how liquid hydrogen is produced？

2023-06-27

Hydrogen production by water gas method

Use anthracite or coke as a raw material to react with water vapor at high temperature to obtain water gas (C+H2O→CO+H2—heat). After purification, it is passed through a catalyst with water vapor to convert the CO into CO2 (CO+H2O →CO2+H2) to obtain a gas with a hydrogen content of more than 80%, and then press it into water to dissolve CO2, and then remove the remaining CO through a solution containing cuprous formate (or cuprous acetate containing ammonia) Compared with pure hydrogen, this method has a lower cost of producing hydrogen and has a large output and more equipment. This method is often used in ammonia synthesis plants. Some also synthesize methanol from CO and H2, and a few places use less pure hydrogen with 80% hydrogen The gas is used for artificial liquid fuel. This method is often used in Beijing Chemical Experimental Plant and small nitrogen fertilizer plants in many places.

Hydrogen production from synthetic gas and natural gas from thermal cracking of petroleum

The by-product of thermal cracking of petroleum produces a large amount of hydrogen, which is often used in hydrogenation of gasoline, hydrogen required by petrochemical and fertilizer plants. This method of hydrogen production is adopted in many countries in the world. Plants, petrochemical bases in Bohai Oilfield, etc. all use this method to produce hydrogen.

Coke Oven Gas Refrigerated Hydrogen Production
Freeze and pressurize the coke oven gas that has been preliminarily extracted to liquefy other gases and leave hydrogen. This method is used in a few places.

Hydrogen by-product of electrolysis of salt water
In the chlor-alkali industry, a large amount of pure hydrogen is produced, which is used for the synthesis of hydrochloric acid, and it can also be purified to produce ordinary hydrogen or pure hydrogen. For example, the hydrogen used in the second chemical plant is the by-product of electrolytic brine.

By-products of the brewing industry
When corn is used to ferment acetone and butanol, more than 1/3 of the hydrogen in the waste gas of the fermenter can produce ordinary hydrogen (above 97%) after repeated purification, and the ordinary hydrogen can be cooled to below -100°C by liquid nitrogen In the silica gel tube, impurities (such as a small amount of N2) can be further removed to produce pure hydrogen (more than 99.99%). For example, Beijing Brewery produces this by-product hydrogen, which is used for firing quartz products and for external units.

2. How is liquid hydrogen transported and what are the modes of transport

At present, the transportation methods of liquid hydrogen mainly include the following types:
The first is tank truck delivery. This method uses specially designed tank trucks to transfer liquid hydrogen from the manufacturer to the user's factory or station. Tank trucks are usually designed with multi-layer insulated shells to keep the temperature and pressure of liquid hydrogen stable during transportation. However, this method requires a lot of cost to build the tanker and is vulnerable to factors such as traffic accidents and distance restrictions.
The second is pipeline delivery. This approach is based on a huge liquid hydrogen delivery pipeline system. Liquid hydrogen is injected into the pipeline system by the production plant, and then transported to the user's factory or hydrogen refueling station through underground pipelines. Pipeline transportation is an economical, efficient and safe way to meet the high-intensity transportation of large amounts of hydrogen. But at the same time, pipeline transportation requires the construction of large-scale infrastructure, and there are certain risks, so strict management and maintenance work are required to ensure its safety.
The third is ship transportation. Liquid hydrogen can also be transported by sea to various regions around the world. Due to the low density of liquid hydrogen, ship transportation requires special storage and transportation facilities and technologies to ensure the stability of the ship and the safety of liquid hydrogen. Ship transportation can meet the long-distance transportation needs of a large amount of liquid hydrogen, but it requires huge economic and technical costs, and strict compliance with maritime safety regulations and international conventions.

3. Is liquid hydrogen difficult to produce?

It is more difficult to produce, and the difficulty lies in the following points:
The cooling temperature is low, the cooling capacity is large, and the unit energy consumption is high;

The ortho-paraconversion of hydrogen makes the work required to liquefy hydrogen far greater than that of methane, nitrogen, helium and other gases, and the ortho-paraconversion heat accounts for about 16% of its ideal liquefaction work;

The rapid change of specific heat causes the sound velocity of hydrogen to increase rapidly with the increase of temperature. This high sound velocity makes the rotor of the hydrogen expander bear high stress, making the design and manufacture of the expander very difficult;

At the temperature of liquid hydrogen, other gas impurities except helium have solidified (especially solid oxygen), which may block the pipeline and cause an explosion.

4. What are the application industries of liquid hydrogen?

Where hydrogen is needed, such as aerospace, aviation, transportation, electronics, metallurgy, chemical industry, food, glass, and even civilian fuel departments, liquid hydrogen can be used. In terms of hydrogen medicine, medical liquid hydrogen can provide hydrogen for hydrogen-rich water machines, hydrogen-rich water cups, and hydrogen absorption devices in large places. At present, the most widely used field of liquid hydrogen in my country is aerospace.

The value of liquid hydrogen in the field of hydrogen storage is mainly manifested in the following aspects. First of all, liquid hydrogen requires a smaller volume than ordinary gaseous hydrogen, which can greatly reduce storage places and transportation costs. Secondly, liquid hydrogen is purer in quality, unlike gaseous hydrogen, which will produce impurities such as oxygen and nitrogen, which will affect the final use effect. The development of liquid hydrogen in the field of hydrogen storage and transportation is also conducive to improving the industrialization of hydrogen and expanding the application range of hydrogen energy in many fields.

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