EP0366759A1

EP0366759A1 - Process for size reduction of brittle grinding material.

Info

Publication number: EP0366759A1
Application number: EP89905398A
Authority: EP
Inventors: Franz Thomas; Herbert Weit
Original assignee: Christian Pfeiffer Maschinenfabrik GmbH and Co KG
Current assignee: Christian Pfeiffer Maschinenfabrik GmbH and Co KG
Priority date: 1988-05-04
Filing date: 1989-05-03
Publication date: 1990-05-09
Anticipated expiration: 2009-05-03
Also published as: DE58906304D1; US5058813A; EP0366759B1; DE3815217C2; DE3815217A1; JPH0751221B2; JPH02501544A; WO1989010790A1

Abstract

Les procédés existants de broyage de matières friables sont basés uniquement sur une première phase de fragmentation de chaque gran et de l'ensemble de la matière et se révèlent peu économiques. Aussi la présente invention propose-t-elle un broyage préliminaire de ladite matière jusqu'à une granulométrie relativement précise, les phases ultérieures étant adaptées en conséquence à ladite granulométrie de manière à réduire le travail nécessaire en fonction de la quantité de matière à broyer.The existing methods of grinding friable materials are based only on a first phase of fragmentation of each gran and all of the material and prove to be uneconomical. Also, the present invention proposes a preliminary grinding of said material to a relatively precise particle size, the subsequent phases being adapted accordingly to said particle size so as to reduce the work required depending on the amount of material to be ground.

Description

Process for crushing brittle regrind

The invention relates to a method for comminuting brittle regrind according to the preamble of claim 1.

Such a continuous process is known from DE 36 09 229 A1. This known method according to the prior art is already based on the objective of improving a comminution method as described in EP 0 084 383 A1, with the latter method already performing single-grain and material bed comminution. This improvement consists above all in that the regrind agglomerates present after comminution of the material bed are brought to dissolution. In this way, the aim is to remove the fine material content contained in the agglomerates by means of a sifting process so that the overall process can be made more economical, including the subsequent further comminution.

The good-bed roller mills usually used for simultaneous single-grain and material-bed comminution have the advantage that they can be used to grind relatively fine-grained and regrind particles <2 mm are possible. In addition to the above-mentioned disadvantage of agglomeration, the fact that even coarser regrind particles pass the material bed roller mill appears even more serious. In addition, a material bed roller mill requires a relatively high investment in comparison to other mills or crushers. However, the coarse particles passing through the material bed roller mill make it necessary, for example, for the downstream comminution by means of a gravity mill and, in particular, a tube mill, also with grinding media of relative. large diameter must be equipped. Large steel balls are inevitably also available due to the coarse particles passing through a material bed roller mill. Added to this is the fact that one has previously worked with a tube mill with a filling degree in the range of approximately 26 to 30 ° C. This is mainly because if the degree of filling is reduced to, for example, 20%, there is a risk that the relatively coarse steel balls will smash the cladding plates as well as the slotted and end wall plates with such a low degree of filling or grinding mirror.

These disadvantageous aspects of the operation of the Gutbett-Kalzenmühle and the required grinding media size mean that even taking into account the degree of filling with regard to the total energy consumption, a comparatively poor efficiency, as in known systems, is achieved.

The present invention is therefore based on the object of designing the generic method in such a way that, on the one hand, the specific energy requirement for a specific quantity of regrind is improved and, furthermore, the overall economy is considerably increased by a sharp reduction in investment costs, with a flexible design ¬ possibility of the method should be given.

According to the invention, this object is achieved in a generic method by the features of the characterizing part of claim 1. An essential core idea of the invention can be seen in ge, the first crushing process of Mahl¬ guts mill no longer be carried out with a relatively expensive material bed Walzen¬ but with a primary crusher and ^'ins¬ particular a centrifugal crusher. When using this primary crusher, it is consciously accepted that the ground material particles leaving the primary crusher are not broken up as finely as, for example, in a vertical bed roller mill. However, less coarse material is produced with a significantly reduced coarse material, which would otherwise hinder the comminution of the coarse material by its buffering action in a second shredding stage. This eliminates the previously serious disadvantage that even relatively large particles are fed to the subsequent processing stages in a fine material bed.

With this measure, to achieve a defined feed material at the exit of the primary crusher, which, however, is not as fine, one can now in a second crushing stage, for which a ball or tube mill with grinding media is particularly suitable, the diameter of the used Keep the grinding media smaller, use the pre-shredded material in a targeted manner and thereby also reduce the degree of filling.

It is thus possible, for example, to use steel balls of 40 to 60 mm in a first chamber of a tube mill for a defined coarse grain smaller than 3 mm at the outlet of the centrifugal crusher used as a primary crusher. Steel balls in the range from 15 to 30 mm, for example, can then be used in the second chamber of the tube mill. Since it is also possible to lower the degree of filling in a targeted manner, a very greatly reduced energy requirement for the operation of the tube mill is achieved. This measure is supplemented by the fact that the semolina obtained at the discharge of the tube mill or the coarse grain are circulated to a classifier. leads, the size of which is fed again to the tube mill. The fine particle-air mixture at the outlet of the tube mill can be passed through a downstream filter, so that the fine particles can be discharged together with the fine material obtained in the classifying process.

By using grinding media with a smaller diameter in the tube mill, less wear is achieved than is necessarily the case with larger steel balls.

The measure of using a centrifugal crusher as a primary crusher, which is in itself an independent feature of the invention, with which one deliberately proceeds from the previous idea of the smallest possible size reduction in the first stage and takes a comparatively contrary measure, brings the advantage less Investments. On the other hand, a centrifugal crusher is usually significantly less maintenance and easier to maintain than a Gutbett roller mill, which is usually designed with oil hydraulics for generating high pressures. In addition, according to the invention, a relatively low construction of the plant can also be achieved. In this way, not only is a cost-effective method implemented in terms of plant technology, but also the specific work and energy requirements can be considerably reduced. Experimentally, values in the range of 2 to 2.5 kWh / t were achieved.

When the pre-broken ground material is fed directly into the tube mill as the second comminution stage, the semolina or the coarse particles of the screening process are suitably returned to the second comminution stage.

If a single-grain and good-bed comminution is already available, for example by means of a good-bed roller mill, the discharge material, which is essentially in the form of agglomerates (slugs), can additionally be added to a downstream centrifugal crusher for deagglomeration and coarse material comminution. be carried out in order to then be available agglomerate-free for further treatment.

Another advantage of the process is that no agglomerates (slugs) are produced in the centrifugal crusher. This also enables problem-free separation of the pre-shredded goods into coarse and fine goods (e.g. by sifting). The fine material is drawn off before the second comminution stage and thus the economy is further increased, since no undesired fine material gets into the second comminution stage.

It is also particularly expedient to connect a sieving process directly after the first comminution so that undesired oversize particles can be fed back into the first comminution in the cyclic process. This ensures that only the desired fine material is fed to the ball or tube mill.

The invention is explained in more detail below with the aid of schematic drawings from which advantageous developments can be found. Show it:

1 shows the basic illustration of a plant for the continuous comminution of regrind, in which, after the first comminution stage, the material is fed directly to a second comminution stage;

FIG. 2 shows a process sequence with the comparable parts of the plant according to FIG. 1, but a visual process is interposed before the second comminution stage and

3 shows a further variant of the invention, in which a screening is carried out after the first comminution and only the ground material up to a certain particle size is fed to the second comminution stage. 1 shows a schematic representation of the process sequence in an alternative, which is preferred. The regrind, which can be cement clinker, for example, is fed to the entire system 1 from a feed bunker 2 via a scale 3. A time-metered supply can be carried out by means of the scale 3. Following the scale 3, the ground material is fed to a primary crusher 4, which is preferably a centrifugal crusher.

In the example according to FIG. 1, the material comminuted up to a relatively defined maximum grain size in the centrifugal crusher 4 is passed directly over a section 5 into the second comminution stage, which is designed here as a two-chamber tube mill 6. The first chamber 7 of the tube mill 6 has, for example, steel balls as grinding media with diameters in the range from 40 to 60 mm. By contrast, the second chamber 8 adjoining the intermediate wall 9 is provided with steel balls in the range from 10 to 30 mm and preferably with diameters in the range from 15 to 30 mm. At the discharge 10 of the tube mill 6, the coarse material is discharged downwards and passes via a conveyor section which is provided with a bucket elevator 11 and the line 17 into a classifier 18. A cross-flow classifier, the size of which is particularly suitable for the classifier 18 the coarse material outlet 20 and the line 21 of the tube mill 6 are fed as a second crushing stage.

The fines particles discharged into the fines outlet are withdrawn from the process circuit via a removal section 16.

The air-fine particle mixture at the outlet 23 of the tube mill 6 is fed via a line 12 to a filter 13 in which the fine particles are separated from the air. The fine material particles are fed via the fine material outlet 15 to the removal section 16, while the air is exits 14, if necessary, is returned to the process cycle.

The regrind 4 comminuted at the exit of the relatively low investment has a well-defined grain size, for which there are largely no larger regrind particles beyond the desired size range.

This makes it possible to work with steel balls of reduced diameter in the second downstream size reduction stage, for which the two-chamber tube mill is provided, and the degree of filling of the tube mill may also be below the usual values.

In this way, on the one hand, less wear occurs in the tube mill. On the other hand, however, the energy requirement is also improved by the smaller filling and the reduced overall weight. In comparison to the prior art, in which steel balls of 90 size are used in the first chamber of the tube mill, it is now possible to use grinding media with a diameter range of 40 to 60 mm, which in the second stage reduces to 15 to 30 mm can be.

FIG. 2 shows a variant of the plant according to FIG. 1 for carrying out the method according to the invention. Corresponding reference numerals relate to the same parts of the system. The difference compared to the embodiment according to FIG. 1 is that the centrifugal crusher 4 of the first crushing stage is now directly followed by the classifier 18.

This ensures that the fine material can already be withdrawn from the process circuit via the fine material outlets 19 and thus no longer stresses the tube mill 6 as the second comminution stage of the ground material. Since the material throughput of the tube mill 6 is reduced, a further improvement in the efficiency of the entire system is sufficient.

The grit of the classifier 18 in the example according to FIG. 2 is now supplied via the coarse material outlet 20 and the line 21 in the circuit of the tube mill 6, the equipment of which with grinding elements is corresponding to the embodiment according to FIG. 1.

3 shows a further variant of the invention. Here, the same reference numerals as in the previous figures denote the same units. In order to ensure that a pre-comminuted ground material up to a certain particle size is fed to the second comminution stage, in the example according to FIG. The regrind leaving the centrifugal crusher 4 is therefore passed through a sieve 35. The oversize particles obtained in the sieve 35 either reach the bucket elevator 11 via the line 36a and are recirculated there or are fed to the centrifugal crusher via the line 36b. On the other hand, the ground material, which is obtained up to a desired particle size, is fed via line 37 to the tube mill 6 for further comminution.

In the example according to FIG. 3, the material fed to the bucket elevator 11 arrives in the sifter 18. The coarse material obtained after the sifting process is again fed into the second comminution stage 6 via the return line 41a.

In this way it can be ensured that no oversize of the pre-comminuted ground material reaches the tube mill 6, so that the second comminution stage can be optimally designed with regard to the size of the grinding media and the degree of filling.

The scope of the method according to the invention is this not only applies to the grinding of cement clinker, but can also be used with comparable materials such as limestone, ores, coal, quartz sand or grit, where these details are only to be understood as examples.

Overall, therefore, the method according to the invention and the plant alternatives provided therefor reduce the specific work required per intended quantity of regrind, this being supplemented by wear reductions at least on the second size reduction stage. In addition, it also requires lower investment costs than comparable systems according to the prior art.

Claims

- O patent claims;

1. Method for comminuting brittle regrind, such as Cement clinker where

(a) the ground material is first subjected to a first comminution,

(b) is then fed directly or indirectly to a further, second comminution after a screening process or screening process,

(c) the grains obtained after the second comminution are subjected to a visual process and

(d) the fines particles are removed from the sighting process and from the second comminution as fines, as a result of which g e k e n e z e i c h n e t,

(e) the first comminution is carried out as a preliminary break, in particular by means of a centrifugal breaker, and

(f) that the second comminution by means of a mill suitable for fine comminution, in particular a multi-stage tube mill or a roller mill, e.g. a material bed roller mill is carried out.

2. The method according to claim 1, characterized in that the semolina obtained from the second comminution are fed to the screening process in a cyclic process, their semen are fed to the second comminution.

3. The method according to claim 1 or 2, characterized in that the second size reduction in a two-stage tube mill with a degree of filling of less than 26 to 30%, when using grinding media with a diameter in the range 40 to 60 mm, in the first Stage of the second comminution and in the second stage of the second comminution with grinding media with a diameter in the range from 10 to 30 mm.

4. The method according to any one of claims 1 to 3, characterized in that the fine material discharge provided after the second comminution is subjected to filtering or cyclone separation.

5. The method according to any one of claims 1 to 4, characterized in that the viewing process is carried out by means of cross-flow screening.

6. The method according to any one of claims 1 to 5, characterized in that the first comminution is followed by a sieving process of the pre-crushed ground material, the resulting fine grain of the second comminution and the oversize obtained in the cycle process being fed indirectly or directly to the first comminution .