EP2384827A1

EP2384827A1 - Method and apparatus for cleaning demister panels

Info

Publication number: EP2384827A1
Application number: EP11161870A
Authority: EP
Inventors: Antonio De Paola
Original assignee: Studio Nuove Applicazioni Industriali Srl
Current assignee: Studio Nuove Applicazioni Industriali Srl
Priority date: 2010-04-13
Filing date: 2011-04-11
Publication date: 2011-11-09
Also published as: ITMI20100620A1; IT1399496B1

Abstract

A method and apparatus (1) is described for cleaning demister panels (2) comprising a frame (3). The apparatus (1) comprises compressed fluid cleaning means (4, 14) suitable for being installed by means of positioning means (8) within the frame (3) and selectively movable therein by means of movement means (9, 11) between a first limit position corresponding to a first edge (5) of the panel and a second limit position corresponding to a second edge (6) of the panel opposite to the first edge (5), thus performing the cleaning substantially of the whole panel (2) during the movement between the first and the second position.

Description

The present invention relates to a method and apparatus for cleaning demister panels.
The demister, also known as mist eliminator or droplet separator, is a device inserted into an apparatus for promoting the separation of the liquid phase (in the form of liquid droplets dragged by the stream) from the gaseous phase in streams of liquid-vapour type.
The use of the demister decreases the time required for the separation, and this results in a smaller volume of the apparatus, and a consequent cost reduction.
The demister is generally formed by a housing which is accessible on two sides, an inlet and an outlet for the stream to be separated, and contains a dense mesh demister, or a metal wire mesh. A collection container is arranged at the outlet of the demister for the liquid phase which has been separated from the gaseous stream.
The operation of the demister is the following: the liquid droplets transported by the gaseous stream knock against the demister meshes, they lose most of their kinetic energy and tend to rest on the demisters meshes; the meshes also provide a surface on which the droplets which remain thereon tend to group together (coalescence) into bigger droplets; when the mass/outer surface ratio of the droplets overcomes a specific quantity, the force of gravity prevails over the force associated with the formation of the liquid-solid interface (related to the surface which defines the small droplets), and the droplets fall into the collection container at the outlet.
It is apparent that cleaning the meshes is fundamental to keep the demister efficient, since an obstruction thereof generates a decreased capacity of the treatable gaseous stream. The chemical-physical nature of the gaseous stream is also typically aggressive and promotes obstructive deposits.
The demister in particular is highly used as a droplet separator for high sulphur fuels, slurry with high concentrations of limestone, salt saturated waters and, in short, chemically and physically aggressive substances, which cause the filtering action of the demisters to decrease if they are not regularly cleaned. These devices are hence subject to frequent machine stops, either for routine cleaning or for extraordinary cleaning.
Incidentally, cleaning the demister panels is generally performed by stopping the system and making the outlet or inlet accessible for the projection of a great quantities of pressurized fluid spray therein, suitable for cleaning the meshes, i.e. filtering material of the panel. Cleaning is performed by specialized personnel who is generally forced to perform it in confined environments, which generates a high percentage of injuries, by orienting a spray-gun with end nozzles towards the panel and passing it over the whole surface. Indeed, the demisters are usually comprised within hollow confining structures in which the operator should enter for the manual cleaning. Access inside said structures is difficult and dangerous for the operator as the closed environment in which the demisters are contained does not promote the disposal of dangerous gases.
Therefore the need was created to perform the cleaning without stopping the system, and thus avoiding putting the personnel in dangerous conditions.
GB-2235393 describes an apparatus for cleaning filtering panels.
Considering the state of the art, it is hence the object of the present invention to resolve the aforesaid drawbacks by proposing a method and an apparatus for cleaning demister panels without the aforesaid limitations and which allows a significant saving of the cleaning fluid.
In accordance with the invention, such an object is achieved with a method and an apparatus for cleaning demister panels as described in claims 1 and 3.
These and other features of the present invention will become increasingly apparent from the following detailed description of its nonlimiting practical embodiments disclosed in the accompanying drawings, in which:

figure 1 shows a side view of a first embodiment of an apparatus according to the invention;
figure 2 shows a side view of a second embodiment of the apparatus according to the invention;
figure 3 shows a front view of a spray-gun according to the invention;
figure 4 shows a side view of a third embodiment of the apparatus according to the invention;
figure 5 shows a diagrammatic side view of a fourth embodiment of the apparatus according to the invention;
figure 6 shows a front view of a head according to the invention;

With reference to the accompanying figures, and in particular to figure 1, an apparatus 1 is shown for cleaning filtering demister panels 2 comprised within a hollow parallelepiped containing structure 100 comprising a frame 3.
In the embodiment herein depicted, structure 100 is formed by four vertical walls of panels 2 with frame 3 horizontal to close structure 100 at the top.
Apparatus 1 comprises compressed fluid cleaning means 4 suitable for being installed by means of positioning means 8 inside structure 100 through an opening 51 of frame 3. Frame 3, together with the panels 2, defines a cavity 52. Said positioning means 8 are external to structure 100. Frame 3 may provide several openings 51 for various cleaning means 4 which are to be very close to the panels 2.
Advantageously the cleaning means are a spray-gun 4 (figures 1, 2, 3) or a rotating head 14 (figures 4, 5, 6).
The spray-gun 4 is selectively movable between movement means 9, 11, they also being external to structure 100, between a first limit position corresponding to a first edge 5 of the panel (figure 3, where the volume occupied by panel 2 with respect to the spray-gun is traced with a dash-dotted line) and a second limit position corresponding to a second edge 6 of the panel (figure 3) opposite to the first edge 5, thus performing the cleaning substantially of the whole panel 2 during the movement of the spray-gun 4 between the first and the second position.
The spray-gun 4 is of the type for pressurized cleaning fluid and is equipped with a body 55 with side arms 13 lying in a plane and equipped with nozzles 7 which eject substantially perpendicular with respect to the plane of the arms 13, and is suitable for allowing the filtering panel 2 to be operated during the cleaning of panel 2 with the spray-gun 4. Advantageously the arms 13 are perpendicular to the spray-gun 4.
The spray-gun 4, the arms 13 and the nozzles 7 (see figure 3 in particular) are positioned so that during operation, the spray-gun covers the width or the length, and in any case the smaller dimension of panel 2 (figure 3 in which panel 2 is represented with the dash-dotted line).
In the preferred embodiment shown in figure 3, the spray-gun 4 is made with material suitable for supporting the high pressures of the cleaning fluid. Body 55 of the spray-gun 4 is equipped with three series of arms 13 having eight nozzles 7.
Advantageously, the positioning means 8 comprise a sleeve 8 for associating the spray-gun 4 with frame 3 suitable for positioning it in front of panel 2 so that the nozzles 7 eject substantially perpendicular to panel 2.
Advantageously, the movement means 9 comprise a manual or electric pulley system 9 equipped with a cable 10 connected to the spray-gun 4, for the movement thereof.
Alternatively, the movement means 11 comprise a pneumatic piston system 11 connected to the spray-gun 4, for the movement thereof.
Advantageously, apparatus 1 comprises a pump 12 associated with the spray-gun 4 for supplying the pressurized fluid.
The operation of the spray-gun 4 provides that the spray-gun 4, the arms 13 and the nozzles 7 are positioned in such a way that during operation, the spray-gun covers the smaller dimension of panel 2, as explained above, and is secured to frame 3 by sleeve 8.
Said sleeve 8 leaves the spray-gun free to slide axially thereon (double arrow in figure 3) to be able to be moved in the direction of the length of the panel or, in any case, along the larger dimension of panel 2, respectively, thus cleaning the whole surface of the panel.
The movement of the spray-gun 4 is performed by the pulley or pneumatic piston systems described, with known methods, by moving it between the first top limit position corresponding to the first edge 5 of panel 2 and the second bottom limit position corresponding to the second edge 6 of panel 2 opposite to the first edge 5. Thereby the nozzles 7 translate on the whole surface of the panel and the cleaning is performed of the whole panel 2 during the operation of the demister panel 2.
The cleaning means may comprise, alternatively to the spray-gun 4, as mentioned above, a rotating head 14. In particular, figure 6 shows panel 2 represented with a dash-dot line. The rotating head 14 is equipped with nozzles 7 with a throw 15 (dash-dash line in figure 6) of pressurized cleaning fluid such as to cover the smaller dimension of panel 2. When the rotating head 14 is moved in the direction of the length or, in any case, along the larger direction of the panel similarly to that seen for the spray-gun, respectively, the throw 15 of the rotating head 14 gradually translates substantially over the whole surface of panel 2, thus cleaning it.
The movement of the rotating head 14 is also performed by the pulley system 9 (figure 4) or pneumatic piston system 11 (figure 5) described above, with known methods, by moving it between the first top limit position corresponding to the first edge 5 of panel 2 and the second bottom limit position corresponding to the second edge 6 of panel 2 opposite to the first edge 5.
Advantageously, sleeve 8 and pump 12 also complement the embodiment with head 14 of the apparatus according to the invention, in the ways shown.
Given the small cross-section surface of the panel blocked by the spray-gun 4 or head 14, by positioning the cleaning means, spray-gun 4 or head 14 inside structure 100, the cleaning is thereby obtained of the whole panel 2 during the operation of panel 2 without stopping the operation thereof.
Control means 200 are also provided of said positioning 8 and movement means 9, 11 which are external to structure 100 so as to protect the operator from any danger.
The state of the art provides that panel 2 is to be stopped to allow the entry by the operator inside cavity 52 for the cleaning thereof. The above-described cleaning apparatus permits a thorough maintenance of the panels 2 without risks for the operator who controls the cleaning means 4 from the outside by means of suitable and known control means 200.
The regularity of the cleaning, which is a consequence of the simplicity thereof, reduces the extraordinary interventions and allows significant savings of cleaning fluid.
Apparatus 1 according to the present invention may, in any case, also be used in the case of horizontal panels 2 comprised within a hollow structure 100 with the due adaptations that a skilled technician is able to do. For example, in the case of horizontal panels 2, the cleaning means 4 will move horizontally along horizontal guides.

Claims

A method for cleaning demister panels (2) comprised in a hollow structure (100), characterized in that it provides the positioning of cleaning means (4, 14) having compressed fluid within the hollow structure (100) and the selective movement (9, 11) thereof between a first limit position corresponding to a first edge (5) of the panel (2) and a second limit position corresponding to a second edge (6) of the panel (2) opposite to the first edge (5), thus performing the cleaning of the whole panel (2) during the movement between the first and the second position, said positioning and said movement occurring by means of control means (200) external to the hollow structure (100).
A method according to claim 1, characterized in that it provides cleaning the panel (2) by means of rotating a head equipped with nozzles (7) suitable for ejecting pressurized cleaning fluid over the whole smaller dimension of the panel (2).
An apparatus (1) for cleaning demister panels (2), characterized in that it comprises positioning means (8) of cleaning means (4, 14) selectively movable by means of movement means (9, 11) between a first limit position corresponding to a first edge (5) of the panel (2) and a second limit position corresponding to a second edge (6) of the panel (2) opposite to the first edge (5), thus performing the cleaning of the whole panel (2) during the movement between the first and the second position, said positioning (8) and movement means (9, 11) being external to a hollow structure (100) comprising the panels (2).
An apparatus (1) according to claim 3, characterized in that the cleaning means (14) comprise a rotating head (14) equipped with nozzles (7) suitable for ejecting pressurized cleaning fluid over the whole smaller dimension of the panel (2).
An apparatus (1) according to claim 3, characterized in that the cleaning means (4) comprise a spray-gun (4) for pressurized cleaning fluid, said spray-gun (4) being equipped with a body (55) with side arms (13) lying in a plane and equipped with nozzles (7) which eject perpendicularly with respect to the plane of the arms (13), said spray-gun (4) being suitable for allowing the operation of the filtering panel (2) during the cleaning of the panel (2) with the spray-gun (4).
An apparatus (1) according to claim 4 or 5, characterized in that the positioning means (8) comprise a sleeve (8) for associating the spray-gun (4) or the rotating head (14) with the frame (3) suitable for positioning them front of the panel (2) so that the nozzles (7) eject substantially perpendicularly to the panel (2).
An apparatus (1) according to claim 5 or 6, characterized in that the arms (13) are perpendicular to the body (55) of the spray-gun (4).
An apparatus (1) according to any one of the claims from 3 to 7, characterized in that the movement means (9) comprise a pulley system (9) equipped with a cable (10) connected to the cleaning means (4, 14) for the movement thereof.
An apparatus (1) according to any one of the claims from 3 to 7, characterized in that the movement means (11) comprise a pneumatic piston system (11) connected to the cleaning means (4, 14) for the movement thereof.
An apparatus (1) according to any one of the claims 3-9, characterized in that it comprises a motor pump (12) associated with the cleaning means (4, 14) for supplying the pressurized fluid.