KR20170099124A - Catalytic performance maintenance apparatus of scr system - Google Patents

Abstract

An apparatus to maintain catalytic performance of an SCR system comprises: an SCR reactor passing exhaust gas having passed through a turbocharger (T/C) through an SCR catalyst; a temperature sensor sensing a temperature of the SCR reactor; an economizer receiving high-temperature engine cooling water discharged after the engine cooling water circulates a cooling water circulation line in an engine, and recovering heat of the exhaust gas on a front end of the T/C to produce steam from the engine cooling water; and an air heater raising temperature of air by a mutual heat exchange between steam produced in the economizer and air, and supplying the high-temperature air to the SCR reactor. The temperature of the SCR reactor is able to be raised to a target temperature or higher through the high-temperature air supplied from the air heater in a state where movement of the exhaust gas into the SCR reactor is blocked. Accordingly, it is possible to improve heat efficiency by reducing energy required to regenerate a catalyst or a heating and venting operations, and to minimize unnecessary catalyst poisoning using air rather than the exhaust gas.

Description

[0001] CATALYTIC PERFORMANCE MAINTENANCE APPARATUS OF SCR SYSTEM [0002]

The present invention relates to an SCR system, and more particularly, to a catalyst performance maintaining apparatus of an SCR system.

The exhaust gas discharged after combustion in the marine engine contains a large number of suspended fine particles and harmful substances such as nitrogen oxides (NOx) and sulfur oxides (SOx).

Therefore, the main exhaust line of the engine is provided with a diesel particulate filter, a selective catalytic reduction (SCR) system, a scrubber (removing the SOx), and the like to remove harmful components in the exhaust gas.

Among them, the SCR system includes an SCR reactor having a built-in SCR catalyst. The SCR reactor chemically reacts nitrogen oxides in the exhaust gas with reducing agents (urea, ammonia, etc.) in the catalyst layer to decompose them into harmless water and nitrogen .

The SCR catalyst is made of a porous catalyst filter formed with an extrusion or a metallic coating, and is equipped with several SCR catalysts installed one or in succession in the SCR reactor.

In the conventional SCR system, the exhaust gas generated from the engine is directly discharged through the bypass line without passing through the SCR reactor (at the time of operation of the SCR system) or after exhausting the nitrogen oxide via the SCR reactor on the main exhaust line Stop).

In such a structure, when the internal temperature of the SCR reactor is lowered, catalyst poisoning occurs due to the sulfur (S) or phosphorus (P) compound contained in the exhaust gas, so that the catalytic activity and the strength are lowered.

For example, when nitrogen oxides (NOx) in the exhaust gas are removed, byproducts such as ABS (Ammonium Bisulfate: NH4HSO4) are produced. When the temperature in the reactor falls below the vaporization temperature of ABS Respectively.

Also, if the exhaust gas temperature is lowered after a lapse of time in stopping the SCR system, the exhaust gas remaining in the SCR reactor is condensed into sulfuric acid (H2SO4) in liquid state to cause internal corrosion.

Also, when the SCR system is shut down, the temperature in the SCR reactor drops to room temperature, and a lot of heat source is consumed during the preheating for system restart.

In order to solve this problem, it is necessary to remove heat by applying the catalyst regeneration operation to vaporize the ABS attached to the SCR catalyst.

In addition, the SCR reactor is kept at a certain temperature or higher by heating to maintain the temperature in the reactor at a high temperature, and venting operation for blowing air into the reactor to remove impurities from the SCR catalyst, And strength reduction shall be prevented.

In this process, the internal temperature of the SCR reactor must be increased by using a separate heat source such as an electric heater or a burner.

Meanwhile, in order to increase the temperature of the SCR reactor during catalyst regeneration, heating and venting operation, hot exhaust gas discharged from the engine may be supplied to the SCR reactor to be utilized as a heat source. In this case, The catalyst activity and the strength reduction due to the catalyst poison are rather promoted by the (P) compound during the long-term operation.

Korean Patent Laid-Open No. 10-2014-0041098 (published on April 4, 2014).

DISCLOSURE Technical Problem The present invention has been proposed in order to solve the problems of the prior art as described above, and it is an object of the present invention to reduce the energy required when the temperature in the SCR reactor is maintained at a constant temperature, And to provide an apparatus for maintaining the catalytic performance of the SCR system.

It is another object of the present invention to provide an apparatus for maintaining the catalytic performance of an SCR system that minimizes unnecessary catalyst poisoning due to exhaust gas by using air other than exhaust gas during catalyst regeneration, heating, and venting operation.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not to be construed as limiting the invention as defined by the appended art. It will be possible.

In order to accomplish the above object, an apparatus for maintaining the catalytic performance of an SCR system according to the present invention includes: an SCR reactor for passing exhaust gas through a T / C (Turbo Charger) through an SCR catalyst; A temperature sensor for sensing a temperature of the SCR reactor; An economizer for receiving high temperature engine cooling water discharged after circulating a cooling water circulation line in the engine and recovering exhaust gas heat at the front end of the T / C to produce steam from the engine cooling water; And an air heater for raising the temperature of the air by mutual heat exchange between steam and air produced in the economizer and supplying high-temperature air to the SCR reactor, wherein in the state that the inflow of exhaust gas into the SCR reactor is blocked, The temperature of the SCR reactor can be raised to the target temperature or higher through the hot air supplied from the SCR reactor.

The apparatus for maintaining the catalytic performance of the SCR system according to the present invention may further comprise a heater for heating the high temperature air supplied from the air heater to the SCR reactor to further increase the temperature.

The apparatus for maintaining the catalytic performance of the SCR system according to the present invention may further include a recirculation line for recirculating the air discharged from the SCR reactor back to the air heater.

The apparatus for maintaining the catalytic performance of the SCR system according to the present invention may further include a flow rate adjusting line connected to a downstream end of the SCR reactor to adjust an air flow rate through the SCR reactor.

The apparatus for maintaining the catalytic performance of the SCR system according to the present invention raises the temperature of the SCR reactor to more than the vaporization temperature of ABS (Ammonium Bisulfate: NH4HSO4) during the catalyst regeneration operation and controls the temperature of the SCR reactor to prevent condensation The temperature of the SCR reactor may be raised to a temperature higher than the preheating temperature for preventing condensation and for preparing the reactor to reactivate during the heating operation.

According to the apparatus for maintaining the catalytic performance of the SCR system according to the present invention, the energy required for maintaining the temperature in the SCR reactor at a constant temperature can be reduced to improve the thermal efficiency to prevent catalytic activity and reduction in strength.

Further, according to the apparatus for maintaining the catalytic performance of the SCR system according to the present invention, unnecessary catalyst poisoning due to exhaust gas can be minimized by using air rather than exhaust gas during catalyst regeneration, heating and venting operations.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of an SCR system to which a catalyst performance maintaining apparatus according to an embodiment of the present invention is applied; FIG.
BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a catalyst performance maintaining apparatus, and more particularly,

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an apparatus for maintaining the catalytic performance of an SCR system according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a diagram showing a schematic configuration of an SCR system to which a catalyst performance maintaining apparatus according to an embodiment of the present invention is applied.

1, the main exhaust line 10, the first bypass line 20, the SCR inflow line 30, the SCR outflow line 40, the second bypass line 50, Each of the lines 60 may include one or a plurality of valves as shown in the figure, and the flow of the exhaust gas can be controlled by selectively opening and closing the valves.

The exhaust gas receiver 110 collects the exhaust gas discharged from each cylinder of the engine 115 (the main engine and / or the view engine) and supplies it to the T / C (Turbo Charger) 120.

The exhaust gas generated from the engine is supplied to the T / C 120 through the exhaust gas receiver 110 to drive the T / C 120, and then to the main exhaust line 10 at the rear stage of the T / C 120 .

The T / C 120 rotates the turbine with the pressure of the exhaust gas of the engine 115 to supply fresh air to the engine 115.

For example, if the hot exhaust gas at the front end of the T / C 120 discharged from the engine 115 has a temperature of about 400 ° C to 450 ° C, the temperature of the hot exhaust gas passing through the T / Lt; RTI ID = 0.0 > 300 C. < / RTI >

The main exhaust line 10 is connected between the rear end of the T / C 120 and the SCR inflow line 30 to direct the exhaust gas passing through the T / C 120 to the SCR reactor 130 side.

The first bypass line 20 bypasses the exhaust gas discharged from the T / C 120 without passing through the SCR reactor 130. On the first bypass line 20, a bypass valve 25 is provided.

The exhaust gas flowing into the main exhaust line 10 flows into the SCR reactor 130 through the SCR inlet line 30 or is discharged through the first bypass line 20 without going through the SCR reactor 130.

That is, the exhaust gas that has passed through the T / C 120 selectively opens and closes the inlet valve 15 on the main exhaust line 10 and the bypass valve 25 on the first bypass line 20, (At the time of the SCR system stop) after being passed through the T / C 120 without passing through the SCR reactor 130 or through the reactor 130 (when the SCR system is operating).

An SCR catalyst (not shown) is installed in the SCR reactor 130 for the SCR catalytic reaction with the exhaust gas. At the front and rear ends of the SCR reactor 130, a passage of the exhaust gas flowing through the main exhaust line 10 And an inlet valve 15 and an outlet valve 41 for blocking are provided.

The SCR reactor 130 passes the exhaust gas flowing through the main exhaust line 10 and the SCR inlet line 30 to the SCR catalyst installed therein to reduce nitrogen oxides in the exhaust gas.

The urea hydrolysis chamber 180 hydrolyzes the urea injected into the interior thereof to produce an ammonia gas to be used as a reducing agent in exhaust gas treatment.

The urea hydrolysis heater 185 (electric heater, heater, etc.) applies heat to the urea hydrolysis chamber 180 during operation of the SCR system to raise the internal temperature of the urea hydrolysis chamber 180 to the hydrolysis reaction temperature.

Further, when the SCR system is stopped and the catalyst regeneration / heating / venting operation is performed, the urea hydrolysis heater 185 further heats the hot air heated by the air heater 160 to further raise the temperature .

The exhaust gas passing through the main exhaust line 10 and the ammonia gas discharged from the urea hydrolysis chamber 180 are mixed in the mixer 190 at the upstream side of the SCR reactor 130 and flow into the SCR reactor 130.

The mixer 190 serves to mix the ammonia produced in the urea hydrolysis chamber 180 with the engine exhaust gas and to be supplied to the SCR reactor 130.

The mixer 190 may be in the form of a chamber, or an AIG (Ammonia Injection Grid) may be installed in the form of a nozzle on the pipe wall of the main exhaust line 10 while a baffle or the like for flow uniformization may be installed inside the pipe It is possible.

The temperature sensor 135 is installed at the inlet of the SCR reactor 130 or inside the SCR reactor 130 to sense the temperature of the SCR reactor 130.

The second bypass line 50 receives part of the exhaust gas discharged from the engine 115 to the exhaust gas receiver 110 directly from the front end of the T / C 120 without going through the T / C 120.

The temperature of the exhaust gas downstream of the T / C 120 is relatively low (for example, approximately 190 to 300 ° C), whereas the temperature of the exhaust gas before the T / C 120 is relatively high (for example, about 400 to 450 ° C) The heat efficiency can be increased by utilizing the hot exhaust gas at the front end of the T / C 120 as a heat source.

The third bypass line 60 is branched from the second bypass line 50 and is connected to the T / C 120 through a part of the hot exhaust gas flowing into the second bypass line 50 from the exhaust gas receiver 110. [ Bypassed to the main exhaust line 10 without passing through.

The economizer 150 raises the temperature of the feed water to the waste heat of the exhaust gas and recovers the lost heat to produce steam of high temperature. The cooler 150 circulates a cooling water circulation line (not shown) in the engine 115 Temperature engine cooling water that is discharged after circulation, and heat-exchanges engine cooling water with exhaust gas generated in the engine 115 to generate steam.

In one embodiment, the economizer 150 is installed on a third bypass line 60 that receives a portion of the hot exhaust gas prior to the T / C 120, The heat of the gas is used to heat the engine coolant to produce steam.

The air heater 160 raises the temperature of the air by mutual heat exchange between the steam produced in the economizer 150 and the air sucked through the blower 170, and then supplies the heated air to the front end of the SCR reactor 130.

The blower 170 sucks the outside air and provides it to the air heater 160.

The operation of the SCR system configured as shown in FIG. 1 will be described below.

First, when the SCR system is in operation, a controller (not shown) closes the bypass valve 25 on the first bypass line 20 and opens the inlet valve 15 and the outlet valve 41 to open the T / C 120 are exhausted after passing through the SCR reactor 130. The exhaust gas flowing into the main exhaust line 10 from the T / C 120 passes through the SCR catalyst in the SCR reactor 130 and is exhausted after the nitrogen oxide reduction process.

On the other hand, when the SCR system is stopped (for example, in the case of running on the high seas), the controller opens the bypass valve 25 on the first bypass line 20 and opens the inlet valve 15 before and after the SCR reactor 130, And the outlet valve 41 are closed so that the exhaust gas discharged from the T / C 120 is discharged directly through the first bypass line 20 without passing through the SCR reactor 130.

In such an SCR system halt state, high temperature air may be supplied to the SCR reactor 130 to perform catalyst regeneration operation or heating operation or venting operation for preventing catalytic activity and strength reduction.

Temperature air supplied from the air heater 160 to the inside of the SCR reactor 130 in a state where the inflow of the exhaust gas into the SCR reactor 130 is blocked so that the temperature of the SCR reactor 130 is lower than a predetermined target temperature .

The engine cooling water is a liquid that cools the heat generated in the engine 115 by circulating the cooling water circulation line in the engine 115. The cooling water is circulated through the cooling water circulation line and then discharged to a state do.

The engine cooling water discharged in a heated state through the cooling water circulation line flows into the economizer 150.

The controller drives the blower 170 to supply the outside air to the air heater 160 while blocking the inflow of the exhaust gas into the SCR reactor 130 and to supply a part of the hot exhaust gas collected in the exhaust gas receiver 110 Bypassed to the third bypass line 60 without going through the T / C 120.

To this end, the first bypass valve 51 on the second bypass line 50 is opened, the second bypass valve 52 is shut off, and the first and second bypass valves 51 and 52 on the third bypass line 60 are opened. The pass valves 61 and 62 are opened and the third bypass valve 63 is closed.

In this state, a part of the hot exhaust gas at the front end of the T / C 120 passes through the third bypass line 60.

The economizer 150 uses hot exhaust gas (for example, about 400 to 450 ° C.) passing through the third bypass line 60 as a heat source by receiving exhausted engine cooling water (for example, about 100 ° C.) The steam of the exhaust gas is produced by the heat of the exhaust gas.

The steam produced in the economizer 150 is delivered to the air heater 160.

The air heater 160 increases the temperature of the air through heat exchange between the steam produced in the economizer 150 and the air sucked through the blower 170. The high temperature air heated by the air heater 160 is supplied to the SCR reactor 130 ) To raise the temperature of the SCR reactor 130 to a required predetermined target temperature or higher.

At this time, according to the embodiment, a heater (an electric heater, a burner, etc.) may be additionally provided so as to further heat the hot air having the increased temperature through the air heater 160 to further raise the temperature.

For example, since the target temperature (for example, 340 ° C) during the catalyst regeneration operation is higher than the target temperature (for example, 200 ° C) of the heating and venting operations, the target temperature can be achieved by utilizing the heater during the catalyst regeneration operation.

In the case of the embodiment shown in FIG. 1, the heater 185 for urea hydrolysis may be used as an auxiliary heat source, and the hot air supplied from the air heater 160 to the SCR reactor 130 may be heated to further raise the temperature.

The target temperature of the SCR reactor 130 may be set differently for each of the catalyst regeneration / heating / venting operations.

During the catalyst regeneration operation, the high temperature air supplied from the air heater 160 is applied to the inside of the SCR reactor 130 to decompose and remove the ABS to perform the catalyst regeneration. In this case, the target temperature of the SCR reactor may be set above the vaporization temperature of the ABS (e.g., above 340 캜).

The heating operation is for maintaining the internal temperature of the SCR reactor 130 at a predetermined temperature or more in a state in which the inlet valve 15 and the outlet valve 41 before and after the SCR reactor 130 are closed and mainly causes internal corrosion To prevent condensation of the exhaust gas and to prepare the reactors for re-operation.

The temperature of the SCR reactor 130 is controlled to be higher than the exhaust gas temperature by using the high temperature air supplied from the air heater 160 during the heating operation (for example, before entering the ECA (Emission Control Area) (For example, about 100 deg. C, preferably 200 deg. C or higher) for preventing condensation and preparing for reactivation of the reactor.

The ventilation operation continuously injects air of high temperature and high pressure to blow foreign substances such as sulfuric acid adhered to the SCR catalyst in the SCR reactor 130. In the venting operation, The temperature of the SCR reactor 130 may be raised to a dew point temperature or more (for example, about 100 캜, preferably 200 캜 or more) for preventing exhaust gas condensation so that exhaust gas condensation does not occur have.

The above-described heating and venting operations may be performed simultaneously.

When engine exhaust gas is used during catalyst regeneration, heating and venting operation, catalyst poisoning may be promoted due to sulfur (P) or phosphorus (P) components in the exhaust gas. On the contrary, if air other than exhaust gas Unnecessary poisoning of the catalyst can be prevented originally.

In addition, by reusing the cooling water to a certain extent and reusing the cooled water to a certain extent, the air heated by the heat exchange with hot exhaust gas is supplied to the SCR reactor 130 and used as a heat source for raising the temperature of the SCR reactor 130, The heat efficiency can be increased.

In the meantime, the embodiment of FIG. 1 constitutes an open loop for performing heat exchange between the air and the steam generated by the engine coolant and the exhaust gas waste heat in the economizer 150.

In the case of constructing such an open loop, a SCR outlet line 40 and a flow rate regulating line 45 branching off may be provided at the rear end of the SCR reactor 130.

The flow rate control line 45 is connected to the rear end of the SCR reactor 130 to regulate the air flow rate through the SCR reactor 130.

At this time, it is effective to configure the flow rate control line 45 as a small-sized pipe having a diameter smaller than that of the SCR outlet line 40 so as to be capable of controlling the minute flow rate.

Then, in the catalyst regeneration / heating / venting operation of the SCR reactor 130, when the outlet valve 41 on the SCR outlet line 40 is closed, the flow regulating valve 46 on the flow regulating line 45 is throttled, It is possible to more effectively perform the flow rate adjustment operation such as mooring the air in the SCR reactor 130 for a certain period of time or flowing it little by little.

FIG. 2 is a schematic view showing an SCR system to which a catalyst performance maintaining apparatus according to another embodiment of the present invention is applied.

In contrast to the open loop shown in one embodiment of FIG. 1, another embodiment of FIG. 2 comprises a closed loop that performs heat exchange between steam and air produced by the engine coolant and waste heat from the economizer 150 will be.

1, the exhaust gas passing through the T / C 120 is discharged through the T / C 120, the main exhaust line 10, the first bypass line 20, and the T / A portion of the hot exhaust gas at the front end of C (120) passes through the third bypass line (60).

The engine cooling water that is circulated through the cooling circulation line in the engine 115 flows into the economizer 150 on the third bypass line 60 and is used as a heat medium and the economizer 150 operates, And the third bypass line (60).

The generated steam is applied to the air heater 160 to raise the temperature of the air and the heated air is applied to the SCR reactor 130 to raise the temperature of the SCR reactor 130.

The same reference numerals are used for the other components corresponding to those in Fig. 1, and a detailed description thereof will be omitted.

2, the recirculation line 70 connected to the SCR outlet line 40 is provided and the inlet valve 15 and the outlet valve 41 before and after the SCR reactor 130 are closed The air exiting the SCR reactor 130 is recirculated back to the air heater 160 by the blower 270 installed in the recirculation line 70 and the recirculation line 70 (during the SCR system shutdown).

One end of the recirculation line 70 is connected to the upstream side of the outlet valve 41 of the SCR outlet line 40 and the other end of the recirculation line 70 is connected to the air heater 160 to circulate the air discharged from the SCR reactor 130 to the air heater 160. [ Thereby allowing the air passing through the SCR reactor 130 to be circulated back to the SCR reactor 130 through the air heater 160.

Recirculation valve 75 is installed in recirculation line 70 and is opened during catalyst regeneration / heating / venting operation under the control of a controller (not shown).

The blower 270 is installed in the recirculation line 70 and is driven during the catalyst regeneration / heating / venting operation under the control of the controller to supply the outside air to the air heater 160, and at the same time, To be introduced into the air heater 160 through the recirculation line 70.

In this manner, heat loss can be minimized during the catalyst regeneration / heating / venting operation by the closed loop, which is recycled through the SCR reactor 130 to reuse the air.

The configuration of the apparatus for maintaining the catalytic performance of the SCR system according to the present invention is not limited to the embodiments described above and can be variously modified within the scope of the technical idea of the present invention.

10: main exhaust line, 30: SCR inflow line,
40: SCR outlet line, 45: Flow control line,
20, 50, 60: bypass line, 70: recirculation line,
110: exhaust gas receiver, 120: T / C (Turbo Charger)
130: SCR reactor, 135: temperature sensor,
150: economizer, 160: air heater,
170, 270: blower, 180: urea decomposition chamber,
185: heater for urea hydrolysis, 190: mixer

Claims (5)

An SCR reactor for passing exhaust gas through a T / C (Turbo Charger) through an SCR catalyst;
A temperature sensor for sensing a temperature of the SCR reactor;
An economizer for receiving high temperature engine cooling water discharged after circulating a cooling water circulation line in the engine and recovering exhaust gas heat at the front end of the T / C to produce steam from the engine cooling water; And
And an air heater for raising the temperature of the air by mutual heat exchange between steam and air produced in the economizer and supplying high temperature air to the SCR reactor,
Wherein the temperature of the SCR reactor is raised to a target temperature or higher through the high temperature air supplied from the air heater in a state where the exhaust gas is prevented from flowing into the SCR reactor.
The method according to claim 1,
Further comprising a heater for heating the high temperature air supplied from the air heater to the SCR reactor to further increase the temperature of the SCR reactor.
The method according to claim 1,
And a recirculation line for recirculating air discharged from the SCR reactor to the air heater again.
The method according to claim 1,
Further comprising a flow rate control line connected to a downstream end of the SCR reactor to regulate a flow rate of air passing through the SCR reactor.
The method according to claim 1,
During the catalyst regeneration operation, the temperature of the SCR reactor is raised above the vaporization temperature of ABS (Ammonium Bisulfate: NH4HSO4)
The temperature of the SCR reactor is raised above the dew point temperature for preventing condensation during the venting operation,
Wherein the temperature of the SCR reactor is raised to a temperature equal to or higher than a preheating temperature for preventing condensation and preparing for reactivation of the reactor during heating operation.

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