JPH0657288B2 - Patty Yule Trap - Google Patents

Description

TECHNICAL FIELD The present invention relates to a particulate trap that collects and cleans dust contained in exhaust gas of, for example, a diesel engine.

"Prior art and its problems" Diesel engine exhaust gas contains dust such as carbon particles, which causes pollution. Therefore, various ceramic filters have been proposed in order to collect the above-mentioned dust contained in the exhaust gas.

As an example of such a ceramic filter, there is known a filter having a honeycomb structure as a whole and having both end faces of cells closed in a zigzag pattern as shown in FIGS. 5 and 6, for example. . In this filter, a honeycomb cell is divided into an exhaust gas inflow passage 1 and a clean gas outflow passage 2, and at the end face on the inflow side of the exhaust gas A, the clean gas outflow passage 2 is closed and the clean gas B is removed. The exhaust gas inflow passage 1 is closed at the end face on the outflow side. Therefore, when the exhaust gas A enters the exhaust gas inflow passage 1 from one end face, it is introduced into the clean gas outflow passage 2 through the air-permeable partition wall. At this time, dust is collected by the partition wall, the gas is purified and becomes the clean gas B, and the clean gas B
Is discharged from the other end surface through the clean gas outflow passage 2.

However, in this filter, all the dust in the exhaust gas A is collected in the partition walls of the exhaust gas inflow passage 1, and the passing pressure loss gradually increases due to the accumulation of the dust. Therefore, the dust accumulated on the partition wall must be removed regularly. As a means for removing dust, a method of burning dust with electric heat or a burner is often adopted. However, in the above filter, the partition wall thickness is normally set to about 0.2 to 3 mm in order to reduce the pressure loss through passage.
There is a problem that the partition walls are burned by the heat generated when the dust is burned. For this reason, it has been proposed that the partition walls carry an oxidation catalyst or the like to oxidize and burn the dust, but it has been difficult to completely remove the dust over a long period of time.

"Object of the invention" In view of the above-mentioned problems of the prior art, an object of the present invention is to provide a particulate wrap capable of keeping the passing pressure loss low for a long time and preventing the filter from being burned when dust is burned and removed. To provide.

"Structure of the Invention" The particulate trap according to the present invention has a ceramic filter having a plurality of substantially linear ventilation passages having inlets and outlets, and the partition walls of the ventilation passages are porous filtration surfaces. And one or more traps formed to surround all of the outlets of the filter,
Further, the trap is provided with means for burning and removing dust.

As described above, the particulate trap according to the present invention includes the filter and the trap, the filter has a plurality of ventilation passages, and the trap is formed so as to surround all of the outlets of the ventilation passages of the filter. Therefore, the filtration area of the filter can be made extremely large compared to the internal area of the trap. Therefore, the clean gas is filtered mainly by a filter having a large filtering area.

Moreover, since the air passage of the filter is almost linear and the outlet of the air passage for dust-containing gas is also open, the dust is not collected much by the filter, and the dust is trapped mainly due to its inertial force. To be collected by.

As described above, since the clean gas is mainly taken out by the filter, the trap need not pass the clean gas at all or only slightly. Therefore, the trap should have a large wall thickness and a material having excellent heat resistance. Is possible. Therefore, if the dust collected in the trap is burned and removed by means such as electric heat or a burner, it is possible to prevent the filter wall as well as the trap wall from being burnt out. In this way, it is possible to obtain a structure in which the filter does not burn when the dust is burned and removed, without increasing the ash content in the filter to increase the passing pressure loss.

In the present invention, the filter has a partition wall made of a porous ceramic having air permeability. The partition wall has a thickness of about 0.1 to 3 mm, an average pore diameter of 5 to 30 μm, and a porosity of about 30 to 50% in order to reduce the size and weight of the partition wall, suppress passage pressure loss to a low level, and improve dust capturing performance. It is preferable. The material is preferably cordierite, mullite, lithium aluminum silicate (β-spodumene, etc.), aluminum titanate, alumina, silicon carbide, silicon nitride and the like.

As a preferred example of the filter, a plurality of porous ceramics flat plates arranged in parallel to each other and ribs provided by connecting to the ceramics flat plates on both sides between adjacent ceramics flat plates are provided, and the traveling direction of the ribs is ceramics. Examples are parallel to every other stage between flat plates and non-parallel with one ceramic flat plate interposed.
In this case, a corrugated plate may be used as at least a part of the rib.

In this filter, dust-containing gas such as exhaust gas is introduced from one end face into a ventilation path formed between flat plates, passes through the flat plate forming the partition wall, and enters the ventilation path running in parallel with it. It becomes a clean gas from the air passage running to and is taken out laterally. Further, most of the dust contained in the dust-containing gas goes straight along the first ventilation path as it is due to inertial force, etc., and enters the trap.

Another preferable example of the filter is one in which a plurality of porous ceramic tubes are arranged in parallel to form a filtering surface, and both ends of these ceramic tubes are hermetically supported by tube plates. In this filter, dust-containing gas is introduced into the ceramic pipe, clean gas is taken out of the pipe through the wall of the ceramic pipe, and most of the dust in the dust-containing gas is
It goes straight through the ceramic tube due to inertial force, etc., and enters the trap as it is.

In the present invention, it is convenient to form one trap so as to surround all the outlets of the ventilation path on the dust-containing gas side of the filter, but by arranging two or more traps together, all traps are included as a whole. You may make it enclose the dust gas side ventilation path outlet with any trap.

By the way, the trap captures dust and treats it, and therefore may have no filtering function at all, but preferably this trap is also made of porous ceramics having a filtering function. By thus providing the trap with a filtering function as well, it is possible to enhance the dust collecting effect by the so-called blow-down action by causing the gas not to pass through but the gas to flow in the trap through the gas. The material, the pore diameter, and the porosity of the trap may be the same as those of the filter described above, but it is preferable that the trap has more heat resistance by a means such as having a larger wall thickness than the filter.

In the example of the preferred particulate trap of the present invention,
The dust accumulated on the filtration surface of the filter is removed by the backwash gas that is intermittently pumped.

By performing backwashing in this way, the pressure loss through the filter can be kept smaller. The filter and the trap are dust tightly sealed by an appropriate sealing means such as packing.

Embodiment of the Invention FIG. 1 shows an embodiment of a particulate trap according to the present invention.

The particulate trap 11 is an inlet for the exhaust gas A.
A casing 14 having an outlet 12 and an outlet 13 for clean gas B is provided, and a filter 15 (only the outline of the cross section is schematically shown in FIG. 1) and a trap 16 are provided in the casing 14 along the gas flow direction. Connected in order. The filter 15 and the trap 16 are supported in the casing 14 by spacers 17 arranged radially, that is, so as not to interrupt the flow of the clean gas B in the outer space of the trap 16. An inlet 18 for the backwash gas C is provided in a portion of the casing 14 close to the filter 15.

The filter 15 has a structure as shown in FIG. 2, for example. That is, a plurality of breathable porous ceramics flat plates 19 are arranged in parallel to form a filtering surface, and a rib 20 or rib 21 made of ceramics is provided in the gap between the adjacent ceramics flat plates 19 and 19 to form the ceramics flat plates 19, 19. Are connected.

The rib 20 is provided on one side of each ceramic flat plate 19, and the rib 21 is provided on the other side. Therefore, the ribs 20 are alternately provided every other space between the ceramic flat plates 19, 19 and the ribs 21 are the same. The ribs 20 are parallel to each other, and the ribs 21 are also parallel to each other. The ribs 20 and 21 are not parallel to each other (the traveling direction is vertical in the example of FIG. 2). Thus, the ventilation passage 2 that runs by intersecting each stage alternately by the ceramic flat plate 19 and the ribs 20 and 21
2, 23 are formed.

In this case, the ribs 20 are formed only on both side edges of the ceramic flat plate 19, and therefore the one ventilation passage 22 does not have a rib inside. Further, a large number of ribs 21 are formed in parallel between the ceramic flat plates 19 at a predetermined interval, so that the other ventilation passage 23 is partitioned into a honeycomb shape. This way, many ribs every other layer
By providing 21 the strength of the entire filter is increased.

In this embodiment, the exhaust gas A flows in from one end surface of the ventilation passage 22 and flows out from the other end surface thereof, and the clean gas B that has passed through the ceramic flat plate 19 passes through the ventilation passage 23 and flows on both sides of the filter 15. It is designed to be taken out from the end face. The ceramic flat plate 19 is made of, for example, a breathable porous ceramic having a thickness of 1 mm.

On the end surface of the filter 15 on the side where the exhaust gas A flows out,
The trap 16 is connected to dusttight so as to surround the entire air passage 22. The trap 16 is also preferably a filter 15
It is made of the same air-permeable porous ceramics and has a thickness larger than that of the ceramic flat plate 19, for example, 15 mm. A heating wire 24 for burning and removing the collected dust is provided on the wall surface of the trap 16.

In the above structure, the particulate trap 11 is arranged in the exhaust gas flow path of a diesel engine or the like, and the exhaust gas A is introduced from the inlet 12. The exhaust gas A is introduced into the ventilation passage 22 of the filter 15, and most of it passes through the porous ceramic flat plate 19 and is guided to the adjacent flow passage 23,
The clean gas B flows out from the lateral end surface of the filter 15. The clean gas B passes between the filter 15, the trap 16 and the casing 14 and is discharged from the outlet 13. Part of the exhaust gas A passes through the filter 15 as it is and is trapped.
The gas enters 16 and becomes clean gas B through the partition wall of the trap 16 and is discharged from the outlet 13.

The dust such as carbon particles contained in the exhaust gas A is
Although it is also trapped inside the air passage 22 of the filter 15, the air passage
At the outlet of 22, the exhaust gas A still has a flow velocity, the dust itself such as carbon particles has inertial force, the gas flow of the exhaust gas A has pulsation in the case of engine exhaust gas, and the exhaust brake In the case of a vehicle diesel engine, etc., the pressure wave generated when the exhaust brake is released has much more energy than the pulsation that is constantly generated by the engine.
The carbon particles deposited on the partition wall surface of 22 are blown off to reduce the pressure loss, and the dust is not deposited enough to block the ventilation path 22.

For this reason, most of the dust in the exhaust gas A is trapped.
Captured by the heating wire 24 and burned off when needed. In this case, since the trap 16 has a relatively thick structure and is excellent in heat resistance, it is not burned by dust burning. Further, since dust does not accumulate in the filter 15 to the extent that combustion removal is required, the partition wall of the filter 15 can be made thin, and a large filtration area can be obtained while keeping the filter small.

The dust accumulated on the inner surface of the air passage 22 of the filter 15 can be removed by intermittently pumping the backwash gas C from the inlet 18 to backwash the filtration surface.

In the above embodiment, the exhaust gas A may be passed through the ventilation passage 23 of the filter 15 and the clean gas B may be taken out from the ventilation passage 22. Also, a small burner or the like may be used instead of the heating wire 24 for burning and removing dust.

FIG. 3 shows another example of the filter 15 applied to the above embodiment. This filter 15 is obtained by replacing most of the ribs 21 in the filter shown in FIG. 2 with a corrugated plate 25 made of ceramics, and functions in the same manner as the filter 15 shown in FIG. Therefore, the same parts are designated by the same reference numerals and the description thereof will be omitted.

FIG. 4 shows still another example of the filter 15 applied to the above embodiment. This filter 15 has a plurality of porous ceramic tubes 26 arranged in parallel as a filtering surface,
Both ends of these ceramic tubes 26 are hermetically supported by tube plates 27 and 28. In this filter 15, for example, by letting the exhaust gas A flow from the end face of the one tube sheet 27, most of the exhaust gas A passes through the wall of the ceramic pipe 26 and is taken out as the clean gas B. Part of the trap passes through the ceramic tube 26 as it is and traps 16
It will flow in.

In addition, in FIG. 1, when a filter 15 having a rectangular parallelepiped shape as shown in FIG. 2 or 3 is used, a trap is generated.
16 is assumed to have a rectangular tubular portion and a semi-cylindrical bottom portion,
When the filter 15 having a substantially cylindrical outer shape as shown in FIG. 4 is used, the trap 16 has a cylindrical portion and a hemispherical bottom portion. Further, the bottom of the trap 16 may have a flat plate shape, and the filter 15 shown in FIGS. 2 and 3 may have a cylindrical outer shape.

The results of actually testing the particulate trap 11 according to the present invention are as follows. As the filter 15, a filter having the structure shown in FIG. 4 and having 52 ceramic tubes 26 having an outer diameter of 6 mm and an effective length of 500 mm was used. The trap 16 used had an outer diameter of 170 mm and an effective length of 450 mm. Then, when the particulate trap 11 was tested using a diesel engine for trucks of 100PS, it was possible to stably capture the carbon particles, and to burn and regenerate the carbon particles captured by the heating wire 24 provided in the trap 16. It was possible to suppress the passing pressure loss to a maximum of 700 mmAq.

"Effects of the Invention" As described above, the particulate trap of the present invention is composed of a filter and a trap, and the filter has a plurality of ventilation passages to increase the filtration area per unit length, The filtration area of the trap that surrounds all the outlets of the dust-containing gas side air passage of the filter is smaller than the filtration area of the filter. Therefore, the clean gas is mainly taken out by a filter having a large filtration area. Further, since the dust-containing gas side air passage of the filter is substantially linear, the dust is mainly trapped by the trap due to its inertial force and the like.

And since the trap does not require great breathability,
It is easy to form a structure having excellent heat resistance, and even if the collected dust is burned and removed, it is possible to prevent burning.

Further, when the present invention is applied to exhaust gas treatment of a diesel engine or the like, it is possible to obtain an effect that the muffler can also serve as a muffler due to a sound absorbing effect that a porous ceramic generally has.

Therefore, the particulate trap of the present invention is suitable for exhaust gas treatment of diesel engines mounted on passenger cars, trucks, bulldozers, power shovels, ships, and stationary generators.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a particulate trap according to the present invention, FIG. 2 is a perspective view showing a filter applied to the particulate trap, and FIG. 3 is a filter applied to the particulate trap. FIG. 4 is a perspective view showing another example, FIG. 4 is a perspective view showing still another example of a filter applied to the particulate trap, and FIG. 5 is a perspective view showing an example of a conventional ceramics filter.
The figure is a cross-sectional view of the ceramics filter of FIG. In the figure, 11 is a particulate trap, 12 is an exhaust gas inlet, 13 is a clean gas outlet, 14 is a casing, 15 is a filter, 16 is a trap, 19 is a ceramic flat plate, 20 and 21 are ribs, 22 and 23 are An air passage, 24 is a heating wire, 25 is a corrugated plate, 26 is a ceramic tube, 27 and 28 are tube plates, A is exhaust gas, and B is clean gas.

Claims (7)

[Claims] 1. A ceramic filter having a plurality of substantially linear ventilation passages having an inlet and an outlet, and the partition walls of the ventilation passages are porous filtration surfaces, and surrounds all the outlets. And one or more traps formed as described above, and the traps are provided with means for burning and removing dust. 2. The filter according to claim 1, wherein the filter is provided by connecting a plurality of porous ceramic flat plates arranged in parallel to each other and ceramic flat plates on both sides between adjacent ceramic flat plates. And a rib, wherein the traveling directions of the ribs are parallel to each other between the ceramic flat plates and are non-parallel with one ceramic flat plate sandwiched therebetween. 3. The filter according to claim 1, wherein a plurality of porous ceramic tubes are arranged in parallel to form a filtering surface, and both ends of these ceramic tubes are hermetically supported by tube plates. Particulate trap consisting of stuff. 4. The particulate trap according to any one of claims 1 to 3, wherein the trap is made of ceramics. 5. The particulate trap according to any one of claims 1 to 4, wherein the trap has a filtering function. 6. The particulate trap according to any one of claims 1 to 5, wherein the dust accumulated on the filtration surface of the filter is removed by a backwash gas which is intermittently pumped. 7. A particulate trap according to any one of claims 1 to 6, wherein the means for burning and removing dust is electric heat or a burner.