NOVELTY - The furnace for steam reforming hydrocarbon fraction having 1-30 carbon atoms to produce hydrogen, comprises a set of vertical tubes (1) partly filled with nickel based catalyst, and long porous burners (2) arranged in rows intercalating between parallel rows of heated tubes. Heat necessary for the steam forming reaction is supplied to tubes through catalytic combustion using burners. The rows of tubes have a distance of 650-1000 mm. Distance between a row of pipes and the closest row of elongated porous burners is 300-500 mm. Combustion air is provided to the oven through gas flues.    USE - The furnace for steam reforming hydrocarbon fraction e.g. naphtha or natural gas having 1-30 carbon atoms to produce hydrogen (claimed).    ADVANTAGE - The furnace is simple and compact and capable of effectively and safely steam reforming the hydrocarbon fraction using efficient and long porous burners thus producing an improved content (32 tonnes/hour) of hydrogen.    DETAILED DESCRIPTION - The furnace for steam reforming hydrocarbon fraction having 1-30 carbon atoms to produce hydrogen, comprises a set of vertical tubes (1) partly filled with nickel based catalyst, and long porous burners (2) arranged in rows intercalating between parallel rows of heated tubes. Heat necessary for the steam forming reaction is supplied to tubes through catalytic combustion using burners. The rows of tubes have a distance of 650-1000 mm. Distance between a row of pipes and the closest row of elongated porous burners is 300-500 mm. Combustion air is provided to the oven through gas flues located at the top or bottom of the furnace, and combustion fumes are collected by flues located at the bottom or top of the furnace. The long porous burners are supplied with fuel containing hydrogen (5-100 molar%), and have an element with porosity of less than 20%, distributors and a distance of 0.5-10 cm between an outer distributor wall and the porous element. The tubes to be heated are of bayonet type with a length of 10-14 m, and suspended from the upper wall of the furnace. The combustion air brought into the furnace is preheated at a temperature of greater than 700 degrees C. Distance between center to center of two consecutive tubes of the same row is 300-400 mm. Central distributor of the porous burner is divided into two sections each having holes with diameter increasing along axial distance in the direction of the fuel flow. An INDEPENDENT CLAIM is included for a process for steam reforming natural gas or naphtha using a furnace.    DESCRIPTION OF DRAWING(S) - The figure shows a side view of burners and tubes of the steam reforming oven.    Tubes (1)    Burners (2)    Fuel. (6)