LU82622A1 - METHOD AND DEVICE FOR INJECTING SOLID FUELS INTO A HOT WIND DUCT FROM A TANK OVEN - Google Patents

Description

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Method and device for injecting solid fuels into a hot wind pipe of a shaft furnace

The present invention relates to a method of injecting solid fuels into a hot wind pipe of a shaft furnace, as well as a device for carrying out this method.

In order to maintain the reduction process in blast furnaces, hot wind, which is embarrassed and very enriched by means of a fuel which is introduced, is injected into this hot wind at the level of the nozzles. Until now, liquid fuels and more particularly petroleum products have been used almost exclusively.

In fact, these liquid fuels have the advantage of being very easy to handle and the means used for their injection into the nozzles are simple, while allowing efficient spraying of these fuels! and a good mix with the hot wind.

I However, the rapid development of the price of petroleum products, as well as the progressive depletion of reserves, have opened the race to the replacement of these products by other fuels, in particular coal or lignite. Unfortunately, the known installations for the injection of liquid fuels cannot be used for the injection of solid fuels, such as lignite and coal powder. This substitution therefore raises new problems.

European patent application 80103206, which describes * a first operating installation for metering and * transporting solid fuels, has made it possible to solve one of the essential problems posed by this substitution. Another problem, the solution of which is the subject of the present invention, is that of the injection of solid fuels into the hot wind introduced through the nozzles into the blast furnace.

Indeed, one of the conditions for carrying out a com-

The complete supplement both of the coal or lignite powder and of the oxygen brought by the hot wind, is that Js "~ ΐΐ> each particle of fuel finds the necessary quantity; 7 "$" t en - 2 - of oxygen for its combustion, that is to say that an effective mixture is needed between the hot wind and the coal powder which is injected into it. Not only must this mixture occur as ideally as possible, but it must also occur rapidly in order for combustion to occur upon injection through the nozzle. Another condition is that this mixing takes place without the fuel particles coming into contact with the refractory lining. Indeed, it would then be quickly destroyed by the excessive temperatures produced by combustion.

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This problem does not exist when injecting liquid fuels. Indeed, it suffices to bring the liquid fuel through a pipe inside the nozzle-15 Ion, or even of the nozzle, where as a result of the high speed of the hot wind, there is produced an immediate and complete spraying. liquid fuel in the hot wind.

On the other hand, if by analogy, the coal powder is brought through a pneumatic line to the interior of the hot wind line, the pressure of the coal propulsion fluid must first be higher at the pressure of the hot wind to perform this injection. This condition being fulfilled, the coal powder injected in this way inside the pipe would propagate with the current of hot wind in the form of a well concentrated flow having approximately the same cross section as before in the pneumatic pipe. In other words, there would be no dispersion of the coal powder in the hot wind, and this more or less concentrated flux of the coal would be injected as it is into the furnace. Consequently, only the outer part of this stream of coal would be in contact with the oxygen of the hot wind and would undergo the necessary combustion, while the coal in the central region of the stream would not be burned.

The object of the present invention is to provide a new method for injecting solid fuels which allows better dispersion of the fuel in the hot wind. The invention also relates to a device for implementing this method.

To achieve this objective, the method according to the invention is characterized in that, before injecting the pneumatic stream loaded with fuel into the pipe, it is divided into at least two partial streams which are injected at places different, but in the same transverse plane of the pipe, so that these partial currents meet inside the pipe and disintegrate mutually.

The simplest way is to inject two partial streams at diametrically opposite locations in the pipe.

The injection is preferably carried out at the level of the nozzle of a blower holder.

The installation for the implementation of this pro-ceded 15 comprises a pneumatic supply line of fuel in pulverulent state to the wind line and is characterized in that, when approaching the line of

Ivent, the pneumatic line is divided into at least two partial pneumatic lines which penetrate, at different places, but in the same transverse plane of the wind line, into it and that, inside this line of hot wind, the ends of these partial pipes are directed at a common point.

The simplest embodiment has two partial pipes which are brought through diametrically opposite points inside the pipe. The partial pipes preferably penetrate at the level of the nozzles in the hot wind pipe.

; ! * According to another characteristic of the invention, the ends of the partial pipes are cut at a bevel parallel to the longitudinal axis of the hot wind pipe.

Instead of making two partial pneumatic lines penetrate the nozzle, it is also possible to provide three, or even more, partial lines. These partial lines are spaced regularly, for example, in the case of three partial pneumatic lines, at an angle of 120 °. The essential condition which must be satisfied by the arrangement of these partial pneumatic lines is always that the pneumatic flows coming from each of them meet at a common point and disintegrate mutually and in this way cause total dispersion. charcoal powder in the current of hot wind. In this way, the fuel particles are mixed with the hot wind immediately downstream from the end of the pneumatic lines and combustion is initiated at the end of the passage through the nozzle and through the nozzle.

10 Other peculiarities and characteristics emerge. derived from the detailed description of an embodiment presented below, by way of illustration, with reference to the single figure which shows a vertical schematic section through the lower end of a wind carrier for the in -15 jection of hot wind in a blast furnace and provided with a solid fuel dispersion system according to the invention.

Reference 2 in this figure schematically represents part of the wall of a blast furnace. The hot wind is injected through a vent holder whose lower end, generally designated by the nozzle, is represented by the reference 4. This nozzle 4 is applied against an injection nozzle 6, generally made of copper, which is anchored in the conical end of a water-cooled 25 8 tympe.

A pneumatic line is represented by the reference 10. This pneumatic line brings a solid fuel, such as coal or lignite powder by means of a propulsion fluid. This pneumatic current 30 can be made in accordance with the aforementioned European patent application. When approaching the nozzle 4, this pipe is divided into two partial branches 10a and 10b which pass through the refractory wall of the nozzle 4 at diametrically opposite locations and the internal ends 12a and 35 12b are directed towards each other, or rather on a common point of intersection on the longitudinal axis of the nozzle 4. j The ends 12a and 12b are cut in a bevel parallel to the axis of the nozzle. On the other hand, it is possible that the ends 12a and 12b are slightly divergent: * V _ - 5 - h |; f | I in order to reduce the speed of penetration of the pneumatic current and to already generate a certain divergence in the flow before leaving the ends 12a and 12b of the conduits 10a and 10b.

5 The fact that the two partial streams meet at a common point and disintegrate mutually causes a dispersion of the fuel streams, both forward 12a and 12b and laterally, so that a mixture occurs effective with hot winds and the majority of particles will come into contact with oxygen from the hot wind.

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Claims (7)

1. A method of injecting solid fuels into a hot wind pipe from a shaft furnace, the fuels being brought in the pulverulent state pneumatically to the pipe, characterized in that, before d 'Inject the pneumatic stream loaded with fuel into the pipe, it is divided into at least two partial streams which are injected at different locations, but in' 10 the same transverse plane of the pipe, so that these partial streams meet inside the line and disintegrate each other. 2. Method according to claim 1, characterized in that two partial streams are injected at diametrically opposite locations of the pipe. 3. Method according to one of claims 1 or 2, characterized in that the injection is carried out at the nozzle of a blower. 4. Installation for the implementation of the pro-20 ceded according to any one of claims 1 to 3, for the injection of solid fuels into a hot wind pipe of a shaft furnace comprising a pneumatic supply pipe of pulverulent fuel to the wind line, characterized in that, at ap-25 near the wind line (4), the pneumatic line (10) is divided into at least two pneumatic lines partial (10a) (10b) which penetrate, in different places, but in the same transverse plane of the wind pipe (4), into it, and that, inside this hot wind pipe ( 4), the ends (12a) (12b) of these partial pipes (10a) (10b) are directed at a common point of intersection. 5. Installation according to claim 4, characterized in that the pneumatic line (10) is divided into two partial lines (10a) (10b) which penetrate at diametrically opposite locations in the hot wind line ij. 6. Installation according to one of claims 4 or 5, characterized in that the penetration of the pipes '' i »i *! i - 7 - partial is carried out at the level of the nozzle (4) of a blower. 7. Installation according to any one of claims 4 to 6, characterized in that the ends 5 (12a) (12b) of the partial pipes (10a) (10b) are cut in a bevel parallel to the longitudinal axis of the pipe hot wind - '/ êr'