EP3074137B1 - Method for producing cement - Google Patents

Description

The invention relates to a method for producing a cement, wherein at least one millbase is ground in at least two devices for grinding to different ground millbase with mutually different grain size distributions, the ground millbase separated from each of the at least two devices for grinding separately, each with its own classifying air stream is supplied to one of at least two rod sifters, in each of the at least two rod sifter classified a fine material fraction and a coarse grain fraction is discharged.

For the production of cement and / or cement raw meal suitable for cement production regrind such as cement clinker, metallurgical or slag sand, limestone and / or gypsum is placed in a device for grinding regrind. In particular, for the crushing of the material to be ground roller presses are used, which are also called 'high-grade roller mill', 'high-pressure roller press' (HPGR). The material to be removed from the roller presses consists of still existing coarse material and a fine material produced during comminution. For the production of the fine material, it is separated from the coarse material in classifiers. For the separation of granular solids into fractions of different grain sizes, the use of dynamic rod basket separators is known in cement production in which cement raw meal and / or cement is precipitated as fines. In order to achieve a high grinding fineness, it is known to circulate the millbase in the process of a Kreislaufmahlanlage until it is removed due to sufficient comminution from the circulation by sifting.

For the strength of the building material cement whose particle size distribution is an essential parameter. In particular, a very steep grain size distribution curve can negatively impact the strength of cement. Thus, it is known from practice that the milling of cement clinker with roller presses leads to steep particle size distributions, since in this case only a small proportion of fines is formed with a particle size that is significantly smaller than the average particle size. Therefore, processes which cause a widening of the particle size distribution or, in principle, allow the particle size distribution to be influenced in order to achieve a high quality of cement are advantageous. For example, a very high cement strength occurs when a fines fraction of grains as small as possible and a fines fraction of larger grains together form a very compact particle arrangement.

Starting from the prior art, a broadened particle size distribution can be achieved by operating at least two similar Kreislaufmahlanlagen. Differences in the roller presses used (in particular in the contact forces) and the rod basket sifters (in particular with regard to speed and dimensions) make it possible to produce different, steep particle size distributions. Out DE 10 2008 019 830 A1 a Umwälzmahlanlage with roller press, static caution and dynamic classifier is known, it being possible to operate in parallel to increase the throughput of several similar systems. Also from WO 2009/068465 A1 is a Kreislaufmahlanlage known, which is composed of several roller presses and corresponding classifiers. With such systems, the desired grain size influencing and distribution can be achieved by bringing together the respective light goods. However, no other method is known for the merger, as to make a waste of each separated from the classifying air streams fine material fractions of the units. Especially to make a blend of the already deposited fine material, means with the construction and operation of a device that is a homogeneous Mixture of the fine material fractions of the units achieved, a disadvantageous economic, energetic and structural complexity in the overall process of cement production.

The object of the invention is therefore to provide a method for producing a cement, which overcomes the disadvantages of the prior art.

The object of the invention is achieved by the method for producing a cement having the features of claim 1. Further advantageous embodiments are specified in the subclaims to claim 1.

According to the invention, it is provided that in at least two grinders at least one grindable material suitable for cement production is ground and that the ground grindbase suspended in separate classifying air streams is in each case supplied pneumatically to a dynamic rod basket sifter. In each rod basket sifter a separation of a coarse grain fraction (grits) and a fine grain fraction is achieved. The grits are taken away. The fine material fractions which are located in the rod basket sifters are discharged from the respective classifying air streams into a common discharge device. In the discharge device, the classifying air streams flow together. The resulting flow field inside the discharge device swirls the fine material particles and leads to a uniform mixing of the fine material fractions from the individual rod basket separators. By the method of mixing the fine material fractions from the individual rod sifter already by unifying the classifying air streams and not to be blended only after separation from the respective classifying air streams, no further step of a blending in the process is needed. This offers economic advantages, and not least in terms of energy costs also economic benefits, as can be dispensed with an additional device for such a blend in the overall process of cement production.

According to the invention it can be provided that the at least two devices for grinding mutually different millbase, for example cement clinker, metallurgical or slag sand, limestone and / or gypsum, is supplied. If at the same time different starting materials are supplied to the devices for grinding as the respective ground material, this can influence the composition of the cement or cement raw meal.

According to a concrete embodiment of the invention, it is provided to use preferably roller presses as devices for grinding. Operating characteristics of roller presses and the nature of the comminuted fresh produce are well known in cement production. In particular, roller presses lead to steep particle size distribution curves. By varying the setting of the crushing properties of the two or more roller presses used, each with a following rod basket sifter, the desired broadened particle size distribution can easily be achieved for the common fine product product. In particular, in the case of two roller presses and two Stabkorbsichtern a composition of a coarser and a finer fines content in the common fines product is produced, resulting in a high strength of cement.

The inventive method is not limited to the use of roller presses. It is possible, in their place, to use other devices known from cement production for grinding regrind, in particular ball mills (tube mills), vertical mills and impact hammer mills. This makes it possible, not least for testing and development purposes, to carry out additional influencing of the particle size distribution in the common fine product product that is fundamentally made possible by the method according to the invention.

According to one embodiment of the invention, it is provided that the ground material to be ground from the at least two devices for grinding is not directed directly into the dynamic rod basket sifter, but first subjected to a pre-seal. For this purpose, the crushed regrind is in each case in a static Caution entered. Caregivers are used in the process of cement production to separate coarse material located in the material to be ground. These are coarse material residues that were not crushed during the grinding process. In addition, there is a proportion of agglomerates in the Austragsgut the roller presses, which were formed by the high contact pressure in the Gutbettzerkleinerung in the roller presses from the particles of cement clinker. It is known to use static cautionary (eg Cascade classifier) for deagglomeration of these so-called scabs in cement production. The coarse material separated in the static cauterizers is removed. The screened fines of each static cauterizer are pneumatically fed with their own classifying air stream for further viewing of each dynamic bar cage sifter.

According to a further embodiment of the invention, the coarse grain fractions discharged from the at least two rod basket sifters are again supplied to the devices for grinding. Such a recirculation of Grießeaustrags offers the known economic advantages of Kreislaufmahlanlagen. For a better control of the grain size distributions, it is provided that the individual grinding cycles are run separately from each other, i. the coarse grain fraction from a rod basket sifter is returned to the corresponding apparatus for grinding, from which forth this Stabkorbsichter also flows the Sichtgut.

In accordance with at least one embodiment of the invention, it is further provided to arrange the at least two rod cage separators separately but in only one housing. This allows an economical material cost for the housing construction of the rod basket sifter and takes up the least space for the devices for sifting. Typically, two rod cage sifters are preferably coaxially stacked for dynamic reasons.

Figur 1:

ein erfindungsgemäßes Verfahren zur Herstellung eines Zements im Ausführungsbeispiel mit zwei als Rollenpressen ausgeführten Vorrichtungen zum Mahlen und zwei im Vertikalschnitt dargestellten Stabkorbsichtern in getrennten Gehäusen;

Figur 2:

ein erfindungsgemäßes Verfahren zur Herstellung eines Zements im Ausführungsbeispiel mit zwei als Rollenpressen ausgeführten Vorrichtungen zum Mahlen, zwei im Vertikalschnitt dargestellten Stabkorbsichtern in getrennten Gehäusen und mit Vorsichtung in zwei statischen Vorsichtern;

Figur 3:

ein erfindungsgemäßes Verfahren zur Herstellung eines Zements in einer Ausführungsform als Kreislaufmahlanlage, im Ausführungsbeispiel mit zwei als Rollenpressen ausgeführten Vorrichtungen zum Mahlen, zwei im Vertikalschnitt dargestellten Stabkorbsichtern in getrennten Gehäusen und mit Vorsichtung in zwei statischen Vorsichtern;

Figur 4a:

ein erfindungsgemäßes Verfahren zur Herstellung eines Zements im Ausführungsbeispiel mit zwei Vorrichtungen zum Mahlen, von denen eine eine Rollenpresse und die zweite eine Kugelmühle ist, und zwei im Vertikalschnitt dargestellten Stabkorbsichtern in getrennten Gehäusen;

Figur 4b:

ein erfindungsgemäßes Verfahren zur Herstellung eines Zements im Ausführungsbeispiel mit zwei Vorrichtungen zum Mahlen, von denen eine eine Vertikalmühle und die zweite eine Prallhammermühle ist, und zwei im Vertikalschnitt dargestellten Stabkorbsichtern in getrennten Gehäusen;

Figur 5:

Ausschnitt aus dem erfindungsgemäßen Verfahren zur Herstellung eines Zements, im Vertikalschnitt darstellend das Ausführungsbeispiel mit zwei Stabkorbsichtern in einem gemeinsamen Gehäuse.

The invention will be explained in more detail with reference to the following figures. It shows:

FIG. 1:

an inventive method for producing a cement in the embodiment with two executed as roller presses devices for grinding and two shown in vertical section Stabkorbsichtern in separate cases;

FIG. 2:

an inventive method for producing a cement in the embodiment with two executed as roller presses devices for grinding, two shown in vertical section Stabkorbsichtern in separate housings and with caution in two static Cautioners;

FIG. 3:

an inventive method for producing a cement in one embodiment as Kreislaufmahlanlage, in the embodiment with two designed as roller presses devices for grinding, two shown in vertical section Stabkorbsichtern in separate housings and with caution in two static cautionary;

FIG. 4a

an inventive method for producing a cement in the embodiment with two devices for grinding, one of which is a roller press and the second is a ball mill, and two shown in vertical section Stabkorbsichtern in separate cases;

FIG. 4b:

an inventive method for producing a cement in the embodiment with two devices for grinding, one of which is a vertical mill and the second is an impact hammer mill, and two in vertical sections shown Stabkorbsichtern in separate housings;

FIG. 5:

Section of the inventive method for producing a cement, in vertical section representing the embodiment with two rod basket sifters in a common housing.

In FIG. 1 the method according to the invention for the production of cement is shown schematically for the exemplary embodiment in which two roller presses 1, 2 are used as devices for comminuting the at least one ground material. The Austragsgut from the roller presses 1, 2 is pneumatically introduced in each case with a Sichtluftstrom 3a, 3b in the housing 6a, 6b each of a dynamic Stabkorbsichters 4, 5. Each of the two rod sifter 4, 5 has its own, speed-adjustable drive 24a, 24b, which puts him about its longitudinal axis in a rotational movement. Speed and direction of rotation of the two rod basket sifter 4, 5 can be controlled independently. The millbase suspended in the classifying air flows laterally toward the respective rod basket classifier 4, 5 and is accelerated by the rotational movement of the rod basket classifier 4, 5 into its zone of vision. The centrifugal forces acting on the particles of the Sichtguts lead in cooperation with the frictional force of the air flow to a separation of the Sichtguts in each case a coarse grain fraction 7, 8 (Grape) and each a fine material fraction 9, 10. The coarse grain fractions 7, 8 are from the Stabkorbsichtern 4, 5 discharged due to gravity down from the respective Sichtzone (Grießeaustrag).

The classified fines 9, 10 are pneumatically transported by the respective classifying air stream from the respective rod basket sifter 4, 5 and both arrive in the discharge device 11. In a substantial phase of the method according to the invention for the production of a cement occurs in the discharge device 11 to a club so far separate classifying air streams. The merger of the classifying air flows leads to a turbulent flow dynamics in the interior of the discharge device 11. This results in a turbulence and in its consequence a uniform mixing of suspended in the classifying air streams fine material fractions 9, 10 to a homogeneous finished product with a correspondingly composed particle size distribution. This leaves as the fine material flow 12, the discharge device 11 and reaches the separation device (here a cyclone) 13. In the separator 13 is the fine material 14 separated from the classifying air stream 15 and can be stored in silos in the further process of cement production (not in the picture).

In the FIGS. 4a and 4b are exemplary embodiments of the inventive method for producing a cement with a roller press 1 and a ball mill 16 ( FIG. 4a ) or with a vertical mill 17 and an impact hammer mill 18 (FIG. FIG. 4b ). In addition, procedures and structure are as in FIG. 1 ,

In FIG. 2 is based on the embodiment of FIG. 1 schematically illustrates an inventive method for producing a cement, in which the Austragsgut from the roller presses 1, 2 each undergoes a Vorsichtung before it is passed into one of the rod basket classifier 4, 5. The Austragsgutstrom 20a, 20b from each roller press 1, 2 is to each a static caution 21, 22, respectively. The discharged into a static cauterizer 21, 22 Austragsgut is separated into this in a fraction of fines 27a, 27b of the static Bewässers 21, 22 and a coarse material fraction, which leaves on the way Grobgutabführung 26a, 26b, the static cautery 21, 22. The separated fines 27a, 27b of the static cauterizer 21, 22 is pneumatically with a classifying air stream 19a, 19b in each one of the rod basket classifier 4, 5 passed.

In FIG. 3 is based on the embodiment of FIG. 2 an extended to a grinding cycle, inventive method for producing a cement shown. With otherwise the same procedure in this embodiment, the Grießeaustrag from the Stabkorbsichtern 4, 5 each returned to the devices for grinding 1, 2. The recirculation takes place separately and to the respectively corresponding roller press 1, 2: For the coarse grain fraction 7 from the rod basket sifter 4, a feed 25a of the coarse grain fraction takes place back to the roller press 1; Similarly, the feed 25b of the coarse grain fraction takes place back to the roller press 2. The roller presses 1, 2 grind the recirculated coarse grain fractions 7, 8 together with that in the fresh material feeds 23a, 23b each supplied grinding stock. The Austragsgutströme 20a, 20b from the roller presses 1, 2 are each passed into the corresponding static caution 21, 22. The coarse material discharge discharged into the coarse material removal lines 26a, 26b of the static cauterizers 21, 22 can - not shown in the figure - be brought together with fresh material directly or after further pre-grinding and likewise fed back into the grinding cycle by way of the fresh material feeds 23a, 23b.

FIG. 5 shows a detail of an embodiment of the method according to the invention, in which the two rod basket viewers 4, 5 are arranged in only one housing 6c. For dynamic reasons, a coaxial arrangement of the rod basket sifter 4, 5 is favorable, as shown. The rod basket separators 4, 5 are separated from each other by the respective Sichtluftstrom 3a, 3b flows. The fines 9, 10 are separated from each other in the discharge 11, in which combines the classifying air streams and the two fines 9, 10 are uniformly mixed. In addition, procedures and structure are as in one of Figures 1 to 4b , <I> LIST OF REFERENCES </ i> 1 roller Press 16 ball mill 2 roller Press 17 vertical mill 3a, 3b Classifying air stream 18 Impact hammer mill 4 Rod basket sifter 19a, 19b Classifying air stream 5 Rod basket sifter 20a, 20b Austragsgutstrom 6a, 6b, 6c casing 21 Static Caution 7 Coarse particle fraction 22 Static Caution 8th Coarse particle fraction 23a, 23b fresh material 9 fines fraction 24a, 24b drive 10 fines fraction 25a, 25b Feeding the coarse grain fraction 11 discharge 12 fine material 26a, 26b Grobgutabführung 13 separating 27a, 27b Fines of static caution 14 fines 15 Classifying air stream

Claims (6)

1. Method for producing cement, wherein

   - at least one material to be ground is ground in at least two grinding devices (1, 2, 16, 17, 18) into differently ground material with grain size distributions that are different from one another,

   - the ground material from each of the at least two grinding devices (1, 2, 16, 17, 18) is fed separately from one another by its own respective classifying air stream (3a, 3b) to one of at least two bar-cage classifiers (4, 5),

   - in each of the at least two bar-cage classifiers (4, 5) a fine material fraction (9, 10)is separated out and a coarse grain fraction (7, 8) is discharged,

   characterized by
   combining the classifying air streams, emerging from the at least two bar-cage classifiers (4, 5) and supporting the fine material fractions (9, 10), inside a common discharge device (11), wherein a uniform mixing of the fine material fractions (9, 10) takes place.
2. Method as claimed in claim 1, characterized in that the at least two grinding devices (1, 2, 16, 17, 18) are preferably roller presses(1, 2).
3. Method as claimed in one of claims 1 to 2,
   characterized in that

   - the ground material is discharged from the at least two grinding devices (1, 2, 16, 17, 18) and is supplied in discharged material flows (20a, 20b) separately from one another each to one of at least two static preliminary sifters (21, 22),

   - in the static preliminary sifters (21 22) a coarse material discharge (26a, 26b) and a separating out of the fine material (27a, 27b) of the static preliminary sifters (21, 22) takes place,

   - the fine material (27a, 27b) of the at least two static preliminary sifters (21, 22) is supplied separated from one another by its own classifying air stream (19a, 19b) into one each of the at least two bar-cage classifiers (4, 5).
4. Method as claimed in one of claims 1 to 3,
   characterized in that
   the coarse grain fractions (7, 8) are discharged from the at least two bar-cage classifiers (4, 5) and are supplied separately from one another to the respective corresponding device of the at least two grinding devices (1, 2, 16, 17, 18).
5. Method as claimed in one of claims 1 to 4,
   characterized in that
   at least two of the at least two bar-cage classifiers (4, 5) are arranged in only one housing (6c).
6. Method as claimed in one of claims 1 to 5,
   characterized in that
   at least one of the at least two grinding devices (1, 2, 16, 17, 18) is a ball mill (16), a vertical mill (17) or an impact hammer mill (18).

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