JP2915687B2 - Exhaust gas denitration equipment for diesel engines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalytic reduction denitration catalyst device for exhaust gas denitration of a large two-cycle diesel engine.

[0002]

2. Description of the Related Art A conventional example will be described with reference to FIG. FIG. 2 is a configuration diagram of a conventional ammonia catalytic reduction catalytic converter for exhaust gas denitration of a large two-cycle diesel engine using heavy fuel oil C as fuel. Conventionally, an ammonia catalytic reduction catalyst device for denitration of exhaust gas from a large two-cycle diesel engine using heavy fuel oil C is an exhaust turbocharger at the outlet of an exhaust manifold with a high exhaust gas temperature in order to avoid the generation of acidic ammonium sulfate which poisons the catalyst device. It is installed at the entrance side of. In the figure, 1 is a large two-stroke diesel engine main body, and 2 is an exhaust manifold connected to an exhaust port of the large two-stroke diesel engine main body 1. Reference numeral 3 denotes an ammonia catalytic reduction catalyst device which is connected to the exhaust manifold 2. Reference numeral 4 denotes an exhaust turbocharger which is connected to a discharge port of the ammonia catalytic reduction catalyst device 3.

The operation of the conventional example will be described. When the large two-stroke diesel engine body 1 is operated, the exhaust manifold 2 collects the exhaust gas and passes it to the ammonia catalytic reduction catalyst device 3. The exhaust gas is denitrated by the ammonia catalytic reduction catalyst device 2, enters the exhaust turbocharger 4, drives it, and is discharged. Since the temperature in the ammonia catalytic reduction catalyst device 3 is high, acidic ammonium sulfate is not generated and the catalyst is not poisoned.

[0004]

In a large low-speed diesel engine using fuel oil C as fuel, the temperature of exhaust gas is low after an exhaust turbocharger which can be easily installed additionally, and catalyst poisoning due to the production of ammonium acid sulfate. Therefore, an ammonia catalytic reduction catalyst device cannot be installed. Therefore, it is installed between the exhaust manifold with high exhaust gas temperature and the exhaust turbocharger,
At the time of engine development, it was necessary to perform a performance test including a catalyst device, and there was a problem that a denitration device could not be easily added, such as a large number of man-hours. An object of the present invention is to provide a large low-speed two-stroke diesel engine using a sulfur-rich fuel such as fuel oil C and having a low exhaust gas temperature at the outlet of an exhaust turbocharger, using an acidic ammonium sulfate at the outlet side of the exhaust turbocharger. An object of the present invention is to provide an ammonia catalytic reduction catalyst device which is easily installed additionally by eliminating poisoning of the catalyst.

[0005]

SUMMARY OF THE INVENTION An exhaust gas denitration system for a diesel engine according to the present invention is a diesel engine exhaust gas denitration system having a low exhaust gas temperature using an ammonia catalytic reduction catalyst device.
Test with ammonia catalytic reduction catalytic device 3 installed in the discharge port of the exhaust gas, provided in an exhaust gas passage downstream of the ammonia catalytic reduction catalytic device 3 a concentration of NO _x of the exhaust gas passage of
A NO _x sensor 5 for output, the hot gas path 6 connecting the inlet side of the engine exhaust manifold 2 ammonia catalytic reduction catalytic device 3 bypassing the exhaust turbo supercharger 4, closing for opening and closing the high-temperature gas passage the valve 7, it has a controller 9 which controls the opening and closing of the said opening and closing valve 7 by the detection signal of the NO _x concentration from the NO _x sensor 5, the concentration of NO _x in the exhaust gas of the ammonia catalytic reduction catalytic device outlet Accordingly, the on-off valve 7 is controlled to open and close, and a portion of the high-temperature exhaust gas is directly guided from the exhaust manifold 2 to the ammonia catalytic reduction catalyst device without passing through the exhaust turbocharger 4.

[0006]

When a large low-speed two-stroke diesel engine equipped with the device of the present invention is operated, the exhaust gas of the engine collects in the exhaust manifold, and then drives the exhaust turbocharger, flows into the ammonia catalytic reduction catalyst device, and flows into the ammonia catalytic reduction catalyst device. are denitration by the catalyst device is discharged at a low concentration of NO _x. However, the temperature of the exhaust gas flowing into the ammonia catalytic reduction catalyst device is relatively low, so that acidic ammonium sulfate is generated. Since the surface of the catalyst is covered with this liquid, the catalyst is poisoned and the performance of the ammonia catalytic reduction catalyst device is reduced. concentration of NO _x in is increased. Concentration of NO _x in the exhaust gas is detected by the NO _x sensor, a portion of the exhaust gas of the exhaust manifold-off valve is opened and closed controlled in accordance with the concentration of NO _x in the exhaust gas by the controller reaches a value where the concentration is determined in It is introduced into the ammonia catalytic reduction catalyst device through the hot gas passage and the on-off valve. As a result, the temperature of the ammonia catalytic reduction catalyst device rises, and the acidic ammonium sulfate is decomposed and vaporized and scattered, and the performance of the ammonia catalytic reduction catalyst device is regenerated. Also Ammoni
Varying the concentration of NO _x A catalytic reduction catalytic device downstream of the exhaust gas passage
Opening and closing the hot gas bypass passage in response to
Even if the exhaust gas temperature at the turbocharger outlet becomes low, the catalyst
In order to optimize the NO _x reduction effect of the device,
Can maintain temperature.

[0007]

An embodiment will be described with reference to FIG. FIG. 1 is a configuration diagram of an exhaust gas denitration apparatus for a diesel engine according to an embodiment. In the figure, 1 is a large two-stroke diesel engine main body, and 2 is an exhaust manifold mounted on the large two-stroke diesel engine main body 1. Reference numeral 4 denotes an exhaust turbocharger which is connected to the exhaust manifold 2. Reference numeral 3 denotes an ammonia catalytic reduction catalyst device which is connected to an exhaust discharge port of an exhaust turbocharger. 5 is provided to the ammonia catalytic reduction catalytic device 3 on the outlet side of the exhaust gas conduit with NO _X sensor. 6
A high-temperature gas passage bypasses the exhaust turbocharger and communicates the exhaust manifold with the inlet side of the ammonia catalytic reduction catalyst device 3. Reference numeral 7 denotes an on-off valve which is provided in the high-temperature gas passage 6 and is normally closed. Reference numeral 8 denotes an on-off valve drive actuator, which is connected to the on-off valve 7. 9 is the controller NO _X
The sensor 5 and the on-off valve drive actuator 8 are connected.

The operation of the above embodiment will be described. When the large two-cycle diesel engine main body 1 is operated, the engine exhaust gas is collected in the exhaust manifold 2, enters the exhaust turbocharger 4, drives the exhaust turbocharger 4, enters the ammonia catalytic reduction catalyst device 3, and enters the ammonia catalytic reduction catalyst device 3. NOx denitration
It is discharged when the concentration of _X falls below the specified value. Since SO ₃ , NH ₃ , and H ₂ O are contained in the exhaust gas, a reaction represented by the following equation takes place. This reaction is a reversible reaction and proceeds to the left as the temperature increases, but after the exhaust turbocharger. Since the temperature of the exhaust gas is relatively low, the reaction proceeds to the right to form NH ₄ HSO ₄ acidic ammonium sulfate. This is a liquid. SO ₃ + NH ₃ + H ₂ O ← → NH ₄ HSO ₄ Accordingly, the catalyst is covered and poisoned by the acidic ammonium sulfate, and the deNOx performance of the ammonia catalytic reduction catalyst device 3 is reduced, so that NO in the exhaust gas at the outlet of the ammonia catalytic reduction catalyst device is reduced. The concentration of _X increases. The controller 9 detects the NO _X concentration by the NO _X sensor 5 and, when the detected value reaches a predetermined value, activates the on / off valve driving actuator 8 to open the on / off valve 7. When the on-off valve 7 is opened, a part of the exhaust gas in the exhaust manifold 2 flows through the high-temperature gas passage 6 and the on-off valve 7 to the ammonia catalytic reduction catalytic device 3, and the remaining exhaust gas flows to the exhaust turbocharger.

In the ammonia catalytic reduction contact device 3, the temperature rises due to the inflow of exhaust gas in the exhaust manifold 2, the reversible reaction proceeds to the left, and the produced acidic ammonium sulfate is decomposed into a gas, and the catalyst is detoxified. Thus, the ammonia catalytic reduction catalyst device 3 is regenerated. Degradation rate of the production rate i.e. denitrification performance of acidic ammonium sulfate ammonia catalytic reduction catalyst device 3 is the value of the concentration of the NO _X in the exhaust gas after the controller 9 ammonia catalytic reduction catalytic device 3 for changing the operating state of the engine or The degree of deterioration of the denitration performance is determined based on the change speed and the like, and the opening degree of the on-off valve 7 is controlled to control the amount of exhaust gas guided to the ammonia catalytic reduction catalyst device 3. Regenerative performance and always obtain good denitration performance.

[0010]

As described above, the present invention uses a fuel containing a large amount of sulfur, such as fuel oil C, and emits a large two-stroke diesel engine having a low exhaust gas temperature at the exhaust turbocharger outlet. An ammonia catalytic reduction catalyst device can be easily and additionally installed at the turbocharger outlet, and poisoning by acidic ammonium sulfate can be eliminated and high denitration performance can always be maintained. Also, when developing the engine, a performance test including the exhaust turbocharger as in the past is sufficient, and problems such as an increase in man-hours during development can be avoided. In addition,
Hot gas is responsive to changes in the concentration of NO _x catalyzer outlet
Since the bypass passage is opened and closed, the exhaust gas temperature at the turbocharger outlet
Even degree is lowered, NO _x reduction effect constantly catalytic device top
The temperature of the catalyst device can be maintained to be good. Accordingly, the present invention eliminates catalyst poisoning at the outlet of the exhaust turbocharger even in a large low-speed two-cycle diesel engine that uses a fuel with a high sulfur content such as heavy oil C and has a low exhaust gas temperature at the outlet of the exhaust turbocharger. Thus, it is possible to provide an ammonia catalytic reduction catalyst device which is easily additionally installed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an exhaust gas denitrification apparatus of an embodiment.

FIG. 2 is a configuration diagram of a conventional exhaust gas denitration apparatus.

[Explanation of symbols]

1 ... large two-stroke diesel engine body, 2 ... exhaust manifold, 3 ... ammonia catalytic reduction catalytic device, 4 ... exhaust turbocharger, 5 ... NO _X sensor, 6 ... hot gas path, 7
... on-off valve, 8 ... on-off valve drive actuator, 9 ... controller.

Continuation of the front page (56) References JP-A-2-286817 (JP, A) JP-A-62-153546 (JP, A) JP-A-56-157665 (JP, U) (58) Fields investigated (Int .Cl. ⁶ , DB name) F01N 3/08 B01D 53/94 F01N 3/24

Claims (1)

(57) [Claims] In an exhaust gas denitration system for a diesel engine having a low exhaust gas temperature using an ammonia catalytic reduction catalyst device, an ammonia catalytic reduction catalyst installed at an exhaust gas discharge port of an exhaust turbocharger (4) of the engine (1). apparatus and (3), NO _x concentration of the exhaust gas passage provided in the exhaust gas passage downstream of the ammonia catalytic reduction catalytic device (3)
A NO _x sensor which detects a (5), hot gas path (6 connecting to bypass the engine exhaust manifold (2) and the ammonia catalytic reduction catalytic device (3) on the inlet side and the exhaust turbocharger (4) a), on-off valve for opening and closing the high-temperature gas passage and (7), NO _x concentration from the NO _x sensor (5)
Detection signals by the result and a controller (9) for opening and closing controls the on-off valve (7) of opening and closing the on-off valve (7) depending on the concentration of NO _x in the exhaust gas of the ammonia catalytic reduction catalytic device outlet controlled, the exhaust gas denitration apparatus of a diesel engine, characterized in that leads to the ammonia catalytic reduction catalytic device directly without passing through the exhaust turbocharger (4) from the exhaust manifold (2) a portion of the hot exhaust gases.