APPARATUS FOR REDUCING GREENHOUSE GAS EMISSION IN VESSEL AND VESSEL INCLUDING THE SAME

Abstract

The present invention relates to an apparatus for reducing greenhouse gas emission in a vessel, and a vessel including the same, which are capable of satisfying IMO greenhouse gas emission regulations by separating and discharging NO.sub.x, SO.sub.x, and CO.sub.2 from exhaust gas exhausted from a vessel engine and increasing CO.sub.2 solubility and CO.sub.2 removal efficiency by removing CO.sub.2 after removing SO.sub.x.

Claims

1. An apparatus for reducing greenhouse gas emission in a vessel, the apparatus comprising: a seawater supply unit that supplies seawater; an ammonia water producing unit that reacts fresh water with NH.sub.3 to produce and supply ammonia water; an absorption tower comprising a CO.sub.2 removing unit that cools exhaust gas discharged from a vessel engine by reacting the exhaust gas with the seawater supplied from the seawater supply unit, and removes CO.sub.2 by reacting the cooled exhaust gas with the ammonia water supplied from the ammonia water producing unit to convert CO.sub.2 into NH.sub.4HCO.sub.3(aq); and an ammonia recycling unit that recycles NH.sub.3 by reacting NH.sub.4HCO.sub.3(aq) discharged from the absorption tower with Ca(OH).sub.2 or Mg(OH).sub.2, and returns the recycled NH.sub.3 back to the ammonia water producing unit.

2. The apparatus according to claim 1, wherein the absorption tower further comprises a NO.sub.x absorbing unit that absorbs and removes NO.sub.x of the exhaust gas discharged from the vessel engine, the CO.sub.2 removing unit cools the exhaust gas, from which the NO.sub.x is removed, by reacting the exhaust gas with the seawater supplied from the seawater supply unit, and removes CO.sub.2 by reacting the cooled exhaust gas with the ammonia water supplied from the ammonia water producing unit to convert CO.sub.2 into NH.sub.4HCO.sub.3(aq), and the ammonia recycling unit recycles NH.sub.3 and returns the recycled NH.sub.3 back to the ammonia water producing unit and the NO.sub.x absorbing unit.

3. The apparatus according to claim 1, wherein the absorption tower further comprises a SO.sub.x absorbing unit that dissolves and removes SO.sub.x while cooling the exhaust gas discharged from the vessel engine by reacting the exhaust gas with the seawater supplied from the seawater supply unit, and the CO.sub.2 removing unit removes CO.sub.2 by reacting the exhaust gas, from which the SO.sub.x is removed, with the ammonia water supplied from the ammonia water producing unit to convert CO.sub.2 into NH.sub.4HCO.sub.3(aq).

4. The apparatus according to claim 1, wherein, in the absorption tower, a NO.sub.x absorbing unit that absorbs and removes NO.sub.x from the exhaust gas discharged from the vessel engine, a SO.sub.x absorbing unit that dissolves and removes SO.sub.x while cooling the exhaust gas, from which the NO.sub.x has been removed, through reaction with the seawater supplied from the seawater supply unit, and the CO.sub.2 removing unit that removes CO.sub.2 by reacting the exhaust gas, from which the SO.sub.x has been removed, with the ammonia water supplied from the ammonia water producing unit to convert CO.sub.2 into NH.sub.4HCO.sub.3(aq) are stacked, and the ammonia recycling unit recycles NH.sub.3 and returns the recycled NH.sub.3 back to the ammonia water producing unit and the NO.sub.x absorbing unit.

5. (canceled)

6. The apparatus according to claim 1, wherein the ammonia water producing unit comprises: a fresh water tank that stores fresh water; a fresh water pump that pumps and supplies the fresh water from the fresh water tank; an ammonia water production tower comprising a tower tank, a NH.sub.3 spray nozzle that is formed at a lower end of the tower tank and sprays NH.sub.3 upward, a fresh water spray nozzle that is formed at an upper end of the tower tank and sprays the fresh water from the fresh water pump downward, a first packing material that is formed between the NH.sub.3 spray nozzle and the fresh water spray nozzle and contacts the fresh water with NH.sub.3 to dissolve NH.sub.3 and generate ammonia water, and a cooling jacket that cools heat generated by the tower tank due to a dissolution reaction; and an ammonia water pump that supplies ammonia water from an ammonia water storage tank, which stores ammonia water drained to a lower end of the ammonia water production tower, to an upper end of the CO.sub.2 removing unit.

7. The apparatus according to claim 6, wherein the ammonia water production tower comprises a mist removal plate that is formed at the upper end of the tower tank in a curved multi-plate shape and returns mist scattered from the fresh water toward the first packing material.

8. The apparatus according to claim 6, further comprising a NH.sub.3 supply pipe through which NH.sub.3 exhausted to the upper end of the ammonia water production tower is supplied to an lower end of the CO.sub.2 removing unit.

9. The apparatus according to claim 6, wherein the first packing material comprises multi-stage distilling column packings designed to increase a contact area per unit volume.

10. The apparatus according to claim 9, wherein a solution redistributor is formed between the multi-stage distilling column packings.

11. The apparatus according to claim 6, wherein a diameter and a height of the tower tank are designed so that a flow velocity of the fresh water and a flow velocity of the NH.sub.3 are ½ of a flooding velocity.

12. The apparatus according to claim 6, wherein the loss and lack of NH.sub.3 are compensated for by supplying NH.sub.3 from the ammonia recycling unit through the NH.sub.3 spray nozzle of the ammonia water producing unit or supplying NH.sub.3 from a separate NH.sub.3 storage tank when the loss and lack of NH.sub.3 occur.

13. The apparatus according to claim 2, wherein the NO.sub.x absorbing unit directly receives NH.sub.3 from the ammonia recycling unit through a blower or a compressor and sprays the received NH.sub.3 to a first NH.sub.3 spray nozzle, or when NH.sub.3 is insufficient, the NO.sub.x absorbing unit receives urea water of a urea water storage tank through a urea water supply pump and sprays the received urea water to a second NH.sub.3 spray nozzle so as to compensate for the lack of NH.sub.3.

14-17. (canceled)

18. The apparatus according to claim 6, wherein the CO.sub.2 removing unit comprises: an ammonia water spray nozzle that is connected to the ammonia water pump and sprays ammonia water downward; a second packing material that contacts CO.sub.2 with the ammonia water and converts CO.sub.2 into NH.sub.4HCO.sub.3(aq); a cooling jacket that is formed in multi-stages for each section of an absorption apparatus filled with the second packing material and cools heat generated by a CO.sub.2 removal reaction; a water spray that collects NH.sub.3 discharged to the outside without reacting with CO.sub.2; a mist removal plate that is formed in a curved multi-plate shape and returns the ammonia water toward the second packing material; a partition wall that is formed so that the ammonia water does not flow backward; and an umbrella-shaped blocking plate that covers an exhaust gas inlet hole of the partition wall.

19. The apparatus according to claim 4, wherein the absorption tower further comprises an exhaust gas economizer (EGE) that is formed between the NO.sub.x absorbing unit and the SO.sub.x absorbing unit and performs heat exchange between waste heat of the vessel engine and boiler water.

20. (canceled)

21. The apparatus according to claim 6, wherein the ammonia recycling unit comprises: a Ca(OH).sub.2 storage tank that stores Ca(OH).sub.2; a mixing tank in which NH.sub.4HCO.sub.3(aq) discharged from the absorption tower is stirred with Ca(OH).sub.2 by an agitator to generate CaCO.sub.3(s) and H.sub.2O and NH.sub.3(g) is recycled; a filter that suctions a solution and precipitate from the mixing tank and separates CaCO.sub.3(s); a high-pressure pump that transfers the solution and precipitate to the filter at high pressure; and a CaCO.sub.3(s) storage tank that stores a slurry or CaCO.sub.3(s) of a solid state.

22. The apparatus according to claim 6, wherein the ammonia recycling unit comprises: a Mg(OH).sub.2 storage tank that stores Mg(OH).sub.2; a mixing tank in which NH.sub.4HCO.sub.3(aq) discharged from the absorption tower is stirred with Mg(OH).sub.2 by an agitator to generate MgCO.sub.3(s) and H.sub.2O and NH.sub.3(g) is recycled; a filter that suctions a solution and precipitate from the mixing tank and separates MgCO.sub.3(s); a high-pressure pump that transfers the solution and precipitate to the filter at high pressure; and a MgCO.sub.3(s) storage tank that stores a slurry or MgCO.sub.3(s) of a solid state.

23. The apparatus according to claim 21, wherein ammonia water or fresh water separated by the filter is supplied to the ammonia water producing unit, or excess ammonia water or excess fresh water additionally generated by the mixing tank compared to a total circulating fresh water is stored in the fresh water tank.

24-25. (canceled)

26. The apparatus according to claim 1, further comprising a discharge unit comprising: a cleaning water tank that stores cleaning water discharged from the absorption tower; a water treatment device comprising a filtering unit that controls turbidity to satisfy an outboard discharge condition of the cleaning water transferred to the cleaning water tank by a transfer pump, and a neutralizing agent injecting unit that controls pH; and a sludge storage tank that separates and stores solid emissions.

27. (canceled)

28. The apparatus according to claim 4, wherein the NO.sub.x absorbing unit directly receives NH.sub.3 from the ammonia recycling unit through a blower or a compressor and sprays the received NH.sub.3 to a first NH.sub.3 spray nozzle, or when NH.sub.3 is insufficient, the NO.sub.x absorbing unit receives urea water of a urea water storage tank through a urea water supply pump and sprays the received urea water to a second NH.sub.3 spray nozzle so as to compensate for the lack of NH.sub.3.

29. The apparatus according to claim 22, wherein ammonia water or fresh water separated by the filter is supplied to the ammonia water producing unit, or excess ammonia water or excess fresh water additionally generated by the mixing tank compared to a total circulating fresh water is stored in the fresh water tank.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] FIG. 1 is a schematic configuration diagram of an apparatus for reducing greenhouse gas emission in a vessel, according to an embodiment of the present invention.

[0039] FIG. 2 is a circuit diagram of a system implementing the apparatus for reducing greenhouse gas emission in a vessel, illustrated in FIG. 1.

[0040] FIG. 3 separately illustrates a seawater supply unit of the apparatus for reducing greenhouse gas emission in a vessel, illustrated in FIG. 2.

[0041] FIG. 4 separately illustrates an ammonia water producing unit of the apparatus for reducing greenhouse gas emission in a vessel, illustrated in FIG. 2.

[0042] FIG. 5 separately illustrates an absorption tower of the apparatus for reducing greenhouse gas emission in a vessel, illustrated in FIG. 2.

[0043] FIG. 6 separately illustrates a SO.sub.x absorbing unit of the absorption tower of FIG. 5.

[0044] FIG. 7 separately illustrates a steam generating unit of the apparatus for reducing greenhouse gas emission in a vessel, illustrated in FIG. 2.

[0045] FIG. 8 separately illustrates an ammonia recycling unit and an ammonia water producing unit of the apparatus for reducing greenhouse gas emission in a vessel, illustrated in FIG. 2.

[0046] FIG. 9 illustrates various packing materials applied to the apparatus for reducing greenhouse gas emission in a vessel, illustrated in FIG. 2.

DETAILED DESCRIPTION OF THE INVETION

[0047] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that the present invention can be easily carried out by those of ordinary skill in the art. The present invention may be embodied in many different forms and is not limited to embodiments of the present invention described herein.

[0048] An apparatus for reducing greenhouse gas emission in a vessel, according to an embodiment of the present invention, includes: a seawater supply unit that supplies seawater; an ammonia water producing unit that reacts fresh water with NH.sub.3 to produce and supply ammonia water; an absorption tower including a CO.sub.2 removing unit that cools exhaust gas discharged from a vessel engine by reacting the exhaust gas with the seawater supplied from the seawater supply unit, and removes CO.sub.2 by reacting the cooled exhaust gas with the ammonia water supplied from the ammonia water producing unit to convert CO.sub.2 into NH.sub.4HCO.sub.3(aq); and an ammonia recycling unit that recycles NH.sub.3 by reacting NH.sub.4HCO.sub.3(aq) discharged from the absorption tower with Ca(OH).sub.2 or Mg(OH).sub.2, and returns the recycled NH.sub.3 back to the ammonia water producing unit.

[0049] At this time, according to the type and specification of the engine (low-pressure engine or high-pressure engine) and the type of fuel supplied to the engine (HFO, MDO, MGO, LNG, ammonia, etc.), the absorption tower may optionally include both the NO.sub.x absorbing unit and the SO.sub.x absorbing.

[0050] In particular, with respect to the SO.sub.x absorbing unit, as described later, since SO.sub.x may be dissolved by reacting with seawater, cooling of exhaust gas and absorption of SO.sub.x may be performed at once.

[0051] On the other hand, according to another embodiment of the present invention, a vessel including the apparatus for reducing greenhouse gas emission may be provided.

[0052] Hereinafter, an embodiment in which the NO.sub.x absorbing unit, the SO.sub.x absorbing unit, and the CO.sub.2 removing unit are stacked on the absorption tower will be described, but the present invention is not limited thereto. As described above, the NO.sub.x absorbing unit and/or the SO.sub.x absorbing unit may or may not be included according to the types of engine and fuel.

[0053] An apparatus for reducing greenhouse gas emission in a vessel, according to an embodiment of the present invention, includes: a seawater supply unit 110 that supplies seawater; an ammonia water producing unit 120 that reacts fresh water with NH.sub.3 to produce and supply ammonia water; an absorption tower 130 including a CO.sub.2 removing unit 133 that cools exhaust gas discharged from a vessel engine 10 by reacting the exhaust gas with the seawater supplied from the seawater supply unit 110, and removes CO.sub.2 by reacting the cooled exhaust gas with the ammonia water supplied from the ammonia water producing unit 120 to convert CO.sub.2 into NH.sub.4HCO.sub.3(aq); and an ammonia recycling unit 140 that recycles NH.sub.3 by reacting NH.sub.4HCO.sub.3(aq) discharged from the absorption tower 130 with Ca(OH).sub.2 or Mg(OH).sub.2, and returns the recycled NH.sub.3 back to the ammonia water producing unit 120. It is possible to satisfy IMO greenhouse gas emission regulations by separating and discharging NO.sub.x, SO.sub.x, and CO.sub.2 from exhaust gas, increase CO.sub.2 removal efficiency by removing CO.sub.2 after removing SO.sub.x, and removing side reactions caused by SO.sub.x remaining during NH.sub.3 removal, thereby preventing impurities from being included during ammonia recovery.

[0054] Hereinafter, the apparatus for reducing greenhouse gas emission in the vessel will be described in detail with reference to FIGS. 1 to 9.

[0055] First, a seawater supply unit 110 supplies seawater to a SO.sub.x absorbing unit 132 of an absorption tower 130. Specifically, as illustrated in FIGS. 2 and 3, the seawater supply unit 110 may include: seawater pumps 111a and 111b that suction seawater from the outside of the vessel through a sea chest (not illustrated) and pump the seawater to the SO.sub.x absorbing unit 132; and a control valve 112 that controls a flow rate of the seawater supplied from the seawater pumps 111a and 111b according to the amount of exhaust gas. Here, the seawater pumps 111a and 111b may include a suction pump 111a that suctions seawater from the outside of the vessel and a seawater transfer pump 111b that pumps and transfers seawater to the SO.sub.x absorbing unit 132.

[0056] For reference, when the vessel is berthing or sailing, seawater may be selectively supplied to the seawater pumps 111a and 111b from a high sea chest that suctions upper seawater or a low sea chest that suctions lower seawater according to the depth of water. That is, when the vessel is berthing, the high sea chest may be used because the upper seawater is cleaner than the lower seawater, and when the vessel is sailing, the low sea chest may be used because the lower seawater is cleaner than the upper seawater.

[0057] Here, the control valve 112 may be a manually operated diaphragm valve or a solenoid type valve that controls the flow rate of seawater, but the present invention is not limited thereto. Any type of valve may be applied as long as the amount of seawater injected through a seawater spray nozzle 132a can be controlled according to the amount of exhaust gas.

[0058] Next, an ammonia water producing unit 120 reacts fresh water with NH.sub.3 recycled or replenished when insufficient to produce and supply ammonia water (NH.sub.4OH(aq)).

[0059] Specifically, as illustrated in FIGS. 2 and 4, the ammonia water producing unit 120 may include: a fresh water tank 121 that stores fresh water; a fresh water pump 122 that pumps and supplies the fresh water from the fresh water tank 121; an ammonia water production tower 123 including a tower tank 123a, a NH.sub.3 spray nozzle 123b that is formed at a lower end of the tower tank 123a and sprays NH.sub.3 upward, a fresh water spray nozzle 123c that is formed at an upper end of the tower tank 123a and sprays the fresh water from the fresh water pump 122 downward, a packing material 123d that is formed between the NH.sub.3 spray nozzle 123b and the fresh water spray nozzle 123c and contacts the fresh water with NH.sub.3 to dissolve NH.sub.3 and generate ammonia water, and a cooling jacket 123e that cools heat generated by the tower tank 123a due to the dissolution reaction based on the following [Chemical Formula 1]; and an ammonia water pump 124 that supplies ammonia water from an ammonia water storage tank 124a, which stores the ammonia water drained to a lower end of the ammonia water production tower 123, to an ammonia water spray nozzle 133a, which is formed at an upper end of a CO.sub.2 removing unit 133.

NH.sub.3+H.sub.2O->NH.sub.4OH(aq), (exothermic reaction, 1650 MJ/ton)   [Chemical Formula 1]

[0060] Here, the fresh water tank 121 may store distilled water produced on board or fresh water (or ammonia water) separated when CaCO.sub.3 or MgCO.sub.3 is separated by a filter 144 and transferred to the ammonia water production tower 123, that is, surplus fresh water additionally produced through a mixing tank 143 and the filter 144 compared to the total circulating fresh water required for ammonia water production and NH.sub.3 recycling (see FIG. 8).

[0061] On the other hand, referring to FIG. 4, the ammonia water production tower 123 may further include a mist removal plate 123f that is formed at an upper end of the fresh water spray nozzle 123c disposed at the upper end of the tower tank 123a in a curved multi-plate shape and returns mist scattered from the fresh water toward the packing material 123d. Since the fresh water may be discharged to the outside through the exhaust gas, the mist may collide with the curved portion so that droplets become larger, and the water may be discharged toward the lower packing material 123d.

[0062] In addition, the ammonia water production tower 123 may further include a NH.sub.3 supply pipe 123g through which NH.sub.3(g) exhausted to the upper end of the ammonia water production tower 123 is supplied to the lower end of the CO.sub.2 removing unit 133. Excess NH.sub.3(g) that is not dissolved and exhausted is absorbed into the ammonia water flowing down through the CO.sub.2 removing unit 133, thereby minimizing the loss of NH.sub.3.

[0063] On the other hand, when the lack of NH.sub.3 occurs or the loss of NH.sub.3 itself occurs because the amount of NH.sub.3 recycled by the ammonia recycling unit 140 is insufficient to produce ammonia water by the ammonia water production tower 123 or supply NH.sub.3 to a first NH.sub.3 spray nozzle 131b of a NO.sub.x absorbing unit 131, a separate NH.sub.3 storage tank 123h may be provided to supply NH.sub.3 so as to compensate for the loss and lack of NH.sub.3. That is, NH.sub.3 may be directly supplied from the ammonia recycling unit 140 to the NH.sub.3 spray nozzle 123b of the ammonia water producing unit 120, or NH.sub.3 may be directly supplied to the first NH.sub.3 spray nozzle 131b of the NO.sub.x absorbing unit 131 through a blower 131a or a compressor, or NH.sub.3 may be supplied from the NH.sub.3 storage tank 123h in the event of the loss or lack of NH.sub.3, thereby replacing the loss or lack of NH.sub.3.

[0064] In addition, the diameter and height of the tower tank 123a are preferably designed so that the flow velocity of fresh water and the flow velocity of NH.sub.3 are ½ of the flooding velocity. In this manner, in a state where NH.sub.3 is sprayed at a pressure slightly higher than atmospheric pressure through the NH.sub.3 spray nozzle 123b, the pressure drop may be offset in the wet state of the tower tank 123a.

[0065] In addition, the packing material 123d may include multi-stage distilling column packings designed to increase a contact area per unit volume. As illustrated in FIG. 9, a distilling column packing suitable for a process may be selected considering the contact area per unit area, the pressure drop of gas, and the flooding velocity.

[0066] On the other hand, a solution redistributor (not illustrated) may be formed between the multi-stage distilling column packings so as to prevent channeling of fresh water.

[0067] In addition, the ammonia water pump 124 may be provided with a centrifugal pump, so that a large amount of ammonia water is pumped and effectively supplied from the ammonia water production tower 123 to the CO.sub.2 removing unit 133.

[0068] In addition, the cooling jacket 123e may be cooled so that the reaction temperature of the dissolution reaction is maintained at 30° C. to 50° C., considering the solubility of NH.sub.3.

[0069] Next, as illustrated in FIGS. 2 and 5, in the absorption tower 130, a NO.sub.x absorbing unit 131 that absorbs and removes NO.sub.x from exhaust gas discharged from the vessel engine 10 of the main engine or power generation engine, a SO.sub.x absorbing unit 132 that dissolves and removes SO.sub.x while cooling exhaust gas, from which NO.sub.x has been removed, through reaction with seawater, and a CO.sub.2 removing unit 133 that removes CO.sub.2 by reacting the exhaust gas, from which SO.sub.x has been removed, with the ammonia water supplied from the ammonia water producing unit 120 to convert CO.sub.2 into NH.sub.4HCO.sub.3(aq) are stacked in the vertical direction to sequentially absorb and remove NO.sub.x, SO.sub.x, and CO.sub.2.

[0070] Here, the absorption tower 130 may include the NO.sub.x absorbing unit 131, the SO.sub.x absorbing unit 132, the CO.sub.2 removing unit 133, and an exhaust gas economizer (EGE) 134 to be described later, may be modularized and combined with individual modules, and may be integrated in a single tower form, or the absorption tower 130 itself may include a single tower or a plurality of towers.

[0071] Specifically, the NO.sub.x absorbing unit 131 is a selective catalyst reactor (SCR). The NO.sub.x absorbing unit 131 may directly receive NH.sub.3 from the ammonia recycling unit 140 through the blower 131a or the compressor and spray the received NH.sub.3 to the first NH.sub.3 spray nozzle 131b, or when NH.sub.3 is insufficient, the NO.sub.x absorbing unit 131 may receive urea water of a urea water storage tank 131c through a urea water supply pump 131d and spray the received urea water to a second NH.sub.3 spray nozzle 131e so as to compensate for the lack of NH.sub.3.

[0072] Here, since NH.sub.3 and CO.sub.2 are generated when the urea water is decomposed, it may be preferable that NH.sub.3 is directly supplied to reduce the amount of CO.sub.2 generated, and a NO.sub.N sensor 131f (see FIG. 5) that senses NO.sub.x concentration may be formed at the upper end of the NO.sub.x absorbing unit 131.

[0073] In addition, the SO.sub.x absorbing unit 132 is a section that is in primary contact with seawater and includes a multi-stage seawater spray nozzle 132a that is connected to the control valve 112 and sprays seawater downward. The SO.sub.x absorbing unit 132 may dissolve SO.sub.x, remove dusts such as soot, and cool the temperature of the exhaust gas to 27° C. to 33° C., preferably about 30° C., which is required by the CO.sub.2 removing unit 133, through the seawater spray nozzle 132a or a separate cooling jacket (not illustrated).

[0074] On the other hand, as illustrated in FIG. 6(a), porous upper plates 132b having a passage through which exhaust gas passes may be respectively formed in multi-stages under the seawater spray nozzle 132a, so that the seawater and the exhaust gas come into smooth contact with each other. As illustrated in FIG. 6(b), an absorption apparatus 132c filled with a packing material for allowing seawater and exhaust gas to come into contact with each other may be respectively formed under the seawater spray nozzle 132a, so that the seawater dissolves SO.sub.x.

[0075] On the other hand, a closed loop system may be applied to add a compound forming alkali ions, for example, a basic chemical of NaOH or MgO, in order to further increase the solubility of SO.sub.x.

[0076] For reference, the closed loop system involves additional consumption of basic chemicals, but has an advantage that the amount of circulating seawater is small, and the open loop system that discharges SO.sub.x dissolved by spraying only seawater to the outside of the vessel has no additional consumption of basic chemicals and is simple. In order to maximize these advantages, a hybrid system in which the open loop system and the closed loop system are combined may be applied.

[0077] In this regard, by removing SO.sub.x through the SO.sub.x absorbing unit 132 and then removing CO.sub.2 through the CO.sub.2 removing unit 133, it is possible to solve the problem that it is difficult to remove CO.sub.2 until SO.sub.x is completely dissolved because the solubility of SO.sub.x is high and thus SO.sub.x is first changed to a compound such as NaSO.sub.3, thereby improving the solubility of CO.sub.2 and the removal efficiency of CO.sub.2.

[0078] Here, cleaning water drained from a discharge unit 160 by the SO.sub.x absorbing unit 132 contains SO.sub.3.sup.−, SO.sub.4.sup.2−, soot, NaSO.sub.3, NaSO.sub.4, MgCO.sub.3, MgSO.sub.4, and other ionic compounds together, and the SO.sub.x absorbing unit 132 may include an umbrella-shaped partition wall 132e that covers an exhaust gas inlet pipe 132d so that the cleaning water does not flow back to the NO.sub.x absorbing unit 131 or the EGE 134.

[0079] In addition, as illustrated in FIGS. 4 and 5, the CO.sub.2 removing unit 133 may include: an ammonia water spray nozzle 133a that is connected to the ammonia water pump 124 and sprays ammonia water downward; a packing material 133b that contacts CO.sub.2 with the ammonia water and converts CO.sub.2 into NH.sub.4HCO.sub.3(aq) based on the following [Chemical Formula 2]; a cooling jacket (not illustrated) that is formed in multi-stages for each section of the absorption apparatus filled with the packing material 133b and cools heat generated by a CO.sub.2 removal reaction to maintain the heat at 30° C. to 50° C.; a water spray 133c that collects NH.sub.3 discharged to the outside without reacting with CO.sub.2; a mist removal plate 133d that is formed in a curved multi-plate shape and returns the ammonia water to the packing material 133b; a partition wall 133e that is formed so that the ammonia water does not flow back to the SO.sub.x absorbing unit 132; and an umbrella-shaped blocking plate 133f that covers an exhaust gas inlet hole 133e-1 of the partition wall 133e.

2NH.sub.4OH+CO.sub.2->(NH.sub.4).sub.2CO.sub.3+H.sub.2O

(NH.sub.4).sub.2CO.sub.3+CO.sub.2+H.sub.2O->2NH.sub.4HCO.sub.3   [Chemical Formula 2]

[0080] Here, since the CO.sub.2 removing unit 133 removes CO.sub.2 by reacting the ammonia water with the exhaust gas from which NO.sub.x and SO.sub.x have been removed, side reactions caused by NO.sub.x and SO.sub.x do not occur during the CO.sub.2 removal process, thereby minimizing the occurrence of impurities and obtaining NH.sub.4HCO with less impurities in a subsequent process.

[0081] In addition, the packing material 133b may include multi-stage distilling column packings designed to increase a contact area per unit volume. As illustrated in FIG. 9, a distilling column packing suitable for a process may be selected considering the contact area per unit area, the pressure drop of gas, and the flooding velocity.

[0082] On the other hand, the absorption tower 130 may further include an EGE 134 that is formed between the NO.sub.x absorbing unit 131 and the SO.sub.x absorbing unit 132 and performs heat exchange between waste heat of the vessel engine 10 and boiler water.

[0083] Next, the ammonia recycling unit 140 reacts NH.sub.4HCO.sub.3(aq) discharged from the absorption tower 130 with Ca(OH).sub.2 or Mg(OH).sub.2 to recycle NH.sub.3, returns NH.sub.3 back to the ammonia water producing unit 120 and the NO.sub.x absorbing unit 131 so as to reuse NH.sub.3, and stores or discharges CO.sub.2 in the form of CaCO.sub.3(s) or MgCO.sub.3(s).

[0084] Specifically, as illustrated in FIGS. 2 and 8, the ammonia recycling unit 140 may include: a Ca(OH).sub.2 storage tank 141 or a Mg(OH).sub.2 storage tank 141 that stores Ca(OH).sub.2 or Mg(OH).sub.2; a mixing tank 143 in which NH.sub.4HCO.sub.3(aq) discharged from the CO.sub.2 removing unit 133 of the absorption tower 130 is stirred with Ca(OH).sub.2 or Mg(OH).sub.2 by an agitator 142 to generate CaCO.sub.3(s) or MgCO.sub.3(s) and H.sub.2O based on the following [Chemical Formula 3] or [Chemical Formula 4] and NH.sub.3(g) is recycled; a filter 144 that suctions a solution and precipitate from the mixing tank 143 and separates CaCO.sub.3(s) or MgCO.sub.3(s); a high-pressure pump 145 that transfers the solution and precipitate to the filter 144 at high pressure; and a CaCO.sub.3(s) storage tank (not illustrated) or a MgCO.sub.3(s) storage tank (not illustrated) that stores a slurry or CaCO.sub.3(s) or MgCO.sub.3(s) of a solid state transferred to a dryer (not illustrated) and solidified.

NH.sub.4HCO.sub.3(aq)+Ca(OH).sub.2->CaCO.sub.3(s)+2H.sub.2O+NH.sub.3(g)   [Chemical Formula 3]

NH.sub.4HCO.sub.3(aq)+Mg(OH).sub.2->MgCO.sub.3(s)+2H.sub.2O+NH.sub.3(g)   [Chemical Formula 4]

[0085] Here, NH.sub.4HCO.sub.3(aq) and Ca(OH).sub.2 or Mg(OH).sub.2 are continuously reacted by the agitator 142 installed in the mixing tank 143, while maintaining at a constant temperature so that the reaction is smoothly performed.

[0086] On the other hand, the waste of fresh water may be eliminated by supplying fresh water (or ammonia water) separated by the filter 144 to the fresh water spray nozzle 123c of the ammonia water producing unit 120, or storing, in the fresh water tank 121, excess fresh water (or excess ammonia water) additionally generated by the mixing tank 143 compared to the total circulating fresh water required for ammonia water production and NH.sub.3 recycling.

[0087] In addition, the Ca(OH).sub.2 storage tank 141 or the Mg(OH).sub.2 storage tank 141 may react the fresh water supplied from the fresh water tank 121 with CaO or MgO to generate Ca(OH).sub.2 or Mg(OH).sub.2, store Ca(OH).sub.2 or Mg(OH).sub.2, and supply Ca(OH).sub.2 or Mg(OH).sub.2 to the mixing tank 143. Here, since the solubility of CaO or MgO is low, it is effective to apply a method of preparing Ca(OH).sub.2(aq) or Mg(OH).sub.2(aq) by adding CaO or MgO to fresh water as necessary. When adding CaO or MgO, heating and stirring have to be accompanied.

[0088] In this manner, there is no reduction in the concentration of ammonia water, the capacity size of the filter 144 may be reduced, and the NH.sub.3 recycling cost may be reduced. That is, in theory, only MgO is consumed and NH.sub.3 and fresh water are reused, thereby significantly reducing the CO.sub.2 removal cost.

[0089] In addition, the filter 144 suctions the solution and precipitate from the mixing tank 143, transfers NaHCO.sub.3 and other by-product precipitates at high pressure by the high-pressure pump 145, separates CaCO.sub.3 or MgCO.sub.3, and stores CaCO.sub.3 or MgCO.sub.3 in a solid state or discharges CaCO.sub.3 or MgCO.sub.3 to the outside of the vessel. Here, as an example of the filter, a membrane filter suitable for precipitate separation by high-pressure fluid transfer may be applied.

[0090] In addition, the NH.sub.3 recycled by the mixing tank 143 is supplied to the NH.sub.3 spray nozzle 123b of the ammonia water producing unit 120 and the first NH.sub.3 spray nozzle 131b of the NO.sub.x absorbing unit 131 so as to be reused for ammonia water production and NO.sub.x removal, thereby minimizing the consumption of relatively expensive NH.sub.3 and reducing costs.

[0091] Next, as illustrated in FIG. 7, the steam generating unit 150 may include: an auxiliary boiler 151 that receives a mixture in the form of saturated water and steam heat-exchanged through the EGE 134, separates the steam by a steam drum (not illustrated), and supplies the separated steam to a steam consumer; a boiler water circulating pump 152 that circulates and supplies boiler water from the auxiliary boiler 151 to the EGE 134; a cascade tank 153 that recovers condensed water condensed and phase-changed after being consumed from the steam consumer; and a supply pump 154 and a control valve 155 that supply boiler water from the cascade tank 153 to the auxiliary boiler 151 while controlling the amount of boiler water. The steam generating unit 150 generates and supplies steam required for heating devices in the vessel.

[0092] Here, when the load of the vessel engine 10 is large, the amount of heat that may be provided from the exhaust gas is large, and thus the amount of steam required in the vessel may be sufficiently produced through the EGE 134; otherwise, the auxiliary boiler 151 itself may burn fuel to produce necessary steam.

[0093] Next, as illustrated in FIG. 2, the discharge unit 160 may include: a cleaning water tank 161 that stores cleaning water discharged from the absorption tower 130; a water treatment device 163 including a filtering unit that controls turbidity to satisfy the outboard discharge condition of the cleaning water transferred to the cleaning water tank 161 by the transfer pump 162, and a neutralizing agent injecting unit that controls pH; and a sludge storage tank 164 that separates and stores solid emissions such as soot. The discharge unit 160 may discharge the cleaning water, which passes through the water treatment device 163 and satisfies the outboard discharge condition, to the outside of the vessel, and may separately store the solid emissions, such as soot, which do not satisfy the outboard discharge conditions, in the sludge storage tank 164.

[0094] On the other hand, NaOH may be used as the neutralizing agent for satisfying the outboard discharge condition. However, assuming that the materials discharged from the absorption tower 130 are acidic and basic, a neutralizing agent capable of neutralizing each of the acidic material and the basic material may be selected and used as necessary.

[0095] Therefore, as described above, according to the structure of the apparatus for reducing greenhouse gas emission in the vessel, NO.sub.x, SO.sub.x, and CO.sub.2 from the exhaust gas exhausted from the vessel engine may be converted into materials that do not affect environments so as to satisfy IMO greenhouse gas emission regulations. The materials may be separately discharged, or may be converted into useful materials and stored. Since CO.sub.2 is removed after SO.sub.x is removed, the CO.sub.2 dissolution reaction rate, the CO.sub.2 solubility, and the CO.sub.2 removal efficiency may be increased. The use of Ca(OH).sub.2 or Mg(OH).sub.2 may reduce the NH.sub.3 recycling cost. The capacity size of the rear end part of the filter may be reduced. When CO.sub.2 is removed, only relatively inexpensive NH.sub.3 loss and Ca(OH).sub.2 or Mg(OH).sub.2 (CaO or MgO) are consumed, reducing removal costs. CO.sub.2 may be stored in the form of CaCO.sub.3(s) or MgCO.sub.3(s) existing in the nature. CaCO.sub.3(s) or MgCO.sub.3(s) may be discharged in sea, and side reactions caused by SO.sub.x remaining during NH.sub.3 recycling may be removed, thereby minimizing the loss of NH.sub.3 and preventing impurities from being included when recovering ammonia. Since only Ca(OH).sub.2 or Mg(OH).sub.2 is added, there is no change in the concentration of ammonia water, and the capacity size of the filter may be reduced.

[0096] The present invention has been described above with reference to the embodiments illustrated in the drawings. However, the present invention is not limited thereto, and various modifications or other embodiments falling within the scope equivalent to the present invention can be made by those of ordinary skill in the art. Therefore, the true scope of protection of the present invention should be determined by the appended claims.