EP3154701B1 - Grinding system and method for comminution of grinding stock - Google Patents

Description

The invention relates to a grinding plant and a method for comminuting grinding material with a first grinding circuit having a roller press and a first classifier and a second grinding circuit having a dynamic classifier and a ball mill.

The ground material used in crushing preferably consists of a brittle material such as limestone, dolomite or ore. In cement production, the ground material also preferably consists of clinker, slag and/or fly ash.

From the DE 43 03 987 A1 A grinding plant with a first and a second grinding circuit is known, whereby the first grinding circuit is operated with a high-pressure roller press and a dynamic sifter arranged above it. The fine material from the first grinding circuit goes into a cyclone and from there into a ball mill. The material ground in the ball mill is separated into finished product and grits in a second dynamic sifter, whereby the grits are returned to the ball mill.

High-pressure roller presses usually have two rollers that are driven in opposite directions and form a grinding gap between them, which are subjected to grinding pressures of 50 MPa and more via a pressing device. Such high pressures lead to so-called material bed comminution in the grinding gap, which means that the crushed material to be ground comes out of the roller press partly in the form of flakes or agglomerates. In order to sift such material to be ground in a dynamic sifter, a deagglomerator is often installed upstream.

In one of the EP 1 506 058 B1 In the known finished grinding circuit with a roller press, the deagglomerator is replaced by a static classifier. For the transport of the ground material to the dynamic classifier, A conveyor unit, in particular a bucket elevator, is used, which is adapted to the quantity to be transported and causes not inconsiderable investment and operating costs. In the EP 1 506 058 B1 The aim was to create a compact circulating grinding plant with a roller press and sifter, in which the problem of mechanical transport of the circulating ground material is minimized. The solution to this problem was to arrange a static cascade sifter below the roller gap of the roller press, while a dynamic post-sifter with its coarse material outlet was provided above the roller press. The static cascade sifter's main task is to deagglomerate the agglomerates and simultaneously sift the sifted material in the cross flow. The sifted material discharged from the static cascade sifter is fed pneumatically into the post-sifter via a riser channel with the sifting air. This solution saves investment costs, operating costs and space for installing a mechanical conveyor unit that would otherwise be necessary, such as a bucket elevator.

From the EP 0 629 448 A2 A grinding plant with a pre-mill and a fine mill as well as a static and a dynamic classifier is known.

With a finished grinding circuit, it is usually possible to achieve a final product fineness of around 3,000 cm ² /g. However, if greater fineness is required and, in particular in the field of cement production, different types of mixed cement are required, a combination grinding plant with a first and a second grinding circuit must be used for energy reasons.

The invention is therefore based on the object of specifying a grinding plant and a method for comminution of grinding material with a first and a second grinding circuit, which are characterized by reduced investment and operating costs.

According to the invention, this object is achieved by the features of claims 1 and 5. Advantageous embodiments of the invention are the subject of the further claims.

The grinding system according to the invention for comminuting grinding material consists essentially of a first grinding circuit having a roller press and a first sifter and a second grinding circuit having a dynamic sifter and a ball mill. The first sifter is designed as a static sifter and is arranged below the roller press, while the dynamic sifter is provided at the level of the roller press or below the roller press. A buffer storage is provided between the dynamic sifter and the ball mill. The grit from the dynamic sifter is fed to the ball mill via the buffer storage. The buffer storage has an overflow connected to the first grinding circuit and/or wherein the amount of grit produced is adapted to the capacity of the ball mill by influencing the amount of fine material from the static sifter.

In the method according to the invention for comminuting ground material, the ground material is comminuted in a first grinding circuit, which has a roller press and a first sifter, and a second grinding circuit, which has a dynamic sifter and a ball mill. The first sifter is designed as a static sifter and is arranged below the roller press. The dynamic sifter is arranged at the level of the roller press or below the roller press. Grit from the dynamic sifter is fed to the ball mill via a buffer storage. The buffer storage has an overflow connected to the first grinding circuit and/or the amount of grit produced is adapted to the capacity of the ball mill by influencing the amount of fine material from the static sifter.

A roller press in the sense of the invention is understood to be a roller mill with two grinding rollers driven in opposite directions and pressed against each other while maintaining a grinding gap. The static classifier is characterized by The main difference between the dynamic classifier and the dynamic classifier is that it has no rotating or turning components during operation. It usually consists of a slanted ventilation base, which can also be designed in a cascade shape and through which a classifying air flow flows. The dynamic classifier usually has a rotating rod basket or rotor.

The conveying distances in the circulation circuits can be minimized by the static classifier of the first grinding circuit arranged below the roller press and the dynamic classifier in the second grinding circuit arranged at the maximum level of the roller press.

According to a further embodiment of the invention, the first grinding circuit further comprises a first conveying unit arranged between a coarse material outlet of the static classifier and a feed shaft of the roller press. Furthermore, a second conveying unit arranged between a discharge opening of the ball mill and a feed opening of the dynamic classifier is provided in the second grinding circuit. This connection means that only the coarse material from the static classifier is returned to the roller press. The first conveying unit provided for this purpose can therefore be made smaller, which can save investment and operating costs.

The dynamic sifter can have a finished product outlet and a semolina outlet. The grinding system according to the invention is preferably designed so that the semolina from the dynamic sifter is only fed to the ball mill. The semolina should only be returned to the first grinding circuit in exceptional cases, in particular when the amount of semolina exceeds the processing capacity of the ball mill. According to a further embodiment of the invention, a buffer storage unit is therefore provided between the dynamic sifter and the ball mill, which has an overflow connected to the first grinding circuit. Instead of or in addition to the overflow, it can also be provided that the amount of semolina produced is adapted to the capacity of the ball mill by influencing the amount of fine material from the static sifter.

This can be done by influencing the quantity of the material to be ground (fresh material) fed into the first grinding circuit and/or by regulating a sifting air flow used in the static sifter so that the quantity of grit accumulating in the dynamic sifter is adapted to the capacity of the ball mill. These or other measures are intended to ensure that more than 80%, preferably more than 90% or more than 95%, most preferably the entire quantity of grit is fed to the ball mill.

Due to the significantly, preferably completely, reduced return of grit to the first grinding circuit, the conveying volume of the first conveying unit can be correspondingly smaller. The reduced conveying volume of the first conveying unit and the reduced conveying head of the second conveying unit result in significant savings in investment and operating costs. The omission of a dynamic sifter above the roller press also results in a relatively compact overall arrangement of the grinding plant.

The invention is explained in more detail below with reference to the description of some embodiments and the drawing.

Fig. 1

schematische Darstellung einer Mahlanlage mit einem auf Höhe der Walzenpresse angeordneten dynamischen Sichter,

Fig. 2

schematische Darstellung einer Mahlanlage mit einem unterhalb der Walzenpresse angeordneten dynamischen Sichter,

Fig. 3

schematische Darstellung eines dynamischen Sichters mit einem Pufferspeicher mit Überlauf und

Fig. 4

schematische Darstellung eines dynamischen Sichters mit einer Füllstandsmesseinrichtung im Pufferspeicher.

Show in the drawing

Fig.1

schematic representation of a grinding plant with a dynamic classifier arranged at the level of the roller press,

Fig.2

schematic representation of a grinding plant with a dynamic classifier arranged below the roller press,

Fig.3

schematic representation of a dynamic classifier with a buffer tank with overflow and

Fig.4

Schematic representation of a dynamic classifier with a level measuring device in the buffer storage.

In Fig.1 a grinding plant for crushing brittle grinding material such as limestone, clinker, dolomite or ore is shown. It essentially consists of a first grinding circuit 3 with a roller press 1 and a static classifier 2 and a second grinding circuit 6 with a dynamic classifier 4 and a ball mill 5. The roller press has two counter-rotating grinding rollers 1a, 1b in the usual way. The two grinding rollers are subjected to grinding pressures of 50 MPa and more via a pressing device (not shown in detail) while maintaining a grinding gap.

The first grinding circuit 3 also has a first conveyor unit 7, in particular a bucket elevator, arranged between a coarse material outlet 2b of the static sifter 2 and a feed shaft 1c of the roller press 1. The roller press is also connected to a feed opening 2a of the static sifter 2 via an outlet opening 1d. The connection between the roller press and the static sifter is expediently made via a chute 8, so that the crushed material is fed into the static sifter by gravity without any energy expenditure. The grinding material (fresh material 9) to be fed into the first grinding circuit 3 is fed in the area of the chute 8 or the feed opening 2a of the static sifter 2. The fresh material 9, which can already contain a certain proportion of fine material, is thus only separated into coarse material and fine material in the static sifter, so that only the coarse material is conveyed to the feed shaft 1c of the roller press 1.

The static classifier 2 has an obliquely arranged ventilation base 2d through which a classifying air flow 10 flows. While the coarse material follows gravity to the coarse material outlet 2b, the fine material is guided together with the classifying air flow via the fine material outlet 2c into the dynamic classifier 4.

The dynamic classifier 4 is designed, for example, as a rod basket classifier with a tangentially arranged inlet opening 4a. The dynamic classifier The ground material supplied is sifted into semolina and finished product, with the semolina being fed to the ball mill 5 via a semolina outlet 4b. The connection can be formed, for example, by a chute or, if the gradient is insufficient, as an air flow channel. The finished product is fed together with the sifting air flow via a finished product outlet 4c to a separator 11, where the finished product 12 is separated from the sifting air flow 10. In the ball mill 5, the semolina is further crushed and then returned to the dynamic sifter 4 either via a further separator 13 or directly via a second conveyor device 14. The further separator 13 can be necessary in particular if the ball mill 5 is operated with an air flow.

The embodiment according to Fig.2 differs from the first embodiment essentially only in that the dynamic classifier 4' of the 2nd grinding circuit 6 is arranged below the roller press 1. The static classifier 2 is in turn arranged below the dynamic classifier 4'. The inlet opening 4'a of the dynamic classifier 4 is this time arranged at the lower end of the classifier, so that the classifying air flow 10 flows into the dynamic classifier 4' together with the fine material from the static classifier 2 from the bottom to the top. The other details of this 2nd grinding system and its mode of operation are the same as those of the first grinding system. Of course, the classifier 4' can also be used instead of the classifier 4 and vice versa.

The two grinding systems are preferably operated in such a way that the grit produced in the dynamic classifier 4 or 4' is returned to the first grinding circuit in as small a quantity as possible, but preferably not at all (return line 15 shown in dashed lines). For this purpose, the dynamic classifier 4 or 4' is equipped with a grit cone or a buffer storage 16 ( Fig.3 and 4 ). The required amount can be fed to the ball mill 5 in a metered manner via a metering device 17, for example a cell lock or a screw. The buffer storage 16 according to Fig.3 is provided with an overflow 18, which is connected to the first grinding circuit 3 via the return line 15. The Return line 15 conveniently opens into the area of the first conveyor device 7.

However, the overflow 18 should only be used in exceptional cases, so that the aim is to operate the grinding system in such a way that no grit is returned to the first grinding circuit via the return line 15. The amount of grit produced depends primarily on the fines content of the static sifter 2. Suitable measurements, such as a flow measurement in the area of the return line 15 to determine the returned grit mass flow or a measurement of the power consumption of the first conveyor device 7 and/or a single-roller belt scale after the first conveyor device 7 to determine the circulating mass flow of the first grinding circuit, can be used to determine whether the amount of grit produced is too large. Any necessary influence on the fines content of the static sifter can essentially be achieved by adjusting the amount of the sifting air flow 10 or regulating the amount of fresh material 9 fed in.

Fig.4 shows yet another variant in which a return line 15 is dispensed with. The dynamic sifter is in turn equipped with a buffer storage 16, which has a level measuring device 19. If the level is too low, for example, the amount of fresh material and/or the sifting air flow 10 is increased. If the level is too high, the amount of fresh material and/or the sifting air flow 10 is reduced.

Claims (10)

1. A grinding installation for comminuting grinding material, having a first grinding circuit (3), which comprises a roller press (1) and a first separator, and having a second grinding circuit (6), which comprises a dynamic separator (4, 4') and a ball mill (5),

   wherein the first separator is in the form of a static separator (2) and is arranged below the roller press (1), whereas the dynamic separator (4, 4') is provided at the level of the roller press or below the roller press

   characterized in that

   a buffer store (16) is provided between the dynamic separator (4, 4") and the ball mill (5) and the grits from the dynamic separator are fed to the ball mill (15) via the buffer store (16);

   wherein the buffer store comprises an overflow connected to the first grinding circuit and/or

   wherein the arising quantity of grit is adapted to the capacity of the ball mill through influencing of the quantity of the fine material of the static separator.
2. The grinding installation as claimed in claim 1, characterized in that the first grinding circuit (5) furthermore comprises a first conveying unit (7) arranged between a coarse-material outlet (2b) of the static separator (2) and a feed shaft (1c) of the roller press (1), and, in the second grinding circuit (6), a second conveying unit (14) is provided which is arranged between a discharge opening of the ball mill (5) and an inlet opening (4a) of the dynamic separator (4).
3. The grinding installation as claimed in claim 1, characterized in that the static separator (2) comprises a fine-material outlet (2d) which is connected to an inlet opening (4a) of the dynamic separator (4) for the supply of fine material of the static separator (2) to the dynamic separator.
4. The grinding installation as claimed in claim 1, characterized in that the dynamic separator (4) comprises a finished-material outlet (4c) and a grit outlet (4b).
5. A method for comminuting grinding material with the following steps:

   comminuting the grinding material in a first grinding circuit (3), which comprises a roller press (1) and a first separator, and in a second grinding circuit (6), which comprises a dynamic separator (4) and a ball mill (5), wherein the first separator is in the form of a static separator (2) and which is arranged below the roller press (1), and wherein the dynamic separator (4) is arranged at the level of the roller press (1) or below the roller press;

   feeding the grits from the dynamic separator to the ball mill (15) via the buffer store (16);

   wherein the buffer store comprises an overflow connected to the first grinding circuit and/or

   wherein the arising quantity of grit is adapted to the capacity of the ball mill through influencing of the quantity of the fine material of the static separator.
6. The method as claimed in claim 5, characterized in that grinding material comminuted in the roller press (1) is separated in the static separator (2) into coarse material and fine material, wherein the coarse material is recirculated to the roller press (1) and the fine material is fed to the dynamic separator (4).
7. The method as claimed in claim 5, characterized in that grinding material supplied to the dynamic separator (4) is separated into grit and finished material.
8. The method as claimed in claim 7, characterized in that the entire quantity of grit arising in the dynamic separator (4) is conducted to the ball mill (5).
9. The method as claimed in claim 8, characterized in that the quantity of fine material of the static separator (2) is adapted by influencing the quantity of grinding material fed to the first grinding circuit (3), and/or by regulating a separating air flow (10) used in the static separator (2), such that the quantity of grit arising in the dynamic separator (4) is adapted to the capacity of the ball mill (5).
10. The method as claimed in claim 5, characterized in that, in the static separator (2), for the separation of the material comminuted in the roller press (1), use is made of a separating air flow (10) by way of which the fine material arising in said static separator is transported to the dynamic separator (4).

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