In natural gas reforming

Orphanides, R, Developments in natural gas reforming technology of syngas, Ammonia Plant Safety, 34 292—312 (1994). 

It is difficult to predict system efficiency of hydrogen production from natural gas and electricity in 2015-25. The European HEP (2007) aims for a conversion efficiency by low-temperature electrolysis of above 70 percent in 2015 and the US DOE (2007) for 71 percent in 2017, but in system efficiency, energy use for compression and refilling also has to be taken into account. Eor the conversion efficiency in natural gas reforming, the US target is 75 percent in 2015 whereas there is no European target. 

Use of adsorbers (e.g., ZnO to remove sulfhr-containing compounds in natural gas reforming)... 

Na.tura.1 Ga.s Reforma.tion. In the United States, most hydrogen is presently produced by natural gas reformation or methane—steam reforming. In this process, methane mixed with steam is typically passed over a nickel oxide catalyst at an elevated temperature. The reforming reaction is... 

Impurities can be removed by formation of a gaseous compound, as in the fire-refining of copper (qv). Sulfur is removed from the molten metal by oxidation with air and evolution of sulfur dioxide. Oxygen is then removed by reduction with C, CO, in the form of natural gas, reformed... 

Natural gas contains both organic and inorganic sulfur compounds that must be removed to protect both the reforming and downstream methanol synthesis catalysts. Hydrodesulfurization across a cobalt or nickel molybdenum—zinc oxide fixed-bed sequence is the basis for an effective purification system. For high levels of sulfur, bulk removal in a Hquid absorption—stripping system followed by fixed-bed residual clean-up is more practical (see Sulfur REMOVAL AND RECOVERY). Chlorides and mercury may also be found in natural gas, particularly from offshore reservoirs. These poisons can be removed by activated alumina or carbon beds. 

This excess hydrogen is normally carried forward to be compressed into the synthesis loop, from which it is ultimately purged as fuel. Addition of by-product CO2 where available may be advantageous in that it serves to adjust the reformed gas to a more stoichiometric composition gas for methanol production, which results in a decrease in natural gas consumption (8). Carbon-rich off-gases from other sources, such as acetylene units, can also be used to provide supplemental synthesis gas. Alternatively, the hydrogen-rich purge gas can be an attractive feedstock for ammonia production (9). 

Thermal cracking tends to deposit carbon on the catalyst surface which can be removed by steaming. Carbon deposition by this mechanism tends to occur near the entrance of the catalyst tubes before sufficient hydrogen has been produced by the reforming reactions to suppress the right hand side of the reaction. Promoters, such as potash, are used to help suppress cracking in natural gas feedstocks containing heavier hydrocarbons. Carbon may also be formed by both the disproportionation and the reduction of carbon monoxide... 

Hydrogen occurs naturally in the form of chemical compounds, most frequently in water and hydrocarbons. Hydrogen can be produced from fossil fuels, nuclear and renewable energy sources by a number of processes, such as natural gas reforming,... 

A typical steam reformed natural gas reformate is presented in Table 9-2. 

Steam, at high temperatures (975-1375 K) is mixed with methane gas in a reactor with a Ni-based catalyst at pressures of 3-25 bar to yield carbon monoxide (CO) and hydrogen (H ). Steam reforming is the process by which methane and other hydrocarbons in natural gas are converted into hydrogen and carbon monoxide by reaction with steam over a nickel catalyst on a ceramic support. The hydrogen and carbon monoxide are used as initial material for other industrial processes. 

The nickel-based reforming catalysts which are commonly used in steam reforming are quite sensitive to sulphur, halogen and heavy metal poisons. Since these elements may all be found in natural gas, a feed gas purification section is normally required. Of the mentioned catalyst poisons, sulphur is by far the most important [6],... 

We successfully demonstrated that hydrogen could be efficiently produced by catalytic steam reforming of carbohydrate-derived bio-oil fractions in a fluidized bed reactor using a commercial nickel-based catalyst. Greater steam excess than that used for natural gas reforming was necessary to minimize the formation of char and coke (or to gasify these carbonaceous solids) resulting from thermal decomposition of complex carbohydrate-derived compounds. 

Natural gas can also be used to make hydrogen fuel. About 95 percent of the hydrogen produced today in the United States is made through a process called steam-methane reforming. During this process, the methane that is in natural gas reacts... 

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