Carbon Dioxide → 13463-39-3

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Reaction Steps

U.S. Pat. No. 4,431,751 describes a method for producing superheated steam with the heat of catalytic methanation of a synthesis gas containing carbon monoxide, carbon dioxide and hydrogen. The process passes a gas stream first through a first internally water-cooled reactor, subsequently through an adiabatic reactor and a subsequent heat exchanger and finally through a second internally water-cooled reactor. The internally water-cooled reactors comprise a cooling system disposed within a catalyst bed through which water flows. As catalyst a nickel-containing catalyst is used. Water is passed in succession, first through the cooling system of the second internally water-cooled reactor for preheating thereof to a temperature approximating the saturated steam temperature, thereafter into the first internally water-cooled reactor for conversion into saturated steam and subsequently to the heat exchanger following the adiabatic reactor for superheating. In the exemplified process the second internally water-cooled reactor is set to operate at a gas entrance temperature between 250° C. and 350° C., specifically 300° C., at an average pressure of 37.5 bar and the product gas flowing out of the second internally water-cooled reactor is 300° C. In the example the water is brought up to a pressure of 110 bar and preheated up to 160° C. before entering the cooling system of the second internally water-cooled reactor (the boiling temperature of water at 110 bars is about 318° C.). A disadvantage of the process of U.S. Pat. No. 4,431,751 is that the very low entrance temperature of the water in the second internally water-cooled reactor, especially in combination with the cooling system used, can lead to cold spots in the catalyst bed which are expected to result deactivation of the nickel catalyst due to the formation of nickel carbonyl. In addition the process of U.S. Pat. No. 4,431,751 requires an adiabatic reactor to allow the steam to become superheated.

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