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| - Large quantities of H2 are needed in the petroleum and chemical industries. The largest applications of H2 is for the processing ("upgrading") of fossil fuels, and in the production of ammonia. The key consumers of H2 in the petrochemical plant include hydrodealkylation, hydrodesulfurization, and hydrocracking.[28] H2 has several other important uses. H2 is used as a hydrogenating agent, particularly in increasing the level of saturation of unsaturated fats and oils (found in items such as margarine), and in the production of methanol. It is similarly the source of hydrogen in the manufacture of hydrochloric acid. H2 is also used as a reducing agent of metallic ores.
- Hydrogen fuel is a zero-emission fuel which uses electrochemical cells, or combustion in internal engines, to power vehicles and electric devices. It is also used in the propulsion of spacecraft and might potentially be mass-produced and commercialized for passenger vehicles and aircraft. 2H 2(g) + O 2(g) → 2 H2O (g) (If carried out in atmospheric air instead of pure oxygen (as is usually the case), hydrogen combustion may yield small amounts of NOx or nitrogen oxides, along with the water vapor.)
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| abstract
| - Hydrogen fuel is a zero-emission fuel which uses electrochemical cells, or combustion in internal engines, to power vehicles and electric devices. It is also used in the propulsion of spacecraft and might potentially be mass-produced and commercialized for passenger vehicles and aircraft. Hydrogen lies in the first group and first period in the periodic table, i.e. it is the first element on the periodic table, making it the lightest element. Since hydrogen gas is so light, it rises in the atmosphere and is therefore rarely found in its pure form, H2. In a flame of pure hydrogen gas, burning in air, the hydrogen (H2) reacts with oxygen (O2) to form water (H2O) and releases energy. 2H 2(g) + O 2(g) → 2 H2O (g) (If carried out in atmospheric air instead of pure oxygen (as is usually the case), hydrogen combustion may yield small amounts of NOx or nitrogen oxides, along with the water vapor.) The energy released enables hydrogen to act as a fuel. In an electrochemical cell, that energy can be used with relatively high efficiency. If it simply is used for heat, the usual thermodynamic Carnot limits on the thermal efficiency apply. Since there is very little free hydrogen gas, hydrogen is in practice only an energy carrier, like electricity, not an energy resource. Hydrogen gas must be produced, and that production always requires more energy than can be retrieved from the gas as a fuel later on. This is a limitation of the physical law of the conservation of energy. Hydrogen production induces environmental impacts.
- Large quantities of H2 are needed in the petroleum and chemical industries. The largest applications of H2 is for the processing ("upgrading") of fossil fuels, and in the production of ammonia. The key consumers of H2 in the petrochemical plant include hydrodealkylation, hydrodesulfurization, and hydrocracking.[28] H2 has several other important uses. H2 is used as a hydrogenating agent, particularly in increasing the level of saturation of unsaturated fats and oils (found in items such as margarine), and in the production of methanol. It is similarly the source of hydrogen in the manufacture of hydrochloric acid. H2 is also used as a reducing agent of metallic ores. Apart from its use as a reactant, H2 has wide applications in physics and engineering. It is used as a shielding gas in welding methods such as atomic hydrogen welding. H2 is used as the rotor coolant in electrical generators at power stations, because it has the highest thermal conductivity of any gas. Liquid H2 is used in cryogenic research, including superconductivity studies. Since H2 is lighter than air, having a little more than 1/15th of the density of air, it was once widely used as a lifting agent in balloons and airships. However, this use was curtailed after the Hindenburg disaster convinced the public that the gas was too dangerous for this purpose. Hydrogen's rarer isotopes also each have specific applications. Deuterium (hydrogen-2) is used in nuclear fission applications as a moderator to slow neutrons, and in nuclear fusion reactions. Deuterium compounds have applications in chemistry and biology in studies of reaction isotope effects. Tritium (hydrogen-3), produced in nuclear reactors, is used in the production of hydrogen bombs, as an isotopic label in the biosciences, and as a radiation source in luminous paints. The triple point temperature of equilibrium hydrogen is a defining fixed point on the ITS-90 temperature scale.
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