Component grinding of cement components

Abstract

The present invention relates to a process for producing cement on the basis of at least two components, characterized in that at least two of the components are ground separately.

Description

[0001] Component grinding of cement components

[0002] The invention relates to a method for the efficient grinding of various components for a cement.

[0003] The substitution rate in cement is increasing. Thus, the proportion of burnt clinker is being progressively reduced. Common substitutes today include unburned limestone, calcined clays, pozzolans, granulated blast furnace slag, steel slag, fly ash, and the like. To still achieve the specified strength classes, the cements usually have to be ground more finely. This leads to higher energy consumption during grinding. In addition, the different components have different grindabilities, so the easier-to-grind components are ground much finer than necessary. This further increases the energy required for grinding.

[0004] Another point to consider is the mill's vibration level. This can be counteracted with moisture, but this is detrimental to the product. It is therefore necessary to maintain the required fineness with as little water as possible and at a sufficiently low vibration level in the mill.

[0005] A method and a device for cement production are known from US 2013 / 0040257 A1.

[0006] EP 3 326 720 B1 discloses a process for the processing of multi-phase mineral raw materials.

[0007] A process for producing cement is known from EP 2 906 510 B1.

[0008] EP 2 980 036 B1 discloses a process for grinding cement clinker.

[0009] CN 105 366 972 B discloses a powder grinding process for improving the grain composition of cement made from stone waste, as well as a cement produced from stone waste by powder grinding. US 2021 / 309 570 A1 discloses a cement preparation containing cement replacement materials, as well as a production method and apparatus therefor.

[0010] The object of the invention is to provide a grinding process in which all components are ground to the required fineness in an energy-efficient manner.

[0011] 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.

[0012] The process according to the invention serves to produce a cement from at least three components: a first component, a second component, and a third component. For example, the cement can be a cement classified as CEM I. Clinker is selected as the first component. Clinker, burnt lime, creates an alkaline environment when mixed with water when it sets. The second component is selected from the list comprising gypsum, unburnt limestone, calcined clays, pozzolans, granulated blast furnace slag, steel slag, fly ash, old concrete, and old cement block. The third component is different from the second component and is selected from the list comprising gypsum, unburnt limestone, calcined clays, pozzolans, granulated blast furnace slag, steel slag, fly ash, old concrete, and old cement block. The first component and the second component are ground separately. The third component can therefore be ground with the first component or together with the second component.Gypsum, for example, can be selected as a second component, which is used as a sulfate carrier to adjust the setting behavior. At least two of the components, namely the first component and the second component, are ground separately. This allows the first component and the second component to be optimally ground individually, depending on their grindability and the fineness required for the end product. This also allows, for example, the more difficult-to-grind component to be ground more finely without the easier-to-grind component being ground unnecessarily finely, thus wasting unnecessary energy. The clinker substitutes have the advantage that the very high carbon dioxide release (from the lime) during clinker production is avoided, thus making it easy to prevent emissions.In addition, some substances, such as pozzolans, can impart advantageous properties to the concrete made from cement, for example in terms of water resistance.

[0013] According to the invention, the second component is ground more finely than the first component. Clinker, as the first component, exhibits high reactivity; virtually all clinker substitutes that can be selected as the second component exhibit lower reactivity, necessitating finer grinding. Therefore, the cement is normally ground as a mixture, which in turn results in the comparatively easily grindable clinker being ground much more finely, making it significantly finer than the third component. By separating the clinker and grinding it more coarsely to the required fineness, grinding energy is saved.

[0014] According to the invention, the first component is refined to a fineness of at least 5250 cm 2 / g according to Blaine. Preferably, a fineness of not more than 6000 cm 2 / g, preferably not above 5750 cm 2 / g, especially preferably not more than 5500 cm 2 / g. The fineness of at least 5250 cm 2 / g according to Blaine corresponds to a residue of less than 8% of the particles on a 25 pm sieve for clinker.

[0015] According to the invention, the second component is refined to a fineness of at least 6000 cm 2 / g according to Blaine. The fineness of at least 6000 cm 2 / g according to Blaine corresponds to a residue of less than 1% of the particles in granulated blast furnace slag on a 32 pm sieve.

[0016] In a further embodiment of the invention, the separate grinding takes place sequentially in the same device. Especially with a vertical roller mill, it is particularly easy to change the grinding material, so that a quick changeover simplifies a separate process in a single device, which in turn reduces the investment. In a further embodiment of the invention, clinker and gypsum are ground together.

[0017] In a further embodiment of the invention, a fineness of at least 5250 cm 2 / g up to 6750 cm 2 / g according to Blaine and a residue of less than 8 wt.% residue on the 25 pm sieve during grinding. This is easily achieved by taking a measurement after grinding and regulating the grinding according to the measured values. Control is usually achieved by adjusting the classifier and the material flow through the mill; the less material is fed through the mill, the finer the product.

[0018] In a further embodiment of the invention, at least a third component is used to produce the cement. The third component is different from the second component and is selected from the list comprising gypsum, unburnt limestone, calcined clays, pozzolans, granulated blast furnace slag, steel slag, fly ash, old concrete, and old cement block. At least two of the components are ground together and at least two of the components are ground separately. For example, the clinker can be ground together with the gypsum (as the third component) and the second component, for example granulated blast furnace slag, can be ground separately, or the gypsum and the second component, for example granulated blast furnace slag, can be ground together and the clinker separately, or the clinker and the gypsum are ground together and the second component, for example granulated blast furnace slag, and the gypsum can also be ground together separately.This means that all components are not mixed and ground together in a single grinding step, as is currently common practice. This makes it possible to specifically take into account the different grindability of the clinker and the second component in particular. In particular, the clinker substitutes selected as the second component usually require a lower fineness than the clinker. At the same time, they have a lower grindability, so that when they are ground together, the more easily grindable material is overground, thus leading to excessive energy consumption. In a further embodiment of the invention, size-selective separation takes place after grinding. The coarse fraction is returned to the mill, and the fine fraction is removed as product. This opens up the possibility of using mills that cannot immediately achieve the necessary fineness for the entire material to be ground.

[0019] For a vertical roller mill, a classifier has proven particularly suitable for size-selective separation, as the material to be ground is carried out of the vertical roller mill in a gas stream and can thus be fed directly to a classifier. The classifier preferably separates only the coarse fraction. The fine fraction is then separated from the gas stream, for example, in a dust filter.

[0020] In a further embodiment of the invention, a vertical roller mill is selected for grinding. The vertical roller mill achieves the required fineness in an energy-efficient manner with a high throughput and can also be converted between different grinding materials relatively quickly and easily.

[0021] In a further embodiment of the invention, a combination of a high-pressure roller mill and a ball mill is used for grinding. Preferably, a size-selective separation device is used, which produces a coarse fraction, a medium fraction, and a fine fraction. For example, this can be a classifier. The material input stream is fed to the size-selective separation device, and the coarse fraction is fed to the high-pressure roller mill. The material comminuted in the high-pressure roller mill is returned to the material input stream. The medium fraction is fed from the size-selective separation device to the ball mill, where it is further comminuted. The material ground in the ball mill is returned to the size-selective separation device. The fine fraction is either removed as product or passed through a second size-selective separation device, whereby the second coarse fraction is fed to the ball mill.This allows for greater fineness to be achieved in a simple manner. The method according to the invention is explained in more detail below using exemplary embodiments illustrated in the drawings.

[0022] Fig. 1 first example

[0023] Fig. 2 second example

[0024] Fig. 1 shows a first exemplary device for carrying out the method according to the invention. A clinker-gypsum or a mixture of activated clay and gypsum is temporarily fed to a vertical roller mill 21 via material feed 10. Gas is also supplied to the vertical roller mill via a gas feed 12. As a result, the light, ground material is discharged with the gas stream and fed to a size-selective separation device 30, which can also be arranged in a housing with the vertical roller mill 21. There, separation takes place into a coarse fraction 32, which is fed back to the vertical roller mill, and a fine fraction, which is fed into a dust separator 40 to separate solids and gas. The gas is discharged via gas outlet 44 and can theoretically be returned to gas inlet 12. The finished product is removed via product outlet 42.By grinding separately, the cement can be produced with all components having the optimum fineness and no component being ground too finely, thus optimising the energy requirement for grinding.

[0025] Fig. 2 shows a second exemplary device for carrying out the method according to the invention. Via the material feed 10, a clinker gypsum or a mixture of activated clay and gypsum is temporarily fed to a size-selective separation device 34, which divides the material into a fine fraction 31, a medium fraction 33, and a coarse fraction 32. The coarse fraction 32 is fed to a material bed roller mill 22 and comminuted there. The ground material 25 is fed to the material feed 10 and thus to further size-selective separation. The medium fraction 33 is fed to a ball mill 23, and the ground material 25 from the ball mill 23 is fed back to the size-selective separation device 34. The fine fraction is fed to a second size-selective separation device 35, and the second coarse fraction 36 from the second size-selective separation device 35 is added to the medium fraction 33 and fed to the ball mill 23.The fine fraction of the second size-selective separation device 35 is fed to a dust separator 40, the gas is discharged via the gas outlet 44 and the product is removed via the product outlet 42.

[0026] Reference symbol

[0027] 10 Material supply

[0028] 12 Gas supply

[0029] 21 Vertical roller mill

[0030] 22 High-pressure roller mill

[0031] 23 Ball mill

[0032] 25 ground material

[0033] 30 size-selective separator

[0034] 31 Fine fraction

[0035] 32 coarse fraction

[0036] 33 Middle Fraction

[0037] 34 size-selective separator

[0038] 35 second size-selective separator

[0039] 36 second coarse fraction

[0040] 40 dust collectors

[0041] 42 Product outlet

[0042] 44 Gas outlet

Claims

Patent claims 1. A method for producing a cement from at least a first component, a second component and a third component, wherein at least two of the components are ground together, wherein the first component is clinker, wherein the second component is selected from the list comprising gypsum, unburned limestone, calcined clays, pozzolans, granulated blast furnace slag, steel slag, fly ash, old concrete, old cement block, wherein the third component is different from the second component and is selected from the list comprising gypsum, unburned limestone, calcined clays, pozzolans, granulated blast furnace slag, steel slag, fly ash, old concrete, old cement block, wherein the first component and the second component are ground separately, characterized in that the second component is ground finer than the first component, wherein the first component is ground to a fineness of at least 5250 cm 2 / g according to Blaine, with the second component being ground to a fineness of at least 6000 cm 2 / g is ground according to Blaine.

2. Method according to claim 1, characterized in that the separate grinding takes place successively in the same device and / or separate device.

3. Process according to one of the preceding claims, characterized in that clinker and gypsum are ground together.

4. A process according to any one of the preceding claims, characterized in that for the first component a fineness of at least 5250 cm 2 / g up to 6750 cm 2 / g according to Blaine and a residue of less than 8 wt.% residue on the 25 pm sieve is achieved during grinding.

5. A method according to any one of the preceding claims, characterized in that at least one third component is used to produce the cement, wherein the third component is different from the second component and is selected from the list comprising gypsum, unburned limestone, calcined Clays, pozzolans, granulated blast furnace slag, steel slag, fly ash, old concrete, old cement block, wherein at least two of the components are ground together and at least two of the components are ground separately.

6. Method according to one of the preceding claims, characterized in that after grinding, a size-selective separation takes place, wherein the coarse fraction (32) is returned to the mill, and the fine fraction (31) is removed as product.

7. Method according to one of the preceding claims, characterized in that a vertical roller mill (21) is selected for grinding.

8. Method according to one of claims 1 to 6, characterized in that a combination of a material bed roller mill (22) and a ball mill (23) is used for grinding.

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