US20130037628A1

US20130037628A1 - Externally mixing multi-component nozzle

Info

Publication number: US20130037628A1
Application number: US13/641,280
Authority: US
Inventors: Dieter Wurz; Stefan Hartig
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-04-16
Filing date: 2011-04-15
Publication date: 2013-02-14
Also published as: EP2558217A1; HUE035691T2; DE102010015497A1; CN102858466A; WO2011128433A1; PL2558217T3; EP2558217B1; ES2637981T3

Abstract

An externally mixing multi-component nozzle for spraying fluids with the assistance of an atomizing gas that is hot in relation to the fluids to be sprayed, said the gas particularly being steam or hot gas. The nozzle has a housing, wherein the housing has an outlet orifice for the atomizing gas, a first annular gap for fluid to be sprayed, surrounding the outlet orifice, and a second annular gap for the atomizing gas, surrounding the first annular gap, as well as a manifold. The manifold has at least one flow channel for fluid to be sprayed, from a connecting line to the first annular gap, and at least one flow channel from an atomizing gas connecting line to the outlet orifice for atomizing gas.

Description

The invention refers to an externally mixing multi-component nozzle for spraying fluids with the aid of an atomizing gas, especially steam or hot gas, which is hot in relation to the fluids which are to be sprayed.
In many process engineering plants, through which flows a primary fluid, especially flue gas, the aim is to mix a secondary fluid, especially water, as homogeneously as possible into the primary fluid and frequently also to evaporate it over the shortest distance. For this purpose, two-component nozzles are frequently used. In these two-component nozzles, the fluid is atomized by means of a gaseous or vaporous auxiliary medium. These two-component nozzles are distinguished by a particularly fine droplet spectrum and also by a very good partial load behavior. In many plants, especially in power plants and waste incineration plants, steam is made available. It can then be sensible, for cost reasons, to use the steam as auxiliary atomizing medium because the provision of a corresponding amount of compressed air would be associated with high investment- and operating costs.
For atomizing with two-component nozzles, two basic types of nozzle are available, specifically internally mixing nozzles on the one hand and, on the other hand, externally mixing nozzles. Examples of internally mixing and externally mixing nozzles are described in Nasr, Jule and Bendig, Industrial Sprays and Atomization, Springer Publishing House, 2002, on page 24, for example.
A spray drying nozzle, in which an atomizing gas is distributed to two concentric annular slots, is known from U.S. printed Pat. No. 3,770,207. An annular slot for the solution to be dried is arranged between the two annular slots for the atomizing gas. The innermost annular slot for the atomizing gas is formed by inserting a conical piece into the central discharge opening.
Described in German unexamined specification DE 195 26 404 A1 is a two-component nozzle for atomizing paste-like fluids, or fluids containing solids, for example slurry, in which the fluid to be atomized is fed through a central, cylindrical passage and at the end of this passage, by means of individual nozzles arranged in a ring-like manner, the atomizing gas is blown into the fluid to be atomized.
Described in German printed patent specification DE 85 79 24 is a drying nozzle in which the fluid to be atomized is atomized between an inner and an outer conical flow consisting of gaseous auxiliary atomizing medium.
With the invention, an externally mixing multi-component nozzle for spraying fluids is to be improved.
According to the invention, for this purpose provision is made for an externally mixing multi-component nozzle for spraying fluids with the aid of an atomizing gas, especially steam of hot gas, which is hot in comparison to the fluids to be sprayed, which nozzle has a housing, wherein the housing has a discharge opening for the atomizing gas, a first annular slot, encompassing the discharge opening, for fluid to be sprayed, and a second annular slot, encompassing the first annular slot, for the atomizing gas, and also a distribution piece, wherein the distribution piece has at least one flow passage for fluid to be sprayed from a connecting line to the first annular passage, and at least one flow passage from an atomizing gas connecting line to the discharge opening for atomizing gas.
The provision of such a distribution piece inside the nozzle housing ensures that fluid to be sprayed and atomizing gas are conducted to the first annular slot, or to the discharge opening, and to the second annular slot over a short distance. Just by the provision of the distribution piece and the short distance attributable thereto, an only low heat transfer from fluid to be sprayed to the atomizing gas is achieved. As a result, the hot atomizing gas being able to already cool down, and possibly even to condense, before leaving the housing can be prevented. Consequently, a much better atomizing effect is achieved. The distribution piece is preferably produced from solid material and the flow passages are provided inside the solid material.
In a development of the invention, the housing has an annular passage for atomizing gas, which at least in sections encompasses the distribution piece.
In this way, the atomizing gas can be conducted from the annular passage over a short distance into the second annular slot and, since the flow passage of the distribution piece for the atomizing gas advantageously originates from the annular passage, the atomizing gas can also be directed to the discharge opening over a short distance. With the present invention, a new-type of nozzle concept is proposed, in which the atomizing gas, inside a small distributor which is integrated into the nozzle housing, is distributed to a central atomizing gas flow through the discharge opening and also to an outer annular slot flow. In this distributor, the fluid to be atomized is also apportioned to an annular slot which is arranged between the central flow and the outer annular slot flow of the atomizing gas. This distributor, or the flow passages in the distributor, are dimensioned so that it is passed both by fluid to be atomized and by the atomizing gas at relatively high velocity so that hardly any time remains for heat transfer. In addition, the surfaces which lead to the heat transfer between atomizing gas and fluid are of very small dimensions and the distances between the individual flow passages, which conduct the cold fluid and the hot atomizing gas respectively, are dimensionally as large as possible. Therefore, for construction related reasons the internal heat transfer from the hot atomizing gas, especially steam, to the fluid to be atomized is minimized or limited to an advantageous value. A certain preheating of the fluid can be quite advantageous because with this, in the interests of good atomization, the surface stress and the viscosity of the fluid to be atomized can be reduced.
In the case of the invention, however, it is not exclusively a question of atomization quality, as can be established on a virgin nozzle in the laboratory under ideal boundary conditions. Rather, the fact that the atomization quality in industrial practice occasionally suffers from the forming of deposits inside the nozzles or at the nozzle mouth is to be taken into consideration. This especially applies when industrial water is used as fluid to be atomized. Even if suspended matter is largely eliminated by means of filtration, in many cases a formation of deposits in the nozzle or at the nozzle mouth as a result of the settling of dissolved solids is to be observed. This applies above all to those cases in which a hot atomizing gas is used, as a result of which heating of the walls which are in contact with the industrial water can then occur. A limitation of the heat transfer inside the nozzle according to the invention can consequently also solve the problem of deposits forming in the nozzle.
In a development of the invention, a thermal insulation is provided, at least in sections, between the flow passage for fluid to be atomized in the distribution piece and said distribution piece.
In this way, a heat transfer between the cold fluid to be atomized and the distribution piece, which is heated by the hot atomizing gas, can be reduced.
In a development of the invention, the flow passage for fluid to be atomized in the distribution piece is formed, at least in sections, by means of a tube which is inserted into the distribution piece.
In this way, a heat transfer between the flow passage and the distribution piece can already be significantly reduced. An air gap is advantageously provided, at least in sections, between the tube and the distribution piece. An air-gap insulation leads to a further, significant reduction of heat transfer from the cold fluid to be sprayed to the distribution piece.
In a development of the invention, the connecting line for fluid to be atomized is of double-walled design, at least in the connecting region to the distribution piece.
In this way, a good thermal insulation, for example by means of an air gap, can be achieved between the connecting line and the housing of the nozzle.
In a development of the invention, a thermal insulation coating is provided between the first annular slot and the housing and also between the first annular slot and the second annular slot.
In this way, a heat transfer between the cold fluid and the hot atomizing gas can additionally be minimized in the annular slot region up to the outlet of the fluid to be atomized from the nozzle. This is of considerable advantage in the case of the externally mixing two-component nozzle according to the invention.
In a development of the invention, the discharge opening for the atomizing gas has the form of a third annular slot.
The fluid to be atomized is consequently received between two annular slot flows of the hot atomizing gas so that a very good atomizing effect is achieved. The third annular slot can be formed, for example, by the insertion of a conical piece into the discharge opening.
In a development of the invention, the boundary of the first annular slot, as seen in the flow direction, is arranged in front of an outer boundary of the second annular slot.
In this way, the fluid to be atomized discharges from the first annular slot and comes into contact with the atomizing gas from the second annular slot just before the atomizing gas has left the nozzle mouth at the end of the second annular slot. The atomizing gas from the second annular slot cannot consequently deviate to the side so that an acceleration of the fluid, which is to be atomized, by means of the flanking gas flows is carried out just before leaving the nozzle mouth. In this way, a finer atomization of the fluid to be sprayed can be achieved.
In a development of the invention, the boundary of the first annular slot is arranged by one to ten times the width of the first annular slot in front of the outer boundary of the second annular slot, as seen in the flow direction.
In a development of the invention, at least one distribution piece is formed from a material, especially high-alloy high-grade steel, with a coefficient of thermal conductivity which is significantly reduced, especially by the factor of 8, compared with brass.
The provision of a material with low thermal conductivity for the distribution piece can already significantly reduce a heat transfer between the fluid to be sprayed and the hot atomizing gas.
In a development of the invention, a section—lying directly upstream of the discharge opening—of the flow passage for the hot atomizing gas is formed in the housing so that it first of all tapers and after passing a constriction widens again up to the discharge opening, as seen in the flow direction.
In this way, a discharge nozzle for the atomizing gas can be of convergent/divergent design. In particular, this discharge nozzle can be designed as a Laval nozzle so that the hot atomizing gas then discharges from the discharge opening at supersonic velocity.

Further features and advantages of the invention are gathered from the claims and the subsequent description of preferred embodiments of the invention in conjunction with the drawings. In the drawings:

FIG. 1 shows an externally mixing multi-component nozzle according to the invention in a sectional view according to a first preferred embodiment,

FIG. 2 shows an enlarged detail of the multi-component nozzle of FIG. 1,

FIG. 3 shows a multi-component nozzle according to the invention according to a second preferred embodiment, and

FIG. 4 shows a detail of a multi-component nozzle according to the invention according to a third embodiment.

The sectional view of FIG. 1 shows a multi-component nozzle 1 according to the invention. In the case of the multi-component nozzle 1 according to the invention, the object of largely overcoming premature enthalpy losses of the atomizing gas as a result of heat transfer to the fluid to be atomized and of preventing deposits forming in the nozzle as a result of temperature-dependent depositing of components of the fluids which are dissolved at low temperature, is achieved in the following way. The steam flow 10 which is fed via the steam feed line to the multi-component nozzle 1 is split into two partial flows in a new-type distribution piece 18 of small dimensions which can therefore be integrated into the nozzle 1. An outer partial flow 30 and a central partial flow 28 of steam or hot atomizing gas are produced. The outer partial flow 30 is blown out via an outer annular slot 29, whereas the central partial flow 28 is blown out via a central nozzle 62 which ends at a discharge opening 60. An annular slot nozzle 20 for discharging the fluid to be sprayed, especially water which is to be atomized, is arranged between the central nozzle 62 having the discharge opening 60 and an outer annular slot nozzle 31. The approach of atomization of the fluid via a central flow and an outer annular slot flow of the auxiliary atomizing medium make the atomization easier. Essential for the invention, however, is the design of the distribution piece 18 for distributing fluid to be sprayed and hot atomizing gas to the individual discharge openings of the nozzle 1.
A characteristic feature of the nozzle 1 is that the fluid to be atomized is not discharged via a central nozzle but via an annular slot. This annular slot can be of relatively large dimensions because in this case a high discharge velocity of the fluid is not necessary. The atomization is carried out according to the invention by the fluid film being introduced between two high-velocity atomizing gas flows. As a result of the shear stress effect of these high-velocity flows, the fluid film is extracted from the annular slot to form a thin fluid lamella which disintegrates into small droplets. Therefore, the risk of material erosion on the annular slot walls of the fluid nozzle, specifically at the annular slot 21, is also greatly reduced and the long-term stability of the throughflow characteristic of such a nozzle does not present a problem in this respect. Such a nozzle, however, also has a very good partial load behavior, completely in contrast to single-component nozzles according to the prior art with swirlers in the fluid duct.
The central nozzle 62 for hot atomizing gas having the discharge opening 60 is designed according to FIG. 1 as a convergent/divergent nozzle in the flow direction. If, for example, steam is delivered with a supercritical pressure ratio, this configuration operates as a Laval nozzle and the steam then discharges at supersonic velocity from the central nozzle 62 at the discharge opening 60. It is also important, however, that the nozzle 1 does not have an end face which is washed by industrial water. This is achieved by the very narrowly formed boundaries of the annular slot 21. Therefore, the problem of stalactite-like deposits, as is to be monitored in end faces of nozzles according to the prior art, does not occur either in this case.
Essential features of the nozzle 1 according to the invention concern the thermal decoupling of the hot atomizing gas, especially steam, from the cold water at the nozzle connection and inside the nozzle. For this purpose, the feed line 4 for the water 5 is of double-walled design.
In addition, through-holes, via which the water 5 is fed to the annular slot 21 and the steam is fed to the central nozzle 62 having the discharge opening 60 or to the outer annular slot 29, are arranged in the distribution piece 18 with the greatest possible distance apart. Inserted into the holes 19 for the feed of the water to the outer part of the nozzle 1 are inner tubes 38 which on the outer side, that is to say at their start and end, are relieved so that a wall contact, which centers the inner tubes 38 in the hole in the distribution piece 18, exists only in the narrow sections. As a result of this, an air-filled cavity, which serves as a thermal insulation, is created between the water-conducting inner tube 38 and the distribution piece 18. In addition, the outer surface of the central nozzle 62 having the discharge opening 60 and the inner surface of the annular slot nozzle 20 having the annular slot 21 are also lined with a thermally insulating layer 35, 36 so that the fluid to be atomized, practically over its entire passage through the nozzle 1 to the direct proximity of the nozzle mouth, is equipped with a thermal insulation against the nozzle housing and especially against the distribution piece 18, and therefore also against the flow of the hot atomizing gas. The effect achieved in this way is that the fluid is only slightly heated, or that the hot atomizing gas, especially the hot steam, suffers only small enthalpy losses as a result of cooling.
Naturally, the possibility exists of also applying a thermal insulation on the side of the nozzle which is acted upon by steam. This, however, would usually be disproportionately costly because the surface which is in contact with the steam is significantly larger than is the case on the water side.
A further interesting possibility is to use a material with low thermal conductivity, at least for the distribution piece 18, which material, on the other hand, is suitable for the predetermined operating temperature of 300° C., for example. The changeover from brass to a high-alloy high-grade steel already leads to a reduction of the thermal conductivity by the factor of 8.
FIG. 1, and FIG. 2 as a detail enlargement of FIG. 1, show the nozzle 1 in a sectional view. The nozzle 1 is intended for being arranged inside a duct 3 which conducts a primary fluid, for example flue gas, into which a fluid to be atomized is to be injected. The duct 3 is only schematically represented by one of its boundaries. The nozzle 1 is therefore located inside the flow of the primary fluid in the duct 3.
The fluid 5 to be atomized is fed via a connecting line 4, via a central connection 17 of the nozzle housing 2, to the distribution piece 18 of the nozzle 1. Via at least one hole 19 in the distribution piece 18, into which an inner tube 38 is inserted, the fluid 5 finds its way into an annular chamber of the annular slot nozzles 20 which inwardly is delimited by a central nozzle piece 27 and outwardly by an intermediate cap 34. From this annulus, the fluid finds its way over the shortest distance to the fluid outlet at the annular slot 21.
The atomizing gas, e.g. hot steam 10, is first of all fed to an annulus 23 in the nozzle housing 2 via a pipe 11 which, like the connecting line 4, leads out of the duct 3. From this annulus 23, the atomizing gas finds its way into a central chamber 26 in the distribution piece 18 via at least one milled out portion 24 and via at least one hole 25 in the distribution piece 18. The hole 25 is of such dimensions that a defined apportioning of the hot steam 10 to two partial flows is carried out, specifically once via the hole 25 to the discharge opening 60 of the central nozzle 62 and once via the annulus of the annular slot nozzle 31 to the annular slot 29 at the nozzle mouth.
In the depicted embodiment of the nozzle 1, the central nozzle piece 27 is screwed into the distribution piece 18 and forms the central nozzle 62 for the central steam jet 28. A flow path of the central nozzle 62 then extends to the central chamber in the distribution piece 18 first of all convergently in a first conically tapering section. A cylindrical section adjoins this first conically tapering section, forming a constriction. Adjoining this, a conically widening section to the discharge opening 60 follows. As is customary in Laval nozzles, the central nozzle 62 therefore extends first of all convergently and then divergently, and the cross-sectional dimensions of the central nozzle 62 are also responsible for the distribution of the steam flow 10 to the central nozzle 62 and to the outer annular gap nozzle 31. The outer steam flow, also referred to as annular slot steam flow 30, is fed via the milled out portion 24 first of all to the annulus of the annular slot nozzle 31 and from here finds its way into the outer annular slot 29. The steam therefore discharges both as a central steam jet 28 from the central nozzle 62 and from the outer annular slot 29.
The outer annular slot 29 is formed between an outer cap 49 and the intermediate cap 34. The steam, at high velocity right up to high supersonic velocities, discharges from the outer annular slot 29 and from the discharge opening 60, as is illustrated by arrows 32, 33 in FIG. 2. As a result of the interaction between the ring-like fluid jet, which discharges from the first annular slot 21, and the flanking steam jets according to the arrows 32 and 33, a droplet spray jet with the boundary 22 is created, as is shown by the dashed lines in FIG. 1.
In many cases, the previously described configuration should already effect an adequate thermal decoupling of hot steam 10, as atomizing gas, and the cold fluid 5 to be atomized. In order to improve such a thermal decoupling and to reduce a heat transfer between fluid 5 to be atomized and the hot steam 10, the connecting line 4 for the fluid 5 is of double-walled design in which provision is made for an inner tube 37 up to the connection to the distribution piece 18. The connecting line 4 is therefore of double-walled design and provided with a thermally insulating air gap 44. Alternatively, the connecting line can also be constructed with a graphite sleeve in order to achieve a thermal insulation.
In addition, the flow passage in the at least one hole 19 in the distribution piece 18 for the feed of water to the annulus of the annular slot nozzle 20 is also of double-walled design with the inner tube 38, wherein, as was explained, an air gap lies between the inner tube 38 and the hole 19 in the distribution piece 18.
The water-conducting annulus of the annular slot nozzle 20 is thermally insulated by layers 35, 36 of suitable material towards the central nozzle piece 27 as well as towards the intermediate cap 34. These insulating layers 35, 36 for example can consist of metal with poor thermal conductivity or from a ceramic material.
In order to further reduce the heat transfer between fluid 5 and hot steam 10, a disk 40 produced from a thermally insulating material is provided on a bottom face 39 of the distribution piece 18 to which the connecting line 4 for fluid 5 is attached. As a result, a heat transfer of from the fluid 5 in the connecting line 4 to the distribution piece 18 can be significantly reduced. The disk 40 is provided with through-holes in order to direct fluid 5 into the at least one hole 19 or into the inner tube 38 in the distribution piece 18.
To which extent the previously described measures are adopted depends upon the operating conditions of the nozzle. Already by the provision of the distribution piece 18 in the housing 2 of the nozzle 1, in many cases an adequate thermal decoupling of hot steam 10 and fluid 5 to be atomized is already achieved so that as a rule such costly additional insulation measures can be dispensed with.
The nozzle housing 2 is of multi-piece design and has a first, approximately cup-shaped component 64 having the connecting line 11 for hot steam and having the connection 17 for the connecting line 4 for fluid 5. The distribution piece 18 is inserted into the cup-shaped component 64 and is screwed onto the connecting line 4, which is also inserted into the component 64, and is supported in the radial direction on the inner wall of the cup-shaped component 64 via ribs 66. Provision is made between the ribs 66 for the milled-out portions 24 via which hot steam 10 finds its way into the flow passage, formed by the hole 25, in the distribution piece 18 and to the outer annular slot 31.
The outer cap 49 is screwed onto the cup-shaped component 64. Arranged inside the outer cap 49 is the intermediate cap 34 which is screwed onto the distribution piece 18. The outer annular slot nozzle 31 for hot atomizing gas is therefore formed between the outer cap 49 and the intermediate cap 34 and ends at the nozzle mouth on the outer annular slot 29.
Inside the intermediate cap 34, the central nozzle piece 27 is screwed into the distribution piece 18. The annular slot nozzle 20 for fluid to be atomized is formed between the central nozzle piece 27 and the intermediate cap 34 and ends at the nozzle mouth on the annular slot 21. As was previously described, an outer side of the central nozzle piece 27, which delimits the annular slot nozzle 20 on one side, is lined, at least in sections, with an insulating layer 35. Only directly upstream of the annular slot 21 is there no longer provision for an insulating layer 35 in order to be able to design the annular slot 21 narrow.
An inner side of the intermediate cap 34, which outwardly delimits the annular slot nozzle 20, is also lined in sections with an insulating layer 36. Only directly upstream of the annular slot 21 is there no longer provision for an insulating layer 36.
The nozzle 1 according to the invention is obviously of a very compact construction and particularly effects a distribution of the hot steam 10 to the central nozzle 62 and to the outer annular slot nozzle 31 inside the housing 2 of the nozzle 1 over a short distance. The flow passage for hot steam in the distribution piece 18, formed by the hole 25, via which hot steam finds its way to the central nozzle 62, is arranged at an angle to the flow passage for fluid 5 to be atomized—also provided in the distribution piece 18—which is formed by the hole 19 and the inner tube 38. The flow passage for hot steam and the flow passage for fluid are therefore arranged inside the distribution piece 18 in a crosswise manner. In the depicted embodiment, an angle of about 45° lies between the center longitudinal axes of the flow passage for hot steam and of the flow passage for fluid.
The distribution piece 18 is produced from high-alloy high-grade steel which has low thermal conductivity. Compared with conventional brass nozzles, a heat transfer from the hot steam 10 to the cold fluid 5, which is reduced by a factor of about 8, is already achieved as a result.
The inner tube 38, which is inserted into the hole 19 of the distribution piece 18, forms a flow passage for the fluid 5 through the distribution piece 18. The inner tube 38 is constructed as a turned part and bears against the inner wall of the hole 19 only in the regions 68, 70. Outside the regions 68, 70, which are shown in black in FIG. 1, an insulating air gap 72 lies between the inner tube 38 and the distribution piece 18.
FIG. 2 shows the nozzle mouth having the discharge opening 60 of the nozzle 1 in an enlarged view. It is to be seen that the discharge opening 60 of the central nozzle 62, the end of the annular slot 21 of the annular slot nozzle 20, and the annular slot 29 which defines the outlet of the annular slot nozzle 31, are located exactly at the same height, as seen transversely to the flow direction. Consequently, mixing of the hot steam jets from the annular slot nozzle 31 and from the central nozzle 62 with the annular slot flow of fluid to be atomized from the annular slot nozzle 20 is carried out just outside the nozzle 1.
The view of FIG. 3 shows a further multi-component nozzle 80 according to the invention according to a second preferred embodiment. The multi-component nozzle 80 is to a great extent constructed identically to the multi-component nozzle 1 in FIG. 1 so that only the features which differ from the nozzle 1 in FIG. 1 are explained.
As is to be seen in FIG. 3, a central body 41, which extends through a central nozzle 82 for hot steam, is screwed into the distribution piece 18. The central body 41 is therefore completely exposed to circumflow by hot steam from the central chamber 26 in the distribution piece 18. In the region of the discharge opening 60, the central body is designed in the form of a widening cone 42 so that the discharge opening 60 is of ring-like design and an inner annular slot 43 is formed for the discharge of the proportion of hot steam 10 which is fed via the hole 25. The ring-like flow of fluid 5 to be atomized is therefore enclosed between two also ring-like hot steam flows.
By providing the cone 42, the central steam also discharges via the annular slot 43. The central cone 42 in this case, however, is only exposed to circumflow by hot steam which is free of solids as far as possible so that no relevant risk of deposits forming on the cone 42 exists. As a result of the cone 42, the steam consumption of the nozzle 80 can be reduced a little more compared with the nozzle 1 without this having a negative effect upon the atomization quality. Also, in the case of the nozzle 80 having the central cone 42, the central nozzle 82 can be constructed as a Laval nozzle. This, however, is not the case in the view of FIG. 3. In order to form the central nozzle 82 as a Laval nozzle, the flow cross section of the annular slot between the central body 41 and the discharge section of the central nozzle 82 must have a divergent progression towards the nozzle mouth.
The view of FIG. 4 shows section-wise a multi-component nozzle 90 according to the invention according to a third preferred embodiment. The nozzle is formed to a great extent identically to the nozzle 1 in FIG. 1 so that only the features which differ from the nozzle 1 are described.
The nozzle 90 has an outer cap 92 which is extended compared with the outer cap 49 of the nozzle 1. As a result, the discharge opening 60 of the central nozzle 62 and the annular slot 21 of the annular slot nozzle 20 for fluid to be atomized are set back in relation to the nozzle mouth. The nozzle mouth is formed in this case by the downstream-disposed end of the outer cap 92. In the case of the nozzle 90, contact consequently already occurs inside the nozzle housing between the ring-like fluid flow from the annular slot 21 and the hot gas flows from the discharge opening 60 and from the annular slot 29. Already created inside the nozzle housing as a result, albeit close to the nozzle mouth, is a free fluid lamella which is no longer braked as a result of wall friction but sharply accelerated by means of the flanking high-velocity flows of auxiliary atomizing medium, for example hot steam. To already implement this inside the nozzle 90 offers the advantage that here the flows of the auxiliary atomizing medium and especially the hot gas flow from the annular slot 29 cannot yet deviate to the side, as is the case after leaving the nozzle. In this way, an even finer atomization of the fluid is brought about. The setting back of the outlet of the fluid nozzle in relation to the position of the nozzle mouth is advantageously one to ten times the width of the annular slot 21 of the annular slot nozzle 20 for the fluid at the nozzle mouth. In the depicted, purely exemplary drawing, the width of the annular slot 21 for the fluid is about 1 mm and this annular slot is set back in relation to the nozzle mouth by about 5 mm, that is to say five times the width of the annular slot 21.
With the invention, provision is therefore made for an externally mixing multi-component nozzle in which a minimum internal heat transfer between the fluid to be sprayed and the atomizing gas is realized. The distribution of the fluid to be atomized and of the atomizing gas is undertaken in a distributor which is integrated into the nozzle body or the nozzle housing. The effect achieved as a result of this design according to the invention is that the heat transfer from the hot atomizing gas to the fluid to be atomized inside the nozzle, especially inside the nozzle housing, is minimized or limited to an advantageous value. The externally mixing multi-component nozzles according to the invention are used in flue gas ducts or in flue gas scrubbing plants in power plants or in the cement industry.

Claims

1. An externally mixing multi-component nozzle for spraying fluids with the aid of an atomizing gas, especially steam or hot gas, which is hot in relation to the fluids to be atomized, with a housing, wherein the housing has a discharge opening for the atomizing gas, a first annular slot, encompassing the discharge opening, for fluid to be atomized, and a second annular slot, encompassing the first annular slot, for the atomizing gas, and also a distribution piece, wherein the distribution piece has at least one flow passage for fluid to be atomized from a connecting line to the first annular slot and at least one flow passage from an atomizing gas connecting line to the discharge opening for atomizing gas.

2. The externally mixing multi-component nozzle as claimed in claim 1, wherein the housing has an annular passage for atomizing gas which encompasses the distribution piece at least in sections.

3. The externally mixing multi-component nozzle as claimed in claim 2, wherein the flow passage of the distribution piece for the atomizing gas originates from the annular passage.

4. The externally mixing multi-component nozzle as claimed in claim 1, wherein a thermal insulation is provided, at least in sections, between the flow passage for fluid to be atomized and the distribution piece.

5. The externally mixing multi-component nozzle as claimed in claim 4, wherein the flow passage for fluid to be atomized is formed, at least in sections, by means of a tube which is inserted into the distribution piece.

6. The externally mixing multi-component nozzle as claimed in claim 5, wherein an air gap is provided, at least in sections, between the tube and the distribution piece.

7. The externally mixing multi-component nozzle as claimed in claim 1 wherein the connecting line for fluid to be atomized is of double-walled design at least in the connecting region to the distribution piece.

8. The externally mixing multi-component nozzle as claimed in claim 1, wherein a thermal insulating layer is provided between the first annular slot and the housing and also between the first annular slot and the second annular slot.

9. The externally mixing multi-component nozzle as claimed in claim 1, wherein the discharge opening for atomizing gas has the form of a third annular slot.

10. The externally mixing multi-component nozzle as claimed in claim 1, wherein the boundary of the first annular slot, as seen in the flow direction, is arranged in front of an outer boundary of the second annular slot

11. The externally mixing multi-component nozzle as claimed in claim 10, wherein the boundary of the first annular slot is arranged by one to ten times the width of the first annular slot in front of the outer boundary of the second annular slot, as seen in the flow direction.

12. The externally mixing multi-component nozzle as claimed in claim 1, wherein at least the distribution piece is formed from a material, especially high-alloy high-grade steel, with a coefficient of thermal conductivity which is significantly reduced, especially by the factor of 8, compared with brass.

13. The externally mixing multi-component nozzle as claimed in claim 1, wherein a section—g directly upstream of the discharge opening—of the flow passage for atomizing gas in the housing first of all tapers and after passing a constriction widens again up to the discharge opening, as seen in the flow direction.