JPH02146212A - Particulate trap device - Google Patents

Abstract

PURPOSE:To prevent a filter from blinding at the time of backwash by specifying the thickness of a partition, the minimum inner diameter of a cell at a dust containing passage side and a ratio of the length of the passage of the cell to the minimum inner diameter in a device providing a filter having a plurality of cells separated by the partition having permeable and porous materials. CONSTITUTION:A cylinder filter 10 housed in a casing 31 having openings at both the upper and the lower ends has a basic structure of a honeycomb separated by porous ceramic made partitions 11 having filtration and having a large number of cells 12, 13 adjacent to each other bounded by the partitions 11. The ends at opposite sides each other in the cells 12, 13 adjacent to each other are closed. A pressurized gas ejection nozzle 40 as a backwash means is provided in an outflow pipe 38 positioned at the right upper part of the casing 31. In this case, the thickness of the partition 11 is set within 0.4-5.0mm and the minimum inner diameter of each cell 12 forming a dust containing gas passage is set over 1.5mm. A ratio of the length of the passage of each cell 2 to the minimum inner diameter is set below 60.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention applies to exhaust gas from diesel engines used in various vehicles such as passenger cars, trucks, buses, and railway vehicles, as well as industrial equipment and ships. The present invention relates to a vaticulate trap device for treating contained particulates.

[Prior Art] Diesel engine exhaust gas contains a considerable concentration of particulates whose main component is carbon (0.3 to 0.7
g/ro 11P/hr) and is a cause of pollution. Therefore, various particulate trap devices have been proposed for collecting and removing particulates from the υ ridge gas of a diesel engine.

For example, Japanese Patent Laid-Open No. 57-35918 discloses a filter 1 as shown in FIGS. 4 and 5. This filter l is a honeycomb horizontal structure having a plurality of cells 3 partitioned by partition walls 2, and as shown in FIG. Blocked in a checkered pattern.

On the other end surface B, the cells 3a that were closed on the one end surface A are open, and the cells 3b that were open on the one end surface A are closed with the sealing material 5, forming a horizontal structure. . When diesel exhaust gas G passes through the other end surface B of this filter l, the exhaust gas G is introduced into the cell 3a forming the dust-containing gas passage and passes through the breathable partition wall 2, and at that time, the dust-containing gas G is The contained particulates are collected on the inner surface of the partition wall 2, and the clean exhaust gas G from which the particulates have been removed forms a clean gas passage in the cell 3b.
It flows out through one end face A.

In a particulate trap device using such a filter, it was necessary to solve the problem that particulates accumulate on the filtration surface of the filter, clogging the filter and gradually increasing pressure loss.

Therefore, in Utility Model Application No. 62-35851, a burner device is installed upstream of the exhaust gas inlet of the filter, and the particulates deposited on the wall of the filter are ignited and burned by high-temperature combustion gas from this burner device. A particulate trap device is disclosed in which the particulate trap is incinerated.

In addition, in Japanese Patent Application Laid-open No. 56-92318, there are two exhaust gas flow paths.
Divided into systems, 9 particulate traps are placed in each flow path, each trap is equipped with a heating means, and trap regeneration by collecting, igniting, and incinerating particulates is performed alternately in each flow path and trap. A particulate trap device is disclosed.

However, in the above-mentioned conventional method of burning the collected particulates, the filter is repeatedly heated to high temperatures, which leads to sintering of the filter, which changes the initial pore size and bore distribution, and reduces the collection efficiency and pressure. Loss changes over time, making it difficult to maintain stable performance. In addition, the heat of combustion may cause loss in the film, and cracks may occur due to thermal shock. Furthermore, there are non-ignorable amounts of non-flammable components in diesel exhaust gas, and these non-flammable components are not removed by combustion and accumulate on the filter, so the pressure loss in the filter gradually increases over a long period of time. There was a problem.

In order to solve such problems, the present applicant.

Japanese Patent Laid-Open No. 63-203087 proposes a particulate trap device in which filter regeneration is performed by backwashing. This device places a filter in the exhaust passage of an internal combustion engine, installs a backwash nozzle downstream of the flow of exhaust gas from this filter, and backwashes the filter by ejecting high-pressure gas from the backwash nozzle at predetermined intervals. do the
It has a horizontal structure in which particulates that have been brushed off from the partition wall of the filter are collected in a re-extracting section and incinerated in the re-extracting section. In this manner, by regenerating the filter through periodic backwashing, the pressure loss of the filter can be maintained at a constant level over a long period of time.

[Problems to be Solved by the Invention] However, in this particulate trap device, the thin wall of the filter may be damaged by cracks or the like due to the pulse flow of high-pressure gas ejected from the backwash nozzle during backwashing. In addition, depending on the engine operating conditions, the exhaust gas temperature may vary to the ignition temperature of particulates (550 to 600 degrees Celsius).
), the accumulated particulates start to burn, and as a result, one wall of the filter is melted and damaged.

There is a problem in that cracks may occur due to the generation of thermal stress due to the distribution of combustion heat. Furthermore, there has often been a problem in that particulates swept away by backwashing cause bridging within the passage and instead of falling to the re-collection section, they instead block the passage.

The present invention has been made in view of the above-mentioned problems of the prior art.The purpose of the present invention is to provide a particulate trap device that regenerates a filter by backwashing, to withstand the impact of backwashing force, and to prevent the accumulation of particles depending on the engine operating conditions. A particulate trap that does not cause the filter to melt even if particulates ignite or burn, and furthermore, the filter cells are not blocked by the particulates that are blown off by backwashing, providing stable filter characteristics. The goal is to provide equipment.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a filter having a dust-containing gas passage and a clean gas passage separated by a partition wall made of a breathable porous material. installed in the filter, and configured so that the exhaust gas passes through the partition wall from the dust-containing gas passage to the clean gas passage, and a filter is installed downstream of the exhaust gas flow from the filter toward the clean gas passage. In a particulate trap device provided with a backwash means for blowing high-pressure gas, the dust-containing gas passage and the clean gas passage of the filter are each divided into a plurality of cells by the partition wall, and the thickness of the partition wall is 0. .4
~5.0■I, at least the minimum inner diameter of each cell of the dust-containing gas passage is 1.5 mm+ or more, and at least the ratio of the passage length to the minimum inner diameter of each cell of the dust-containing gas passage is It is characterized by being 60 or less.

In a preferred embodiment of the present invention, the filter is made of a honeycomb body having a large number of cells extending in the same direction,
A predetermined cell has one end sealed, and the remaining two cells have a horizontal structure with the other end sealed.

Further, the partition wall of the filter has a porosity of 30 to 50%.
, made of a material with a pore diameter of 100 μm or less.

Furthermore, when the backwashing means is activated, the pressure in the exhaust passage on the downstream side of the filter is 1000 to 6000+ nmA compared to the pressure in the exhaust passage on the upstream side of the filter.
g is made to be high.

[Function] In the present invention, the thickness of the partition wall of the filter is 0.4 to 5.0 m.
m, so it has sufficient strength to withstand the pressure of high-pressure gas caused by backwashing, and also prevents the filter from melting and cracking even if particulates accumulated on the filter ignite and burn. be able to. The thickness of the partition wall is 0.
If the diameter is less than 4 mm, sufficient strength cannot be obtained even if the required inner diameter of the cell is secured, and the filter is likely to be damaged by external forces applied during accommodation in a casing or during backwashing.

Furthermore, when particulates ignite and burn within the filter, the partition walls are eroded. Note that the thickness of the partition wall is 0.
．． It is more preferable to set the thickness to 6 mm or more. On the other hand, if the thickness of the partition wall exceeds 5.0 mm, it becomes difficult to increase the filtration area per unit volume, and the size of the filter,
The weight 1 increases, which prevents the device from being made more compact. Note that the thickness of the partition wall is 0.6 to 1. ! It is more preferable to set it to +mm.

Further, in the present invention, since the minimum inner diameter of each cell of at least the dust-containing gas passage in the filter is set to 1.5+am or more, particulates brushed off by backwashing are less likely to cause bridging in the passage. Blockage of the passageway due to bridging is prevented. If the minimum inner diameter of each cell in the metal gas passage is less than 1.5 mm, particulates swept away by backwashing will cause bridging while falling down the passage in the cell, making it easy to block the passage. Note that the minimum inner diameter of a cell here is, for example, when the end face shape of the cell is square, it is the length of one side at the inner periphery, and when the end face shape of the cell is rectangular, it is the length of one side at the inner periphery. If the end face shape of the cell is polygonal, it is the diameter of the inscribed circle; if the end face shape of the cell is circular, it means the diameter at the inner periphery. .

Furthermore, in the present invention, at least the ratio between the passage length and the minimum inner diameter of each cell of the dust-containing gas passage (passage length/minimum inner diameter) is set to 60 or less, so that the bridging phenomenon described above can be more effectively prevented. can. In other words, the longer the length of one passage, the more likely the bridging phenomenon will occur, so the minimum inner diameter of the cell needs to be larger. It will also be a good thing. The above passage length/minimum inner diameter is 6
If it exceeds 0, particulates brushed off by backwashing will cause bridging while falling down the passage, making it easy for one passage to become clogged. However, the length of one passage/
If the minimum inner diameter is too small, a problem arises in that the filter becomes large in order to secure the necessary filtration area, which impairs the ability to make the device compact. Therefore, the passage length/minimum inner diameter is preferably 30 to 60, and 35
It is more preferable to set it to 55.

Further, in a preferred embodiment of the present invention, the filter is made of a honeycomb body having a large number of cells extending in the same direction, and one end of a predetermined cell is sealed, and the other end of the remaining cells is sealed. In the case of a closed horizontal structure, the horizontal structure can have a large filtration area per unit volume with a relatively simple horizontal structure.

Further, when the flexible wall of the filter is made of a material with a porosity of 30 to 50% and a pore diameter of 100 μm or less, the required particulate collection rate can be ensured while keeping the pressure loss level of the filter low. When the porosity exceeds 50%,
The collection rate of particulates with secondary particle diameters of several μm or less contained in exhaust gas from diesel engines and the like rapidly decreases, and along with this, material strength also decreases. Further, if the porosity is less than 30%, the ventilation resistance of the filter becomes too low to be ignored, and the pressure drop level becomes high. On the other hand, when the maximum pore diameter exceeds 1100 LL, particulates tend to easily pass through the partition walls, and the particulate collection rate tends to decrease significantly.

Furthermore, when the backwashing means is activated, if the pressure in the exhaust passage on the downstream side of the filter is set to be 1000 to 6000 mmAg higher than the pressure in the exhaust passage on the upstream side of the filter, the backwashing effect can be reduced. By maximizing this, the positive phase of the filter can be maintained at a low level for a long period of time. When the above-mentioned backwash differential pressure is less than IO port OmAg, a sufficient backwash effect cannot be obtained and it becomes difficult to stabilize the pressure loss level of the filter over a long period of time. Further, when the backwashing differential pressure exceeds 6000 mAg, strong pressure is applied to the filter, making it easy for cracks to occur.

[Embodiment] FIG. 1 shows an embodiment of a particulate trap device according to the present invention. This device basically employs a horizontal construction similar to that of the above-mentioned Japanese Patent Application Laid-Open No. 63-203087.

That is, a cylindrical filter IO is housed inside a casing 31 having openings on the upper and lower sides, with a required seal member 32 interposed therebetween. The filter 10 has a filtration capacity (
In other words, it is partitioned by a porous ceramic partition wall 11 that allows gas to pass through, but does not allow most, especially substantially all, of solid particles such as carbon to pass through. The basic horizontal structure is a honeycomb body with a large number of adjacent cells 12 and 13. Each cell 12.13 extends parallel to the elongated direction.

Approximately half of the cells 12 have their ends on the one end surface 17 side of the filter IO closed with the sealing material 15, and the filter IO
The other end surface 16 side is open. The remaining cell 13 is one end face of the filter IO! The end on the 7 side is open, and the other end face 16 side of the filter 10 is closed with a 1.l material 14. Nine cells 12 and 13 are arranged alternately in a checkerboard pattern. The cell 12 constitutes a dust-containing gas passage in the present invention, and the cell 13 constitutes a clean gas passage in the present invention.

Further, the cells 12, 13 extend in the vertical direction, and the sealing material 14
, 15 are located on the bottom and top surfaces of the filter IO, respectively. For simplification of illustration, in FIG.
In reality, a much larger number of thin partition walls II are formed with a smaller pitch, thereby forming a larger number of cells 12, 13. The outer wall 18 forming the side periphery of the filter IO is thicker than the partition wall 11 to prevent damage to the filter opening, and is also non-ventilated to prevent particles from accumulating on the inside. It is planned.

A particulate re-capturing section 41 is formed directly below the casing 31, and between the casing 31 and the re-capturing section 41 is an inlet pipe 3 for introducing diesel engine exhaust gas from the side.
7 is open.

The recapture unit 41 has a hollow cylindrical shape, and has a lid 4 that can be opened and closed at the bottom.
It has 2. Slightly above M42, a filter plate 43 provided with an electric resistance heating type heater 46 is installed at a gentle slope. An ash outlet 44 with an i47 that can be opened and closed and is normally closed is connected to the filter plate 43.
It opens just above the side.

Note that M42 can be kept open during operation to constantly form a small amount of downflow, thereby promoting re-collection of particulates and combustion.

An exhaust gas outflow pipe 38 is connected to the upper part of the casing 31. Casing 3! Outflow pipe 38 located directly above the
Inside, a nozzle 40 for spraying pressurized gas as a backwashing means in the present invention opens toward the end surface 17 on the outlet side of the filter IO.

To further explain the filter 10, which is a feature of the present invention, the partition wall 1 of the filter 10 is as follows.
1 is made of a breathable porous material, such as porous ceramics, sintered metal, inorganic fibers, etc. From the viewpoint of heat resistance and strength, cordierite, mullite, S
A porous fired ceramic body such as iC is more preferably used.

Further, as shown in FIG. 2, the wall thickness t of the partition wall 11 is
The range is 4 to 5.0 mm, and from the viewpoint of heat resistance, strength, and weight, the range is more preferably 0.6 to 1.511111.

The minimum inner diameter (in this embodiment, the length of the shorter side on the inner periphery of the rectangle) W of each cell I2.13 is as follows: 1.
The diameter is 5 mm or more, and more preferably 2.5 to 61 TIII+ from the viewpoint of preventing cell clogging due to particulates brushed off by backwashing and the overall size of the device per weight.

Further, the ratio (R/W) between the passage length β and the minimum inner diameter W of each cell 12.13 is 60 or less, and more preferably in the range of 30 to 60 from the viewpoint of the overall size and weight of the device. . Note that the passage length 2 essentially means the length of the filter IO, as shown in FIG. Moreover, as shown in FIG. 3, when each cell 12.13 forms a polygon,
The minimum inner diameter W means the diameter of the inscribed circle R.

In addition, the ratio of the minimum inner diameter W and the passage length e to the minimum inner diameter W (
I2/W) is particularly required for the cell 12 forming the dust-containing gas path, and may not be within the above range for the cell 13 forming the clean gas path.

Furthermore, the partition wall 11 is made of a material with a porosity of 30 to 50% and a pore diameter of 100 μm or less.

Next, the operation of this particulate trap device will be explained.

Exhaust gas from the diesel engine passes through the exhaust gas introduction pipe 37 and is guided from the lower end surface 16 of the filter IO into the cell 12 whose end surface is not closed. The exhaust gas flows upward through the cell 12, but since the upper end surface of the cell 12 is closed by the closing material 15, it passes through the partition wall 11 and flows out into the adjacent cell 13.

Since the lower end face 16 of the cell 13 is closed by the closing material 14 and the negative end face 17 is open, the exhaust gas flows out from the upper end face 17 of the filter IO, passes through the exhaust gas outflow pipe 38, and exits from the particulate trap device. be discharged. Particulates contained in exhaust gas are
When the exhaust gas passes through the partition wall 11, it is collected and deposited on the wall surface on the cell 12 side. The gas passing through the cell 13 and flowing out from the outflow pipe 38 becomes clean gas.

If you continue this collection work, the filter! 0 cell I
2. The amount of particulates deposited on the inner wall increases and the exhaust gas ventilation pressure loss increases, causing problems in engine operation.

Therefore, after continuing the above-mentioned collection operation for an appropriate time, when the ventilation pressure loss of the filter IO reaches a predetermined level, pressurized gas is injected from the backwash nozzle 40 for, for example, 0.1 to 1.0 seconds. The particulates accumulated on the wall of the cell [2] are removed from the filter 10. The filter lO from which the particulates have been removed has its ventilation resistance returned to its original level, and the collection operation can be restarted. Incidentally, by setting the pressure on the downstream side of the filter 10 at the time of backwashing to be 1000 to 60 ports (1 mmAg higher) than the pressure on the upstream side of the filter 10, the accumulated particulates can be effectively removed. be able to.

In this case, the present invention uses a filter! Since the thickness of the O partition wall 11 is set to 0.4 to 5.0 ++ ua, it is possible to prevent cracks from forming in the partition wall 11 during the above-mentioned backwashing. In particular, the minimum inner diameter W of the cell 12 is 1.5
+na+ or more, and the ratio (g/W) of the passage length β to the minimum inner diameter W is set to be 60 or less, so particulates brushed off by backwashing cause bridging within the cell 12. Blocking of the passageway is prevented. Furthermore, since the partition wall 11 of the filter IO is made of a material with a porosity of 30 to 50% and a pore diameter of 100 μm or less, particulates can be effectively collected.

On the other hand, the particulates that have been brushed off are transferred to the re-extracting section 41 located below the filter IO due to the downflow effect by the filter plate 43 and the effect of gravity as described above.
Recaptured to. Then, the particulates are ignited by the electric heater 46 similarly arranged above the filter plate 43 of the re-extracting section 41, and the particulates are combusted and incinerated. In addition,
During the backwash operation, the exhaust gas flow is temporarily blocked by the backwash flow, so the backwash time is preferably extremely short, preferably about 0.1 to 0.5 seconds.

In a further preferred embodiment, the exhaust passage of the internal combustion engine is branched into a plurality of passages, each of the branched passages is provided with this particulate trap device, and the exhaust gas flow is appropriately switched to perform backwashing alternately in each passage. .

In the above embodiment, a honeycomb body in which cells 12 and 13 whose end faces in different directions are closed is alternately arranged is used as the filter 10, but the present invention uses the filter 10 as described above. For example, it is possible to use a filter in which a dust-containing gas passage and a clean gas passage are formed in layers, and each passage is opened in different directions.

Test Example The horizontal particulate trap device described above was prototyped and an operational test was conducted.

Five types of filters shown in the following table were used as the filter 10. In addition, the material of the filter IO is cordierite,
The material used had a porosity of 40 to 45%, an average pore diameter of 35 μm, and a maximum pore diameter of 75 to 115 μm (between the two on the scale of the measuring instrument).

The engine used was a 6.7 ff direct injection non-supercharged diesel engine. In this case, part of the exhaust gas is released through the bypass pipe, and the amount of gas introduced into the filter IO is approximately 160 m2 per unit area of each filter.
3/hr-m".

In addition, the backwash differential pressure during backwash is 1300 to 160
It was set to 0 mAg.

The results of the operation test are shown in the table below. From the results, 1.
1.2, it can be seen that damage and clogging of the filter are prevented. However, device No. 3 with thin partition wall II
FM of the filter occurs, and in device N014 where the ratio β/W of the passage length to the minimum cell inner diameter is large, filter clogging is observed, and the minimum cell inner diameter W is small (,12/
It can be seen that in device No. 5 where w is even larger, the filter clogging becomes more noticeable.

(Hereinafter, blank space) [Effects of the Invention] As explained above, according to the present invention, the filter is regenerated by a backwash method in which pressurized gas is ejected from the backwash nozzle, so that the accumulated particulates are removed from the filter surface. Compared to the above combustion method, problems such as filter erosion and cracks can be solved.

In addition, since the thickness of the filter partition wall is in the range of 0.4 to 5.0 mm, it can sufficiently withstand high pressure during backwashing, and depending on the engine operating conditions, the exhaust gas temperature may exceed the ignition temperature of particulates. Even if the accumulated particulates are ignited and burned, the problem of melting and cracking of the filter can be solved.

Furthermore, the minimum inner diameter of the cell in at least the dust-containing gas passage of the filter is 1.5 mm or more, and the ratio of the passage length of the cell in the dust-containing gas passage to the minimum inner diameter is 603. ], it is possible to solve the problem that particulates brushed off by backwashing cause bridging in the cells while falling inside the cells, causing clogging of the cells. .

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view showing an embodiment of a particulate trap device according to the present invention. Fig. 2 is a partial cross-sectional view of a filter used in the present invention. Fig. 3 is another example of a filter used in the present invention. 4 is a partially cutaway perspective view showing an example of a conventionally used filter, and FIG. 5 is a longitudinal sectional view of the same filter. In the figure, 510 is a filter, 11 is a partition wall, 12.13 is a cell, 14.15 is a sealing material, 16.17 is an end face, 31 is a casing, 37 is a wandering gas introduction pipe, 38 is an exhaust gas outflow pipe, 40
4 is a backwash nozzle, 41 is a recollection unit, 43 is a filter plate, and 4 is a backwash nozzle.
6 is the heater, t is the thickness of the partition wall, W is the minimum inner diameter of the cell, 2
is the length of the cell path. Figure 2 Figure 3 Figure 5

Claims (4)

[Claims] (1) A filter having a dust-containing gas passage and a clean gas passage separated by a partition made of a porous breathable material is installed in an exhaust passage of an internal combustion engine, and exhaust gas passes through the partition from the dust-containing gas passage. In the particulate trap device, the particulate trap device is configured to flow out into the clean gas passage, and is provided with backwashing means for blowing high-pressure gas toward the clean gas passage downstream of the flow of exhaust gas from the filter. The dust-containing gas passage and clean gas passage of the filter are
Each cell is divided into a plurality of cells by the partition wall, the partition wall has a thickness of 0.4 to 5.0 mm, and the minimum inner diameter of each cell of the dust-containing gas passage is at least 1.5 mm.
A particulate trap device having the above structure and characterized in that the ratio between the passage length and the minimum inner diameter of each cell of the dust-containing gas passage is 60 or less. (2) The filter consists of a honeycomb body having a large number of cells extending in the same direction, and has a horizontal structure in which one end of a predetermined cell is sealed and the other end of the remaining cells is sealed. The particulate trap device according to claim 1. (3) The partition wall of the filter has a porosity of 30 to 50.
% and a pore diameter of 100 μm or less. (4) When the backwashing means is activated, the pressure in the exhaust passage downstream of the filter is 1000 to 6000 mmAg compared to the pressure in the exhaust passage upstream of the filter.
The particulate trap device according to claim 1, 2 or 3, wherein the particulate trap device is made high.