A process and apparatus for producing a hydrogen-containing gas in a reformer where a furnace, which is independent of the reformer, heats the effluent from a prereformer prior to reacting the prereformer effluent in the reformer. The prereformer effluent may be heated in a heat exchange tube in the furnace where the heat exchange tube is positioned in the furnace to preclude direct radiation from any flames in the furnace thereby preventing local overheating of the heat exchange tube and preventing carbon formation in the heat exchange tube. Fuel and oxidant gas may be introduced into the furnace with significant excess oxidant gas, having a stoichiometric ratio of 1.8 to 2.8 for controlling the temperature of the heat exchange tube.