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Hydrogen production is the family of industrial methods for generating hydrogen. Currently the dominant technology for direct production is steam reforming from hydrocarbons. Many other methods are known including electrolysis and thermolysis. In 2006, the United States was estimated to have a production capacity of 11 million tons of hydrogen. 5 million tons of hydrogen were consumed on-site in oil refining, and in the production of ammonia (Haber process) and methanol (reduction of carbon monoxide). 0.4 million tons were an incidental by-product of the chlor-alkali process. Hydrogen production is an estimated $100 billion industry. According to the U.S. Department of Energy, only in 2004, 53 million metric tons were consumed worldwide. There are no natural hydrogen deposits, and for this reason the production of hydrogen plays a key role in our modern society. Currently, the majority of hydrogen (∼95%) is produced from fossil fuels by steam reforming or partial oxidation of methane and coal gasification with only a small quantity by other routes such as biomass gasification or electrolysis of water. ==Steam reforming== (詳細はnatural gas with approximately 80% efficiency, or from other hydrocarbons to a varying degree of efficiency. Specifically, bulk hydrogen is usually produced by the steam reforming of methane or natural gas.〔(Fossil fuel processor )〕 The production of hydrogen from natural gas is the cheapest source of hydrogen nowadays. This process consists of heating the gas in the presence of steam and a nickel catalyst. The resulting exothermic reaction breaks up the methane molecules and forms carbon monoxide CO and hydrogen H2. The carbon monoxide gas can then be passed with steam over iron oxide or other oxides and undergo a water-gas shift reaction. This last reaction produces even more H2. The downside to this process is that its major byproducts are CO, CO2 and other greenhouse gasses.〔 Depending on the quality of the feedstock (natural gas, rich gases, naphtha, etc.), one ton of hydrogen produced will also produce 9 to 12 tons of CO2. For this process at high temperatures (700–1100 °C), steam (H2O) reacts with methane (CH4) in an endothermic reaction to yield syngas.〔(【引用サイトリンク】 publisher = U.S. Department of Energy )〕 :CH4 + H2O → CO + 3 H2 In a second stage, additional hydrogen is generated through the lower-temperature, exothermic, water gas shift reaction, performed at about 360 °C: :CO + H2O → CO2 + H2 Essentially, the oxygen (O) atom is stripped from the additional water (steam) to oxidize CO to CO2. This oxidation also provides energy to maintain the reaction. Additional heat required to drive the process is generally supplied by burning some portion of the methane. ===CO2 sequestration=== Steam reforming generates carbon dioxide (CO2). Since the production is concentrated in one facility, it is possible to separate the CO2 and dispose of it without atmospheric release, for example by injecting it in an oil or gas reservoir (see carbon capture), although this is not currently done in most cases. A carbon dioxide injection project has been started by a Norwegian company StatoilHydro in the North Sea, at the Sleipner field. Integrated steam reforming / co-generation - It is possible to combine steam reforming and co-generation of steam and power into a single plant. This can deliver benefits for an oil refinery because it is more efficient than separate hydrogen, steam and power plants. Air Products recently built an integrated steam reforming / co-generation plant in Port Arthur, Texas.〔(Port Arthur II Integrated Hydrogen/Cogeneration Facility, Port Arthur, Texas ) Power magazine, September 2007〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hydrogen production」の詳細全文を読む スポンサード リンク
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