Hydrogen has a wide range of applications, among which the large amount of hydrogen is used as an important petrochemical raw material for the production of synthetic ammonia, methanol and hydrogenation in the petroleum refining process. Hydrogen is widely used in electronic industry, metallurgy industry, food processing, float glass, fine chemical industry, organic synthesis, aerospace industry and other fields. As an energy source, hydrogen is the fuel of fuel cells for future power generation and electric vehicles.

（1） Petrochemical

Hydrogen is one of the basic raw materials of modern oil refining industry and chemical industry. Hydrogen is widely used in petrochemical industry in various forms. The main raw materials for ammonia production in China are coal to gas, natural gas, naphtha and heavy oil. For a 1000t/d ammonia plant, about 336m3 hydrogen is required for every 1t ammonia production. Like synthetic ammonia, most hydrogen in synthetic methanol is also produced from coal to gas, natural gas, naphtha or heavy oil. A methanol plant with a daily output of 1000 tons requires about 560 m3 of hydrogen for each ton of methanol produced.. As methanol is a basic organic chemical raw material and can also be used as an alternative fuel, its demand is growing, so the amount of hydrogen used for methanol synthesis is likely to continue to grow.

The hydrogen consumption of petroleum refining industry is only inferior to that of synthetic ammonia. During petroleum refining, hydrogen is mainly used for naphtha hydrodesulfurization, crude diesel hydrodesulfurization, fuel hydrodesulfurization, aircraft fuel performance improvement and hydrocracking; In the petrochemical field, hydrogen is mainly used for C3 fraction hydrogenation=gasoline hydrogenation, C6-C8. Distillate hydrodealkylation and cyclohexane production.

Hydrogenation of catalytic reforming feedstock is to remove sulfide, nitride, lead, arsenic and other impurities from naphtha, which is a process used early in the petroleum refining industry. Hydrocracking is a catalytic cracking process in the presence of hydrogen. The main feature of the reaction is C-C bond breaking. Selective hydrogenation is mainly used for high-temperature cracking products. Ethylene fraction is hydrogenated in gas phase, and propylene fraction is hydrogenated in liquid phase.

Hydrorefining is also a process to remove harmful compounds. In addition to hydrogen sulfide, mercaptan and total sulfur, alkynes, olefins, metals and quasi metals can be removed during hydrogenation. Therefore, in the process of modern petrochemical processing, the use of hydrogenation process can improve the quality of petrochemicals, increase the output of * * * valuable petrochemicals, reduce the generation of heavy oil residues and tar, reduce the amount of carbon deposition, and improve the adaptability of petroleum processing plants. Many valuable petrochemicals can be obtained from petroleum processing wastes, purify a series of products, and remove harmful impurities. Hydrogen is a general cross chemical agent for modern petroleum processing industry products, which can improve the production capacity of large-scale cracking units.

In the petrochemical field, hydrogen and carbon monoxide can also be used to react to synthesize a variety of organic compounds, such as the synthesis of ethylene glycol, the synthesis of polymethylene, the homologous reaction of alcohols, and the reaction with unsaturated hydrocarbons to produce aldehydes. In addition, selective hydrogenation can be used to produce alcohols from aldehydes, olefins from alkynes, aniline from nitrobenzene and hydrogenated naphthalene from naphthalene.

（2） Electronic industry

In the growth of some electronic materials and the preparation of substrates, oxidation process, epitaxy process and chemical vapor deposition (CVD) technology, hydrogen is used as the reaction gas, reduction gas or protection gas. Semiconductor integrated circuit production requires high gas purity, such as the allowable concentration of oxygen impurities of 10-12. The "doping" of trace impurities will change the surface characteristics of semiconductors, even reduce the yield of products or cause waste products.

High purity hydrogen is also needed in the manufacture of amorphous silicon solar cells. Amorphous silicon thin film semiconductor is a new material that has been successfully developed in the world in the past decade. It has shown an attractive application prospect in solar energy conversion and information technology.

The application and development of optical fiber have been used on a large scale. Quartz glass fiber is the main type of optical fiber. In the manufacturing process of optical fiber preform, it needs to be heated by hydrogen oxygen flame. After tens of times of deposition, there are certain requirements for hydrogen purity and cleanliness.

（3） Production process of float glass

The gases widely used in the glass industry are hydrogen, acetylene, oxygen and nitrogen. During the production of float glass, in order to prevent the liquid tin in the tin bath from being oxidized, nitrogen hydrogen mixture is used to protect the tin bath. The purity of gas is high, and the purity of hydrogen is 99.999%.

（4） Metallurgical industry

In the metallurgy industry, hydrogen is mainly used as reducing gas to reduce metal oxides into metals. In addition to reducing several metal oxides to make pure metals, hydrogen is often used as a protective gas in high-temperature forging of some metal equipment to prevent metal from being oxidized.

（5） Food processing industry

Many natural edible oils are highly unsaturated. After hydrogenation, the products can be stored stably, resist the growth of bacteria, and improve the viscosity of oil. The hydrogen used for hydrogenation of vegetable oil has high purity requirements. Generally, it can be used only after being strictly purified. The products of edible oil hydrogenation can be processed into human butter and edible protein. Non edible oil can be hydrogenated to produce raw materials for soap and animal feed. The process includes hydrogen saturated unsaturated acid (oleic acid, linoleic acid, etc.) glycerides, introducing hydrogen into the composition of liquid fats or vegetable oils.

（6） Space technology and gas applications

As an aviation fuel, hydrogen has many advantages. It can not only meet many requirements for future aviation fuel, but also does not pollute the environment.

The use of hydrogen as fuel is superior to hydrocarbon fuel in many aspects. In the 1960s, foreign countries began to develop the problem of using hydrogen as vehicle fuel. Conventional internal combustion engines can use hydrogen as fuel with a few modifications.

Japan has conducted a feasibility study on superconducting maglev train using liquid hydrogen as fuel. Boeing and Lewis Research Center have conducted feasibility studies on liquid hydrogen aircraft. It can be predicted that hydrogen will replace hydrocarbon as fuel in the near future.

Hydrogen and oxygen can be used for welding or metal and nonmetal melting. The temperature of hydrogen burning in oxygen can exceed 3100K. When hydrogen passes through the arc flame, it is decomposed into atomic hydrogen, which can be used for melting and welding of * * * refractory metals, high carbon steels, corrosion-resistant materials, non-ferrous metals, etc. The advantage of using atomic hydrogen for welding is that the hydrogen atomic beam can prevent the welding part from being oxidized, so that no oxide skin will be produced at the welding place.

As an energy source, hydrogen is the fuel of fuel cells for future power generation and electric vehicles. Fuel cell is to directly convert the chemical energy of hydrogen fuel and oxidant into electric energy. It has high conversion efficiency, and the product is water. It is known as "zero emission" without pollution to the environment. Hydrogen is a clean energy in the future of mankind.

（7） Other applications

(1) Because hydrogen has a high thermal conductivity, hydrogen is often used as coolant in large generator sets.

(2) Hydrogen is often used as refrigerant in scientific research that requires ultra-low temperature.

(3) Hydrogen is often used as carrier gas in gas chromatographic analysis.

(4) Due to the low density of hydrogen, it can also be used to fill balloons and airships.

(5) Heat pump cycle or heat absorption compressor can be established by using the properties of hydrogen absorption, heat release and dehydrogenation of metal hydride.