LU88139A1 - Injection of pulverised coal into a blast furnace - by prodn. of an annular hollow jet of coal from a hot blast tuyere - Google Patents

Abstract

In the combined injection of pulverised coal and a combustive gas into the hearth of a shaft furnace, notably a blast furnace, through a hot blast tuyere, the pulverised coal is injected into the hot blast in the form of an annular hollow jet at the level of the mouth of the tuyere. The combustive gas, which is pref. oxygen, is injected inside the hollow annular jet formed by the pulverised coal. The lance used to inject this mixture of pulverised coal and combustive gas into a shaft furnace is also claimed and comprises two coaxial tubes and a distribution block equipped with a central bore for the pulverised coal. The tuyere in which the injection lance can be mounted and the device for injecting the pulverised coal and combustive gas are also claimed.

Description

PROCESS AND DEVICE FOR INJECTING SPRAYED COAL INTO A BLAST FURNACE

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 method 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 outlet 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 until the release of pyrolysis gases, 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 object of the present invention is to present a new process for the combined injection of pulverized coal and a gaseous oxidizer in a blast furnace crucible, by means of a lance opening into a hot-wind nozzle, which allows 'Significantly improve the combustion efficiency, especially when working with high pulverized coal flow rates.

This objective is achieved by a process characterized in that, at the mouth of the nozzle in the crucible, said lance injects the coal sprayed into the hot wind in the form of a hollow annular jet and in that said lance introduces the gaseous oxidant 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 gaseous oxidizer, for example oxygen, is no longer injected around the jet of pulverized coal, but it is introduced directly by the lance into the hollow of the annular jet of pulverized coal. This way of proceeding has multiple advantages. First, at the exit of the lance oxygen 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 jet undergoes an ultra rapid expansion which literally explodes from the inside said hollow annular jet of pulverized coal. 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 so much 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 carbon and of the oxidizing gas 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 the 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 impossible for hot ashes to 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 by the ashes. The injection of pulverized coal. And of the oxidant at the mouth of the nozzle in the crucible consequently makes it possible to increase the life of the nozzles equipped with an injection of pulverized coal, without however reducing the yield of combustion.

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 duct 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 the pulverized coal into the lance body is a straight flow, which is not subject to any 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 at a wall of the lance body could possibly lead to a sudden rupture of this wall, with imminent danger of 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 duct, with an annular cavity delimited around said central blind bore over part of its length and axially extending said annular duct, with at least two first channels arranged symmetrically around said central blind bore and opening on one side into said annular cavity and on the other side into said first connection sleeve, of at least one second channel arranged between said first channels and connecting said central channel to said second sleeve connection. 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.

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

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 of allowing easy assembly and disassembly of said inner conduit in the connection device.

Said outer conduit is. advantageously provided with a mistletoe flange is fixed by screws on said second semi-block.

An object of the present invention is also to present 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 dq 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 the 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 mounting 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. Other characteristics and advantages of the present invention will emerge from the detailed description of an advantageous embodiment presented below by way of illustration and with reference to the accompanying 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 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 .chaud wind nozzle, specially designed for this purpose; - Figure 6 shows a section through a nozzle specially designed for mounting the lance according to the invention.

A 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 device connector 14. The latter is used to connect the lance 10 to a supply circuit for the pulverized coal suspended in an inert gas and a supply circuit for a gaseous oxidizer. This gaseous oxidizer can for example be oxygen.

The lance body essentially 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 of 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 oxidizer. 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 compliance with the process 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 the lance by screws. In FIG. 3 we see two bores 38 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 for the oxidant, gas, terminates. The first connecting sleeve 30 ends axially through a base 42 in a cavity 43 of said cylindrical body. On the side of the opposite base 44 said solid 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 part 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 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 opposite side 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 90 ° apart.

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 Figure 3. We can see on the

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 peripheral annular chamber 40 into which they open. Two other 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 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 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. This 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 connecting 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 3.8 to end in the center of the annular base 60. The small base of this frustoconical bore 70 corresponds to the section of passage of the tube 18, while the large base has a diameter which is equal to the diameter of a circumference in which are inscribed all the mouths of the channels 54 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 neck 74, that is to say at the place where the flow of pulverized coal comes into contact with the inner tube 16, a sleeve 84 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.

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 process: according to the present invention, to introduce the end 26 of this lance 10 into the nozzle 100, so that the injection nozzles of pulverized coal 20 ′ and of oxidizer gaseous 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 in FIG. using Figure 6.

The nozzle 100 consists of a double wall 114 which forms, in a manner known per se, a frustoconical body defining axially 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 conduit 116 by an annular recess serving as a support surface for the nozzle 108. At the level of the small base of said ,, frustoconical body, the wall 114 defines the mouth 1.21 of the conduit 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 11: 4 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 fitting 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 lance connection device 10 abuts against the press fitting packing 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 the 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 (12)

1. A method for the combined injection of pulverized coal and a gaseous oxidant in a blast furnace crucible by means of a lance opening into a hot-wind nozzle, characterized in that at the mouth of the nozzle in the crucible, said lance injects the pulverized coal into the hot wind in the form of a hollow annular jet, and in that said lance introduces the gaseous oxidant inside said hollow annular jet. 2. Method according to claim 1, characterized in that the oxidizing gas is oxygen. '3. Lance for implementing the method according to claim 1 or 2 comprising in a lance body (12) separate conduits for the pulverized coal (20) and the gaseous oxidant (22), characterized in that said lance body ( 12) has, at its end (26) opening into the hot-wind nozzle (100) an injection mouth (20 ') for the pulverized coal arranged annularly around an injection mouth (22') for the gas oxidizer. 4. Lance according to claim 3, characterized in that said lance body (12) comprises an inner tube (16) forming an inner conduit (22) for the gaseous oxidizer and an outer tube (18) surrounding the inner tube (16), so as to define with the latter an annular duct (20) for the pulverized coal. 5. Lance according to claim 4, characterized by a connection device (14) mounted on the end, of said lance body (12) which is opposite the end (26) opening into the nozzle (100) and comprising a first connection sleeve (30) to a distribution network of pulverized coal suspended in an inert gas, a second connection sleeve (32) to a distribution network of a gaseous oxidizer, 'first channels (54) connecting the first connector sleeve (30) to said annular conduit (20) and second channels (56) arranged between said first channels (54) for connecting the second connector sleeve (32) to said interior conduit (22). 6. Lance according to claim 5, characterized in that said connecting device (14) comprises a distribution block (34) provided with two opposite faces (42, 61), said lance body (12) opening out through one of said faces (61) and said first coupling sleeve (30) opening in the extension of the axis of said lance body (12) through the opposite face (42) in the distribution block (34), the latter being provided with '' a central blind bore (52) extending axially said inner conduit (22) in said block (34), of an annular cavity (72) delimited around said central bore (52) over a part of its length and axially extending said conduit annular (20) in said block (34), at least two first channels (54) arranged in the axial extension of said annular cavity (72) symmetrically around said central bore (52) and opening on one side into said cavity annular (72) and on the other side in said first sleeve on connection (30), at least a second channel (56) arranged between said first channels (54) and connecting said central channel (52) to said second connection sleeve (32). 7. Lance according to claim 6, characterized in that the free surface of the annular cross section of said annular cavity (72) decreases continuously from the mouth of said first channels (54) towards the mouth of said annular duct (20). 8. Lance according to claim 6 or 7, characterized in that said distribution block (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 coupling sleeve (32) opens into this annular peripheral chamber (40). 9. Lance according to claim 6, 7 or 8, characterized in that said distribution block (34) consists of two semi-blocks (36, 38) assembled along the axis of the lance body (12) by screws , 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 sleeve fitting (30), said inner tube (16) being connected to the free end (48) of said axial extension (46, 48) in which extends said central bore (52) and which is surrounded at its base by a surface annular (50) into which open said first channels (54), in that the second semi-block (38) has an axial cylindrical bore (62) serving as a seat for said external tube (18) and a form bore (70) frustoconical extending axially by flaring the conduit formed by the outer tube (18), and in that said frustoconical bore (70) cooperates with said axial extension (46, 48) to form said annular cavity (70) during the assembly of the two semi-blocks (36, 38). , ..... 10. Lance according to claim 9, characterized in that said outer tube (18) is provided with a flange (66) which is fixed by screws on said second semi-block (38). 11. Nozzle for mounting the lance according to any one of claims 3 to 8, said nozzle (100) consisting of a double wall (114) defining a hot wind duct (116) opening into the crucible (106 ) of the blast furnace and being characterized by a straight channel (126) serving as a sheath for said lance body (12), said channel (126) being integrated in said double wall (114) of the nozzle (100) and opening out from a side in an annular surface (118) surrounding said 'hot wind duct (116) at its upstream end, and on the other side in said hot wind duct (116), so that the extension of the axis of said channel (126) in the direction of the mouth (121) of the nozzle (100) does not meet the wall (114) of the latter. 12. 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 10 which is mounted in a nozzle (100 ) according to claim 11 so that its injection ports of pulverized coal (20 ') and of gaseous oxidizer (22') are located at the mouth (121) of the nozzle (100) in the crucible from above stove (106).