BE1030823B1 - Reduction of CO2 emissions in the production of cement clinker - Google Patents

Abstract

The present invention relates to a plant for producing cement clinker, wherein the plant has a raw material supply 10, a mill 50, a preheater 60, a calciner 70, a kiln 80 and a material cooler 90, wherein the material flow from the raw material supply 10 is guided via the mill 50, the preheater 60, the calciner 70, the kiln 80 and the material cooler 90, wherein the material cooler 90 has a product outlet, characterized in that the plant has a screening device 30, wherein the screening device 30 is connected to the raw material supply 10 for supplying raw material, wherein the screening device 30 is designed to separate a coarse particle flow and a fine particle flow, wherein the plant has a shaft furnace 40, wherein the screening device 30 is connected to the shaft furnace 40 for transferring the coarse particle flow, wherein the shaft furnace 40 is connected to the mill 50 for transfer of the thermally treated raw material.

Description

' BE2022/5684

Reduction of CO2 emissions in the production of cement clinker

The invention relates to a device and a method for simple partial

Separation of CO», which is produced during the production of cement clinker.

On the one hand, there is the possibility of washing and separating CO2 from the exhaust gas of any plant. Such processes can be used universally.

However, due to the high nitrogen content, they are complex. For this reason, there are systems that work with pure oxygen, for example, so that in the end practically pure CO: is produced and separation is therefore not necessary. However, this usually involves redesigning the system.

DE 10 2018 206 673 A1 and DE 10 2018 206 674 A1 contain annexes to

Production of cement clinker, where the process uses oxygen that is as highly enriched as possible, making the exhaust gas as pure as possible

carbon dioxide, so that it can be separated relatively easily for use or storage. The disadvantage, however, is that an existing

A system must be completely rebuilt or a system must be newly constructed.

There is therefore interest in modifying existing plants in a simple way to reduce at least some of the CO2 emissions without having to build a completely new

The focus is therefore on a quick and easy

Implementation, but only a partial separation.

A lime shaft kiln is known from DE 10 2021 204 175.

An annular shaft furnace is known from DE 10 2021 202 485.

DE 11 2010 004 030 B4 describes a vertical kiln with three concentric

cylinders known.

EP2018353B1 discloses a process and a plant for the production of

Cement clinker is known.

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The object of the invention is to provide a plant for the production of cement clinker which separates part of the CO: in a simple manner starting from a conventional plant.

This object is achieved by the system with the features specified in claim 1

Features and the method with the features specified in claim 5.

Advantageous further developments result from the subclaims, the following

Description and drawing.

The plant according to the invention is used to produce cement clinker. The plant has a raw material supply, a mill, a preheater, a calciner, a kiln and a material cooler. The raw material supply can be a stockpile, a

Delivery point, for example an unloading station, a silo or the like.

The material flow is led from the raw material supply through the mill, the preheater, the calciner, the kiln and the material cooler. The material cooler has a

Product outlet. This is a conventional system for

Production of cement clinker. In particular, it can also be an existing

It could be a plant for the production of cement clinker which is reworked in accordance with the invention in order to reduce part of the CO2 emissions in a simple manner.

The plant for the production of cement clinker according to the generic term is

Expert therefore known.

A corresponding state-of-the-art plant is thus modified in accordance with the invention in order to separate a portion of the CO2 in a simple manner and thus to at least quickly reduce the climate impact within the framework of a simple measure.

The system has a screening device. The screening device is designed to feed

Raw material is connected to the raw material supply. The screening device is for

Separation of a coarse particle stream and a fine particle stream. For example, a sieve with a hole size of 30 mm is used, which would theoretically result in an ideal fine particle fraction with all particles smaller than 30 mm and a

Coarse particle fraction with particles larger than 30mm. Thus, the

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Fine particle fraction in the fine particle stream and the coarse particle fraction in the

Coarse particle flow. The plant has a shaft furnace. Shaft furnaces are generally known, for example and preferably it can be a shaft furnace according to the

DE 10 2021 204 175 or DE 10 2021 202 485. The screening device is connected to the shaft furnace to transfer the coarse particle stream. In the

The thermal treatment of only the coarse particle fraction takes place in the shaft furnace.

Shaft furnace is connected to the mill for transfer of the thermally treated raw material.

The burning of carbonate rock in a GGR shaft furnace has been known for about 60 years. Such a GGR furnace, known for example from WO 2011/072894 A1,

Shaft furnace has two vertical, parallel shafts that work cyclically, with only one shaft, the respective firing shaft, firing takes place, while the other

Shaft works as a regenerative shaft. The combustion shaft is supplied with oxidation gas in

Direct current is fed to the material and fuel, whereby the resulting hot exhaust gases, together with the heated cooling air supplied from below, are passed over the

overflow channel into the exhaust shaft, where the exhaust gases are discharged upwards in countercurrent to the material and preheat the material. The

Material is usually fed into the shaft from above together with the oxidizing gas, whereby fuels are injected into the combustion zone. The material to be burned

In each shaft, material usually passes through a preheating zone to preheat the material, an adjoining firing zone in which the material is fired, and an adjoining cooling zone in which cooling air is supplied to the hot material.

It has been shown that, especially in the coarse fraction, the large lime particles enable easy separation of the CO2, especially from the starting material.

A second advantage is that the grindability of the material and especially of the large particles is improved by the thermal treatment.

Complete decarbonization does not have to be achieved in the shaft furnace.

Rather, for the most efficient use of the overall system, it is advantageous to decarbonize the coarse particle fraction only by 80 to 90%.

The material thermally treated in the shaft furnace is fed via the mill to the usual process in the preheater, calciner and furnace, so that a complete thermal

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Treatment takes place here, especially in the furnace. The shaft furnace reduces the fuel requirement in the calciner as well as the release of CO2 from the raw material. This means that the existing plant can remain unchanged, the

Separation of CO: is simply done for the CO2 emissions of the shaft furnace.

For example, a lime kiln system with at least one shaft kiln for

Burning and cooling material, such as carbonate rocks, wherein the lime kiln system comprises two shafts and a channel which extends between the two shafts. The shaft kiln comprises exactly one of the shafts of the lime kiln system, wherein the shaft has a material inlet for letting material to be burned into the shaft and, in the direction of flow of the material, a preheating zone for preheating the material, a burning zone for burning the material, a cooling zone for cooling the material and a material outlet for letting the material out of the shaft. The channel has a closure device for gas-technically closing the channel so that a gas flow between the two shafts through the channel is prevented by means of the closure device. The material to be burned is preferably limestone or dolomite stone with a grain size of 10 to 200 mm, preferably 15 to 120 mm, most preferably 30 to 100 mm. The cooling gas is, for example, air. The lime kiln system is preferably a shaft kiln that can be operated as a cocurrent countercurrent regenerative shaft kiln, whereby the channel for connecting the shafts, in particular the combustion zones of the shafts, has been closed. The lime kiln system has at least one shaft kiln. For example, the shaft kiln system has two

Shaft kilns, each of which contains exactly one of the shafts of the lime kiln system.

The shaft kilns are preferably separated from each other in terms of gas technology and can be operated separately from each other for firing material. The shaft of the at least one shaft kiln of the lime kiln system preferably has a

Material inlet for letting material to be burned into the shaft, whereby the material inlet is located in particular at the upper end of the shaft so that the material falls into the shaft due to gravity. The material inlet and/or the

Material outlet is/are designed in particular as a lock for admitting and/or discharging material into the shaft furnace. A lock designed as a

Material inlet is preferably designed in such a way that only the material to be burned

raw material enters the shaft, but not the ambient air. Preferably, the

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The lock is designed in such a way that it seals the shaft airtight against the environment and allows solids, such as the material to be burned, to enter the shaft. In the direction of flow of the material, the material flows through a preheating zone after the material inlet to preheat the material to a

Temperature of, for example, about 600 °C to 800 °C. The firing zone preferably adjoins the preheating zone directly and is used to fire the material, which is preferably heated to a temperature of about 900 °C to 1600 °C. The

The cooling zone preferably adjoins the firing zone directly and serves to cool the fired material to a temperature of, for example, 100 °C. The

Material outlet is, for example, in a cooling zone adjacent to the

Outlet funnel arranged, wherein the material outlet has, for example, a turntable or push table for discharging material from the cooling zone into the

Outlet funnel. The cooling gas is preferably fed into the

Cooling zone of the shaft furnace. The cooling gas inlet is preferably in the

Cooling zone, especially below the turntable. In the combustion zone of the

A plurality of burners, in particular burner lances, are preferably arranged in the shaft. It is also conceivable that the shaft has a plurality of

side burners that extend through the shaft wall into the combustion zone.

The side burners are preferably designed as burner lances and in particular tubular. They are used to conduct fuel and preferably a

Oxidizing agent, which is introduced into the combustion zone together with exhaust gas. The

The closure device preferably extends over the entire cross-section of the

Channel. The gas-technical closure of the channel by means of a closure device enables the two shafts of the lime kiln system to be operated separately. For further embodiments, please refer to DE 10 2021 204 175.

In a further embodiment of the invention, the shaft furnace is designed for operation with a gas containing at least 50% oxygen, preferably at least 90% oxygen. With pure oxygen (and no other oxygen produced from the raw material),

Gases) would be the exhaust gas stream from the combustion and the lime escaping

CO: (after separation of water) pure carbon dioxide, which can then be easily reused or stored. Since only one additional shaft furnace needs to be installed when retrofitting an existing cement plant, this can be used for operation with highly enriched oxygen.

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Calciner and kiln must be converted to this. The use of enriched oxygen makes CO2 separation much easier.

In a further embodiment of the invention, the shaft furnace is provided with a CO:-

This can be carried out particularly easily if the shaft furnace is designed for operation with a gas of at least 50 %

oxygen, preferably at least 90% oxygen. Separation of

Water is usually always necessary. The CO2 separator can be a

Dust separators or other usual pretreatments may be installed beforehand.

In a further embodiment of the invention, the plant has two shaft furnaces.

In particular, the shaft furnaces are designed according to DE 10 2021 204 175 and are operated alternately. Such an arrangement is called a direct current

Regenerative lime shaft kiln.

In a further aspect, the invention relates to a process for producing

Cement clinker. Preferably, a plant according to the invention is used for the process according to the invention. The process comprises the following steps: a) sieving the raw material into a coarse fraction and a fine fraction, b) thermally treating the coarse fraction in a shaft furnace, c) mixing the fine fraction and the thermally treated coarse fraction and subsequent grinding or grinding the fine fraction and grinding the thermally treated coarse fraction and subsequent mixing, dg) preheating the material, e) calcining the material, f) firing the material in a furnace, g) cooling the product.

In step a), the coarse fraction is separated. Optionally, an oversized fraction, for example for particles with a size of more than 100 to 200 mm, can also be separated. For example, before step a), the

starting material in a crusher, in this case the oversized

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Fraction is returned to the crusher. This prevents particles that are too large from being contained in the coarse fraction.

Thermal treatment in a shaft furnace b) can produce a significantly coarser

fraction is thermally treated. In addition, the coarser fraction is particularly

Calcium carbonate-containing. Therefore, a simple thermal treatment and thus a

Separation of the CO2 produced in this step is possible, whereby the rest of the plant can be operated unchanged according to the state of the art. In addition to the separation of CO2: in a comparatively simple manner, the grindability of the

material, which in turn reduces the energy consumption especially for the largest particles and thus further increases the overall efficiency of the process.

In step c) there are two options. In the first step, the fine fraction and the thermally treated coarse fraction are first mixed and then ground together.

In a second step, the two fractions are ground separately and then mixed. It is important that at the end the fractions are mixed again and the

Cement clinker process in steps d) to g).

An important point here is that less energy is required for calcination in step e), since part of the material (the coarse fraction) is already decarbonized. Therefore, in

Calcinator requires less energy and therefore less fuel and thus produces less CO2, which is then released into the environment according to the state of the art.

Thus, a portion of the CO: originating from the fuel is also generated in the shaft furnace by the process according to the invention and thus separated.

In a further embodiment of the invention, the screening in step a) is carried out on a

Size from 20 to 50 mm, for example to 30 mm. This results in the usual

Raw materials a good size distribution of the starting material for the shaft furnace.

At the same time, this creates the possibility of 20 to 40% of the resulting

CO: into the shaft furnace so that this CO: can be easily separated without having to adapt the rest of the system, in particular the furnace and calciner.

It is therefore relatively easy and quick to obtain a relevant share of the

To avoid CO2 emissions.

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In a further embodiment of the invention, prior to sieving in step a), a

Breaking the raw material.

In a further embodiment of the invention, the thermal treatment in

Step b) in two shaft furnaces in alternating order. For the implementation with two shaft furnaces, reference is made, for example and in particular, to DE 10 2021 204 175.

In a further embodiment of the invention, the coarse fraction after the

Treatment in the shaft furnace a carbon dioxide content of between one and eight

percent by mass, preferably between three and five percent by mass. The

Carbon dioxide is present in the form of carbonate, i.e. chemically bound. This means that the coarse fraction releases this carbon dioxide from the carbonate during further treatment in the calciner and kiln. This area enables the greatest possible CO2 separation, and the residual content leads to an improved product after the actual treatment.

The system according to the invention is explained in more detail below using an embodiment shown in the drawing.

Fig. 1 Scheme of a system

Fig. 1 shows a schematic representation of a plant. In a raw material supply 10, the starting raw material for the production of cement clinker is provided. This contains, for example, calcium carbonate in particular. The raw material is processed in an optional

Crusher 20 and screened in a screening device 30. The coarse fraction, for example everything over 20 mm, is fed to a shaft furnace 40 and thermally treated. The fine fraction from the screening device 30 and the thermally treated

Material from the shaft furnace 40 are fed together to a mill 50 and ground together and mixed intimately. The material ground in the mill 50

The product is preheated in a preheater 60, acidified in the calciner 70 and finally fired in the kiln 80, in particular a rotary kiln. The finished fired cement clinker is cooled in the material cooler 90.

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It is important to note that, compared to a conventional system, only the

Screening device 30 and, above all, shaft furnace 40 are added. This makes it very easy to retrofit existing plants quickly and easily and thus save at least some of the CO2 emissions.

Reference symbols

Raw material supply 20 Crusher 30 Screening device 10 40 Shaft furnace 50 Mill 60 Preheater 70 Calciner 80 Oven 90 Material cooler

Claims (9)

Patent claims 1. Plant for producing cement clinker, the plant having a raw material supply (10), a mill (50), a preheater (60), a calciner (70), a furnace (80) and a material cooler (90), the material flow from the raw material supply (10) being guided via the mill (50), the preheater (60), the calciner (70), the furnace (80) and the material cooler (90), the material cooler (90) having a product outlet, characterized in that the plant has a screening device (30), the screening device (30) being connected to the raw material supply (10) for supplying raw material, the screening device (30) being designed to separate a coarse particle flow and a fine particle flow, the plant having a shaft furnace (40), the screening device (30) being connected to the shaft furnace (40) for transferring the coarse particle flow, the shaft furnace (40) is connected to the mill (50) for transferring the thermally treated raw material. 2. Plant according to claim 1, characterized in that the shaft furnace (40) is designed for operation with a gas of at least 50% oxygen, preferably at least 90% oxygen. 3. Plant according to one of the preceding claims, characterized in that a CO2 separation device is connected downstream of the shaft furnace (40). 4. Plant according to one of the preceding claims, characterized in that the plant has two shaft furnaces (40). 5. A process for producing cement clinker, the process comprising the following steps: a) screening the raw material into a coarse fraction and a fine fraction, b) thermally treating the coarse fraction in a shaft furnace (40), c) mixing the fine fraction and the thermally treated coarse fraction and then grinding or grinding the fine fraction and grinding the thermally treated coarse fraction and then mixing, d) preheating the material, e) calcining the material, f) firing the material in a furnace, g) cooling the product. 6. Process according to claim 5, characterized in that the sieving in step a) is carried out to a size of 20 to 50 mm. 7. Process according to one of claims 5 to 6, characterized in that the raw material is broken before sieving in step a). 8. Method according to one of claims 5 to 7, characterized in that the thermal treatment in step b) is carried out in two shaft furnaces (40) in alternating sequence. 9. Process according to one of claims 5 to 8, characterized in that the coarse fraction after the treatment in the shaft furnace has a carbon dioxide content of between one and eight percent by mass, preferably between three and five percent by mass.