KR20190135701A - Low Pressure Selective Catalytic Reduction System - Google Patents

Abstract

The present invention relates to a low-pressure selective catalytic reduction (LP SCR) system, which removes nitrogen oxides included in exhaust gas, and more specifically, to an LP SCR system, which is configured to allow a catalyst to be regenerated by removing an ABS in an SCR reactor by using exhaust gas at a high temperature and pressure. To this end, the LP SCR system of the present invention comprises: an exhaust line in which exhaust gas generated in an engine of a vessel is exhausted after sequentially passing through an exhaust gas receiver and a turbo charger (T/C); a urea decomposition chamber which decomposes urea to generate ammonia; a gas mixer which mixes the exhaust gas branched from the exhaust line with the urea introduced from the urea decomposition chamber; an SCR reactor which causes nitrogen oxides of the exhaust gas introduced after being mixed with the urea in the gas mixer to produce a catalytic reaction to be returned to water and nitrogen; a first bypass pipe branched from the exhaust line to sequentially pass through the gas mixer and the SCR reactor before being connected to the exhaust line, and bypassing the exhaust gas in the exhaust line; and a second bypass pipe bypassing the exhaust gas of a high temperature and a high pressure at the exhaust gas receiver to the urea decomposition chamber.

Description

LP SCR System {Low Pressure Selective Catalytic Reduction System}

The present invention relates to a LP SCR (Low Pressure Selective Catalytic Reduction) system that removes nitrogen oxides contained in exhaust gas. In particular, by removing the ABS (Ammonium Bisulfate: NH4HSO4) inside the SCR reactor using exhaust gas of high temperature and high pressure, It is configured to enable catalyst regeneration.

In general, a ship is installed with a main engine driving a propeller to propel a ship, and a plurality of power generation engines for supplying power to various equipment or equipment mounted on the ship.

Exhaust gases emitted after combustion in such ship engines contain a number of suspended particulates and harmful substances such as nitrogen oxides (NOx) and sulfur oxides (SOx).

Therefore, the exhaust line of the engine is equipped with a diesel particulate filter (DPF), a selective catalytic reduction (SCR), and a scrubber (SCRubber, SOx removal) to remove harmful components in the exhaust gas.

Among them, the LP SCR system includes an SCR reactor having an internal catalyst layer and installed on an exhaust line, and chemically reacts nitrogen oxides (NOx) in the exhaust gas with a reducing agent such as ammonia (NH3) and urea (Urea) in the catalyst layer. It is decomposed into water and nitrogen, which is harmless to humans, and then discharged. Urea is pyrolyzed or hydrolyzed and converted to ammonia (NH3).

And SCR catalyst (Catalyst) is composed of a porous catalyst filter is formed by extrusion or coating, one or two consecutively installed in the SCR reactor installed in the exhaust line to remove harmful components in the exhaust gas.

Existing SCR systems for large engines require high temperatures of 250 ° C or higher, depending on the sulfur content in the fuel, to prevent the formation of ABS (Ammonium Bisulfate: NH4HSO4) and to remove NOx. It is installed in front of the engine charger (T / C) whose gas temperature is 250 ~ 500 ℃.

As such, when the SCR system is installed at the front end of the T / C, since the pressure of the exhaust gas flowing into the SCR system is high, it is called an HP High Pressure Selective Catalytic Reduction (SCR) system.

However, if the SCR system is installed at the front end of the T / C, it is difficult to arrange the SCR system due to the narrow engine room.

In order to solve this problem, the exhaust gas temperature is 150 ~ 300 ℃, the pressure can be installed in the SCR system after the T / C at the atmospheric pressure level.

When the SCR system is installed at the rear of the T / C, the SCR system can be installed outside the engine room, and thus the SCR system can be freely placed without any space limitation. This system configuration is called LP SCR (Low Pressure Selective Catalytic Reduction) system.

1 is a conceptual diagram showing an LP SCR system according to the prior art.

As shown in FIG. 1, the exhaust gas generated in the engine 10 is introduced into the exhaust gas receiver 20 and then exhausted through the T / C 30 to the atmosphere.

In order to remove harmful nitrogen oxides (NOx) in the exhaust gas, first, the ABS inside the SCR reactor 80 must be removed. To this end, the exhaust gas of the exhaust line 1 is sucked into the blower 40 and flows to the SCR reactor 80. The exhaust gas sucked through the blower 40 reaches a temperature of about 350 ° C. for removing ABS. Since it does not heat the exhaust gas through the burner (50). The heated exhaust gas enters the SCR reactor 80 after passing through the urea decomposition chamber 60 and the gas mixer 70 and is discharged to the atmosphere. The ABS which prevents the catalytic reaction is vaporized by the temperature of the heated exhaust gas. Removed.

Afterwards, the LP SCR system operates normally, and harmful nitrogen oxides contained in the exhaust gas are chemically reacted with a reducing agent such as ammonia (NH 3) and urea (Urea) in the catalyst layer to be decomposed into water and nitrogen, which are harmless to the human body, and then discharged. Urea is pyrolyzed or hydrolyzed and converted to ammonia (NH3).

As described above, the LP SCR system is installed at the rear end of the T / C 30 so that the temperature of the exhaust gas is about 200 to 260 ° C. or less, thereby separately removing the burner 50 to remove the ABS inside the SCR reactor 80. In addition, a blower 40 is required to flow the exhaust gas of atmospheric pressure to the SCR reactor.

Typically, the time required for regenerating the catalyst of the LP SCR system is about 6 hours, so that a large amount of the burner 50 and the blower 40 are required to remove the ABS in this short time.

As an example, if the annual ship's SCR operation is estimated to be about 600 hours, the heat capacity of the burner used for the decomposition of urea is less than 50% of the heat capacity of the burner due to the removal of ABS. There is a drawback to selecting a burner and a blower.

Korean Patent Registration No. 10-1735535 (Notification Date; May 29, 2017)

The present invention has been invented to solve the problems of the prior art as described above, the inlet of the high temperature and high pressure exhaust gas discharged from the engine into the SCR reactor through the bypass line before entering the T / C, the normal operation of the LP SCR system The purpose is to provide an LP SCR system that has been previously configured to prevent the decomposition and generation of ABS.

LP SCR system according to the present invention for achieving the above object is ammonia by decomposing the exhaust line and exhaust gas generated in the ship engine through the exhaust gas receiver, turbocharger (T / C) sequentially and urea Catalytic reaction between the urea cracking chamber to be produced, the gas mixture mixing the exhaust gas branched from the exhaust line and the urea introduced from the urea cracking chamber, and the nitrogen oxide of the exhaust gas mixed with the urea in the gas mixer with water and nitrogen And a high temperature and high pressure exhaust gas of the first bypass pipe and the exhaust gas receiver, which are branched from the exhaust line and connected to the exhaust line through the gas mixer and the SCR reactor, sequentially bypassing the exhaust gas of the exhaust line. It is characterized by including a second bypass hall to bypass the.

In addition, according to a preferred embodiment of the present invention, it further comprises a return pipe extending from the second bypass pipe to the exhaust line.

Further, according to a preferred embodiment of the present invention, the first valve mounted on the second bypass pipe between the exhaust gas receiver and the branch point on the basis of the branch point where the return pipe branched from the second bypass pipe, the branch point and the urea decomposition chamber And a second valve mounted on the second bypass pipe between the third valve and the third valve mounted on the return pipe.

Further, according to a preferred embodiment of the present invention, on the basis of the branching point of the first bypass pipe in the exhaust line, a fourth valve mounted on the first bypass pipe, and a fifth valve mounted on the exhaust line extending to the atmosphere. And a sixth valve mounted to the rear of the SCR reactor.

In addition, according to a preferred embodiment of the present invention,

The temperature of the exhaust gas flowing into the SCR reactor through the urea decomposition chamber and the gas mixer along the second bypass pipe in the exhaust gas receiver is 350 ° C or higher.

As described above, the LP SCR system according to the present invention removes the ABS using the exhaust gas before the operation of the SCR system and removes the existing blower and the exhaust gas for sucking the exhaust gas discharged through the T / C. It is possible to use a small capacity blower and burner even if the configuration of the heating burner or the like is not required, thereby reducing the manufacturing cost and operating cost of the vessel.

1 is a conceptual diagram showing an LP SCR system according to the prior art.
2 is a conceptual diagram illustrating an LP SCR system according to the present invention;
3 is a conceptual diagram showing the flow relationship of the exhaust gas at the time of stopping operation of the LP SCR system,
4 is a conceptual diagram showing the flow relationship of the exhaust gas for the removal of ABS in the LP SCR system,
5 is a conceptual diagram showing the exhaust gas flow relationship in the operation mode of the LP SCR system.

Hereinafter, with reference to the accompanying drawings a preferred embodiment of the LP SCR system according to the present invention will be described in detail.

2 is a conceptual diagram showing the LP SCR system according to the present invention, Figure 3 is a conceptual diagram showing the flow relationship of the exhaust gas when the operation of the LP SCR system is stopped, Figure 4 is a removal of ABS in the LP SCR system Figure 5 is a conceptual diagram showing the flow relationship of the exhaust gas for, Figure 5 is a conceptual diagram showing the flow relationship of the exhaust gas in the operation mode of the LP SCR system.

As shown in FIG. 2, the exhaust gas generated from the engine 110 is configured to be exhausted to the atmosphere via the exhaust gas receiver 120 and the T / C 130 through the exhaust line 200.

In the exhaust line 200, the first bypass pipe 201 is provided with an exhaust line such that the exhaust gas flowing along the exhaust line 200 flows into the SCR reactor 180 when operating the LP SCR system to remove nitrogen oxides. Branched at 200, the gas mixture 170 and the SCR reactor 180 are returned to the exhaust line 200 and exhausted to the atmosphere.

On the other hand, the LP SCR system according to the present invention is a second bypass pipe (EGB; Exhaust Gas) that can be partially introduced into the SCR reactor 180 exhaust gas of high temperature and high pressure to regenerate the catalyst of the SCR reactor 180 before normal operation Bypass 202 is installed.

The second bypass tube 202 extends from the exhaust gas receiver 120 to be connected to the urea decomposition chamber 160. The exhaust gas of the exhaust gas receiver 120 is connected to the urea decomposition chamber along the second bypass tube 202. 160, the gas mixer 170 and the SCR reactor 180 sequentially pass through the exhaust line 200.

As described above, the high temperature and high pressure exhaust gas passes through the SCR reactor 180 and vaporizes and discharges ABS which interferes with the catalytic reaction, thereby enabling normal operation of the LP SCR system.

The return pipe 203 branches from the second bypass pipe 202 to the exhaust line 200 so that the exhaust gas flows from the second bypass pipe 202 into the exhaust line 200 when the LP SCR system is stopped. And the first valve 211 is installed between the exhaust gas receiver 120 and the branch point on the basis of the branch point of the return pipe 203, and between the branch point and the urea decomposition chamber 160. 212) is mounted.

In addition, a third valve 213 is also mounted on the return pipe 203 to allow the exhaust gas to flow into the urea decomposition chamber 160 through the second bypass pipe 202.

As described above, a fourth valve 214 is installed in the first bypass pipe 201 extending from the exhaust line 200 to the gas mixer 170. The fourth valve 214 is opened during the operation of the LP SCR system, and the fourth valve 214 is closed when the LP SCR system is stopped.

The fifth valve 215 is installed at the rear of the exhaust line 200 on the basis of the branching point of the first bypass pipe 201 in the exhaust line 200, from the SCR reactor 180 to the exhaust line 200. The sixth valve 216 is installed in the extended first bypass pipe 201.

The following describes the operation relationship of the LP SCR system configured as described above.

As shown in FIG. 3, the second valve 212, the fourth valve 214, and the sixth valve 216 are closed when the LP SCR system is stopped. Here, the first valve 212 is for exhausting some exhaust gas for performance matching of the engine, that is, T / C performance, and when the LP SCR system is stopped, the second valve 212 is substantially closed. The first valve 211 is kept open.

Then, the exhaust gas discharged from the engine 110 passes through the exhaust gas receiver 120 and the T / C 130 to the atmosphere through the exhaust line 200, and a part of the exhaust gas is opened in the first valve 211. And the third valve 213 is exhausted to the atmosphere through the second bypass pipe 202 and the return pipe 203.

Meanwhile, in order to remove the ABS inside the SCR reactor 180 before the operation of the LP SCR system, as illustrated in FIG. 4, the first valve 211, the second valve 212, and the sixth valve 216 are removed. The third valve 213, the fourth valve 214, and the fifth valve 215 are closed. Then, the high temperature and high pressure exhaust gas discharged from the engine 110 is introduced into the exhaust gas receiver 120, the urea decomposition chamber 160, the gas mixer 170, the SCR reactor 180, and then flows to the exhaust line 200. do. And it is exhausted to the atmosphere through the exhaust line 200.

At this time, the ABS inside the SCR reactor 180 is removed by using the exhaust gas of high temperature and high pressure as described above. When the ABS is removed, the catalyst of the SCR reactor 180 is regenerated to decompose nitrogen oxide of the exhaust gas introduced into the SCR reactor 180 into water and nitrogen.

Meanwhile, as shown in FIG. 5, the second valve 212 and the fifth valve 215 are closed while the ABS inside the SCR reactor 180 is removed, and the fourth valve 214 and the sixth valve 216 are closed. ) To exhaust the exhaust gas discharged from the engine 110 to the atmosphere through the gas mixer 170, SCR reactor 180.

Then, as described above, the exhaust gas is introduced into the SCR reactor 180 in the state of being mixed with ammonia and urea in the gas mixer 170 to catalyze the decomposition, thereby decomposing the nitrogen oxide contained in the exhaust gas.

In the LP SCR system of the present invention operating as described above, the exhaust gas exhausted from the engine 110 flows into the SCR reactor 180 to remove the ABS in the SCR reactor 180 and exhaust gas of sufficient temperature and flow rate. Must be supplied to the SCR reactor 180.

Typically, the temperature of the exhaust gas supplied to the SCR reactor 180 is effective to remove the ABS when about 350 ℃.

In order to satisfy such exhaust gas conditions, the temperature and flow rate of the exhaust gas generated when the ship's engine is under high load, that is, about 75% or more, is effective in removing ABS.

Table 1 below shows the conditions of the exhaust gas, and the box marked part in Table 1 shows the effect of removing ABS, and it can be seen that the ship's engine is in a high load state of 75%.

As described above, the LP SCR system according to the present invention requires a configuration such as a blower for sucking the exhaust gas discharged through T / C and a burner for heating the exhaust gas as the ABS is removed using the exhaust gas before operation. Smaller blowers and burners can be used, if not needed, to reduce costs and operating costs.

110: engine
120: exhaust gas receiver
130: T / C
160: urea decomposition chamber
170: gas mixer
180: SCR reactor
200: exhaust line
201, 202: Bypass Hall
203: Return piping
211 ~ 216: valve

Claims (5)

An exhaust line 200 in which exhaust gas generated from the ship engine 110 is exhausted sequentially through an exhaust gas receiver 120 and a turbocharger (T / C) 130;
Urea decomposition chamber 160 for decomposing urea to produce ammonia;
A gas mixer 170 for mixing the exhaust gas branched from the exhaust line 200 and the urea introduced from the urea decomposition chamber 160;
An SCR reactor 180 for catalytically reacting nitrogen oxides of exhaust gas introduced by mixing with urea in the gas mixer 170 with water and nitrogen;
A first bypass pipe 201 branched from the exhaust line 200 and connected to the exhaust line 200 through the gas mixer 170 and the SCR reactor 180 in order to bypass the exhaust gas of the exhaust line 200;
A second bypass tube 202 for directing the high temperature and high pressure exhaust gas of the exhaust gas receiver 120 directly to the urea decomposition chamber 160 before the normal operation of the LP SCR system,
Before the normal operation of the LP SCR system, the high temperature and high pressure exhaust gas is exhausted into the atmosphere through the exhaust gas receiver 120, the urea decomposition chamber 160, the gas mixer 170, and the SCR reactor 180, thereby removing the ABS inside the SCR reactor. LP SCR system, characterized in that to remove.
The method of claim 1,
LP SCR system, characterized in that it further comprises a return pipe (203) extending from the second bypass pipe (202) to the exhaust line.
The method of claim 2,
The first valve 211 mounted on the second bypass tube 202 between the exhaust gas receiver 120 and the branch point based on the branch point where the return pipe 203 branched from the second bypass tube 202, and the branch point And a second valve 212 mounted on the second bypass pipe 202 between the urea decomposition chamber 160 and a third valve 213 mounted on the return pipe 203. SCR system.
The method of claim 3,
Based on the branch point of the first bypass pipe 201 in the exhaust line 200, it is mounted on the fourth valve 214 mounted on the first bypass pipe 201 and the exhaust line 200 extending to the atmosphere. LP SCR system characterized in that it further comprises a fifth valve (215), and a sixth valve (216) mounted to the rear of the SCR reactor 180.
The method according to claim 1, wherein
The temperature of the exhaust gas flowing into the SCR reactor 180 through the urea decomposition chamber 160 and the gas mixer 170 along the second bypass pipe 202 in the exhaust gas receiver 120 is 350 ° C. or more. LP SCR System.

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