reference point) increases with the increase of temperature (about 5% at 100 K, about 15% at 150 K, and nearly 20% above 200 K). Therefore, it is a feasible idea to realize the measurement of para hydrogen concentration based on the specific enthalpy value difference of ortho-para hydrogen.

[0041] Based on this, the present application discloses a heat balance para hydrogen concentration measurement method and device based on specific enthalpy difference analysis to meet the requirement of continuous and accurate measurement of para hydrogen concentration under most working conditions of the low temperature hydrogen energy industry chain.

[0042] The technical solutions of the present application will be described clearly and completely in combination with the drawings and specific embodiments.

[0043] As shown in the drawings, Figure 1 The present application provides a heat balance para hydrogen concentration measurement device based on specific enthalpy difference analysis, which comprises a heating unit and a measurement unit. The heating unit comprises a heating channel 4 and a heating layer 3 arranged on the outer surface of the heating channel 4. One end of the heating channel 4 is an air inlet 1, and the other end is an air outlet 5. The air inlet 1 of the heating channel 4 is connected with a gas path to be measured.

[0044] The measurement unit comprises an inlet measurement assembly and an outlet measurement assembly. The inlet measurement assembly comprises a first temperature sensor 11, a first pressure sensor 12 and a mass flow sensor 13 arranged at the air inlet 1. The outlet measurement assembly comprises a second temperature sensor 51 and a second pressure sensor 52 arranged at the air outlet 5. In order to improve the measurement accuracy, the measurement accuracy of the first temperature sensor 11 and the second temperature sensor 51 is not less than ±0.05 K; the measurement accuracy of the first pressure sensor 12 and the second pressure sensor 52 is not less than ±0.05%; and the measurement accuracy of the mass flow sensor 13 is not less than ±0.05%. The measurement accuracy is relatively high.

[0045] In this embodiment, the heating layer 3 is an electric heating layer. The electric heating layer is uniformly arranged on the outer surface of the heating channel 4 to ensure the heating effect and uniformity of the heating channel 4. At the same time, the heating power of the electric heating layer can be adjusted according to the working condition of the sample hydrogen, so that the temperature of the sample hydrogen at the air outlet 5 is above 150 K (as shown in the drawings, the specific enthalpy difference of ortho-para hydrogen is obvious when the temperature of the hydrogen outlet is above 150 K), thereby improving the reliability of the measurement result. Figure 2

[0046] A heat preservation layer 2 is further arranged outside the electric heating layer to reduce the influence of heat leakage on the measurement result. The heat preservation layer 2 is a heat insulation heat preservation layer, which is heat preserved in a vacuum multi-layer heat insulation mode.​

[0047] In order to improve the heat exchange efficiency of the sample hydrogen in the heating channel 4, the heating channel 4 adopts a high-efficiency micro-channel form, and the heating channel 4 can be a winding pipe channel or a plate-fin channel, wherein the plate-fin channel can be a straight fin, a perforated fin, a sawtooth fin, a corrugated fin and a louver fin, etc., and the specific structure of the heating channel 4 can also be designed according to the actual situation.

[0048] The heating channel 4 is also provided with a flow disturbing device inside, which can be a protrusion arranged on the inner surface of the heating channel 4, or a guide vane structure, etc., aiming to strengthen the heat exchange efficiency of the heating channel 4.

[0049] The application also provides a heat balance para-hydrogen concentration measuring method based on specific enthalpy difference analysis, which comprises the following steps:

[0050] Step 1: connecting the heating channel 4 on the gas path to be measured, and connecting one or more heating channels 4 according to the test requirements, and independently measuring each test point through each heating channel 4.

[0051] Step 2: the sample hydrogen enters from the gas inlet 1, the mass flow of the sample hydrogen is measured by the mass flow sensor 13, the temperature and pressure of the sample hydrogen at the gas inlet 1 are measured by the first temperature sensor 11 and the first pressure sensor 12 respectively, and the specific enthalpy values of the ortho-hydrogen and para-hydrogen in the sample hydrogen at the gas inlet 1 of the heating channel 4 are obtained by inquiry.

[0052] The source of the sample hydrogen can be hydrogen under all working conditions of the low-temperature hydrogen energy industry chain, the temperature span of the sample hydrogen is 20-300K, the para-hydrogen concentration span in the sample hydrogen is 25-100%, and the sample hydrogen can be hydrogen in a liquefaction process, liquid hydrogen in a liquid hydrogen storage tank and evaporated hydrogen, etc.

[0053] Step 3: heating the sample hydrogen in the heating channel 4 with a known heat power; the heating can be performed in an electric heating mode, and the specific heating power can be adjusted according to the working condition of the sample hydrogen, so that the sample hydrogen at the gas outlet 5 reaches a suitable temperature state (the outlet temperature of the sample hydrogen reaches 150K or above, at which the specific enthalpy difference of the ortho-hydrogen and para-hydrogen is obvious, and belongs to a suitable outlet temperature state).

[0054] Step 4: measuring the temperature and pressure of the sample hydrogen at the gas outlet 5 by the second temperature sensor 51 and the second pressure sensor 52 respectively, and obtaining the specific enthalpy values of the ortho-hydrogen and para-hydrogen in the sample hydrogen at the gas outlet 5 of the heating channel by inquiry.

[0055] Step 5: based on the measurement results of step 2 and step 4, the mass flow m of the sample hydrogen, the specific enthalpy difference value ΔH of the ortho-hydrogen in the sample hydrogen at the gas inlet 1 and the gas outlet 5, and the para-hydrogen concentration c of the sample hydrogen are obtained. oand the enthalpy difference of secondary hydrogen in the sample hydrogen at the inlet 1 and the outlet 5 p The concentration of secondary hydrogen in the sample hydrogen is obtained by the enthalpy difference analysis and the heat balance calculation.

[0056] The calculation equation of the heat balance is: W = m (x DeltaH p + (1-x) DeltaH o ), and the concentration of secondary hydrogen in the sample hydrogen x is obtained.

[0057]

[0058] Wherein, W is the heat power of the sample hydrogen in the heating process, m is the mass flow of the sample hydrogen, DeltaH o is the enthalpy difference of primary hydrogen in the sample hydrogen at the inlet 1 and the outlet 5, and DeltaH p is the enthalpy difference of secondary hydrogen in the sample hydrogen at the inlet 1 and the outlet 5.

[0059] The application is based on the obvious enthalpy difference of primary and secondary hydrogen in the low-temperature process, the sample hydrogen is heated by a certain power, and then the temperature and pressure state of the sample hydrogen before and after the device are measured, the concentration of secondary hydrogen in the sample hydrogen is obtained by the enthalpy difference analysis and the heat balance calculation, and the application has the advantages of simple and reliable measurement principle, convenient implementation and operation, mature processing technology, low cost, high feasibility, fast reaction speed and wide application range, and can meet the requirements of continuous and accurate measurement of the concentration of secondary hydrogen under most working conditions of the low-temperature hydrogen energy industry chain.

[0060] The above-described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the application.

Claims

1. A method for measuring parahydrogen concentration in thermal equilibrium based on specific enthalpy difference analysis, characterized in that: The following steps are involved: Step 1: Connect the heating channel to the gas path to be tested; Step 2] Measure the mass flow rate, temperature, and pressure of the sample hydrogen at the air inlet of the heating channel to obtain the specific enthalpy values ​​of orthohydrogen and parahydrogen in the sample hydrogen at the air inlet of the heating channel; Step 3] Heating the sample hydrogen in the heating channel with a known thermal power; Step 4] Measure the temperature and pressure of the sample hydrogen at the outlet of the heating channel to obtain the specific enthalpy values ​​of orthohydrogen and parahydrogen in the sample hydrogen at the outlet of the heating channel; Step 5] Based on the measurement results of step 2] and step 4], the parahydrogen concentration in the sample hydrogen is obtained by specific enthalpy difference analysis and heat balance calculation.

2. The method for measuring parahydrogen concentration in thermal equilibrium based on specific enthalpy difference analysis according to claim 1, characterized in that: In step 5], the calculation formula for the parahydrogen concentration x in the sample hydrogen is: Where W is the thermal power of the sample hydrogen heating process, m is the mass flow rate of the sample hydrogen, ΔH o is the specific enthalpy difference between the orthohydrogen in the sample hydrogen at the inlet and outlet, ΔH p is the difference in specific enthalpy of parahydrogen in the sample hydrogen at the inlet and outlet of the heating channel.

3. The method for measuring parahydrogen concentration in thermal equilibrium based on specific enthalpy difference analysis according to claim 2, wherein: In step 2], the sample hydrogen is hydrogen in the liquefaction process or liquid hydrogen or evaporated hydrogen in a liquid hydrogen storage tank.

4. The method for measuring parahydrogen concentration in thermal equilibrium based on specific enthalpy difference analysis according to any one of claims 1 to 3, characterized in that: The temperature of the sample hydrogen gas ranges from 20 to 300 K; The concentration of parahydrogen in the sample hydrogen gas ranges from 25% to 100%.

5. The method for measuring parahydrogen concentration in thermal equilibrium based on specific enthalpy difference analysis according to claim 1, characterized in that: The heating in step 3] is performed by electric heating so that the temperature of the sample hydrogen at the outlet reaches above 150K.

6. A device for measuring parahydrogen concentration in thermal equilibrium based on specific enthalpy difference analysis, for implementing the method for measuring parahydrogen concentration in thermal equilibrium based on specific enthalpy difference analysis according to any one of claims 1 to 5, characterized in that: including a heating unit and a measuring unit; The heating unit comprises a heating channel (4) and a heating layer (3) arranged on the outer surface of the heating channel (4); one end of the heating channel (4) is an air inlet (1), and the other end is an air outlet (5), wherein one end of the air inlet (1) is connected to the air path to be tested; The measuring unit comprises an inlet measuring assembly and an outlet measuring assembly; the inlet measuring assembly comprises a first temperature sensor (11), a first pressure sensor (12) and a mass flow sensor (13) arranged at the air inlet (1); the outlet measuring assembly comprises a second temperature sensor (51) and a second pressure sensor (52) arranged at the air outlet (5).

7. The thermal equilibrium parahydrogen concentration measuring device based on specific enthalpy difference analysis according to claim 6, characterized in that: The heating unit further comprises a heat-insulating layer (2), and the heat-insulating layer (2) is located on the outer surface of the heating layer (3).

8. The thermal equilibrium parahydrogen concentration measuring device based on specific enthalpy difference analysis according to claim 6, characterized in that: The heating channel (4) is a pipe-wound channel or a plate-fin channel, and a flow disturbance device is also provided inside the heating channel (4).

9. The thermal equilibrium parahydrogen concentration measuring device based on specific enthalpy difference analysis according to claim 6, characterized in that: The measurement accuracy of the first temperature sensor (11) and the second temperature sensor (51) is not less than ±0.05K; The measurement accuracy of the first pressure sensor (12) and the second pressure sensor (52) is not less than ±0.05%; The measurement accuracy of the mass flow sensor (13) is not less than ±0.05%.

10. The thermal equilibrium parahydrogen concentration measuring device based on specific enthalpy difference analysis according to claim 7, characterized in that: The heating layer (3) is an electric heating layer; The thermal insulation layer (2) is a heat-insulating layer, and is heat-insulated by a vacuum multi-layer thermal insulation method.

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