Vertical centrifugal roll mill

Abstract

The present invention relates to a method for operating a vertical centrifugal roll mill, characterized in that activated clays are fed via the pneumatic classifier material inlet (80), while a material selected from the list encompassing clinker, gypsum, limestone and used hardened cement stone is fed via the primary material inlet (90).

Description

[0001] Vertical roller mill

[0002] The invention relates to a vertical roller mill with an extended size distribution for the particles to be ground.

[0003] Vertical roller mills consist of a rotating grinding table and stationary grinding rollers. The material to be ground is fed into the center of the grinding table, and the rotating motion moves the grinding bed of material outward and thus beneath the grinding rollers. The grinding bed is crucial for the smooth running of the vertical roller mill. In addition to moisture, for example, the particle size of the material to be ground also plays a role. The ground material is then absorbed by a gas stream and conveyed upwards. Coarse material is separated in a classifier and returned to the grinding table, while the fine product leaves the vertical roller mill with the gas stream. Such a vertical roller mill is known, for example, from DE 10 2012 107 127 A1.

[0004] EP 0 525 423 A1 discloses a device and a method for comminuting material of different grain sizes.

[0005] From EP 0 370 267 A2 a device for supplying material to a part of a system is known.

[0006] A grinding process and a grinding plant are known from EP 0 164 512 A1.

[0007] To reduce CO2 emissions, clinker in cement production is increasingly being replaced with activated clays, for example. However, it has been observed that activated clays, particularly the presence of very fine material, negatively impact the smooth running of vertical roller mills and can cause vibrations.

[0008] The object of the invention is to provide a method for operating a vertical roller mill that can also be used for any activated clay without vibration problems. This object is achieved by the method having the features specified in claim 1. Advantageous further developments emerge from the subclaims, the following description, and the drawings.

[0009] A vertical roller mill for carrying out the method according to the invention has a grinding chamber with a rotatable grinding table and at least one grinding roller. The material to be ground is placed on the grinding table, which rotates. The grinding bed forming on the grinding table is conveyed beneath the grinding roller and ground there. The vertical roller mill has a gas supply arranged beneath the grinding table. The gas flows upwards past the sides of the grinding table, entraining the ground material in the gas stream. A classifier is arranged above the grinding table. This serves to separate the insufficiently ground material and feed it back for further grinding. A gas transfer line for transferring the gas stream laden with the material to be ground from the gas supply is arranged between the grinding chamber and the classifier. The classifier has a coarse fraction return line to the grinding table, via which the coarse fraction is returned to the grinding table.The classifier also has a gas outlet for the fine fraction. The product is removed through the gas outlet and can be removed from the gas stream, for example, in a downstream dust separator. This corresponds to the design of a standard state-of-the-art vertical roller mill, as described, for example, in DE 10 2012 107 127 A1.

[0010] According to the invention, the vertical roller mill has a classifier material inlet. The classifier material inlet opens into the gas transfer. The material is therefore not fed directly onto the grinding table as before, but enters the gas flow between the grinding table and the classifier. This ensures that the fine fraction is removed first from the newly fed material, and only the coarse fraction reaches the grinding table. This prevents the grinding bed from exhibiting unfavorable properties that lead to vibrations in the vertical roller mill, even with activated clays with a high proportion of fine material.

[0011] In a further embodiment of the invention, the vertical roller mill has a primary material inlet. The primary material inlet is designed for the direct feeding of material onto the grinding table. The primary material inlet corresponds to the material inlet currently used in state-of-the-art vertical roller mills. The advantage of combining the two different inlets is that they can be selected for different reactants, either separately for separate grinding or simultaneously for joint grinding. For example, clinker with a sulfate carrier, such as gypsum, can be fed through the primary material inlet, and activated clay can be fed through the separator material inlet, thus producing a mixture for cement.

[0012] In a further embodiment of the invention, the vertical roller mill has a baffle plate in the gas transfer area to distribute the material entering the separator material inlet. This is preferred when the material is fed through the separator material inlet as a pure solid and not as a solid fluidized in a gas stream. The baffle plate achieves a more pronounced distribution in the gas stream.

[0013] In a further embodiment of the invention, the gas transfer device has a cross-sectional constriction in the area of ​​the separator material inlet. This locally increases the flow velocity, which in turn improves the carrying capacity of the gas flow.

[0014] The invention relates to a method for operating a vertical roller mill. Here, activated clays are fed via the classifying material inlet. Preferably, the activated clay is fed entirely via the classifying material inlet. Exceptionally, a portion of the activated clay may be fed via the primary material inlet. This may be the case, for example, if two very different activated clays are to be fed. It may also be the case that feeding a small portion of the activated clay via the primary material inlet has a positive influence on the grinding result without generating burns due to the small amount, particularly if other components fed via the primary material inlet, such as clinker and / or gypsum, are fed in.If only activated clay is fed and ground, it is preferably fed entirely and exclusively through the separator material inlet. Feeding activated clay in this way is particularly advantageous because the fine fraction is separated first. This ensures that only the coarse fraction to be ground reaches the grinding table, which in turn prevents vibrations caused by excessively fine material. Clinker, for example, is preferably applied via an optional primary material inlet and only via the separator material inlet if no primary material inlet is available. Therefore, clinker is preferably fed via the primary material inlet.

[0015] In a further embodiment of the invention, the activated clay is added at a temperature of up to 120°C. The activated clay can also be added at ambient temperature, especially when removed from a storage facility. The activated clay is preferably not warmer than 120°C.

[0016] According to the invention, a material is fed through the primary material inlet. The material is selected from a list including clinker, gypsum, limestone, and old cement brick. This allows for the simple production of ready-to-use cement, avoiding the application of the often excessively fine activated clay to the grinding table, which in turn prevents vibrations in the mill, for example. It also avoids the unnecessary addition of grinding energy to activated clay that is already sufficiently fine.

[0017] In a further embodiment of the invention, the proportion of the mass flow supplied via the separator material inlet is selected to be less than 50% of the sum of the mass flows supplied via the separator material inlet and the primary material inlet. Preferably, the proportion of the mass flow supplied via the separator material inlet is selected to be between 10% and 40%, preferably between 15% and 30% of the sum of the mass flows supplied via the separator material inlet and the primary material inlet.

[0018] In a further embodiment of the invention, the amount of gas supplied through the gas supply is selected such that the gas flow is 1.5 to 6 m 3 , preferably from 2.5 to 4.5 m 3 , per kg of product fed via the classifier material inlet and the primary material inlet.

[0019] In a further embodiment of the invention, the grinding table is provided with a radial acceleration of 11.5 to 22.0 m / s 2 , preferably from 13.0 to 18.0 m / s 2 , operated.

[0020] In a further embodiment of the invention, the vertical roller mill is operated at a temperature of 60 to 160 °C, preferably 75 to 120 °C.

[0021] The vertical roller mill according to the invention is explained in more detail below using an embodiment shown in the drawings.

[0022] Fig. 1 State of the art

[0023] Fig. 2 example according to the invention

[0024] Fig. 1 shows a prior art vertical roller mill. Material is fed via a primary material inlet 90 onto the rotating grinding table 10. This moves the material beneath the grinding rollers 20, which are adjustable via roller guides 22. The ground material is moved further outward and over the edge of the grinding table 10, where it is entrained by the gas stream supplied through the gas inlet 30 and conveyed through the gas inlet 50 into the separator 40. Separation occurs in the separator 40; the coarse fraction returns to the grinding table 10 via the coarse fraction return 60, and the fine fraction leaves the vertical roller mill via the gas outlet 70.

[0025] Fig. 2 now shows, in comparison, the modification according to the invention. An additional separator material inlet 80 is added (optionally, the primary material inlet 90 could be omitted). The separator material inlet 80 leads into the gas transfer line 50, so that the material fed through the separator material inlet 80 is first separated in the separator 40, thus ensuring that the fine fraction of the material fed through the separator material inlet 80 never reaches the grinding table. Reference symbol

[0026] 10 grinding tables

[0027] 20 grinding rollers

[0028] 22 Roller guide 30 Gas supply

[0029] 40 sifters

[0030] 50 Gas transfer

[0031] 60 coarse fraction recirculation

[0032] 70 Gas outlet 80 Classifier material inlet

[0033] 90 Primary material input

Claims

Patent claims 1. A method for operating a vertical roller mill, wherein the vertical roller mill has a grinding chamber with a rotatable grinding table (10) and at least one grinding roller (20), wherein the vertical roller mill has a gas supply (30) arranged below the grinding table (10), wherein a classifier (40) is arranged above the grinding table (10), wherein a gas transfer (50) for transferring the gas stream laden with the material to be ground from the gas supply (30) is arranged between the grinding chamber and the classifier (40), wherein the classifier (40) has a coarse fraction return (60) to the grinding table (10), wherein the classifier (40) has a gas outlet (70) for the fine fraction, wherein the vertical roller mill has a classifier material inlet (80), wherein the classifier material inlet (80) opens into the gas transfer (50), wherein the vertical roller mill has a primary material inlet (90),wherein the primary material inlet (90) is designed to supply material to the grinding table (10), characterized in that activated clays are supplied via the separator material inlet (80), wherein a material is supplied via the primary material inlet (90), wherein the material is selected from the list comprising clinker, gypsum, limestone, old cement brick., 2. Process according to claim 1, characterized in that the activated clay is supplied at a temperature of up to 120 °C.

3. Method according to one of claims 1 to 2, characterized in that the proportion of the mass flow which is supplied via the classifier material inlet (80) is selected to be less than 50% of the sum of the mass flows which are supplied via the classifier material inlet (80) and the primary material inlet (90).

4. Method according to claim 3, characterized in that the proportion of the mass flow which is supplied via the classifier material inlet (80) is selected between 10% and 40%, preferably between 15% and 30% of the sum of the mass flows which are supplied via the classifier material inlet (80) and the primary material inlet (90).

5. Method according to one of claims 1 to 4, characterized in that the amount of gas supplied through the gas supply (30) is from 1.5 to 6 m 3 , preferably from 2.5 to 4.5 m 3 , per kg / product of material fed via the classifier material inlet (80) and the primary material inlet (90).

6. Method according to one of claims 1 to 5, characterized in that the grinding table (10) is moved with a radial acceleration of 11.5 to 22.0 m / s 2 , preferably from 13.0 to 18.0 m / s 2 , is operated.

7. Process according to one of claims 1 to 6, characterized in that the vertical roller mill is operated at a temperature of 60 to 160 °C, preferably 75 to 120 °C.

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