Abstract: A tubular furnace uses a fluid to be heated which is prevented from coking or a heating tube which is prevented from burning. Heat is provided through a smaller heat transfer area and problems of corrosion at low temperature of the heating pipe in the tubular furnace due to sulfur content in the fuel are solved, to thereby achieve a high efficiency. A coil path(3) is divided into a plurality of zones(2a,2b,2c,2d), each with at least one regenerative-heating-type alternate combustion system(4). The system supply combustion air to burners(5,6) through regenerative beds(7,7) and the discharge of combustion gas therefrom. Combustion is independently controlled in each zone to create a desired heat flux pattern such that a boundary layer temperature of the fluid to be heated in the zones(2a,2b,2c,2d) of the coil path(3) is lower than a coking temperature or lower than an allowable maximum temperature to be determined by the material of the heating pipe.