JPH05288041A - Nitrogen oxide decreasing device for continuous combustion device - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] The present invention is intended to reduce and purify nitrogen oxides in exhaust gas of a continuous combustion device regardless of the oxygen concentration in the exhaust gas without reducing the efficiency of the combustion device. The purpose is to [Composition] A cooling device, a hydrogen supply device, and a catalyst device for purifying nitrogen oxides are sequentially installed on the exhaust passage of the continuous combustion device to optimize the temperature of the exhaust gas before purifying the nitrogen oxides in the exhaust gas. By lowering the temperature to a region showing a purification rate, the purification rate of nitrogen oxides was improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for reducing nitrogen oxides discharged from a continuous combustion device such as an external combustion engine and a boiler, and particularly to a device for reducing nitrogen oxides without impairing the fuel economy of an engine such as a Stirling engine. The present invention relates to a purification system for effectively reducing and purifying oxides.

[0002]

2. Description of the Related Art A Stirling engine, which is one of external combustion engines, has a process in which a burner disposed in a combustion chamber burns fuel to heat and expand a working gas. The heating of the working gas by the combustion of the burner normally utilizes combustion heat generated by high temperature combustion by supplying fuel and combustion air into the combustion chamber. Then, the combustion exhaust gas is discharged into the atmosphere through the discharge passage. In this case, the fuel is completely combusted at a high temperature together with the combustion air, and the exhaust gas does not contain harmful components. Although the unburned HC and CO are small, nitrogen oxide (NOx) is not contained. Inevitable.

As a method for reducing nitrogen oxides in exhaust gas in a continuous combustion device, a lean combustion method, a method using a ternary purification catalyst, etc. can be considered. However, when considering the continuous combustion device of the Stirling engine, in the lean burn method, the air supply amount is increased and the combustion flame temperature is lowered to lower the thermal efficiency, and the air supply blower is used to increase the air supply amount. There is a problem that power consumption increases and engine efficiency decreases.

Therefore, it is considered effective to use a ternary purification catalyst. The method using the ternary purification catalyst is a method in which NOx, CO, and HC present in the exhaust gas are chemically converted into harmless components such as N ₂ , CO ₂ , and H ₂ O by the purification catalyst. Since this chemical change proceeds simultaneously with oxidation and reduction, it is necessary to keep the exhaust gas in a low oxygen concentration state in order to improve the reduction efficiency, and the allowable range of the oxygen concentration change is extremely narrow. Therefore, when this method is adopted, it is necessary to control the supply amounts of fuel and combustion air extremely accurately. Further, in the continuous combustion, even if the air excess ratio is low, the components such as HC and CO are small, so that it is not necessary to use the ternary catalyst. If this three-way catalyst is used, the exhaust gas temperature must be 400 to 450 ° C or higher. In that case, the air cannot be sufficiently preheated by the exhaust gas, and the air supplied to the combustion unit cannot be preheated. Is low, which results in a decrease in engine efficiency, which is not preferable. Further, the exhaust gas has a high temperature, so that the durability of the catalyst is deteriorated and the cost is increased because an expensive precious metal is used.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is possible to reduce nitrogen oxides in exhaust gas discharged from a continuous combustion device such as an external combustion engine and a boiler.
The technical problem is to reduce and purify the exhaust gas regardless of the oxygen concentration in the exhaust gas without lowering the efficiency of the combustion device.

[0006]

The technical means of the present invention taken to solve the above-mentioned technical problem of the present invention is a combustion chamber and an exhaust passage for exhausting exhaust gas generated in the combustion chamber. And a catalyst device arranged on the discharge passage, and a hydrogen supply means and an exhaust gas cooling means arranged on the upstream side of the catalyst device on the discharge passage, to form a nitrogen oxide reduction device of a continuous combustion device. That is.

[0007]

According to the nitrogen oxide reducing apparatus in the combustion apparatus of the present invention, the exhaust gas discharged from the combustion chamber is
After being appropriately cooled by the exhaust gas cooling means so that the catalyst device can operate with high efficiency, hydrogen flows into the catalyst device in a mixed state, and nitrogen oxides are catalytically reduced and purified in a low temperature state. ..

[0008]

Embodiments Embodiments embodying the above-mentioned technical means of the present invention will be described below.

A nitrogen oxide reducing apparatus 10 for a continuous combustion apparatus according to a first embodiment of the present invention will be described with reference to FIG. In this embodiment, it is applied to a combustion device of a Stirling engine.

Here, the combustion chamber 11 is surrounded by a heat insulating wall surface 12.
It has a bottomed cylindrical shape covered with, and a heating pipe 13 filled with a working gas for operating the Stirling engine is provided substantially radially at the bottom thereof. Further, an air preheater 14 for preheating the combustion air with the heat of the high-temperature exhaust gas is arranged inside the heat insulating wall surface 12 in a substantially cylindrical shape. The air preheater 14 has an exhaust gas passage and a combustion air passage which are not shown. An ignition unit 16 including a fuel injection nozzle 15 and an ignition device (not shown) is provided at the center of the top facing the heating pipe 13. Further, the combustion air, which is pressure-fed from a blower (not shown), is preheated by the air preheater 14 and then supplied to the ignition unit 16 in a state where a swirl flow is applied by the swirler 17.

The discharge passage 18 opens in a part of the side wall near the bottom of the combustion chamber 11 and connects the combustion chamber 11 and the outside. Then, on the discharge passage 14, cooling means 19,
A mixer 20 and a catalyst device (NOx reduction catalyst) 21 are arranged.

First, in the cooling means 19, the cooler 29
Is a so-called water-cooled type, and has an exhaust gas passage and a cooling water passage (not shown), both ends of the exhaust gas passage communicate with the discharge passage 14, and one end of the cooling water passage has a supply pipe 22.
And the other end communicates with the discharge pipe 23. Supply pipe 2
A control valve 24 is arranged above the control valve 2, and the opening degree of the control valve 24 is controlled by the control device 2.
Controlled by 5. Further, in order to control the opening degree of the control valve 24, the temperature information of the exhaust gas flowing into the catalyst device 21 is input to the control device 25 via the temperature sensor 26 arranged at the inlet of the catalyst device 21. ing. Here, the cooling water discharged from the discharge pipe 23 has a high temperature, is cooled by an external cooling means (not shown), and is then supplied again to the supply pipe 2.
2 is supplied.

Next, the mixer 20 constitutes a hydrogen supply means 27 for mixing hydrogen obtained by fuel reforming utilizing combustion heat in the hydrogen supply source and the combustion chamber 11 (not shown) into the exhaust gas.

The operation of the nitrogen oxide reduction system 10 of the continuous combustion system having the above construction will be described.

For example, LNG fuel is injected from the fuel injection nozzle 15 to the ignition section 16. At the same time, the air sent under pressure from the blower is preheated by the air preheater 14 and then swirler 1
A swirl flow is given by 7 and supplied to the ignition part 16. Here, the fuel and air are mixed and ignited to form a flame, which is ejected into the combustion chamber 11. In the combustion chamber 11, the ignition part 1
The heating pipe 13 is heated by the flame ejected from 6 and the combustion gas generated by the flame, and the Stirling engine is continuously driven. Then, the combustion exhaust gas is cooled by exchanging heat with the combustion air in the air preheater 14, and the cooler 2
It flows into 9.

As shown in FIG. 2, the NOx purification rate in the catalyst device 21 is closely related to the temperature of the exhaust gas flowing therein. According to the experimental example shown in FIG. 2, a high purification rate is exhibited when the exhaust gas temperature is around 100 ° C. regardless of the concentration of hydrogen mixed. For example, in the air preheater 14, the exhaust gas is cooled only to about 850 ° C. to about 230 ° C., and therefore the exhaust gas needs to be further cooled by using the cooling means 19. That is, the control device 25 checks the temperature of the exhaust gas flowing into the catalyst device 21 with the temperature sensor 26, and controls the opening degree of the control valve 24 so that the temperature is around 100 ° C. As a result, the cooling water corresponding to the opening degree of the control valve 24 is supplied to the cooler 29, and the temperature of the exhaust gas flowing into the catalyst device 21 is maintained at around 100 ° C.

Further, hydrogen is mixed into the exhaust gas via the mixer 20 and flows into the catalyst device 21. And
Nitrogen oxides in the exhaust gas are discharged into the atmosphere in a state of being reduced and purified by hydrogen gas. The amount of hydrogen mixed is controlled by an appropriate control means so that the purification rate of nitrogen oxides in the catalyst device 21 is optimized.

Next, a nitrogen oxide reducing apparatus 40 for a continuous combustion apparatus according to a second embodiment of the present invention will be described with reference to FIG.
In this embodiment, only the structure of the cooling means 19 is different from that of the first embodiment. Therefore, the other parts are denoted by the same reference numerals as those of the first embodiment, and the description thereof is omitted.

In the cooling means 19, the cooler 30 is of a so-called air-cooling type and has an exhaust gas passage and a cooling fin (not shown), and both ends of the exhaust gas passage communicate with the exhaust passage 14. A cooling fan 31 faces the cooler 30, and its rotation speed is controlled by the controller 25. Further, in order to control the rotation speed of the cooling fan 31, the temperature information of the exhaust gas flowing into the catalyst device 21 is input to the control device 25 via the temperature sensor 26 arranged at the inlet of the catalyst device 21. ing.

Accordingly, the control device 25 checks the temperature of the exhaust gas flowing into the catalyst device 21 with the temperature sensor 26, and the cooling fan 3 is controlled so that the temperature becomes around 100.degree.
Controls the number of rotations of 1. As a result, the temperature of the exhaust gas flowing into the catalyst device 21 is maintained at around 100 ° C. The other operations are substantially the same as those in the first embodiment, and the description thereof will be omitted.

[0021]

According to the present invention, the nitrogen oxide contained in the exhaust gas discharged by the combustion in the external combustion engine and the continuous combustion device such as the boiler is controlled in an amount corresponding to the amount of the nitrogen oxide. By supplying hydrogen gas and by cooling the exhaust gas flowing into the catalyst device in advance by the cooling means, it is possible to easily reduce and remove under low temperature conditions of about 100 ° C. regardless of the oxygen concentration in the exhaust gas. it can.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a nitrogen oxide reduction device of a continuous combustion device according to a first embodiment of the present invention.

FIG. 2 shows a characteristic diagram of nitrogen oxide purification rate.

FIG. 3 is a configuration diagram of a nitrogen oxide reduction device of a continuous combustion device according to a second embodiment of the present invention.

[Explanation of symbols]

 11 combustion chamber, 18 exhaust passage, 19 exhaust gas cooling means, 20 hydrogen supply means, 21 catalyst device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Naoki Minamoto, Inventor Naoki Minamoto 2-1, Asahi-cho, Kariya city, Aichi Aisin Seiki Co., Ltd. (72) Inventor, Yasushi Fujiwara 2-chome, Asahi-cho, Kariya city, Aichi prefecture Address: Aisin Seiki Co., Ltd. (72) Inventor Yujiro Oshima, 41, Nagakute, Nagakute-cho, Aichi-gun, Aichi-gun, No. 41 Yokomichi, Toyota Central Research Institute Co., Ltd. (72) Inventor Hideaki Muraki Nagakute, Aichi-gun, Aichi 1 in 41 Chuo-ken Yokodori, Machi-cho, Toyota Central Research Institute Co., Ltd. (72) Inventor Katsushi Abe 1 in 41-long Yokochi, Nagakute-cho, Aichi-gun, Aichi Prefecture Toyota Central Research Institute (72) Invention Person Yokota Koji Harajuku, Aichi-gun, Aichi-gun, Nagakute-cho 1 41, Yokomichi Toyota Central Research Institute Co., Ltd. (72) Inventor Kasei Kawahara Aichi-gun, Aichi Nagakute-machi, Oita, Nagaminato, Yoko 41, 1

Claims (2)

[Claims] 1. A combustion chamber, a discharge passage for discharging exhaust gas generated in the combustion chamber, a catalyst device arranged on the discharge passage, and an upstream side of the catalyst device on the discharge passage. A nitrogen oxide reduction device of a continuous combustion device having a hydrogen supply means and an exhaust gas cooling means disposed on the side. 2. The nitrogen oxide reducing apparatus for a continuous combustion device according to claim 1, wherein the cooling means is controlled in operation according to the temperature of exhaust gas flowing into the catalyst device.