Hydrogen liquefaction device with precooling throttling

Abstract

The present invention belongs to the technical field of hydrogen production equipment, and specifically relates to a hydrogen liquefaction device with precooling and throttling, including a hydrogen liquefaction route for conveying raw hydrogen and a hydrogen circulation route for conveying circulating hydrogen, the two routes respectively pass through a primary precooling section, a secondary precooling section and a liquefaction section in sequence; the primary precooling section is provided with a heat exchanger 1 and a normal pressure liquid nitrogen precooler, and the secondary precooling section is provided with a heat exchanger 2 and a negative pressure liquid nitrogen precooler; after the hydrogen liquefaction route is precooled by heat exchanger 1 and the normal pressure liquid nitrogen precooler, it enters heat exchanger 2 and a negative pressure liquid nitrogen precooler for further cooling. The hydrogen liquefaction device with precooling and throttling provided by the present invention adopts a secondary precooling structure of a normal pressure liquid nitrogen precooler and a negative pressure liquid nitrogen precooler, and the liquefaction effect is better.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrogen production equipment, and in particular relates to a hydrogen liquefaction device with precooling and throttling. Background Art

[0002] Existing hydrogen liquefaction equipment usually uses a single liquid nitrogen precooling device for precooling, such as the invention patent application with publication number CN108469150A. The liquefaction effect of the raw hydrogen in the single precooling liquefaction system is poor, which affects the hydrogen production efficiency. Summary of the invention

[0003] The purpose of the present invention is to provide a hydrogen liquefaction device with precooling throttling, which adopts a two-stage precooling structure of a normal pressure liquid nitrogen precooler and a negative pressure liquid nitrogen precooler, and has a better liquefaction effect.

[0004] The object of the present invention is achieved as follows: a hydrogen liquefaction device with precooling throttling includes a hydrogen liquefaction route for conveying raw hydrogen and a hydrogen circulation route for conveying circulating hydrogen, the two routes respectively pass through a primary precooling section, a secondary precooling section and a liquefaction section in sequence; the primary precooling section is provided with a heat exchanger 1 and a normal pressure liquid nitrogen precooler, the secondary precooling section is provided with a heat exchanger 2 and a negative pressure liquid nitrogen precooler, and the liquefaction section is provided with a heat exchanger 3 and a liquid hydrogen supercooler; after the hydrogen liquefaction route is precooled by the heat exchanger 1 and the normal pressure liquid nitrogen precooler, it enters the heat exchanger 2 and the negative pressure liquid nitrogen precooler for further cooling, and then After that, it passes through heat exchanger three, enters the liquid hydrogen supercooler for supercooling, and finally enters the gas-liquid separation tank after throttling by throttle valve three; the hydrogen circulation route is pre-cooled through heat exchanger one and the atmospheric pressure liquid nitrogen precooler, and then enters heat exchanger two and the negative pressure liquid nitrogen precooler for further cooling; after the secondary precooling, the hydrogen circulation route is divided into two branches, the first branch is throttled by throttle valve one and passes through heat exchanger two and heat exchanger one as reflux hydrogen again, and finally merges back to the hydrogen circulation route; the second branch continues to cool through heat exchanger three, and then merges into the liquid hydrogen supercooler after throttling valve two, which is used for supercooling of raw hydrogen.

[0005] Furthermore, the first-stage precooling section is also provided with adsorber 1, adsorber 2, and normal-parahydrogen conversion 1. After the hydrogen liquefaction route is precooled through heat exchanger 1 and atmospheric pressure liquid nitrogen precooler, it passes through adsorber 1 to adsorb impurities, and then undergoes catalytic conversion through normal-parahydrogen conversion 1, returns to the atmospheric pressure liquid nitrogen precooler for heat exchange again, and then enters heat exchanger 2; after precooling, the hydrogen circulation route passes through adsorber 2 to adsorb impurities and then enters heat exchanger 2.

[0006] Furthermore, the liquefaction section also includes a second normal-parahydrogen conversion device. The hydrogen liquefaction route passes through a third heat exchanger, enters a liquid hydrogen supercooler for supercooling, then undergoes a second normal-parahydrogen conversion device for catalytic conversion, returns to the liquid hydrogen supercooler for supercooling, and finally enters a gas-liquid separation tank after throttling through a third throttling valve.

[0007] Furthermore, the hydrogen gasified in the gas-liquid separation tank and the liquid hydrogen supercooler passes through heat exchanger three, heat exchanger two, and heat exchanger one and then flows into the hydrogen circulation route.

[0008] Furthermore, the adsorber 1 and the adsorber 2 are molecular sieve adsorbers.

[0009] Furthermore, the atmospheric pressure pipeline of the atmospheric pressure liquid nitrogen precooler is connected to the atmosphere after passing through the first heat exchanger; the negative pressure pipeline of the negative pressure liquid nitrogen precooler is connected to the vacuum pump after passing through the second heat exchanger and the first heat exchanger.

[0010] Furthermore, adsorber 1 and adsorber 2 are shown to operate in pairs, one for purification and the other for regeneration or in standby mode.

[0011] Furthermore, the hydrogen circulation route is pressurized by compressor one and compressor two in sequence, compressor one is connected to the circulating hydrogen replenishing port, the first branch is pressurized by compressor two and then merged into the hydrogen circulation route, and the hydrogen vaporized in the gas-liquid separation tank and the liquid hydrogen supercooler is finally pressurized by compressor one and compressor two and then merged into the hydrogen circulation route.

[0012] Compared with the prior art, the present invention has the following outstanding and beneficial technical effects: the liquefaction device first performs two-stage precooling and then performs liquefaction to ensure the hydrogen liquefaction effect. In the precooling stage, a molecular sieve adsorber is used to implement a cooling and purification step to remove impurities (carbon monoxide, carbon dioxide, methane, inert gas, etc.); two catalytic conversions are performed in the precooling section and the liquefaction section to convert orthohydrogen into parahydrogen, thereby reducing the irreversibility of the process and enhancing thermal efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is an overall principle diagram of a hydrogen liquefaction device with precooling and throttling in an embodiment of the present invention.

[0014] Figure 2 It is a hydrogen liquefaction route map in an embodiment of the present invention.

[0015] Figure 3 It is a hydrogen cycle route map in an embodiment of the present invention.

[0016] Figure symbols: E1, heat exchanger one; E2, heat exchanger two; E3, heat exchanger three; E4, normal pressure liquid nitrogen precooler; E5, negative pressure liquid nitrogen precooler; E6, liquid hydrogen supercooler; A1, adsorber one; A2, adsorber two; K1, normal-parahydrogen conversion one; K2, normal-parahydrogen conversion two; V1, gas-liquid separation tank; V2, liquid hydrogen storage tank; J1, throttle valve one; J2, throttle valve two; J3, throttle valve three; Y1, compressor one; Y2, compressor two. DETAILED DESCRIPTION

[0017] The specific implementation modes of the present invention are further described in detail below with reference to the accompanying drawings.

[0018] A hydrogen liquefaction device with precooling throttling, such as Figure 1 As shown, it includes a hydrogen liquefaction route for conveying raw hydrogen and a hydrogen circulation route for conveying circulating hydrogen, and the two routes respectively pass through a primary precooling section, a secondary precooling section and a liquefaction section in sequence.

[0019] The first-stage precooling section is equipped with a heat exchanger E1, a normal pressure liquid nitrogen precooler E4, and an adsorber A1 and an adsorber A2 for adsorbing impurities in hydrogen, a normal-parahydrogen conversion K1 filled with a catalyst, and the normal pressure liquid nitrogen precooler E4 is connected to the atmosphere through a normal pressure pipeline, and the normal pressure pipeline passes through the heat exchanger E1. In order to improve and ensure the conversion efficiency of normal hydrogen to parahydrogen, more than two normal-parahydrogen conversion K1s can be connected in series.

[0020] The secondary precooling section is provided with a second heat exchanger E2 and a negative pressure liquid nitrogen precooler E5. The negative pressure liquid nitrogen precooler E5 is connected to a vacuum pump through a negative pressure pipeline so that the inside of the negative pressure liquid nitrogen precooler E5 is maintained at a vacuum or negative pressure. The negative pressure pipeline passes through the second heat exchanger E2 and the first heat exchanger E1.

[0021] The liquefaction section is provided with a heat exchanger E3 and a liquid hydrogen supercooler E6, as well as a normal-parahydrogen conversion tank K2 for secondary catalytic conversion of the raw hydrogen, and a gas-liquid separation tank V1 for gas-liquid separation. In order to improve and ensure the conversion efficiency of normal hydrogen to parahydrogen, two or more normal-parahydrogen conversion tanks K2 can be connected in series.

[0022] Combination Figure 1 and Figure 2 The pipeline layout of the hydrogen liquefaction route is as follows: raw hydrogen → heat exchanger E1 → atmospheric pressure liquid nitrogen precooler E4 → adsorber A1 → normal-parahydrogen conversion K1 → atmospheric pressure liquid nitrogen precooler E4 → heat exchanger E2 → negative pressure liquid nitrogen precooler E5 → heat exchanger E3 → liquid hydrogen supercooler E6 → normal-parahydrogen conversion K2 → liquid hydrogen supercooler E6 → throttle valve J3 → gas-liquid separation tank V1 → liquid hydrogen storage tank V2

[0023] Combination Figure 1 and Figure 3 The pipeline layout of the hydrogen circulation route is as follows: circulating hydrogen → compressor 1 Y1 → compressor 2 Y2 → heat exchanger 1 E1 → atmospheric pressure liquid nitrogen precooler E4 → adsorber 2 A2 → heat exchanger 2 E2 → negative pressure liquid nitrogen precooler E5 → two branches

[0024] Among them, the first branch → throttle valve 1 J1 → heat exchanger 2 E2 → heat exchanger 1 E1 → compressor 2 Y2

[0025] Among them: Second branch → heat exchanger three E3 → liquid hydrogen subcooler E6

[0026] Hydrogen gasified in liquid hydrogen subcooler E6 → heat exchanger three E3 → heat exchanger two E2 → heat exchanger one E1 → compressor one Y1 → compressor two Y2

[0027] Gasified hydrogen in gas-liquid separation tank V1 → heat exchanger E5 → heat exchanger E3 → heat exchanger E1 → circulating hydrogen

[0028] In summary, the liquefaction device in this embodiment mainly includes two cooling steps: first two-stage precooling, and then liquefaction. In the precooling stage, there is a cooling and purification step to remove impurities (carbon monoxide, carbon dioxide, methane, inert gas, etc.), otherwise the impurities may freeze at the temperature of the hydrogen liquefier and block the heat exchanger. Carbon monoxide and nitrogen must be removed before entering the liquefaction section. We achieve the removal of carbon monoxide and nitrogen by adsorption in an adsorber installed in the first precooling zone.

[0029] In order to achieve a satisfactory purification level, we use molecular sieve as adsorbent. Both adsorber A1 and adsorber A2 use two containers to operate side by side: one of them handles the hydrogen to be purified, while the other is regenerated or in standby mode. The designed switching cycle is about 8 days for adsorption and 1.5 days for regeneration. According to the set sequence, a set of valves is used to achieve adsorber switching and maintain stable operation of hydrogen liquefaction.

[0030] Primary precooling stage: The raw hydrogen and circulating hydrogen are first cooled in the heat exchanger E1 with the reflux nitrogen and hydrogen, and then enter the atmospheric pressure liquid nitrogen precooler E4 to be precooled to about 80K.

[0031] Secondary precooling stage: The hydrogen after primary precooling enters the negative pressure liquid nitrogen precooler E5 in vacuum or negative pressure state, and is further cooled by liquid nitrogen to about 65K-75K. The circulating hydrogen after secondary precooling is divided into two streams, one of which is throttled by throttle valve J1 and used as reflux hydrogen to cool the forward hydrogen; the other stream and the raw hydrogen enter the heat exchanger of the low temperature liquefaction section for further cooling.

[0032] Liquefaction section: The hydrogen at 65K-75K is cooled to close to 20K-25K through the liquefaction section for liquefaction. After being cooled, the circulating hydrogen is throttled to normal pressure through the throttle valve J2 and enters the liquid hydrogen supercooler E6 to liquefy and supercool the raw hydrogen. The liquefied raw hydrogen is throttled to normal pressure and enters the gas-liquid separation tank V1, through which the liquid hydrogen product is provided to the user; the hydrogen vaporized in the gas-liquid separation tank V1 merges with the normal pressure circulating hydrogen refluxed from the liquid hydrogen supercooler E6, and is heat exchanged with the positive flow hydrogen through the heat exchanger to be reheated to normal temperature, and then enters the compressor Y1 inlet again.

[0033] Catalytic conversion of ortho-parahydrogen: In order to liquefy hydrogen, it is important to convert ortho-hydrogen into para-hydrogen. These two forms of hydrogen coexist and are distinguished by the direction of their electron spin. At various temperatures, the ratio of these two hydrogens has a corresponding equilibrium value. At room temperature, the equilibrium ratio of ortho-parahydrogen is about 75 / 25, while at low temperatures, it is about 2 / 98. At low temperatures, ortho-hydrogen is in an unstable state and gradually changes to more stable para-hydrogen, releasing heat and causing hydrogen to evaporate in the storage container. Since ortho-hydrogen accounts for 75% of hydrogen at room temperature, its endothermic vaporization will greatly increase the difficulty and cost of storing liquid hydrogen. This conversion process is quite slow, so a catalyst is needed to accelerate it, and some additional cooling is needed to compensate for the heat released by the exothermic reaction. In the process pipeline, the catalyst is loaded in the heat exchanger or special container of the primary pre-cooling section and the liquefaction section for two catalytic conversions. This disperses the heat of conversion throughout the process, thereby reducing the irreversibility of the process and thus enhancing thermal efficiency.

[0034] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A hydrogen liquefaction device with precooling and throttling, characterized in that: It includes a hydrogen liquefaction route for conveying raw hydrogen and a hydrogen circulation route for conveying circulating hydrogen, and the two routes respectively pass through a primary precooling section, a secondary precooling section and a liquefaction section in sequence; The first-stage precooling section is provided with a heat exchanger 1 (E1) and a normal-pressure liquid nitrogen precooler (E4), the second-stage precooling section is provided with a heat exchanger 2 (E2) and a negative-pressure liquid nitrogen precooler (E5), and the liquefaction section is provided with a heat exchanger 3 (E3) and a liquid hydrogen subcooler (E6); The hydrogen liquefaction route is precooled by heat exchanger 1 (E1) and atmospheric pressure liquid nitrogen precooler (E4), then enters heat exchanger 2 (E2) and negative pressure liquid nitrogen precooler (E5) for further cooling, then passes through heat exchanger 3 (E3), enters liquid hydrogen subcooler (E6) for subcooling, and finally enters gas-liquid separation tank (V1) after throttling by throttle valve 3 (J3); After being precooled by heat exchanger 1 (E1) and normal pressure liquid nitrogen precooler (E4), the hydrogen circulation route enters heat exchanger 2 (E2) and negative pressure liquid nitrogen precooler (E5) for further cooling; after secondary precooling, the hydrogen circulation route is divided into two branches, the first branch is throttled by throttle valve 1 (J1) and passes through heat exchanger 2 (E2) and heat exchanger 1 (E1) as reflux hydrogen again, and finally merges back into the hydrogen circulation route; the second branch continues to be cooled by heat exchanger 3 (E3), and then enters liquid hydrogen supercooler (E6) after throttle valve 2 (J2) for supercooling raw hydrogen.

2. The hydrogen liquefaction device with precooling and throttling according to claim 1 is characterized in that: The primary precooling section is also provided with adsorber 1 (A1), adsorber 2 (A2), and normal-parahydrogen conversion 1 (K1). After being precooled by heat exchanger 1 (E1) and atmospheric pressure liquid nitrogen precooler (E4), the hydrogen liquefaction route passes through adsorber 1 (A1) to adsorb impurities, and then passes through normal-parahydrogen conversion 1 (K1) for catalytic conversion, returns to atmospheric pressure liquid nitrogen precooler (E4) for heat exchange again, and then enters heat exchanger 2 (E2); after being precooled, the hydrogen circulation route passes through adsorber 2 (A2) to adsorb impurities and then enters heat exchanger 2 (E2).

3. The hydrogen liquefaction device with precooling and throttling according to claim 1 or 2, characterized in that: The liquefaction section also includes a normal-parahydrogen conversion unit 2 (K2). The hydrogen liquefaction route passes through a heat exchanger 3 (E3), enters a liquid hydrogen supercooler (E6) for supercooling, and then undergoes catalytic conversion through a normal-parahydrogen conversion unit 2 (K2). After returning to the liquid hydrogen supercooler (E6) for supercooling, the hydrogen finally enters a gas-liquid separation tank (V1) after throttling through a throttle valve 3 (J3).

4. The hydrogen liquefaction device with precooling and throttling according to claim 1 is characterized in that: The hydrogen gasified in the gas-liquid separation tank (V1) and the liquid hydrogen supercooler (E6) is fed into the hydrogen circulation route after passing through the heat exchanger three (E3), the heat exchanger two (E2) and the heat exchanger one (E1).

5. The hydrogen liquefaction device with precooling and throttling according to claim 2 is characterized in that: The adsorber 1 (A1) and the adsorber 2 (A2) are molecular sieve adsorbers.

6. The hydrogen liquefaction device with precooling and throttling according to claim 1 is characterized in that: The atmospheric pressure pipeline of the atmospheric pressure liquid nitrogen precooler (E4) is connected to the atmosphere after passing through the first heat exchanger (E1); the negative pressure pipeline of the negative pressure liquid nitrogen precooler (E5) is connected to the vacuum pump after passing through the second heat exchanger (E2) and the first heat exchanger (E1).

7. The hydrogen liquefaction device with precooling and throttling according to claim 2 is characterized in that: As shown, adsorber 1 (A1) and adsorber 2 (A2) are operated in pairs, one for purification and the other for regeneration or standby.

8. The hydrogen liquefaction device with precooling and throttling according to claim 4 is characterized in that: The hydrogen circulation route is pressurized by compressor one (Y1) and compressor two (Y2) in sequence, compressor one (Y1) is connected to the circulating hydrogen replenishing port, the first branch is pressurized by compressor two (Y2) and then merged into the hydrogen circulation route, and the hydrogen vaporized in the gas-liquid separation tank (V1) and the liquid hydrogen supercooler (E6) is finally pressurized by compressor one (Y1) and compressor two (Y2) and then merged into the hydrogen circulation route.

Images