JP2002161730A - Exhaust gas cleaning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas cleaning device having a filter that excels in the rate of regeneration because of having a superior thermal insulation efficiency in the course of regenerating process for combustion removing the accumulated particulates in the filter. SOLUTION: The exhaust gas cleaning device is the one that is equipped with a filter for cleaning exhaust gas within a casing to which are connected a guiding pipe leading in the exhaust gas discharged from an internal combustion engine and a discharge pipe letting out the foregoing exhaust gas, and the device has a characteristic of having a thermal insulating member that has a function of venting air on the exhaust gas discharging side of the foregoing filter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exhaust gas purifying apparatus for removing particulates and the like in exhaust gas discharged from an internal combustion engine such as a diesel engine.

[0002]

2. Description of the Related Art Recently, it has become a problem that particulates contained in exhaust gas discharged from internal combustion engines such as vehicles such as buses and trucks and construction machines cause harm to the environment and human bodies. Various ceramic filters have been proposed which purify the exhaust gas by collecting the particulates in the exhaust gas by passing the exhaust gas through a porous ceramic.

[0003] Such ceramic filters are usually
As in the honeycomb filter 40 shown in FIG. 3, a plurality of porous ceramic members 30 are bound together via an adhesive layer 42 to form a ceramic block 41, and a sealing material 43 is formed on the outer peripheral portion thereof. ing. As shown in FIG. 4, the porous ceramic member 30 has a large number of through holes 31 arranged in the longitudinal direction, and a partition wall 33 separating the through holes 31 functions as a filter.

[0004] That is, as shown in FIG. 4 (b), the through hole 31 formed in the porous ceramic member 30 has a filler 32 on either the inlet side or the outlet side of the exhaust gas.
The exhaust gas that has been plugged in and has flowed into one through-hole 31 always flows through the partition wall 33 separating the through-hole 31 and then flows out from the other through-hole 31. Among such porous ceramic members 30, for example, a porous silicon carbide member is used for various large-sized vehicles and the like because of extremely excellent heat resistance and easy reprocessing.

[0005] In the exhaust gas purifying apparatus, the honeycomb filter 40 having such a configuration is provided in the exhaust passage of the internal combustion engine, and the particulates in the exhaust gas discharged from the internal combustion engine pass through the honeycomb filter 40 when passing through the honeycomb filter 40. The exhaust gas is captured by the partition walls 33 and purified.

FIG. 5 is a sectional view schematically showing a conventional exhaust gas purifying apparatus. As shown in FIG. 5, in the exhaust gas purifying device 50, an introduction pipe 54 into which exhaust gas from an internal combustion engine is introduced is connected to one end of a casing 51, and a honeycomb filter 40 is connected to the other end. A discharge pipe 55 for discharging the exhaust gas that has passed to the outside is provided. The honeycomb filter 40 is provided inside the casing 51 via a holding seal body 53.

Further, an electric heater 56 for burning the particulates accumulated in the honeycomb filter 40 is provided at a portion on the exhaust gas introduction side with respect to the honeycomb filter 40, and a temperature sensor 57 is connected to the honeycomb filter 40. A pipe (not shown) for feeding air or the like when performing combustion is connected.

Exhaust gas is supplied from the inlet pipe 54 to the casing 5.
1 and pass through the honeycomb filter 40,
The particulates are captured by the partition wall 33 and discharged from the discharge pipe 55. When the amount of accumulated particulates increases and the pressure loss of the honeycomb filter 40 increases, a regeneration process for burning and removing the particulates is performed.

In the regeneration processing of the honeycomb filter 40 using such a conventional exhaust gas purifying apparatus 50, the honeycomb filter 40 is usually energized by supplying air to the electric heater while sending air from the pipe into the casing 51. This is performed by raising the temperature to the burning temperature of the particulates, and burning out and removing the particulates accumulated in the honeycomb filter 40.

However, when the filter is regenerated using such a conventional exhaust gas purifying apparatus, the heat applied to heat the filter is radiated to the outside from the exhaust gas outlet side end face of the filter. Therefore, heat loss was large, and the heat retention efficiency of the filter was poor. As a result, a temperature distribution occurs in the filter, and in particular, the temperature in the vicinity of the filter cannot be heated to the particulate combustion temperature, and the regeneration rate of the filter is not very high.

[0011]

DISCLOSURE OF THE INVENTION The present invention has been made to solve these problems. In a regeneration treatment for burning and removing particulates accumulated in a filter, the filter has an excellent heat retaining efficiency. It is an object of the present invention to provide an exhaust gas purifying apparatus having an excellent regeneration rate of the filter.

[0012]

According to the present invention, there is provided an exhaust gas purifying apparatus comprising: a casing in which an introduction pipe for introducing exhaust gas discharged from an internal combustion engine and a discharge pipe for discharging the exhaust gas are connected; An exhaust gas purifying apparatus provided with an exhaust gas purifying filter, wherein a gas permeable heat shielding member is disposed on an exhaust gas outflow side of the filter.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an exhaust gas purifying apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view schematically showing one example of the exhaust gas purifying apparatus of the present invention. As shown in FIG.
An exhaust gas purifying apparatus 10 of the present invention includes an exhaust gas purifying apparatus 10 in a casing 11 to which an introduction pipe 14 for introducing exhaust gas discharged from an internal combustion engine and a discharge pipe 15 for discharging the exhaust gas are connected. The filter 12 is installed via a holding seal 13, and a heat shielding member 20 is installed on the exhaust gas outflow side of the filter 12.

An electric heater 16 for burning particulates accumulated in the filter 12 is provided at a portion on the exhaust gas introduction side with respect to the filter 12, and a temperature sensor 17 is in contact with the filter 12. It is installed in. Although not shown, a pipe for feeding air or the like when performing combustion may be connected to the introduction pipe 14.

In the exhaust gas purifying apparatus 10 of the present invention, similarly to the above-described conventional exhaust gas purifying apparatus 50, the exhaust gas flowing into the casing 11 from the introduction pipe 14 passes through the filter 12, The curate is captured by the filter 12 and discharged from the discharge pipe 15. When the amount of accumulated particulates increases and the pressure loss or the like of the filter 12 increases, a regeneration process for burning and removing the particulates is performed.

The heat shielding member 20 serves to radiate heat to the filter 12 by being heated in association with the heating at the time of the regeneration processing of the filter 12 and to emit electromagnetic waves such as infrared rays radiated from the filter 12. Filter 12
The exhaust gas purifying apparatus of the present invention improves the heat retaining efficiency of the filter 12 from the heat radiation of the heat shielding member 20 and the reflection of electromagnetic waves such as infrared rays. . The heat shielding member 20 has air permeability. This is because it is necessary to discharge the exhaust gas flowing into the casing 11 to the outside.

The heat shield member 20 preferably has an aperture ratio of 20 to 60%. If the opening ratio is less than 20%, it is not possible to smoothly discharge the exhaust gas, and the fuel combustion efficiency of the internal combustion engine is reduced. On the other hand, if the aperture ratio exceeds 60%, the emissivity of heat and the reflectance of electromagnetic waves such as infrared rays decrease, so that it is not possible to improve the heat retaining efficiency of the filter 12, and the strength of the filter 12 is reduced and the filter 12 is easily deformed. .

The diameter of the opening formed in the heat shielding member 20 is preferably 2 to 10 mmφ. If the diameter of the opening is less than 2 mmφ, the exhaust gas may not be able to flow smoothly,
It is necessary to provide a very large number of openings in order to secure the above-mentioned opening ratio, which increases the manufacturing cost. On the other hand, if the diameter of the opening exceeds 10 mmφ, it is difficult to secure the strength of the heat shielding member 20, and the amount of radiation of heat and reflection of electromagnetic waves such as infrared rays may decrease.

The heat shielding member 20 is preferably made of metal or ceramic. The heat shielding member 20 has a certain degree of heat resistance so as not to be deformed, broken, decomposed, or the like by the temperature at the time of the regeneration processing of the filter 12, and is not deformed by the exhaust gas discharged. This is because it is necessary to have a certain strength. The surface of the heat shielding member 20 made of such a metal or ceramic on the filter 12 side may be a mirror surface or a rough surface. When the surface is a mirror surface, electromagnetic waves such as infrared rays can be reflected well, and when the surface is rough, the heat shielding member 2
0 heat transfer area can be increased, and emissivity can be improved.

The metal is not particularly restricted but includes, for example, SUS and iron. SUS is desirable among these metals. This is because it has higher heat resistance and strength.

The ceramic is not particularly limited.
For example, non-oxide ceramics such as silicon carbide, silicon nitride, aluminum nitride, boron nitride, titanium nitride, and titanium carbide, and oxide ceramics such as alumina, cordierite, mullite, silica, zirconia, and titania can be given. . Among these ceramics, silicon carbide is desirable. This is because both heat resistance and strength are excellent.

The heat shielding member 20 has a thickness of 400 to 700.
It is desirable that the emissivity at ° C is 0.5 or more.
When the emissivity is less than 0.5, the amount of heat radiated from the heat shielding member 20 is small, and when the filter 12 is regenerated,
It becomes difficult to improve the heat retention efficiency of the filter 12.

The shape of the heat shielding member 20 is not particularly limited, and is usually formed in the same shape as the cross-sectional shape of the filter 12. When the heat shielding member 20 is installed in the casing 11, It is desirable to adjust the size so that there is no gap between the inner wall of the heat shield member 11 and the outer peripheral portion of the heat shield member 20. Inner wall of casing 11 and heat shielding member 2
This is to prevent electromagnetic waves, such as infrared rays, from leaking out from the space between the outer circumference of the zero point.

The thickness of the heat shielding member 20 is 1.0 to 1.0.
Preferably, it is 5 mm. If the thickness is less than 1.0 mm, the strength may be insufficient, and the material may be deformed. On the other hand, if the thickness exceeds 5 mm, the material has sufficient strength. If the thickness is more than 5 mm, heat is absorbed and the radiation effect is lost. Furthermore, it is economically disadvantageous, and the weight of the exhaust gas purifying device 10 increases.

The heat shielding member 20 is desirably installed in the casing 11 so that its main surface is parallel to the end surface of the filter 12. This is for efficiently transmitting electromagnetic waves such as radiant heat and reflected infrared rays to the filter 12.

The installation position of the heat shielding member 20 in the casing 11 is desirably 1 to 100 mm from the end face of the filter 12 on the exhaust gas outflow side. If the installation position is less than 1 mm, the heat shielding member 20 may be too close to the filter 12 and the filter may be damaged at the time of installation.
The filter 12 and the heat shielding member 20 come into contact with each other due to vibration or the like generated during use of the filter 0, and the filter 12 may be chipped or cracked. Further, the through hole 31 of the filter 12 may be closed, and the pressure loss of the filter 12 may be increased. On the other hand, when the installation position exceeds 100 mm, the distance to the filter 12 is too long, so that electromagnetic waves such as radiant heat from the heat shielding member 20 and reflected infrared rays cannot be sufficiently transmitted to the filter 12,
In some cases, the heat retention efficiency of the filter 12 cannot be improved. More preferably, the installation position is 5 to 10 mm.

The filter 12 is a honeycomb filter for purifying exhaust gas, comprising a porous ceramic sintered body in which a large number of through holes are arranged in the longitudinal direction and partition walls separating the through holes function as filters. It is preferred that While having sufficient heat resistance, it has excellent durability and particulate collection efficiency, and in the regeneration process, the regeneration time can be relatively short,
This is because the reproduction rate is high. The specific structure of the porous ceramic sintered body is substantially the same as that of the above-described prior art porous ceramic member 30, and a description thereof will be omitted. Further, examples of other filters include, for example, a columnar porous ceramic filter and the like.

The porous ceramic member is preferably made of a ceramic crystal having an average particle size of 2 to 150 μm, more preferably 10 to 70 μm.
When the average particle diameter is less than 2 μm, the pore diameter of the pores present inside the porous ceramic member is too small,
Immediate clogging causes difficulty in functioning as a filter. On the other hand, the average particle size is 150 μm
If it exceeds, the pore diameter of the pores present therein becomes too large, and the strength of the porous ceramic member may be reduced. It also has a predetermined percentage of open pores,
It is not very easy to produce a porous ceramic member having a ceramic crystal having an average particle size exceeding 150 μm. The average pore diameter of such a porous ceramic member is desirably 1 to 40 μm.

The shape of the filter 12 is not particularly limited, and may be cylindrical or prismatic. Usually, a cylindrical filter as shown in FIG. 3 is often used.

The material of the filter 12 is not particularly limited.
Various ceramics can be used, and among these, silicon carbide having high heat resistance, excellent mechanical properties, and high thermal conductivity is preferable.

The holding seal body 13 is wound around the outer periphery of the filter 12 for the purpose of heat insulation or the like, and a material having a high heat insulation property such as a conventionally used ceramic fiber can be used. When the filter 12 is installed in the casing 11, the thickness of the filter 1
It is adjusted so that the space formed by the inner wall 2 and the inner wall of the casing 11 can be completely closed.

The material of the casing 11 is not particularly limited, and examples thereof include stainless steel. Also, the shape is not particularly limited, and may be cylindrical,
The cylinder may have a two-part shell shape obtained by dividing the cylinder into two parts in the axial direction. The size of the casing 11 is not particularly limited, and is appropriately adjusted so that the filter 12 can be installed via the holding seal 13.

As described above, the exhaust gas purifying apparatus of the present invention is configured as described above. When the filter is subjected to the regeneration treatment, the filter is directly heated by an electric heater or the like, It is also heated by radiant heat from the member and electromagnetic waves such as infrared rays reflected by the heat shielding member. Therefore, the exhaust gas purifying apparatus of the present invention can improve the heat retaining efficiency of the filter, can reduce the temperature distribution generated in the filter, and can improve the regeneration rate of the filter.

Further, the exhaust gas purifying apparatus of the present invention includes a back pressure sensor for measuring the pressure loss of the filter, and it is necessary to perform a regeneration process when the back pressure rises above a predetermined value. A device or the like for displaying the fact may be provided.

When the exhaust gas purifying apparatus of the present invention is provided in a vehicle, two or more exhaust gas purifying apparatuses of the present invention may be provided in parallel. In this case, two exhaust gas purifiers are connected to the exhaust gas pipe, and one of them is used by using a switching valve or the like, and the other is regenerated during that time.

Further, N is added to the exhaust gas purifying apparatus of the present invention.
A catalyst layer for removing harmful gases such as Ox and CO may be provided so that both harmful gases and particulates can be removed. Further, according to the present invention, at the time of regeneration, the exhaust gas can be used as a combustion assisting gas. When the regeneration process is separately performed using a pump, the regeneration process can be performed by sending air into the filter using the pump.

In the exhaust gas purifying apparatus of the present invention, for example, instead of a method of heating a filter using an electric heater, for example, an oxidation catalyst is carried on the filter, and hydrocarbons are introduced into the filter carrying the oxidation catalyst. By letting
The filter may generate heat, and an oxidation catalyst may be disposed upstream of the filter, and hydrocarbon may be supplied to the exhaust gas inflow side of the oxidation catalyst to cause the oxidation catalyst to generate heat. A method of heating the filter may be used. Since the reaction between the oxidation catalyst and the hydrocarbon is an exothermic reaction, the filter can be regenerated in parallel with the purification of the exhaust gas by utilizing a large amount of heat generated during the reaction. However, even in such a case, as described in the exhaust gas purifying apparatus of the present invention, by installing a gas permeable heat shielding member on the exhaust gas outlet side of the filter, the heat retaining efficiency of the filter is improved. Can be done. As a result, it is possible to prevent the temperature distribution from being generated in the filter, and it is possible to improve the regeneration rate of the filter.

When assembling the exhaust gas purifying apparatus of the present invention, for example, the honeycomb filter 4 having the structure shown in FIG.
After the holding sealing body 13 is wound around the honeycomb filter 40, the honeycomb filter 40 is placed in the casing 11 in which the heat shielding member 20 is provided at a predetermined position, and the casing 11 having the honeycomb filter 40 and the heat shielding member 20 is removed. It may be disposed between the introduction pipe 14 and the discharge pipe 15 or may be connected to the introduction pipe 14 after attaching the discharge pipe 15 to the casing 11.

[0040]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 An organic binder, water and the like were added to a silicon carbide powder, kneaded, extruded to form a honeycomb-shaped formed body, and subsequently dried, degreased, and fired. As shown in FIG. 4, a porous ceramic member 30 made of a silicon carbide sintered body having an average pore diameter of 5 to 20 μm, 31 cells / cm ² , and a partition wall thickness of 0.3 mm was produced.

Next, this porous ceramic member 30 is
By bundling a large number using a heat-resistant adhesive containing inorganic fibers such as ceramic fibers or inorganic particles such as silicon carbide, and then cutting using a diamond cutter, the diameter as shown in FIG. A ceramic block 41 having a length of 165 mm and a length of 150 mm was produced.

Then, a honeycomb filter 40 was manufactured by forming a layer of the holding seal 13 having the same composition as the heat-resistant adhesive on the outer peripheral portion of the ceramic block 41.
Note that the thickness of the holding seal body 13 was 4 mm.

Using the honeycomb filter 40 produced by the above method, an exhaust gas purifying apparatus 10 having the honeycomb filter 40 and the heat shielding member 20 therein as shown in FIG. 1 was produced. Although not shown, an electric heater for heating the honeycomb filter 40 is provided at a portion on the exhaust gas introduction side of the honeycomb filter 40, and a temperature sensor is provided so as to be in contact with the end face of the honeycomb filter 40. I have.

Here, the form of the heat shielding member 20 is shown in FIG.
As shown in (a), a heat shielding member 20a made of SUS having a large number of openings 22a in a disc-shaped substrate 21a, the opening diameter is 8.0 mmφ, the opening ratio is 41.9%, and the opening pitch is 12mm, thickness 2mm, diameter 143.8m
m, the emissivity was 0.9 at 400 to 700 ° C. Such a heat shielding member 20a is connected to the honeycomb filter 40 in the casing 11 from the end face on the exhaust gas outflow side by 5 mm.
mm.

Next, a particulate collection test was conducted in which the introduction pipe 14 of the exhaust gas purifying apparatus 10 was connected to the exhaust gas outlet of the engine and the engine was operated at 1500 min ^-1 and 20 N · m for 3 hours. Was.

Thereafter, a regeneration process for burning and removing accumulated particulates by heating the honeycomb filter 40 to 600 ° C. using the electric heater is performed for 40 minutes. Was about 50 ° C., and then the regeneration rate of the honeycomb filter 40 was 94.0%
Met.

Embodiment 2 The heat shielding member is a disk-shaped substrate 2 as shown in FIG.
An exhaust gas purifying apparatus was manufactured in the same manner as in Example 1 except that a heat shielding member 20b made of SUS having many openings 22b in 1b was used.

Here, the opening diameter of the heat shielding member 20b is 2.
5 mmφ, aperture ratio 35%, aperture pitch 4 mm, thickness 1 mm, diameter 143.8 mm, emissivity 400 to 7
The value was 0.95 at 00 ° C., and the honeycomb filter was set at a position 10 mm from the end face on the exhaust gas outflow side.

The exhaust gas purifying apparatus according to the second embodiment thus manufactured is subjected to a particulate collection test under the same conditions as in the first embodiment, and a regenerating process for removing and burning the particulates thereafter. When the temperature difference between the vicinity of the center and the vicinity of the periphery was measured, it was about 40 ° C., and thereafter, the regeneration rate was measured, and was 96%.

Comparative Example 1 An exhaust gas purifying apparatus was manufactured in the same manner as in Example 1 except that the heat shielding member 20a was not used.

The exhaust gas purifying apparatus according to Comparative Example 1 thus manufactured was subjected to a particulate collection test under the same conditions as in Example 1 and a subsequent regeneration treatment for removing and burning the particulates. When the temperature difference between the vicinity of the center and the vicinity of the periphery was measured, it was about 100 ° C., and then the regeneration rate was measured, and it was 78.9%.

As is clear from the results shown in Examples 1 and 2 and Comparative Example 1, in the regeneration processing of the honeycomb filters according to Examples 1 and 2, the temperature difference between the center and the periphery of the honeycomb filter, and Each of the regeneration rates of the honeycomb filters was superior to the temperature difference between the vicinity of the center and the vicinity of the periphery and the regeneration rate of the honeycomb filter according to Comparative Example 1.

[0054]

As described above, the exhaust gas purifying apparatus of the present invention can improve the heat retention efficiency of the filter in the regeneration processing of the filter, thereby preventing the temperature distribution from being generated in the filter. And the regeneration rate of the filter can be increased.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing one example of an exhaust gas purifying apparatus of the present invention.

FIG. 2A is a plan view schematically showing an example of a heat shielding member used in the exhaust gas purifying apparatus of the present invention,
FIG. 5B is a plan view schematically illustrating another example of the heat shielding member.

FIG. 3 is a perspective view schematically showing an example of a honeycomb filter used for an exhaust gas purifying device.

4A is a perspective view schematically showing a porous ceramic member used for the honeycomb filter shown in FIG. 3, and FIG. 4B is a cross-sectional view taken along line AA.

FIG. 5 is a cross-sectional view schematically showing an example of a conventional exhaust gas purification device.

[Explanation of symbols]

 10, 50 Exhaust gas purifier 11, 51 Casing 12 Filter 13, 53 Holding seal 14, 54 Introducing pipe 15, 55 Discharging pipe 20, 20a, 20b Heat shielding member 21a, 21b Substrate 22a, 22b Opening 30 Porous ceramic member DESCRIPTION OF SYMBOLS 31 Through hole 32 Filler 33 Partition wall 40 Honeycomb filter 41 Ceramic block 42 Adhesive layer 43 Sealing material

Claims (4)

[Claims] 1. An exhaust gas purifying apparatus comprising: a casing connected to an inlet pipe for introducing exhaust gas discharged from an internal combustion engine and an exhaust pipe for discharging the exhaust gas, wherein an exhaust gas purifying filter is installed. An exhaust gas purifying device, wherein a gas-permeable heat shielding member is provided on an exhaust gas outflow side of the filter. 2. The exhaust gas purifying apparatus according to claim 1, wherein the heat shielding member has an aperture ratio of 20 to 60%. 3. The exhaust gas purifying apparatus according to claim 1, wherein the heat shielding member is made of metal or ceramic. 4. The heat shielding member according to claim 1, wherein the emissivity at 400 to 700 ° C. is 0.5 or more.
An exhaust gas purifying apparatus as described in the above.