GB2112672A - Electro-filter - Google Patents

Abstract

An electro-filter for horizontal through-flow of the gas to be purified, in which the gas flows between several spaced adjacent electrode planes (15, 16), parallel to the gas flow direction, the electrode planes having several parallel electrodes, elongate in the vertical direction, in which the electrodes in every other electrode plane (15) are negatively charged emission electrodes and the electrodes in the remaining electrode planes (16) are grounded precipitation electrodes which may be equipped with a striking device (9, 10) for detaching the dust adhering to them and for causing it to fall into a collection pocket (6) beneath. According to the invention, the electro-filter casing is equipped with a hatch (11) in the top, through which the electrodes can be cleaned from outside the electro-filter and in the longitudinal direction of the electrodes, without substantially damaging them. <IMAGE>

Description

SPECIFICATION Electro-filter The present invention relates to an electrofilter for a horizontal through-flow of the gas to be purified, and this invention relates in particular to an electro-filter having an electrofilter casing the opposite ends of which have an inlet for the gas to be purified and an outlet for the purified gas freed of dustlike impurities, and the lower part of which has at least one collection pocket for the dust which has been separated.In the electro-filter casing of the electro-filter of the invention there have also been fitted, in adjacent vertical planes which are parallel in the gas flow direction and spaced at a distance from each other, oblong parallel electrodes at a distance from each other in the gas flow direction, in which case preferably the emission electrodes in every other plane are negatively charged and the other, precipitation electrodes, are grounded and preferably equipped with striking devices for detaching the dust adhering to them and for causing the dust to fall into the collection pocket under the electrodes. In addition, the filter casing has at least one opening hatch for the cleaning of the electrodes in the filter casing.

By means of electro-filters it is possible to separate dustlike particles from gases very thoroughly. In electro-filters of the above-mentioned type, the dust particles are separated by charging the dust particles electrically by means of electrons liberated from the emission electrodes, the electrons tending to move towards the grounded precipitation electrodes owing to the effect of the power of the electrostatic field.In this manner, the dust particles can be caused to adhere to the precipitation electrodes without being recaptured in the gas flow, whereafter the dust particles can be separated from the precipitation electrodes, and possibly also from the emission electrodes, by striking them at certain time intervals in order to detach the dust material and to cause it to fall into the collection pockets below the electrodes; from the pockets the dust material can be carried away by means of, for example, screw conveyors or similar mechanical devices. In order to achieve a sufficient separation efficiency, the electrode planes must be placed as close to each other as possible, but not so close that they touch each other.However, in the event that too much dust collects on the electrodes, a contact may be produced between them, whereby the electrostatic field between the emission and the precipitation electrodes practically disappears. Such a situation may be produced in spite of the shaking and striking of the electrodes, and in such a case, or preferably before it at regular intervals, the electrodes must be cleaned manually. For this purpose there is, in the lower part of the side wall of the electro-filter casing of the electrofilter, one or several manholes, through which a man can creep inside the electro-filter casing to clean the electrodes.

The precipitation electrode planes usually consist of several stiffened precipitation electrodes which are oblong in their vertical direction and equipped with bent edges and a flat intermediate part, and the emission electrode planes between the precipitation electrodes consist of several vertical electrode wires. The cleaning of such electrodes from inside the electro-filter casing is very unpleasant and cumbersome.First of all, the temperature prevailing inside an electro-filter casing is often rather high, even if the casing has been allowed to cool for a while before the cleaning; second, cleaning in the transverse direction of emission electrodes which are oblong and wire-like in the vertical direction and precipitation electrodes which have a corrugated cross section is very cumbersome; and third, such cleaning in the transverse direction easily damages the thin and tautly strung emission electrodes in particular, in which case the electro-filter casing must be opened and the damaged electrode plane must be replaced or repaired. In addition to heat, the worker is also exposed to very dusty air inside the electro-filter casing, which hampers both breathing and visibility.For economic reasons it is often necessary to make the electro-filters high, in which case the length of the electrodes is also great, for example 10 m or more. In such a case the worker carrying out the cleaning must climb very high inside the electrode casing, which is very dangerous in the prevailing poor visibility conditions.

The object of the present invention is thus to provide an electro-filter in which the cleaning of the electrodes is easier and more pleasant than previousiy, and in which the cleaning procedure does not substantially strain the electrodes mechanically. A further object of the invention is to provide an electro-filter in which the electrode planes can be simply removed from the electro-filter casing for replacement, maintenance or additional cleaning.

The main characteristics of the invention are given in accompanying Claim 1.

In the electro-filter according to the invention, the cleaning problem has been solved very simply in such a way that the cleaning hatch has been fitted in the top of the electrofilter casing, above the electrodes, in which case the cleaning can be carried out from outside the electro-filter casing, without exposure to the heat and dust prevailing in the electro-filter casing, and the cleaning is in this case carried out in the longitudinal direction of the electrodes, and thus the corrugated cross sectional profile of the precipitation electrodes does not have an adverse effect, and the tautly strung emission electrodes are subjected to no transverse strains, the straining being substantially in the longitudinal direction of the wire, a direction in which its strength is very good.

When the top of the electro-filter casing has been opened, the dust adhering to the electrodes can be detached effectively by merely striking the upper end of the electrode and, if a cleaning brush is used, its operation can be automated by means of a mechanical lifting device, since the cleaning brush now moves in the vertical direction, along the electrodes.

In this case the great length of the electrodes and the great height of the electrode planes do not greatly complicate the cleaning.

It has now been observed that an electrofilter can be provided with a large hatch without its air-tightness being adversely affected. According to a preferred embodiment of the present invention, this is achieved by framing the opening in the top of the electrofilter casing of the electro-filter with a sand pocket or the like, in which the edge projecting from the lower surface of the hatch which covers this opening and is of the same size and shape settles tightly. During operation, there prevails a vacuum in the electro-filter casing, in which case the outside air pressure tends to press the hatch edge tightly against the sand pocket surrounding the opening.

The upper side of the hatch is preferably provided with one or several lifting handles or the like, by which the hatch can be lifted by means of a lifting device from top of the electro-filter and be moved aside for the cleaning of the electrodes.

In case the opening to be closed with a hatch in the top of the electro-filter casing is so large that the electrode planes can be removed from the filter casing, the electrode planes are preferably detachably supported by supports inside the electro-filter casing, the supports of the emission electrode planes being in this case insulated from the electro-filter casing and electrically connected to an outside source of current for charging the emission electrodes negatively.

The invention is described below in greater detail with reference to the accompanying drawings, in which Figure 1 is a perspective representation of an electro-filter according to the invention, partly in section, Figure 2 depicts a cross sectional side view of the electro-filter of Fig. 1, and Figure 3 is a partial perspective representation of several electrode planes used in the electro-filter of Fig. 1.

In Fig. 1, the electro-filter casing is indicated by numeral 1. At the two opposite ends 2 and 3 of the electro-filter casing there are respectively an inlet 4 for the gas to be purified and an outlet 5 for the purified gas, in which case the gas to be purified flows in the horizontal direction through the filter casing 1. The lower part of the filter casing has a dust collection pocket 6 for collecting the dust separated from the gas and for removing it from the filter casing 1.The top of the filter casing 1 is covered with two hatches 11, which have lifting handles 1 7 for lifting the hatches 11 and for moving them aside from above the electrode planes 1 5 and 1 6 inside the filter casing 1, the electrode planes being flitted, as seen in the gas flow direction, in two successive zones 22 and 23, in which the electrode planes 1 5 and 1 6 are situated adjacently at short intervals from each other, in parallel to the side walls 21 of the filter casing 1, in such a way that narrow flow channels are formed between the filter planes 1 5 and 16.

The cross sectional Fig. 2 shows in greater detail the placement of the adjacent filter planes 1 5 and 16. The emission electrode plane 1 5 is supported, in such a way that it can be detached and lifted, by supports 1 8 bearing on the electric filter casing 1, and by means of insulators 20 electrically insulated from the filter casing and connected to the negative pole of an external source of current (not shown). Furthermore, the emission electrode planes 1 5 are equipped with a striking device 9 for detaching any dust possibly adhering to the emission electrodes and for causing it to fall into the collection pocket 6 situated beneath.The precipitation electrode planes 1 6 are suspended from support beams 19, which bear, in such a way that they can be detached and lifted, on the electro-filter casing 1, in addition to which the filter electrode planes 1 6 are equipped with a striking device 10 for striking the precipitation electrodes in order to detach the dust adhering to them and to cause it to fall into the collection pocket 6 beneath.

In order that the electrodes could be cleaned from outside the electro-filter casing 1, in the longitudinal direction of the electrodes, and that the electrode planes 1 5 and 1 6 could, when necessary, be removed from the electro-filter casing 1, the top side of each separation zone 22 and 23 has an opening 1 2 so large that the electrode planes 1 5 and 1 6 can be removed from the electro-filter casing 1 through these openings 12, in addition to which the electrodes can be easily cleaned from above and from outside the electro-filter casing when the hatches 11 covering these openings 1 2 are lifted off and moved aside from above the openings 1 2.

The cleaning can be carried out by striking the upper ends of the electrodes and/or by lifting or lowering a cleaning brush in the narrow clearances between the electrode planes 1 5 and 1 6. In this case, the cleaning takes place in the longitudinal direction of the electrodes, and a lifting device can be used as an aid. The person carrying out the cleaning need not descend into the electro-filter casing but can stand on, for example, the beams 1 9 supporting the filter electrode planes 1 6.

In order to seal the hatches 11, there is around the edge of each opening 1 2 a sand pocket 13, into which the edge 1 4 bent downwards from the edges of the hatch 11 has been fitted to settle tightly. The vacuum prevailing in the electro-filter during operation causes the ambient air pressure to press the edges 14 of the cover 1 effectively into the sand pockets 13.

The electro-filter shown in Figs. 1 and 2 is also provided with manholes 24 in the lower part of its side walls 21, but these need no longer be used for the purpose of cleaning the electrodes but only, for example, for the maintenance of the devices inside the electro-filter casing 1, such as the striking devices 9 and 10.

The structure of the electrode planes 1 5 and 1 6 is shown in greater detail in Fig. 3. As can be seen from Fig. 3, the emission electrode planes 1 5 consist of a tube frame 26, the wires 7 serving as emission electrodes having been strung vertically, at regular intervals from each other between the horizontal parts of the frame. The precipitation electrode planes 16, on the other hand, consist of profiled sheets 8 having a corrugated cross section, suspended from the support beams 19, the lower ends of the sheets being attached to bars 25, the ends of which the striking device 10 shown in Fig. 2 has been fitted to strike in order to detach the dust adhering to the precipitation electrodes 8.

As clearly seen from Fig. 3, the clearance left between the electrode planes 1 5 and 1 6 is not very great, and thus it is clear that the cleaning is considerably easier to carry out in the vertical direction than in the transverse direction. When the cleaning is carried out in the vertical direction, the profilation of the precipitation electrode sheet 8 does not complicate the cleaning, and the thin emission electrode wires 7 are not broken as easily as they would if the cleaning were carried out in the transverse direction. The present invention thus means a considerable improvement over prior known electro-filters, which have to be cleaned from the inside.

Claims (9)

1. An electro-filter for the horizontal through-flow of the gas to be purified, such electro-filter comprising an electro-filter casing having at one end an inlet for the gas to be purified and at the opposite end an outlet for the gas which has been purified of dust-like impurities, and in the lower part one or several collection pockets for the separated dust; several parallel, vertically extending oblong electrodes in the electro-filter casing in adjacent vertical planes which are parallel in the gas flow direction and are spaced form each other, some of which electrodes serve as emission electrodes and are negatively charged and the other electrodes, serving as precipitation electrodes, are grounded; wherein the filter casing has at least one opening hatch for the cleaning of the electrodes in the filter casing, said hatch being in the top of the electro-filter casing, above the electrodes, so that the cleaning can be carried out from the outside in the longitudinal direction of the electrodes.

2. An electro-filter according to Claim 1, wherein said emission electrodes are disposed in every alternate one of said spaced vertical planes.

3. An electro-filter according to Claim 1 or 2, wherein said precipitation electrodes are equipped with striking devices for detaching the dust adhering to them and for causing it to fall into the or a collection pocket beneath the precipitation electrode.

4. An electro-filter according to Claim 1, 2 or 3, wherein the hatch is hermetically fitted over an opening in the top of the electro-filter casing by means framing this opening, and by an edge of the same size and shape as the framing means projecting from the lower surface of the hatch to engage the framing means.

5. An electro-filter according to Claim 4, wherein said framing means is a sand pocket.

6. An electro-filter according to any one of the preceding Claims, wherein spaced electrode planes are defined by frames, and the hatch closes an opening in the top of the electro-filter casing which opening is of such a size that the electrode frames can be removed from the filter casing for replacement, maintenance or cleaning.

7. An electro-filter according to any one of the preceding Claims, wherein the upper side of the hatch has one or several lifting handles.

8. An electro-filter according to Claim 6 or 7, wherein the electrode frames are supported by supports inside the electro-filter casing, at least the supports of the emission electrode frames being insulated from the electro-filter casing.

9. An electro-filter constructed and arranged substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.