阅读说明：本技术 两级研磨回路和借助于两级研磨工艺来生产研磨产品的方法 (Two-stage grinding circuit and method for producing a ground product by means of a two-stage grinding process ) 是由 圭多·卡什 迈克尔·维尔切克 比约恩-奥拉夫·阿斯曼 于 2018-07-10 设计创作，主要内容包括：本发明涉及一种两级研磨回路,其主要包括：第一研磨级(1),其包括立式辊磨机(10),该立式辊磨机具有研磨台(11)、与研磨台(11)配合的至少一个研磨辊(12)和第一动态分离器(13),第一动态分离器(13)包括用于排出细料(5)的细料出口(15)和用于将沙砾(8)返回至研磨台(11)的沙砾返回器(16)；以及第二研磨级(2),其具有由搅拌球磨机或球磨机形成的第二研磨机(20),该第二研磨机(20)包括入口(21)和出口(22)。此外,设置有用于提取一部分沙砾(8)的沙砾提取装置(18),该沙砾提取装置连接至沙砾返回器(16)并且连接至第二研磨机(20)的入口(21)。(The invention relates to a two-stage grinding loop, which mainly comprises: a first grinding stage (1) comprising a vertical roller mill (10) having a grinding table (11), at least one grinding roller (12) cooperating with the grinding table (11) and a first dynamic separator (13), the first dynamic separator (13) comprising a fines outlet (15) for discharging fines (5) and a grit return (16) for returning grit (8) to the grinding table (11); and a second grinding stage (2) having a second grinding mill (20) formed by a stirred ball mill or a ball mill, the second grinding mill (20) comprising an inlet (21) and an outlet (22). Furthermore, a sand extraction device (18) for extracting a portion of the sand (8) is provided, which is connected to the sand reflector (16) and to the inlet (21) of the second mill (20).)

1. A two-stage polishing circuit, comprising:

a. a first grinding stage (1) comprising a vertical roller mill (10), the vertical roller mill (10) having a grinding table (11), at least one grinding roller (12) cooperating with the grinding table (11) and a first dynamic separator (13), wherein the first dynamic separator comprises a fines outlet (15) for discharging fines (5) and a grit return (16) for returning grit (8) to the grinding table (11), and

b. a second grinding stage (2) comprising a second grinding mill (20) formed by a stirred ball mill or a ball mill, wherein the second grinding mill (20) comprises an inlet (21) and an outlet (22),

characterized in that a gravel extraction device (18) for extracting a portion of the gravel (8) is also provided, connected to the gravel return (16) and communicating with the inlet (21) of the second grinding mill (20).

2. A two-stage grinding circuit according to claim 1, characterized in that a single-stage or multi-stage separating or classifying device (23) is arranged between the grit extraction device (18) and the inlet (21) of the second grinding mill (20), which separating or classifying device comprises an inlet for extracted grit, a first outlet for coarser grit (8a) and a second outlet for finer grit (8b), wherein the inlet of the separating or classifying device (23) communicates with the grit extraction device (18), the first outlet communicates with the vertical roller mill (10) and the second outlet communicates with the second grinding mill (20).

3. A two-stage grinding circuit according to claim 1, characterized in that the second grinding stage (2) comprises a second dynamic separator (25) having an inlet, a fines outlet and a coarse outlet, wherein the outlet (22) of the second grinding mill (20) is connected to the inlet of the second dynamic separator (25) and the coarse outlet of the second dynamic separator (25) is connected to the inlet (21) of the second grinding mill (20).

4. A two-stage grinding circuit according to claim 1, characterized in that the fines outlet (15) of the first dynamic classifier (13) and/or the outlet (22) of the second grinder (20) are in communication with a bin of finished material.

5. A method for producing an abrasive product by means of a two-stage grinding process, wherein,

a. in a first grinding stage (1), the material to be ground is ground in a vertical roller mill (10) having a grinding table (11) and at least one grinding roller (12) cooperating with the grinding table (11) and is separated in a first dynamic separator (13) into fines (5) and grit (8), wherein at least a portion of the fines (8) is returned to the grinding table (11) and

b. in the second grinding stage (2), further grinding takes place in a second grinding mill (30) formed by a stirred ball mill or ball mill,

characterized in that a part of the sand (8) of the first dynamic separator (13) is at least partly diverted and conveyed to the second grinding mill (20).

6. Method according to claim 5, characterized in that the diverted gravel is separated or classified in one or more stages before it is conveyed to the second grinding mill (20), wherein coarser and finer gravel (8a, 8b) is formed and only the finer gravel (8b) is conveyed to the second grinding mill (20), whereas the coarser gravel (8a) is returned to the vertical roller mill (10).

7. A method according to claim 5, characterized in that in the second grinding stage the material ground in the second grinding mill (20) is separated in a second dynamic separator (25), wherein the coarse material thus formed is returned to the second grinding mill (20).

8. The method according to claim 7, characterized in that the fines formed in the second dynamic separator (25) and the fines of the first dynamic separator are extracted as finished material.

9. The method according to claim 5, characterized in that the second mill (20) is operated as a continuous flow mill, extracting the material discharged by the second mill and the fines of the first dynamic separator (13) as finished material.

10. A method according to claim 5, characterized in that the material ground in the second grinding mill (20) is fed to the first dynamic separator (13).

Technical Field

The invention relates to a two-stage grinding circuit with a vertical roller mill and a stirred ball mill, and to a method for producing ground products by means of a two-stage grinding process.

Background

A two-stage grinding circuit for energy-efficient comminution of cement containing ground granulated blast furnace slag is known from DE 102017046834B 4. In the first grinding stage, a ball mill, a high-pressure roller mill or a vertical roller mill is used. As a grinding mill of the second grinding stage, in particular a ball mill, a vertical roller mill or a stirred ball mill is used.

DE 19501616 a1 also discloses a device for comminuting material to be ground, preferably for finely and very finely grinding pre-ground material to be ground, wherein a roller press or a high-pressure roller press is used as the first grinding stage and a stirred ball mill is used as the second grinding stage in order to achieve energy-saving two-stage grinding. The first grinding stage is provided with a separator which returns coarse material of the material to be ground, which is comminuted in the first grinding stage, to the grinding stage. The fines then enter a second grinding stage, which is again combined with a separator.

Disclosure of Invention

The invention is based on the object of increasing the efficiency of a two-stage comminution.

According to the invention, this object is achieved by the features of claims 1 and 5.

The two-stage grinding circuit according to the invention consists substantially of:

a. a first grinding stage comprising a vertical roller mill having a grinding table, at least one grinding roller cooperating with the grinding table and a first dynamic separator, wherein the first dynamic separator comprises a fines outlet for discharging fines and a grit return for returning grit to the grinding table; and

b. a second grinding stage comprising a second grinder formed by a stirred ball mill or a ball mill, wherein the second grinder comprises an inlet and an outlet.

A grit extraction device for extracting a portion of the grit is also provided, the grit extraction device being connected to the grit reflector and communicating with the inlet of the second mill.

The method according to the invention for producing an abrasive product by means of a two-stage grinding process provides for:

a. in a first grinding stage, the material to be ground is ground in a vertical roller mill having a grinding table and at least one grinding roller cooperating with the grinding table and separated in a first dynamic separator into fines and grit, wherein at least a portion of the grit is returned to the grinding table, and

b. in the second grinding stage, further grinding is carried out in a second grinding mill formed by a stirred ball mill or ball mill.

Furthermore, a portion of the grit of the first dynamic separator is at least partially diverted and conveyed to a second grinding mill.

The material to be ground comminuted in the first grinding stage consists, for example, of clinker, into which further constituents, such as granulated blast furnace slag, limestone, natural and naturally tempered pozzolans, fly ash, shale or silicate dust, can be admixed. It is also possible to convey each of the above-mentioned components as material to be ground to the first grinding stage.

The ground product to be produced is in particular cement or ground granulated blast furnace slag.

In the two-stage grinding circuits known hitherto, all the grit of the separator of the first grinding circuit is returned to the first grinding stage, while only the fines enter the second grinding stage. However, according to the invention, a part of the sand of the first grinding circuit will now also enter the second grinding stage together with the fines.

The particle size of the fresh material delivered to the first grinding stage is typically up to 30,000 μm. In vertical roller mills, the comminuted material is conveyed via a gas flow to a separator, which is usually arranged above the grinding table. Fines, which usually have an average particle size of <63 μm, are discharged there through the rotor cage together with the gas flow. The coarse material has an average particle size of about 45 to 8000 μm and is thrown out through the rotor cage and falls under gravity via a gravel cone back onto the grinding table.

However, since the coarse material has been comminuted at least once on the grinding table and has been conveyed by the gas stream to the separator, the average particle size (<8000 μm) of the coarse material is much smaller than that of the fresh material (<30,000 μm). This higher fineness leads to a reduction in the grinding efficiency of the vertical roller mill, since the bulk density of the bulk material on the grinding table increases and the porosity thereby decreases due to the wider particle size distribution. In the case where the comminution of the bed is carried out in a vertical roller mill, the porosity of the bed before loading is a criterion for the comminution efficiency. Thus, at higher void fractions, the grinding forces are dissipated over a small number of particles, which can therefore be subjected to greater loads and broken up. At smaller void fractions, the abrasive forces are dissipated over a larger number of particles and a larger surface area, so that the individual particles are subjected to significantly less loading.

According to the invention, the partial flow of the grit of the separator is no longer directed back onto the grinding table, so that the packing density of the material bed on the grinding table is correspondingly reduced before loading. Accordingly, not only the fines of the separator of the first grinding stage are fed to the second grinding stage, but also a portion of the grit of the separator is fed to the second grinding stage. Although this means that also in the second grinding stage a coarser material to be ground needs to be comminuted, the efficiency of the vertical roller mill is still significantly increased even more, so that for the grinding process as a whole a more efficient comminution is obtained, which is characterized in particular by a lower energy consumption.

Further embodiments of the invention are the subject of the dependent claims.

According to another embodiment of the invention, a single-stage or multi-stage separation or classification device may be arranged between the sand extraction device and the inlet of the second mill, which separation or classification device comprises an inlet for extracted sand and a first outlet for coarser sand and a second outlet for finer sand. The inlet of the separating or classifying means is in communication with the grit extraction means, the first outlet is in communication with the vertical roller mill and the second outlet is in communication with the second mill. This has the advantage that only the finer fraction of the grit of the separator of the first grinding stage is supplied to the second grinding mill, while the coarser grit is returned to the vertical roller mill, thereby further increasing the void fraction therein and thus the efficiency.

Furthermore, a second dynamic separator having an inlet, a fines outlet and a coarse outlet may also be provided in the second grinding stage, wherein the outlet of the second grinding mill is connected to the inlet of the second dynamic separator and the coarse outlet of the second dynamic separator is connected to the inlet of the second grinding mill.

Finally, a finished material silo can be provided, which communicates with the fines outlet of the first dynamic separator and/or the second dynamic separator and/or with the outlet of the second mill.

In the method according to the invention, the transferred grit can be further subjected to a single-stage or multi-stage separation or classification before it is conveyed to the second grinding mill, wherein coarser and finer grit is formed and only the finer grit is conveyed to the second grinding mill, while coarser grit is returned to the vertical roller mill.

It is also conceivable that in the second grinding stage the material ground in the second grinding mill is separated in a second dynamic separator, wherein the coarse material thus formed is returned to the second grinding mill. The fines formed in the second dynamic separator and the fines of the first dynamic separator may be extracted as finished material and optionally conveyed to a finished material silo. However, instead of the second dynamic separator, it is also conceivable to operate the second mill as a continuous-flow mill, the discharge material of which and the fines of the first dynamic separator being extracted as finished material.

It is further provided that the second mill (that is to say, the stirred ball mill or the ball mill) is operated dry, that is to say, without addition of liquid.

Further advantages and embodiments of the invention are explained in more detail by means of the following description of some exemplary embodiments and the accompanying drawings.

Drawings

In the figure:

figure 1 is a schematic diagram of a two-stage grinding circuit according to the invention according to a first exemplary embodiment,

figure 2 is a schematic diagram of a two-stage grinding circuit according to the invention according to a second exemplary embodiment,

FIG. 3 is a schematic view of a vertical roller mill, and

fig. 4 is a schematic diagram of a two-stage grinding circuit according to the present invention according to a third exemplary embodiment.

Detailed Description

The first exemplary embodiment of the two-stage grinding circuit shown in fig. 1 comprises a first grinding stage 1 and a second grinding stage 2. The first grinding stage 1 comprises a vertical roller mill 10, which is shown in somewhat more detail in fig. 3. It comprises in particular a grinding table 11, a plurality of grinding rollers 12 cooperating with the grinding table, and a dynamic separator 13. The new material 3 to be comminuted may comprise, in addition to the cement clinker, in particular one or more of the components listed below: granulated blast furnace slag, limestone, natural and naturally tempered pozzolans, fly ash, shale, silicate dust.

The fresh stock 3 enters the middle of the grinding table 11 via a fresh stock chute 14, where the fresh stock 3 slides outwards under the grinding rollers 12 due to centrifugal forces. The material comminuted below the grinding rollers 12 passes over the edge of the grinding table, where it is carried along by the air flow 4 supplied below the grinding table and is conveyed to a first dynamic separator 13 arranged above the grinding table. There, the fines 5 are entrained with the gas flow 4 via the fines outlet 15 and conveyed to the cyclone 6. The fines 5 separated in the cyclone 6 are discharged as finished material. When a part of the airflow cleaned by the cyclone separator 6 is further dust-removed in a further dust separator 7, another part is returned to the vertical roller mill as separated air. These portions may range from 0% to 100%.

The fine particles 8 ejected in the dynamic separator 13 are returned to the grinding table via a sand return 16 in the form of a sand cone. At the end of the sand reflector 16 a mixing box 17 is arranged, in which mixing box 17 the returned sand 8 and the fresh material 3 supplied via the fresh material chute 14 are mixed together before the mixture reaches the centre of the grinding table.

The gravel extraction device 18 is further connected to a gravel return 16 via which a part of the gravel can be discharged from the vertical roller mill 10. The sand extraction device 18 is formed, for example, by a conveyor which projects into the sand reflector 16 in the form of a sand cone. There, the extraction device 18 cooperates with a collecting funnel 19, for example, in order to guide a portion of the sand 8 thrown by the rotor to the sand extraction device 18.

The second grinding stage 2 comprises a second grinder 20 in the form of a ball mill or stirred ball mill, which second grinder comprises an inlet 21 and an outlet 22. The gravel extraction means 18 communicates directly or indirectly with the inlet 21 of the second mill 20 via a separation or classification device 23. In the exemplary embodiment shown, such a separation or fractionation device 23 is provided and may be in the form of a single stage or multiple stages. Which separates the sand entrained via the sand extraction device 18 into coarser sand 8a and finer sand 8 b. The coarser gravel 8a is returned to the fresh-material chute 14 together with the abrasive material 8c falling on the edge of the grinding table 11 via a bucket elevator 30 and possibly another conveyor 31. On the other hand, finer sand 8b enters the second mill via the inlet 21. The crushed finished material 9 is discharged via the outlet 22 of the second mill 20 and combined with the fines 5 of the cyclone separator 6 via suitable conveying means. The second mill 20 can be used with a gas stream that is free of dust from the dust separator 24.

In the second exemplary embodiment according to fig. 2, the second mill 20 in the second grinding stage 2 is also combined with a dynamic separator 25, so that the comminuted material of the second mill 20 is first conveyed to the second dynamic separator 25, the coarse material 25a thereof being conveyed to the inlet 21 of the second mill 20, while the fine material is separated in the separator 26 as finished material 9.

In the third exemplary embodiment according to fig. 4, a second grinding mill 20 is likewise used in the second grinding stage 2, but the product of the second grinding stage is thus conveyed via the separator cover to the separator of the vertical roller mill, so that the product fineness can be adjusted via the dynamic separator 13 of the vertical roller mill.