LU101809B1

LU101809B1 - Method and System for Cleaning a Coke Oven Component

Info

Publication number: LU101809B1
Application number: LU101809A
Authority: LU
Inventors: Stefan Schneider
Original assignee: Wurth Paul Sa
Priority date: 2020-05-19
Filing date: 2020-05-19
Publication date: 2021-11-19
Also published as: WO2021233998A1; TW202202606A

Abstract

The invention relates to a method and system for cleaning a coke oven component (1). In order to provide means for facilitating cleaning of a coke oven component, the invention provides that the method comprises: - positioning a laser emitter (11) with respect to the coke oven component (1) so that a target area (26) of the laser emitter (11) is within a contaminated surface area (4) of the coke oven component (1); - emitting a laser beam (25) onto the contaminated surface area (4), whereby a contaminant (5, 6, 7) at least partially absorbs the laser beam (25) and is heated; and - at least partially removing the heated contaminant (5, 6, 7) from the surface area (4).

Description

Method and System for Cleaning a Coke Oven Component Technical field

[0001] The invention relates to method for cleaning a coke oven component and to a system for cleaning a coke oven component.

Background of the Invention

[0002] In coke oven plants, exireme temperature conditions and constant exposure to dust and other contaminant materials regularly lead to pollution and contamination of most surfaces. Among others, this applies to the surfaces of a coke oven door, which becomes encrusted with a contaminant layer. This contaminant layer typically comprises dust particles as well as oil, grease and other components. Some of these components may be liquid or semi-solid and bind solid components to the surface of the oven door. The contaminant layer can seriously affect the mechanical function of the coke oven door as well as its | sealing capabilities. Therefore, the coke oven door, in particular the inner surface | thereof, needs to be cleaned at certain time intervals. |

[0003] Current cleaning systems for coke oven doors are based mainly on | mechanically scrapers, metal brushes or rotating grinders. The cleaning results | achieved by such mechanical cleaners are often insufficient, i.e. not enough for | customer request. Also, since the mechanical cleaners inevitably get into direct | contact with the surface of the oven door, they can damage or wear the material of | the oven door. Likewise, wear of the mechanical cleaners themselves leads to | high maintenance costs for the brushes, scrapers or the like. Other systems use | high-pressure water or a combination of mechanical cleaning and high-pressure | water. The cleaning results achieved by these wet cleaning systems are good, but | they have high running costs, mostly due to the power needed for the pump motor | and the water usage. Also, collecting and treating the waste water generated by | the cleaning process can be complex and leads to additional costs. |

[0004] Good cleaning results are also obtained using dry ice blasting with the | use of CO». However, the required CO» blasters, pelletisers, storage tanks are | rather costly. Also, in the context of today’s drive towards CO» emission reduction, the acceptability of dry ice blasting is nowadays questionable.

Object of the invention

[0005] It is thus an object of the present invention to provide means for facilitating cleaning of a coke oven component. This object is solved by a method according to claim 1 and by a system according to claim 15.

General Description of the Invention

[0006] The invention provides a method for cleaning a coke oven component.

In this context, “a” coke oven component is to be understood as referring to at least one coke oven component and the method could also be theoretically applied to a coke oven in its entirety.

[0007] The method comprises positioning a laser emitter with respect to the | coke oven component so that a target area of the laser emitter is within a | contaminated surface area of the coke oven component. In this context, the laser | emitter is a device that is configured to emit a laser beam. This may be the laser | itself, i.e. the device that generates the laser beam or it may be an optical device | that receives and redirects the laser beam, e.g. at least one fibre optic cable, at / least one lens, at least one mirror or the like. Insofar, positioning the laser emitter | may not comprise positioning the laser as such. The laser (i.e. the active | component that generates the laser beam) could remain stationary while the | emitter is positioned. Also, positioning the laser emitter with respect to the coke | oven component also includes the possibility that the laser emitter remains | stationary while the coke oven component is positioned accordingly. However, due | to the typical dimensions of a coke oven component, in almost every case, the | laser emitter is positioned, i.e. moved into a predetermined position. The target | area of the laser emitter is of course an area into which the laser beam can be | emitted, i.e. that can be irradiated or illuminated by the laser beam. Usually, this | target area is very small and could also be referred to as a (zero-dimensional) | target point. However, the target area could also be one-dimensional, i.e. line- | shaped, or even two-dimensional (e.g. rectangular or circular). The laser emitter is | positioned so that the target area is within a contaminated surface area. The contaminated surface area is an area of the surface of the coke oven component that is contaminated in the broadest sense, i.e. there is some contaminant or deposit on the surface. The surface itself may be made of metal, e.g. steel, which is generally the case for coke oven doors. However, the surface may also be made of stone or refractory material, which may e.g. be the case for plugs connected to the coke oven doors. The contaminant may comprise a first contamination layer with e.g. an oxide layer and a second contaminant layer comprising substances like grease, oil, tar and/or dust particles. It will be understood that the target area is normally much smaller than the contaminated surface area or all contaminated surface areas, wherefore the method normally comprises repeated or continuous (re)positioning of the laser emitter. Normally, the laser emitter is not positioned manually, but automatically.

[0008] The method also comprises emitting a laser beam onto the contaminated surface area, whereby a contaminant at least partially absorbs the laser beam and is heated. While this step is mentioned separately from positioning of the laser emitter, it should be noted that these steps do not need to be performed sequentially but could also be performed simultaneously. In particular, if the laser emitter is repositioned repeatedly or continuously, the laser beam can be emitted while the laser emitter is being repositioned, and vice versa. As the laser beam is emitted and hits the target area, the contaminant in the target area is irradiated and at least partially absorbs the laser beam. It will be understood that a part of the laser beam can also be reflected or scattered by the contaminant. However, the portion of the laser beam that is absorbed leads to a heating of the contaminant. Depending on the characteristics of the laser beam, it is possible to heat the contaminant in the target area by several hundred degrees Celsius within a fraction of a second.

[0009] The method further comprises least partially removing the heated contaminant from the surface area. Once the contaminant has been removed, the | surface area can be regarded as clean or partially clean, if only a portion of the | contaminant is removed. As will be explained below, the removing may be a result of the heating as such, i.e. the heating can cause the contaminant to be removed | from the surface area. While the laser cleaning according to the present method generally warrants sufficient cleaning of the contaminated surface, it may in some circumstances be desired to provide additional action to remove the heated contaminant. However, even in this case, the removal is facilitated by heating the contaminant. This may be due to various effects, e.g. melting the contaminant, evaporating the contaminant, inducing tensions in the contaminant etc. The action of the laser emitter is contactless and bears no or minimal risk of damaging or wearing the surface of the component. Also, there is no wear, or at least only negligible wear, to the laser emitter in contrast to mechanical cleaning systems. A system for performing the inventive method requires very little maintenance and the energy consumption the laser itself is very low in comparison fo mechanical or wet cleaners. Also, the laser beam can be directed very precisely at a desired target area, wherefore the inventive method works with a precision that cannot be achieved by mechanical or wet cleaning. |

[0010] In general, the method can be applied to any component of the coke | oven. In particular, the coke oven component may be a coke oven door. Other | components, such as e.g. a coke oven door frame or plugs connected to the coke | oven door may also be cleaned using the present method.

[0011] While it may be conceivable to use an additional process such as e.g. | directing a high-speed gas stream at the surface area to clean the surface, it is | highly preferred that the contaminant is removed from the surface area by the / heating process alone, In other words, the heating process itself causes the | contaminant to be removed from the contaminated surface area. This means that, | apart from the laser beam that is directed onto the surface area, no additional | measures need to be applied. This makes the method extremely energy-efficient | and cost-efficient. |

[0012] Preferably, the contaminant is at least partially evaporated. In other | words, the heating causes at least a portion of the contaminant to become | gaseous {which in this context includes becoming a plasma). The gaseous phase | may be reached from the solid state through a liquid state or, normally, directly by | sublimation. It should be noted that the sudden evaporation of some parts of the | contaminant and the coinciding sudden expansion of gas may cause other parts, e.g. dust particles, to be blasted off the surface even though they remain solid. In other words, the action of the laser beam may lead to micro-explosions or micro- plasma bursts, shock waves and thermal pressure that serve to break up the contaminant layer and e.g. remove solid particles. As a result, the removed contaminant may be present in the atmosphere around the target area of the laser beam as a mixture of gas/plasma and dust.

[0013] The waveform of the laser is generally not limited within the scope of the invention. At least temporarily, the laser beam could be emitted as a continuous waveform, which could be modulated if necessary. It is preferred, though, that the laser beam is emitted as a sequence of laser pulses. Each laser pulse can have an extremely high intensity which could not be achieved with a continuous laser beam. Since this high intensity of the laser beam can be concentrated on a very small target area, a small volume of contaminant can be evaporated even if the length of the pulse is short. In fact, a series of pulses may be more effective than a continuous wave even if the overall energy emitted over a certain time interval is the same. Frequency and/or amplitude within each pulse may be varied as a function of time. Also, different pulses may have different lengths, amplitudes and/or frequencies. The average intensity of the laser beam may be changed e.g. by changing the length of the pulses in relation to the interval between consecutive pulses and/or by changing the amplitude of each pulse.

[0014] Of course, a primary goal, apart from removing the contaminant from the surface, is to leave the surface intact, i.e. not to melt or evaporate surface material by the laser beam. One option would be to remove the contaminant layer by layer and to stop laser action before the surface is reached. However, this is almost impossible to achieve with sufficient accuracy. According to a preferred option, a laser beam is emitted that is adapted to be primarily absorbed by the contaminant while being primarily reflected by the surface of the coke oven component. In other words, the characteristics of the laser beam, such as e.g. its frequency or the frequency spectrum may be adapted to be absorbed by typical contaminant components, leading to a maximum absorption in the contaminant. In this context, a first contaminant layer (e.g. an oxide layer) that may be present on the surface of the coke oven component is also considered as part of the contaminant and the spectrum of the laser beam may in particular be adapted to be absorbed by such a first contaminant layer. Mostly, the surface material of the coke oven component (usually metal, e.g. steel) will show a significant absorption at different frequencies, so that even if the laser beam reaches the surface, the probability of any (significant) damage to the surface is low. An optimum frequency spectrum for the laser can be determined in advance by examining the typical composition of the contaminant.

[0015] In some cases, it is desirable to completely remove any contaminant from the surface area. In other cases, it may be advantageous to leave an amount of contaminant on the surface. For example, in case of a coke oven door, the sealing properties of the door can be enhanced by leaving a smaller layer of contaminant like tar or grease on the surface. In this case, the plastic properties of the surface layer allow for a better sealing effect than the mostly rigid material (e.g.

steel) of the surface. Also, a small layer of contaminant on the sealing surface or a refractory part may be used a protective layer. According to such an embodiment, | only an upper layer of the contaminant is removed while a lower layer of the | contaminant is intentionally left on the surface area. “An upper layer” and “a lower | layer” is of course to be understood as referring to at least one upper/lower layer | or may also referred to one upper/lower layer that has an interior layered structure. | Selective removal of the upper layer may be achieved by adjusting the radiation / time or intensity of the layer or by adjusting the frequency spectrum to the | absorption maximum of an upper layer component, if this is different from the | lower layer. |

[0016] To provide for an efficient cleaning process that requires no or minimal | human intervention, it is preferred that the target area of the laser beam is moved | automatically along a surface of the coke oven component. This may be achieved | by translationally moving and/or rotating the laser emitter. As the target area | moves along the surface, different surface areas can be cleaned. |

[0017] Preferably, the method comprises moving the laser emitter with a three- | dimensionally movable positioning mechanism. In particular, the laser emitter can | be mounted to an articulated robot arm, which may in turn be mounted on additional horizontal and/or vertical rail systems. Such a robot arm may comprise e.g. two or three arm segments that are movable relative to each other and to a base about respective joints that define rotation axes. The additional horizontal and/or vertical rail systems allow increasing the range of the mechanism, without increasing the dimensions and costs of the articulated robot arm. Other positioning mechanisms are possible, but an articulated arm normally provides the highest | degree of variability to handle different geometries of a coke oven component. It is understood that in this embodiment, the laser emitter (and the target area) is normally moved automatically, i.e. without human intervention. |

[0018] Especially if one and the same component is cleaned by the inventive method time and again, a predefined motion pattern may be used for the laser emitter. Especially, but not exclusively, if a variety of different components need to be cleaned, the method may comprise automatically detecting a geometry of the surface and automatically positioning the laser emitter according to the detected geometry. The surface geometry or surface shape may be detected in various ways, wherein non-contact methods are preferred. Such methods include recording and processing a video image as well as using ultrasonic sensors, radar sensors or lidar sensors.

[0019] As mentioned above, the removed contaminant may in particular be in the form of gas or dust particles. Either way, it can be easily be removed with a gas stream. According to a preferred embodiment, the method comprises conveying removed contaminant to a disposal area at least partially applying underpressure. In other words, an underpressure is created with respect to the volume around the target area of the laser beam, and this under pressure sucks the contaminant along with a gas stream to the disposal area. In the disposal area or on the way to the disposal area, the contaminant may be removed from the gas stream by an active or passive filter or by other gas cleaning devices. Normally, the underpressure is applied to the disposal area itself.

[0020] Even if the method is carried out within the coke oven plant itself and even though a certain degree of contamination is normal in such a plant, it is desirable to prevent the removed contaminant from escaping to the environment. Therefore, the method may comprise positioning the coke oven component and the laser emitter in a closed container (which may also be referred to as “cleaning box”), whereby gas exchange between the inside of the container and the outside is at least reduced. If the laser emitter is moved by a three-dimensionally movable positioning system, it is preferred to place the entire system (e.g. the robot arm) inside the container. The term “container” is to be understood in a wider sense and may also refer to a room or chamber inside a building that can be separated from its surroundings. On the other hand, the container does not need to have a solid or rigid wall but could be established by gas-tight sheets placed around the coke oven component and the laser emitter. In general, gas exchange between the inside of the container the outside does not need to be prevented totally, but only needs to be reduced or controlled. One could also say that uncontrolled gas exchange is prevented. Such a container comprising the cleaning system therein may be mounted on a movable platform (e.g. of a coke oven service machine) and moved towards the coke oven component to be cleaned. Alternatively, the container comprising the cleaning system may be located stationary in the coke oven area and include a frame to hold the coke oven component placed there by e.g. a coke oven machine.

[0021] Preferably, removed contaminant is conveyed by underpressure from the inside of the container to the disposal area. Normally, an underpressure is applied to the disposal area itself so that a pressure difference exists between the inside of the container and the disposal area, accordingly, a gas stream that contains the removed contaminant is sucked from the inside of the container. It is understood that in order to maintain the gas stream, fresh gas needs to be provided to the inside of the container. Normally, the gas stream entirely or mostly consists of ambient air, which can be provided to the inside of the container from the environment.

[0022] In some cases, the cleaning method is performed with the coke oven component installed at the coke oven. Usually however, surface areas that are in critical need to be cleaned may not be sufficiently accessible while the component is installed. Thus, the method may comprise, before positioning the laser emitter,

removing the coke oven component from the coke oven by means of a service machine. The service machine then positions the coke oven component to be cleaned inside the above-mentioned container. Of course, the coke oven component is re-installed after all relevant surface areas have been cleaned.

[0023] The invention further provides a system for cleaning a coke oven component. The system comprises a laser emitter and is configured to position the laser emitter so that a target area of the laser emitter is within a contaminated surface area of the coke oven component, emit a laser beam onto the contaminated surface area, whereby a contaminant at least partially absorbs the laser beam and is heated, and remove heated contaminant from the surface area..

All these terms have been explained above with respect to the inventive method and therefore will not be explained again. Preferred embodiments of the inventive system correspond to those of the inventive method. According to some preferred embodiments, the system may comprise a three-dimensionally movable | positioning mechanism to which the laser emitter is mounted, a container inside which the laser emitter and the coke oven component can be positioned, a piping for connecting the inside of the container with a disposal area, a vacuum source for creating and underpressure to convey a gas stream (with removed contaminant) from the container to the disposal area, at least one device for separating contaminant from the gas stream etc.

Brief Description of the Drawings

[0024] Further details and advantages of the present invention will be apparent from the following detailed description of not limiting embodiments with reference to the attached drawing, wherein: Fig.1 is a sectional view of a contaminated surface area of a coke oven component; Fig.2 is a sectional view corresponding to fig. 1 schematically illustrating the working principle of the inventive method; and Fig.3 schematically shows a system for performing the inventive method. | RE AE |

| P-PWU-786/LU 10 LU101809 Description of Preferred Embodiments

[0025] Fig.1 shows a sectional view of a surface area 4 of a coke oven door 1. The surface area 4 is contaminated after the coke oven being in operation for an extended time period. A contaminant 5, 6, 7 is disposed on a metal substrate 2 which forms a surface 3 of the coke oven door 1. Such a contaminant 5, 6, 7 may comprise a first and a second contamination layer 5, 6 comprising grease, oil, tar and/or inorganic contaminants. Various dust or dirt particles 7 may be partially disposed within the second contamination layer 6 and partially on top of it.

[0026] According to the inventive method, the contaminated surface area 4 can be cleaned using a laser beam 25 as illustrated in Fig.2. The laser beam 25, which comprises a sequence of high-intensity pulses, is directed at a target area 26 (or target point) within the contaminated surface area 4 and irradiates the contaminant 5, 6, 7. The laser beam 25 is primarily absorbed by the contamination layer 5, 6. The characteristics of the laser beam 25 (e.g. its frequency spectrum) is adapted so that it is primarily reflected by the metal substrate 2, which is therefore mostly unaltered by the laser beam 25. Most components of the contaminant, on the other hand, are evaporated and turned into gas or plasma 8 by the heating effect caused by absorption of the laser beam 25. The sudden expansion of the gas or plasma 8 leads to shockwaves which may also blast some parts of the contaminant 5, 6, 7 off the surface even if they are not evaporated. Thus, the contaminant 5, 6, 7 can be removed from the surface 3. As schematically shown in Fig.2, the removed contaminant, i.e. the plasma 8 along with dust 9, can then be collected by a suction device 22 that works by a pressure difference. The suction device 22 is only schematically depicted in Fig.2 as a tube in proximity to the target area 26. Although such a configuration is possible, a different configuration may be preferred, if sufficient space is available, as will be described with respect to Fig.3.

[0027] Fig.3 schematically shows a system 10 for performing the inventive method. An articulated robot arm 12 with a laser emitter 11 is disposed in proximity of an oven door 1 that needs to be cleaned. A container 16 (which may also be referred to as a cleaning and safety box) is disposed around the robot arm

12 as well as the coke over door 1. In order to protect the robot arm from the plasma 8 and dust 9, it is covered by a flexible protection suit 15. The walls of the container 16 may be made of gas-tight sheets or other suitable material that serves to at least reduce gas exchange between the inside of the container and the outside.

À suction hood 17 is disposed at the top of the container 16 and is connected via a piping 18 to a vacuum pump 20 in a disposal area 21. A dedusting and filter device 19 is disposed between the vacuum pump 20 and the suction hood 17. The laser emitter 11 is connected to a laser supply unit 13 that is disposed outside of the container 16 and supplies the laser beam 25 to the laser emitter 11 via an optical cable 14. In Fig.3, the coke oven door 1 is shown being carried by a door handling tool 30 of a coke oven service machine.. The door handling tool 30 is designed and configured to remove the coke oven door 1 from the coke oven and to move it so as to position it within the container 16. The door handling tool 30 is further designed and configured to move the coke oven door 1,

after cleaning, back into its position in front of the coke oven and to reinstall it. | Alternatively, the coke oven door 1 may be placed by the door handling tool 30 | onto a holding frame, which may be moved in position within the container 16. | | While the coke oven door 1 may be placed in the container by the door handling | tool 30 or the holding frame, it should be noted that it is also possible to move the | container 16 so as to encompass the coke oven door 1. During the cleaning / process, the laser emitter 11 is positioned automatically by the robot arm 15 so | that the target area 26 is in a surface are that needs to be cleaned.

In order to | clean the entire door 1, the laser emitter 11 is moved by the robot arm 15 so that | the target area 26 is moved along the surface 3 of the coke oven door 1. The robot | arm itself may be mounted on additional horizontal and/or vertical rail systems (not | shown). The motion pattern of the robot arm 15 can be predefined according to a | known geometry of the coke oven door 1. Alternatively, the geometry can be | detected automatically, e.g. by non-contact sensors (such as for example | cameras, laser scanners) installed in the robot arm 15 or the on the container 16, | and an appropriate motion pattern can be determined based on the detected | geometry. ‘

[0028] Fig.2 shows a complete removal of all contaminant 5, 8, 7 from the surface 3 of the coke oven door 1. Alternatively, only an upper layer could be removed while a lower layer is intentionally left on the surface 3. For instance, the first contamination layer 5 and at least a part of the second contamination layer 6 could remain on the surface 3, while the particles 7 are removed. This could be achieved by adjusting the total exposure time of the contaminant to the laser beam 25 or by adapting the characteristics of the laser beam 25 so that it is mostly absorbed by the particles 7. The optimum characteristics of the laser beam 25 for a desired absorption effect can be determined in advance by experiment.

Claims

13 LU101809 | Claims |

1. A method for cleaning a coke oven component (1), the method comprising: | - positioning a laser emitter (11) with respect to the coke oven component | (1) so that a target area (26) of the laser emitter (11) is within a | contaminated surface area (4) of the coke oven component (1); | - emitting a laser beam (25) onto the contaminated surface area (4), | whereby a contaminant (5, 6, 7) at least partially absorbs the laser beam | (25) and is heated; and : - at least partially removing the heated contaminant (5, 6, 7) from the | surface area (4). :

2. A method according to claim 1, characterized in that the coke oven | component (1) comprises a coke oven door. |

3. A method according to any of the preceding claims, characterized in that the | contaminant (5, 6, 7) is at least partially removed from the surface area (4) by | the heating process. |

4. A method according to any of the preceding claims, characterized in that the : contaminant (5, 6, 7) is at least partially evaporated. |

5. A method according to any of the preceding claims, characterized in that the : laser beam (25) is emitted as a sequence of laser pulses. :

6. A method according to any of the preceding claims, characterized in that a | laser beam (25) is emitted and is adapted to be primarily absorbed by the contaminant (5, 6, 7) while being primarily reflected by the surface (3) of the | coke oven component (1). |

7. A method according to any of the preceding claims, characterized in that only | an upper layer of the contaminant (5, 6, 7) is removed while a lower layer of ; the contaminant (5, 6, 7) is intentionally left on the surface area (4). |

8. A method according to any of the preceding claims, characterized in that the | target area (26) of the laser beam (25) is moved automatically along a ; surface (3) of the coke oven component. |

14 LU101809 |

9. A method according to any of the preceding claims, characterized in that it | comprises moving the laser emitter (11) with a three-dimensionally movable | positioning mechanism (12). |

10. A method according to any of the preceding claims, characterized in that it | comprises automatically detecting a geometry of the surface (3) and | automatically positioning the laser emitter (11) according to the detected | geometry. |

11. A method according to any of the preceding claims, characterized in that it | comprises conveying removed contaminant (8, 9) to a disposal area (21) at | least partially by applying underpressure. |

12. A method according to any of the preceding claims, characterized in that it | comprises positioning the coke oven component (1) and the laser emitter | (11) in a closed container (16), whereby gas exchange between the inside of .

the container (16) and the outside is at least reduced. .

13. A method according to any of the preceding claims, characterized in that | removed contaminant (8, 9) is conveyed by underpressure from the inside of .

the container (16) to the disposal area (21). |

14. A method according to any of the preceding claims, characterized in that it | comprises, before positioning the laser emitter (11), removing the coke oven | component (1) from the coke oven and, after removing the contaminant (5, 6, . 7) from the surface area (4), re-installing the coke oven component (1). ;

15. A system (10) for cleaning a coke oven component (1), the system ‘ comprising a laser emitter (11) and being configured to: .

- position the laser emitter (11) so that a target area (26) of the laser | emitter (11) is within a contaminated surface area (4) of the coke oven | component (1); .

- emit a laser beam (25) onto the contaminated surface area (4), whereby | a contaminant (5, 6, 7) at least partially absorbs the laser beam (25) ! and is heated; and | - remove heated contaminant (5, 6, 7) from the surface area. ,