CN-121977325-A - Small-size hydrogen liquefaction system

CN121977325ACN 121977325 ACN121977325 ACN 121977325ACN-121977325-A

Abstract

The invention relates to a small hydrogen liquefaction system which comprises a helium refrigeration cycle unit, a hydrogen liquefaction unit and a bearing protection gas supply unit, wherein the helium refrigeration cycle unit takes helium as a working medium to operate according to the inverse brayton cycle, a pipeline is connected with a large helium buffer tank, a compressor, a heat exchange unit in a cold box and a dynamic pressure gas bearing turbine expander, a flow path of the hydrogen liquefaction unit penetrates through the heat exchange unit in the cold box and a low-temperature J-T throttle valve to a liquid hydrogen Dewar, the heat exchange unit comprises an integrated heat exchanger integrating a normal-secondary hydrogen catalyst, the gas inlet end of the small helium buffer tank of the bearing protection gas supply unit is connected with the high-pressure output end of the compressor, and the gas outlet end of the small helium buffer tank is connected with the dynamic pressure gas bearing gas supply port of the turbine expander through a pipeline with a control valve, the inverse brayton cycle realizes the efficient refrigeration to reduce the specific power consumption, the integrated heat exchanger guarantees the high conversion liquefaction rate under a compact structure, and the independent gas supply unit ensures the bearing gas source stability, improves the reliability and maintenance-free period of the system, and solves the problems of low energy efficiency and reliability deficiency of the small hydrogen liquefaction device.

Inventors

YANG HUILIN
WANG QIAN
Yan Xuze
ZHOU HAN
WANG SHAOGANG

Assignees

中山先进低温技术研究院

Dates

Publication Date: 20260505
Application Date: 20260130

Claims (10)

1. A compact hydrogen liquefaction system, comprising: The helium refrigeration cycle unit takes helium as a working medium and operates according to an inverse brayton cycle, and comprises a big helium buffer tank, a compressor, a heat exchange unit in a cold box and a turbine expander which are sequentially connected through pipelines, wherein the turbine expander adopts a dynamic pressure gas bearing; The flow path of the hydrogen liquefying unit sequentially penetrates through the heat exchange unit and a low-temperature J-T throttle valve in the cold box and is terminated at a liquid hydrogen Dewar, wherein the heat exchange unit comprises at least one positive-para-hydrogen conversion integrated heat exchanger integrated with a positive-para-hydrogen conversion catalyst; And the bearing protection air supply unit comprises a small helium buffer tank, the air inlet end of the small helium buffer tank is communicated with the high-pressure output end of the compressor, and the air outlet end of the small helium buffer tank is connected to the air supply port of the dynamic pressure gas bearing of the turboexpander through a pipeline with a control valve.
2. The compact hydrogen liquefaction system of claim 1, wherein the heat exchange unit further includes a first heat exchanger having upper and lower heat exchange chambers that are independent of each other; The upper heat exchange cavity is arranged in a flow path of the hydrogen liquefying unit and is used for precooling raw material hydrogen; the lower heat exchange cavity is arranged in a flow path of the helium refrigeration cycle unit and is used for precooling high-pressure helium.
3. The compact hydrogen liquefaction system of claim 2, wherein the integral normal-to-para-hydrogen heat exchanger includes a second heat exchanger and a third heat exchanger disposed in sequence in the fluid direction within the cold box, the interiors of both the second heat exchanger and the third heat exchanger being filled with the normal-to-para-hydrogen conversion catalyst.
4. The small-sized hydrogen liquefaction system according to claim 3, wherein the inlet end of the turbo expander is provided with a main path and a bypass in parallel, the main path is provided with a first valve, the bypass is provided with a second valve, the system further comprises a temperature sensor for detecting the temperature in the cold box, and the temperature sensor, the first valve and the second valve are in signal connection with a control system and are used for controlling the switching of the opening and closing states of the first valve and the second valve according to the signals of the temperature sensor.
5. The small-sized hydrogen liquefying system according to claim 1, wherein the bearing protection gas supply unit further comprises a pressure sensor for monitoring the gas pressure at the dynamic pressure gas bearing, a first electromagnetic valve is arranged on a pipeline at the gas outlet end of the small helium buffer tank, and the pressure sensor and the first electromagnetic valve are in signal connection with a control system so as to control the first electromagnetic valve to be opened when the pressure detected by the pressure sensor is lower than a set threshold value.
6. A compact hydrogen liquefaction system according to claim 3, wherein an adsorber is provided in the flow path of the hydrogen liquefaction unit, the adsorber being located in the line section between the first heat exchanger and the second heat exchanger.
7. The compact hydrogen liquefaction system of claim 3, further comprising a liquid nitrogen pre-chilling system including a large liquid nitrogen storage tank disposed outside the cold box and a small liquid nitrogen storage tank disposed inside the cold box; the small liquid nitrogen storage tank is communicated with the lower heat exchange cavity of the first heat exchanger through a liquid nitrogen supply pipeline; the gas phase space of the small liquid nitrogen storage tank is communicated with the upper heat exchange cavity of the first heat exchanger through a low-temperature nitrogen pipeline.
8. The compact hydrogen liquefaction system of claim 7, wherein the small liquid nitrogen storage tank is also in communication with the second heat exchanger through another liquid nitrogen supply line.
9. The compact hydrogen liquefaction system of claim 1, wherein the design operating pressure of the small helium buffer tank is lower than the pressure of the high pressure helium working medium entering the helium refrigeration cycle unit of the cold box.
10. The small-sized hydrogen liquefaction system according to claim 1, further comprising an oil filtering system and a gas control panel, wherein the oil filtering system is connected to a high-pressure output end of the compressor, the oil filtering system, the big helium buffer tank, the small helium buffer tank and the gas control panel are integrally arranged on a first skid-mounted substrate, and the cold box, the internal equipment thereof and the turbo expander are integrally arranged on a second skid-mounted substrate.

Description

Small-size hydrogen liquefaction system Technical Field The invention relates to the technical field of chemical processes, in particular to a small hydrogen liquefaction system. Background Hydrogen energy acts as a clean secondary energy source and plays a key role in the progress of achieving the goal of "carbon peak, carbon neutralization". Compared with high-pressure gaseous hydrogen storage, the liquid hydrogen (liquid hydrogen) has the remarkable advantages of high storage and transportation density, low pressure, good economy and the like, and is particularly suitable for aviation, high-end scientific research, distributed energy and other scenes. In this context, there is an increasing demand for small hydrogen liquefaction devices (usually in the hundreds of liters of liquid hydrogen produced in daily life) capable of providing small, instant supplies of liquid hydrogen to universities, scientific research institutions and small and medium-sized enterprises. However, the existing technical schemes suitable for the miniaturized scene have obvious bottlenecks, and are mainly reflected in the aspects of efficiency, reliability and maintenance cost: The first category is cryocooler solutions represented by "GM refrigerator in combination with J-T throttling". Such schemes, while relatively simple in construction and easy to miniaturize, have low refrigeration efficiency, resulting in extremely high specific power consumption of the system (typically up to 70kWh/kg of liquid hydrogen or more). More critical, the mechanical abrasion exists on the moving parts (such as a piston and a cold head) in the GM refrigerator at extremely low temperature, and the GM refrigerator needs to be shut down for maintenance or replacement every thousands of hours, so that the use cost is increased, the continuity and the reliability of hydrogen supply are also affected, and the GM refrigerator is difficult to meet the occasion of long-time stable operation. The second category is to reference the "helium reverse brayton cycle" refrigeration scheme employed by large hydrogen liquefaction plants. The cycle is in principle more thermodynamically efficient. However, when it is miniaturized, the core component, the turboexpander, faces serious challenges. If a traditional oil bearing or a static pressure gas bearing requiring continuous high-pressure gas supply is adopted, the system becomes complex, the energy consumption is increased, and the risk of pollution of working media or dependence on a complex external gas supply system exists. In particular, when the system suddenly stops, the turbine rotation speed suddenly drops, if the bearing air supply cannot be maintained in time and stably, the bearing and the shaft neck are easily damaged instantaneously due to dry friction, and the high reliability advantage of the miniaturized reverse brayton system is difficult to realize. In addition, how to integrate the normal para-hydrogen conversion function in a small space to improve the quality of liquid hydrogen is a problem that needs to be solved by the miniaturized design. Therefore, the prior art lacks a small hydrogen liquefaction system capable of simultaneously realizing low energy consumption (high efficiency), long-period maintenance-free (high reliability) and guaranteeing safe operation of a turbine expander under a small scale. The invention aims to solve the comprehensive technical problem. Disclosure of Invention The invention provides a small hydrogen liquefying system aiming at solving one or more problems existing in the background art. The small hydrogen liquefaction system comprises a helium refrigeration cycle unit, a bearing protection gas supply unit and a bearing protection gas supply unit, wherein the helium refrigeration cycle unit takes helium as a working medium and operates according to the reverse brayton cycle, the unit comprises a large helium buffer tank, a compressor, a heat exchange unit in a cold box and a turbine expander which are sequentially connected through pipelines, the turbine expander adopts a dynamic pressure gas bearing, a hydrogen liquefaction unit sequentially penetrates through the heat exchange unit in the cold box and a low-temperature J-T throttle valve and is terminated at a liquid hydrogen Dewar, the heat exchange unit comprises at least one normal-to-secondary hydrogen conversion integrated heat exchanger integrated with a normal-to-secondary hydrogen conversion catalyst, and the bearing protection gas supply unit comprises a small helium buffer tank, the gas inlet end of the small helium buffer tank is communicated with the high-pressure output end of the compressor, and the gas outlet end of the small helium buffer tank is connected to the gas supply port of the dynamic pressure gas bearing of the turbine expander through a pipeline with a control valve. The heat exchange unit further comprises a first heat exchanger, wherein the first heat exchanger is provided with an