DK180366B1 - Method and apparatus for cleaning boiler surfaces in an incineration plant - Google Patents

Abstract

When cleaning open boiler draft surfaces in an open draft (17, 18, 19) of an incineration plant in use, an apparatus with a rotating nozzle head mounted on a line (7) of cleaning liquid is used. During a first cleaning, the nozzle head (4) is rotated in one direction and during a second cleaning, it is rotated in an opposite direction, which has an improved cleaning effect.

Description

TECHNICAL FIELD The present invention relates to a method and an apparatus for cleaning open boiler draft surfaces in an incineration plant. The invention also relates to a cleaning head. Background Art In apparatus for cleaning boiler surfaces in an incinerator, it is known to use a nozzle head with several nozzles to supply a cleaning liquid to the boiler surfaces to be cleaned, where the nozzle head is rotated and moved linearly into and out of the combustion chamber. An apparatus of this kind is known from US 5,579,726, which describes such a device for cleaning a boiler in use, the device comprising a lance and a rotating nozzle head mounted on the end of the lance, as well as means for providing a linear movement into and out of the combustion chamber and means for rotating the cleaning head. The lance in this device is a rigid construction and the rotary and linear movements are provided by means of motors mounted externally on the combustion chamber to be cleaned. In all constructions shown and described in this document, the linear movement is in the horizontal direction, and therefore the lance must have a rigid structure. Another cleaning apparatus is known from DE 1 262 496. Another principle for a vertical movement is described in EP1291598, where the nozzle head comprises a turbine and an exchange such that the head rotates more slowly than the turbine. In order to achieve the best possible results for boiler cleaning, there is a continuing need for improvements.

Disclosure of the Invention It is the object of the present invention to provide an improvement in the technical field. In particular, it is an object to provide an improved method and apparatus for cleaning open boiler draft surfaces in an incinerator of the type indicated above. This object is achieved with a method for cleaning open boiler draft surfaces in an open draft of an incineration plant in use as explained below.

The method comprises - providing an apparatus with a cleaning head mounted on a conduit, typically on one end of the conduit, for example flexible hose which carries cleaning fluid to the cleaning head, the cleaning head having a rotating nozzle head driven by the flow of the cleaning liquid itself through the cleaning head, for example by means of a turbine and gear as explained in EP1291598, - to carry out a cleaning by introducing, for example immersing, this cleaning head in the open draft and - to remove deposits on the boiler draft surfaces by spraying cleaning liquid from the cleaning head towards the boiler draft surfaces during cleaning with rotation from the nozzle head.

It has been found that the method of immersing a cleaning head as described in EP1291598 can be improved by a very simple measure in which the direction of rotation is changed periodically between rotation of the nozzle head counterclockwise and clockwise.

By changing the direction of rotation, it has been found that not only corners are cleaned more efficiently but also surfaces, as the strong expansion of the liquid during evaporation on contact with the walls works better if it takes place at changing angles of incidence on the wall.

In addition, it is easier to reach into cracks and behind pipes.

Experimental results of such an approach far exceed what would be expected from a theoretical consideration.

The apparatus is then provided in one embodiment with a cleaning head, where the direction of rotation of the nozzle head can be changed.

A suitable gear then shifts between the directions of rotation.

Alternatively, the apparatus comprises a single cleaning head with two nozzle heads, for example arranged in extension of each other and driven simultaneously in opposite directions by a gear connected to each nozzle head for rotation thereof in opposite directions.

In another alternative, a first cleaning head is replaced with a second corresponding cleaning head between a first and a second cleaning, the first and second cleaning heads having nozzle heads with opposite rotation.

For example, the apparatus is designed for cleaning with only a single cleaning head at a time, and where the two cleaning heads are designed with a coupling for optional mounting of one or the other cleaning head on the pipe.

DK 180366 B1 3 Using two nozzle heads with different directions of rotation instead of a single one with a mechanism to change direction of rotation results in a simpler construction, which is typically more robust than if mechanical elements, for example gears, are added to change direction of rotation in a single cleaning head. It may immediately seem like a simple consideration, but it should be remembered that the nozzle head is immersed in the boiler, but it is in operation, which means that the nozzle head is introduced, for example immersed, in an aggressive flue gas environment where there is a temperature of 800-1000 degrees Celsius and where the water sprayed on the walls expands 1500-1700 times with a similar turbulence in the draft, which puts a significant load on the nozzle head, regardless of whether it is continuously cooled with the water running through the nozzle head. In order to provide high reliability and long durability, a simple construction of the nozzle head is preferable.

It has also been found that it is not necessary to change direction every time the nozzle head is immersed. For example, it is sufficient to change direction after a number of cleaning processes of 2 to 14 times, for example after two weeks of use. This means in practice that two one-way rotating nozzle heads with opposite direction of rotation can be used, where switching between the cleaning heads takes place after a number of cleaning processes.

The cleaning head is then for insertion in the open draft and during cleaning mounted on a wire, for example a flexible hose in case of hoisting, typically steel-reinforced hose. The flexible hose is advantageously a bellows-type metal hose, preferably of stainless steel. It is typically immersed through an opening located at the top of the open draft to be cleaned and passed downwards, while cleaning fluid is supplied to the nozzles for supply to the surfaces to be cleaned in an efficient manner. The flexible hose construction minimizes the size of the space required to insert the cleaner into the open draft, allowing the appliance to be used in conjunction with existing plants substantially without modification.

Alternatively, the cleaning head is inserted with a rigid wire, such as a hollow rod, in a horizontal or inclined direction.

DK 180366 B1 4 Since the appliance is placed inside the open draft only during the cleaning operations, the construction can be relatively simple, as the cleaning liquid will largely keep the construction cold during the cleaning operation, and the construction will therefore not have to withstand the high temperatures of typically 800-1000 degrees Celsius inside the open draft in the incineration plant in use. In practical embodiments, the cleaning head comprises a turbine chamber and a nozzle head connected thereto rotatably with several nozzles, from which the cleaning liquid is sprayed out towards the boiler draw surfaces during rotation of the nozzle head. The turbine chamber contains a turbine driven by the cleaning fluid in its flow from the line, for example the hose, to the nozzles, where a gear exchange between the turbine and the nozzle head drives the nozzle head and reduces the speed of the nozzle head rotation relative to the turbine. A typical rotational speed of the nozzle head is between 1 and 50, preferably between 5 and 10, revolutions per minute. minute.

In some embodiments, the apparatus comprises a mechanism for providing a substantially linear, for example vertical, movement of the nozzle head within the open feature. For example, the mechanism comprises a hose wheel with a drive unit for lowering and raising the cleaning head on the flexible hose, for example on the end of the flexible hose, downwards and upwards within the open pull. For example, the drive unit for the hose reel is a speed-controlled gear motor. Typically, cleaning fluid is supplied to the nozzle head from a feedwater pump, which passes the cleaning fluid through the line, for example the flexible hose, at a predetermined pressure. The feed water pump is, for example, pressure controlled to a pressure level of less than 10 bar for the cleaning liquid. It is an advantage that the nozzles of the nozzle head are of a type which keeps the jet flowing out of the nozzles concentrated with only a small solution in drops. In particular, it is noted here that there may be a distance of 10-20 meters from the nozzle to the wall of the draft, and a atomization is then undesirable, not least due to the high turbulence due to the strong expansion of the cleaning liquid during evaporation.

DK 180366 B1 It has also been found to be advantageous in certain situations to reduce the amount of water. This is not a simple problem, as a reduction in the amount of water can mean that the water jet does not keep its direction during rotation to hit the wall at a distance of several meters if it is not strong enough. It must thus be ensured that the water jet 5 has the correct pressure. With a nozzle head according to the prior art, as described in EP1291598, it has been found to give problems of the above kind with a lower amount of water supply. In particular, it has been found that a lower amount of water is not able to drive the turbine sufficiently strongly so that the rotation becomes slower. A completely new dimensioning is complex, as not only must it be ensured that the head rotates sufficiently but also that there is still sufficient pressure and flow in the water to provide a satisfactory cleaning of the boiler.

This problem has been solved in a simple manner in relation to the cleaning head in EP1291598 by tilting the inlet ducts of the cleaning liquid to the turbine. By hitting the turbine with the cleaning fluid at a steeper angle, it has surprisingly been found that there is more traction on the turbine with less consumption of cleaning fluid, for example water, while at the same time there is sufficient pressure on the nozzle to produce a jet with several meters range for cleaning the walls of the boiler draft.

For example, the turbine chamber contains a turbine flange with channels that conduct cleaning fluid from the line to the turbine. The turbine has an axis of rotation and turbine blades that have a surface with a normal that extends perpendicular to the surface. The normal of the turbine blade is angled by an angle w in relation to the axis of rotation of the turbine. In a particularly advantageous embodiment, the ducts are inclined at an angle v relative to the axis of rotation in order to strike the turbine at a steeper angle of incidence thereto. For example, the ratio vw is in the range 0.1 to 0.9, preferably between 0.2 and 0.8. For example, the angle v is in the range of 20-40 degrees. As an example, the angle v is in the range of 25-35 degrees, such as about 30 degrees, and the angle w of the normal is in the range of 40-50 degrees, such as about 45 degrees. The ratio is then in the latter concrete case v: w = 30: 45 = 0.67.

Preferred embodiments of the cleaning apparatus according to the present invention, the advantages of which will be described in the following detailed part of the present invention, are set out in the subclaims.

BRIEF DESCRIPTION OF THE DRAWINGS In the following detailed description of the present invention, the invention will be explained in more detail with reference to an exemplary embodiment of an apparatus for cleaning open boiler draft surfaces in an incineration plant according to the invention and shown in the drawing, in which fig. 1 - schematically shows an incineration plant in which the present invention is implemented, fig. Fig. 2 schematically shows a cleaning head in cross section, as is known from the prior art and which can in principle be used for the improved cleaning method; 3 - schematically shows a hose reel with a drive unit for controlled lowering and raising of the cleaning head as well as a pump unit for supplying cleaning liquid to the flexible hose, and fig. 4 - shows a set of two nozzle heads with opposite direction of rotation; fig. 5 - shows a strange that two opposite turbines with a) perspective towards the turbine blade and b) with perspective on top of the turbine flange.

Description of the Preferred Embodiment The incinerator shown in FIG. 1 comprises three successive open features 17, 18, 19, where heat is transferred from flue gases to boiler pipes covering the walls of the open features 17, 18, 19. After the open features 17, 18, 19, a superheater 20 or several such superheaters or other boiler constructions. In such a plant it is desired to keep the heat exchanger surfaces clean in the open features 17, 18, 19 in order to reduce the heat transmission resistance from flue gases to boiler pipes.

The cleaning apparatus implemented in the incinerator shown in fig. 1, which is in principle known from EP1291598, comprises a cleaning head 1, as shown in FIG. 2, mounted on the end of a flexible hose 7 for insertion and immersion inside the open draft 17 through an opening 16 centrally located at the top of the open draft 17.

DK 180366 B1 7 the linear movement of the wood 1 inside the open pull 17 is provided by the rotating hose roller 6, on which the hose 7 is mounted. The rotation of the nozzle head 4, as shown in fig. 2, is provided by means of a turbine 2 driven by cleaning liquid, for example water, which enters the cleaning head 1 from the flexible hose 7 and is supplied to the turbine 2 in the turbine chamber 22 through channels 21 in a turbine flange 23 in which the turbine 2 is camped. In order to reduce the rotational speed of the nozzle head 4, there is an exchange 3 between the turbine 2 and the nozzle head 4. The exchange comprises an external gear 31 arranged on the turbine shaft, which drives a gear 32, the shaft of which drives a gear by means of an external toothing 33 34 attached to the cleaning head 4. Several nozzles 5 are mounted on the nozzle head 4 to distribute the cleaning liquid in different directions during the rotation of the nozzle head 4.

As shown in FIG. 3, the hose reel 6 is suspended for rotation on a shaft driven by a drive unit 8 for the hose reel 6, the drive unit 8 comprising an electric motor 9 and a reduction gear mechanism 10. As also shown in fig. 3, the electric motor 9 is controlled from a control unit 15, which controls the motor speed and the direction of rotation of the motor 9.

As also shown in FIG. 3, the cleaning fluid is supplied to the hose 7 by means of a pump unit 11 comprising an electric motor 12 which drives a pump 13. The electric motor 12 is controlled by the control unit 15 to be able to control the pressure of the cleaning fluid supplied to the flexible hose 7 The connection between the pump 13 and the hose reel 6 comprises a rotary coupling 14 to allow the hose reel 6 to rotate relative to the fixed pump 13. As can be seen from fig. 1, each of the open features 17, 18, 19 has a centrally located opening 16 for insertion of the cleaning head 1 and the flexible hose 7 and for lowering and raising the cleaning head 1 downwards and upwards in the open features 17, 18, 19. During immersion and raising of the cleaning head 1, cleaning liquid is supplied through the flexible hose 7, whereby the nozzle head 4 is rotated, and cleaning liquid is supplied to the inner surfaces of the open features 17, 18, 19 through nozzles 5. These nozzles 5 are dimensioned to supply a sex-

DK 180366 B1 8 centered jet of cleaning liquid to the inner surfaces of the open features 17, 18, 19 substantially without the concentrated jets being dissolved in droplets. The cleaning liquid is preferably water which evaporates when it hits the inner surfaces of the open features 17, 18, 19, whereby the water expands to a volume approximately 1500-1700 times its original volume, which expansion provides the forces which are needed to remove dirt from the affected surfaces. As already mentioned, the cleaning is performed during use, ie. the incinerator burns fuel and generates heat, and the surfaces to be cleaned have a high temperature necessary to provide evaporation of the cleaning liquid.

In the event that cleaning is carried out during the operation of the plant, the cleaning can be carried out whenever it is deemed necessary, e.g. by registered rising temperature of flue gases entering the superheater 20, due to dirt on the boiler surfaces, which reduces the heat transmission from the flue gases in the open drafts 17, 18, 19. It is thus possible to keep the temperature of the flue gases passing in a controlled manner into the superheater 20, below a desired maximum temperature of e.g. 600-650 ° C.

In this way, corrosion on the superheater pipes is reduced, and furthermore, a reduction in the temperature of the flue gases in the superheater 20 leads to less sticky deposits on the superheater surfaces. In a typical incinerator, cleaning of each open draft 17, 18, 19 is performed approximately every week, e.g. one of each of the open features 17, 18, 19 is cleaned every other day. In this way it has been found possible to lower the temperature of the flue gases at the entrance to the superheater 20 by approx. 100 ° C.

In an experimental setup, the cleaning liquid used was water and the flexible hose 7 was fed at a jerk of approx. 4 - 5 bar on top of the open features 17, 18, 19, and the nozzle head- it was equipped with 6 nozzles. The time involved in cleaning a single open feature 17 was approx. 5-10 minutes and approx. 1,000 in water was used for the purification.

By the fact that the cleaning system should only be used approx. once a week, a single cleaning system can operate several open features 17, 18, 19 by providing suitable means for inserting the cleaning head 1 and the flexible hose 7 through the corresponding openings.

16.

Although the invention has been described above in connection with a preferred embodiment of the invention as shown in the figures, it will be clear to a person skilled in the art that several deviations are conceivable within the scope of the following claims, such as deviation. - gels, which i.a. comprises providing several openings 16 for each of the open features 17, 18, 19 to be cleaned, to move the cleaning head 1 up and down closer to the surfaces, the openings 16 being located at a distance from the central part of each open features 17, 18, 19, providing automatic means for opening and closing the openings 16, providing several cleaning systems, e.g. a cleaning system for each open feature 17, 18, 19, each such cleaning system comprising its respective cleaning head 1, flexible hose 7 and hose roller 6, etc. FIG. 4 shows a set of cleaning heads 1 with turbine chamber 22 and nozzle heads 4 with nozzles 5 oriented to radiate in opposite directions. In addition, turbines 2 are provided inside the nozzle heads, which are oriented in opposite directions, respectively, as shown in fig. So. The turbine blades 28 have an oblique orientation relative to the axis of rotation 27. The normal 29 to the surface of the turbine blades 28 has an angle w relative to the axis of rotation of the turbine 2

27. In the case of bending turbine blades, the normal 29 is the average normal in the area where the cleaning fluid from the channel 21 hits the turbine blade 28. To increase the pressure of cleaning fluid on the turbine 2, the channels 21 in the turbine flange 23 are inclined at an angle relative to the axis of rotation 27 , which is indicated by the oblique line 25 in fig. 5b relative to the dashed line 26 parallel to the axis of rotation 27. It is noted that the corresponding line 25 'in the second turbine flange is inclined in the opposite direction and adapted to the second turbine having an opposite direction of rotation. ning. By being inclined, the ducts 21 cause a more targeted force effect on the turbine blades 28, which has proven to be an advantage especially with less water flow, which reduces water consumption without deteriorating the cleaning ability. For example, the ratio v: w is in the range 0.1 to 0.8, preferably between 0.2 and 0.8. In the example shown, the angle v is about 30 degrees and the normal angle w is about 45 degrees, so the ratio is about v: iw = 30: 45 = 0.67. FIG. Sc shows a line drawing of the turbine flange 23.

Claims (10)

DK 180366 B1 10 PATENTKRAV A method of cleaning open boiler draft surfaces in an open draft (17, 18, 19) of an incinerator in use, the method comprising - providing an apparatus with a cleaning head (1), the cleaning head (1) being mounted on a line (7) which carries cleaning liquid to the cleaning head (1), the cleaning head (1) having a rotating nozzle head (4), preferably driven by the flow of the cleaning liquid through the cleaning head (1), - to introduce this cleaning head (1) into the open drafts and remove coatings on the boiler draft surfaces by spraying cleaning fluid from the cleaning head (1) against the boiler draft surfaces during cleaning with rotation from the nozzle head (4); characterized in that a first cleaning is performed with rotation in one direction and a second cleaning with rotation in an opposite direction. A method according to claim 1, characterized in that the second cleaning is performed after the first cleaning, and wherein between the first and the second cleaning a first cleaning head is replaced with a second corresponding cleaning head, wherein the first and the second cleaning head have nozzle heads with opposite rotation. Method according to any one of the preceding claims, characterized in that the cleaning head (1) comprises a turbine chamber (22) and a nozzle head (4) rotatably connected thereto with several nozzles (5) from which the cleaning liquid is sprayed out towards the boiler the traction surfaces during rotation of the nozzle head (4), the turbine chamber containing a turbine (2) driven by the cleaning liquid in its flow from the line (7) to the nozzles (5), wherein an exchange (3) between the turbine (2) and the nozzle head (4) reduces the speed of rotation of the nozzle head (1) relative to the turbine (2). Method according to claim 3, characterized in that the turbine chamber contains a turbine flange with channels (21) which direct cleaning fluid from the line (7) to the turbine (2), the turbine (2) having an axis of rotation (27) and turbine blades (28 ) having a normal to their surface, the normal being angled at an angle wi relative to the axis of rotation (27), the channels (21) being inclined at an angle vi relative to the axis of rotation (27) to strike the turbine at a steep angle thereto. angle of incidence, where the ratio v: w is in the range 0.1 to 0.9, preferably between 0.2 and 0.8. DK 180366 B1 11 Apparatus for a method according to any one of the preceding claims, wherein the apparatus comprises a cleaning head (1) for immersion in an open draft (17, 18, 19) of an incinerator in use for cleaning open boiler draft surfaces by spraying. cleaning fluid from the cleaning head (1) towards the boiler draft surfaces during cleaning; wherein the cleaning head (1) is mounted on a conduit (7) which carries cleaning liquid to the cleaning head (1), the cleaning head (1) comprising a turbine chamber (22) and a nozzle head (4) rotatably connected thereto with several nozzles (5) from which the cleaning liquid can be sprayed out towards the boiler draw surfaces during rotation of the nozzle head (4), the turbine chamber containing a turbine (2) driven by cleaning liquid in its flow from the line (7) to the nozzles (5), where an exchange (3) between the turbine (2) and the nozzle head (4) reduces the speed of rotation of the nozzle head (1) relative to the turbine (2); characterized in that the apparatus comprises a first and a second nozzle head (4), the first and the second nozzle head having mutually opposite rotation. Apparatus according to claim 5, characterized in that the apparatus comprises a first and a second cleaning head (1), wherein the first cleaning head (1) comprises the first nozzle head (4), and the second cleaning head (1) comprises the second nozzle head ( 4). Apparatus according to claim 6, characterized in that the apparatus is designed for cleaning with only a single cleaning head at a time, and wherein the two cleaning heads (1) are designed with a coupling for optional mounting of one or the other cleaning head on the line (7). ). Apparatus according to claim 5, 6 or 7, characterized in that the turbine chamber contains a turbine flange with channels (21) which conduct cleaning fluid from the line (7) to the turbine (2), the turbine (2) having an axis of rotation (27) and turbine blades (28) having a normal to their surface, the normal being angled at an angle wi relative to the axis of rotation (27), the channels (21) being inclined at an angle vi relative to the axis of rotation (27) to frame the turbine at a steep angle of incidence, where the ratio v: w is in the range 0.1 to 0.9, preferably between 0.2 and 0.8. Apparatus according to claim 8, characterized in that the angle v is in the range 25-35 degrees and the angle w of the normal is in the range 40-50 degrees. DK 180366 B1 12 A cleaning head for a method according to any one of claims 1-4 or for an apparatus according to any one of claims 5-10, wherein the cleaning head (1) comprises a coupling to a cleaning liquid-carrying line (7) which leads cleaning liquid for the cleaning head (1), the cleaning head (1) comprising a turbine chamber (22) and a nozzle head (4) rotatably connected thereto with several nozzles (5) from which the cleaning liquid can be sprayed out towards the boiler draw surfaces during rotation of the nozzle head (4 ), wherein the turbine chamber contains a turbine (2) driven by cleaning fluid in its flow from the line (7) to the nozzles (5), wherein an exchange (3) between the turbine (2) and the nozzle head (4) reduces the speed of the nozzle head ( 1) rotation relative to the turbine (2); wherein the turbine chamber contains a turbine flange with channels (21) which conduct cleaning fluid from the line (7) to the turbine (2), wherein the turbine (2) has an axis of rotation (27) and turbine blades (28) having a normal to their surface, where the normal is angled at an angle wi relative to the axis of rotation (27), characterized in that the channels (21) are inclined at an angle vi relative to the axis of rotation (27) to strike the turbine at a steep angle of incidence thereto. , that the angle v is in the range 25-35 degrees, and the normal angle wi in the range 40-50 degrees.