DK155042B - METHOD OF MANUFACTURING CEMENT - Google Patents

Description

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DK 155042 B

The invention relates to a process for making cement, preferably belit cement, of the normal raw materials.

The most important silicate binder is portland cement, which is first burned to clinker according to the wet, semi-dry or dry method with heating gradients up to 100 K / min at a final firing temperature of approx. 1450 ° C and a residence time in the sinter zone of 25 minutes or more. Then the cooling follows e.g. in planetary drum or grate chillers with cooling gradients from a firing temperature up to approx. 1200 * ...

1300 ° C in the oven of approx. 20K / min and then paint in ball mills.

10 In order to save the high investment and energy costs of producing portland cement, it has been proposed from portland cement with the main phase alite and the biphasic belit (dicalcium silicate corresponds to C2S), tricalcium aluminate and calcium aluminum ferrate to switch to the belit cement containing the main phase and the other phases of 15 Portland cement, but no alit. In Portland cement, belit is predominantly in the 3 modification. It is generally known about this phase that it is inactive, ie. only very slowly seems hardening due to its low rate of hydration. For this reason, the phase only contributes to the late strength. A cement consisting essentially of 3 "C2S" is, in the opinion of the experts, useless. Therefore, it has been suggested to use other modifications of C2S which have a more advantageous strength-curing time ratio. Like 3-C2S, all of these phases are metastable at room temperature. To stabilize the individual modifications, according to DDR patent 11,992, alkali, according to French patent no. 928 boric acid or boronaceous substances for the belitra meal. A belit cement with high proportions of gypsum to form the phase 3 CaO · 3 A1203 ·

CaSO4 next to belit discloses Russian patent specification 283,880.

First, the disadvantages of the prior art proposals are the use of feed additives which, as boron or phosphorus-containing compounds, in many cases belong to the raw materials of import raw materials or expensive cement the final product. Second, as a result of their thermal dissociation, calcium sulfate-containing additives lead to SO2 flue gas pollution. Finally, the manufacture of - 2 -

DK 155042 B

debonding active cements based on high temperature C2S phases stabilized with foreign substances, combustion temperatures from 1430 ° C.

This results in greater heat losses than in the phase fJ-C2S produced at lower temperature.

The object of the invention is to produce a belit cement that has the properties of port landings, but requires less material and heat consumption.

The object of the invention is to make a belit cement so that it arises in active form, ie. that its strength-curing time function 10 corresponds to normal cements.

According to the invention, in a process for the production of cement, preferably belit cement, of the normal raw materials subjected to such a burning, cooling and grinding regime, it is proposed that the compound dicalcium silicate, which with respect to stabilization, is known to be little active. is obtained in such an active state that the strength-curing time function corresponds to normal cement, that the belit drum with a limiting standard of 75 to 85 without the prescribed heating regime, but preferably with the heating gradient from the normal Portland cement manufacture, is heated to the firing temperature between 1350 and 1450 ° C, preferably in the lower part of this temperature range, and for up to 20 minutes, preferably 5 to 10 minutes, is burned in air or water vapor-enriched atmosphere and cooled normally, and the latch is preferably subjected to quenching with cooling gradients greater than 500 K / min. or a gradual cooling and ground into ball mills and then subjected to an intensive paint.

With the invention, in addition to the optimization of the belit raw flour recipe, manufacturing conditions were found which enable large-scale production of a hydration and hardening active belit cement. The method according to the invention is characterized first and foremost in the determination of the lime standard. According to the well-known formulas of Bogue, a pure, ie alit-free, belit cement has a lime standard after cooling of 75.

Due to the accuracy of the chemical analysis methods, deviations of ± 1.0 occur at the lime standard. Thus, the effective lime standard can e.g. amount to only 74, which theoretically causes a reduction in the amount of belit.

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DK 155042 B

It was found that a lime standard of 75 to 85 has to be set for the manufacture of belit cement. This gives the belit cement some proportions of alit, but the economic benefits of the belit cement are completely preserved.

5 The heating regime plays an important role in the production of portland cement. The highest lime bonding rates are obtained at maximum heating gradients between the deacidification temperature and the burning temperature. It was found quite unexpected / that the heating gradient is of no significance to the strength development of the belit cement.

In addition, it was found that the optimum firing temperature in the manufacture of belit cement - having regard to the two later described principles of treatment according to the invention of belit clinker - is between 1350 and 1450 ° C, preferably in the lower part of this temperature range, and that residence times between 0 and 20 minutes, preferably 5 to 10 minutes, are sufficient for final burning with fresh content <2% and for the development of the clinker minerals. The characteristics described in the manufacture of belit clinker show that the aggregates which are normal in the Portland cement industry, such as preheater, e.g. shaft preheater and cyclone preheater, optionally calcination plants and combustion units, such as e.g. rotary kilns, vortex reactors, can be used for the technical manufacture of these belit clinkers. Following the aforementioned composition, the aforementioned firing regime, and normal clinker cooling or in compliance with the known Portland cement manufacturing regime, belit cements occur which are inactive. Such inactive belitems in their compressive strength-curing time functions are well below port landings.

According to the treatment principle of the invention, the preparation of an active belit cement succeeds in adhering to a particular cooling regime of the belit clinker from the final firing temperature.

30 Highly active belit cements occur when the cooling gradient goes to infinity (dt / dT · * · 0 »). With decreasing cooling gradient, the activity of the belitment, i.e. its strength-cure-time curve is less advantageous than portlandorders. Belitements with the best strength-cure-time ratio, even exceeding portland durations, occur by quenching the clinker in water after firing. For technical purposes - 4 -

DK 155042 B

it is sufficient to perform the rapid cooling of the belit clinkers from temperatures between 1250 * ··· 1350 * C to 800 * .. · 1000 * C. The cooling gradient in this range must be greater than 500 K / min. Water or other liquids and air are suitable as refrigerants for the quick cooling phase.

5 The required amount of water can be calculated from the known clinker flow and the required temperature drop. The cooling gradients above and below said rapid cooling range are immaterial, so that in these temperature ranges the cooling methods that are normal in Portland cement technology can be used. Known solutions are available for the technical realization of the rapid cooling area, e.g. the material discharge device for shaft-operated shaft furnaces consisting of water troughs and beaker, or the splashing device for water to reduce the clinker temperature to prevent iron (IX) oxidation in white cement production.

In conjunction with the quenching of the clinker with water, it was found that the resulting partial pressure of water vapor in the furnace atmosphere causes a reduction of the deacidification times and the final burning times. This effect can be utilized such that first anhydrous clinker cooling is carried out in the high temperature range, e.g. quenching with air, the subsequent further cooling of the clinker is carried out with air and water, and this water vapor-containing air is used wholly or partially for combustion.

After cooling the clinker, the grout is painted in ball mills and subjected to an intensive paint in swing mills, beam mills, disintegrators, rolling chairs and the like.

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WORKING EXAMPLES

The invention will now be explained by way of example. The accompanying drawings show in FIG. 1 and 2 compressive strength curing time functions for cement.

Here means:

Ordinate: compressive strength CD in MPa

Abscissa: curing time τ in days d 35 Curves 2, 3, 4 + 5 function of compressive strength / curing time in eczema- DK 155042 B -½ MAY 1988

Patent Directorate no. No. 5 - piers 2-5 PZ: the compressive strength / curing time of Portland cement 1/375 according to TGL 28101/01 ZZ: the compressive strength / curing function of a ce.

5 ment with grinding material according to TGL

2801/02 fJ-C2S: the compressive strength / curing time function of a cement which is preferably made up of Ø-CgS and was manufactured according to the known regime for portland cement.

To prepare a comparison cement, the raw materials were limestone and clay worked in a known manner and mixed to give a lime standard of 75. The raw material was heated in a gradient oven to 950 ° C for 15 minutes and acidified at this temperature over 11 minutes. there air atmosphere. Next, it was heated to the firing temperature of 1450 ° C with a gradient of 70 K / min. The residence time after reaching the final firing temperature was 20 minutes. Next, the clinker cooling followed with cooling gradients in the upper temperature range of 20 ca. 70 K / min and in the lower temperature range of approx. 20 K / min. The Belit clinkers burned according to the said Portland cement regime were painted together with the normal plaster cast according to Blaine in a ball mill for 2 approx. 3200 cm / g and their compressive strength was determined. The obtained compressive strength curing time function is seen in Figure 2, curve 0-C2S, and confirms the known inactivity of the coating.

According to Example 1, belitre flour was prepared with lime standard 75 as in the comparative belit cement and acidified. The selected heating gradient was between 950 and 1340 ° C at 1000 K / min. and between 1340 and 1425 ° C at 70 K / min. After a residence time of 5 minutes after reaching 30 of the firing temperature of 1425 ° C, the clinker was quenched in water, which corresponded to a cooling gradient of approx. 2,104 K / min. After drying the 2 clink, grind in a ball mill for approx. 3200 cm / g according to Blaine and the normal gypsum addition, the compressive strength was determined and recorded in figure 1, curve 2. The content of free lime of the belit clinker was 0.05%. The coating cement corresponds in the 7-day strength to a cement with grinding material - 6 -

DK 155042 B

rial (Figure 1, curve ZZ), however, significantly exceeds this in the 28-day strength. Belit Cements with lime standard 75 are characterized by a low heat of hydration and are particularly suitable for hydrotechnical buildings.

According to Example 2, belitre flour, like the saramen equation belit but with lime standard 80, was prepared and acidified. The firing, cooling and grinding regime was as in Example 1 (heating gradient between 950 'and 1340 * C at 1000 K / min, between 1340 and 1425 * C at 70 K / min. Burning temperature 1425 * C. 5 minutes residence time. in water. Ball milling of the latch). The measured compressive strengths show Figure 2, 10 curve 3. The content of free lime in the belit clinker was 0.04%.

The belit cement follows the strength of Portland cement 1/375 (Figure 2, curve PZ) and surpasses this in the 28-day strength. The active belit cement according to the invention is the superior belit and 8-C2S course according to the Portland cement regime (Figure 2, curve), respectively.

In accordance with Example 3, belitre flour was prepared, just like joint belit one, but with lime standard 80, and acidified. The heating gradient between 950 * and 1385 * C was 100 K / min. Burning temperature 1385 * C, residence time 5 minutes, quenching of the latch in water, ball painting of the latch. The measured compressive strengths are shown in Figure 2, curve 4. The content of free 20 lime in the belit clinker was 0.54%. The belit cement follows the strength course of Portland Cement 1/375 (Figure 2, curve PZ) with superiority in the 28-day strength.

According to Example 4, belitre flour of lime standard 75 was prepared in a similar manner to the comparison belit and acidified. The heating gradient between 950 * and 1350 * C was 1000 K / min. Burning temperature 1350 * C. Duration 2 minutes. The latch was cooled by quenching with air, causing a cooling gradient of 1.3 · 10 K / min. Bullet aging of the latch. The compressive strengths of the samples are prepared in Figure 1, curve 5. The content of free lime in the belit clinker was 1.9%.

30 Also, this belit cement, manufactured under unfavorable conditions with respect to the firing temperature and residence time, meets the conditions of a cement with additives (Figure 1, curve ZZ) and exceeds its 28-day strength.

According to Example 5, belitre flour was prepared in the same manner as the comparator belit but with lime standard 80 and acidified. Heating - 7 -

DK 155042 B

the gradient was between 950 * and 1340 * C at 1000 K / min. and between 1340 * and 1385 * C at 70 K / min. Burning temperature 1385 * C. Stay time 5 minutes. The clink cooling proceeded until a temperature of approx. 1300 * C with a gradient of about 20 K / min. Next, a rapid cooling period followed 5 to approx. 900 * C with a gradient greater than 500 K / min. by spraying water. Ball paint of the latch. The compressive strength-curing time function was similar to a portland landing.

According to Example 6, belitre flour was made just like the comparison belit but with lime standard 80. To the furnace atmosphere, 10 steam was added, so that its proportion was approx. 20%. The water vapor addition made it possible to lower the deacidification time at 950 ° C from 11 to 9 minutes. The heating gradient was between 950 'and 1340 ° C at 1000 K / min. and between 1340 ° C and 1385 ° C at 70 K / min. Burning temperature 1385 ° C. The addition of water vapor allowed the holding time of 5 minutes as in Example 2 to be reduced to 2 minutes. Quenching in water. Ball paint of the latch. The content of free lime in the belit clinker was 0.69%. The Belit cement is similar to the strength ratio of a Portland cement.

The advantages of the belit cement made according to the invention consist in that the material input factor, i.e. the mass ratio of raw flour sinks, which corresponds to a raw material savings of up to 3%. This eliminates the cost of extraction and processing of raw materials. In addition, the specific heat consumption decreases, taking into account the thermal efficiency of e.g. a rotary kiln with up to 370 kJ / kg latch. The reduction of the fuel temperature below 1450 ° C allows the use of 25 less valuable fuels. As a consequence of the lowering of the temperature, a decrease in the alkali content of the circuits occurs, the nitrogen oxide content of the waste gas decreases, the durability of the fire-aggregate liner is extended, which, in addition to a cost saving, improves the temporal efficiency of the plant and 30 The KR principle can be drawn up to 100% of the combustion air through the sinter unit. A further advantage of the invention consists in shortening the residence times by increasing the water vapor partial pressure due to the effect of the water vapor on the dust conversions by deacidification and burning. The proposed transition from 35 Portland cement to belit cement results in a reduction in hydration response - 8 -

DK 155042 B

but at approx. 120 kJ / kg sound. An important advantage of the belit making according to the invention is that substantial aggregates from the present-day Portland cement technology can be retained.

5

Claims (5)

1. A process for producing cement / preferably belit cement, of the normal raw materials subjected to such a firing, cooling and grinding regime that the compound dicalcium silicate, known for its stabilization, is obtained in such an 5 in the active state, the strength-curing time function corresponds to normal cement, characterized in that the belit bar with a lime standard of 75 to 85 without the prescribed heating regime, but preferably with the heating gradient from the normal portland cement manufacture, is heated to the firing temperature of between 1350 ° and 1450 ° C, preferably in the lower part of this temperature range, and for up to 20 minutes, preferably 5 to 10 minutes, is burned in air or water-vapor-enriched atmosphere and cooled normally, and the clink is preferably subjected to quenching with cooling gradients greater than 500 K / min. or a gradual cooling and ground into ball mills and then an intensive paint is thrown away. Process according to claim 1, characterized in that the quenching of the hot latch is effected with water. Process according to claim 1, characterized in that the quenching of the hot latch is effected with air or an air-water mixture. Process according to claims 1 to 3, characterized in that the quenching of the hot latch by gradual cooling is preferably limited to the temperature range from 1350 to 1250 ° C as upper limit temperature and 1000 to 800 ° C as lower limit temperature. Process according to claims 1 to 4, characterized in that, in addition to the water fraction of the raw and fuel substances, the furnace atmosphere is further added to steam. 30