JP2014034887A - Exhaust gas treatment device and method for diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress accumulation of dust in exhaust gas purification means.SOLUTION: An exhaust gas treatment device for a diesel engine 1 has a denitration catalyst 5 to remove nitrogen oxide in exhaust gas in an exhaust gas passage 2. A combustion device 4, to combust dust in the exhaust gas by heating the same passing through the exhaust gas passage 2, is arranged at an upstream side of the denitration catalyst 5 in the exhaust gas passage 2. The combustion device 4 is constantly operated when the diesel engine is in operation.

Description

  The present invention relates to an exhaust gas processing apparatus and an exhaust gas processing method for removing dust in exhaust gas of a diesel engine.

In recent years, application of a denitration device that purifies nitrogen oxides in exhaust gas has been studied in a diesel engine used in a ship, along with an increase in exhaust gas purification requirements. As a denitration apparatus, for example, a catalytic reduction method using a catalyst is known. In this catalytic reduction method, a reducing agent such as ammonia is used to cause nitrogen oxides to undergo a reduction reaction on a catalyst provided in an exhaust gas passage, and decompose into harmless water and nitrogen to purify the exhaust gas.
The exhaust gas of a diesel engine is mixed with particulate dust made of soot in addition to nitrogen oxides. Accordingly, there is a problem in that dust accumulates on the catalyst as the engine is operated, leading to a reduction in exhaust purification performance of the catalyst.

Therefore, it is conceivable to provide a filter for capturing dust on the upstream side of the catalyst.
Further, there is provided a method of regenerating the filter by providing a burner for heating the filter provided in the exhaust gas passage of the diesel engine, operating the burner when dust is accumulated on the filter, and removing the dust accumulated on the filter by combustion. It has been proposed (Patent Document 1).

JP 2011-518985 A

However, when the displacement is relatively large like a marine diesel engine and low quality oil such as C heavy oil or bunker oil is used, the amount of dust generated increases, so the filter regeneration frequency is high. It will increase. Further, even if the burner is operated when dust or the like is accumulated on the filter as in Patent Document 1, it is difficult to burn and remove the dust sufficiently and quickly because of the large amount of dust accumulated on the filter. .
In marine diesel engines and the like, as a method for regenerating a filter, soot blow is performed to remove dust from the filter by injecting compressed air or the like to the filter in a direction opposite to the flow direction of the exhaust gas. It is desirable to reduce the frequency of soot blow.

  Further, in a marine diesel engine, a two-stroke engine is often used to achieve high efficiency. In a two-stroke engine, the lubricating oil is mixed into the exhaust gas and the exhaust temperature is relatively low. Therefore, especially when the exhaust temperature is low, such as at the start-up, the lubricating oil in the exhaust gas becomes a binder and becomes a filter. There is a risk that dust adheres firmly. Therefore, there is a problem that it is difficult to remove dust from the filter even if the filter is regenerated by soot blow as described above.

  The present invention has been made paying attention to the above-described conventional problems, and is an exhaust gas treatment for a diesel engine that suppresses dust accumulation in an exhaust gas purification means such as a filter or a catalyst provided in an exhaust gas passage of the diesel engine. An apparatus and an exhaust gas processing method are provided.

  The invention according to claim 1 of the present invention is an exhaust gas treatment apparatus for a diesel engine comprising exhaust gas purification means for removing dust or nitrogen oxide in exhaust gas in an exhaust gas passage, wherein the exhaust gas purification means The exhaust gas passage upstream of the engine is provided with combustion means for heating the exhaust gas passing through the exhaust gas passage to burn dust in the exhaust gas, and the combustion means is always in operation when the diesel engine is in operation. It is operated.

  As a result, in the exhaust gas treatment device for a diesel engine according to claim 1, the dust made of soot in the exhaust gas is burned by the combustion means before flowing into the exhaust gas purification means. Since the combustion means always operates during the operation of the engine, the dust in the exhaust gas generated during the operation of the engine is always burned and removed, and the inflow of dust to the exhaust gas purification means is suppressed.

The invention according to claim 2 of the present invention is characterized in that, in claim 1, heat recovery means for recovering heat of the exhaust gas is provided in the exhaust gas passage downstream of the exhaust gas purification means.
Thus, in the exhaust gas treatment apparatus for a diesel engine according to claim 2, the heat of the exhaust gas heated by the combustion means is recovered by the heat recovery means, and can be effectively used for applications such as power generation.

The invention according to claim 3 of the present invention is characterized in that, in claim 1 or 2, the combustion means is a burner that generates a flame.
Thus, in the exhaust gas treatment device for a diesel engine according to claim 3, since the combustion means is a burner that generates a flame, for example, using the fuel of the diesel engine, the combustion means is configured simply and inexpensively, The exhaust gas can be heated. Further, when the diesel engine is a two-stroke engine, the lubricant in the exhaust gas can be burned by the burner, so that the lubricant becomes a binder component and the dust in the exhaust gas adheres to the exhaust gas purification means. This can be prevented, and the regeneration of the exhaust gas purification means can be facilitated.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the exhaust gas passage on the upstream side of the exhaust gas purification means includes a turbocharger turbine, and the combustion means includes the It is arranged in the exhaust gas passage between the turbine and the exhaust gas purification means.
Thus, in the exhaust gas processing device for a diesel engine according to claim 4, the exhaust pressure of the engine can be efficiently utilized by the turbocharger, and the heat of the exhaust gas heated by the combustion means is efficiently obtained by the heat recovery means. It is recovered well.

  The invention according to claim 5 of the present invention is an exhaust gas treatment method for a diesel engine provided with exhaust gas purification means for removing dust or nitrogen oxide in exhaust gas in an exhaust gas passage, wherein the exhaust gas purification means The exhaust gas passage upstream is provided with combustion means for heating the exhaust gas passing through the exhaust gas passage to burn the dust in the exhaust gas, and the combustion means is always operated when the diesel engine is in operation The dust in the exhaust gas before flowing into the exhaust gas purification means is burned.

  Accordingly, in the exhaust gas processing method for a diesel engine according to claim 5, dust in the exhaust gas is burned by the combustion means before flowing into the exhaust gas purification means. Since the combustion means always operates during the operation of the engine, the dust in the exhaust gas generated during the operation of the engine is always burned and removed, and the inflow of dust to the exhaust gas purification means is suppressed.

In the exhaust gas processing apparatus and the exhaust gas processing method for a diesel engine according to the present invention, the combustion means is always operated during the operation of the engine, and the dust in the exhaust gas generated during the operation of the engine is always burned and removed. The inflow of dust to the gas purification means is suppressed. Therefore, the accumulation of dust in the exhaust gas purification means is suppressed, the exhaust purification performance in the exhaust gas purification means is maintained, the increase in pressure loss in the exhaust gas passage is suppressed, and the output of the diesel engine and the decrease in fuel consumption are suppressed. Can do. In addition, the frequency of regeneration work to remove dust from the exhaust gas purification means is suppressed,
Maintenance can be improved.

It is a block diagram of the exhaust system of the diesel engine which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the structure of the combustor of one Embodiment. It is a block diagram of the exhaust system of the diesel engine which concerns on the 2nd Embodiment of this invention. It is sectional drawing which shows the structure of the combustor of other embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an exhaust system of a diesel engine 1 according to a first embodiment of the present invention.
A diesel engine 1 according to an embodiment of the present invention is a main engine that is mounted on a ship and drives a screw or generates electric power, and is operated at a large size and at a low rotation speed in order to improve efficiency. Is adopted.

In the first embodiment of the present invention, a turbocharger turbine 3, a combustor 4 (combustion means), a denitration catalyst 5 (exhaust gas purification means), in order from the upstream side, in the exhaust gas passage 2 of the diesel engine 1, An economizer 6 (heat recovery means) is provided. Further, a bypass passage 7 for bypassing the denitration catalyst 5 is provided in the exhaust passage 2 between the combustor 4 and the economizer 6.
This bypass passage 7 introduces a part of the exhaust gas to the economizer 6 without passing through the denitration catalyst 5, and ensures the exhaust purification performance by the denitration catalyst 5 and improves the heat recovery rate by the economizer 6. In addition, the flow path cross-sectional area is set so as to reduce the pressure loss. Alternatively, the exhaust flow rate may be controlled by providing a damper or the like at the branch point between the bypass passage 7 and the exhaust gas passage 2.

  The turbocharger drives a compressor or a generator (not shown) by the rotational driving force of the turbine 3 driven by using exhaust pressure and exhaust heat. The compressor is disposed in the intake passage of the diesel engine 1 and is capable of improving the output and fuel consumption of the diesel engine 1 by supercharging the intake air.

The denitration catalyst 5 has a function of removing nitrogen oxides in the exhaust gas. The denitration catalyst 5 includes a catalyst layer configured by, for example, supporting titanium oxide or the like on a lattice-shaped carrier. A reducing agent is supplied upstream of the catalyst layer. As the reducing agent, ammonia, or ammonia water or urea water that generates ammonia is used. Then, the nitrogen oxide in the exhaust gas and ammonia are reacted on the catalyst layer, and the nitrogen oxide is reduced to harmless nitrogen.
In the present embodiment, the NOx removal catalyst 5 is provided with a filter (not shown) that collects dust such as soot on the upstream side of the catalyst layer, but the filter is not essential and may not be provided.

  The economizer 6 is configured by installing a pipe having fins or the like in the exhaust gas passage 2, and passes the exhaust gas and the pipe passing through the exhaust gas passage 2 by passing water or steam as a heat medium through the pipe. It has a function to exchange heat with water. The water heated by exchanging heat with the exhaust gas in the economizer 6 becomes steam and is used in power generation and other ships.

The combustor 4 has a function of heating the exhaust gas.
FIG. 2 is a cross-sectional view showing the structure of the combustor 4 of one embodiment.
For example, as shown in FIG. 2, the combustor 4 includes a burner 11 in an exhaust pipe 10 that forms part of the exhaust gas passage 2.

The burner 11 is disposed so as to burn the fuel of the diesel engine 1 and generate a flame f in the exhaust pipe 10, for example. Therefore, by operating the combustor 4, that is, by generating the flame f in the exhaust pipe 10 by the burner 11, the exhaust gas passing through the exhaust pipe 10 is directly heated by the flame f, soot in the exhaust gas, etc. Burn dust consisting of
In this embodiment, the burner 11 in the combustor 4 is always operated during operation of the diesel engine 1.

  As described above, in this embodiment, the combustor 4 is provided in the exhaust gas passage 2 upstream of the denitration catalyst 5, and the exhaust gas before flowing into the denitration catalyst 5 is heated by the combustor 4. Dust such as soot can be removed by combustion. Further, since the combustor 4 is always operated during the operation of the diesel engine 1, dust such as soot generated during the operation of the diesel engine 1 can always be burned and removed, and the dust is prevented from flowing into the denitration catalyst 5. can do. Therefore, accumulation of dust in the denitration catalyst 5 can be suppressed, and the reduction and removal performance of nitrogen oxides in the denitration catalyst 5 can be maintained, and an increase in pressure loss in the exhaust gas passage 2 can be suppressed, and the output of the diesel engine 1 and A reduction in fuel consumption can be suppressed.

  In addition, since the large-sized diesel engine 1 for ships has a large amount of dust generation, dust may be removed from the denitration catalyst 5 by soot blow. In soot blow, compressed air or the like is passed through the denitration catalyst 5 in the direction opposite to the flow direction of the exhaust gas to remove dust accumulated on the denitration catalyst 5 and regenerate the denitration catalyst 5. There is also a method of passing compressed air or the like in the forward direction of the exhaust gas flow direction. Even if soot blow is performed in this way, the frequency of regeneration of the denitration catalyst 5 by soot blow can be reduced by suppressing the accumulation of dust on the denitration catalyst 5 using the combustor 4 as in this embodiment. it can.

In the present embodiment, since the exhaust gas is heated by the combustor 4, the dust can be sufficiently removed by combustion even when the diesel engine 1 with a low exhaust temperature and a large amount of dust is started. it can.
Further, since the diesel engine 1 of the present embodiment is a two-stroke engine, lubricating oil is mixed in the exhaust gas, but the lubricating oil in the exhaust gas can also be burned by the burner 11 of the combustor 4. Therefore, inflow of the lubricating oil to the denitration catalyst 5 can be prevented, and soot and the lubricating oil can be prevented from mixing and becoming dust with high viscosity and adhering to the denitration catalyst 5. Accordingly, even when dust accumulated on the denitration catalyst 5 is removed by soot blow or the like, the operation can be facilitated.

  Furthermore, in this embodiment, the economizer 6 is provided on the downstream side of the denitration catalyst 5, and the thermal energy of the exhaust gas can be recovered and used effectively. As described above, the exhaust gas is heated by the combustor 4 to raise the exhaust gas temperature. Since the heat energy of the heated exhaust gas is recovered by the economizer 6, the recovered thermal energy is In addition, even if fuel is consumed in the combustor 4 by using it for other purposes in the ship, the fuel efficiency of the entire engine in the ship can be improved.

FIG. 3 is a schematic configuration diagram of an exhaust system of the diesel engine 1 according to the second embodiment of the present invention. In addition, in FIG. 3, the part different from 2nd Embodiment is shown with the dashed-two dotted line as a schematic block diagram of the exhaust system of the diesel engine 1 which concerns on 3rd Embodiment.
As shown in FIG. 3, the second embodiment of the present invention is different from the first embodiment in that the positions of the combustor 4 and the turbine 3 of the turbocharger are opposite to each other. That is, in the exhaust gas passage 2 of the diesel engine 1, a combustor 4, a turbocharger turbine 3, a denitration catalyst 5, and an economizer 6 are arranged in order from the upstream side.

  In the second embodiment, since the turbine 3 is downstream of the combustor 4, the exhaust pressure in the turbine 3 is lower than in the first embodiment, and the supercharging effect by the turbocharger is reduced, but the combustor 4. The heat energy of the exhaust gas heated by the can be recovered by the turbine 3.

  In the third embodiment of the present invention, as shown by a two-dot chain line in FIG. 3, a denitration catalyst 5 is disposed between the combustor 4 and the turbine 3 of the turbocharger as compared with the second embodiment. Is different. That is, in the exhaust gas passage 2 of the diesel engine 1, a combustor 4, a denitration catalyst 5, a turbocharger turbine 3, and an economizer 6 are arranged in order from the upstream side.

  In the third embodiment, since the turbine 3 is downstream of the denitration catalyst 5, the heat energy of the exhaust gas heated by the combustor 4 and passing through the denitration catalyst 5 can be recovered by the turbine 3.

  The first to third embodiments differ in the position of the turbine 3 of the turbocharger. Therefore, a difference occurs in the effect of the turbocharger in the first to third embodiments, and accordingly, the amount of heat recovered in the economizer 6 also differs. Comparing the first to third embodiments, generally, the first embodiment in which the turbine 3 of the turbocharger is disposed closest to the diesel engine 1 is different depending on the capacity of various exhaust system devices. However, the turbocharger is most effectively used, and the output and fuel consumption of the diesel engine 1 itself are improved, and the fuel consumption of the entire engine is also improved.

The present invention is not limited to the first to third embodiments.
For example, the combustor 4 only needs to have a function of burning exhaust gas and burning dust such as soot in the exhaust gas.
FIG. 4 is a cross-sectional view showing the structure of the combustor 20 of another embodiment.

In a combustor 20 (combustion means) of another embodiment shown in FIG. 4, a cylindrical body 21 formed of a steel plate or the like having high heat conductivity is disposed coaxially in a cylindrical exhaust pipe 22, and the cylindrical body 21. A burner 11 is arranged so that a flame f is generated inside. The exhaust gas is introduced into the exhaust pipe 22 from the side of the cylindrical body 21 and passes downstream along the outer periphery of the cylindrical body 21. Therefore, the cylinder 21 is heated by the flame f of the burner 11 and becomes high temperature, and the exhaust gas comes into contact with the cylinder 21 that has become high temperature and the exhaust gas is heated. In addition, since the soot and lubricating oil in exhaust gas combust at 400 degreeC or more, what is necessary is just to set the capability of the burner 11, etc. so that the temperature of the outer peripheral wall of the cylinder 21 may be 400 degreeC or more.
In this embodiment, the combustor 20 does not directly heat the exhaust gas to the flame f of the burner 11 like the combustor 4 and heats the exhaust gas indirectly through the cylindrical body 21. However, as in the combustor 4, dust such as soot in the exhaust gas can be combusted.

  Further, the combustors 4 and 20 may use fuels other than the fuel of the diesel engine 1 (for example, kerosene or light oil), and exhaust the exhaust gas by heating the exhaust gas without using the burner 11. Any material having a function of burning dust such as soot in the gas may be used. However, by using the fuel of the diesel engine 1 using the burner 11, the combustors 4 and 20 can be configured easily and inexpensively.

  Further, the present invention can be applied to a diesel engine without a turbocharger or an economizer 6. However, it is desirable from the viewpoint of the efficiency of the entire engine that the economizer 6 is provided downstream of the combustors 4 and 20.

  The present invention is effective not only for the denitration catalyst 5 but also for other catalysts provided in the exhaust gas passage of the diesel engine and filters such as DPF (diesel particulate filter). In the above embodiment, the denitration catalyst 5 is provided with a catalyst and a filter for reducing and removing nitrogen oxides in the exhaust gas, and according to the present invention, it is possible to suppress the accumulation of dust on the filter located upstream. For example, in a diesel engine having a single DPF upstream of the catalyst, by providing the combustors 4 and 20 upstream of the DPF, it is possible to suppress dust accumulation on the DPF and to remove dust from the DPF or The frequency of regeneration of the DPF can be reduced.

Further, even when there is no filter such as DPF in the exhaust gas passage, by providing the combustors 4 and 20 on the upstream side of the catalyst, it is possible to suppress the accumulation of dust on the catalyst and maintain the exhaust purification performance in the catalyst. it can.
In addition, the present invention can be applied to a four-stroke diesel engine, and the present invention can be widely applied to diesel engines other than ships.

1 Diesel engine 2 Exhaust gas passage 3 Turbine 4 Combustor (combustion means)
5 Denitration catalyst (exhaust gas purification means)
6 economizer (heat recovery means)
11 Burner 20 Combustor (combustion means)

Claims (5)

An exhaust gas treatment device for a diesel engine provided with exhaust gas purification means for removing dust or nitrogen oxides in the exhaust gas in an exhaust gas passage,
The exhaust gas passage upstream of the exhaust gas purification means includes combustion means for heating the exhaust gas passing through the exhaust gas passage to burn dust in the exhaust gas,
The exhaust gas treatment device for a diesel engine, wherein the combustion means is always operated when the diesel engine is operated.   The exhaust gas processing apparatus for a diesel engine according to claim 1, further comprising heat recovery means for recovering heat of the exhaust gas in the exhaust gas passage on the downstream side of the exhaust gas purification means.   The exhaust gas processing apparatus for a diesel engine according to claim 1 or 2, wherein the combustion means is a burner that generates a flame. A turbocharger turbine is provided in the exhaust gas passage upstream of the exhaust gas purification means;
The exhaust gas processing apparatus for a diesel engine according to any one of claims 1 to 3, wherein the combustion means is disposed in the exhaust gas passage between the turbine and the exhaust gas purification means. . An exhaust gas processing method for a diesel engine comprising exhaust gas purification means for removing dust or nitrogen oxides in the exhaust gas in an exhaust gas passage,
The exhaust gas passage upstream of the exhaust gas purification means includes combustion means for heating the exhaust gas passing through the exhaust gas passage to burn dust in the exhaust gas,
An exhaust gas treatment method for a diesel engine, in which the combustion means is always operated during operation of the diesel engine, and dust in the exhaust gas before flowing into the exhaust gas purification means is combusted.

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