CS270044B1 - The way to grind cementitious ellnk - Google Patents

Abstract

Rašeni refers to the method of grinding cement slag or/β etrueka for the production of cement with a surface area of 240 or 580 m/kg, which is possibly free of gypsum, in a continuous mill, or a circulating mill with at least one sorter, with the addition of an aqueous solution of a synthetic sulfonated polyelectrolyte, especially dodecylbenzenesulfonic acid or its derivative or salt, or with alkanol mill, as a grinding intensifier to the preparatory proetor before the mill and/or to the mill and/or to the returning semolina. The essence of the proposed solution is that aa ayntatlck aulfonated polyalactrolyte is added to the cement and/or atruaca before milling and/or during milling and/or to the returned semolina in the form of an aqueous solution with a dry matter content of 5 to 20% by weight. Advantageously, the mentioned solution of synthetic euphonated polyelectrolyte is added to the mentioned returnable semolina, as long as the specific surface area is equal to at least 170 mz/Kg· Preferably, and during grinding, a constant mass ratio of returnable semolina to the finished product is maintained in a spread of 2 tl to 10 tl.

Description

The invention relates to a process for grinding cement slag and / or slag for the production of cement with a specific surface area of 240 to 580 m 2 / kg.

Due to the high energy intensity of grinding, increasing the efficiency of cement production is a subject of e-focused interest. The development of new grinding processes is further driven by the need to produce high-quality and special cements. Developments in the field of grinding are focused on the development of new grinding equipment and on the study of substances that affect the grinding process. These substances, which are used in either solid or liquid form, prevent agglomeration of the particles and facilitate the process of comminuting the ground material. In technical practice, mostly liquid grinding additives are used due to their better dosing in comparison with solid grinding intensifiers. Examples of grinding intensifiers are aminoacetates, ethylene glycol, propylene glycol and triethanol amine. In some cases, ee grinding intensifiers not only affect the actual grinding process, but also affect the properties of the finished cement. Thus, for example, the author's certificate No. 257 315 describes a binder based on hydraulically active substances, in particular cement line, which contains 0.005 to 0.5% of alkylolamides of linear alkylarylsulfonic acids or alkylolamides of sulfated fatty acids, or their salts or mixtures of these alkylolamides with esteramines or etheramides of these acids, where the number of carbon atoms in the alkyl residue of the acid is 10 to 20. These alkylolamine derivatives in combination with a sulfonated polyelectrolyte (ligninsulfonate, sulfonated polyphenolate) and an alkaline compound (e.g. sodium carbonate) delay the onset of solidification of the mixture and improve their processability. at the same time, they affect the hydration process and stabilize the onset of setting of gypsum-free cements under disturbing conditions.

For the preparation of gypsum-free cements, a method for grinding cementitious slag (author's certificate No. 175,802) in the presence of lignin sulfonate in powder form as a milling intensifier in a concentration of 0.2 to 0.4% by weight of slag is known. Author's certificate No. 195 787 discloses a method for grinding hydraulically active materials with the addition of one or more lignin-based substances in a concentration of 0.01 to 10% by weight, where the basic building blocks of these substances are p-oxy-m-methoxyphenol nuclei and propane. or an propylene chain terminated by an alcoholic or aldehyde group. Author's certificate No. 227 205 describes a method for grinding hydraulically active substances, in particular cement line, with the addition of powdered lignin sulfonate, powdered carbonate and possibly powdered polyphenolate. The preparation of gypsum-free cementitious materials with a higher mild surface area at a low water content requires a different method of preparation, which is accompanied by a higher energy consumption during wetting (spreading) of the binder, as is evident from the author's certificate No. 202 771.

During the actual milling process, there are technological difficulties due to the necessary accurate dosing of the powder milling feed to the mill. Therefore, the vast majority of the known technical solutions used for grinding to a higher specific surface are realized by using liquid grinding bowls, the accurate dosing of which is easier (W. Duda: Cement-Data-Book, 3rd edition, 1985). In the preparation of gypsum-free cements with two additives (author's certificate No. 202 771) there are additional technological difficulties in grinding to a higher specific surface with two minor additives (for example powdered lignin sulfonate and powdered sodium carbonate), especially difficulties content of these substances in cement. From a chemical point of view, it is necessary to mention the fact that in the presence of both additives (for example ligninsulfonate and sodium carbonate), during their dissolution in water (in the mixture), at the same rate, the reaction of eline with water occurs simultaneously. Compared to gypsum cements, which are treated with additives previously dissolved in water, these mixtures have a shorter onset of setting and a higher viscosity, thus also poorer workability. Due to the presence of both additives in the powder form of cement (especially sodium carbonate), difficulties in storing the cement occur due to their wetting. Furthermore, the presence of both ingredients in powder form means the need for more intensive

CS 270044 Bl processing (spreading) of mixtures of gypsum-free cements, as follows from the author's certificate No. 202 771.

It follows from the above that suitably selected grinding aids, for example dodecylbenzene sulfonic acid derivatives or other eulfonated polyelectrolytes, used in the form of an aqueous solution, favorably affect the properties of Portland clinker based on clinker ground in the presence or absence of gypsum. In practice, however, even with the use of aqueous solutions of said grinding intensifiers, optimal results are not obtained when grinding cementitious plants. The milling process is often destabilized and does not achieve reproducible values of the specific surface area of the resulting product. Now that the milling process has been studied in detail experimentally, it has surprisingly been found that under certain defined values of the operating conditions of the milling process there is a drastic improvement in the milling process with a significant increase in the specific surface area of the ground product. ,

The above-mentioned disadvantages of the prior art are thus substantially eliminated by a method of grinding cementitious alumina and / or Etruscan for the production of cement with a specific surface area of 240 to 580 m 2 / kg, optionally free of gypsum, in a continuous mill, preferably a circulating mill and at least one with the addition of an aqueous solution of a synthetic sulfonated polyelectrolyte, preferably dodecylbenzeneulfonic acid or its derivative or aeol, optionally in shell and alkanolamines as grinding intensifiers to the pre-mill pre-mill and / or to the mill and / or to the return semolina, the essence of which consists in that the synthetic eulfonated polyelectrolyte is added to the cement clinker and / or etruece before milling and / or during milling and / or to the return semolina in the form of an aqueous solution with a dry matter content of 5 to 20% by weight. Preferably, said aqueous solution of synthetic sulfonated polyelectrolyte is added to said gate. semolina with a specific surface area equal to or greater than 170 m / kg. Preferably, the ee maintains a constant ratio of return semolina to finished product in the range of 2: 1 to 10: 1 during milling. This ratio is expressed by weight.

The feasibility of the process according to the invention, as well as the new and higher effect which it achieves in this way, will be demonstrated in the following examples of a specific embodiment of the process according to the invention. Example 1

Cement-based cements were produced on a cement mill for the production of Portland cement under various technological conditions, both in the presence of gypsum and in its absence. The cement mill ee consists of a two-chamber circulating mill e with mechanical circulation of the grist, wind sorters, conveying equipment and dedusting equipment. The mill has dimensions of 4.4 (diameter) x 15 m, the drive of the mill has an input of 2x2 250 kW, the amount of supplied air is 80,000 m ^ / h, the screens of the screens have an output of 260 t / h, the product transport elevator has an output of 350 t / h . The first chamber has a load of 100 t, while the second chamber has a load of 140 t. The flour falls over the outlet chamber by sliding into elevators, which transport both the finished product and the return semolina to the wind classifier. The wind sorter sorts the finished product, i.e. the cement of the required fineness from the coarser parts forming the returnable semolina as well as the returnable semolina ee is returned by the transport master by weight back to the mill. The finished product is transported by a conveyor belt and weighed to bucket elevators for the transport of cement to the eila. The entire grinding process is eluted and regulated by a control eyelet, the core of which is a control computer. The following table shows the characteristic values of technological parameters obtained when grinding standard Portland cement class PC 400, further when grinding cement clinker without added gypsum and when dosing dodecylbenzeneulfonic acid alkalolamides in various concentrations, this dosing was performed by a return semolina dosing device.

OS 270044 Bl

Table

Grinding parameters

PC 400 Clinker + aqueous solution of grinding intensifier with dry matter content% 15%

Mill output (t / h) 80 to 90. 30 to 60 35 to 50 Specific surface of cement (m ² / kg) 330, to 340 350 to 390 240 to 580 Pressure difference on electro- filters (Pa) 250 100 100 Returnable semolina (t / h) 250 to 350 250 to 350 250 to 350 Screen speed per minute 600 to 800 1 400 1 400 Mill temperature (° C) 90 to 100 100 to 110 100 to 110

From the above results it is clear in particular that the use of a milling intensifier in an aqueous solution with a low dry matter content falling within the scope of the invention results in a significant increase in the specific surface area of the ground milling compared to an aqueous solution with a higher milling intensifier content outside the scope of the invention. product, essentially while maintaining the performance of the mill. In addition, in the process according to the invention, a perfect stabilization of the intensifying effect was found, which was manifested by the stabilization of the grinding circuit and the stabilization of the metered amount of clinker as well as the reversible semolina. When adjusting the viscosity of the liquid intensifier / flight (reduction of dry matter content), a less complicated dosing method was found. During the actual grinding process, there is then a higher intensifying effect. Furthermore, it has been found that the grinding method according to the invention does not abruptly grind and grind the mill if there is an uneven dosing of the liquid grinding intensifier. In the grinding method according to the invention, in which the liquid grinding intensifier was sprayed onto the returnable semolina, the grinding intensifier was perfectly dispersed in the final product (dry mixture). When dosing on the return semolina, the effect of tensile conditions on the dosing of the grinding intensifier (drift of the intensifier around the mill chamber) is removed. In the process according to the invention, stable values of the specific surface area of the ground cement were achieved even at higher values of the specific surface area.

Example 2

Mortar and concrete were produced from the cement produced in the production plant according to Example 1. From each production batch, mortars were prepared from continuous granulometry sand (1 t 3) at a water coefficient w 0.32. The following additives were used: 1.5% NagCO 3 and 0.6% Cortane PM, based on the weight of the cement. Both ingredients were dissolved in the exchange water. The onset of solidification was after 50 to 60 minutes. After 24 hours of hydration, the mortars reached the following strengths: for cement with a specific surface area of 406 m / kg 34.4 MPa in pressure and 5.5 MPa in tao hu for bending) for cement with a specific surface area of 380 m / kg 30 MPa in pressure and for cement with a specific surface area of 350 m / kg 27 MPa in pressure. The production batch of cement with a specific surface area above 450 ®7 / kg reached a compressive strength of 42 MPa after 24 hours. Compressive strengths after 28 days of hydration exceeded the values of 50 to 55 MPa in pressure in the monitored production batches. Next, concrete with a composition of 1 (cement) was prepared: 2.48 (fraction 0 to 8 mm): 2.52 (fraction 8 to 16 mm) at a water to cement ratio of 0.27. The cement dose was 510 kg / nP concrete. Cement with a specific surface area of 390 m ² / kg was used in this experiment. This mixture had a workability of about 10 to 15 s with VeBe and an onset of solidification of more than 50 minutes. As additives, soda and Kortan PM were dissolved in the mixing water in concentrations adjusted according to the chemical analysis of sand and aggregates. During the preparation of concrete on a conventional measuring device at an ambient temperature of .3 ° C, the concrete blocks were placed in the open at temperatures of -5 to +8 ° C. The concrete reached a strength after 24 hours (control cube 150x150x150 mm) 27 MPa and after 28 days 51 MPa in compression.

Claims (3)

OBJECT OF THE INVENTION A process for grinding cement clinker and / or slag for the production of cement with a specific surface area of 240 to 580 m 2 / kg, optionally free of gypsum, in a continuous mill or in a circulating mill with at least one classifier, with the addition of an aqueous solution of synthetic sulfonated polyelectrolyte. , in particular dodecylbenzenesulphonic acid or its derivative or salt, or in a mixture with alkanolamines, as a grinding intensifier to the preparation space before the mill and / or to the mill and / or to the return semolina, characterized in that ae synthetic sulfonated polyelectrolyte is added to cement clinker and / or and slag before grinding and / or during grinding and / or in returnable semolina in the form of an aqueous solution with a dry matter content of 5 to 20% by weight. 2. The method according to item 1, characterized in that the aqueous solution of the synthetic sulfonated polyelectrolyte is added to a reversible semolina whose specific surface area is at least 170 m ² / kg. 3. The process according to items 1 and 2, characterized in that a constant weight ratio of return semolina to finished product in the range of 2: 1 to 8: 1 is maintained during grinding.