EP0576869A2 - Method and apparatus for injecting pulverized coal into a blast furnace - Google Patents

Abstract

Process for the combined injection of pulverised coal and of a gaseous oxidising agent into a crucible of a shaft furnace, especially a blast furnace, through a hot blast tuyere. At the mouth opening of the tuyere into the crucible the pulverised coal is injected into the hot blast in the form of a hollow annular jet and the gaseous oxidising agent is injected inside the hollow annular jet. A lance for making use of the process comprises two coaxial pipes (16 and 18) and a distribution block provided with a central bore (52) for the pulverised coal. <IMAGE>

Description

The present invention relates to a method for the combined injection of pulverized coal and a gaseous oxidizer into a blast furnace crucible by means of a lance opening into a hot-wind nozzle.

There is also presented a lance and a nozzle which can be advantageously used for the implementation of said method.

It is well known that the injection of pulverized coal in the hot wind, which is blown through hot-wind nozzles in the upper part of the crucible of a blast furnace, has multiple advantages. In particular, it increases the production capacity of the blast furnace and makes it possible to replace large quantities of coke with cheaper coal.

This injection of pulverized coal is conventionally carried out by an injection lance in the hot wind at a certain distance upstream from the mouth of the nozzle in the crucible. The pulverized coal is suspended in an inert gas. The oxidizer is either constituted by the hot wind, enriched or not with oxygen, or by pure oxygen, brought by a separate pipe near the mouth of the lance. In the latter case, pure oxygen is used to form a primary combustible mixture with the pulverized coal at the outlet of the lance, and the hot wind constitutes the secondary combustion air.

From German patent specification DE-4008963 C1 there is known a process for the combined injection of pulverized coal and oxygen in a blast furnace crucible by means of a lance opening with one end in a hot-wind nozzle. The lance body comprises an inner tube for pulverized coal and an outer tube forming with said inner tube an annular conduit for oxygen. According to the process disclosed in the aforementioned patent specification, the jet of pulverized coal is directly surrounded at its periphery by a jet of annular oxygen. Although this method is satisfactory at low flow rates, problems remain in connection with the introduction of larger quantities of pulverized coal into the crucible.

Indeed, to work efficiently during the injection of pulverized coal in a blast furnace, it is necessary to carry out a combustion as complete as possible of the coal in the turbulent zone 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 zone, which is particularly the case when working with large flows of coal pulverized in a nozzle, large quantities of powdery residue from the combustion s' accumulate in the blast furnace and in the filters thereof and considerably increase the resistance to the flow of hot gases.

The difficulty in obtaining complete combustion in said turbulent zone is due on the one hand to the short distance available and on the other hand to the high speed of the hot wind in the nozzle. During the extremely short time available for the combustion of coal particles at the exit of the lance, the compact jet of coal pulverized in suspension in a neutral gas must be dissociated, the isolated particles of coal must be reheated until causing the release of pyrolysis gas, the pyrolysis gases must mix with the oxidizer, the ignition of this gas mixture must take place and the solid residues from the pyrolysis must react with the oxidant in a heterogeneous oxidation reaction. One of the major problems of injecting pulverized coal into the crucible is therefore to increase the kinetics of the course of these combustion mechanisms described very briefly above.

The aim of the present invention is to present a new process for the combined injection of coal pulverized and a gaseous oxidizer in a blast furnace crucible, by means of a lance leading into a hot-wind nozzle, which makes it possible to appreciably improve the combustion efficiency, especially when working with high flow rates of pulverized coal.

This objective is achieved by a process characterized in that, at the mouth of the nozzle in the crucible, the pulverized coal is injected in the hot wind in the form of a hollow annular jet and the oxidant gas is injected into the inside said hollow annular jet.

According to the present invention the pulverized coal is therefore no longer injected in the form of a full compact jet but rather in the form of a hollow annular jet. This procedure has the direct advantage that the jet is more easily dissociable into isolated particles than a full compact jet carrying the same flow rate of pulverized coal. In addition, the outside surface of the jet is increased, as well as the thickness of the jet is reduced, which exposes the isolated particles of carbon more directly to radiation.

The oxidizing gas, for example oxygen, is no longer 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 constitutes a cold screen between the hot wind and the jet of pulverized coal. Next, it should be noted that the annular jet of pulverized coal is exposed with its exterior surface to hot wind, and with its interior surface to gaseous oxidizer. The particles of carbon in the annular jet are consequently contained in a thin layer sandwiched between two streams of oxidizers, which has a beneficial influence on the rapid formation of a flammable mixture. Finally, it should be particularly noted that under the influence of a significant calorific contribution, due to the high temperatures prevailing in the crucible, the oxidizing gas introduced into the hollow of the pulverized coal jet undergoes an ultra-rapid expansion which literally causes said hollow annular jet of pulverized coal to explode from the inside. This explosion projects and disperses the oxidant, the hot wind and the fuel, forming an ideal turbulent mixture in the crucible area near the nozzle where spontaneous combustion takes place.

All these phenomena support each other to dramatically and unexpectedly increase the combustion efficiency when introducing pulverized coal through the hot wind nozzle into a blast furnace crucible. However, since the combustion efficiency is clearly improved, it is possible to work with much higher pulverized coal flow rates, without risking blocking the filters of the hot gas circuit of the blast furnace. Large quantities of coke can therefore be replaced by cheaper coal.

According to an additional characteristic of the present invention, the injection of pulverized coal and of the gaseous oxidant is carried out at the mouth of the nozzle in the crucible. For all intents and purposes it is recalled that until now the injection of pulverized coal had to be done at a certain distance upstream from 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 coal jet takes place almost immediately at the outlet of the nozzle. It follows that the path required for the combustion mechanism to run is extremely short, and that an injection lance can almost penetrate the crucible without reducing the combustion efficiency.

A direct advantage of this characteristic is that the hot wind duct of the nozzle is less stressed from the 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 prevents clogging of the hot wind pipe by the ashes. The injection of pulverized coal and of the oxidant at the mouth of the nozzle into the crucible consequently makes it possible to increase the life of the nozzles equipped with an injection of pulverized coal, without however reducing the combustion efficiency. .

The present invention also provides a lance for implementing the method. This lance comprises in a lance body separate conduits for the pulverized coal and the gaseous oxidizer and is characterized in that said lance body has at its end opening into the hot-wind nozzle an injection mouth for the pulverized coal disposed annularly around an injection mouth for the oxidizing gas.

Said lance body advantageously comprises an inner tube forming an inner conduit for the gaseous oxidizer and an outer tube surrounding the inner tube, so as to define with the latter an annular conduit for pulverized coal.

This execution of the lance allows a particularly simple embodiment of the annular injection mouth of the pulverized coal surrounding the injection mouth of the gaseous oxidant. It will be appreciated that the flow of coal sprayed into the lance body is a straight flow, which is not subject to any major deviation. In this context, it should indeed be pointed out that the pulverized coal has a significant abrasive power, and that any wall causing a deviation of the flow path undergoes significant wear. However, such wear on a wall of the lance body could possibly lead to a sudden rupture of this wall, with danger imminent complete destruction of the lance and the hot wind duct.

A device for connecting the lance body to a distribution network of pulverized coal suspended in an inert gas and to a distribution network of a gaseous oxidant, for example oxygen, is preferably located outside the hot wind duct. This device is then mounted on the end of the lance body which is opposite the end opening into the nozzle, which allows easy introduction of the lance body through a sleeve penetrating the duct of the hot wind.

An objective sought in a preferred embodiment of a connection device is to avoid any wear by the abrasive flow of pulverized coal.

This objective is achieved by dividing in the connection device the flow of pulverized coal between several channels of pulverized coal connected to said annular duct, and by passing the gaseous oxidant through channels connected to said inner duct and arranged between the coal channels. sprayed. The connection device therefore comprises first channels connecting the first connection sleeve to said annular conduit and second channels arranged between said first channels to connect the second connection sleeve to said interior conduit. In this way the gaseous oxidant channels must not pass through the pulverized coal flow and are therefore not subject to wear by this highly abrasive flow.

The connection device advantageously comprises a distribution block provided with two opposite faces, said lance body opening out through one of said faces and said first connection sleeve opening out in the axial extension of said lance body through the opposite surface in the block distribution, the latter being provided with a central blind bore axially extending said inner conduit, with an annular cavity extending axially said annular conduit, by at least two first channels arranged symmetrically around said central bore and opening on one side into said annular cavity and on the other side into said first connector sleeve, by 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 embodiment of said connecting device is particularly compact while having a design which advantageously avoids any wear by the abrasive flow of the pulverized coal.

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

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

A preferential execution of the supply of gaseous oxidant, comprising an annular peripheral chamber into which several of said second channels open around said central channel, has the advantage of reducing the pressure drop of the flow of gaseous oxidant at the device fitting.

Said connection device advantageously consists 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 to allow easy assembly and disassembly of said inner conduit in the connection device.

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

An interesting variant of the proposed lance includes:
a lance body opening 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 subject the stream of pulverized coal in a simple and effective manner to the action of an electric field; which has a favorable influence on the kinetics of combustion at the outlet of the lance, in particular on the formation of a reactive mixture between the particles of coal, which are suspended in an inert gas, and the oxidizing gas. It 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 dispensing block made of a hard dielectric material, that is to say which is very resistant to wear by pulverized coal. It is for example a ceramic material, in particular a material ceramic based on aluminum oxide. Thanks to this distribution block made of dielectric material, it is possible to solve in a simple and effective manner the problems of electrical insulation between the outer tube and the inner tube of the lance body.

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 makes it possible to bring the oxidizing gas into the inner tube and the pulverized coal into the outer tube, without risking erosion of the oxidizing gas lines by the flow of pulverized coal and without risk of electrical short circuit.

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 front semi-block, which supports said outer tube, said distribution block advantageously comprises tie rods which connect said front semi-block to said first front plate.

The inner tube is advantageously provided with a flange which is housed axially between said distribution block and said front semi-block and which is blocked there by the axial assembly of the distribution block and the front semi-block. This flange constitutes a simple and effective solution for fixing the inner tube to the connection device and at the same time ensures the tightness 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 the direction of the distribution block. The surface which delimits said recess is preferably a curve which is defined by a conical section and which is tangent to the internal surface of the external tube. The inner tube is then advantageously provided at its mouth in the distribution block with a sleeve having substantially the shape of a bottle neck which, after assembly of the lance, is arranged in said recess of the semi-block before so as to define an annular channel which almost opens tangentially in said annular duct of the lance body. It is an execution which significantly reduces the erosion work of the pulverized coal at the level of the passage of the dielectric block in said annular channel of the lance body. In addition, it ensures a good distribution of the flow of coal sprayed into said annular channel of the lance body.

It will be noted that, in all the embodiments of the lance, the inner tube is advantageously provided, at its outlet mouth, with a deflector designed so as to promote a radial burst of the jet of gaseous oxidizer at the exit from the lance. This deflector comprises for example a helical element integrated in the injection mouth formed by the inner tube.

An object of the present invention is also to propose a preferred solution allowing the injection lance to be introduced in a simple and safe manner into the hot wind duct up to the level of the mouth of the nozzle in the crucible.

In this context it should be recalled that until now the introduction of the lance was done through a conduit disposed upstream of the nozzle. This duct, which is called a nozzle, forms with its nose a spherical articulation on the nozzle in order to allow a relative angular displacement of the nozzle and the nozzle under the effect of thermal stresses in all of the hot wind conduits. However, if one wants to penetrate through the nozzle with the lance head up to the level of the mouth of the nozzle, one is forced 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 the lance in the hot wind duct is high, and that the centering of the lance head in the nozzle becomes difficult, uncertain and unstable, all the more so since has 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 strikes the head of the wall delimiting the hot wind duct. It will therefore be highly appreciated that in the context of the present invention a solution is presented which does not have these disadvantages.

This solution consists in introducing the lance through a channel arranged in a double wall which defines the hot wind duct of a nozzle. This assembly of the lance ensures precise and reliable adjustment of the lance head in the hot wind duct, at the mouth of the nozzle in the blast furnace crucible.

• 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 used for implementing the method according to the invention is described with the aid of FIGS. 1 to 4. It mainly consists of an oblong lance body 12 which is fixed with one of its ends to a connection device 14. The latter is used to connect the lance 10 to a supply circuit for pulverized coal suspended in an inert gas and a supply circuit for a gaseous oxidizer. The oxidizing gas may for example be oxygen.

The lance body consists of a double conduit (20, 22) formed by 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 an annular conduit 20 between the two tubes 16 and 18. This annular conduit 20 is intended for the passage of pulverized coal, while the first tube 16 itself defines a cylindrical conduit 22 which is intended for the passage of the gaseous oxidant .

In Figure 1A there is a front view of the lance body 12 in the direction of arrow 24 of Figure 1. It is noted that the lance body 12 defines at its free end 26 a double mouth. The latter comprises an annular injection mouth 20 ′, to which said annular conduit 20 leads, and a circular injection mouth 22 ′, to which said cylindrical conduit ends 22. The injection mouth 20 ′ for pulverized coal is more precisely arranged annularly around the injection mouth 22 'for the gaseous oxidant. With this lance 10 it is possible to produce a hollow annular jet of pulverized coal and to introduce the gaseous oxidant inside the hollow annular jet, in perfect accordance with the method according to the present 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 the flow of pulverized coal , they are preferably made of a hard material, not very sensitive to abrasion.

The connection device 14 comprises a first connection sleeve 30 for the 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 lance 12 by screws. In FIG. 3 we see two bores 39 intended to receive these screws, which extend from the semi-block 36 into the semi-block 38.

The semi-block 36 comprises a solid cylindrical body 37, surrounded by an annular peripheral chamber 40, into which the second connecting sleeve 32 ends for the gaseous oxidizer. The first connector sleeve 30 axially terminates 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 a cylindrical axial extension 46 of diameter substantially smaller than the solid cylindrical body 37 and which ends in a frustoconical part 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 a flat annular ring 44 surrounding the base 50.

A central blind bore 52 extends axially from the end of said frustoconical portion 48 as far as in said solid cylindrical body 37. This central bore 52 has substantially the same internal diameter as the tube 16. Around this central bore 52, in the solid cylindrical body 37 extend 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, into which the sleeve 30 terminates. The channels 54 are preferably arranged symmetrically around the blind bore 52. In the embodiment shown in the Figures, there are altogether four channels 54, spaced each time by 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 significantly increased relative to the volume of the cavity 43. Opposite the mouth of the sleeve of connection 30 in this cavity 43 ', the body 37 is provided with a deflection surface 45 made of a material very resistant to erosion by pulverized coal. This deflection surface 45 can be part of an insert, be made of a filler material, or be obtained by an adequate surface treatment. It is preferably rounded in order to avoid catching of fibrous materials contained in the pulverized coal.

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

The semi-block 38 constitutes a cylindrical sleeve which bears with an annular base 60 on the annular base 44 of said semi-block 36. In the opposite base 61 of said sleeve axially ends 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 using screws on the sleeve 38 on the side of its base 61. In Figure 3 we see two of the bores 68 provided for these screws. It will be appreciated that the outer tube 18 can thus be very easily replaced, without dismantling the connection device 14 or the inner tube 16.

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

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

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 brazing, before assembling the two semi-blocks 36 and 38.

It will be noted that at the level of the neck 74, that is to say at the place where the flow of pulverized coal comes into contact with the internal tube 16, a sleeve 76 has been provided. The latter can be fixed by brazing at the frusto-conical part 48. Made of a more wear-resistant material, it effectively protects the inner tube 16 against abrasion wear, due to a slight deflection of the annular flow at the junction between the annular cavity 72 and the annular duct 20.

Figures 7 and 8 show a second embodiment of a lance used for the implementation of the method according to the invention. This lance 210 comprises a lance body 212 which is fixed with one of its ends to a connection device 214. The lance body 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 pulverized coal, while the first tube 216 itself defines a cylindrical conduit 222, which is intended for the passage of gaseous oxidant.

A feature of the lance 210 shown in Figures 7 and 8 is that it is designed to apply between the two tubes 216 and 218 a potential difference. In other words, the lance 210 is designed to create in the annular conduit 220 an electric field which makes it possible to charge the particles of coal which are charged, suspended 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 apart by spacers 228 of a dielectric material, for example a ceramic material based on oxide. aluminum. The outer surface of the inner tube 216 can also advantageously be provided with a dielectric coating, for example a ceramic coating based on aluminum oxide, 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 for this purpose comprises a distribution block 236, into which the two connection sleeves 230 and 232 open, and a front semi-block, through which opens the lance body 212. The two parts 236 and 238 are assembled axially between two front plates 246 and 248. The latter are connected by tie rods 280 and bear on axially opposite front surfaces and two parts 236 and 238.

The outer tube 218 is fixed to the semi-block 238, which is preferably made of an electrically conductive metal. 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 widens from the mouth of the outer tube 218 in the direction of the distribution block 236 to define a mouth opposite the latter. It will be noted 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 the distribution block 234, a slightly tapered end 282. On this tapered end is fitted a sleeve 254. This sleeve 254, which is made of a hard material having good resistance to erosion by pulverized coal has substantially the shape of a bottle neck. It is arranged in the recess 270 so as to define an annular channel 272 which opens quasi-tangentially in said annular conduit 220 of the lance body 212. It will be noted that, by the cooperation of the surfaces delimiting the recess 270 and the sleeve 254, the annular channel 272 defines a passage section which decreases continuously in the direction of the flow of the pulverized coal.

The distribution block 236 is, in this embodiment, made of a dielectric material of high hardness. It is for example a prismatic block made of ceramic material, for example a ceramic material based on aluminum oxide. It has a rear face 242 which is supported through a seal 286 on the rear front plate 246. At the place where the sleeve 230 opens out through said front plate 246, this rear face 242 is provided with a cavity 243 which penetrates into the distribution semi-block 236. A front face 244 of the prismatic block 236 bears on the semi-block 238 around the mouth of the recess 270 by means of a gasket tightness 288. In the axis of the inner tube 216, a blind central bore 252 opens into the front face 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. L the central bore 252 extends axially through the prismatic block 236 up 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 arranged two channels 254 which terminate, on one side, in the front cavity 243 and, on the other side, in said annular channel 272 defined in the 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 into said central bore 252. A flange 290, integral with this end 282 of the inner tube 216, bears by means of a seal 292 on a base 294 of the prismatic block 236 which surrounds the central bore 252. The flange 290 therefore ensures a tight closure of the central bore 252 around the inner tube 216. In addition, this flange 290 allows the fixing and centering of the inner tube 216 in the device connection 214. To this end, it preferably has a square shape and is housed in a corresponding cavity of the semi-block 238. If the parts 236 and 238 are then assembled axially, by tightening for example 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 orifices communicating these channels 254 with ec said annular channel 272. It will be noted that between the flange 290 and the semi-block 238 is disposed a dielectric material in order to avoid an electrical short circuit between the inner tube 216, which is integral with the flange 290, and the outer tube 218, which is integral with the semi-block 238.

The prismatic block 236 is disposed between two side plates 298 and 300. The plate 298 is supported on the lateral surface 255 into which opens said second channel 256, while the plate 300 is supported on an opposite lateral surface of the prismatic block 236 In plate 298 is fitted the connector 232 for the gaseous oxidizer. A seal 302 between the plate 298 and the block prismatic 236 seals between the connector 232 and said second channel 256. The opposite plate 300 supports an electrical connector 304 for applying an electrical potential to the inner tube 216. This electrical connector 304 comprises for example an insulating sleeve 306, which is mounted in a sealed manner in the plate 300 and an electrode 308 passing through, preferably in a sealed manner, the insulating sleeve 306 to penetrate through a channel 310 of the prismatic block 236 in said central bore 252. In the latter, the electrode 308 is supported with its front end on the inner tube 216. The seal between the plate 300 and the prismatic block 236 is ensured 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 the contact between the tip of the electrode 308 and of the rear end 282 of the inner tube 216. The electrode 308 is ra preferably connected to a positive terminal of a direct current source, while the external metal parts of the lance 210 (in particular the external tube 218, the semi-block before 238, the plates 298, 300, etc.) are connected to the negative terminal of this source.

In this way, one can create, in the annular space 220, between the inner tube 216 and the outer tube, an electric field. This electric field has a favorable influence on the reactivity of the coal particles which pass through the annular space 220 suspended in an inert gas, most often nitrogen. It is believed that this increase in the reactivity of the carbon particles can be explained by the fact that the electric field prevents the molecules of the suspension gas from sticking to the carbon particles and thus creating a barrier for the reaction of these carbon particles. with the oxidizing gas at the outlet of the lance 210. It is however understood that the value of the present invention is not in no way depends on the accuracy of the scientific explanation provided.

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

In Figure 5 there is a hot wind nozzle 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 blast furnace to blow the hot wind into the crucible 106. On the nozzle 100 is supported a conduit 108, called busillon. The bearing surface between the nozzle and the nozzle forms a spherical articulation 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 mounting device for a lance of the type described above. This device 112 makes it possible, in accordance with the method according to the present invention, to introduce the end 26 of this lance 10 into the nozzle 100, so that the injection ports of pulverized coal 20 ′ and of gaseous oxidant 22 'are located at the mouth of the nozzle 100 in the crucible 106.

In Figure 5 is shown schematically, in broken lines, the template of the lance, when the latter is mounted in the mounting device 112. This mounting device allows 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 level of 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 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 hot-air duct 116. At the level of the large base of said frustoconical body, 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 bearing surface for the nozzle 108. At the level of the small base of said frustoconical body, the wall 114 defines the mouth 121 of the duct 116 for injecting the hot wind into the crucible 106. The double wall 114 defines interior cavities 122 which are connected to a cooling circuit. The reference 124 designates a connection for the admission of a cooling fluid.

The nozzle 100 is distinguished from a nozzle according to the prior art, by a straight channel 126 integrated in said double wall 114 of the nozzle and opening on one side into the surface 118 at the upstream end of the nozzle, and on the other side in the hot wind duct 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 a sheath for introducing the upstream end of the lance body 12 into the nozzle 100; it therefore has a slightly larger passage section than the cross section of the front end of the lance body 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 the tympe 102 and the nozzle 108. It is preferably screwed with one of its ends in said channel 126, which is provided with 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 connection 140.

To mount the lance, it suffices therefore to open the ball valve 138, to insert the lance body through the gland fitting 140 and the ball valve 138. The non-return valve 136, which prevents hot gases to go out when the valve 138 is open, is raised by the end 26 of the lance, during its advancement in the direction of the sheath 130. When the connection device of the lance 10 abuts against the gland connection 140 of said mounting device 112, it is certain that the injection ports 20 ′ and 22 ′ are exactly adjusted in the hot wind duct 116 at their intended location, that is to say at the level of the mouth 121 of the nozzle 100 in crucible 106.

It will be appreciated that the cantilever length of the lance body which is subjected to the flow of the hot wind is reduced to a minimum, 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 the nozzle 100.

Claims (22)

Process for the combined injection of pulverized coal and a gaseous oxidant in a crucible of a shaft furnace, in particular a blast furnace, through a hot-wind nozzle, characterized in that at the mouth of the nozzle in the crucible, the pulverized coal is injected into the hot wind in the form of a hollow annular jet, and the oxidant gas is injected inside said hollow annular jet. Method according to claim 1, characterized in that the oxidizing gas is oxygen. Lance for implementing the method according to claim 1 or 2 comprising
a lance body (12, 212)
a first injection mouth (22 ', 222') located at the free end of said lance body (12, 212),
a second injection mouth (20 ', 220') arranged annularly around said first injection mouth (22 ', 222')
characterized by means for connecting said first injection mouth (22 ', 222') to a gas oxidant supply circuit and for connecting said second injection mouth (20 ', 220') to a supply circuit in pulverized coal. Lance according to claim 3, characterized in that said lance body (12, 212) comprises an inner tube (16, 216) forming an inner conduit (22, 222) for the gaseous oxidizer and an outer tube (18, 218) surrounding the inner tube (16, 216), so as to define with the latter an annular duct (20, 220) for the pulverized coal. Lance according to claim 4, characterized by a device (14, 214) for distributing pulverized coal and gaseous oxidizer which is mounted on the end of said lance body (12, 212) which is opposite to said injection nozzles (20 ', 22' 220 ', 222'). Lance according to claim 5, characterized in that said dispensing device comprises
a first connection sleeve (30, 230) which can be connected to a distribution network of pulverized coal suspended in an inert gas,
a second connection sleeve (32, 232) which can be connected to a distribution network of a gaseous oxidizer,
first channels (54, 254) connecting the first connection sleeve (30, 230) to said annular duct (20, 220) and
at least one second channel (56, 256) arranged between said first channels (54, 254) for connecting the second connector sleeve (32, 232) to said interior conduit (22). Lance according to claim 5, characterized in that said dispensing device (14, 214) comprises
two axially opposite surfaces (42, 242, 61, 261), said lance body (12, 212) opening out through one of said surfaces (61, 261) and said first connector sleeve (30, 230) opening out into the extension of the axis of said lance body (12, 212) through the opposite surface (42, 242) in said distribution device (14, 214)
a blind central bore (52, 252), which extends said inner duct (22, 222) axially in said distribution device (14, 214),
an annular cavity (72, 272) extending axially said annular duct (20, 220) in said distribution device (14, 214),
at least two first channels (54, 254) arranged symmetrically around said central bore (52, 252) and opening on one side into said annular cavity (72, 272) and on the other side into said first connector sleeve (30 , 230),
at least one second channel (56, 256) arranged between said first channels (54, 254) and connecting said bore central (52, 252) to said second connecting sleeve (32, 232). Lance according to claim 7, characterized in that the free surface of the annular cross section of said annular cavity (72, 272) decreases continuously from the mouth of said first channels (54, 254) towards the mouth of said annular duct (20, 220). Lance according to claim 7 or 8, characterized in that said outer tube (18) is provided with a flange (66) which is fixed on the surface (61) of the dispensing device (14) through which said outer tube in this last. Lance according to claim 7, 8 or 9, characterized in that said distribution device (34) is provided with several second channels (56), distributed around said central channel (52) and opening into an annular peripheral chamber (40) surrounding said distribution block (34) over part of its length, and in that said second connecting sleeve (32) opens into this annular peripheral chamber (40). Lance according to any one of claims 7 to 10, characterized in that said first coupling sleeve (30) opens into a cavity (43 ') of the dispensing device (14) opposite a deflection surface (45) rounded. Lance according to any one of Claims 7 to 11, characterized
in that said dispensing device (14) consists of two semi-blocks (36, 38) assembled along the axis of the lance body (12),
in that the first semi-block (36) comprises said connection sleeves (30, 32), said first and second channels (54, 56) and an axial extension (46, 48) located on the opposite side of said first connection sleeve (30), said inner tube (16) being connected to the free end (48) of said axial extension (46, 48), and the latter being traversed by said central bore (52) and being surrounded at its base by a surface (50) in which open out said first channels (54),
in that the second semi-block (38) has an axial bore (62) serving as a seat for said outer tube (18) and a recess (70) extending axially, by flaring, the conduit formed by the outer tube (18 ), and
in that said recess (70) cooperates with said axial extension (46, 48) to form said annular cavity (72) during the assembly of the two semi-blocks (36, 38). Lance according to any one of claims 4 to 11 characterized
by means for electrically isolating said inner tube (216) from said outer tube (218) and
by means (304) for applying a potential difference between the outer tube (218) and the inner tube (216) and thereby create an electric field in said annular channel (220). Lance according to claim 13 characterized by a distribution device (214) pulverized carbon and gaseous oxidizer which comprises a distribution block (236) made of a hard dielectric material. Lance according to claim 14, characterized in that said distribution block (236) is a prismatic block, having first and second bases (244, 242) and several lateral surfaces, which comprises
a blind central bore (252) in said first base (244) for receiving one end (282) of said inner tube (216),
a cavity (243) opening into said second base (242),
channels (254) surrounding said central bore (252) and extending said cavity (243) to open into said first base (244),
a first lateral bore (256) situated between said channels (254), so as to define a mouth in a first lateral surface (255) and to open into said central bore (252), and
a second lateral bore (310) located between said channels (254) so as to define a mouth in a second lateral surface and to open into said central bore (252). Lance according to claim 15, characterized in that said dispensing device (214) comprises
a first front plate (246) which rests on said second base (242) of said prismatic block (236) and which supports in the extension of said cavity (243) a connection sleeve (230) for the pulverized coal,
a front semi-block (238) which supports said outer tube (218) and which rests on said first base (244) of said prismatic block (236),
a first side plate (298) which rests on said first side surface (255) of said prismatic block (236) and which supports in the extension of said first side bore (256) a coupling sleeve (232) for the gaseous oxidizer, and
a second side plate (300) which rests on said second side surface of said prismatic block (236) and which supports in the extension of said second side bore (310) an electrode (308) penetrating through the latter in said central bore ( 252). Lance according to claim 16, characterized in that said dispensing device (214) comprises tie rods (280) which connect said front semi-block (238) to said first front plate (246). Lance according to claim 16 or 17, characterized in that the inner tube (216) is provided with a flange (290) which is housed axially between said distribution block (236) and said front semi-block (238) and which is blocked by the axial assembly of the distribution block (236) and the front semi-block (238). Lance according to claim 18, characterized in that the inner tube (216) is provided, at its mouth (282) in the distribution block (236), with a sleeve (254) having substantially the shape of a bottle neck which, after assembly of the lance (210), is arranged in said recess (270) of the front semi-block (238) so as to define an annular channel (272) which opens almost tangentially into said annular conduit (220 ) of the lance body (212). Lance according to any one of claims 3 to 19, characterized in that said first injection mouth (22 ', 222') is provided with a helical deflector. Nozzle for mounting a lance according to any one of claims 3 to 19, comprising a double wall (114) which defines a hot-air duct (116) between an upstream inlet orifice and a mouth ( 121) in the crucible (106) downstream, characterized by a channel (126) serving as a passage sheath for said lance body (12), said channel (126) being integrated in said double wall (114) of the nozzle (100) and opening on one side into an annular surface (118), surrounding the inlet orifice of said hot wind duct (116), and on the other side in said hot wind duct (116), so that the extension of the axis of said channel (126) towards the mouth (121) of the nozzle (100) does not meet the wall (114) of the latter. Device for injecting pulverized coal and a gaseous oxidant into a blast furnace crucible (106), characterized by a lance (10) according to any one of claims 3 to 19 which is mounted in a nozzle (100) according to claim 11 so that its injection ports of pulverized coal (20 ', 220') and of gaseous oxidizer (22 ', 222') are located nearby from the mouth (121) of the nozzle (100) in the blast furnace crucible (106).

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