WO2000033945A1

WO2000033945A1 - Method and device for cleaning effluents

Info

Publication number: WO2000033945A1
Application number: PCT/NO1999/000363
Authority: WO
Inventors: Torfinn Johnsen; Kjetil Naesje
Original assignee: Applied Plasma Physics AS
Current assignee: Applied Plasma Physics AS
Priority date: 1998-12-04
Filing date: 1999-12-03
Publication date: 2000-06-15
Anticipated expiration: 2001-06-04
Also published as: NO985703D0; NO985703L; AU1699000A; NO308238B1

Abstract

A method and a device are described for employing low temperature plasma and electrostatic filter technology to remove particles and other pollutants from effluent from incinerators, especially from furnaces and combustion chambers which are used in heating houses and office buildings. This is implemented by arranging substantially axially in a channel (3) which carries such pollutants, for example in a chimney leading from an incinerator, and electrode (1) which is connected to a high-voltage generator (4; 5; 11). The inner walls of this channel are electrically connected to earth, if necessary by applying an electrically conductive agent thereto. In a preferred embodiment the invention is realized in the form of an integrated part of the channel, for example in the form of a chimney cowl.

Description

Method and device for cleaning effluents

The present invention relates to a method and a device for using low temperature plasma and electrostatic filter technology in order to remove particles and other pollutants from effluents from incinerators, especially from furnaces and combustion chambers which are employed in heating houses and office buildings.

The discharge of pollutants in connection with the heating of houses and office buildings, especially involving the combustion of wood or petroleum products, is a major problem in large towns. Efforts to reduce such emissions have primarily been linked to the use of new clean-burning furnaces.

In the case of industrial effluents the use is known of electrostatic filters and purification plants based on non-thermal plasma. The use of such technology, however, has demanded a high level of investment and access to powerful energy sources, and has therefore been impractical for installation in connection with smaller systems intended for heating buildings.

By means of the present invention a solution has been provided which can easily be installed in chimneys and similar ventilation channels in private houses, office and business premises and the like, and which does not entail major investments nor require access to powerful energy sources. The characterizing features of the invention are set forth in claim 1. The associated claims indicate further features and advantageous embodiments of the invention.

By mounting a thin wire in the longitudinal direction in an exhaust channel and connecting it to a high-voltage generator while connecting the walls of the actual exhaust channel to ground, a simple filter is formed. The wire, which is mounted insulated from the exhaust channel's walls, forms a center electrode which will emit electrons to the environment. This will lead to oxidation of a large percentage of the particles in the effluent gases before they are discharged from the channel. In addition, particles which are too large to be oxidized are charged and attracted to the grounded channel wall as in an electrostatic filter. When used in surroundings such as those described above, i.e. primarily for heating of houses and office or business premises, extremely low outputs are required compared to those in previously known applications of similar systems for the purification of industrial effluents.

Within the scope of the invention there is room for a large number of variations and adaptations, particularly depending on the shape of the exhaust channel and what kind of material it is made of, as well as any other variations in the environment. The invention will therefore be described in further detail in the form of embodiments with reference to the attached drawings. Parts which correspond to one another in the different figures have the same reference numerals.

Figures la-c illustrate an embodiment of the invention mounted on the top of a chimney with rectangular and circular cross section respectively, together with a side section of such an embodiment.

Figures 2a-c illustrate an embodiment of the invention mounted on the side of a chimney with a rectangular and a circular cross section respectively, together with a side section of such an embodiment.

Figure 3 illustrates an embodiment of the invention mounted in a chimney cowl.

Figure 1 illustrates an embodiment of the invention in its simplest form. In figure l a and lb respectively there is illustrated a rectangular and a round variant of this embodiment. Figure l c is a sectional view of a similar embodiment. In this embodiment an electrode 1 is mounted on the outside of an insulator 2 which protrudes into the center of a chimney 3. The electrode is in the form of a thin rod or a wire hanging down into the chimney 3 from the insulator 2. The electrode 1 is connected to a generator (not shown) which generates the voltage required to establish an electric field in the chimney and detach a sufficient quantity of electrically charged particles to produce the desired reactions in the gas discharged through the chimney 3. The insulator may be mounted in a frame 4 which is mounted on the top of the chimney. The frame preferably has the same shape as the chimney's cross section. In a preferred embodiment the high-voltage generator will be designed in such a manner that it can be mounted inside this frame, thus facilitating installation of the system, since all the system's parts are mounted at one location and in one operation. In figure 2 there is illustrated an alternative embodiment where the insulator 2 is attached to an attachment means 5 mounted on the outside of the chimney. In this case it will be advantageous for the attachment means 5 to include the high-voltage generator. Otherwise this embodiment is similar to that illustrated in figure 1.

The insulator 2 will preferably be attached to frame 4 (fig. 1) or attachment means 5 (fig. 5) by means of a device which makes it possible to adjust how far the insulator protrudes into the chimney 3, for example by means of a telescopic design, a screw connection or in another known per se manner. This will make it possible to ensure that the electrode 1 can be centered accurately in the chimney 3 without the insulator 2 being specially adapted thereto.

In order to achieve the greatest possible degree of electron detachment, the electrode 1 should preferably be designed with sharp geometry, for example with a diameter of less than 1 mm, or in the form of a straight brush electrode, which is an electrode consisting of a straight center electrode from which a large number of thin electrodes protrude approximately perpendicularly to the center electrode's axis. To ensure that the electrode 1 is kept centered in the chimney passage a weight 6 may advantageously be mounted at the electrode's lower end. If it is desirable to avoid ionization below the weight 6 it may be designed without sharp edges, for example as a ball. If on the other hand it is desirable to maximize the ionization down in the chimney, the weight 6 may be designed with sharp edges, for example as an inverted drop. However, it is also possible to keep the electrode 1 centered in the chimney passage by means of one or more additional insulators (not shown) which may be attached to the chimney's inner walls or to an electrically conductive material which is arranged inside these walls.

In order to achieve the aforementioned effect corresponding to an electrostatic filter, where particles which are too large to be oxidized are charged and attracted to the chimney's inner wall, the chimney's internal walls should be grounded. If these walls are of metal or another electrically conductive material this is no problem. If this is not the case, in a preferred embodiment of the invention an electrically conductive material will be applied to the chimney's inner walls at least in the area of the chimney where the electrode 1 is located, for example by spraying on such a material. This material must then be connected to ground. Alternatively, a metal chimney may be provided on the inside of the original chimney, for example as a part of a chimney cowl. In such an embodiment, electrode, insulator and high- voltage generator will also preferably be premounted in the chimney cowl, thus making installation of the system extremely simple.

If the dimensions of the chimney are too large to enable an electric field to be established which is powerful enough to achieve the desired effect, the inside of the chimney can be divided up into several smaller chimneys, each containing an electrode 1. This too can be advantageously implemented by the multiple chimneys forming part of a chimney cowl.

Figure 3 illustrates a preferred embodiment of a system according to the present invention designed in the form of a chimney cowl. This chimney cowl is shaped like an H, where the inlet 7 leads the effluent which is to be purified into a channel which constitutes the H's transverse part 8. From this transverse channel 8 the effluent is led in both directions to both the vertical legs 9 of the H, the chimney cowl's outlet 10 being between these legs, both above and below. This is because both upwardly and downward-moving external air flows in the vertical legs of the H will give a low pressure and increased draught in the actual chimney, thus reducing the possibility of the purification system having any undesirable negative effects on the smoke's ability to rise in the original chimney.

In this embodiment the electrode 1 will be mounted in the transverse channel 8 of the chimney cowl, attached to at least one insulator 2 which extends from the inner wall to the chimney cowl. The high-voltage generator 1 1 will preferably be mounted on the outside of this transverse channel in the immediate vicinity of an insulator. The conductor which supplies voltage to the insulator will then be able to pass through the center of the insulator 2.

It has been shown that for chimneys on houses very low power outputs are sufficient to achieve a satisfactory degree of purification. The high-voltage generator can therefore be designed for low outputs (less than 500 W and preferably as low as 50 W - 200 W), thus avoiding problems associated with insulation and heat transport and permitting the use of surface-mounted components. The necessary length of the electrode 1 will depend on other dimensions of the chimney as well as on the effluent which is to be purified. The same applies to the voltage level for the generator. In a chimney with a diameter of approximately 10 cm, however, an electrode with a length between 10 cm and 200 cm will suffice. The voltage from the generator will preferably be of the order of 30 kV.

Even though the invention is described in the form of embodiments, a person skilled in the art will appreciate that a number of alternatives and modifications are possible within the scope of the invention. In the embodiments, for example, reference is made to chimneys, but a system according to the present invention will be capable of being adapted to other ventilation and exhaust systems. Furthermore, a person skilled in the art will understand that the dimensions of the system with respect to the electrode's length, voltage level from the generator etc. will have to be calculated according to the type and amount of effluent which is to be purified, the diameter of the chimney or exhaust system, how much of the length of the chimney or exhaust system is actually accessible for mounting such a system and other similar considerations. This, however, will be a matter of technical adaptations which must be implemented in each individual case.

Claims

PATENT CLAIMS

1. Method for removing particles and other pollutants from effluent from channels such as chimneys, ventilation and exhaust channels and the like, characterized in mounting an electrode (1) in the center of such a channel (3) and connecting said electrode (1) to a high-voltage source (4; 5; 11) and applying a voltage thus releasing charges to the channel, so that the charges cause oxidation of particles in the effluent, the channel's walls being electrically connected to earth with the result that particles which are not oxidized but charged will be attracted to the channel's (3) walls.

2. Method according to claim 1, characterized in that an electrode (1) with sharp geometry is employed.

3. Method according to claim 1 , characterized in that an electrode (1) is employed which has a diameter of less than 1 mm.

4. Method according to claim 1, characterized in that an electrode (1) is employed which is designed as a straight brush electrode.

5. Method according to one of the preceding claims, characterized in that an electrode (1) is employed which has a length of between 10 cm and 200 cm.

6. Method according to one of the preceding claims, where said channel (3) is substantially vertical, characterized in attaching said electrode's (1) upper end to an insulator (2) which protrudes into the middle of the channel (3) and attaching a weight (6) to said electrode's (1) lower end.

7. Method according to one of the preceding claims, characterized in that the channel's (3) inner walls are made electrically conductive by means of the application of an electrically conductive material, for example by spraying.

8. Method according to one of the claims 1 to 5, characterized in attaching said electrode (1) by means of at least one insulator (2) to the inside of an integrated part of the channel (3) which also includes the high- voltage generator (4; 5; 1 1), the channel walls in the said integrated part being made of an electrically conductive material.

9. Method according to claim 8, characterized in that the integrated part of the said channel (3) is a chimney cowl.

10. Device for removing particles and other pollutants from effluent from a channel such as a chimney, a ventilation or exhaust channel or the like, characterized in that it comprises an electrode (1) which is arranged substantially axially in the channel (3) and attached to the channel wall or in the vicinity thereof by means of one or more insulators (2), and that it further comprises a high-voltage generator (4; 5; 1 1) which is arranged to apply a voltage to the said electrode (1) which is sufficient to release charges to the channel, said charges causing oxidation of particles in the effluent, the channel's walls being adapted to be electrically connected to ground with the result that particles which are not oxidized but charged will be attracted to the channel's (3) walls.

1 1. Device according to claim 10, characterized in that the said electrode (1) has a sharp geometry.

12. Device according to claim 10, characterized in that the said electrode (1) has a diameter of less than 1 mm.

13. Device according to claim 10, characterized in that the said electrode (1) is a straight brush electrode.

14. Device according to claim 10, characterized in that the said electrode (1) has a length of between 10 cm and 200 cm.

15. Device according to one of the claims 10 to 14, characterized in that the said electrode's (1) upper end is attached to an insulator (2) which protrudes into the middle of the channel (3) and that a weight (6) is attached to the said electrode's (1) lower end.

16. Device according to claim 15, characterized in that the said weight (6) is designed without sharp edges in order to prevent the emission of charges from the weight (6).

17. Device according to claim 15, characterized in that the said weight (6) is designed with sharp edges in order to facilitate the emission of charges down the channel (3).

18. Device according to one of the claims 10 to 17, characterized in that it further comprises an electrically conductive agent which is applied to the channel's (3) inner walls, for example by spraying.

19. Device according to one of the claims 10 to 14, characterized in that it is designed as an integrated part of said channel (3) comprising the electrode (1), the insulator (2) and the high-voltage generator (4; 5; 1 1), the channel walls in the integrated part being made of an electrically conductive material.

20. Device according to claim 19, characterized in that the said integrated part is a chimney cowl.

21. Device according to claim 19 or 20, characterized in that the integrated part includes an inlet (7) which goes into a transverse channel (8), this transverse channel (8) being connected at both ends with respective vertical channels (9) whose upper and lower openings form the outlets (10) from said integrated part, said electrode (1) being arranged by means of the at least one insulator (2) in said transverse channel (8) and connected to the high- voltage generator (1 1).