There are various ways to achieve hydrogen compression, mainly including the following:
1. Positive displacement compressor
Liquid ring compressor
Working principle: The impeller of the liquid ring compressor is eccentrically installed inside the cylindrical pump casing. When the impeller rotates, the working fluid forms a liquid ring under the action of centrifugal force, and the space between the liquid ring and the impeller hub is divided into multiple chambers. As the impeller rotates, the volume of these chambers constantly changes, thereby achieving gas suction, compression, and discharge.
Features: Relatively simple structure, smooth operation, low vibration and noise. Capable of handling gases containing certain impurities and moisture, with relatively low purity requirements for hydrogen gas. Suitable for hydrogen compression in the medium pressure range, but with relatively low efficiency, especially under high pressure ratios. Regular replacement of working fluids is required, resulting in high maintenance costs. The exhaust pressure is limited and not suitable for high-pressure hydrogen compression.
Piston compressor
Working principle: The piston performs reciprocating motion inside the cylinder, and compresses the gas by changing the working volume inside the cylinder. During the inhalation process, the piston moves backwards, creating a low-pressure area inside the cylinder where hydrogen gas is drawn into the cylinder; During the compression process, the piston moves forward to compress the hydrogen gas inside the cylinder, increasing its pressure, and then discharging the high-pressure hydrogen gas through the exhaust valve.
Features: Wide applicability, capable of achieving high pressure ratio hydrogen compression. The compression efficiency is relatively high, especially in the case of multi-stage compression. Mature technology and high reliability. But it has a large volume and occupies a large area. The vibration and noise generated by piston movement are relatively large, and the maintenance workload is relatively high, requiring regular replacement of vulnerable parts.
Diaphragm compressor
Working principle: Compressing and transporting gas by reciprocating the diaphragm in the cylinder. The diaphragm is clamped by two restriction plates along the periphery and forms a cylinder. The diaphragm is driven back and forth in the cylinder by mechanical or hydraulic means. The cylinder is divided into two parts: the air chamber and the oil chamber. The diaphragm is driven by hydraulic oil to compress the hydrogen gas in the air chamber, thereby achieving the compression and transportation of hydrogen gas.
Characteristic: During the compression process, the gas is completely isolated from the lubricating oil, ensuring the purity of hydrogen gas. Good sealing performance, high compression ratio, capable of achieving high-pressure hydrogen compression. Smooth operation, minimal vibration, and low noise. However, the diaphragm is a critical component with a limited lifespan and requires regular replacement, resulting in higher costs. The displacement is relatively small and not suitable for high flow hydrogen compression. The equipment is expensive.
Roots Blower
Working principle: Compressing and transporting gas through the rotation of two impellers (usually three or two blades). Two impellers rotate relative to each other under the drive of synchronous gears, compressing and discharging gas in the space between the impellers and the casing.
Features: Simple structure and easy maintenance. Moderate pressure range, suitable for compression of medium and low pressure hydrogen gas. The flow is relatively stable and can be adjusted within a certain range. But the compression ratio is relatively low, which is not suitable for high-pressure hydrogen compression. The noise is loud and noise reduction measures need to be taken. Relatively low efficiency and high energy consumption.
2. Power compressor
Centrifugal compressor
Working principle: By using a high-speed rotating impeller to do work on the gas, centrifugal force is generated, thereby increasing the pressure and velocity of the gas. After entering the impeller of the centrifugal compressor, hydrogen gas is accelerated and thrown out under the rotation of the impeller, and then enters the diffuser. In the diffuser, the velocity of the gas decreases, the pressure increases, and finally discharged from the compressor.
Features: High flow rate, suitable for large-scale hydrogen compression and transportation. But there are certain requirements for the molecular weight and density of the gas, which are not suitable for the compression of low molecular weight hydrogen gas. The start-up and operation are relatively complex and require professional technical personnel. The equipment cost is high and the manufacturing difficulty is high.
3. Other compression methods
In addition to the common types of compressors mentioned above, there are also other ways to achieve hydrogen compression, such as:
Membrane compressor: fast heat dissipation, compression process close to isothermal process, can have higher compression ratio, up to 20:1. But due to the small flow rate, it is mainly used in situations where hydrogen pressure is high but the flow rate is not large.
Screw compressor: compresses gas through the rotation of the screw, which has the advantages of compact structure and smooth operation. However, its application in hydrogen compression is relatively limited.
In summary, there are various ways to achieve hydrogen compression, and the appropriate compressor type and specifications should be selected according to specific application scenarios and needs.
In addition to the previously mentioned hydrogen compression methods such as liquid ring compressors, piston compressors, diaphragm compressors, centrifugal compressors, and Roots blowers, there are several other ways to achieve hydrogen compression, including:
Screw compressor:
A screw compressor compresses gas by the rotation of two interlocking screws (male screw and female screw). As the screw rotates, gas is drawn in and compressed in the space between the screw and the casing, and then discharged.
Screw compressors have the advantages of compact structure, smooth operation, and low vibration and noise. However, its application in hydrogen compression is relatively limited, possibly due to its high requirements for hydrogen sealing and purity.
Ionic compressor:
The ion compressor uses a liquid (ionic liquid) with special physical and chemical properties to fill the cylinder and compress the gas under the drive of a hydraulic piston. Ionic liquids are almost incompressible, do not dissolve or contaminate hydrogen gas, and have good lubrication and cooling properties.
The ion compressor solves the hydrogen sealing problem and hydrogen pollution problem of hydraulic pistons, and can frequently start and stop under load. Theoretically, it can operate for a long time without maintenance. But its cost is relatively high, and currently most of the company's products are not mature enough, with few domestic applications.
Membrane compressor:
Membrane compressors use the reciprocating motion of membranes to compress gases. The diaphragm is clamped inside the cylinder and forms an air chamber, which is driven back and forth by mechanical or hydraulic means to compress the hydrogen gas inside the cylinder.
Membrane compressors have the advantages of fast heat dissipation and a compression process close to isothermal, which can result in higher compression ratios. However, due to its relatively small flow rate, it is mainly used in situations where hydrogen pressure is high but the flow rate is not large.
Scroll compressor:
A scroll compressor is a type of compressor that uses a scroll disc for gas compression. Two vortex disks mesh with each other, forming multiple enclosed spaces. As the vortex disks rotate, the volume of these enclosed spaces constantly changes, thereby achieving gas suction, compression, and discharge.
Vortex compressors have the advantages of compact structure, high efficiency, low vibration and noise. However, its application in the field of hydrogen compression is relatively limited, possibly due to its manufacturing difficulty and high cost.
Adsorption compressor:
Adsorption compressors use adsorbents (such as activated carbon, zeolite, etc.) to adsorb and desorb hydrogen gas to achieve gas compression. During the adsorption process, hydrogen gas is adsorbed on the surface of the adsorbent; During the desorption process, hydrogen gas is desorbed from the adsorbent surface by changing pressure or temperature, thereby achieving gas compression.
Adsorption compressors have the advantages of simple structure, no moving parts, and easy maintenance. But its compression efficiency is low and it requires regular replacement of the adsorbent.
It should be noted that different hydrogen compression methods have their own advantages and disadvantages, and should be comprehensively considered according to specific application scenarios and requirements. When choosing a hydrogen compression method, factors such as hydrogen purity, pressure, flow rate, as well as compressor efficiency, cost, and maintenance difficulty need to be considered.
