| 摘要 |
<p>1413287 Natural gas substitute IMPERIAL CHEMICAL INDUSTRIES Ltd 11 Jan 1973 [26 Jan 1972] 3685/72 Heading C5E A natural gas substitute is produced at least partly from a hydrocarbon of higher molecular weight than methane in a first catalytic stage in which methane or a hydrocarbon of higher molecular weight than methane is reacted with steam over an externally heated steam reforming catalyst at an outlet temperature of 600- 900‹ C. to give a first gas containing carbon oxides, hydrogen and methane, the methane content of the gas being less than 30% by volume on a dry basis; a second catalytic stage in which the first gas, steam (residual and/or added) and hydrocarbon feedstock of higher molecular weight than methane are reacted together over a steam reforming and methanation catalyst to give a second gas having a methane content greater than that of the first gas and 20-40% by volume on a dry basis; and a third catalytic stage in which the second gas is reacted over a methanation catalyst at an outlet temperature of 250-450‹ C. in heat exchange with boiling water generating steam at a pressure of at least 35 atm. or with co-, currently flowing cool feed gas, whereby heat is continuously removed from the process. For heat exchange with boiling water, the third stage catalyst may be in tubes of internal diameter 20-75mm. and the hydrogen content of the feed gas to that stage may be over 15%. For co-current heat exchange, the third stage catalyst is in one or more tubes 10-60 mm. in diameter or in a space surrounding such tube or tubes and the hydrogen content of the feed gas to that stage is 8-20%. Steam may be removed from the second gas such that the gas feed to the third stage contains under 15% steam. Carbon dioxide may be removed from the second gas, e.g. such that the feed gas to the third stage contains 2-6% carbon dioxide. The second gas may be compressed before being fed to the third stage.</p> |
