Coal nozzle assembly for a steam generation apparatus

Abstract

A steam generating system includes a furnace, a nozzle tip assembly for pulverized coal and primary air as well as means for conveying secondary air in the furnace. The nozzle according to the invention comprises a nozzle body (3) and several channels (5) being connected with the nozzle body, the channels are diverging from each other. At the exit faces (17) of the channels obstructions (13) are disposed to induce huge turbulences of the primary air when entering the furnace. Due to these turbulences the primary air and the entrained coal are mixed very well before being combusted in the furnace. This results in a better more effective combustion with reduced NOx-emissions.

Claims

1. A coal nozzle tip assembly for a steam generation apparatus, comprising: a nozzle body and several channels connected to the nozzle body, the channels arranged to diverge from each other, wherein at an end distal from the connection between the nozzle body and the channels each channel comprises an exit face, wherein a single obstruction is disposed in each exit face, the obstructions arranged to form a square interrupted by hollow spaces between the channels.

2. The coal nozzle tip assembly according to claim 1, wherein at the connection between nozzle body and the channels, the nozzle body has a polygonal cross section area, the channels have a polygonal cross section area, and the cross section areas of the channels equals the cross section area of the nozzle body.

3. The coal nozzle tip assembly according to claim 2, wherein at the connection between nozzle body and channels, the nozzle body has a square or rectangular cross section area and the channels have a square or rectangular cross section area.

4. The coal nozzle tip assembly according to claim 1, wherein the cross section area of each channel increases starting from the connection between nozzle body and the group of channels towards the exit faces at the distal ends of the channels.

5. The coal nozzle tip assembly according to claim 1, wherein the cross section area of each channel at the distal ends of the channels is greater than their cross section areas at the connection between nozzle body and the channels by a factor between 1.4 and 1.8.

6. The coal nozzle tip assembly according to claim 5, wherein the factor is 1.6.

7. The coal nozzle tip assembly according to claim 1, wherein the obstructions are in the form of a bar extending between two opposite corners of the channels.

8. The coal nozzle tip assembly according to claim 1, wherein the obstructions cover approximately 50% of the cross section area of its exit face.

9. The coal nozzle tip assembly according to claim 1, wherein the nozzle body, the channels and the obstructions are made of plain sheet metal.

10. The coal nozzle tip assembly according to claim 1, wherein the nozzle tip is surrounded by an outer shroud that conveys secondary air.

11. The coal nozzle tip assembly according to claim 1, wherein the nozzle tip is pivotally mounted to the nozzle body by pivot members.

12. The coal nozzle tip assembly according to claim 11, further comprising sealing plates between the nozzle tip and the nozzle body.

13. The coal nozzle tip assembly according to claim 1, wherein a catalyst is applied to the obstructions.

14. The coal nozzle tip assembly according to claim 13, wherein the catalyst is Lanthanum Strontium Titanate doped with metals.

15. The coal nozzle tip assembly according to claim 13, wherein the catalyst is of the perovskite-type having catalytic activity in a temperature range from 500° C. to 900° C.

16. A steam generating system, comprising: a furnace; at least one coal nozzle tip assembly to direct a flow of solid particles entrained in primary air into the furnace, wherein the at least one coal nozzle tip assembly includes a nozzle body and several channels connected to the nozzle body, the channels arranged to diverge from each other, wherein at an end distal from the connection between the nozzle body and the channels, each channel comprises an exit face, wherein a single obstruction is disposed in each exit face, the obstructions arranged to form a square interrupted by hollow spaces between the channels.

17. The steam generating system according to claim 16, further comprising at least one duct to convey secondary air into the furnace, wherein the at least one duct is distant from the at least one coal nozzle tip assembly.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1: A side view of a first embodiment of a nozzle tip assembly according to the invention,

(2) FIG. 2: a simplified front view of the nozzle tip assembly according to the invention,

(3) FIG. 3: a cross section of the nozzle tip assembly for the second embodiment for tilting nozzle tips,

(4) FIG. 4: a cross sectional view of the first embodiment,

(5) FIG. 5: a cross section and front view of the second embodiment,

(6) FIG. 6: a cross sectional view along the line B-B in FIG. 1 (generally applies to first and second embodiments) and

(7) FIG. 7: a more detailed front view of the nozzle tip assembly according to the invention (generally applies to first and second embodiments).

DETAILED DESCRIPTION OF THE DRAWINGS

(8) FIG. 1 shows a side view of a first embodiment of the claimed nozzle tip assembly 1. The primary air with the entrained coal particles is conveyed from a coal mill through an appropriate duct work (not shown) and enters a nozzle body 3 of a nozzle tip assembly 1 on the left side in FIG. 1. Connected to the nozzle body 3 are four channels 5 (only two of them being visible in FIG. 1). The connection 7 between the nozzle body 3 and the channels 5 in most cases is a weld.

(9) As can be seen from FIG. 1, the channels 5 diverge from each other. In other words: The longitudinal axis 9 of the channels includes an angle of approximately 5° to 10° with regard to a longitudinal axis 11 of the nozzle body 3.

(10) The nozzle body 3 of this embodiment has a square cross section area as well as each of the four channels 5.

(11) FIG. 2 shows a simplified front view of the nozzle tip assembly 1, since it only shows the walls of the channels 5 and the obstruction 13 in each exit face of the channels 5. At the left part of FIG. 3 a single obstruction 13 is illustrated. This obstruction 13 may be cut out from a sheet metal and welded into the channels 5. As can be seen from FIG. 2, the obstructions 13 are arranged so that they build an “interrupted square”. Between the channels 5 there are hollow spaces 50 that do not have any function. In most cases they are filled with a refractory (not shown).

(12) FIG. 3 shows a side view of a second embodiment of the claimed nozzle tip assembly 1. The primary air with the entrained coal particles is conveyed from a coal mill through an appropriate duct work (not shown) and enters the nozzle body 3 (or coal burner pipe) on the right side in FIG. 3. The nozzle body 3 of the second embodiment and the first embodiment may increase the velocity of the primary air.

(13) In this second embodiment the nozzle tip 1 is pivotally connected to the nozzle body 3 or an outer shroud 20 by a pair of pivot members 16. The pivot members 16 allow the nozzle tip 1 to be rotated or to be tilted about an axis (in most cases a horizontal axis) so that the fuel and combustion air can be directed upwardly or downwardly with respect to a vertical axis of the furnace. The pivotal connection of the nozzle tip 1 allows a redirection of the air within a range of approximately ±30°.

(14) As can be seen from FIG. 4, the channels 5 of the nozzle tip diverge from each other. In other words: The longitudinal axis 9 of the channels includes an angle of approximately 5° to 10° with regard to a longitudinal axis 11 of the nozzle body 3 if the nozzle tip 1 is in a horizontal position. The nozzle body 3 of the second embodiment has a square cross section area as well as each of the four channels 5.

(15) To ensure that the primary air and the entrained coal particles enter the nozzle tip 1 seal plates 18 are located between nozzle body 3 and the nozzle tip 1.

(16) The nozzle body 3 and most of the nozzle tip 1 are surrounded by an outer shroud 20 for conveying secondary air into the furnace (not shown). Since the gap between the outer shroud 20 and the nozzle tip 1 of this embodiment gets narrower towards the furnace the velocity of the secondary air is increased before it enters the furnace.

(17) In FIG. 4 a longitudinal section along of the first embodiment is shown. From this cross section the hollow space 15 between the channels 5 can be seen. It further can be seen that the channels 5 are built as a diffusor, which means that the cross section area near the connection 7 is smaller than the cross section area near the exit faces 17 of the channels 5.

(18) An angle α1 between the outer wall 23 of the channels 5 and a longitudinal axis 11 of the nozzle body 3 is approximately 8°. An angle α2 between the inner walls 25 of the channels 5 and the longitudinal axis 11 of the nozzle body 3 is approximately 5°. The angle α1 may range from 5° to 15°. The angle α2 may range between 2° and 10°.

(19) In any case, the angle α1 is greater than the angle α2. Due to that fact the channels 5 are diffusors and the cross section area of the channels 5 at the exit faces 17 is larger than the cross section area at the connection 7. The same applies with regard to the nozzle tip 1 of the second embodiment.

(20) FIG. 5 shows a simplified front view of a nozzle tip 1 according to the invention (first and second embodiment). Other than in FIG. 2 the obstructions 13 in each exit face of the channels 5 are less wide. They are welded on the two adjacent walls of the channels 5 that limit the hollow spaces 50.

(21) FIG. 6 illustrates a view along the line B-B. It illustrates that the channels 5 are diverging. This can be seen for example by looking to the inner edges 19 of the channels 5. It further can be seen by the fact that the exit faces 17 of the channels 5 are distant from each other. A small part of the obstructions 13 in each channel can be seen in FIG. 5, too.

(22) FIG. 6 also illustrates that each wall of the channels 5 can be cut out from a plane sheet metal and the claimed nozzle tip assembly can be manufactured by welding these sheet metal plates together. In FIG. 6 four welds 21 that connect the outer walls 23 of the channels 5 have the reference numeral 21.

(23) FIG. 7 shows a front view with all visible lines of the nozzle tip assembly of the first embodiment. This front view is somehow confusing and for this reason a simplified front view has been explained in detail in FIG. 3. In FIG. 7 no reference numerals have been drawn to avoid overloading of this Figure with information.

LIST OF REFERENCE NUMERALS

(24) 1 Coal nozzle tip assembly 3 nozzle body 5 channels 7 connection between nozzle body and channels 9 longitudinal axis of the channels 11 longitudinal axis of the nozzle body 13 obstruction 15 hollow space 16 pivot members 17 exit faces 18 seal plates 19 inner edges of the channels 20 outer shroud α angle 21 weld 23 outer wall of the channels 5 25 inner wall of the channels 5 27 catalyst