WO1988004580A1

WO1988004580A1 - Device for purification of gases

Info

Publication number: WO1988004580A1
Application number: PCT/SE1987/000609
Authority: WO
Inventors: Thore Haraldson
Original assignee: Thore Haraldson
Priority date: 1986-12-16
Filing date: 1987-12-16
Publication date: 1988-06-30
Also published as: SE459320B; AU1086388A; SE8605390D0; SE8605390L

Abstract

A device for purification of gases mixed with dust, for example car exhaust fumes, flue gases and other gases containing electrically conductive or actuatable dust particles, said device comprising a flow channel extending from an inlet for the gases to be purified to an outlet for the purified gases, within which channel an electric high voltage field is arranged between electrodes of opposite polarity. In order to obtain an improved efficiency the flow channel (26) is provided with ionization means (41) arranged consecutively in the direction of flow, having the same or opposite polarity and disposed before each their electric high voltage field (27, 31; 27, 31) as seen in the direction of flow of the gas through the flow channel.

Description

Device for Purification of Gases

This invention relates to an electric purifying filter, more specifically a device for purification of gases mixed with dust, for example car exhaust fumes, also from diesel-driven vehicles, flue gases from combustion plants for solid as well as fluid fuels and other gases containing electrically conductive or actuatable dust particles, said device comprising a flow channel extending from an inlet for the gases to be purified to an outlet for the purified gases, an electric field being disposed between electrodes of opposite polarity in said flow channel, the outer surface of the flow channel being one of the electrodes, With increased acidification demands for ever better and effective purification of car exhaust fumes as well as flue gases and other gases have increased and the increased demands have also resulted in that more and more countries require purification of car exhaust fumes and establish limit values for the impurities in exhaust, flue gas and other gas discharges. In order to manage these limit values catalytic exhaust purification is used today in the car industry almost exclusively, which purification is relatively expensive, not the least due to the fact that the catalyst requires a careful control of the fuel-air mixture to the engine to operate maximally efficiently and requires relatively much power. Moreover, the catalytic exhaust purification has the disadvantage that it cannot purify exhausts from diesel engines in an efficient way.

It is therefore the object of this invention to provide a universally useful gas purifier which can be used for purification of car exhaust fumes, also from diesel engines, as well as flue gases from big as well as small combustion plants for solid or fluid fuels and other gases containing electrically conductive or actuatable particles and requires for its operation a low power and gives a high degree of purification despite this. If the present device for gas purification is used as car exhaust purifier it should be at least as efficient as the catalytic exhaust purifier and operate quite independently of the mixture of fuel and air to the engine. Moreover, the present gas purifier should be so constituted that it can be installed with ease everwhere where required to obtain an efficient purification of gases, i.e. also in exhaust systems of such motor vehicles lacking exhaust purification.

This object is achieved in that the device of the invention has been given the characteristic features defined in the claims.

The invention is described in greater detail in the following with reference to the enclosed drawings, wherein Fig. 1 shows schematically the inventive object in the form of an exhaust purifier for cars, Fig. 2 shows schematically an alternative embodiment of the exhaust purifier for cars, Fig. 3 shows schematically the inventive object in the form of an exhaust purifier for flue gases, Fig . 4 shows a voltage regulator of the present gas purifier in the form of a block diagram, Fig. 5 shows a section of another embodiment of the present device, Fig. 6 shows a section substantially taken along the line VI-VI in fig. 5 and Fig. 7 shows a plane view of an electrode plate included in the embodiment according to Figs. 5 and 6. Fig. 1 shows an embodiment of the invention intended for purification of car exhaust fumes and formed for connection to the exhaust system of a motor vehicle. More specifically, the exhaust purifier comprises an outer casing 1 of an electrically conductive material having an axially or radially directed inlet 2 for connection to the exhaust pipe of a car engine to lead in the exhaust gases to be purified and an axially or radially directed outlet 3 for the purified exhaust gases. A rod 4 of electrically conductive material is placed within the outer casing 1, which rod has the same cross-sectional form as the outer casing but a substantially smaller cross-sectional area and which is concentrically arranged within the outer casing 1 to form a gap 5 between the outer casing 1 and the rod 4 operating as a flow channel for the exhausts. This gap 5 should have the same or substantially the same width all around independently of the cross-sectional form of the casing and the rod which can be circular, square, rectangular, elliptic, polygonal, rhombic or have any other plane geometrical form.

The rod 4 is supported within the outer casing 1, completely electrically insulating from this, by means of insulators 6, preferably of tephlon or a corresponding non-electrically conductive material which can be rod-shaped in order to constitute a flow obstacle for the exhaust as little as possible. The rod-shaped insultors 5 are connected with the inside of the casing and with the outside of the rod and are arranged relatively close to the ends of the rod. At the front end of the rod as seen in the direction of flow an ionization wire 7, for example of cobalt or another equivalent material, is arranged which need not have the shape shown in Fig. 1 but can in principle have any form and extension. For example, it can comprise a single wire extending axially from the end of the rod or have a coil form that widens in parallel with or outwards from the end of the rod. This ionization wire 7 connected to the rod 4 is connected as anode to a regulating and adjustable voltage source 8 (Fig. 4) for a high D.C. voltage to which the outer casing 1 is connected as cathode to create an electric field between the inside of the outer casing serving as negative electrode and the rod 4 serving as positive electrode, i.e. in the flow channel through the exhaust purifier, the applied D.C. voltage amounting to 10-30 kgV. depending on the gap width which can vary between 5 and 30 mm.

In Fig. 2 an alternative embodiment of the exhaust purifier is shown schematically which is also intended for purification of exhausts from combustion engines inclusive of diesel engines and connectable to the exhaust pipe of the engines with an entering pipe 10 serving as inlet and terminating at some distance from an end wall 11 of an inner casing 12 enclosing the entering pipe 10 and serving as anode, said inner casing replacing the rod 4 in the embodiment according to Fig. 1.

The inner casing 12 is arranged concentrically in the outer casing 1 of the exhaust purifier and electrically insulated from this by means of preferably rod- -shaped insulators 6. The outer casing 1 is tightly connected to the entering pipe 10 of the exhaust purifier by means of an end wall located at some distance from the open end of the inner casing, with which the inner casing 12 ends in the outer casing 1. Thus, incoming exhausts are made to flow through the entering pipe 10 and thereafter in opposite direction through the gap 24 between the outside of the entering pipe and the inside of the inner casing to be diverted and flow next through the gap 25 between the outside of the inner casing and the inside of the outer casing and finally stream out purified through the outlet 3 of the exhaust purifier. One or more ionization wires 7 are thereby arranged at the end of the entering pipe 10 and connected either to the inner casing 12 serving as po sitive electrode or to the inlet pipe 10 serving as negative electrode and, further, ionization wires 7a are arranged after the inner casing 12 in the direction of flow which are either connected to the inner casing 12 serving as anode or to the inlet pipe 10 serving as cathode. Moreover, ionization wires 14 can be arranged at the beginning of the flow channel formed by the inlet pipe 10 and the inner casing 12 as well as at the beginning of the flow channel formed by the inner casing 12 and the outer casing 1, these ionization wires having the same polarity as the ionization wires 7 and 7a, respectively.

By this embodiment of the present gas purifier a purification in two steps of the gases is achieved, the first step being in the gap 24 between the entering pipe 10 and the inner casing 12 and the second step m the gap 25 between the inner casing 12 and the outer casing 1. The distance between anode and cathode should then be greater m step 1 than m step 2. In connection with step 1 isotopes can be arranged at the end wall 11 of the inner casing, the use of which has been found to be advantageous for achieving a still better purification degree.

In order to achieve the required electric field between anode 12 and cathode 1 and consequently m the flow channel through the exhaust purifier this is connected to the voltage source 8 for high D.C. voltage shown in Fig. 4. The applied voltage should preferably oe higner in tne first, man m the second purification step

In Fig. 3 a gas purifier according to tne invention is snown scnemat icaliy wnich is intended for purification of flue gases m a cnimney and comprises an outer casing 1 serving as cathoαe with inlet 2 and outlet 3 Concentrically witnin tne outer casino 1 is ar ranged an inner casing 15 supported electrically insulated from the outer casing 1, within this by the aid of insulators 6. A relatively narrow rod 16 also of an electrically conductive material extends through the inner casing 15 serving as anode and open at both ends, said rod being located in the center of the inner casing at a distance to the inside of the inner casing that should be the same as the gap width between the outside of the inner casing and the inside of the outer casing. At its ends this rod 16 is supported by supports 17 of electrically conductive material attached to the outer casing and spaced from the ends of the inner casing and which are of spoke type to be the least possible flow obstacle for the exhausts to be purified. The. rod 16 like its supports 17 serves like the outer casing 1 as cathode.

Also in this embodiment ionization wires 7, for example of cobalt or another equivalent material are connected, also in electric respect, to the inner casing 15 serving as anode, which wires can extend along the inside and/or outside of the inner casing straight or helically and/or be placed in the direction of flow before the inner casing 15 in the form of concentric circles, at least one of which should have a diameter smaller than the inner diameter of the inner casing while at least one other circle should have a larger diameter than the outer diameter of the inner casing to be on a level with the gap between the rod 16 and the inner casing 15 and between the inner casing 15 and the outer casing 1, respectively. In order to provide the required electric field between the rod 16 and the inner casing 15 and between this and the outer casing 1 this embodiment is also intended to be connected to the voltage source 8 shown in Fig. 4 for generation of a high D.C. voltage. The voltage source 8 which is adjustable comprises a voltage converter 20 for convertion of A.C. voltage into D.C. voltage connectible to a current source, for example a 12 V or 24 V battery or to the mains. This voltage converter 20 is connected to an oscillator 21 with amplifier driving a high voltage transformer 22 giving an output voltage of for example 2-5 kgV to a cascaded rectifier 23 having an output voltage of 10-30 kgV, the plus pole of which is connected to the anode of the exhaust purifier and the minus pole of which is connected to the cathode of the exhaust purifier. The oscillator 21 is steplessly adjustable for regulating the D.C. voltage from the rectifier 23 to the intended value. Tests have shown that the energy consumption for driving an exhaust purifier according to this invention only amounts to about 40 W.

In Figs. 5-7 another embodiment of the exhaust gas purifier is shown comprising a casing 26 consisting of an electrically conductive material defining a flow channel for the gases to be purified extending from an inlet 2 to an outlet 3 and which is intended to be enclosed by a protective casing which is shown only schematically in Fig. 5 with dashed lines 25. In the first purification step located immediately at the inlet 2 a number of electrode plates 27 are included which extend between the opposite side walls 28 of the casing and are connected with these, for example by welding or lugs 29 extending through holes in the side walls 28 and reveted on the outside so that an intimate contact is obtained between the plates 27 and the casing 26 which are shown with a rectangular cross-sectional form but can have another suitable such form, for example circular. The side walls 30 of the casing also function as electrode plates 27 and electrode plates 31 of opposite polarity are suspended between these electrode plates 27, 30 in two transversal rods 51 extending through openings 32 in the side walls 30 of the casing and attached to brackets 33 outside the casing. These are supported by and connected to insulators 34 which are each adjustably connected at their outer ends to brackets 35 attached to the casing 26, for example by means of a bolt 37 projecting from the very insulator body 36 and locking nuts 38 located on both sides of the associated bracket 35 so that the electrode plates can be brought into a position parallel with the electrode plates 27 in order to obtain the same gap width between the electrode plates 27, 30 and 31. In order to simplify this adjustment two insulators 34 can be arranged on one side of the casing 26 and one single on the other side meaning a suspension of the electrode plates 31 in three points which plates are electrically insulated from the electrode plates 27 and the casing 26 by the insulators 34.

Distance means 39 in the form of sleeves which are arranged on the rods 51 between the plates 31 and the brackets 33 hold the electrode plates 31 at a proper mutual distance. Said distance means clamp the electrode plates 31 immovably by means of nuts 40 on the threaded end sections of the rods outside the brackets 33.

Straight in front of each electrode plate 31 in the direction of flow before the electrode plates 27, 31 an ionization wire 41, for example of cobalt or another equivalent material, is arranged which wire 41 lies on the same plane as its associated electrode plate 31 and is spaced from its end 42 which should be about the same or exactly the same as the distance between two electrode plates 31 and 27. In the embodiment shown in Figs. 5 and 6 the ionization wires 41 are clamped hetween the side walls 28 of the casing, as shown in Fig. 6, and will then have the same polarity as the casing 26 and the electrode plates 27. If the ionization wires should have the same polarity as the electrode plates 31 electrode plates of the type shown in Fig. 7 are preferably used, in which the ionization wire 41 is supported by and clamped between two pins 43 projecting from the very plate 42.

This type of electrode plates 31 are used in the second purification step of the embodiment shown in Figs. 5 and 6 and these electrode plates 31 are suspended and arranged in exactly the same way as the electrode plates 31 in the first purification step with the only difference that the distance between the electrode plates in the second step is less than between the electrode plates in the first step and therefore corresponding more electrode plates 27, 30, 31 are included m the second purification step. Like in the first step the distance between the electrode plates 27, 30, 31 in the second step decides the placement of each ionization wire in respect of distance relative to the associated electrode plate 31, i.e. the ionization wires 41 of the second purification step should be at a distance in front of the respective plate 31 that corresponds to the distance between the adjacent electrode plates 31 and 27.

From the aspect of purification the distance between the two purification steps has been found to be of slight importance but, on the other hand, an improved purification is oDtamed witn a flow plate 44 provided with holes which has tne same polarity as tne electrode plates 31 ana tnrough whicn tne gases leave tne respective purification step As snown in Figs. 5 and 6 each purification step can preferaoly comprise such a flow plate 44, but it is also possible tnat only the first or the second purification step is provided with such a plate 44 which can preferably be attached between the brackets 33 and be in contact with the end sections 45 of the electrode plates 31.

In order to prevent the gases from passing at the side of the casing 26, i.e. between this and the surrounding protective casing, the members 35a of the brackets projecting perpendicularly from the casing 26 form a tightly fitting wall between the two casings 26 and 25. In the embodiment shown in Figs. 5 and 6 the electrode plates 27 and the protectively earthed casing 26 serve as cathodes and the electrode plates 31 as anodes and in accordance with this are connected to a voltage source B to obtain an electric high voltage field between cathodes and anodes, an applied voltage in the first purification step being substantially higher than in the second purification step and adapted to the existing distance between cathode and anode. The first step can preferably have a voltage of 12-13 kgV at a low gas velocity and the second step a voltage of 7-9 kgV and a suitable guiding value is 1000 V/mm. If the distance between anode and cathode for instance amounts to 20 mm the voltage will consequently be 20 kgV. The higher flow rate the gases have, the greater the difference between anode and cathode should be in the two purification steps.

This invention is not limited to what has been described above and shown on the drawings but can be amended and modified in several different manners with- in the scope of the inventive idea defined in the claims.

Claims

CLAIMS 1. A device for purification of gases mixed with dust, for example car exhaust fumes, flue gases and other gases containing electrically conductive or actuatable dust particles, said device comprising a flow channel extending from an inlet for the gases to be purified to an outlet for the purified gases, within which channel an electric high voltage field is arranged between electrodes of opposite polarity, c h a r a c t e r i z e d in that the flow channel has ionization means (7, 7a; 41) arranged consecutively in the direction of flow, having the same or opposite polarity and disposed before each their electric high voltage field as seen in the direction of flow of the gas through the flow channel.

2. The device of claim 1, c h a r a c t e r i z e d in that the first high voltage field has a higher potential than the second electric high voltage field in the direction of flow.

3. The device of claim 1 or 2, c h a r a c t e r i z e d in that the first ionization means in the direction of flow consists of one or more ionization wires (7; 41) which are all connected to either negative or positive electrode and the second ionization means consists of one or more ionization wires

(7a; 41) in the direction of flow which are all connected to either negative or positive electrode.

4. The device of any one of the preceding claims, c h a r a c t e r i z e d in that a number of electrodes (31) of opposite polarity to the outer surface of the flow channel is arranged at a definite mutual distance in the direction of flow and that further electrodes (27) having the same polarity as said outer surface are arranged straight between these electrodes (31).

5. The device of claim 4, c h a r a c t e r i z e d in that an ionization wire (41) having positive or negative polarity is arranged straight in front of each electrode having a polarity opposite to the outer surface of the flow channel.

6. The device of any one of the preceding claims, c h a r a c t e r i z e d in that a number of electrodes (31) having a polarity opposite to the outer surface of the flow channel is arranged in the direction of flow after the second ionization means (41) and that further electrodes having the same polarity as said outer surface are arranged straight between these electrodes (31).

7. The device of claim 6, c h a r a c t e r i z e d in that an ionization wire (41) having positive or negative polarity is arranged straight in front of each electrode (31) having a polarity opposite to the outer surface of the flow channel.

8. The device of claim 7, c h a r a c t e r - i z e d in that the second ionization means (41) has a polarity opposite to the first ionization means which can be connected to the outer surface of the flow channel or to the electrodes (31) having a polarity opposite to said outer surface.

9. The device of any one of the preceding claims, c h a r a c t e r i z e d in that a plate (44) provided with holes and having a polarity opposite to the outer surface of the flow channel or the same polarity as this is arranged in connection with the first and/or second high voltage field.

10. The device of any one of claims 1-3, c h a ra c t e r i z e d in that the electrodes generating the first high voltage field comprise a concentric inner casing (12) sealed at one end and supported by means of insulators (6) and a pipe (10) enclosed con centrically by the inner casing (12) entering and connected to the inlet of the flow channel or forming this inlet and that the electrodes generating said second high voltage field comprise said outer and inner casing (1 and 12, respectively), said outer casing (1) and said entering pipe (10) having the same polarity and said first ionization wire (7) being arranged in connection with the end of said entering pipe and said second ionization wire (7a) in connection with the open end of the inner casing.