SU1043126A1 - Method for making belite cement - Google Patents

Abstract

The invention relates to the manufacture of an active belite cement which behaves in the manner of Portland cement at a calcium rating of between 75 and 85, the heating and deacidifying process up to 950 DEG C being unimportant as far as the compressive strength of the cement is concerned, as is the heating process from 950 DEG C up to the sintering temperature which lies within the range between 1350 DEG C and 1450 DEG C. The clinker is subjected to mechanical activation, for example, in a ball mill, either subsequent to grinding in the ball mill or in place thereof, or the active condition of the belite is reached by the cooling process. Cooling is effected by quenching the clinker or tempering it or by gradual cooling, whereby the cooling gradient should be >500 cal/min in the temperature range between from 1350 DEG C to 1250 DEG C (upper limit) and from 1000 DEG C to 800 DEG C (lower limit).

Description

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The invention relates to the building materials industry primarily to a method for the manufacture of belite cement.

A known method of making belite cement by preparing a raw mix, burning, cooling clinker and subsequent grinding (USSR patent 283880, class C 04 B 7/36, 1970).

The disadvantage of this method is that, as additives to the raw material mixture, expensive substances such as boron or phosphorus containing compounds are added. Calcium sulfate, due to their thermal dissociation, leads to environmental pollution due to 50 waste gases:; In addition, the production of actively hardening tse.-; Based on the high-temperature Ci2S phases stabilized by impurities, the firing temperature is from 1.430 ° C. As a result, there are higher heat losses compared to the phase (i - CjS, obtained at a low temperature.

The aim of the invention is the specific consumption of heat for clinker formation while maintaining the strength of Cement.

This goal is achieved by the fact that according to the method of making belite cement by preparing the raw mix, burning, cooling the clinker and subsequent grinding, firing the raw mix with KH 0.75-0.85 is carried out at 1350-1450 ° C with a holding time of 5-10 min, and the clinker cooling in the range of 1350 - 1250 C and 1000 - 800 ° C is carried out at a speed of r = 500 ° C / min.

FIG. Figures 1 and 2 show the functional dependences of the compressive strength on the hardening time of the cement.

In this case, the ordinate is the ultimate compressive strength, MPa; abscissa hardening time in days; curves 2f 3, 4 and 5 are the functional dependence of the compressive strength on the hardening time of signs 2 - 5; PZ - functional dependence of the compressive strength on the time of hardening of Portland cement; 27, - the functional dependence of the compressive strength on the time of hardening of the cement with the additive during milling is functional; p is a functional dependence of the compressive strength-on the hardening time of the cement, consisting essentially of i- and manufactured according to the Known mode.

For the manufacture of control belite cement, the raw materials are limestone and the clay is prepared as usual and mixed in such a way that the lime saturation factor is 75. The raw meal is heated in a furnace for 9 minutes to 950 ° C and neutralized at this temperature for C. minutes at atmosphere air flow. After that, heating is carried out to a firing temperature of 1450 ° C with a gradient of 70 ° C / min. The holding time after reaching the full calcination temperature is 20 minutes. After that, the cooling of a clinker with a cooling gradient is carried out at an upper temperature limit of about 70 ° C / min and at a lower temperature limit of about 20 C / min. Annealed, according to the Portland cement regime, the belite clinker is ground in a ball mill with the usual addition of gypsum to 3200 cm / g and its compressive strength is determined (Fig. 2, Kjy CjS).

Example. An inactive belite clinker was made by burning and cooling as described for the control belite cement. A rocking mill is used for intensive grinding of clinker with the addition of gypsum to 3200 cm / g. The optimal duration of grinding depends on the properties of the milled cements and paralyieTpOB mills (Fig. 1, curve JiZ).

Example 2: Belite raw meal with a lime saturation factor of 75 is prepared and neutralized as with a control belite cement. The selected heating gradient lies between 950 and 1340 ° C / min and between 1340 and C at 70 ° C / min. After holding for 5 minutes from the moment the firing temperature reaches 1.425 ° C, the clinker is quenched in water to correspond to a cooling gradient of about 2-10 C / min. After drying the clinker and grinding in a ball mill to 3200 cm / g and the usual addition of gypsum, the compressive strength limits are determined (Fig. 1, curve 2).

The content of free lime of white clinker is 0.05%. Belite cement is sufficient with a tensile strength after 7 days. cement with the grinding substance (Fig. 1, curve 22), but significantly surpasses it in the limit of strength after 28 days. Belite cements with lime lime 75 are characterized by low heat of hydration and are particularly suitable for hydraulic structures.

EXAMPLE 3 Belite raw meal was manufactured and neutralized, as in the control belite, but with a lime saturation of 80. The firing, cooling and pomel modes correspond to example 2 (the heating gradient is between 950 and 1340 C at 1000 C / min, between 1340 and 1425 ° C / min. Firing temperature 1425 ° C, 5 minutes dwell time. Hardened in water. Grinding of clinker in a ball mill). The measured compressive strengths are shown in FIG. 2, curve 3. The content of free lime of whitish clinker is tCO1 = 0.4%. Belit cement corresponds to the strength properties of Portland cement (Fig. 2, –RV PH curvature) p exceeds its strength in 28 days. Proposed active belite cement. exceeds the well-known belite or A- (Fig. 2, curve (b -). EXAMPLE 4. Belite raw meal I.ZGOTLJA and neutralize. as with the control belite, but with a lime saturation factor 80 Gradient heating between 950 and 13 85 ° C lies at 10 oC / mi. The firing temperature is 1385 ° C, the curing time is 5. min, the hardening of the clinker in water, and the grinding of the clinker in a ball mill. 4. The content of free lime of belite wedge-; ker is 0.54%. Belite cement corresponds to the strength properties of Portland Enta (Fig. 2, P2i curve) with superior strength in 28 days. EXAMPLE 5. Belite raw meal with a saturation factor of 1 st 75 is made and neutralized as with control belite. The gradient of preheating is between 950 and 1350 s lies at 1000 S / min. The burning temperature is 1350 ° C. The extraction time is 2 minutes. The cooling of the clinker is made by quenching in air, which corresponds to a cooling gradient of 1,310 s / min. Grinding clinker in sha. RANOY mill. Strength limits, when compressing samples are depicted in FIG. curve 5. The content of whiten clinker free from the message is 1.9%. Example Belite raw meal is manufactured and neu tralized as with a control bleaching agent, but with a lime saturation factor of 80 The heating gradient lies between 950 and 1340 ° C at 100 C / min and between 1340 and 13850s at. 7 o s / min Firing temperature Hold time 5. min. The clinker is cooled down to 1300 s with a gradient of about 20 ° C / min and then rapidly cooled to 900 ° C with a gradient above 500 ° C / min by spraying with water. Grinding clinker in a ball mill. EXAMPLE 7 Belite raw meal is produced as with control belite, but with a lime saturation factor of 80. Water vapor is added to the furnace atmosphere in such a way that its proportion is 20%. The addition of water vapor makes it possible to shorten the neutralization time from 11 to 9 min at 950 ° C. The heating gradient lies between 950 and 1340 C at 1000 C / min and between 1340 and at 70 ° C / min. Firing temperature The addition of water vapor allows the exposure time to be reduced to 5 minutes, as in Example 2, to 2 minutes. Water hardening. Grinding I clinker in ball melbnitsa. The content of free lime of belite clinker is 0.69%. Belitovy cement corresponds to the strength of Portland cement. The advantages of belite cement manufactured by the proposed method are that the consumption coefficient of the material decreases, i.e. the mass ratio of raw meal, which corresponds to savings of 3%. As a result, costs are no longer long. receiving and preparation of raw materials; In addition, the specific heat consumption is reduced, taking into account the thermal efficiency, for example, a rotary kiln, to 370 kJ / kg. clinker. Lowering the firing temperature below 1450s allows the use of less valuable fuel. Thus, the proposed method for the manufacture of Belitite cement makes it possible to reduce the specific heat consumption for clinker formation while maintaining the strength of the cement. It is recognized as an invention according to the results of the examination carried out by the Office for the Invention of the German Democratic Republic.

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Claims (1)

METHOD FOR PRODUCING WHITE CEMENT by preparing the raw mix, roasting, cooling clinker and subsequent grinding, characterized in that, in order to reduce the specific heat consumption for clinker formation while maintaining the strength of the cement, the roasting of the raw mix with KN 0.75-0.85 is carried out at 1350-1450 ⁰ C with a shutter speed of 5-10 minutes, and clinker cooling in the range of 1350-1250 ° C. And 1000 - 800 ° C is carried out at a speed of>: 500 ° s / min. g (A>