COAL NOZZLE WITH A FLOW CONSTRICTION

Abstract

The invention concerns a pulverized solid fuel, in particular coal, nozzle (10) comprising an inlet opening (12) for receiving a stream of coal/air mixture (16) and an outlet opening (14) for discharging said stream (16) into a burner. The inlet opening (12) and the outlet opening (14) are fluidically connected by a flow section (18), and a flow cross section (20) of the flow section (18) varies along a flow direction (22) of the stream of coal/air mixture (16). The flow section (18) comprises a flow constriction (24) with a, preferentially globally, minimal flow cross section (26). The flow constriction (24) is fluidically located between the inlet opening (12) and the outlet opening (14) and the flow section (18) has a flow cross section (20) that, in particular continuously, increases from the flow constriction (24) to the outlet opening (14).

Claims

1. A pulverized solid fuel, in particular coal, nozzle (10) comprising an inlet opening (12) for receiving a stream of coal/air mixture (16) and an outlet opening (14) for discharging said stream (16) into a burner, wherein the inlet opening (12) and the outlet opening (14) are fluidically connected by a flow section (18), wherein a flow cross section (20) of the flow section (18) is varying along a flow direction (22) of the stream of coal/air mixture (16) and wherein the flow section (18) comprises a flow constriction (24) with a, preferentially globally, minimal flow cross section (26), characterized in that the flow constriction (24) is fluidically located between the inlet opening (12) and the outlet opening (14) and in that the flow section (18) has a flow cross section (20) that, in particular continuously, increases from the flow constriction (24) to the outlet opening (14).

2. Nozzle (10) according to claim 1, characterized in that the flow section (18) comprises a first expansion section (28) and a second expansion section (30) fluidically located between the flow constriction (24) and the outlet opening (14), wherein the rate of change of the flow cross section (20) of the first expansion section (28) is higher than the rate of change of the flow cross section of the second expansion section (30).

3. Nozzle (10) according to claim 1, characterized in that the first expansion section is arranged before the second expansion section (30) in flow direction (22), preferably wherein the first expansion section (28) is abutting the second expansion section (30).

4. Nozzle (10) according to claim 1, characterized in that the flow cross section (20) of the first expansion section (28) and/or the second expansion section (30) increases proportionally to the square of the respective extend in flow direction (22) of the first expansion section (28) and/or the second expansion (30).

5. Nozzle (10) according to claim 1, characterized in that the cross sectional area of the flow cross section (20) of the flow section (18) is at least locally, preferentially along its entire length, of circular shape.

6. Nozzle (10) according to claim 1, characterized in that an igniter (68) is located in the flow section (18) of the nozzle (10), preferentially between the flow constriction (24) and the outlet opening (14).

7. Nozzle (10) according to claim 1, characterized in that the wall (38) of the flow section (18) of the nozzle (10) between the flow constriction (24) and the outlet opening (14) is at least locally, preferentially along its entire extend in flow direction (22), coated with a coating (70) that comprises a catalyst (72), suitable for catalyzing the reaction of coal with oxygen.

8. Nozzle (10) according to claim 1, characterized in that the nozzle (10) comprises cooling means (32), wherein the cooling means (32) are preferentially arranged in flow direction (22) at least also between the flow constriction (24) and the outlet opening (14).

9. Nozzle (10) according to claim 8, characterized in that the cooling means (32) comprise a fluid, in particular liquid, coolant jacket (34), preferentially wherein the coolant jacket (34) surrounds the wall of the flow section (18) at least also between the flow constriction (24) and the outlet opening (14) and/or wherein the coolant jacket (34) surrounds the wall (38) of the flow section (18) before and after the flow constriction (24) and/or wherein the coolant jacket (34) extends in flow direction (22) from before the flow constriction (24) to near the outlet opening (14).

10. Nozzle (10) according to claim 8, characterized in that the nozzle (10) comprises at least one coolant supply line (42) with an inlet (44) near the inlet opening (12) of the nozzle (10) and an outlet (46) into the coolant jacket (34), wherein the outlet (46) is preferably located near the outlet opening (14) of the nozzle (10).

11. Nozzle (10) according to claim 9, characterized in that the coolant jacket (34) comprises a thermal expansion compensation joint (50) for compensating different thermal expansions of different segments of the nozzle (10) due to unequal temperature distribution along the nozzle (10) during operation.

12. Nozzle (10) according to claim 11, characterized in that the thermal expansion compensation joint (50) comprises a corrugated tube (52).

13. Nozzle (10) according to claim 1, characterized in that the nozzle (10) comprises a pivoting mechanism (74) that allows for pivoting of the outlet opening (14) relative to the inlet opening (12).

14. Nozzle (10) according to claim 1, characterized in that the nozzle (10) comprises a cylindrical segment (54) and in flow direction (22) behind the cylindrical segment (54) a converging conical segment (56) and in flow direction (22) behind the converging conical segment (56) a first diverging conical segment (58) and in flow direction (22) behind the first diverging conical segment (58) a second diverging conical segment (60) wherein the first diverging conical segment (58) has a first angle of divergence (62) that is higher than a second angle of divergence (64) of the second diverging conical segment (60).

15. Nozzle (10) according to claim 1, characterized in that the flow section (18) is at least between the flow constriction (24) and the outlet opening (14), preferentially along is entire length, insert-free.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1: A perspective view of a nozzle according to the invention;

[0027] FIG. 2: A side view of the nozzle of FIG. 1; and

[0028] FIG. 3: cut view of the nozzle of FIGS. 1 and 2,

[0029] FIG. 4: an alternative embodiment of a nozzle in the view of FIG. 3;

[0030] FIG. 5: an alternative embodiment of a nozzle in the view of FIG. 3; and

[0031] FIG. 6: an alternative embodiment of a nozzle in the view of FIG. 3.

DETAILED DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 shows perspective view of a nozzle 10 for solid fuel injection according to the invention. The nozzle 10 comprises an inlet opening 12 and an outlet opening 14. The inlet opening 12 is for receiving a stream of coal/air mixture 16 which is symbolically indicated via an arrow. The outlet opening 14 is for discharging said stream 16 into a not shown burner.

[0033] The inlet opening 12 and the outlet opening 14 are fluidically connected by a flow section 18, as shown in FIG. 3. A flow cross section 20 of the flow section 18 is varying along a flow direction 22 of the stream of coal/air mixture 16. The flow section 18 comprises a flow constriction 24 with a, in the embodiment of the figures, globally minimal flow cross section 26 i.e. the flow cross section 20 has its minimum at the minimal flow cross section 26. The flow constriction 24 is fluidically located between the inlet opening 12 and the outlet opening 14, i.e. the stream of coal/air mixture 16 first passes the inlet opening 12 then the flow constriction 24 and then the outlet opening 14. The flow cross section 20 of the flow section 18 increases from the flow constriction 24 to the outlet opening 14. In the current embodiment the flow cross section 20 of the flow section 18 continuously increases over the entire extension of the flow section 18 from the flow constriction 24 to the outlet opening 14.

[0034] The flow section 18 comprises a first expansion section 28 and a second expansion section 30 fluidically located between the flow constriction 24 and the outlet opening 14. The rate of change of the flow cross section 20 of the first expansion section 28 is higher than the rate of change of the flow cross section 20 of the second expansion section 30. The first expansion section 28 is arranged before the second expansion section 30 in flow direction and abuts the later.

[0035] The flow cross section 20 of the first expansion section 28 and the second expansion qsection 30 increases proportionally to the square of the respective extend in flow direction 22, since the cross sectional area of the flow cross section 20 in each of the expansion section 28, 30 is circular and the diameter of this circular cross-sectional area increases proportional to the extent in flow direction 22.

[0036] The nozzle 10 comprises cooling means 32 which in the current embodiment are implemented as a coolant jacket 34. The cooling means 32, i.e. the coolant jacket 34 is arranged in flow direction at least also between the flow constriction 24 and the outlet opening 14. More specifically the coolant jacket extends from before the flow constriction 24 along the extend of the nozzle 10 until close to the outlet opening 14.

[0037] The coolant jacket 34 is constructed to accommodate a liquid coolant 36 indicated symbolically via an arrow. The coolant jacket 34 surrounds a wall 38 of the flow section 18. The coolant jacket 34 extends in this surrounding fashion in flow direction 22 from before the flow constriction 24 to near the outlet opening 14.

[0038] The coolant jacket 34 is constructed such that a coolant flow direction 40 within the coolant jacket 34 is opposite to the flow direction 22 of the stream of coal/air mixture 16.

[0039] The nozzle 10 comprises several coolant supply lines 42 in the form of pipes. The coolant supply lines 42 each have an inlet 44 near the inlet opening 12 of the nozzle 10 and an outlet 46 into the coolant jacket 34, wherein the outlet 46 is located near the outlet opening 14 of the nozzle 10. The coolant 36 leaves the coolant jacket 34 coolant exit lines 48. In the current embodiment the coolant jacket 34 is adapted and arranged to be used with water as the coolant 36. Using other liquids as a coolant 36 is possible and within the scope of this invention.

[0040] The coolant jacket 34 comprises a thermal expansion compensation joint 50 for compensating different thermal expansions of different segments of the nozzle 10 due to unequal temperature distribution along the nozzle 10 during operation.

[0041] The thermal expansion compensation joint 50 in turn comprises a corrugated tube 52.

[0042] The nozzle in the current embodiment comprises a cylindrical segment 54 and in flow direction 22 behind the cylindrical segment 54 a converging conical segment 56 and in flow direction 22 behind the converging conical segment 56 a first diverging conical segment 58 and in flow direction 22 behind the first diverging conical segment 58 a second diverging conical segment 60 wherein the first diverging conical segment 58 has a first angle of divergence 62 that is higher than a second angle of divergence 64 of the second diverging conical segment 60.

[0043] The flow section 18 in the current embodiment is insert-free. Insert-free refers to a flow section 18 or a part of it in which there is no inserts in the cross section of the flow section 18 that would cause significant abrupt change in the cross-sectional area of the flow section 18. As can be seen in FIG. 3 there are thermo-elements 66 extending into the flow section 18. However these thermo-elements 66 are of such small the dimensions, that they do not cause significant abrupt change in the cross-sectional area of the flow section 18. Therefore they are considered not to constitute inserts within the meaning of the current invention. That static or dynamic mixers arranged in the flow section 18, however, would be considered to constitute inserts within the meaning of the current invention.

[0044] FIG. 4 shows an embodiment that is constructed similar to the embodiment of FIGS. 1 to 3. In the embodiment of FIG. 4 the nozzle 10 additionally comprises an igniter 68 (shown schematically) which is located in the flow section 18 of the nozzle 10. More specifically in the current embodiment the igniter 68 is located between the flow constriction 24 and the outlet opening 14.

[0045] FIG. 5 shows an embodiment that is constructed similar to the embodiment of FIGS. 1 to 3. In the embodiment of FIG. 5 the wall 38 of the flow section 18 of the nozzle 10 between the flow constriction 24 and the outlet opening 14 is coated with a coating 70 (shown schematically) that comprises a catalyst 72, suitable for catalyzing the reaction of coal with oxygen.

[0046] FIG. 6 shows an embodiment that is constructed similar to the embodiment of FIGS. 1 to 3. In the embodiment of FIG. 6 the nozzle comprises a pivoting mechanism 74 (shown schematically) that allows for pivoting of the outlet opening 14 relative to the inlet opening 12.

[0047] Obviously it is also within the scope of the current invention to combine the igniter 68 with the coating 70 and/or the pivoting mechanism 74 or to combine the coating 70 with the pivoting mechanism 74.

[0048] In the operation of the embodiments described above the stream of coal/air mixture 16 is blown into the Inlet opening 12 then propagate along the nozzle 10 passes the flow constriction 24 and subsequently reduces its flow speed. Either the stream of coal/air mixture 16 is ignited by the igniter 68 and the flame front is located within the nozzle 10 already due to this ignition and remains there due to the reduced flow speed behind the flow constriction 24 or the stream of coal/air mixture 16 is ignited outside of the nozzle 10, i.e. after it has passed the outlet opening 14. In the later case due to the reduced flow speed behind the flow constriction 24 the flame front propagates into the nozzle 10 and remains between the flow constriction 24 and the outlet opening 14 during operation of the nozzle 10.

[0049] Since the flame front is located within the nozzle 10 burning of the coal or other solid fuels begins in a fuel rich environment. This burning in a fuel rich environment produces a chemistry that is transported along with the stream of coal/air mixture 16 that is already burning and reduces the NOx formation during the burning taking place outside of the nozzle 10. In total this leads to a significant reduction in the NOx formation during burning of the stream of coal/air mixture 16.

[0050] Auxiliary air can be blown along the outside of the nozzle 10 and can enhance the burning process.

[0051] The coating 70 comprising the catalyst 72, if present, facilitates the location of the flame front within the nozzle 10 since it decreases the amount of energy necessary to start the reaction between coal and oxygen, i.e. the burning of the coal.

LIST OF REFERENCE NUMERALS

[0052] 10 nozzle [0053] 12 inlet opening [0054] 14 outlet opening [0055] 16 stream of coal/air mixture [0056] 18 flow section [0057] 20 flow cross section [0058] 22 flow direction [0059] 24 flow constriction [0060] 26 minimal flow cross section [0061] 28 first expansion section [0062] 30 second expansion section [0063] 32 cooling means [0064] 34 coolant jacket [0065] 36 liquid coolant [0066] 38 wall of flow section [0067] 40 coolant flow direction [0068] 42 coolant supply line [0069] 44 inlet [0070] 46 outlet [0071] 48 coolant exit lines [0072] 50 thermal expansion compensation joint [0073] 52 corrugated tube [0074] 54 cylindrical segment [0075] 56 converging conical segment [0076] 58 first diverging conical segment [0077] 60 second diverging conical segment [0078] 62 first angle of divergence [0079] 64 second angle of divergence [0080] 66 thermo-elements [0081] 68 igniter [0082] 70 coating [0083] 72 catalyst [0084] 74 pivoting mechanism