Fired heater with heat pipe preheater

Abstract

An improved fired heater with air preheating provided by one or more heat pipes. The fired heater may include at least one burner for combusting a fuel stream and an air stream and producing heated exhaust gases; a hot gas flow path and at least one conduit containing a process fluid to be heated by heat transfer from the heated exhaust gases; and an air preheater comprising at least one heat pipe having a first section exposed to the heated exhaust gases and a second section exposed to the air stream, wherein the heat pipe is positioned and arranged to transfer heat from the heated exhaust gases to the air stream, wherein the at least one heat pipe contains a working fluid sealed within the heat pipe, wherein said working fluid transfers heat from the heated exhaust gas to the air stream to be preheated.

1 . A fired heater comprising:
 at least one burner for combusting a fuel stream and an air stream and producing heated exhaust gases;   a hot gas flow path and at least one conduit containing a process fluid to be heated by heat transfer from the heated exhaust gases; and   an air preheater comprising at least one heat pipe having a first section exposed to the heated exhaust gases and a second section exposed to the air stream, wherein the heat pipe is positioned and arranged to transfer heat from the heated exhaust gases to the air stream, wherein the at least one heat pipe contains a working fluid sealed within the heat pipe, wherein said working fluid transfers heat from the heated exhaust gas to the air stream to be preheated.   
     
     
         2 . The fired heater of  claim 1 , wherein the air preheater comprises a plurality of heat pipes. 
     
     
         3 . The fired heater of  claim 1 , wherein the first section of the heat pipe extends into the hot gas flow path. 
     
     
         4 . The fired heater of  claim 1 , wherein the air preheater includes a passageway for passage of the heated exhaust gases therethrough. 
     
     
         5 . The fired heater of  claim 4 , wherein the passageway is contiguous with a convection section of the fired heater, the convection section including the at least one conduit containing the process fluid, and wherein the passageway is fluidly connected to the hot gas flow path. 
     
     
         6 . The fired heater of  claim 4 , wherein the air preheater provides a pressure drop of less than 0.8 inch w.c. for a flow velocity of 11 ft/sec through an inlet of the passageway. 
     
     
         7 . The fired heater of  claim 1 , further comprising an exhaust stack positioned downstream of the convection section, wherein the first section of the heat pipe is positioned at a same level or above the conduit of the convection section and below or inside the exhaust stack. 
     
     
         8 . The fired heater of  claim 1 , wherein the second section of the heat pipe is elevated relative to the first section of the heat pipe. 
     
     
         9 . The fired heater of  claim 8 , wherein the heat pipe has a center axis extending through the first section and second section and the center axis forms an angle of at least 10 degrees with respect to the horizon. 
     
     
         10 . The fired heater of  claim 1 , wherein the heated flue gas moves through the convection section and air preheater solely by natural draft. 
     
     
         11 . The fired heater of  claim 1 , wherein the air stream is fed through the air preheater and to the at least one burner solely by a forced draft fan. 
     
     
         12 . The fired heater of  claim 10 , wherein the air stream is fed through the air preheater and to the at least one burner solely by a forced draft fan. 
     
     
         13 . The fired heater of  claim 1 , wherein the fired heater is a delayed coker. 
     
     
         14 . The fired heater of  claim 1 , wherein the heated exhaust gas stream is cooled in a tubular air preheater before it passes by the first section of the heat pipe. 
     
     
         15 . A method for operating a fired heater comprising:
 (a) combusting a fuel stream and an air stream to produce heated exhaust gases;   (b) exposing the heated exhaust gases to a conduit transporting a process fluid to be heated by heat transfer from the heated exhaust gases;   (c) exposing the heated exhaust gases to at least one heat pipe downstream of the conduit;   (d) transferring heat from the heated exhaust gases to a working fluid in the at least one heat pipe; and   (e) transferring heat from the working fluid to the air stream to preheat the air stream.   
     
     
         16 . The method of  claim 15 , wherein steps (a)-(e) are performed without the assistance of an induced draft fan.