Furnace having bent/single-pass tubes

A fired heater for heating process fluid comprising:

• radiant section enclosure means for defining at least one radiant section of said heater,
• at least one row of single-pass radiant conduit means through which said process fluid flows in use extending within said radiant section, said conduit means each having an inlet section connected to a common inlet manifold and an outlet section connected to receiving means to which heated process fluid is fed in use, and
• at least one row of burners arranged adjacent to said row of radiant conduit means to heat said process fluid as it flows through said radiant conduit means in use,
• wherein each of said radiant conduit means is bent in that it has at least a first conduit section through which said process fluid flows in use in a first flow direction and at least a second conduit section through which said process fluid flows in use in a second flow direction, said first and second conduit sections being transversely and longitudinally offset in fluid flow communication by interconnecting means,
• wherein said first and second conduit sections and said interconnecting means define a process fluid flow path that changes between said first conduit section and said interconnecting means and between said interconnecting means and said second conduit section, each change by an angle of about 10.degree.-75.degree., and
• wherein said radiant conduit means are each bent in substantially parallel planes, whereby a predisposition is imparted to said conduit means to move during heater operation in substantially the same direction with respect to said row of burners.

A fired heater for pyrolyzing normally gaseous or normally liquid aromatic and/or aliphatic hydrocarbon feedstocks to obtain olefins and other products comprising:

• refractory enclosure means defining at least one radiant pyrolysis section,
• at least one convection section,
• at least one row of bent, single-pass radiant tubes extending within said refractory enclosure means to define a corresponding coil plane, and
• at least one row of burners arranged adjacent to said row of radiant tubes within each radiant pyrolysis section to heat said radiant tubes,
• wherein each bent tube has a lower, substantially straight inlet tube section rigidly attached to an inlet manifold and an upper, substantially straight outlet tube section rigidly attached to receiving means for receiving pyrolyzed hydrocarbon from the tube, such that during pyrolysis differential thermal growth between the individual tubes in said row is constrained by said rigid connections,
• wherein said inlet and outlet tube sections are transversely and longitudinally offset in fluid flow communications by an interconnecting tube section to absorb differential thermal growth between the tubes in said row during pyrolysis,
• wherein said inlet and outlet tube sections and said interconecting tube section define a hydrocarbon flow path that changes between said inlet tube section and said interconnecting tube section and between said interconnecting tube section and said outlet tube section, each change by an angle of about 10.degree.-75.degree., and
• wherein said first and second tube sections and said interconnecting tube section all lie in said corresponding coil plane to define at least one row of substantially mutually parallel tubes, whereby a predisposition is imparted to said tubes to move during heater operation in substantially the same direction with respect to said row of burners.