RU2470880C2 - Method of producing cement - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to the technology of producing water cement used in construction products. In the method of producing cement, involving grinding raw components, mixing, moistening the mixture, briquetting under pressure and then firing the obtained briquettes with size of not less than 20 mm, cement - calcium sulphoaluminate of the following composition in wt % is obtained: CaO 37.9, SiO₂ 0.96, Al₂O₃ 47.3, Fe₂O₃ 1.7, SO₃ 12.0, or the chemical composition, wt %: CaO 37.4, SiO₂ 0.99, Al₂O₃ 48.4, Fe₂O₃ 0.15, SO₃ 12.6, MgO 0.46, or portland cement with the following chemical composition, wt %: CaO 66.84, SiO₂ 22.07, Al₂O₃ 6.05, Fe₂O₃ 3.55, MgO 1.07, SO₃ 0.42, wherein components are mixed first and then dried and ground; moistening is carried out to 13%, briquetting is carried out under pressure of 100-300 MPa, and firing is carried out at temperature of 800-1300°C.

EFFECT: wider raw material base and range of obtained cement, low power consumption of the process and mass loss when producing cement.

3 ex, 8 tbl, 4 dwg

Description

The invention relates to a technology for the production of hydraulic cements used in construction products.

A known method of producing cement, the so-called wet method (Butt Yu.M. Technology of cement and other binders / Yu.M. Butt // M .: Stroyizdat, 1964) [1], including grinding and mixing of raw materials, supply sludge formed in the kiln, firing to clinker and joint grinding of clinker with technological additives. The disadvantage of this method is the significant energy consumption due to the high humidity of the sludge (32-45%) entering the kiln.

A known method of producing cement (Taylor X. Chemistry of cement / X. Taylor // M .: Mir, 1996) [2], including drying the raw materials, their joint grinding, homogenization, calcination, roasting the raw mix and grinding with technological additives, which can conditionally be called the dry method. Compared to the wet method [1], the known dry method [2] is characterized by a reduction in energy consumption for cement production due to the lower moisture content of the raw material mixture supplied for firing (maximum value 8-12%). According to X. Taylor [2], the total heat demand for clinker production by wet method is 5699 kJ / kg, and by dry method - 3306 kJ / kg. The disadvantage of the dry method is the implementation of technological operations with raw materials in a dry pulverized state, which leads to significant entrainment of dust. In rare cases, in the presence of soft raw material, granulation of the raw material mixture is used, however, the humidity of the mixture in this case rises to 20-25% and the energy advantages of the dry method compared to wet are reduced.

A known method of producing alumina cement (RF Patent No. 2353596, publ. 04/27/2009) [3], including grinding lime and aluminate components, their dosage, the addition of alumina cement, mixing, moistening, briquetting under a pressure of at least 15 MPa s the size of the briquettes is not more than 60 mm, followed by firing of the obtained briquettes at a temperature of 1200-1250 ° C and fine grinding of firing products. When implementing the method, it is possible to introduce 1-3% finely ground, short-flame solid fuels, such as petroleum coke, and 1-2% plasticizer and the calcining product into a raw material mixture to a particle size of not more than 50 microns in the presence of a plasticizer and an additive of alumina.

The known method [3] has advantages in comparison with both dry [1] and wet [2] cement production methods by using briquetting, which reduces dust removal and energy consumption for firing due to the low humidity of briquettes 13-17%, however, the method involves firing an excessively wet raw mixture. To remove excess moisture, additional energy is required during firing. An excessively moistened raw material mixture is also poorly pressed, since excess water, being an incompressible liquid, interferes with the compressibility of briquettes when pressing.

In addition, the known method [3] involves pressing the raw material mixture at a pressure of at least 15 MPa without specifying an upper limit on the pressure value. However, our studies have shown that pressing at pressures above 300 MPa does not provide additional advantages for firing the mixture (lowering the firing temperature), since even at pressing pressures of 150 MPa, for most raw material mixtures, the average density approaches true, and a further increase in pressing pressure only leads to to reduce the reliability of equipment and an additional increase in energy consumption for pressing. Studies have also shown that when the pressing pressure is increased to 300 MPa, the firing temperature of some raw mixes to obtain cement can be reduced to 800 ° C, and the upper limit should not exceed 1300 ° C, because when raw briquettes are heated above this temperature, the raw mix is melted.

The objective of the present invention is to expand the technological capabilities of the method of producing hydraulic cements from briquetted raw materials by expanding the raw material base and the range of cements obtained, as well as to reduce the energy consumption of the process and mass loss in the production of cements.

To solve this problem, the method of producing cements includes grinding raw materials, mixing, moistening the mixture, briquetting under pressure, followed by firing the obtained briquettes with a size of at least 20 mm, receive cement - calcium sulfoaluminate of chemical composition, wt.%: CaO 37.9, SiO ₂ 0.96, Al ₂ O ₃ 47.3, Fe ₂ O ₃ 1.7, SO ₃ 12.0, or chemical composition, wt.%: CaO 37.4, SiO ₂ 0.99, Al ₂ O ₃ 48 4, Fe ₂ O ₃ 0.15, SO ₃ 12.6, MgO 0.46, or Portland cement of chemical composition, wt.%: CaO 66.84, SiO ₂ 22.07, Al ₂ O ₃ 6.05, Fe ₂ O _3, 3,55, MgO 1,07, SO ₃ 0.42 by first mixing the components is performed, ATEM drying and grinding, humidification is carried out up to 13%, briquetting is performed at a compaction pressure of 100-300 MPa and briquetted mixture of baking is performed at a temperature of 800-1300 ° C.

установлено, что прессование сырьевой смеси при давлениях от 100 до 300 МПа, позволяет снизить температуру обжига сырьевой смеси при получении сульфатированных цементов на 50-150°С, а оптимальной для прессования этого вида сырья является влажность брикета 5-7%. Установлено также, что практически для всех прессованных сырьевых смесей при обжиге выше 1300°С наблюдается расплавление брикетов, а в зависимости от состава сырьевой смеси, возможно получение хорошего цемента при температуре обжига всего 800°С. Размер брикета в заявленном способе меньший, чем 20 мм, создает дополнительное сопротивление потоку горячего газа, идущего на обжиг сырьевой смеси, снижая эффективность тепломассопереноса, при этом верхний предел влажности брикета (13%) выбран из условий препятствия излишней влаги прессованию и исключения энергозатрат на удаление дополнительной влаги.In studying the effect of pressing on the synthesis of sulfated wedge-forming minerals of composition

it was found that pressing the raw material mixture at pressures from 100 to 300 MPa allows to reduce the firing temperature of the raw material mixture when receiving sulfated cements by 50-150 ° C, and the briquette moisture content of 5-7% is optimal for pressing this type of raw material. It was also established that for almost all pressed raw mixes when firing above 1300 ° C, briquettes melt, and depending on the composition of the raw mix, it is possible to obtain good cement at a firing temperature of only 800 ° C. The briquette size in the inventive method is smaller than 20 mm, which creates additional resistance to the flow of hot gas going to the firing of the raw material mixture, reducing the heat and mass transfer efficiency, while the upper limit of the briquette moisture (13%) is selected from the conditions of preventing excessive moisture from pressing and excluding energy consumption for removal extra moisture.

Thus, the new technical result achieved by the claimed method lies in the efficiency of heat and mass transfer during firing of the raw material mixture, eliminating energy consumption for removing additional moisture during briquette pressing, lowering the temperature of firing the raw material mixture.

The claimed method is illustrated by the following examples.

модулямExample 1. Cement was obtained during the synthesis of calcium sulfoaluminate. Technical alumina, phosphogypsum of Voskresensk Mineral Fertilizers OJSC and calcium hydroxide were used as raw materials. The composition of the feed mixture for the preparation of calcium sulfoaluminate was calculated from aluminate Am and sulfate

modules

The estimated composition of the raw mixture of Ca (OH) ₂ is 38.0%, Al ₂ O ₃ is 40.3%, phosphogypsum is 21.7%. The chemical composition of the raw mix and clinker in wt.% Are shown in table 1.

The raw material mixture was prepared according to the calculated modular characteristics and mixed at natural humidity. After mixing, the raw material mixture was dried, subjected to grinding and water was introduced into it with stirring to the optimum value for pressing - 5-7%. After preparation, the raw material mixture was pressed at pressures of 0, 100, 200 and 300 MPa. The pressing of the raw mixture was carried out at temperatures of 700, 900, 1100 and 1300 ° C. The resulting samples were studied by x-ray phase analysis. X-ray phase analysis was performed on a DRON-3 device. Fully synthesized minerals were crushed to a residue on sieve 008 no more than 5%. The binder obtained in this way was closed with water at a weight of 0.4 and placed in a 2 × 2 × 2 mold. After daily hardening, the samples were removed and immersed in water. The compressive strength was determined after 1, 3, 7, 14 and 28 days of hardening. The results of an x-ray phase analysis of the synthesis of calcium sulfoaluminate are presented in Fig. 1.

In the X-ray diffraction patterns shown in Fig. 1, it can be seen that as the pressing pressure increases, the intensity of the X-ray peaks of the synthesized mineral increases. At a firing temperature of 1300 ° C, the briquettes were partially melted, and a decrease in the physicomechanical properties of cement was observed. Figure 2 shows the contours of the diffraction maximum of calcium sulfoaluminate with d = 3.72 Å depending on the pressing pressure and the firing temperature of the raw material mixture.

The results of processing the experimental data indicate that, without pressing, the nuclei of a new phase (intensity of more than 100 units) are fixed at a temperature of 1050 ° С, and when pressing a raw mixture at a pressure of 300 MPa already at a temperature of 900 ° С.

To determine the physicomechanical properties of calcium sulfoaluminate, the raw material mixture of the calculated composition was pressed at a pressure of 200 MPa and fired at an optimum temperature of 1200 ° C. The kinetics of the set strength of calcium sulfoaluminate synthesized at 1200 ° C are presented in table 2.

Example 2. For the synthesis of Portland cement used limestone, clay and pyrite cinder. The modular characteristics of the synthesized cement were KN = 0.9; n = 2.3 and p = 1.7. The chemical composition of the raw mix and clinker in wt.% Are shown in table 3.

The raw material mixture prepared in accordance with the calculated data was dried to constant mass and subjected to joint grinding in a ball mill. After grinding, the raw mixture was moistened to a moisture content of 5-7% and was pressed at pressures of 0, 100, 200 and 300 MPa. Pressed raw material mixture was fired at temperatures of 1200, 1250, 1300, 1350 and 1400 ° C. In similarly obtained samples, the content of free lime was determined by the sugar-glycerate method. The physicomechanical properties of the cement synthesized in a similar way were determined as for sulfoaluminate cements, and a composition pressed at a pressure of 300 MPa with a firing temperature of 1300 ° C was chosen. Figure 3 shows contours of equal content in the samples of free lime depending on the pressing pressure and firing temperature.

The data presented indicate that the content of free lime in the studied samples of less than 5% is achieved in samples pressed at a pressure of 300 MPa at a firing temperature of about 1275 ° C, and to achieve such a value for the content of free lime in unpressed samples, they should be fired like ordinary Portland cement at a temperature of more than 1400 ° C.

The kinetics of the set strength of Portland cement synthesized at 1300 ° C is presented in table 4.

Example 3. Calcium sulfoaluminate was synthesized with the modular characteristics shown in Example 1. Calcium oxide (aspiration metallurgical lime) with an activity of 98.9%, calcined at a temperature of 600 ° C, technical alumina and phosphogypsum anhydrite was used as raw materials obtained by firing phosphogypsum at 600 ° C. The chemical composition of the starting components and clinker in wt.% Are presented in table 5.

The raw material mixture was prepared according to the calculated modular characteristics and mixed in a dry state. After mixing, the raw material mixture was subjected to joint grinding to a residue of sieve 008 of not more than 15%. After preparation, the raw material mixture was dry pressed at pressures of 0, 100, 200 and 300 MPa. The pressing of the raw mixture was carried out at temperatures of 700, 800, 900 and 1000 ° C. After firing, it turned out that the pressed samples calcined at a temperature of 1000 ° C melted, so only samples calcined at temperatures from 700 to 900 ° C were given for X-ray phase analysis. The resulting samples were studied by x-ray phase analysis. X-ray phase analysis was performed on a DRON-3 device.

Figure 4 shows the contours of the diffraction maximum of calcium sulfoaluminate with d = 3.72 Å depending on the pressing pressure and the firing temperature of the raw material mixture.

The results of processing the experimental data indicate that the maximum intensity of the diffraction maximum with d = 3.72 Å, equal to the absolute intensity of 450 units, is achieved in a mixture pressed at 300 MPa at a firing temperature of approximately 840-850 ° C.

The minerals synthesized in this way were crushed to a residue on sieve 008 of not more than 5%. The resulting binder was closed with water at a w / w 0.4 and placed in a 2 × 2 × 2 mold. After daily hardening, the samples were removed and immersed in water. The compressive strength was determined after 1, 3, 7, 14 and 28 days of hardening.

The kinetics of the strength set of calcium sulfoaluminate synthesized at 850 ° C are presented in table 6.

The test results shown in examples 1-3, indicate that using carbonate, clay, ferrous and sulfate components of the raw material mixture, the inventive method can be used to synthesize cements of various mineralogical composition. Tables 7 and 8 below contain the parameters of comparative tests and the physicomechanical properties of the tested samples, respectively.

In accordance with the requirements of GOST 31108-2003 "Cement for general construction. Technical conditions ”the synthesized in the test conditions cements can be assigned the following grades:

Example 1 - CEM 1 52.5B, GOST 31108-2003; Example 2 - CEM 1 42.5N, GOST 31108-2003; Example 3 - CEM 1 42.5N, GOST 31108-2003.

It should be noted that the cement from example 1 and the cement from example 3 do not meet the requirements of GOST in terms of setting, therefore, for these cements, you should develop your own regulatory framework.

Thus, in relation to the prototype of the claimed method is characterized by wider technological capabilities for producing hydraulic cements from briquetted raw materials, including expanding the range of cements obtained, as well as reducing the energy intensity of the process and mass loss in production.

Table 1 The chemical composition of the raw mix and clinker, wt.% Component CaO SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ SO ₃ MgO Δm _PPH. Metallic Lime Calcium Hydroxide 54.0 0.01 0.02 0,03 0 0 45.5 Technical Alumina 0.3 0.2 85.0 0.1 0 0 6.0 Phosphogypsum 32.02 2,8 0.45 0.24 40.15 0 22.56 Clinker 37.9 0.96 47.3 1.7 12.0 0 0

table 2 Kinetics of Strength Calcium Sulfoaluminate Synthesized at 1200 ° C Name of material Compressive Strength, MPa, in days 0 one 3 7 fourteen 28 Calcium Sulfoaluminate 0 16.6 30.9 41.97 51 60.1

Table 3 The chemical composition of the raw mix and clinker, wt.% Raw material CaO SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ MgO SO ₃ Δm _PPH. Limestone 52.89 1.38 1.55 0.35 0.46 0.19 43.18 Clay 2.69 73.68 15.02 3.69 1.8 0.31 2.81 Pyrite cinder 2.88 13.74 1,53 76.95 0.32 3.78 0.8 Clinker 66.84 22.07 6.05 3,55 1,07 0.42 -

Table 4 Kinetics of Portland Cement Strength Synthesized at 1300 ° C Name of material Compressive Strength, MPa, in days 0 one 3 7 fourteen 28 Portland cement 0 2.9 17.47 30.95 41.9 53.1

Table 5 The chemical composition of the raw mix and clinker, wt.% Component CaO SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ SO ₃ MgO Δm _PPH. Calcium oxide 98.9 0.018 0,037 0,055 0 0 0 Technical Alumina 0.35 0.234 99.3 0.117 0 0 0 Anhydrite 41.5 3.63 0.583 0.311 52.04 1.9 0 Clinker 37,4 0.99 48,4 0.15 12.6 0.46 0

Table 6 Kinetics of Strength Calcium Sulfoaluminate Synthesized at 850 ° C Name of material Compressive Strength, MPa, in, days 0 one 3 7 fourteen 28 Calcium Sulfoaluminate 0 15,2 27.8 39,4 48,2 53,2

Table 7 Comparative Test Parameters Name of cements and test parameters Content, wt.% Example 1 Example 2 Example 3 Name of cement Calcium Sulfoaluminate Portland cement Calcium Sulfoaluminate The moisture content of the raw mix, wt.% 5.0-7.0 5.0-7.0 0 Pressing Pressure, MPa 200 300 300 Firing temperature, ° С 1200 1275 850

Table 8 Physico-mechanical properties of tested cements Name of cement and example S, m ² / kg R ₀₀₈ % NG,% Setting time
h - min W / C RK Rszh, MPa,
in days Start end 2 28 Sample 1, calcium sulfoaluminate 328 3.0 28.0 0-5 0-10 0.36 114 23.8 60.1 Sample 2, Portland cement 302 4.2 24.5 4-20 9-15 0.35 113 11.1 53.1 Sample 3, calcium sulfoaluminate 330 3.6 30,0 0-31 1-10 0.36 115 15.8 53,2

Claims (1)

A method of producing cements, including grinding raw materials, mixing, moistening the mixture, briquetting under pressure, followed by firing the obtained briquettes with a size of at least 20 mm, characterized in that cement is obtained - calcium sulfoaluminate of chemical composition, wt.%: CaO 37.9, SiO ₂ 0.96, Al ₂ O ₃ 47.3, Fe ₂ O ₃ 1.7, SO ₃ 12.0, or chemical composition, wt.%: CaO 37.4, SiO ₂ 0.99, Al ₂ O ₃ 48.4, Fe ₂ O ₃ 0.15, SO ₃ 12.6, MgO 0.46, or Portland cement of chemical composition, wt.%: CaO 66.84, SiO ₂ 22.07, Al ₂ O ₃ 6.05 , Fe ₂ O ₃ 3,55, MgO 1,07, SO ₃ 0,42, while the components are first mixed, I eat drying and grinding, humidification is carried out up to 13%, briquetting is carried out at a pressing pressure of 100-300 MPa, and firing is carried out at a temperature of 800-1300 ° C.

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