CN115803100A

CN115803100A - System comprising two scrubbers connected to an electrostatic precipitator and method for purifying exhaust gas using the same

Info

Publication number: CN115803100A
Application number: CN202180043883.2A
Authority: CN
Inventors: J·法布里蒂乌斯; J·乔基卢马
Original assignee: Valmet Technologies Oy
Current assignee: Valmet Technologies Oy
Priority date: 2020-06-16
Filing date: 2021-06-02
Publication date: 2023-03-14
Also published as: KR20230025442A; EP4164773A1; JP2023530916A; WO2021255329A1; FI20205629A1; FI130699B1

Abstract

A method for cleaning at least a first exhaust gas (EG 1) and a second exhaust gas (EG 1). The method comprises scrubbing the first and second off-gases (EG 1, EG 2) in first and second scrubbers (710, 720) to produce scrubbed first and second off-gases (SEG 1, SEG 2); and passing at least a portion of the scrubbed first and second off-gases (SEG 1, SEG 2) to an electrostatic precipitator (100). The method also includes cleaning one or both of the at least partially scrubbed first off-gas (SEG 1) and the at least partially scrubbed second off-gas (SEG 2) in an electrostatic precipitator (100) to produce a clean off-gas (CEG). A system for performing the method.

Description

System comprising two scrubbers connected to an electrostatic precipitator and method for purifying exhaust gas using the same

Technical Field

The present invention relates to cleaning exhaust gases (exhaust gas), in particular exhaust gases of more than one internal combustion engine. The invention is particularly useful for ships having only a limited installation space, in particular for ships comprising a plurality of internal combustion engines. The present invention relates to desulfurization of exhaust gas (i.e., flue gas) by scrubbing. The invention relates to cleaning of scrubbed exhaust gases.

Background

Fossil fuel combustion is used in industrial processes for many different purposes, including internal combustion engines. Depending on the quality of the fuel, the flue gas (i.e., the flue gas) may contain different amounts of pollutants, including sulfur oxides (SOx). Marine vessels, i.e. ships, typically include internal combustion engines and use low grade fuels, both of which result in high levels of SOx and particulates in the exhaust gas (i.e. flue gas). One possibility to reduce the SOx content of the flue gas is to use a desulphurization technique, in particular a wet scrubbing process, in which the discharged flue gas/flue gas is brought into intimate contact with an aqueous scrubbing solution. The purpose of these processes is to provide high absorption efficiency and to remove or significantly reduce the concentration of particles, droplets or substances in the scrubbed flue gas/flue gas. Marine scrubbers (scrubers) for scrubbing gas exhausted from marine engines are known from publications EP 1 857 169, US 3 781 407 and WO 99/44722. The scrubber disclosed therein operates in a closed-loop mode, a semi-closed-loop mode, and an open-loop mode, respectively.

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

Disclosure of Invention

It has been found that the scrubbed exhaust gas can be further cleaned by using an electrostatic precipitator (ESP). Because the flue gas exits the scrubber or scrubbers in a moisture content saturated state, the ESP may be referred to as a wet ESP (i.e., WESP) because of the humidity of the scrubbed flue gas/gases. Furthermore, it has been found that the same wet ESP can be used to further clean scrubbed exhaust gas that is available from more than one scrubber. Using only one wet ESP for at least two scrubbers reduces the space requirement of the plant. Furthermore, the device makes it possible to use wet ESPs to clean only such exhaust gases that need to be cleaned. The arrangement also allows that on board the vessel, whichever engine is operating in harbour condition (typically only one or two engines are operating), gas from one or more internal combustion engines can be purified in a wet ESP, which significantly improves flexibility in the operation of the vessel. The environmental requirements regarding a ship may vary greatly depending on where the ship is operating. For example, at sea, wet ESP may not be needed at all, which enables maintenance of wet ESP. In contrast, near ports, wet ESPs may be required due to local environmental laws. Furthermore, close to the port, one or more engines of the ship may only be operated at partial power, whereby a single wet ESP may be sufficient near the port, although a single wet ESP is not sufficient when all engines are operated at full power (e.g. at sea).

The device is disclosed in claim 1 in more specific terms. The method is disclosed in claim 9 in more specific terms. The dependent claims define advantageous embodiments. The specification discloses further details of the embodiments.

Drawings

Fig. 1 shows a ship with a device for cleaning exhaust gases.

Fig. 2a to 2d show a device for cleaning exhaust gases.

Fig. 3a to 3d show a device for uniform distribution of scrubbed exhaust gas within a wet ESP.

Fig. 4a shows a side view of the interior of a wet electrostatic precipitator.

Fig. 4b shows a top view of the settling zone of the wet electrostatic precipitator.

Fig. 5a shows a top view of a settling zone of another wet electrostatic precipitator.

Fig. 5b shows a top view of the settling zone of another wet electrostatic precipitator.

FIG. 6 shows an arrangement for cleaning exhaust gases, where a scrubber serves a number of combustion engines, an

Fig. 7 shows an arrangement for cleaning flue gases, wherein a wet electrostatic precipitator serves more than two scrubbers.

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

Detailed Description

Fig. 1 shows a ship 910 which is equipped with (i.e. comprises) a device 900 for cleaning a first exhaust gas EG1 and a second exhaust gas EG2. Vessel 910 is an example of a more general vehicle in which apparatus 900 may also be used in other locations where space for apparatus 900 is limited. Fig. 2a to 2d show examples of useful devices 900, as indicated above.

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

In a typical ship (or vehicle), there are a number of different sources of exhaust gas. Thus, typically, the vessel (or vehicle) is equipped with at least two

scrubbers

710, 720. Accordingly, the apparatus 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 fig. 2a to 2 d). The second scrubber 720 comprises an inlet 722 for receiving the second exhaust gas EG2 and an outlet 724 for letting out scrubbed second exhaust gas SEG2 (see fig. 2a to 2 d). The

scrubbers

710, 720 are configured to desulfurize and clean the exhaust gases EG1, EG2, respectively, at least to some extent.

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

For cleaning the scrubbed exhaust gases SEG1, SEG2, the device comprises an electrostatic precipitator (ESP) 100.ESP100 includes a first inlet 112 for receiving at least some of the scrubbed first exhaust gas SEG1 and a second inlet 114 for receiving at least some of the scrubbed second exhaust gas SEG2.

Such inlets

112, 114 are shown, for example, in fig. 2b and 4 a. As will be described in detail below, not all of the scrubbed first exhaust SEG1 needs to be cleaned in the ESP 100; and not all of the scrubbed second exhaust gas SEG2 needs to be cleaned in the ESP100. For this reason, the apparatus 900 includes a first primary conduit 716 configured to convey at least some of the scrubbed first exhaust gas SEG1 to the first inlet 112 of the electrostatic precipitator 100 and a second primary conduit 726 configured to convey at least some of the scrubbed second exhaust gas SEG2 to the second inlet 114 of the electrostatic precipitator 100. These

conduits

716, 726 are shown in fig. 2a to 2 d. The ESP100 is of the type of a wet electrostatic precipitator, i.e. a wet ESP, WESP, in order to clean (i.e. after the wet scrubber) the substantially moisture-saturated gas.

Referring to fig. 4a, the wet ESP100 includes an inlet zone Z1. The first inlet 112 and the second inlet 114 are arranged in the inlet zone Z1. In other words, the inlet zone Z1 is equipped with a first and a second inlet (112, 114). In marine applications, the inlet zone Z1 is preferably short. More specifically, in a preferred embodiment, the height of the inlet zone Z1 is at most 30% of the height of the wet ESP100. The height of the inlet zone Z1 may for example be at most the same as the height of the settling zone Z2 of the wet ESP. Further, preferably, the inlet zone Z1 overlaps with the rest of the wet ESP100 in the height direction of the wet ESP. In other words, preferably, the inlet zone Z1 does not protrude radially from the rest of the wet ESP100. More preferably, the cross-section of the inlet zone Z1 in the horizontal plane is the same as the cross-section of the wet ESP100 in the horizontal plane.

The wet ESP includes a settling zone Z2. The scrubbed exhaust gas is configured to be cleaned in the settling zone Z2 following the principles of electrostatic precipitation. Thus, wet ESP100 includes discharge electrodes 220 and collection surface 210, as will be described in detail below (see, e.g., fig. 4b, 5a, and 5 b). The collection surface 210 is also an electrode. Thus, when considered feasible, the discharge electrodes 220 and the collection surfaces 210 are simply referred to as electrodes. The

electrodes

210, 220 are used to electrodeposit at least one of the scrubbed first exhaust gas SEG1 and the scrubbed second exhaust gas SEG2. The electrodes (210, 220) are arranged within the settling zone Z2 of the wet ESP100. The height of the settling zone Z2 may be equal to the length of the collection surface 210.

The wet ESP100 comprises an outlet 132 for letting out clean exhaust gas CEG (see fig. 3a to 3 d). In use, scrubbed exhaust gas further cleaned in the wet ESP100 flows through the settling zone Z2 from the inlet/

inlets

112, 114 to the outlet 132. Thus, the settling zone Z2 is arranged between the inlet zone Z1 and the outlet 132 of the wet ESP100.

For proper operation and to shorten the maintenance interval, the gas/gases SEG1, SEG2 cleaned using wet ESP100 should be evenly distributed to the settling zone Z2. Thus, in an embodiment, the wet ESP100 comprises a perforated plate 150 between the inlet zone Z1 and the settling zone Z2, as shown in fig. 3a, 3c and 3 d. The purpose of the perforated plate 150 is to distribute the gas SEG, SEG2 evenly between the

electrodes

210, 220 of the wet ESP100. In an embodiment, wet ESP100 comprises at least two perforated plates 150, or more than two perforated plates 150, between inlet zone Z1 and settling zone Z2 for distributing gas SEG, SEG2 more evenly between

electrodes

210, 220 of wet ESP100.

Another possibility (not excluding the perforated plate 150) is to use one perforated tube 152 or a plurality of

perforated tubes

152, 154 in the inlet zone Z1. Referring to fig. 3b and 3c, in an embodiment, the wet ESP100 comprises a first perforated pipe 152 in the inlet zone Z1, which is configured to convey the first scrubbed exhaust gas SEG1 into the inlet zone Z1. Furthermore, in an embodiment, the wet ESP100 comprises in the inlet zone Z1 a second perforated pipe 154 configured to convey the second scrubbed exhaust gas SEG2 into the inlet zone Z1. The first perforated pipe 152 may comprise a bend(s) in order to more evenly spread the first scrubbed exhaust gas SEG1 into the inlet zone Z1. The second perforated pipe 154 may include a bend(s) to more evenly diffuse the second scrubbed exhaust gas SEG2 into the inlet zone Z1. Baffles may be arranged inside the

perforated pipes

152, 154 to further balance the flow of the scrubbed exhaust gas/gases SEG1, SEG2 into the inlet zone Z1. The

perforated pipes

152, 154 may be connected together to form a single perforated pipe 152, as shown in fig. 3d, to which both scrubbed exhaust gases SEG1, SEG2 are delivered, although not necessarily simultaneously. In fig. 3b, 3c and 3d, the first perforated pipe 152 is configured to convey at least the first scrubbed exhaust gas SEG1 into the inlet zone Z1.

As shown in fig. 3c, the wet ESP100 may include a perforated plate 150 and first and second

perforated pipes

152, 154 between the inlet zone Z1 and the settling zone Z2. As shown in fig. 3d, the wet ESP100 may include a perforated plate 150 between the inlet zone Z1 and the settling zone Z2 and only a first perforated tube 152.

When the device 900 is operating, a method for cleaning exhaust gas is performed. As described above, in an embodiment of the method, the wet electrostatic precipitator 100 is arranged on a vehicle (such as a vessel 910). The method includes scrubbing the first offgas EG1 in the first scrubber 710 to produce a scrubbed first offgas SEG1, and scrubbing the second offgas EG2 in the second scrubber 720 to produce a scrubbed second offgas SEG2. The method further comprises passing at least a portion of the scrubbed first effluent gas, SEG1, to the wet electrostatic precipitator 100 and passing at least a portion of the scrubbed second effluent gas, SEG2, to the wet electrostatic precipitator 100. Furthermore, the method comprises cleaning at least one of the at least partially scrubbed first effluent gas SEG1 and the at least partially scrubbed second effluent gas SEG2 in the wet electrostatic precipitator 100 to produce a clean effluent gas CEG.

A preferred embodiment of the method comprises cleaning both (i) the at least partially scrubbed first effluent gas SEG1 and (ii) the at least partially scrubbed second effluent gas SEG2 in the wet electrostatic precipitator 100 to produce a clean effluent gas CEG. However, both the first and second scrubbed effluent gases SEG1 and SEG2 need not be present at 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 subsequently cleaned using the same wet ESP100. In addition, further details regarding the problem of "at least partially" scrubbed exhaust gases (SEG 1, SEG 2) will be given below in connection with the first and

second valve arrangements

754 and 764.

It has been found that scrubbing of the exhaust gases EG1, EG2 (and thus also wet desulphurization) is particularly effective when the scrubbing solution is sprayed onto the gas to be scrubbed. Alternatively or additionally, the gas may be passed through a bath (bath) of scrubbing solution. However, spraying is more effective because it increases the contact area between the gases EG1, EG2 and the scrubbing solution. For these reasons, a preferred embodiment of the apparatus 900 includes a first circulation 718 for spraying the first scrubbing solution SS1 in the first scrubber 710 to scrub the first exhaust gas EG1 by contacting the first exhaust gas EG1 with the first scrubbing solution SS 1. This is depicted in fig. 2a to 2 d.

Accordingly, the first scrubber 710 includes a nozzle 719 (see fig. 2a to 2 d) for spraying the washing solution SS1 and forming droplets of the first washing solution SS1 into the first scrubber 710. In addition, the first scrubber 710 includes a pump 715 for delivering the washing solution to the nozzle 719. During the scrubbing, the first exhaust gas EG1 is brought into contact with the droplets of the first scrubbing solution SS1 thus formed. Accordingly, one 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 EG1 with the droplets of the first scrubbing solution SS 1.

The first scrubbing solution SS1 (or second scrubbing solution SS2 as defined later) may be an aqueous solution of water, fresh water, seawater, or any other compound or compounds known to bind or absorb one or more components of the exhaust/flue gas to be scrubbed. Acid gases, such as SOx, are typically removed from solution by scrubbing with an alkaline solution (an aqueous solution of an alkaline compound such as caustic soda or other alkaline substances).

The first cycle 718 may be an open loop cycle, as shown in fig. 2b and 2 c. Wherein seawater may be used as the scrubbing solution. More specifically, seawater may be used as a common (first) scrubbing solution for both the first and

second scrubbers

710, 720, as in the embodiment of fig. 2 b. Seawater may be used as the first scrubbing solution SS1 used in the first scrubber 710 and the second scrubbing solution SS2 used in the second scrubber 720, which are shown in the embodiment of fig. 2 c.

The first cycle 718 may be a closed loop cycle, as shown in fig. 2a and 2 d. Closed loop cycles may be available when environmental constraints are stringent. If a closed loop cycle is used, the wash solution SS1 or the wash solutions SS1 and SS2 are preferably formed from water (seawater and/or fresh water) and an alkaline substance. In this case, it is even more preferable that the washing solution SS1 or the washing solutions SS1 and SS2 are formed of fresh water and an alkaline substance. Solids may be removed from one or more of the wash solutions SS1, SS2 by one or

more cycles

718, 728.

When the first cycle 718 is a closed loop cycle, as shown in fig. 2a and 2d, the temperature of the first scrubbing solution tends to rise because the scrubbed exhaust gas is hot. However, when the temperature increases, the first scrubbing solution SS1 has a reduced ability to capture SOx from the first exhaust gas EG1. Also, the water evaporated from the process into the atmosphere increases, which may significantly increase the consumption of make-up water and result in a heavy visible plume (plume) after the stack. Therefore, preferably, the first cycle 718 comprises a heat exchanger 717 (see fig. 2a and 2 d) for cooling the first scrubbing solution SS 1. The coolant C1 used in the shipboard heat exchanger 717 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. When the apparatus includes the second circulation 728 and the second circulation 728 is a closed-loop type, the second circulation 728 includes a heat exchanger 727 (see fig. 2 a) for cooling the second scrubbing solution SS 2.

In fig. 2a and 2d, the pump (715, 725) of the cycle (718, 728) is arranged downstream of the heat exchanger (717, 727) of the cycle. However, in an embodiment, such a

pump

715, 725 of the

cycle

718, 728 is arranged upstream of the

heat exchanger

717, 727 of the

cycle

718, 728.

Mixed mode scrubbers may also be used as one or both of the first and second scrubbers. The mixed mode scrubber includes one or more valves (not shown) such that, at a first time, the sprayed scrubbing solution is taken from the scrubber (as shown in fig. 2a and 2 d), and at a second time, the sprayed scrubbing solution is taken from the ocean (as shown in fig. 2b and 2 c).

The same (first) cycle 718 may be used to supply the same (first) wash solution SS1 to both the first and

second scrubbers

710, 720, as shown in fig. 2b and 2 d. In this embodiment, the first cycle 718 is adapted to spray the first scrubbing solution SS1 in the second scrubber 720 to scrub the second offgas EG2 by contacting the second offgas EG2 with the first scrubbing solution SS 1. A corresponding method includes, in the second scrubber 720, spraying the first scrubbing solution SS1 to form droplets of the (first) scrubbing solution SS1 and contacting the second exhaust gas EG2 with the droplets of the (first) scrubbing solution SS 1.

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

With respect to some structural details of the wet ESP100, the wet ESP100 includes a discharge electrode 220 and a collection surface 210 at the settling zone Z2. The settling zone Z2 is shown from the side in fig. 4a and from the end in fig. 4 b. In fig. 4a, reference sign Sl denotes the longitudinal direction of the discharge electrode 220 or the collecting surface 210, or in other words the flow direction of the scrubbed exhaust gas or gases SEG1, SEG2 within the wet ESP. In use, the longitudinal direction Sl may be substantially vertical. However, when on a ship, the direction Sl may change as the ship rolls (i.e. swings). Preferably, in use, the longitudinal direction Sl forms an angle of at most 45 degrees with the vertical direction Sz.

Fig. 4b, 5a and 5b show a transverse cross section of the settling zone Z2. In fig. 4b and 3a, each second electrode has a tubular shape, while the other electrodes are arranged coaxially within the tubular electrode. In fig. 5b, the electrode has the shape of a flat plate. The tubular electrodes in fig. 4b and 5a have a tubular shape extending in the longitudinal direction Sl. The planar electrodes in fig. 5b extend in a plane comprising the longitudinal direction Sl. Generally, the wet ESP100 comprises a tool 222 for discharging (discharging) electric charges onto particles of at least one of the scrubbed first exhaust gas SEG1 and the scrubbed second exhaust gas SEG2.

The operating principle of wet ESP is that the tool 222, for example for discharging an electric charge, charges the particles of the gas SEG1, SEG2 to be cleaned. Thereafter, the gas is transferred between the discharge electrode 220 and the collection surface 210. Since the particles have an electric charge, the

electrodes

210, 220 attract the particles and the particles collide therewith. Typically, the means 222 for discharging the electric charge are arranged as part of the discharge electrode 220 (most commonly at a potential below the collecting surface 210), whereby they emit electrons to the particles to be removed. Accordingly, the particles collide with and are retarded by the collection surface 210 (arrest). Thus, in a preferred embodiment, the area of the collecting surface 210 is larger than the area of the discharge electrode 220, as shown in fig. 4 b. The means 222 for discharging the electric charge may be a sharp projection on the discharge electrode 220. For these reasons, in a preferred embodiment the collecting surface 210 has a tubular shape extending in a longitudinal direction Sl, and each discharge electrode 220 extends coaxially with one of the collecting surfaces 210 in the longitudinal direction Sl, as shown in fig. 4 b; the discharge electrode 220 is laterally surrounded by the collecting surface 210.

To generate the electric field, the device 900 or wet ESP100 comprises a power supply 230 and a wire 232 configured to convey a first potential V1 to the collecting 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 electric field strength between the

electrodes

210, 220 may be, for example, from 0.1kV/cm to 10kV/cm.

It has been found that the wet ESP100 is particularly useful when used after a scrubber, i.e. a wet scrubber operating with scrubbing solutions SS1, SS 2. This arrangement is useful because the scrubbed exhaust gas SEG1, SEG2 entering the wet ESP100 is substantially saturated with moisture. Thus, the moisture of the gases SEG1, SEG2 condenses on the

electrodes

210, 220 of the wet ESP, and in use flushes (flush) the electrodes so that at least some particles colliding with the electrodes are flushed by the condensed water. This increases the maintenance interval of the wet ESP. Furthermore, due to the rinsing, in an embodiment of the device 900, the wet electrostatic precipitator 100 comprises a secondary outlet 140 at a lower portion of the wet electrostatic precipitator 100 for discharging the effluent EFF from the wet electrostatic precipitator 100, as shown in fig. 2a to 4 a. The sewage EFF includes condensed water of the washed exhaust gases SEG1, SEG2, and may further include a rinsing (flushing) solution RS, as detailed below. A relatively small angle between the above-mentioned longitudinal direction Sl and the vertical direction Sz is also advantageous from the viewpoint of flushing the electrodes.

As suggested in the background, low-grade fuels include significant amounts of sulfur, but are otherwise attractive because they are inexpensive. The problem of high sulfur content can be mitigated by using the apparatus 900 as described above. In particular, low grade fuels may be used in internal combustion engines. Accordingly, an embodiment of the apparatus 900 includes a first internal combustion engine 810 and a first secondary conduit 891 configured to route a first exhaust gas EG1 of the first internal combustion engine 810 to an inlet 712 of the first scrubber 710. Therefore, when the internal combustion engine is running, the first exhaust gas EG1 generated by the first internal combustion engine 810 is at least partially delivered to and scrubbed in the first scrubber 710. Further, the embodiment includes a second internal combustion engine 820 and a second secondary pipe 892 configured to deliver the second exhaust gas EG2 of the second internal combustion engine 820 to the inlet 722 of the second scrubber 720. Therefore, when the internal combustion engine is running, the second exhaust gas EG2 generated by the second internal combustion engine 820 is at least partially passed to the second scrubber 720 and scrubbed therein. Reference is made to fig. 1, 2a, 2c, 2d, 6 and 7.

As described above, the scrubbed exhaust gases SEG1, SEG2 are moist. This also applies to the clean exhaust CEG discharged from the wet ESP100. When discharged into the atmosphere, some of the moisture may become visible, referred to as an exhaust plume, or simply as a plume. However, people often confuse visible moisture with smoke. Since smoke emissions are generally considered to be harmful to the environment, an embodiment of the apparatus 900 comprises a plume reduction device 160 configured to reduce the plume of clean exhaust gases CEG, as shown in fig. 2a, 2c and 2 d. The plume abatement device 160 may include at least one fan for mixing the deflubular gas DPG with the clean exhaust gas CEG. The defleave gas DPG may be a dry and/or hot gas (e.g., air) in order to reduce the plume of the CEG. For these reasons, an embodiment of the method includes mixing the defluxing gas DPG with the clean exhaust gas CEG to reduce the plume of the clean exhaust gas CEG. The plume reduction device 160 eliminates water vapor from the clean exhaust gas after the wet ESP100. This means that white smoke is eliminated and corrosion on the top 162 of the exhaust gas duct is avoided.

The wet ESP100 of the device 900 may be used to clean only such exhaust gas that requires cleaning. The environmental requirements regarding a ship may vary greatly depending on where the ship is operating. For example, at sea, wet ESP may not be needed at all, which enables maintenance of wet ESP. Closer to the port, wet ESP may be required due to local environmental laws. However, closer to the port, one or more engines of the ship may only be operating at partial power, whereby a single wet ESP may be sufficient near the port, although a single wet ESP may not be sufficient when all engines are operating at full power (e.g. at sea). Furthermore, closer to the port, the ship may run only one engine, whereby a single wet ESP may be used to clean the exhaust gas from only one engine.

In order to enable a multi-functional use of the single wet ESP100 in connection with the first 710 and second 720 scrubbers, in an embodiment of the plant 900 the first primary pipe 716 comprises a first outlet 752 for letting out some of the scrubbed first exhaust gas SEG1 from the first primary pipe 716 elsewhere (e.g. to the atmosphere) instead of to the wet electrostatic precipitator 100. Therefore, the scrubbed first exhaust gas SEG1 is transferred to the first outlet 752 bypassing the wet ESP100. Such a first outlet 752 is shown in fig. 2a to 2 d. Furthermore, the first primary conduit 716 comprises a first valve arrangement 754 for conveying at least some of the scrubbed first effluent gas SEG1 to the first outlet 752 and at least some of the scrubbed first effluent gas SEG1 to the first inlet 112 of the wet electrostatic precipitator 100. Accordingly, the first valve device 754 is also adapted to pass all scrubbed first offgas SEG1 to the first outlet 752, and accordingly, no scrubbed first offgas SEG1 is passed to the first inlet 112 of the wet electrostatic precipitator 100. The first valve device 754 may thus be used to convey none, only part or all of the scrubbed first exhaust gas SEG1 directly to the first outlet 752 and, for example, to the atmosphere. The first valve device 754 may thus be used to convey all, only part or none of the scrubbed first exhaust gas SEG1 to the first inlet 112 of the wet ESP100. Depending on the circumstances, by using a wet ESP, it may not be necessary to further clean SEG1. Further, in an embodiment, the second primary conduit 726 includes a second outlet 762 for letting out some of the scrubbed second effluent SEG2 from the second primary conduit 726 elsewhere than to the wet electrostatic precipitator 100; and a second valve arrangement 764 for routing at least some of the scrubbed second effluent gas, SEG2, to the second outlet 762 and for routing at least some of the scrubbed second effluent gas, SEG2, to the second inlet 114 of the wet electrostatic precipitator 100. Therefore, the scrubbed second exhaust gas SEG2 is transferred to the second outlet 762 bypassing the wet ESP100. The second valve arrangement 764 may be used in a similar manner (mutatis mutandis) as the first valve arrangement 754.

The first and

second valve arrangements

754, 764 may, for example, be used in such a way that, during a first time period, (i) the scrubbed first exhaust gas SEG1 or a portion thereof and (ii) the scrubbed second exhaust gas SEG2 or a portion thereof are both conveyed to the wet ESP100. In particular, the

valve arrangements

754, 764 may be used such that, for 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 are conveyed to the wet ESP100. Regarding the latter, when only a portion of the scrubbed first exhaust gas SEG1 is cleaned with the wet ESP100, the wet ESP100 does not need to be as large as if it had been designed to clean all of the scrubbed first exhaust gas SEG1. Such use is possible (e.g. at sea).

The first and

second valve arrangements

754, 764 may, for example, be used in such a way that, during the second time period, only one of (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 ESP100. Depending on the circumstances, other sources of exhaust gas may be turned off (e.g., one of the

engines

810, 820 is not running) or its scrubbed exhaust gas may be vented directly to atmosphere through an outlet (752, 762) of the conduit.

The first and

second valve arrangements

754, 764 may, for example, be used in such a way that, during the third period of time, (i) the scrubbed first exhaust gas SEG1 or a portion thereof and (ii) the scrubbed second exhaust gas SEG2 or a portion thereof are not conveyed to the wet ESP100. Depending on the circumstances, the source for other exhaust gases may be shut off (e.g., neither

engine

810, 820 is operating, such as when anchored) or their scrubbed exhaust gases or both may be vented directly to the atmosphere through the outlet (752, 762) of the conduit. Therefore, the wet ESP100 is not in use during the third period of time. This may be possible, for example, at sea, when no further cleaning of the scrubbed exhaust gases SEG1, SEG2 is required.

When the wet ESP100 is not used, maintenance may be performed. As mentioned above, wet ESP is not necessary on board ships and offshore. Maintaining the wet ESP preferably includes at least cleaning. The wet ESP may be cleaned with a flushing solution RS. Cleaning preferably includes cleaning at least some of the

electrodes

210, 220 of wet ESP 100; in particular, such an electrode that collects impurities is typically a collection surface 210 (e.g., an electrode at a higher potential). For these reasons, in an embodiment of the apparatus 900, the wet electrostatic precipitator 100 comprises an inlet 120 for letting in a rinsing solution RS and a tool 122 for cleaning at least some of the

electrodes

210, 220 of the wet electrostatic precipitator 100 with the rinsing solution RS. The tool 122 may include a nozzle for spraying the rinse solution RS onto the electrode being cleaned (such as onto at least the collection surface 210). Such a tool 122 and inlet 120 are depicted in, for example, fig. 2a, 2c and 2 d.

Referring to fig. 6, the first scrubber 710 may also be used to scrub the first exhaust gas EG1 and some of the third exhaust gas EG3. The third exhaust gas EG3 may be generated in the third internal combustion engine 830. In addition (as shown in fig. 6) or alternatively (not shown), a second scrubber 720 may be used to scrub the second exhaust gas EG2 and some of the fourth exhaust gas EG4. The fourth exhaust gas EG4 may be generated in the fourth internal combustion engine 840.

Referring to fig. 7, wet ESP100 may comprise a third inlet 116 for receiving at least some of the scrubbed third exhaust SEG3. The scrubbed third off-gas SEG3 may be received from the third scrubber 730. The third scrubber 730 may be configured to scrub the third exhaust gas EG3 of the third internal combustion engine 830. As shown in fig. 7, the arrangement may comprise a third valve arrangement for conveying all, none or only a part of the scrubbed third exhaust SEG3 to the wet ESP100, and none, all or only a part of the scrubbed third exhaust SEG3, respectively, to elsewhere, for example to the atmosphere. When the wet ESP100 includes the third inlet 116, the first, second and

third inlets

112, 114 and 116 are arranged within the inlet zone Z1. Also in this case the height of the inlet zone Z1 is preferably small as described above, even if not shown in fig. 7.

Claims

1. An apparatus (900) comprising:

-a first scrubber (710) comprising an inlet (712) for receiving the first exhaust gas (EG 1) and an outlet (714) for letting out scrubbed first exhaust gas (SEG 1),

-a second scrubber (720) comprising an inlet (722) for receiving the second off-gas (EG 2) and an outlet (724) for letting out scrubbed second off-gas (SEG 2),

-an electrostatic precipitator (100) comprising:

an inlet zone (Z1) equipped with a first inlet (112) for receiving the scrubbed first exhaust gas (SEG 1) and a second inlet (114) for receiving the scrubbed second exhaust gas (SEG 2),

-a discharge electrode (220) and a collection surface (210) for electro-precipitating the scrubbed exhaust gases (SEG 1, SEG 2), the discharge electrode (220) and the collection surface (210) being arranged in a precipitation zone (Z2) of the electrostatic precipitator (100), and

an outlet (132) for discharging Clean Exhaust Gas (CEG), wherein

The settling zone (Z2) is arranged between the inlet zone (Z1) and the outlet (132) of the electrostatic precipitator (100), and

-a first primary duct (716) configured to convey the scrubbed first exhaust gas (SEG 1) to the first inlet (112) of the electrostatic precipitator (100), and

-a second primary duct (726) configured to convey the scrubbed second exhaust gas (SEG 2) to the second inlet (114) of the electrostatic precipitator (100).

2. The apparatus (900) of claim 1, wherein

-the device (900) comprises a first cycle (718) for spraying a first scrubbing solution (SS 1) inside the first scrubber (710) for scrubbing the first exhaust gas (EG 1) by bringing the first exhaust gas (EG 1) into contact with the first scrubbing solution (SS 1), and

[A]

-the first circulation (718) is adapted to spray the first scrubbing solution (SS 1) inside the second scrubber (720) to scrub the second exhaust gas (EG 2) by bringing the second exhaust gas (EG 2) into contact with the first scrubbing solution (SS 1), or

[B]

-the plant (900) comprises a second circulation (728) for spraying a second scrubbing solution (SS 2) inside the second scrubber (720) for scrubbing the second exhaust gas (EG 2) by bringing the second exhaust gas (EG 2) into contact with the second scrubbing solution (SS 2);

preferably, the first and second electrodes are formed of a metal,

-the first cycle (718) comprises a heat exchanger (717) for cooling the first scrubbing solution (SS 1).

3. The device of claim 1 or 2, wherein

-the electrostatic precipitator (100) comprises a secondary outlet (140) at a lower portion of the electrostatic precipitator (100) for discharging contaminated water (EFF) from the electrostatic precipitator (100).

4. The apparatus of any of claims 1 to 3, comprising:

-a first internal combustion engine (810),

-a first secondary duct (891) configured to convey a first exhaust gas (EG 1) of the first internal combustion engine (810) to an inlet (712) of the first scrubber (710),

-a second internal combustion engine (820), and

-a second secondary duct (892) configured to convey a second exhaust gas (EG 2) of the second internal combustion engine (820) to an inlet (722) of the second scrubber (720).

5. The device of any one of claims 1 to 4, wherein

-said first primary conduit (716) comprises:

a first outlet (752) for discharging some of said scrubbed first exhaust gas (SEG 1)

Is discharged from the first primary conduit (716) to another location than to the electrostatic precipitator (100), an

-a first valve device (754) for conveying at least some of the scrubbed first exhaust gas (SEG 1) to the first outlet (752) and at least some of the scrubbed first exhaust gas (SEG 1) to the first inlet (112) of the electrostatic precipitator (100);

preferably, the first and second electrodes are formed of a metal,

-said second primary duct (726) comprises:

a second outlet (762) for some of said scrubbed second offgas (SEG 2)

Is discharged from the second primary conduit (726) to another location than to the electrostatic precipitator (100), an

-second valve means (764) for conveying at least some of said scrubbed second exhaust gas (SEG 2) to said second outlet (762) and at least some of said scrubbed second exhaust gas (SEG 2) to said second inlet (114) of said electrostatic precipitator (100).

6. The apparatus of any of claims 1 to 5, comprising:

-a perforated plate (150) or perforated plates (150) between said inlet zone (Z1) and said settling zone (Z2); and/or

-a first perforated pipe (152) configured to convey at least said first scrubbed exhaust gas (SEG 1) to said inlet zone (Z1).

7. The device according to any one of claims 1 to 6, wherein the electrostatic precipitator (100) comprises:

-an inlet (120) for letting in a Rinsing Solution (RS), an

-means (122) for washing at least some of the collecting surface (210) and/or the discharge electrodes (220) of the electrostatic precipitator (100) with the Rinsing Solution (RS).

8. A vehicle, such as a ship (910), comprising the apparatus (900) of any one of claims 1 to 7.

9. A method for cleaning at least a first exhaust gas (EG 1) and a second exhaust gas (EG 1), the method comprising:

-scrubbing the first off-gas (EG 1) in a first scrubber (710) to produce a scrubbed first off-gas (SEG 1),

-scrubbing the second off-gas (EG 2) in a second scrubber (720) to produce a scrubbed second off-gas (SEG 2),

-passing at least a portion of said scrubbed first exhaust gas (SEG 1) to an electrostatic precipitator (100),

-passing at least a portion of the scrubbed second exhaust gas (SEG 2) to the electrostatic precipitator (100),

-cleaning one or both of at least a part of the scrubbed first exhaust gas (SEG 1) and at least a part of the scrubbed second exhaust gas (SEG 2) in the electrostatic precipitator (100) to produce a Cleaned Exhaust Gas (CEG).

10. The method of claim 9, comprising:

-spraying a first scrubbing solution (SS 1) in the first scrubber (710) to form droplets of the first scrubbing solution (SS 1) and contacting the first exhaust gas (EG 1) with the droplets of the first scrubbing solution (SS 1), and

-spraying the first scrubbing solution (SS 1) or the second scrubbing solution (SS 2) in the second scrubber (720) to form droplets of the first scrubbing solution (SS 1) or the second scrubbing solution (SS 2), and contacting the second exhaust gas (EG 2) with the droplets of the first scrubbing solution (SS 1) or the second scrubbing solution (SS 2);

preferably, the method comprises:

-cooling the first scrubbing solution (SS 1) using a first heat exchanger (717), preferably using water, such as seawater, as coolant (C1),

more preferably, the amount of the organic solvent is,

-said first washing solution (SS 1) comprises water, for example fresh water, and a base.

11. The method according to claim 9 or 10, comprising:

-generating a first exhaust gas (EG 1) in a first internal combustion engine (810),

-generating a second exhaust gas (EG 2) in a second internal combustion engine (820),

-passing the first exhaust gas (EG 1) to the first scrubber (710), and

-passing the second exhaust gas (EG 2) to the second scrubber (720).

12. The method according to any one of claims 9 to 10, comprising:

-in a first time period, both (i) the scrubbed first exhaust gas (SEG 1) or part thereof and (ii) the scrubbed second exhaust gas (SEG 2) or part thereof are conveyed to the electrostatic precipitator (100), and/or

-in a second time period, only one of (i) the scrubbed first exhaust gas (SEG 1) or part thereof, or (ii) the scrubbed second exhaust gas (SEG 2) or part thereof is conveyed to the electrostatic precipitator (100), and/or

-in a third time period, neither (i) the scrubbed first off-gas (SEG 1) or part thereof nor (ii) the scrubbed second off-gas (SEG 2) or part thereof is conveyed to the electrostatic precipitator (100).

13. The method of any one of claims 12, comprising

-during said first period of time, transferring to said electrostatic precipitator (100):

either [ A ] (i) only a part of the scrubbed first exhaust gas (SEG 1) and (ii) all of the scrubbed second exhaust gas (SEG 2), or

Both of (i) only a portion of the scrubbed first exhaust gas (SEG 1) and (ii) only a portion of the scrubbed second exhaust gas (SEG 2), and/or

-in the second period of time, only one of (i) only a part of the scrubbed first exhaust gas (SEG 1) or (ii) only a part of the scrubbed second exhaust gas (SEG 2) is conveyed to the electrostatic precipitator (100), and/or

-rinsing the electrostatic precipitator (100) with a Rinsing Solution (RS) during the third time period.

14. The method of any of claims 9 to 13, comprising:

-mixing a deflubular gas (DPG) with the Clean Exhaust Gas (CEG) to reduce the plume of the Clean Exhaust Gas (CEG).

15. The method according to any of claims 9-14, wherein the electrostatic precipitator (100) is arranged on a vehicle, such as a ship (910).