GB2451058A

GB2451058A - Disposable particulate collector for electrostatic precipitators

Info

Publication number: GB2451058A
Application number: GB0709281A
Authority: GB
Inventors: Colin Lawrence Amess
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-05-15
Filing date: 2007-05-15
Publication date: 2009-01-21
Anticipated expiration: 2027-05-15
Also published as: GB2451058B; GB0709281D0

Abstract

An electrostatic collector comprises a disposable roll of flexible conductive material 3 provided between a supporting shaft 7 and a take-up shaft 8. A winding mechanism 9 is provided to advance the material onto the take-up shaft and a high voltage charging means maintains the conductive material at a high voltage. In use, in an electrostatic precipitator, when the conductive material becomes covered in particulates, the winding mechanism rolls the material to expose a clean length and when all the material has been wound onto the take-up shaft, the cartridge may be replaced.

Description

I

DISPOSABLE PARTICULATE COLLECTOR FOR ELECTROSTATIC

PRECIPITATORS

This invention relates to the dust collection stages of electrostatic precipitators Air filters that work on the principles of Electrostatic precipitation are well known for their ability to remove particulates from the air without significantly impeding the airflow through the filter chamber, In such a device, air is drawn into an ionising chamber or duct whereupon particulates earned within the air become electrically charged. The air and charged particulates are then passed through an affangement of conductive plates held at high voltages forming an electrostatic field between the plates acting in a plane normal to the flow of air across the plates. The charged particulates contained within the air migrate to collector plates that are of opposite polarity to the charged particulates.

It is well known that the collection efficiency of such precipitators reduces as the surface of the collection plates become covered by a layer of particulates. The captured particulates tend to form an insulating layer leading to a reverse or back' electric field as the electrically restive layer allows surface particulates to become inductively charged.

Methods attempting to overcome this problem by removing the collected dust include mechanical vibration or rapping' of the plates, spraying with water and automated methods to wipe the plates. An alternative measure to provide clean collector plates employs the use of disposable collector assemblies. These assemblies are usually made of inexpensive materials and often use metalised film as the collector plates. In all cases the disposable collector plates are flat sheets or sheets formed into tubes or other shapes and fixed in position and supported by insulating materials.

I

In all cases of the electrostatic filters previously described, the filter efficiency declines until the collector plates are cleaned or disposed off and replaced.

According to the present invention as claimed in claim!, there is provided an electrostatic filter wherein the collector plates comprise an electrically conductive flexible material on a roll that is unwound at an appropriate rate to expose a clean proportion of collection surface while the dirty or dust covered proportion of the surface is wound onto a second roll trapping the collected dust between successive layers of the roll. Efficient operation of the filter is therefore maintained by ensuring that a winding mechanism always exposes a sufficient area of clean plate available for incoming dust to be attracted to. It should be noted that the flexible conductive material may be aluminium foil, metal vacuum deposited synthetic film or any other flexible material that can be covered with a thin electrically conductive substance.

When the entire length of the conductive collector material has been used up, the roll of used conductive collector can be disposed off with the collected dust trapped between the layers of the roll preventing the release of the dust during the replacement procedure.

The feed and take-up roll assembly may also be integrated into a cartridge or cassette wherein a provision can be made for the rollers to engage with a motor or other winding mechanism forming a sub assembly attached to the filters body. Provision may also be made to electronically detect that the source of the conductive material is at its end and then not allow the motor to attempt to wind on more conductive material. A warning sounder or visual indicator may be used to signal that the filter collector material is exhausted and needs changing.

When dust enters the corona stage of an electrostatic filter, there is a proportional increase of coronode current as the mass of dust particles that take up charge. Further detectors may be used to monitor the DC current flowing to the coronode. The speed of the motor that winds out the conductive electrode material can then be controlled by an electronic circuit that varies the feed of clean conductive material according to the amount of dust being captured.

As described above, collector plates are arranged in pairs with large electrical potential differences between the electrode plates forming an electric field between the plates. A charged particle will be repulsed from one plate and attracted to the other plate. Only one plate in each pair therefore, becomes the collector or receptor of captured particles. The repelling plate in evely pair will remain substantially clean and free of captured dust. According to the present invention, either the attractor electrode surface or both attraction and repulsion electrode sur!ce plates may comprise an electrically conductive material on a roll. If an electrically conductive material on a roll is used as a repelling electrode to pair an electrically conductive material on a roll forming a collecting electrode, the rate of feed of clean conductive material from the repelling electrode will need only be a fraction of the collecting electrodes' rate of feed. Because the repelling electrode remains substantially clean, there may be cost advantages for the repelling electrode to take the form of a fixed electrode plate in many applications.

A specific embodiment of the invention will now be described by example with reference to the accompanying drawings in which:-Figure 1 shows a side and plan elevations of a motorised feed and take-up roll assembly; Figure 2 shows a pair of schematically simplified motonsed feed and take-up rolls arranged as a pair of electrode collection plates forming part of an electrostatic filter; Figure 3 shows a of schematically simplified motorised feed and take-up roll used in conjunction with a fixed conductive plate electrode to form a pair of electrode collection plates as part of an electrostatic filter: Figure 4 shows two schematically simplified motorised feed and take-up rolls separated by a fixed conductive plate electrode to form two pairs of electrode collection plates as part of an electrostatic filter: Figure 5 shows multiple pairs of schematically simplified motorised feed and take-up rolls and flat plate electrodes arranged to form alternate pairs of electrostatic electrode collection plates as part of an electrostatic filter; Figure 6 shows multiple pairs of schematically simplified motorised feed and take-up rolls arranged to form alternate pairs of electrostatic electrode collection plates as part of an electrostatic filter.

Referring to figure 1, a roll of disposable flexible conductive material I is supported by a shaft 7 that locates in keyed core 4 and a friction mechanism 11. A length of disposable flexible conductive material 3 is attached to a mandrel 2 supported by a take-up shaft 8 that locates in keyed core 5. An electric motor and ratchet gearbox 9 rotates mandrel 2 until the sheet of conductive material 3 is held under tension against the opposing friction mechanism 11. Shaft 7 and shall 8 are held at a fixed spacing determined by the length of member 10. When the conductive material becomes covered in attracted particulates, the electric motor can be energised thus winding a desired length of clean conductive material onto the take-up mandrel. The rate at which the conductive material is unwound may be a fixed amount per unit time.

Alternatively, a control circuit may monitor the quantity of charged particulates per unit time and thus provide the demand for the electric motor to unwind a clean length of conductive material.

It should be noted that the above description provides for a simplified illustration of the invention. It should be obvious that there are many ways to provide alternative mechanical and electrical configurations to achieve the same ends. The conductive roll and take-up mechanism may, for example be integrated within an inexpensive disposable cassette or cartridge.

Referring to figure 2. Two lengths of conductive material 3 are spaced parallel to each other under tension forming parallel conductive sheets in the body of an electrostatic precipitator 17. A high DC voltage source is connected to each of the disposable conductive sheets to maintain a large electrical potential difference between the sheets as shown symbolically. The conductive sheet polarities indicated are for a positive corona charging stage and should be reversed for a negative corona charging stage.

An electric fan 16 draws air or gas between grounded electrodes 12 and past a corona wire 13. Particulates trapped within the air passing between electrodes 12 and the corona wire or coronode become charged. As air is drawn between the conductive sheets, the charged particulates are deflected by the electric field formed between the conductive sheets towards the conductive sheet of opposite electrical potential. The clean air is expelled by the fan from the fan housing 10. Is

Referring to figure 3. A single roll of disposable conductive material is used in combination with a conventional flat plate collector. A high DC voltage source is connected to the roll of disposable conductive sheet 3 to and to the flat plate 18 in order to maintain a large electrical potential difference between the sheets as shown symbolically. The charged particulates are collected on the disposable conductive material.

Referring to figure 4. Two rolls of disposable conductive material are used in combination with a conventional flat plate collector. This arrangement forms a dual cell collection stage while deploying only one flat plate collector 18. High voltage DC sources are connected to the rolls of disposable conductive sheet 3 to and to the flat plate 18 in order to maintain a large electrical potential difference between the sheets as shown symbolically. The charged particulates are collected on each of the disposable conductive material sheets.

Referring to figure 5. A single roll of disposable conductive material is used in combination with two conventional flat plate collectors. This arrangement forms a dual cell collection stage. High voltage DC sources are connected to the rolls of flexible disposable conductive sheet 3 to and to the flat plates 18 in order to maintain a large electrical potential difference between the sheets and plate as shown symbolically. The charged particulates are collected on both sides of the disposable conductive material sheet It should be noted that in cases where both sides of the conductive sheet are to be used as a particulate collector, it is aerodynamically advantageous to arrange for the air to flow parallel to the axis of the rolls supporting the tensioned flexible conductive sheets.

Referring to figure 6. A plurality of rolls of disposable conductive material 3 is used to form multiple particulate collection cells. High voltage DC sources are connected to the rolls of flexible disposable conductive sheet 3 in order to maintain a large electrical potential difference between the sheets as shown symbolically. The charged particulates are collected on the flexible disposable conductive material sheet. l0

Claims

Claims 1. Apparatus forming part of an electrostatic precipitator for the collection of charged particulates comprising a disposable roll of electrically conductive flexible material tensioned between a supporting shaft and a take-up shaft, a means to incrementally advance the conductive material onto the take-up shaft, a high voltage charging means to maintain the conductive material at a high voltage potential difference referenced to other electrodes.