EP3079828A1

EP3079828A1 - Closed-circuit grinding plant having a pre-classifier and a ball mill

Info

Publication number: EP3079828A1
Application number: EP14809390.9A
Authority: EP
Inventors: Jörg BINNER
Original assignee: KHD Humboldt Wedag AG
Current assignee: KHD Humboldt Wedag AG
Priority date: 2013-12-11
Filing date: 2014-12-09
Publication date: 2016-10-19
Also published as: US20160288135A1; DE102013020888A1; WO2015086554A1; CN105899295A

Abstract

The invention relates to a closed-circuit grinding plant for grinding fresh material, comprising: a first device (2, 26, 27) for grinding the fresh material; a static pre-classifier (4) for pre-classifying the ground grinding material (3), having an input opening (5) for the ground grinding material (3), an output opening (7) for a coarse meal fraction (9), and a further output opening (6) for a fine-grained output material (8); a device (15) for separating out fine material (18), having an output opening (16) for a coarse-grained fraction (17), with subsequent recirculation to the first device for grinding, an output opening (19) for fine material (18), and at least one input opening (14a, 14b), wherein an input opening (14a, 14b) is connected to the output opening (6) of the static pre-classifier (4); and a second grinding device (11). According to the invention, the static pre-classifier (4) is a cascade classifier (4) and the second grinding device (11) is present in the form of a ball mill (11), wherein the ball mill (11) has a material inlet (10) connected to the output opening (7) for the coarse meal fraction (9) of the cascade classifier (4) and a material outlet (12) connected to an input opening (14a, 14b) of the device (15) for separating out fine material (18).

Description

Kreislaufmahlanlage with caution and ball mill

The invention relates to a Kreislaufmahlanlage for grinding of fresh goods, comprising a first apparatus for grinding the fresh material, wherein the first device for grinding the fresh material ground millbase produces a static waiter for precaution of the ground millbase with an entry port for the ground millbase, a discharge opening for a sifted coarse semolina fraction and a further discharge opening for the discharge of a fine-grained Austragsguts, a device for prospecting of fines with a discharge for discharging a separated coarse grain fraction, with subsequent recirculation to the first apparatus for grinding the fresh material, a discharge for the fine material and at least an entry opening, wherein one of the at least one entry opening communicates with the discharge opening for the fine-grained discharge material of the static cautery, a second device for grinding Mahlg ut, wherein the second apparatus for grinding regrind produces a ground regrind.

In order to obtain granular fines from a fresh material present as coarse material, the fresh material is placed in a device for grinding regrind. 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. A prime example is the production of cement and / or cement raw meal by grinding cement clinker, blastfurnace slag, limestone and / or gypsum. In particular, roller presses are used for comminuting the fresh product. Roll Press ',' Good Bed Roll Mill 'or English, High Pressure Grinding Roller Press' (HPGR) are called. The ground regrind from the apparatus for grinding the fresh material usually consists of still existing coarse material and a finer-grained fraction. In order to recover the fines, the milled material to be ground is separated from the coarse material and separated in a prospecting device. For the separation of granular solids in fractions of different particle size, the use of dynamic classifiers, in particular rod basket classifiers, is known in cement production. Also known are two-stage processes in which the dynamic classifier is preceded by a static guardian, for example a cascade classifier. This not only reduces the wear of the dynamic classifier. In the cascade classifier, moreover, good agglomerates which are produced in roller presses and other grinding devices are disagglomerated.

From DE 102 21 739 A1 a Kreislaufmahlanlage is known in which the ground millbase is fed to a high-pressure roll mill or roller press a arranged underneath cascade classifier. This is another classifier, for example, downstream of a dynamic rod basket sifter, the Sichtgutaustrag the cascade classifier is supplied pneumatically, which leads by waiving mechanical conveyors to lower operating and investment costs and less space. The Nachsichter is arranged above the roller press, in which the coarse material discharge is recirculated. Two options are proposed for the further treatment of the coarse material separated in the cascade classifier: Either this fraction is again fed to the roller press; or in the lower part of the cascade classifier an impact crusher is integrated, which uses a rotor to hurl the material back into the cascade classifier. The disadvantage of the latter approach, however, is that here only the disagglomeration process is improved by repeated passage through the cascade sifter. For a further comminution of fractions in the coarse grain fraction, which are not agglomerated, the Impact effect is not enough. A return to be made according to the first procedure of this fraction in the roller press requires not only purely mechanical and thus energy and costly transport. Also known are venting and Materialpressschwierigkeiten in the nip of roller or roller presses, if here in addition to the fresh comparatively small-grain Good, as it is present in the discharge of the cascade classifier, is abandoned. In addition, the grinding of cement clinker with roller presses leads to a low proportion of fines with a particularly fine particle size, and thus to a steep particle size distribution curve. In the case of cement production, the particle size distribution determines the strength of the building material cement. Due to a then very compact arrangement of fine particles, a particularly high strength of cement can be achieved when the Zementfeingut is given as a mixture of a fine material fraction of the smallest possible grains and a fine material fraction of larger grains. Thus, a broader grain size distribution is desirable than given with the grain size distribution curve of a roller press.

It may therefore be advantageous to turn on a further apparatus for grinding regrind in the Kreislaufmahlanlage, such as a ball mill (tube mill, tubular ball mill). DE 10 2006 017 510 A1 describes a Kreislaufmahlanlage with a first grinding unit, such as a roller press for Vormahlung fresh food, a dynamic classifier and a tube mill. The dynamic classifier can be preceded by a cascade classifier. A separation into two grinding circuits is provided, which are coupled via the two-chamber dynamic rod basket classifier. In the first grinding cycle the first grinding unit (roller press) and, if present, the static cautery are arranged, in the second the tube mill. The tube mill is used exclusively for grinding the fine siftings discharged in the dynamic sifter. Since the coarse grit discharge is recirculated from the rod cage sifter to the roller press, the use of the tube mill does not result in a costly lowers the number of cycles in the first cycle. Although not described in detail, it is also to be assumed that the separated coarse fraction from the cautioner should either go back to the roller press, which would lead to the disadvantages already mentioned above, or would be eliminated from the circulation to the detriment of the efficiency of the process. In addition, the advanced technique of the multi-chamber classifier required here in practice is associated with higher investment and maintenance costs than with simple rod basket sifters.

In DE 39 05 123 A1 a circulation grinding plant with Gutbettzerkleinerungs- roller press, tube mill and classifier with separate recirculation of classifier semolina fractions is described. In this case, the discharge of the roller press (via a possibly existing pre-shredding device) is fed to the tube mill without precaution. The tube mill has a deagglomerating chamber. The disadvantage here is that the deagglomeration process in the ball mill is very time consuming. In particular, however, there remains a fraction of coarser, not crushed particles whose grain size is not based on agglomeration. Due to their size, they are so heavy that they are not accessible to the pneumatic transport from the ball mill into the sifter. This portion would have to be specially removed from the deagglomeration chamber and fed to the sifter (or again the roller press) in a mechanical manner, ie by means of a bucket elevator, by means of a bucket elevator.

In DE 33 02 176 A1, an embodiment of a crushing plant is disclosed in which ground in a roll machine Good is fed to a sizing. The out-classified coarser fraction is passed into a tube mill, while the finer fraction is fed to a classifier, in which also the exit material passes out of the tube mill. The coarse semolina fraction of the classifier can be returned to the mill machine or tube mill in the grinding cycle. The disadvantage, however, is that a sizing screen without rapid wear or no inadequate disagglomeration effect on the Gutagglome- rate or scabs of emerging from the roll press ground material has. In addition, the sizing strainer suitable in particular for the required high throughputs not only sort out a pure fine fraction, but merely separate a fine and medium fraction from a coarse fraction, which adversely affects the efficiency of the screening process in the downstream classifier or the particle size distribution of the end product and / / or economically unfavorable additional measures required.

The object of the invention is therefore to provide a Kreislaufmahlanlage for grinding of fresh goods available, which overcomes the disadvantages of the prior art.

The object of the invention is achieved by the Kreislaufmahlanlage for grinding fresh food with the features of claim 1. Further advantageous embodiments of the invention are specified in the subclaims.

According to the invention, it is provided that a static cascade classifier is used as the static guardian. It is further provided as a second apparatus for grinding regrind a ball mill so turn on the Kreislaufmahlanlage for grinding of fresh goods, that firstly the Guteinlauf the ball mill is connected to the discharge for the coarse Grießefraktion of the static cautionary. The separated in the direction of coarse-grained fraction is thus fed to the further grinding of the ball mill. For the benefit of material transport, it is obvious to arrange the ball mill below the caution. Secondly, the material discharge of the ball mill is connected to an entry opening of the device for prospecting of fine material, so that the fine material portion is selected from the ground product to be discharged from the ball mill.

According to the invention, a Kreislaufmahlanlage is thus provided, is ground in the fresh material in a first apparatus for grinding, the resulting ground millbase in a static caution in a fine granular and a coarse-grained fraction is separated. The fine-grained fraction can be supplied to the apparatus for prospecting fine material in a pneumatic, ie energy and cost-effective way. The coarser semolina fraction is first ground in the ball mill and then passes as a ground discharge material also in the classifier, where a fine material fraction is deposited and a coarse grain fraction discharged and recirculated to the first device for grinding. This structure, in which therefore a division of the grinding circuit is provided in two sub-circuits, offers a number of advantages. As a precautionary measure, the cascade classifier employs a classifier that not only guards the ground material from the first milling device, but also deagglomerates it, thus obviating the need for ball mill desaggregation processes (with the disadvantages described above). Furthermore, the semolina fraction from the static precautionary need not be returned mechanically to the first apparatus for grinding (with the disadvantages also described above), but is ground in the ball mill. This results in ground material to be discharged, which can be conveyed completely pneumatically and, together with the fines content of the first device for milling fresh material to be discharged, leads to a favorable particle size distribution of the cement or cement raw meal. In addition, the milling of the semolina fraction from the static cautery in the ball mill in the second partial cycle leads to a reduction in the number of cycles in the first partial cycle. And the use of a static cautery between the two grinders reduces the volume of the crop into the ball mill by looking at the fine-grained stock in the static cautery.

According to the invention, it is provided that the static guardian is a cascade classifier. Cascade classifiers not only allow a separation of coarse-grained and finer-kings in the ground regrind. In addition, they bear the impact of the good particles they contain on the cas- kadenartig arranged sheets in their sighting shaft to a considerable extent at a deagglomeration of agglomerated Mahlgutpartikel at, as they arise in devices for grinding regrind, especially in roller presses or high-pressure roller presses.

In an embodiment of the invention, it is provided to use as a device for the prospect of fines a rod basket sifter. Such a dynamic Sichtertypus is well known from practice, low maintenance and can be pneumatically flowed for the Guteintrag, which is energy and cost. Both the static cautery viewing process and the ball milling process result in such fine-grained, i.e. light Austragsgut that this, in the embodiment of the invention, in each case suspended in a Sichtluftvolumenstrom and pneumatically the Stabkorbsichter can be supplied. Depending on the classifier design, the view air volume flows pass through the same entry opening or through two different entry openings into the housing of the rod cage sifter for the common view. The sieved fines are collected in a discharge device of the bar cage and pneumatically guided to a separator where the fines are separated from the classifying air. The pneumatic transport of the ground output of the ball mill offers significant advantages over mechanical transport in terms of energy consumption, investment and maintenance costs. Should it be unavoidable because of the overall structure of a plant for cement production, a first part of the way from the ball mill to the rod basket sifter could also be bridged by means of a mechanical device, such as a bucket elevator.

In a particular embodiment of the invention, a roller press, a vertical mill or an impact hammer mill is used as the first device for grinding the fresh material. The invention is not limited to a Mahlvorrichtungsart here, but it may be useful to use different grinding devices according to the desired particle size distribution of the cement and depending on the nature of the fresh product. Regarding energy Cost, efficiency and material throughput and ease of operation is particularly close to the use of roller presses and vertical mills. Impact hammer mills also have energy advantages compared to ball mills.

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

Figure 1: a Kreislaufmahlanlage invention for grinding fresh food in the embodiment with roller press, ball mill, cascade classifier and shown in vertical section Stabkorbsichter;

Figure 2a: a section of the Kreislaufmahlanlage invention

Milling of fresh material, representing the embodiment with impact hammer mill as the first device for grinding the Frischguts;

Figure 2b: a section of the Kreislaufmahlanlage invention for

Milling fresh food, representing the embodiment with vertical mill as the first device for grinding the fresh material.

In Figure 1, the Kreislaufmahlanlage as a first device (2, 26, 27) for grinding of fresh goods, which is supplied via the fresh material supply 1, a roller press 2. The ground material to be ground 3 is mechanically placed in a arranged below the roller press 2, static caution, the cascade classifier 4, from above. By means of separately and transversely supplied thereto Sichtluft a separation of a fine-grained and a coarse-grained fraction is effected in the cascade classifier 4 by the fine material is classified in the air stream and discharged as fine-grained Austragsgut 8 still above through the discharge opening 6. (The processes in the interior of the cascade classifier 4 are not shown.) The fine-grained material to be discharged 8 is supplied with the classifying air volume flow 24 to the rod basket classifier 15 by pneumatic means. Furthermore, in the cascade classifier 4, the coarse-grained fraction falls downwards, cascading baffles arranged downwards. As a result of the impact of the coarse-particle slab material on the sheets, the material agglomerates therein are desag- glomerated and discharged downwards as semolina fraction 9 from the cascade classifier 4 through the discharge opening 7. The semolina fraction 9 falls into the product inlet 10 of a ball mill 1 1 arranged below the cascade classifier 4. The milled Austragsgut 13 leaves the ball mill 1 1 through the Gutauslauf 12. It is the Stabkorbsichter 15 supplied by pneumatic means through the Sichtluftvolumenstrom 25. It could be on the way between ball mill 1 1 and rod basket sifter 15 first, a mechanical transport of the ground Austragsguts 13, for example by means of a bucket elevator, done (not shown).

The classifying air volume flows 24, 25 with the fine-grained Austragsgut 8 from the cascade classifier 4 and the ground Austragsgut 13 from the ball mill 1 1 are introduced through at least one entry port 14a, 14b in the rod basket sifter 15. The suspended in the classifying air Austragsgut 8, 13 flows to the rod basket sifter 15 as shown laterally and is accelerated by the rotational movement of the rod basket sifter 15 in the viewing zone. The centrifugal forces acting on the particles of the Sichtguts result in cooperation with the friction force of the air flow to a separation of the Sichtguts into a coarse grain fraction 17 and a fraction of fines 18. The coarse grain fraction 17 is from the rod basket sifter 15 by gravity down from the viewing zone and through the discharge opening 1 6 discharged. Subsequently, the coarse grain fraction 17 is returned by mechanical means from above to the roller press 2 (recirculation), where it is ground together with the fresh material from the fresh material supply 1. The sieved fines 18 are transported pneumatically by the classifying air stream out of the rod cage sifter 15 and reach the discharge device 28. The discharge air flow 20 leaves the discharge air flow 20 with the fines and reaches the discharge device (here a cyclone) 21. In the separation device 21, the fine material 23 is separated from the classifying air stream 22 and can thus be stored in further processes of cement production in silos (not in the picture). FIG. 2 a shows a detail of the cycle grinding plant according to the invention for grinding fresh food. In the illustrated embodiment, the first device (2, 26, 27) for grinding the fresh product instead of a roller press 2 as shown in Figure 1 by an impact hammer mill 26 is formed. In addition, the structure and method are as shown in Figure 1.

In the same way, a section of the Kreislaufmahlanlage invention for grinding fresh food is shown in Figure 2b. In the illustrated embodiment, the first device (2, 26, 27) for grinding the fresh product instead of a roller press 2 as in Figure 1 or an impact hammer mill 26 as shown in Figure 2a by a vertical mill 27 is formed. In addition, the structure and method are as shown in Figure 1.

E N G L I S H E S T E

Frischgutzuführung 16 discharge opening

Roller press 17 Coarse grain fraction Ground regrind 18 fines

Cascade classifier 19 discharge opening

Inlet opening 20 Classifying air flow with fine material

Discharge opening 21 Separating device

Discharge opening 22 Classifying air

fine-grained material to be discharged 23 fines

Semolina fraction 24 View air volume flow

Guteinlauf 25 View air volume flow

Ball mill 26 Impact hammer mill

Gutauslauf 27 vertical mill

ground discharge material 28 discharge device

entry opening

Rod basket sifter

Claims

P A T E N T A N S P R E C H E

Milling plant for grinding fresh food, comprising a first device (2, 26, 27) for grinding the fresh product, wherein the first device (2, 26, 27) for grinding the fresh material ground grinding material (3) generates a static caution (4) for the precured grinding of the ground material (3) with an entry opening (5) for the ground material (3), a discharge opening (7) for a coarse semisolid fraction (9) and a further discharge opening (6) for the discharge of a fine-grained product (8 ), a device (15) for prospecting of fine material (18) with a discharge opening (1 6) for the discharge of a separated coarse grain fraction (17), with subsequent recirculation to the first device (2, 26, 27) for grinding the fresh product, a Discharge opening (19) for the selected fines (18) and at least one entry opening (14a, 14b), wherein one of the at least one entry opening (14a, 14b) with the discharge opening (6) for the fine-grained discharge good (8) of static cautery (4), a second device (11) for grinding regrind, the second device (11) for grinding regrind producing a ground material to be discharged (13), characterized in that the static cautery (4) is a cascade classifier (4), and the second device (1 1) for grinding material in the form of a ball mill (1 1) is present, wherein the ball mill (1 1) with the discharge opening (7) for the coarse Grießefraktion (9) of the cascade classifier (4) in conjunction having standing Guteinlauf (10), and one with one of the at least one entry opening (14a, 14b) of the device (15) for prospecting of fines (18) in connection Gutauslauf (12) for the ground Austragsgut (13).

2. Plant according to claim 1, characterized in that the device (15) for prospecting of fine material (18) is a rod basket sifter (15).

3. Plant according to claim 2, characterized in that a pneumatic feed of the fine-grained Austragsguts (8) from the cascade classifier (4) in one of the at least one entry port (14a, 14b) of the Stabkorbsichters (15), and a pneumatic feed of the ground Austragsguts (13) from the ball mill (1 1) in one of the at least one entry opening (14a, 14b) of the rod basket sifter (15) is provided, each with a classifying air volume flow (24, 25).

4. Installation according to one of claims 1 to 3, characterized in that the first device (2, 26, 27) for grinding the fresh material is an impact hammer mill (26) or preferably a roller press (2) or a vertical mill (27).