FI127048B - METHOD AND APPARATUS FOR PREPARING CEMENT - Google Patents

Description

METHOD AND APPARATUS FOR PREPARING CEMENT

The invention relates to a method as defined in the preamble of claim 1 and to an apparatus for the manufacture of cement as defined in the preamble of claim 8.

Powdered limestone is used to make the cement needed for concrete making. the clay and the mixture are burned in a clinker furnace where the material is sintered to form cement minerals. The clinker modules, which are the raw material of the cement, are ground to a cement powder, for example in a ball mill, and in the course of grinding, additives and alloying agents are added to the material to achieve the desired properties. For example, gypsum is added to the material to adjust the setting time. The setting rate can be adjusted, for example, by the grain size of the cement powder. One problem with cement production is that it produces very high levels of CCk emissions. For the purposes of this application, ground clinker is referred to as cement powder, whether it is pure clinker powder or a mixture in which alloying and additives are added to the Klink clay material before or during grinding.

Fly ash has been used as a compounding agent in cement production according to prior art, but the results may not have been good enough for the strength of the concrete obtained, since fly ash has been commonly used as such without any sorting, whereby concrete with unsorted fly ash or not at all. Fly ash-filled cements in prior art solutions generally contain about 15-40% fly ash. The use of untreated fly ash is typically seasonal, has limited use, and has yielded little benefit from stringent technical limits.

In prior art solutions, untreated fly ash is added, for example, with other alloying materials to the clinker material used as a raw material in the cement making process before the cement is ground, after which the crushed and doped cement powder is transferred to storage and distribution. The problem with these solutions is, among other things, that the grinding results in a cement mixture in which the grain size may not be fully controlled. This is due, among other things, to differences in hardness between the clinker material and the various alloying elements, for example the slag used as the alloying agent may be significantly harder or softer than the clinker material. Similarly, fly ash can contain particles that are harder than clinker. As a result, a harder ingredient may not be ground down enough, or a softer ingredient may be ground too small, resulting in a cement powder that is not homogeneous enough in grain size, but is indefinite and the cement quality suffers. It is an object of the present invention to overcome the above drawbacks and to provide an inexpensive and reliable method and apparatus for producing high quality cement. The purpose of this is, among other things, to try to produce cement, from which the strength properties and workability of the concrete to be made are better than the known solutions. In addition, the aim is to make cement that can be used in the finished product to a lesser extent than existing concrete grades. The method according to the invention is characterized in what is stated in the characterizing part of claim 1. Correspondingly, the apparatus according to the invention is characterized by what is set forth in the characterizing part of claim 8. Other embodiments of the invention are characterized in what is set forth in the other claims.

One of the great advantages of the solution according to the invention is, among other things, the reduction of the C02 emissions caused by cement production, since clinker is required for the production of cement, while less well-sorted fly ash replaces part of the clinker. However, replacing clinker material with fly ash is not so successful with unsorted fly ash. Concrete products made from cement made by the method and equipment according to the invention are of uniform quality and technically reliable, whereby the amount of use required in concrete production is lower than in concrete products made from conventional cement. In this way, the raw material, transport and energy costs can be reduced, which results in a lower ecological footprint than concrete products made from traditional cement. A further advantage is that the cement and fly ash particles mix optimally when the fly ash particles are of a controlled circular shape and suitably smaller than the cement particles, thereby increasing the binding and strength reaction area of the particles in the mixture and also the amount of water required. decreases. The result is an improved strength of the concrete after a certain cure time.

The invention will now be described in more detail by way of example with reference to the accompanying simplified drawings, in which Fig. 1 is a side and simplified schematic view of one prior art, Fig. 2 is a schematic side and simplified schematic view of Fig. and Fig. 4 shows a substantially enlarged and schematic view of the sampling point shown in dotted lines in Fig. 3.

In the prior art method and apparatus, i.e., shorter solution, of the prior art cement clinker is stored in a storage container 101, from which the required amount of clinker material is transported by means of transfer equipment 102 to clinker dispensing containers 103, from which clinker is transported and transported. Along with the dispensing apparatus, alloying agents such as gypsum, slag and, for example, unsorted fly ash, are added to the clinker material, which are conveyed by conveyor apparatus 105 to refining apparatus 106 where both clinker and alloying agents are ground together. After grinding, the ground and mixed cement powder is conveyed by means of transfer equipment 107 to cement storage and dispensing tanks 108, from which the finished cement powder is dispensed for distribution, for example to delivery vehicles 109 or distribution containers 110.

In the method and apparatus according to the invention shown in Fig. 2, or in a shorter solution, the main cement clinker is stored in a storage container 1, from which the necessary amount of clinker material is transported by In the case of a dispensing apparatus comprising one or more metering tanks 3, the admixtures in the clinker material, such as gypsum, slag, and e.g. , wherein both the clinker and the alloying elements are ground together in a manner known in the art. The average fineness (D50) of the screened coarse fly ash is essentially about 40-60 μπι. After grinding, the powdered and mixed cement powder is transported by means of transfer equipment 8 to cement storage and dispensing tanks 9, from which the finished cement powder is dispensed for distribution, for example to delivery vehicles 15 or distribution containers 16.

However, unlike prior art solutions, it is now the case that conventional cement making equipment has been preceded by a fly ash dispensing device 12 of the sorted grain size desired to provide the same cement making equipment with a the concrete thus made has other desirable properties, such as slow or rapid strength gain.

The fly ash dispensing apparatus 12 includes a weighing unit 12a and a mixing unit 12b, wherein the ingredients weighed by the weighing unit 12a are mixed together and transported by a conveyor device 13 to special cement storage and dispensing containers 14, from which special cement powder is dispensed or dispensed, e.g.

The apparatus according to the invention comprises one or more auxiliary material reservoirs 5, 5a which are connected by means of a conveyor device 10 to a weighing unit 12a of the metering apparatus 12. In the example solution, there are two additive tanks, but there can be only one or more than two, for example 3, 4, 5 or 6. The first additive canister 5 has a very fine, pre-sorted fly ash with a mean refinement (D50) of e.g. 8 pm. Similarly, the second additive container 5a may have a coarser grain size, pre-sorted fly ash having a mean particle size (D50) of between 8 and 16 pm, the third additional ingredient container may have a coarser grain size, pre-sorted fly ash (D50) e.g. , etc. In addition to the carefully selected grain size, it is advantageous that the screened fly ash particles have a substantially circular shape, whereby the amount of water required to make the concrete is reduced, which further increases the strength of the concrete.

The pre-sorted fly ash from the additive reservoir 5 or 5a, etc. is conveyed by means of conveyor 10 directly to the weighing unit 12a for weighing and further after weighing to the mixing unit 12b, which is also supplied with alloying elements. For example, the aforementioned powdered cement powder is separated from the material entering the storage and dosing containers 9 by means of a dispensing device 8a in connection with the transfer apparatus 8 and passed through the conveyor device 11 to the weighing unit 12a and after mixing to the mixing unit 12b.

According to the invention, the pre-ground cement powder is blended in a mixing unit 12b with an appropriate proportion of fly ash of very low grain size, whereby the strength and workability of the concrete made from the improved cement powder thus obtained are improved compared with prior art cement. In this case, the cement powder to which said fine fly ash is added may contain only ground clinker, or small amounts of additives or other alloying agents, such as gypsum, may be present in the clinker. In addition, in some cases, the clinker may include, in addition to or instead of the aforementioned additives and alloying agents, slag and / or said coarse fly ash which has been ground in a grinding apparatus 7 together with the clinker.

Table 1 shows an excerpt from a test result in which fly ash was sorted with a test device for use in the method and apparatus of the invention. In it, Product # 1 (Product 1) is a substantially unsorted rough starting material and Product # 5 is the finest material of all. The vertical columns show four different volume percentages: D10 corresponding to 10%; D50 corresponding to 50%; D97 corresponding to 97%; and D100, which corresponds to 100%. The decimal figures in the columns are the grain size of the fly ash material in micrometres (pm).

table 1

For example, if you look at the lowest product # 5, you will see that the sorting has gone through 100% of the entire material through a 4 µm screen, i.e. the largest grain size of the sorted product is 4 µm. However, the generally more important criterion is the grain size of D97, which is usually sufficient instead of D100, and the product is generally rated at D50, which determines the average grain size of the product. Table 1 shows that the average fineness D50 of product # 5 is thus 1.46 µm and more than 10% of the product is material with a particle size of less than 1 µm, i.e., some of the product is already in the nanometer size range.

Handling and sorting fly ash into products of a particular particle size enables these products to be economically and appropriately utilized for a variety of applications. For example, fly ash, which has the right grain size as an additive to cement used in concrete, improves the quality and strength of the concrete, as well as lowering the price of the concrete and reducing the clinker consumption of the concrete.

Table 2 shows an excerpt from a test result testing the development of compressive strength of K40 strength concrete. The products to be compared were concrete made from prior art cement and concrete made from special cement according to the invention, in which very fine, granulated fly ash was added to the ground clinker material.

Table 2

The benchmark was thus concrete made from prior art cement (Prior Art) using 300 kg cement without fly ash. Full compression strength gradually developed so that after the first day the compression strength was 15 MPa and after 28 days 45 MPa.

Similarly, in order to achieve the same strength properties, the concrete made with the special cement according to the invention required only 225 kg of cement and 15 kg of very fine, sorted fly ash mixed with the cement powder after the clinker grinding. The missing volume could be replaced by nature's own material, sand. A 25% lower amount (225 kg) of cement according to the invention was sufficient compared to the original amount of cement (300 kg), provided that 15 kg of fly ash was added to the cement, which is 5% of the initially required amount of cement (300 kg). In this context, percentages refer to percentages by weight. Because the amount of cement could be reduced to achieve the same result and the cement production with its CCb emissions is a lot of burden on the environment, the cement mixture produced according to the invention is not only more advantageous but also more environmentally friendly than prior art cement.

In addition, using ash fly ash graded to the correct grain size as a cement additive for concrete production, less fly ash can be used than prior art solutions to achieve the same result, i.e. instead of 15-40% fly ash requires only 2-14% of other cement material. . For example, the grain size of the fly ash is, for example: D50 between 1-8 µm, D97 between 2-60 µm and D100 between 3-80 µm. Similarly, D10 is in the range of 0.5 to 2 µm.

Table 3 shows an excerpt from another test result testing the development of compressive strength of concrete. Comparable products were state-of-the-art cement concrete with fly ash added to the clinker material prior to clinker grinding, and three concretes made with special cement according to the invention, with varying percentages of ultra-fine, smaller grain size and smaller particle size ash.

Table 3

Column Priority (20-25%) in Table 3 shows the compressive strengths of concrete made from prior art cement mixture 1, 7, 28 and 91 days after concrete casting. In this case, unsorted or very coarse sorted fly ash is added as a weight percentage to the clinker material by about 20-25% before grinding the clinker material.

Correspondingly, column 1 of the Invention 1 (20%) shows the compressive strengths of concrete made from one cementitious mixture according to the invention 1, 7, 28 and 91 days after concrete casting. In this case, fly ash smaller than the grain size of the clinker material, sized according to the invention, is added as a weight percentage to 20% substantially pure cement powder, which is about 95% pure and doped only with other conventional alloys such as gypsum. Thus, the fly ash is added only after the clinker has been ground. Column 2 of the Invention 2 (25%) shows the compressive strengths of concrete made from another cement mixture according to the invention 1, 7, 28 and 91 days after the concrete casting. In this case, fly ash has been added in the same way as in the previous column but now 25% by weight of the amount of powdered clinker. And column 3 of the Invention (5%) shows the compressive strengths of concrete made from one third of the cement mixture according to the invention 1, 28 and 91 days after the concrete casting. Again, fly ash has been added in the same way as in the previous two columns, but now only 5% by weight of the amount of ground clinker.

It is very clear from the test results in Table 3 that the compressive strength of the concrete made from the cementitious compositions according to the invention (Invention 1-3) is significantly higher than that of the prior art concrete made from fly ash. For example, the cementitious composition Inventive 3 achieves a compressive strength of 15 MPa already one day after casting, i.e. twice the compressive strength of a concrete made from a cement composite Prior Art.

It can also be concluded from the test results in Table 3 that, if one wishes to emphasize the good initial strength, the fly ash graded according to the invention is mixed with an additive to the ground cement powder used in concrete production than if it is desired to emphasize a good final strength. For example, the compressive strength of the cementitious composition of Invention 3 is still 28 days after the concrete casting is higher than the other cementitious compositions of Invention 1 and Invention 2, whereas their compressive strength is only higher after 91 days of concrete casting. Thus, the final strength is improved when more than 5% but less than 25% of fly ash graded according to the invention is mixed with the powdered cement powder as an additive. However, the exact percentages have not been determined in the experiments.

However, it may be determined, for example, that, when emphasizing the initial strength of the concrete produced, the fly ash, sorted according to the invention, is added to the ground cement powder as a percentage by weight of about N% of the cement powder amount N 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, , 13 or 14, or fractions of these integers. Similarly, when emphasizing the final strength of the concrete produced, the fly ash, sorted according to the invention, is added to the ground cement powder in a weight percentage of about N% of the amount of cement powder where N is 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26 ... 40 or parts of these integers.

Fig. 3 is a schematic and simplified view of a freshly mixed wet concrete with reinforced cement gel 17 as a binder with both small stones 18 and larger stones 19. Additionally, concrete and other reinforcements may be present but are not shown. Fig. 3 is also supplemented with a dotted line sampling point 20, which is shown at a much enlarged level in Fig. 4.

The concrete sample of Fig. 4 is schematic and simplified showing only how the fly ash particles or granules 21 according to the invention are positioned between the larger cement particles or cement granules 22, thereby compacting the structure of the cementitious mass which acts as a binder. Without the cement granules 22, the fly ash particles 21 of smaller size would leave too much empty space between the cement granules 22, for example about 2-15%, which would weaken the structure. The fly ash used as a cement additive, which is smaller in size than the cement granules and which has the right grain size for use, physically increases the reaction surface area of the mixture particles and thereby the cement strength, thereby enhancing concrete and concrete made from fly cement. In addition, small particle size particles replace the amount of water and cement used, since the voids of the cement granules 22 would otherwise be filled with cement-water mixture. This feature also helps to save the cement used as a raw material. Similarly, drying cracks and frost resistance, among other things, are reduced by the use of pre-sorted small fly ash particles 21 among cement particles 22.

According to prior art cement fly ash of unsorted grain size is added to the clinker material before grinding the clinker material. However, in this case, it is not possible to obtain fly ash of the correct grain size with respect to the properties of the cement quality being produced. According to the invention, fly ash of just the right grain size is added to the clinker material with small amounts of optional additives and alloying agents, only after the material has been ground, whereby the grain size of the fly ash used depends on the intended use of the cement. Cement containing granules 22 of this size is supplemented with fly ash of higher grain size and fly ash with less granule is added to cement containing smaller granules 22. This gives high quality cement mixes for various applications. The mean grain size (D50) of both fly ash and cement powder is used to determine the grain size.

According to the invention, fly ash particles 21 smaller than cement granules 22 are mixed with cement for the production of concrete to fill the voids between the cement granules 22. Thus, the solution according to the invention comprises at least one fly ash additive container 5, which contains a fly ash of grain size sorted, having a particle size 21 of average particle size (D50) of about (0.1-0.8) * particle size 22 of clinker material. 0.2 ... 0.7) * particle size 22 of clinker material particles, preferably approx. (0.3-0.6) * particle size 22 of clinker material particles and preferably approx. (0.4 ... 0.5) * the grain size of the clinker material particles 22. The above particle grain sizes are defined by the average fineness (D50) of the fly ash particles 21 and the clinker material particles 22.

From the additive material container 5, 5a, etc., suitable fly ash is added to the respective cement grade, such that after grinding the clinker material, a fly ash of a pre-sorted particle size (D) with a finely divided particle size of Corresponding average grain size (D50) grain size. Then, according to the desired cement quality, the fly ash, which has been pre-sorted and selected according to grain size, is mixed with clinker material 7, ie cement powder containing about 0-4% by weight of any required additives and admixtures. 2 to 14% by weight of the material, suitably for example about 3 to 10% and preferably for example about 5 to 8% or any suitable percentage within the above ranges, i.e. about 4, 6, 7, 9, 11, 12 or 13% or parts thereof . For example, when the powdered clinker material, or cement powder, with its possible additives and admixtures, is 100 kg, the fly ash is mixed with the cement powder with 3-12 kg in a mixing ratio of 3-12%. The fly ash to be mixed is taken, for example, from the additive reservoir 5, conveyed to the dispensing unit 12 by means of a conveyor device 10 and weighed and mixed by means of the dispensing unit 12 with the clinker material from the refining plant 7, i.e. cement powder. Thus, the amount of fly ash used in cement production can be much smaller than the approximately 15-40% of the amount of clinker material used in the prior art, due to the fine granulate sorting, although more savings in the amount of clinker are achieved. In addition, a higher percentage of sorted fly ash after clinker grinding, allows for greater compressive strength of the concrete as the concrete hardens further, i.e., higher final strength of the concrete.

The special cement produced by the method and apparatus according to the invention is well suited for the production of high strength concrete, for example in connection with the production of ordinary concrete with high strength strength.

It will be apparent to one skilled in the art that the various embodiments of the invention are not limited to the examples above, but may vary within the scope of the following claims. It is essential that an additive product, such as fly ash, graded according to the intended use is used, whereby the grain size of said additive product is substantially accurately known, and that the additive product is added to the cement mixture after grinding the clinker material.

Claims (11)

1. A process for the production of cement, in which process is added to the clinker material ground to cement powder to improve the properties of the cement, additives and / or blends, such as fly ash sorted by grain size, whose particles (21) have a smaller grain size than cement powder cement particles (22), and in which sorted fly ash are essentially round fly ash particles, characterized in that in order to emphasize the initial strength as an additive in the cement powder used in the production of cement, fly ash in weight percent mixes about N% of the amount of cement powder, where N is 2 , 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14 or parts of these integers, and to emphasize the final strength of the cement powder used in the manufacture of concrete as an additive, fly ash mixes in the weight percentages about N% of the amount of cement powder, where N is 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26 ... 40 or your parts of these integers. 2. A process according to claim 1, characterized in that, in the cementing process in the cement powder milled from clinker material, according to the grain size, carefully sorted fly ash with an average degree of fineness within the range 1-8 μπι in the weight percentages is added about 2-25%, or about 3 -14%, preferably 4-10% and preferably about 5-8% of the amount of ground tile material. A method according to claim 1 or 2, characterized in that fine grain size fly ash with a grinding device (7) is added to the milled clinker material after grinding by transferring the clinker material coming from the grinding device (7) to a dosing device (12). connection to the device, to which is also added the grain-sized fly ash to be added, which is contained in a fly ash additive container (5, 5a) and weigh the amounts of material in a weighing unit (12a) of the metering device (12) and mix the weighted amounts of material in a mixing unit (12b) in the metering device (12) and transferring the special cement thus mixed to storage and metering containers (14). A method according to claim 1 or 2, characterized in that fine grain size fly ash with a grinding device (7) is added to the milled clinker material after grinding by transferring a portion of the clinker material (7) coming from the grinding device (7) to the dosing device (12), to which is also transferred the grain-sized fly ash to be added, and weighing the amounts of material in the weighing unit (12) of the dosing device (12a) and mixing the weighed amounts of material in the mixing unit (12b) of the dosing device (12b) and transferring it to this way, the special cement was mixed into storage and dosing containers (14). A process according to any one of the preceding claims, characterized in that the reaction surface of the cement mixture particles is increased by adding to the cement powder particle fly ash (21) with a grain size smaller than the grain size of the cement mixture particles (22) which the empty spaces between the cement particles (22). 6. A process according to any one of the preceding claims, characterized in that the ground fly size material is added according to the grain size sorted fly ash, whose particles (21) have a grain size with an average degree of fineness (D50) in the range of about (0.1). 0.8) * the grain size according to the average degree of fineness (D50) in the particles of the clinker material (22), preferably about (0.2 ... 0.7) * the grain size according to the average degree of fineness (D50) in the particles of the clinker material (22) , preferably about (0.3 ... 0.6) * grain size according to the average degree of fineness in the particles of the clinker material (22) and most preferably about (0.4 ... 0.5) * grain size according to the average degree of fineness (D50 ) in the particles of the clinker material (22). A method according to any one of the preceding claims, characterized in that the grain sizes of the fly ash added to the ground clinker material are one or more of the following: D10 is in the range 0.5-2 pm; D50 is in the range of 1-8 µm; D97 is in the range 2-40 pm and D100 is in the range 3-80 pm. A device for making cement, to which the device belongs to at least one group of dispensing containers (3), a transfer path formed by a group of conveyor and displacement devices (6, 8) for passing the material to be handled from one place to another as a material flow, as well as a grinding device (7) and one or more receptacles (5, 5a) for supplementary blend material comprising fly ash containing fly ash particles which are sorted by grain size and are essentially round and a group of cement storage and dispensing containers (9, 14), and that the device comprises at least one metering device (12b) provided with a mixing unit (12), which is connected by means of a first conveyor device (10) to one or more containers for supplementary mixing material (5, 5a), by means of a second conveyor device (8.11) with a material flow of cement powder ground by clinker and with the help of a third conveyor device ng (13) with a cement storage and dispensing container (14) mixed in said mixing unit (12b) by said fly ash and said cement powder, characterized in that there is in connection with the first end of the conveyor device (8, 11) distribution device (8a), whereby a portion of the cement powder obtained from the grinding device (7) is separated to be transferred to the dosing device (12) and the other part of said cement powder is passed to be transferred to a storage and dosing container (9). A device according to claim 8, characterized in that the grinding device (7) is connected to the dosing device (12) by means of the conveyor device (8, 11) for transferring the cement powder ground with the grinding device (7) directly to the dosing device (12). A device according to claim 8 or 9, characterized in that the device comprises a weighing device (12a) for weighing the amounts of cement powder obtained from the grinding device (7) and fine grain fly ash to be mixed in the cement powder before the said ingredients are mixed in the mixing unit (12b). ). Apparatus according to claim 8, 9 or 10, characterized in that at least one additional blend container (5) is arranged to contain sorted fly ash, wherein the fly ash particles (21) have a grain size with an average degree of fineness (D50) within the range about (0.1 ... 0, 8) * the grain size according to the average degree of fineness (D50) in the particles of the clinker material (22), suitably about (0.2 ... 0.7) * the grain size according to the average fine degree of density (D50) in the particles of the clinker material (22), preferably about (0.3 ... 0, 6) ) * grain size according to the average degree of fineness (D50) of the particles of the clinker material (22).