RU2237628C1 - Process of manufacturing belite portland cement clinker involving dust control during the firing operation, and cement based on this clinker - Google Patents

Abstract

FIELD: manufacture of building materials.

SUBSTANCE: process comprises (i) providing starting cement mix containing carbonate, aluminosilicate, and ferrous ingredients, (ii) firing thereof until caking in rotating furnace with flame combustion of process fuel, and (iii) cooling thus obtained clinker, which contains free CaO, β-C₂S, C₃S, C₃A, and C₄AF. According to invention, firing is conducted under neutral atmosphere with content of oxygen in gases leaving rotating furnace 0.2-0.7 wt % until first clinker melt is formed at 1050-1179^оС from mixture of CaO-C, CF₂, RF, RA contained in fired material, which is partially granulated and crystallized from free CaO melt with dendrite and dot microstructure, after which a second eutectic clinker melt is formed from the preceding melt at 1230-1270^оС and second clinker is then granulated therefrom with following proportions of principal phases, wt %: free CaO 5-25, β-C₂S 40-60, C₃S 3-10, C₃A 0.01-10, and C₄AF 8-20. Carbonate and aluminosilicate ingredients of raw mix and fineness of their grinding are selected from the criterion of at least partial overlapping of firing temperature ranges for decarbonization of carbonate ingredient and dehydroxylation of aluminosilicate ingredient of raw mix at weight ratio of these ingredients within a range of 0.5 to 0.6 corresponding to lime saturation factor for raw mix. Caking is completed when porosity of belite clinker achieves 35-47 vol %. Silica modulus of raw mix varies from 0.05 to 0,8. Combustion flame of process fuel in rotating furnace during firing of clinker is approached to segment of the material being fired so adjusting central angle of segment to 115-125^о, whereas fuel supply is controlled until full transparency of surface atmosphere is reached. Cement obtained upon joint grinding of indicated belite clinker with separately fired alite Portland cement clinker including at least 60% alite, and gypsum component further contains active mineral additive with 3-8% moisture and finally contains, wt %: belite clinker 15-30, alite clinker 45-50, mineral additive 10-35, and gypsum component 3-10. During the grinding, free CaO contained in belite clinker is simultaneously converted into calcium hydroxide with degree of conversion 70-98%. Gypsum component is selected from reagent-grade calcium sulfate, gypsum stone, gypsum-anhydrite stone, phosphogypsum, borogypsum, titanogypsum, and their mixture.

EFFECT: reduced dust formation during clinker firing operation, diminished furl consumption, increased strength and grinding ability of cement, productivity of furnaces and mills.

7 cl, 1 tbl, 2 ex

Description

The invention relates to the field of building materials, namely, to a method for manufacturing clinker and cement made on its basis.

; коэффициент при оксиде становится подстрочным индексом.The prior art method for the manufacture of Portland cement clinker, including the preparation of a cement raw material mixture of carbonate, aluminosilicate and ferrous ingredients, its burning before sintering in a rotary kiln, cooling the resulting clinker and its joint grinding with a gypsum component [1]. The specified Portland cement clinker includes the following main clinker minerals: tricalcium silicate (3CaO · SiO ₂ ), dicalcium silicate (2CaO · SiO ₂ ), tricalcium aluminate (3CaO · Al ₂ O ₃ ), calcium aluminoferrite [2CaO · (Al ₂ O ₃ x (Fe ₂ O ₃ ) _1-x ], x from 1/3 to 2/3 (in industrial clinkers, these minerals containing impurities, as suggested by V. Ternebom, 1897, are also called, respectively, alite, belite, highly basic calcium aluminate and celite ; here and below, in the description of the invention, the abbreviated notation used in cement chemistry is used: A ₂ O ₃ = A; CaO = C; Fe ₂ О ₃ = F; F ^- (fluoride ion) = f; Н ₂ О = Н; К ₂ О = К; MgO = M; Na ₂ O = N; Р ₂ O ₅ = Р; sum of alkali metal oxides in terms of per sodium oxide Na ₂ O + 0.658K ₂ O = R ₂ O = R; SiO ₂ = S; SO ₃ =

; the oxide coefficient becomes a subscript.

So, Ca ₃ SiO ₅ = 3CaO · SiO ₂ = C ₃ S, etc .; in addition, the losses during calcination are abbreviated as ppt, and the insoluble residue is n.o., with the following ratio of these minerals (wt.%): alite 60-65, bleach 15-20, tricalcium aluminate 3-12 Calcium aluminoferrite 8-15. Such Portland cement clinker, including more than 60 wt.% Alite, is called alite [2], corresponding in composition to the value of the clinker saturation coefficient of lime (KN) of 0.88-0.95. Note that the value of KH is determined, according to V.A. Kind [3], by the formula: KH = [C- (1.65A + 0.35F)] / 2.8S; silicate n and alumina p modules are calculated according to the formulas, respectively: n = S / (A + F), p = A / F.

For this well-known technical solution that defines the traditional level of technology, the following are characteristic: 1) low productivity of furnaces; 2) increased fuel costs for firing said Portland cement clinker; 3) high dust formation during firing of the cement raw material mixture due to the increased content of carbonate ingredient (CaCO ₃ ) (CaCO ₃ ) in it, the particles of which during the removal of CO ₂ often explode and form dust (particle fraction less than 0 , 1 mm) in the amount of about one fifth of the mass of the carbonate ingredient, and also: 4) the low grindability of the specified clinker, which determines the reduced productivity of cement mills, and 5) the low hydraulic activity of the specified clinker, also manifested in slow hardening of Portland cement made of it in the initial period of hardening, namely within 1-3 days. These phenomena are caused by a high level of activation energy calculated by the S. Arrhenius equation (more than 1880 kJ / mol) and a long induction period of reactions of formation of the most important clinker mineral - tricalcium silicate (alite) - in the calcined material in the sintering zone of clinker kilns, and the longer this period, the lower the hydration rate of this mineral and the lower the strength of the cement stone after grinding the specified clinker and mixing the cement obtained from it with water.

The simplest technical solution to improve the situation is the method of manufacturing Portland cement clinker, in which the latter leaves free calcium oxide, that is, the clinker is not burned to reduce fuel consumption [4]. A similar approach was also used by O. P. Mchedlov-Petrosyan and N. P. Kogan [5]. However, in the unburnt clinker, along with the mentioned main clinker minerals, impurities remain, such as mayenite (C ₁₂ A ₇ ), dicalcium ferrite (C ₂ F), monocalcium ferrite (CF), which reduce the strength characteristics of cement and the durability of concrete [6]. In the last of the works in this field [7], these impurities are called marginal phases, since they do not carry useful functions, but only waste aluminum and iron oxides, as well as thermal energy.

A known method of manufacturing a belite Portland cement clinker, comprising preparing a cement raw material mixture of carbonate, aluminosilicate and ferrous ingredients, firing it before sintering in a rotary kiln and cooling the obtained belite clinker, characterized in that the firing of the raw material mixture is carried out with significant savings in process fuel [8] . The fuel economy effect according to the links given is due to a decrease in the proportion of carbonate ingredient in the raw material mixture for calcining belite clinkers compared to alitic clinkers and, consequently, a decrease in energy consumption for decarbonization of raw materials in the heat balance of the furnace. However, the classical calculation schemes of such a balance, on which these works relied, are now outdated, since they do not take into account what has become obvious (as a result of the work of B. Entin et al. [6, 7], as well as V.I. Shein, T .Yu.Shchetkina and their employees - see, for example, the work of one of their students [9]) the cyclical nature of a number of mineral formation reactions. Without taking into account these high-temperature cyclic reactions, namely, by the heat of dissolution of the corresponding clinkers in mixtures of nitric and hydrofluoric acids, it was found that the chemical energy “stored” in the clinker minerals of belite clinker is 1580-1690 kJ / kg against 1900-1910 kJ / kg - in minerals of alite clinker, or 13-17% lower. But it was found that it should not be identified with energy consumption for firing belite and alite Portland cement clinkers, equal, as shown by the experiments of their sintering in a calorimetric bomb, respectively 720 and 726 kJ / kg, that is, almost the same [10]. The last group of researchers from the Russian Technical University named after D.I.Mendeleev, headed by A.P. Osokin, this result seemed unexpected, because in many domestic and foreign works the aforementioned point of view was held on the possibility of saving fuel on firing by reducing the KN value of Portland cement clinker or firing of whiteite clinkers (see, for example, the latest review in this area by Albats et al. [11]). However, in foreign literature on this issue, in fact, the opposite point of view prevails, supported by the results of the aforementioned calorimetric studies of Osokin and employees. It was first expressed by domestic researchers D.A. Chernobaev and G.A. Vologdin in 1912 in a paper published on the submission of Acad. A. Le Chatelier in the Reports of the French Academy of Sciences, where they reported that when firing belite clinkers in a calorimetric bomb, energy consumption does not decrease compared to alite clinkers [12]. Chernobaev published the results of relevant studies in more detail in a monograph published in Russia [13]. Note that before his present description there was not a single reference to his work in the domestic patent and scientific literature. But the results of Chernobaev were cited by R. Bogg (USA) in 1955 in his classic monograph on the chemistry of Portland cement [14], which, in the opinion of a number of researchers, became “the main book of the 20th century in this area” (H. Calieha, C. Gilioli , X. Uchikawa). Bogg explained the data of Chernobaev and, therefore, Osokin et al. That the firing of belite clinkers increases the thickness of the belite shells on the particles of the material to be fired that react with each other in the clinker melt. This causes an increase in the activation energy of mineral formation reactions in connection with an increase in the height of diffusion barriers, leading to an increase in the required energy consumption, which compensates for the mentioned difference in energy consumption for decarbonization in the heat balance. Bogg points out that it is for this reason that there are no factors in the formulas for calculating the productivity of rotary kilns related to the chemical composition of the raw material mixture. The last statement, true in 1955, remains valid today: there are still no design formulas that relate the performance of clinker kilns of any type with the KN values of the Portland cement clinkers burned in them. Moreover, in one of the research papers there was an increase in specific fuel consumption during firing of belite clinkers. These are the data of M.T. Vlasova, V.N. Kalyanova and one of the authors of this invention: during long-term, lasting more than eight months, experiments on continuous firing in the rotary kilns of the wet method of belite clinker (KN 0.76-0.8), including not more than 1% by weight of free calcium oxide (CaO _svob ), with a strict rejection of products that did not meet the latter indicator (NIIITsement, scientific and technical report, M .: 1960). In these experiments, it was found not only that there is no saving in process fuel, but also its overspending compared to alitic clinkers, due to the fact that the layer of belite clinker in a rotary kiln is more porous compared to alitic clinkers, the fuel combustion torch heats up worse, and a random deviation of the mode the operation of the furnace, accompanied by the appearance in the indicated clinker of CaO _freedom in excess amounts, leads to a prolonged production of substandard products, and attempts to eliminate this phenomenon are traditional a continuous long increase in fuel consumption (within 24-48 hours) in the furnace does not give a positive result, and in this case it was easier to stop the firing, unload all the unfinished material from the furnace and start firing again. All this led to the over-consumption of process fuel (as compared to the burning of alite clinker) during many months of firing of belite Portland cement clinker under conditions of strict quality control of the latter. By duration, none of the experiments mentioned in the last review [11] came close to the experiments of Vlasova et al. and - most importantly - not one of them was accompanied by such strict quality control of belite clinker.

There is also known a method of manufacturing a belite Portland cement clinker, comprising preparing a cement raw material mixture from carbonate, aluminosilicate and ferrous ingredients, firing it before sintering in a rotary kiln, and cooling the obtained belite clinker, characterized in that said clinker is cooled at the maximum achievable speed (more than 100 degrees Celsius per minute) to obtain the phase composition of the specified clinker extremely remote from the equilibrium [15]. This method really improves the quality of belite clinker, but it is difficult to implementation in an industrial environment, since it is characterized by the above-described difficulties in complying with the standard level of CaO in _svob belite clinker.

Closest to the present invention is a method of manufacturing a whitish Portland cement clinker, comprising preparing a cement raw material mixture of carbonate, aluminosilicate and ferrous ingredients, firing it before sintering in a rotary kiln with flaring process fuel, dust suppression and cooling of the obtained belite clinker, characterized in that the specified cement raw mix is conducted in an oxidizing atmosphere until the formation of the first clinker melt at (1250-1280) ° C in Gigue material therefrom and crystallization of clinker minerals with the following ratio of phases in the finished belite clinker, wt.%:

Free calcium oxide (CaO _svob) 0.5-3

Belite (β -C ₂ S) 40-48

Alite (C _s S) 15-35

Tricalcium aluminate (C ₃ A) 0.01-7

Aluminoferritic phase (C ₄ AF) 8-18

moreover, gypsum is introduced into the composition of the specified raw material mixture as a stabilizer for belite in an amount of 1-5 wt.%, and dust emission from the furnace is 10-15% of the clinker mass [16]. Dust suppression in this case is due to the fact that the cement raw mix for the specified belite clinker contains more clay than for alite. This reduces the removal of dust from areas of the rotary kiln in which the properties of clay to bind the particles of the calcined material prevail over abrasion when the specified material moves along the kiln. In addition, a decrease in the carbonate component content, decreasing the CO ₃ content in the exhaust gases and the total volume of the latter, reduces the gas flow rate in the furnace, which, as is known [2], proportionally reduces dust emission. The minimum dust emission - 10% in the technical solution for the closest analogue corresponds exactly to the belite clinker [16, s. 362].

The objective of the invention in terms of a method of manufacturing a portite cement clinker with dust suppression during its firing is the complete elimination of dust formation in the furnace during firing of a portland cement clinker, with a significant reduction in energy consumption for firing and reducing the resistance of the specified clinker to grinding.

This problem is solved by the fact that in the method of manufacturing belitovogo Portland cement clinker with dust suppression during its firing, including the preparation of a cement raw material mixture containing carbonate, aluminosilicate and ferrous ingredients, its firing before sintering in a rotary kiln with flaring of the technological fuel and cooling of the obtained whitish portland cement wedge containing free calcium oxide (CaO _svob ), belite (β-C ₂ S), alite (C ₃ S), tricalcium aluminate (C ₃ A) and aluminoferrite phase (C ₄ AF), roasting The cementitious raw material mixture is conducted in a neutral atmosphere with an oxygen content in the exhaust gases of a rotary kiln in the range of 0.2-0.7 wt.% until the formation of the first clinker melt at 1050-1170 ° С based on a mixture of CaO - С, CaO · 2Fe ₂ O ₃ - CF ₂ , R ₂ O · Fe ₂ O ₃ - RF, R ₂ O · Al ₂ O ₃ - RA in the calcined material with partial granulation of the latter and crystallization of the _free dendritic and point microstructure from the indicated CaO melt and subsequent formation from the specified the melt of the second clinker melt of eutectic composition at 1230-1270 ° C with granulation floor chennogo therefrom clinker at the following ratios of the main phases in the latter, wt.%:

Specified CaO _freedom 5-25

β -C ₂ S 40-60

C ₃ S 1-10

C ₃ A 0.01-10

C ₄ AF 8-20

In an embodiment of the invention, the carbonate and aluminosilicate ingredients of the specified raw material mixture and the fineness of their grinding are selected according to the criterion of at least partial overlapping during firing of the temperature ranges of decarbonation of the carbonate and dehydroxylation of the aluminosilicate ingredients of the specified raw mixture with the mass ratio of these components corresponding to the lime saturation coefficient of the specified raw mixture in the range of 0.5-0.6, and firing before sintering is carried out until the porosity of the specified belite clinker 35-47 about.%.

In another embodiment of the invention take the specified raw material mixture, characterized by an alumina module in the range of 0.05-0.8.

In a further embodiment of the invention, the combustion torch of the process fuel in a rotary kiln during firing of said belite clinker is brought closer to the segment of the fired material, bringing the central angle of the indicated segment to 115-125 °, and the fuel supply is regulated until the furnace atmosphere is completely transparent.

The essence of the invention in terms of a method of manufacturing a whitish Portland cement clinker is the early formation of the first clinker melt, namely about 1050 ° C, exhibiting fastening properties when melting according to the Tamman rule, that is, at a temperature of 15% lower than the melting point, on average 895 ° C, thereby almost completely covering the temperature range of decarbonization of the carbonate ingredient of the cement raw material mixture, comprising (870-930) ° C - according to differential thermal analysis (DTA), Whether about (920-1010) ° C - in the production of the rotary kiln - a melting endothermic effect compared with the control mixture at normal firing schedule Alitova clinker furnace body temperature curve corrected for the heat absorption of the refractory lining. Decarbonation “dry”, that is, in the absence of clinker melt in the furnace, which often occurs with explosive destruction of particles of the carbonate component of the cement raw material mixture, known from the prior art, is the main cause of dust formation in brick kiln and, accordingly, smoke plume from pipes of cement plants. The binding properties of the first clinker melt indicated above make it possible to suppress dust formation in the furnace during the manufacture of the Belite Portland cement clinker according to the invention, up to dust collector in the amount of 2-3% of the mass of clinker versus dust collector at a level of 10-15% of the mass of clinker exiting the prior art.

The main factor that determines the appearance and the above expression of the useful properties of low-temperature obscheklinkernogo melt - is in this case free of calcium oxide (CaO _svob) leaving a belite clinker according to the invention, a compound which with dvuhkaltsevym calcium ferrite (CF _2), ferrites of alkali metals, preferably sodium (RF), aluminates of alkali metals, mainly potassium (RA), passing at the end of the stage into a solid solution of calcium oxide (CaO) with dicalcium ferrite (C ₂ F) with a final composition of 18.5 CaO · Fe ₂ O ₃ with the displacement of the remaining oxides, it is the basis of the first clinker melt. This melt differs from the known primary melts formed in the presence of mineralizers in that the latter are surface-active films surrounding the particles of the calcined material and separating them from each other, having minimal binding properties [17], while the first melt in the specified calcined material based on the cement raw material mixture according to the invention is a bulk liquid phase impregnating the grains of the material and fastening them into primary (“white”) granules, corresponding to the lower temperature range the formation of melt fracture without passing then into normal clinker granules are formed from the primary granules after their formation and impregnating the second clinker melt eutectic composition. White granules can be seen by temporarily extinguishing the fuel burning torch and allowing these primary granules to appear at the exit of the furnace. The role of a neutral atmosphere, corresponding to the oxygen content in the exhaust gases (0.2-0.7) wt.% And the minimum coefficient of excess air a (within 1.01-1.03), in which existing standards [18] do not allow firing conventional Portland cement clinker (required and in the range of 1.05-1.15 [1]), is a higher reactivity and smaller size of the Fe ²⁺ ion compared to the Fe ³⁺ ion. This not only accelerates the formation of the indicated first melt, but also allows iron (II) ions, due to their smaller diameter, to more quickly occupy Schottky defects (vacancies) in the CaO _free crystal lattice, forming first CF ₂ and then C _18.5 F, strengthening the binders properties of the specified clinker melt and granulation. It is this that significantly suppresses dusting in the furnace, since it occurs in the most hazardous dust generation zone of the specified furnace - in the decarbonization zone.

It should be noted that the neutral nature of the furnace atmosphere in this case is characterized by the oxygen content in the exhaust gases of rotary kilns, since this is the most easily determined parameter in practice. The specified content according to the invention is maintained in the range of (0.2-0.7) wt.% Against (1.0-1.8) wt.% In a normal oxidizing atmosphere depending on the type of fuel (solid, liquid, gaseous [19] ), and with the transition from the first type of fuel to the last, the standard oxygen content in the furnace exhaust gases gradually increases within the specified limits both with the prior art (according to [19]) and in the method according to the invention.

The dendritic or point microstructure of free calcium oxide generated during crystallization of the liquid phase determines its high hydration activity, and the admixture of iron in it determines the absence of free valencies that are found in free lime, which is an undesirable impurity in conventional Portland cement clinker, and causes irritation mucous membranes in the staff, in particular tearing. When firing a belite clinker by the method according to the invention, this phenomenon is not observed, and both its firing and grinding are carried out without any inconvenience to the production personnel.

In an embodiment of the invention, an additional factor is taken into account, which reduces dust generation in the furnace to less than 2% of the mass of the specified clinker by preventing explosive decarbonization of particles of the specified raw mix due to overlapping or partial coincidence of the temperature ranges of decarbonization of lime and dehydroxylation of aluminosilicate ingredients of the specified mixture, which is determined by the selection of the composition raw materials. According to Hadwall [20], the coincidence of the temperature ranges of the decomposition of the ingredients during firing of the cement raw material mixture accelerates the solid-phase reactions between them (the Hadwall effect), which under the considered conditions reduces dust formation due to the formation of shells from reaction products that bind the interacting particles of carbonate and aluminosilicate ingredients. So, chalk is usually decarbonized at (830-920) ° С (according to DTA) or at (850-970) ° С in a rotary kiln, and montmorillonite clays are dehydroxylated at (770-840) ° С (according to DTA) or at (820-900) ° C in a rotary kiln. By selecting raw ingredients including chalk and similar clays, it is possible to further reduce dust emission during the firing of the Portland cement clinker according to the invention. A change in the fineness of grinding of these raw ingredients shifts the indicated temperature ranges of their decomposition, with an increase in dispersion - in the direction of lowering the boundary values of these temperatures, and a decrease - in the direction of increasing them. Thus, the decomposition interval of the finer carbonate ingredient to a greater extent covers the decomposition interval of the aluminosilicate ingredient, which contributes to a more noticeable reduction in dust formation in the furnace. This decrease is most noticeable in the indicated range of KH values of the specified raw material mixture in the range of 0.5-0.81, with a total porosity of sintered belite clinker in the range of (35-47)%, which is a very high level compared to the prior art - (18-24)% [21] and is explained by reduced fire shrinkage of the calcined material at the above KN values of the specified raw material mixture according to the method according to the invention.

In a further embodiment of the invention, it is taken into account that the increase in the relative iron content in the melt in the calcined raw material mixture, determined by the range of the alumina module in its composition from 0.05-0.7, reduces the primary appearance temperature by about (15-40) ° С clinker melt during firing of the specified belite clinker, which, in turn, helps to reduce dust formation in the furnace.

An embodiment of the invention takes into account that the enhancement of radiant heat transfer between the fuel combustion torch in a rotary kiln by bringing the fuel combustion torch closer to the segment of the material to be fired reduces fuel consumption and, consequently, the amount and speed of exhaust gases in the furnace. The latter contributes to a decrease in the content of CO ₂ in the furnace atmosphere in connection with a decrease in the proportion of calcium carbonate in the cement raw material mixture, calculated on the calcination of the specified belite clinker. An increase in the content of Fe ^{2+ ions} due to the ingress of part of the material to be burned to the periphery of the fuel flame and the general neutral furnace atmosphere in this case allows, by lowering fuel consumption, to accelerate the combustion process due to the increased availability of the flame to secondary air, which increases the temperature in the sintering zone of the furnace , leads to the approach of the zone of formation of the first clinker melt to the furnace head and, accordingly, to the zone of formation of the second clinker melt. This, in the presence of the Hadwall effect and in fine grinding of the raw material mixture and the other process parameters mentioned above, according to the invention, leads to complete transparency of the furnace atmosphere, which is determined by the fact that when the fuel flame is temporarily turned off from the furnace head, the details of the chain curtain in the furnaces are clearly visible wet production method, and there is completely no dust emission from the furnace even with completely disabled dust precipitation devices on the exhaust gas path. This latter is also observed when firing the specified clinker in dry process furnaces.

It should be added that when the mentioned primary “white” granules fall into the zone of formation of the second all-clinker melt, their progress along the longitudinal axis of the furnace slows down. In this case, a “hill” is formed from the calcined material in the second sintering zone of the furnace, close to the furnace head. Behind the said hill, looking from the side of the fuel burning torch, in the form of a second bright zone in the rotary kiln, the primary sintering zone of the calcined material of the white composition is visible, and behind it is the entire longitudinal section of the kiln, right up to chain curtains in the initial part of the rotary kiln of the wet production method. Thus, the partial overlap of two bright zones of the furnace by adjusting the flow of process fuel after the furnace enters the operating mode according to the invention for the first time becomes possible to adjust by visual inspection, without turning off the fuel flame. In this case, as a rule, the primary light gray (“white”) granules of the calcined material are impregnated with a second, high-temperature melt without their destruction. Impregnation begins with their outer zones and proceeds very quickly, much faster than during the burning of alite clinkers, obviously, due to the increased porosity of the belite clinker and greater mobility of the melt compared to those observed during the burning of alite clinkers. This allows you to accelerate the progress of the calcined material through the furnace, to increase the productivity of the furnace while completely eliminating clinker dusting both in the rotary kiln and in the clinker cooler. As a result, the main technical effect of the invention is achieved, which is at the same time the main element of its unexpectedness - the complete absence of dust formation during clinker burning in a rotary kiln.

The invention becomes clearer from an example of its implementation.

Example 1

Raw materials:

- carbonate ingredient: chalk composition (wt.%): pp 42, 29; SiO ₂ 1.61; Al ₂ O ₃ 0.69; Fe ₂ O ₃ 0.33; CaO 54.10; MgO 0.38; SO ₃ 0.25; the sum of 99.65, impurities - the rest, the temperature range of decarbonization in the state of the powder with 10% residue on sieve No. 02: (855-920) ° C;

- aluminosilicate ingredient: clay composition (wt.%): pp 5.33; SiO ₂ 67.07; Al ₂ O ₃ 12.48; Fe ₂ O ₃ 5.08; CaO 2.82; MgO 2.25; SO ₃ 1.96; R ₂ O 2.65; the sum of 99.64, impurities - the rest, the temperature range of dehydroxylation in the state of the powder with 1% residue on sieve No. 02: (775-860) ° C;

- glandular ingredient: pyrite cinder composition (wt.%): p.p. 0; SiO ₂ 8.18; Al ₂ O ₃ 2.02; Fe ₂ O ₃ 79.68; CaO 1.84; MgO 1.33; SO ₃ 4.99; amount 98.04; impurities - the rest.

To obtain clinker and cement according to the proposed method, a rotary kiln with a diameter of 3.6 and a length of 70 m with flaring of natural gas with a calorific value of about 6700 kcal / kg, or about 28000 kJ / kg, is used as a clinker kiln.

In the first series of experiments, when firing a control feed mixture with a fineness of grinding according to the residue on sieve No. 02 of 2.8-3 wt.%, The average productivity of the furnace for clinker in the control mode according to the closest analogue was 12 t / h, and when firing the feed mixture with that the same fineness of grinding to obtain a Portite cement clinker according to the invention is 13.6 t / h (+ 13 wt.%), with the following average characteristics of a Portland cement clinker (KK-1) and said belite clinker according to the invention (BK-1):

KK-1: KH 0.91, n 1.93, p 1.03; mineralogical composition (according to V.A. Kind, wt.%): C ₃ S 58, C ₂ S 16; C ₃ A 5.5; C ₄ AF 16; CaO _free 0.7, impurities - the rest;

BK-1: KH 0.53, n 2.14, p 0.72; mineralogical composition (wt.%): C ₃ S 10, C ₂ S 52; C ₃ A 1; C ₄ AF 14; CaO _freedom 14.5, impurities - the rest.

When firing in DTA conditions of the control feed mixture to obtain a control clinker, the appearance of a general clinker melt using an electrical conductivity characteristic above the level of 4 · 10 ^-8 Ohm ^-1 / cm ^{-1 was} recorded at 1250 ° C. When firing under the same conditions of the raw material mixture according to the invention, the indicated level of electrical conductivity is achieved twice: for the first time at 1070 ° C, then, after a temporary decrease, for the second time at 1245 ° C.

The firing mode of the control clinker and said belite clinker in the first series of experiments is characterized by the location of the gas burner in the furnace along its central axis. The central angle of the segment of calcined material during firing of the control clinker is 90 °, while firing the specified belite clinker 116 °. The oxygen content in the exhaust gases during firing of the control clinker corresponds to the norm: (1.3-1.5) wt.% [22]; when firing the specified belite clinker by reducing the vacuum, the oxygen content is reduced to (0.2-0.5) wt.%. When scanning the temperature of the furnace body, the following was established:

- in the control clinker firing mode: one minimum of the body temperature with a decrease of 30 ° C compared to neighboring sections - at a distance of 10-11 m from the furnace head, where the beginning of the sintering zone with the corresponding “hill” of the fired material is fixed - due to the endothermic melting effect parts of the material to be fired and deceleration in this zone of its movement along the axis of the specified furnace;

- in the firing mode of the indicated belite clinker: two minima of the body temperature - with a decrease of 18 ° C compared to neighboring sections - at a distance of 18-19 m from the furnace head, where the end of the decarbonization zone and the first (“white”) granulation of the fired material are noted , and with a decrease of 23 ° C - at a distance of 12-13 m from the furnace head, where the second (“normal”) granulation of the calcined material with the corresponding “hills” of the calcined material is noted in connection with the slowdown of its movement along the furnace.

When the “white” clinker was discharged from the furnace through a hatch located at the end of the decarbonization zone, the content of free calcium oxide was recorded in it within 22–26 mass%; The petrographic analysis of granules with their strengthening by rosin impregnation made it possible to detect characteristic active, mainly dendritic forms of crystallization of free calcium oxide. X-ray phase analysis of these granules after grinding to powder showed the presence of belite, mainly in β-modification, the practical absence of C ₃ A, the presence of Ca and alkali metals; the presence of RA has not been established. After a 20-minute shutdown of the fuel burning torch, the “white” clinker was released through the furnace edge into the refrigerator; in the sample taken from the sawn-off shotgun of the furnace, the content of free calcium oxide decreased to 18-20 wt.%, and in free calcium oxide, in addition to dendritic, point forms are clearly observed, which are clearly the product of partial melting of dendrites in a clinker melt. As a result of the study of the finished belite clinker according to the invention by means of petrographic analysis, the presence of alite and belite was found in amounts approximately corresponding to the above calculated data; the presence of C ₃ A and alkaline aluminates and ferrites was recorded in the form of traces. In the normally calcined said belite clinker, the content of free calcium oxide averaged, as already mentioned, 14 wt.%.

Determination of the irrevocable dust collector in the furnace exhaust gas samples (without the use of precipitation devices) made it possible to detect the presence of dust in the exhaust gases in the following amounts (g / m ³ ): during firing of the control clinker 22.4 and the specified belite clinker 1.8, which is an order of magnitude lower .

In the second series of experiments when firing the raw mix with fineness of grinding according to the residue on sieve No. 02, 1.8-2 wt.%, The average productivity of the kiln for clinker in the control mode according to the closest analogue was 12.5 t / h, and for the belite portland cement clinker according to the invention - 15.2 t / h (+22 wt.%), With the following average characteristics of the control Portland cement clinker (KK-2) and the specified belite clinker according to the invention (BK-2):

KK-2: KH 0.92, n 1.98, p 1.00; mineralogical composition (according to V.A. Kind, wt.%): C ₃ S 60, C ₂ S 15; C ₃ A 5.5; C ₄ AF 15; CaO _free 0.5, impurities - the rest;

BK-2: KH 0.74, n 2.10, p 0.74; mineralogical composition (wt.%): C ₃ S 4, C ₂ S 58; C ₃ A 1; C ₄ AF 14; CaO _freedom 12.5, impurities - the rest.

When firing in the DTA conditions of the control feed mixture to obtain a control clinker, the appearance of a general clinker melt using a conductivity characteristic above the level of 4 · 10 ^-8 Ohm ^-1 / cm ^{-1 was} recorded at 1245 ° C. When firing under the same conditions of the feed mixture according to the invention, said the conductivity level is achieved twice: for the first time at 1050 ° C, then, after a slight decrease, for the second time at 1225 ° C, however, it can be considered that, starting from 1050 ° C, in the calcined raw material mixture according to the invention is continuously risutstvuet clinker melt because there ionic conduction component.

The firing mode of the specified belite clinker in the second series of experiments is characterized by the location of the gas burner in the furnace, close to the segment of the material being fired along the normal to its surface by about a third of the distance from the central axis so that, at the selected level of furnace productivity, the central angle of the segment of fired material 123 °. The oxygen content in the exhaust gases during firing of this clinker corresponds to: (0.3-0.7) wt.% At the same vacuum level as in the first series of experiments. The firing parameters of the control clinker (KK-2) were left consistent with the first series of experiments. When scanning the temperature of the furnace body, the following were installed:

- in the control clinker firing mode: one minimum of the body temperature with a decrease of 20 ° C compared to neighboring sections - at a distance of 11-12 m from the furnace head, where the beginning of the sintering zone with the corresponding “hill” of the fired material is fixed - due to the endothermic melting effect parts of the material to be fired and deceleration in this zone of its movement along the axis of the specified furnace;

- in the firing mode of the specified belite clinker: a gentle minimum of the body temperature - with a decrease of 15 ° C compared with neighboring sections - at a distance of 13-20 m from the furnace head; this corresponds to the formation of a continuous sintering zone with a gradual transition from the end of the decarbonization zone and the first (“white”) granulation of the calcined material to the second (“normal”) granulation of the calcined material in the absence of “hills” of the calcined material due to the acceleration of its movement along the furnace, which had a positive effect on increasing the productivity of the latter. In the normally calcined said belite clinker, the content of free calcium oxide averaged, as already mentioned, 12.5 wt.%.

Determination of the irrevocable dust collector in the furnace exhaust gas samples (without the use of precipitation devices) made it possible to fix the presence of dust in the exhaust gases in the second series of experiments in the following amounts (g / m ³ ): during firing of the control clinker 20.3 and the specified belite clinker 0.3, which corresponds to the absence of dust formation in the furnace, and the dust loop from the furnace, very weakly expressed in the first series of experiments when firing the clinker according to the invention, completely disappeared when firing the specified clinker in the second series of experiments. When viewed from the furnace head, despite the burning of fuel, in this firing mode, a chain curtain was clearly visible near the cold end of the furnace, with fluctuations in the outlines of the chains caused by convective currents of a completely transparent furnace atmosphere.

Measurements of the total porosity of said clinker leaving the furnace edge in the first and second series of experiments are the most convenient method for determining the degree of sintering of a belite clinker according to the invention and, accordingly, its readiness. They are carried out using the usual method of weighing a clinker granule (weight p ₁ ), waxing it, re-weighing (weight with paraffin p ₂ ) and then hydrostatic weighing in water (p ₃ ), which allows to calculate the total porosity of the clinker granule according to the formula:

where ε is the porosity,%;

ρ _steam - the density of paraffin (on average 0.85 g / cm ³ );

ρ _wedge is the density of the indicated belite clinker determined by the pycnometric method, in particular, the standard one [23]. According to the data obtained, in contrast to the total porosity of an ordinary alite clinker equal to (18-24)%, the porosity of this belite clinker with hydration-active free lime is in the first series of experiments (42-46)%, and in the second series of experiments (37- 41)%. This corresponds to a bulk density of clinker in a 1 liter tank of about 1.15-1.2 kg versus 1.45-1.5 kg in a control alite clinker.

When taking the specific fuel consumption for firing the control clinker KK-1 in the first series of experiments for 100%, the fuel consumption for firing the second control clinker KK-2 is 97%, and the belite clinkers obtained by the method according to the invention in the first series of experiments (BK- 1) an average of 78%, and in the second series of experiments (BK-2) - an average of 72%. Accordingly, the grinding resistance of these clinkers by the time to reach the specific surface of 300 ± 50 m ² / kg in the standardized laboratory mill MBL-1 [24] is: KK-1 58 min, KK-2 53 min, BK-1 24 min, BK-2 22 min, which corresponds to more than a twofold increase in the grindability of clinkers according to the invention.

Note that when the specified furnace operates in other modes, namely, when the oxygen content in the exhaust gases exceeds the specified limits ((0.2-0.7) wt.%}, The first clinker melt is formed too early (at a temperature below 1050 ° C), with a lower or higher content of free lime in the specified belite clinker compared to the specified limits {(5-25) wt.%} And, accordingly, a higher or lower alite content in the latter compared to the specified limits {(3-10) wt. .%} the above advantages of the invention over the level of technology and reduced due to unfavorable changes in the microstructure of CaO _svob in said clinker and its density, as well as adverse influence of other factors. So, when the porosity of said clinker is higher than 47%, which is typical for the reducing regime of clinker burning (when the oxygen content in the exhaust gases of the specified furnace is less than 0.2 wt.%), Clinker dusting starts in the furnace and the advantage of dust suppression is lost; when the oxygen content in the exhaust gases is higher than 0.7 wt.% and the alumina module of the specified raw material mixture is higher than 0.8, rings appear in the furnace, which impede firing, reduce the productivity of the furnace, the density of said belite clinker increases (porosity drops below 35 vol.%) and clinker grinding is reduced. In addition, with an increase in the content of free lime in excess of 25 wt.%, Part C ₃ A goes into marginal C ₁₂ A ₇ , which reduces the strength characteristics of cement and the durability of concrete. Similarly, at a KH below 0.5, the grindability of the indicated belite clinker decreases and the likelihood of the presence of C ₁₂ A ₇ instead of C ₃ A in this clinker with the above adverse effects increases. When KN is higher than 0.81, the composition of the belite clinker approaches the usual Portland cement clinker with the corresponding consequences for the technical and economic effects of the invention. Finally, without approaching the fuel combustion flame to the material to be fired (when the central angle of the segment of the latter in the specified furnace is about a maximum of 110 °, known from the prior art [25]), the required increase in productivity of the specified furnace is not achieved compared with the prior art.

From the above data it follows that for the first time in the 90-year history of operation of this furnace, there was a complete absence of a dust loop from a 25-meter pipe during clinker firing, which was perceived by external observers as the result of an emergency stop of the furnace. The measurements showed the achievement without filters of the concentration of dust in the emission, which was 3-5 times lower than the maximum permissible concentration in the atmosphere after the filters, which indicates the absence of dust emission during firing and cooling of the specified clinker. This is accompanied by a significant increase in furnace productivity compared to burning alite clinker - on average by 25 wt.%, With a maximum of up to 28 wt.% - with an average content of free calcium oxide in the firing product (8-15) wt.% And emissions outside the specified range to the content of CaO _freedom not less than 5 and not more than 25 wt.%.

From the obtained results it follows that when the ratio of alite and belite components in the finished cement is from 3: 1 to 2: 1, the final increase in the average productivity of the furnace is from 8 to 15 wt.% With approximately 30-fold or more reduction of the irrevocable dust extractor from the furnace.

The foregoing shows that, according to the method according to the invention, a belite Portland cement clinker is obtained, the production process of which is characterized by a very significant reduction in both fuel consumption and dust extraction from furnaces compared to firing normal alite Portland cement clinker. This is the main element of the surprise and novelty of the present invention in terms of a method of manufacturing a portite cement Portland cement clinker with dust suppression during its firing compared to the prior art. The specified belite Portland cement clinker, in contrast to the belite clinkers known in the prior art, is also characterized by approximately twice as high grindability as compared with conventional alite Portland cement clinker. This is the second element of the surprise and novelty of the invention in its specified part.

Thus, this method of manufacturing a dustproof suppression clinker Portland cement clinker according to the invention has significant advantages over the prior art, characterized by novelty elements and is more economical in the consumption of process fuel, having environmental advantages due to the reduction of environmental pollution and being multivariate, not requiring tight binding to a narrow raw material base or designs of rotary kilns, which is essential for I am reducing production costs and competitiveness in a market economy.

The technological advantages associated with this method are associated with the indicated characteristics of the obtained belite clinker and its advantages, revealed due to the effective composition of cement based on the specified clinker.

Cement is known, including, along with alite Portland cement clinker, also a belite Portland cement clinker, called poly-clinker cement (the term “poly-clinker” was introduced in [26]). The main idea of such cements, as indicated in the last source, expressed back in 1940 by S.D. Chetverikov (Giprocement, Leningrad), is that in polyclinker cement the disadvantages of clinker components and cements based on them are reduced: hardening of whiteite is accelerated component (S. D. Okorokov proved the acceleration of hydration of belite in the presence of alite [2]), and the alite component decreases excessive heat generation, which promotes self-drying of concrete, especially in conditions of heat and moisture treatment in which we are not completely gap of water vapor atmosphere.

An analogue of the present invention is a multi-clinker cement proposed by I. V. Kravchenko et al. [27], in which the above alite and belite components are ground separately and then mixed. Polyclinker cement obtained in this way in terms of hardening speed (initial strength) and strength in the later stages of hardening (28 days), determined in standard cement-sand samples according to [28], surpasses both the alite and belite components of which it consists, taken in wt. 3: 1 ratio. At the same time, hydraulic activity (strength of standardly manufactured samples from a cement-sand mortar of the composition cement: sand 1: 3 by weight at 28 days of age after normal storage for 1 day in an air-moist environment and 27 days in water at 20 ± 3 ° C) of multi-clinker cement exceeds the activity of cement based on alite clinker by about 5 MPa, and the activity of cement based on alitic clinker by 12-15 MPa [29]. There is practically no fuel economy for clinker firing, but the hydraulic activity of poly-clinker cement is at least one step higher (grade, grade) than the hydraulic activity of any of the components. Such a multi-clinker cement in 1967-1972 was produced at the Bolshevik cement plant of the Volsky group as a high-strength Portland cement, which, according to a modern assessment of strength indicators, has a grade of 600 [30] or a class of 52.5 [31].

Taking into account the advisability of not only improving the quality of cement, but also reducing energy costs for cement production, L.Ya. Goldstein in 1986 proposed the closest to the present invention polyclinker cement (prototype) based on jointly ground white and aligo clinkers, corresponding to the composition of the values of KH respectively 0.78-0.85 and 0.88-0.95 at wt. the ratio of belite and alite components in optimal compositions is from 1: 1 to 1: 3 [32]. The content of the gypsum component in the polyclinker cement is not reported, but it is understood that it is introduced into the composition of this cement. Achieved: savings in the total specific fuel consumption for firing both clinkers compared to firing a conventional Portland cement clinker with a KN of about 0.88, corresponding to an increase in the estimated total productivity of rotary kilns by 2.5 wt.%, An increase in the hydraulic activity of polyclinker cement based on a mixture of these whiteite and alite Portland cement clinkers by 8-12% compared with the alite component and saving energy costs for grinding poly-clinker cement composition (whiteite component) / (alite vy component) of 1: 3 to 3%. The increase in strength of multi-clinker cement compared to alitic component is explained [32] by the narrower particle size distribution of multi-clinker cement compared to alitic. A feature of this technical solution is the relatively small beneficial effects, although the increase in hydraulic activity - (8-12)% - is quite large. However, the inconvenience arising in the manufacture of this cement (the need to prepare raw mixes of two compositions and roasting two different clinkers - alite and belite - followed by their separate supply and separate dosage in cement mills) should have serious justifications for achieving significant effects. The above increase in strength is slightly less than that achieved during the transition from the production of cement of grade 500 (class 42.5) to cement of grade 600 (class 52.5), which follows from the data obtained by simply replacing the first cement with the second in concrete with an increase in the strength of the latter in an average of (12–16)% [33]. For this reason, the production of polyclinker Portland cement grade 600 at the mentioned Volsky cement plant was replaced in 1972 by the production of ordinary high-strength cement grade 600 based on alite clinker [34]. Thus, industrial practice indicates the lack of competitiveness of multi-clinker cement, known from the prior art, in comparison with high-quality alite Portland cement.

It should be added that in the previous Goldstein report at the 10th International Congress on Cement Chemistry in 1997 [32] similar to the work of L. Ya. Goldstein, the range of declared mixtures of belite and alite components was somewhat expanded compared to the closest analogue mentioned above - to the ranges (5:95) - (65:35) [35]. A comparison of the two mentioned works by Goldstein [32, 35] shows that in [35] more non-optimal compositions of polyclinker cement are included, while the claimed effects are approximately the same in both works.

The marked increase in the productivity of furnaces during the production of individual components of polyclinker cement, which is equal to 2.5 wt.% According to Goldstein [32], corresponds to a ratio of belite and alite components in polyclinker cement of 1: 1 to an increase in the productivity of furnaces during roasting of clite clinker by about 5% compared to with alite. Thus, Goldstein considers acceptable only a half-reduced level of the useful effect of burning belite (low-base) clinkers compared to burning alite clinkers, which in the review by Albats et al. [11] in the same collection of reports of the 10th International Congress on Cement Chemistry (1997 ) is considered equal to approximately 10%. Nevertheless, the indicator given by Goldstein can also be considered controversial on the basis of [13] and [14], as well as the above-mentioned equal values of the heat consumption for firing belite and alite clinkers in a calorimetric bomb [10], and performed under production conditions, the above observations of Vlasova et al., also confirmed at least the equality of the indicated heat costs. He does not mention fuel economy when firing belite clinkers (with reference to Chernobaev [12]) in his fundamental work and R. Bart [26]. The presence of this effect was not found in recent production experiments of the authors of the present invention, performed at Russian cement plants in 1998-2002.

The objective of the present invention is a much more significant reduction in energy consumption in the production of multi-clinker cement due to the inclusion of an active mineral additive and the achievement of a higher increase in the strength of such cement in comparison with the prior art multi-clinker cement with an active mineral additive.

This problem is solved by the fact that cement based on belite Portland cement clinker, made on the basis of a cement raw material mixture containing carbonate, aluminosilicate and ferrous ingredients, is calcined before sintering in a rotary kiln with torch burning of process fuel and dust suppression, and cooled, obtained by joint grinding of said clinker separately burned with alite Portland cement clinker, including alit in the amount of 60 wt.%, and a gypsum component, characterized in that the cement raw material mixture is calcined in a neutral atmosphere with an oxygen content in the exhaust gases of a rotary kiln within (0.2-0.7) wt.% with the formation of the first clinker melt at (1050-1170) ° C based on a mixture of С, СF ₂ , RF, RA in the calcined material with partial granulation of the latter and crystallization from the indicated melt of free calcium oxide (CaO _svob ) of the dendritic and point microstructure, followed by the formation of a second clinker melt of eutectic composition at (1230-1270) ° С with granulation of the clinker obtained from it at the following ratios of the main phases in the latter, wt.%:

Specified CaO _freedom 5-25

β -C ₂ S 40-60

C ₃ S 2-10

C ₃ A 0.01-10

C ₄ AF 8-20

and the cement obtained by co-grinding these components further includes an active mineral additive with a moisture content of about (3-8) wt.% in the following ratio of components in cement, wt.%:

Specified Belite Clinker 15-30

Specified Alite Clinker 45-50

Specified Active Mineral Additive 10-35

Gypsum component 3-10

with the achievement in the process of the specified grinding conversion of the specified free calcium oxide contained in the specified belite clinker, calcium hydroxide, with the degree of the specified conversion (70-98) wt.%.

In an embodiment of the invention, materials of the group: calcium sulfate reagent, gypsum stone, gypsum anhydrite stone, phosphogypsum, borogypsum, titanogypsum, or mixtures thereof are used as the specified gypsum component of cement.

The essence of the invention lies in the fact that the belitic component of the multi-clinker cement according to the invention contains free lime, which, unlike all its known forms, is characterized by its dendritic and / or point microstructure, with such a high hydration activity that it has almost completely extinguished, i.e. calcium hydroxide during the joint grinding of cement components due to hygroscopic moisture contained in the active mineral additive.

It is this feature of the proposed technical solution that is the main element of the novelty of this cement, containing freshly formed, highly highly active hydrated lime, localized mainly in the pores of particles of belite clinker, which, along with the particularly high porosity of the latter, contributes to a significant increase in the grindability of cement according to the invention and increase its strength properties . On the other hand, this novelty element defines three other advantages of the considered technical solution:

- the possibility of incomplete drying of the active mineral additives before grinding - to a moisture content of (3-8) wt.% against the usually required (0.05-2) wt.%, which corresponds to fuel economy for drying additives in sizes of about 30%; the possibility of incomplete drying of the mineral additive is, in turn, a significant contribution to the economic effect of this technical solution;

- the increase in the hydraulic activity of the cement according to the invention in comparison with the control cement without the specified belite component is due in this case not only to the activation of belite in polyclinker cement by its alite component (in this case, it would not exceed a modest increase by 8-12% in accordance with the nearest analogue), but first of all, by activation of hardening of belite by directly contacting calcium hydroxide, the amount of which by weight is from one third to about half the mass of belite in polik inkernom cement. Moreover, in the cement hydration products according to the invention, gel-like (sub microfiber) hydrosilicates of the С-S-Н (I) composition with a C / S ratio of less than 1.5 are predominant against microfibrous hydrosilicates of the С-S-Н (II) composition with a C / S ratio of more 1,5 - in cement hydration products according to the closest analogue. This structurally determines the greater increase in the hydraulic activity of cement according to the invention in comparison with cement according to the closest analogue (prototype);

- in the presence of a significant amount of a mineral additive in the composition of the multi-clinker cement according to the invention, its increased strength is also explained by the initiation of a pozzolanic reaction between the specified free lime and the active mineral additive, which begins even in the process of joint grinding of the cement components. The degree of this reaction in 28-day-old samples stored under standard conditions (see above), according to the data obtained, is (35-40)% versus (15-25)% when hardening pozzolanic Portland cement, known from the prior art, which explains increased strength of the cement according to the invention in comparison with the known with equal content of active mineral additives.

A necessary condition for this is the humidity of the active mineral additive in the specified limits, which completely contradicts the known standards for drying mineral additives when they are introduced into the cement [22, p. 88-106] and is almost more unexpected than the need to maintain a significant content of free calcium oxide in the composition of polyclinker cement.

The introduction of various forms of the gypsum component makes it possible to obtain not only the technical effects that are usual in this case, but due to the indicated mineralogical composition of the mixture of belite in the belite clinker with free lime according to the invention and the alite clinker, acting differently on each of these components, each form of the gypsum component generates its own specific effect. Thus, calcium sulfate is two-water, chemically pure, as well as gypsum anhydrite stone, due to the high reactivity in the presence of free lime in a highly active form, they can add an admixture of sulfate ion to calcium hydrosilicates in the cement stone, which greatly facilitates their coalescence with hydroaluminates, hydrosulfoaluminates and other multi-water hydrates of AFm and AFt types. Gypsum stone, introduced in increased amounts close to the allowable standard limit of 4% of the mass of cement in terms of SO ₃ , is capable, in the presence of the indicated amounts of highly active free lime, to form hydrates almost exclusively from AFt phases with small amounts or absence of AFm phases, which increases the strength of cement and increases the resistance of cement stone and concrete to environmental influences, first of all - frost resistance of concrete. Chemical gypsum - phosphogypsum, borogypsum and titanogypsum - in the presence of highly active free lime lose their negative properties, since the free mineral acids present in them lose this lime almost immediately into calcium salts, which, as electrolytes, accelerate the hardening of cement according to the invention.

A change in the ratio of the components of the specified cement against the above, in particular, a decrease in the content of said belite clinker to a level of less than 15 wt.% Or an increase in its content in excess of 30%, a decrease in the content of alite clinker to a level of less than 45 wt.% Or an increase in its content in excess of 50 wt. .%, as well as a decrease in the content of the specified active mineral additives to a level of less than 10 wt.% or an increase in its content in excess of 35 wt.% worsen the technical properties of the cement according to the invention and bring it closer to those known from the level of hniki. Thus, a decrease in the content of the specified mineral additive with an increase in the content of the specified belite component, while maintaining a significant amount of quicklime in the cement composition, reduces its crack resistance and the durability of concrete based on it. An increase in the content of alite clinker above the level of 50 wt.% Leads to the beginning of the replacement of activation of belite clinker in the cement hardening process according to the invention according to the calc mechanism with activation by the alitic mechanism, which brings the cement properties according to the invention closer to the properties of cement according to the closest analogue (prototype), significantly reducing technical effects achieved according to the invention and the like.

The invention in terms of cement becomes clearer from an example of its implementation.

Example 2

The cement according to the invention and the closest analogue (prototype) is made by co-grinding the components in cement mills, in this case in the laboratory drum mill MBL-1 of a two-chamber, periodic action lined with cast iron armor plates, with the dimensions of each chamber: length 0.28 m, diameter 0.5 m, rotation speed 48 min ^-1 , drive power 1.1 kW, engine speed 930 min ^-1 , grinding load per chamber (with the sum of 10 kg of components for each chamber): balls with a diameter of 60 mm - 6 kg, diameter 50 mm - 8 kg, d ametrom 40 mm - 8 kg, with a diameter of 30 mm - 8 kg, cylpebs with a diameter of 20 mm and a length of 32 mm - 25 kg of 55 kg. Before weighing, the components of the cement are crushed to a fraction of 1-2 mm in a laboratory jaw crusher. By grinding the components in this mill, the cements of the invention are made.

Source components:

- alite Portland cement clinker - according to example 1-KK-2;

- Belite clinker made by the method according to the invention - BK-1;

- active mineral additive: flask composition: pp 17,36; SiO ₂ 52.03; Al ₂ O ₃ 6.25; Fe ₂ O ₃ 3.54; CaO 17.31; MgO 1.67; SO ₃ 0.05; Na ₂ O 0.25; K ₂ O 1.54; including the content of water-soluble alumina - 4 wt.%; humidity 4 wt.%;

- gypsum stone composition (wt.%): two-water gypsum - 98, mudstones - 2.

Grinding a mixture of components in wt. a ratio of 50: 30: 15: 5 is carried out to the specific surface by the method of breathability in accordance with the standard (see [23]), equal to 330-370 m ² / kg in a mixture of clinker components. The latter term means that the grinding time of the specified mixture of components is selected according to the time during which the specified specific surface of the mixture of the indicated alite and belite clinker components is reached in the same mill (in the absence of mineral additives and gypsum components), since the latter make comparison difficult due to their increased grinding cement by fineness of grinding. The degree of quenching of free lime is 85% according to x-ray phase analysis (according to the intensity of the reflex at 4.91 · 10 ^-10 m).

For comparison, separately made: 1) alitic Portland cement based on alitic Portland cement clinker (A, as in example 1), 2) belitic Portland cement based on belitic Portland cement clinker (B) of the following composition (wt.%): C ₃ S 39, C ₂ S 37, C ₃ A 5.5, C ₄ AF 15.5, CaO _free 0.4, impurities - the rest; 3) polyclinker Portland cement according to the closest analogue (prototype) of the above alite (A) and belite (B) clinkers at wt. the ratio of the latter components is 3: 1 (or 75:25). Of the last three cements, the specific surface area of the first two (A) and (B) is chosen so that their main characteristics (strength in the early stages of hardening, hydraulic activity) correspond to the average characteristics of cements of the corresponding compositions available on the market, namely 320 and 360 m ² / kg; the specific surface of cement according to the closest analogue (prototype) is selected in accordance with the data given in [32] for the residues on sieve No. 008 - (9.0–9.6) wt.%, which corresponds to a specific surface of 310-330 m ² / kg The specific surface area of the cement according to the invention is chosen to be 330-370 m ² / kg, since it also corresponds to the indicated residue on the specified sieve when grinding the clinker part of the cement according to the invention, that is, without an active mineral additive and gypsum component.

For reference purposes, the following is also made: 4) belite cement based on a belite Portland cement clinker made by the method according to the invention (clinker BK-1 according to example 1). Cements 1) to 4) are obtained by co-grinding these clinkers with a gypsum component taken in an amount of 3% of the mass of these clinkers in terms of SO ₃ .

Physico-mechanical tests of cements were carried out according to the current domestic standards [36, 23, 37, 28].

The results are presented in the table, which also collects data on the performance of the above clinkers.

The data presented allow us to conclude the following.

1. Portland cement according to the invention is characterized by a significant advantage over the prior art, first of all in terms of construction and technical properties: it is significantly superior to those known both in early strength (at one-, three-day old) and in strength in the later stages of hardening, in particular, in 28 day-old age - more than 15%.

2. According to the invention, the cement production method also has significant advantages (for explanations of the terms expressing the advantage of the invention, see the notes to the table):

- reduced fuel consumption for clinker firing, reduced to 1 ton of cement according to the invention - due to the low fuel consumption for firing a belite component of cement according to the invention, containing 5-25% free calcium oxide in rapidly hydrating form (active CaO _free );

- increased productivity of clinker kilns - due to the growth of this indicator during firing of the belite component of cement according to the invention with active CaO _freedom ;

- reduced dust formation during firing of clinker - due to a decrease in this indicator during firing of the belite component of cement according to the invention with active CaO _freedom ;

- increased grindability of the mixture of components in connection with the increased porosity of the belite component of cement compared with the known clinkers and the interaction of the last and active mineral additives with active CaO _freedom in the process of grinding cement, facilitating grinding;

- an increase in the productivity of cement mills, or with a corresponding reduction in the time to reach a given level of dispersion when grinding cement according to the invention, associated with increased grinding of this cement.

The advantages given in the table relate to the optimum cement compositions according to the invention. It should be noted the following.

1. The change in the content in cement according to the invention of the indicated belite component in excess of 30 and less than 10 wt.% Leads to a significant decrease in both its strength characteristics in all periods of hardening, and to reduce other advantages - saving specific energy consumption for clinker roasting and grinding of cement, reduction irrevocable pyleunosa, etc.

2. Similarly, a change in the content in cement according to the invention of the indicated active mineral additive in excess of 35 and less than 10 wt.% Leads to a significant decrease in both its strength properties at 28 days of age and to a decrease in other advantages - saving in specific energy consumption for grinding cement according to the invention, reducing pyleunosa when grinding the latter.

3. Changes in the content of the alitic component and the gypsum component in the cement according to the invention do not significantly affect its properties, however, in this case, outside the above limits, the advantages of the cement according to the invention are reduced.

The determining factor in this case is the moisture level of the active mineral supplement. The following conditions are considered necessary:

W (active mineral supplement) ≅ 1.3 [CaO _freedom ] (from a belite component) (2)

Here W is the content in the cement introduced by the specified additive hygroscopic moisture, wt.%; [CaO _svob ] - the content in the cement introduced by the belite component of free calcium oxide. It is easy to notice that this condition, found empirically, approximately corresponds to the stoichiometry of the quenching reaction of the indicated free lime with free moisture from a mineral additive. Deviation from the specified condition leads to going beyond the required degree of slaking lime, namely (70-98)%; with a lesser degree of quenching, the early strength of the cement is reduced, and with a greater degree of quenching, the transportation, loading, storage and unloading of said cement begins to lump and hinder.

To this should be added:

- in principle, any gypsum components mentioned above are suitable for incorporation into the cement according to the invention, but the cement according to the invention is more compatible with the so-called chemical gypsum - phosphogypsum, borogypsum, titanogypsum and their mixtures compared to cement known from the prior art all because free lime immediately neutralizes the acidic components of chemical gypsum, and in this case they do not adversely affect the hydration rate of the clinker part of the cement according to the invention; therefore, very wide limits on the concentration of impurities of phosphoric, boric and sulfuric acids, respectively, in the indicated chemical gypsum are permissible;

- the difference between the belite clinkers according to the invention - BK-1 and BK-2 (according to example 1) - when used in the cement according to the invention is negligible. Similarly, the cement according to the invention is less affected by changes in the content of alite (C ₃ S) and tricalcium aluminate (C ₃ A) in its alite component. The alite content in the latter can range from 60 to 80 wt.%, And with an increase in the alite content in the alite component, a monotonic increase in the cement performance according to the invention occurs, although the increase in the alite content is in excess of 80 wt.% And a decrease below 60 wt.% In the alite component reduces the reduction of energy consumption in the manufacture of cement according to the invention. The C ₃ A content in the alite component in a manner known in the prior art affects the early cement strength and the choice of gypsum component content in the latter: with an increase in C ₃ A content, the early strength increases, but in order to avoid the associated decrease in cement strength in the later stages of hardening, it is necessary within standard limits - up to 4 wt.% in terms of SO ₃ - increase the content of the gypsum component in the cement.

From the description and examples of the invention, it follows that it is characterized by a number of elements of novelty and surprise, not arising from the prior art, and significantly exceeds the latter in terms of manufacturing methods and properties of the resulting clinker and cement based on it.

The above also indicates the preparedness of the invention for industrial implementation.

Notes: 1 - when the standard content in clinker of free CaO is not more than 1%; 2 - when the standard content in the clinker of free CaO is not less than 5 and not more than 25%; 3 - calculated data per unit mass of a mixture of components: alite Portland cement clinker, belite portland cement clinker made according to the method according to the invention, active mineral additives and gypsum; 4 - the term “moderate (s)” means a value corresponding to the average calculated indicators for this type of equipment or the average strength indicators of Portland cement, known from the prior art and currently available on the market; the term “lowered (s)” means a value deviating from a moderate downward not less than 10%, with an accuracy of ± 2%; the term “increased (s)” means a value deviating from moderate upward not less than 10%, with an accuracy of ± 2%; the term “high” (s) (s) denotes a value deviating from moderate upward not less than 15%, with an accuracy of ± 2%; the term “low” (s) denotes a value deviating from moderate downward by at least 15%, with an accuracy of ± 2%; 5 - the term “absent” means the complete cessation of visible dust emission from the furnace, that is, the absence of a dust loop above the chimney, the complete transparency of the gas-air environment in the furnace, when the dust content in the exhaust gases is less than 0.5 mg / m ³ ; 6 - normal refers to the hardening mode according to GOST 10178-85 (see text) at 17-23 ° С; heat-moisture treatment (TVO) is understood as the hardening mode according to the same GOST, which provides for keeping molded samples for 2 hours in an air-wet storage chamber, heating the air-vapor medium for two hours in a chamber with samples in molds under covers up to 85 ° C, keeping samples in forms under covers for six hours at the indicated temperature, in fact at (80-85) ° С - the so-called isothermal heating, then cooling for two hours to (20-25) ° С; abbreviated mode is indicated: 2 + 3 + 6 (80-85 ° C) +2 (h); it is generally accepted that this mode on average models the heat and humidity treatment of products and structures adopted at precast concrete enterprises; this provision was mainly true for the aggregate-flow method of manufacturing prefabricated reinforced concrete products and structures in the 70s - 80s of the XX century, that is, in the years of development and implementation of this standard; currently, in view of fuel economy in TVO, the average temperature of isothermal heating in the precast industry has decreased to (40-50) ° C, and the duration of the latter has increased from 6 to 8-12 hours. This provides additional advantages to the cement according to the invention compared to the known from the prior art, since it increases the degree of pozzolanic reaction from about 40% in the standard TBO mode to 50-55% in the specified elongated mode with a low heating temperature, which provides an additional increase in strength age concrete based on cement of the invention.

Sources of information

1. Butt Yu.M. and other Chemical technology of binders. Textbook for high schools. Ed. V.V. Timasheva. M.: Higher School, 1980, 472 p.

2. Okorokov S. D. The interaction of minerals of Portland cement clinker in the process of cement hardening. M.-L.: Stroyizdat, 1945, 94 p.

3. Kind V.A. Chemical characteristics of Portland cement. L.-M.: Gosstroyizdat, 1932, 56 p.

4. Druzhinin S.I. Building Materials, 1932, No. 11, p. thirty.

5. Kogan N.P. The study of high-speed firing of Portland cement mixture in suspension and some properties of the obtained cements. Abstract. diss. on, competition. student step. Cand. tech. Sciences - M.: NIIITsement, 1968, 22 p.

6. Entin Z.B. et al. Alitogenesis model during liquid-phase sintering of Portland cement clinker. Thes. doc. V All-Union Conference on Chemistry and Cement Technology. M .: Stroyizdat, 1978, p. 67-68. See also Proceedings of the V All-Union Conference on Chemistry and Cement Technology. M .: Stroyizdat, 1980, p. 46-50.

7. Entine Z.B. et al. The liquid phase alite generation model in sintering portland cement clinker. 10th International Congress on the Chemistry of Cement. Gothenburg, Sweden, June 2-6, 1997. Proceedings, ed. by H. Justnes, Publ. by “Amarkai”, Gothenburg, 1997, v. 1, li046. 4 pp.

8. Toropov N.A. Chemistry of cement. M .: Gosstroyizdat, 1956, p. 70 and below; Butt Yu.M. and other technology of binders. M .: Higher school, 1965, 619 p., See p. 64 and below.

9. Budedegde K. Rozrobka that dyslidzhennya physical and chemical models of reaction clinker. Abstract. dis. on health. sciences. stupas Cand. tech. sciences. K .: Polytechn. Institute, 2002, 20 p.

10. Osokin A.P. et al. The thermochemical activation of clinker formation. 10th International Congress on the Chemistry of Cement. Gothenburg, Sweden, June 2-6, 1997. Proceedings, ed. by H. Justnes, Publ. by “Amarkai”, Gothenburg, 1997, v. 1, li006, 5pp.

11. Albats B.S. et al. High quality portland cement produced from low-base raw mix with low energy consumption. 10th International Congress on the Chemistry of Cement. Gothenburg, Sweden, June 2-6, 1997. Proceedings, ed. by H. Justnes, Publ. by “Amarkai”, Gothenburg, 1997, v. 1, 1i1015. 4 pp.

12. Tshemobaeff, D. et al. Compt. rend., v. 154, 1912, p. 66.

13. Chernobaev D.A. Determination of heat of formation of silicates according to the Le-Chatelier method. Kiev: type. "AND. H. Kushnorev ”, 1913. 111 p.

14. Bogue R.H. The Chemistry of Portland Cement. N.Y., "Reinhold", 1955, 793 pp., See pp. 137-138.

15. Sudakas L.G. et al. Scientific basis for the production of active low-base clinkers. Cement (Leningrad), 1989, No. 3, p. 16-17.

16. Barta R. Chemie a technologie cementu. Praha, Nakl. CAV, 1961, 1104 s, vid. s. 725, 745 - on the composition of belite clinker; s. 582 - on the content of free calcite oxide in clinker; s. 512, 513 - on the temperature of formation of the first clinker melt; s. 60, 512, 534 - on the introduction of gypsum as a stabilizer in the raw mix; s. 535 - on the composition of the furnace atmosphere; s. 362, 449, 537 - on the suppression of dust during firing of belite clinker; s. 346 - about clinker dusting due to belite decay.

17. Volkonsky B.V. Mineralizers in the cement industry. Ed. H.A. Toropova. M.-L.: Stroyizdat, 1964, 198 p.

18. Norms of technological design and technical and economic indicators of cement plants. Ed. 2nd, L., 1975, 129 p.

19. Khodorov E.I. Furnaces of the cement industry. Ed. 2nd, L .: Stroyizdat, 1968, 456 p.

20. Hadwall, G.A. Discussion. VI International Congress on the chemistry of cement. Proceedings. M .: Stroyizdat, 1976, v. 1, p. 225-227.

21. Melnitsky G.A. The study of the structure of the pore space of clinkers and its effect on their grindability. Abstract. diss. for a job. student step. Cand. tech. sciences. M .: MKhTI them. D.I. Mendeleev, 1973, 25 pp.

22. Rules for the operation of equipment and the organization of the process at the enterprises of the cement industry. Part I. M .: Organizational project cement. 1989, 156 p. see p. 36-60.

23. GOST 310.2-76 Cement. Methods for determining the fineness of grinding.

24. Tovarov V.V. Determination of grinding characteristics of materials. M .: CBTI VNIINSM, 1959.

25. Duda V.G. Cecent. M .: Stroyizdat, 1981, 464 p., See p. 308-309.

26. Entin 3.B. and other multicomponent cements. Proceedings of the Research Institute of Cement, issue 107, 1994, p. 3-74.

27. Auth. testimonial. USSR. No. 237667, 1967.

28. GOST 310.4-81. Cement. Methods for determining the tensile strength in bending and compression.

29. Potryasov A.V. and others. Cement, 1967, No. 6, p. 18 and below.

30. GOST 10178-85. Portland cement and slag Portland cement. Technical conditions

31. GOST 30515-97 Cements. General specifications.

32. Goldstein L. Ya. Energy saving technology of cement production by means of combined grinding of clinkers of variable compositions. 10th International Congress on the Chemistry of Cement. Gothenburg, Sweden, June 2-6, 1997. Proceedings, ed. by H. Justnes, Publ. by “Amarkai”, Gothenburg, 1997, v. 1, li013. 4 pp. (prototype).

33. Kravchenko I.V. and others. High-strength and especially quick-hardening Portland cement. M .: Stroyizdat, 1971, 231 p., See p. 220.

34. Kravchenko I.V. and others. Chemistry and technology of special cements. M .: Stroyizdat, 1979, 208 p., See p. 135, 147.

35. Auth. testimonial. USSR No. 1346607, 1986.

36. GOST 310.1-76 Cements. Test methods. General Provisions

37. GOST 310.3-76 Cements. Methods for determining normal density, setting time and uniformity of volume change.

Claims (7)

1. A method of manufacturing a belitic Portland cement clinker with dust suppression during its firing, comprising preparing a cement raw material mixture containing carbonate, aluminosilicate and ferrous ingredients, firing it before sintering in a rotary kiln with flaring of technological fuel, and cooling the obtained belitovy Portland cement clinker containing free calcium oxide (CaO _svob), belite (β-C ₂ S), alite (C ₃ S), trohkaltsievy aluminate (C ₃ A) and alyumoferritnuyu phase (C ₄ AF), characterized in that the firing of said cement yrevoy mixture is carried out in an inert atmosphere with an oxygen content in the exhaust gases of the rotary kiln in the range 0.2-0.7% by weight to form a first clinker melt at 1050-1170 ° C from a mixture of CaO -. C, CaO · 2Fe ₂ O ₃ -CF ₂ , R ₂ O · Fe ₂ O ₃ - RF, R ₂ O · Al ₂ O ₃ - RA in the calcined material with partial granulation of the latter and crystallization of the _free dendritic and point microstructure from the indicated CaO melt and the subsequent formation of the second melt from the specified melt eutectic clinker melt at 1230-1270 ° C with granulation of the blade obtained from it RA at the following ratios of the main phases in it, wt.%: Specified CaO _Freedom 5-25 β-C ₂ S 40-60 C ₃ S 3-10 C ₃ A 0.01-10 C ₄ AF 8-20 2. The method according to claim 1, characterized in that the carbonate and aluminosilicate ingredients of the specified raw material mixture and the fineness of their grinding are selected according to the criterion of at least partial overlap during firing the temperature ranges of decarbonization of the carbonate and dehydroxylation of aluminosilicate ingredients of the specified raw material mixture in the mass ratio of these ingredients corresponding to the coefficient of lime saturation of the specified raw material mixture in the range of 0.5-0.6, and firing before sintering is carried out until the porosity of the specified white about clinker 35-47 vol.%. 3. The method according to any one of claims 1 and 2, characterized in that they take the specified raw material mixture, characterized by an alumina module in the range of 0.05-0.8. 4. The method according to any one of claims 1 and 2, characterized in that the combustion torch of the process fuel in the rotary kiln during firing of said belite clinker is brought closer to the segment of the fired material, bringing the central angle of the indicated segment to 115-125 °, and the fuel supply is controlled up to until complete transparency of the furnace atmosphere. 5. The method according to claim 3, characterized in that the combustion torch of the process fuel in the rotary kiln during firing of the specified belite clinker is brought closer to the segment of the fired material, bringing the central angle of the indicated segment to 115-125 °, and the fuel supply is regulated until complete transparency furnace atmosphere. 6. Cement based on a belitic Portland cement clinker made on the basis of a cement raw material mixture containing carbonate, aluminosilicate and ferrous ingredients, calcined prior to sintering in a rotary kiln with torch burning of process fuel and dust suppression and cooled, obtained by co-grinding the specified clinker with separately calcined alimantol port clinker, including alit in an amount of not less than 60 wt.%, and a gypsum component, characterized in that the specified cement raw mix calcined in a neutral atmosphere with an oxygen content in the exhaust gases of a rotary kiln in the range of 0.2-0.7 wt.% with the formation of the first clinker melt at 1050-1170 ° C based on a mixture of C, CF2, RF, RA in the calcined material with partial granulating and last crystallization of said melt CaO _svob dendritic microstructure and pitting, followed by formation of said second melt clinker melt eutectic at 1230-1270 ° C with the granulation prepared therefrom under the following proportions of clinker phases basic therein, wt.%: Specified CaO _Freedom 5-25 β-C ₂ S 40-60 C ₃ S 3-10 C ₃ A 0.01-10 C ₄ AF 8-20 and cement obtained by co-grinding these components further includes an active mineral additive with a moisture content of 3-8 wt.% in the following ratio of components in cement, wt.%: Specified Belite Clinker 15-30 Specified Alite Clinker 45-50 Specified Active Mineral Additive 10-35 Gypsum component 3-10 with the achievement in the process of the specified grinding conversion of the specified free calcium oxide contained in the specified belite clinker, calcium hydroxide, with the degree of the specified conversion of 70-98 wt.%. 7. Cement according to claim 6, characterized in that the material from the group of calcium sulfate is used as the gypsum component — a reagent, gypsum stone, gypsum anhydrite stone, phosphogypsum, borogypsum, titanogypsum, or a mixture thereof.