WO2008154995A1

WO2008154995A1 - Gas nozzle and reactor with the same

Info

Publication number: WO2008154995A1
Application number: PCT/EP2008/004006
Authority: WO
Inventors: Michael Missalla; Mukund Parthasarathy; Joachim Werther; Erwin Schmidbauer
Original assignee: Outotec Oyj
Priority date: 2007-06-18
Filing date: 2008-05-20
Publication date: 2008-12-24
Also published as: EA016316B1; DE102007028438A1; BRPI0813264B8; AU2008266579A1; AU2008266579B2; EA201000031A1; BRPI0813264A2; BRPI0813264B1; DE102007028438B4; UA102375C2

Abstract

This invention relates to a gas nozzle (1, 1', 1 ') for introducing a gas or gas mix ture in a reactor or the like, comprising a nozzle tube (2) for passing through a gas, at least one nozzle opening (11) arranged near an end of the nozzle tube (2) for discharging the gas from the nozzle tube (2) to the surroundings, and a pot-like hood (4). The hood (4) closes the nozzle tube (2) with a hood cover (7) at the end at which the at least one nozzle opening (11) is provided. The hood (4) includes a hood apron (9) connected with the hood cover (7), which enclosing the nozzle tube (2) by forming an annular gap (10) extends away from the end at which the at least one nozzle opening (11) is provided. The hood apron (9) preferably has a length (L) of at least about 100 mm. Furthermore, this invention relates to a reactor with such gas nozzle (1, 1', 1 ').

Description

Gas Nozzle and Reactor with the same

This invention relates to a gas nozzle for supplying gas or gas mixtures in a reactor, in particular in a reactor in which a fluidized bed is formed, which can be used for processing solids. The gas nozzle includes a nozzle tube through which the gas is passed, at least one nozzle opening arranged near an end of a nozzle tube for discharging the gas from the nozzle tube to the surroundings, and a pot-like hood, with a hood cover which is located at the end of the nozzle where at least one nozzle opening is provided. The hood together with the hood cover forms a seal of the nozzle tube, which is preferably tight, e. g. gas tight. A hood apron is attached to the hood cover which encloses the nozzle tube forming an annular gap that extends away from the end at which the at least one nozzle opening is pro- vided. Furthermore, this invention relates to a reactor with such a gas nozzle.

For introducing gas or gas mixtures, nozzles are frequently used, which have one or normally several nozzle openings, which directly open into the reactor space in which a fluidized bed of solid particles is formed. With these types of nozzle it is possible that solid particles from the reactor enter into the nozzle openings thus leading to nozzle blockages. As a countermeasure, frequently the gas velocity in the nozzle openings is increased to such an extent that solid particles are either blown out of the nozzle openings or cannot enter the openings in the first place. This is described for instance in WO 03/103825 A1. In some applications, how- ever, a high gas velocity in the nozzle openings is regarded as undesirable or disadvantageous, as this often leads to the particle breakage in the solids to be treated and contributes to increased wear in the nozzle itself.

Therefore, gas nozzles were proposed, which have nozzle openings which do not point directly into the interior of the reactor. Such a gas nozzle is known for in- stance from EP 1 499 434 B1. This gas nozzle includes lateral nozzle openings, whereby the risk of intrusion of solid particles is reduced. In many applications, solids can still laterally enter the nozzle tube and therefore this nozzle design is still inadequate and lends itself to further improvement.

In the 'Handbook of Fluidisation and Fluid-Particle Systems', various examples of gas nozzles with lateral nozzle openings as well as gas nozzles with a hood, as mentioned above, are described. Even in the case of gas nozzles with hoods, the problem of solid particles entering into the nozzle openings is still possible and therefore this design also lends itself to further improvement. In addition, the construction of the gas nozzles with hoods is quite expensive, and there is a risk that the hoods are detached from the nozzle tube as a result of the load during operation in a reactor.

Therefore, it is the object of the present invention to provide a gas nozzle as mentioned above, which not only achieves a careful treatment or fluidisation of solid particles but also prevents solids from entering into the nozzle openings. Furthermore, it is an object of the invention to improve the reliability of the nozzle both with regard to the avoidance of back-flow of particles and with regard to the me- chanical durability of the gas nozzle.

In accordance with the invention, this object substantially is solved in that the hood apron has a length of at least about 100 mm extending away from the hood cover and the end at which the at least one nozzle opening is provided. Preferably, the length of the hood apron is greater than about 110 mm, in particular greater than 120 mm.

In comparison to other known gas nozzle designs, the distinctly extended hood apron design of the invention, prevents the intrusion of solid particles into the annular gap between the nozzle tube and the hood apron.. The longer hood apron, also enables a more uniform gas flow, which renders the intrusion of particles much more difficult. Therefore, it is almost impossible that solid particles can reach the nozzle openings and clog the same against the force of gravity and against the flow direction of the gas, since a fluidization of the gas flow in the annular gap is avoided or no longer present at the end of the gap. By means of the very long hood apron, the gas velocity of the gas or gas mixture leaving the annular gap can be reduced at the same time to such an extent that no undesired damage of the solid particles occurs.

By extending the hood apron it is possible to reduce the gas velocity, so that the result of the product of

V² * L (1 )

has a value between 7 and 19 m³/s², preferably 8 to 17 m³/s², wherein V is the velocity at the nozzle outlet (annular gap) and L is the length of the hood apron.

With these values, the intrusion of the particles is prevented and at the same time the gas velocity is kept so low that a decomposition of particles is reduced. Par- ticularly preferred examples for the use of a nozzle in accordance with the invention in a reactor include the combustion or calcination of solids in the fluidized bed, the drying or chemical treatment of fine-grained particles, e.g. hydrous gypsum, CaCO₃, the heating or cooling of particles, or classifying or conveying solids. The nozzle is particularly useful for applications which require a low intake velocity of the fluidizing gas, such as in the case of fragile solid particles or particles with a tendency to clinker.

Another advantage of the configuration of the gas nozzle in accordance with the invention is the fact that even when the gas flow through the gas nozzle into the fluidized bed is stopped, the backflow of particles will not progress beyond the - A -

hood apron at the worst, and in any case well before the nozzle openings. In this way, the start-up operation with fluidized beds is simplified considerably, as there is no more clogging of the nozzles. This ensures a more uniform fluidization.

The nozzle can be used for all gases and gas mixtures over a wide range of temperatures. Gases or gas mixtures which usually are passed through such nozzle include e.g. preheated air, air enriched with oxygen, oxygen-, nitrogen-, steam-, CO₂-, CO-, SO₂- and SO₃-containing gases.

In accordance with a preferred embodiment of the invention, the length of the hood apron, the size of the annular gap formed by the same, and the size of the at least one nozzle opening optimised with respect to each other such that the flow velocity of the gas or gas mixture at the end of the hood apron facing away from the hood cover is less than 35% of the flow velocity of the gas or gas mixture in the at least one nozzle opening. It is in particular preferred, that the gas velocity from the at least one nozzle opening to the region where the gas or gas mixture is discharged from the annular gap has been reduced to less than 25%, preferably less than 18% and particularly preferably to about 10% to about 14% of the flow velocity in the at least one nozzle opening. The gas velocity in the vicinity of the at least one nozzle opening thus can be chosen to be comparatively high, so that clogging of the at least one nozzle opening is effectively avoided. At the same time, a damage of the solid particles (particle breakage) is avoided by the low gas velocity in the vicinity of the exit of the gas from the annular gap where the gas comes in contact with the solid particles.

In accordance with a development of this invention it is provided that the length of the hood apron, the size of the annular gap formed by the same, and the size of the at least one nozzle opening are adjusted to each other such that the flow velocity of the gas or gas mixture at the end of the hood apron facing away from the hood cover is about 6 to 18 m/s, preferably 7 to 15 m/s, particularly preferably 8 to 13 m/s, and in the at least one nozzle opening about 65 to 140 m/s, preferably 70 to 120 m/s, and particularly preferably 75 to 100 m/s. These gas velocities have turned out to be particularly advantageous, in preventing clogging of the nozzle openings and at the same time have ensured a careful treatment of the solid particles.

Alternatively or in addition to the features mentioned above, a gas nozzle in accordance with the invention is characterized by the fact that the nozzle tube, the transition portion with the hood cover, and the hood apron constitute three sepa- rate and interconnected components. This allows a particularly simple construction of the gas nozzle of the invention, wherein in essence standard components can be used in essence. Preferably, the transition portion includes at least one nozzle opening. In particular, the hood apron and the nozzle tube preferably are simple tubular components. Furthermore, the transition portion is shaped such that it is easy to cast, turn, stamp or fabricate in any desired way, and the nozzle openings of the nozzle are easy to drill. As a result, the nozzle can also be fabricated easily, quickly and at low cost. Furthermore, the configuration of the nozzle is such that in the case of castings, the casting serves as an additional protection against abrasion with respect to the product, i.e. with respect to the particles.

The stability of the gas nozzle with the hood can further be improved in that the nozzle tube, a transition portion including at least one nozzle opening with the hood cover, and the hood apron are made of steel, with these components being welded to each other. It is particularly preferable that the nozzle tube is connected with the transition portion via a first, annular welding seam, and said transition portion or the hood cover integrally formed with the same is connected with the hood apron via a second, annular welding seam. This construction provides for connecting the three components with each other with comparable weld lengths and with welding seams that are easily accessible for welding. This greatly mini- mises the risk that these components are detached from each other during opera- tion. Furthermore, these long and easily accessible welding seams contribute to a simplified, robust, more accurate, faster and less expensive fabrication of the nozzles, as such welding operations can be automated more easily.

Depending on the requirements of the reactor, the composition of the gas or gas mixture and the particle treatment performed, suitable materials are e.g. heat- resistant stainless steels, simple unalloyed steels, structural steels, or cast steel. If necessary, components of different materials can also be combined with each other.

It was found to be particularly advantageous when the ratio of the wall thickness of the portion having at least one nozzle opening to the diameter of the at least one nozzle opening is at least about 2:1 , preferably at least 2.5:1.

In order to prevent the intrusion of solid particles into the nozzle tube on one hand and on the other to be able to introduce a large enough gas quantity into the reactor the invention envisages, a plurality of nozzle openings that are distributed in at least one ring-shaped line around the periphery of the nozzle tube (circumferential row) or the transition portion in accordance with a preferred embodiment of the invention. The number of these circumferential rows, on which the nozzle openings are arranged, is preferably small. Thus, for instance up to 10, in particular 1 to 6 circumferential rows, preferably 2 to 5 circumferential row can be provided, on which the nozzle openings preferably are arranged regularly distributed.

This invention furthermore relates to a reactor, in particular a fluidized-bed reactor with a fluidized bed for the thermal and/or chemical and/or physical treatment of solids, which includes at least one gas nozzle as mentioned above for supplying gas or a gas mixture. The invention will subsequently be explained in detail by means of embodiments and with reference to the drawing. All features described and/or illustrated per se or in any combination form the subject-matter of the invention, independent of their inclusion in the claims or their back-reference.

In the drawing:

Fig. 1 schematically shows a sectional view of a gas nozzle in accordance with a first embodiment of the invention,

Fig. 2 schematically shows a sectional view of a gas nozzle in accordance with a second embodiment of the invention,

Fig. 3 schematically shows a section through the gas nozzle of Fig. 2 along line A-A, and

Fig. 4 schematically shows a sectional view of a gas nozzle in accordance with a third embodiment of the invention.

The gas nozzles 1 and V as shown in Figures 1 and 2 substantially have the same construction and consist of a nozzle tube 2, a transition portion 3 arranged at an end of the nozzle tube 2, and a hood 4 which surrounds the nozzle tube 2.

For supplying a gas or a gas mixture, the nozzle tube 2 extends through the lining 5 indicated in Figure 2 of a non-illustrated reactor into the interior thereof. In the illustrated embodiments, the nozzle tube 2 extends substantially vertical, wherein the upper end, from which the gas or gas mixture is discharged, protrudes into the reactor space. The transition portion 3 is firmly connected with the upper end of the nozzle tube 2 as shown in Figures 1 and 2 via a ring-shaped, circumferential first welding seam 6. Subsequent to the first welding seam 6, the transition portion 3 of the preferred embodiment as shown in Figures 1 to 3 has an increased wall thickness as com- pared to the nozzle tube 2, but in principle the same, i.e. a constant wall thickness is also possible here, as is shown in Figure 4. The transition portion 3 is formed integrally with a hood cover 7 of the hood 4, which in the illustrated embodiments extends substantially horizontally.

The transition portion 3 preferably includes a taper or broadening of the wall thickness, which is not abrupt, but has an inclination. This inclination has an angle α of at least 45°, preferably 50 to 80°, usually 55 to 70°. By means of this inclined taper of the transition portion it is possible to render the gas flow more uniform and prevent turbulences or vortices of the gas. As a result, less particles are drawn into a turbulent gas flow and conveyed in the direction of the nozzle opening against the general gas flow.

Via an annular, circumferential second welding seam 8, the radially outer edge of the circular hood cover 7 is connected with a substantially cylindrical hood apron 9, which extends downwards from the hood cover 7 shown in Figures 1 and 2. As measured from the second welding seam 8 to its lower end shown in Figures 1 and 2, the hood apron 9 has a length L of more than 130 mm, in the illustrated embodiments about 150 mm. Thus, the hood cover 7 and the hood apron 9 together form the hood 4, which approximately has the shape of an inverted pot and closes the nozzle tube 2 with respect to the interior of the reactor.

Between the nozzle tube 2 and the hood apron 9, an annular gap 10 is defined, which in Figures 1 and 2 is closed towards the top by the hood cover 7 and is open towards the bottom. In order to pass the gas or gas mixture from the nozzle tube 2 into the interior of the reactor, a plurality of nozzle openings 11 are formed in the vicinity of the transition portion 3, i.e. near the upper end of the nozzle tube 2 shown in Figures 1 and 2.

In the embodiment as shown in Figure 1 , a circumferential ring-shaped line is defined at the periphery of the transition portion 3, in which a plurality of nozzle openings 11 are provided regularly distributed around the periphery. In accordance with the embodiment of Figure 2, however, a total of 4 rows are formed one above the other, on which usually 7 to 16 nozzle openings 11 are arranged. In the embodiment as shown in Figures 2 and 3, nozzle openings 11 are provided on each row 13 regularly distributed around the periphery.

As compared to the wall thickness of the transition portion 3 and as compared to the width of the gap 10 between the nozzle tube 2 and the hood apron 9, the size of the nozzle openings 11 is small. Thus, the wall thickness of the transition por- tion 3 in the embodiment of Figure 1 is about three times as large as the diameter of the nozzle openings 11. The size of the gap 10 is many times larger than the diameter of the nozzle openings 11.

In this way, it is achieved that the gas or gas mixture flows out of the nozzle open- ings 11 with a high flow velocity, in the embodiment of Figure 2 about 80 to 90 m per second, whereas the gas velocity in the vicinity of the lower end of the gap 10 shown in the Figures is very much lower, in the embodiment of Figure 2 about 9 to 11 m per second. The value V²*L here is 9 to 16 m³/s².

The high gas velocity in the vicinity of the nozzle openings 11 prevents clogging of the nozzle openings 11. The preferred smaller gap in the transition piece reduces the gas velocity after the nozzle openings 11 , and the angled taper in the middle region renders the flow of the gas discharged from the nozzle more uniform. By means of this uniform, hardly turbulent flow at the nozzle outlet 10, the entry of particles into the nozzle is prevented despite the low gas velocity. The low gas velocity in the vicinity of the lower end of the gap 10 shown in the Figures then prevents the solid particles to be treated in the reactor from being damaged or clinkered.

The nozzle 1" shown in Figure 4 is suitable for smaller air quantities per nozzle and is fabricated of standard materials. This is a nozzle tube 2 with a row of bores for the nozzle openings 11 , a hood cover 7 designed as a stamped part, and a hood apron 9. The tubes are all planned as standard tubes. The connection of these components is effected via welding seams 8a and 8b at the transition to the hood cover 7 and provides for an increased welding surface. The transition portion 3 can be formed integrally with the nozzle tube 2.

The nozzle 1¹ of Figure 2, however, is suitable for greater air quantities and thus has a plurality of rows of nozzle openings (e.g. primary air nozzles). In this em- bodiment, the transition portion 3 is formed integrally with the hood cover 7 as one casting, in which the casting skin is directed to the outside.

Reference numerals:

1 ,1M" gas nozzle

2 nozzle tube

3 transition portion

4 hood

5 reactor lining

6 first welding seam

7 hood cover

8,8a,8b second welding seam

9 hood apron

10 gap

11 nozzle opening

L length of the hood api α anαle at the transition

Claims

Claims:

1. A gas nozzle for introducing a gas or gas mixture in a reactor or the like, comprising a nozzle tube (2) through which a gas is passed, at least one nozzle opening (11 ) arranged near an end of the nozzle tube (2) for discharging the gas from the nozzle tube (2) to the surroundings, and a pot-like hood (4), which seal- ingly closes the nozzle tube (2) with a hood cover (7) at the end at which the at least one nozzle opening (11 ) is provided, wherein the hood (4) includes a hood apron (9) connected with the hood cover (7), which enclosing the nozzle tube (2) by forming an annular gap (10) extends away from the end at which the at least one nozzle opening (11 ) is provided, characterized in that the hood apron (9) has a length (L), which extends away from the hood cover (7) and the end at which the at least one nozzle opening (11) is provided, of at least about 100 mm, preferably more than about 110 mm.

2. The gas nozzle according to claim 1 , characterized in that the length (L) of the hood apron (9), the size of the annular gap (10) formed by the same, and the size of the at least one nozzle opening (11 ) are adjusted to each other such that the flow velocity of the gas or gas mixture at the end of the hood apron (9) facing away from the hood cover (7) is less than about 35%, in particular less than about 25%, and particularly preferably about 10% to about 14% of the flow velocity of the gas or gas mixture in the at least one nozzle opening (11 ).

3. The gas nozzle according to any of claims 1 or 2, characterized in that the length (L) of the hood apron (9), the size of the annular gap (10) formed by the same, and the size of the at least one nozzle opening (11 ) are adjusted to each other such that the flow velocity (V) of the gas or gas mixture at the end of the hood apron (9) facing away from the hood cover (7) is about 6 to 18 m/s and in the at least one nozzle opening (11 ) about 65 to 140 m/s.

4. The gas nozzle according to any of the preceding claims, characterized in that the nozzle tube (2), a transition portion (3) including the at least one nozzle opening (11 ) with the hood cover (7), and the hood apron (9) constitute three separate components connected with each other, in particular welded to each other.

5. The gas nozzle according to claim 4, characterized in that the nozzle tube (2), a transition portion (3) including the at least one nozzle opening (11 ) with the hood cover (7), and the hood apron (9) are made of steel, wherein the nozzle tube (2) is connected with the transition portion (3) via a first, circumferential welding seam (6) and the same or the hood cover (7) formed integrally with the same is connected with the hood apron (9) via a second, circumferential welding seam (8).

6. The gas nozzle according to any of the preceding claims, characterized in that the ratio of the wall thickness of the portion (3) including the at least one nozzle opening (11 ) to the diameter of the at least one nozzle opening (11) is at least about 2:1.

7. The gas nozzle according to any of the preceding claims, characterized in that a plurality of nozzle openings (11 ) are arranged distributed in ring-shaped circumferential rows around the periphery of the nozzle tube (2) or the transition portion (3), wherein the number of the ring-shaped rows preferably is about two to about ten, in particular about four.

8. A reactor, in particular a fluidized-bed reactor with a fluidized bed for the thermal and/or chemical and/or physical treatment of solids, wherein the reactor includes at least one gas nozzle (1 , 1¹, 1 ") according to any of the preceding claims for supplying gas or a gas mixture.

9. Use of a gas nozzle (1 , 1', 1 ") according to any of claims 1 to 7 in a reactor for the combustion or calcination of solids in the fluidized bed, for the drying and/or chemical treatment of fine-grained particles, such as hydrous gypsum or CaCO₃, for heating or cooling particles and/or for classifying and/or conveying solids, wherein the product of the square of the flow velocity (V) of the gas or gas mixture at the end of the hood apron (9) facing away from the hood cover (7) with the length (L) of the hood apron (9) has a value (V^2*L) between 7 and 19 m³/s².