Hydrogen Liquefier

Hydrogen liquefaction system The hydrogen gas produced from lignite is refined to a high purity and pressure-fed to a hydrogen liquefaction system by pipeline. The hydrogen gas is cooled to approximately 20 K (-253°C) and liquefied by a hydrogen liquefier.

The LH2 is loaded into containers and tank trucks equipped with thermal insulated tanks, and transported to the shipping terminal. In a large-scale chain, the hydrogen gas is sent to the shipping terminal by pipeline, and liquefied by a hydrogen liquefier established at the terminal. At the shipping terminal, the LH2 is temporarily stored in a tank.

A significant feature of hydrogen is that it exists as high-energy-level ortho-hydrogen and low-energy-level parahydrogen, according to the spin direction of the nucleus. Hydrogen gas at room temperature is normal hydrogen comprising 25% para-hydrogen and 75% ortho-hydrogen, whereas LH2 is 99.8% para- hydrogen.

In the liquefaction process from normal hydrogen to LH2, it is important to maintain the equilibrium-state ortho-para composition ratio during the pre-cooling process. Also, the critical pressure for LH2 (1.28 MPa) is smaller than that of LNG (4.6 MPa), and it is important to take into account significant physical changes near the critical condition.