FR2691718A1 - Sepn. of ferrous and non-ferrous materials - at discharge from an iron@ ore reduction installation - Google Patents

Abstract

Process is for sepn. of ferrous materials and non-ferrous materials after their simultaneous extraction from an ion ore reduction installation, in which: (a) the temp. of the ferrous materials is lowered below the Curie point; (b) the trajectory of the ferrous materials is deviated by the application of a magnetic field to the mixt. of ferrous and non-ferrous materials; (c) and the ferrous materials are collected in at least one channel situated away from the preferential route taken by the non-ferrous materials. The device used to put this process into service is also claimed. USE/ADVANTAGE - To separate ferrous and non-ferrous materials during their simultaneous extraction from an iron ore reduction installation, notably one in which the ore is circulated in a fluidised bed. In particular it allows the quantity of semi-coke in a mixt. of materials that have been subjected to fluidised bed redn. to be lowered prior to a smelting operation, thus reducing the overall carbon consumption in the production of the hot metal. The degree of sepn. is controlled by increasing the number of fluidised beds or magnetic separations imposed in the process.

Description

PROCESS FOR SEPARATING FERROUS AND CARBONACEOUS MATERIALS
EXIT FROM AN IRON ORE REDUCTION PLANT, AND
DEVICE FOR IMPLEMENTING IT
The invention relates to the field of reduction of iron ore, in particular in installations operating with a circulating fluidized bed of ore.

 Currently, research is actively carried out in order to develop steel processes which could replace the blast furnace. The drawbacks of the blast furnace that such processes aim to eliminate are its lack of operating flexibility, and the need to associate a coking plant and an iron ore agglomeration installation to it. Furthermore, the new processes should maintain the excellent energy performance of the blast furnace.

 These new processes are often designated by the term: "fusion reduction" or "smelting reduction" processes. One of them combines two reactors. One of these reactors produces very strongly reduced metal ore from iron ore, which is placed in the second reactor to be transformed into liquid iron. The gas circuits of these two reactors can be linked to each other, or be completely independent.

A particular embodiment of such a process is described for example in the article "Reduction of fine ore in the circulating fluid bed as the initial stage in smelting reduction (Metallurgical Plant and Technology International, March 1991, pp 28-32) and in French Patent Application No. 91.14467 in the name of the applicant. The reduction reaction of iron ore is carried out by reacting a circulating fluidized bed formed by particles of ore being reduced and of semi-coke, with a reducing gas (mixture CO / C02 / H2 / H20) which also ensures fluidization
This takes place in the first part of the reactor. The gases loaded with particles of ore being reduced and semi-coke then pass through a cyclone. The gases then escape from the reactor, while the particles descend into a gasifier, where carbon or oxygen are introduced separately or together in order to form CO and hydrogen which will contribute to the reduction of the ore. The solids and gases then return to the first part of the reactor, from which a fraction of the solids (reduced ore and semi-coke) is extracted periodically or continuously. New ore is introduced into the material stream between the cyclone and the gasifier. The gases which have escaped from the cyclone are purified and reintroduced into the gasifier and at the base of the first part of the reactor, where they can replay their role of fluidizing and reaction medium.

 The solids extracted from the reactor are then sent to the melting reactor to help produce liquid iron. As has been said, these materials are mainly composed of a mixture of greatly reduced iron ore (at least about 75%) and semicoke with incidentally other non-ferrous materials impurities from the ore and additives possible. Their semi-coke content (which can reach 50%) is in fact higher than that which is necessary to form the cast iron (of the order of 5 to 25%). This leads to an excessive production of carbonaceous gases in the fusion reactor, and to a high consumption of carbonaceous materials throughout the installation, consumption which it is desirable to lower. It is therefore necessary to develop means allowing a selective exit of the metallized iron and of the semi-coke in order to be able to adjust the carbon contents of the fluidized bed and of the product extracted from the reduction reactor to different levels and compatible with a good functioning of the reactors. reduction and fusion.

 The object of the invention is to reduce the quantity of semi-coke in the solid materials intended to be put into the fusion reactor, while reducing the overall consumption of carbonaceous materials by the entire installation for the production of pig iron. , this while maintaining at its usual level the carbon content of the solid particles circulating in the reduction reactor.

 To this end, the subject of the invention is a process for the separation of ferrous materials and non-ferrous materials after their simultaneous extraction from an iron ore reduction installation, characterized in that the temperature of said ferrous materials is lowered by below the Curie point, in that the trajectory of said ferrous materials is deflected by applying a magnetic field to said ferrous and non-ferrous materials, and in that said ferrous materials are collected in at least one pipe situated at the deviation from the preferential route for non-ferrous materials.

 The invention also relates to a device for separating ferrous materials and non-ferrous materials extracted from an iron ore reduction installation, characterized in that it comprises a main pipe ensuring the transport of said materials extracted from said installation. and provided with means for cooling said materials, means for applying to said materials a magnetic field capable of deflecting said ferrous materials outside the preferred path of said non-ferrous materials, and means for collecting said ferrous materials.

 As will be understood, the invention consists in applying to the materials leaving the reduction reactor a magnetic field which deflects the ferrous materials towards one or more lateral pipes connected to the main pipe.

It therefore only collects non-ferrous materials, mainly carbonaceous materials, which can be recycled in the reduction installation. The ferrous materials collected are sent to the fusion reactor, or it is possible to add to them only the quantity of carbonaceous materials necessary for the proper functioning of the apparatus.

The invention will be better understood on reading the description which follows, referring to FIG. 1 attached, which represents in longitudinal section for FIGS. 1 a) and 1 b), and in cross section for FIG. 1 c) a example of an installation for producing a mixture of greatly reduced iron ore and semi-coke, equipped with a first form of device according to the invention;
Figure la) shows an iron ore reduction installation according to the patent application FR 91.14467 already cited, essentially composed of three parts. A first reactor 1 contains at its base a bed 2 of solid materials, essentially containing iron ore which is for the most part in a reduced state, mixed with semicoke. This mixture may also incidentally include other non-ferrous materials (mineral impurities and any additives) which will not be taken into account in the following text. This bed 2 rests on a support 3 permeable to gases. A fluidization gas stream passes through the bed 2 which circulates it through the installation, as indicated by the arrows 4, 4 ′, 4 ". This fluidization gas is a reducing gas, namely a mixture
CO / CO2 / H2 / H20 which is injected at the base of reactor 1 via a pipe 5. During their passage through reactor 1, the iron ore particles undergo reduction to metallic iron by CO and hydrogen fluidizing gases. The gases and the solids then enter a cyclone 6. The gases are evacuated from the cyclone by a pipe 7, while the solids fall back into the lower part of the cyclone 6. The gases are purified of CO2 and steam water they contain in a suitable reactor 24, are returned by the pump 8 and the line 9 to the base of the reactor 1, after passing through a preheater 26, and are again used for fluidization and reduction of the ore. The solid materials leaving the cyclone 6 are brought through a line 10 to a gasification reactor 11. On this line 10 is connected a hopper 12 containing new ore to be reduced, the admission of which into the installation is controlled by the valve 13 .

 The gasification reactor 11 has the function of generating the gas used for the fluidization and the circulation of materials, and of supplying the energy necessary for the equilibrium of the thermal balance. To this end, injections of oxygen and carbonaceous materials, such as coal, are carried out there, these carbonaceous materials being in excess. CO and hydrogen are thus formed (with a certain proportion of CO2 and water vapor) which, in the rest of the installation will react with the ore to reduce it to iron and oxidize themselves into CO2 and H2O, while excess coal turns into semi-coke.

 In the installation shown, the carbonaceous materials 14, contained for example in a hopper 15, are introduced by a valve 16 into a burner 17. This burner 17 is also supplied with oxygen contained in a container 18 provided with a valve 19. In this burner 17 takes place the CO combustion of the carbonaceous materials 14 and the formation of hydrogen, then the CO and the hydrogen thus formed are introduced into the gasification reactor 11. It is also possible to inject oxygen and carbonaceous materials separately and directly in the reactor 11, the formation of CO and hydrogen would then take place in the reactor 11 itself. Part of the CO / CO2 / H2 / H2O mixture is also introduced at the base of the gasification reactor 11 through a line 20 connected to line 9 which brings these same gases to the first reactor. This ensures the fluidization of the solid particles in the gasification reactor. The gasification reactor 11 is also provided in its lower part with a gas-permeable grid 25 preventing an excessive fall of solid matter in the pipe 20. The pipe 21 ensures communication between the gasification reactor 11 and the first reactor 1. A direct current of circulating solid materials (ore, iron and semi-coke) is thus obtained through the three main parts of the installation.

 In theory, the entire installation constitutes a perfectly stirred reactor, in which, under steady conditions, the chemical composition of the materials transported is the same at all times and in all points of the reactor. Despite the possible effects of variations in density by reduction in metallic iron or variations in grain dimensions by bonding or agglutination phenomena, the operating conditions generally ensure this homogeneity down to the bottom of reactor 1 It is therefore at the bottom of reactor 1 that takes place , by a discharge pipe 22 provided with a valve 23, the periodic or continuous extraction of solid materials from the installation. These materials, composed of iron ore reduced to at least 75% and semi-coke, are then ready to be introduced into a fusion reactor, not shown, where the cast iron will be produced.

 In order to solve the problem set out in the introduction, namely to reduce the quantity of semi-coke present with the reduced ore directed towards the fusion reactor, the following device, shown in FIG. 1b, is installed after line 22) . Said pipe 22, vertical or substantially vertical, is equipped over a part of its length with cooling means, such as a double-walled wall 27 with water circulation.

These cooling means are designed so that the reduced ore from the first reactor 1, which is initially at a temperature of approximately 950 "C., sees its temperature lowered below 770" C. The latter temperature corresponds to the Curie point of iron, i.e. the temperature below which the iron particles become ferromagnetic, and therefore can be deflected by a magnetic field. Preferably, the target temperature should be of the order of 700 "C to ensure the success of the operation, while avoiding excessive cooling of the materials which would deteriorate the energy balance of the melting stage. The heat extracted from the materials in circulation must therefore be of the order of 100 th / t, if it is assumed that they contain 50% semi-coke.

Below these cooling means 27, the pipe 22 continues. It has a rectangular section and is made of a non-magnetic material resistant to the temperatures to which it is subjected (for example stainless steel). On the other hand, it is adjoined by a C-shaped inductor 28 whose three branches are parallel to three of the sides of the pipe 22. This inductor produces a transverse field which has the effect of attracting the iron particles (symbolized by white circles) towards one of the two lateral branches of C (branch 37 in FIGS. 1b and 1c), therefore towards one of the lateral walls of the pipe 22.

The semi-coke particles (symbolized by black circles) are not deflected. Below the inductor 28, the pipe 22 is divided into two sub-pipes 29 and 30.

The sub-pipe 29 is connected to the pipe 22 on the part of its section which is close to the face of the pipe 22 to which the iron particles are attracted.

inductor 28. It therefore collects all of the reduced iron ore which has been attracted to inductor 28, mixed with the fraction of semi-coke which has fallen vertically from the sub-pipe 29. The sub-pipe 30 is connected to the pipe 22 on the remainder of its section and collects only the pieces of semi-coke which fall vertically.

The relative importance of the sections of the sub-conduits 29 and 30 must be calculated according to the degree of separation of the semi-coke and the reduced ore which it is desired to obtain, and the power of attraction of the inductor 28 on the reduced ore.

 This device cannot therefore prevent a certain proportion of semi-coke from falling into the sub-pipe 29 collecting the pieces of reduced ore. But since carbonaceous materials must in any case be added to the melting reactor, it will suffice to take into account for this addition of the semi-coke collected by the sub-pipe 29. The process described therefore consists of an enrichment of controlled iron in the flow of materials leaving the reduction facility and directed to the melting stage. If it is desired to obtain a higher degree of separation between the ore and the semi-coke, it is of course possible to install an additional separation installation, similar to the previous one, on the sub-pipe 29. Another solution to accentuate the separation between the particles of reduced ore and of semi-coke would consist in implanting additional means of fluidization upstream of the valve 23. These means would be regulated so as to selectively brake the fall of the particles of semi-coke, so as to avoid that the majority of them do not pass through the pipe 22. This would then very largely collect the reduced ore particles, the magnetic separation means of which would further improve the purity.

 As a variant, in the two examples of configurations which have been described, it is possible to add to the installation means for ensuring a fluidization of the flow of solid materials circulating in the pipe 22. This fluidization can be ensured by a neutral gas or reducing agent, for example by a fraction of the gases produced in the reduction installation and previously cooled. One effect of this fluidization would be to improve the heat transfers in the cooling zone (in particular due to the braking of the descent of the solid materials and better homogenization of the ambient temperature).

On the other hand, it would promote the mobility of these same materials and thus facilitate the deflection of iron particles by the magnetic field. These fluidization means can be constituted by gas injection nozzles 31, 32, 33, 34, 35, 36 located on the pipe 22 below the inductor 28 and above the level where the pipe 22 divides in two sub-conduits 29 and 30.

 Of course, the invention is not limited to the particular configurations which have just been described. One can, in particular, plan to multiply the number of sub-pipes connected to the main pipe 22, or to provide one or more inductors of configurations different from that which has been exemplified. It is applicable to any type of ore reduction reactor of iron producing a mixture of ferrous and non-ferrous materials, the latter term designating not only carbonaceous materials, but any material other than reduced iron ore which could have been mixed originally with the preceding materials, voluntarily or fortuitously.

Claims (5)

 1) Process for the separation of ferrous materials and non-ferrous materials after their simultaneous extraction from an iron ore reduction installation, characterized in that the temperature of said ferrous materials is lowered below the Curie point, in that 'Deviating the path of said ferrous materials by applying a magnetic field to said ferrous and non-ferrous materials, and in that said ferrous materials are collected in at least one pipe located away from the preferred path of non-ferrous materials.  2) Device for separating ferrous materials and non-ferrous materials extracted from an iron ore reduction installation, characterized in that it comprises a main pipe (22) ensuring the transport of said materials extracted from said installation and provided means (27) for cooling said ferrous materials below the Curie point, means (28) for applying to said materials a magnetic field capable of deflecting said ferrous materials outside the preferential trajectory of said non-ferrous materials, and means for collecting said ferrous materials.  3) Device according to claim 2, characterized in that it comprises means (31, 32, 33, 34, 35, 36) for fluidizing ferrous materials and non-ferrous materials flowing in said main pipe (22).  4) Device according to claim 2 or 3, characterized in that said means for applying a magnetic field consist of at least one inductor (28), adjoining the main pipe (22), producing a field transverse to the direction for moving ferrous and non-ferrous materials, and attracting ferrous materials in a portion of the section of said main pipe (22), and in that said means for collecting said ferrous materials comprise at least one connected sub-pipe (29) downstream of said inductor (28) on the portion of the section of said main pipe (22) in which the ferrous materials are attracted by the inductor (28).  5) Device according to claim 4, characterized in that said inductor (28) is C-shaped and produces a transverse field, so as to attract the particles towards a lateral branch (37) of the inductor (28).