METHOD AND DEVICE FOR CLEANING A SURFACE OF A CONVEYOR BELT OF RESIDUES OF RAW MATERIALS AND COVER MATERIAL CONVEYED IN MINING The present invention relates to a method and an apparatus for cleaning a surface of a conveyor belt of residues of raw materials conveyed in the context of mining, such as ores and/or coal and overburden.
Conveyors with conveyor belts are regularly used to transport raw materials and overburden conveyed in the context of mining, for example to transport them from a place where the raw material is extracted to further processing or to transport them from a bunker to a loading point.
The corresponding conveyors are specially adapted to the conditions arising when transporting raw materials and overburden, in particular with regard to the material, surface, length, width and design of the conveyors.
These are often operated over lengths of one kilometre or more.
Dust formation is a problem which regularly arises when transporting raw materials or overburden.
The resulting dust is released into the environment.
The dust is generated, inter alia, at the idler rollers, reversing rollers or drive rollers over which the conveyor belt is guided, since this is where the deposits on the conveyor belt are rubbed off.
Conveyor wipers are known for removing these deposits, for example from DE 10 2011 016 954 A1. These have proven to be disadvantageous, particularly when transporting raw materials conveyed in the context of mining, since virtually complete removal of said deposits from the conveyor belt is not possible with conveyor wipers.
A method is also assumed to be known in which the conveyor belt is sprayed with water on one side in order to moisten the surface.
It has become apparent, in this case, that this method does not result in maximally comprehensive removal of deposits and at the same time, in particular, the supporting structures of the conveyor belt are exposed to greater corrosion.
US 2014/374046 A1 discloses a method for cleaning a machine for paper manufacture.
CN 207 827 276 U discloses a method for cleaning a conveyor belt used to transport animal carcasses.
GB 1,091,544 B discloses a method for cleaning sludge from a conveyor belt.
US5355992A discloses an apparatus according to the preamble of claim 1. Taking this as the starting point, the object of the present invention is to overcome at least in part the disadvantages known from the prior art and in particular to specify a method and an apparatus with which a conveyor belt can be cleaned easily and effectively even of residues of raw materials conveyed in the context of mining, at the same time avoiding corrosion especially of conveyor belt supporting structures.
This object is achieved by the features of the independent claims.
Further advantageous embodiments of the invention are indicated in the dependent claims.
The features listed individually in the dependent claims can be combined with one another in a technologically meaningful manner and can define further embodiments of the invention.
In addition, the features indicated in the claims are explained more precisely and in greater detail in the description, with further preferred embodiments of the invention being presented.
As a precaution, it should be noted that the numbers used here (“first”, “second”, etc.) serve primarily (merely) to distinguish between several similar objects, variables or processes, i.e. in particular they do not mean that any dependency and/or sequence of these objects, variables or processes relative to one another is mandatory.
Should a dependency and/or seguence be necessary, this is explicitly stated here or is obvious toa person skilled in the art from studying the specifically described embodiment.
The method according to the invention for cleaning a surface of a conveyor belt moving in one movement direction of residues of materials conveyed in the context of mining, in particular overburden and/or raw materials conveyed in the context of mining, comprises the following steps:
a) subjecting the surface to a plurality of fluid jets at an operating pressure of at least 30 bar at a predefinable impingement angle of less than 90*, counter to the movement direction, for the purpose of removing the residues;
b) removing at least some of the fluid from the surface.
A conveyor belt is understood to mean a continuous belt which runs on idler rollers and drive rollers and which serves simultaneously as a supporting and traction means.
In particular, the conveyor belt has a carcass that includes textile or metal cable inserts that transmit tractive forces.
This carcass is preferably surrounded by a casing.
For conveyor belts for transporting raw materials and overburden conveyed in the context of mining, such as ores or coal, this is preferably surrounded by a casing that is surrounded by elastomeric materials, in particular with a thickness of 10 mm to 70 mm [millimetres]. The conveyor belt is preferably part of a conveyor, in particular a belt or band conveyor.
A conveyor is understood to mean in particular an apparatus comprising at least one drive roller, at least one idler roller and at least two reversing stations which are supported by a supporting structure and which guide the conveyor belt.
The impingement angle of the fluid jets is less than 90°, with the fluid jets being directed counter to the movement direction.
The impingement angle is preferably chosen as between 20° and 60°. Particularly efficient cleaning can be achieved in this angular range.
Before step a), the surface of the conveyor belt is preferably guided over at least one coarse mechanical wiper (primary and/or secondary wiper) to wipe off coarse residues.
A coarse mechanical wiper means in particular a type of lip that is brought into contact with the surface of the conveyor belt.
This lip is in particular made of an elastomeric plastics material, in particular polyurethane (PU), and/or a metal, in particular comprising tungsten carbide (WC), for example as a plastics element with a metallic edge.
By guiding the surface over the coarse mechanical wiper, coarser residues in particular are wiped off the surface, such that residues remain downstream of this coarse wiper which cannot be removed by a coarse mechanical wiper.
The fluid jets are generated by nozzles that direct the fluid jet onto the surface.
The nozzles are pressurised in particular with a fluid such as in particular water.
Cleaning additives can optionally be added, which are selected according to the raw material in question.
The fluid jets are preferably designed as fluid cones that have an aperture angle.
Nozzles that generate such fluid cones are preferably used.
In the case, in particular, of a fluid cone, the impingement angle is understood to be the angle between the cone axis and the tangent of the surface at the point of impingement of the cone axis.
Sufficient fluid jets are preferably used for the entire width of the conveyor belt to be covered.
In particular, the fluid jets are used in such a way that they do not overlap in the jet, so that the desired direction of momentum of the fluid jet is not changed by an overlap.
The corresponding nozzles are therefore preferably adjusted accordingly with regard to their aperture angle of the fluid cone and with regard to the distance from the surface and the orientation.
The orientation of the fluid jets with respect to the surface cannot be changed over time, which means in particular that the fluid jets are not moved relative to the surface.
An impingement angle is thus obtained which is selected such that an optimum cleaning effect can be achieved in step a). In method step b), in addition to the fluid, any residue deposits that may still be present are removed, which may have only been loosened but not removed in method step a). The surface of the conveyor belt means the supporting surface of the conveyor belt.
Owing to the circulating movement over drive rollers, idler rollers and reversing stations, the supporting surface and thus the surface of the conveyor belt is always on the outside, such that the surface of the conveyor belt can preferably be cleaned when it is no longer covered with material to be transported but only the residues remain, for example in the region of the reversing stations or in the lower region of the conveyor belt.
Method step b) is preferably carried out using an adhesion roller, optionally in combination with at least one wiper lip.
An adhesion roller is understood to mean a roller over which the conveyor belt is guided and which is pressed against the conveyor belt.
Moisture on the conveyor belt is adhesively bound to the adhesion roller, and centrifugal forces remove the moisture from the adhesion roller again when it is no longer in contact with the conveyor belt.
The corresponding drops of fluid are preferably collected in a collecting trough and discharged.
Efficient drying of the conveyor belt can be achieved with this embodiment.
The method described here allows efficient cleaning of the conveyor belt.
At the same time, the cleaned belt is then guided over the other drive rollers and transport rollers without the residues (which are then no longer present) being rubbed off.
The dust on the rollers caused by abrasion thus does not arise, such that effective dust reduction is achieved.
According to one advantageous embodiment, the fluid jets have an aperture angle of 20° to 60°. An aperture angle of 20° to 60° leads to a high impingement momentum on the conveyor belt and thus to efficient cleaning.
The use of fluid jets with different aperture angles is possible according to the invention.
According to one advantageous embodiment, the fluid comprises water.
The use of water is particularly preferred since a conventional high-pressure pump and conventional high-pressure lines can be used here and no further measures for cleaning the fluid have to be taken apart from filtering.
Furthermore, discharge of water to the environment is possible without major problems, without further precautions having to be taken.
According to the invention, after step a) and in particular before step b), the surface of the conveyor belt is guided over a fine mechanical wiper.
The fine mechanical wiper, which is embodied in particular as an elastomeric lip, on the one hand wipes off residues that have been loosened from the conveyor belt in step a) but not removed, and on the other hand wipes fluid off the conveyor belt before further removal in step b). This further improves drying of the conveyor belt and further reduces the risk of corrosion.
The fine mechanical wiper can in particular comprise one or more wiper lips.
According to one advantageous embodiment, the operating pressure is determined according to at least one of the following parameters: i) the type of material conveyed in the context of mining, ii) — environmental conditions, in particular temperature and/or humidity; ili) the thickness of the residues determined on the surface; and iv) the speed of movement of the conveyor belt.
The type of material conveyed in the context of mining is understood in particular to mean whether ore, coal, overburden or the like is being transported.
The type of substance or raw material has an influence on the deposits on the conveyor belt.
Ambient conditions are understood to mean, in particular, the ambient temperature and the (relative) humidity, which have an influence on the adhesion behaviour on the surface.
One or more of the specified parameters i), ii), iii) and iv) are preferably used to determine the operating pressure in order in this way to be able to set an operating pressure which reliably enables residues to be removed in step a). According to one advantageous embodiment, the fluid jets are guided onto the surface as a flat cone, the fluid jets being formed in such a way that adjacent fluid jets on the surface do not overlap.
The fluid jets are here preferably designed in such a way that the fluid jets nonetheless impinge over the entire width of the conveyor belt.
For the purposes of this document, a flat cone is understood to mean a fluid jet that resembles a cone that is compressed in a cross-sectional direction.
Thus, in a cross section, a flat cone does not have a round shape, but rather an oval shape or the shape of a ‘racetrack’ (straight sides connected together by curved regions). Such flat cone-shaped fluid jets can be generated in particular by flat-jet nozzles.
By configuring the fluid jets as flat cones, the number of fluid jets required to cover the entire width of the conveyor belt can be significantly reduced.
At the same time, a reliable fluid jet definition can be achieved through the use of appropriate nozzles.
Particularly effective cleaning is achieved by preventing the fluid jets from overlapping on the surface.
Overlapping regions would lead to vectorial accumulation of the momentum at the surface in these regions, which can lead to a reduction in cleaning efficiency.
According to one advantageous embodiment, the materials conveyed in the context of mining include at least one of the following raw materials:
a) ores;
b) salts;
c) brown coal;
d) hard coal;
e) anthracite;
f) bauxite;
g) industrial minerals; and h) overburden.
According to a further aspect, an apparatus is proposed for cleaning a surface of a conveyor belt movable in a movement direction of residues of raw materials conveyed in the context of mining, in particular using the method according to the invention, comprising: a nozzle bar having a plurality of nozzles for applying fluid jets to the surface of the conveyor belt; at least one fluid-removal element for removing at least some of the fluid from the surface, a high-pressure fluid supply for providing a fluid to the nozzle bar at an operating pressure of at least 30 bar which is distinguished in that the nozzles are designed and oriented such that the fluid jets impinge on the surface, in a direction counter to the movement direction, at an impingement angle of less than 90°. According to one advantageous embodiment, the nozzles have an aperture angle of 20° to 60°. This means nozzles that generate a fluid cone with an aperture angle of 20° to 60°. According to one advantageous embodiment, the nozzles are designed in the form of flat-jet nozzles and are designed and arranged such that adjacent fluid jets do not overlap on the surface.
A flat-jet nozzle is understood to mean, in particular, a nozzle which generates a flat-jet cone during operation.
Flat-jet nozzles are advantageously usable since the jet cone generated has an even liquid and pressure distribution.
According to one advantageous embodiment, the nozzles are designed and arranged such that fluid can applied over the entire width of the conveyor belt by way of the fluid jets which can be generated by the nozzles.
According to the invention, the fluid removal element comprises an adhesion roller.
The details and advantages disclosed for the method according to the invention can be transferred and applied to the apparatus according to the invention and vice versa.
The method according to the invention is implemented with an apparatus according to the invention.
The invention and the technical environment are explained in greater detail below with reference to the figures.
It should be noted that the exemplary embodiments shown are not intended to limit the invention.
In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects from the substantive matter explained in the figures and to combine them with other components and/or insights from the present description and/or the figures.
In particular, it should be noted that the figures and in particular the relative proportions shown are only schematic in nature.
The same reference signs designate the same objects, meaning that explanations from other figures can optionally additionally be applied.
In the figures, which are schematic: Figure 1 is a view of an apparatus for cleaning a surface of a conveyor belt; Figure 2 shows a nozzle bar of the apparatus according to figure 1 in a first view; Figure 3 shows the nozzle bar of figure 2 in a second view; Figure 4 shows a spray pattern of a nozzle; Figure 5 shows a nozzle of a nozzle bar according to figure 2 or 3; Figure 6 is a perspective view of an apparatus for cleaning a surface of a conveyor belt; Figure 7 shows a longitudinal section of a conveyor belt with an adhesion roller; Figure 8 shows a longitudinal section of a conveyor belt with different impingement angles of the fluid jets; Figure 9 is a longitudinal section of a further example of an apparatus for cleaning a surface of a conveyor belt.
Like elements are provided with identical reference signs.
Figure 1 shows a detail of an apparatus 1 for cleaning a conveyor belt 2. The apparatus 1 comprises a nozzle bar 3 with a plurality of nozzles 4 for applying fluid jets 5 to a surface 6 of the conveyor belt 2, which moves in the movement direction 16. The surface 6 is the supporting surface of the conveyor belt 2, which is used to transport raw materials and overburden, not shown here, which are conveyed in the context of mining.
The conveyor belt 2 is continuous and is guided, inter alia, over two reversing devices 7, such that the surface 6 is at the top in the upper region and at the bottom in the lower region.
The surface 6 is therefore always on the outside.
The nozzles 4 are flat-jet nozzles and are designed in such a way that the fluid jet 5 is applied to the surface 6 counter to the movement direction 16 at an impingement angle 8 of less than 90° and in particular of 20° to 60°. The impingement angle 8 is here defined as the angle between the fluid jet 5 or a cone axis of the fluid jet 5 and a tangent 9 at the point of impingement 10 of the fluid jet 5 or the cone axis of the fluid jet 5. During operation, the nozzle bar 3 is supplied with the fluid, in particular water, at a pressure of at least 30 bar, which then leaves the nozzle bar 3 through the nozzles 4 and forms the fluid jets 5, which exit from the nozzle 4 at high pressure and then impinge on the surface 6. The shallow impingement angle 8 in the curved region of the conveyor belt 2 results in efficient cleaning of the conveyor belt 2 of residues from raw materials and/or overburden conveyed in the context of mining.
It should be expressly noted that a configuration of the apparatus 1 is also possible in which the fluid jets 5 impinge on a straight portion of the conveyor belt 2. Figure 2 shows a first view of a nozzle bar 3 with a plurality of nozzles 4. For the sake of clarity, only some of these are provided with reference signs.
Each nozzle 4 is designed to emit a fluid jet 5 onto the surface 6. Each fluid jet 5 has an identical aperture angle 11. The nozzle bar 3 is formed over the transverse direction of the conveyor belt 2 and parallel to it.
Figure 3 shows a plan view as a second view of the nozzle bar 3, and figure 4 shows a nozzle 4 in detail.
The nozzles 4 are oriented such that the flat cones 14 of the fluid jets 5 are rotated by a certain rotational angle 12 relative to a longitudinal axis 13 of the nozzle bar 3, such that a flat cone longitudinal axis 15 forms the rotational angle 12 with the longitudinal axis 13 of the nozzle bar 3. Together with a selection of the distances between adjacent nozzles 4 according to the aperture angle 11, the rotational angle 12 and the distance between the nozzle bar 3 and the conveyor belt 2, this means that the fluid jets designed as flat cones 14 do not overlap one another.
A defined momentum can thus be transferred locally to the surface 6. Should fluid jets 5 overlap, a vectorial interaction of these fluid jets 5 occurs, which reduces the cleaning effect.
However, due to the offset arrangement of the nozzles 4, the entire width of the conveyor belt 2 is covered by the fluid jets 5. Figure 5 shows a detail of the nozzle bar 3 in cross section.
The nozzle 4 is screwed into a thread in the nozzle bar 3. Figure 6 shows a perspective view of an example of an apparatus 1 for cleaning a conveyor belt 2 that moves in a movement direction 16 at a speed of up to 7.5 m/s [metres per second]. On entry into the apparatus 1, the conveyor belt 2 is guided over a first guide roller 17. The apparatus 1 is constructed in the lower region of the conveyor belt such that the surface 6 and thus the supporting surface are at the bottom here.
The conveyor belt 2 is then guided over the nozzle bar 3 with a plurality of nozzles 4 (not all of which are provided with reference signs for the sake of clarity). The nozzles 4 are oriented counter to the movement direction 16 of the conveyor belt 2. As described, the corresponding fluid jets (not shown here) clean the surface 6 of the conveyor belt 2 of residues of raw materials conveyed in the context of mining.
In the movement direction 16 downstream of the nozzle bar 3, two fine wipers 18 with wiper lips 19 are provided, which wipe any remaining raw material residues from the conveyor belt 2. At the same time, fluid adhering to the surface 6 is wiped off.
The wiper lips 19 are preferably formed from an elastomer, in particular from polyurethane.
Before leaving the apparatus 1, the conveyor belt 2 is guided downstream of the fine wiper 18 over a second guide roller 20,
which, however, has no contact with the moist surface 6 of the conveyor belt 2. An adhesion roller 21 is in contact with the surface 6 and adhesively removes the remaining moisture from the surface 6. The adhesion roller 21 thus acts as a moisture removal element 24. The adhesion roller 21 is preferably made of steel and, according to the invention, has an elastomeric coating on its circumference.
The apparatus 1 has a housing 22 which is made of stainless steel in the present example.
This receives fluid that drips off the surface 6 of the conveyor belt 2 or is removed by the wiper lips 19 or the adhesion roller 21. This fluid flows out through a waste pipe 29. In addition, flushing pipes 23 are provided, through which additional fluid can be introduced into the housing 22 in order to flush out any residues of the raw materials that may remain in the housing 22. Furthermore, the apparatus 1 comprises a high-pressure fluid supply 25 which supplies the nozzle bar 3 with the fluid at a pressure of from at least 30 bar up to 150 bar.
This operating pressure is adjustable.
Figure 7 is a schematic representation of the working principle of an adhesion roller 21 for removing moisture from a conveyor belt 2. The adhesion roller 21 rotates according to the speed of movement of the conveyor belt 2 and thereby rolls on the conveyor belt 2 and adhesively binds the moisture on the surface 6 of the conveyor belt 2. Drying efficiency can be further increased in that the adhesion roller 21 is designed and pressed against the conveyor belt in such a way that it elastically deforms the conveyor belt 2 in a flexing region 26. After leaving the flexing region 26, the moisture is adhesively bound to the surface of the adhesion roller 21. In the course of rotation of the adhesion roller 21, the moisture is removed from the adhesion roller 21 again due to the centrifugal forces present.
Figure 8 is a schematic representation of possible angles of impingement 8 onto the conveyor belt 2. The apparatus 1, which is not shown in its entirety, is designed in such a way that the fluid jets 5 impinge on the conveyor belt 2 in a straight region.
The tangent at the point of impingement thus runs on the surface of the conveyor belt 2. Figure 8 shows, by way of example, angles of impingement 8 of 20°, 45° and 60°. A distance 28 between the nozzle bar 3 and the surface 6 of the conveyor belt 2 here remains constant.
The different angles of impingement 8 are realised by varying the position of the nozzle bar 3. Figure 9 is a schematic representation of an embodiment of the apparatus 1 in which the fluid jets 5 impinge on the straight region of the conveyor belt 2. Reference is made to the statements made above.
List of reference signs
1 Apparatus for cleaning a conveyor belt 2 Conveyor belt 3 Nozzle bar 4 Nozzle Fluid jet 6 Surface 7 Reversing device 8 Impingement angle 9 Tangent Point of impingement 11 Aperture angle 12 Rotational angle 13 Longitudinal axis 14 Flat cone Flat cone longitudinal axis 16 Movement direction 17 First guide roller 18 Fine wiper 19 Wiper lip Guide roller 21 Adhesion roller 22 Housing 23 Flushing pipe 24 Moisture removal element High-pressure fluid supply 26 Flexing region 28 Distance 29 Waste pipe