FR2530496A1 - METHOD, DEVICE AND INSTALLATION FOR DEDUSTING A GAS CHARGED WITH DUST PARTICLES - Google Patents

Abstract

1. A dedusting device for a gas vein charged with fine dust passing in a high tension electric field to ionize the particles, said device comprising a guiding surface and an assembly of ionization electrodes placed facing the guiding surface and defining with them a succession of ionized areas separated by non-ionized areas, the guiding surface being raised to low or nil potential, and the ionization electrodes being raised to a high potential, said device being characterised in that the guiding surface (3) is a cylindrical surface (11) and the ionization electrodes (S1 , S2 ...) are formed by wires (5, 6) placed inside the tube (4) formed by the cylindrical surface (11) at a specific distance from the latter to constitute areas (7, 8) which can be assimilated to sectors of a circle, the gas vein describing a spiral path inside the geometrical area defined by the ionization sectors.

Description

The invention relates to a method for dedusting a gas vein

  charged with fine dust, the method of passing the gas stream through a voltage electrical field

  high to ionize particles.

  Two types of dust collection devices are mainly known, depending on the dimensions of the installation.

  dust collection facilities of gigantic size make up

  killed by high cylinders, having a wire-shaped ionization electrode The potential difference between the electrode and the surface of the cylinder surrounding the electrode is

  several hundred KV

  require special precautions for their implementation,

  and are intended for the dedusting of very large gas flows.

  Such facilities are not suitable for

  small amounts of gas, especially in

  air conditioning plants or industrial installations

trielles of medium size.

  There is a second type of dust collector intended for medium airflows. Such a device is schematically

  shown in Figure 1 which shows a dust removal device

  known rage which consists of a set of plates 1 defining parallel corridors, to be traversed by the gas stream to dust at the entrance to each corridor is an ionization wire 2 at a high voltage relative to to the

  plate voltage I which is usually the mass.

  The difference in voltage between the wires 2 and the plates 1 creates an electric field making it possible to ionize more or less the dust particles which pass into this electric field. These charged particles are then fixed on

the plates 1.

  To have a device of this type, which is relatively

  Efficiently, the plates 1 must be brought very close together to create a sufficiently intense electric field between the wires and the plates without having to apply a too great electrical potential to the wire 2. In general, the potential difference between the wires 2 and plates 1 is of the order of one

tens of KV.

  Practice shows that these dedusting devices

  which are used to remove suspended fine particles

  in the gases, are not particularly effective and their cleaning is relatively

disassembly of the group of plates.

  The present invention proposes to create a method and a dedusting device allowing a very effective dedusting by simple means, likely to

clean easily.

  To this end, the invention relates to a method that can be read above, characterized in that it creates a succession of zones in which there is a high electric field of the same direction, separated by zones in which there is no electric field, or a weak electric field, and one guides the gas vein through this alternation of ionized zones and

non-ionized areas.

  Through the passage of the gas stream in a succession of zones or ionized areas and alternating with non-ionized sectors, an efficient accumulation of charges on the dust particles is obtained, allowing the fixation of

  these particles on the guiding surface of the gas vein.

  A particularly interesting and simple embodiment of a device for carrying out the method according to the invention is characterized in that the surface of

  guiding is a cylindrical surface and the electrodes dif-

  are formed by wires placed inside the tube at a determined distance from it to form

  areas comparable to sectors of the circle.

  Such a device is very easy to make and is itself a device that does not require special support As it is a tubular element

  which may be of a non-conductive material coated internally with

  The manufacture of this element is particularly simple The fixing of the ionization electrodes inside this tube is also very simple for setting up an electrode support.

  ionization inside the tube.

  Particularly advantageously there is provided a baffle at the inlet of the dedusting device so as to communicate to the vein of gas to dust off an impulse along a helical path so that the gas stream crosses several times the same ionized areas to increase the particle charges and so /

3 -2530496

the effectiveness of dusting.

  A set of such dedusting devices can be grouped into a battery inside a box so as to operate in parallel. This box-shaped embodiment allows a double modular manufacturing both for the dedusting devices themselves and for caissons grouping a number of such dedusting devices This facilitates the manufacture and inventory management of both new parts and spare parts while allowing to adapt the invention to gas flows to

  dusting vary in very large proportions.

  FIG. 1 is a diagram of a known electrostatic precipitator

  Figure 2 is a schematic diagram of a provision

  Dust extraction system according to the invention. FIGS. 3 and 4 are perspective views.

  and in section of a device selo N the invention.

  Figure 5 is a more detailed view of a

  dust collector battery, according to Figures 3 and 4.

  FIG. 6 is a sectional view along VI-VI of the

battery of figure 5.

  Figure 2 is a block diagram of a device

  dedusting, according to the invention.

  The dedusting device, according to the invention, for dusting a gas valve charged fine dust particles and whose largest particles have already been removed by a mechanical filter, consists of a guide plate 3 of the gas vein circulating in the direction of the arrow A along the plate 3 This plate may be flat or curved With respect to and at a distance from the plate 3 are ionization son Fi, F 2, Fn carried by supports 51 , 52, Sne n The guide plate 3 is at a potential VO and the wires

  ionization F 1, F 2 Fn are at potentials Vi, V 2 P Vn.

  In general, the potential V O is that of the mass and the potentials

  V, V 2 'Vn which may be equal or neighboring are

  relatively high potentials of the order of ten KV.

  Between the sonizations F 1, F 2 Fn and the guide plate 3 are formed substantially triangular ionization sectors Si 52 Sn The gas stream guided by the guide plate 3 passes into the different sectors 51, 52 Sn, these sectors Su 52 * * Sn alternating with zones Z 1, Z 2, Zn which are not ionized There is thus an alternation of ionized zones and non-ionized zones. The gas stream A thus crosses this alternating succession of ionized zones and non-ionized zones and the particles are charged with electricity. According to the physicochemical characteristics of the particles, the intensity of the electric fields in the zones of ionization, etc., the particles are charge more or less quickly and detach from the next gas vein

  arrows B, C and D to stick to the wall 3.

  FIGS. 3 and 4 show an embodiment of a dedusting device implementing the general principle,

according to Figure 2.

  In FIG. 3, the guiding surface of the gas stream consists of a tube, for example a cylindrical tube 4 which contains two ionization wires 5, 6 set at potential VI, the surface

  tube 4 or the entire tube 4 being at a potential

VO.

  This gives two ionization sectors 7 and 8.

  By the impulse imparted to the gas stream at the entrance to the tube 4, this gas stream describes a spiral path so that the gas stream passes through the ionization sectors 7 and 8 several times; as previously described, the particles

  charge electricity through the ionization sectors.

  7 and 8 and when the load is sufficient, the particles

  of dust stick to the wall of the tube 4.

  This movement of the gas vein is shown schematically

  In fact, it is a simplified diagram since only a few particles are charged sufficiently to cross a single sector in order to obtain the path of a particle. stick to the

wall of the tube 4.

  Although, in the embodiment of Figures 3 and 4, the tube has only two ionization son 5 and 6, the number of telsefils can be increased depending on the nature of the gas to be treated, etc. Figures 5 and 6 , four dedusting devices, tubular It are placed inside a box 12 Each tube It

  contains a support 13 carrying for example two ionization wires 14.

  The H-shaped section support 13 is arranged along the axis of the tube being held therein by a stop in the form of a must, isolating, maintaining the appropriate spacing.

relative to the wall of the tube 11.

  The inlet 16 of the gas stream to be dusted in the box 12 is located on the side of the gas vein

  circulates in the direction of the arrows A, along the outer walls

  11, descending (according to FIG. 5) to first traverse a grid 17 which retains the larger particles and then up (arrow B) through a cyclone baffle 18 constituted by a helix mounted free to rotate, and penetrate inside the tubes 11 to be ionized and dusted The gas stream back in the tubes It following the arrows C to exit these tubes from above To avoid the shortcircuit of the gas vein, the upper part of the tubes 11 is sealingly connected to a plate 18 itself sealingly secured in the

box 12.

  In the upper part is a fan 19

  circulation of the gas vein.

  Figures 5 and 6 show the juxtaposition

  two such batteries with four dust collectors.

  Dusting tests were done using a prototype These tests consisted of counting the number of particles in 5 liters of air before and after

  Filtration This double counting allowed to give by different

  The efficiency of the device is between 98 and 9997 Due to the size of the particles The results of the measurements are given in Tables 1, 2 and 3 below: In these tables the particles are counted

  according to their diameter (diameter threshold) measured in micro-

  The efficiency of the filtration corresponds to 100 particles of entry, to the number of particles removed by filtration The efficiency thus corresponds to the difference

  the number of particles of entry minus the number of

  output particles, based on 100 particles.

TABLE 1

I

619,153

5107 o 5

352,304

32> i 4 37

325,523

Before filtration

> O O 7> 1 4 _

215,521

178,975

249 132 4 i 1 '> 458

42,736

34,339

29,947

28 v Wi

29,039

> 3 1> 5

  I 648 I 581 2 268 I 876 Average 4226 d 102 293 1863 55

TABLE 2 -

  After filtration> 0 5> 0.7> 1 4> 3> s

7541 1734 237 4 O

8877 2043 244 7 2

4984 1424 186 6 1

4183 1218 177 3 2

4270 1325 184 4 3

Average 5971 1549 206 4 8 1 6

TABLE 3

  Use of the diameter> 0 5> O J 7>> 1 4> 3> 5 in mk: rorf 3 F Ilactrd (d n% 986 994 99 _ 7 _ 99> o 5 1 i

Claims (4)

R E V E N D I C A T I 0 N S   ) Method of dedusting a gas vein   loaded with fine dust, a process by which one does not   the gas stream in an electric field of high voltage to ionize the particles, characterized in that a series of zones is created in which a high electric field of the same direction prevails, separated by zones in which   which does not have an electric field, or an electric field   weak and guide the gas vein through this   ionized zones and non-ionized zones.   2) dedusting device for implementing the method according to claim 1, characterized in that it comprises a guide surface (3) and a set of ionization electrodes (F 1, F 2 Fn) placed in view of the guide surface (3) and defining therewith a succession of   ionized zones (F 1, F 2 Fn) separated by nonionic zones   (Z, Z 2 Zn I) the guide surface (3> being set to a low or zero potential (V 0) and the ionization electrodes (F 1,   F 2 Fn) being placed at a high potential (V 1, V 2 Vn).   3) Dust extraction device according to the claim   2, characterized in that the guiding surface (3) is a sur-   cylindrical face (11) and the ionization electrodes (Fit F 2 * 2) are constituted by wires (5, 6) placed inside the tube (4) at a determined distance therefrom to form   areas (7, 8) comparable to sectors of a circle.   4) Dedusting plant formed of a set   dedusting device according to claims 2 and 3,   characterized in that the tubular dedusting devices   lair (11) are grouped in a box (12) with parallel axes and internally contain supports (13) for   the ionization wires (14) parallel to the axis of the tubes (11).   Installation according to claim 4, characterized in that the inlet of the tubes (11) is provided with a deflector (18)   communicating with the gas vein a helical movement to the interior.   corresponding tube (11) to cut the sectors   ionized several times by the gas vein.   ) Installation according to any one of the claims   4 and 5, characterized in that the electrode support (13) is a H-shaped section support, held in a central position inside the tube (11) by spacers (15) insulators.