KR101236305B1 - Apparatus for removing nitrogen oxides and method for removing nitrogen oxides thereof - Google Patents

Abstract

PURPOSE: Apparatus for removing nitrogen oxide and a method thereof are provided to reduce hot idling of an engine by minimizing space capacity inserted between the engine and a supercharger turbine. CONSTITUTION: Apparatus(100) for removing nitrogen oxide comprises a reducing agent feeder(130) and a catalyst reducing unit. The reducing agent feeder sprays initial materials to exhaust gas of a first engine. The reducing agent feeder produces a reducing agent from the sprayed initial materials through a thermal reaction generated by contact between the exhaust gas and the initial materials. The catalyst reducing unit removes the nitrogen oxide in the exhaust gas of a second engine by a catalytic reduction reaction. [Reference numerals] (AA) Outlet

Description

Nitrogen oxide removal device and its nitrogen oxide removal method {APPARATUS FOR REMOVING NITROGEN OXIDES AND METHOD FOR REMOVING NITROGEN OXIDES THEREOF}

The present invention relates to a nitrogen oxide removal device and a nitrogen oxide removal method thereof, and more particularly, to a nitrogen oxide removal device and nitrogen oxide removal method thereof for effectively removing nitrogen oxide contained in the exhaust gas of an engine.

Engines, among which diesel engines, produce nitrogen oxides (hereinafter referred to as NOx) mainly composed of NO and NO ₂ in the combustion process inside the cylinder. Since NOx is a representative pollutant, various efforts have been made to remove NOx.

In particular, the International Maritime Oraganization (IMO) under the United Nation regulates the emissions of nitrogen oxides from ships. According to Annex 6 of the Marine Pollution Treaty, MARPOL Treaty 73/78, from 2016, ships sailing offshore should reduce their NOx emissions to the current quarter.

Selective Catalytic Reduction (hereinafter referred to as SCR) is widely used as a method for removing nitrogen oxides. SCR is a method of converting nitrogen oxides into stable nitrogen molecules by injecting a nitrogen oxide and a reducing agent into the catalyst and inducing a catalytic reduction reaction. At this time, a titanium-vanadium-based catalyst is used as the catalyst, and ammonia is mainly used as the reducing agent.

Since ammonia is a poisonous substance with a strong irritating odor, it is difficult to handle. When ammonia is used as a reducing agent, a storage tank should be installed in an open area (for example, an open area on the upper deck) to prevent leakage of ammonia, and a leak detection sensor. Special equipment such as double outer wall or ventilation system is required. Therefore, in recent years, the method of generating ammonia by spraying pyrolysis by spraying the urea aqueous solution (henceforth urea water) which is easy to handle in high temperature exhaust gas is proposed. Thus, the general content of the nitrogen oxide removal device using ammonia is disclosed in Republic of Korea Patent Publication No. 10-2012-00305533.

At this time, in order to generate ammonia from urea water, a temperature level of a predetermined range (about 320 ° C to 400 ° C) is required. If the temperature of the exhaust gas to which urea water is injected is low, urea water is not completely decomposed and a number of by-products such as burette and saanuric acid are generated, which causes deterioration of nitrogen oxide removal performance.

SUMMARY OF THE INVENTION An object of the present invention is to provide a nitrogen oxide removal apparatus and a method for removing nitrogen oxides thereof, which improve the reducing agent production efficiency and suppress the formation of by-products.

Another object of the present invention is to provide a nitrogen oxide removal device having a common denitrification device for a plurality of engines, which reduces installation and manufacturing costs, and a method for removing the nitrogen oxides thereof.

Another object of the present invention is to provide an apparatus for removing nitrogen oxide and a method for removing nitrogen oxide thereof, which minimizes the reduction of the driving force of the supercharger turbine.

Another object of the present invention is to provide a nitrogen oxide removal device and a method for removing nitrogen oxides thereof which minimize the space capacity inserted between the engine and the turbocharger turbine.

Another object of the present invention is to provide a nitrogen oxide removal apparatus having a porous inner cylinder for suppressing the formation of by-products and solidification, and a method for removing the nitrogen oxides thereof.

Another object of the present invention is to provide a nitrogen oxide removal device and a nitrogen oxide removal device having a static mixer in which the lateral swing motion and the longitudinal vortex are formed in a double flow to improve the uniformity of the exhaust gas and the uniformity of the flow rate distribution. To provide a way.

The nitrogen oxide removal device according to the present invention comprises a reducing agent supply for generating a reducing agent from the initial material through a thermal reaction using the thermal energy of the exhaust gas of the first engine; And a catalytic reduction unit for removing nitrogen oxides contained in the exhaust gas of the second engine by the catalytic reduction reaction using the reducing agent, wherein the exhaust gas of the second engine does not pass through the reducing agent supply unit without the reduction agent supplying unit. Is provided.

In an embodiment, the exhaust gas of the first engine is hotter than the exhaust gas of the second engine.

In an embodiment, the first engine is a power generation engine of the ship, and the second engine is a propulsion engine of the ship.

In an embodiment, the upstream side is connected to the exhaust passage of the second engine (hereinafter referred to as the second exhaust passage), the downstream side is connected to the catalytic reduction section, and the exhaust passage of the reducing agent supplier between the upstream and the downstream side ( Hereinafter, the vent pipe which the 1st exhaust path) joins further is included.

In example embodiments, the reducing agent supplier may exhaust the mixed gas in which the exhaust gas of the first engine and the reducing agent are mixed through the first exhaust path, and the exhausted mixed gas may flow in the second exhaust path from the second exhaust path. 2 is provided to the catalytic reduction unit through the vent pipe together with the exhaust gas of the engine.

In example embodiments, the catalytic reduction unit may include a static mixer that mixes the exhausted mixed gas and the exhaust gas of the second engine, wherein the static mixer includes the exhaust gas of the exhausted mixed gas and the second engine. And a screw plate for inducing vortex in the exhaust gas of the exhaust gas or the exhaust gas of the second engine during the passage.

In an embodiment, the valve may further include a valve for selectively inducing exhaust gas of the second engine to the catalytic reduction unit or an external outlet.

The nitrogen oxide removal device according to the present invention comprises an exhaust pipe for inducing exhaust gas of the engine to the supercharger turbine; A dynamic pressure generator for extracting a part of the exhaust gas flowing in the exhaust pipe; A reducing agent supplier for mixing the extracted gas with a reducing agent and providing the exhaust pipe to the exhaust pipe; And an SCR reactor connected to a rear end of the supercharger turbine and removing nitrogen oxide contained in the exhaust gas by a catalytic reduction reaction using the reducing agent, wherein the additional gas provided to the exhaust pipe is connected to the exhaust pipe through the exhaust pipe. It is led sequentially to the supercharger turbine and the SCR reactor.

In an embodiment, the dynamic pressure generator extracts a part of the exhaust gas from a downstream side of the exhaust pipe, and the reducing agent supplier provides the extracted gas and the reducing agent upstream of the exhaust pipe.

In an embodiment, the dynamic pressure generator may include: a dynamic pressure plate for extracting a part of the exhaust gas and providing the reduced pressure to the reducing agent supplier; And a Z-axis that couples the dynamic pressure plate to the exhaust pipe.

In an embodiment, the reducing agent supplier generates the reducing agent from the initial material through a thermal reaction using the thermal energy of the additional gas.

In an embodiment, the reducing agent supply includes a nozzle for providing the initial material to a thermal reaction zone; And a porous inner cylinder located between the outer cylinder of the reducing agent supplier and the thermal reaction zone and having a plurality of holes on the surface.

In an embodiment, the reducing agent supplier further includes a swirler for generating a turning force in a space inside the porous inner cylinder.

In an embodiment, a static mixer includes the reducing agent and the exhaust gas, wherein the static mixer includes a screw plate that induces vortex in the exhaust gas while the exhaust gas passes through the static mixer.

The nitrogen oxide removal device according to the present invention comprises a static mixer for mixing the fluid by inducing vortex in the fluid; And an SCR reactor for removing nitrogen oxide contained in the fluid through a catalytic reduction reaction, wherein the static mixer includes an inlet for receiving the fluid; A discharge part for discharging the fluid; And a screw plate that induces vortex in the fluid while the fluid moves from the inlet to the outlet.

In an embodiment, the vortex is a bi-vortex vortex comprising a longitudinal vortex and a transverse swirl movement.

In an embodiment, the screw plate has a centered shape.

In an embodiment, the outer diameter of the screw plate is in contact with the inner diameter of the outer cylinder of the static mixer.

In an embodiment, the fluid includes an exhaust gas of an engine and a reducing agent of the catalytic reduction reaction.

In an embodiment, the apparatus further includes a reducing agent supply for providing the reducing agent, and the static mixer is installed between the reducing agent supply and the SCR reactor.

In an embodiment, the reducing agent is ammonia gas, and the reducing agent supplier generates the reducing agent from urea through a thermal reaction using thermal energy of the exhaust gas.

The nitrogen oxide removal device according to the present invention includes a reducing agent supplier for generating a reducing agent from an initial material through a thermal reaction using thermal energy of exhaust gas, wherein the reducing agent supplier is spaced apart from a wall surface of the reducing agent supplier in the reducing agent supplier. A porous inner cylinder disposed on the surface and having a plurality of holes through which the exhaust gas passes; And a nozzle providing the initial material.

In an embodiment, the nozzle sprays the initial material toward the interior of the porous inner cylinder.

In an embodiment, the plurality of holes is in the form of a circle or a rod.

In an embodiment, the plurality of holes decreases in area as they are closer to the nozzle.

In an embodiment, the reducing agent supply further includes a swirler for generating a turning force to the air inside the porous inner cylinder.

In an embodiment, the method may further include an SCR reactor for removing nitrogen oxide through a catalytic reduction reaction using the reducing agent.

In an embodiment, the initial material is urea and the reducing agent is ammonia gas.

Nitrogen oxide removal method according to the invention comprises the steps of generating a reducing agent from the initial material through a thermal reaction using the thermal energy of the exhaust gas of the first engine; And removing nitrogen oxide contained in exhaust gas of the second engine by a catalytic reduction reaction using the reducing agent.

In an embodiment, the nitrogen oxide removal device is connected upstream with a second exhaust path for exhausting the exhaust gas of the second engine, and downstream is connected with a catalytic reduction part in which the catalytic reduction reaction is performed. And a vent pipe through which the first exhaust passage, through which the reducing agent flows, joins downstream.

In an embodiment, the exhaust gas of the first engine is hotter than the two exhaust gases of the second engine.

According to the present invention, there is provided a nitrogen oxide removal device and a method for removing nitrogen oxides thereof, which improve the reducing agent production efficiency and suppress the production of by-products.

Moreover, the common denitrification apparatus is provided with respect to several engine, and the installation and manufacture cost of a nitrogen oxide removal apparatus is reduced.

In addition, the reduction of the driving force of the supercharger turbine is minimized.

It also minimizes the space capacity that is inserted between the engine and the supercharger turbine, thereby reducing engine hunting.

Also provided are a nitrogen oxide removal apparatus having a porous inner cylinder for suppressing the formation of by-products and solidification, and a method for removing the nitrogen oxides thereof.

In addition, the homogeneity of the exhaust gas and the uniformity of the flow rate distribution are improved.

1 is a view showing a nitrogen oxide removal device according to a first embodiment of the present invention.
2 is a view showing a specific embodiment of the dynamic pressure generator and the reducing agent supply shown in FIG.
3 and 4 are exploded views showing embodiments of the porous inner cylinder shown in FIG. 2.
FIG. 5 is a diagram illustrating an embodiment of the swirler illustrated in FIG. 2.
6 is a cross-sectional view illustrating an embodiment of the static mixer shown in FIG. 2.
FIG. 7 is a plan view from above of the screw plate shown in FIG. 6.
8 is a view showing a nitrogen oxide removal device according to a second embodiment of the present invention.
9 is a view showing a specific embodiment of the reducing agent supply unit shown in FIG.
10 is a flow chart showing a nitrogen oxide removal method according to the present invention.

The foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the claimed invention. Therefore, the present invention is not limited to the embodiments described herein and may be embodied in other forms. The embodiments disclosed herein are provided so that the disclosure can be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

In this specification, when it is mentioned that a certain element includes an element, it means that it may further include other elements. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Nitrogen oxide removal equipment using a selective catalytic reduction method is a problem when applied to engines with relatively low exhaust gas temperatures. For example, the ship's propulsion engine has a temperature of about 250 ° C. in the exhaust gas passing through the supercharger turbine. In this case, since the temperature of the exhaust gas does not reach a suitable temperature (about 320 ° C. to 400 ° C.) for generating a reducing agent (eg, ammonia), the nitrogen oxide removal device generates a large amount of by-products in the process of producing the reducing agent. Done.

Meanwhile, Korean Patent Laid-Open Publication No. 10-2012-0030553, which is a related prior art, focuses on the fact that the temperature of the exhaust gas before passing the supercharger turbine is relatively high, thereby extracting the exhaust gas flowing through the pipe leading from the engine to the turbocharger turbine. To produce ammonia. However, according to this method, since a part of the exhaust gas is discharged through the catalytic reaction device (or the SCR reactor) without driving the turbocharger turbine, the power of the turbocharger turbine is reduced.

SUMMARY OF THE INVENTION The present invention provides a nitrogen oxide removal device and a method for removing the nitrogen oxides thereof, while providing a sufficiently hot exhaust gas for producing a reducing agent while at the same time minimizing the reduction in power of the supercharger turbine.

1 is a view showing a nitrogen oxide removal device according to a first embodiment of the present invention. Referring to FIG. 1, the nitrogen oxide removing device 100 includes an initial material tank 120, a pump 121, a reducing agent supply 130, an exhaust pipe P1, a dynamic pressure generator 140, and first and second valves ( 170a, 170b), static mixer 180, and SCR reactor 190. The surrounding components include the engine 110, the receiver 111, the air supply cooler 161, the blower 160, and the supercharger turbine 150.

The air supply M1 flows in from the outside for starting the engine. The air supply M1 passes through the blower 160 and is provided to the air supply cooler 161, and the air supply cooler 161 cools the provided air supply and provides it to the engine 110.

The engine 110 burns fuel using the provided air supply, and exhausts the exhaust generated in the combustion process to the receiver 111. In an embodiment, the engine 110 may be a diesel engine having a two stroke cycle. In addition, as an embodiment, the engine 110 may be a propulsion engine of a ship. Hereinafter, the nitrogen oxide removal apparatus 100 is demonstrated assuming the engine 110 as a ship's propulsion engine.

The receiver 111 temporarily stores the exhaust gas from the engine 110 and provides it to the exhaust pipe P1.

The exhaust pipe P1 directs the exhaust gas to the supercharger turbine 150. At this time, a part of the exhaust gas flowing through the exhaust pipe P1 may be additionally extracted (or extracted) by the dynamic pressure generator 140.

The dynamic pressure generator 140 can extract a part of the exhaust gas from the exhaust pipe P1. In an embodiment, the dynamic pressure generator 140 may be controlled to open and close according to the operation mode of the ship. For example, when a ship operates a sea area (hereinafter referred to as a regulated sea area) that regulates nitrogen oxide content, the dynamic pressure generator 140 is controlled to open to remove nitrogen oxides of the exhaust gas. Then, the dynamic pressure generator 140 extracts a part of the exhaust gas from the exhaust pipe P1. On the other hand, when the ship is operating in a non-regulated area, the dynamic pressure generator 140 is controlled to be closed, and the dynamic pressure generator 140 does not extract the exhaust gas. In this case, all of the exhaust gas passing through the exhaust pipe P1 is led to the supercharger turbine 150.

A detailed configuration and operation of the dynamic pressure generator 140 will be described later with reference to FIG. 2.

The reducing agent supplier 130 provides a reducing agent and mixes the gas and the reducing agent extracted by the dynamic pressure generator 140. Then, the reducing agent supplier 130 returns a mixed gas (hereinafter referred to as a mixed gas) of the additional gas and the reducing agent to the exhaust pipe P1. As will be described later, the reducing agent included in the returned gas is used in the catalytic reduction reaction generated in the SCR reactor 190 to remove nitrogen oxides. The returned mixed gas is guided to the supercharger turbine, joins the exhaust gas, and is used to drive the supercharger turbine.

In an embodiment, the reducing agent supplier 130 may generate a reducing agent using thermal energy of the additional gas.

In an embodiment, the reducing agent supplier 130 may generate a reducing agent from the initial material through a thermal reaction using thermal energy of the additional gas. In this case, the nitrogen oxide removal device 100 stores the initial material in the initial material tank 120, and provides the initial material to the reducing agent supplier 130 through the pump 121.

In an embodiment, the reducing agent provided by the reducing agent supply 130 may be ammonia and the initial material may be urea. In this case, the initial material tank 120 stores the urea and provides the urea to the reducing agent feeder 130 through the pump 121. The reducing agent supplier 130 injects urea toward the hot additional gas, and ammonia is generated from the urea by thermal reaction using the heat energy of the additional gas.

A detailed description of the configuration and operation of the reducing agent supplier 130 will be described later with reference to FIGS. 2 to 5.

According to the configuration of the dynamic pressure generator 140 and the reducing agent supply 130 as described above, the exhaust gas for reducing agent generation is added before the supercharger turbine 150. The exhaust gas passes through the supercharger turbine 150, and consumes a part of the thermal energy it has to drive the supercharger turbine 150. Therefore, the temperature of the exhaust gas is considerably lowered while passing through the supercharger turbine 150. Therefore, when a high temperature is required for the reduction agent generation, by reducing the exhaust gas before the supercharger turbine 150 as in the present invention, the reducing agent generation performance can be improved. For example, when ammonia is produced from urea, the exhaust gas is extracted before the supercharger turbine 150, and urea is injected into the additional gas. Thereby, the urea is pyrolyzed to ammonia by the relatively high exhaust gas, and the generation of by-products such as biuret and saanuric acid can be minimized.

In addition, the additional exhaust gas is returned to the exhaust pipe P1 together with the reducing agent, and guided to the supercharger turbine 150. Therefore, the gas extracted by the dynamic pressure generator 140 also returns to the exhaust pipe P1 to join the exhaust gas and is used to drive the supercharger turbine 150. That is, the reduction in power of the supercharger turbine 150 generated by the dynamic pressure generator 140 to extract the exhaust gas may be minimized.

In addition, since only the reducing agent supplier 130 having a relatively small space capacity is inserted between the receiver 111 and the turbocharger turbine 150, engine hunting phenomenon is reduced. If, in order to use the hot exhaust gas, assume that a nitrogen oxide removal device including the SCR reactor 190 is inserted between the receiver 111 and the supercharger turbine 150. In such a case, since the capacity of the SCR reactor 190 is very large, the driving of the supercharger turbine 150 does not follow the load variation of the engine when the load variation of the engine is frequent. As a result, temporary engine hunting may occur. However, according to the present invention, since only the reducer feeder 130 having a small space capacity is inserted, the supercharger turbine 150 can quickly follow the load change of the engine.

Subsequently, the exhaust gas guided to the supercharger turbine 150 passes through the supercharger turbine 150 and then reaches the first valve 170a along the exhaust pipe P2. At this time, the exhaust gas consumes a part of the excitation energy passing through the supercharger turbine 150 to drive the supercharger turbine 150.

The first valve 170a directs the exhaust gas to one of the exhaust pipes P3 and P5. According to an embodiment, which exhaust pipe the first valve 170a directs may be determined according to the operation mode of the ship. For example, in regulated water, the first valve 170a directs the exhaust gas to the exhaust pipe P3 for nitrogen oxide removal. On the other hand, in the non-regulated area, the first valve 170a directs the exhaust pipe P5 to discharge the exhaust gas to the outside.

The exhaust gas guided to the exhaust pipe P3 by the first valve 170a is provided to the static mixer 180.

The static mixer 180 mixes the exhaust gas and the reducing agent included in the exhaust gas to improve the nitrogen oxide removal efficiency of the SCR reactor 190. That is, the static mixer 180 induces the reducing agent to be homogeneously distributed in the exhaust gas.

In an embodiment, the static mixer 180 induces pivotal movement on the flow cross section to the exhaust gas. Thus, the flow rate of the exhaust gas provided to the SCR reactor 190 is induced to be uniform on the flow cross section.

A detailed description of the configuration and operation of the static mixer 180 will be described later with reference to FIG. 6.

The exhaust gas passing through the static mixer 180 is provided to the SCR reactor 190.

The SCR reactor 190 removes nitrogen oxides contained in the exhaust gas provided by the selective catalytic reduction reaction. At this time, the reducing agent contained in the exhaust gas is used as the reducing agent of the selective catalytic reduction reaction. SCR reactor 190 includes a catalyst unit 191 therein.

Since the specific configuration and operation of the SCR reactor 190 is well known in the art, a description thereof will be omitted.

According to the above configuration, since relatively high temperature exhaust gas is used to provide the reducing agent, the efficiency of reducing agent generation is increased. In addition, since the exhaust gas extracted for providing the reducing agent is guided back to the supercharger turbine 150, power reduction of the supercharger turbine 150 is minimized. In addition, since only the reducing agent supplier 130 having a small space capacity is inserted between the receiver 111 and the supercharger turbine 150, temporary engine hunting is minimized.

2 is a view showing a specific embodiment of the dynamic pressure generator and the reducing agent supply shown in FIG. Referring to FIG. 2, the dynamic pressure generator 140 includes a dynamic pressure plate 141 and a rotation shaft 142. In addition, the reducing agent supplier 130 includes an inlet 135, an outlet 136, and an outer cylinder 133, and includes a nozzle 131, a swirler 132, and a porous inner cylinder 134 therein.

The dynamic pressure generator 140 extracts a part of the exhaust gas flowing in the exhaust pipe P1 and provides it to the reducing agent supplier. At this time, the dynamic pressure plate 141 is opened toward the exhaust pipe (P1), the exhaust gas flows into the open portion of the dynamic pressure plate (141). Thus, when the dynamic pressure plate 141 is provided in the passage of the gas having kinetic energy, high dynamic pressure is applied to the opening of the dynamic pressure plate 141. Then, the gas in the exhaust pipe P1 is extracted into the dynamic pressure generator 140 by using the dynamic pressure.

For example, when the exhaust gas Mp1 flows in from the upstream of the exhaust pipe P1, a part of the Mp Mp3 is added into the dynamic pressure generator 140 by the dynamic pressure plate 141. Then, only the remaining exhaust gas Mp2 is exhausted downstream of the exhaust pipe P1.

The rotating shaft 142 couples the dynamic pressure plate 141 to the exhaust pipe P1, and operates as the rotating shaft when the dynamic pressure plate 141 moves. That is, the dynamic pressure plate 141 is opened or closed toward the exhaust pipe P1 with the rotation shaft 142 as the axis.

On the other hand, the dynamic pressure generator 140 has been described in the configuration for extracting the exhaust gas flowing through the exhaust pipe (P1) using the dynamic pressure plate 141 and the rotating shaft 142. However, the present invention is not limited thereto, and the dynamic pressure generator 140 may include any means for adding the exhaust gas flowing in the exhaust pipe P1 to the reducing agent supplier 130.

The reducing agent supplier 130 receives the exhaust gas extracted by the dynamic pressure generator 140 through the inlet 135. The exhaust gas and the reducing agent are mixed in the outer cylinder 133, and the exhaust gas Mp4 in which the reducing agent is mixed is returned to the exhaust pipe P1 through the discharge part 136. The returned exhaust gas Mp4 joins the exhaust gas Mp1 flowing through the exhaust pipe P1.

In an embodiment, the reducing agent supplier 130 may generate a reducing agent from the initial material through a thermal reaction using the thermal energy of the additional gas. Hereinafter, the reducing agent supplier 130 will be described, taking the case where a reducing agent (ammonia) is generated from the initial material (urea).

 The nozzle 131 obtains the element M2 from the initial material tank 120 via the pump 121. In an embodiment, the element M2 may be in an aqueous solution. Then, the nozzle 131 sprays or provides the element M2 toward the inside of the porous inner cylinder 134.

The swirler 132 generates a turning force to the air inside the porous inner cylinder 134. This improves the rate at which the injected elements mix, evaporate and heat with the exhaust gases. A detailed configuration and operation of the swinger 132 will be described later with reference to FIG. 5.

The porous inner cylinder 134 is a cylinder structure surrounding a predetermined region inside the reducing agent supplier 130. The porous inner cylinder 134 has a plurality of holes in the surface. Then, the exhaust gas passing between the porous inner cylinder 134 and the outer cylinder 133 of the reducing agent supplier is introduced into the porous inner cylinder 134 through the hole of the porous inner cylinder 134.

On the other hand, since the nozzle 131 injects the urea into the interior of the porous inner cylinder 134, the exhaust gas introduced through the hole of the porous inner cylinder 134 is discharged in the inner region of the porous inner cylinder 134 (hereinafter, referred to as a thermal reaction region). Meet with the injected element. The exhaust gas reaching the thermal reaction zone then provides the thermal energy necessary for the thermal reaction to produce ammonia from the urea.

The porous inner cylinder 134 surrounds the area where the urea is injected, thereby preventing the urea or by-product (eg, saanuric acid) from contacting the outer cylinder 133 having a relatively low temperature. Therefore, the element or the by-product solidifies the outer cylinder 133 and does not stick.

In addition, since the inside and the outside of the porous inner cylinder 134 are surrounded by a high temperature exhaust gas, the temperature of the porous inner cylinder 134 is maintained at a high temperature near the exhaust gas temperature. Thus, even if the urea or by-product is in contact with the porous inner cylinder 134, a continuous thermal reaction occurs due to the high temperature of the porous inner cylinder 134. Therefore, the element or by-product contacted with the porous inner cylinder 134 has an effect of being converted into ammonia without solidifying.

In addition, the porous inner cylinder 134 guides a path through which exhaust gas is directed to the urea, and exhaust gas is uniformly supplied from the inlet portion 135 to the discharge portion 136 of the reducing agent supply 130 to the inside of the porous inner cylinder 134. To get into As a result, the exhaust gas and ammonia or urea are mixed uniformly.

In an embodiment, the porous inner cylinder 134 may be in the form of a cylinder having a plurality of holes in its surface.

An exemplary form of the porous inner cylinder 134 will be described below in conjunction with FIGS. 3 and 4.

Meanwhile, in the present embodiment, the dynamic pressure generator 140 extracts exhaust gas from downstream of the exhaust pipe P1, and the reducing agent supply 130 mixes the reducing agent with the additional gas and adds the additional gas upstream of the exhaust pipe P1. Return to However, the scope of the present invention is not limited thereto, the dynamic pressure generator 140 extracts the exhaust gas from any point of the exhaust pipe (P1), and also the reducing agent supply 130 is added to any other point of the exhaust pipe (P1). Gas can be returned. For example, the dynamic pressure generator 140 extracts the exhaust gas from the upstream of the exhaust pipe P1, and the reducing agent supplier 130 mixes the reducing agent with the additional gas and returns the additional gas to the downstream of the exhaust pipe P1. Can be.

3 and 4 are exploded views showing embodiments of the porous inner cylinder shown in FIG. 2. Referring to FIG. 3, the porous inner cylinder 134 includes an inner cylinder surface 134a and a plurality of circular holes. Referring to FIG. 4, the porous inner cylinder 134 includes an inner cylinder surface 134a and a plurality of rod-shaped holes.

3 is a view illustrating a first embodiment of the porous inner cylinder 134. The porous inner cylinder 134 may have a cylindrical shape. When the cylindrical inner cylinder 134 having a cylindrical shape is cut in the longitudinal direction and developed, the cylindrical inner cylinder 134 is formed as shown in FIG. 3. The porous inner cylinder 134 includes a plurality of holes on the inner cylinder surface 134a. The hole 134b on the inner cylinder surface 134a is circular, and the exhaust gas enters in from the outside of the porous inner cylinder 134 through the hole 134b.

In an embodiment, the plurality of holes on the inner tube surface 134a may be larger as they are located farther from the nozzle 131 (see FIG. 2). The exhaust gas passing between the porous inner cylinder 134 and the outer cylinder 133 (see FIG. 2) proceeds in the direction that the nozzle 131 faces. Then, the exhaust gas flows into the porous inner cylinder 134 through the holes on the inner cylinder surface 134a as it proceeds. Therefore, the closer to the nozzle 131, the higher the exhaust gas density between the porous inner cylinder 134 and the outer cylinder 133. Therefore, in order to make the amount of exhaust gas flowing into the inner cylinder 134 toward each hole even, the radius of the hole may increase as it moves away from the nozzle 131.

4 is a view illustrating a second embodiment of the porous inner cylinder 134. Likewise, the porous inner cylinder 134 may be cylindrical. When the cylindrical inner cylinder 134 having a cylindrical shape is cut in the longitudinal direction and developed, the cylindrical inner cylinder 134 has a shape as shown in FIG. 4. The porous inner cylinder 134 includes a plurality of holes on the inner cylinder surface 134a, and exhaust gas enters in and out of the porous inner cylinder 134 through the holes.

On the other hand, in the second embodiment of the porous inner cylinder 134, the plurality of holes on the inner cylinder surface 134a is in the form of a rod.

In an embodiment, the plurality of holes on the inner cylinder surface 134a may be larger as they are located farther from the nozzle 134 (see FIG. 2). For example, each of the holes 134b, 134c, 134d is located further away from the nozzle 131 in turn. In this case, the hole 134b closest to the nozzle 131 may have the narrowest width w1, and the hole 134d farthest from the nozzle 131 may have the widest width w3. On the other hand, the hole 134c located in the middle has a middle width w2.

In the above, specific embodiments of the porous inner cylinder 134 have been described. However, this is exemplary, and the porous inner cylinder 134 of the present invention is not limited to that shown in FIGS. 3 and 4. For example, the porous inner cylinder 134 may not be a cylinder but a square cylinder or a triangular cylinder. In addition, the holes on the inner cylinder surface 134a may each have various shapes and sizes.

FIG. 5 is a diagram illustrating an embodiment of the swirler illustrated in FIG. 2. Referring to FIG. 5, the swirler 132 (see FIG. 2) includes an outer fixing ring 132c, an inner fixing ring 132d, a plurality of wings 132a, and a ventilation space 132b between the wings. do.

The outer fixing ring 132c and the inner fixing ring 132d fix the plurality of wings 132a.

Ventilation space 132b partially penetrates the front and rear of the swirler to provide a space for gas to pass through.

The wing 132a is coupled to the outer fixing ring 132c and the inner fixing ring 132d, and forms an angle (hereinafter, referred to as wing angle) with the outer or inner fixing rings 132c and 132d. And the wing | blade 132a induces a turning flow, when gas passes through the ventilation space 132b.

In an embodiment, the vane angle θ may vary depending on the flow rate of the exhaust gas flowing into the swirler 132 or the intensity of the required swinging motion. To this end, the swirler 132 may be provided with a separate angle control means 132e.

On the other hand, the swirler 132 described in FIG. 5 is an example, and any means for causing a swirl flow in the gas passing through the swirler may be included in the swirler according to the present invention.

6 is a cross-sectional view illustrating an embodiment of the static mixer shown in FIG. 2. Referring to FIG. 6, the static mixer 180 includes an inlet 181, an outer cylinder 182, an outlet 184, and a screw plate 183 located inside the outer cylinder 182.

The center 185 of the screw plate 183 is an empty space. In an embodiment, the center 185 may be an empty space having a cylindrical shape. At this time, the center 185 is configured to form a sufficient flow cross-sectional area passage.

In an embodiment, the outer edge (or outer diameter) of the screw plate 183 may contact the inner surface (or inner diameter) of the outer cylinder 182.

When the exhaust gas Mk1 introduced into the inlet 181 flows in, part Mk2 proceeds through the center 185, and part Mk3 is blocked by the screw plate 183. The exhaust gas Mk3 blocked by the screw plate 183 proceeds while turning along the screw plate 183. On the other hand, the exhaust gas Mk2 passing through the center 185 proceeds at an angle close to a right angle with the inner edge (or the inner diameter) of the screw plate 183. Therefore, the exhaust gas Mk2 causes the longitudinal vortex Mk4 on the back surface of the screw plate 183.

As described above, the exhaust gas passing through the screw plate 183 having an empty center is induced with a longitudinal vortex Mk4 and a lateral turning motion Mk3. In addition, the longitudinal vortex Mk4 activates the exchange of the material in the radial direction and the momentum, thereby exchanging the exhaust gas traveling along the inside of the screw plate 183 and the exhaust gas running along the outside. At this time, when the exhaust gas which has advanced along the outer side of the screw plate 183 is moved inward, the exhaust gas turns at a higher speed by the law of conservation of momentum.

As a result, in the exhaust gas Mk1 passing through the screw plate 183, the vortex in the lateral direction and the vortices in the longitudinal direction are formed in a double flow, and the exhaust gas Mk1 is mixed well by the formed double flow. Therefore, the exhaust gas Mk1 can be improved at the same time in the circumferential homogeneity and the radial homogeneity.

In addition, since the exhaust gas Mk5 passing through the screw plate 183 and exiting the discharge unit 184 is in a turbulent state with strong turning force, the catalyst unit 191 and FIG. 1 included in the SCR reactor 182 (see FIG. 1). The flow rate at the inlet can be uniform on the flow cross section.

FIG. 7 is a plan view from above of the screw plate shown in FIG. 6. Referring to FIG. 7, the screw plate 183 included in the static mixer 180 has an empty center 185 therein.

As described in FIG. 6, some of the exhaust gas introduced into the static mixer 180 passes straight through the center 185, and some of the exhaust gas travels along the screw plate 183.

In an embodiment, the outer diameter and the inner diameter of the screw plate 183 may be a circular shape having a constant diameter (r1, r2).

In an embodiment, the outer diameter r1 of the screw plate 183 may be the same as the inner diameter of the outer cylinder 182 (see FIG. 6).

In an embodiment, the screw plate 183 may be installed to have a predetermined width l.

8 is a block diagram illustrating a nitrogen oxide removing device according to a second embodiment of the present invention. Referring to FIG. 8, the nitrogen oxide removal apparatus 200 includes an initial material tank 240, a pump 241, a reducing agent supplier 250, and a catalytic reduction unit 260. The low temperature engine 210, the high temperature engines 220a, 220b and 220c and the plurality of valves 230a, 230b, 203c and 230d are provided as peripheral components. Meanwhile, the high temperature engines 220a, 220b and 220c may be plural.

In the present embodiment, for convenience of description, the high temperature engines 220a, 220b, and 220c are engines for generating power of a ship having a four stroke cycle, and the low temperature engine 210 is a propulsion engine of a ship having a two stroke cycle. Assume that However, this is merely illustrated for convenience of description without any intention to limit the scope of the present invention thereto.

Although not shown in FIG. 8, exhaust paths R1, R4a, R4b, and R4c of each engine may pass through a supercharger turbine (not shown).

When the exhaust gas is discharged from the high temperature engines 220a, 220b, and 220c, the valves 230b, 230c, and 230d selectively guide the exhaust gas to any one of a plurality of paths. For example, when a vessel is operating in regulated water, the valves 230b, 230c, 230d direct exhaust gases to the first paths R5a, R5b, R5c for nitrogen oxide removal. Otherwise, the valves 230b, 230c, 230d guide the exhaust gas to the second paths R6a, R6b, R6c and discharge them to the outside.

When the exhaust gas is guided to the first paths R5a, R5b and R5c, the exhaust gases exhausted from the respective high temperature engines 220a, 220b and 220c are joined to each other in the exhaust pipe R7. The combined exhaust gas is provided to the reducing agent supplier 250.

The reducing agent supplier 250 provides a reducing agent and mixes the reducing agent with the exhaust gas. In addition, the exhaust gas in which the reducing agent is mixed is exhausted through the exhaust path of the reducing agent supplier 250.

In an embodiment, the reducing agent supplier 250 may generate a reducing agent using thermal energy of exhaust gas.

In an embodiment, the reducing agent supplier 250 may generate a reducing agent from an initial material through a thermal reaction using thermal energy of exhaust gas. In this case, the nitrogen oxide removal device 200 stores the initial material in the initial material tank 240 and provides the initial material to the reducing agent supplier 250 through the pump 241.

In an embodiment, the reducing agent provided by the reducing agent supplier 250 may be ammonia and the initial material may be urea. In this case, initial material tank 240 stores urea and provides urea to reductant feeder 250 via pump 241. The reducing agent supplier 250 injects the urea toward the hot exhaust gas. The injected urea is converted into ammonia by thermal reaction using the thermal energy of the exhaust gas.

At this time, since the exhaust gas of the high temperature engines 220a, 220b, and 220c has a high temperature, the exhaust gas of the high temperature engines 220a, 220b, and 220c has a temperature (for example, 350 ° C or more) sufficient for thermal reaction even after passing through a supercharger turbine (not shown). Thus, by using the heat energy of the exhaust gas, urea is sufficiently converted to ammonia, and generation of by-products (for example, biuret or saanuric acid) is suppressed.

Details of the initial material tank 240 and the pump 241 are the same as described in FIG. The reducing agent supplier 250 according to the second embodiment of the present invention will be described later in detail with reference to FIG. 9.

On the other hand, the exhaust passage of the reducing agent supplier 250 is connected to a separate vent pipe (R2). The exhaust gas (hereinafter referred to as low temperature exhaust gas) of the low temperature engine 210 flows in from the upstream of the vent pipe R2. And, downstream of the vent pipe R2 is connected with the catalytic reduction part 260.

The exhaust gas flowing along the exhaust path of the reducing agent supplier 250 proceeds to the vent pipe R2 and merges with the low temperature exhaust gas between upstream and downstream of the vent pipe R2. Then, the combined exhaust gases are provided to the catalytic reduction unit 260.

Meanwhile, in an embodiment, the low temperature exhaust gas discharged from the low temperature engine 210 may be selectively induced into the discharge pipe R3 or the vent pipe R2 by the operation of the valve 230a. At this time, the valve 230a may be controlled with reference to the operation mode of the ship.

The catalytic reduction unit 260 includes a static mixer 262 and an SCR reactor 261. The static mixer 262 mixes the introduced exhaust gas, and the SCR reactor 261 removes nitrogen oxides of the exhaust gas through a selective catalytic reduction reaction using a reducing agent included in the exhaust gas.

Meanwhile, the details of the static mixer 262 and the SCR reactor 261 are the same as described above.

In addition, the exhaust gas from which the nitrogen oxides have been removed is exhausted to the outlet through the valve 270.

According to the configuration as described above, since the exhaust gas of the high-temperature engine (220a, 220b, 220c) (hereinafter referred to as the hot exhaust gas) for generating the reducing agent, the reducing agent generation efficiency is improved. And the production of by-products is suppressed.

In addition, since the low temperature exhaust gas is provided to the catalytic reduction unit 260 together with the high temperature exhaust gas, a reducing agent included in the high temperature exhaust gas may be used to remove nitrogen oxides of the low temperature exhaust gas. Thus, the problem (e.g., by-product generation) that occurs when generating a reducing agent using low temperature exhaust gas is eliminated.

In addition, since the common catalytic reduction unit 260 is provided for the low temperature engine 210 and the high temperature engines 220a, 220b, and 220c, the exhaust gas of the plurality of engines is denitrated through one catalytic reduction unit 260 (De). -NOx). Therefore, the installation cost of the nitrogen oxide removal device can be reduced.

9 is a view showing a specific embodiment of the reducing agent supply unit shown in FIG. 9, the reducing agent supply 250 includes an inlet 251, an outer cylinder 256, an outlet 257, a nozzle 252, a nozzle holder 253, a swirler 254, and a porous inner cylinder 255. ).

Details of the outer cylinder 256, the nozzle 252, the swirler 254 and the porous inner cylinder 255 are the same as described above.

The nozzle holder 253 supports the nozzle 252. In addition, the nozzle holder 253 may be used to support the swinger.

The inlet 251 is connected to the exhaust pipe R7 (see FIG. 8) to receive the exhaust gas Mr1. Some of the exhaust gas Mr1 passes through the swirler and flows into the interior of the porous inner cylinder 255. Some of the exhaust gases (Mr2, Mr3, Mr4, Mr5) proceed between the porous inner cylinder 255 and the outer cylinder 256, and flows into the interior of the porous inner cylinder 255 through the hole of the porous inner cylinder 255.

The exhaust gas Mr7 introduced into the inside of the porous inner cylinder 255 meets the urea and causes a thermal reaction. The exhaust gas Mr7 is mixed with a reducing agent produced by the thermal reaction. At this time, the swirler 254 induces the turning motion (Mr8) to the exhaust gas to improve the mixing of the exhaust gas reducing agent. The exhaust gas Mr9 mixed with the reducing agent is exhausted through the discharge part 257 to the exhaust path of the reducing agent supplier 250.

10 is a flow chart showing a nitrogen oxide removal method according to the present invention. Referring to FIG. 10, the method of removing nitrogen oxides includes steps S110 to S160.

In operation S110, the nitrogen oxide removing device 200 (see FIG. 8) provides the exhaust gas of the first engine to the reducing agent supply reducing agent supplying tank). In this case, the first engine may be a high temperature engine 220a, 220b, 220c (see FIG. 8). In addition, since the exhaust gas of the first engine (hereinafter referred to as high temperature exhaust gas) has a high temperature, it has a relatively high temperature (for example, a temperature suitable for thermal reaction for producing a reducing agent) even after passing the supercharger turbine. .

In step S120, the nitrogen oxide removal device 200 generates a reducing agent from the initial material through a thermal reaction using the thermal energy of the hot exhaust gas. In addition, the nitrogen oxide removal device 200 mixes a high temperature exhaust gas and a reducing agent.

In an embodiment, the initial material is urea and the reducing agent may be ammonia.

The specific method of generating the reducing agent by the nitrogen oxide removal apparatus 200 is the same as described with reference to FIG. 8.

In operation S130, the nitrogen oxide removing device 200 provides the exhaust gas (hereinafter, low temperature exhaust gas) of the second engine to the vent pipe R2 (see FIG. 8). The second engine may be a low temperature engine 210 (see FIG. 8). In addition, the nitrogen oxide removing device 200 provides a hot exhaust gas containing a reducing agent to the vent pipe R2.

The hot exhaust gas and the low temperature exhaust gas are joined in the vent pipe R2, and the nitrogen oxide removal device 200 provides the combined exhaust gases to the catalytic reduction unit 260 (see FIG. 8). In this case, the reducing agent included in the hot exhaust gas is also provided to the catalytic reduction unit 260.

The specific method in which the low temperature and the high temperature exhaust gas are sequentially provided to the vent pipe R2 and the catalytic reduction part 260 is the same as described with reference to FIG. 8.

In step S140, the nitrogen oxide removing device 200 mixes the hot exhaust gas, the cold exhaust gas, and the reducing agent by using the static mixer 262 (see FIG. 8). Specific configuration and operation of the static mixer 262 is the same as described above.

In step S150, the nitrogen oxide removal device 200 provides the exhaust gas mixed by the static mixer 262 to the SCR reactor 261 (see FIG. 8). In addition, the nitrogen oxide removal apparatus 200 removes nitrogen oxides included in the hot exhaust gas or the low temperature exhaust gas through a selective catalytic reduction reaction using a reducing agent included in the mixed exhaust gas.

In operation S160, the nitrogen oxide removing device 200 discharges the denitrated (De-NOx) hot exhaust gas or the cold exhaust gas to the outside through the discharge port.

According to the above configuration, since the high-temperature exhaust gas is used for generating the reducing agent, the reducing agent generating efficiency is improved. And the production of by-products is suppressed.

In addition, since the low temperature exhaust gas is provided to the catalytic reduction unit 260 together with the high temperature exhaust gas, a reducing agent included in the high temperature exhaust gas may be used to remove nitrogen oxides of the low temperature exhaust gas. Thus, the problem (e.g., by-product generation) that occurs when generating a reducing agent using low temperature exhaust gas is eliminated.

In addition, since the common catalytic reduction unit 260 is provided for the low temperature engine 210 and the high temperature engines 220a, 220b, and 220c, the exhaust gas of the plurality of engines is denitrated through one catalytic reduction unit 260 (De). -NOx). Therefore, the installation cost of the nitrogen oxide removal device can be reduced.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.

For example, although the initial material is urea and the reducing agent is ammonia, the present invention is exemplified, but the present invention can be applied to a nitrogen oxide removal device using other initial materials or reducing agents. That is, the technical idea of the present invention can be applied to any nitrogen oxide removal device requiring a high temperature to generate a reducing agent.

As another example, the first embodiment of the present invention can be applied to any nitrogen oxide removal apparatus for adding exhaust gas to mix the reducing agent with the exhaust gas, and the scope of the present invention extends to this.

In addition, although specific terms are used herein, they are used for the purpose of describing the present invention only and are not used to limit the scope of the present invention described in the claims or the claims. Therefore, the scope of the present invention should not be limited to the above-described embodiments, but should be determined by the equivalents of the claims of the present invention as well as the claims of the following.

100, 200: nitrogen oxide removal device
110, 210: engine or low temperature engine 220a, 220b, 220c: high temperature engine
111: Receiver
120, 240: initial material tank 121, 241: pump
130, 250: reducing agent supply 140: dynamic pressure generator
150: supercharger turbine 160: blower
161: air supply cooler 170a, 170b: valve
180, 262: static mixer 190, 261: SCR reactor
230a, 230b, 230c, 230d: valve 260: catalytic reduction part
P1, R7: Exhaust Pipe R2: Vent Pipe
131, 252: nozzle 132, 254: turning machine
133, 182, 256: outer cylinder 134, 255: porous inner cylinder
135, 181, 251: inlet 136, 184, 257: outlet
132a: wing 132b: aeration space
132c: external retaining ring 132d: internal retaining ring
132e: control means
134a: inner plate 134b, 134c, 134d: hole
141: copper plate 142; Rotating shaft
183: screw plate 185: center

Claims (30)

A reducing agent supplier for injecting initial material toward the exhaust gas of the first engine and generating a reducing agent from the injected initial material through a thermal reaction generated by the injected initial material in contact with the exhaust gas of the first engine; And
Including a catalytic reduction unit for removing nitrogen oxides contained in the exhaust gas of the second engine by a catalytic reduction reaction using the reducing agent,
The exhaust gas of the second engine is provided to the catalytic reduction unit without passing through the reducing agent supply unit. The method of claim 1,
The nitrogen oxide removal apparatus of which the exhaust gas of the said 1st engine is hotter than the exhaust gas of the said 2nd engine. The method of claim 2,
The first engine is a power generation engine of the ship,
The second engine is a nitrogen oxide removal device that is the engine for propulsion of the ship. The method of claim 1,
Upstream is connected to the exhaust passage of the second engine (hereinafter referred to as the second exhaust passage), downstream is connected to the catalytic reduction section, and the exhaust passage of the reducing agent supplier (hereinafter referred to as the first) between the upstream and the downstream. And a vent pipe through which the exhaust passage) joins. The method of claim 4, wherein
The reducing agent supplier exhausts the mixed gas of the exhaust gas of the first engine and the reducing agent through the first exhaust path,
And the exhaust gas mixture is provided to the catalytic reduction unit through the vent pipe together with the exhaust gas of the second engine introduced from the second exhaust path. The method of claim 5, wherein
The catalytic reduction unit includes a static mixer to mix the exhaust gas of the exhaust gas and the exhaust gas of the second engine,
The static mixer,
And a screw plate for inducing vortex to the exhaust gas of the exhaust gas or the exhaust gas of the second engine while the exhaust gas and the exhaust gas of the second engine pass through the static mixer. The method according to claim 6,
And the vortex is a bi-vortex vortex comprising a longitudinal vortex and a transverse swirl movement. The method according to claim 6,
The screw plate is a nitrogen oxide removal device having a centered shape. The method of claim 8,
And the outer diameter of the screw plate is in contact with the inner diameter of the outer cylinder of the static mixer. The method of claim 1,
And a valve for selectively inducing exhaust gas of the second engine to the catalytic reduction unit or an external outlet. The method of claim 1,
The reducing agent supply unit,
A nozzle providing the initial material to a thermal reaction zone; And
And a porous inner cylinder located between the outer cylinder of the reducing agent supply and the thermal reaction zone and having a plurality of holes. The method of claim 11,
And the nozzle sprays the initial material toward the inside of the porous cylinder. The method of claim 11,
The plurality of holes are nitrogen oxide removal device in the form of a circle or rod. The method of claim 13,
And the plurality of holes are smaller in area as they are closer to the nozzle. The method of claim 11,
The reducing agent supplier further comprises a swirler for generating a turning force to the air inside the porous inner cylinder nitrogen oxide removal device. The method of claim 1,
The initial material is urea,
And the reducing agent is ammonia gas. In the nitrogen oxide removal method of the nitrogen oxide removal device,
Injecting an initial material toward the exhaust gas of the first engine and generating a reducing agent from the injected initial material through a thermal reaction generated by the injected initial material in contact with the exhaust gas of the first engine; And
Removing nitrogen oxide contained in the exhaust gas of the second engine by a catalytic reduction reaction using the reducing agent. The method of claim 17,
The nitrogen oxide removal device,
Upstream is connected to the second exhaust passage for exhausting the exhaust gas of the second engine, downstream is connected to the catalytic reduction unit in which the catalytic reduction reaction is carried out, and the reducing agent is introduced between the upstream and the downstream 1 A nitrogen oxide removal method comprising a vent pipe joined by an exhaust passage. The method of claim 17,
The exhaust gas of the first engine is hotter than the exhaust gas of the second engine. delete delete delete delete delete delete delete delete delete delete delete

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