US3440800A - Device for purifying exhaust gas by means of electric filters - Google Patents

Description

April-29, 1969 G. MESSEN-JASCHIN 3,440,

DEVICE FOR PURIFYING EXHAUST GAS BY MEANS OF ELECTRIC FILTERS Filed May 5, 1967 Sheet of 2 INVENTOR.

April 29, 1969 G. MESSEN-JASCHiN 3,440,800

DEVICE FOR PURIFYING EXHAUST GAS BY MEANS OF ELECTRIC FILTERS Filed May 5, 1967 Sheet 2 of 2 a N 40 Fig 2 Fig.4

INVENTOR.

3,440,800 DEVICE FOR PURIFYING EXHAUST GAS BY MEANS F ELECTRIC FILTERS Gregori Messen-Iaschin, Schlenggenried,

Sarerl, Switzerland 1 Filed May 3, 1967, Ser. No. 640,772 Claims priority, application Switzerland, May 6, 1966,

6,7 66 Int. Cl. 1303c 3/49, 3/00, 3/82 US. Cl. 55122 4 Claims ABSTRACT OF THE DISCLOSURE This invention relates to devices for cleaning exhaust gases.

The continuing rapid increase in the use of internal combustion engines in road vehicles and for the operation of stationary or mobile machinery, e.g., construction machines, makes it desirable that the exhaust gas be purified before being released to the atmosphere, in order to protect human beings against the toxic effects of such gas. Already, large numbers of trials have been carried out and proposals made, in the context of burning the main toxic gas, CO, contained in the exhaust gases, prior to discharge to the atmosphere. Although it has been possible to reduce the combustion temperature of CO from above 600 C. down to about 300 C., using suitable catalysts, the combustion chambers used really constitute ovens or furnaces which, because of the large quantities of heat they develop, can only be employed in very rare instances.

It is also known to clean exhaust gas using electrostatic filters. It is possible to precipitate out only solid and liquid particles such as soot and oil, but also toxic gases, if the latter can be induced to condense prior to entry into the electrostatic filter. The hydrocarbon gases can in particular be precipitated in this way. To this end, therefore, it has already been proposed that the hot exhaust gases be cooled until condensation films develop. This takes place at about 80-50" C., and the aerosol can then be agglomerated to form droplets, by the introduction of fresh air. These droplets can then be ionised in an electrostatic filter and precipitated.

The known exhaust-gas-cleaning devices equipped with electrostatic filters unfortunately are so large that hitherto they have only been suitable for use on very large diesel engines in static installations, or in locomotives.

The present invention consists in a device for cleaning exhaust gases including, a housing, a cylindrical collecting electrode located in said housing, a plurality of ionising electrodes projecting radially outwards from a shaft located within and coaxial with, the collecting electrode, means for maintaining an electrostatic potential between the collecting and ionising electrodes, wherein the exhaust gas flows into a central tube and passes with a radial component of motion through the collecting electrode to finally leave the housing axially, wherein means are provided for introducing fresh air into the ionisation space, and wherein the housing is preceded by a turbine chamber equipped with a gas inlet connection and with a hot-gas turbine for rotating the shaft about its axis.

nited States Patent 0 3,440,800 Patented Apr. 29, 1969 Using a device in accordance with the invention it is possible to achieve reliable continuous exhaust gas cleaning due to the fact that the hot exhaust gases are expanded and precooled in a preliminary chamber where they drive the turbine. Solid particles may be deposited in a cyclone prior to entry into the ionising chamber, the gas then entering the latter chamber where fresh air is mixed with it in order to cool it until the hydrocarbon gases condense out. Due to this expansion of the gases the bipolar selfionisation of the hot gas may be suppressed. Further, particles adhering to the ionising electrode spikes are removed by centrifugal force. Finally, the electrode shaft may carry a fan at the exit end of the housing which sucks the expanded gas through the filter, and in order to reduce the toxicity of the carbon monoxide content in the clean gas, fresh air can again be introduced into it in order to dilute it.

A method of performing the invention will now be described with reference to the accompanying diagrammatic drawings in which:

FIGURE 1 is a longitudinal section through a device in accordance with the invention;

FIGURE 2 is an elevation of the device illustrated in FIGURE 1;

FIGURE 3 is a cross-section on the line AA of FIG- URE 1; and

FIGURE 4 is a plan view of the device illustrated in FIGURES 1 to 3.

The drawings show a cylindrical casing 11 in which there is arranged a cylindrical collecting electrode 12 which is provided at its bottom end with an annular shoulder 13 abutting against a peripheral frustoconical portion .14 of the casing 11. The casing 11 is closed off at the bottom by a flat end wall 15 carrying a central upwardly directed tube 16 mounted on the frustum 14 by means of radial ribs 17. The frustum 14 is advantageously mounted on the casing 11 by means of radial ribs 18. The casing 11 is provided at the top with a cover 19 in the form of a collar 20 with a cylindrical ring 21 and a central frustum 22. The frustum 22 is mounted on the collar 20 by means of radial ribs 23 and has an annular shoulder 24 which holds the upper end of the collecting electrode 12.

A shaft 29 coaxial with the casing 11 is rotatably mounted in a top bearing 26 supported on the central frustum 22 through radial ribs 25 and a lower bearing 28 supported on the central tube 16 through radial ribs 27. The shaft is provided above the bearing 26 with a fan 30; between the two bearings it carries the ionising electrode; and below the bearing 28 it carries a frustoconical boss 31 on which a tube 33 is mounted by means of radial ribs 32. The tube 33 projects downwardly out of the tube 16 and a substantially gas-tight seal is formed between the two tubes. The tube 33 is the hub of a hot-gas turbine which adjoins the end wall 15 and has a spiral casing with a connecting pipe 35. The turbine rotor has downwardly directed large drive blades 36 fixed to the tube 33 and upwardly directed smaller braking blades 37. The turbine casing is divided into two chambers by a partition 38, in order to give separate gas feed to these blade sets. This measure is taken in order to limit the rotational velocity of the turbine. Attached to the lower side of the turbine casing is a box 40 detachably held in place by draw bolts 39.

In the casing 11, between the peripheral frustum 14 and the end wall 15, holes 41 uniformly distributed upon the periphery are provided for the entry of cooling air, the air flow being regulated by means of a slider ring 42. Above the peripheral cone 14, two rings of holes 43 are arranged for the purpose of mixing fresh air with the clean gas, the air flow here likewise being regulated by slider rings 44.

The ionising electrode includes a tube 46 carried on the shaft 29 by two insulators 45. Spike electrodes 47 project radially from the tube 46 and electrodes are maintained at a high voltage. The spike electrodes are spaced at uniform intervals both around the tube periphery and in the axial direction. The high voltage required for ionisation is generated in an equipment 52 located outside the casing 11. The supply of the high voltage is effected through a cable 48, a lead-through insulator 49 in the frustum 22, a brush 50 and a slip ring 51.

The cylindrical collecting electrode 12 consists of permeable material, e.g., wire wool, carried by a lattice arrangement. It takes the form of a disposable electrode and can be exchanged after the cover has been lifted off.

The apparatus can be built directly into the exhaust system of an internal combustion engine, e.g., a diesel engine. The exhaust gases then enter the turbine chamber at a high temperature and high velocity and drive the turbine with the ionising electrode shaft and the fan. The exhaust gases are thus radically expanded and pre-cooled. In order to limit the speed of rotation of the ionising electrode shaft, the turbine rotor carries a braking blade ring. After leaving the turbine rotor, the gas follows a cyclonic path in the box 40, where soot particles and oil droplets are precipitated out. The fan 30 draws the gas, together with fresh air, through the electrostatic filter.

The expanded gas passes through the central tube 16 into the ionisation space. As a consequence of the expansion taking place in the turbine, the bipolar self-ionisation of the gas is virtually suppressed and the gas is ionised in the ionisation space virtually entirely in unipolar fashion. If, nevertheless, self-ionisation should take place and give rise to oppositely polarised particles being deposited upon the ionising spikes 47, such particles are thrown off radially as a consequence of the centrifugal effect associated with the speed of rotation. As a result the ionising spikes 47 remain free of any deposit even when the gas is hot.

On entering the ionisation space, the gas undergoes further expansion, with consequent additional cooling. In addition, fresh air is drawn into the ionisation space through the apertures 41 in the housing. This fresh air enters the ionisation space in a ring around the gas flow. The gas is cooled to such an extent that the hydrocarbon gas is condensed out and the resultant condensate films are agglomerated to droplet form as a consequence of the radial infiow of fresh air. These droplets are ionised and as the gas passes through the collecting electrode 12 are deposited thereon.

The carbon monoxide contained in the exhaust gases cannot be precipitated out in the electrostatic filter since it does not condense at normal temperature. Since carbon monoxide only becomes toxic at a specific concentration, it can be rendered harmless by adequate dilution with fresh air. To this end, the gas flow has fresh air mixed with it through the apertures 43 after passing through the collecting electrode 12. The quantity of fresh air can be regulated by means of the rings 44. The quantity of fresh air fed to the ionisation space can be regulated by means of the ring 42.

The collecting electrode 12 can advantageously take the form of a disposable electrode, the electrode cylinder being made of loose wire wool, held in place between two sets of metal mesh, e.g., wire mesh or perforated sheet. Disposable electrodes of this type present a large area for deposition and present only very little resistance to the incident gas fiow. After removal of the cover 19, with the fan 30, the collecting electrode 12 can be taken out and replaced by a new one. Beyond a periodic exchange of the collecting electrode 12 and possible emptying of the cyclone box 40, the equipment requires no other maintenance. It can be operated either vertically or horizontally. The measures proposed in accordance with the invention enable a reduction in the volume of the installation to be achieved, as a consequence of which it is possible to employ the equipment for cleaning the exhaust gases of diesel engines used in road vehicles. This reduction in volume is made possible by virtue of the fact that the invention enables the expansion of the gas, its cooling and its condensation by admixture of fresh air, ionisation, precipitation, dilution and detoxication, all to take place in a single chamber.

What I claim is:

1. A device for cleaning exhaust gases including means defining a flow-path, said flow-path means including a housing with an input end and an output end, a per meable cylindrical collecting electrode located in said housing and defining an ionization space, a shaft located in and coaxial with said collecting electrode, a plurality of ionizing electrodes projecting radially outward from said shaft, means for maintaining an electrostatic potential between said collecting and ionizing electrodes, said flow-path means further including a turbine chamber preceding said housing, said chamber being equipped with a gas inlet connection and with a hot gas turbine including a turbine rotor engaging said shaft for rotating said shaft about its axis, gas tube input means centrally positioned with respect to said collecting electrode so that exhaust gases enter said ionizing space and pass with a radial component of motion through said permeable collecting electrode, said gas tube input means opening into said turbine chamber and aperture means of variable cross-section surrounding said input tube for the introduction of fresh air into said ionization space.

2. A device as defined in claim 1 wherein the housing includes a peripheral frustoconical portion at said input end and a central frustoconical portion at said output end, said frustoconical portions carrying the collecting electrode and bearings for said shaft, and wherein said gas tube input means projects into said turbine chamber and forms the hub of said turbine rotor.

3. A device as claimed in claim 2 wherein a fan driven by the hot-gas turbine is arranged at the output end of the housing.

4. A device as claimed in claim 3 wherein the housing contains variable apertures for introducing fresh air in order to dilute the cleaned exhaust gases.

References Cited UNITED STATES PATENTS 1,329,859 2/1920 Schmidt et a1 55135 X 1,456,044 5/1923 Strong 55-149 2,094,531 9/1937 Fraser 55-404 X 2,119,297 5/1938 Scott 5514 X 2,335,420 11/1943 Jones 23311 2,448,048 8/1948 Porter 55404 2,659,449 11/1953 Kaiser et a1 55134 X 2,661,076 12/1953 Walker 55404 X 2,841,242 7/1958 Hall 23174 X 3,046,716 7/1962 Rodger 55-152 3,238,702 3/1966 De Seversky 551l9 FOREIGN PATENTS 142 9/1911 Great Britain.

HARRY B. THORNTON, Primary Examiner.

DENNIS E. TALBERT, JR., Assistant Examiner.

US. Cl. X.R.

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