EP2011575A1

EP2011575A1 - A collecting electrode for a liquid flushed electrical precipitator

Info

Publication number: EP2011575A1
Application number: EP07013152A
Authority: EP
Inventors: Mikael Dalhus
Original assignee: Envirtek AS
Current assignee: Envirtek AS
Priority date: 2007-07-05
Filing date: 2007-07-05
Publication date: 2009-01-07

Abstract

This invention relates to electrical precipitation for use when separating suspended materials from gasses, and it relates especially to collecting electrodes being used in a liquid flushed electrical precipitator where a thin film of liquid is passed over the surface of the collecting electrodes upon which the collected material is precipitated.

Description

FIELD OF THE INVENTION

The present invention relates to electrical precipitation for use when separating suspended materials from gasses, and it relates especially to collecting electrodes being used in a liquid flushed electrical precipitator where a thin film of liquid is passed over the surface of the collecting electrodes upon which the collected material is precipitated.
US 3,785,118 describes a liquid spraying electrical precipitator comprising a pair of electrically conductive walls and a plurality of spouts on each wall. A cleaning liquid such as water is applied to one of the walls, as by drippers at the top thereof, and flows downwardly to the spouts thereon. The liquid is caused to transit the gap between the walls by application of a strong electrical field. Preferably the wall of initial application is grounded, and the other wall is connected to a source of high positive potential. The electrical field so created causes negatively charged drops to be sprayed from the spouts on the first wall and to follow a somewhat downwardly directed trajectory until they impinge upon the second wall. Water impinging on the second wall runs downwardly to spouts thereon and is resprayed as positively charged drops across the gap to the first wall. This process is continually repeated until the water finally exits at the bottom of the precipitator. A stream of dirty gas flows upwardly through the precipitator and is cleansed by the action of the positively and negatively charged drops continually spraying and respraying back and forth between the walls.
US 4,389,225 describes an electrostatic precipitator with a discharge electrode having dimensional and configuration characteristics which provide high field strength and high current density particularly in a wet electrostatic precipitator. The round cylindrical collector tube of length (L) and with an inner diameter (D) has a coaxially positioned discharge electrode having an electrode supporting mast of a diameter from 0.25 to 0.40 D with an electrically conducting closed screw flight secured to the mast. The screw flight has an overall diameter (d) of from 0.33 to 0.67 D with a pitch of from D-d/2 to D-d and an overall length of from one screw revolution to L-(D-d), preferably one-half L or less and most preferably one to two revolutions. The short screw flight is economical and readily adjusted. The screw flight has a thickness of from about 0.05 to 0.15 inch and has a symmetrically curved outer edge. The collector tube is flared at its lower end to direct water away from the electrode mast as the water is discharged from the tube. The discharge electrode is supported from above and centered by means of adjustable tie rods at its lower end.
US 2,631,685 describes a filter system where tubular and hollow collector electrodes are used and which on their inside are sprinkled with a thin film of water.

OBJECT AND SUMMARY OF THE INVENTION

The object of the invention is to provide a collecting electrode assembly to be used as a liquid flushed electrical precipitator with effective precipitation properties.
The invention is described in the independent claims, and embodiments of the invention are described in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, preferred embodiments of the invention will be described referring to the figures, where

figure 1 illustrates a collecting electrode assembly,
figure 2 illustrates the principle behind a collecting electrode comprising a control chamber,
figure 3 illustrates a collecting electrode with a structured surface,
figure 4 illustrates a collecting electrode comprising a control chamber comprising means for eddying said liquid,
figure 5 illustrates a rotor template for creating a rotational flow.

DESCRIPTION OF EMBODIMENTS

Figure 1 illustrates a collecting electrode assembly where liquid 103 is passed over the surface of a cylinder shaped electrical precipitator 101 with a ground connection. Ionized gas with suspended materials 102 is forced over the liquid passed surface of the cylinder shaped electrical precipitator 101, whereby suspended materials are precipitated in the liquid passed surface and led to a container (not shown). Non-contaminated gas without suspended materials 107 hereafter leaves the collecting electrode assembly.
Figure 2 illustrates the principle behind a collecting electrode comprising a control chamber 205. Liquid 203, which can be optionally pressurized, is led into control chamber 205 at the top as indicated by the arrow 204. From the control chamber 205 the liquid 203 is led to the surface of the electrical precipitator 201. The liquid 203 can for instance be led directly to the surface of the electrical precipitator 201 from the control chamber. Alternatively, the liquid 203 can be led to the surface of the electrical precipitator 201 through the electrical precipitator itself. In this embodiment, the electrical precipitator 201 is made from a permeable or porous material such as perlite. The electrical precipitator 201 can have many geometrical forms and shapes such as plates and rods.
Figure 3 illustrates a collecting electrode with a structured surface 306. Liquid (not shown), which can be optionally pressurized, is led into the control chamber 305 at the top as indicated by the arrow 304. From the control chamber 305 the liquid (not shown) is led to the structured surface 306 of the electrical precipitator 301. The structured surface 306 could be formed as an integrated part of the electrical precipitator 301 such as e.g. a grinded finish. In another embodiment the structured surface 306 could be web or fabric drawn over the electrical precipitator 301 such as a net or mesh. The liquid (not shown) can for instance be led directly to the surface of the electrical precipitator 301 from the control chamber 305. Alternatively, the liquid (not shown) can be led to the surface of the electrical precipitator 301 through the electrical precipitator itself. In this embodiment, the electrical precipitator 301 is made from a permeable or porous material such as perlite having the ability to both absorb and emit liquid. The electrical precipitator 301 can have many geometrical forms and shapes such as plates and rods. By having a structured surface the retention of time of the liquid passing over the electrical precipitator 301 is prolonged compared to a surface having smooth finish. Moreover, the structured surface of the electrical precipitator 301 'breaks up' the substantially laminar flow of contaminated gas (not shown), creating turbulence around the electrical precipitator 301 which contributes to a more effective precipitation of the suspended materials from the contaminated gas (not shown). The advantages of the structured surface 306 of the electrical precipitator 301 are obtained regardless of whether liquid is passed over its surface or not. Hence, in an embodiment of a grounded electrical precipitator with a structured surface the suspended materials of an ionized gas are still precipitated.
Figure 4 illustrates a collecting electrode comprising a control chamber 405 comprising means for eddying said liquid. The control chamber comprises a pressure chamber 411, a rotor template 413, and a prerotation chamber 415. The liquid 403 is pulsed into the pressure chamber 411 under pressure at the top of the control chamber 405 as indicated by the arrow 404. The pulse is generated by fluctuation of the pressure. In the pressure chamber the pulsed pressurized liquid 403 is led to the rotor template 413 (for a detailed description see also figure 5) which is a disc with a groove on its side having a helical course along its rotational axis. The rotor template 413 has an inlet to the groove and a corresponding outlet at the top and bottom sides of the disc, respectively. The pressurized liquid 403 enters the groove inlet on the top of the rotor template 413 and causes the rotor template to rotate about its axis. As the liquid 403 is pulsed into the pressure chamber 411, the rotational speed varies. Due to the helical groove on the side of the rotor template 413 and its rotation, the liquid 403 exits the rotor template as an eddy. Due to the varying rotational speed of the rotor template 413, the eddied liquid 403 leaves the rotor template 413 in waves. In the pre-rotation chamber 415, the eddy of liquid is focused before it enters the structured surface 406 of the electrical precipitator 401 having a ground connection. On the structured surface 406 of the electrical precipitator 401, the eddied liquid 403 continues its helically shaped movement and is eventually led into a container (not shown). When ionized gas with suspended material (not shown) is forced over the liquid passed surface of the electrical precipitator 401, the suspended materials are precipitated in the eddied liquid 403 passing along the structured surface 406 of the electrical precipitator 401 and led to a container (not shown). By eddying the liquid 403 and having a structured surface, the retention time of the liquid passing along the structured surface 406 of the electrical precipitator 401 is prolonged considerably, creating a more effective precipitation and a more efficient use of the resources in that process. Moreover, the structured surface 406 contributes to the precipitation process as this 'breaks up' the substantially laminar flow of contaminated gas (not shown), creating turbulence around the electrical precipitator 401 which contributes to a more effective precipitation of the suspended materials from the contaminated gas (not shown).
Figure 5 illustrates a rotor template 513 for creating an eddied flow. The rotor template 513 is a disc which can be rotated about an axis 522. The rotor template 513 comprises a groove 528 on its side having a helical course along the axis of rotation, resembling e.g. a piece of a worm shaft or a threaded screw. The rotor template 513 has an inlet 524 to the groove and an outlet 526 of groove. The pressurized liquid enters inlet 524 of the rotor template 513 and exits at the outlet 526 and causes rotation of the rotor template 513. Due to the rotation of the rotor template 513, the liquid exits the rotor template as an eddy. The rotational speed of the rotor template 513 can vary by pulsing the pressurized liquid which causes the eddied liquid (not shown) to leave the rotor template 413 in waves. Depending on from which direction the pressurized liquid enters the rotor template 513, the inlet 524 can be an outlet 526, and vice versa.

NOMENCLATURE

101, 201, 301, 401: Collecting electrode
102: Ionized gas with suspended materials
103, 203, 303, 403: Liquid
204, 304, 404: Arrow indicating inlet of pressurized liquid to the control chamber
205, 305, 405: Control chamber
306, 406: Structured surface
107: Non-contaminated gas
411: Pressure chamber
413, 513: Rotor template
415: Pre-rotation chamber
522: Hub
524: Groove inlet (outlet)
526: Groove outlet (inlet)
528: Groove

Claims

A collecting electrode assembly for a liquid flushed electrical precipitator, said collecting electrode comprising a collecting surface having a surface for forming a film of liquid flowing on said collecting surface, characterized in that said collecting electrode further comprises a control chamber positioned above said collecting electrode for receiving and focusing a liquid input to form a liquid film flowing down said collecting surface.
A collecting electrode according to claim 1, wherein said collecting surface is structured.
A collecting electrode according to claims 1-2, wherein said collecting surface is at least partly covered by a masked net.
A collecting electrode according to claims 1-3, wherein said collecting electrode is cylinder shaped.
A collecting electrode according to claim 4, wherein said control chamber is adapted to ensure that said liquid surface further comprises means for eddying said liquid, whereby said formed liquid film on said collecting surface flows down and around said cylinder shaped electrode.
A collecting electrode according to claim 5, wherein said means comprises a snail shaped rotor template for creating a rotational flow and a pre-rotation chamber for stabilizing said rotational flow before forming said liquid film flowing down and around said collecting surface.
A collecting electrode according to claims 1-3, wherein said collecting surface of the collecting electrode is a plate.
A collecting electrode according to claims 1-7, wherein said collecting electrode is hollow and the collecting surface is permeable and wherein said control chamber guides the water input to an inner part of the electrode resulting in a liquid film on said collecting surface.
A collecting electrode according to claims 1-8, wherein said liquid input to said control chamber is delivered with a pressure.
A collecting electrode according to claims 1-9, wherein said liquid input to said control chamber is delivered as liquid pulses.
A collecting electrode according to claims 1-10, wherein said control chamber comprises a pressure chamber increasing the pressure of the liquid input.