Main equipment and process flow of hydrogen production and hydrogenation station outside the station

The process flow is mainly composed of the following system configuration: Discharge system, pressurization system, hydrogen storage system, hydrogenation system, nitrogen system and release system.

Discharge system

Hydrogen is transported by high-pressure hydrogen (18-20 MPa) from the gas source to the hydrogenation station. Besides, three long-tube trailer parking Spaces are set up on site, and one is available.Hydrogen pressure on the long pipe trailer is higher than the hydrogen pressure in the tank, using the high and low pressure difference, through the unloading column, the berth on the long pipe tank, when the pressure and the fixed cylinder pressure balance, compressor start, continue to unload the hydrogen tank to the fixed hydrogen storage tank.

pressurization system

pressurization system includes: cylinder lubrication system, cooling system, motor, piston, etc.Oil-free lubricating compressors have become increasingly popular (fuel cell vehicles require high hydrogen purity, and lubricating oil can also cause pollution).The cooling system in multi-stage compression can use air cooling or freezing liquid, the air cooling is simple but the cooling system and cylinder life is short, and the power consumption is large, so choose water cooling as far as possible.Drivers can be driven by electric motors or natural gas engines, but a few are also aerodynamic ones (such as the UC-Irvine station in California).

Hydrogen storage system

There are two hydrogen compression filling schemes in the hydrogen refueling station: one is graded inflation, which is the traditional pressure injection method. In order to make the pressure of the vehicle cylinder to reach 35 MPa, the pressure of the hydrogenation station needs up to 40-45 MPa to obtain rapid gas filling.The other is pressurization and compression. At this time, the pressure of the middle hydrogen storage tank of the hydrogenation station can be relatively low (e. g., 25 MPa). After partially stamping the on-board hydrogen storage bottle, the pressurization compressor is started, so that the on-board hydrogen storage bottle can reach 35 MPa.

Hydrogenation system

Hydrogenation system mainly includes high pressure pipeline, valve, air adding gun, filter, throttle protection, user display panel, metering, temperature compensation, control system and emergency pipeline system, etc.Pressure sensor, pressure sensor, overpressure protection, hose pull and fracture protection and priority filling control system are installed on the pneumatic gun.

Nitrogen system

The special fuel cell hydrogenation station for the Shanghai World Expo is equipped with a nitrogen bottle set, which serves as the gas source of the gas control system and the pipeline and equipment of the hydrogenation station.The basic process of the nitrogen supply system is as follows: the high pressure nitrogen from the nitrogen bottle group, the pressure drops to 0.7MPa after decompression, and then divided into two ways to supply the pneumatic actuator of each emergency shutdown valve as its control gas; the other gas is sent to the actuator of each pneumatic valve in the compressor to start the opening and closing of the valve.At the same time, the interface is reserved on the nitrogen conveying pipeline. When the system needs to purge, the hose is connected to the reserved interface, and nitrogen is used for purge and air replacement during system debugging and maintenance.

Release system

Hydrogen is flammable and explosive. In order to improve the safety of the station, the station adopts hydrogen centralized release system, in which the unloading column, compressor, fixed gas cylinder and hydrogenation machine are connected to the main pipe and shall not be dispersed on the spot.Nitrogen gas is non-toxic and non-combustible, and can be directly dispersed on the equipment side.

Security monitoring system

Hydrogen is a colorless, odorless, odorless gas in the standard state (0℃, 101.325 kPa) at a density of 0.08987g / L.Hydrogen molecule moves at the fastest speed, so it has the maximum diffusivity and a very high thermal conductivity. Its thermal conductivity is 7 times that of air.Hydrogen has a high ignition point of 574℃, but it can be very small, easy to catch fire, and easy to catch fire under small electrostatic sparks.The explosion limit of hydrogen in the air is (20℃, 101.325 kPa) 4.0% -74.5%, the explosion limit range is very large, plus its very small ignition energy and the maximum diffusivity, it is easy to meet the fire and explosion.Therefore, considering the characteristics of easy diffusion, expansion, combustion and explosive hydrogen, it is necessary to add a special security monitoring system in the station to ensure the operation safety of the station.