EP0576869B1 - Apparatus for injecting pulverized coal into a blast furnace - Google Patents

Description

The present invention relates to a lance and a device for injecting pulverized coal and a oxidizing gas in a blast furnace crucible.

German patent specification DE-4008963 C1 and the international application WO 91/14791 we know a spear for the combined injection of pulverized coal and oxygen in a blast furnace crucible. The lance includes a lance body emerging with one end in a hot wind nozzle. The lance body includes a tube inside for pulverized coal and an outside tube forming with said inner tube an annular conduit for oxygen. A connection device, comprising a connection for pulverized coal and a connection for oxygen, is mounted on the end of the lance body which is opposite to the injection ports. The connection for pulverized coal opens axially through a convergent in the tube interior. The oxygen connection opens laterally in an annular chamber surrounding the inner tube. This annular chamber communicates with the conduit annular in the lance body. The lance allows to form at its mouth a compact jet of pulverized coal surrounded at its periphery by a jet of annular oxygen. Although this lance is satisfactory at low flows problems, there are still problems related to the introduction of larger quantities of coal pulverized in the crucible.

Indeed, to work effectively during injecting pulverized coal into a blast furnace, as complete a combustion as possible of the coal in the turbulent area in the immediate vicinity of the mouth of the nozzle in the crucible. If this combustion does not take place properly before or in this area, which is particularly the case when working with high flows of pulverized coal in a nozzle, large amounts of powdery residue from the combustion accumulate in the blast furnace and in the filters and greatly increase the resistance to hot gas flow.

Difficulty obtaining complete combustion in said turbulent zone is due on the one hand to the low distance available and secondly at the high speed of the hot wind in the nozzle. During the time extremely short available for burning particles of coal at the exit of the lance, the compact jet of coal sprayed in suspension in a neutral gas must be dissociated, the isolated particles of coal must be reheated to cause the release of gas from pyrolysis, the pyrolysis gases must mix with the oxidizer, the ignition of this gas mixture must have place and the solid residue from pyrolysis must react with the oxidizer in a heterogeneous oxidation reaction. One of the major problems of coal injection sprayed into the crucible is therefore to increase the kinetics of the development of these combustion mechanisms described very briefly above.

Document EP 0390766 discloses a method according to which is injected, using a lance introduced axially in a blast furnace nozzle, a gas oxidizer in the form of a central jet and coal sprayed in the form of a peripheral jet surrounding the oxidizer central jet. This process improves significantly the combustion efficiency, especially when working with large coal flows sprayed. About the spear used for setting process, document EP 0390766 specifies basically that the lance body has two tubes coaxial. The inner tube serves as a conduit for the oxidizer gas and the annular space between the two tubes serves as leads to pulverized coal. The document does not specify however not how one can supply these conduits in pulverized coal and oxidizing gas.

The purpose of the present invention is to provide a lance and a device for implementing the method described in document EP 0390766. This problem finds a solution in a lance according to claim 1, respectively in an injection device according to the claim 16.

With the lance of the present invention the coal sprayed is therefore no longer injected in the form of a jet compact full but fine in the form of an annular jet hollow. This procedure has the advantage direct that the jet is more easily dissociable by isolated particles than a full compact jet carrying the same flow of pulverized coal. Plus the surface the outside of the jet is increased, as is the thickness of the jet is decreased, which exposes the isolated particles of charcoal more directly to radiation.

The oxidant gas, for example oxygen, is not more injected around the jet of pulverized coal but it is introduced directly into the hollow of the annular jet of pulverized coal. This way of proceeding has multiple advantages. First, the oxidizer no longer forms a screen cold between the hot wind and the jet of pulverized coal. Then, it should be noted that the annular jet of coal sprayed is exposed with its outer surface to the wind hot, and with its interior surface to gaseous oxidizer. The carbon particles in the annular jet are in consequence contained in a thin layer taken in sandwich between two oxidant streams, which has a beneficial influence on the rapid formation of a mixture flammable. Finally, it is particularly advisable to note that under the influence of a calorific intake important, due to the high temperatures prevailing in the crucible, the oxidizing gas introduced into the hollow of the jet of pulverized coal undergoes an ultra rapid expansion which makes literally explode from inside said annular jet pulverized coal hollow. This explosion projects and disperses oxidizer, hot wind and fuel, forming an ideal turbulent mixture in the crucible area near the nozzle where spontaneous combustion has location.

All these phenomena support each other for dramatically and unexpectedly increase the yield combustion when introducing pulverized coal to through the hot wind nozzle in a tall crucible furnace. However, since the combustion efficiency is significantly improved we can work with flow rates of much higher pulverized charcoal, without risk of blocking the filters in the hot gas circuit of the blast furnace. We can therefore replace large amounts of coke by better coal market.

Injection of pulverized coal and gaseous oxidizer preferably done at the mouth of the nozzle in the crucible. For all intents and purposes it is recalled than with conventional lances the injection of carbon sprayed had to be done some distance upstream of said mouth, so as to increase the path available for the unwinding of the combustion mechanism. However, with the present invention, the dissociation of the jet of coal takes place almost immediately at the exit of the nozzle. It follows that the path necessary for the unfolding of the combustion mechanism is extremely short, and that a injection lance can almost penetrate the crucible without reducing the combustion efficiency.

A direct benefit of this feature is that the less hot wind pipe from the nozzle thermal point of view. In addition, it is almost excluded that hot ashes stick to the cold walls of the nozzle, which not only has a beneficial effect on the lifetime of the latter, but also avoids clogging of the hot wind pipe with ash. Injection of pulverized coal and oxidant at the level from the mouth of the nozzle into the crucible allows consequence of increasing the life of the nozzles equipped with an injection of pulverized coal, without as much decrease the combustion efficiency.

The lance according to the present invention comprises a body lance with separate coal pipes sprayed and oxidizing gas. This spear body present in its end opening into the nozzle hot wind an injection mouth for pulverized coal arranged annularly around an injection mouth for oxidizing gas. The lance body includes a tube interior forming an interior conduit for the oxidizer gas and an outer tube surrounding the inner tube, of so as to define with the latter an annular conduit for pulverized coal.

A device for connecting the lance body to a network distribution of pulverized coal suspended in a inert gas and to an oxidizer distribution network gaseous, for example oxygen, is located outside the hot wind duct, where it is mounted on the end of the lance body which is opposite to the through end into the nozzle, allowing easy introduction of the lance body through a sleeve entering the conducts hot wind. In the connection device the flow of pulverized coal is divided between at least two channels of pulverized coal connected to said conduit annular. The oxidant gas passes through at least one channel connected to said interior duct and arranged between the pulverized coal channels. The connection device therefore comprises at least two first channels connecting the first connection sleeve to said annular duct and to at least one second channel arranged between said first channels for connecting the second connection sleeve to said conduit interior. In this way the gaseous oxidant channels do not must not cross the pulverized coal flow and are therefore not subject to wear by this flow highly abrasive.

The connection device advantageously comprises a distribution block provided with two opposite faces, said lance body emerging through one of said faces and said first coupling sleeve opening into the axial extension of said lance body through the opposite surface in the distribution block, the latter being provided with a central blind bore extending axially said inner duct, of an annular cavity extending said annular duct axially by at least first two channels arranged symmetrically around said central bore and opening on one side into said cavity annular and on the other side in said first sleeve connection, of at least one second channel arranged between said first channels and connecting said central bore to said second connector sleeve. It will be appreciated that this execution of said coupling device is particularly compact while having a design that avoids advantageously any wear by the abrasive flow of the pulverized coal.

Indeed, pulverized coal is introduced almost axially in said annular duct of the lance, in a flow with symmetry of revolution and without imposing on it significant changes in direction.

To further improve uniformity of feeding of said annular duct, the annular cavity extending axially said annular duct in the block of distribution advantageously has a section which decreases continuously from the mouth of said first channels towards the mouth of said conduit annular. It will be noted that this execution also avoids any discontinuity in the internal walls of the block of distribution.

Preferential execution of feeding in gaseous oxidizer, comprising a peripheral chamber ring in which several of the said open out second channels distributed around said central channel, a the advantage of reducing the pressure drop of the oxidizing gas at the connection device.

Said connection device advantageously comprises of two semi-blocks assembled axially by screws. The inner tube is then fixed to the first semi-block and the outer tube to the second semi-block. This execution has the advantage of being composed of easily achievable parts and allow easy assembly and disassembly of said conduit inside in the connection device.

Said external duct is advantageously provided with a flange which is fixed by screws on said second semi-block.

un corps de lance débouchant avec une extrémité dans une tuyère à vent chaud d'un creuset d'un four à cuve, notamment un haut-fourneau, ledit corps de lance englobant un tube intérieur formant un conduit intérieur pour le comburant gazeux et un tube extérieur entourant le tube intérieur de façon à définir avec ce dernier un conduit annulaire pour le charbon pulvérisé ;

un dispositif de distribution pour raccorder le tube intérieur à un circuit d'alimentation pour le comburant gazeux et ledit conduit annulaire à un circuit d'alimentation pour le charbon pulvérisé,

des moyens pour isoler électriquement ledit tube intérieur dudit tube extérieur, et

des moyens pour appliquer une différence de potentiel entre le tube extérieur et le tube intérieur et ainsi créer un champ électrique dans ledit canal annulaire.

An interesting variant of the proposed lance includes:

a lance body opening out with one end into a hot-wind nozzle of a crucible of a shaft furnace, in particular a blast furnace, said lance body including an inner tube forming an inner conduit for the gaseous oxidizer and a tube outside surrounding the inner tube so as to define with the latter an annular duct for the pulverized coal;

a distribution device for connecting the inner tube to a supply circuit for the gaseous oxidizer and said annular duct to a supply circuit for the pulverized coal,

means for electrically isolating said inner tube from said outer tube, and

means for applying a potential difference between the outer tube and the inner tube and thus creating an electric field in said annular channel.

The main advantage of this variant is to be able to simply and efficiently submit the flow of coal pulverized by the action of an electric field; what has a favorable influence on the kinetics of combustion at the exit of the lance, in particular on the formation of a reactive mixture between the coal particles, which are suspended in an inert gas, and the oxidizing gas. he will be noted that the length of this electric field can be equal to the length of the lance body.

Said dispensing device of this variant advantageously comprises a distribution block in one hard dielectric material, i.e. which is very resistant to wear by pulverized coal. It is by example of a ceramic material, in particular a material ceramic based on aluminum oxide. Thanks to this block of distribution in dielectric material, it is possible to simple and effective problem solving electrical insulation between the outer tube and the tube inside the lance body.

d'un alésage central borgne dans ladite première base pour recevoir une extrémité dudit tube intérieur ;

d'une cavité débouchant dans ladite deuxième base ;

de canaux entourant ledit alésage central et prolongeant ladite cavité pour déboucher dans ladite première base ;

d'un premier alésage latéral situé entre lesdits canaux, de façon à définir une embouchure dans une première surface latérale et à déboucher dans ledit alésage central ; et

d'un deuxième alésage latéral situé entre lesdits canaux et définissant une embouchure dans une deuxième surface latérale et débouchant dans ledit alésage central.

This distribution block is advantageously a prismatic block having a first and a second base and several lateral surfaces and being provided with:

a blind central bore in said first base for receiving one end of said inner tube;

a cavity opening into said second base;

channels surrounding said central bore and extending said cavity to open into said first base;

a first lateral bore located between said channels, so as to define a mouth in a first lateral surface and to open into said central bore; and

a second lateral bore located between said channels and defining a mouth in a second lateral surface and opening into said central bore.

It is a particularly simple execution, which brings the oxidant gas into the inner tube and coal sprayed into the outer tube, without risking erosion of the oxidant gas lines by the flow of pulverized coal and without risk of short circuit electric.

une première plaque frontale qui s'appuie sur ladite deuxième base dudit bloc prismatique et qui supporte dans le prolongement de ladite cavité un manchon de raccord pour le charbon pulvérisé ;

un semi-bloc avant qui supporte ledit tube extérieur et qui s'appuie sur ladite première base dudit bloc prismatique ;

une première plaque latérale qui s'appuie sur ladite première surface latérale dudit bloc prismatique et qui supporte dans le prolongement dudit premier alésage latéral un manchon de raccord pour le comburant gazeux ; et

une deuxième plaque latérale qui s'appuie sur ladite deuxième surface latérale dudit bloc prismatique et qui supporte dans le prolongement dudit deuxième alésage latéral une électrode pénétrant à travers ce dernier dans ledit alésage central.

To make the various connections to said dielectric prismatic block simple and efficient, said distribution device advantageously comprises:

a first front plate which rests on said second base of said prismatic block and which supports in the extension of said cavity a connection sleeve for pulverized coal;

a front semi-block which supports said outer tube and which rests on said first base of said prismatic block;

a first side plate which rests on said first side surface of said prismatic block and which supports in the extension of said first side bore a connector sleeve for the gaseous oxidizer; and

a second side plate which rests on said second side surface of said prismatic block and which supports in the extension of said second lateral bore an electrode penetrating through the latter into said central bore.

To assemble said prismatic block and said semi-block front, which supports said outer tube, said block advantageously includes tie rods which connect said front semi-block to said first plate frontal.

The inner tube is advantageously provided with a flange which is housed axially between said block of distribution and said front semi-block and which is blocked there by the axial assembly of the distribution block and the semi-block before. This flange is a simple solution and effective for fixing the inner tube to the fitting and at the same time ensures sealing of said blind bore around the inner tube.

The front semi-block is advantageously provided with a recess which widens from the mouth of the outer tube in distribution block management. The area that delimits said recess is preferably a curve which is defined by a conical section and which is tangent to the inner surface of the outer tube. The inner tube is then advantageously provided at its mouth in the distribution block of a sleeve having substantially the shape of a bottle neck which, after assembly of the lance, is arranged in said recess of the front semi-block so as to define an annular channel which almost opens tangentially in said annular duct of the body of launch. It is an execution which significantly reduces the erosion of the pulverized coal at the passage of the dielectric block in said annular channel of the body of launch. In addition, it ensures a good distribution of the flow of coal sprayed into said annular channel of the body of launch.

It will be noted that in all modes of execution of the lance, the inner tube is advantageously provided, at level of its outlet mouth, a deflector designed to so as to promote a radial burst of the oxidizer jet gas at the exit of the lance. This deflector includes by example a helical element integrated in the mouth injection formed by the inner tube.

An object of the present invention is also to propose a preferential solution making it possible to introduce a simple and safe way the injection lance in the hot wind duct up to the level of the mouth of the nozzle in the crucible.

In this context it should be remembered that up to present the introduction of the spear was done through a duct arranged upstream of the nozzle. This conduit, which is called busillon, forms with its nose a joint spherical on the nozzle to allow movement relative angle of the nozzle and the nozzle under the effect thermal stresses in all of the hot wind. Now, if we want to penetrate through the busillon with the lance head up to the level of the mouth of the nozzle, we have to choose a very small angle between the axis of the lance and the axis of the nozzle. It follows that the cantilever length of lance in hot wind duct is high, and that the centering of the lance head in the nozzle becomes difficult, uncertain and unstable, all the more more than there is the possibility of a relative displacement of the nozzle and the nozzle. However, a misalignment of the end of the lance in the nozzle inevitably causes ruin of the latter, when the jet of pulverized coal hits the wall defining the duct hot wind. It will therefore be highly appreciated that in the framework of the present invention a solution is presented which does not have these disadvantages.

This solution consists of an introduction of the lance through a canal arranged in a double wall which defines the hot wind duct of a nozzle. This montage of the lance ensures precise and reliable adjustment of the lance head in the hot wind duct, at the level from the mouth of the nozzle into the tall crucible furnace.

• la Figure 1 représente une vue en perspective d'une réalisation avantageuse d'une lance d'injection selon l'invention ;
• la Figure 1A représente une vue de face des bouches d'injection de la lance de la Figure 1 ;
• la Figure 2 représente une vue éclatée de la lance selon la Figure 1 ;
• la Figure 3 représente une coupe longitudinale de la lance selon la Figure 1 ;
• la Figure 3A montre dans une coupe une variante d'exécution d'un détail de la Figure 3 ;
• la Figure 4 représente une coupe longitudinale de la lance selon la Figure 1, selon un plan de coupe faisant un angle de 45° avec le plan de coupe de la Figure 3 ;
• la Figure 5 montre une coupe schématique à travers un dispositif pour le montage de la lance selon l'invention dans une tuyère à vent chaud, spécialement conçue à cet effet ;
• la Figure 6 montre une coupe à travers une tuyère spécialement conçue pour le montage de la lance selon l'invention ;
• la Figure 7 représente une coupe longitudinale d'une lance d'injection selon l'invention qui permet de soumettre le charbon pulvérisé dans la lance à un champ électrique ;
• la Figure 8 représente une coupe à travers la lance d'injection selon la Figure 7, par un plan de coupe faisant un angle de 90° avec le plan de coupe de la Figure 7..

Other characteristics and advantages of the present invention will emerge from the detailed description of advantageous embodiments presented below by way of illustration with reference to the appended drawings, in which:

• Figure 1 shows a perspective view of an advantageous embodiment of an injection lance according to the invention;
• Figure 1A shows a front view of the injection ports of the lance of Figure 1;
• Figure 2 shows an exploded view of the lance according to Figure 1;
• Figure 3 shows a longitudinal section of the lance according to Figure 1;
• Figure 3A shows in a section an alternative embodiment of a detail of Figure 3;
• Figure 4 shows a longitudinal section of the lance according to Figure 1, along a cutting plane making an angle of 45 ° with the cutting plane of Figure 3;
• Figure 5 shows a schematic section through a device for mounting the lance according to the invention in a hot-air nozzle, specially designed for this purpose;
• Figure 6 shows a section through a nozzle specially designed for mounting the lance according to the invention;
• Figure 7 shows a longitudinal section of an injection lance according to the invention which makes it possible to subject the coal sprayed in the lance to an electric field;
• Figure 8 shows a section through the injection lance according to Figure 7, by a section plane making an angle of 90 ° with the section plane of Figure 7 ..

A first lance 10 according to the invention is described using Figures 1 to 4. It mainly consists of a body of oblong lance 12 which is fixed with one of its ends to a connection device 14. The latter is used to connect the launches 10 to a coal feed system sprayed in suspension in an inert gas and a circuit supply for a gaseous oxidizer. The oxidizer gaseous may for example be oxygen.

The lance body consists of a double conduit (20, 22) formed of an inner tube 16 and an outer tube 18. The tube 16, which has a cross section smaller than the tube 18, is introduced axially into the latter so as to define a annular conduit 20 between the two tubes 16 and 18. This annular duct 20 is intended for the passage of coal sprayed, while the first tube 16 defines itself a cylindrical conduit 22 which is intended for the passage of the oxidizing gas.

In Figure 1A we see a front view of the body of launches 12 in the direction of arrow 24 in Figure 1. We finds that the lance body 12 defines at its end free 26 a double mouth. The latter includes a annular injection mouth 20 ′, to which said end leads annular duct 20, and an injection mouth circular 22 ', to which said conduit ends cylindrical 22. Injection nozzle 20 'for coal sprayed is more precisely arranged annularly around the injection mouth 22 'for the oxidizer gaseous. With this lance 10 it is possible to produce a hollow annular jet of pulverized coal and introduce the oxidant gas inside the hollow annular jet, in perfect compliance with the process according to this invention.

In Figure 2 we see that the tube 16 is provided with spacers 28, which provide radial spacing of the outer tube 18 relative to the inner tube 16. As these spacers are exposed to flow of pulverized coal, they are preferably made in a hard material, not very sensitive to abrasion.

The connection device 14 comprises a first sleeve connection 30 for pulverized coal and a second connection 32 for the gaseous oxidizer. The two fittings 30 and 32, as well as the lance body 12, are advantageously mounted on a distribution block 34 preferably composed of two semi-blocks 36 and 38, which are assembled in the extension of the axis of the body of the throws 12 by screws. In Figure 3 we see two bores 39 intended to receive these screws, which extend from the semi-block 36 in semi-block 38.

The semi-block 36 comprises a solid cylindrical body 37, surrounded by a peripheral annular chamber 40, in which leads to the second connecting sleeve 32 for the oxidizing gas. The first connecting sleeve 30 ends axially through a base 42 in a cavity 43 of said cylindrical body 37. On the side of the opposite base 44 said cylindrical body 37 has an axial extension cylindrical 46 of diameter substantially smaller than the solid cylindrical body 37 and which ends in a part frustoconical 48. At its base the axial extension 46 is surrounded by a base 50, so that the base 44 of said cylindrical body 37 is reduced to an annular crown plane 44 surrounding the base 50.

A central blind bore 52 extends axially to from the end of said frustoconical part 48 into said full cylindrical body 37. This bore central 52 has substantially the same internal diameter as the tube 16. Around this central bore 52, in the body full cylindrical 37, extend from the first channels 54, which open into the annular surface defined by the base 50 around said axial extension 46. On the side of the base 42 of the cylindrical body 37, these channels 54 are extended in said axial cavity 43, in which ends the sleeve 30. The channels 54 are preferably symmetrically arranged around the blind bore 52. In the example of execution shown in the Figures, there are all four channels 54, each spaced 90 °.

Figure 3A shows an alternative embodiment of the mouth of the connecting sleeve 30 in the body 37. The volume of the cavity 43 ′ is appreciably increased by compared to the volume of the cavity 43. Opposite the mouth of the coupling sleeve 30 in this cavity 43 ', the body 37 is provided with a deflection surface 45 consisting of a material highly resistant to erosion by carbon sprayed. This deflection surface 45 can be part an insert, be made of a material filler, or be obtained by a surface treatment adequate. It is preferably rounded to avoid attachment of fibrous materials contained in coal sprayed.

Figure 3 shows a longitudinal section through said connecting device 14 through a plane passing through two of the four channels 54. FIG. 4 however represents a longitudinal section through a plane at an angle of 45 ° with the section plane of Figure 3. We see on the Figure 4 that the solid cylindrical body 37 is provided in this plan of two second channels 56 which extend from the bore central 52 towards the peripheral annular chamber 40 in which they lead to. Two more of these second channels are located in a plane making an angle of 90 ° with the section plane of Figure 4.

The semi-block 38 constitutes a cylindrical sleeve which is supported with an annular base 60 on the base annular 44 of said semi-block 36. In the opposite base 61 said sleeve axially terminates a cylindrical bore 62 having an inside diameter equal to the outside diameter of the tube 18. This bore 62 serves as a seat at the end 64 of the tube 18, which is integral with a flange 66. The latter, which is for example welded to the tube 18, can be fixed to using screws on the sleeve 38 on the side of its base 61. On Figure 3 shows two of the bores 68 provided for these screw. It will be appreciated that the outer tube 18 can thus be very easily replaced, without dismantling the fitting 14 or the inner tube 16.

The outer tube 18 opens into a bore frustoconical 70 which extends axially, widening, to through said semi-block 38 to reach the center of the annular base 60. The small base of this bore tapered 70 corresponds to the passage section of the tube 18, while the large base has a diameter which is equal to the diameter of a circumference in which register all the mouths of the channels 54 on the side of the base 50.

By assembling the two semi-blocks 36 and 38, said tapered bore 70 of semi-block 38 cooperates with said coaxial extension 46,48 of the semi-block 36 to define a annular cavity 72. The latter therefore surrounds the central bore 52 over part of the length of this last to extend said conduit axially annular 20 towards said mouths of channels 54. It will be noted that the free area of the section annular transverse of the annular cavity 72 decreases by continuously towards the mouth of said conduit annular 20, to present a neck 74 just before the penetration into said annular duct 20. In this way the distribution of carbon in the annular duct 20 is advantageously standardized.

The inner tube 16 is mounted with its end 80 axially in the frustoconical part 48 of the semi-block 36. This assembly of the inner tube 16 will be done, for example by soldering, before assembly of the two semi-blocks 36 and 38.

It will be noted that at the level of the neck 74, that is to say at where the pulverized coal flow comes in contact with the inner tube 16, a sleeve 76. The latter can be fixed by brazing to the frustoconical part 48. Made of a more material wear resistant, it effectively protects the tube interior 16 against abrasion wear, due to small deviation of the annular flow at the junction between the annular cavity 72 and the annular conduit 20.

Figures 7 and 8 show a second mode execution of a lance used for the implementation of the method according to the invention. This lance 210 includes a lance body 212 which is fixed with one of its ends to a coupling device 214. The body of lance consists of a double conduit 220, 222, which is formed of an inner tube 216 and an outer tube 218. The tube 216, which has a smaller section than the tube 218, is introduced axially into the latter so as to define an annular conduit 220 between the two tubes 216 and 218. This annular conduit 220 is intended for the passage of coal sprayed, while the first tube 216 defines itself a cylindrical conduit 222, which is intended for passage to the oxidizing gas.

A special feature of the lance 210 represented on the Figures 7 and 8 is that it is designed to apply between the two tubes 216 and 218 a potential difference. In in other words, the lance 210 is designed to create in the annular conduit 220 an electric field which allows charge the coal particles which are cut, suspension in an inert gas, through the conduit annular 220. The two tubes 216 and 218 are therefore made of a material which is a good conductor of electricity and are spaced out by pieces spacer 228 of a dielectric material, for example a ceramic material based on aluminum oxide. The outer surface of inner tube 216 can also advantageously be provided with a dielectric coating, for example a ceramic coating on an oxide basis aluminum, which at the same time has good resistance to wear by pulverized coal.

1) connecter le conduit annulaire 220 à un manchon de raccord 230 pour le charbon pulvérisé ;

2) connecter le conduit intérieur 222 à un manchon de raccord 232 pour le gaz comburant ;

3) connecter entre le tube extérieur 218 et le tube intérieur 216 une différence de potentiel.

The connection device 214 is specially designed to fulfill its triple role, namely:

1) connect the annular duct 220 to a connection sleeve 230 for the pulverized coal;

2) connect the inner conduit 222 to a connector sleeve 232 for the oxidizing gas;

3) connect a potential difference between the outer tube 218 and the inner tube 216.

The connection device 214 comprises for this purpose a distribution block 236, into which the two open connection sleeves 230 and 232, and a front semi-block, through which the lance body 212 opens. The two parts 236 and 238 are assembled axially between two front plates 246 and 248. These are connected by tie rods 280 and rest on surfaces axially opposite frontal and two parts 236 and 238.

The outer tube 218 is fixed to the semi-block 238, which preferably consists of a conductive metal of electricity. The assembly of the outer tube 218 and the semi-block 238 can be done by brazing or by a flange (not shown). The semi-block 238 is provided with a recess 270 which flares from the mouth of the outer tube 218 in direction of distribution block 236 to define a mouth opposite the latter. Note that the surface which delimits the recess 270 is preferably a surface of revolution which is tangent to the inner surface of the outer tube 218.

The inner tube 216 has, at its mouth in distribution block 234, one end slightly tapered 282. On this tapered end is adjusted a sleeve 254. This sleeve 254, which is produced in a hard material with good resistance to erosion by pulverized charcoal, roughly shaped like a neck bottle. It is arranged in the recess 270 so as to define an annular channel 272 which opens almost tangentially in said annular duct 220 of the body 212. It will be noted that, through the cooperation of surfaces delimiting the recess 270 and the sleeve 254, the annular channel 272 defines a passage section which decreases continuously towards the flow of the pulverized coal.

The distribution block 236 is, in this embodiment, made of a high hardness dielectric material. he this is for example a prismatic block in matter ceramic, for example a ceramic material based aluminum oxide. It has a rear panel 242 which is supported by a seal 286 on the rear faceplate 246. Where the sleeve 230 opens out through said front plate 246, this face rear 242 is provided with a cavity 243 which enters the distribution semi-block 236. A front face 244 of the block prismatic 236 is supported on the semi-block 238 around the mouth of the recess 270 via a seal 288. In the axis of the inner tube 216, a blind central bore 252 opens into the face before 244 of the prismatic block 236. The diameter of this central bore 252 is slightly larger than the end 282 of the inner tube 216. The bore central 252 extends axially through the block prismatic 236 to the level of a lateral bore 256, which opens into a lateral surface 255 of said block prismatic 236. Around the central bore 252 are two channels 254 which end on one side in the front cavity 243 and, on the other side, in said annular channel 272 defined in semi-block 238. The channels 254 are preferably symmetrical with respect to the central axis of the prismatic block 236.

The inner tube 216 opens with its end 282 in said central bore 252. A flange 290, integral with this end 282 of the inner tube 216, bears by through a seal 292 on a base 294 of the prismatic block 236 which surrounds the bore central 252. The flange 290 therefore provides a tight sealing of the central bore 252 around the tube interior 216. In addition, this flange 290 allows fixing and centering the inner tube 216 in the device fitting 214. To this end, it preferably has a square shape and is housed in a corresponding cavity of the semi-block 238. If parts 236 and 238 are then axially assembled, for example by tightening the tie rods 280, the inner tube 216 is blocked between these semi-blocks 236 and 238 via the flange 290. At the mouth of the two channels 254, the flange 290 is provided with passage holes communicating these channels 254 with said annular channel 272. It will be noted that between the flange 290 and the semi-block 238 is disposed a dielectric material to avoid short circuit electric between the inner tube 216, which is integral of the flange 290, and the outer tube 218, which is integral with the semi-block 238.

The prismatic block 236 is disposed between two plates side 298 and 300. Plate 298 rests on the surface lateral 255 into which said second channel 256 opens, while the plate 300 rests on a lateral surface opposite of the prismatic block 236. In the plate 298 is fitted connection 232 for the gaseous oxidizer. A joint seal 302 between plate 298 and block 236 prismatic seal between fitting 232 and said second channel 256. The opposite plate 300 supports a electrical connection 304 for applying a potential electrical connection to the inner tube 216. This electrical connection 304 includes for example an insulating sleeve 306, which is mounted tightly in the plate 300 and an electrode 308 passing through, preferably tightly, the sleeve insulator 306 to penetrate through a channel 310 of the block prismatic 236 in said central bore 252. In this last, electrode 308 is supported with its end front on the inner tube 216. The seal between the plate 300 and the prismatic block 236 is provided by a seal 312. A spring 314 is arranged between the electrode 308 and a cap 316 screwed onto the sleeve 306 so as to elastically maintain contact between the tip of the electrode 308 and the rear end 282 of the inner tube 216. The electrode 308 will preferably be connected to a positive terminal of a current source continuous, while the outer metal parts of lance 210 (in particular the outer tube 218, the semi-block before 238, plates 298, 300, etc.) are connected to the negative terminal of this source.

In this way, we can create, in space annular 220, between the inner tube 216 and the tube outside, an electric field. This electric field has a favorable influence on the reactivity of particles of charcoal passing through the annular space 220 in suspension in an inert gas, most often nitrogen. We believe to be able to explain this increase in the reactivity of particles of coal by the fact that the electric field prevents molecules of the suspension gas from sticking on the coal particles and thus create a barrier for the reaction of these coal particles with the gas oxidizer at the exit of the lance 210. It is however implied that the value of the present invention is not not dependent on the accuracy of the explanation scientist who provided it.

It will also be noted that in the front end of the tube interior 216, a deflector 320 is integrated. deflector 320, which preferably has a helical shape, aims to promote rapid bursting of the gas jet oxidizer at the outlet of the inner tube 216.

In Figure 5 there is a wind nozzle hot 100 which is mounted in a manner known per se, using a tympe 112, in a wall 104 of a blast furnace. This nozzle opens into the upper part of a blast furnace crucible 106. It constitutes the last conduit of a set of conduits arranged around the top furnace for blowing the hot wind in the crucible 106. On the nozzle 100 is supported a conduit 108, called busillon. The support surface between the nozzle and the nozzle forms a spherical joint 110 which allows a relative angular displacement of the two conduits 100 and 108 to allow relative angular deformations of thermal origin.

The reference 112 generally designates a device for mounting for a lance of the type described above. This device 112 allows, in full compliance with the method according to the present invention, to introduce the end 26 of this lance 10 in the nozzle 100, of so that the 20 'pulverized coal injection ports and gaseous oxidizer 22 'are located at the mouth of the nozzle 100 in the crucible 106.

In FIG. 5, there is shown schematically, in broken lines, the size of the lance, when the latter is mounted in the mounting 112. This mounting device makes it possible to introduce the lance body 12 between the tympe 102 and the nozzle 108, directly through a wall 114 of the nozzle 100, up to the mouth of the nozzle 100 in the crucible 106. It will be noted that the nozzle 100 is a nozzle of new design which is described using the Figure 6.

The nozzle 100 consists of a double wall 114 which forms, in a manner known per se, a frustoconical body axially defining a cylindrical wind duct hot 116. At the level of the large base of said body frustoconical, the wall 114 forms an annular surface 118. The latter is limited around the mouth of the duct 116 by an annular recess serving as a surface to support the busillon 108. At the level of the small base of said frustoconical body, the wall 114 defines the mouth 121 of the conduit 116 for injecting the hot wind into the crucible 106. The double wall 114 defines cavities 122 which are connected to a circuit cooling. Reference 124 designates a fitting for the admission of a cooling fluid.

The nozzle 100 is distinguished from a nozzle according to the prior art, by a channel straight 126 integrated in said double wall 114 of the nozzle and opening on one side into the surface 118 at the end upstream of the nozzle, and on the other side in the conduit to hot wind 116, so that the extension of the axis of the channel 126 towards the mouth 121 of the nozzle does not meet the wall 114 of the latter.

This channel serves as an introduction sheath of the end upstream of the lance body 12 in the nozzle 100; he has in as a result a slightly larger passage section that the cross section of the front end of the body lance 12.

On the side of the annular surface 118 this channel 126 is advantageously extended by a cylindrical sheath 130. The latter extends in an annular free space 132 available between tympe 102 and busillon 108. It is preferably screwed with one of its ends in said channel 126, which has a thread 134 on the side of its mouth in said annular surface 118. At the other end this sheath 130 is extended axially by a non-return valve 136, a ball valve 138 and a gland fitting 140.

To mount the lance, it suffices to open the ball valve 138, insert the lance body to through the gland fitting 140 and the valve spherical 138. The check valve 136, which prevents hot gases to exit when valve 138 is open, is lifted by the end 26 of the lance, when advancement towards the sheath 130. When the lance 10 connection device abuts against the gland connection 140 of said mounting device 112, it is certain that the injection ports 20 'and 22' are exactly fitted in the hot wind duct 116 to their intended location, i.e. at the level of the mouth 121 of the nozzle 100 in the crucible 106.

It will be appreciated that the cantilevered length of the body spear which is subject to the flow of hot wind is minimized, and that the position of the end 26 of the lance 10 in the hot wind duct 116 is no longer affected by a relative displacement of the nozzle 108 and of the nozzle 100.

Claims (17)

1. Lance for the combined injection of pulverised coal and a gaseous oxidant into the hearth of a shaft furnace, particularly a blast furnace, comprising:

   a lance body (12, 212) comprising an inner pipe (16, 216) forming an inner duct (22, 222) and an outer pipe (18, 218) surrounding the inner pipe (16, 216) so as to define with the latter an annular duct (20, 220), a first injection nozzle (22', 222') located at one end of the said lance body (12, 212) and connected to the said inner duct (22, 222) and a second injection nozzle (20', 220') positioned in an annular manner around the said first injection nozzle (22', 222') and connected to the said annular duct (20, 220), and

   a connecting device (14, 214) which is mounted on the end of the said lance body (12, 212) which is opposite the said injection nozzles (20', 22', 220', 222') and which comprises a first connecting sleeve (30, 230) intended to be connected to a distribution network for pulverised coal, and a second connecting sleeve (32, 232) intended to be connected to a distribution circuit for a gaseous oxidant,

   characterised in that the said connecting device comprises a distribution block (34, 234) into which the said inner duct (22, 222) and the said annular duct (20, 220) emerge, and in which are made:

   at least two first channels (54, 254) connecting the first connecting sleeve (30, 230) to the said annular duct (20, 220), so that the flux of pulverised coal flowing through the first connecting sleeve (30, 230) is distributed over these first channels (54, 254) before flowing into the said annular duct (20, 220), and

   at least one second channel (56, 256) positioned between the said first channels (54, 254) so as to connect the second connecting sleeve (32, 232) to the said inner duct (22).
2. Lance according to Claim 1, characterised in that the said distribution block (34, 234) comprises:

   two axially opposite surfaces (42, 242, 61, 261), the said lance body (12, 212) emerging through one of the said surfaces (61, 261) and the said first connecting sleeve (30, 230) emerging in the extension of the said lance body (12, 212) through the opposite surface (42, 242) into the said distribution block,

   a blind central bore (52, 252), which axially extends the said inner duct (22, 222) into the said distribution block (34, 234),

   an annular cavity (72, 272) axially extending the said annular duct (20, 220) into the said distribution block (34, 234),

   at least two first channels (54, 254) positioned symmetrically around the said central bore (52, 252) and emerging at one end into the said annular cavity (72, 272) and at the other end into the said first connecting sleeve (30, 230),

   at least one second channel (56, 256) arranged between the said first channels (54, 254) and connecting the said central bore (52, 252) to the said second connecting sleeve (32, 232).
3. Lance according to Claim 2, characterised in that the free surface of the transverse annular cross-section of the said annular cavity (72, 272) decreases continuously from the outlet of the said first channels (54, 254) in the direction of the outlet from the said annular duct (20, 220).
4. Lance according to Claim 2 or 3, characterised in that the said outer pipe (18) is provided with a flange (66) which is attached to the surface (61) of the distribution block (34) through which the said outer pipe emerges into the latter.
5. Lance according to Claim 2, 3 or 4, characterised in that the said distribution block (34) is provided with several second channels (56), distributed around the said central channel (52) and emerging in an annular peripheral chamber (40) surrounding the said distribution block over a part of its length, and in that the second connecting sleeve (32) emerges into this annular peripheral chamber (40).
6. Lance according to any one of Claims 1 to 5, characterised in that the said first connecting sleeve (30) emerges into a cavity (43') of the distribution block opposite a rounded deflecting surface (45).
7. Lance according to any one of Claims 1 to 6, characterised

   in that the said distribution block (34) consists of two half-blocks (36, 38) assembled along the axis of the lance body (12),

   in that the first half-block (36) incorporates the said connecting sleeves (30, 32), the said first and second channels (54, 56) and an axial extension (46, 48) located on the opposite side of the said first connecting sleeve (30), the said inner pipe (16) being connected to the free end (48) of the said axial extension (46, 48) and the latter being traversed by the said central bore (52) and being surrounded at its base by a surface (50) into which the said first channels (54) emerge,

   in that the second half-block (38) incorporates an axial bore (62) serving as a seat for the said outer pipe (18) and a hole (70) axially extending, by widening, the duct formed by the outer pipe (18), and

   in that the said hole (70) cooperates with the said axial extension (46, 48) to form an annular cavity (72) when the two half-blocks (36, 38) are assembled.
8. Lance according to any one of Claims 1 to 7, characterised

   by means for electrically insulating the said inner pipe (216) from the said outer pipe (218) and

   by means (304) for applying a potential difference between the outer pipe (218) and the inner pipe (216) and thus creating an electric field in the said annular channel (220).
9. Lance according to Claim 8, characterised by a distribution block (234) made from a hard dielectric material.
10. Lance according to Claim 9, characterised by a prismatic block having a first and a second base (244, 242) and several lateral surfaces, which comprises

    a blind central bore (252) in the said first base (244) to receive one end (282) of the said inner pipe (216),

    a cavity (243) emerging in the said second base (242),

    channels (254) surrounding the said central bore (252) and extending the said cavity (243) to emerge into the said first base (244),

    a first lateral bore (256) located between the said channels (254) so as to define an outlet in a first lateral surface (255) and to emerge into the said central bore (252), and

    a second lateral bore (310) located between the said channels (254) so as to define an outlet in a second lateral surface and to emerge into the said central bore (252).
11. Lance according to Claim 10, characterised by

    a first face-plate (246) which bears against the said second base (242) of the said prismatic block (236) and which supports, in the extension of the said cavity (243), a connecting sleeve (230) for the pulverised coal,

    a front half-block (238) which supports the said outer pipe (218) and which bears against the said first base (244) of the said prismatic block (236),

    a first lateral plate (298) which bears against the said first lateral surface (255) of the said prismatic block (236) and which supports, in the extension of the said first lateral bore (256), a connecting sleeve (232) for the gaseous oxidant, and

    a second lateral plate (300) which bears against the said second lateral surface of the said prismatic block (236) and which supports, in the extension of the said second lateral bore (310), an electrode (308) penetrating through the latter into the said central bore (252).
12. Lance according to Claim 11, characterised in that the said distribution device (214) incorporates tie-rods (280) which connect the said front half-block (238) to the said first face-plate (246).
13. Lance according to Claim 11 or 12, characterised in that the inner pipe (216) is provided with a flange (290) which is housed axially between the said distribution block (236) and the said front half-block (238) and which is locked in that position by the axial assemblage of the distribution block (236) and the front half-block (238).
14. Lance according to Claim 13, characterised in that the inner pipe (216) is provided, at the level of its outlet (282) in the distribution block (236), with a sleeve (254) having substantially a bottle-neck shape which, after assembly of the lance (210), is positioned in the said hole (270) of the front half-block (238) so as to define an annular channel (272) which emerges almost tangentially into the said annular duct (220) of the lance body (212).
15. Lance according to any one of Claims 1 to 14, characterised in that the said first injection nozzle (22', 222') is provided with a helical deflector.
16. Apparatus for the injection of pulverised coal and a gaseous oxidant into a blast furnace hearth (106), characterised by a lance (10) according to any one of Claims 1 to 16 and by a tuyere in which the lance (10) is mounted so that the nozzles for the injection of pulverised coal (20', 220') and of gaseous oxidant (22', 222') are located near the outlet (121) of the tuyere (100) in the blast furnace hearth (106).
17. Apparatus according to Claim 16, characterised in that the tuyere comprises a double wall (114) defining a hot air duct (116) between an intake upstream and an outlet (121) in the hearth (106) downstream, together with a channel (126) serving as a conduit for the passage of the said lance body (12), the said channel (126) being incorporated into the said double wall (114) of the tuyere (100) and emerging at one end into an annular surface (118) surrounding the intake of the said hot air duct (116), and at the other end into the said hot air duct (116) so that the extension of the axis of the said channel (126) in the direction of the outlet (121) of the tuyere (100) does not encounter the wall (114) of the latter.

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