Combustion of gaseous fuel

Abstract

A fuel gas is passed into one set of channels in a compact reactor ( 12 ) consisting of a plurality of metal sheets ( 41 ) arranged to define first and second gas flow channels ( 14 and 15 ), the channels being arranged alternately to ensure good thermal contact between the gases in them and each channel containing a removable metallic heat conducting insert ( 44 ) coated with a ceramic. In the set of channels carrying the fuel the ceramic supports particles of a transition metal oxide, which is reduced by the combustion gas to form metal particles. In the other set of channels the ceramic supports particles of a transition metal, and these channels carry a flow of an oxidizing gas, which oxidises the metal. The flows to the two sets of channels are then exchanged. If the oxidizing gas is steam, the result is a stream of pure hydrogen.

1 . An apparatus for performing combustion of a gaseous fuel, the apparatus comprising a compact reactor consisting of a plurality of metal sheets arranged to define first and second gas flow channels, the channels being arranged alternately to ensure good thermal contact between the gases in them and each channel containing a removable metallic heat conducting insert coated with a support ceramic, in one set of channels the ceramic incorporating particles comprising an oxide of a transition metal and in the other set of channels the ceramic incorporating particles of a transition metal, and the apparatus comprising means to supply a gaseous fuel to the channels containing the oxide particles and an oxidizing gas to the channels containing the metal particles, and means to exchange the gases supplied to the channels at intervals.  
     
     
         2 . An apparatus as claimed in  claim 1  wherein the oxide or metal particles are less than 50 μm in size.  
     
     
         3 . An apparatus as claimed in  claim 1  wherein the oxide or metal particles are larger than about 10 nm.  
     
     
         4 . An apparatus as claimed in  claim 1  wherein the transition metal is one or more selected from chromium, copper, cobalt, nickel, iron or manganese.  
     
     
         5 . An apparatus as claimed in  claim 4  wherein the proportion of the transition metal is in the range 5-50% by weight of the ceramic.  
     
     
         6 . An apparatus as claimed in  claim 1  wherein both the first and the second gas flow channels are between 1 mm and 5 mm deep in the direction normal to the sheets.  
     
     
         7 . An apparatus as claimed in  claim 1  also comprising sheets to define channels for generating superheated steam.  
     
     
         8 . A method for performing combustion of a gaseous fuel, the method using a compact reactor consisting of a plurality of metal sheets arranged to define first and second gas flow channels, the channels being arranged alternately to ensure good thermal contact between the gases in them and each channel containing a removable metallic heat conducting insert coated with a support ceramic, in the first flow channels the ceramic initially incorporating particles comprising an oxide of a transition metal and in the second flow channels the ceramic initially incorporating particles of a transition metal, and the method comprising two steps carried out alternately: 
 a) supplying a gaseous fuel to the first flow channels containing oxide particles, and supplying an oxidizing gas to the second flow channels containing metal particles;    b) supplying the said gaseous fuel to the second flow channels and supplying the oxidizing gas to the first flow channels; each step being carried out for sufficient time that a substantial proportion of the oxide particles have been reduced, and the gas flows then being exchanged so the other step is carried out.    
     
     
         9 . A method as claimed in  claim 8  wherein the exhaust gases from the channels to which the gaseous fuel is supplied re processed so as to sequester carbon dioxide.  
     
     
         10 . A method as claimed in  claim 8  wherein the oxidizing gas is steam, so as to produce hydrogen as a product.