Apparatus and process for hydrocarbon steam cracking

A cracking furnace (100) for steam cracking a hydrocarbon feedstock, wherein the furnace (100) comprises

• one or more reactor tubes, wherein each reactor tube comprises one or more tube passes (110) for transporting the hydrocarbon feedstock and dilution steam, and wherein the one or more tube passes are arranged in a lane (115), wherein one side of the lane is in contact with a 1st plane (111);
• and
• an electrically heated infrared emitter (130) comprising one or more electrically powered heating elements (132) for transferring heat to the reactor tubes (110), wherein the one or more electrically powered heating elements (132) are arranged in contact with a 2nd plane (112) and are configured to emit their electromagnetic radiation with a wavelength of between 0.7 μm and 1 mm, and,
• an enclosure (150) surrounding the one or more reactor tubes (110) and the electrically heated infrared emitter (130), wherein the enclosure (150) comprises an enclosing inner wall surface (152), wherein the enclosing inner wall surface (152) comprises a material with a reflectance for wavelengths in the infrared range of at least 0.1, and wherein the enclosure (150) comprises one or more layers (154) concentrically arranged around the inner wall surface (152), and wherein each layer (154) comprises a material with a thermal conductivity λ that is lower than the nearest enclosed wall within, for example at least 0.05 W/m·K, lower, and
• wherein the 1st and 2nd planes are parallel to one another, and separated by a distance (d) equal to at least one times an outer diameter of the reactor tube, or at least 2 times, or at least 3 times, or at least 4 times the outer diameter of the reactor tube, and wherein the distance (d) is at least 0.15 m to at most 0.30 m, and wherein the electrically heated infrared emitter (130) is configured to produce a radiation heat flux of at least 20 000 W/m2.