Electrostatic precipitator

Abstract

 An electrostatic precipitator includes an ionisation unit (1) with electrodes (11,12) to charge oily particles in an air flow and downstream a particle precipitating unit (2) for entrapping the charged particles in the air flow from the ionisation unit (1) by means of an electrostatic field produced between a plurality of adjacent and alternately charged electrode plates (21,22). Scrapers (4) being mounted between adjacent plates (21,22) for removing deposits from the plates (21,22) with a collecting unit (3) located underneath the precipitating unit (2) for collecting the deposits. The scrapers are attached to arms (42) which swing in an arc over the surface of the plates driven by oscillating shaft 41.

Description

[0001] The invention relates to an electrostatic precipitator which may make use of a plurality of scrapers to remove the oily dust particles precipitated on respective rotatable electric plates.

[0002] In conventional electrostatic precipitators, oily dust particles are often adhered to electric plates by their own viscosity after a charge neutralization. When such particles are accumulated on electric plates to form a layer of oil matter over a period of time, the cleaning thereof is usually by patting or water wash. However, patting is not workable, while water wash must use a detergent. As regular detergents are unable to entirely decompose such oil matter, which will be mixed with water during the process of water wash, and then discharged into the sea through the sewage system, thus causing a secondary pollution. Besides, after water wash, electric plates shall not be re-used until they are entirely dried. It is time consuming and often needs a stand-by precipitator, thereby increasing the cost.

[0003] The invention has been accomplished under the aforesaid circumstances. It is therefore the main object of the invention to provide an electrostatic precipitator which is equipped with a plurality of scrapers for scraping away the oily dust particles precipitated on electric plates, and such particles thus scraped away can be collected by a collecting unit for disposal to prevent from a secondary pollution.

[0004] The invention will now be described in more detail by way of example and with reference to the accompanying drawings, in which:

Fig. 1 is a plan view of a prior art precipitator;

Fig. 2 is a plan view showing a preferred embodiment of an electrostatic precipitator according to the invention;

Fig. 3 is a sectional view of the electrostatic precipitator of Fig. 2;

Fig. 4 is a perspective view of the electrostatic precipitator of Fig. 2;

Fig. 5 is a plan view showing a modification of the electrostatic precipitator of Fig. 2;

Fig. 6 is a plan view showing another modification of the electrostatic precipitator of Fig. 2;

Fig. 7 is a plan view showing still another modification of the electrostatic precipitator of Fig. 2;

Fig. 8 is a plan view showing still another modification of the electrostatic precipitator of Fig. 2;

Fig. 9 is a plan view showing still another modification of the electrostatic precipitator of Fig. 2;

[0005] Referring to Figs. 2 to 4, an electrostatic precipitator in accordance with the invention is generally comprised of an ionization unit 1, a dust precipitating unit 2, a collecting unit 3, and a plurality of scrapers 4.

[0006] The ionization unit 1 comprises a plurality of metal wires for discharge of applied high voltage D.C. power and a plurality of metal ground plates 12 arranged in parallel with each other. The dust precipitating unit 2 comprises pairs of large and small electric plates 21, 22 reversed in conductivity and alternatively disposed in parallel at equal interval, wherein the large electric plates 21 are connected to positive electricity and mounted on a rotary shaft 23, each having four holes 24 spaced around the axis thereof at equal distance through which negative conductors 25 pass to connect with the small electric plates 22 in such a manner that does not contact the large electric plates 22. The air flowing in the dust precipitating unit 2 through the ionization unit 1 can flow out at the back of the dust precipitating unit 2. Each scraper 4 is mounted on a respective driving bar 42 disposed between a pair of large and small electric plates 21, 22 and connected to a swing link 41 for being driven thereby. When both sides of scrapers 4 respectively contact the adjacent large and small electric plates 21, 22 to remove the oily dust particles precipitated thereon, the particles thus removed are collected by a collecting unit 3 located underneath the dust precipitating unit 2.

[0007] With such an arrangement, when oily dust particles enter in the ionization unit 1, they are ionized to become charged particles and then enter in an electrostatic field produced by large and small electric plates 21, 22, making them attracted thereto by the action of coulombic force.

[0008] Over a period of time, electric plates 21, 22 would be covered by a layer of oily dust particles precipitated thereon, thus weakening the coulombic force of the electrostatic field and losing the function to attract charged oily dust particles. Under the circumstances, it is required to remove the oily dust particles thus precipitated in order to resume the working efficiency.

[0009] By starting the rotary shaft 23 and the swing link 41 in the dust precipitating unit 2, the scrapers 4 on respective driving bars 42 will be driven to scrape away the oily dust particles thus precipitated. As large and small electric plates 21, 22 in the dust precipitating unit 2 are coaxially rotated, and the scrapers 4 disposed therebetween can make a sector swing motion from the axis thereof towards the periphery, the route of swing motion made by the scrapers 4 would, in cooperation with the rotation of the dust precipitating unit 2, substantially cover the entire dust precipitating surfaces on the electric plates 21, 22, thus enabling the scrapers 4 to remove the oily dust particles precipitated on electric plates 21, 22 at the same time when they move along the swing route, and the oily dust particles thus removed would fall into the collecting unit 3 by their own weight for disposal to prevent the occurrence of secondary pollution.

[0010] Referring to Fig. 5, therein illustrated is a modification of the invention comprising a plurality of scrapers 4 spaced along a driving bar 42 at a predetermined interval. Each scraper 4 is designed to remove the oily dust particles precipitated on a specific circle of area on the large or small electric plates 21, 22 whose entire dust precipitating surface is then covered by the combination of these scrapers 4. By a cam mechanism 5, the driving bar 42 can make a linear reciprocating movement between the axis of electric plates 21 or 22 and the periphery thereof, helping increase the scraping area of the scrapers 4 to assure a better scraping effect.

[0011] It is understood that such plurality of scrapers 4 could be replaced by an elongated one-piece scraper 6 having a continuous cutting edge or a plurality of discontinuous cutting edges spaced thereon.

[0012] Fig. 6 shows another modification, in which an elongated one-piece scraper 6 is mounted on a fixed post 31 in the collecting unit 3. When the dust precipitating unit 2 is rotated making the electric plates 21, 22 passed over the scraper 6, the oily dust particles precipitated thereon are then removed by the scraper 6.

[0013] Referring to Fig. 7, therein illustrated is still another modification having four holes 24 spaced on either of large electric plates 21 around the periphery, and a driving shaft 43 may be additionally mounted in between large and small electric plates 21, 22 for connecting to a driving bar 44 of the scraper 6, which driving shaft 43 and the rotary shaft 23 are coaxial but are respectively driven by two different driving sources. When the driving shaft 43 is rotated, the scraper 6 on the driving bar 44 is carried to rotate for removing the oily dust particles precipitated on the electric plates 21, 22.

[0014] Fig. 8 shows a modification of Fig. 7, in which the driving shaft 43 is fixed holding the scrapers 6 on the driving bars 44 still, so as to remove the oily dust particles precipitated on the electric plate 21, 22 by the rotation of the dust precipitating unit 2.

[0015] In addition, various modifications and changes may be made to the invention. For example, the holes 25 spaced on either of the large electric plate 21 may be arranged at unequal intervals through which the negative conductors 25 pass to connect with the small electric plates 22; or such negative conductors 25 may be mounted on a coaxial socket in relation to the rotary shaft 23, with an insulating material disposed therebetween to avoid any short circuit. Further, as shown in Fig. 9, the negative conductors 25 may be spaced around the border of either large electric plates 21 having no holes 24 thereon for connecting to the small electric plates 22. Also, either scraper 4 may be designed to contact respective plates 21, 22 only at the time of carrying out the scraping operation, when the scraper 4 may turn at a certain angle holding its cutting edge against the electric plates for scraping off the oily dust particles precipitated thereon. If the scraper 4 is designed to scrape off the precipitated oily dust particles during the operation of dust precipitation, then such scraper 4 must be made from insulating material to avoid any electric conduction.

[0016] Moreover, the dust precipitating unit 2 may be otherwise surrounded or covered for protection thereof from deteriorating, and any deformation occurred to the surfaces of electric plates 21, 22 may be corrected for producing a constant electrostatic field.

[0017] At last, if the invention is used in a room with heavy oily dusts, a scraper may be installed for scraping the oily dusts adhered to the dust precipitating unit 2.

Claims

1. An electrostatic precipitator, comprising an ionisation unit (1) with a plurality of first electrodes (11) for connection to a high voltage D.C. source and a plurality of ground plates (12) forming second electrodes, the electrodes being arranged in parallel with each other to effect ionisation and to electrically charge particles in a flow of air through said unit; characterised by:-
   a particle separating unit (2) for entrapping charged particles from the air flow through said ionisation unit, said unit comprising adjacent pairs of parallel electrode plates (21,22) connected alternately to respective electrical conductors and mounted on a rotary shaft (23);
   a plurality of scrapers (4) each mounted between said adjacent pairs of electrode plates (21,22) with scraping edges contacting said plates (21,22) for removing particles precipitated thereon; and
   a collecting unit (3) located underneath said unit (2) for collecting the particles removed by said scrapers (4).

2. An electrostatic precipitator in accordance with Claim 1, characterised in that alternate plates (21) are connected electrically to the shaft (23) forming one conductor, and the other alternate plates (22) are electrically connected to rods (25) parallel to and spaced around said shaft (23), the rods forming a second conductor, said conductors being connected each to an opposite pole of a D.C. voltage source to establish an electrostatic field between adjacent pairs of plates (21,22), the rods (23) mechanically connecting the plates (22) with the plates (21).

3. An electrostatic precipitator in accordance with Claim 1 or 2, characterised by the plurality of scrapers (4), being mounted on arms (42) pivoted about an axis (41) parallel to and spaced from that of said rotary shaft (23), said arms (42) moving said scrapers (4) over an arc extending from the axes (23) of said plates (21,22) towards the periphery thereof, so as to cover substantially the entire precipitating surfaces of said plates (21,22) during rotation thereof.

4. An electrostatic precipitator in accordance with Claim 1 or 2, characterised in that the scrapers are mounted on arms (42) driven in a linear reciprocating movement from the peripheries of said plates (21,22) to adjacent the axes thereof, so as to cover substantially the entire precipitating surfaces of said plates (21,22) during rotation thereof.

5. An electrostatic precipitator in accordance with Claim 1 or 2, characterised in that the scrapers (4) are mounted on fixed posts (31) in said collecting unit (3) to form elongate one-piece scraper blades (6) extending from the periphery of the plates to adjacent the axes.

6. An electrostatic precipitator according to Claim 1 or 2, characterised in that a second driving shaft (43) is coaxial with the drive shaft (23) and rotatable relative thereto, the scrapers being mounted on arms (44) carried by said second shaft (43).

7. An electrostatic precipitator according to Claim 6, characterised in that said driving shaft (43) is fixed and holds said scrapers (4) and said arms (44) stationary.

8. An electrostatic precipitator according to any preceding claim characterised in that the conductor rods (25) connect the plates (22) with the plates (21) and are spaced around the periphery thereof.

Drawing