| 摘要 |
A gas containing a high proportion of methane (e.g. 90 percent or more) is produced by (i) reacting a preheated mixture of steam and the vapor of a predominantly paraffinic hydrocarbon feedstock having a final boiling point of not more than 300 DEG C. in the presence of a steam-reforming catalyst to give a gas containing methane, hydrogen, carbon oxides and undecomposed steam, the reaction zone being cooled by a heat exchanger; (ii) reacting the stage (i) product gas in the presence of a methanation catalyst to increase the methane concentration, the reaction zone being cooled by a heat exchanger, and (iii) removing steam and optionally carbon dioxide from the gas leaving stage (ii). Both stages are operated at as low a temperature as possible to maximize the production of methane. The heat exchangers are preferably fluid-cooled internal heat exchangers. The fluid coolant may be water or steam. Water may be used in stage (iii) to remove (by cooling) steam; passed into the stage (ii) heat exchanger and converted into steam; passed into the stage (i) heat exchanger; and then used as the process steam.
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