JP7779608B2 - System including two scrubbers connected to an electrostatic precipitator and method for cleaning exhaust gases using the same - Google Patents

Description

The present invention relates to the cleaning of exhaust gases, particularly exhaust gases from two or more combustion engines. The present invention is particularly usable on ships with limited space for equipment, particularly ships containing multiple combustion engines. The present invention relates to the desulfurization of exhaust gases, i.e., flue gases, by scrubbing. The present invention relates to the cleaning of scrubbed exhaust gases.

The combustion of fossil fuels is used in industrial processes for many different purposes, including combustion engines. Depending on the quality of the fuel, flue gases (i.e., exhaust gases) can contain varying amounts of pollutants, including sulfur oxides (SOx). Marine vessels, i.e., ships, typically contain combustion engines and use low-grade fuels, which result in high levels of SOx and particles in the exhaust gases (i.e., flue gases). One possibility for reducing the SOx content in exhaust gases is to use desulfurization techniques, particularly wet scrubbing processes, in which the emitted exhaust/flue gases are brought into close contact with an aqueous scrubbing solution. The objective of these processes is to provide high absorption efficiencies and to remove or significantly reduce the concentration of particles, droplets, or substances in the scrubbed exhaust/flue gases. Marine scrubbers for cleaning gases emitted from marine engines are known from U.S. Pat. Nos. 5,629,999, 5,729,963, and 5,829,973. The scrubbers disclosed therein operate in closed-loop mode, semi-closed-loop mode, and open-loop mode, respectively.

EP 1 857 169 U.S. Pat. No. 3,781,407 International Publication No. 99/44722

However, scrubbing does not remove all exhaust gas pollutants. Small particles may escape the scrubber. Such pollutants may be harmful to the environment. Therefore, further cleaning may be necessary. When exhaust gases are generated onboard ships, there is limited space available for additional cleaning equipment.

It has been discovered that scrubbed exhaust gas can be further cleaned by using an electrostatic precipitator (ESP). Because the exhaust gas leaves the scrubber at saturated moisture content, the ESP can be referred to as a wet ESP (i.e., WESP) due to the humidity of the scrubbed exhaust gas. Furthermore, it has been discovered that the same wet ESP can be used to further clean the scrubbed exhaust gas obtained from two or more scrubbers. Using only one wet ESP for at least two scrubbers reduces the equipment's space requirements. Furthermore, this configuration allows the wet ESP to be used to clean only the exhaust gas that requires cleaning. This arrangement allows the wet ESP from one or more combustion engines to be cleaned on a ship, even when one of the engines is operating in port conditions (typically when only one or two engines are operating), greatly increasing the operational flexibility of the ship. Environmental requirements for ships can vary significantly depending on where the ship operates. For example, at sea, a wet ESP may not be needed at all, allowing for wet ESP maintenance. In contrast, near a port, local environmental laws may require a wet ESP. Furthermore, near a port, the ship's engines may be operated at only partial power, so a single wet ESP may be sufficient near a port, even if it would not be sufficient if all engines were operating at full power (e.g., at sea).

The composition is disclosed in more specific terms in claim 1. The method is disclosed in more specific terms in claim 9. The dependent claims define preferred embodiments. The description discloses further details of the embodiments.

FIG. 1 shows a vessel having an arrangement for cleaning exhaust gases. Figures 2a to 2d show an arrangement for cleaning exhaust gases. 3a-3d show arrangements for evenly distributing scrubbed exhaust gas in a wet ESP. FIG. 4a shows a side view of the inside of a wet electrostatic precipitator. FIG. 4b shows a top view of the collection area of a wet electrostatic precipitator. FIG. 5a shows a top view of the dust collection area of another wet electrostatic precipitator. FIG. 5b shows a plan view of the dust collection area of another wet electrostatic precipitator. FIG. 6 shows an arrangement for cleaning exhaust gases, where the scrubber serves multiple combustion engines. FIG. 7 shows an arrangement for cleaning exhaust gases, in which a wet electrostatic precipitator is associated with two or more scrubbers.

In the figure, directional arrows Sz, Sx, and Sy indicate the upward vertical direction and two orthogonal horizontal directions, respectively. Directional arrow Sl indicates the longitudinal direction of the electrodes of the wet electrostatic precipitator, which may be substantially vertical in use. Directional arrows St1 and St2 indicate orthogonal directions perpendicular to the longitudinal direction Sl.

Figure 1 shows a vessel 910 equipped with (i.e., including) an arrangement 900 for cleaning a first exhaust gas EG1 and a second exhaust gas EG2. The vessel 910 is an example of a more general vehicle; the arrangement 900 can also be used in other locations where space for the arrangement 900 is limited. Figures 2a-2d show examples of arrangements 900 that can be used as described above.

The exhaust gases EG1 and EG2 are produced in the combustion process, are hot, and contain sulfur oxides (SOx). To reduce the amount of sulfur oxides, the arrangement 900 includes a wet scrubber. However, exhaust gases from a source are often cleaned in a dedicated wet scrubber that cleans the exhaust gases of that source only, to avoid transporting hot exhaust gases over long distances on a vehicle. In the following, the term "scrubber" refers to a wet scrubber, i.e., a scrubber in which the gases to be scrubbed are brought into contact with a scrubbing solution.

A typical ship (or vehicle) has multiple different exhaust gas sources. Therefore, the ship (or vehicle) typically has at least two scrubbers 710, 720. Accordingly, the arrangement 900 includes a first scrubber 710 and a second scrubber 720. The first scrubber 710 includes an inlet 712 for receiving the first exhaust gas EG1 and an outlet 714 for discharging the scrubbed first exhaust gas SEG1 (see Figures 2a-2d). The second scrubber 720 includes an inlet 722 for receiving the second exhaust gas EG2 and an outlet 724 for discharging the scrubbed second exhaust gas SEG2 (see Figures 2a-2d). The scrubbers 710, 720 are configured to at least partially desulfurize and purify the exhaust gases EG1, EG2, respectively.

The source of the first exhaust gas EG1 may be, but is not limited to, the first combustion engine 810. The source of the second exhaust gas EG2 may be, but is not limited to, the second combustion engine 820.

To clean the scrubbed exhaust gases SEG1 and SEG2, the arrangement includes an electrostatic precipitator (ESP) 100. The ESP 100 includes a first inlet 112 for receiving at least a portion of the scrubbed first exhaust gas SEG1 and a second inlet 114 for receiving at least a portion of the scrubbed second exhaust gas SEG2. Such inlets 112, 114 are shown, for example, in Figures 2a and 4a. As described in more detail below, not all of the scrubbed first exhaust gas SEG1 needs to be cleaned by the ESP 100, and not all of the scrubbed second exhaust gas SEG2 needs to be cleaned by the ESP 100. As such, the arrangement 900 includes a first primary piping 716 configured to convey at least a portion of the scrubbed first exhaust gas SEG1 to the first inlet 112 of the ESP 100, and a second primary piping 726 configured to convey at least a portion of the scrubbed second exhaust gas SEG2 to the second inlet 114 of the electrostatic precipitator 100. These piping 716,
726 is shown in Figures 2a-2d. The ESP 100 is of the wet electrostatic precipitator or wet ESP or WESP type for cleaning gases that are substantially saturated with humidity (i.e., after the wet scrubber).

Referring to FIG. 4a, the wet ESP 100 includes an inlet region Z1. The first inlet 112 and the second inlet 114 are disposed within the inlet region Z1. That is, the inlet region Z1 comprises the first and second inlets (112, 114). For marine applications, it is preferable that the inlet region Z1 be short. More specifically, in a preferred embodiment, the height of the inlet region Z1 is a maximum of 30% of the height of the wet ESP 100. The height of the inlet region Z1 may, for example, be at most the same as the height of the precipitation zone Z2 of the wet ESP. Furthermore, it is preferable that the inlet region Z1 overlaps with the remainder of the wet ESP 100 in the height direction of the wet ESP. That is, it is preferable that the inlet region Z1 does not protrude radially from the remainder of the wet ESP 100. More preferably, the cross section of the inlet region Z1 on a horizontal plane is the same as the cross section of the wet ESP 100 on a horizontal plane.

The wet ESP includes a dust collection zone Z2. The scrubbed exhaust gas is configured to be cleaned in the dust collection zone Z2 according to the principle of electrostatic collection. Therefore, the wet ESP 100 includes a discharge electrode 220 and a collecting surface 210, as described below (see Figures 4b, 5a, and 5b). The collecting surface 210 is also an electrode. Therefore, where feasible, the discharge electrode 220 and the collecting surface 210 will simply be referred to as electrodes. The electrodes 210 and 220 are for electrically collecting dust from at least one of the scrubbed first exhaust gas SEG1 and the scrubbed second exhaust gas SEG2. The electrodes (210 and 220) are disposed within the dust collection zone Z2 of the wet ESP 100. The height of the dust collection zone Z2 may be equal to the length of the collecting surface 210.

The wet ESP 100 includes an outlet 132 for discharging the cleaned exhaust gas CEG (see Figures 3a-3d). In use, the scrubbed exhaust gas, which is further cleaned in the wet ESP 100, flows from the inlets 112, 114 through the dust collection zone Z2 to the outlet 132. The dust collection zone Z2 is therefore located between the inlet zone Z1 and the outlet zone 132 of the wet ESP 100.

For good performance and short maintenance intervals, the gases SEG1 and SEG2 purified by the wet ESP 100 should be evenly distributed in the dust collection zone Z2. Therefore, in one embodiment, the wet ESP 100 includes a perforated plate 150 between the inlet zone Z1 and the dust collection zone Z2, as shown in Figures 3a, 3c, and 3d. The purpose of the perforated plate 150 is to evenly divide the gases SEG and SEG2 between the electrodes 210 and 220 of the wet ESP 100. In one embodiment, the wet ESP 100 includes at least two perforated plates 150 or more perforated plates 150 between the inlet zone Z1 and the dust collection zone Z2 to more evenly divide the gases SEG and SEG2 between the electrodes 210 and 220 of the wet ESP 100.

Another possibility, not limited to the perforated plate 150, is to use perforated pipes 152 or perforated plates 152, 154 in the inlet region Z1. Referring to Figures 3b and 3c, in one embodiment, the wet ESP 100 includes a first perforated pipe 152 in the inlet region Z1 configured to deliver the first scrubbed exhaust gas SEG1 to the inlet region Z1. Furthermore, in one embodiment, the wet ESP 100 includes a second perforated pipe 154 in the inlet region Z1 configured to deliver the second scrubbed exhaust gas SEG2 to the inlet region Z1. The first perforated pipe 152 may include a bend to more evenly spread the first scrubbed exhaust gas SEG1 across the inlet region Z1. The second perforated pipe 154 may include a bend to more evenly spread the second scrubbed exhaust gas SEG2 across the inlet region Z1. Guide plates may be positioned within the perforated pipes 152, 154 to further smooth the flow of scrubbed exhaust gases SEG1, SEG2 into the inlet zone Z1. The perforated pipes 152, 154 may be connected to each other to form a single perforated pipe 152 through which both scrubbed exhaust gases SEG1, SEG2 are conveyed (not necessarily simultaneously), as shown in FIG. 3d. In FIGS. 3b, 3c, and 3d, the first perforated pipe 152 is configured to deliver at least the first scrubbed exhaust gas SEG1 to the inlet zone Z1.

As shown in FIG. 3c, the wet ESP 100 may include a perforated plate 150 between the inlet region Z1 and the dust collection region Z2, and first and second perforated tubes 152, 154t. As shown in FIG. 3d, the wet ESP 100 may include only the perforated plate 150 and the first perforated tube 152 between the inlet region Z1 and the dust collection region Z2.

When the arrangement 900 is operated, a method for purifying exhaust gas is performed. As described above, in one embodiment of the method, the wet electrostatic precipitator 100 is disposed on a vehicle, such as a boat 910. The method includes scrubbing a first exhaust gas EG1 in a first scrubber 710 to produce a scrubbed first exhaust gas SEG1 and scrubbing a second exhaust gas EG2 in a second scrubber 720 to produce a scrubbed second exhaust gas SEG2. The method further includes conveying at least a portion of the scrubbed first exhaust gas SEG1 to the wet electrostatic precipitator 100 and conveying at least a portion of the scrubbed second exhaust gas SEG2 to the wet electrostatic precipitator 100. The method further includes cleaning at least a portion of the scrubbed first exhaust gas SEG1 and at least a portion of the scrubbed second exhaust gas SEG2 in a wet electrostatic precipitator 100 to produce a cleaned exhaust gas CEG.

A preferred embodiment of the method includes cleaning both (i) at least a portion of the scrubbed first exhaust gas SEG1 and (ii) at least a portion of the scrubbed second exhaust gas SEG2 in a wet electrostatic precipitator 100 to produce a cleaned exhaust gas CEG. However, it is not necessary for both the scrubbed first exhaust gas SEG1 and the scrubbed second exhaust gas SEG2 to be present in the wet electrostatic precipitator 100 at the same time. For example, (i) at least a portion of the scrubbed first exhaust gas SEG1 and (ii) at least a portion of the scrubbed second exhaust gas SEG2 may be cleaned sequentially using the same wet electrostatic precipitator 100. Further details regarding the issue of "at least a portion" of the scrubbed exhaust gases (SEG1, SEG2) are described below in connection with the first valve arrangement 754 and the second valve arrangement 764.

It has been found that scrubbing, and therefore wet desulfurization, of exhaust gases EG1 and EG2 is particularly efficient when a scrubbing solution is sprayed onto the gas being scrubbed. Alternatively or additionally, the gas can be conveyed through a bath of scrubbing solution. However, spraying is much more efficient due to the increased contact area between the gases EG1 and EG2 and the scrubbing solution. For these reasons, a preferred embodiment of arrangement 900 includes a first circulation 718 for scrubbing the first exhaust gas EG1 by spraying the first scrubbing solution SS1 within the first scrubber 710 and contacting the first exhaust gas EG1 with the first scrubbing solution SS1. This is illustrated in all of Figures 2a-2d.

To that end, the first scrubber 710 includes a nozzle 719 (see Figures 2a-2d) for spraying the first scrubbing solution SS1 and forming droplets of the first scrubbing solution SS1 in the first scrubber 710. Furthermore, the first scrubber 710 includes a pump 715 for delivering the scrubbing solution to the nozzle 719. When scrubbed, the first exhaust gas EG1 is contacted with the formed droplets of the first scrubbing solution SS1. To that end, an embodiment of the method includes spraying the first scrubbing solution SS1 in the first scrubber 710 to form droplets of the first scrubbing solution SS1 and contacting the first exhaust gas EG1 with the droplets of the first scrubbing solution SS1.

The first scrubbing solution SS1 (or second scrubbing solution SS2, described below) can be water, freshwater, seawater, or any other aqueous solution of one or more compounds known to bind or absorb one or more components of the exhaust/flue gas being scrubbed. Typically, acid gases such as SOx are removed from solution by scrubbing with an alkaline solution, such as an aqueous solution of alkaline compounds such as caustic soda or other alkaline substances.

The first circulation section 718 may be an open-loop circulation section, as shown in Figures 2b and 2c. Here, seawater may be used as the scrubbing solution. More specifically, as in the embodiment of Figure 2b, seawater may be used as a common (first) scrubbing solution for both the first scrubber 710 and the second scrubber 720. In the embodiment of Figure 2c, seawater may be used as both the first scrubbing solution SS1 used in the first scrubber 710 and the second scrubbing solution SS2 used in the second scrubber 720.

The first circulation section 718 may be a closed-loop circulation section, as shown in Figures 2a and 2d. A closed-loop circulation section may be usable where environmental regulations are strict. When a closed-loop circulation section is used, the scrubbing solution SS1 or the scrubbing solutions SS1 and SS2 are preferably made from water (seawater and/or freshwater) and alkali. In such cases, the scrubbing solution SS1 or the scrubbing solutions SS1 and SS2 are more preferably made from freshwater and alkali. Solids may be removed from the scrubbing solutions SS1 and SS2 through the circulation sections 718 and 728.

As shown in Figures 2a and 2d, when the first circulation section 718 is a closed-loop circulation section, the temperature of the first scrubbing solution tends to increase due to the high temperature of the exhaust gas being scrubbed. However, as the temperature increases, the ability of the first scrubbing solution SS1 to capture SOx from the first exhaust gas EG1 decreases. Also, increased evaporation of water from the process into the atmosphere significantly increases makeup water consumption, which can result in a thick visible plume after stacking. Therefore, the first circulation section 718 preferably includes a heat exchanger 717 for cooling the first scrubbing solution SS1 (see Figures 2a and 2d). The coolant C1 used in the heat exchanger 717 on a ship is typically seawater. In other applications, for example, air or water (e.g., fresh water or seawater) may be used as the coolant C1 in the heat exchanger 717. If the arrangement includes a second circulation section 728 and the second circulation section 728 is of the closed loop type, the second circulation section 728 includes a heat exchanger 727 for cooling the second scrubbing solution SS2 (see Figure 2a).

2a and 2d, the pumps (715, 725) of the circulation sections (718, 728) are located downstream of the heat exchangers (717, 727) of the circulation sections. However, in one embodiment, the pumps 715, 725 of such circulation sections 718, 728 are located upstream of the heat exchangers 717, 727 of the circulation sections 718, 728.

It can also be used as either one or both of the first and second scrubbers. Hybrid mode scrubbers include valves (not shown) so that the scrubbing solution to be sprayed is taken from the scrubber a first time (as in Figures 2a and 2d) and the scrubbing solution to be sprayed is taken from the sea a second time (as in Figures 2b and 2c).

As shown in FIGS. 2b and 2d, the same (first) circulation section 718 may be used to supply the same (first) scrubbing solution SS1 to both the first scrubber 710 and the second scrubber 720. In this embodiment, the first circulation section 718 is suitable for scrubbing the second exhaust gas EG2 by spraying the first scrubbing solution SS1 into the second scrubber 720 and contacting the second exhaust gas EG2 with the first scrubbing solution SS1. A corresponding method includes spraying the first scrubbing solution SS1 in the second scrubber 720 to form droplets of the (first) scrubbing solution SS1 and contacting the second exhaust gas EG2 with the droplets of the (first) scrubbing solution SS1.

Alternatively, the arrangement 900 may include a second circulation section 728 for scrubbing the second exhaust gas EG2 by spraying the second scrubbing solution SS2 into the second scrubber 720 and contacting the second exhaust gas EG2 with the second scrubbing solution SS2 (see Figures 2a and 2c). A corresponding method includes spraying the second scrubbing solution SS2 in the second scrubber 720 to form droplets of the (second) scrubbing solution SS2 and contacting the second exhaust gas EG2 with the droplets of the (second) scrubbing solution SS2.

Regarding some structural details of the wet ESP 100, the wet ESP 100 includes a discharge electrode 220 and a collection surface 210 in a collection zone Z2. The collection zone Z2 is shown from the side in FIG. 4a and from its beginning to its end in FIG. 4b. In FIG. 4a, the reference S1 indicates the longitudinal direction of the discharge electrode 220 or collection surface 210, i.e., the direction of flow of the scrubbed exhaust gases SEG1, SEG2 within the wet ESP. In use, the longitudinal direction S1 may be substantially vertical. However, in the case of a ship, the direction S1 may change as the ship rolls (i.e., sways). In use, it is preferred that the longitudinal direction S1 forms an angle of up to 45 degrees with the vertical direction Sz.

Figures 4b, 5a, and 5b show cross sections of the particulate collection zone Z2. In Figures 4b and 3a, all of the second electrodes are tubular, with the other electrodes arranged coaxially within the tubular electrodes. In Figure 5b, the electrodes are plate-shaped. The tubular electrodes in Figures 4b and 5a have a tubular shape extending in the longitudinal direction S1. The planar electrodes in Figure 5b extend in a plane that includes the longitudinal direction S1. Typically, the wet ESP 100 includes means 222 for discharging an electric charge to particles in at least one of the scrubbed first exhaust gas SEG1 and the scrubbed second exhaust gas SEG2.

The operating principle of wet ESP is, for example, a means 222 for discharging electric charge on particles of the gases SEG1 and SEG2 to be cleaned. The gas is then transported between the discharge electrode 220 and the collection surface 210. Since the particles have an electric charge, the electrodes 210 and 220 attract the particles, which collide with them. Typically, the means 222 for discharging electric charge is arranged as part of the discharge electrode 220 (in most cases, at a lower potential than the collection surface 210), thereby releasing electrons onto the particles to be removed. Correspondingly, the particles collide with the collection surface 210 and are stopped there. Therefore, in a preferred embodiment, the area of the collection surface 210 is larger than the area of the discharge electrode 220, as shown in Figure 4b. The means 222 for discharging electric charge can be a sharp protrusion on the discharge electrode 220. For these reasons, in a preferred embodiment, as shown in FIG. 4b, the collecting surfaces 210 have a tubular shape extending in the longitudinal direction S1, and each discharge electrode 220 extends coaxially with one of the collecting surfaces 210 in the longitudinal direction S1. The discharge electrodes 220 are laterally surrounded by the collecting surfaces 210.

To generate the electric field, the arrangement 900 or wet ESP 100 includes a power source 230 and wiring 232 configured to deliver a first potential V1 to the collection surface 210 and a second potential V2 to the discharge electrode 220. In one embodiment, the second potential V2 is less than the first potential V1. The strength of the electric field between the electrodes 210, 220 can be, for example, 0.1 kV/cm to 10 kV/cm.

The wet ESP 100 has proven particularly useful when used after a scrubber, i.e., a wet scrubber operating with scrubbing solutions SS1 and SS2. This arrangement is useful because the scrubbed exhaust gases SEG1 and SEG2 entering the wet ESP 100 are substantially saturated with moisture. As a result, moisture from the gases SEG1 and SEG2 condenses on the electrodes 210 and 220 of the wet ESP, flushing the electrodes during use so that at least a portion of the particles impinging on the electrodes are flushed with the condensate. This extends the maintenance intervals for the wet ESP. Furthermore, due to the flushing, in one embodiment of the arrangement 900, the wet electrostatic precipitator 100 includes a secondary outlet 140 at the bottom of the wet electrostatic precipitator 100 for discharging effluent EFF from the wet electrostatic precipitator 100, as shown in FIGS. 2a-4a. The waste EFF contains a condensate of the scrubbed exhaust gases SEG1 and SEG2 and may further contain a cleaning solution RS, as described in more detail below. The aforementioned relatively small angle between the longitudinal direction Sl and the vertical direction Sz is also beneficial from the standpoint of flushing the electrodes.

As noted above, low-grade fuels are high in sulfur, but are also attractive because they are inexpensive. The problem of high sulfur content can be mitigated using the aforementioned arrangement 900. Specifically, the low-grade fuel can be used in a combustion engine. As such, one embodiment of arrangement 900 includes a first combustion engine 810 and a first secondary pipe 891 configured to convey a first exhaust gas EG1 from the first combustion engine 810 to the inlet 712 of the first scrubber 710. As such, during operation of the combustion engine, at least a portion of the first exhaust gas EG1 produced by the first combustion engine 810 is conveyed to the first scrubber 710 for scrubbing therein. Additionally, this embodiment includes a second combustion engine 820 and a second secondary pipe 892 configured to convey a second exhaust gas EG2 from the second combustion engine 820 to the inlet 722 of the second scrubber 720. Therefore, during operation of the combustion engine, at least a portion of the second exhaust gas EG2 produced by the second combustion engine 820 is conveyed to the second scrubber 710 and scrubbed therein. See Figures 1, 2a, 2c, 2d, 6 and 7.

As previously detailed, the scrubbed exhaust gases SEG1 and SEG2 have a high humidity. This also applies to the cleaned exhaust gas CEG emitted from the wet ESP 100. When emitted into the atmosphere, some of the humidity may become visible, known as an exhaust gas plume, or simply plume. However, visible humidity is often mistaken for smoke. Because smoke emissions are generally considered harmful to the environment, one embodiment of the arrangement 900 includes a plume reduction arrangement 160 configured to reduce the plume of the cleaned exhaust gas CEG, as shown in FIGS. 2a, 2c, and 2d. The plume reduction arrangement 160 may include at least a fan for mixing the depluming gas DPG with the cleaned exhaust gas CEG. The depluming gas DPG may be a dry gas and/or a hot gas, such as air, to reduce the plume of the CEG. For these reasons, one embodiment of the method includes mixing the de-plumming gas DPG with the cleaned exhaust gas CEG to reduce the plume of the cleaned exhaust gas. The plume reduction arrangement 160 removes water vapor from the cleaned exhaust gas after the wet ESP 100. This means that white smoke is eliminated and corrosion of the upper part 162 of the exhaust pipe is avoided.

The wet ESP 100 of the arrangement 900 can be used to clean only the exhaust gases that need to be cleaned. Environmental requirements for a vessel can vary greatly depending on where the vessel is operated. For example, at sea, a wet ESP may not be required at all, allowing for wet ESP maintenance. Near a port, a wet ESP may be required due to local environmental laws. However, near a port, the vessel's engines may be operating at only partial power, so a single wet ESP may be sufficient near a port, even though a single wet ESP would not be sufficient if all engines were operating at full power (e.g., at sea). Furthermore, near a port, the vessel may be operating with only one engine, so a single wet ESP may be used to clean the exhaust gases from only that one engine.

To enable universal use of a single wet ESP 100 in conjunction with the first scrubber 710 and the second scrubber 720, in one embodiment of the arrangement 900, the first primary piping 716 includes a first outlet 752 for discharging a portion of the scrubbed first exhaust gas SEG1 from the first primary piping 716 to a location other than the wet electrostatic precipitator 100, e.g., to the atmosphere. Thus, the scrubbed first exhaust gas SEG1 conveyed to the first outlet 752 bypasses the wet ESP 100. Such a first outlet 752 is shown in Figures 2a-2d. Furthermore, the first primary piping 716 includes a first valve arrangement 754 for conveying at least a portion of the scrubbed first exhaust gas SEG1 to the first outlet 752 and for conveying at least a portion of the scrubbed first exhaust gas SEG1 to the first inlet 112 of the wet electrostatic precipitator 100. Therefore, the first valve arrangement 754 is also suitable for conveying all of the scrubbed first exhaust gas SEG1 to the first outlet 752 and, correspondingly, for conveying none of the scrubbed first exhaust gas SEG1 to the first inlet 112 of the wet electrostatic precipitator 100. Therefore, the first valve arrangement 754 can be used to convey only a portion or all of the scrubbed first exhaust gas SEG1 directly to the first outlet 752 and, for example, to the atmosphere, or to convey none of the first exhaust gas SEG1. Therefore, the first valve arrangement 754 can be used to convey only a portion or all of the scrubbed first exhaust gas SEG1 to the first inlet 112 of the wet ESP 100, or to convey none of the first exhaust gas SEG1 to the first inlet 112. In some cases, further cleaning of SEG1 by using a wet ESP may not be necessary. Furthermore, in one embodiment, the second primary piping 726 includes a second outlet 762 for discharging a portion of the scrubbed second exhaust gas SEG2 from the second primary piping 726 to a location other than the wet electrostatic precipitator 100, and a second valve arrangement 764 for conveying at least a portion of the scrubbed second exhaust gas SEG2 to the second outlet 762 and for conveying at least a portion of the scrubbed second exhaust gas SEG2 to the second inlet 114 of the wet electrostatic precipitator 100. As such, the scrubbed second exhaust gas SEG2 conveyed to the second outlet 762 bypasses the wet electrostatic precipitator 100. The second valve arrangement 764 can be used in the same manner as the first valve arrangement 754.

The first valve arrangement 754 and the second valve arrangement 764 can be used, for example, to convey, during a first period of time, both (i) the scrubbed first exhaust gas SEG1 or a portion thereof and (ii) the scrubbed second exhaust gas SEG2 or a portion thereof to the wet ESP 100. In particular, the valve arrangements 754, 764 can be used to convey, during a first period of time, [A] both (i) only a portion of the scrubbed first exhaust gas SEG1 and (ii) all of the scrubbed second exhaust gas SEG2, or [B] both (i) only a portion of the scrubbed first exhaust gas SEG1 and (ii) only a portion of the scrubbed second exhaust gas SEG2 to the wet ESP 100. Regarding the latter, if only a portion of the scrubbed first exhaust gas SEG1 is cleaned by the wet ESP 100, the wet ESP 100 is as large as if it were designed to clean all of the scrubbed first exhaust gas SEG1. Such use may be possible, for example, offshore.

The first valve arrangement 754 and the second valve arrangement 764 can be used, for example, so that during the second time period, only (i) the scrubbed first exhaust gas SEG1 or a portion thereof or (ii) the scrubbed second exhaust gas SEG2 or a portion thereof is conveyed to the wet ESP 100. In some cases, the other exhaust gas source can be turned off (e.g., one of the combustion engines 810, 820 is not operating) or the scrubbed exhaust gas can be discharged directly to the atmosphere via the piping outlets (752, 762).

The first valve arrangement 754 and the second valve arrangement 764 can be used, for example, to ensure that during the third time period, neither (i) the scrubbed first exhaust gas SEG1 or a portion thereof nor (ii) the scrubbed second exhaust gas SEG2 or a portion thereof is conveyed to the wet ESP 100. In some cases, other exhaust gas sources may be turned off (e.g., when neither of the combustion engines 810, 820 is operating (e.g., when the ship is at anchor)) or the scrubbed exhaust gases or both are released directly to the atmosphere via the piping outlets (752, 762). Therefore, during the third time period, the wet ESP 100 is not used. This may be possible, for example, when further cleaning of the scrubbed exhaust gases SEG1, SEG2 is not required, such as when at sea.

When the wet ESP 100 is not in use, it may be maintained. As detailed above, wet ESPs are not always used on ships and at sea. Maintenance of a wet ESP preferably includes at least cleaning. The wet ESP may be cleaned with cleaning fluid RS. Cleaning preferably includes at least cleaning a portion of the electrodes 210, 220 of the wet ESP 100, particularly the electrode that captures contaminants, which is typically the collection surface 210 (e.g., the electrode with the higher potential). For these reasons, in one embodiment of the arrangement 900, the wet electrostatic precipitator 100 includes an inlet 120 for introducing cleaning fluid RS and means 122 for cleaning at least a portion of the electrodes 210, 220 of the wet electrostatic precipitator 100 with the cleaning fluid RS. The means 122 may include a nozzle for spraying cleaning fluid RS onto the electrode to be cleaned, for example, onto at least the collection surface 210. Such means 122 and inlet 120 are shown, for example, in Figures 2a, 2c, and 2d.

Referring to FIG. 6, a first scrubber 710 can also be used to scrub the first exhaust gas EG1 and a portion of the third exhaust gas EG3. The third exhaust gas EG3 can be produced by a third combustion engine 830. Additionally (as in FIG. 6) or alternatively (not shown), a second scrubber 720 can be used to scrub the second exhaust gas EG2 and a portion of the fourth exhaust gas EG4. The fourth exhaust gas EG4 can be produced by a fourth combustion engine 840.

7, the wet ESP 100 may include a third inlet 116 for receiving at least a portion of the scrubbed third exhaust gas SEG3. The scrubbed third exhaust gas SEG3 may be received from a third scrubber 730. The third scrubber 730 may be configured to scrub the third exhaust gas EG3 of the third combustion engine 830. As shown in FIG. 7, this arrangement may include a third valve arrangement for conveying all or only a portion of the scrubbed third exhaust gas SEG3 into the wet ESP 100, or none of it, and for conveying all or only a portion of the scrubbed third exhaust gas SEG3 elsewhere, for example, to the atmosphere, or none of it. When the wet ESP 100 includes the third inlet 116, the first inlet 112, the second inlet 114, and the third inlet 116 are arranged within the inlet region Z1. Even in this case, although not shown in Figure 7, it is preferable that the height of the entrance region Z1 be small, as detailed above.

Claims (15)

1. A vessel comprising an arrangement, the arrangement comprising:
a first combustion engine;
a second combustion engine; and
a first wet scrubber including an inlet for receiving the first exhaust gas and an outlet for discharging the scrubbed first exhaust gas, the first wet scrubber configured to desulfurize and clean the first exhaust gas;
a first secondary pipe configured to convey a first exhaust gas of the first combustion engine to an inlet of the first wet scrubber;
a second wet scrubber including an inlet for receiving the second exhaust gas and an outlet for discharging the scrubbed second exhaust gas , the second wet scrubber configured to desulfurize and clean the second exhaust gas;
a second secondary pipe configured to convey a second exhaust gas of the second combustion engine to an inlet of the second wet scrubber; and
An electrostatic precipitator,
an inlet region including a first inlet for receiving the scrubbed first exhaust gas and a second inlet for receiving the scrubbed second exhaust gas;
a discharge electrode and a collection surface for electrostatically collecting the scrubbed exhaust gas, the discharge electrode and the collection surface being located within a collection region of the electrostatic precipitator;
an outlet for discharging the cleaned exhaust gas;
an electrostatic precipitator comprising:
a first primary pipe configured to convey the scrubbed first exhaust gas to a first inlet of the electrostatic precipitator;
a second primary pipe configured to convey the scrubbed second exhaust gas to a second inlet of the electrostatic precipitator;
Vessels including. The arrangement is
a first circulation section for scrubbing the first exhaust gas by spraying a first scrubbing solution in the first wet scrubber and contacting the first exhaust gas with the first scrubbing solution;
a second circulation section for scrubbing the second exhaust gas by spraying a second scrubbing solution in the second wet scrubber and contacting the second exhaust gas with the second scrubbing solution;
2. The watercraft of claim 1, comprising: the arrangement includes a first circulation section for scrubbing the first exhaust gas by spraying a first scrubbing solution in the first wet scrubber and contacting the first exhaust gas with the first scrubbing solution;
2. The marine vessel of claim 1, wherein the first circulation section is adapted to scrub the second exhaust gas by spraying a first scrubbing solution in the second wet scrubber to contact the second exhaust gas with the first scrubbing solution. A vessel as described in any one of claims 1 to 3, wherein the electrostatic precipitator includes a second outlet at a lower portion of the electrostatic precipitator for discharging wastewater from the electrostatic precipitator. The first primary piping includes:
a first outlet for discharging a portion of the scrubbed first exhaust gas from the first primary piping to a location other than the electrostatic precipitator;
a first valve arrangement for conveying at least a portion of the scrubbed first exhaust gas to the first outlet and for conveying at least a portion of the scrubbed first exhaust gas to a first inlet of the electrostatic precipitator;
5. A watercraft according to any one of claims 1 to 4 , comprising : A vessel as described in any one of claims 1 to 5, including one or more perforated plates located between the inlet region and the dust collection region. The vessel described in any one of claims 1 to 6, including a first perforated pipe configured to deliver at least the scrubbed first exhaust gas to the inlet region. The electrostatic precipitator comprises:
an inlet for receiving a cleaning solution;
means for cleaning at least a portion of the collection surface and/or discharge electrode of the electrostatic precipitator with the cleaning solution;
8. A watercraft according to any one of claims 1 to 7, comprising: 1. A method for cleaning at least a first exhaust gas and a second exhaust gas, the method comprising:
generating the first exhaust gas from a first combustion engine;
conveying the first exhaust gas to a first wet scrubber;
scrubbing the first exhaust gas in the first wet scrubber by contacting the first exhaust gas with a first scrubbing solution to produce a scrubbed first exhaust gas;
producing the second exhaust gas in a second combustion engine;
conveying the second exhaust gas to a second wet scrubber;
scrubbing the second exhaust gas in the second wet scrubber by contacting the second exhaust gas with a second scrubbing solution to produce a scrubbed second exhaust gas;
conveying at least a portion of the scrubbed first exhaust gas to an electrostatic precipitator;
conveying at least a portion of the scrubbed second exhaust gas to the electrostatic precipitator;
cleaning both at least a portion of the scrubbed first exhaust gas and at least a portion of the scrubbed second exhaust gas in the electrostatic precipitator to produce a cleaned exhaust gas;
Including,
the first scrubbing solution comprises water and alkali;
the second scrubbing solution comprises water and alkali;
The electrostatic precipitator is disposed on a vessel. spraying the first scrubbing solution in the first wet scrubber to form droplets of the first scrubbing solution and contacting the first exhaust gas with the droplets of the first scrubbing solution;
spraying the second scrubbing solution in the second wet scrubber to form droplets of the second scrubbing solution and contacting the second exhaust gas with the droplets of the second scrubbing solution;
10. The method of claim 9, comprising: 11. The method of claim 9 or 10, comprising cooling the first scrubbing solution using a first heat exchanger. 12. The method of claim 11, comprising cooling the first scrubbing solution using the first heat exchanger and using water as a refrigerant, the water comprising seawater. during a first period of time, conveying both (i) the scrubbed first exhaust gas or a portion thereof and (ii) the scrubbed second exhaust gas or a portion thereof to the electrostatic precipitator; and/or during a second period of time, conveying only either (i) the scrubbed first exhaust gas or a portion thereof or (ii) the scrubbed second exhaust gas or a portion thereof to the electrostatic precipitator; and/or
during a third time period, conveying neither (i) the scrubbed first exhaust gas or a portion thereof nor (ii) the scrubbed second exhaust gas or a portion thereof to the electrostatic precipitator;
13. The method of claim 9 or 12, comprising: During the first period of time,
[A] conveying both (i) only a portion of the scrubbed first exhaust gas and (ii) all of the scrubbed second exhaust gas to the electrostatic precipitator, or [B] both (i) only a portion of the scrubbed first exhaust gas and (ii) only a portion of the scrubbed second exhaust gas to the electrostatic precipitator during the second period, and/or conveying only (i) a portion of the scrubbed first exhaust gas or (ii) only a portion of the scrubbed second exhaust gas to the electrostatic precipitator during the third period, and/or cleaning the electrostatic precipitator with a cleaning solution;
14. The method of claim 13 , comprising: 15. A method according to any one of claims 9 to 14 , including mixing a de-plumming gas with the cleaned exhaust gas to reduce the plume of the cleaned exhaust gas.