stoichiometric ratio of 0 5 when all the co is converted with the result that total hydrogen remains about 2 moles per mole of methane at the very low ratios further hydrogen can be formed by adding excess water as shown in the figure such 34 shift 34 reactions require cooling perhaps in a cylinder located downstream from the burner cooled as by a spiral heat exchanger with air flowing therethrough in addition heat loss is proportional to external areas and the configuration of fig4 does not minimize this area the prior art burner is indicated by numeral 45 having a housing 46 with an internal combustion chamber 47 the heat exchanger 48 accepts fuel via inlet 48 and air via inlet 50 with a portion of fuel being introduced via inlet 51 the fuel air is initially combined in a tube 52 which is open ended so that the combined fuel air is directed towards a baffle 53 as indicated by the flow of arrows such that the flow is reversed upon itself and exists through the tube 52 inside a cup 53 where the streams impinge on the baffle 53 flow direction is changed 90 degrees radially outwardly and then 90 degrees to an opening 54 in a plate 55.