Burner for a kiln

Abstract

A burner for a rotary kiln comprising an elongated tubular body (6) having a longitudinal axis (L) and a discharge end (7) adjacent a combustion zone comprising a flame, at least one fuel supply pipe for transporting and ejecting fuel through a fuel pipe outlet (10) at the discharge end (7), the fuel being alternative fuel or a mixture of alternative fuel and fossil fuel, and at the discharge end (7), a number of high speed primary air jet outlets for ejecting primary air and being arranged, when seen towards the discharge end, along a closed line, such as a circle, outwardly of the fuel outlet (10) and surrounding the fuel outlet,
wherein at least one of the primary air outlets and preferably a number of the primary air outlets comprise a single orifice outlet or a multiple orifice outlet forming a flat jet air outlet (11) having a major axis and a minor axis and being configured to eject a flat jet air stream (13) having a flat fan pattern with a predetermined fan angle v.

Claims

1. A burner for a kiln comprising an elongated tubular body having a longitudinal axis and a discharge end adjacent a combustion zone comprising a flame, at least one fuel supply pipe for transporting and ejecting fuel through a first fuel pipe outlet at the discharge end, a number of high speed first primary air jet outlets for ejecting primary air, the first primary air jet outlets being located at the discharge end and being arranged, when viewed towards the discharge end, along a circular closed line, radially outwardly of the first fuel outlet and surrounding the first fuel outlet, wherein at least one of the first primary air jet outlets comprises a single orifice outlet or a multiple orifice outlet forming a flat jet air outlet having a major axis and a minor axis, the flat jet air outlet being configured to eject a flat jet air stream having a flat fan pattern with a predetermined fan angle; the flat jet air outlet being oriented such that its major axis is not tangent to the circular closed line when viewed towards the discharge end.

2. The burner of claim 1, wherein a majority of the first primary air jet outlets comprise a single orifice outlet or a multiple orifice outlet forming a flat jet air outlet.

3. The burner of claim 1, wherein the flat jet air outlet further comprises a major axis length along the major axis, and a minor axis length along the minor axis, and a ratio between the major axis length and the minor axis length is at least 1.5:1 and less than 20:1, respectively.

4. The burner of claim 1, wherein the first primary air jet outlets are spaced to allow neighboring flat jet air streams ejected from neighbouring first air jet outlets to overlap.

5. The burner of claim 1, wherein all of the first primary air jet outlets comprise flat jet air outlets.

6. The burner of claim 1 comprising an additional primary air channel comprising a swirl air-generating device with a number of additional primary air outlets, the additional primary air outlets being arranged, when viewed towards the discharge end, inwardly of the first primary air jet outlets and being arranged on a second circular closed line, the swirl air-generating device being configured to eject multi-point air streams of additional primary air from the additional primary air outlets.

7. The burner of claim 6, wherein the first fuel pipe outlet is an annular fuel outlet being arranged, when viewed towards the discharge end, between the first primary air jet outlets and the additional primary air outlets and surrounded by the first primary air jet outlets and surrounding the additional primary air outlets.

8. The burner of claim 6, wherein the first fuel pipe outlet comprises a central fuel pipe outlet being arranged, when viewed towards the discharge end, inwardly of the additional primary air outlets and surrounded by the additional primary air outlets.

9. The burner of claim 8 comprising an additional annular fuel outlet being arranged, when viewed towards the discharge end, between the first primary air jet outlets and the additional primary air outlets and surrounded by the first primary air jet outlets and surrounding the additional primary air outlets.

10. The burner of claim 8, wherein the central fuel supply pipe and the additional primary air channel are retractable from a forward position in which the first primary air jet outlets, the additional primary air outlets, and the first fuel pipe outlet are essentially arranged in a common plane at the discharge end and a second position in which the first fuel pipe outlet and the additional primary air outlets are retracted and spaced from the first primary air jet outlets along the longitudinal axis.

11. The burner of claim 10, wherein the central fuel supply pipe and the additional primary air channel are axially retractable over a length being between 0.2 and 2.0 times the diameter of the second circular closed line on which the additional primary air outlets are arranged.

12. The burner of claim 1, wherein said at least one of the first primary air jet outlets is provided in a respective nozzle comprising a nozzle body having an outer cylindrical portion, wherein the nozzle is angularly adjustable by rotating the nozzle body to change an angle between the major axis of the flat jet air outlet and a tangent of the circular closed line when viewed towards the discharge end, and wherein the nozzle is arranged in a front plate of the burner or at an outer end of a respective air tube of the burner.

13. The burner of claim 12, wherein the nozzles are angularly adjustable during operation of the burner.

14. The burner of claim 12, wherein the nozzle comprises an inner air duct comprising an inlet portion having a circular cross section and an outlet portion gradually changing from the circular cross section of the inlet portion to a cross section of the flat air jet outlet, the inner air duct being angled such that the flat fan pattern of the flat jet air stream is ejected from the nozzle and towards the longitudinal axis in a plane that is not parallel to the longitudinal axis of the burner, the angle between the inlet portion and the outlet portion of the nozzle being between 0 and 30.

15. The burner of claim 12, wherein the nozzle is configured such that the angle between the major axis of the flat jet air outlet and a tangent of the circular closed line when viewed towards the discharge end is infinitely adjustable.

16. The burner of claim 1, wherein at least one other of the first primary air jet outlets comprises a single orifice outlet or a multiple orifice outlet forming a flat jet air outlet having a major axis, a minor axis, a major axis length, and minor axis length which is less than the major axis length, the flat jet air outlet being configured to eject a flat jet air stream having a flat fan pattern with a predetermined fan angle; the flat jet air outlet being oriented such that its major axis is tangent to the circular closed line when viewed towards the discharge end.

17. The burner of claim 1, wherein the at least one of the first primary air jet outlets is provided to a lower portion of the discharge end and configured to allow secondary air passage to prevent fuel ejected through the first fuel pipe outlet from dropping out of the flame.

18. A rotary kiln comprising the burner of claim 1.

19. A burner for a kiln comprising an elongated tubular body having a longitudinal axis and a discharge end adjacent a combustion zone comprising a flame, at least one fuel supply pipe for transporting and ejecting fuel through a first fuel pipe outlet at the discharge end, and a number of high speed first primary air jet outlets for ejecting primary air, the first primary air jet outlets being located at the discharge end and being arranged, when viewed towards the discharge end, along a circular closed line, radially outwardly of the first fuel outlet and surrounding the fuel outlet, wherein at least one of the first primary air jet outlets comprises a single orifice outlet or a multiple orifice outlet forming a flat jet air outlet having a major axis and a minor axis, the flat jet air outlet being configured to eject a flat jet air stream in a direction which is converging relative to the longitudinal axis; the flat jet air stream having a flat fan pattern with a predetermined fan angle, the flat jet air stream being configured to regulate an amount of secondary air used for combusting fuel ejected through the first fuel pipe outlet; and, the flat jet air outlet being oriented such that its major axis is not tangent to the circular closed line when viewed towards the discharge end.

20. A burner for a kiln comprising an elongated tubular body having a longitudinal axis and a discharge end adjacent a combustion zone comprising a flame, at least one fuel supply pipe for transporting and ejecting fuel through a first fuel pipe outlet at the discharge end, and a number of high speed first primary air jet outlets for ejecting primary air, the first primary air jet outlets being located at the discharge end and being arranged, when viewed towards the discharge end, along a circular closed line, radially outwardly of the first fuel outlet and surrounding the fuel outlet, wherein at least one of the first primary air jet outlets comprises a single orifice outlet or a multiple orifice outlet forming a flat jet air outlet having a major axis and a minor axis, the flat jet air outlet being provided to a lower portion of the discharge end and being configured to eject a flat jet air stream having a flat fan pattern with a predetermined fan angle; wherein the flat jet air outlet is configured to be adjusted or set to allow secondary air to pass a barrier formed by adjacent flat jet air outlets to prevent fuel ejected through the first fuel pipe outlet from dropping out of the flame; and wherein the flat jet air outlet being oriented such that its major axis is not tangent to the circular closed line when viewed towards the discharge end.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 is a diagrammatic longitudinal sectional view of a rotary kiln provided with a burner according to the invention,

(2) FIG. 2 is an enlarged end view of a burner according to the invention as seen from the kiln towards a discharge end of the burner,

(3) FIG. 3 is an end view similar to that shown in FIG. 2 and where ejection of flat primary jet air streams from flat jet air outlets is arranged in a first position of the outlets,

(4) FIG. 4 is an end view similar to that in FIG. 3, but where the outlets are arranged in a second position angularly rotated 30 from the position shown in FIG. 3,

(5) FIG. 5 is a perspective and sectional view of the forward end of a burner according to the invention comprising the fuel supply pipe and with an additional primary air channel arranged in a forward position,

(6) FIG. 6 is a view similar to that in FIG. 6, but where the part comprising the fuel supply pipe and an additional primary air channel has been retracted to a retracted position,

(7) FIG. 7 is a perspective view of an outlet nozzle having a flat fan air outlet, and

(8) FIG. 8 is a longitudinal sectional view of the nozzle shown in FIG. 7.

DETAILED DESCRIPTION OF THE INVENTION

(9) FIG. 1 diagrammatically discloses a rotary kiln 1 defining a kiln chamber 4 and being provided with a burner 2 according to the invention arranged at an outlet end of the kiln where the clinker leaves the kiln through a clinker cooler 3. From the kiln cooler, heated secondary air sa having a temperature of about 1000 C. is supplied to the kiln chamber through a kiln hood 5. The opposite end of the kiln is an inlet end where the kiln is supplied with raw material rm. The burner 2 comprises an elongated tubular body 6 having a longitudinal axis L and a discharge end 7 at which a combustion zone comprising a flame is formed during operation of the burner 2, see also FIGS. 2-6.

(10) Additionally, the burner 2 comprises an essentially central fuel supply pipe 9 for transporting and supply fuel to the flame 8 in the kiln chamber 4 through an essentially central fuel pipe outlet 10 at the discharge end 7. The fuel supplied through the supply pipe 9 can be both alternative fuel and fossil fuel and a mixture of alternative and fossil fuels. In addition to the central fuel supply pipe 9 with the central fuel pipe outlet 10, the burner can also comprise one or more additional supply lines with a supply line outlet at the discharge end 7 in order to supply fossil fuel to the flame. A number of high-speed first primary air jet outlets 11 are arranged at the discharge end. The air is supplied to the primary air jet outlets through a common tubular channel and/or through individual air pipes 12 and ejected through the first primary air jet outlets 11 being arranged, when seen towards the discharge end, along a closed line radially outwardly of the central fuel outlet 10 and surrounding the central fuel outlet, see especially FIGS. 5 and 6.

(11) The figures disclose that all the first primary air outlets are flat jet air outlets 11 having a major axis ma and a minor axis mi and being configured to eject a flat jet air stream 13 having a flat fan pattern with a predetermined fan angle v, see also FIGS. 3 and 4.

(12) The terms major axis ma and minor axis have been defined previously and are illustrated in FIGS. 2 and 7. As indicated in FIG. 2 and as disclosed in FIGS. 5 and 6, the primary jet air outlets 11 can be provided by nozzles being arranged at the end of respective air pipes 12 and be individually angularly adjustable during operation of the burner, as illustrated by the outlet 11a in FIGS. 5 and 6. The ratio between the length of the major axis ma and the length of the minor axis is about 3:1 for the outlet 11a. Alternatively, the nozzles can be arranged individually angularly adjustable, i.e. pre-adjustable or pre-settable, in a front plate 14 of the burner as illustrated by means of the outlet 11b in FIG. 2. The ratio between the length of the major axis ma and the length of the minor axis mi is about 3:1 for the outlet 11b. The nozzle can be of the type shown in FIGS. 7 and 8 described below. A further possibility is to provide the primary air jet outlets directly in the front plate 14 of the burner 2 as illustrated by the outlet 11c in FIG. 2. The ratio between the length of the major axis ma and the length of the minor axis is about 4:1 for the outlet 11c. The outlets can be formed by a single orifice as illustrated by the above outlets 11a, 11 b 11c. However, the outlets 11 can also be formed by a number of adjacent orifices, as illustrated by the outlets 11d, 11e, 11f in FIG. 2 and comprising 2, 3 and 4, respectively, adjacent circular orifices 15 arranged in line. For the outlets 11d, 11e, 11f, the ratio between the length of the major axis ma and the length of the minor axis is 2:1, 3:1 and 4:1, respectively.

(13) The nozzle 16 shown in FIGS. 7 and 8 comprises an outer cylindrical body portion 17 and an outer cylindrical flange portion 18 at the outlet end of the nozzle, and additionally an inner duct 19 comprising an inlet portion 20 having a circular cross section, and an outlet portion 21 gradually changing from the circular cross section of the inlet portion 21 to the cross section of the flat jet air outlet 11g with the major and minor axis, the inner portion 21 being angled along a line parallel to the major axis, the flat fan thereby being ejected from the nozzle in a plane that is angled, i.e. not parallel to the longitudinal axis of the burner. The ratio between the length of the major axis ma and the length of the minor axis mi of the outlet 11g is about 2:1

(14) The angle between the inlet portion and the outlet portion of the nozzle can be 2-30, such as 3-20. In the embodiment shown it is about 5.

(15) In embodiments of the invention where the flat fan air nozzles are individually adjustable, they can, by angular rotation thereof, be adjusted to eject flat fan-shaped air sprays diverging or converging relative to the axis of the burner and additionally be adjusted to any intermediate position.

(16) The fan-shaped jet air streams 13 ejected provide a barrier against secondary air entering the flow of fuel when the major axis ma of the flat jet air outlets is arranged essentially tangentially to the closed line on which the primary jet air outlets are arranged and mutually spaced so that the formed jet air streams 13 overlap mutually as shown in FIG. 3. However, when the minor axis ma of the outlets is arranged perpendicular to the mentioned closed line, essentially no barrier against the secondary air is provided. The barrier against secondary air can be changed by selecting the corresponding intermediate positions of the major or minor axis of the flat jet air outlet 11, as shown in FIG. 4, where all the flat jet air outlets are arranged so that the major axis ma thereof forms an angle of about 30 with the closed line on which the primary outlets are arranged. By choosing the correct orientation of the flat jet air outlets for the fuel in question, it is advantageously possible to optimize the flame and the shape thereof in order to obtain the desired combustion. As an example, lower flat jet air outlets can be adjusted or set to allow hot secondary air to pass the barrier formed by adjacent flat outlets to prevent fuel dropping out at the bottom or lower portion of the flame.

(17) It should be noted that although it is shown that all the first primary jet air outlets are flat jet air outlets ejecting a flat jet air stream 13 having a flat fan pattern, this need not be the case. The use of a single or a number of flat jet air outlets ejecting a flat jet air stream 13 having a flat fan pattern may be sufficient in order to obtain the desired shape of the flame and the desired combustion of the fuel. However, the possibility of obtaining flame and combustion optimization is improved with the number of flat jet air outlets, and especially the possibility of providing a barrier against secondary air at desired points around the flame. Arranging a mixture of ordinary, i.e. point-shaped, jet air outlets and flat jet air outlets along the closed line is also a possibility.

(18) As an example, every second outlet can be a point-shaped outlet and every second outlet a flat jet air outlet. If a complete barrier against a flow of secondary air past the primary air is desired, adjacent primary air outlets have to be arranged at a mutual spacing providing an overlap of air streams ejected from adjacent outlets independent of whether the primary air outlets are ordinary point-shaped outlets or flat jet air outlets.

(19) In addition to the first primary flat jet air outlets 11, the shown embodiment of the burner also comprises an additional primary air channel 23 comprising a swirl air-generating device with a number of additional primary air outlets 22, the additional primary air outlets 22 being arranged, when seen towards the discharge end 7, on a closed line between the central fuel outlet 10 of the fuel supply pipe 9 and the primary air jet outlets 11 and surrounding the former and being surrounded by the latter, the swirl air-generating device being configured to eject a multi-point annular air stream of additional primary air from the additional primary air outlets, see FIG. 2 and FIGS. 5-6.

(20) As shown in FIGS. 5 and 6, the burner can additionally comprise an annular coal supply channel 24 having an annular coal outlet at the discharge end 7 of the burner. The coal outlet 25 is arranged, as seen towards the discharge end 7, between the closed line on which the first primary air outlets 11 are arranged and the closed line on which the additional primary air outlets 22 are arranged. Further the burner can alternatively or additionally comprise an annular gas supply channel 26 with a gas outlet 27 at the discharge end. The gas outlet 27 is arranged, as seen towards the discharge end 7, between the closed line on which the first primary air outlets 11 are arranged and the closed line on which the additional primary air outlets 22 are arranged. In the embodiment shown the gas supply channel 26 and gas outlet 27 are arranged outwardly of the coal supply channel 24 and coal outlet 25.

(21) It should further be noted that the central fuel outlet can be omitted and the burner thereby only supply fuel through the coal supply channel and coal outlet and/or through the gas supply channel and gas outlet.

(22) The primary air ejected from the primary air jet outlets 11 and the additional primary air ejected from the additional primary air outlets 22 are combined to a stream of axial air and swirl air.

(23) Controlling the axial air flow, swirl air flow and the ratio between them enables additional flame and the combustion adjustability and flexibility.

(24) The swirling, additional primary air is ejected with a tangential velocity component that is higher than the tangential velocity component of the predominantly axially ejected air from the primary air outlets.

(25) By comparing FIGS. 5 and 6, it can be seen that in FIG. 6, the central fuel supply pipe 9 and the additional primary air channel 23 with the additional primary air outlets 22 are together retractable from a forward position in which the primary jet air outlet 11, the additional primary air outlets 22 and the fuel outlet 10 are essentially arranged in a common plane at the discharge end 7, and a second position in which the fuel outlet 10 and the additional primary air outlets 22 are retracted and spaced from the plane of the primary jet air outlets 11.

(26) Changing the position of the central fuel outlet 10 and the additional primary air outlets 22 offers a further possibility of optimizing the flame structure and shape for the fuel or combination of fuels in question.

(27) In the forward position, the additional primary air is ejected as a multi-point annular stream of jets, whereas in the retracted position, the jets ejected from the additional primary outlets 22 merge to form an annular swirling or rotating air stream. In this way, the fuel speed in the flame can be reduced.

(28) Finally, it should be noted that although the present invention has been described with reference to a burner for a rotary kiln for cement production, it is also useable for other types of kilns, and that the present invention also relates to a kiln comprising a burner according to the invention.

LIST OF REFERENCE NUMERALS

(29) 1 rotary kiln 2 Burner 3 clinker cooler 4 Kiln chamber 5 Kiln hood 6 Elongated body 7 Discharge end 8 Flame 9 Central fuel supply pipe 10 Central fuel outlet 11, 11a, 11b, first primary (jet) air outlets, flat jet 11c, 11d, 11e, air outlet 11f, 11g 12 Individual air pipes 13 flat jet air stream 14 front plate 15 circular orifices 16 Nozzle 17 cylindrical body portion 18 Flange portion 19 Inner duct 20 Inlet portion 21 Outlet portion 22 Additional primary air outlets 23 Additional primary air channel 24 coal supply channel 25 Coal outlet 26 gas supply channel 27 gas outlet L longitudinal axis ma major axis mi minor axis v fan angle sa secondary air rm raw material