Method for operating a plant for producing cement clinker

Abstract

The invention relates to a method for operating a plant (100) for producing cement clinker, wherein the plant comprises as plant units (AG), in the direction of gas flow, at least one clinker cooler (110), at least one rotary kiln (120), at least one calciner (130), at least one heat-exchanger line (140), consisting of heat-exchanger cyclones (150, 151, 152), and and at least one device (160) for crushing raw meal and / or cement clinker, and also relates to a corresponding plant (100) for producing cement clinker. The invention envisages enclosing at least one plant unit (AG), whereby the plant unit (AG) is provided with a second covering (200) with respect to the atmosphere, and wherein the enclosure in the form of the covering (200) is subjected to process gas (P) by a compressor (210).

Description

[0001] Method for operating a plant for the production of cement clinker

[0002] The invention relates to a method for operating a plant for producing cement clinker, wherein the plant has, in the gas flow direction, at least one clinker cooler, at least one rotary kiln, at least one calciner, at least one heat exchanger train consisting of heat exchanger cyclones, and at least one device for comminuting raw meal and / or cement clinker as plant units, and a corresponding plant for producing cement clinker.

[0003] Modern plants for the production of cement clinker are operated using an oxy-fuel process. In this process, a large part or all of the nitrogen-containing carrier air is replaced by carbon dioxide (CO2), which comes from the combustion for the heat treatment of the raw meal used as a raw material in the production process. The purpose of this alternative process is to obtain a low-nitrogen to nitrogen-free exhaust gas that consists primarily of carbon dioxide (CO2). This carbon dioxide (CO2)-rich exhaust gas can then be compressed underground. The absence of nitrogen eliminates unnecessary compression work. A pleasant side effect of the different gas composition is the inevitable reduction in the emission of nitrous gases, since there is no longer any nitrogen present to form nitrous gases.This alternative process approach presents the problem in older and retrofitted plants that high gas flow velocities cause atmospheric contamination to be drawn into the plant at certain points. Depending on the entry point, this atmospheric contamination can lead to the formation of nitrous gases. The introduced contamination also increases the compression work required later for compression. In retrofitted plants that no longer have measures to prevent nitrous gases due to the different process approach, the introduction of contamination is particularly undesirable, as nitrogen oxide formation could then occur unhindered.

[0004] The subsequently published application DE 10 2021 119 755 A1 discloses a housing for system seals in order to suppress the ingress of false air through these seals.

[0005] The object of the invention is to prevent the ingress of false air at all conceivable points in the system.

[0006] The object of the invention is thereby achieved by a method for operating a plant for producing cement clinker having the features of claim 1. A corresponding plant for producing cement clinker is claimed in claim 6. Further advantageous embodiments of the method are specified in the subclaims to claim 1. Further advantageous embodiments of the plant are specified in the subclaims to claim 6.

[0007] According to the concept of the invention, at least one plant unit is housed, whereby the plant unit has a second shell against the atmosphere, and wherein the housing is supplied with process gas via a compressor. In principle, two supply types are possible. With a first supply type, the process gas is taken from the plant immediately before entering the plant unit. This is possible at points where the temperature of the process gas is not too high, so that the taken process gas can be compressed by a compressor without the compressor being damaged by the high gas temperature or having to be replaced too early. With another supply type, the process gas can be taken from the plant at a suitable, central point.Suitable locations are where the process gas has already cooled somewhat, i.e., in the heat exchanger cyclones located slightly downstream in the direction of gas flow. Low-dust locations in the plant can also serve as process gas sources. This process gas then does not require extensive filtering. Depending on the plant unit, the shell can be quite thin and constructed like a shell within a shell. However, it is also possible to house the plant unit in a small hall or container, so that the hall or container serves as the enclosure. To stabilize the overpressure, a compressor control system can be provided. The pressure can also be kept constant by controlling a discharge valve.

[0008] Plant units that can be enclosed include separators, classifiers, vertical mills, impact hammer mills, clinker crushers at the outlet of a clinker cooler, tube mills, bucket elevators, conveyor belts, combinations of a cage separator and a V-shaped cascade separator, heat exchanger cyclones, and even compressors. Combustion plants on the accessible side can also be enclosed with process gas. In this case, it is possible to operate the plant process gas pressure at between 10 mbar and 50 mbar, or at up to 70 mbar below atmospheric pressure. The enclosure, on the other hand, is operated by compressing the process gas, which is kept under negative pressure compared to the atmosphere, to a pressure of 1 mbar, 2 mbar, and even 5 mbar below atmospheric pressure. Operating in negative pressure ensures that no process gas can escape to the atmosphere. However, operating in negative pressure means that atmospheric air can be drawn in.The enclosures ensure that unwanted incoming false air originates from the process gas itself. Alternatively, it is possible to operate the system with process gas overpressure. Points where false air can be drawn in are locations where a Bernoulli vacuum develops due to the high flow velocities of the process gas, which can lead to the intake of false air despite the nevertheless low system overpressure. The enclosure ensures that the unwanted incoming false air consists of the process gas itself.

[0009] The invention is explained in more detail with reference to the following figures. It shows:

[0010] Fig. 1 is a view of a ball mill of a plant for the production of cement clinker from the PRIOR ART,

[0011] Fig. 2 the ball mill from Figure 1 , which is provided with a housing,

[0012] Fig. 3 is a schematic diagram of a plant unit of a plant for the production of cement clinker, which according to a first embodiment is provided with a central process gas supply,

[0013] Fig. 4 is a schematic diagram of a plant unit of a plant for the production of cement clinker, which is provided with a nearby process gas supply according to a second embodiment,

[0014] Fig. 5 is a schematic diagram of a plant unit of a plant for the production of cement clinker, which is provided with a nearby process gas supply according to a third embodiment,

[0015] Fig. 6 a heat exchanger cyclone of a plant for the production of cement clinker from the PRIOR ART,

[0016] Fig. 7 a heat exchanger cyclone of a plant for the production of cement clinker, which is provided with a housing,

[0017] Fig. 8 a plant for the production of cement clinker with partially enclosed plant units.

[0018] Figure 1 shows a view of a ball mill 161 of a plant 100 for producing cement clinker from the PRIOR ART. The ball mill shown here is free-standing or under a roof for protection from the weather. For operation, the ball mill 161 is pneumatically supplied from the left with ground material M suspended in process gas P. Inside the ball mill, the ground material is crushed and leaves the ball mill 161 as dust with the escaping process gas P on the right side, with the dust from the ground material M suspended in the process gas. Although ball mills are operated at a slight overpressure compared to the free atmosphere due to the pneumatic feeding, high flow velocities in the supply pipes can create a Bernoulli vacuum, which draws in atmospheric air L and thus mixes the process gas with false air.The mixing of the process gas P with atmospheric air L takes place at the transitions of the ball mill 161 with static pipes for the process gas P. These points are marked with a wavy arrow. To illustrate the scale of such a ball mill 161, a human being is shown to the right of the ball mill, approximately at the same scale.

[0019] Figure 2 shows the ball mill 161 from Figure 1, which is provided with a casing 200. The ball mill 161 is completely enclosed by the casing 200, with the process gas P with the ground material M suspended therein being passed through the casing 200 on the left side. The outlet of the process gas P is also passed through the casing 200 on the right side. In this embodiment, it is provided that other process gas P is introduced from a central point 220 of the plant 100 for producing cement clinker via a beaded line shown here top right into the casing 200 and there maintains an excess pressure compared to the gas pressure in the ball mill 161. It is not intended that the process gas P flows out of the casing 200. Rather, leaks form through which the process gas P introduced under excess pressure flows out of the casing.The idea of ​​the invention is that process gas P is now drawn into the ball mill 161 at the points where, for example, false air is drawn into the ball mill due to the formation of a Bernoulli vacuum. This prevents the process gas P in the ball mill 161 from being contaminated by false air. This sketch also shows a person to the right of the enclosed ball mill, standing in front of an open inspection door. When open, a signal lamp and horn located above signal the open and therefore dangerous state of the inspection door, through which process gas P can be directed to locations where fresh breathing air is needed for the personnel present there.

[0020] Figure 3 shows a schematic diagram of a plant unit AG of a plant 100 for producing cement clinker, which, according to a first embodiment, is provided with a central process gas supply. In this first embodiment, process gas P is supplied from a central location, compressed via a local compressor 210, and guided into the shell 200 enclosing the plant unit AG. In order to keep the overpressure in the shell constant, this embodiment provides for a regulator 260 to control the compressor. The regulator 260 increases the compressor output when the overpressure in the shell 200 drops compared to the pressure of the process gas P in the plant unit AG, and vice versa. Especially with a central supply of process gas P, local compression of the process gas P immediately upstream of the shell 200 is advantageous in order to avoid control fluctuations in the underlying gas supply network.Alternatively or cumulatively, it can be provided that the same or a second regulator 161 controls a discharge valve 250, the opening width of which is adjusted by the regulator 161 such that the opening width is increased with increasing overpressure and vice versa.

[0021] Figure 4 shows a further schematic diagram of a plant unit AG of a plant 100 for producing cement clinker, which, according to a second embodiment, is provided with a nearby process gas supply. In the embodiment shown here, the shell is designed to add as little bulk as possible and to enclose the original plant unit very tightly. The beads of the shell 200, indicated by bulges, and spacers not explicitly shown here keep the shell stable. Process gas P is drawn from the plant unit AG itself and compressed by a local compressor 210 and fed into the plant unit AG's own shell 200. To keep the overpressure of the process gas P in the shell 200 constant, a regulator 260 can regulate the compressor output of the compressor 210 such that if the overpressure in the shell 200 increases, the compressor output is reduced and vice versa.

[0022] Figure 5 shows a further schematic diagram of a plant unit AG of a plant 100 for producing cement clinker, which, according to a third embodiment, is provided with a nearby process gas supply. In the embodiment shown here, the shell is designed to add as little bulk as possible and to enclose the original plant unit very tightly. The beads of the shell 200, indicated by bulges, and spacers not explicitly shown here keep the shell stable. Process gas P is drawn from the process gas flow downstream to the plant unit AG and compressed by a local compressor 210 and fed into the plant unit AG's own shell 200. To keep the overpressure of the process gas P in the shell 200 constant, a controller 260 can regulate the compressor output of the compressor 210 such that if the overpressure in the shell 200 increases, the compressor output is reduced and vice versa.In the embodiment shown here, it is provided that the process gas extracted downstream of the gas flow is fed back to the gas inlet side of the plant unit, wherein the process gas in the housing in this configuration has the pressure of the process gas pressure upstream of the gas flow.

[0023] Figure 6 shows a heat exchanger cyclone 150 of a plant 100 for producing cement clinker, based on the PRIOR ART. Heat exchanger cyclones of a plant 100 for producing cement clinker can even reach a height of up to 10 m. To illustrate the scale, a person is shown at one level of a heat exchanger line to the right of the heat exchanger cyclone 150. High flow velocities are deliberately generated in heat exchanger cyclones to intensify the mixing of the raw meal with the oncoming process gas. Due to the high flow velocities, false air can be drawn into the heat exchanger cyclone 150 at leaky points due to a Bernoulli vacuum. Leaks cannot be completely prevented in a plant 100 that "works" through fluctuations in the process gas pressure and expands and contracts due to changing temperatures.Together with the high temperature prevailing there, small openings can form due to corrosion or excessive stress, which can quickly become so large due to the ingress of false air that the ingress of false air can no longer be ignored.

[0024] Compared to Figure 5, Figure 7 shows a heat exchanger cyclone 150 of a plant 100 for producing cement clinker, which is provided with a casing 200 as a housing. The entire heat exchanger cyclone 150 is arranged within the casing 200, and the casing 200 is supplied with process gas P by a local compressor 210 located on the same level as the heat exchanger cyclone 150. Should unwanted leaks occur in the heat exchanger cyclone 150, only the process gas P would be drawn in as false air, which was taken from the heat exchanger cyclone 150 immediately before the process gas P entered the heat exchanger cyclone 150. Here, too, a control system can be provided, as explained for the abstract embodiments of Figures 3 and 4. The control system can be a control of the compressor output and / or the control of a discharge valve 250.

[0025] Finally, Figure 8 shows a sketch of a plant 100 for producing cement clinker with partially enclosed plant units AG. The plant units can be selected from the group consisting of the clinker cooler 110, the rotary kiln 120, the calciner 140, the individual heat exchanger cyclones 150, 151, and 152 of a heat exchanger train, and also a ball mill or a vertical mill, as shown here as plant 160 for comminution. High-pressure roller presses can also be considered for enclosure by a casing 200.

[0026] LIST OF REFERENCE SYMBOLS

[0027] System A exhaust air

[0028] Clinker cooler AG plant unit

[0029] Rotary kiln B fuel

[0030] Calcinator L Air

[0031] Heat exchanger line M regrind

[0032] Heat exchanger cyclone P process gas

[0033] Heat exchanger cyclone R raw meal

[0034] Heat exchanger cyclone Z cement clinker

[0035] Device for shredding

[0036] ball mill

[0037] Covering

[0038] Compressor central location

[0039] drain valve

[0040] Controller

Claims

PATENT CLAIMS Method for operating a plant (100) for the production of cement clinker, wherein the plant comprises, in the direction of gas flow, at least one clinker cooler (110), at least one rotary kiln (120), at least one calciner (130), at least one heat exchanger string (140) consisting of heat exchanger cyclones (150, 151, 152), and at least one device (160) for comminuting raw meal and / or cement clinker as plant assemblies (AG), characterized by Enclosing at least one plant unit (AG), whereby the plant unit has a second shell (200) facing the atmosphere, and wherein the enclosure as a shell (200) is supplied with process gas (P) over a compressor (210). Method according to claim 1, characterized by The enclosure (200) of the at least one plant unit (AG) is pressurized with process gas (P), which is drawn off in the direction of gas flow immediately upstream of the enclosed plant unit. Method according to claim 1. The enclosure (200) of the at least one plant unit is pressurized with process gas, which is drawn from the plant at a central point (220). A method according to any one of claims 1 to 3, characterized by Rules of the compressor (210) concerning the overpressure in the enclosure as a shell (200) relative to the pressure of the extracted process gas, whereby the compressor power is reduced with increasing pressure and vice versa. Method according to any one of claims 1 to 4, characterized by Regulation of a drain valve (250), which is connected in flow communication with the interior of the enclosure as a shell (200), via the overpressure in the enclosure as a shell (200) relative to the pressure of the withdrawn process gas, wherein the opening width of the drain valve (250) increases with increasing pressure and vice versa. Plant (100) for the production of cement clinker, wherein the plant comprises, in the direction of gas flow, at least one clinker cooler (110), at least one rotary kiln (120), at least one calciner (130), at least one heat exchanger string (140) consisting of heat exchanger cyclones (150, 151, 152), and at least one device (160) for comminuting raw meal and / or cement clinker as plant units, characterized in that at least one plant unit has an enclosure as a shell (200), whereby the plant unit has a second shell vis-à-vis the atmosphere. wherein the enclosure (200) is in flow connection with a compressor (210), which supplies the enclosure (200) with process gas. System according to claim 6, characterized in that the compressor (210) is connected to the system (100) on its inlet side, this connection being arranged in the gas flow direction of the system (100) immediately upstream of the system unit. System according to claim 6, characterized in that the compressor (210) is connected to the system (100) on its inlet side, this connection being arranged at a central location (220) in the gas flow direction of the system (100). System according to any one of claims 6 to 8, characterized in that the compressor (210) is connected to a regulator (260) which controls the compressor (210) via the overpressure in the enclosure (200) relative to the pressure of the extracted process gas. wherein the regulator (260) reduces the compressor output with increasing pressure and vice versa. System according to one of claims 6 to 9, characterized in that the housing as a shell (200) is in flow communication with a drain valve (250) and wherein the drain valve (250) is in control communication with a regulator (260), wherein the regulator (260) increases the opening width of the drain valve (250) with increasing pressure and vice versa.

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