Fluid injection element for a furnace or a burner of a furnace and method for operating a furnace

Abstract

A fluid injection element is disclosed, especially for a furnace or a burner of a furnace, having a pipe and a shroud element, such that the shroud element circumferentially surrounds an axial section of the pipe extending from an axial end of the pipe, such that at least one cavity is provided at the shroud element, and the at least one cavity is in fluid communication with an interior of the pipe and the at least one cavity extends to an opening at an axial end of the shroud element.

What we claim is: 
     
         1 . A fluid injection element comprising a pipe and a shroud element, wherein the shroud element circumferentially surrounds an axial section of the pipe extending from an axial end of the pipe, characterised in that
 at least one cavity is provided at the shroud element, wherein the at least one cavity is in fluid communication with an interior of the pipe and wherein the at least one cavity extends to an opening at an axial end of the shroud element.   
     
     
         2 . The fluid injection element according to  claim 1 , wherein an opening in a wall of the pipe connects the interior of the pipe and the at least one cavity thereby establishing the fluid communication between the interior of the pipe and the at least one cavity. 
     
     
         3 . The fluid injection element according to  claim 1 , wherein in a first axial section of the pipe the diameter of the interior of the pipe has a first value, wherein in a second axial section of the pipe subsequent to the first axial section the diameter of the interior of the pipe decreases from the first value to a second value, wherein in a third axial section of the pipe subsequent to the second axial section the diameter of the interior of the pipe has the second value, the third axial section axially extending to the axial end of the pipe, and
 wherein the shroud element circumferentially surrounds at least the second axial section and the third axial section.   
     
     
         4 . The fluid injection element according to  claim 2 , wherein the opening in the wall of the pipe connecting the interior of the pipe and the at least one cavity is provided in the second section. 
     
     
         5 . The fluid injection element according to  claim 1 , wherein one single cavity continuously extends in a circumferential direction inside the shroud element or
 wherein several cavities are provided inside the shroud element distributed in predetermined circumferential distances to each other.   
     
     
         6 . The fluid injection element according to  claim 1 , wherein at least one bleed hole is provided in the shroud element extending from the at least one cavity to a radial end of the shroud element. 
     
     
         7 . The fluid injection element according to  claim 1 , wherein an expansion of the at least one cavity in radial direction has different values or differently varying values in different subsequent axial sections of the at least one cavity. 
     
     
         8 . The fluid injection element according to  claim 1 , wherein the pipe is adapted to be connected with a fluid supply such that a first amount of a fluid is conducted through the interior of the pipe and ejected throughout the axial end of the pipe with a first velocity, particularly a sonic or supersonic velocity, a second amount of the fluid is conducted through the at least one cavity of the shroud element and ejected throughout the opening of the at least one cavity at the axial end of the shroud element with a second velocity smaller than the first velocity. 
     
     
         9 . A furnace comprising a burner with a fuel supply and an oxidant supply, characterised in that
 at least one fluid injection element comprising a pipe and a shroud element, wherein the shroud element circumferentially surrounds an axial section of the pipe extending from an axial end of the pipe, comprising at least one cavity is provided at the shroud element, wherein the at least one cavity is in fluid communication with an interior of the pipe and wherein the at least one cavity extends to an opening at an axial end of the shroud element is provided for providing an oxidant to the burner.   
     
     
         10 . A method for operating a furnace, wherein fuel is provided to a burner of the furnace, wherein an oxidant is provided to the burner via at least one fluid injection element comprising a pipe and a shroud element, wherein the shroud element circumferentially surrounds an axial section of the pipe extending from an axial end of the pipe, comprising at least one cavity is provided at the shroud element, wherein the at least one cavity is in fluid communication with an interior of the pipe and wherein the at least one cavity extends to an opening at an axial end of the shroud element
 such that a first amount of the oxidant is provided with a first velocity, and a second amount of the oxidant is provided with a second velocity smaller than the first velocity.   
     
     
         11 . The method according to  claim 10 , wherein the first amount of the oxidant is provided as a first oxidant jet and wherein the second amount of the oxidant is provided as at least one second oxidant jet circumferentially surrounding the first oxidant jet. 
     
     
         12 . The method according to  claim 10 , wherein the first amount of the oxidant is provided via the interior of the pipe of the at least one fluid injection element and wherein the second amount of the oxidant is provided via the at least one cavity of the shroud element of the at least one fluid injection element. 
     
     
         13 . The method according to  claim 10 , wherein the first amount of the oxidant is between 75% to 90% and wherein the second amount of the oxidant is between 10% and 25%.