A Method to Produce Methane-Containing Gas
Hydrogen and carbon oxides are reacted to form methane by passing an inlet stream of preheated methanation synthesis gas together with a recycle stream of product gas through a catalyst bed in an adiabatic methanation reactor. The inlet temperature is between 250-350oC, the outlet temperature between 500-700oC. The recycle stream is withdrawn from the outlet stream after the latter has been cooled to a temperature between 250-350oC and being, however, at least 50oC above the dew point. A preferred means for withdrawing the recycle stream is an ejector driven by the inlet stream or by added steam.
A method is suggested to produce methane-containing gas by contacting a mixture of carbon monoxide and hydrogen, preliminary heated to 259-339°C, with nickel catalyst at an elevated temperature and a pressure of 26-71 atm in an adiabatic reactor (the first step). The outgoing gas flow, which is carried off the first step at a temperature of 500-700°C, is cooled to 250-350°C, provided that its dew point lays below this temperature by not less than 51°C, and transported to the second methanization step. To improve the process economic efficiency, a part of the cooled gas is injected into the first step reactor by means of steam or feed stream to provide a 500-700°C temperature of the outgoing gas flow.