METHOD FOR THE PREPARATION OF FINE GRAIN MINERALS DESCRIPTION OF THE INVENTION The present invention relates to a process for the preparation of fine-grained minerals, the minerals are subjected to gas classification by means of a gas, in which, it is formed the classification of two fractions, that is, a coarse fraction and a first fine fraction, the coarse fraction is completely separated and the first fine fraction is entrained with the gas, then completely separated from the gas and at least for the most part it is fed by processing together with the coarse fraction and to an installation to carry out the process. In fluid bed processes, for example those used for the direct reduction of fine-grained minerals, cyclones are used to completely separate and recycle the material which is discharged with the fluidizing gas. The separation capacity, that is, the efficiency and separation of grain size from the cyclones, is adversely affected by the formation of binders and adhesion in the cyclone, with the result that more material is discharged from the fluid bed reactor together with the fluidizing gas. In the case of direct reduction of fine-grained minerals, for example iron ores, it is
REF: 135334 principally at least, partially reduced fine mineral dust, which causes this agglutination and adhesion. The increased discharge resulting from the material either has to be recorded as a loss or, in the case of multi-step processes carried out in current-to-low fluid bed reactors, causes problems by blocking the holes in the manifold bases. these fluid bed reactors. The fine dust which causes these problems, is formed primarily through the mechanical abrasion of the material, which is reduced in the fluid bed process and second when it is introduced with the filler material. Particularly, when fine iron minerals are used, the proportion of so-called adhesion and fine grains presents a problem. On the other hand, this material is involved in the formation of binders and adhesion, and second, it is discharged from the system and lost. For dry fine iron ores, it is the state of the art to use fluid bed dryers, by means of which the load of the material is simultaneously separated into a coarse fraction and a fine fraction. These material flows are used to set the size of the load grain in a controlled manner.
A process for this type is known, for example, from AT-B-400 578. In this known process, the fine mineral is dried with the help of a hot drying gas, which flows around the mineral particles of the fine mineral, and 5 the drying gas after it has flowed around the mineral particles, it is cleaned, with the removal of the dust particles of the minerals, removed. The mineral dust particles are collected and mixed with the fine dry minerals. The drying takes place at the same time as the classification of the gas of the fine minerals in the fluid bed process, the drying gas is passed through the fine minerals to form a fluid bed, and the speed of the drying gas is set at a level at which the mineral powder particles which are smaller, 15 are entrained to pre-selected sizes. The mineral dust particles that are entrained by the drying gas are completely separated, collected and mixed with the dry fine minerals in measured quantities. When the minerals which have been treated in this way in a direct fluid bed reduction process are used, the fine minerals may under certain circumstances, quasar problems by, in at least a partially reduced state, lead to agglutination and adhesion in the fluid bed reactor.
A "* Mai3 -» - ^ - Ji A. ^ MMt US-A-3 917 480 has described a process for the preparation of the particulate material for use in fluid bed reactors, in which, in a first step of the process , 20-70% of the fine fraction of the material is completely separated and the remaining fraction is introduced into a fluid bed, a fine fraction in addition, is completely separated in the fluid bed, discharged and mixed with the fine fraction obtained in the The first step of the process, the fine fractions are formed into pellets and added to the fluid bed.
The disadvantage of this process is that at least a negligible fine fraction enters the fluid bed, where it can cause the aforementioned problems, such as adhesion and agglutination. DE-A-197 11 629 shows a process for the pre-treatment of fine minerals having a wide grain size range for direct reduction as it is known, in which, fine ores belonging to the size fraction of grain of less than 6.3 mm and preferably less than 3 mm, are dried by means of a flow of hot air or
20 combustion gases during a pneumatic transport operation, if appropriate with the majority of the material to be recycled, the fraction of 6.3 min or 3 mm low to approximately 0.04 mm, being selected from the fine mineral
t? Ej¡U¡ÍBllÍlß * '- * ~ * ~ ..'. * ..to. A * J * ?? dry and being fed by direct reduction. The fraction of fine ore of a size which is smaller than about 0.4 mm and is discharged from the cyclone connected downstream of the dryer together with the drying air or the combustion gas, passes through ultrafine separation in a multicyclone. The fine ore which is separated, is fed here to a pelletizing device and is formed into pellets, water and binders being supplied, these pellets are finally added to the dryer via a supply device. The multicyclone which is provided by the ultra thin separation, is an extremely complex apparatus. The present invention is based on the object of providing a process for the production of fine-grained minerals and an installation for carrying out the process, in accordance with which, the ore is produced in such a way that, when the ore is subsequently used in a fluid bed reactor, the problems mentioned above, such as agglutination and adhesion in a cyclone and a fluid bed reactor, are avoided. The process should, in particular, be easy to carry out without major equipment operation expenses. According to the invention, this object is achieved in a process for the type described in the introduction, by the fact that the first fine fraction is subjected to an additional classification of gas by means of a gas, in which, a second Fine fraction and an ultrafine fraction are formed, and the second fine fraction is fed by the processing together with the coarse fraction and the ultrafine fraction are entrained with the gas and then completely separated from the gas. The invention is based on the discovery that the ultrafine fraction of the mineral, in the at least partially reduced state, is mainly responsible for the agglutination and adhesion in the fluid bed reactors. Furthermore, it has been found that this ultrafine fraction adheres to the first fine fraction, which is separated from the filler by means of the first gas classification. After the reduction, ie in at least the partially reduced state, during the processing of the second fine fraction together with the coarse fraction, the ultrafine fraction as known, for example from AT-B-400 578 mentioned above, causes the problems mentioned above in the fluid bed reactor. In accordance with the invention, this is avoided by the separation of the ultrafine fraction from the first fine fraction.
? u? M. . . ^^ j ,. «^^^ ^^^. . "^ > . ***. ».. *." ~ *,. - Preferably, the ultrafine fraction which has been completely separated from the gas, is mixed with a binder, granulated and fed by the process or discharged. In the case of granulation and further processing, the ultrafine fraction advantageously is not lost to the additional process. Conveniently, the granules which are formed from the ultrafine fraction are further processed together with the coarse fraction and the second fine fraction. By way of example, the additional processing involves the direct reduction current below the production of the ore. Nevertheless, in accordance with a further preferred embodiment, the granules which are formed from the ultrafine fraction, can also be mixed with the fine-grained mineral which is subjected to the first gas classification. Conveniently, the gas from which the entrainment of the ultrafine fraction has been removed is subjected to further cleaning, in which an extremely ultrafine fraction is completely separated, and this fraction, preferably together with the ultrafine fraction, is granulated and fed. for processing or is downloaded. As a
t? ~ i \ »L.? lÍ * i .b? > lá? .k ~? -1ltS ~ U **. ,. - - AA. ,,., A A ... .. «- ..,. * .. * ... A - .A A. . TO? .i. L? As a result, it is also possible to substantially use the powder fractions, which are still present in the gas after the ultrafine fraction has completely separated. According to a preferred embodiment, at least a partial amount of the second ultrafine fraction is likewise granulated, preferably together with the ultrafine fraction and / or extremely ultrafine fraction. In this way, the problems with the agglutination and adhesion of the mineral in the powder formed in subsequent processes are particularly reliably avoided. In the process according to the invention, the first fine fraction is completely separated from the fine gold ore by means of the first gas classification, preferably with a particle size of up to 150 μm, and the ultra fine fraction is completely separated from the first ultrafine fraction with a particle size of up to 20 μm by means of the additional gas classification. According to a preferred embodiment of the process according to the invention, a drying gas is used at least in the first gas classification. In this case, the drying takes place at the same time as the
go * - A & a. . .-.- gas classification of the cargo material. The binder used for the granulation is advantageously calcined lime or bentonite. Preferably, the gas which is used in the first gas classification and from which the first fine fraction has been removed, is used for the classification of additional gas. An installation for carrying out the process according to the invention, having a first gas classifier, provided with a feeder for fine-grained minerals, a gas supply line, an output line for a coarse fraction and a line outlet for gas and a first fine fraction entrainment with the gas, and having a first gas cleaning device, which is connected downstream of the first gas classifier and separates the first fine fraction out of the gas, characterized in that an outlet line for the first fine fraction, which leads outside the first gas cleaning device, has a connection line to an additional gas classifier, which has a gas supply line, an outlet line for a second fraction fine and a gas outlet line and an ultrafine fraction drag with the gas, and in that one second
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Gas cleaning device, which separates the ultrafine fraction out of the gas, is connected downstream of the additional gas classifier. Preferably, an outlet line for the ultrafine fraction leading outside the second gas cleaning device has a connection line to a granulation apparatus, a feed line for a binder opening within the granulation apparatus. In accordance with a further preferred embodiment, the granulation apparatus has a connection line to the feeder for feeding the fine grain ore to the first gas classifier. Advantageously, a common flushing apparatus is provided for the coarse fraction, the second fine fraction and the ultrafine fraction, which is subjected to granulation. Gas cleaning devices are conveniently designated as cyclones. Preferably, an additional gas cleaning device for completely separating an extremely ultrafine fraction, which is entrained with the gas, is connected downstream of the second gas cleaning device, to an outlet line for the extremely ultrafine fraction leading to the cleaning device of additional gas that has a connection line to a granulation apparatus. In accordance with a further embodiment of the installation according to the invention, the outlet line for the second fine fraction, which leads outside the additional gas classifier, has a connection line to a granulation device. Conveniently, at least the first gas classifier is designated as a dryer, a feed line for the opening of the drying gas within the gas classifier. Advantageously, a gas outlet line leading outside the first gas cleaning device has a connection line to the gas supply line leading to the additional gas classifier. This invention is explained in more detail below with reference to the drawings and on the basis of an exemplary embodiment. Figure 1, diagrammatically shows a flow chart for a preferred embodiment of the invention. Figure 1 illustrates a gas classifier 1, which is designated as a fluid bed unit and in which
the fine-grained ore 2 is introduced via a feeder 3. The fine-grained ore 2, which forms a bed 4 in the gas classifier 1, is fluidized and subjected to gas classification by means of a gas supplied via a feed line 5. In the process, it is separated into a coarse fraction 6, which is discharged via an outlet line 7, and a first fine fraction 8, which is entrained with the gas. In the exemplary embodiment shown, the fine-grained mineral 2 used has a grain size from 0 to 12 mm. It is separated into the coarse fraction 6, with a grain size from 0.15 to 12 mm, and the first fine fraction 8, with a grain size from 0 to 0.15 mm, by gas classification. The gas used is a drying gas, the fine-grained mineral 2 is subjected to drying as well as gas classification. The coarse fraction 6, which is discharged via the outlet line 7, is applied to a discharge apparatus, which is designated as a conveyor belt 9, and is fed for further processing, e.g., direct reduction. The first fine fraction 8 is discharged from the gas classifier 1, together with the gas via an outlet line 10, and is completely separated from the gas. A separator
The blow 11 and a cyclone 12 are used for this purpose. The fraction 8 which has been separated passes in a storage hopper 13, and from there, via a line 14, in an additional gas classifier 15, which is likewise designated as a fluid bed unit. In the additional gas classifier 15, the first fine fraction 8 forms a bed 6. The gas used is gas from which the first fine fraction 8 has been removed by cyclone 12 and which is supplied via a feed line 17. In the additional gas classifier 15, the first fine fraction 8, with a grain size from 0 to 0.15 mm, is separated into a second fine fraction 18, with a grain size from 20 to 150 μm, and a fraction ultrafine 19, with a grain size from 0 to 20 μm. The second fine fraction 18 is discharged from the additional gas classifier 15, via an outlet line 20, is applied to the conveyor belt 9 and is fed for further processing together with the coarse fraction 6. The gas and the ultrafine fraction 19, the which is entrained with the gas, are discharged from the additional gas classifier 15 via an outlet line 21. The gas is cleaned by means of a cyclone 22, in which the ultrafine fraction is completely separated.
... ítiL tl? í tl itt - étlH t ** -. * «< . rft a .. «.i», i sA.ll The ultrafine fraction 19 passes in a feed hopper 23, and thereafter, to a granulation apparatus 24. A feed line 25 for a binder 26 for the granulation of the ultrafine fraction 5 is opened in the granulation apparatus 24. The binder 26 used in the exemplary embodiment shown is calcined lime or bentonite. The ultrafine fraction 19 is granulated to form granules 27 with a grain size from 0.5 to 4 mm, and 10 the granules 27 are likewise applied to the conveyor belt 9. They are fed for further processing together with the coarse fraction 6 and the second fine fraction 18. • However, it is also possible for granules
15 27, to be fed to the first gas classifier 1 via a line (not shown in detail in figure 1), and to be introduced into this classifier together with the fine-grained mineral 2. In accordance with a preferred embodiment, the
The ultrafine fraction 19 is not fed to the granulation apparatus 24, but preferably, as indicated by the dotted lines 28 in FIG. 1, it is discharged and fed, for example, filled with earth. The advantage of this variant
is that the granulation step of the ultrafine fraction 19, which in quantitative terms, forms a relatively small proportion of the total charge of the fine-grained ore 2 removed, yet at the same time that the ultrafine fraction 19 is prevented from causing breakage in the subsequent processing steps, in particular to cause agglutination and adhesion. The smaller amount of lost charge material is only of subordinate importance if the mineral particles are low. In the exemplary embodiment shown, the gas which has been cleaned by cyclone 22 is fed to an additional gas cleaning device 29, which may for example be an electrostatic filter. By means of the additional gas cleaning device 29, an extremely ultrafine fraction 30, which is still entrained after cleaning in the cyclone 22, is completely separated from the gas and is likewise fed to the granulation apparatus 24 and granulated together with the ultrafine fraction 19. However, it is also equally possible for the extremely ultrafine fraction 30 to be discharged and filled with earth as indicated by dotted line 28 in Figure 1. The second fine fraction 18, which is discharged from the second gas classifier 15, and is not entrained with the gas, can at least in part, be fed, via a line 31, which is indicated in dotted lines in Figure 1, to the granulation apparatus 24, where it is granulated together with the ultrafine fraction 19 and the extremely ultraf fraction to 30 and is fed for further processing. The invention is also explained in further details on the basis of the following exemplary embodiment: The fine-grained ore 2 with a grain size from 0 to 12 mm, which represents 100% of the filler material, is introduced into the first classifier of gas 1, and is separated into a coarse fraction 6, with a grain size from 0.15 to 12 mm, and a first fine fraction 8, with a grain size from 0 to 0.15 mm. The coarse fraction 6 produces 67- of the charge. The first fine fraction, which makes 33% of the charge, is introduced into the additional gas classifier 15, and is separated into a second fine fraction 18, with a grain size from 20 to 150 μm, and an ultrafine fraction. , with a grain size from 0 to 20 μm. The second fine fraction 18, produces 29% of the fine-grained ore 2 which is used, and the ultra-fine fraction 19 produces 4% of the filler material. Electrostatic filters are used to separate
- & i L ?, an extremely ultrafine fraction with a grain size of up to 1 μm outside the gas from which the ultrafine fraction 19 has been removed. The invention is not restricted to the exemplary embodiment given above. Naturally, there is a considerable field for variations with respect to the grain size of the material used and with respect to the grain size of the fractions which are completely separated and their quantitative proportions in the material used. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention is that which is clear from the present description of the invention. fifteen
twenty