Grinding system

Abstract

The grinding system according to the invention has an agitator ball mill having an inlet for grinding material to be comminuted and an outlet for comminuted grinding material, and a first separation unit arranged separately from the agitator ball mill, wherein the first separation unit is connected to the outlet for comminuted grinding material and has an outlet for a first fine material and an outlet for a first coarse material. Furthermore, a second separation unit is provided which is arranged separately from the agitator ball mill, is connected directly or indirectly to the outlet for comminuted grinding material of the agitator ball mill and has an outlet for a second fine material and an outlet for a second coarse material.

Description

[0001] Grinding plant

[0002] The invention relates to a grinding plant for crushing material to be ground, comprising at least one agitator ball mill and a separation unit.

[0003] Examples of materials used for grinding include limestone, dolomite, ores, clinker, fly ash, slag, and other cement clinker substitutes. A grinding plant for such materials is known from DE 10 2014 015 549 Al. To reduce the clinker factor in the cement industry and thus lower CCE emissions, efforts are being made to use cement clinker substitutes (such as calcined clays or slag) or more reactive clinkers for cement products. One way to increase the reactivity of clinker and cement clinker substitutes is to finely grind these materials. Industrially, this fine grinding is achieved, for example, using a dry-operated stirred ball mill.

[0004] Cement clinker substitutes often contain components that are difficult to grind. These components cannot be efficiently milled using conventional vertical roller mills and / or ball mills because the difficult-to-grind portion of the material accumulates in the mill's circulation and is thus primarily carried back to the mill via the classifier grit. This, in turn, leads to the more easily ground material being over-milled. As a result, the specific energy input increases and the plant's throughput decreases. A further challenge is that the final product must not only have the desired fineness but also a specified particle size distribution.

[0005] A multi-stage grinding cycle is known from US 2020 / 261920 Al.

[0006] From EP 3 665 133 Bl a process and a plant for the production of cement are known.

[0007] A vertical mill with external circulation for cement, combined with a high-performance grinding process system, is known from CN 113 976 277 B. The invention is based on the objective of making the operation of the grinding plant with a stirred ball mill more efficient.

[0008] According to the invention, this problem is solved by a grinding system according to claim 1. Further embodiments of the invention are the subject of the dependent claims.

[0009] The grinding system according to the invention comprises a stirred ball mill with an inlet for material to be ground and an outlet for ground material, as well as a first separation unit arranged separately from the stirred ball mill. The first separation unit is connected to the outlet for ground material and has an outlet for a first fine product and an outlet for a first coarse product. Furthermore, a second separation unit is provided, arranged separately from the stirred ball mill, which is connected directly or indirectly to the outlet for ground material of the stirred ball mill and has an outlet for a second fine product and an outlet for a second coarse product.

[0010] According to the invention, the ground material can be fed to two different or two identical separation units connected in parallel or in series. In a parallel connection, the product flow can be variably divided, for example 50 / 50, 80 / 20, etc., so that the load on each individual separation unit can be precisely adjusted. According to the invention, more than two separation units can also be used.

[0011] Furthermore, the two separation units can be variably configured, allowing the production of fines with different particle size distributions. These fines can then be selectively mixed to obtain a finished product with a predetermined fineness, particle size distribution, and distribution width. This allows for targeted control over the subsequent quality properties of the cement (such as water demand, slump, etc.).

[0012] Furthermore, independently adjustable separation units make it possible to selectively remove components that are difficult to grind. This is achieved, for example, by setting a relatively coarse and broad particle size distribution on one of the separation units, allowing coarse, difficult-to-grind particles to leave the grinding circuit. To achieve the desired target fineness, the remaining separation unit(s) are adjusted accordingly to a finer setting.

[0013] The agitated ball mill used preferably has an agitator rotating about an axis, with the inlet for the material to be ground being located at one axial end of the agitator and the outlet for the ground material at the opposite axial end. Furthermore, the inlet of the agitated ball mill can be configured for feeding the material to be ground with or without air, while the outlet of the agitated ball mill has a pneumatic discharge opening for the pneumatic discharge of a first portion of the ground material together with air, and the outlet also provides a gravity discharge opening for the discharge of a second portion of the ground material by gravity, with the first separation unit being connectable to the pneumatic discharge opening and the second separation unit to the gravity discharge opening.Furthermore, the first and second separation units can each have a coarse material outlet that connects to the inlet of the stirred ball mill and / or another process unit (e.g., a peripheral grinding unit in a different grinding circuit; a mixer; a hopper / silo to utilize material for other products). It is also possible to feed one or both coarse materials (completely or partially) to another process step (e.g., storage, mixing, grinding in a different grinding circuit, thermal processes).

[0014] The first and second separation units can be formed, in particular, by sieves, static classifiers, electrostatic sifters, or dynamic classifiers. According to the invention, however, airflow classifiers, especially crossflow rotary basket classifiers, are used for both separation units, which are particularly efficient for medium particle sizes in the range of 0.5 pm to 30 pm. The separation limit of this type of classifier is essentially determined by the centrifugal acceleration at the outer rotor diameter. Therefore, very high centrifugal accelerations are required to obtain very fine products (medium particle size < 10 pm, possibly < 5–7 pm). Furthermore, higher peripheral speeds are required for a constant centrifugal acceleration with increasing rotor diameter (azF = u). 2 / rR O t orDue to this relationship and design constraints, air classifiers for fine grinding should not exceed a certain size. Since preferably at least two air classifiers are provided, the grinding plant can be implemented with correspondingly higher throughputs. Furthermore, if the air classifiers are operated independently of each other, for example by adjusting their airflow rates independently, both types of fines produced can be specifically controlled.

[0015] If the separation units are designed as airflow classifiers, a first separator is connected to the first fines outlet of the first separation unit to separate the first fines from the classifying air, and a second separator is connected to the second fines outlet of the second separation unit to separate the second fines from the classifying air. In this way, two different types of fines can be produced.

[0016] The two resulting fine materials can be fed into separate or a shared fine material silo. Furthermore, it may be advantageous to feed one or both fine materials to another processing unit (e.g., a separate milling unit).

[0017] In a further embodiment of the invention, a mixing device is provided for mixing the first fine material with the second fine material. This allows a finished product with a desired particle size distribution to be specifically produced.

[0018] Further embodiments of the invention are explained with reference to the following description of some exemplary embodiments and the drawing.

[0019] In the drawing, Fig. 1 shows a schematic representation of a grinding plant according to the invention in a first embodiment,

[0020] Fig. 2 shows a schematic representation of a grinding plant according to the invention in a second embodiment,

[0021] Fig. 3 shows a schematic representation of a stirred ball mill,

[0022] Fig. 4 shows a schematic representation of a grinding plant according to the invention in a third embodiment,

[0023] Fig. 5 shows a schematic representation of a grinding plant according to the invention in a fourth embodiment,

[0024] Fig. 6 shows a schematic representation of a grinding plant according to the invention in a fifth embodiment and

[0025] Fig. 7 shows a schematic representation of a grinding plant according to the invention in a sixth embodiment.

[0026] The grinding plant shown in Fig. 1 comprises a stirred ball mill 1, a first separation unit 2 designed as an air classifier, and a second separation unit 3 also designed as an air classifier. The stirred ball mill 1 has an inlet 1.1 for material to be ground 4 and an outlet 1.2 for ground material 4'. The material to be ground 4 consists of one or more components 4.1, 4.2 held in storage silos 5, 6, as well as recycled coarse material, and is fed to the inlet 1.1 of the stirred ball mill 1 via at least one conveying element 7.

[0027] The agitated ball mill 1 used has an agitator 1.3 rotating about an axis, with the inlet 1.1 for the material 4 to be ground being located at one axial end of the agitator 1.3 and the outlet 1.2 for the ground material 4' being located at the opposite axial end of the agitator 1.3. Furthermore, the inlet 1.1 of the agitated ball mill 1 can be configured to feed the material 4 to be ground with or without conveying air. The grinding action is carried out by the agitator 1.3 in conjunction with grinding balls.

[0028] 1.4 within the grinding chamber 1.5. At the end of the grinding chamber 1.5 facing the outlet, a separating device 1.6 is provided, which allows the sufficiently ground material 4' to pass through and the grinding balls 1.4 in the grinding chamber.

[0029] 1.5 retains. Via a conveying device 1.7, for example a screw conveyor, the crushed material 4' reaches the outlet 1.2, from where it is transported either pneumatically and / or mechanically to the two separation units 2, 3.

[0030] In the first embodiment, the material 4' ground in the stirred ball mill 1 is divided into two partial streams 4.1' and 4.2', with one partial stream 4.1' being fed to the first separation unit 2 and the second partial stream 4.2' being fed to the second separation unit 3. Both separation units 2 and 3 are thus in direct communication with the outlet 1.2 of the stirred ball mill 1.

[0031] The first separation unit 2 has an outlet 2.1 for a first fines 8 and an outlet 2.2 for a first coarses 9. Similarly, the second separation unit 3 has an outlet 3.1 for a second fines 10 and an outlet 3.2 for a second coarses 11. While the two coarses 9 and 11 are conveyed back to the inlet 1.1 of the agitator ball mill for further comminution, the two fines 8 and 10, together with the classifying air, enter a separator 12 or 13, where the fines 8 and 10 are separated from the classifying air. The adjustment of the sight air volume flow of the two separation units 2, 3 is effected by a fan 14, 15 downstream of the respective separator 12, 13. In principle, it is also conceivable that only one common fan is provided, whereby, if necessary, the volume flow control of the sight air in the two separation units 2, 3 can be effected, for example, by dampers.

[0032] The maximum size of an air classifier for the desired fineness, particularly < 6 pm, is limited, whereas the stirred ball mill 1 can certainly be designed for larger throughputs. By providing two separation units 2, 3 and thus being able to divide the ground material 4' between the two separation units, a grinding plant with higher throughputs can be realized. Furthermore, it is possible to produce two different fine materials 8, 10, which can be used individually or mixed together.

[0033] In the following descriptions of exemplary embodiments, the same reference numerals are used for identical components.

[0034] While the two separation units 2, 3 of the first embodiment are arranged parallel to each other, Fig. 2 shows a second embodiment with the two separation units 2, 3 connected in series. Here, all the material 4' ground in the stirred ball mill 1 is fed to the first separation unit 2, which is again designed as an air classifier. There, in combination with the separator 12, the first fines 8 are separated. All the coarse material 9 from the first separation unit 2 is fed to the second separation unit 3, which, in combination with the separator 13, produces the second fines 10. The coarse material 11 from the second separation unit 3 is returned to the inlet 1.1 of the stirred ball mill 1 and fed in together with the fresh material from the storage silos 5, 6.

[0035] This grinding system efficiently removes fine particles from the ground material (4') through double screening, thus largely preventing over-grinding. Furthermore, different materials suitable for grinding can be selectively removed. The system's circulation rate can also be optimized for energy-efficient operation.

[0036] The stirred ball mill 1 used in the following embodiments (Figs. 4 to 7) is shown in Fig. 3 and differs only in the design of the outlet 1.2 from the stirred ball mill 1 used in Figs. 1 and 2. These embodiments could, in principle, also be implemented with a stirred ball mill 1 according to Fig. 1. For all embodiments, it is also possible to discharge or recirculate the ground material in a defined ratio.

[0037] The outlet 1.2 has a discharge housing 1.2.1 with a pneumatic discharge opening 1.2.2 for the pneumatic discharge of a first partial stream 4.1' of the comminuted material 4' together with air 16 introduced either into the discharge housing 1.2.1 or supplied via the inlet 1.1 of the stirred ball mill. Furthermore, a gravity discharge opening 1.2.3 is provided for the discharge of a second partial stream 4.2' of the comminuted material 4' by gravity. Thus, a pre-classification of the comminuted material 4' takes place in the discharge housing 1.2.1, such that the pneumatically discharged partial stream 4.1' contains a finer component and the gravity-discharged partial stream 4.2' contains a coarser component. This has the advantage that the two separation units 2, 3 can be adjusted in a more targeted manner, thus enabling more efficient screening.Optimal coordination of the milled product and the two vision circuits is also possible.

[0038] The third embodiment according to Fig. 4 corresponds essentially to the first embodiment, except that the separation of the material 4' ground in the stirred ball mill 1 (according to Fig. 3) is not based on quantity, but rather on pneumatic discharge for the partial stream 4.1' and gravity discharge for the partial stream 4.2', with partial stream 4.1' being fed to the first separation unit 2 and partial stream 4.2' to the second separation unit 3. Furthermore, a pre-classification of the ground material 4' takes place in the discharge housing 1.2.1 of the stirred ball mill 1. Here, too, optimal coordination of the milled product and the two classification circuits is possible.

[0039] Fig. 5 shows an optional variant of the third embodiment according to Fig. 4, in which the fines 10 from the second separation unit 3 are fed wholly or partially to the first separation unit 2. Furthermore, only one fan 14 is used for both separation units 2 and 3. Separate fans for each separation unit would also be conceivable. With this grinding plant, it is particularly advantageous to design the first separation unit 2 as an ultrafine classifier for separating a mean particle size of less than 6 pm, while the second separation unit 3 can be designed as a conventional classifier for separating a mean particle size greater than 6 pm.

[0040] This circuit is particularly suitable for producing the largest possible quantity of fines with an average particle size of less than 6 g / m². Furthermore, it allows for an optimized selection of classifiers with regard to the mill's material discharge.

[0041] The fifth embodiment according to Fig. 6 again shows a series connection of the two separation units 2, 3, wherein all the comminuted material 4' (partial streams 4.1' and 4.2') is fed to the first separation unit 2. Although a stirred ball mill 1 according to Fig. 3 is used here, a stirred ball mill according to Figs. 1 and 2 can also be provided. The fines 8 from the first separation unit 2 are fed wholly or partially to the second separation unit 3. The coarses 9 from the first separation unit 2 enter a third separation unit 17, which is formed, for example, by a screen or a static classifier, wherein the fines from the third separation unit 17 are also fed to the second separation unit 3, while the coarses 18 from the third separation unit 17 are discharged or, together with the coarses 11 from the second separation unit 3, are fed back to the stirred ball mill 1.

[0042] In this circuit, the second separation unit 2 is expediently designed as an ultrafine classifier for separating average particle sizes of less than 6 pm. The first separation unit can be configured as a conventional airflow classifier or as an ultrafine classifier for separating average particle sizes of less than 6 pm. Furthermore, more efficient loading of the ultrafine classifier is possible. The resulting intermediate products can be used for various types of cement (clinker reduction / CCE reduction / cements of the future).

[0043] The grinding plant according to Fig. 7 essentially corresponds to the grinding plant according to Fig. 4, with the only addition being a mixing device 19 for mixing the first fine material 8 with the second fine material 10 to produce a finished product 20. The desired particle size distribution in the finished product 20 can be set by adjusting the mixing ratio.

[0044] This grinding system allows the particle size distribution of the finished product 20 (mixture of the two fine products 8, 10) to be very precisely controlled with regard to fineness,

[0045] Adjusting particle size distribution and distribution width makes it possible to influence the subsequent quality properties of the cement (water demand, spread, etc.).

Claims

Patent claims:

1. Grinding plant with a stirred ball mill (1) having an inlet (1.1) for material to be ground (4) and an outlet (1.2) for ground material (4') and a first separation unit (2) arranged separately from the stirred ball mill (1), which is connected to the outlet (1.2) for ground material (4') and has an outlet (2.1) for a first fine product (8) and an outlet (2.2) for a first coarse product (9), characterized in that a second separation unit (3) arranged separately from the stirred ball mill (1) is provided, which is directly or indirectly connected to the outlet (1.2) for ground material (4') of the stirred ball mill (1) and has an outlet (3.1) for a second fine product (10) and an outlet (3.2) for a second coarse product (11), wherein the first separation unit (2) and the second separation unit (3) is designed as an airflow classifier and is connected to the first fines outlet (2.1) of the first separation unit (2) a first separator (12) for separating the first fines (8) from the classifying air and to the second fines outlet (3.1) of the second separation unit (3) a second separator (13) for separating the second fines (10) from the classifying air is connected.

2. Grinding plant according to claim 1, wherein the stirred ball mill (1) has an agitator (1.3) rotating about an axis and the inlet (1.1) for material to be ground (4) is located at an axial end of the agitator (1.3) and the outlet (1.2) for ground material (4') is located at an opposite axial end of the agitator (1.3).

3. Grinding plant according to one of the preceding claims, wherein the inlet (1.1) of the stirred ball mill (1) is designed for feeding the material (4) to be ground and the outlet (1.2) of the stirred ball mill has a pneumatic discharge opening (1.2.2) for pneumatically discharging a first partial stream (4.1') of the ground material (4') together with air and the outlet (1.2) further comprises a gravity discharge opening (1.2.3) for discharge provides for a second partial stream (4.2') of the crushed material (4') by means of gravity.

4. Grinding plant according to one of the preceding claims, wherein the first separation unit (2) and the second separation unit (3) each have a coarse material outlet (2.2; 3.2) which are connected to the inlet (1.1) of the stirred ball mill (1) and / or another process unit.

5. Grinding plant according to one of the preceding claims, wherein the first separation unit (2) and the second separation unit (3) are designed as airflow classifiers, the classifying air volume flows of which are independently adjustable.

6. Grinding plant according to one of the preceding claims, wherein a common or two separate fines silos are provided for the first fines (8) and the second fines (10).

7. Grinding plant according to one of the preceding claims, wherein at least one further process unit is provided for further processing of the first and / or second fine material (8, 10).

8. Grinding plant according to one of the preceding claims, wherein a mixing device (19) is provided for mixing the first fine material (8) with the second fine material (10) to produce a finished product (20) with an adjustable particle size distribution.

9. Grinding plant according to one of the preceding claims, wherein the first separation unit (2) and the second separation unit (3) are arranged in a series circuit or a parallel circuit.

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