Method and apparatus for producing cement clinker

Abstract

The present invention relates to a method for producing cement clinker (50), said method comprising the steps of preheating raw materials (20) in a preheater (12), calcining the preheated raw materials (26) in a calciner (14) and combusting the preheated, pre-calcined raw meal (32) in a kiln (16) to obtain a cement clinker (38), wherein combustion gases (42) containing an oxygen proportion of more than 20 vol.%, in particular more than 40 vol.%, preferably more than 60 vol.%, are supplied to the kiln (16). , and cooling the cement clinker (38) in a cooler (18), the cooler (18) having a first cooling zone (18a) and a second cooling zone (18b) in a conveying direction of the cement clinker (38), the exhaust gas of the first cooling zone (18a) forming the combustion gas (42) and the exhaust gas (24) of the second cooling zone (18b) being fed to the calciner (14) and having an oxygen proportion of at most 15 vol.%, in particular at most 10 vol.%, preferably at most 5 vol.%.

Description

[Technical field]

[0001] The present invention relates to a process for producing cement clinker. [Background technology]

[0002] From the prior art it is known to introduce oxygen-containing gas for the combustion of fuel into the rotary kiln or calciner of a cement production plant. In order to reduce the amount of off-gas and to be able to dispense with complex cleaning steps, it is necessary to introduce CO 2 The use of combustion gases that are as oxygen-rich as possible so as to have a high content is known, for example, from DE 10 2018 206 673 A1, which discloses introducing oxygen-rich gas into the cooler inlet region in order to preheat the gas and cool the clinker.

[0003] DE 19844038 A1 discloses a process for producing white cement.

[0004] In such an operating mode, very high temperatures in the calciner and, for example, a high solids content of the gas in the calciner occur, which can lead to material deposits in the calciner and therefore, in the worst case, clogging and damage to the inner walls of the calciner. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] DE 102018206673 [Patent Document 2] German Patent Application Publication No. 19844038 Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, the object of the present invention is to overcome the above-mentioned drawbacks and at the same time to obtain CO from the off-gas in a simple manner. 2 The object of the present invention is to provide a process and a plant for producing cement clinker which allows the separation of: [Means for solving the problem]

[0007] This object is achieved according to the invention by a process having the features of the independent process claim 1 and by a cement production plant having the features of the independent apparatus claim 11. Advantageous developments will become apparent from the dependent claims.

[0008] According to a first aspect, a process for producing cement clinker comprises the steps of: Preheating the raw meal in a preheater; calcining the preheated raw meal in a calciner; Combustion of the preheated and pre-calcined raw meal in a kiln to form a cement clinker, the kiln being supplied with combustion gases having an oxygen content of more than 50% by volume, in particular more than 80% by volume, preferably more than 95% by volume; cooling the cement clinker in a cooler, the cooler having a first cooler section and a second cooler section in a conveying direction of the cement clinker, and exhaust gas from the first cooler section forms combustion gases that are fed to the kiln; Includes.

[0009] The off-gas from the second cooler zone is fed to the calciner and has an oxygen content of at most 15 vol.%, in particular at most 10 vol.%, preferably at most 5 vol.%. The off-gas from the second cooler zone preferably has an oxygen content of more than 75 vol.% CO 2 Preferably, the off-gas from the second cooler region is fed completely or partly to the calciner, the amount of off-gas fed to the calciner being preferably adjustable.

[0010] The fluid fed to the second cooler region has an inert portion of at least 60% by volume, in particular at least 80% by volume, preferably at least 90% by volume. The inert portion of the fluid consists of water, carbon dioxide or water and carbon dioxide. The fluid fed to the second cooler region can contain further constituents. For example, to ensure complete combustion, a residual oxygen content of 1% by volume to 5% by volume is typical. Furthermore, as further inert gas, for example argon may be present. Furthermore, as further inert gas, nitrogen may also be present. Nitrogen oxides and / or sulfur oxides may also be present, in particular, preferably only in trace amounts.

[0011] Compared to the prior art of supplying air or nitrogen at this point, the use of a fluid with water and / or carbon dioxide as the inert part ensures that this gas increases the conveying capacity of the feedstock but does not introduce additional gas into the system that would be disruptive in the subsequent separation. If the intention is ultimately to separate carbon dioxide, this is easier the purer the preheater off-gas is, and especially the less nitrogen it contains. Thus, avoiding nitrogen as a conveying gas for the process reduces the CO2 content in the entire process. 2 This results in easier separability.

[0012] The off-gas from the second cooler zone preferably serves as a carrier gas in the calciner and ensures an increase in the amount of gas in the calciner and / or preheater, which prevents the calciner from overheating and reduces the solids content in the calciner gas, thus avoiding material build-up in the calciner.

[0013] The combustion gas fed to the kiln has, for example, an oxygen content of more than 50% by volume, in particular more than 80% by volume, preferably more than 95% by volume. The combustion gas, for example, consists of pure oxygen only, the oxygen content of the combustion gas being 100% by volume.

[0014] Oxygen content and CO 2 The content is preferably a volume percentage, especially based on dry gas.

[0015] The kiln is preferably a rotary kiln, rotatable about its longitudinal axis and preferably having a rotary tube slightly inclined in the direction of conveying the material so that the material to be burned is moved in the conveying direction as a result of the rotation of the rotary tube and gravity. The kiln preferably has a material inlet at one of its ends for receiving preheated and precalcined raw meal and a material outlet at the end opposite the material inlet for discharging the burned clinker to a cooler. The kiln head is preferably arranged at the material outlet end of the kiln and preferably comprises a burner for burning the material and a fuel inlet for receiving fuel to the kiln, preferably to the burner. The kiln preferably has a calcination zone, in which the material is at least partially melted and has a temperature in particular between 1500°C and 1800°C, preferably between 1450°C and 1700°C.

[0016] The cooler for cooling the cement clinker is preferably adjacent to the material outlet of the kiln. In the cooler, the cement clinker to be cooled is preferably transported in a conveying direction towards the outlet of the cooler via a conveyor device. In the conveying direction, the cooler preferably has at least two, preferably three, cooler zones. The first cooler zone is upstream in the conveying direction, in particular directly adjacent to the kiln, and is preferably arranged such that the cement clinker burned in the kiln falls, preferably by gravity, from the material outlet of the kiln into the first cooler zone. The first cooler zone has, for example, a static or dynamic grate. Preferably, a first and a second cooling gas are fed to the cooler. In particular, the first cooling gas is fed to the first cooler zone. The first cooler zone has, in particular, a cooling gas inlet below the static or dynamic grate, through which the first cooling gas is introduced and flows from below through the static or dynamic grate and the cement clinker to be cooled thereon. The first cooler section preferably has an off-gas outlet for discharging the first cooling gas, the off-gas outlet being connected to the kiln, in particular the kiln head, so that the off-gas is conducted to the kiln and preferably completely forms the combustion gases of the kiln.

[0017] In particular, the second cooling gas is fed to the second cooler zone. The second cooler zone preferably has a dynamic grate for transport of the cement clinker to be cooled, in particular a cooling gas inlet is arranged below the dynamic grate through which the second cooling gas is introduced and flows from below through the dynamic grate and the cement clinker to be cooled thereon. The second cooler zone preferably has an off-gas outlet for discharging the second cooling gas. The second cooler zone is preferably directly adjacent to the first cooler zone in the direction of conveying the cement clinker and is in particular separated from the first cooler zone in terms of gas, so that the first cooling gas flows exclusively through the first cooler zone and does not enter the second cooler zone. The second cooling gas preferably flows exclusively through the second cooler zone and does not enter the first cooler zone. To separate the first and second cooler zones in terms of gas, the cooler preferably has separating means, such as flaps, curtains or gas dividers. The separation means is for example a pressure difference between the first and second cooler regions, whereby a separation of the cooling gas in the cooler regions is achieved.

[0018] The cooler is preferably further supplied with a third cooling gas, which is introduced into the third cooler zone. The third cooler zone preferably has a dynamic grate for transport of the cement clinker to be cooled, in particular a cooling gas inlet is arranged below the dynamic grate, through which the third cooling gas is introduced and flows from below through the dynamic grate and the cement clinker to be cooled thereon. The third cooler zone preferably has an off-gas outlet for discharging the third cooling gas as cooler exhaust. The third cooler zone is preferably directly adjacent to the second cooler zone in the direction of transport of the cement clinker and is in particular separated from the second cooling zone in terms of gas, so that the second cooling gas flows exclusively through the second cooler zone and does not enter the third cooling zone. The third cooling gas preferably flows exclusively through the third cooler zone and does not enter the first or second cooling zone. To separate the second and third cooler regions with respect to the gas, the cooler preferably has further separating means, such as a flap, a curtain or a gas divider.

[0019] The process described above results in lower CO emissions in the kiln. 2 This results in a partial pressure of CO, which results in the remaining calcination of the incompletely calcined material, and requires only a small amount of heat energy to be expended for this remaining calcination. 2 The increase in partial pressure results in the production of CO based on wet off-gas. 2 The concentration is preferably less than 40% by volume, so that the effort for cleaning the so-called deposit is reduced. The deposit is generally understood to be a mineral phase, a solid phase, which is formed in significant part from temperatures above 850° C. The mineral phase may be, for example, a sparlite or belite phase. In order to keep the cleaning effort within a reasonable range, the degree of pre-calcination may be reduced by operating the calciner with a degree of pre-calcination of less than 90% by volume, or at a lower temperature. The remaining calcination is carried out at a lower CO 2 Due to the partial pressure, the above described process in a kiln can be carried out faster at the same temperatures, for example calcination of the raw materials can also proceed spontaneously.

[0020] According to a first embodiment, a cooling gas is supplied separately to the first and second cooler regions in each case, the cooling gas supplied to the second cooler region having an oxygen content of at most 15 vol.%, in particular 10 vol.%, preferably 5 vol.%. The second cooling gas supplied to the second cooler region preferably has an oxygen content of at least 75 vol.%, in particular at least 80 vol.%, preferably at least 90 vol.% CO. 2 Oxygen is preferably supplied to the second cooling gas and / or to the off-gas from the second cooler region, so that the oxygen content of the off-gas before entering the calciner is at most 15% by volume, in particular 10% by volume, preferably 5% by volume.

[0021] According to a further embodiment, the oxygen concentration of the calciner off-gas is determined downstream of the calciner and the oxygen concentration of the off-gas from the second cooler section that is fed to the calciner is adjusted in response to the determined oxygen concentration.

[0022] Preferably, the oxygen content of the calciner off-gas is determined by a measuring device and the amount of off-gas from the second cooler zone and / or the oxygen content of the off-gas is adjusted, in particular increased or reduced, depending on the determined oxygen content. In particular, the volumetric flow of off-gas from the second cooler zone is kept constant. The determined oxygen content is preferably compared with a predefined limit value and, in case of deviation from this limit value, the amount of off-gas from the second cooler zone and / or the oxygen content of the off-gas fed to the calciner is increased or reduced. If the limit value of the oxygen content is exceeded, the amount of off-gas from the second cooler zone and / or the oxygen content of the off-gas fed to the calciner is preferably reduced. If the limit value of the oxygen content is not reached, the amount of off-gas from the second cooler zone and / or the oxygen content of the off-gas fed to the calciner is preferably increased.

[0023] The off-gas from the second cooler zone is fed to the calciner and for example partially forms the combustion gas of the calciner. The off-gas from the kiln also forms the combustion gas of the calciner, at least partially or completely. A predetermined amount of oxygen is preferably fed to the kiln and the calciner, the respective ratios of oxygen to the kiln and the calciner being preferably adjustable. The oxygen content of the combustion air fed to the kiln is preferably adjusted according to the oxygen content of the off-gas from the second cooling zone fed to the calciner. A high oxygen concentration in the combustion gas to the kiln, in particular in the calciner zone, allows for an improvement of the combustion kinetics and simplifies the treatment of the fuel. Furthermore, the complexity and operating costs of the kiln burners are reduced. The grinding process, which may be connected upstream, is also simplified or entails lower operating costs. It is also conceivable that a high proportion of substitute fuels is used. A high oxygen concentration in the kiln ensures a high calciner zone temperature and produces a clinker with a higher alite content, which allows the clinker content in the cement to be reduced. For example, clinker is made up of limestone, fly ash, calcined clay, etc. 2 Replaced by less condensed materials, resulting in a lower CO2 content of cement and subsequent products for the same strength values. 2 The high calcination zone temperature also allows for a reduction in the residence time of the solids in the kiln, as the formation of the clinker phase occurs more quickly, which allows the kiln to be operated at a higher clinker throughput.

[0024] According to a further embodiment, at least a portion of the offgas from the second cooler region is fed to the preheater. The amount of offgas from the second cooler region to the calciner and the preheater is preferably adjustable. In particular, a metering element such as a valve or a flap is arranged in the conduit between the second cooler region and the preheater or the calciner. Conducting the offgas at least partially to the preheater allows optimal adjustment of the combustion conditions in the calciner.

[0025] According to a further embodiment, the off-gas from the preheater is fed to a conditioning device. The conditioning device is, for example, a filter, a heat exchanger, a gas mixer, a condenser or a spray tower. Preferably, the conditioning device is arranged downstream of the preheater in the gas flow direction, in particular connected to the second or third cooler region, so that the off-gas from the conditioning device forms the first or second cooling gas. The gas is preferably dehumidified and / or cleaned in the conditioning device.

[0026] According to a further embodiment, following the conditioning device the gas is fed to a second cooler region. Preferably, the off-gas from the preheater treated by the conditioning device forms at least partially or completely the second cooling gas.

[0027] According to a further embodiment, following the conditioning device the gas is fed to a third cooler region. Preferably, the off-gas from the preheater treated by the conditioning device forms the third cooling gas at least partially or completely.

[0028] According to a further embodiment, the off-gas from the third cooler zone is fed to the second cooler zone. Preferably, water is fed to the third cooler zone, whereby the water content of the off-gas from the third cooler zone is preferably adjusted. Before entering the second cooler zone, the off-gas from the third cooler zone is preferably dedusted and / or cooled.

[0029] According to a further embodiment, water is supplied to the second cooler region. The water is preferably supplied to the second cooler region via a humidifier. The humidifier preferably comprises a number of spray nozzles for injecting water into the second cooler region. In particular, the water is introduced into the second cooler region separately from the second cooling gas. Preferably, a water content of more than 10% by volume, in particular more than 20% by volume, preferably more than 30% by volume is set in the second cooler region by the humidifier. As a result, a corresponding water content is also set in the calciner. This is because the CO 2 in the calciner is not easily oxidized. 2This results in a reduction of the partial pressure. Water in the off-gas, especially in the preheater off-gas, can be easily condensed, which increases the partial pressure of CO in the off-gas, and as a result, the subsequent separation of CO is simplified. 2 increases the partial pressure of CO 2 and thus simplifies the subsequent separation of CO.

[0030] Preferably, the temperature and / or the volumetric flow of the off-gas from the second cooler region are determined by a measuring device, and the amount of water introduced into the second cooler region via the humidifying device is adjusted according to the determined temperature and / or volumetric flow, in particular increased or decreased. In particular, the volumetric flow of the off-gas is kept constant. The determined volumetric flow and / or the determined temperature are preferably compared with respective predetermined limit values, and if a deviation from this limit value occurs, the amount of water to the second cooler region is increased or decreased. If the limit value of the volumetric flow and / or temperature is exceeded, the amount of water to the second cooler region is preferably increased. If the limit value of the volumetric flow and / or temperature is not reached, the amount of water to the second cooler region is preferably decreased.

[0031] According to a further embodiment, the cooling gas supplied to the second cooler region has a water content of more than 10% by volume, in particular more than 20% by volume, preferably more than 30% by volume. Preferably, the off-gas from the second cooler region has a water content of more than 10% by volume, in particular more than 20% by volume, preferably more than 30% by volume.

[0032] According to a further embodiment, the fluid supplied to the second cooler region is taken from the preheater off-gas. This achieves a circulation of the carrier gas, and as a result, no additional gas, especially additional nitrogen, which would otherwise have to be separated again laboriously, is supplied.

[0033] According to a further embodiment, the gas flow of the preheater off-gas is split and a sub-stream of the preheater off-gas is supplied to the second cooler region.

[0034] According to a further embodiment, the gas stream of the preheater off-gas is dehumidified and at least a part of the separated water in liquid form is fed to the second cooler region, particularly preferably by spraying, so that the heat of vaporization is also used to cool the product.

[0035] According to a further embodiment, the gas stream of the preheater off-gas is split and a sub-stream of the preheater off-gas is fed to the second cooler region. The gas stream of the preheater off-gas is further dehumidified and at least a portion of the separated water in liquid form is fed to the second cooler region.

[0036] The present invention also provides a preheater for preheating the raw meal; a calciner for calcining the preheated raw meal; - a kiln for burning raw meal to form cement clinker; a cooler for cooling cement clinker, the cooler having a first cooler section and a second cooler section in the conveying direction of the clinker, the first cooler section being gas-wise connected to the kiln such that off-gases from the first cooler section can be fed to the kiln as combustion gas; The present invention relates to a cement manufacturing plant having a

[0037] The second cooler section is gas-wise connected to the calciner such that off-gas from the second cooler section can be fed to the calciner and optionally further to the preheater.

[0038] The second cooler zone is connected to the preheater off-gas 30 so that a portion of the preheater off-gas stream is conducted to the second cooler zone. Compared to the prior art of feeding air or nitrogen at this point, the use of the preheater off-gas ensures that this circulating gas increases the conveying capacity of the feedstock but does not introduce additional gas into the system. If the intention is ultimately to separate carbon dioxide, this is easier the purer the preheater off-gas is, and in particular the less nitrogen it contains. Thus, avoiding nitrogen as a conveying gas for the process reduces the CO2 emissions in the entire process. 2 This results in easier separability.

[0039] The advantages and features described with reference to the process for producing cement clinker also apply in a corresponding manner with respect to the apparatus to the cement production plant.

[0040] Preferably, the second cooler section is connected to the calciner via a conduit for conducting gases, in particular extending from the cooling gas outlet of the second cooler section to the gas inlet of the calciner. The second cooler section may be connected to the preheater via a conduit for conducting gases. The calciner preferably has a riser conduit through which the off-gas from the kiln and the raw material to be calcined flow at least partially in co-current. Furthermore, the calciner preferably has a combustion chamber or burner connected to the riser conduit for burning a fuel in the calciner.

[0041] According to one embodiment, a conditioning device for treating the off-gas from the preheater is arranged downstream of the preheater in the gas flow direction.

[0042] According to a further embodiment, the cooler has a third cooler region adjacent to the second cooler region, and the conditioning device is gas-wise connected to the second cooler region or to the third cooler region.

[0043] According to a further embodiment, the third cooler section is connected to the second cooler section for recirculating off-gas from the third cooler section to the second cooler section.

[0044] According to a further embodiment, the cooler comprises a humidification device for humidifying the cooling gas in the cooler.

[0045] According to a further embodiment, the second cooler region is gas-conductively connected directly to the preheater off-gas, so that a side flow of the preheater off-gas can be guided directly to the second cooler region.

[0046] According to a further embodiment, the preheater off-gas is guided to a dehumidifier, which is connected in a fluid conductive manner to the second cooler region, in particular liquid water separated in the dehumidifier is introduced into the second cooler region by a spray device.

[0047] The invention is explained in more detail below on the basis of several exemplary embodiments with reference to the accompanying drawings. [Brief description of the drawings]

[0048] [Figure 1] 1 is a flow chart illustrating a schematic illustration of a cement manufacturing plant, in accordance with an illustrative embodiment. [Diagram 2] 1 is a flow chart illustrating a schematic illustration of a cement manufacturing plant according to a further exemplary embodiment. [Diagram 3] 1 is a flow chart illustrating a schematic illustration of a cement manufacturing plant, in accordance with an illustrative embodiment. [Figure 4] 1 is a flow chart illustrating a schematic illustration of a cement manufacturing plant according to a further exemplary embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0049] FIG. 1 shows, for example, a cement manufacturing plant 10 having a single string preheater 12 for preheating raw meal, a calciner 14 for calcining the raw meal, a kiln 16, particularly a rotary kiln, for combusting the raw meal to form clinker, and a cooler 18 for cooling the clinker combusted in the kiln 16.

[0050] The preheater 12 preferably comprises a plurality of cyclones for separating raw meal from the raw meal gas stream. For example, the preheater 12 has five cyclones arranged one by one successively downward in four cyclone stages. The preheater 12 particularly has a material inlet for receiving the raw material 20, particularly the raw meal, preferably at the uppermost cyclone stage of the preheater 12. The raw material 20 continuously flows countercurrently through the cyclones of the cyclone stages of the preheater 12 to the kiln and / or calciner off-gas, thereby being heated to give hot meal 26. For example, the calciner 14 is arranged between the last cyclone stage and the second last cyclone stage. The calciner 14 preferably has a riser with at least one combustion zone for heating the hot meal 26 heated in the preheater such that the raw meal is calcined in the calciner 14. Furthermore, the calciner 14 has a fuel inlet for introducing the fuel 22 into the riser of the calciner 14. The calciner 14 preferably also has a gas inlet for receiving gas, particularly the conveying gas 24, into the riser of the calciner 14. The calciner off-gas 28 is introduced into the preheater 12, preferably into the second last cyclone stage, and exits the preheater 12 as preheater off-gas 30 downstream of the uppermost cyclone stage.

[0051] The kiln 16 is connected downstream of the preheater 12 and the calciner 14 in the flow direction of the raw meal so that the raw material 32 preheated in the preheater 12 and calcined in the calciner 14 flows into the kiln 16. The material inlet of the kiln 16 is preferably connected directly to the riser of the calciner 14 so that the kiln off-gas 34 flows into the calciner 14 and then into the preheater 12. The kiln 16 is, by way of example, a rotary kiln having a rotary tube rotatable about its longitudinal axis and arranged at a slightly inclined angle. At the material outlet end in the rotary tube, the kiln 16 preferably has a burner and an associated fuel inlet for receiving fuel 36 into the kiln 16. The material outlet of the kiln 16 is arranged at the end of the rotary tube opposite the material inlet, so that the raw material 32 to be burned is transported in the rotary tube by the rotation of the rotary tube in the direction of the burner and the material outlet. The raw materials 32 are combusted in the kiln 16 to form cement clinker 38. Preferably, the temperature within the kiln 16, and particularly within the calcination zone of the kiln 16, is between about 1450°C and 1800°C, preferably between 1500°C and 1700°C.

[0052] A cooler 18 for cooling the clinker is adjacent to the material outlet of the kiln 16. The clinker is transported through the cooler 18 in a conveying direction F. The cooler 18 has a first cooler area 18a in the conveying direction F of the clinker 38 to be cooled and a second cooler area 18b adjacent to the first cooler area 36 in the conveying direction F. Furthermore, the cooler 18 has a third cooler area 18c adjacent to the second cooler area 18b in the conveying direction F. The kiln 16 is connected to the cooler 18 via the material outlet of the kiln 16 such that the clinker 38 burned in the kiln 16 falls into the cooler 18.

[0053] The first cooler area 18a is preferably arranged below the material outlet of the kiln 16 so that the cement clinker 38 falls from the kiln 16 into the first cooler area 18a. The first cooler area 18a constitutes the suction area of ​​the cooler 18 and preferably has a static grate that receives the clinker 38 leaving the kiln 16. The static grate is in particular arranged completely within the first cooler area 18a of the cooler 18. Preferably, the clinker 38 falls from the kiln 16 directly onto the static grate. The static grate 40 preferably extends such that the clinker slides along the static grate in the conveying direction F. The first cooler area 18a has, for example, in addition to the static grate or exclusively, a dynamic grate for conveying the clinker in the conveying direction F through the cooler 18.

[0054] Adjacent to the first cooler zone 18a is a second cooler zone 18b of the cooler 18, to which the hot clinker 46 cooled in the first cooler zone 18a is fed. In the first cooler zone 18a of the cooler 18, the clinker is cooled, in particular to a temperature below 1100°C, the cooling being carried out in such a way that the liquid phase present in the clinker is completely solidified into the solid phase. On leaving the first cooler zone 18a of the cooler 18, the hot clinker 46 is preferably present in the completely solid phase and at a temperature of at most 1100°C, in particular at most 1000°C. In the second cooler zone 18b of the cooler 18, the hot clinker 48 is further cooled, preferably to a temperature below 700°C. In the third cooler zone 18c the clinker is cooled, in particular to a temperature below about 100° C., and leaves the cooler 18 as cold clinker 50. Preferably, the second cooled gas stream may be divided into multiple gas sub-streams having different temperatures.

[0055] The static or dynamic grate of the first cooler region 18a has, for example, a passage through which the first cooling gas 40 enters the first cooler region 18a. The first cooling gas 40 preferably flows from below through the static or dynamic grate into the first cooler region 18a. The first cooling gas stream 40 is, for example, pure oxygen or a gas having a nitrogen content of 15% by volume or less and an oxygen content of 50% by volume or more. The first cooling gas 40 flows through the clinker and then into the kiln 16. The first cooling gas 40, in particular the off-gas from the first cooler region 18a, forms, for example, partially or completely the combustion gas 42 of the kiln 16. The high proportion of oxygen in the combustion gas 42 results in a preheater off-gas 30 consisting essentially of CO 2 and water vapor, having the advantage that complex downstream cleaning steps for off-gas cleaning can be omitted. Furthermore, the amount of process gas is reduced, and as a result, the plant can be given a considerably smaller size.

[0056] The first cooler region 18a and the second cooler region 18b are preferably separated from each other with respect to the gas via separation means, such that the first cooling gas 40 flows exclusively into the first cooler region 18a and exits the first cooler region 18a as off-gas 42, in particular the combustion gas 42 for the kiln 16. The first cooling gas 40 preferably does not enter the second cooler region 18b or the third cooler region 18c. The second cooling gas 44 preferably flows exclusively into the second cooler region 18b and exits the second cooler region 18b as off-gas 24, in particular the combustion gas 24 for the calciner 14. The third cooling gas 52 preferably flows exclusively into the third cooler region 18c and exits the third cooler region 18c as cooler exhaust 54. It is optionally conceivable that the first cooler region 18a and the second cooler region 18b are not separated from each other with respect to the gas, which would mean that the cooling gases 40 and 44 flow into both the first cooler region 18a and the second cooler region 18b.

[0057] Preferably, between the first 18a and second 18c cooler zones, and optionally between the second 18b and third 18c cooler zones, separation means are installed to separate the cooler zones with respect to gas. The separation means are, for example, mechanical separation means, such as flaps or curtains. The separation means may also be a means for separating the CO 2 The cooling means may comprise a gas divider, in which a separation gas such as is supplied between the cooling sections 18a-c. The separation means may also be a pressure difference established between the first and second cooling regions. Such a pressure difference results in a controlled separation of the gases in the cooling regions.

[0058] In the cooler 18, the clinker to be cooled is moved in a conveying direction F. The second cooler area 18b preferably has a dynamic, in particular a movable grate, adjacent to the first cooler area 18b in the conveying direction F. The dynamic grate in particular has a conveying unit which transports the clinker in the conveying direction F. The conveying unit is, for example, a sliding floor conveyor with a plurality of conveying elements for transporting the bulk material. In the case of a sliding floor conveyor, the conveying elements are a plurality of plates, preferably grate plates, which form an aerated floor. The conveying elements are arranged adjacent to one another and can be moved in the conveying direction F and against the conveying direction F. The cooling gas can flow through the conveying elements in the form of conveying or grate plates, which are arranged over the entire length of the second cooler area 18b of the cooler 18 and form the surface on which the clinker rests. The conveying unit may also be a pusher conveyor, which comprises a fixed aerated bed through which the cooling gas flow can flow and a number of conveying elements which can be moved relative to the aerated bed. The conveying elements of the pusher conveyor are preferably arranged above the aerated bed and have entrainment elements extending transversely to the conveying direction. To transport the clinker along the aerated bed, the conveying elements can be moved in the conveying direction F and against the conveying direction F. The conveying elements of the pusher conveyor and the sliding bed conveyor may be mobile according to the "walking bed principle", in which the conveying elements are all moved simultaneously in the conveying direction and non-simultaneously against the conveying direction. As an alternative to this, other conveying principles used in bulk material technology are also conceivable.

[0059] A plurality of fans may be arranged below the dynamic grate, whereby a second cooling gas 44 is blown in from below through the dynamic grate. The second cooling gas 44 is preferably a gas poor in oxygen having an oxygen content of at most 15% by volume, in particular at most 10% by volume, preferably at most 5% by volume. The oxygen content is, in particular, oxygen in volume % units based on the dry gas. In particular, the second cooling gas 44 contains a mixture of CO 2 and water. The off-gas 24 of the second cooler region 18b is preferably fed completely or partially to the calciner 14, preferably to form a conveying gas in the calciner 14. The conveying gas 24 introduced into the calciner 14 preferably has an oxygen content of at most 15% by volume, in particular at most 10% by volume, preferably at most 5% by volume. To achieve such an oxygen content, the cooling gas preferably has such an oxygen content, or the off-gas 24 from the second cooler region 18b is subjected to oxygen enrichment to establish an oxygen content of at most 15% by volume in the off-gas 24 before entering the calciner. The conveying gas 24, in particular the off-gas from the second cooler region 18b, preferably has a CO content of at least 75% by volume based on the dry gas. The conveying gas 24 ensures an improvement in the solid transport in the calciner 14 and the amount of gas in the calciner 14 is increased. The low oxygen content and high CO 2 content in the conveying gas enables a simple separation of CO 2 in the preheater off-gas 30, for example using cryogenic processes. 2

[0060] The amount of the conveying gas 24 conducted to the calciner 14 is preferably adjustable. In particular, the amount of the conveying gas 24 and / or the oxygen content of the conveying gas 24 are adjusted. Preferably, the oxygen content of the calciner off-gas 28 is determined by a measuring device and the amount of the conveying gas and / or the oxygen content of the conveying gas 24 are adjusted, in particular increased or reduced, depending on the determined oxygen content. In particular, the volume flow of the off-gas 24 is kept constant. The determined oxygen content is preferably compared with a predefined limit value and, in the event of deviation from this limit value, the amount of the conveying gas 24 and / or the oxygen content of the conveying gas 24 are increased or reduced. If the limit value of the oxygen content is exceeded, the amount of the conveying gas 24 and / or the oxygen content of the conveying gas 24 is preferably reduced. If the limit value of the oxygen content is not reached, the amount of the conveying gas 24 and / or the oxygen content of the conveying gas 24 is preferably increased.

[0061] By way of example, the second cooler zone 18b is adjoined by a third cooler zone 18c, which has, for example, a dynamic grate for transporting the hot clinker 48 in the conveying direction F, as explained above. A third cooling gas 52 is preferably supplied to the third cooler zone 18c and, after cooling the hot clinker 48 therein, is discharged therefrom as cooler exhaust 52 from the cooler 18. The third cooling gas 52 is, for example, air.

[0062] Figure 2 shows a cement production plant 10 which essentially corresponds to the cement production plant 10 shown in Figure 1. Identical elements are provided with identical reference symbols. In contrast to Figure 1, in the cement production plant of Figure 2 the off-gas 24 from the second cooler area is separated into two gas sub-streams, the first gas sub-stream 24a being conducted to the calciner 14 as carrier gas and the second gas sub-stream 24b being conducted to the preheater 12. The amount of the gas sub-stream based on the off-gas 24 can preferably be adjusted. As a result, the amount of gas to the calciner 14 and to the preheater 12 can be adjusted so that an optimal fuel consumption in the calciner 14 can be achieved.

[0063] FIG. 3 shows a cement production plant 10 which essentially corresponds to the cement production plant 10 shown in FIG. 1. Identical elements are provided with identical reference symbols. In contrast to FIG. 1, the cement production plant 10 has a conditioning device 56, to which the preheater off-gas 30 is at least partially fed. The conditioning device 56 is, for example, a filter, a heat exchanger, a gas mixer, a condenser or a spray tower. The conditioning device 56 is preferably configured such that it treats the preheater off-gas, in particular cools it, filters dust or coarser particles from the preheater gas and / or increases or reduces the moisture content of the preheater off-gas. The conditioning device 56 is preferably configured such that, on leaving the conditioning device 56, the preheater off-gas has an oxygen content of at most 15% by volume, in particular at most 10% by volume, preferably at most 5% by volume, and preferably has a CO content of at least 75% by volume, in particular preferably has a CO content of at least 75% by volume. 2 CO content 2 The preheater off-gas treated in the conditioning device 56 preferably forms, in whole or in part, the second cooling gas 44 and is introduced into the second cooler section 18b.

[0064] In contrast to the cement production plant of FIG. 1, the cement production plant 10 of FIG. 3 has a humidifier device 58 configured and arranged for the introduction, in particular injection, of water into the second cooler region 18b. Preferably, a water content of more than 10 vol.-%, in particular more than 20 vol.-%, preferably more than 30 vol.-%, is set in the second cooler region 18b by the humidifier device 58. As a result, a corresponding water content is also set in the calciner 14. The calciner off-gas 28 and the preheater off-gas 30 preferably have a corresponding water content. This is preferably achieved by reducing the CO 2 in the off-gas, in particular in the preheater off-gas 30, after condensation of the water present in the off-gas, for example in a condenser or gas scrubber. 2 This results in an increase in the partial pressure of CO at lower electrical energy consumption. 2 This allows for the subsequent separation of

[0065] Preferably, the temperature and / or the volumetric flow of the off-gas 24 from the second cooler region 18b is determined by a measuring device and the amount of water introduced into the second cooler region 18b via the humidification device 58 is adjusted, in particular increased or reduced, depending on the determined temperature and / or volumetric flow. In particular, the volumetric flow of the off-gas 24 is kept constant. The determined volumetric flow and / or the determined temperature are preferably compared with respective predefined limit values ​​and, in case of deviation from said limit values, the amount of water to the second cooler region 18b is increased or reduced. In case of exceeding the limit values ​​of the volumetric flow and / or the temperature, the amount of water to the second cooler region 18b is preferably increased.

[0066] Preferably, a side stream of the preheater off-gas 30 is fed to the conditioning device 56, and the remaining side stream of the preheater off-gas 30 is discharged. It is also conceivable that the preheater off-gas 30 is fed completely to the conditioning device 56, and following the conditioning device 56, only the side stream forms the second cooling gas 44, and the remaining side stream is discharged from the cement production plant 10.

[0067] Figure 4 shows a cement production plant 10 that essentially corresponds to the cement production plant 10 shown in figure 3. Identical elements are provided with identical reference numbers. In contrast to figure 3, in the exemplary embodiment of figure 4, the preheater off-gas 30 treated by the conditioning device 56 is fed to the third cooler zone 18c to partially or completely form the third cooling gas 52. The off-gas 54 from the third cooler zone 18c is preferably fed completely or partially to the second cooler zone 18b to form the second cooling gas 44. The third cooler zone 18c has a further humidification device 58, which is arranged, by way of example, to introduce water into the third cooler zone 18c.

[0068] Preferably, between the second cooler region 18b and the third cooler region 18c, a further conditioning device is arranged, which is not shown in FIG. 4, such that on leaving the conditioning device 56, the off-gas from the third cooler region 18c has an oxygen content of at most 15 vol.-%, in particular at most 10 vol.-%, preferably at most 5 vol.-%, and preferably has an oxygen content of at least 75 vol.-% CO. 2 CO content 2 The preheater off-gas treated in the further conditioning device is preferably fully or partially formed into a second cooling gas 44 and introduced into the second cooler region 18b. This makes it possible to reduce the amount of off-gas from the cooler 18.

[0069] The exemplary embodiment differs from the exemplary embodiment shown in Figure 3 by an additional dehumidifier 60, which dehumidifies the preheater off-gas 30, for example, prior to carbon dioxide separation. The water separated in the dehumidifier 60 is fed via a fluid stream 62 to the second cooler region 18b, in particular sprayed in the second cooler region 18b. [Explanation of symbols]

[0070] 10. Cement manufacturing plant 12 Preheater 14 Calcination furnace 16 Kiln 18 Cooler 18a First Cooler Region 18b Second Cooler Area 18c Third Cooler Region 20 Raw materials 22 Fuel 24 Offgas from the second cooler section / carrier gas to the calciner 26 Hot meals / heated ingredients 28 Calciner off-gas 30 Preheater off-gas 32 Calcined raw materials 34 Kiln off-gas 36 Fuel 38 Hot cement clinker 40 First cooling gas 42 Offgas from first cooler area / combustion gas to kiln 44 Second Cooling Gas 46 Hot clinker 48 Hot clinker 50 Cold Clinker 52 Third Cooling Gas 54 Cooler exhaust 56 Adjustment device 58 Humidifier 60 Dehumidifier 62 Fluid flow F. Direction of clinker transport in cooler 18

Claims

1. A process for producing cement clinker (50), comprising the steps of: Preheating the feedstock (20) in a preheater (12); calcining the preheated raw material (26) in a calciner (14); burning the preheated, calcined raw meal (32) in a kiln (16) to form a cement clinker (38), said kiln (16) being supplied with combustion gases (42) having an oxygen content of more than 50% by volume; cooling the cement clinker (38) in a cooler (18), the cooler (18) having a first cooler section (18a) and a second cooler section (18b) in a conveying direction of the cement clinker (38), and exhaust from the first cooler section (18a) forms the combustion gases (42); setting a moisture content in said second cooler region (18b) to greater than 20% by volume with a humidifier (58); Including, off-gas (24) from the second cooler section (18b) is fed to the calciner (14) and has an oxygen content of up to 15% by volume; The fluid supplied to the second cooler region (18b) has an inert portion of at least 60% by volume, the inert portion of the fluid being comprised of water, carbon dioxide, or water and carbon dioxide. A process characterized by:

2. 2. The process of claim 1, wherein the kiln (16) is supplied with combustion gas (42) having an oxygen content of greater than 80% by volume.

3. 2. The process of claim 1, wherein the kiln (16) is supplied with combustion gas (42) having an oxygen content of greater than 90% by volume.

4. 2. The process of claim 1, wherein the off-gas (24) from the second cooler section (18b) is fed to the calciner (14) and has an oxygen content of up to 10% by volume.

5. 2. The process of claim 1, wherein the off-gas (24) from the second cooler section (18b) is fed to the calciner (14) and has an oxygen content of up to 5% by volume.

6. 2. The process of claim 1, wherein the fluid supplied to the second cooler section (18b) has an inert fraction of at least 80% by volume.

7. 2. The process of claim 1, wherein the fluid supplied to the second cooler section (18b) has an inert fraction of at least 90% by volume.

8. 2. The process of claim 1, characterized in that cooling gas (40, 44) is supplied separately to the first cooler zone (18a) and the second cooler zone (18b), and the cooling gas (44) supplied to the second cooler zone (18b) has an oxygen content of at most 15% by volume.

9. The process described in claim 1, wherein cooling gases (40, 44) are supplied separately to the first cooler region (18a) and the second cooler region (18b), and the cooling gas (44) supplied to the second cooler region (18b) has an oxygen content of up to 10 volume percent.

10. The process described in claim 1, wherein cooling gases (40, 44) are supplied separately to the first cooler region (18a) and the second cooler region (18b), and the cooling gas (44) supplied to the second cooler region (18b) has an oxygen content of up to 5 volume percent.

11. 11. The process according to any one of claims 1 to 10, characterized in that an oxygen concentration of the gas (28) is determined downstream of the calciner (14) and the oxygen concentration of the off-gas (24) from the second cooler section (18b) which is fed to the calciner (14) is adjusted in response to the determined oxygen concentration.

12. The process of claim 1, characterized in that at least a portion of the off-gas (24) from the second cooler section (18b) is fed to the preheater (12).

13. 2. The process according to claim 1, characterized in that the preheater off-gas (30) is fed to a conditioning device (56) for processing, including heat treatment, humidification and / or cleaning.

14. 14. The process of claim 13, characterized in that following the conditioning device (56), the preheater off-gas is fed to the second cooler section (18b).

15. 15. The process according to claim 13 or 14, characterized in that the cooler (18) has a third cooler section (18c) adjacent to the second cooler section (18b), and that following the conditioning device (56), the preheater off-gas is supplied to the third cooler section (18c).

16. 16. The process of claim 15, characterized in that off-gas (54) from the third cooler section (18c) is fed to the second cooler section (18b).

17. 2. The process of claim 1, characterized in that water is supplied to the second cooler area (18b).

18. The process described in claim 1, characterized in that cooling gases (40, 44) are supplied separately to the first cooler region (18a) and the second cooler region (18b), and the cooling gas (44) supplied to the second cooler region (18b) has a water content of more than 10 volume %.

19. The process described in claim 1, wherein cooling gases (40, 44) are supplied separately to the first cooler region (18a) and the second cooler region (18b), and the cooling gas (44) supplied to the second cooler region (18b) has a water content of more than 20 volume percent.

20. The process described in claim 1, wherein cooling gases (40, 44) are supplied separately to the first cooler region (18a) and the second cooler region (18b), and the cooling gas (44) supplied to the second cooler region (18b) has a water content of more than 30 volume percent.

21. The process of claim 1, wherein the step of setting the moisture content to greater than 20% by volume includes the step of setting the moisture content to greater than 30% by volume.

22. A cement manufacturing plant (10), comprising: - a preheater (12) for preheating the raw material (20), a calciner (14) for calcining the preheated raw material (26), - a kiln (16) for combusting the calcined raw material (32) to form cement clinker (38); a cooler (18) for cooling the cement clinker (38), said cooler (18) having, in a conveying direction (F) of the cement clinker (38), a first cooler section (18a) and a second cooler section (18b), said first cooler section (18a) being gas-wise connected to said kiln (16) such that off-gases (42) from said first cooler section (18a) can be fed to said kiln (16) as combustion gas; a humidification device (58) for humidifying the cooling gas in the cooler (18), the humidification device (58) setting a water content of more than 20% by volume in the second cooler region (18b); having the second cooler section (18b) is gas-wise connected to the calciner (16) such that off-gas (24) from the second cooler section (18b) can be fed to the calciner (14); The second cooler section (18b) is connected to a preheater off-gas stream (30) such that a portion of the preheater off-gas stream (30) is conducted to the second cooler section (18b). A cement manufacturing plant (10).

23. 23. A cement production plant (10) according to claim 22, characterized in that a conditioning device (56) for treating the preheater off-gas (30) is arranged downstream of the preheater (12) in the gas flow direction.

24. 24. The cement production plant (10) according to claim 23, characterized in that the cooler (18) has a third cooler section (18c) adjacent to the second cooler section (18b), and the conditioning device (56) is connected with respect to the gas to the second cooler section (18b) or to the third cooler section (18c).

25. 25. The cement production plant (10) of claim 24, characterized in that the third cooler zone (18c) is connected to the second cooler zone (18b) for recirculating off-gas (54) from the third cooler zone (18c) to the second cooler zone (18b).

26. 23. The cement production plant (10) according to claim 22, characterized in that the second cooler section (18b) is directly connected in gas conductive manner to the preheater off-gas (30).

27. 23. The cement production plant (10) according to claim 22, characterized in that the preheater off-gas (30) is guided to a dehumidifier (60), the dehumidifier (60) being connected in liquid communication with the second cooler section (18b).

28. A cement manufacturing plant (10) as described in claim 22, wherein the humidification device (58) sets the water content in the second cooler region (18b) to greater than 30% by volume.

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