JPH02268812A - Exhaust gas purification device - Google Patents

Abstract

PURPOSE:To collect the particulate in exhaust gas with a filter and to oxidize the hydrocarbon passing through the filter with an oxidizing catalyst to discharge as harmless components by providing the oxidizing catalyst in the downstream of gas flow from the filter. CONSTITUTION:A gathering cone 14 is provided in the downstream side of exhaust gas from filters 13a, 13b, and a catalyst body 15 is provided in the downstream side of the cone. The end parts of the corrugated honeycomb cell of alumina-silica fiber in the filters 13a, 13b into which the exhaust gas of engine flows are alternatively plugged so that the particulate is filtered and separated when the exhaust gas passes through the wall of cell and moves to the next cell the outlet side of which is opened, and the particulate flows into the gathering cone 14. The high boiling point component of hydrocarbon in the exhaust gas is absorbed by granular substance and remains in the filters 13a, 13b as particulate, and the unadsorbed high boiling point component and low boiling point component reach the catalyst body 15 from the gathering cone 14 to be oxidized into CO2 and are discharged in the form of water vapor into the air.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention collects particulates (particulate matter such as soot) emitted from diesel engines and collects them into the atmosphere.
This invention relates to an exhaust gas purification device that prevents η pollution.

Problems to be Solved by the Invention Various types of filters have been proposed for removing particulates from exhaust gas from diesel engines. These devices generally use a method in which particulates are filtered and collected using a filter, and the particulates are incinerated as they are on the filter for regeneration. However, although these methods can collect particulates, they do not remove low-boiling components of hydrocarbons in exhaust gas. Furthermore, high-boiling components of hydrocarbons are adsorbed by particulate matter as particulates and collected in filters, but if the exhaust gas temperature rises or the filter temperature rises during regeneration,
Due to desorption and evaporation, it was removed from the filter and mixed into the exhaust gas, which was then released into the atmosphere. These hydrocarbons have a unique unpleasant odor and are known to be substances that should be removed from the perspective of preventing air pollution.

Means for solving the problem: An oxidation catalyst for oxidizing hydrocarbons is provided behind the exhaust gas flow of the filter that collects particulates.With the above configuration, particulates in the exhaust gas are collected by the filter and passed through the filter. Hydrocarbons are oxidized by an oxidation catalyst and discharged as harmless components. Since the oxidation catalyst is located behind the filter, it can sufficiently treat not only the low-boiling point hydrocarbons that have passed through the filter, but also the hydrocarbons in the particulates that come off the filter as the temperature rises. Further, the oxidation catalyst is not covered with particulates and the catalyst activity is not reduced, so that exhaust gas treatment can be carried out effectively at all times.

Embodiments The present invention will be explained based on the drawings. FIG. 1 is a longitudinal sectional view of an exhaust gas purification device for a diesel engine according to an embodiment of the present invention. The exhaust gas purification device is installed at a connection port 1.2 in the middle of the exhaust pipe of a diesel engine. 3 is a burner, and a fuel atomizing nozzle 4 is attached to the center. The fuel atomizing nozzle 4 has an atomizing air supply port 5 and a fuel supply port 6, and is connected to an air pump (not shown) and an oil pump (not shown), respectively. Reference numeral 7 denotes an igniter, which is attached from the side toward the vicinity of the tip of the atomizing nozzle 4. 8 is a combustion chamber, the burner 3 is attached to one end, the other end is connected to a four-way valve 9, and an oval vane 10 is installed.
The case 12a112b is covered with a cushioning material 11 through
It communicates with two filters 13a and 13b housed in the.

A collection cone 14 is located downstream of the exhaust gas filters 13a and 13b.
There is a catalyst body 15 on the downstream side thereof. This catalyst body 15 is covered with a buffer material 16 and the collecting cone 1
The catalyst case 17 is connected to the catalyst case 17. The catalyst case 17 is then connected to the exhaust pipe 18 and reaches the connection port 2.

The filters 13a and 13b are made by corrugating a sheet obtained by wet-forming alumina-silica fibers and ceramic raw material powder into a cardboard shape while filling one end with a plug, and then filling the other end with a plug raw material. The material used was one obtained by winding up the material while filling it and firing it at 1250''C in an electric furnace to form a ceramic.

Further, the same material as the filter 13a1b was used for the catalyst carrier supporting the catalyst and constituting the catalyst body 15. however,
The catalyst carrier was constructed as a wall-through type (both ends of the cell are open) without a plug.

Next, the operation in this embodiment will be explained. First, during normal operation, the elliptical minor axis of the elliptical vane 10 of the four-way valve 9 and the line connecting the two opposing outlets are in the same direction, and all openings connected to the four-way valve 9 are in communication.

At this time, exhaust gas from the engine passes through the four-way valve 9 and flows into both filters 13a1b.

The ends of the corrugated honeycomb cells of this filter 13a1b are plugged alternately, and the exhaust gas flows into the open corrugated honeycomb cells, passes through the wall of the cell, and when moving to the adjacent cell whose outlet side is open, particulates are generated. The curate is filtered and separated and flows into the collection funnel 14. High boiling point components of hydrocarbons in the exhaust gas are adsorbed by particulate matter and are passed through the filters 13a, b as particulates.
The high-boiling point components and low-boiling point components that remained and were not adsorbed reach the catalyst body 15 from the collecting cone 14 and undergo oxidation, resulting in C
O2 becomes water vapor and is released into the atmosphere.

Next, a certain amount of particulate filter 13azb
This section explains when regeneration becomes necessary due to accumulation of particles. First, the elliptical vane 10 is rotated 90 degrees to communicate the combustion chamber 8 and the filter 13a, and the connection port 1 and the filter 13b, respectively.

Next, a high voltage is applied to the igniter 7 to cause spark discharge at the tip, and at the same time, fuel and air are supplied to atomize the fuel and inject it toward the combustion chamber 8. The spouted fuel is ignited by the spark of the igniter 7, forms a flame in the combustion chamber 8, and burns, producing high-temperature gas. The high-temperature gas maintained at 750° C. passes through the four-way valve 9 and heats the filter 13a in the case 12a, thereby incinerating the accumulated particulates. During this time, exhaust gas from the engine is flowing through the other filter 13b and continues to collect particulates. (The state at this time is shown in the figure.) After a few minutes, the oval bay 710 is rotated 180 degrees to switch the flow path, and high-temperature gas is sent to the filter 13b to incinerate the particulates. On the other hand, Ut gas from the engine flows into the filter 13a that has finished regeneration, and collection of particulates has started. Similarly, when the regeneration of the filter 13b is completed, the burner 3
At the same time, the oval vane 10 is rotated 90 degrees to return to its original state, and both filters 13 are removed again.
Particulates are collected using a1 and b. During this regeneration, the filter is gradually heated by the high temperature gas from the upstream end of the exhaust gas to the downstream side, so
The high-boiling components of hydrocarbons that are collected in the filter as particulates are removed from the filter. Since more than 20-60% of the total weight of the residue on the filter is adsorbed as particulates, the hydrocarbons cannot be ignored. However, in the present invention, since the catalyst IS is provided behind the filter, the hydrocarbons generated in this way are also oxidized together with the hydrocarbons in the exhaust gas flowing from the other filter, and are harmless. It is released into the atmosphere as clean exhaust gas. Further, even when the exhaust gas temperature rises while the diesel engine is operating, hydrocarbons are released from the filter, and in this case as well, they are treated in the same manner by the catalyst body 15.

In this example, a mixed catalyst of copper oxide, platinum, and palladium was used as the catalyst, but other oxidation catalysts such as lanthanum cerium perovskite type catalysts may be used without limitation.

Effects of the Invention As described above, the present invention enables stable removal of particulates and hydrocarbons during operation of a diesel engine, and has excellent effects in removing unpleasant odors from exhaust gas and preventing air pollution. It is.

[Brief explanation of drawings]

The figure is a cross-sectional view showing the state of the exhaust gas purification device in one embodiment of the present invention during filter glue generation. 3. Burner, 8. Fist combustion chamber, 9. Four-way valve, 13a1 b. No. 15. Name of my catalyst agent. Patent attorney Shigetaka Awano Filter, and 1 other person.

Claims (3)

[Claims] (1) An exhaust gas purification device including a built-in filter for removing particulates from exhaust gas, characterized in that a catalyst for oxidizing hydrocarbons is provided downstream of the filter in the flow of the exhaust gas. (2) The exhaust gas purification device according to claim 1, wherein the catalyst is supported on a honeycomb structure. (3) The exhaust gas purification device according to claim 2, wherein the honeycomb structure is a corrugated honeycomb structure using alumina-silica fibers.