Apparatus and process for hydrocarbon steam cracking

Abstract

The present invention relates to an apparatus for hydrocarbon steam cracking. more specifically to a cracking furnace for steam cracking a hydrocarbon feedstock, wherein the furnace comprises one or more reactor tubes for transporting the hydrocarbon feedstock and dilution steam; wherein each reactor tube comprises one or more tube passes, and wherein the furnace comprises an electrically heated infrared emitter comprising one or more electrically powered heating elements for transferring heat to the reactor tubes, and wherein the furnace comprises an enclosure surrounding the one or more reactor tubes and the electrically heated infrared emitter. The present invention also relates to a process for hydrocarbon steam cracking using said apparatus.

1 - 22 . (canceled) 
     
     
         23 . 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 1 st  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 2 nd  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 1 st  and 2 nd  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/m 2 .   
     
     
         24 . The cracking furnace ( 100 ) of  claim 23  wherein the one or more electrically powered heating elements ( 132 ) are configured to emit at least 50%, preferably at least 60%, more preferably at least 70%, or even 100%, of their electromagnetic radiation with a wavelength of between 0.7 μm and 1 mm. 
     
     
         25 . The furnace ( 100 ) according to  claim 23 , wherein the one or more tube passes ( 110 ) are disposed parallel to each other. 
     
     
         26 . The furnace ( 100 ) according to  claim 23 , wherein the tube passes are arranged in a lane ( 115 ), wherein said lane is configured as a single-lane, or a dual-lane, or a triple-lane, or a x-lane arrangement of tube passes, wherein x is 4 or more. 
     
     
         27 . The furnace ( 100 ) according to  claim 23 , wherein the 1 st  and 2 nd  planes are parallel to one another, and separated by a distance (d) of at least 0.20 m to 0.30 m, for example about 0.30 m. 
     
     
         28 . The furnace ( 100 ) according to  claim 23 , wherein the one or more electrically powered heating elements ( 132 ) are arranged in contact with a 2 nd  plane ( 112 ), and wherein the enclosing inner wall surface ( 152 ) of the enclosure and the 2 nd  plane are parallel to one another, and separated by a distance (d e ) of at most 1.0 m. 
     
     
         29 . The furnace ( 100 ) according to  claim 23 ,
 wherein the tube passes ( 110 ) and electrically powered heating elements ( 132 ) are arranged in a reaction unit ( 120 ), wherein the reaction unit comprises one lane ( 115 ) of tube passes,   wherein one side of the lane contacts the 1 st  plane ( 111 ), and the other side of the lane contacts a 3 rd  plane ( 113 ) parallel to the 1 st  plane, wherein the 3 rd  plane is separated from the 1 st  plane by the lane ( 115 ) of tube passes ( 110 ),   wherein some of the electrically powered heating elements ( 132 ) are arranged contacting the 2 nd  plane ( 112 ) and some of the electrically powered heating elements ( 132 ) are arranged contacting a further 4 th  plane ( 114 ),   wherein the 1 st  and 2 nd  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, for example about 0.30 m, and   wherein the 3 rd  and 4 th  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, for example about 0.30 m.   
     
     
         30 . The furnace ( 100 ) according to  claim 29 , comprising more than one reaction unit ( 120 ,  120 ′), preferably wherein the reaction units are arranged in parallel, and preferably in a direction perpendicular to a longitudinal axis of the lane. 
     
     
         31 . The furnace ( 100 ) according to  claim 23 , wherein the enclosing inner wall surface ( 152 ) of the enclosure ( 150 ) comprises a material with a thermal conductivity λ, measured at 1000° C., of at most 0.50 W/m·K, preferably at most 0.40 W/m·K, preferably at most 0.30 W/m·K, preferably at most 0.25 W/m·K, preferably at most 0.20 W/m·K. 
     
     
         32 . The furnace ( 100 ) according to  claim 23 , wherein the enclosing inner wall surface ( 152 ) of the enclosure ( 150 ) comprises a material with a reflectance for wavelengths in the infrared range of at least 0.2, or at least 0.3, or at least 0.4, or at least 0.5. 
     
     
         33 . The furnace ( 100 ) according to  claim 23 , wherein the enclosing inner wall surface ( 152 ) of the enclosure ( 150 ) comprises a material selected from the group comprising alumino-silicate refractory bricks, silicate bricks, and corundum (alumina) bricks. 
     
     
         34 . The furnace ( 100 ) according to  claim 23 , wherein the one or more reactor tubes or reactor tube passes are coated with an infrared receiving material and/or wherein the one or more reactor tubes or reactor tube passes are made of infrared receiving material, preferably wherein said infrared receiving material is a material having an emissivity of at least 0.80, preferably at least 0.90, and most preferably at least 0.93. 
     
     
         35 . The furnace ( 100 ) according to  claim 23 , wherein the electrically heated infrared emitter ( 130 ) is configured to produce a radiation heat flux of at least 40 000 W/m 2 , and more preferably at least 60 000 W/m 2 , for example about 80 000 W/m 2 . 
     
     
         36 . The furnace ( 100 ) according to  claim 23 , wherein said one or more electrically heating elements ( 132 ) are selected from the group comprising: ceramic heating elements, carbon-based heating elements, carbide-based heating elements, silicide-based heating elements; heating elements in a quartz tube, and metal or metal alloy heating elements, and any combinations thereof. 
     
     
         37 . The furnace ( 100 ) according to  claim 23 , wherein the one or more electrically powered heating elements are planar emitters or scallop emitters configured to emit radiation at one side; or planar emitters or scallop emitters configured to emit radiation at both sides; or cylindrical emitters configured to emit radiation in all directions; or any combinations thereof. 
     
     
         38 . The furnace ( 100 ) according to  claim 23 , wherein the electrically heating elements ( 132 ) are not electrical wires. 
     
     
         39 . A process for steam cracking a hydrocarbon feedstock to produce olefins, comprising the steps of:
 feeding a hydrocarbon feedstock and dilution steam to one or more reactor tubes ( 110 ) in a cracking furnace ( 100 ) according to  claim 23 ; and,   exposing the hydrocarbon feedstock and dilution steam in the one or more reactor tubes ( 110 ) to infrared radiation from the electrically heated infrared emitter ( 130 ) to crack at least a portion of the hydrocarbon feedstock.   
     
     
         40 . The process according to  claim 39 , wherein the electrically heated infrared emitter ( 130 ) comprises one or more electrically powered heating elements ( 132 ) for transferring heat to the reactor tubes ( 110 ), wherein the electrically powered heating elements ( 132 ) emit at a temperature of at least 1200 K to at most 1800 K, for example at least 1400 K to at most 1600 K, for example at least 1450 K to at most 1550 K, for example about 1500 K.