EP4676896A1

EP4676896A1 - Method and plant for manufacturing composite cement and composite cement

Info

Publication number: EP4676896A1
Application number: EP24710522.4A
Authority: EP
Inventors: Zaal SADUNISHVILI; Mikheil KITRIASHVILI; Zakaria ADUASHVILI; Teona ROBAKIDZE; Giorgi GURASPASHVILI; Zurab MENABDISHVILI; Ivane JAVAKHISHVILI; Vakhtang CHKHEIDZE; Kakha GOCHITASHVILI; Neli KESAURI
Original assignee: Kartuli Cement LLC
Current assignee: Kartuli Cement LLC
Priority date: 2023-03-07
Filing date: 2024-03-07
Publication date: 2026-01-14
Also published as: EP4194417C0; WO2024184851A1; EP4194417A1; RS66814B1; HUE071651T2; CN121013828A; ES3025132T3; HRP20250610T1; EP4194417B1; PL4194417T3

Abstract

The present disclosure refers to a method for manufacturing a composite cement comprising the steps of providing a cement raw meal, preheating the cement raw meal to provide preheated cement raw meal, precalcination of the preheated cement raw meal to provide precalcined cement raw meal, sintering the precalcined cement raw meal in a rotary kiln to provide cement clinker, and cooling the cement clinker in a cooler. In addition, the step of adding zeolite to the cement clinker in the cooler at a position where the temperature of the clinker provides the energy for calcining the zeolite for obtaining the composite cement is comprised. Further, the present disclosure refers to a plant (1) for manufacturing a composite cement, with a feeding, transport and dosage system (2), a cooler (4) and a kiln (5), wherein the kiln (5) feeds heated cement clinker (2000) into the cooler (4) and the feeding, transport and dosage system (2) feeds zeolite (1000) into the cooler (4) such that the zeolite (1000) is calcinated by heat provided by the cement clinker (2000) in the cooler (4). Still further, the present disclosure refers to a composite cement manufacture with said method and/or in said plant.

Description

METHOD AND PLANT FOR MANUFACTURING COMPOSITE CEMENT AND COMPOSITE CEMENT

Description

The present disclosure relates to a method for manufacturing a composite cement comprising the steps of providing a cement raw meal, preheating the cement raw meal to provide preheated cement raw meal, precalcination of the preheated cement raw meal to provide precalcined cement raw meal, sintering the precalcined cement raw meal in a rotary kiln to provide cement clinker, and cooling the cement clinker in a cooler. Further, the present disclosure refers to a plant for manufacturing a composite cement, with a feeding, transport and dosage system, a cooler and a kiln. Still further, the present disclosure refers to a composite cement manufacture with said method and/or in said plant.

Cement is one of the most widely used products in construction. The cement industry is struggling with high CO2 emissions related to the production of cement clinker. A major part of the CO2 emissions related to the clinker production originates from the raw materials used, i.e., from limestone. As environmentally friendlier alternatives to limestone do not exist at large enough scale, reduction of the raw material emissions by limestone substitution is not possible. Thus, reducing the requirement of natural resources in manufacturing cement, both mineral raw materials and fuels, has been a target for decades. Exchanging raw materials and fuels with waste and by-products is especially beneficial as is the use of such materials instead of cement clinker, i.e., as supplementary cementitious material (abbreviated SCM herein).

Unfortunately, reduction of cement and concrete industry environmental footprint by utilization of industrial waste and by-products as SCM for clinker replacement has reached global availability limits of useful materials (fly ashes and granulated blast furnace slag). By no means all by-products and waste products are suitable as SCM. The pozzolanic or latent hydraulic reactivity may not be too low, as otherwise the properties of the building material created from the cement and SCM will be negatively impacted. The availability of the two most important SCM - fly ashes and blast furnace slags - is expected to decrease with the progressing decarbonation of the electricity sector and increased steel recycling, respectively. As a result, it is an object to provide alternative SCM.

Widely available and accepted materials are limestone, clay, and recycled concrete fines. The suitable amount of limestone is limited, since it does not comprise reactive silicate and/or aluminate phases. Clay is abundant and shows high reactivity when suitably calcined, but only specific qualities are easily used. Those high-quality clays have other beneficial uses with which the manufacturing of composite cement would compete. Recycled concrete fines can be very reactive and are about to be included in the standard, but their use is complicated due to their very variable composition.

Another option are natural pozzolans. To be useful they need to contribute to cement hardening, usually by a chemical reaction of the phases in the SCM with hydration products of OPC-clinker and water. Natural pozzolans often show relatively low reactivity and individual phases comprised in them can have very different reactivity. Further, the availability of sufficiently reactive natural pozzolans is differing from location to location. A transportation over long distances is undesirable, since the benefit of using SCM is rapidly overbalanced by transportation cost and the associated CO2 emissions. Thus, known reactive natural pozzolans cannot solve the above object.

At some locations zeolites are abundant. Zeolites are aluminosilicates mainly consisting of silicon, aluminum, and oxygen accommodating a wide variety of cations, such as Na⁺, K⁺, Ca²⁺, Mg²⁺ and others. Since these positive ions are often loosely held and can readily be exchanged for others they are well known as ion exchange materials. Zeolites have microporous structures with a typical diameter of 0.3 - 0.8 nm which renders them useful as molecular sieves. The Si/AI molar ratio is normally greater than 1. Natural zeolites usually have Si/AI molar ratios below about 3. Some of the more common mineral zeolites are analcime, chabazite, clinoptilolite, heulandite, natrolite, phillipsite, and stilbite. Natural zeolites form by reaction of volcanic rocks and ash layers with alkaline groundwater. Zeolites also crystallize in post-depositional environments like in shallow marine basins over periods ranging from thousands to millions of years. Naturally occurring zeolites are rarely pure and are contaminated to varying degrees by other minerals, for example by quartz or other zeolites. Other impurities like metals are also frequently found. Therefore, natural zeolites are seldom useful as ion exchange material or molecular sieve without extensive treatment and synthetic zeolites are provided for these uses. The use of natural zeolites as SCM in composite cements is possible because neither a mixture of various zeolites nor the presence of further minerals interferes with this. But the high surface area of zeolites causing inter alia a high water demand is a considerable drawback. Thus, they have only been used in low amounts so far.

As is known for clay and oil shale, the phases of natural pozzolans can sometimes be transformed to metastable and thus reactive phases by calcination, i.e., a heat treatment changing crystalline and/or chemical structure. However, such heat treatment has the drawback of requiring allocated resources, like heat-supply and material handling. It consumes fuel thereby releasing CO2. The calcination of clay is also quite complicated when several clay phases with differing optimum calcination temperature are present. Proposals for improved clay calcination processes are found e.g., in EP 2 253 600 Al , US 5,626,665 A , WO 2016/082936 Al , WO 2021 /124261 Al , and not prior published EP 21198584.1 , as well as in EP 3 070 064 Bl and WO 2022/106966 Al . The latter two proposals rely on a calcination of the clay inside the clinker cooler. To achieve this, a double-inlet valve and specific compositions of the so-called low carbon cement made are described as necessary.

US 4 078 882 A discloses a method for burning pulverous or granular raw material such as cement raw meal in a rotary kiln plant by directing a first flow of raw material to a cyclone preheater, preheating the first flow of raw material in the cyclone preheater, and directing the preheated raw material from the cyclone preheater to a rotary kiln for burning the material in the kiln. The burnt kiln product is directed to a cooler which may be of several types and which communicates with the material outlet of the kiln while a second flow of fresh raw material is directed to the cooler to at least partially cool the burnt kiln product by transferring heat therefrom to the second flow of fresh raw material in the cooler. The method further involves combining the preheated, at least partially calcined second flow of material with the first flow of preheated, at least partially calcined material prior to directing the combined flows to the rotary kiln and thereafter directing the combined flows to the kiln for burning and for subsequent cooling in the cooler.

CN 1 065 445 A discloses a method for improving Portland cement production quality, reducing energy consumption, and reducing smoke and dust, with calcining atmosphere of a kiln and using perlite and zeolite to replace part of the clay.

Florez Cristian et al conclude in the article with the title "Effects of calcination and milling pre-treatments on natural zeolites as a supplementary cementitious material", published in Construction And Building Materials, Elsevier, Netherlands, vol. 310, research, that calcination at 300 °C and 800 °C managed to tenuous improve the pozzolanic activity of NZ, although calcination at 300 °C is comparable to that of zeolite in its natural state, calcination at 800 °C subtly increased the pozzolanic activity of zeolites.

It is the object of the present disclosure to further develop the known method according to the pre-amble of claim 1 to overcome the drawbacks of the prior art.

This object is archived according to the present disclosure by adding zeolite to the cement clinker in the cooler at a position where the temperature of the cement clinker provides the energy for calcining the zeolite for obtaining the composite cement.

It is proposed that a size of the zeolite is adjusted to a D90 of 100 mm, preferably a D90 of 50 mm, most preferred a D90 of 30 mm, and/or a D10 of at least 1 mm, preferably of at least 5 mm, most preferred at least 10 mm.

It is also proposed that the zeolite is selected from analcime, chabazite, clinoptilolite, heulandite, natrolite, phillipsite, stilbite or mixtures of two or more thereof.

Further it is proposed that the zeolite is selected to comprise mineral phases like quartz, feldspar, clay minerals, mica, calcite and/or impurities like metals, wherein preferably an amount of the mineral phases and impurities is below 60 wt.-%, in particular below 55 wt.-%, most preferred below 50 wt.-%, with respect to the total zeolite mass. Still further, it is proposed that the zeolite is selected with a Si/AI molar ratio below 3, preferably from 1 to 3.

Furthermore, it is proposed that the zeolite is added in an amount ranging from 1 to 60 wt.-% with respect to the clinker weight, preferably from 5 to 30 wt.-%, most preferred from 7 to 15 wt.-%.

In addition it is proposed that amount and point of addition of the zeolite are adjusted, in particular to obtain a reduction of the BET surface area of the zeolite of at least 5 %, preferably of at least 10 %, most preferred of at least 15 %.

It is preferred that the zeolite is added to a temperature in the range from 600 to 800 °C .

Also, it is proposed that the cement clinker is selected from Portland cement clinker, calcium sulfoaluminate cement clinker, or calcium aluminate cement clinker, preferably Portland cement clinker.

Still further, it is proposed that one or more supplementary cementitious material, especially fly ash, ground granulated blast furnace slag, carbonated recycled concrete fines, calcined clay, hyaloclastite, and mixtures of two or more thereof, are added, and/or one or more additives, especially pigments, fibers, mineral fillers, reinforcing elements, self- healing agents, and mixtures of two or more thereof, are added.

The present disclosure also solves the problem to further develop the known plant to overcome the drawbacks of the prior art.

This problem is solves in that the kiln feeds heated cement clinker into the cooler and the feeding, transport and dosage system feeds zeolite into the cooler such that the zeolite is calcinated by heat provided by the cement clinker in the cooler.

Embodiments of the plant are characterized in that the feeding, transport and dosage system comprises a feeding device, a transport device and a dosage device, wherein preferably the feeding device comprises a feed hopper, the transport device comprises one or more belt conveyors, and/or the dosage device comprises a funnel-shaped collecting container and/or a gas tight valve.

According to further aspects the zeolite is entered into the cooler via the gas tight valve in a controlled manner, in particular determined by one or more belt drift switches, at least one belt scale, at least one magnetic separator, at least one variable frequency drive and/or at least one level control sensor.

According to other aspects the at least one level control sensor comprises a first level control sensor for determining a stop of feeding the funnel-shaped collecting container and/or a second level control sensor for determining the regulation of the gas tight valve.

Certain embodiments are characterized in that the gas tight valve comprises two flaps, of which only one is open at a time, wherein preferably a first amount of zeolite can enter the gas tight valve while an upper flap is open, and a second amount of zeolite can enter into the cooler while the lower flap is open.

According to further aspects the cooler is provided with a housing having at least one connection to a kiln outlet, preferably provided by a kiln hood, for entering the heated cement clinker from the kiln and at least one grate cooler outlet for exiting a blend of cement clinker and calcinated zeolite, wherein preferably the blend is guided via the grate cooler outlet to a grinding device.

Yet, further embodiments are characterized by one or more means for entering fresh air into the cooler, with the fresh air flowing preferably from the bottom of a cement clinker bed within the cooler and through the cement clinker bed to leave the cooler as hot air via the kiln outlet and/or at least one additional opening at the top of the cooler.

In addition, embodiments can be characterized in that the kiln outlet and the additional opening are arranged remote from the entry point of the zeolite into the cooler, which preferably is within a middle zone of the cooler. The plant according to the present invention can further comprise a divertor for determining the point within the cooler, at which the zeolite is added to the cement clinker, and/or for determining the temperature range of the cement clinker, to which the zeolite is added.

Further embodiments can be characterized by the divertor is controlled, wherein the control depends on the kind of added zeolite and/or the control allows a rotation within a range of 70°.

The present invention also provides a composite cement manufactured with a method according to the present disclosure and/or in a plant according to the present disclosure.

It is also proposed that the composite cement further comprises one or more additives, especially pigments, fibers, mineral fillers, reinforcing elements, self-healing agents, and mixtures of two or more thereof, and/or one or more supplementary cementitious material, especially fly ash, ground granulated blast furnace slag, carbonated recycled concrete fines, calcined clay, hyaloclastite, and mixtures of two or more thereof.

Surprisingly, it was now found that zeolites can be activated by adding them to the clinker cooler with a simple gas tight valve when the point of addition is adjusted so that the added zeolite is heated to a temperature in the range from 600 to 800 °C. For sufficient activation, also heat-transfer by duration of exposure to this temperature is required, which is provided by the time the clinker and added zeolite travel through the cooler between the point of addition and the cooler exit. Calcined zeolite was not usual before the present disclosure was made, instead, zeolite was merely dried before mixing with the cement or cement clinker.

Thus, the above problem is solved by a method for manufacturing a composite cement comprising the steps: providing a cement raw meal, preheating the cement raw meal to provide preheated cement raw meal, precalcination of the preheated cement raw meal to provide precalcined cement raw meal, sintering the precalcined cement raw meal in a rotary kiln to provide the cement clinker, and cooling the cement clinker in a cooler, wherein a zeolite is added with a gas tight valve to the clinker in the cooler at a position where the temperature of the clinker causes a heating of the added zeolite to a temperature in the range from 600 to 800 °C. The object is also achieved by a composite cement obtained by providing a cement raw meal, preheating the cement raw meal to provide preheated cement raw meal, precalcination of the preheated cement raw meal to provide precalcined cement raw meal, sintering the precalcined cement raw meal in a rotary kiln to provide the cement clinker, and cooling the cement clinker in a cooler, wherein a zeolite is added with a gas tight valve to the clinker in the cooler at a position where the temperature of the clinker causes a heating of the added zeolite to a temperature in the range from 600 to 800 °C, and grinding the cooled clinker and zeolite.

The present disclosure relies on the heat released by the clinker in the clinker cooler of a rotary kiln. The zeolite is typically fed approximately to the center of the clinker cooler. From the top of the cooler-roof the zeolite is falling onto the hot clinker. The energy for calcining the zeolite is provided by the high temperature of the clinker. By radiation from the clinker bed the heat is transferred from the clinker to the zeolite. At the same time by the airflow through the clinker bed the clinker is cooling.

Thereby, neither an additional device nor fuel are needed to calcine the zeolite. The calcination at a temperature in the range from 600 to 800 °C results in an activated material having a reduced BET surface area (determined according to ISO 9277:2022 and based on the analysis of isotherm data by a method developed by Brunauer, Emmett and Teller) with changes in crystallography, especially an increase in content of X-ray amorphous phase/phases. This can reduce water demand, and/or result in a shorter setting time, and/or enable a lower mortar spread and/or provide a faster strength development when compared to using a merely dried zeolite.

All zeolites as described above and especially also mixtures of two or more of them and/or zeolites containing a considerable amount of other mineral phases are suitable according to the disclosure. The zeolites can be used as obtained from the quarry or subjected to a pretreatment before being added to the cooler.

Other aluminosilicate materials can be calcined in the same way, optionally at another temperature range when such is optimum for the specific aluminosilicate. For example, clay (materials containing a significant amount (e.g., 20 wt.-% or 30 wt.-% or 50 wt.-% or more) of clay minerals like such from the kaolin group, smectite group and/or illite group, specifically but not limited to the following: kaolinite, dickite, halloysite, nacrite, montmorillonite, nontronite, beidellite, saponite, illite, palygorskite, sepiolite) can be added and calcined at a temperature from 400 to 950 °C, preferably 600 to 850 °C. Also, other pozzolans such as but not limited to trass, diatomite, perlite, pumice, tuff, hyaloclastite, lava sand etc. are expected to benefit in the same way as zeolites. In the following, only zeolite is described in detail, but other aluminosilicate material can be calcined and form composite cements in the same way or analogously to zeolites.

Advantageously, the size of the zeolite is adjusted to a D90 of 100 mm, preferably a D90 of 50 mm, most preferred a D90 of 30 mm. Often, the particles obtained from the quarry already have this size. If not, the size can be reduced by crushing and/or grinding, combined with sieving and/or classifying when desired. It is not worthwhile to provide the zeolite with a D10 below 1 mm because the calcined zeolite will be ground together with the cement clinker anyway. Handling is also more complicated for smaller particle sizes. Therefore, the D10 is preferably at least 1 mm, more preferred at least 5 mm, and most preferred at least 10 mm. Particle sizes in this range are determined by sieving as is usual.

Preferred zeolites mainly comprise zeolite phases like analcime, chabazite, clinoptilolite, heulandite, natrolite, phillipsite, and stilbite or mixtures of two or more thereof. Typically, the Si/AI molar ratio is below about 3, preferably from 1 to 3. The zeolites can comprise other mineral phases, e.g., quartz, feldspar, clay minerals, mica and calcite, and also impurities like metals. The amount of such non-zeolite components is preferably below 60 wt.-%, more preferred below 55 wt.-% and most preferred below 50 wt.-% with respect to the total zeolite material added.

The foregoing summary, as well as the following detailed description, will be better understood when read in conjunction with the appended drawings. For the purpose of illustration, certain examples of the present description are shown in the drawings. It should be understood, however, that the disclosure is not limited to the precise arrangements and instrumentalities shown. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an implementation of system, apparatuses, and methods consistent with the present description and, together with the description, serve to explain advantages and principles consistent with the disclosure. Figure 1 is a schematic side view of a plant for manufacturing composite cement according to the present disclosure, partially in cross-section along line A-A of figure 2, and Figure 2 is another side view of the plant, partially taken along line B-B of figure 1.

The cement clinker manufacturing steps according to the method of the present disclosure are based on usual steps and may be implemented with commonly used devices for manufacturing of any kind of Portland cement clinker, calcium aluminate clinker, calcium sulfoaluminate clinker and calcium sulfoaluminate belite clinker. As one of ordinary skill in the art is acquainted with suitable conditions to carry out clinker manufacturing, known devices and conditions will be only briefly described herein. In fact, it is one advantage of the present disclosure that an existing cement manufacturing line can easily be retrofitted for zeolite addition to convert it into a plant according to the present disclosure.

In the following, first a method according to the present disclosure and then a specific plant according to the present disclosure are described.

As usual, cement raw meal is provided in a first step for the cement manufacturing. Typically, cement raw materials are ground and mixed as well as dried when necessary to obtain the cement raw meal. Mix design and particle sizes are adjusted as usual. Exhaust gas from the cement clinker production process (kiln) is usually used for drying cement raw materials within the grinding process.

The cement raw meal is then preheated, usually in counter current flow with exhaust gas from the cement clinker kiln. A useful preheating section comprises at least two, often three or four, cyclones. The preheating is often coupled with a calcination to decarbonate a substantial amount of the calcium carbonate in the preheated cement clinker raw meal. Typically, decarbonation is not complete, a minor amount of the carbonate is only decarbonated in the kiln. Usually, the calciner receives preheated raw meal and gas which is heated by a calciner burner and/or in a separate burning chamber connected to the calciner. The burning process in the calciner can take place with conventional fossil fuels like gas, petroleum, and coal. It also works with alternative fuels like combustible municipal, industrial and commercial waste, refuse-derived fuels, and biomass. The preheated and subsequently precalcined cement clinker raw meal typically comprises from a few percent, e.g., from 1 to 5 wt.-%, up to 30 or 40 wt.-% carbonate.

The precalcined cement raw meal is fed to the kiln, normally a rotary kiln, as usual. It is also possible to feed the preheated raw meal to the kiln and accomplish the complete decarbonation in the kiln. Inside the kiln the raw meal is sintered to provide the cement clinker. The kiln burner can work with fossil fuels and/or with alternative fuels. Using at least partly alternative fuels is preferred. The combustion air for the kiln burner comes from the cement clinker cooler as known per se.

The obtained cement clinker passes from the kiln to a cooler where it is cooled down, typically with a counter current air stream. All known cooler types are useful, preferred are grate coolers. A part of the air heated up during cement clinker cooling is normally used as a first combustion air for sintering cement clinker raw meal in the kiln. Another part (called tertiary air) may be guided directly into the cement clinker raw meal calciner or is used otherwise, e.g., for drying cement clinker raw materials, also as usual.

The clinker is arriving to the cooler downstream from the kiln. The zeolite is arriving from the top or side to the cooler. Both material streams are combined in the cooler. Further, the materials continue to travel as blend, i.e. as blended mix of clinker and zeolite, via the remaining of the cooler to the clinker storage. There is no separation of the materials downstream. Hence, there are no resources for separate material handling required.

Feeding and dosage of the zeolite are advantageously accomplished by a transport device with mass flow sensor, especially with a belt weigh feeder, and a gas tight valve. The zeolite is usually provided in a silo, buffer hopper or any other storage unit able to discharge the zeolite as desired. A prior drying of the zeolite is possible but normally superfluous. The particle size can be adjusted if necessary, as described above. The preferred belt weigh feeder transports the selected amount of zeolite to the gas tight valve. The valve allows an addition to the cooler without any hot air escaping. The valve may have two flaps of which only one is open at a time. While the upper flap is open, zeolite enters the valve. After closing the upper flap, the lower one opens, and the zeolite falls down onto the clinker travelling in the cooler. Then, the lower flap closes, and the cycle is repeated. Other valves allowing to feed the zeolite and at the same time preventing gas from escaping from or entering the cooler are likewise possible. Contrary to what EP 3 070 064 Bl and WO 2022/106966 Al describe, it is not necessary and in fact overly complicated to use a double inlet valve requiring two valve chambers. Due to the fast operating of a simple gas tight valve, it is not necessary to have two dispensing chambers of which one opens when the other closes.

The point of addition is chosen such that the clinker comprises sufficient heat to calcine the added zeolite at a temperature from 600 to 800 °C. Usually, this point is at about the middle of the cooler. When higher amounts of zeolite are added and/or a temperature at the higher end (e.g., 700 to 800 °C) is desired, the point is nearer to the kiln. In case a lower amount of zeolite is added and/or calcination shall take place at the lower end of the temperature range (e.g., 600 to 700 °C) an addition nearer the cooler exit is appropriate.

Typically, amounts of zeolite ranging from 1 to 60 wt.-% with respect to the clinker weight, preferably from 5 to 30 wt.-%, most preferred from, 7 to 15 wt.-%, for example about 10 wt.- %, are added. The amount is limited by the specific heat carriage by the clinker and adjusted to assure sufficient thermal treatment of the zeolite.

The calcination of the zeolite provides a supplementary cementitious material with a reduced BET surface area. Preferably, a reduction of the surface area of the zeolite of at least 5 %, more preferred of at least 10 % and most preferred of at least 15 % of the surface area is aimed at. The calcination further provides a change in crystallography, mainly an increase in X-ray amorphous phase or phases. Without wishing to be bound by this theory it is hypothesized that those effects result in the improved reactivity compared to the merely dried zeolite used before.

The clinker exits the cooler intimately mixed with the added zeolite. Both have cooled down to a temperature in the range from ambient to 200 °C when they leave the cooler. As known per se, the clinker (and with it the calciner zeolite) is ground to the desired fineness to obtain the composite cement. The grinding can be carried out in any known device such as but not limited to a ball mill. As is customary, a classifier can be used. Further, the grinding can take place in a two-stage mill. The fineness of the ground mixture obtained preferably ranges from 2500 cm<2>/g to 8000 cm<2>/g, more preferred from 3000 cm<2>/g to 7000 cm<2>/g and most preferred from 3500 cm<2>/g to 6000 cm<2>/g according to Blaine (determined according to EN 196-6:2018).

Preferably, an amine grinding aid is added for grinding. Preferred substances are diisopropanolamine, methyldiethanolamine, triethanolamine, triisopropanolamine, and diethanol-isopropanolamine, most preferred are triethanolamine, triisopropanolamine, and diethanol-isopropanolamine. These can also be added to improve reactivity of the activated zeolite even further.

The cement clinker is preferably selected from Portland cement clinker, calcium sulfoaluminate cement clinker, and calcium aluminate cement clinker. Especially preferred is Portland cement clinker.

The composite cement according to the disclosure, obtained by the method according to the disclosure, can also contain other components. Typically, a sulfate carrier such as gypsum or anhydrite is added to obtain Portland composite cement.

In a preferred embodiment, the composite cement according to the disclosure contains from 1 to 30 wt.-%, preferably from 5 to 25 wt.-%, more preferred from 10 to 20 wt.-%, most preferred from 12 to 17 wt.-% mineral filler with respect to the total composite cement weight. A preferred mineral filler is stone dust, especially limestone. Carbonated recycled concrete fines, dolomite, precipitated calcium and/or magnesium carbonate are also possible. The filler can be co-ground with the clinker and zeolite (and possibly also one or more further components) or ground separately. Preferably it is ground separately. Some fillers do not need grinding since they are fine enough as obtained. The fineness according to Blaine of the filler preferably ranges from 2500 cm<2>/g to 12000 cm<2>/g, more preferred from 3000 cm<2>/g to 9000 cm<2>/g, and most preferred from 3500 cm<2>/g to 8000 cm<2>/g.

Further optional components of the composite cement according to the disclosure are other SCM such as but not limited to fly ash, GGBFS (ground granulated blast furnace slag), carbonated recycled concrete fines, calcined clay, hyaloclastite, and mixtures of two or more thereof. If used they are typically contained in the amounts allowed by the applicable standard, e.g., EN 197-1 or EN 197-5. The composite cement can also comprise additives such as but not limited to pigments, polymers, fibers, reinforcing elements, self-healing agents etc. and mixtures of two or more thereof. All these can be added in the amounts known per se.

The composite cement can also comprise admixtures, although admixtures are usually only added to the building material made with the cement, e.g., to a concrete, mortar, or construction chemical composition. The mode of addition also depends on whether an admixture is a dry substance or provided as a solution or suspension. A solution or suspension in water is mostly added to the building material and not to the cement.

Admixtures are used to optimize the properties like setting time, hardening time, spread, viscosity and homogeneity as well as to impart desired properties to the final concrete part like strength, flexural modulus, freeze-thaw-resi stance and many more. These admixtures are known per se and are used in their usual amounts, wherein the amount is adapted to a specific binder and special needs in the known manner.

For use, the composite cement is made e.g., into mortar or concrete by mixing with water. Typically, a water/cement weight ratio (w/c) from 1 to 0.1, preferably from 0.75 to 0.15, and most preferred from 0.65 to 0.35 is used. The zeolite and one or more optional additional SCMs are included into the amount of cement for calculating the w/c.

The building material, e.g., mortar or concrete, usually also contains aggregates. Aggregate can be any aggregate known as such. Normally sand and/or gravel of selected particle sizes is/are used. In some cases, lightweight aggregate is used, typically as part of the aggregate but also as sole aggregate.

Figures 1 and 2 show a plant 1 according to the present disclosure, in two partial cross- sectional views, to illustrate the relative arrangement of a feeding, transport and dosage system 2 arranged on a floor 3 for feeding zeolite 1000 to a cooler 4 in order to be calcinated by heat provided by cement clinker, referred to simply by clinker 2000 in the following, which is feed from a kiln 5. The zeolite 1000 is mixed with the clinker 2000 such that the clinker 2000 exits the cooler 4 intimately mixed with the calcinated zeolite 1000 in particular to enter a grinding device e.g. in form of a roller crusher 6.

The feeding, transport and dosage system 2 comprises a feeding device, a transport device 20 and a dosage device 30 for entering the zeolite 1000 from the top of the cooler 4. For that purpose, the feeding device comprises a feed hopper 100, which may be filled with zeolite 1000 by a front loader 7, and the transport device 20 comprises one or more belt conveyors 200. The dosage device 30 comprises a funnel-shaped collecting container 300 to allow entering of the zeolite 1000 into the cooler 4 via a gas tight valve 310 in a controlled manner. The control is achieved via belt drift switches 201, 205, a belt scale 202, a magnetic separator 203, a variable frequency drive 204, and at least one level control sensor 301, 302, in addition to the dosage via the gas tight valve 310.

The belt drift switches 201, 205 are arranged in particular in loading zones of the belt conveyors 200. The belt scale 202 allows to determine a mass flow. The magnetic separator 203 and the variable frequency drive 204 secure a homogenous distribution of the zeolite at least in unloading zones. A first level control sensor 301 may be configured for a feeding stop in case the funnel-shaped collecting container 300 gets overloaded; and a second level control sensor 302 for feeding regulation may be arranged in or at the funnel-shaped collecting container 300 close to the gas tight valve 310. The gas tight valve 310 may have two flaps to avoid hot air escaping from the cooler 4 in an uncontrolled manner, as described above.

The cooler 4 is provided with a housing 400 being connected to a kiln outlet 401 of a not shown kiln hood for entering the heated clinker 2000 from the kiln 5 and having a grate cooler outlet 402 for exiting a blend 5000 in form of a blended mix of cement clinker 2000 and calcinated zeolite 1000 such that the blend 5000 may be ground to the desired fineness by the roller crusher 6. The energy for calcining the zeolite 1000 within the cooler 4 is provided by the high temperature of the clinker 2000. The clinker 2000 forms a clinker bed 2010 within the cooler 4, and by radiation from the clinker bed 2010, heat is transferred from the clinker 2000 to the zeolite 1000. Further, fresh air 3000 is entered into the cooler 4 via an air injector, cooling fan 403 or the like such that the respective airflow through the clinker bed 2010 is cooling the clinker 2000. Hot air 4000 will, at the same time, ascends within the cooler 4 and be sucked to leave the same at the kiln outlet 401 and an additional opening 404 at the top of the cooler 4. The kiln outlet 401 and the additional opening 404 are arranged remote from the entry region of the zeolite 1000, which may be in a middle zone of the cooler 4.

As the clinker 2000 comprises the heat to calcine the added zeolite 1000, the amount of the added zeolite 1000 as well as the point/region of addition of the zeolite 2000 is chosen such that the added zeolite 1000 can be calcinated at a temperature from 600 to 800 °C. The amount of the added zeolite 1000 can be controlled via the specific feeding to the cooler 4 as described above, and the point, which is usually in the middle of the cooler 4, can be controlled via a divertor 320. The divertor 320 allows e.g. a range of around 70° by pivoting an outlet of the divertor 320 by an angle a. This control of both, the amount and the point of adding zeolite 1000 depends on the kind of zeolite 1000, with different kinds of zeolite 1000 requiring different temperatures for calcination.

It is the astonishing perception of the present disclosure that the heat released by cement clinker in a clinker cooler arranged downstream of a rotary kiln provides the energy for calcining the zeolite for obtaining composite cement. With a zeolite feed control into the cooler the composite cement can be optimized.

The present disclosure will be illustrated further with reference to the examples that follow, without restricting the scope to the specific embodiments described. The disclosure rather includes all combinations of described and especially of preferred features that do not exclude each other. If not otherwise specified any amount in % or parts is by weight and in the case of doubt referring to the total weight of the composition/mixture concerned. A characterization as "approximately", "around" and similar expression in relation to a numerical value means that up to 10 % higher and lower values are included, preferably up to 5 % higher and lower values, and in any case at least up to 1 % higher and lower values, the exact value being the most preferred value or limit. The term "substantially free" means that a particular material is not purposefully added to a composition and is only present in trace amounts or as an impurity. As used herein, unless indicated otherwise, the term "free from" means that a composition does not comprise a particular material, i.e., the composition comprises 0 weight percent of such material. Example 1

Zeolite with the properties shown in table 1 was obtained with particle sizes from 0 to 30 mm. It was calcined at temperatures of 400 °C, 600 °C, 800 °C and 900 °C and then cooled in air. The same zeolite only dried at 105 °C was provided as comparison. The properties of the calcined zeolites are also listed in table 1.

The compressive strength of composite cements comprising 25 wt.-% and 40 wt.-% of the zeolite and CEM I are presented in figures 3 and 4. CEM I is included for comparison. Strength was measured on standard mortar prisms according to EN 196-1. As can be seen from figure 3, an addition of 25 wt.-% zeolite calcined at 600 or 800 °C allowed early strengths at 1 and 2 days comparable to that of CEM I. The strength at 28 days exceeded that of CEM I, i.e., an additional reduction of the clinker content is possible. In figure 4 a higher clinker replacement of 40 wt.-% zeolite was used. Here the early strength was lower than for CEM I, but at 28 days the composite cement still achieved a strength as required by the standard. This demonstrates that calcined zeolite is able to provide composite cements with a high clinker replacement of 40 wt.-%.

Example 2

In a long-term industrial experiment, 8 wt.-% zeolite with respect to the clinker weight were added to the clinker cooler. Different composite cements were made, a CEM I with only the 8 wt.-% zeolite, a CEM I A-L with the 8 wt.-% zeolite and 10 wt.-% limestone and a CEM II BM with the 8 wt.-% zeolite and 30 wt.-% limestone. Figure 5 shows the compressive strength determined according to EN 196-1 on mortar prisms after 2 and 7 days. Figure 6 shows the water demand. It is apparent that the compressive strength after 2 and 7 days hardening was higher than that of the same cement without the 8 wt.-% zeolite addition to the clinker cooler. Furthermore, the workability of the standard mortar is not negatively impacted by the calcined pozzolana.

It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that the disclosure disclosed herein is not limited to the particular embodiments disclosed, and is intended to cover modifications within the spirit and scope of the present disclosure.

Reference Signs

1 plant feeding, transport and dosage system floor cooler

5 kiln

6 roller crusher

7 front loader

10 feeding device 0 transport device

30 dosage device

100 feed hopper

200 belt conveyor

201 belt drift switches

202 belt scale

203 magnetic separator

204 variable frequency drive

205 belt drift switches

300 funnel-shaped collecting container

301 level control sensor for feeding stop

302 level control sensor for feeding regulation

310 gas tight valve

320 divertor

400 housing

401 kiln outlet

402 grate cooler outlet

403 cooling fan

404 opening

1000 zeolite

2000 clinker

2010 clinker bed

3000 fresh/cold air 4000 hot air

5000 blend a zeolite feed angle range

Claims

1. Method for manufacturing a composite cement comprising the steps:

• providing a cement raw meal,

• preheating the cement raw meal to provide preheated cement raw meal,

• precalcination of the preheated cement raw meal to provide precalcined cement raw meal,

• sintering the precalcined cement raw meal in a rotary kiln to provide cement clinker, and

• cooling the cement clinker in a cooler, characterized by adding zeolite to the cement clinker in the cooler at a position where the temperature of the cement clinker provides the energy for calcining the zeolite for obtaining the composite cement.

2. Method according to claim 1, wherein a size of the zeolite is adjusted to a D90 of 100 mm, preferably a D90 of 50 mm, most preferred a D90 of 30 mm, and/or a DIO of at least 1 mm, preferably of at least 5 mm, most preferred at least 10 mm.

3. Method according to claim 1 or 2, wherein the zeolite is selected from analcime, chabazite, clinoptilolite, heulandite, natrolite, phillipsite, stilbite or mixtures of two or more thereof.

4. Method according to any one of the preceding claims, wherein the zeolite is selected to comprise mineral phases like quartz, feldspar, clay minerals, mica, calcite and/or impurities like metals, wherein preferably an amount of the mineral phases and impurities is below 60 wt.-%, in particular below 55 wt.-%, most preferred below 50 wt.-%, with respect to the total zeolite mass.

5. Method according to any one of the preceding claims, wherein the zeolite is selected with a Si/AI molar ratio below 3, preferably from 1 to 3.

6. Method according to any one of the preceding claims, wherein the zeolite is added in an amount ranging from 1 to 60 wt.-% with respect to the clinker weight, preferably from 5 to 30 wt.-%, most preferred from 7 to 15 wt.-%.

7. Method according to any one of the preceding claims, wherein amount and point of addition of the zeolite are adjusted, in particular to obtain a reduction of the BET surface area of the zeolite of at least 5 %, preferably of at least 10 %, most preferred of at least 15 %.

8. Method according to any one of the preceding claims, wherein the zeolite is added to a temperature in the range from 600 to 800 °C .

9. Method according to any one of the preceding claims, wherein the cement clinker is selected from Portland cement clinker, calcium sulfoaluminate cement clinker, or calcium aluminate cement clinker, preferably Portland cement clinker.

10. Method according to any one of the preceding claims, wherein one or more supplementary cementitious material, especially fly ash, ground granulated blast furnace slag, carbonated recycled concrete fines, calcined clay, hyaloclastite, and mixtures of two or more thereof, are added, and/or one or more additives, especially pigments, fibers, mineral fillers, reinforcing elements, self- healing agents, and mixtures of two or more thereof, are added.

11. Plant (1) for manufacturing a composite cement, in particular configured to perform the method according to any one of the preceding claims, wherein the plant (1) comprises a feeding, transport and dosage system (2), a cooler (4) and a kiln (5), characterized in that the kiln (5) feeds heated cement clinker (2000) into the cooler (4) and the feeding, transport and dosage system (2) feeds zeolite (1000) into the cooler (4) such that the zeolite (1000) is calcinated by heat provided by the cement clinker (2000) in the cooler (4).

12. Plant according to claim 11, wherein the feeding, transport and dosage system (2) comprises a feeding device, a transport device (20) and a dosage device (30), wherein preferably the feeding device comprises a feed hopper (100), the transport device (20) comprises one or more belt conveyors (200), and/or the dosage device (30) comprises a funnel-shaped collecting container (300) and/or a gas tight valve (310).

13. Plant according to claim 12, wherein the zeolite (1000) is entered into the cooler (4) via the gas tight valve (310) in a controlled manner, in particular determined by one or more belt drift switches (201, 205), at least one belt scale (202), at least one magnetic separator (203), at least one variable frequency drive (204) and/or at least one level control sensor (301, 302).

14. Plant according to claim 13, wherein the at least one level control sensor comprises a first level control sensor (301) for determining a stop of feeding the funnel-shaped collecting container (300) and/or a second level control sensor (302) for determining the regulation of the gas tight valve (310).

15. Plant according to any one of the claims 12 to 14, wherein the gas tight valve (310) comprises two flaps, of which only one is open at a time, wherein preferably a first amount of zeolite (1000) can enter the gas tight valve (310) while an upper flap is open, and a second amount of zeolite (1000) can enter into the cooler (4) while the lower flap is open.

16. Plant according to any one of the claims 11 to 15, wherein the cooler (4) is provided with a housing (400) being connected with a kiln outlet (401), preferably provided by a kiln hood, for entering the heated cement clinker (2000) from the kiln (5) and having at least one grate cooler outlet (402) for exiting a blend (5000) of cement clinker (2000) and calcinated zeolite (1000), wherein preferably the blend (5000) is guided via the grate cooler outlet (402) to a grinding device (6).

17. Plant according to any one of the claims 11 to 16, further comprising one or more means (403) for entering fresh air (3000) into the cooler (4), with the fresh air (3000) flowing preferably from the bottom of a cement clinker bed (2010) within the cooler (4) and through the cement clinker bed (210) to leave the cooler (4) as hot air (4000) via the kiln outlet (401) and/or at least one additional opening (404) at the top of the cooler (4).

18. Plant according to claim 17, wherein the kiln outlet (401) and the additional opening (404) are arranged remote from the entry point of the zeolite (1000) into the cooler (4), which preferably is within a middle zone of the cooler (4).

19. Plant according to any one of the claims 11 to 18, further comprising a divertor (320) for determining the point within the cooler (4), at which the zeolite (1000) is added to the cement clinker (2000), and/or for determining the temperature range of the cement clinker (2000), to which the zeolite (1000) is added.

20. Plant according to claim 19, wherein the divertor (320) is controlled, wherein the control depends on the kind of added zeolite (1000) and/or the control allows a rotation within a range of 70°.

21. Composite cement manufactured with a method according to any one of the claims 1 to 10, and/or in a plant according to any one of the claims 11 to 20.

22. Composite cement according to claim 21, further comprising one or more additives, especially pigments, fibers, mineral fillers, reinforcing elements, self- healing agents, and mixtures of two or more thereof, and/or one or more supplementary cementitious material, especially fly ash, ground granulated blast furnace slag, carbonated recycled concrete fines, calcined clay, hyaloclastite, and mixtures of two or more thereof.