CN111470472A - A self-testable ortho-parahydrogen conversion device - Google Patents

Abstract

The invention is a complete mechanical device for converting ordinary hydrogen at normal temperature into para-hydrogen and equipped with a testing system, including a vacuum system, a catalytic conversion device, a purity testing device and a gas storage cylinder; wherein the vacuum system It is composed of a mechanical pump, gas path and multiple valves. The gas path through which hydrogen enters the vacuum is prevented from air pollution by controlling the valve. The catalytic conversion device is composed of a cold pump and a catalyst. And the flow rate is controlled by a flow meter to ensure the catalytic efficiency; the purity testing device measures the gas purity by adding liquid nitrogen and using the thermal conductivity method; the prepared pure parahydrogen is stored in an aluminum gas cylinder to prolong the gas life. The invention can quantitatively convert ordinary hydrogen into para-hydrogen, and is a set of normal-para-hydrogen conversion device integrating conversion and purity inspection.

Description

A self-testable ortho-parahydrogen conversion device

technical field

The present invention relates to a self-checking hydrogen positive and secondary conversion device.

Background technique

Hydrogen is an extremely flammable, colorless, transparent, odorless and tasteless gas. Hydrogen has important applications in many industries such as hydrogen biological effects, industry, medicine, and fuel applications. Hydrogen has three states of solid, liquid and gas, among which liquid hydrogen has the advantages of easy storage and large gasification expansion rate, and is one of the important ways of hydrogen energy storage. Liquid hydrogen can usually be used as a propellant for launch vehicles, and in recent years, it has also been used in superconducting magnetic energy storage technology.

Hydrogen molecules have two forms, ortho-hydrogen and para-hydrogen. Two hydrogen atoms with the same spin direction are called ortho-hydrogen, and two hydrogen atoms with opposite spin directions are called para-hydrogen. Parahydrogen-induced polarization (PHIP) technology has been applied in various fields such as chemistry, medicine and biology due to its unique polarization properties. For example, parahydrogen can be used as a diagnostic tool for catalytic hydrogenation reactions, which can detect very small amounts of catalytic intermediates in catalytic hydrogenation reactions. Parahydrogen is also a medium for laser Raman conversion. Stimulated rotational Raman scattering generated by parahydrogen as a medium can generate a tunable laser in the 16um band, which has important applications in laser chemistry and spectroscopy. Parahydrogen is also an important link in the process of preparing liquid hydrogen. The raw material for preparing liquid hydrogen requires that the content of parahydrogen is more than 95%.

Under natural conditions, hydrogen molecules are composed of para-hydrogen molecules and ortho-hydrogen molecules in a ratio of 1:3. Parahydrogen has an antisymmetric nuclear spin structure, which only corresponds to the energy level with an even rotational quantum number; orthohydrogen has a symmetrical nuclear spin structure, only corresponding to an energy level with an odd rotational quantum number. According to the selection rule, the transition between ortho- and para-hydrogen is forbidden. However, due to the weak interaction between nuclear spin and electrons, intermolecular collisions can lead to transitions between para-hydrogen and ortho-hydrogen, but this process often takes several months and requires constant low temperature conditions for conversion to occur. occur.

There are three ways for the catalytic conversion of n-parahydrogen: single-stage liquid-phase conversion, multi-stage conversion and continuous conversion. There are generally three types of reactors for normal and parahydrogen conversion: adiabatic type, isothermal type and continuous type. The adiabatic reactor does not need to be cooled by an external cold source, the process is simple, and the generated heat of transformation is taken away by increasing the temperature of the reaction gas stream. The isothermal reactor has the habit of being equipped with a catalyst, and the reaction process is ensured by liquid nitrogen or liquid hydrogen. A continuous reactor, also known as a constant-propulsion reactor, is actually a heat exchanger with a catalyst. The feedstock is cooled by heat exchange with the cold air stream. The traditional ortho-parahydrogen conversion technology needs to consume expensive liquid nitrogen or liquid helium as a cooling material, and the conversion process cannot detect the purity at any time. The detection of hydrogen is also usually performed by a chromatographic analyzer, or Raman laser means as a detection tool, which requires complex equipment and costs. The thermal conductivity method is an effective method for gas analysis, but it is difficult for conventional gas analyzers to measure normal parahydrogen molecules whose thermal conductivity is sensitive at 175K.

SUMMARY OF THE INVENTION

Aiming at the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a positive-secondary conversion device for hydrogen.

A self-testable ortho-parahydrogen conversion device, comprising first to twelfth valves, a cold pump, a catalyst, a mechanical pump, a pressure gauge, a purity inspection device, and a gas cylinder,

The catalyst is placed in a metal tube with two ends open, and the outer wall of the metal tube is in contact with the cold head of the cold pump;

Both the metal tube and the cold head of the cold pump are located in a closed chamber, the two open ends of the metal tube respectively protrude out of the chamber through the wall of the chamber, and one open end of the metal tube passes through the second valve and the first valve in turn. The pipeline is connected with the ordinary hydrogen gas source, and the other open end of the metal pipe is connected with the gas cylinder through the pipeline through the third valve and the sixth valve in turn;

The wall of the airtight chamber is provided with an air suction through hole, which is connected to the air inlet of the mechanical pump through a pipeline through the twelfth valve; the air inlet of the mechanical pump is connected to the mechanical pump through the ninth valve and the tenth valve in turn. The connecting pipeline between the second valve and the first valve is communicated;

The air inlet of the mechanical pump is connected to the sample gas inlet of the purity inspection device through the pipeline through the fourth valve, the fifth valve, the eighth valve and the eleventh valve in turn;

The connecting pipeline between the ninth valve and the tenth valve and the connecting pipeline between the fifth valve and the eighth valve are respectively connected with pressure gauges;

The connecting pipeline between the third valve and the sixth valve communicates with the connecting pipeline between the fourth valve and the fifth valve.

Use a mechanical pump to evacuate the gas circuit system, cold pump, and storage gas cylinder, use a cold pump cold head to reduce the catalyst temperature, use a valve system and a flow meter to allow the target gas to pass through the catalyst at a certain flow rate, and the converted parahydrogen is stored in In the gas storage bottle; use the valve system to realize the diverted ordinary hydrogen and the prepared parahydrogen into the purity inspection device to realize the purity measurement.

The granular catalyst is placed in a copper tube with two ends open, and the copper tube is wound on the outer wall of the columnar cold head of the cold pump, so that the cold pump can directly cool the catalyst.

Both the cold head and the catalyst pipeline are in a vacuum environment, and the temperature is monitored to reduce the temperature to below 21K.

The purity inspection device is composed of an external regulated DC power supply, a liquid nitrogen cold barrel and a closed gas storage vacuum barrel placed in the liquid nitrogen cold barrel; a filament is arranged in the gas storage vacuum barrel, and the two ends of the filament pass through the wire and the DC power supply respectively. The positive and negative electrodes are connected to each other; the gas storage vacuum barrel is provided with a sample gas inlet, and the sample gas inlet is connected to the gas source to be tested and the vacuum pump respectively through the conduit, and the parahydrogen purity is measured by the thermal conductivity method.

The connecting pipeline between the ninth valve and the tenth valve and the connecting pipeline between the fifth valve and the eighth valve are respectively connected to the pressure gauge through the seventh valve.

The cold head of the cold pump is provided with a temperature monitoring element, such as a temperature measuring thermocouple.

A flow meter is arranged on the connecting pipeline between the third valve and the sixth valve.

The gas cylinder is a storage aluminum gas cylinder.

The preparation principle of this device is similar to that of an isothermal reactor. By using a cold pump (also known as a cryogenic pump, a cryogenic vacuum pump, and a condensing pump) for cooling, it does not need to consume liquid nitrogen and liquid helium. transform. At the same time, the device can realize the continuous preparation of parahydrogen molecules with a purity of up to 97%. The background pressure of a single preparation is under the storage gas cylinder of 200 psi, and the continuous preparation of parahydrogen gas can be realized by simply switching the valve and replacing the storage gas cylinder. The parahydrogen thus prepared can maintain almost unchanged purity for more than two weeks. At the same time, through the design of the vacuum circuit, the gas purity test can be carried out at any time during the preparation process to ensure the gas purity.

The present invention has the following advantages and beneficial effects:

1. It has the ability to continuously and rapidly prepare parahydrogen.

2. Through flow control, automatic gas preparation can be realized.

3. With the function of testing the purity, the purity testing can be realized at any time, and the operation is convenient.

In the attached picture:

1 is the first valve, 2 is the second valve, 3 is the third valve, 4 is the fourth valve, 5 is the fifth valve, 6 is the sixth valve, 7 is the seventh valve, 8 is the eighth valve, and 9 is the The ninth valve, 10 is the tenth valve, 11 is the eleventh valve, 12 is the twelfth valve, 13 is the cold pump, 14 is the catalyst, 15 is the temperature monitoring element, 16 is the flow meter, 17 is the mechanical pump, 18 It is a pressure gauge, 19 is a gas inspection device, 20 is a gas cylinder, 21 is ordinary hydrogen, 22 is parahydrogen, 23 is a DC voltage stabilized power supply, 24 is a filament, and 25 is liquid nitrogen.

Description of drawings

FIG. 1 is a schematic structural diagram of the present invention.

FIG. 2 is a structural diagram of the cold pump catalyst of the present invention.

FIG. 3 is a structural diagram of the gas inspection device of the present invention.

Figure 4 shows the thermal conductivity curve of parahydrogen corresponding to the filament of the present invention.

Detailed ways

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

The detailed structure of the cold pump catalyst is shown in Figure 2. The copper tube containing the catalyst is wound around the cold head of the cold pump, and the low temperature working environment of the catalyst is realized by contacting the cold head in operation. The catalyst needs to be below 25K to effectively realize the catalytic function, where the cold head and pipeline are located in the vacuum environment of the cold pump. The catalyst in the line is in a separate vacuum line environment. The cold pump is an Austin Scientific model M600, the catalyst is Fe ₃ O ₄ , and the powder is about 1 mm in size.

The design of the hydrogen testing device is shown in Figure 3. The temperature measurement principle is that the thermal conductivity of para-H2 and normal-H2 changes significantly at low temperature (100-200K). The system is as shown in the figure. An impervious steel tank is evacuated and then immersed in liquid nitrogen. The tank is equipped with a heatable tungsten wire. During the measurement, about 80 Torr of the gas to be tested is filled into the tank cooled by liquid nitrogen. Then, the tungsten filament is heated by a DC regulated power supply, and the temperature of the filament is determined by the applied voltage and the heat dissipation capacity of the environment. When the same voltage is applied to the filament, the temperature of the filament will be completely determined by the heat dissipation capacity of the surrounding environment of the filament, that is, the thermal conductivity of the charged gas. Because the temperature of the filament is linearly related to the resistance of the filament, it can be measured by measuring the filament The resistance change to measure the purity of the gas charged.

Normal parahydrogen conversion operation method:

Turn on the mechanical pump 17, and open all the first to twelfth valves (1-12) at the same time. After pumping the pipeline and the cold pump 13 to a vacuum of ^10-2 Torr, close all other valves, open the twelfth valve 12, and open the cold pump. Pump 13 until the cold pump temperature drops to 20-21K. Then open the first and second valves (1, 2), put hydrogen into the catalyst, the cold pump will heat up at this time, and after the temperature drops to 20-21K, open the third and sixth valves 3, 6 to adjust the flow The meter controls the flow rate so that the parahydrogen slowly enters the gas cylinder. Increase the back pressure and pay attention to controlling the flow rate, so that the temperature indication of the temperature monitoring element 15 is kept below 25K, and the ordinary hydrogen can be continuously converted into parahydrogen into the storage gas cylinder. At this point, the gas check operation can be performed at any time.

Gas inspection operation method:

Pour liquid nitrogen into the gas inspection device, close the first, second, third, sixth, and twelfth valves (1, 2, 3, 6, 12), and open the seventh, eighth, and eleventh valves ( 7, 8, 11), slowly open the fifth valve 5, put 80 Torr parahydrogen into the gas testing device, and use a multimeter to measure its resistance R _detection . Close the fifth valve 5, open the ninth valve 9, use the mechanical pump 17 to evacuate the purity inspection device 19 (in the gas storage vacuum barrel), and close the ninth valve 9. Slowly open the tenth valve 10 and charge the gas detection device with 80 Torr ordinary hydrogen gas, and measure the resistance R _ordinary . Then the resistance difference is RD=R _detection -R _normal . Using the calibrated thermal conductivity formula in Figure 4, the purity of the gas to be tested is P-H2(%)=11.25*RD+28.05, thus obtaining the parahydrogen purity.

Close all the first to twelfth valves (1-12), open the first, second, third, sixth, and twelfth valves (1, 2, 3, 6, 12), the positive hydrogen gas can be continued. Secondary conversion.

Device shutdown steps:

After a sufficient amount of gas is prepared, the cold pump is turned off and the power is checked for purity. Close the first, sixth, and twelfth valves (1, 6, 12), open all other valves, use the mechanical pump 17 to vacuum the pipeline, and close all the first to twelfth valves (1-12). After waiting for the cold pump to heat up, the twelfth valve 12 is opened, the cold pump is evacuated, and the twelfth valve 12 is closed. Turn off the mechanical pump. Device shutdown is complete.

Claims (9)

1. An orthosteric hydrogen conversion device capable of self-checking comprises first to twelfth valves (1-12), a cold pump (13), a catalyst (14), a mechanical pump (17), a pressure gauge, a purity checking device (19) and a gas cylinder, and is characterized in that:

the catalyst is arranged in a metal tube with an opening at one end and the other end, and the outer wall surface of the metal tube is attached to the cold head of the cold pump;

the metal pipe and the cold head of the cold pump are both positioned in a closed cavity, two open ends of the metal pipe respectively penetrate through the wall surface of the cavity and extend out of the cavity, one open end of the metal pipe is connected with a common hydrogen gas source through a second valve (2) and a first valve (1) in sequence through a pipeline, and the other open end of the metal pipe is connected with a gas cylinder (20) through a third valve (3) and a sixth valve (6) in sequence through a pipeline;

the wall surface of the closed chamber is provided with an air exhaust through hole, and the air exhaust through hole is connected with an air inlet of the mechanical pump (17) through a twelfth valve (12) by a pipeline; an air inlet of the mechanical pump (17) is communicated with a connecting pipeline between the second valve (2) and the first valve (1) through a ninth valve (9) and a tenth valve (10) in sequence;

an air inlet of the mechanical pump (17) is connected with a sample gas inlet of the purity testing device (19) through a fourth valve (4), a fifth valve (5), an eighth valve (8) and an eleventh valve (11) in sequence through a pipeline;

a connecting pipeline between the ninth valve (9) and the tenth valve (10) and a connecting pipeline between the fifth valve (5) and the eighth valve (8) are respectively connected with a pressure gauge;

the connecting pipeline between the third valve (3) and the sixth valve (6) is communicated with the connecting pipeline between the fourth valve (4) and the fifth valve (5).

2. An orthopara-hydrogen conversion device according to claim 1, wherein: vacuumizing a gas circuit system, a cold pump and a storage gas cylinder by using a mechanical pump, reducing the temperature of a catalyst by using a cold head of the cold pump, allowing a target gas to pass through the catalyst at a certain flow rate by using a valve system and a flowmeter, and storing converted para-hydrogen into a gas cylinder; and the separated common hydrogen and the prepared parahydrogen enter a purity inspection device by using a valve system to realize purity measurement.

3. An orthopara-hydrogen conversion device according to claim 1, wherein: the granular catalyst is arranged in the copper pipe with the opening at the first end and the second end, and the copper pipe is wound on the outer wall surface of the columnar cold head of the cold pump, so that the cold pump can directly cool the catalyst.

4. An orthopara-hydrogen conversion device according to claim 1 or 3, wherein: the cold head and the catalyst pipeline are both in a vacuum environment, and the temperature is monitored to be reduced to below 21K by using the temperature.

5. An orthopara-hydrogen conversion device according to claim 1, wherein: the purity inspection device consists of an external voltage-stabilizing direct-current power supply, a liquid nitrogen cooling barrel and a closed gas storage vacuum barrel arranged in the liquid nitrogen cooling barrel; a filament is arranged in the gas storage vacuum barrel, and two ends of the filament are respectively connected with the positive electrode and the negative electrode of the direct current power supply through leads; the gas storage vacuum barrel is provided with a sample gas inlet which is respectively connected with a gas source to be measured and a vacuum pump through a conduit, and the purity of parahydrogen is measured by using a thermal conductivity method.

6. An orthopara-hydrogen conversion device according to claim 1, wherein: and a connecting pipeline between the ninth valve (9) and the tenth valve (10) and a connecting pipeline between the fifth valve (5) and the eighth valve (8) are respectively connected with a pressure gauge (18) through a seventh valve (7).

7. An orthopara-hydrogen conversion device according to claim 1, wherein: a temperature monitoring element (15) such as a temperature thermocouple is arranged at the cold head of the cold pump.

8. An orthopara-hydrogen conversion device according to claim 1, wherein:

a flow meter (16) is arranged on a connecting pipeline between the third valve (3) and the sixth valve (6).

9. An orthopara-hydrogen conversion device according to claim 1, wherein: the gas cylinder is a storage aluminum gas cylinder (20).

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