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 nozzle, comprising: an inlet opening for receiving a stream of coal/air mixture and an outlet opening for discharging the stream of coal/air mixture into a burner, wherein the inlet opening and the outlet opening are fluidically connected by a flow section, wherein a flow cross section of the flow section is varying along a flow direction of the stream of coal/air mixture, and wherein the flow section comprises a flow constriction with a globally, minimal flow cross section, wherein the flow constriction is fluidically located between the inlet opening and the outlet opening, and the flow cross section of the flow section continuously, increases over an entire extension of the flow section from the flow constriction to the outlet opening, wherein the flow section comprises a first expansion section and a second expansion section fluidically located between the flow constriction and the outlet opening, wherein the rate of change of the flow cross section of the first expansion section higher than the rate of change of the flow cross section of the second expansion section, wherein a wall of the first expansion section is in direct, physical contact with a wall of the second expansion section in the flow section after the flow constriction in the flow direction.

2. The pulverized solid fuel nozzle according to claim 1, wherein the first expansion section is arranged before the second expansion section in the flow direction, wherein the first expansion section is abutting the second expansion section.

3. The pulverized solid fuel nozzle according claim 1, wherein the flow cross section of the first expansion section and/or the second expansion section increases proportionally to the square of the respective extend in flow direction of the first expansion section and/or the second expansion.

4. The pulverized solid fuel nozzle according to claim 1, wherein the cross sectional area of the flow cross section of the flow section comprises a circular shape.

5. The pulverized solid fuel nozzle according to claim 1, further comprising an igniter located in the flow section of the nozzle between the flow constriction and the outlet opening.

6. The pulverized solid fuel nozzle according to claim 5, wherein the igniter is located in the flow section proximate the flow constriction, distal to the outlet opening.

7. The pulverized solid fuel nozzle according to claim 1, wherein the wall of the flow section of the nozzle between the flow constriction and the outlet opening is coated with a coating that comprises a catalyst for catalyzing the reaction of coal with oxygen.

8. The pulverized solid fuel nozzle according to claim 1, further comprising cooling means, wherein the cooling means is arranged in the flow direction between the flow constriction and the outlet opening.

9. The pulverized solid fuel nozzle according to claim 8, wherein the cooling means comprises a fluid coolant jacket, wherein the coolant jacket has an arrangement that comprises one or more of: wherein the coolant jacket surrounds the wall of the flow section between the flow constriction and the outlet opening, wherein the coolant jacket surrounds the wall of the flow section before and after the flow constriction, and wherein the coolant jacket extends in flow direction from before the flow constriction to near the outlet opening.

10. The pulverized solid fuel nozzle according to claim 9, wherein the coolant jacket comprises a thermal expansion compensation joint for compensating different thermal expansions of different segments of the nozzle due to unequal temperature distribution along the nozzle during operation.

11. The pulverized solid fuel nozzle according to claim 10, wherein the thermal expansion compensation joint comprises a corrugated tube.

12. The pulverized solid fuel nozzle according to claim 10, wherein the thermal expansion compensation joint is placed over the wall of the flow section above the flow constriction.

13. The pulverized solid fuel nozzle according to claim 8, wherein the nozzle comprises at least one coolant supply line with an inlet near the inlet opening of the nozzle and an outlet into the coolant jacket, wherein the outlet is located near the outlet opening of the nozzle.

14. The pulverized solid fuel nozzle according to claim 1, wherein the outlet opening is configured to pivot relative to the inlet opening.

15. The pulverized solid fuel nozzle according to claim 1, wherein the nozzle comprises a cylindrical segment, a converging conical segment in the flow direction behind the cylindrical segment, a first diverging conical segment in the flow direction behind the converging conical segment, a second diverging conical segment in the flow direction behind the first diverging conical segment, wherein the first diverging conical segment has a first angle of divergence that is higher than a second angle of divergence of the second diverging conical segment.

16. The pulverized solid fuel nozzle according to claim 1, wherein the flow section is at least between the flow constriction and the outlet opening, and is insert free along its entire length.

17. The pulverized solid fuel nozzle according to claim 1, further comprising thermo-elements disposed in the flow section between the inlet opening and the flow constriction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1: A perspective view of a nozzle according to the invention;

(2) FIG. 2: A side view of the nozzle of FIG. 1; and

(3) FIG. 3: cut view of the nozzle of FIGS. 1 and 2,

(4) FIG. 4: an alternative embodiment of a nozzle in the view of FIG. 3;

(5) FIG. 5: an alternative embodiment of a nozzle in the view of FIG. 3; and

(6) FIG. 6: an alternative embodiment of a nozzle in the view of FIG. 3.

DETAILED DESCRIPTION OF THE DRAWINGS

(7) 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.

(8) 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.

(9) 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.

(10) The flow cross section 20 of the first expansion section 28 and the second expansion section 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.

(11) 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.

(12) 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.

(13) 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.

(14) 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.

(15) 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.

(16) The thermal expansion compensation joint 50 in turn comprises a corrugated tube 52.

(17) 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.

(18) 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.

(19) 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.

(20) 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.

(21) 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.

(22) 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.

(23) 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.

(24) 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.

(25) Auxiliary air can be blown along the outside of the nozzle 10 and can enhance the burning process.

(26) 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

(27) 10 nozzle 12 inlet opening 14 outlet opening 16 stream of coal/air mixture 18 flow section 20 flow cross section 22 flow direction 24 flow constriction 26 minimal flow cross section 28 first expansion section 30 second expansion section 32 cooling means 34 coolant jacket 36 liquid coolant 38 wall of flow section 40 coolant flow direction 42 coolant supply line 44 inlet 46 outlet 48 coolant exit lines 50 thermal expansion compensation joint 52 corrugated tube 54 cylindrical segment 56 converging conical segment 58 first diverging conical segment 60 second diverging conical segment 62 first angle of divergence 64 second angle of divergence 66 thermo-elements 68 igniter 70 coating 72 catalyst 74 pivoting mechanism