JPH06137134A - Particulate trap for diesel engine - Google Patents

Abstract

(57) [Summary] [Purpose] A particulate trap that is quickly incinerated in the combustion chamber to retain unburned particulates and its ash and causes electric heaters to overheat due to combustion heat and not to be thermally damaged. provide. [Composition] Combustion chamber is made of cylindrical heat-resistant steel, electric heater is provided on the outer periphery of the combustion chamber, air inlet is provided near the inlet, and means for swirling the mixed gas flow in the combustion chamber is provided for mixing. Swirl the gas stream to facilitate the incineration of particulates.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a particulate trap that traps and incinerates particulates (black smoke particles) in exhaust gas of a diesel engine.

[0002]

2. Description of the Related Art As a particulate trap for backwashing particulate matter in exhaust gas of a diesel engine captured by a ceramics filter and moving it to another place and then incinerating it, a cross flow type is disclosed in JP-A-1-77715. The one provided with a ceramics filter is disclosed in JP-A-1-15.
It is proposed that 9408 is provided with a Hamicam type ceramics filter.

Non-combustible components that remain as ash when burned are contained in the particulates, and if the particulates are incinerated with the particulates trapped in the ceramic filter, clogging of the filter cannot be avoided.
For this reason, it is better to backwash the ceramics filter and move the particulates to a different location, then ignite and incinerate it, to avoid clogging of the ceramics filter, and to prevent erosion of the ceramics filter sometimes occurring when incinerating on the filter. It has the advantage of avoiding damage.

For example, in the case of a diesel engine for a ship or a diesel engine for power generation which is used in a fixed state, it is often operated for a long time under a high load, so Contains a large amount of particulates, and because the type of fuel used is heavier than in the case of cars and the additives are different, during the particulates, it is emitted from the diesel engine of the car. Compared to the particulate matter in the exhaust gas, it contains a large amount of non-combustible components other than carbon,
A particulate trap for backwashing is more suitable. The particulate trap that processes particulates in the exhaust gas of vehicle-mounted diesel engines is compact enough to be mounted on a vehicle, and it can respond to driving conditions that change momentarily depending on roads and driving conditions, resulting in long-term durability and durability. It is required to be reliable.

Japanese Unexamined Patent Publication No. 2-185611 proposes a particulate trap for an on-vehicle diesel engine equipped with a cross-flow type ceramics filter, which is used for combustion so that the collected particulates are not burnt in the incineration part. It has been proposed to provide air. Further, in the particulate trap proposed in Japanese Patent Laid-Open No. 3-168313, its combustion chamber has the structure shown in FIG.

In FIG. 4, 1 is a combustion chamber, 4 is an electric heater, 6 is a nozzle for compressed air, 7 is a recollection part of particulates, 14 is a cross-flow type ceramic filter, 15 is a casing, and 16 is a seal. Material, 20 is an exhaust gas inlet, 21 is a clean gas flow path of a ceramics filter, 22 is a dust-containing gas flow path of a ceramics filter, 23
Is a backwash nozzle, 24 and 29 are solenoid valves, 25 is a tank for compressed air, 26 is an exhaust pipe, 27 is a butterfly valve, and 28 is an orifice plate.

That is, the particulates separated from the ceramics filter 14 by backwashing are sent to the combustion chamber (incinerator) 1 together with a part of the exhaust gas and incinerated, but air for promoting the combustion of the particulates. Is supplied to the combustion chamber 1 from a compressed air nozzle 6 for supplying combustion air.

In the particulate trap,
Particularly immediately after backwashing, a part of the particulates separated from the ceramics filter 14 floats in the exhaust gas, and the particulates including the floating particulates are sent to the combustion chamber 1 and the ceramics filter 14 again. It is effective to send a part of the exhaust gas (for example, 0.2 to 5% of the exhaust gas introduced into the particulate trap) to the combustion chamber 1 together with the particulates in order to prevent the accumulation in the combustion chamber 1. .

However, in order to complete the incineration of the particulates sent to the combustion chamber 1 in a relatively short time, it is necessary to increase the load on the electric heater 4, and unburned particulates or particulate ash. Electric heater 4
When the electric heater 4 stays in the vicinity of the electric heater 4, the electric heater 4 is easily overheated because the electric heater 4 is partially overheated due to the heat of particulate combustion and the electric heater 4 is partially overheated. There is a problem that the durability of 4 is not enough.

[0010]

The present invention solves these problems and promptly completes the incineration of particulates, and also secures the durability of the electric heater for a diesel engine which is durable and reliable. It is intended to provide a particulate trap.

[0011]

The present invention has been made to achieve the above-mentioned object, and a particulate trap for a diesel engine of the present invention uses a ceramics filter to remove particulates in the exhaust gas of a diesel engine. The trapped particulates are separated from the ceramic filter by backwashing, the separated particulates are placed on a part of the exhaust gas flow, transferred to a combustion chamber equipped with an electric heater, and the particulates are incinerated in the combustion chamber. It is a curate trap, the combustion chamber is made of cylindrical heat-resistant steel, the electric heater is arranged on the outer periphery of the cylindrical heat-resistant steel, and an inlet for the air for particulate incineration is provided near the inlet of the combustion chamber. , The combustion chamber is equipped with a means for giving swirl to the mixed gas flow of exhaust gas and air, while the mixed gas flow is swirling Particulates, characterized in that it is incinerated in a baking chamber in.

In the particulate trap for a diesel engine of the present invention, an electric heater is arranged around the outer periphery of the combustion chamber made of heat-resistant steel in a cylindrical shape, and swirls a mixed gas of exhaust gas and air in the combustion chamber. Because it has a means,
In the combustion chamber, the particulates swirl together with the flow of the mixed gas, and the heat of the electric heater arranged on the outer periphery of the combustion chamber is converted into the particulates by the centrifugal force pressing the particulates against the wall of the combustion chamber made of heat-resistant steel. It is easy to transmit, the ignition to the particulate is ensured, and the flow velocity of the mixed gas of air and exhaust gas is increased due to the swirling, so the contact between the particulate and the mixed gas is good, and the combustion progresses quickly. Produce an effect.

Further, since there is no protrusion inside the combustion chamber made of cylindrical heat-resistant steel that obstructs the flow of gas, particulates or particulate ash does not stay inside the combustion chamber, and There is no fear that a part of the electric heater arranged across the wall or the wall made of heat-resistant steel will be overheated and thermally damaged.

As the electric heater, it is preferable to use a sheath electric heater for on-vehicle use, and for stationary use, a bare coiled resistance heating element such as a Kanthal wire surrounded by a heat-resistant insulator can also be used. . Further, as means for giving swirl to the mixed gas flow of exhaust gas and air, a compressed air nozzle is used as the air inlet, the introduction pipe to the cylindrical combustion chamber is eccentric, or the tangent line of the cylindrical combustion chamber is used. There are means such as providing a spiral guide fin in the combustion chamber.

In a preferred embodiment of the particulate trap for a diesel engine of the present invention, the exhaust gas sent to the combustion chamber is 0.5 to 3% of the exhaust gas introduced into the particulate trap. In order to move the particulates captured by the ceramics filter and released from the ceramics filter by backwashing to the combustion chamber, and swirling the particulates in the combustion chamber with the mixed gas of exhaust gas and air, 0.5% or more is required. It is preferable to send the exhaust gas to the combustion chamber.

Further, the exhaust gas of the vehicle-mounted diesel engine contains oxygen capable of incinerating the particulates except for a very limited period of time when the diesel engine is operated under a large load, and the air for incinerating the particulates is It is preferable to use the exhaust gas as much as possible to save the compressed air so that the compressed air supply system including the tank does not become bulky.

On the other hand, if too much exhaust gas is sent to the combustion chamber, the residence time of particulates in the combustion chamber may be shortened and incineration may not be completed. Therefore, it depends on the size of the combustion chamber. It is preferably 3% or less. In particular, when the load on the diesel engine is large and the amount of oxygen in the exhaust gas is small, it is advisable to reduce the amount of exhaust gas sent to the combustion chamber and increase the injection amount of incineration air.

In another preferred embodiment of the particulate trap for a diesel engine according to the present invention, a spiral guide fin is provided as a means for giving a swirling flow to the mixed gas. The guide fin is a preferable means for reliably rotating the mixed gas when the mixed gas has a certain flow rate. Further, it is preferable that the guide fins are provided along the axis of the combustion chamber and are arranged apart from the wall of the combustion chamber so that there is no place where particulates stay.

In another preferred embodiment of the particulate trap for a diesel engine according to the present invention, a sheath electric heater is provided near the axis of the combustion chamber. By arranging the sheath heater in the axial center of the combustion chamber, the amount of heat that can be input to the heater is increased, the rise of the particulate trap at the start of the diesel engine can be accelerated, and the temperature inside the combustion chamber can be controlled quickly. Available.

Further, if the sheath electric heater provided near the axis is integrated with the guide fins, the heat of the sheath electric heater is quickly conducted to the guide fins, the temperature in the combustion chamber can be easily controlled uniformly, and the particulates can be easily controlled. The incineration can be completed more reliably and quickly.

Further, if the electric heater arranged outside the cylindrical combustion chamber is divided in the circumferential direction and / or axial direction of the cylinder and the temperature of each part is controlled, a partial abnormality in the combustion chamber will occur. Supports combustion and overheating prevention,
It is possible to reliably prevent thermal damage to the electric heater and the cylindrical heat resistant steel. Further, by controlling the injection amount of the compressed air for combustion, it is possible to control the temperature in the combustion chamber such as emergency cooling in the combustion chamber.

[0022]

EXAMPLES The present invention will be described below with reference to specific examples, but the present invention is not limited to these examples.

FIG. 1 is a side sectional view showing an outline of an embodiment of a particulate trap for a diesel engine according to the present invention, and FIG. 2 is a plan sectional view downstream of the combustor of FIG. In both figures, 1 is a combustion chamber made of cylindrical heat-resistant steel (stainless steel), 2 and 9 are introduction pipes of a mixed gas of exhaust gas and air containing collected particulates, 3 is an outlet pipe, and 4 is An electric heater, 5 is a heat insulating material, 6 is a nozzle of compressed air, 7 is a recollection part of particulates, 8 and 12 are solenoid valves for air, 11 is a pressure equalizing chamber, 10 is a solenoid sluice valve, and 13 is a throttle valve. , 14 is a cross-flow type ceramics filter, 15 is a casing, and 16 is a sealing material.

The particulates in the exhaust gas of the diesel engine (not shown) collected by the ceramics filter 14 are blown off from the ceramics filter 14 by backwashing (backwashing means not shown), and the casing is removed. Collected in the recollection section 7 provided at the bottom of 15,
It is sent to the introduction pipe 2 together with a part of the exhaust gas.

A compressed air nozzle 6 for ejecting compressed air is provided between the recollection section 7 and the introduction pipe 2 in the direction of the combustion chamber 1. When, for example, 5 kg / cm ² ) is ejected from the nozzle 6 of compressed air, the ejected compressed air entrains the surrounding exhaust gas to form a mixed gas into the combustion chamber 1 and swirls into the combustion chamber 1. Create a flow. In this case, even if the introduction pipe 2 is provided at the position of the introduction pipe 9, a similar swirl flow can be obtained in the combustion chamber 1.

The particulates in the mixed gas flowing into the combustion chamber 1 come into contact with the wall of the combustion chamber 1 by the centrifugal force and are ignited. An electric heater 4 composed of a coil of four-divided Kanthal wire is arranged on the outer periphery of the combustion chamber 1, and each divided electric heater 4 is appropriately arranged so that the wall of the adjacent combustion chamber 1 does not overheat. The temperature is controlled separately to maintain the temperature.

Since the outside of the electric heater 4 is kept warm by the heat insulating material 5 and the heat generated by the combustion of particulates is generated in the combustion chamber 1, it is not necessary to consume so much electricity in the electric heater 4. . The ignited particulate moves in the combustion chamber 1 while swirling, and burns during this period to form a very small amount of ash, which is sent to the outlet pipe 3 together with the mixed gas.

Two electromagnetic gate valves 10 are connected in series downstream of the outlet pipe 3, and a pressure equalizing chamber 11 is provided between them. In the pressure equalizing chamber 11, a pressure wave generated when the ceramic filter 14 is backwashed reaches the combustion chamber 1 and a mixed gas containing unburned particulates entrained with particulates is discharged from the outlet pipe 3. To prevent
When backwashing is performed, the electromagnetic sluice valve 10 is closed immediately before, and the solenoid valve 12 for pressure equalization is opened at the same timing as when the compressed air is blown into the ceramics filter 14 to prevent the pressure wave and the accompanying discharge of unburned particulates. To do.

A few seconds after backwashing, the electromagnetic valve 12 is closed, the electromagnetic gate valve 10 is opened, and the incineration of particulates is continued again. The throttle valve 13 is provided to control the amount of exhaust gas flowing into the combustion chamber, and the amount of blowdown of exhaust gas into the combustion chamber is maintained at, for example, about 1% of the total exhaust gas flowing into the particulate trap. It Downstream of the throttle valve 13, the exhaust gas is discharged to the external system as it is, joined to the exhaust pipe of the cleaned exhaust gas, or discharged to the external system after removing ash.

As the electromagnetic sluice valve 10, for example, a butterfly valve used for an exhaust brake in a truck or the like can be preferably used. As means for preventing the particulates from being blown out from the outlet pipe in the unburned state, the pressure equalizing chamber 11 and the ceramics filter 14 are also provided.
There is also a method of connecting the space in the casing 15 in which the pressure is stored by piping to balance the pressure.

In order to continuously treat the exhaust gas discharged from the diesel engine by the particulate trap, the two series of particulate traps are connected in parallel and the backwash is alternately performed.

FIG. 3 is a plan view of an example of a finned sheath electric heater inserted into the combustion chamber of the particulate trap according to the present invention. In the figure, 17 is a sheath electric heater, 18 is a guide fin, and 19 is a terminal box of the sheath electric heater. By inserting this sheathed electric heater with guide fins into the axial center of the combustion chamber, it is possible to reliably swirl the mixed gas flow to accelerate incineration, and to quickly heat up the combustion chamber when starting the diesel engine. Can be done.

Test Example An attempt was made to remove particulates from exhaust gas discharged from a diesel engine for power generation by using a particulate trap having the configuration shown in FIGS. 1 and 2. That is, the combustion chamber 1
Made of stainless steel with an inner diameter of 200 mm, wall thickness of 7 mm,
A cylinder with a length of 720 mm is used.
A Kanthal wire coil, which was divided and had a total heating capacity of 5 kW, was used, and the length of the heating portion of the combustion chamber 1 was set to about 500 mm.

The temperature of each electric heater was separately controlled to control the temperature of the wall of the combustion chamber to about 800 ° C. The dimensions of the portion including the combustion chamber 1, the electric heater 4, and the heat insulating material 5 had an outer diameter of about 560 mm and a total length of about 1000 mm. A 20 A (inner diameter of about 20 mm) stainless steel pipe was used for the introduction pipe 2 of the combustion chamber 1, and a 32 A (inner diameter 32 mm) stainless steel pipe (SUS310S) was used for the outlet pipe 3.

After passing through the particulate recollecting section 7 and the introduction pipe 2, 0.42 kg / hour of particulates and 3.2 Nm ³ / hour of exhaust gas (about 1% of the amount of exhaust gas introduced into the particulate trap) And the combustion air from the nozzle 6 to 6.3 Nm ³ /
The gas was ejected in a timed manner, sent as a mixed gas into the combustion chamber 1 and swirled, the particulates were incinerated in the combustion chamber 1, and the combustion gas was exhausted from the outlet pipe 3. Also, in this test, the exhaust gas of the diesel engine was exhausted directly from the bypass to the outside system for about 10 seconds when the ceramic filter was backwashed.

When the exhaust gas discharged from the outlet pipe 3 was examined, the content of all solid particles composed of unburned particulates and ash in the exhaust gas was maintained at 0.02 kg / hour or less. Next, the diesel engine is maintained in various operating states, and the particulates that are similarly captured by the ceramics filter and collected in the recollection section 7 by backwashing are stored in the combustion chamber 1 together with about 1% of the total exhaust gas amount at that time. By sending in a proper amount of combustion air from the compressed air nozzle 6 to the combustion chamber 1, the particulates could be almost completely incinerated inside the combustion chamber 1.

In this test example, the temperature of the wall of the combustion chamber is set to 800.
The solid particles (mainly ash) in the outlet pipe 3 with respect to the total weight of the particulates that flowed into the combustion chamber by controlling at ℃
Could be suppressed to 2% by weight or less. Also, the outlet pipe 3
The solid particles in Example 2 were discharged into the atmosphere together with about 1% of the exhaust gas introduced into the particulate trap, but the amount was almost unrecognizable as smoke.

After the use of about 10 particulate traps, the combustion chamber was opened and checked, but no particulates or particulate ash remained in the combustion chamber. Further, if the temperature in the combustion chamber 1 is raised to 900 ° C. and maintained, the total solid particles discharged from the outlet pipe 3 is suppressed to 1.5% by weight or less with respect to the total weight of the particulates introduced into the combustion chamber 1. I was able to.

In this example, the electromagnetic sluice valve 1 is provided downstream of the outlet pipe 3.
Two 0s are provided in series and a pressure equalizing chamber 11 is provided between them, and a pressure wave generated when backwashing the ceramics filter 14 of the particulate trap reaches the combustion chamber 1 and entrains the particulates. Therefore, it is prevented from being discharged from the outlet pipe 3 without burning.

When the ceramic filter 14 is backwashed, the electromagnetic sluice valve 10 is closed and the pressure equalizing air solenoid valve 1 is closed.
2 was opened to prevent the pressure wave and the accompanying flow of unburned particulates from flowing out, and the pressure-equalized air was continuously supplied for several seconds after the backwashing was completed. After that, the solenoid valve 12 for the pressure equalizing air was closed, the solenoid sluice valve 10 was opened, and the normal operation was restored.

When the throttle valve 13 for controlling the blowdown gas amount to about 1% is provided,
As the electromagnetic gate valve 10, for example, a butterfly valve used for an exhaust brake in a truck or the like can be used.

Further, a spiral trap fin (made of stainless steel) was attached to the outer circumference of a thick sheath electric heater as shown in FIG. 3, and the particulate trap inserted in the center of the combustion chamber 1 was tested. In this case, the chance of contact with the wall surface of the combustion chamber including the particulate guide fins was increased, and compulsory swirling could complete the combustion of the particulates.

As a result, the temperature in the combustion chamber can be kept slightly low, the heat resistance of the combustion chamber and the electric heater can be further extended, and the power consumption of the electric heater can be reduced as a whole. did it. Even if the spiral guide fin (made of stainless steel) was omitted and only the sheath electric heater was inserted into the combustion chamber 1, similar effects were obtained to some extent.

[0044]

EFFECTS OF THE INVENTION Since unburned particulates and their burnt ash no longer stay near the electric heater or in a part of the combustion chamber, damage such as disconnection due to overheating of the electric heater and overheating of the combustion chamber wall. The inconveniences such as deformation and damage due to are avoided. Further, there is no need for maintenance to occasionally remove solid particles such as ash containing unburned particulates from the particulate trap, and it is also possible to collect and incinerate particulates from a plurality of ceramic filters into one combustion chamber, It is also possible to downsize the entire particulate trap.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an outline of an example of a particulate trap for a diesel engine according to the present invention.

2 is a plan cross-sectional view downstream of the combustor of FIG.

FIG. 3 is a plan view of an example of a sheathed electric heater with guide fins inserted into the combustion chamber of the particulate trap according to the present invention.

FIG. 4 is a cross-sectional view showing an outline of an example of a conventional diesel engine particulate trap.

[Explanation of symbols]

 1: Combustion chamber 2, 9: Inlet pipe 3: Outlet pipe 4: Electric heater 5: Heat insulating material 6: Nozzle of compressed air 7: Particulate recollection unit 8, 12, 24, 29: Solenoid valve 10: Electromagnetic partition Valve 11: Pressure equalizing chamber 13: Throttle valve 14: Ceramics filter 15: Casing 16: Sealing material 17: Sheath electric heater 18: Guide fin 19: Terminal box 20: Inlet port 21: Clean gas flow path 22: Dust-containing gas flow Line 23: Backwash nozzle 25: Compressed air tank 26: Exhaust pipe 27: Butterfly valve 28: Orifice plate

Claims (4)

[Claims] 1. A particulate matter in exhaust gas is trapped by a ceramics filter, the trapped particulates are removed from the ceramics filter by backwashing, and the detached particulates are partially carried on the flow of exhaust gas, and an electric heater is provided. A particulate trap that is transferred to a combustion chamber and incinerates particulates in the combustion chamber, the combustion chamber being made of cylindrical heat-resistant steel, and an electric heater being disposed on the outer periphery of the cylindrical heat-resistant steel. An inlet for air for particulate incineration is provided in the vicinity of the inlet of the chamber, and means for giving a swirl to the mixed gas flow of exhaust gas and air is provided in the combustion chamber, and the mixed gas flow swirls in the combustion chamber. A particulate trap for diesel engines, which is characterized in that the particulates are incinerated. 2. The particulate trap for a diesel engine according to claim 1, wherein the exhaust gas sent to the combustion chamber is 0.5 to 3% of the exhaust gas introduced into the particulate trap. 3. A particulate trap for a diesel engine according to claim 1, wherein a spiral guide fin is provided as a means for giving a swirling flow to the mixed gas. 4. The particulate trap for a diesel engine according to claim 1, wherein a sheath electric heater is provided near the axis of the combustion chamber.