BE1021830B1 - DEVICE FOR SEPARATING SOLID PARTICLES FROM THE EXHAUST GASES OF AN ENGINE - Google Patents

Abstract

Device (1) for separating particles (5) from the exhaust gases of an engine, the device comprising a cylindrical vessel (2) with an outlet (4) for the separated particles (5), an outlet (6) for the purified exhaust gas and in which a fixed Archimedes screw (9) is mounted around a central tube (7). Optionally, post-treatment means (27) can be coupled to the outlets (4) and (6] for temporarily storing the separated particles (5).

Description

DEVICE FOR SEPARATING FIXED PARTS FROM THE EXHAUST GASES OF AN ENGINE.

TECHNICAL DOMAIN OF THE INVENTION

The invention relates to a device for separating solid particles from the exhaust gases of a combustion engine, hereinafter referred to as a soot separator. With the sharp increase in freight traffic with heavy diesel engines, air pollution from exhaust gases with insufficiently filtered soot particles has become an acute public health problem worldwide, especially in densely populated areas. In today's combustion engines, more and more atomizers are now being used for the fuel to mists of increasingly finer droplets at very high pressures. This promotes a faster ignition, but at the same time creates more extremely fine sub-micron dust particles. It is now established that precisely those smallest soot particles with submicron dimensions are by far the most harmful to health and that these are still not sufficiently separated from the exhaust gases of diesel and gasoline engines and therefore seriously and dangerously contaminate the air. The invention also optionally provides post-treatment means for the separated particles which means can be coupled to the soot separator outlets.

STATE OF THE ART

It has long been known to remove dust particles from air, combustion and other waste gases by passing the laden gas stream through a spiral channel space. This space then acts as a sort of cyclone in which the heavier dust particles are driven against the inner wall of the channel by centrifugal force. The purified gas stream is then discharged from the slightly more centrally located zone of the channel space. It is known from EP 802309 to apply this principle in an adapted manner for removing soot particles from the exhaust gases of a combustion, more particularly a diesel engine. To that end, the muffler of such an engine comprises a fixed, hollow, helical flow-through space for the combustion gas, wherein the soot particles are driven centrifugally against the inner wall of this space and collected for their separation from the exhaust gases thus purified. The purified gas stream and the separated soot particles are discharged separately against the inner wall of the muffler near its end 4.

Another soot separator for exhaust gases from combustion engines is known from DE 2835741. A heat-resistant filter cloth is provided against the inner wall of the thermally insulated silencer for collecting the soot particles separated centrifugally therein. The gas stream then reverses near an additional heated end of the muffler in a central outlet tube for the purified gas. The additional heating thereby aims at burning off the soot in the exhaust system itself.

BRIEF DESCRIPTION OF THE INVENTION

It is now a main object of the invention to provide a soot separator which also removes practically all sub-micron soot particles from the exhaust gases with high efficiency. Moreover, the invention allows this to be done for the first time in a mechanically not so complicated manner and without the use of expensive catalysts, or of additional heating of the exhaust system.

It is an additional object to provide means for quickly discharging the separated soot particles from the exhaust system and collecting them in a more or less bonded, less harmful form for disposal after a possible after-treatment. In particular, the after-treatment has the objective of avoiding any harmful effect on the environment through the spread of particulate matter after the separation.

The device which meets the main purpose for separating solid particles from the exhaust gases of an internal combustion engine comprises a cylindrical vessel with an inlet opening for the combustion gases near a first end of the vessel and a first outlet opening near the second end of the vessel for the separated particles. Near this second end the vessel also comprises a second outlet opening for the purified exhaust gas.

According to an important feature of the invention, the second outlet opening connects to a central concentric fixed tube in the cylindrical vessel. At least one inflow opening is provided in the wall of this tube near its outlet end for the purified gas to be discharged from the device to this central tube.

According to another particularly important feature, a fixed Archimedes screw is fixed around this central tube with a continuous, helically extending hollow interior. The inlet opening for the combustion gases connects to this hollow interior of the cylindrical vessel near the first end of the vessel. This Archimedes screw moreover has, according to the invention, near its tapered helical outer edge of the screw suitable passages for the substantially radial outflow of the particles to be separated near the cylindrical inner wall of said vessel.

Finally, in the wall of the cylindrical vessel near its second end, discharge holes are provided for transporting the separated solid particles to the first outlet opening for these particles.

In this device according to the invention, a transverse seal is preferably incorporated in the fixed tube upstream of the inflow opening for the purified gas. This seal thus defines a damping chamber in the tube. At least one opening is then provided in the cylindrical wall of this tubular damping chamber near the first end of the vessel. The non-purified combustion gas has access to the damping chamber through this opening.

With regard to the after-treatment means according to the invention provided, it is important that they can be coupled to at least the said first outlet opening of the cylindrical vessel of the device for temporarily storing the particles separated in the device. To that end, the after-treatment means comprise a housing with emptyable storage space for the separated particles in a more or less compacted form.

At least one filter chamber is mounted in the housing with a highly porous filter plate rotatable about its axis and spraying means for wetting that plate. Said spray means comprise an after-treatment liquid for discharging the particles collected in the filter plate to the empty storage space.

BRIEF DESCRIPTION OF THE FIGURES

All this, including suitable after-treatment means for the separated particles, will now be further elucidated with reference to an embodiment of the device according to the invention and with reference to the appended figures. It is obvious that the protection is not limited to this embodiment. It can only be taken as an example to clarify the scope of protection claimed in the claims.

Figure 1 is a view of the device with a helical cavity extending into the surrounding cylindrical vessel.

Figure 2 is a cross-sectional view along the longitudinal direction of the device of Figure 1.

Figure 3 shows a perspective post-treatment means for coupling to the outlet openings of the device according to Figures 1 and 2.

Figure 4 shows the opposite side of the after-treatment means according to Figure 3.

DETAILED DESCRIPTION

Figures 1 and 2 outline the device 1 for separating solid particles 5 from the exhaust gases of a combustion engine according to the invention. The fuel can be either diesel oil or gasoline or gas. The device is usually placed close to the exhaust system for the hot exhaust gases from the engine. The device comprises a cylindrical vessel 2 with an inlet opening 3 for the combustion gases near a first end 11 of the vessel 2. The vessel 2 further comprises a first outlet opening 4 near the second end 16 of the vessel for the separated particles 5 and a second outlet opening 6 for the purified exhaust gas.

A central concentric fixed tube 7 is mounted in the cylindrical vessel 2. This tube 7 connects near its outlet end 15 to the said second outlet opening 6 of the vessel 2. Around the central tube 7 a fixed Archimedes screw 9 is fixed with a continuous helical inner space 10. The combustion gases to be purified are removed from the inlet opening 3 of the vessel 2 passed through this spiral hollow inner space 10 in the direction of the second outlet opening 6.

Now, according to a very advantageous feature of the invention, at least one inflow opening 8 is provided in the peripheral wall of the central tube 7, near its outlet end 15, for discharged, meanwhile purified, gas from the device to the central tube 7, as will be explained below . The combustion gases firstly follow their spiral path through the device to the inflow opening 8 in the tube wall. Then there is another pressure drop in the stream of purified combustion gases downstream past this inflow opening 8 towards the outlet opening 6.

The helical cavity 10 is bounded near the inner wall 14 of the cylindrical vessel 2 by a number of turns of a tapered helical outer edge 12 of the screw 9. In this outer edge 12, according to the invention, from the second turn suitable passages 13 are present for the substantially radial outflow of the particles 5 to be separated, around fine dust, in particular soot particles, near the inner cylindrical wall 14 of the vessel 2. That radial outflow is mainly obtained by the centrifugal force on the particles 5 carried by the spirally propelling flow of combustion gases in the cavity 10. However, the first turn 24 near the inlet opening 3 connects to the inner wall 14 of the vessel because the unpurified combustion gases must be sent directly into the cavity 10 near their inlet opening 3.

Further on, near the second end 16 of vessel 2, discharge holes 17 are provided in the wall of vessel 2 for the separated solid particles 5 to the outlet opening 4 for these particles. The separated particles thus end up via a ring-shaped discharge channel 23 in the first outlet opening 4 for the particles 5.

In this device, a transverse seal 19 is preferably accommodated in the central 7 tube upstream of the inlet opening 8 for the purified gas. This can be done, for example, via the attachment of the closure 19 to a central rod 18 which runs along the longitudinal axis of vessel 2 and tube 7. Moreover, at least one opening 21 can be provided in the cylindrical wall near the first end 11 of the vessel of the tube 7. Thus, the central tube 7 then acts as an advantageous (additional) damping chamber 20 in the exhaust device 1 for the combustion gases between this first end 11 and the transverse seal 19 via this opening 21 in the tube wall 7.

According to the invention, a narrow gap is provided at the level of the helical outer edge 12 of the screw 9 for the substantially radial discharge through the passages 13 of the particles 5 collected (separated from the gas flow) near this gap. The length of each passage 13 can vary between 5 mm and 20 mm, preferably between 5 and 10 mm, while its width is preferably approximately 300 micrometres. The closed gap 26 (i.e. the distance) between two successive passages 13 in the outer edge 12 is preferably 2 to 3 mm. This dimensioning of the passages 13 and spaces 26 thus surprisingly allows the (soot particles 5 there to flow out of the hollow space 10 appropriately). The particles 5 discharged via the passages 13 thus collide with this inner gap against the inner wall 14 of the vessel and become subsequently laterally further along this wall in the direction of the discharge holes 17 to the annular discharge channel 23 near the second end 16. Of the majority of the particles are usually separated in the last turns 25 of the screw 9. The distance that they to extend to the discharge holes 17 is therefore quite short.

To promote the centrifugal movement of the particles 5 to their passages 13 - and thus the separation of the soot particles 5 from the gas stream - suitable partitions 22 on the outer wall of the tube can be installed in the successive turns of the hollow inner space 10 of the screw 9 7 are confirmed.

A very interesting embodiment of after-treatment means 27 for the particles 5 separated in the device 1 is outlined in figures 3 and 4. These after-treatment means essentially concentrate the particles 5 into a more or less compacted mass 46 (sediment) and store them temporarily in the bottom of a voidable storage space 29 in the housing 28 for the means 27. The compacted particle mass 46 can then be periodically smoothly removed from said storage space 29, as will be explained below.

The after-treatment means 27 are connected with their first input coupling 31 to the second outlet opening 6 (already purified exhaust gas) of the separation device 1. Said input coupling 31 is connected to a first filter chamber 30 in the housing 28. The filter chamber 30 comprises a first about its axis 32, rotatable highly porous filter plate 34 with the aid of a motor drive 33. At the top of the first filter chamber 30, spraying means 35 are now provided for an after-treatment liquid 36 for wetting the first filter plate 34. A drain element 37 (Figure 4) is of course also mounted to the outlet channel 39 and to the outside environment for the gas 38 additionally purified after the after-treatment. This gas flow 38 has a considerable flow rate and is therefore additionally purified by the after-treatment (if necessary or desirable) additionally to the gas flow from the outlet opening 6 of device 1.

The after-treatment means 27 also comprise an important second filter chamber 40 in the housing 28 with a second input coupling 41 for connection to the first outlet opening 4 for the now-separated particles 5 from the device 1. A second highly porous filter plate 42 is also around the axis 32 with rotatably mounted using motor 33. At the top of the second filter chamber 40 spraying means 35 are also provided for an after-treatment liquid 36 for wetting the second filter plate 42. The first and second filter chamber 30 and 40 are separated from each other by a partition 48. Finally, a suction tube 43 for the purified residual gas 44 from the second filter chamber 40 is mounted.

The first resp. second filter plate 34 resp. 42 may, for example, have a metal foam structure or comprise a (temperature-resistant) non-woven fabric. It is known that particles 5 to be separated, in particular. quickly adhere soot particles (stick, adsorb) to the wetted pore walls of these filter plates. The nozzles 35 for the filter chambers can be fed via a circulation pump for the after-treatment liquid 36. This liquid 36 is in fact a washing liquid which is capable of washing out the separated particles stored in the filter plates from the pores of the filter plates.

The after treatment proceeds as follows. In the first instance, the purified combustion gases which flow out from the second outlet opening 6 of the device 1 enter the first filter chamber 30 and flow through the first highly porous filter plate 34. Any remaining particles (in this gas stream already purified in device 1 from the second outlet opening) 6) collected in this first filter plate. When the pressure in a filter chamber 30 or 40 reaches the preset allowable pressure, well-known and suitably arranged detectors will signal the nozzles 35 to deliver their washing fluid 36 to the outer surface of the filter plate in question.

At the same time, the detectors send a signal to the motor drive 33 for the axis of rotation 32 to cause the filter plates 34 and 42 to rotate slowly so that they are completely wetted (soaked) by the washing fluid 36, whereby the particles 5 collected in the filter plates are released from their pores.

At this time, a signal is given by the detectors to make the filter plates rotate faster for a short period of time so that the trapped particles 5 are centrifuged with the washing liquid 36 against the inner wall of the filter chamber 30, 40 concerned. The washing liquid 36 loaded with particles 5 then drips down that wall into the storage space 29 where the particles 5 sink. The washing liquid 36 floats to the top in the space 29 to be taken up and sent back by the circulation pump to the nozzles 35. When the sediment of mass 46 of particles 5 compacted into a type of knit or paste has reached a sufficient degree of filling in the storage space 29 ( indicated by a sensor) this mass must be drained (drained), e.g. via the discharge pipe 47. This will of course preferably be done with a stationary vehicle with the combustion engine switched off.

In the second instance, at the same time the highly charged stream of particles from the first outlet opening 4 of the device 1 is supplied via the second input coupling 41 to the second filter chamber 40. The flow rate of this residual flow is considerably smaller than that from the second outlet opening 6. The flow numerous particles 5 are collected in the second filter plate 42.

The finally purified residual gas 44 (with low flow) is preferably sent via a tube 43 into the larger channel 39. As a result, a suction effect (venturi) is created at the mouth 48 of the tube 43 in this channel 39. As a result of this effect, the purified residual gas 44 is sucked out there into the stream 38 of the additionally purified gas. The second filter plate 42 can reach its predetermined pressure level earlier than the first filter plate 34.

EXAMPLE

A soot separator 1 as illustrated in figures 1 and 2 was connected to a diesel engine (type Euro-3/2004) of a bus at the normal location where the muffler would otherwise be inserted, in particular to the exhaust pipe near its connection to the engine. The cylindrical vessel 2 had an outer diameter of 500 mm. In the vessel an Archimedes screw 9 with four to five turns was mounted on a central tube 7. The aforementioned length and width of the passages 13 (with a length of 5 mm) and the spaces 26 were used. The soot fraction that was separated and collected at the exit 4 was analyzed. The analysis clearly confirmed that sub-micron soot particles (PM-1 to PM-0.1) and soot particles with caliber PM-10 (i.e. with an aerodynamic diameter of less than 10 microns) were separated. These sub-micron particles - in fact the most dangerous particles for health - are therefore indeed removed from the exhaust gases by the soot separator according to the invention.

It is therefore a very important advantage of the invention that this can happen with a hardly hindered flow of the combustion gases through the device 1, i.e. without having to build up an adverse pressure in the device 1 at the same time. An adverse pressure build-up with conventional soot filters can after all require increased compression pressure in the engine. This can require a higher fuel consumption, an undesirably higher temperature build-up and ultimately a lower efficiency of the engine. The connection of a device 1 to the collector of the hot exhaust gases against the engine thus avoids the major disadvantage of the higher pressure build-up that is often inherent to the connection of traditional soot filters in exhaust systems.

The analysis of the particles 5 collected at the first outlet 4 of the device and also in the compacted mass 46 in the storage space 29 of the after-treatment means 27 also indicates the presence of soot particles PM-10 which can be recycled and recovered from this mass for addition as filler to rubber for, for example, car tires. Similarly, PM-1 particles may be useful and recovered as a binder and thus as a reinforcing agent for such rubbers because of their known erratic (lob shaped) surface. The collected soot can therefore be reused in a useful and environmentally friendly way.

The invention is of course not limited to the embodiments described above. Numerous variants evident to those skilled in the art on the composition and construction of the device 1 and of the after-treatment means 27 and their components for substantially the same functions are conceivable. It can also be considered to only couple after-treatment means 27 to their inlet 41 on a first outlet opening 4 of the device 1. Then a first filter chamber 30 with its parts and accessories is then omitted. The exhaust tube 43 with venturi effect for the residual gas 44 from the filter chamber 40 can then, for example, open into an outlet tube which is directly coupled to the second outlet opening 6 for the purified gas from the device 1. The invention and the scope of protection therefore comprise in particular also these and all other embodiments as defined below in the appended claims.

For passenger cars (e.g. with a diesel engine) one can even consider omitting the actual soot separator, i.e. the device 1, and thus only after-treatment means 27 without using a first filter chamber 30. It is therefore possible to couple these means 27 directly with an input coupling 41 directly against the silencer at the rear (and at the bottom) of the car and with an outlet opening 49 to the area of the purified combustion gases. The after-treatment means 27 therefore act as the actual separator of particles 5, in particular. of soot particles in a storage space 29 and instead of the device 1.

Claims (10)

CONCLUSIONS A device (1] for separating solid particles (5) from the exhaust gases of an internal combustion engine, which device comprises a cylindrical vessel (2] with an inlet opening (3) for the combustion gases near a first end (11] of the vessel and a first outlet opening (4) near the second end (16] of the separated particle vessel (5] and a second outlet opening (6] for the purified exhaust gas, the second outlet opening (6) connecting to a central concentric fixed tube (7 ] in the vessel (2), wherein, in the wall of this tube, at least one inflow opening (8) is provided near its outlet end (15] for the purified gas to be discharged from the device to the tube (7] and around which said tube (7) is a fixed Archimedes screw (9) mounted with a continuous helical interior space (10]; the inlet opening (3) connects to this interior space of the vessel (2) near its first end (11] and where near the tapered helical outer edge (12] of the screw (9) is provided with suitable passages (13) for substantially radially outflow of the particles to be separated (5) near the inner cylindrical wall (14] of vessel 2 and wherein, near the second end (16] of vessel (2), discharge holes (17) are provided in the wall of the vessel (2) for the separated solid particles (5) to the outlet opening (4) for the particles (5). Device according to claim 1, wherein a transverse seal (19) is accommodated upstream of the purified gas inflow opening (8) in the tube (7) and wherein at least one opening (21) is provided near the first end (11) of the vessel ) is arranged in the cylindrical wall of the tube (7). Device according to claim 1, wherein the length of a passage (13) is between 5 mm and 20 mm and the distance (26) between two successive passages (13) is between 2 and 3 mm. Device according to claim 1, wherein suitable partitions (22) are mounted on the tube (7) in the hollow interior spaces (10) to promote the separation of the soot particles (5). Device as claimed in claim 1, wherein after-treatment means (27) are coupled to the first (4) and second (6) outlet openings for temporarily storing the particles (5) separated from the combustion gases in the device (1). Device according to claim 5, wherein the after-treatment means (27) comprise a housing (28) - with an emptyable storage space (29) for the separated particles (5) in a more or less bound compacted form; - with a first filter chamber (30) in the housing (28) with a first input coupling (31) for connection to the second outlet opening (6); - with a first highly porous filter plate (34) rotatable about its axis (32), with the aid of a motor drive (33); -with spraying means (35) for an after-treatment liquid (36) for wetting the first filter plate (34) and - with a discharge element (37) for the gas (38) additionally purified after the after-treatment to the outlet pipe (39); - with a second filter chamber (40) in the housing (28) with a second input coupling (41) for connection to the first outlet opening (4) for the separated particles (5); - with a second highly porous filter plate (42) rotatable about its axis (32) by means of motor (33); - with spraying means (35) for an after-treatment liquid (36) for wetting the second filter plate (42) and - with a suction pipe (43) for the purified residual gas (44) from the second filter chamber. Device according to claim 6, wherein the suction pipe (43) opens into the outlet pipe (39) for the additional purified gas (38). Device as claimed in claim 1, wherein after-treatment means (27) are coupled to the first outlet opening (4) for temporarily storing the particles (5) separated from the combustion gases at this outlet opening (4) in the device (1). Device according to claim 8, wherein the after-treatment means (27) comprise a housing (28) with an emptyable storage space (29) for the separated particles (5) in a compacted form; - with a filter chamber (40) in the housing (28) with an input coupling (41) for connection to the first outlet opening (4) for the separated particles (5); - with a highly porous filter plate (42) rotatable about its axis (32) with the aid of a motor drive (33); - with spraying means (35) for an after-treatment liquid (36) for wetting the filter plate (42) and - with a suction tube (43) for the purified residual gas (44) from the filter chamber. Device as claimed in claim 9, wherein the extraction tube (43) opens into an outlet tube which is directly connected to the second outlet opening (6) for the purified gas from the device (1).