Impact rapping device

Abstract

The present application relates to an impact rapping device (10) for removing solid matter on components of a boiler of an incineration plant, comprising an impact cylinder (12) comprising a cylinder housing (14) containing an impact piston (16) linearly movable between a retracted position and an extended position, an attachment element (20) for attaching the impact cylinder (12) to a boiler (24), a linearly movable anvil (22) arranged between the impact piston (16) and a component (26) of the boiler, and a linearly movable impact weight element (34) arranged between the impact piston (16) and the anvil (22), wherein the impact weight element (34) is located outside of the cylinder housing (14), wherein the impact weight element (34) is connected to the impact piston (16) via a piston rod (18), and wherein the impact rapping device (10) is arranged so that when the impact cylinder is attached to a boiler, activation of the impact piston (16) from the retracted position forces the impact weight element (34) to impact the anvil (22) and the anvil to impact the component (26) of the boiler.

Description

[0001] IMPACT RAPPING DEVICE

[0002] TECHNICAL AREA

[0003] The present application relates to an impact rapping device to be used for removing solid matter on components in a boiler of an incineration plant.

[0004] BACKGROUND OF INVENTION

[0005] Incineration plants are used widely in the world for incinerating waste material of different types. These plants comprise boilers in which the heat from the incineration is recovered. In this regard, the boiler comprises a plurality of pipes in which liquid is circulated. The liquid is heated by the heat to form steam, which steam drives steam turbines that in turn drive generators for creating for instance electricity.

[0006] The incineration process, apart from heat, creates solid matter such as ash and soot. The solid matter is handled in the process to avoid as much as possible that the exhaust gases from combustion contain solid substances. However, in the incineration process, the solid matter tends to adhere to components inside the boiler, e.g. on the pipes and headers inter-connecting the pipes. The adherence of solid matter will deteriorate the efficiency of heat transfer to the liquid and thus the performance of the process.

[0007] In order to remove solid matter from components inside the boiler, different methods and equipment have been developed, such as blowing with steam, pressurized air or sonically. Also mechanical solutions have been developed such as rapping devices. The rapping devices will hit components of the boiler in order to create rapid vibrations with low amplitude. The vibrations cause the solid matter to loosen from the components.

[0008] A conventional rapping solution comprises a plurality of anvils extending through the boiler wall, with an inner end in contact with the boiler components. A rotating shaft with movable weights is arranged outside the boiler, and as the shaft rotates, the weights hit outer ends of the anvils, thereby creating the vibrations. These mechanical solutions are noisy, difficult to service and it is not possible to provide individual rapping schemes for individual anvils. Another solution has been developed wherein individual pneumatic cylinders are used for each anvil. When the cylinders are activated, they create an impact force on the anvils, in turn creating the vibrations. The advantage with this solution is that it is less noisy and that the individual cylinders may be activated independent of other cylinders, thereby providing individual rapping schemes.

[0009] A drawback is that it is difficult for conventional, more standardized, cylinders to create the required impact force needed for a good rapping result. One solution is then to provide the cylinder with a movable piston that has an increased weight in comparison with the standardized cylinders in order to obtain the necessary impact force. However, it has been shown that the weight of the piston has adverse effects on the cylinder, causing it to break down which leads to inferior cleaning of the boilers and increased maintenance and replacement of components.

[0010] There is thus room for further improvements in this technical area.

[0011] BRIEF DESCRIPTION OF INVENTION

[0012] The aim with the present application is to remedy the drawbacks with the state of the art solutions. This aim is obtained with an impact rapping device according to the independent patent claim. Preferable embodiments of the impact rapping device form the subject of the dependent patent claims.

[0013] According to an aspect of the invention, an impact rapping device for removing solid matter on components of a boiler of an incineration plant is provided, that may comprise an impact cylinder comprising a cylinder housing containing an impact piston linearly movable between a retracted position and an extended position, an attachment element for attaching the impact cylinder to a boiler, a linearly movable anvil arranged between the impact piston and a component of the boiler, and a linearly movable impact weight element arranged between the impact piston and the anvil, wherein the impact weight element is located outside of the cylinder housing, wherein the impact weight element is connected to the impact piston via a piston rod, and wherein the impact rapping device is arranged so that when the impact cylinder is attached to a boiler, activation of the impact piston from the retracted position forces the impact weight element to impact the anvil and the anvil to impact the component of the boiler.

[0014] With this solution, a rather conventional and standardized cylinder may be used that together with the impact weight element creates the energy required for good rapping results. Thus, no special or essentially modified cylinders are required, thus lowering the cost of the impact rapping device. Moreover, maintenance of the device is simplified, while the functionality of individually controlled rapping devices is maintained.

[0015] In order to provide impacts with a certain frequency, the impact cylinder may be arranged for reciprocal movement of the impact piston and the impact weight element. Moreover, in order to create the required impact energy, a distance may be provided between the anvil and the impact weight element in the retracted position so as to obtain an acceleration of the impact weight element before impacting the anvil.

[0016] According to a further aspect, the impact weight element may be located in the attachment element and the attachment element may be formed as a guide for the impact weight element so as to ascertain correct impact of the impact weight element against the end surface of the anvil.

[0017] According to yet an aspect, the impact rapping device may further comprise a spring element for biasing the anvil in contact with the boiler component, in order to prevent a gap between the anvil and the component.

[0018] According to another aspect, the activation pressure of the impact cylinder and the weight of the impact weight element may be chosen so as to create an impact energy of between 100 - 200 Joule, preferably around 150 Joule. This magnitude of impact energy has shown to provide vibrations that remove solid matter while minimizing the risk of damage to the components. In this regard, the weight of the impact weight element may be between 3 - 7 kg, preferably around 5 kg. The impact cylinder of the impact rapping device may be driven by pressurized air. Further, a boiler for an incineration plant is further provided, comprising an impact rapping device according to the application.

[0019] These and other aspects of, and advantages with, the present invention will become apparent from the following detailed description of the invention and from the accompanying drawings.

[0020] BRIEF DESCRIPTION OF DRAWINGS

[0021] In the following detailed description of the invention, reference will be made to the accompanying drawings, of which

[0022] Fig. 1 is a schematic side view of an impact rapping device in a first position, and

[0023] Fig. 2 is a schematic side view of the impact rapping device of Fig. 1 in a second position.

[0024] DETAILED DESCRIPTION OF THE INVENTION

[0025] An impact rapping device 10 is shown in Fig. 1. It comprises an impact cylinder 12 with a cylinder housing 14. Inside the cylinder housing 14, a linearly movable impact piston 16 is arranged. An impact piston rod 18 is attached to the impact piston 16, and the impact piston rod 18 extends through a passage of the cylinder housing 14 with a free end external of the cylinder housing 14. The impact cylinder 12 may be driven by pressurized air from a source of pressurized air, such as a compressor, via suitable conduits. In this regard, it is also feasible that the impact cylinder is hydraulically driven with pressurized oil. The impact cylinder 12 is provided with two inlets on each side of the impact piston 16 so as to allow a reciprocal movement of the impact piston 16 between a first retracted position and a second extended position. The impact cylinder 12 is attached to a boiler with an attachment element 20. In the embodiment shown, the attachment element 20 is tubular.

[0026] Further, an anvil 22 is provided in the form of an elongated rod that is linearly movable. The anvil 22 extends through the wall 23 of a boiler 24 and in contact with a component 26 inside the boiler 24, for example recovery tubes or headers of tube banks. The anvil 22 is supported by a tubular support element 28. The anvil 22 is further provided with a compression spring 30 that is biased between a support surface of the anvil 22 and a support surface of the attachment element 20 so that the anvil 22 is biased to be in contact with the component 26 inside the boiler 24. Moreover, the impact cylinder 12 and the impact piston rod 18 are aligned with the anvil 22, wherein they coincide with a centre axis A.

[0027] According to the application, an impact weight element 34 is attached to the external end of the impact piston rod 18 of the impact cylinder 12. The impact weight element 34 is arranged to impact an outer end surface of the anvil 22. Further, the attachment element 20 may be designed such that the impact weight element 34 is guided by it. For example, the impact weight element 34 may have a circular cross-section and the attachment element being tubular 20. The length of the attachment element 20 and the length of the impact weight element 34 may be chosen such that there is a distance 36 between the impact weight element 34 and the end of the anvil 22 when the impact piston 16 of the impact cylinder 12 is in the retracted position.

[0028] When the impact cylinder 12 is activated, the impact piston 16 and the impact piston rod 18 are moved rapidly from the retracted position towards the extended position, Fig. 2, whereby the impact weight element 34 is accelerated and impacts the anvil 22 with a certain energy, which energy is transferred to the component 26, causing vibrations in the component 26 and further components attached thereto. The vibrations cause solid matter that has been deposited on the component or components to loosen. After the impact, the impact piston 16 of the impact cylinder 12 and the impact weight element 34 are moved back to the retracted position. The activation of the impact cylinder 12 is then performed at certain intervals in order to clean the components inside the boiler.

[0029] It has been shown that an impact energy of about 100 - 200 Joule, preferably around 150 Joule, is sufficient for effectively removing solid matter without causing excessive mechanical stress on the components subjected to the impacts. In this regard, the pressure of the pressurized air or liquid as well as the weight of the impact weight element are chosen such that the required impact energy is obtained. A suitable weight of the impact weight element 34 has been shown to be about 3 - 7 kilograms, preferably around 5 kilograms, for the required impact energy.

[0030] It is to be understood that the embodiment described above and shown in the drawings is to be regarded only as a non-limiting example and that it may be modified in many ways within the scope of the patent claims.

Claims

PATENT CLAIMS1 . An impact rapping device (10) for removing solid matter on components of a boiler of an incineration plant, comprising- an impact cylinder (12) comprising a cylinder housing (14) containing an impact piston (16) linearly movable between a retracted position and an extended position,- an attachment element (20) for attaching the impact cylinder (12) to a boiler (24),- a linearly movable anvil (22) arranged between the impact piston (16) and a component (26) of the boiler, and- a linearly movable impact weight element (34) arranged between the impact piston (16) and the anvil (22), wherein the impact weight element (34) is located outside of the cylinder housing (14), wherein the impact weight element (34) is connected to the impact piston (16) via a piston rod (18), and wherein the impact rapping device (10) is arranged so that when the impact cylinder is attached to a boiler, activation of the impact piston (16) from the retracted position forces the impact weight element (34) to impact the anvil (22) and the anvil to impact the component (26) of the boiler.

2. The impact rapping device (10) according to claim 1 , wherein the impact cylinder (12) is arranged for reciprocal movement of the impact piston (16) and the impact weight element (34).

3. The impact rapping device (10) according to claim 2, wherein a distance (36) is provided between the anvil (22) and the impact weight element (34) in the retracted position so as to obtain an acceleration of the impact weight element (34) before impacting the anvil (22).

4. The impact rapping device (10) according to any one of the preceding claims, wherein the impact weight element (34) is located in the attachment element (22) and the attachment element (22) is formed as a guide for the impact weight element (34).

5. The impact rapping device (10) according to any one of the preceding claims, further comprising a spring element (30) for biasing the anvil (22) in contact with the boiler component (26).

6. The impact rapping device (10) according to any one of the preceding claims, wherein the activation pressure of the impact cylinder (12) and the weight of the impact weight element (34) are chosen so as to create an impact energy of between 100 - 200 Joule, preferably around 150 Joule.

7. The impact rapping device (10) according to claim 6, wherein the weight of the impact weight element (34) is between 3 - 7 kg, preferably around 5 kg.

8. The impact rapping device (10) according to any one of the preceding claims, wherein the impact cylinder (12) is driven by pressurized air.

9. A boiler (24) for an incineration plant comprising an impact rapping device (10) according to any one of the preceding claims.

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