JPH02157415A - Exhaust gas denitrizing device for internal combustion engine - Google Patents

Abstract

PURPOSE:To make mechanism small, suppress the cost, and enhance the reliability and denitrizing performance by injecting ammonium or a precurser thereto into combustional exhaust gas, producing mixture, and using the exhaust gas as a carrier gas. CONSTITUTION:In a position close to the exhaust valve 5 of a cylinder 3, an injection valve 8 is installed to add ammonium or a precurser thereto to the combustional exhaust gas by the use of exhaust gas from a supply pipe 15 as a carrier gas. In continuity thereto an addition control device is installed, which is equipped with a crank angle sensor 12 and a valve opening controller 11 and which makes valve opening control of the injection valve 8 in the period from immediately before opening of the exhaust valve 5 till prior to opening of a scavenging hole 13. This ensures that the ammonium or its precurser is added in favorable timing to produce a well mixed admixture, and nitrogen oxide in the combustional exhaust gas will react in good efficiency an be decomposed. Using the exhaust gas as carrier should enhance the mixing performance and decomposing efficiency, which allows sparing of ammonium or its precurser to a great extent. This should enhance the denitrizing performance and reliability remarkably.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an exhaust denitrification device for an internal combustion engine, which is characterized by a denitrification mechanism that reduces high-temperature combustion exhaust gas generated within the engine in the presence of oxygen. It is.

(Prior Art) A conventional example of an exhaust denitration device for an internal combustion engine will be explained with reference to FIG. 4. An exhaust pipe (102) of an internal combustion engine (101)
and an air supply pipe (109), a K exhaust supercharger (103) is installed, and a catalyst-equipped reactor (103) is installed behind the exhaust pipe (104).
08) and exhaust pipe (1o4) in front of the reactor with catalyst (108) K ammonia injection: fP (105
), an ammonia pump (106), and an ammonia bomb-? (107) is connected in series, and ammonia (NH3) is added to the relatively low temperature (about 250 to 450'C) exhaust gas after driving the exhaust turbo of the exhaust supercharger (103) to perform a catalytic reaction. vessel(
108) to decompose nitrogen oxides in the exhaust gas and denitrify them.

(Problems to be Solved by the Invention) The conventional exhaust gas denitrification device adds ammonia to relatively low-temperature exhaust gas after driving an exhaust supercharger, and transfers the ammonia onto a catalyst in a catalyst-equipped reactor. However, the use of a catalyst increases the size of the device, resulting in low ammonia addition efficiency and low NOx reduction efficiency, leading to high costs.

It is efficient to add ammonia or an ammonia precursor (urea, etc.) to high-temperature combustion exhaust gas and cause it to interact with nitrogen oxides and oxygen in the combustion exhaust gas to produce a reducing effect, decomposing nitrogen oxides without a catalyst. Although it is inexpensive, for example,
If only ammonia gas is introduced as a reducing agent, the amount of input is small, so the momentum is small and it is not mixed sufficiently into the exhaust gas. Moreover, if air, which is commonly considered, is used as a carrier gas, a considerable amount of ammonia gas will be decomposed before it is mixed with exhaust gas, resulting in a low NOx reduction efficiency.

Especially when considering input into an internal combustion engine, the exhaust gas when ammonia is added is at high temperature and pressure, and the reaction rate with oxygen, which becomes ammonia oxide, is also high.

Problems include the high probability that ammonia will be decomposed before it is mixed with exhaust gas.

The present invention was developed to address the above-mentioned problems, and its purpose is to introduce ammonia or an ammonia precursor into the combustion exhaust gas near the exhaust valve of the cylinder or exhaust bait in a timely manner. An object of the present invention is to provide an exhaust gas denitrification device for an internal combustion engine, which has a smaller mechanism, reduced cost, and improved denitrification performance and reliability by injecting and adding the exhaust gas and using exhaust gas as a carrier gas.

(Means for Solving the Problems) The present invention provides an injection valve that adds ammonia or an ammonia precursor to the combustion exhaust gas using the exhaust gas as a carrier gas, in the vicinity of the exhaust valve of the cylinder or exhaust port of an internal combustion engine. The invention is characterized by a configuration in which an addition control device is connected to the injection valve and includes a crank angle sensor and a valve opening controller and controls the opening of the injection valve from immediately before the opening of the exhaust valve to before the opening of the scavenging hole, Injecting and adding ammonia or an ammonia precursor into the combustion exhaust gas near the exhaust valve of the cylinder or exhaust port by an injection valve, and controlling the opening of the injection valve by the addition control device to improve the addition timing and mixing, By using exhaust gas as a carrier gas, mixing performance is further improved and nitrogen oxide decomposition efficiency is increased.

(Function) The injection valve is controlled to open by the addition control device from just before the exhaust valve opens to before the scavenging hole opens, and the opening control of the injection valve causes ammonia or ammonia precursor to be released into the cylinder or exhaust port. By being injected and added directly into the flue gas near the valve, ammonia or an ammonia precursor is added to the flue gas in a timely manner, resulting in very good mixing, and by applying the flue gas as a carrier gas. The mixing of ammonia or an ammonia precursor into the flue gas becomes even better, and the decomposition of nitrogen oxides in the flue gas is efficiently carried out at the high temperature of the flue gas and in the presence of oxygen.

(Example) Figures 1 and 2 show a first example of the present invention.
The internal combustion engine shown in the figure includes a piston (1), a cylinder head (2), a cylinder head (3), an exhaust port (4), an exhaust valve (5), an exhaust manifold pipe (6), a fuel injection valve (7), Consisting of scavenging holes a3, etc., cylinders (2,
An injection valve (8) that adds ammonia or an ammonia precursor (urea, etc.) to the combustion exhaust gas using the exhaust gas as a carrier gas is installed in the vicinity of the exhaust valve (5) in step 3). An internal combustion engine equipped with a controller aυ and connected to the injection valve (8) with an addition control device (11, 12) that controls the opening of the injection valve (8) from just before the exhaust valve (5) opens until before the scavenging hole 0 opens. It serves as the engine's exhaust denitrification device.

The injection valve (8) is arranged in the cylinder head "+3" and close to the exhaust valve (5) and directly injects ammonia or an ammonia precursor (such as urea) into the combustion exhaust gas in the upper part of the combustion chamber. It has a structure in which it is added by injection, and is connected to the ammonia cylinder C1l via a supply pipe (8a) and an ammonia pump (9), and is further connected to an exhaust collecting pipe (6).
) and the supply pipe (8a), a carrier gas supply pipe α9 with a pump α pump is connected, and the exhaust gas in the exhaust manifold pipe (6) is supplied as a carrier gas for ammonia or an ammonia precursor. Increased efficiency and savings in precursors.

The addition control device (11, 12) consists of a crank angle sensor ab that detects the crank angle of the internal combustion engine, and a valve opening controller αυ connected between the crank angle sensor (1z) and the injection valve (8). The valve controller αυ outputs an opening control signal for the injection valve (8) based on the detection signal of the crank angle of the crank angle sensor (1z), and opens the injection valve (8).
8) Open control.

The control of the injection valve (8) by the valve opening controller αυ is such that the injection valve (8) is opened 5 to 10 degrees before the exhaust valve (5) is opened, and Injection valve (8
) is the crank angle of 35 to 40 degrees after the exhaust valve (5) is opened.
After being controlled to open for a period of Often sprayed and added.

The first embodiment of the present invention has the above-mentioned configuration, and the operation will be described in detail.Addition control device (11, 12)
Due to the opening control of the injection valve (8), ammonia or an ammonia precursor is introduced into the combustion exhaust gas near the exhaust valve (5) in the upper part of the cylinder of the internal combustion engine from immediately before the opening of the exhaust valve (5) to the scavenging hole ( The nuclear combustion exhaust gas is injected and added until before the opening of the scavenging hole, and the nuclear combustion exhaust gas is at a high temperature (1000 to 800°C) and in the presence of an appropriate amount of oxygen, and the ammonia or ammonia precursor is added at a timing close to the scavenging hole. When added well, the mixing performance is enhanced, and the nitrogen oxides in the fuel exhaust gas are efficiently reacted and decomposed. By using the exhaust gas as a carrier gas, ammonia or an ammonia precursor is effective in decomposing the nitrogen oxides. The catalyst is no longer necessary, and the denitrification performance and reliability are significantly improved.

In this case, the amount of ammonia gas or ammonia precursor (urea, etc.) added will be small, and unless it is added with some kind of carrier gas, sufficient mixing with the combustion exhaust gas will not be achieved and the expected denitrification effect will not be obtained. When exhaust gas is used as the gas, the amount of oxygen contained is low, so it is possible to reduce the amount of anthonia that is lost in the following reaction equation before mixing with combustion exhaust gas.

NH+O→N2. N.

Reducing the amount of ammonia lost is extremely important for denitrification of exhaust gas from internal combustion engines (diesel engines). That is,
When trying to inject ammonia into the combustion exhaust gas in the optimum temperature range for denitration reaction (800 to 1000°C), the reactivity is high at that point, at 5 to 10 Kg/cm2, so for example, if air is used as a carrier gas, The amount of ammonia lost is extremely large, so if nitrogen gas, algol gas, steam, etc. are used as a carrier gas, the loss of ammonia can be suppressed, but it will be a heavy economic burden, and it is extremely advantageous to use exhaust gas as a carrier gas. Become.

FIG. 3 shows a second embodiment of the present invention, and compared to the first embodiment, the injection valve (8) is disposed at the discharge port (4) and the injection position is closer to the scavenging valve (5). ammonia or an ammonia precursor to the exhaust port (4).
), the composition of the oil is the same as that of the first embodiment, and the opening control of the injection valve (8) is the same as that of the first embodiment shown in FIG. Similarly, the first
The same effects as in the example can be obtained.

The present invention is widely applicable not only to large, low-speed engines, but also to medium-speed 4-stroke, high-speed 2-stroke, 4-stroke engines, compression ignition engines, spark ignition engines, etc. Since this method requires a threshold time, it is particularly effective for low-speed engines where there is sufficient time for the exhaust process.

(Effects of the Invention) The present invention has the above-described configuration, and by controlling the opening of the injection valve by the addition control device, ammonia or an ammonia precursor is added to the combustion exhaust gas near the positive air valve of the cylinder or exhaust port of the internal combustion engine. The substance is injected and added from before the exhaust valve opens to before the scavenge hole opens, and ammonia or ammonia precursor is added in a well-timed manner in the presence of oxygen at the high temperature of the combustion exhaust gas and near the scavenge valve. Mixability is improved, and nitrogen oxides in the combustion exhaust gas are efficiently reacted and decomposed. By using the exhaust gas as a carrier gas, mixing performance and decomposition efficiency are improved, resulting in significant savings in ammonia and ammonia precursors. , the catalyst is no longer necessary, and the denitrification performance and reliability are significantly improved.

It has the advantage that the mechanism is significantly cleaner and smaller, and that ammonia and ammonia precursors are saved, resulting in lower cost.

Although the present invention has been described above with reference to embodiments, it goes without saying that the present invention is not limited to such embodiments, and that various design modifications can be made without departing from the spirit of the present invention. .

[Brief explanation of the drawing]

Fig. 1 is a longitudinal mechanical diagram showing the first embodiment of the present invention, and Fig. 2 shows the opening of the injection valve, exhaust valve, and scavenging hole, and +Ifi of the opening.
FIG. 3 is a longitudinal mechanical diagram showing the second embodiment, and FIG. 4 is a longitudinal mechanical diagram of the conventional example. 2.3 Niji cylinder 4: Exhaust port 5: Exhaust valve 8 Two injection valves 11; Valve opening controller 12: 2' Link angle sensor Agent Patent attorney Shige Okamoto 2 people outside of the text Figure 2 Closed Figure 4 Sodemen

Claims (1)

[Claims] An injection valve for adding ammonia or an ammonia precursor to the combustion exhaust gas using the exhaust gas as a carrier gas is provided in the vicinity of the exhaust valve of the cylinder or exhaust port of an internal combustion engine, and the exhaust valve is equipped with a crank angle sensor and a valve opening controller. 1. An exhaust gas denitrification device for an internal combustion engine, characterized in that an addition control device is connected to the injection valve to control opening of the injection valve from immediately before opening of the scavenging hole to before opening of the scavenging hole.