JPH10159542A - Diesel engine with denitration device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve accelerating performance and responsiveness of an engine in a large operating region of an engine load by arranging a bypass pipe passage for bypassing a denitration device interposed in an exhaust passage, and open/close controlling a control valve interposed in the bypass pipe passage on the basis of an engine operating condition such as an exhaust gas temperature of an engine load and an engine. SOLUTION: Exhaust gas delivered from a diesel engine 1 is purified by a denitration catalyst of a high temperature denitration device 2, and is delivered from an exhaust passage 6 having a control valve 11 to an outside bypassing a supercharger 5. At this time, In a large load operating region of an engine 1, an opening of a control valve 10 in the bypass pipe 3 and an opening of the control valve 11 are controlled so as to increase according to increase of a load, on the basis of a detecting signal of an opening condition such as a load L, exhaust gas temperature T1 , T2 , and the like by a valve regulating device 4. Accelerating performance of the engine 1 is improved, the control valve 11 is fully opened, and the control valve 10 is fully closed, in the high load region. The whole quantity of high temperature exhaust gas is passed the high temperature denitration device 2, and NOx is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diesel engine provided with a denitration device for purifying exhaust gas.

[0002]

2. Description of the Related Art Diesel engines are widely used for power generation (stationary use) in addition to main engines for ships and vehicles, because of their high thermal efficiency. Such diesel engine, while having a high thermal efficiency as described above, due to the high combustion temperatures, nitrogen oxides emissions gasoline engine (NO _X), etc., suffer from the problem that increased compared to other internal combustion engines cage, in order to cope with this, especially in stationary diesel engine such as for power generation by installing a denitrator denitration catalyst is So鎭in an exhaust passage of the engine, is performed to reduce the NO _X.

FIG. 3 shows an installation mode of a conventional denitration apparatus in the diesel engine. FIG. 3A shows a case where a diesel engine 1a whose exhaust gas temperature at the outlet of the exhaust turbocharger exceeds about 300 ° C. is used. In this case, the exhaust gas temperature at the turbocharger outlet is high. Since the high-temperature denitration device, that is, the high-temperature denitration device 2 is operable, the high-temperature denitration device 2 is provided in the exhaust passage 6 at the engine outlet.

FIG. 3B shows a case where a diesel engine 1b whose exhaust gas temperature at the outlet of the exhaust turbocharger is 300 ° C. or less is used. A denitration device 22 is provided in the exhaust passage 6.

FIG. 3C shows that the exhaust gas temperature at the inlet of the exhaust turbocharger 5 exceeds 300 ° C.
The exhaust gas temperature at the outlet of the exhaust turbocharger 5 becomes 300 ° C. or less.
Is provided in the exhaust passage 6 on the inlet side of the exhaust turbocharger 5.

[0006]

Such as the [0006] In the power generation (stationary) and diesel engine for a vehicle, in recent years the strengthening of environmental standards, the concentration of several tens ppm levels of the NO _X discharged from the engine It is required to be reduced. However, in order to reduce the exhaust gas concentration to the above-mentioned level, it is necessary to maintain the denitration rate of the denitration apparatus at a high value of 90% or more.

In order to obtain a high denitration rate as described above, there is a method of increasing the amount of the denitration catalyst or increasing the performance of the denitration catalyst itself. A large-capacity denitration device larger than the capacity of the engine body is required, and there is a problem in installation space. On the other hand, in the latter case, that is, in order to increase the performance of the denitration catalyst itself and to keep the installation space within an acceptable range, it is necessary to use a high-temperature denitration catalyst used at an ambient temperature of 300 ° C. or higher. Become.

In general, in the case of a low-speed large-sized diesel engine for marine use or large-capacity power generation, an engine outlet of exhaust gas, that is,
Usually because the temperature of the exhaust turbocharger outlet is 300 ° C. or less, in the arrangement so as to install the denitration apparatus supercharger outlet, NO _X reduction in the exhaust gas to the target is not performed. For this reason, such a low-speed large-sized diesel engine adopts a structure in which a denitration device is installed between each cylinder outlet where the exhaust gas temperature becomes 300 ° C. or higher and the turbine inlet of the supercharger 5.

However, in an engine having such a structure, the exhaust gas energy supplied from the engine 1 to the supercharger 5 is used to increase the temperature of the denitration device due to the heat capacity of the denitration device (denitration catalyst and its holder). Therefore, the time required for the exhaust gas energy to reach the supercharger 5 is prolonged. This tendency is particularly noticeable when the load of the engine increases from a cold state.

For this reason, the above-mentioned phenomenon causes a time difference between the energy supplied to the turbocharger 5 and the engine load, thereby limiting the rising speed of the engine load and significantly impairing the response to the load fluctuation. Becomes Such a delay in the response of the supercharger 5 causes a shortage or excess of the amount of air supplied to the engine, which makes it difficult to operate the engine stably.

The present invention has been made in view of the above-mentioned problems of the prior art, and maintains the acceleration and responsiveness of the engine in an operating range where the load is large, such as when the engine is started from the start. It is an object of the present invention to provide a diesel engine with a denitration device capable of performing denitration with a high denitration rate in a high load operation range.

[0012]

According to the present invention, in order to solve the above-mentioned problems, a denitration apparatus having a denitration catalyst is installed in an exhaust passage between an exhaust outlet of a diesel engine and an exhaust turbocharger. In a diesel engine with a denitration device, the exhaust gas is branched from an exhaust passage between the diesel engine and the denitration device, bypasses the denitration device, and the denitration device is connected to an exhaust passage between the exhaust turbocharger. A bypass pipe is provided, and a control valve for opening and closing the pipe is provided in the bypass pipe, and a detection signal of an engine operating state such as an engine load and an exhaust gas temperature of the engine is input.Based on the detection signal,
A diesel engine with a denitration device is provided, which is provided with a valve adjusting device for opening and closing the control valve.

[0013] Preferably, in addition to the above means, a second control valve for opening and closing the exhaust passage is provided in a portion of the exhaust passage downstream of the denitration device upstream of a junction of the bypass pipe.

According to the invention, when the diesel engine starts up from a start to a certain load, the valve adjusting device increases the opening degree of the first control valve or opens the bypass pipe line by fully opening the first control valve, and simultaneously sets the second control valve to the second control valve. Reduce the opening of the control valve. By this valve operation, most of the exhaust gas from the engine is sent directly to the exhaust turbocharger through the bypass line to drive it.

Accordingly, in the start-up operation region from the start to the constant load, the exhaust gas is directly sent to the supercharger bypassing the denitration catalyst, and there is no time delay caused by flowing through the denitration device. The supercharger operates with high responsiveness, and quick acceleration of the engine is obtained.

Further, at the time of the start-up, the exhaust gas reaches the denitration device, so that the denitration device is sufficiently warmed up and can be brought into a state capable of coping with an increase in the amount of exhaust gas.

When the load on the engine increases and reaches a certain load, the valve control device closes the first control valve and fully opens the second control valve to allow the entire amount of exhaust gas to flow through the deNOx catalyst.
This catalyst in the denitration apparatus is warmed up sufficiently as described above reacts with the hot exhaust gases, to evacuate gas purification action of removing NO _X I than with a high denitrification rate.

As described above, the valve adjusting device adjusts the opening degree of the first and second control valves while detecting the operating state of the engine, thereby controlling the temperature of the exhaust gas flowing through the denitration device to the catalyst. Can be maintained at a temperature at which the device operates effectively.

By such an operation, when the engine is started after the start of the engine, the engine output is rapidly increased, the operation with good responsiveness is performed, and the denitration catalyst can be sufficiently warmed up.

Further, during a load operation requiring full-scale operation of the denitration catalyst, the temperature of the exhaust gas passing through the denitration catalyst is excessively increased by adjusting the opening of the two control valves by the valve adjusting device. It is possible to maintain a constant temperature at which the catalyst is activated without causing the catalyst to be activated.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be illustratively described in detail below with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. It's just

FIG. 1 is a system diagram of a diesel engine with a denitration device according to an embodiment of the present invention, and FIG. 2 is a control diagram. In FIG. 1, reference numeral 1 denotes a diesel engine (in this example, a large-sized low-speed diesel engine), 6 denotes an exhaust passage through which exhaust gas from the diesel engine 1 flows, and 5 denotes an exhaust turbocharger driven by the exhaust gas. (Hereinafter, abbreviated as a supercharger), 2 is a high-temperature denitration device. 7 is the supercharger 5
This is an air supply passage for supplying supercharged air from the engine to the engine 1.

The high-temperature denitration device 2 is equipped with a high-temperature denitration catalyst used at an exhaust gas temperature of about 300 ° C. or more, and an exhaust passage 6 upstream of a turbine inlet of the supercharger 5.
(That is, the exhaust passage between the diesel engine 1 and the supercharger 5)
It is provided in.

Reference numeral 3 denotes an exhaust gas bypass pipe which branches off from an exhaust passage 6 on the upstream side of the high-temperature denitration apparatus 2, bypasses the denitration apparatus 2, and connects the outlet of the denitration apparatus 2 and the supercharger 5. It is joined to the exhaust passage 6 between the inlet.

The bypass pipe 3 is provided with a control valve (A) 10 for opening and closing the pipe 3 to adjust the passage area thereof, and a junction 1 between the high-temperature denitration apparatus 2 and the bypass pipe 3.
A control valve (B) 11 for adjusting a flow passage area of the exhaust passage 6 is provided between the exhaust passage 6 and the exhaust passage 6.

Reference numeral 4 denotes a valve adjusting device, which has an engine load L and an exhaust gas temperature T _{1 at the} outlet of the engine.
_An operation state detection signal indicating the engine operation state such as ₂ and the operation state of the denitration apparatus is input, and based on the operation state detection signal, the opening degree of the two control valves (A) 10 and (B) 11 is determined. Is calculated, and the control valves (A) 10 and (B) 11 are opened and closed.

The operation of the diesel engine with the denitration device having the above configuration will be described with reference to FIGS. Exhaust gas temperature higher than 300 ° C. discharged from the engine 1 enters the high-temperature denitration apparatus 2 through the exhaust passage 6, where NO _X by reaction with the denitration catalyst is purified are removed, the control valve (B) It is sent to the supercharger 5 through the exhaust passage 6 having 11, and after being driven, the supercharger 5 is discharged to the outside. The supply air pressurized by the supercharger 5 is supplied to the engine 1 through the supply passage 7.

During an operation with a large load change such as when the load rises from the start of the diesel engine 1 (load increase region in FIG. 2), the valve adjusting device 4 controls the load L and the exhaust gas temperatures T ₁ and T ₁ . based on the detection signal of the operating state of _2, etc., as shown in (2) in FIG. 2, is the opening of the control valve (a) 10 from the starting to the constant load Y ₁ is fully opened, the control valve (B) 11 It is fully closed the opening from the start to a constant load Y ₂ rising is controlled so as to increase the degree of opening in accordance here with an increase in load.

With this control, the exhaust gas from the engine does not flow through the denitration device 2 and is sent to the supercharger 5 through the bypass pipe 3 without a time delay caused by the exhaust gas. The engine 1 operates quickly, and an amount of air corresponding to the load is supplied to the engine 1 from the supercharger 5. Thereby, the engine 1 is operated with high acceleration while improving the acceleration performance.

On the other hand, even if the control valve (B) 11 is closed,
Since high-temperature exhaust gas is fed to the high-temperature denitration device 2, the catalyst in the denitration device 2 is warmed up in a short time.

Then, the valve adjusting device 4 increases the opening of the control valve (B) 11 in accordance with the increase in the engine load.
₍ Fully open at ₄ ) Increase the amount of high-temperature exhaust gas flowing through the high-temperature denitration device 2 Thus, the effectively removes this of the NO _X react denitration apparatus 2 warmup and 300 ° C. or more exhaust gas as.

When the load on the engine 1 increases to a constant load Y ₁ , the amount of exhaust gas increases, and the temperature rises, the valve adjusting device 4 starts closing the control valve (A) 10 and changes the load Y ₃ . And fully closed.

[0033] Thus, the control valve in the Y ₃ or more loads (B) 11 is fully opened, the control valve (A) 10 is fully closed, the total amount of the high-temperature exhaust gas passes through the high-temperature denitration apparatus 2, removal of the NO _X Is made.

Here, the valve adjusting device 4 determines the load L, the exhaust temperature T ₁ at the engine outlet (inlet of the denitration device) and the denitration device 2
Based on the detection signal of the operating condition such as an exhaust temperature T ₂ at the outlet,
When the temperature of the exhaust gas passing through the denitration device 2 rises excessively, the opening of the control valve (A) 10 is increased and the opening of the control valve (B) 11 is decreased, and the exhaust gas passes through the denitration device 2 according to the operating state of the engine. Increase the load while preventing the exhaust gas temperature from rising excessively.

That is, the valve adjusting device 4 includes two control valves (A)
The opening degrees of 10 and (B) 11 are adjusted while detecting the operating state of the engine, so that the temperature of the exhaust gas flowing through the denitration device does not become excessive and the exhaust gas temperature at which the high-temperature catalyst operates sufficiently is adjusted. Can be held.

It should be noted that the engine speed or the scavenging pressure can be used as a factor for detecting the operating state of the engine.

It is also possible to omit the control valve (B) 11 and open and close the bypass line 3 by the control valve (A) 10. In this case, if the control valve (A) is fully opened at the time of start-up and subsequent startup, exhaust gas flows through both the bypass pipe 3 and the high-temperature denitration device 2 and enters the supercharger 5, but the bypass pipe 3 Is sent to the supercharger 5 without a time delay.

[0038]

As described above, according to the present invention,
During operation with large load fluctuations, such as when the engine is started and subsequent startups, the control valve is opened and the exhaust gas is led directly to the turbocharger through the bypass pipe to achieve quick acceleration and good responsiveness operation. And the warm-up of the denitration catalyst can be sufficiently performed.

Further certain load or more during high load operation by passing a sufficiently warm-up denitration catalyst almost all of the hot exhaust gases, reducing of the NO _X in the exhaust gas I than with a high denitrification rate Can be done,
By adjusting the opening degrees of the two control valves, the temperature of the exhaust gas flowing through the denitration catalyst can be controlled to an appropriate temperature.

[Brief description of the drawings]

FIG. 1 is a system diagram of a diesel engine with a denitration device according to an embodiment of the present invention.

FIG. 2 is a performance curve of the engine in the embodiment.

FIG. 3 is a system diagram showing three examples of a conventional diesel engine with a denitration device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Diesel engine 2 High temperature denitration apparatus 3 Bypass pipe 4 Valve adjustment device 5 Exhaust turbocharger 6 Exhaust passage 7 Supply air passage 10 Control valve (A) 11 Control valve (B)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02B 37/00 302 F02B 37/02 E 37/02 B01D 53/36 101A

Claims (2)

[Claims] 1. A diesel engine with a denitration device comprising a denitration device provided with a denitration catalyst in an exhaust passage between an exhaust outlet of the diesel engine and an exhaust turbocharger, wherein the diesel engine and the denitration device A bypass pipe which is branched from an exhaust passage between the exhaust pipe and the exhaust pipe and bypasses the denitration apparatus, and is connected to an exhaust passage between the denitration apparatus and the exhaust turbocharger. A control valve for opening and closing the control valve, a detection signal of an engine operating state such as an engine load and an exhaust gas temperature of the engine is input, and a valve adjusting device for controlling the opening and closing of the control valve based on the detection signal is provided. Diesel engine with denitration equipment. 2. The denitration apparatus according to claim 1, further comprising a second control valve that opens and closes the exhaust path in a portion of the exhaust passage downstream of the denitration device upstream of a junction of the bypass pipe. With diesel engine.