Low consumption assisted flare apparatus and method

Abstract

An assisted flare apparatus and method which increase the amount of air which is inducted into each of the flare combustion tip assemblies used in the apparatus by injecting the steam or other assist media used in each tip assembly into an inner conduit of the tip assembly which is configured such that at least a lower portion of the inner conduit is in the form of a venturi flow structure in which a straight venturi flow section is followed by a diverging venturi bell outlet section.

What is claimed is: 
     
         1 . An apparatus for combusting a flare gas comprising one or more flare nozzle assemblies, each of the flare nozzle assemblies comprising:
 an outer conduit having a longitudinal axis, a rearward longitudinal end, and a forward longitudinal end;   an inner conduit for a flow of an entrainment media and air, the inner conduit comprising
 an inlet opening at a rearward longitudinal end of the inner conduit, 
 a discharge opening at a forward longitudinal end of the inner conduit, 
 a longitudinally extending straight venturi section of substantially constant interior cross-sectional area, and 
 a longitudinally extending diverging venturi section which increases in interior cross-sectional area as the diverging venturi section extends forwardly from a forward longitudinal end of the straight venturi section; 
   an injection structure positioned outside of the inlet opening of the inner conduit for injecting the entrainment media into the inlet opening of the inner conduit;   the inner conduit extending into the rearward longitudinal end of the outer conduit such that (i) the rearward longitudinal end of the inner conduit is positioned outside of the rearward longitudinal end of the outer conduit and (ii) the discharge opening of the inner conduit is positioned substantially at the forward longitudinal end of the outer conduit; and   a longitudinally extending flow annulus for the flare gas which is formed in the outer conduit between an interior surface of the outer conduit an exterior of the inner conduit, wherein the longitudinally extending flow annulus (i) laterally surrounds the longitudinal axis of the outer conduit and (ii) has an inlet opening at the rearward longitudinal end of the outer conduit for receiving the flare gas.   
     
     
         2 . The apparatus of  claim 1  wherein:
 the inner conduit further comprises a venturi inlet bell structure at the rearward longitudinal end of the inner conduit and 
 the longitudinally extending straight venturi section of the inner conduit extends forwardly from the venturi inlet bell structure. 
 
     
     
         3 . The apparatus of  claim 1  wherein the inner conduit further comprises a longitudinal discharge section of substantially constant internal cross-sectional area which extends forwardly from a forward longitudinal end of the longitudinally extending diverging venturi section of the inner conduit to the discharge opening of the inner conduit. 
     
     
         4 . The apparatus of  claim 3  wherein the forward longitudinal end of the longitudinally extending diverging venturi section of the inner conduit is located outside of the rearward longitudinal end of the outer conduit. 
     
     
         5 . The apparatus of  claim 3  wherein the forward longitudinal end of the longitudinally extending diverging venturi section of the inner conduit is located inside of the outer conduit. 
     
     
         6 . The apparatus of  claim 1  further comprising a plenum for the flare gas, the plenum having an interior, an upper wall, and a lower wall and, wherein for each of the one or more flare nozzle assemblies:
 the rearward longitudinal end of the outer conduit of the flare nozzle assembly is located inside the interior of the plenum or at the upper wall of the plenum such that the inlet opening of the flow annulus of the flare nozzle assembly is in fluid communication with the interior of the plenum; 
 the forward longitudinal end of the outer conduit of the flare nozzle assembly is located outside of plenum; 
 the inner conduit of the flare nozzle assembly extends through the lower wall of the plenum; and 
 the inlet opening of the inner conduit of the flare nozzle assembly is located outside of the plenum. 
 
     
     
         7 . The apparatus of  claim 6  comprising a plurality of the flare nozzle assemblies. 
     
     
         8 . The apparatus of  claim 6  further comprising a flare stack having an upper end on which the plenum is located. 
     
     
         9 . The apparatus of  claim 1  wherein
 the longitudinally extending straight venturi section of the inner conduit has a cylindrical interior surface and 
 the longitudinally extending diverging venturi section of the inner conduit comprises an interior surface having a conical shape. 
 
     
     
         10 . The apparatus of  claim 1  further comprising an upper steam injection ring or assembly positioned outside of and around the forward longitudinal end of the outer conduit. 
     
     
         11 . A method of combusting a flare gas comprising the steps of:
 a) delivering the flare gas upwardly through an annulus between an inner surface of an outer conduit and an exterior of an inner conduit, the inner conduit extending upwardly into a lower end of the outer conduit, the inner conduit having a discharge opening substantially at the upper end of the outer conduit, and the inner conduit having an inlet opening at a lower end of the inner conduit which is positioned outside of and spaced downwardly from the lower end of the outer conduit;   b) injecting an entrainment media into the inlet opening of the inner conduit from an injection structure which is spaced downwardly from the inlet opening of the inner conduit so that the entrainment media inducts an amount of air into the inner conduit as the entrainment media travels through a gap between the injection structure and the inlet opening of the inner conduit; and   c) increasing the amount of air inducted into the inner conduit by the entrainment media in step (b) by delivering the entrainment media upwardly through a venturi structure, which forms at least a lower portion of the inner conduit, and out of the discharge opening of the inner conduit substantially at the upper end of the outer conduit,   wherein the venturi structure comprises (i) an upwardly extending straight venturi section of the inner conduit having a substantially constant interior cross-sectional area followed by (ii) a diverging venturi section of the inner conduit which increases in interior cross-sectional area as it extends upwardly from the straight venturi section.   
     
     
         12 . The method of  claim 11  wherein the entrainment media is steam. 
     
     
         13 . The method of  claim 11  wherein the inner conduit further comprises a venturi inlet bell structure at the lower end of the inner conduit. 
     
     
         14 . The method of  claim 11  wherein the inner conduit further comprises an upper discharge section having a substantially constant internal cross-sectional area which extends upwardly from the diverging venturi section of the inner conduit to the discharge opening of the inner conduit.