Method for cleaning cement kilns

Abstract

The invention discloses a cement kiln cleaning method comprising the following process steps: a) reducing the temperature inside a cement kiln to a temperature range between 300 °C and 600 °C, b) opening a first opening of the cement kiln, which is arranged at the highest possible point in relation to the overall height of the cement kiln, c) inserting a nozzle head of a water jet cleaning tool, wherein the nozzle head – connected via a line to a high-pressure pump – has at least one nozzle which moves about a vertical axis during operation and thereby discharges a high-pressure water jet, d) positioning the nozzle head inside the cement kiln from a first position such that the water jet discharged during operation of the nozzle head strikes contaminants on an inner wall of the cement kiln, e) operating the water jet cleaning tool, f) optionally moving the nozzle head to a second position.which is located below the first position and operating the water jet cleaning tool in this second position, g) Optionally repeating process step f) by moving the nozzle head to further positions, h) removing the nozzle head from the cement kiln and closing the first opening.

Description

[0001] The invention relates to a cement kiln cleaning process. Cement kilns are usually designed as rotary kilns or rotary tube kilns and serve as kilns for the production of cement clinker in cement production.

[0002] New kiln systems for cement plants today typically have cyclone preheater kilns with a calciner, a tertiary air line and a grate cooler.

[0003] Cyclone preheaters typically consist of four to six cyclone or vortex chamber stages arranged one above the other in towers up to 100 meters high. During operation, the exhaust gas from the actual furnace flows through the tower from bottom to top.

[0004] The so-called raw meal is added to the top stage and heated to gas temperature while suspended in the counterflowing exhaust gas. In the cyclone stages, it is separated from the gas and deposited in the stage below. The process is repeated in each stage at increasingly higher temperatures, partially deacidifying the limestone (calcium carbonate CaCO3) contained in the raw meal. The exhaust gas leaves the preheater at a temperature of 280 °C to 350 °C.

[0005] Rotary kilns are refractory-lined tubes with diameters of up to approximately 6 m that rotate at 1.3 to 3.5 revolutions per minute. The rotational movement and the inclination of the kiln axis of 3° to 4° move the firing material from the kiln inlet toward the burner installed at the kiln outlet. After a residence time of 10 to 20 minutes in the sintering zone, the firing material reaches temperatures of approximately 1450 °C and begins to melt, at least in part (sintering), forming the so-called clinker phases from the starting materials. A clinker or grate cooler is connected to the kiln outlet.

[0006] Over time, the entire process leads to significant contamination, particularly buildup on the interior walls of the cement kiln. This ultimately leads to reduced efficiency, malfunctions, and downtime. For this reason, the interior of the cement kilns is cleaned regularly. Cleaning personnel enter the interior of the cement kiln through one or more manholes and clean the interior walls and components by hand or using a digging technique. For an average-sized cement kiln, this process takes several days, typically around 10 shifts, and is extremely physically demanding.

[0007] Additionally, the cement kiln must be cooled down beforehand, which can also take up to 24 hours. Accordingly, the cleaning costs are extremely high due to the personnel requirements and the downtime of the cement kiln.

[0008] The Chinese publication CN 108 662 600 A describes a process essentially carried out by mining personnel, in which cleaning personnel, equipped with fire-resistant clothing, remove deposits and crusts from the cement kiln with a type of lance. This requires determining the location of the deposits in advance using an infrared camera.

[0009] The object of the invention is therefore to provide a method that avoids the aforementioned disadvantages of the prior art. Cleaning should be carried out with less physical strain on the cleaning personnel, and the downtime of the cement kiln should be reduced compared to the prior art cleaning method.

[0010] This object is achieved by a method according to claim 1. The method according to the invention accordingly comprises the following method steps: a) Reducing the temperature inside a cement kiln to a temperature range between 300°C and 600°C, b) Opening a first opening of the cement kiln, which is arranged at the highest possible point in relation to the overall height of the cement kiln, c) Inserting a nozzle head of a water jet cleaning tool through the first opening, wherein the nozzle head is connected to a high-pressure pump via a line and has at least one nozzle that moves around a vertical axis during operation and discharges a high-pressure water jet, d) Positioning the nozzle head inside the cement kiln from a first position such that the water jet discharged during operation of the nozzle head impinges on contaminants on an inner wall of the cement kiln, e) Operating the water jet cleaning tool, f) Optionally moving the nozzle head to a second position,which is located below the first position and operating the water jet cleaning tool in this second position, g) Optionally repeating the process step f) by moving the nozzle head to further positions, h) Removing the nozzle head through the first opening from the cement kiln and closing the first opening, , wherein the cleaning of the inner wall of the cement kiln (20) is carried out unmanned and exclusively by the nozzle head (40) of the water jet cleaning tool (38).

[0011] A key advantage of the invention is that the cleaning process can be completed in a significantly shorter time. It eliminates the need for personnel to enter the cement kiln. No strenuous and / or even hazardous activities are required.

[0012] The invention is essentially based on the idea of ​​not cleaning the cement kiln manually, i.e., using a mining method, but rather using a largely automated cleaning process. By inserting a nozzle head through an opening as high as possible, it is possible to clean the inner wall of the cement kiln and other internal components using a water jet discharged from the nozzle head. The necessary opening in the cement kiln is either already present or can be created for the purpose of cleaning.

[0013] The nozzle head is moved through the opening into the cement kiln to a specific initial position and operated there for an appropriate period of time. This period depends on the degree of contamination and can, for example, be between 5 and 15 minutes.

[0014] The water jet discharged through the nozzles of the nozzle head strikes contaminants and loosens them from internal components or the inner wall of the cement kiln. The contaminants fall downward due to gravity and can be mixed into the product being produced after the cleaning process.

[0015] It has been shown that for an average cement kiln, a high-pressure pump can be used to pump the water. This pump generates approximately 1000 bar of pressure and delivers approximately 200-250 liters of water per minute. The water is fed to the nozzle head via a high-pressure line or hose, which then discharges it through the nozzles. Alternatively, high-pressure pumps with higher power or higher flow rates can be used. Depending on the contamination, lower power levels are also conceivable.

[0016] A nozzle head that not only has a single nozzle that can be rotated around a vertical axis, but is also equipped with at least one additional nozzle or even several nozzles, is particularly suitable. In a preferred embodiment, the entire nozzle head rotates around a vertical axis; however, it is also conceivable for only the nozzles to rotate around the vertical axis.

[0017] In a particularly advantageous design variant, the nozzles, or rather the nozzle head, rotate not only around a vertical axis, but also around a horizontal axis. This is particularly advantageous when components inside the cement kiln that extend horizontally need to be cleaned. Such components can then be cleaned from above and below, so to speak. For this purpose, the nozzles are rotatably mounted on the nozzle head.

[0018] The nozzle head can be equipped with nozzles that are each moved only around the vertical axis or the horizontal axis, but a design is also possible in which each of the nozzles is moved around both the vertical and the horizontal axis.

[0019] Advantageously, the nozzles are driven by the discharged water jet. Alternatively, a design is also possible in which the nozzles are set in motion independently of the water jet by an additional drive.

[0020] The nozzle head can be suspended solely from the hose, but it can also be attached to an additional steel cable or chain. A cable or chain made of a plastic material is also conceivable.

[0021] After the nozzle head has been operated in its first position for a certain period of time, it is lowered down within the cement kiln and moved to a second position. There, the cleaning process is restarted so that the next section of the cement kiln can be cleaned. In principle, the cement kiln is traveled from top to bottom. Additional positions may follow, to which the nozzle head can be moved for cleaning.

[0022] Due to the angled design of a cement kiln, it may be advantageous to create additional openings in the kiln through which the housing head can be inserted. After the nozzle head has been inserted through the first opening and has passed through the cement kiln from top to bottom, the nozzle head is withdrawn through the first opening, and a second cleaning process is initiated through a second opening. Depending on the design of the cement kiln, additional openings may be provided to allow for additional cleaning processes.

[0023] Cleaning takes place from the highest point, which is usually around 100 m, to the lowest position, which is located at a height of around 20 m.

[0024] A key advantage of the invention is that the cement kiln does not need to be completely cooled down before the cleaning process. On the contrary, it is advantageous if a temperature of approximately 300°C to 600°C is maintained within the cement kiln throughout the entire cleaning process. This ensures that the introduced water evaporates during the cleaning process and does not fall to the bottom as water and have to be drained away. Since no personnel are required to work inside the cement kiln, such a high temperature is easily possible.

[0025] The line connecting the nozzle head to the high-pressure pump, for example, has a pressure resistance of up to 1800 bar. DN 20 hoses with an inner diameter of 33 mm have proven particularly advantageous.

[0026] According to the invention, the cement kiln can be visually inspected following the cleaning process. In a particularly simple embodiment, the inspection is carried out using mirrors that allow the interior of the cement kiln to be viewed. Alternatively, it is also possible to check the cleaning success using an imaging method, for example, with a rotating or 360° photo or video camera that is lowered or raised inside the cement kiln.

[0027] The invention is described in more detail with reference to the following figures. The figures are intended solely to illustrate the invention and are not to be understood as limiting. In particular, they are merely schematic representations; scales or details may differ from reality. They show: Figure 1: a schematic diagram of a cement kiln, Figure 2: a schematic diagram of a water jet cleaning tool.

[0028] Figure 1 shows the structure of a conventional cement kiln 20, which includes a rotary kiln 22 as its central component. Raw meal (not shown) is introduced from above into a cyclone preheater 24, which has several cyclone or vortex chamber stages 26. Exhaust gas flows through the cement kiln 20 in the opposite direction, i.e., from bottom to top, heating the crude oil to the desired temperature. In the cyclone stages 26, it is then separated from the gas and deposited in the stage below.

[0029] The almost complete calcination takes place in a calciner 28. The calcined flour leaves the calciner 28 and, together with the calciner's combustion exhaust gases, is fed to the final stage of the preheater. In this stage, the flour is separated from the gases and falls back into the rotary kiln 22. Also visible is a tertiary air line 30 leading to a burner 32. Cement clinker (not shown) is produced or burned in the burner 32. A cooler 34 is also provided for this purpose.

[0030] For purely exemplary purposes, openings 36 are symbolically depicted through which a water jet cleaning tool 38 can be inserted into the interior of the cement kiln 20. A first opening 36-1 is located at the highest point of the cement kiln 20, and a second opening 36-2 is located at a lower position. The openings 36 are arranged such that the cement kiln 20 can be cleaned from top to bottom with a nozzle head 40.

[0031] Figure 2 shows a simplified schematic diagram of a water jet cleaning tool 38. It shows a high-pressure pump 42, which is connected to the nozzle head 40 via a hose-like line 44.

[0032] In the illustrated embodiment, the nozzle head 40 has two nozzles 56 that are movable or rotatable about a vertical axis ZZ and a horizontal axis XX, indicated by the arrows. Advantageously, the nozzles are driven by the respective discharged water jets 48. The movement can be controlled or random.

[0033] Also shown is an optional cable 50, preferably a steel cable. The nozzle head 40 can be lowered within the cement kiln 20 using this cable. The cable 50 is attached to the nozzle head via a swivel joint 51, which allows rotation of the nozzle head 40 about the vertical axis ZZ. The cable 50 can also be connected to the high-pressure pump 42 as shown, but it can also be secured exclusively or additionally to external components of the cement kiln 20; in particular, it can also be wound onto a cable winch.

[0034] The invention is not limited to the embodiment shown, but also includes other useful features and technical aspects relating to the invention.

Claims

1. A cement kiln cleaning method, having the following method steps: a) reducing the temperature in the interior of a cement kiln (20) to a temperature range between 300°C and 600°C, b) opening a first opening (36-1) of the cement kiln (20), which is arranged at a position which is as high as possible in relation to a total height of the cement kiln (20), c) introducing a nozzle head (40) of a water jet cleaning tool (38) through the first opening (36-1), wherein the nozzle head (40) - is connected by means of a line (44) to a high-pressure pump (42), - has at least one nozzle (56) which moves about a vertical axis (Z-Z) during operation and in the process ejects a water jet (48) at high pressure, d) positioning the nozzle head (40) in the interior of the cement kiln (20) starting from a first position (A) in such a manner that the water jet (48) ejected during operation of the nozzle head (40) hits contaminants on an internal wall of the cement kiln (20), e) operating the water jet cleaning tool (38), f) optionally moving the nozzle head (40) to a second position (B) which is located below the first position (A) and operating the water jet cleaning tool (38) in this second position, g) optionally repeating the method step f) by moving the nozzle head (40) into further positions (C1, C2...), h) removing the nozzle head (40) from the cement kiln (20) through the first opening (36-1) and closing the first opening (36-1), wherein the cleaning of the internal wall of the cement kiln (20) takes place in an unmanned manner and exclusively by means of the nozzle head (40) of the water jet cleaning tool (38).

2. The cement kiln cleaning method according to Claim 1, characterized by repeating the method according to Claim 1 by introducing the nozzle head (40) through a second and possibly further opening (36-2) in the cement kiln (20), wherein the subsequently used openings (36-2, 36-3...) are arranged below one another, so that the cement kiln (20) is cleaned from top to bottom.

3. The cement kiln cleaning method according to Claim 1 or Claim 2, characterized in that the nozzle (56) also moves about a horizontal axis (X-X).

4. The cement kiln cleaning method according to Claim 2, characterized in that the nozzle (56) moves chaotically about the vertical (Z-Z) and about a horizontal axis (X-X).

5. The cement kiln cleaning method according to any one of Claims 1 to 4, characterized in that the movement of the nozzle (56) is generated by the ejected water jet.

6. The cement kiln cleaning method according to any one of Claims 1 to 5, characterized in that the temperature range between 300°C and 600°C is maintained during the entire cleaning process.

7. The cement kiln cleaning method according to any one of Claims 1 to 6, characterized in that two or more nozzle heads (40) are used at the same time.

8. The cement kiln cleaning method according to any one of Claims 1 to 7, characterized in that a visual inspection takes place following the cleaning of the cement kiln (20).

9. The cement kiln cleaning method according to Claim 8, characterized in that the visual inspection takes place with the aid of a mirror.

10. The cement kiln cleaning method according to Claim 8, characterized in that the visual inspection takes place with the aid of a camera which is introduced into the cement kiln (20).

11. The cement kiln cleaning method according to any one of Claims 1 to 10, characterized in that the water jet cleaning tool (38) is operated in each position of the nozzle head (40) for a time period of 5 min to 15 min.

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