EP4089325B1 - Nozzle for blowing gas into a combustion plant with a pipe and a swirl generator, flue with such a nozzle and method of using such a nozzle - Google Patents

Description

The invention relates to a nozzle for blowing gas into a combustion system with a pipe and a swirl generator, a flue gas flue with such a nozzle and a method for using such a nozzle.

According to the current state of the art, secondary air nozzles in waste incineration plants are designed as jet nozzles. Here, pressure and nozzle diameter are the primary design parameters. The pressure primarily influences the inlet velocity, the diameter the volume flow. The total volume flow results from the number of nozzles. The nozzle inserts can be manufactured as a cast component.

In incinerators, there is often a poorly mixed area of air starvation at the front wall, which can lead to increased CO concentrations and CO peaks, particularly where the fuel has a high calorific value, such as when using cooking caloric fuels and grate-fired incinerators can occur.

The EP 0611 919 A1 describes a nozzle for supplying a combustion gas, with which a swirling secondary gas jet is generated, which intensively mixes an area near the boiler wall and enriches it with oxygen. The amount of volumetric flow supplied is set in the gas nozzle with a control body which is arranged so that it can be displaced axially to the longitudinal axis of the nozzle, which at least partially blocks the nozzle cross-section and is provided with an adjustment device which can be guided out of the nozzle for speed-controlling the supply of the secondary gas. There are spacer elements on the displaceable control body, which are designed as swirl bodies in the form of curved guide vanes and are guided on the inner wall of the nozzle.

When using these nozzles, flue gas can get to the control body arranged in the nozzle cone and deposits on the swirl body can impair its mobility.

The U.S. 5,727,480 describes a nozzle tube that is concentrically surrounded by another nozzle tube. Air flow in the inner nozzle tube causes gas to be drawn in through the annular gap between the concentric tubes. Baffles are provided in this annular gap, which direct the gas flowing through the annular gap from the inner tube to the outer tube, so that a very special gas flow is created at the nozzle outlet.

The nozzle is complex to use, since two regulated gas feeds have to be provided.

The WO 2012/096319 A1 also describes concentric tubes for the targeted delivery of gas. A swirl body is arranged in the inner tube so that it can be displaced axially with respect to the longitudinal axis of the nozzle by means of a rod.

A nozzle for injecting gas into an incinerator having a cylindrical tube and a swirl generator mounted in the tube or on the inside of the tube is known from US Pat CN 110 848 693 B and the EP 3 739 264 A1 known. More such nozzles are from CN 105 737 203 A , the GB 2 551 166 A , the WO 2005/078348 A1 and the DE 10 2007 030269 A1 known. A generic nozzle is off U.S. 2010/205971 A1 known.

In use, contamination on the pipes and especially on the swirl body is to be expected, which will impede the gas flow.

The invention is therefore based on the object of further developing a nozzle for combustion systems in such a way that it has a long service life in rough use and leads to a greater jet expansion with the same volume flow and pressure. A method for using such nozzles is also presented.

This object is achieved with a nozzle having the features of patent claim 1, a flue gas flue with such a nozzle according to claim 15 and a method having the features of patent claim 19.

With the same volume flow and pressure, the developed swirl nozzles lead to a stronger jet expansion and thus to a lower penetration depth. This is achieved by dividing the impulse into an axial and a tangential component. With jet nozzles, the momentum is entirely in the axial direction. Through the use of swirl nozzles as secondary air nozzles, particularly in waste incineration plants, a Lack of air near the wall, especially on the front wall, can be reduced.

The developed nozzle insert has a special injection characteristic. As with air outlets of ventilation systems arranged on the ceiling of living spaces, when the nozzle according to the invention is used in an incineration system, a uniform "air curtain" is produced near the boiler wall in order to prevent CO strands from breaking through. With known nozzle inserts, the highest possible impulse of the injected medium has hitherto been generated in order to achieve the highest possible mixing of the flue gas with the lowest possible use of supplied combustion air.

Even if two different media (e.g. recirculated flue gas and air) are injected with one nozzle, a high impulse for effective mixing of the flue gas over the entire cross-section of the boiler is important.

However, the known methods always have the disadvantage that, due to the distance between the individual nozzles and the air jets that are not very fanned out near the wall, zones are formed that are not thoroughly mixed. Here, exhaust gas containing CO can pass through the secondary combustion level unhindered.

The aim of the design is to construct a twist insert that has a similar pressure-volume flow characteristic as a conventional jet nozzle while generating the strongest possible twist. This is achieved by using a tube that is cylindrical over its entire length. The inlet is preferably not rounded. If the pressure loss is too high, the nozzle diameter would have to be greatly increased in order to achieve sufficient volume flows in the conventional pressure range. Higher pressures would only be achievable with an additional fan/compressor. The component costs for the larger swirl generator would also be higher. This should be avoided for cost reasons.

An additional goal of the design is to generate a swirl flow that is as uniform as possible at the nozzle outlet, if possible without backflow into the nozzle pipe, in order to prevent the potential entry of ash particles and hot flue gases. This is to prevent contamination and corrosion of the swirl generator. Straight blades are preferable to twisted blades, and blades with a straight inlet section are preferable to blades without a straight inlet section.

Many factors have different effects on the effectiveness of the nozzles. A diffuser or a radius at the nozzle outlet reduce the pressure loss, but an attached flow can only be expected in combination with a small swirl generator. In addition, the formation of backflow areas is increased, which increases the risk of contamination and corrosion of the nozzle interior.

A hole in the center of the swirler reduces the formation of backflow areas and also reduces the pressure drop. A connection of the blades in the middle (e.g. as a pin or ring) is more of a disadvantage, as this intensifies the formation of backflow areas and also increases the pressure loss. A more rigid construction and manufacture of the swirl generator without an outer, connecting ring are advantageous here.

A straight inlet section of the blades reduces the pressure loss and is therefore an advantage. The transition to the swirl-generating part of the blades can be designed in different ways, e.g. as a radius or a curved profile. The swirl generating part of the blades can also be curved. The blades can also be designed with increasing blade height from the inlet to the nozzle outlet.

The swirl generator should be moved slightly inwards to reduce the risk of contamination and corrosion. However, this also reduces the swirl effect. If there is excessive wear during system operation, the swirl generator can be moved further inside the pipe, which can be compensated for by a higher swirl angle. Although this leads to a higher pressure loss, this can be compensated for by a larger nozzle diameter or a diffuser.

The twist generator can also be used in a conically converging part of a conventional jet nozzle insert. It is also advantageous to generate a swirl by introducing the air tangentially into the nozzle with a plurality of inlet channels distributed over the circumference. However, this requires a more expensive construction and a complex design.

In terms of manufacturing technology, it is advantageous if the tube is arranged in an outer tube. The twist insert thus consists of a tube in which the twist generator is arranged. This tube is welded into the outer tube. This creates a Nozzle insert that can be inserted into a nozzle tube. The tube preferably has a wall thickness of 2 to 5 mm. The inner diameter of the tube is preferably 40 to 80 mm and is approximately 50 mm in the exemplary embodiment.

It has proven to be advantageous if the swirl generator has blade profiles which have an angle of 15° to 60° and preferably of 40° to 50° to generate the swirl. An exemplary embodiment has an angle of 45°. At larger angles, the twisting effect increases. However, this leads to a higher pressure loss and the formation of backflow areas.

In order to protect the nozzle, it is suggested that the distance between the swirl generator and the pipe outlet and thus from the boiler inlet is about 10 to 30 mm. The twist generator should therefore be offset inward in the pipe by at least 5 mm and preferably about 10 mm.

The swirl generator preferably has more than 4 and, for example, 6 swirl vanes distributed over the circumference. As a rule, the number of blades is 4 to 8 pieces.

The vanes of the swirler should have an average airfoil thickness between 1 and 6 mm and preferably between 2 and 4 mm. Its length in the axial direction of the nozzle tube is 20 to 60 mm and preferably about 30 mm, of which 30 to 70% and preferably about 50% is designed as a straight inlet section in order to reduce the pressure loss.

Fouling of the vanes is reduced if the swirler has swirl vanes forming a central free passage with a diameter greater than 20% of the inside diameter of the tube. It is advantageous if the blades do not touch. In practice, the diameter of the clear hole in the center of the blades should be 10 to 30 mm, such as 16 mm. That is then about 30% of the inner diameter of the pipe.

A variable setting of the twist is suggested as an additional option. This can be achieved either by means of a mechanically adjustable angle of attack of the swirl generator or by means of two concentric channels with different swirl angles (eg swirl-free core jet and swirled annular gap). The channels can use one variable volume flow ratio. For example, two collectors can each be provided with a pressure control via a control valve. Such a design is primarily advantageous for a flexible mode of operation and makes sense, for example, when the combustion zone is shifted by varying the average calorific value of the waste or when varying the load. It is also possible to introduce and mix different gases (e.g. air with recirculation gas or air with steam).

A special embodiment therefore provides that the swirl generator has movable swirl vanes.

An alternative embodiment provides that the tube has at least one and preferably several tangential inlet channels distributed around the circumference. Alternatively or cumulatively, the nozzle can also have a tube with at least one and preferably a plurality of spiral-shaped gas ducts distributed around the circumference.

It is advantageous if the Mach number Ma of the nozzle is below 0.4.

If the nozzle is installed in a furnace, then it should be located in a wall of a flue, preferably at the front wall of a flue. It is advantageous if two of the nozzles are arranged next to one another and exert a twist in opposite directions.

Also, a non-swirl gas injection nozzle, also called a jet nozzle, may be arranged next to a swirl gas injection nozzle, also called a swirl nozzle.

A method for using such a nozzle serves to blow in a gas, such as in particular air or oxygen for oxygen enrichment, for example on a wall and in particular the front wall of an incinerator such as a waste incineration plant, preferably already in the first pass. This method is particularly suitable for a high calorific value (e.g. substitute fuel) and for grate firing.

The nozzles can be used to expand existing combustion air systems in the area of secondary combustion. The swirl nozzles can replace individual nozzles or be used in addition. An opposite direction is advantageous Direction of rotation of adjacent nozzles.

In this method, it is advantageous if the gas volume flow that is passed through the nozzle is set to 100 to 1500 Nm ³ /h per nozzle. This results in an operating pressure in the collector at the nozzle level of approx. 5 to 100 mbar and the entry speed is 10 to 100 m/s. In one embodiment, the air volume flow is 100 to 500 Nm ³ /h at an operating pressure in the collector of 10 to 60 mbar and an entry speed of 20 to 80 m/s.

For example, the nozzle can also be used for air, recycle gas, steam, CO ₂ , O ₂ and N ₂ and mixtures thereof. However, when recirculation gas, which is mostly particle-laden, or steam is introduced, higher wear due to contamination and corrosion is to be expected.

Such nozzles can be manufactured as a twist insert using 3D printing from stainless steel (e.g. 17-4PH or 1.4548) and alternatively also, for example, using investment casting or CNC milling.

A twist insert can be welded into an outer tube. However, the twist insert can also be implemented as a welded construction, for example with sheet metal welded into a tube - as an alternative to 3D printing, investment casting or CNC milling.

A further reduction in the risk of contamination and corrosion is possible, for example, with rounded blades or with a central nose or point.

Depending on the embodiment, the swirl nozzle can also have a lower suction effect compared to jet nozzles, which leads to fewer particles entering the corresponding boiler wall.

Figur 1

ein Rohr mit einem Drallerzeuger

Figur 2

einen Blick in einen Drallerzeuger

Figur 3

einen Dralleinsatz in einem Außenrohr, die als Düseneinsatz in einem Düsenrohr angeordnet sind,

Figur 4

eine Gasverteilung am Ausgang einer an der vorderen Kesselwand angeordneten Dralldüse,

Figur 5

eine Gasverteilung einer an derselben Stelle wie in Figur 1 angeordneten und mit gleichem Volumenstrom und Druck betriebenen herkömmlichen Strahldüse,

Figur 6

einen Rauchgaszug mit 4 Strahldüsen und links unten mit einer Strahldüse als kleine Düse

Figur 7

den in Figur 6 gezeigten Rauchgaszug mit rechts unten einer Dralldüse als kleine Düse,

Figur 8

einen Rauchgaszug mit 4 Strahldüsen und links oben mit einer Strahldüse als kleine Düse

Figur 9

den in Figur 8 gezeigten Rauchgaszug mit rechts oben einer Dralldüse als kleine Düse,

Figur 10

links ein Außenrohr einer Düse, mittig zwei Dralleinsätze mit Rohr und Drallerzeuger und rechts einen Düseneinsatz aus einem Außenrohr mit einem eingeschweißten Dralleinsatz,

Figur 11

eine Düse mit einer Drallerzeugung durch tangentiale Einbringung des Gases in einem konischen Bereich der Düse und

Figur 12

ein Rohr mit einer Drall erzeugenden Innenkontur als Düse oder Zuleitung zu einer Düse.

Exemplary embodiments of the invention are shown in the drawing and are explained in more detail below. It shows the

figure 1

a tube with a swirl generator

figure 2

a look into a swirl generator

figure 3

a swirl insert in an outer tube, which are arranged as a nozzle insert in a nozzle tube,

figure 4

a gas distribution at the outlet of a swirl nozzle arranged on the front boiler wall,

figure 5

a gas distribution a in the same place as in figure 1 arranged and operated with the same volume flow and pressure conventional jet nozzle,

figure 6

a flue gas flue with 4 jet nozzles and at the bottom left with a jet nozzle as a small nozzle

figure 7

the in figure 6 shown flue with a twist nozzle as a small nozzle at the bottom right,

figure 8

a flue with 4 jet nozzles and at the top left with a jet nozzle as a small nozzle

figure 9

the in figure 8 shown flue with a swirl nozzle as a small nozzle at the top right,

figure 10

on the left an outer tube of a nozzle, in the middle two swirl inserts with tube and swirl generator and on the right a nozzle insert made of an outer tube with a welded-in swirl insert,

figure 11

a nozzle with a swirl generation by tangential introduction of the gas in a conical area of the nozzle and

figure 12

a tube with an inner contour that generates a twist as a nozzle or feed line to a nozzle.

The figure 1 shows a nozzle 1 as a swirl insert 26 from a tube 20 in which six swirl vanes 24 (numbered only as an example) are arranged as swirl generators 21 . The twist blades have no bend in the flow direction of the gas over a length of about 40 mm and thus form a straight inlet section 27. They are then bent and form a twist angle 28 of around 45° to the straight inlet section.

In the figure 2 a twist insert is shown from a different perspective, in which the central free passage 25 can be seen.

The figure 3 shows a nozzle tube 28 in which a twist insert 26 held in an outer tube 23 is arranged as a nozzle insert 29 .

The figure 4 shows a nozzle 1 as a swirl nozzle for blowing gas 2 into an incineration plant 3. The incineration plant is shown schematically as the first flue gas flue 4 figure 5 a conventional jet nozzle 5, which promotes the same volume flow of gas in the flue 4. Comparing the figures clearly shows that the injected gas is 2 in figure 4 remains on the front wall 6 of the flue 4 and does not penetrate as far into the flue 4 as in the figure 5 , in which the gas 2 reaches the middle of the flue gas train 4 much further and is only distributed there in a fan shape.

The advantages of the swirl nozzle in practice are also shown by the Figures 6 to 9 . There, the reference numerals 7 and 8 show large jet nozzles on the rear wall 9 of the flue gas flue 4. On the front wall 6 are in the Figures 6 and 7 each above large jet nozzles 10 and including a rear large jet nozzle (not shown) arranged to promote the gas 2 in the flue gas flue 4.

Smaller nozzles are arranged horizontally next to the lower, covered, large jet nozzles, which are used in the in figure 6 shown example as a small jet nozzle 11 and in figure 7 are designed as a small swirl nozzle 12. A small nozzle 11, 12 differs from a large nozzle 8, 9, 10 in that a small nozzle 11, 12 conveys a lower volume flow of gas into the flue gas flue 4.

While primary combustion gas 16 is supplied through the grate from the very bottom, in figure 6 on the front wall 6 an area 14 with a lack of air and in the area of the rear wall 9 an area 15 with excess air. The figure 7 shows, however, that the use of the small swirl nozzle 12 in the flue gas flue 4 results in a more even air distribution and improved mixing of combustion gases and air.

It is similar when as in the Figure 8 and 9 shown horizontally next to the upper hidden, large jet nozzles 10 smaller nozzles 13 and 14 are arranged. At the in figure 8 shown example, these are smaller nozzles 13 and 14 than small jet nozzle 13 and at the in figure 9 shown example formed on the right side as a small swirl nozzle 14. Below each large jet nozzles 15 and 16 are arranged. This also leads to the result that in figure 8 an area 14 with a lack of air is created on the front wall 6 and an area 15 with excess air is created in the area of the rear wall 9 . The figure 9 shows, however, that the use of the small swirl nozzle 14 in the flue gas flue 4 results in a more even air distribution and improved mixing of combustion gases and air.

The figure 10 12 now shows an outer tube 23, a twist insert 26 with the cylindrical tube 20 and the twist generator 21. The twist generator 21 is located inside a tube 20 which is welded to the inside 22 of the outer tube 23. FIG. The swirl insert 26 consists of the tube 20, on the inside of which swirl vanes 24 are fastened as swirl generators 21. In the center of the blades is a central free passage 25, since the ends of the blades do not touch there.

In the figure 11 The nozzle 30 shown has a nozzle tube 31 with tangential inlet channels 32, 33, 34 distributed around the circumference. The inlet channels are distributed evenly around the circumference in a conical area 35 of the nozzle tube 31 and allow gas to be fed in there in addition to the gas guided in the nozzle tube 31 in order to generate a swirl in the nozzle 30 . The inlet channels 32 , 33 , 34 thus serve as swirl generators attached to the inside of the nozzle tube 31 .

Ultimately, the figure 12 a nozzle pipe 41 with a spiral gas guide 42 attached to the inner circumference.

Claims (19)

1. Nozzle (1) for blowing gas (2) into a combustion plant (3) with a pipe (20, 31, 41) and a swirl generator (21), wherein the pipe (20, 31, 41) is cylindrical and the swirl generator (21) is attached on the inner side (22) of the pipe (20, 31, 41), wherein the swirl generator has swirl vanes with a straight inlet section, characterized in that the swirl vanes (24) have a length of 20 to 60 mm, of which 30% to 70% and preferably approximately 50% is designed as a straight inlet section.
2. Nozzle according to claim 1, characterized in that the pipe (20) is arranged in an outer pipe (23).
3. Nozzle according to claim 2, characterized in that the pipe (20) is welded into the outer pipe (23).
4. Nozzle according to one of claims 2 or 3, characterized in that the pipe (20) has a wall thickness of 2 to 5 mm.
5. Nozzle according to one of the preceding claims, characterized in that the inner diameter of the pipe (20, 31, 41) is 40 to 80 mm and preferably approximately 50 mm.
6. Nozzle according to one of the preceding claims, characterized in that the swirl generator (21) has a swirl angle of 15° to 60° and preferably from 40° to 50°.
7. Nozzle according to one of the preceding claims, characterized in that the swirl generator (21) is offset inwardly in the pipe (20, 31, 41) by at least 5 mm and preferably by approximately 10 mm.
8. Nozzle according to one of the preceding claims, characterized in that the swirl generator (21) has more than 4 and preferably 6 swirl vanes (24) distributed across the circumference.
9. Nozzle according to one of the preceding claims, characterized in that the swirl generator (21) has swirl vanes (24) with an average thickness of the vane profile of between 1 and 6 mm and preferably between 2 and 4 mm.
10. Nozzle according to one of the preceding claims, characterized in that the swirl vanes (24) form a central free passage (25) whose diameter is greater than 20% of the free inner diameter of the pipe (20, 31, 41).
11. Nozzle according to one of the preceding claims, characterized in that the swirl generator (21) has movable swirl vanes (24).
12. Nozzle according to one of the preceding claims, characterized in that the pipe (20, 31, 41) has at least one and preferably multiple tangential inlet channels (32, 33, 34) distributed on the circumference.
13. Nozzle according to one of the preceding claims, characterized in that the pipe (20, 31, 41) has at least one and preferably multiple spiral-shaped gas ducts (42) distributed on the circumference.
14. Nozzle according to one of the preceding claims, characterized in that the Mach number Ma of the nozzle is less than 0.4.
15. Flue gas pipe with a nozzle (1) according to one of the preceding claims, characterized in that the nozzle is arranged in a wall of the flue gas pipe (4).
16. Flue gas pipe according to claim 15, characterized in that the nozzle (1) is arranged on the front wall (6) of the flue gas pipe (4).
17. Flue gas pipe according to claim 15 or 16, characterized in that two of the nozzles (1) are arranged adjacent to one another and exert a swirl in opposite directions.
18. Flue gas pipe according to one of claims 15 to 17, characterized in that a nozzle for blowing in gas (2) without a swirl, which is designated as a jet nozzle, is arranged next to a nozzle for blowing in gas (2) with a swirl according to one of claims 1 to 14, which is also designated as a swirl nozzle.
19. Method for using a nozzle according to one of preceding claims 1 to 14, characterized in that a volume flow made from air and/or flue gas, which is guided through the nozzle (1), is set to 100 to 1500 Nm³/h.

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