Electrofilter for the purification of smoke from in particular minor straw boilers

Abstract

An electrofilter for smoke purification having a set of mutually parallel positive electrodes, which form a number of mutually parallel ducts through which the smoke to be purified can pass and by a set of negative electrodes, which are suspended midway between the collection plates, the collection plates are designed as circular plates mounted at a uniform mutual distance on a rotating shaft, and the discharge wires are suspended from a common frame on which a vibrator is mounted which can vibrate and thus clean the discharge wires of collected dust. On the frame of the electrofilter between each collection plate, stationary scrapers are mounted which bear against each collection plate and clean them of dust.

Claims

1. An electrofilter for smoke purification consisting of several sets of positive collection plates and negative discharge wires, wherein the collection plates comprise steel plates which are earthed by a wire and fixed in parallel at a mutual distance of 100 to 400 mm, whereby parallel ducts are created between the collection plates through which the smoke to be purified passes in a horizontal flow, and the negative discharge wires are suspended midway between the collection plates, wherein the electrofilter is designed with a row of circular collection plates which are mounted at a uniform mutual distance on a rotating shaft, wherein, between each collection plate and a neighbouring plate, one or more discharge wires are mounted, which are suspended from a common frame on which a vibrator is mounted, which can vibrate and clean the discharge wires of collected dust, wherein, on a frame of the electrofilter, between each pair of collection plates, stationary scrapers are mounted for each of the collection plates which bear against and are able to clean the collection plates of dust, and wherein each of the collection plates is designed with evenly distributed cutouts, or through bores which can absorb any shear, expansion, or contraction of the collection plates owing to temperature fluctuations, so that the collection plates remain fully or approximately plane in operation, and wherein, at each collection plate, guide rollers are mounted that bear against the collection plate and keep this plane to ensure an efficient scraping process.

2. The electrofilter according to claim 1, wherein the evenly distributed cutouts are shaped as parts of circular rings which are mutually displaced in each quadrant.

3. The electrofilter according to claim 1, wherein the evenly distributed cutouts are rectilinear and approximately radial.

4. The electrofilter according to claim 2, wherein one side of a cutout of the evenly distributed cutouts is slightly inclined in relation to the other side of the cutout of the evenly distributed cutouts, which is perpendicular to the surface of the collection plate.

5. The electrofilter according to claim 1, wherein the evenly distributed cutouts are shaped as a row of through bores which can have a conical cross section.

6. The electrofilter according to claim 1, wherein the guide rollers are mounted so that they bear against the periphery of each collection plate.

Description

(1) The invention is explained in detail below with reference to the drawing, in which

(2) FIG. 1 is a known electrofilter,

(3) FIG. 2 shows the purification principle of the electrofilter shown in FIG. 1,

(4) FIG. 3 is a perspective and partial section view of an electrofilter with rotating collection plates,

(5) FIG. 4 is a side view of an electrofilter with rotating collection plates

(6) FIG. 5 shows a drawing corresponding to the drawing shown in FIG. 4, viewed from one end and with the discharge wires in drawn out position,

(7) FIG. 6 shows a rotating collection plate in which each quadrant is designed with cutouts shaped as parts of circular rings which are mutually offset at the transition from one quadrant to the next.

(8) FIG. 7 shows a sectional view following the line I-I in FIG. 6,

(9) FIG. 8 shows a rotating collection plate with rectilinear, approximately radial cutouts, and

(10) FIG. 9 shows a rotating collection plate in which the cutouts are shaped as through bores.

(11) When the voltage between the discharge wires and the collection plates is sufficiently high, the discharge wires will start emitting electrons e, which will immediately move towards the positive collection plates 1 which are earthed by a wire 1. This is called corona charging. On the way the electrons e will ionize the air molecules m, which will then be attracted by the neutral dust particles s whereby these become negatively charged and attracted by the collection plates, see FIG. 2.

(12) As shown in FIGS. 3 and 4 an electrofilter 6 according to the invention is designed with a row of, by way of example eleven, rotating circular collection plates 1 mounted at a uniform mutual distance on a rotating shaft 8. Between each collection plate 1 and a neighbouring plate discharge wires are placed which can be mounted on a frame 4, on which a vibrator 5 is mounted that can clean the discharge wires 3 of dust. Moreover, the electrofilter 6 is fitted with stationary scrapers 10 which bear against each of the rotating collection plates 1 and clean them of dust, which drops into hoppers 11 and 12 below. The gas to be purified is led into the electrofilter through an entry hole 13 and after purification out through an exit hole 14.

(13) As shown in FIGS. 6 and 8 the rotating collection plates 1 are designed with cutouts 15, which can be circular as shown in FIG. 6 or rectilinear and approximately radial as shown in FIG. 8. As shown in FIG. 7 one side 16 of a cutout can be slightly inclined in relation to the other side 17 which is perpendicular to the surface of the collection plate 1. This way a cutting effect can be obtained at temperature fluctuations in a collection plate 1, which can break up any lumps of dust that may have collected in the cutouts.

(14) As shown in FIG. 9 the collection plates 1 may also be designed with rows of through bores 18 instead of cutouts.

(15) The cutouts may also be shaped otherwise than shown in FIGS. 6 and 8.

(16) Designing the collection plates with cutouts or through bores has the effect that the collection plates do not shrink and/or buckle at temperature fluctuations. Thus the desired and necessary cleaning effect can be obtained if stationary scrapers are used. To make it even more certain that the collection plates 1 will not buckle, guide rollers not shown in the drawing are mounted at each collection plate.