WO2016105153A1

WO2016105153A1 - Selective catalytic reduction system

Info

Publication number: WO2016105153A1
Application number: PCT/KR2015/014247
Authority: WO
Inventors: 이재문; 황진우; 김기모; 이균; 이창희
Original assignee: 두산엔진주식회사
Priority date: 2014-12-24
Filing date: 2015-12-24
Publication date: 2016-06-30
Also published as: KR101627052B1

Abstract

A selective catalytic reduction system according to an embodiment of the present invention comprises: a main exhaust passage through which exhaust gas of an exhaust gas discharging source is transferred; a reactor which is installed on the main exhaust passage, the reactor comprising a catalyst for reducing nitrogen oxide contained in the exhaust gas; a reducing agent injection unit which is installed on the main exhaust passage to inject a reducing agent to the exhaust gas that is transferred to the reactor; a decomposition chamber which receives and decomposes a reducing agent precursor to thereby prepare a reducing agent to be supplied to the reducing agent injection unit; a heat flux supply source which supplies, to the decomposition chamber, heat energy necessary for decomposing the reducing agent precursor; a heat flux supply flow passage which connects the heat flux supply source and the decomposition chamber; and a heat flux bypass flow passage which is branched from the heat flux supply flow passage and controls a heat flux supplied to the decomposition chamber.

Description

Selective catalytic reduction system

The present invention relates to a selective catalytic reduction system for reducing the nitrogen oxide contained in the exhaust gas discharged from the exhaust gas source.

BACKGROUND In general, power devices used in ships and the like include a low speed diesel engine, a turbocharger, and the like. Selective catalytic reduction (SCR) is a system for reducing nitrogen oxides by purifying exhaust gases generated from diesel engines.

In the selective catalytic reduction system, the nitrogen oxide contained in the exhaust gas and the reducing agent react with each other while passing the exhaust gas and the reducing agent together in a reactor in which the catalyst is installed therein, and the reduction process is performed with nitrogen and water vapor.

The selective catalytic reduction system is mainly used to hydrolyze urea as a reducing agent to reduce nitrogen oxides. That is, ammonia (NH ₃ ) generated by hydrolysis of urea is used as a reducing agent for reducing nitrogen oxides.

However, if urea is directly injected into the exhaust gas when the temperature of the exhaust gas is lower than 250 degrees Celsius or less, the urea may not be completely decomposed in the exhaust gas.

Therefore, in order to improve the hydrolysis efficiency of urea, the heated fluid is supplied to the hydrolysis chamber through a separate electric heater or burner to raise the internal temperature of the hydrolysis chamber to the hydrolysis reaction temperature, and the urea is A method of supplying ammonia (NH 3) and isocyanic acid (HNCO) produced by stable decomposition to a reactor is used.

However, there is a problem not only when the internal temperature of the hydrolysis chamber is lower than the hydrolysis reaction temperature of urea, but also when the internal temperature of the hydrolysis chamber is too high than the hydrolysis reaction temperature of urea.

For example, if the internal temperature of the hydrolysis chamber is too high, there may be a problem that the hydrolysis reaction does not occur or rather the whole system due to the increase in pressure.

Embodiments of the present invention provide a selective catalytic reduction system capable of effectively controlling the heat flow rate supplied to the decomposition chamber for producing a reducing agent.

According to an embodiment of the present invention, the selective catalytic reduction system for reducing the nitrogen oxide contained in the exhaust gas discharged from the exhaust gas source is on the main exhaust flow path to which the exhaust gas of the exhaust gas source is moved, and the main exhaust flow path A reactor including a catalyst installed to reduce nitrogen oxides contained in the exhaust gas, a reducing agent injector for injecting a reducing agent into the exhaust gas provided on the main exhaust flow path and moving to the reactor, and receiving a reducing agent precursor A decomposition chamber for decomposing and generating a reducing agent to be supplied to the reducing agent injection unit, a heat flow supply source for supplying heat energy necessary for decomposing a reducing agent precursor to the decomposition chamber, and a heat flow supply passage connecting the heat flow source and the decomposition chamber. And branched from the heat flow supply flow path to the decomposition chamber. And a heat flow bypass flow path for adjusting the heat flow rate.

The selective catalytic reduction system may further include a reducing agent precursor supply unit for supplying a reducing agent precursor to the decomposition chamber.

The selective catalytic reduction system includes a first flow rate control valve provided on the heat flow rate supply flow path between the heat flow bypass flow path and the heat flow supply flow path and the decomposition flow chamber, and a first flow control valve installed on the heat flow bypass flow path. It may further comprise one or more of the two flow control valve.

The selective catalytic reduction system may further include a flow meter installed on the heat flow bypass channel.

The heat flow bypass channel may be joined to the main exhaust channel in front of the reducing agent injection unit.

In addition, the heat flow bypass channel may be joined to the main exhaust channel between the reducing agent injection unit and the reactor.

In addition, the heat flow bypass channel may be directly connected to the reactor.

The selective catalytic reduction system may further include a reducing agent supply passage connecting the decomposition chamber and the reducing agent injection unit, and the heat flow bypass channel may bypass the decomposition chamber and join the reducing agent supply passage.

According to an embodiment of the present invention, the selective catalytic reduction system can effectively control the heat flow rate supplied to the decomposition chamber for producing the reducing agent.

1 is a block diagram of a selective catalytic reduction system according to a first embodiment of the present invention.

2 is a block diagram of a selective catalytic reduction system according to a second embodiment of the present invention.

3 is a block diagram of a selective catalytic reduction system according to a third embodiment of the present invention.

4 is a block diagram of a selective catalytic reduction system according to a fourth embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

In addition, in various embodiments, components having the same configuration will be representatively described in the first embodiment using the same reference numerals, and in other embodiments, only the configuration different from the first embodiment will be described. do.

It is noted that the figures are schematic and not drawn to scale. The relative dimensions and ratios of the parts in the figures are shown exaggerated or reduced in size for clarity and convenience in the figures and any dimensions are merely exemplary and not limiting. And the same reference numerals are used to refer to similar features in the same structure, element or part shown in more than one figure.

Embodiments of the invention specifically illustrate ideal embodiments of the invention. As a result, various modifications of the drawings are expected. Thus, the embodiment is not limited to the specific form of the illustrated region, but includes, for example, modification of the form by manufacture.

Hereinafter, the selective catalytic reduction system 101 according to the first embodiment of the present invention will be described with reference to FIG. 1.

The selective catalytic reduction system 101 according to the first embodiment of the present invention reduces the nitrogen oxide contained in the exhaust gas discharged from the exhaust gas discharge source 100. Here, the exhaust gas discharge source 100 is various, such as a marine diesel engine or an onshore power plant.

As shown in FIG. 1, the selective catalytic reduction system 101 according to the first embodiment of the present invention includes a main exhaust passage 610, a reactor 300, a reducing agent injection unit 710, a decomposition chamber 400, The heat flow rate supply source 500, the heat flow rate supply flow path 650, and the heat flow rate bypass flow path 680 may be included.

In addition, the selective catalytic reduction system 101 according to the first embodiment of the present invention includes a reducing agent precursor supply unit 450, a first flow control valve 810, a second flow control valve 820, a flow meter 850, and The reducing agent supply passage 640 may further include.

The main exhaust passage 610 moves the exhaust gas discharged from the exhaust gas discharge source 100.

For example, when the exhaust gas source 100 is a marine diesel engine, the exhaust gas moving along the main exhaust flow path 610 has a temperature of 150 degrees Celsius or more and 250 degrees centigrade while passing through an additional configuration of a marine diesel engine such as a supercharger. Can be lowered below degrees. In general, the supercharger serves to improve the efficiency of the diesel engine by supplying fresh air to the diesel engine by turning the turbine to the pressure of the exhaust gas of the diesel engine.

The reactor 300 is installed on the main exhaust passage 610. The reactor 300 includes a catalyst for reducing nitrogen oxides (NOx) contained in the exhaust gas discharged from the exhaust gas discharge source 100. The catalyst catalyzes the reaction between the nitrogen oxide (NOx) contained in the exhaust gas and the reducing agent to reduce the nitrogen oxide (NOx) to nitrogen and water vapor.

The catalyst may be made of various materials known to those skilled in the art, such as zeolite, vanadium, platinum and the like. In one example, the catalyst may have an active temperature in the range of 250 degrees Celsius to 350 degrees Celsius. Here, the active temperature refers to a temperature at which the catalyst can be stably reduced without poisoning the catalyst. If the catalyst reacts outside the active temperature range, the efficiency decreases with poisoning.

In addition, the housing of the reactor 300, for example, may be made of stainless steel (stainless steel) material.

The reducing agent injector 710 injects the reducing agent to the exhaust gas moving along the main exhaust passage 610 to the reactor 300. In detail, the reducing agent injector 710 may be installed on the main exhaust passage 610 in front of the reactor 300. The reducing agent injected from the reducing agent injector 710 is mixed with the exhaust gas moving through the main exhaust passage 610, and then reduces nitrogen oxide in the catalyst of the reactor 300. Here, the reducing agent comprises ammonia (NH ₃ ).

The decomposition chamber 400 generates a reducing agent to be supplied to the reducing agent injection unit 710. Decomposition chamber 400 is supplied with a reducing agent precursor urea (urea, CO (NH ₂ ) ₂ ) is hydrolyzed or pyrolyzed to produce ammonia (NH ₃ ). When the temperature in the decomposition chamber 400 is maintained within the range of 300 degrees Celsius to 500 degrees Celsius, urea is easily hydrolyzed or pyrolyzed to produce ammonia (NH ₃ ) and isocyanic acid (HNCO). Ansan (HNCO) is broken down into ammonia (NH ₃ ) and carbon dioxide (CO ₂ ).

The reducing agent precursor supply unit 450 supplies urea, which is a reducing agent precursor, to the decomposition chamber 400.

The reducing agent supply passage 640 connects the decomposition chamber 400 and the reducing agent injector 710 to transfer the reducing agent generated in the decomposition chamber 400 to the reducing agent injector.

The heat flow source 500 decomposes urea, a reducing agent precursor, to supply the heat flow necessary to generate a reducing agent to the decomposition chamber 400.

In the first embodiment of the present invention, as the heat flow source 500, various means known to those skilled in the art capable of supplying heat flow to the decomposition chamber 400 may be used.

For example, a blower may be used to draw in fresh air from the outside or to recycle the exhaust gas passed through the reactor 300, and heat it with a heating member such as a burner or a heater to supply the decomposition chamber 400.

In addition, when the exhaust gas discharge source 100 is a marine diesel engine, a part of the exhaust gas discharged from the diesel engine and before passing through the supercharger may be branched, and may be heated by a heating member such as a burner or a heater and supplied to the decomposition chamber 400. have.

In the first embodiment of the present invention, the heat flow rate supplied by the heat flow source 500 to the decomposition chamber 400 may have a temperature in the range of 400 degrees Celsius to 600 degrees Celsius.

The heat flow rate supply passage 650 connects the heat flow rate source 500 and the decomposition chamber 400. The heat flow bypass channel 680 is branched from the heat flow supply flow path 650 to adjust the heat flow rate supplied to the decomposition chamber 400 through the heat flow supply flow path 650.

In the first embodiment of the present invention, the heat flow bypass channel 680 may join the main exhaust channel 610 in front of the reducing agent injection unit 710.

The first flow control valve 810 is provided on the heat flow supply flow path 650 between the branch point of the heat flow bypass channel 680 and the heat flow supply flow path 650 and the decomposition chamber 400, and the second flow control The valve 820 may be installed on the heat flow bypass channel 680.

The first flow control valve 810 adjusts the heat flow rate supplied to the decomposition chamber 400, and the second heat flow control valve 820 adjusts the heat flow rate moving through the heat flow bypass channel 680.

In the first embodiment of the present invention, one of the first flow control valve 810 or the second flow control valve 820 may be omitted.

The flow meter 850 is installed on the heat flow bypass channel 680 and may be used for precise control of the heat flow bypassed through the heat flow bypass channel 680.

That is, in the first embodiment of the present invention, using the first flow control valve 810, the second flow control valve 820, and the flow meter 850, the decomposition chamber 400 is used to set the appropriate temperature required to generate the reducing agent. It is possible to control the heat flow rate supplied to the decomposition chamber 400 to maintain.

In addition, in the first embodiment of the present invention, since the heat flow rate bypass flow path 680 joins the main exhaust flow path 610 in front of the reducing agent injection portion 710, the heat flow rate that bypasses the decomposition chamber 400 and moves. It may be used incidentally to increase the temperature of the exhaust gas moving through the main exhaust passage 610.

As such, the heated exhaust gas may be usefully used as a heat source required to generate ammonia by re-decomposing isocyanic acid in addition to ammonia generated by decomposition of urea in the decomposition chamber 400.

By such a configuration, the selective catalytic reduction system 101 according to the first embodiment of the present invention can effectively control the heat flow rate supplied to the decomposition chamber 400 for producing a reducing agent.

Specifically, the temperature of the decomposition chamber 400 for decomposing urea as a reducing agent precursor to generate ammonia as a reducing agent may be effectively maintained within the urea hydrolysis or pyrolysis reaction temperature range.

In particular, since the excessive heat flow rate is supplied to the decomposition chamber 400, the pressure may be excessively increased to impede the whole system or exceed the appropriate reaction temperature, thereby preventing the hydrolysis or pyrolysis reaction from occurring. have.

In addition, the heat flow rate moved through the heat flow bypass channel 680 may be used to increase the temperature of the exhaust gas moving through the main exhaust flow path 610.

Hereinafter, the selective catalytic reduction system 102 according to the second embodiment of the present invention will be described with reference to FIG. 2.

As shown in FIG. 2, in the selective catalytic reduction system 102 according to the second embodiment of the present invention, the heat flow rate bypass flow path 680 branches from the heat flow supply flow path 650 to open the decomposition chamber 400. Bypass and joins the main exhaust passage 610 between the reducing agent injection portion 710 and the reactor 300.

As such, in the second embodiment of the present invention, the heat flow bypass channel 680 joins the main exhaust channel 610 between the reducing agent injection unit 710 and the reactor 300, thereby bypassing the decomposition chamber 400. The moved heat flow helps to effectively mix the reducing agent injected from the reducing agent injector 710 with the exhaust gas flowing along the main exhaust passage 610.

The selective catalytic reduction system 102 according to the second embodiment of the present invention is the same as the first embodiment except for the confluence of the branched heat flow bypass channel 680.

By such a configuration, the selective catalytic reduction system 102 according to the second embodiment of the present invention can also effectively control the heat flow rate supplied to the decomposition chamber 400 for generating the reducing agent.

In addition, the heat flow moved through the heat flow bypass channel 680 may be utilized to mix the reducing agent and the exhaust gas.

Hereinafter, the selective catalytic reduction system 103 according to the third embodiment of the present invention will be described with reference to FIG. 3.

As shown in FIG. 3, in the selective catalytic reduction system 103 according to the third embodiment of the present invention, the heat flow rate bypass flow path 680 branches from the heat flow supply flow path 650 to open the decomposition chamber 400. Bypasses and is connected directly to the reactor 300.

As described above, in the third embodiment of the present invention, since the heat flow rate bypass flow path 680 is directly connected to the reactor 300, the heat flow rate bypassed the decomposition chamber 400 moves to a temperature inside the reactor 300. It can be used incidentally to boost.

For example, the heat flow rate directly supplied to the reactor 300 through the heat flow bypass channel 680 may be utilized to regenerate a catalyst installed in the reactor 300.

When a reduction reaction occurs to reduce the nitrogen oxides contained in the exhaust gas at a relatively low temperature of more than 150 degrees Celsius and less than 250 degrees Celsius, the sulfur oxides (SOx) and ammonia (NH ₃ ) of the exhaust gases react to form a catalyst. Toxic substances are produced. The catalyst poisoning substance may include one or more of ammonium sulfate (NH ₄ ) ₂ SO ₄ ) and ammonium bisulfate (NH ₄ HSO ₄ ). These catalyst poisoning substances are adsorbed on the catalyst to lower the activity of the catalyst. Since the catalyst poisoning substance decomposes at a relatively high temperature, that is, a temperature in the range of 350 degrees Celsius to 450 degrees Celsius, the catalyst of the reactor 300 may be heated to regenerate the poisoned catalyst.

The selective catalytic reduction system 103 according to the third embodiment of the present invention is the same as the first embodiment except for the confluence of the branched heat flow bypass channel 680.

By such a configuration, the selective catalytic reduction system 103 according to the third embodiment of the present invention can also effectively control the heat flow rate supplied to the decomposition chamber 400 for generating the reducing agent.

In addition, the heat flow rate moved through the heat flow bypass channel 680 may be used for regeneration of the catalyst in the reactor 300.

Hereinafter, the selective catalytic reduction system 104 according to the fourth embodiment of the present invention will be described with reference to FIG. 4.

As shown in FIG. 4, in the selective catalytic reduction system 104 according to the fourth embodiment of the present invention, the heat flow rate bypass flow path 680 branches from the heat flow supply flow path 650 to open the decomposition chamber 400. Bypassing and joining with the reducing agent supply flow path 640 again.

As described above, in the fourth embodiment of the present invention, since the heat flow rate bypass flow path 680 joins the reducing agent supply flow path 640, the heat flow rate bypassed the decomposition chamber 400 moves to the urea in the decomposition chamber 400. In addition to the ammonia produced by the decomposition, isocyanic acid may be usefully used as a heat source required to generate ammonia by re-decomposing it again.

In addition, in the fourth embodiment of the present invention, the overall piping design of the selective catalytic reduction system 104 can be relatively simplified.

The selective catalytic reduction system 104 according to the fourth embodiment of the present invention is the same as the first embodiment except for the confluence of the branched heat flow bypass channel 680.

By such a configuration, the selective catalytic reduction system 104 according to the fourth embodiment of the present invention can also effectively control the heat flow rate supplied to the decomposition chamber 400 for generating the reducing agent.

In addition, the overall piping design of the selective catalytic reduction system 104 can be relatively simplified.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains can understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential features. will be.

Therefore, the embodiments described above are to be understood as illustrative and not restrictive in all respects, and the scope of the present invention is represented by the following detailed description, and the meaning and scope of the claims and All changes or modifications derived from the equivalent concept should be interpreted as being included in the scope of the present invention.

The selective catalytic reduction system according to the embodiment of the present invention can be used to effectively control the heat flow rate supplied to the decomposition chamber for producing the reducing agent.

Claims

In the selective catalytic reduction system for reducing the nitrogen oxide contained in the exhaust gas discharged from the exhaust gas source,

A main exhaust flow path through which the exhaust gas of the exhaust gas discharge source moves;

A reactor installed on the main exhaust passage and including a catalyst for reducing nitrogen oxides contained in exhaust gas;

A reducing agent injector installed on the main exhaust passage to inject a reducing agent into the exhaust gas moving to the reactor;

A decomposition chamber receiving and reducing a reducing precursor to generate a reducing agent to be supplied to the reducing agent injection unit;

A heat flow source for supplying heat energy necessary for decomposing a reducing agent precursor to the decomposition chamber;

A heat flow supply flow path connecting the heat flow supply source and the decomposition chamber; And

Heat flow bypass flow path for controlling the heat flow rate is supplied to the decomposition chamber branched from the heat flow supply flow path

Selective catalytic reduction system comprising a.
In claim 1,

Selective catalytic reduction system further comprises a reducing agent precursor supply for supplying a reducing agent precursor to the decomposition chamber.
In claim 1,

A first flow control valve provided on the heat flow rate supply flow path between a branch point of the heat flow bypass channel and the heat flow supply flow path and the decomposition chamber; And

A second flow control valve installed on the heat flow bypass flow path

Selective catalytic reduction system further comprising one or more of.
In claim 3,

Selective catalytic reduction system further comprises a flowmeter installed on the heat flow bypass flow path.
The method according to any one of claims 1 to 4,

And the heat flow bypass channel joins the main exhaust flow path in front of the reducing agent injection unit.
The method according to any one of claims 1 to 4,

And the heat flow bypass channel joins the main exhaust channel between the reducing agent injection unit and the reactor.
The method according to any one of claims 1 to 4,

And the heat flow bypass channel is directly connected to the reactor.
The method according to any one of claims 1 to 4,

Further comprising a reducing agent supply flow path connecting the decomposition chamber and the reducing agent injection,

And the heat flow bypass flow passage bypasses the decomposition chamber and joins the reducing agent supply flow passage.