EP0377794B1 - Electrofilter made from plastics and/or metal, in particular lead - Google Patents

Description

The invention relates to an electrostatic filter made of plastic and / or metal, in particular lead, as a tube filter with axially parallel tubes with a polygonal cross section and with axially extending spray electrodes in each tube, the walls of the tubes acting as precipitation electrodes and the walls of adjacent tubes lying directly next to one another each aligned and a series of parallel and evenly spaced support beams is provided, which extend over the entire width of the electrostatic filter and support the walls (see US-A-2 853 150).

An electrostatic filter is generally understood to mean a device with the aid of which it is possible to separate solid and liquid suspended particles from the carrier gas with the aid of an artificial electrical charge. The charged suspended particles migrate to the precipitation electrode and are then mechanically removed from the filter. Electrostatic precipitators are also known as electrical separators.

Such electrostatic precipitators generally consist of spray electrodes which are electrically charged and of walls in the vicinity of the spray electrodes which act as precipitation electrodes. These spray electrodes can be wire-shaped, for example.

So-called open alleys are known as the simplest form, i.e. two plates parallel to each other, between which the spray electrodes run at equal intervals in the middle parallel to each other. Due to the inhomogeneous fields, the filter effect is only very unsatisfactory, especially in the area between the wire-shaped spray electrodes.

So-called square streets have been introduced as an improvement. In these, partition walls extending perpendicular to these are additionally introduced between the parallel plates and divide the space between the plates into long tubes with a square cross section. A wire-shaped spray electrode runs axially in each tube. The spray electrodes and tubes usually run vertically in order to be able to use the rising or falling of the carrier gas during the separation.

The problem with the square lanes is that the corners of the squares are relatively far from the spray electrodes. This affects the filter effect. Even when using special or special electrodes, relatively uncleaned carrier gas flows can pass through at the corners. These special electrodes are e.g. Projections or side branches are provided on the axially extending wire in order to reach the corners a little better. Such special electrodes are described for example in EP 0 163 047 A2.

In contrast, circular-cylindrical tube arrangements are cheaper than square ones. However, these have the considerable disadvantage that only one side of the tube wall is effective as a separating surface. In the square streets described above, however, each wall serves as a limitation for two adjacent tubes, which leads to a considerable saving in material and space. This is of particular interest for filters made of steel or lead, which are used, for example, in the wet cleaning of SO₂ gases in the sulfuric acid industry. This applies in particular to downstream wet gas cleaning in ore processing with sulfur-containing metal ores, such as pyrrites. However, lead filters or filters made of solid steel with a lead coating are very heavy, so that care should therefore be taken to use as little material as possible.

Material-saving solutions result, for example, from DF 26 41 114 B2, DE-AS 10 01 240 or CA-PS 1 159 773, which each describe honeycomb filters with tubes with a hexagonal cross section - these filters have the advantage of greater homogeneity of the electric field compared to square alley filters, but each wall can still be used for two adjacent tubes.

These honeycomb filters with hexagonal tubes in cross-section have therefore proven their worth and are well established, but only in plastic in a construction in which there is no need for a suspension, because the plates forming the tube walls are connected to one another over the entire length of the nodal points that arise.

However, these hexagonal tubes have a disadvantage that is particularly noticeable in electrostatic filters made of heavy materials. These, especially those made of lead, require plates that are no longer self-supporting. It should be borne in mind that the resulting tubes are sometimes orders of magnitude more reach than 5 m in length. It would therefore be advantageous if the panels that form the walls could be hung in stable supports. With a honeycomb filter, however, it is not possible to provide continuous, stable supports, since the plates are pivoted by 120 ° from corner to corner and zigzag, so to speak.

The object of the invention is therefore to propose a generic electrostatic filter which shows the best possible filtering action and can nevertheless be equipped with continuous supports.

In other words, a stable concept should be proposed that improves the filtering effect compared to the square aisles without accepting the disadvantages of the hexagonal honeycomb filter.

This object is achieved in an electrostatic filter described at the outset in that the walls each form tubes with an octagonal cross section.

Such an electrostatic filter is an alley filter. A row of parallel plates can be hung on continuous supports. Nevertheless, a better degree of filtering is achieved compared to the square-lane filter, since the tubes each have an octagonal cross-section. The side surfaces and corners are therefore spaced considerably more evenly from the axially extending spray electrodes, so that no angles and corners can form in which unpurified particle streams can flow.

Four of the eight sides are aligned with the four tubes that are adjacent to the tube under consideration. The same four sides belong to walls that the tube in question has in common with neighboring tubes.

The remaining pages cut off the corners.

Approximately 50% of the wall surfaces are therefore used twice by neighboring tubes as separating surfaces, the homogeneity of the electric field practically corresponds to that of tubes with a circular cross-section, and it is possible to use continuous supports. These advantages more than outweigh the use of all wall surfaces in the case of honeycomb filters with a hexagonal cross section.

It is particularly preferred if the tubes are regular octagons in cross section. This ensures the greatest possible homogeneity. Alternatively, the walls, which are common to neighboring tubes, can be somewhat longer than the others, whereby the proportion of common walls increases above the 50% mark, but the uniformity of the electric field decreases somewhat.

A particularly stable construction results if transverse beams are provided perpendicular to the row of the support beams, to which profiles are fastened, which form the walls of the tubes which do not run parallel to the support beams.

This is further promoted if the beams are also provided with flange projections facing the tubes, which follow the profile of the pipe wall on the face. These flange projections also shut off those shafts in the electrostatic precipitator that lie between the octagonal cross sections of the different tubes. This prevents particularly easily and safely that unpurified gases can get through these shafts.

It is advantageous if the profiles in cross section form a Y mirrored at its base with a vertical base. The cross-section thus consists of a line, from the two end points of which two arms point symmetrically obliquely outwards. If such profiles are used in an alley, an octagon is formed between two adjacent profiles that are used spaced apart.

If the arms of the Y also enclose an angle of 135 ° with the foot, a regular octagon as a cross-section of the tubes can be achieved automatically if the distances are correctly dimensioned.

A structurally particularly interesting alternative or preferred embodiment arises when vertically running profiles are attached to the walls of the tubes running parallel to the support beams, which form an angle with two legs, both legs being attached to the wall, while the apex to the neighboring one Wall protrudes. A corresponding profile is then arranged symmetrically on the adjacent wall and a wall plate arranged transversely to the walls parallel to the carrier is inserted between the vertices of two mutually opposite profiles.

As a result, the angular profile can be welded from the outset directly to the continuous longitudinal plates at the uniform distances provided by the intended dimensions of the electrostatic filter. After setting up can then from above between the two vertices the wall plate forming the transverse side are inserted, for which purpose a corresponding groove or other protrusions are provided in the region of the vertex outside.

In order to maintain symmetry, it is preferred if the angle of the profile is 90 °, as a result of which the resulting octagon is formed regularly.

The plate can be made in one piece with the crossbeam. Then you can insert the crossbar together with the plate between the two vertices from above during assembly.

This construction is structural and particularly simple to assemble and therefore relatively inexpensive and also particularly stable, since the individual parts are intertwined.

A particular advantage of the octagon filter compared to the honeycomb filter is that it is easy to install and easy to repair. All internals for the octagon filter can easily be put together on site like a puzzle.

If an alley is defective in a hexagonal honeycomb filter, the entire alley of this filter must be closed and thus fails. If there are several defective lanes, this means that the entire filter or at least a large part of the filter must be replaced completely as a closed package. In the octagon filter according to the invention, however, only the part affected in each case has to be replaced in the event of a repair; this is particularly the case with the preferred embodiments with the crossbars attached profiles noticeable. In the filter concerned, only the corresponding crossbar with the plates attached to it must be pulled out and replaced. The rest of the filter does not need to be touched.

Two exemplary embodiments of the invention are explained in detail below with reference to the drawing.

Fig. 1

eine schematische Darstellung eines Röhrenfilters schräg von oben,

Fig. 2

eine Draufsicht auf Fig. 1,

Fig. 3

eine Ansicht schräg von oben auf ein erfindungsgemäßes Profil,

Fig. 4

einen Schnitt durch Fig. 3,

Fig. 5

eine schematische Darstellung einer anderen Ausführungsform schräg von oben,

Fig. 6

einen Schnitt durch Fig. 5 und

Fig. 7

eine Draufsicht auf ein Element aus Fig. 6.

Show it:

Fig. 1

1 shows a schematic illustration of a tube filter obliquely from above,

Fig. 2

2 shows a plan view of FIG. 1,

Fig. 3

a view obliquely from above onto a profile according to the invention,

Fig. 4

3 shows a section through FIG. 3,

Fig. 5

1 shows a schematic illustration of another embodiment obliquely from above,

Fig. 6

a section through Fig. 5 and

Fig. 7

6 shows a plan view of an element from FIG. 6.

The structure of the electrostatic filter according to the invention can be seen in particular from FIGS. 1 and 2. Non-uniform electrostatic filters are shown in both figures, but rather three lanes in each drawing: a conventional first lane 11 consisting of only two parallel plates, an improved so-called square lane 12 made of tubes with a square cross-section and a third lane 13 according to the invention made of tubes with octagonal cross section.

According to the invention, the electrostatic filter would particularly preferably only be constructed from tubes with an octagonal cross section.

The problem with electrostatic filters and the advantage achieved with the invention is particularly clear from the illustration in FIG. 2. Spray electrodes 21 can be seen, of which only one or two are shown in each lane for the sake of clarity. The walls of the respective alleys or tubes act as precipitation electrodes 22. Electrical fields 23 form between the spray electrodes 21 and the precipitation electrodes 22, the line course of which is indicated.

It can be seen that a very inhomogeneous field is built up in the conventional pure alley filter from two parallel plates. In the area between two spray electrodes, areas with only a slight field influence and thus unsatisfactory filter action are formed.

In the middle so-called square alley 12 with the tubes 4a, 4b, 4c with the square cross-section, there is no longer a virtually field-free space between the spray electrodes 21; however, there are still inhomogeneities, especially when comparing the corners of the square cross-section with the central areas of the sides.

In contrast, a considerable improvement in the homogeneity of the electric field 23 and thus also the filtering action of the electrostatic filter is achieved in the third alley 13 in the tubes 8a, 8b, 8c with the octagonal cross section. The electric field 23 is practically homogeneous, since the cross section has already approximated a circular cross section.

Although there are now field-free corners 28 that can no longer be used for the filter, this disadvantage is more than overcome by the improved homogeneity canceled. In relation to the square, about 17% of the usable cross-sectional area would be lost.

At the same time, it is clear that exactly half of the wall surface, namely four of the eight sides of the octagon, simultaneously serve as precipitation electrodes for two adjacent tubes, for example for tubes 8a and 8b or 8b and 8c. In the case of an electrostatic filter according to the invention, which continues spatially in each direction, this would also extend upward or downward in FIG.

The construction of electrostatic filters, in particular made of lead, has support beams, of which the support beams 31, 32, 33, 34 can be seen in the example of FIGS. 1 and 2. They are parallel and evenly spaced from each other and run across the entire width of the electrostatic filter. The figures here only show a section. These support beams 31 to 34 carry most of the walls, namely plates 36, 37, 38 and 39. These plates are made of lead or steel with a lead jacket. Since the aggressive and corrosive components of the gas or fluid to be filtered are to be deposited on them, they must be resistant to these components. The high weight of the plates 36 to 39 necessitates a corresponding stability of the support beams 31 to 34. This stability is difficult to achieve in the case of support beams running in a zigzag pattern or respectively pivoted through 120 °.

1 and 2, the support beams 31 to 34 each belong to the different embodiments of the filter. The plates 36 to 39 are also used when the entire electrostatic filter consists of tubes 8 with an octagonal cross section.

While the spray electrodes 21 are the only one in the alley 11 between the two plates 36 and 37 (cf. FIG. 2), in the square alley 12 additional cross elements 41a, 41b and 41c are used between the two supports 32 and 33. These cross elements 41 each have a cross beam 42 which is supported on the support beams 32 and 33 and extends perpendicular to them. Plate-shaped profiles 43 hang on the crossbeams 42. These plate-shaped profiles 43 together with the plates 37 and 38 each form the tubes 4a, 4b and 4c with a square cross-section. The plate-shaped profiles 43 consist of the material of the plates 36 to 39 and are correspondingly heavy. The crossbars 42 must therefore also be stable. The weight of these crossbeams 42 with the plate-shaped profiles 43 hanging on them must be absorbed and carried by the support beams 32 and 33.

The third alley 13 with the tubes 8a, 8b and 8c with the octagonal cross section is formed between the plates 38 and 39 on the support beams 33 and 34. The transverse elements 81a, 81b and 81c are located between these support beams 33 and 34. These cross elements each have a cross bar 82, which is supported on the support beams 33 and 34 and are fastened to the profiles 83. These profiles 83 also consist of the material of the plates 38 and 39. However, they are not in the form of a clean plate, but instead they consist of a special profile, which is particularly evident from FIGS. 3 and 4.

4 shows the cross section of these profiles. They consist of a Y with a vertical base mirrored at its base 85. The Y each has a foot 86a or mirrored 86b and two arms 87a and 87b or 87c and 87d. There is an angle of 90 ° between the arms and therefore an angle of 135 ° between each arm and one foot. The foot 86a of the Y forms a straight line with its mirror image 86b.

Arms 87 are all the same length; the middle part consisting of the foot 86a and its mirror image 86b has the same length between the branching points of the arms.

From Fig. 3 it can be seen that 83 flange projections 84 are attached to the front ends of the profile. These correspond to the profile on the end face and increase the strength and stability of the transverse elements 81. The transverse beam 82 adjoins the flange projections.

The entire cross element 81 is supported and supported with its cross beam 82 on the two support beams 33 and 34. Two mutually adjacent transverse elements 81 are arranged at such a distance that a tube 8 with an octagonal cross section is formed between them, taking into account the plates 38 and 39. The eight sides of the octagon are formed clockwise by the arm 87a, the foot 86 and the arm 87c of the second cross element 81d, the plate 39 on the support beam 34, the arm 87d, the foot 86 and the arm 87b of the first cross element 81a and the Plate 38 on the beam 33. All these eight pages are of equal length. The wall sides 80a, 80b, 80c, 80d, 80e, 80f, 80g and 80h are created.

5 to 7 show another embodiment for an electrostatic filter according to the invention. 5 shows the essential elements in an oblique plan view a tube 8d with sections of adjacent tubes.

The support beam 33 and the support beam 34 are indicated schematically. The plates 38 and 39, which form the longitudinal walls and pass through several tubes 8d etc., hang on this support beam. Between the support beams 33 and 34 are transverse beams 82, the upper edge of which is flush with the upper edge of the support beams 33 and 34 and which each bridge the entire distance between the two adjacent support beams.

Wall plates 95 are formed in one piece with the crossbars 82. These are thus perpendicular to the plates 38 and 39. FIG. 7 shows the shape of the crossbars 82 with the wall plates 95 more clearly.

Before these wall plates 95 are inserted, profiles 91 and 94 are welded to the plates 38 and 39, which form an angle 92 with two legs 93. The ends of the legs that go vertically are welded to the plates 38 and 39. The angle 92 is approximately 90 °. The legs 93 thus enclose an angle of 45 ° with the plates 38 and 39. The two profiles 91 and 94 are welded and arranged opposite one another and symmetrically projecting from one another by the two plates 38 and 39. The wall plates 95, which are fastened to the crossbeams 82, can then be suspended exactly between the vertices at the angles 92 of the profiles 91 and 94. For this purpose, vertically continuous grooves 96 are provided on the outer sides of the profiles 91 and 94, respectively. The wall plate 95 can be inserted into this from above. The crossbars 82 are then supported on the top of the profiles 91 and 94 and protrude above them. For stabilization entanglement elements 97 can also be provided there.

In this embodiment too, the tube 8d is formed with an octagonal cross section. The eight sides are formed in each case by sections of the plates 38 and 39, by the wall plates 95 which hang from two adjacent cross beams 82 or are formed in one piece therewith and each by four legs 93 of four different profiles 91 and 94; two each, which are assigned to a crossbar 82. The legs which are not required in each case for delimiting the octagonal tube 8d are used for delimiting different neighboring tubes in each case.

Claims (9)

1. Electrofilter made of synthetic material and/or metal, particularly lead, designed as a tube filter with tubes (8) with polygonal cross sections running axially parallel with respect to each other and with axially arranged emission electrodes (21) in each tube, whereby the tube walls act as collecting electrodes and the respective immediately adjacent walls of neighboring tubes are aligned and a row of parallel and evenly spaced support beams is provided, extending over the entire width of the electrofilter and supporting the walls, characterized in that the walls (80) form tubes (8) with an octagonal cross section.
2. Electrofilter according to claim 1, characterized in that the cross section of the tubes (8) is a regular octagon.
3. Electrofilter according to claim 1 or 2, characterized in that perpendicularly to the row of support beams (31, 32, 33, 34) crossbeams (82) are provided to which profiles (83) are fastened, which form the wallings (80) of the tubes (8a) which do not run parallelly with respect to the support beams (31, 32, 33, 34).
4. Electrofilter according to claim 3, characterized in that the crossbeams (82) are provided with flange projections (84) facing the tubes (8), which follow the frontal contour of the tube walling profile (83).
5. Electrofilter according to claim 3 or 4, characterized in that the profiles (83) seen in cross section form a Y with vertical leg (86) mirrored at its base point (85).
6. Electrofilter according to claim 5, characterized in that the arms (87) and the leg (86) of each Y define between them an angle of 135°.
7. Electrofilter according to one of the preceding claims, characterized in that to the walls (80) of the pipes (8) which are parallel to the support beams (31, 32, 33, 34) vertically running profiles (91) are fastened, forming an angle (92) with two sides (93), whereby both sides (93) are fastened to the wall (80), while the apex extends towards the neighboring wall, that on the neighboring wall a corresponding profile (94) is symmetrically arranged and that between the apexes of two opposite profiles (91, 94) a wall plate (95) is inserted, which is arranged transversely with respect to the wallings (80) parallel to the support beams.
8. Electrofilter according to claim 7, characterized in that the angle (92) defined between the two sides (93) has approximately 90°.
9. Electrofilter according to claim 3 and 7 or 8, characterized in that the crossbeams (82) extend over the entire distance between the two parallel neighboring support beams (31, 32, 33, 34) this way reaching over the profiles (91, 94), while the walling plates (95) are solid with the crossbeams (82).

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