JPH1030429A - Particulate burning method and filter structure of exhaust black smoke removing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide particulates burning method and a filter structure of an exhaust black smoke removing device which can reactivate the filter at a low temperature by adding fuel additive to fuel supplied to a diesel engine. SOLUTION: Exhaust gas from an engine 1 passes through a vent type porous filter 3. Particulates in the exhaust gas are captured by the filter 3 and burned. Fuel additive added to the fuel supplied to the engine is made up of liquid formed by solving oxydized catalyst containing at least one of cerium, cupper and iron into petroleum solvent. The filter is composed of silicon carbide. It is a honeycomb filter having a mean diameter size of minute holes of 14 micrometers, porosity of 40 to 50%, and thickness of 150mm in a direction for passing the exhaust gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust black smoke removing apparatus in which a fuel additive is added to fuel supplied to a diesel engine, and fine particles in exhaust gas discharged from the engine are captured by a filter and incinerated. The present invention relates to a fine particle incineration method for increasing the frequency of filter regeneration and stabilizing the regeneration process, and a filter structure.

[0002]

2. Description of the Related Art Exhaust gas of a diesel engine contains a large amount of fine particles mainly containing carbon (for example, 200 mg / Nm).
³ ) Various DPF (Diesel Particulate Filter) systems have been proposed that capture and remove these particulates from exhaust gas using filters because they are included and cause air pollution. In conventional DPF systems, it is known that cordierite porous ceramic filters have a high filter efficiency for particulates.

As a technique for regenerating the filter by removing fine particles deposited on the filtration surface of the filter, a technique of igniting, burning, and incinerating a high-temperature combustion gas generated by a burner provided near the exhaust gas inlet is used. However, it is known, for example, from Japanese Utility Model Application Laid-Open No. 62-35849. However, when a burner is used, there is a problem in that the filter is melted or cracked due to high-temperature combustion heat. Experiments have shown that in order for the filter to be safe, the filter outlet temperature must not exceed 650 ° C. In order to incinerate particulates in the filter at such a filter outlet temperature, The use of catalysts was known to be necessary, and the use of cerium-based fuel additives was promising (eg, SAE).
Paper 960135).

A DPF system that regenerates a filter at a low regeneration temperature by adding a certain fuel additive to fuel supplied to a diesel engine has an advantage that the system is simple. Since the agent is accumulated and regeneration does not occur unless the filter temperature reaches a certain level or more, regeneration is unlikely to occur when traveling in an urban area, etc., the pressure loss of exhaust gas increases, fuel efficiency deteriorates, or excessive particulates accumulate. In such a state, regeneration occurs at a stretch, and cracks and erosion of the filter occur.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to obviate the disadvantages of the prior art of conventional DPF systems and to reduce the fuel added to the diesel engine by adding certain fuel additives. An object of the present invention is to provide a method for incinerating fine particles of an exhaust black smoke removing apparatus and a filter structure, which can regenerate a filter at a temperature. It is another object of the present invention to increase the frequency of filter regeneration and stabilize filter regeneration. Another object of the present invention is to reduce the pressure loss of the exhaust black smoke removing device and prevent deterioration of fuel efficiency. Still another object of the present invention is to reduce the size and life of the exhaust black smoke removing device. Other objects and advantages of the present invention will become apparent from the following description.

[0006]

In the method for incinerating fine particles of an exhaust black smoke removing apparatus according to the present invention, an additive supply mechanism is provided in a fuel supply system of a diesel engine to add a fuel additive to fuel supplied to the engine. Then, exhaust gas discharged from the engine is passed through a filter made of a gas-permeable porous material, and fine particles in the exhaust gas are captured by the filter and incinerated. The fuel additive is made of a liquid obtained by dissolving an oxidation catalyst containing at least one of cerium, copper, and iron in a petroleum-based solvent, and the filter is a honeycomb filter made of silicon carbide.

In the present invention, the filter of the exhaust black smoke removing device is made of silicon carbide, has an average diameter of micropores of about 14 μm, a porosity of 40 to 50%, and a thickness of about 40 to 50% in a direction in which exhaust gas passes. In a diesel engine exhaust gas using a fuel comprising a 150 mm honeycomb filter and a fuel additive containing a liquid obtained by dissolving an oxidation catalyst containing at least one of cerium, copper, and iron in a petroleum-based solvent. The fine particles are captured by a filter and incinerated.

[0008]

According to the method of the present invention, an additive supply mechanism is provided in a fuel supply system of a diesel engine to supply at least one of cerium, copper, and iron to a fuel supplied to the engine. A fuel additive consisting of a liquid obtained by dissolving an oxidation catalyst containing two components in a petroleum-based solvent is used. The fuel additive brings the particulate combustion temperature to a relatively low level in the filter without significantly affecting the total particulate emissions. In the present invention, the incineration of the fine particles can be easily performed at a relatively low temperature without the need to apply heat from outside the engine by the action of the oxidation catalyst. Therefore, the frequency of regeneration of the filter due to incineration of the fine particles increases, and the regeneration is stabilized. Also, the structure of the filter can be simplified.

In the present invention, the filter is made of silicon carbide, has an average diameter of micropores of about 14 μm, a porosity of 40 to 50%, and a thickness of about 15 in the direction in which exhaust gas passes.
It consists of a 0 mm honeycomb filter. Since the volume of the filter is small, the amount of the fuel additive per unit deposition is increased, and the filter can be easily regenerated by burning the fine particles. Further, since the volume of the filter is small, the temperature rises, and the incineration and regeneration of the fine particles easily occur.

[0010]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of the present invention.
1 is a layout diagram schematically illustrating an entire DPF system that regenerates a filter using a fuel additive. In FIG. 1, fuel is supplied from a fuel tank 4 to a diesel engine 1 via a fuel pipe 5. The fuel tank 4 is connected to an additive tank 8 via an additive supply pipe 6 having an additive pump 7. The additive pump 7 is controlled by the controller 9 and supplies an appropriate amount of fuel additive to the fuel tank 4 according to the amount of fuel. The exhaust gas from the diesel engine is
It is discharged through the filter 3 arranged therein.

The fuel additive supplied from the additive tank 8 to the fuel tank 4 via the additive pump 7 includes cerium,
An oxidation catalyst containing at least one of copper and iron is dissolved in a petroleum-based solvent such as naphtha to form a liquid.

FIGS. 2A and 2B are views showing the structure of a DPF comprising a divided honeycomb filter 3 used in an embodiment of the present invention. FIG. 2A is a side view, FIG. 2B is a front view, and FIG. It is the elements on larger scale of FIG. 2B. As shown in FIGS. 2A and 2B, the filter 3 has a large number of filter pieces 12 in a polygonal prism side wall formed by a heat insulating agent.
And a split-type honeycomb filter having a structure connected and arranged by the above. The filter 3 of FIG. 2B has 52 complete filter pieces 12 and 1/4 of the filter pieces 12.
Includes two. The thickness L of the filter piece 12 shown in FIG. 2A in the direction in which the exhaust gas passes is about 150 mm. FIG.
Is an enlarged view of the filter piece 12, showing a height H and a width W.
Is 33 mm each.

Table 1 shows the specifications and characteristics of the filters of FIGS. As shown in Table 1, the honeycomb filter 3
Is made of silicon carbide and has an average pore diameter of about 14
μm, the porosity is 40 to 50%, and the thickness in the direction in which the exhaust gas passes is about 150 mm. This honeycomb filter starts combustion at a relatively low temperature, that is, at a temperature of about 300 ° C. by acting on an oxidation catalyst by capturing fine particles in the exhaust gas of a diesel engine, incinerating the fine particles captured by the filter, and filtering the filter. Reproduce.

[0014]

Table 1 Specifications and characteristics of filter (FIG. 2) Basic dimensions (mm) of filter piece: 33 × 33 × 150 (W × H × L) Number of filter pieces: 52+ (１ ／) × 12 = 55 (whole) Volume (liter): 9.0 (55 pieces) Cell dimensions: Pitch (mm): 1.8 Wall thickness (mm): 0.3 Average pore diameter (μm): 14 Porosity (%): 40-50 heat resistance (° C) (decomposition point): 2300

[0015]

As described above, the SiC honeycomb filter used in the present invention has the same fine particle collection amount and low pressure loss as compared with the cordierite honeycomb filter used in the conventional exhaust black smoke removing apparatus. 30
% To 50%, and the heat capacity can be reduced to 15 to 50%.
It can be reduced by 40%, the thermal conductivity is about 25 times, and the heat-resistant temperature (melting point) is 1400 ° C for cordierite.
About 2200 ° C. Therefore, the present invention has the following advantages.

(1) Since the filter volume is small, the amount of the fuel additive per unit volume increases, and the filter regeneration combustion is likely to occur.

(2) Since the filter volume is small, the filter temperature rises by that amount and regenerating combustion easily occurs.

(3) SiC honeycomb filter Due to good thermal conductivity, fine particles are not locally burned in the filter, and the regeneration is uniform and stable. Also,
Since no extreme temperature gradient occurs in the filter, cracking of the filter can be prevented.

(4) Since the SiC honeycomb filter has a high heat-resistant temperature, there is an advantage that the filter is not easily melted even when overheating occurs.

(5) In the present invention, the reliability of the function of the DPF system can be improved by using the SiC honeycomb filter, and deterioration of the fuel efficiency of the engine can be prevented by reducing the pressure loss.

[Brief description of the drawings]

FIG. 1 is a layout diagram schematically showing an entire DPF system according to an embodiment of the present invention for regenerating a filter using a fuel additive.

FIG. 2 is a diagram showing a structure of a split type honeycomb filter used in an embodiment of the present invention, FIG. 2A is a side view, and FIG. 2B is a front view.

FIG. 3 is a partially enlarged view of FIG. 2B.

[Explanation of symbols]

1: diesel engine, 2: exhaust pipe, 3: filter, 4:
Fuel tank, 5: fuel pipe, 6: additive supply pipe, 7: additive pump, 8: additive tank, 9: controller.

Claims (2)

[Claims] A fuel supply system of a diesel engine is provided with an additive supply mechanism to add a fuel additive to fuel supplied to the engine, and exhaust gas discharged from the engine passes through a filter made of a porous porous material. In the method for incineration of particulates in an exhaust black smoke removing apparatus in which particulates in exhaust gas are captured by a filter and incinerated, the fuel additive comprises an oxidizing catalyst containing at least one of cerium, copper, and iron in a petroleum system. A method for incinerating particulates in an exhaust black smoke removing apparatus, wherein the filter is a honeycomb filter made of a liquid dissolved in a solvent, and the filter is made of silicon carbide. 2. An additive supply mechanism is provided in a fuel supply system of a diesel engine, and cerium,
A fuel additive consisting of a liquid obtained by dissolving an oxidation catalyst containing at least one of copper and iron in a petroleum-based solvent is added, and a filter made of a gas-permeable porous material is provided in an exhaust system of the engine. A filter structure of an exhaust black smoke removing device that captures and incinerates fine particles by a filter, wherein the filter is made of silicon carbide, the average diameter of micropores is about 14 μm, the porosity is 40 to 50%, and the exhaust gas A filter structure for an exhaust black smoke removing device, comprising a honeycomb filter having a thickness of about 150 mm in a passing direction.