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.

Claims

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%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The invention is illustrated schematically in the drawings on the basis of exemplary embodiments and will be described in detail in the following with reference to the drawings.

[0031] FIG. 1 is a schematic showing a melting furnace with a fluid injection element according to a preferred embodiment of the invention in a sectional side view.

[0032] FIG. 2a is a schematic showing a preferred embodiment of a fluid injection element according to the present invention in a sectional side view.

[0033] FIG. 2b is an enlarged view of the shroud element.

DETAILED DESCRIPTION OF THE INVENTION

[0034] FIG. 1 schematically shows a melting furnace 100 according to a preferred embodiment of the invention in a sectional side view.

[0035] In the present example, the melting furnace 100 is a rotary furnace. However, the melting furnace 100 could also be of a different kind, for example a reverberatory furnace or the like.

[0036] The melting furnace 100 comprises a chamber 101 in which a metallic material 103 to be melted can be provided. For example, the melting furnace 100 can be provided to melt an aluminium material 103. The chamber 101 can be locked with a door 102.

[0037] An exhaust flue 104 for exhausting waste gas from the chamber 101 is provided such that an opening of the exhaust flue 104 is arranged in the door 102.

[0038] Further, a burner 105 is provided in the door 102. The burner 105 comprises a fuel injection element 110, which is fluidly connected with a fuel supply 111 such that a fuel, e.g. natural gas, methane or propane, can be provided to the burner 105. The burner 105 further comprises at least one oxidant injection element 120. Though only one oxidant injection element 120 is shown in FIG. 1 for reasons of clarity, the burner 105 can comprise several oxidant injection elements 120, preferably two or four oxidant injection elements 120. Each of these oxidant injection elements 120 is connected with an oxidant supply 121 and is arranged inside the door 102 for providing an oxidant to the burner 105, e.g. oxygen.

[0039] A control unit 140 is provided for operating the melting furnace 100. For this purpose, the control unit 140 is particularly adapted to perform a preferred embodiment of a method according to the invention.

[0040] According to this method, the oxidant, e.g. oxygen is provided is provided in the form of two different oxidant jets 130, 131. By means of each oxidant injection element 120 a first amount of the oxidant, e.g. 90% of the oxidant is provided in the first jet 130 with a sonic or supersonic velocity. A second amount of the oxidant, e.g. 10% is provided in the form of second jets 131 surrounding the first jet 130 with a velocity smaller than the velocity of the first jet 130.

[0041] For this purpose, each oxidant injection element 120 is provided as a fluid injection element according to a preferred embodiment of the present invention. A fluid injection element of that kind according to a preferred embodiment of the present invention is schematically shown in FIG. 2a and referred to as 200.

[0042] As shown in FIG. 2a, the fluid injection element 200 comprises a pipe 210 and a shroud element 220, which circumferentially surrounds an axial section of the pipe 210 extending from an axial end 211 of the pipe 210. The shroud element 220 can e.g. be made of 304 grade stainless steel or preferred 316 L stainless steel or Inconel 600.

[0043] FIG. 2b shows an enlarged view of the shroud element 220, when the fluid injection element 200 is arranged inside the door 102.

[0044] As can be seen in FIG. 2b, the shroud element 220 comprises cavities 221, which are in fluid communication with an interior 212 of the pipe 210 by means of openings 213 in a wall of the pipe 210. The cavities 221 extend from these openings to openings 222 at an axial end 223 of the shroud element 220.

[0045] By means of these cavities 221 in the shroud element, the first amount of e.g. 90% of the oxidant is conducted through the interior 212 of the pipe 210 and ejected throughout the axial end 211 of the pipe 210 in form of the first jet 130 with a first velocity, particularly a sonic or supersonic velocity.

[0046] Further, the second amount of e.g. 10% of the fluid is conducted through the cavities 221 of the shroud element 220 and ejected throughout the openings 222 of the cavities 221 at the axial end 223 of the shroud element 220 in the form of the second jet with a second velocity smaller than the first velocity.

[0047] Further, a bleed hole 224 can be provided extending in radial direction from the cavity 221 to an outer end or radial end of the shroud element 220. This bleed hole 224 can be provided as a low pressure or low velocity bleed hole such that oxidant 132 can be ejected for reasons of pressure compensation.

[0048] As can be seen in FIG. 2b, the pipe comprises three different axial sections. In a first axial section 231 of the pipe 210 the diameter of the interior 212 of the pipe has a first value. In a second axial section 232 subsequent to the first section 231 the diameter of the interior 211 of the pipe 210 decreases from the first value to a second value. In a third axial section 233 subsequent to the second section 232 the diameter of the interior of the pipe has the second value. Further, this third section 233 axially extends to the axial end 211 of the pipe 210.

[0049] The shroud element 220 circumferentially surrounds at least the second section 232 and the third section 233. Further, the openings 213 in the wall of the pipe 210 connecting the interior 212 of the pipe 210 and the cavities are provided in the second section 232.

[0050] As can further be seen in FIG. 2b, the cavities 221 inside the shroud element 210 can have different individual shapes. For example the above cavity 221 shown in FIG. 2b comprises three different axial sections, wherein in a first axial section adjacent to the opening 213 a radial expansion increases along the axial direction. In a second axial section subsequent to this first axial section the radial expansion decreases along the axial direction. In a third axial section subsequent to this second axial section the radial expansion increases again. The lower cavity 221 shown in FIG. 2b comprises e.g. two different axial sections, wherein in a first axial section adjacent to the opening 213 the radial expansion increases. In a second axial section subsequent to this first axial section the radial expansion decreases.

[0051] By means of the second low velocity jet 131 of oxidant surrounding the first high velocity jet 130, accretions or depositions on or near or around the tip of the fluid injection element 200 can be prevented or at least significantly reduced. The second oxidant jet 131 is particularly sucked into the first oxidant jet 130 at a position relatively close to the axial ends 211, 223 of the pipe 210 and the shroud element 220. Therefore, in this zone, in which the second oxidant jet 131 is sucked into the first oxidant jet 130, dust or dirt particles are not sucked into the first oxidant jet 130. These particles are indicated in FIG. 2b by reference numeral 240. The recirculation zone, in which these kinds of particles 240 are recirculated, is therefore moved further inside the furnace 100 away from the axial ends 211, 223 of the pipe 210 and the shroud element 220. Thus, these particles 240 cannot deposit on or near or around the tip of the fluid injection element 200. Thus, maintenance intervals of the fluid injection element 200 and therefore of the corresponding furnace 100 can be increased. Costs and effort to operate the furnace 100 can thus be reduced.

REFERENCE LIST

[0052] 100 melting furnace, rotary furnace [0053] 101 chamber [0054] 102 door [0055] 103 metallic material [0056] 105 burner [0057] 110 fuel injection element [0058] 111 fuel supply [0059] 120 oxidant injection element, fluid injection element [0060] 121 oxidant supply [0061] 130 first jet of oxidant [0062] 131 second jets of oxidant [0063] 140 control unit [0064] 200 fluid injection element [0065] 210 pipe [0066] 211 axial end of the pipe 210 [0067] 212 interior of the pipe 210 [0068] 213 wall of the pipe 210 [0069] 220 shroud element [0070] 221 cavity in the shroud element 220 [0071] 222 opening 222 of the shroud element 220 [0072] 223 axial end of the shroud element 220 [0073] 224 bleed hole [0074] 225 oxidant ejected for reasons of pressure compensation [0075] 231 first axial section [0076] 232 second axial section [0077] 233 third axial section [0078] 240 particles into a vortex created by a burner