The present invention relates to a washing tower/scrubber. Especially the present invention relates to a sequential scrubber for exhaust and a method thereof for washing off oil, particles and/or noxious gases (e.g. SO2) from the exhaust using a vertical scrubber wherein the washing is based on a plurality of integrated washing sections/sequences in series.

Background

Washing systems are applicable in connection with IMO, MARPOL regulations Annex VI, which determine the requirements for SO2 emission for vessels in international and ECA waters, and wherein washing of exhaust has been allowed as an approved secondary solution.

Most liquid-based washing systems used today are based on counter-current scrubbers where the gas is introduced from the bottom of the scrubber, and water is introduced in the opposite direction and runs towards the gas stream, often through a layer of packing structures. This provides for a good water utilization since the fresh water meets the gas at the end of the washing process. The problem with such a solution is that the velocity of the gas stream must be limited in order to avoid "water built up", and thereby creating unstable conditions in the scrubber. This leads to high dimensions of the scrubber with belonging problems such as weight, placing/assembling onboard existing vessels etc.

It also exists co-current systems in use having higher gas velocity and/or less weight, however the problems with the known co-current scrubbers is that large amounts of water must be added at the end of the washing process to achieve the cleaning requirements for the gas, which leads to an unnecessary high water consumption and belonging problems related to the effect requirements for inter alia water pumps, and problems related to water cleaning systems. Chemical compounds (e.g. NaOH) can be added to the washing process to reduce the water consumption to some extent, but this increases the costs with regard to the chemical

consumption. Generally, high gas velocity involves less tower volume than low velocity counter-current washing systems, and corresponding lower costs with regard to the building and installation of the scrubber.

Summary of the invention

It is an object of the present invention to provide a vertical scrubber for washing off oil, particles and/or noxious gases (e.g. SO2) from exhaust gas using a vertical scrubber. A further object of the present invention is to provide a vertical scrubber having an upwardly rotating co-current flow of washing liquid and exhaust gas of relatively high velocity, which provides for an efficient washing of exhaust gas avoiding accumulation of washing liquid within the scrubber which may cause unstable conditions within the scrubber.

It is further an object of the present invention to provide a co-current scrubber wherein the washing effect of a bulk portion of the washing liquid is utilized to its maximum.

It is further an object of the present invention to provide a co -current scrubber for removal of oil, particles and/or noxious gases from exhaust gas according to IMO regulations.

It is a further object of the present invention to provide a scrubber having a washing process which is considerably downscaled compared to known scrubbers, thus providing a scrubber with a reduced footprint. It is a further object of the present invention to increase the absorbing surface of the washing liquid to improve the capture/absorption of gas particles in the washing process.

It is a further object of the present invention to provide a scrubber having a plurality of washing sections arranged in series to provide for a plurality of sequential washing steps within the scrubber obtaining a maximum washing effect.

It is a further object of the present invention to provide a scrubber that easily can be mounted to existing funnels on board vessels.

It is a further object of the present invention to provide a scrubber having a minimum need for maintenance. It is further an object of the present invention to provide a method for washing off oil, particle and/or noxious gases from exhaust gas by using the vertical scrubber.

The present invention is set forth and characterized in the independent claims, while the dependent claims describe other characteristics of the invention.

In general, the present invention involves a vertical scrubber for washing exhaust gas where washing liquid and exhaust gas flow co -currently in the same upwards direction of the scrubber. The washing liquid which is added closer to the end of the washing process, and retracted after flowing a short distance, is re-injected further down in the scrubber having more polluted exhaust gas.

The present invention provides a vertical scrubber for removal of oil, particles and/or noxious gases such as S0 ₂ from exhaust gas. The vertical scrubber comprises an upper part and a lower part, an outer cylindrical vertical pipe, and an inner cylindrical vertical pipe arranged coaxially within the outer cylindrical pipe. The scrubber further comprises a gas inlet channel for exhaust gas arranged in the lower part of the scrubber, and a gas outlet channel for scrubbed/washed exhaust gas arranged in the upper part of the scrubber. A spiral is arranged between the outer cylindrical vertical pipe and the inner cylindrical vertical pipe forming an upwardly rotational path for the gas flow. A first washing section is arranged within the rotational path and comprises a first washing liquid injection device for adding washing liquid to the gas flow and a first washing liquid collector for subsequent removal of a bulk portion of said added washing liquid. A second washing section arranged within the rotational path comprising a second washing liquid injection device for adding washing liquid to the gas flow and a second washing liquid collector for subsequent removal of a bulk portion of said added washing liquid, displaced upward relative to the first washing section. Further a washing liquid guiding channel is arranged within the scrubber configured to guide/reinject the washing liquid removed from the second washing section into the washing liquid injection device of the first washing section.

The outer cylindrical vertical pipe is extending at least from the lower part of the scrubber to the upper part of the scrubber having an inner cylindrical vertical pipe placed coaxially therein. The spiral arranged between the inner surface of the outer cylindrical vertical pipe and the outer surface of the inner cylindrical vertical pipe can be attached to the inner cylindrical vertical pipe by attaching means.

Within the rotational path of the scrubber formed by the spiral, the scrubber comprises at least two washing sections wherein each of the washing sections comprises a washing liquid injection device for adding washing liquid to the gas flow and a washing liquid collector for subsequent removal of a bulk portion of said added washing liquid.

In an aspect of the invention, the first washing liquid collector of the first washing section comprises a washing liquid outlet channel for guiding the washing liquid to the exterior of the scrubber during operation.

In another aspect of the invention, the first washing liquid collector of the first washing section comprises a washing liquid outlet channel for guiding the washing liquid to a reservoir arranged in the lower part of the scrubber during operation.

In a further aspect vertical scrubber comprises at least one additional washing section arranged within the upwardly rotational path wherein each additional washing section comprises a washing liquid injection device for adding washing liquid to the gas flow, a washing liquid collector for subsequent removal of a bulk portion of said added washing liquid and a washing liquid guiding channel configured to guide the washing liquid from at the least one washing section to another washing section displaced downward said at least one washing section or a washing liquid outlet channel for guiding the washing liquid to the exterior of the scrubber. In an exemplary embodiment of the invention the scrubber comprises three washing sections; the fist, the second and an additional washing section. The additional washing section can be arranged upstream the first washing section or downstream the second washing section. The first and second washing sections are herein arranged in series. If the additional washing section is arranged downstream the second washing section; a washing liquid guiding channel can be arranged within the scrubber to guide/reinject the washing liquid collected from this additional washing section into the washing liquid injection device of the second washing section. If the additional washing section is arranged upstream the first washing section, the additional and first sections comprise a washing liquid outlet channel arranged to guide the washing liquid collected to the exterior of the scrubber or to the reservoir. The additional and the first section are arranged in the beginning of the washing process, close to the lower part of the scrubber where exhaust gas enters the rotational path provided by the at least one spiral. The washing liquid added to the exhaust gas in the beginning of the washing process will be highly polluted by the exhaust gas when collected. The washing liquid will, after being collected and removed from these sections, have a small absorption capacity, in thus not be useful for reinjection. However, the second washing section arranged closer to the end of the washing process closer to the upper part of the scrubber receives exhaust gas that has been washed by the additional and first preceding washing sections, and the clean washing liquid added through the washing liquid injection device of the second washing section will when collected by the washing liquid collector still have high absorption capacity when reinjected, since the exhaust gas has already been washed such that most of the oil, particles and/or noxious gases have been remove. In the washing section closer to the end of the washing process, the washing liquid will need to absorb only a remaining part of oil, particles and/or noxious gases from the exhaust which in a preferred embodiment is small, and the washing liquid collected will still have a high absorption capacity when reinjected.

A person skilled in the art will understand that a numerous of different

combinations of washing sections are possible wherein at least one of the washing sections guide s/reinjects the collected washing liquid to a washing injection device of another washing section displaced downward. The amount of washing sections within a scrubber will depend on different factors such as the composition of the exhaust gas, the removal efficiency of oil, particles and/or noxious gases, the rotational velocity of the gas flow etc. The combined rotational and vertical velocity of the exhaust gas inside the scrubber should exceed a minimum value for a bulk portion of the added washing liquid to be removed in the same section. The velocity of the gas flow may be between 3 and 25 m/s, more preferably between 5 and 15 m/s, even more preferably between 6 and 10 m/s, for example 8 m/s.

The guiding channel configured to guide the washing liquid collected from one washing section into a washing liquid injection device of another washing section may use the static pressure of the washing liquid due to the drop from a higher to a lower level. Thus, the washing liquid can be reinjected without using pumps or other devices for assisting the reinjection.

In a further aspect of the invention, the guiding channel comprise a washing liquid seal such as a u-bend to compensate for different static pressure between washing sections to avoid backflow of gas through guiding channel.

In a further aspect at least the first and the second washing sections further comprises a mixing element arranged downstream the at least first and/or second washing liquid injection devices for increasing the absorbing surface of the washing liquid during operation.

The mixing element may be a flow restrictor such as a lattice, packing material or tower packings creating turbulence in the fluid flow. In another aspect at least both the first and second washing liquid collector comprises a vertical fluid barrier protruding inward from an inner surface of the outer cylindrical vertical, the vertical fluid barrier being configured to act as a fluid barrier for the washing liquid flowing along said inner surface during operation. The fluid barrier collects the washing liquid running alongside the surface of the outer cylindrical vertical pipe but does not collect the gas running closer to the inner cylindrical vertical pipe. The vertical barrier may cover/protrude from 2 to 25 % of the radial width of the path and from 70 to 100 % of the height of the path, more preferably from 4 to 15 % of the radial width of the section channel and from 80 to 100 % of the height, even more preferably from 5 to 10 % of the radial width of the section channel and from 95 to 100 % of the height. The fluid barrier may have a radial angle such that the washing liquid accumulates at the barrier element. The radial angle may be from 10 to 80 relative to the radial axis extending from the position of the barrier element at the inner surface of the outer vertical cylindrical pipe towards the vertical centre axis of the outer cylindrical vertical pipe. The radial angle is preferably from 30 to 80°, even more preferably from 50 to 80°, for example 70°.

In a further aspect the at least the first and second washing liquid collectors comprises a deflector arranged on the spiral in proximity of, and upstream of, each washing liquid collector and configured to deflect washing liquid being blocked by the vertical fluid barrier. The deflector may have a wing shape protruding vertically upwards from the spiral blocking the washing liquid from running downwards the spiral. When the scrubber is operating below the minimum velocity value, e.g. less than 3 m/s, a bulk portion of the added washing liquid in one section will be removed by the deflector of the previous section. When exhaust gas and washing liquid enters the packing material at low velocities, the fluid will mix and the washing liquid will absorb oil, particles and/or noxious gases and thereafter fall downward the spiral due to the gravity forces, and be collected by the deflector of the preceding section.

In another aspect the scrubber further comprises a washing liquid reservoir arranged in lower part of the scrubber, wherein the washing liquid reservoir surrounds at least partly the gas inlet channel. The reservoir may be configured to collect the washing liquid. During operation of the scrubber, some of the washing liquid may run along the spiral down to the lower part of the scrubber and be collected by the reservoir. The reservoir may also be connected to an outlet channel removing used washing liquid from a washing section. Thus, the used washing liquid removed from the washing section by the outlet channel can thereby be guided into the reservoir. The reservoir also includes an outlet for washing liquid to be routed to an external washing liquid cleaning process.

In another aspect the scrubber further comprises a bypass valve arranged at an upper end of the inner cylindrical vertical pipe. Thus, if any problems occur within the path configured by the spiral, the exhaust can be lead through the inner cylindrical pipe by opening the valve at the upper end of the pipe. The washing liquid injection device can be any kind of injector allowing the washing liquid to be injected and thereafter guided co -currently with the gas flow within the scrubber. The washing liquid injection device may comprise a plurality of nozzles or jets.

In another aspect the vertical scrubber comprises a plurality of spirals having a common axis of rotation, wherein the plurality of spirals are arranged vertically displaced from each other, thereby enabling the exhaust gas to follow a plurality of gas flow paths simultaneously during operation.

A person skilled in the art will understand that the plurality of spirals making the plurality of flow paths render a numerous of possibilities for reinjection of washing liquid from one washing section to another. Each gas flow path has a plurality of washing sections arranged in series, where each path provides for one series of washing sections. A plurality of washing paths provides for in increased washing efficiency of the exhaust gas to be washed. In one aspect the reinjection of washing liquid from one washing section to another occur between sections arranged in the same path.

In another aspect the reinjection of washing liquid from one washing section to another occur between sections arranged in different paths. The washing liquid used for absorbing oil, particles and/or noxious gases (e.g. S0 ₂ , CO2) from the exhaust gas may be wash water, such as sea water or fresh water. Further, the wash water may comprise chemicals (e.g. NaOH) for increasing the absorption of the oil, particles and/or noxious gases.

In another aspect the invention involves a method for scrubbing oil, particles and/or noxious gases from exhaust gas using the scrubber. The method comprises the following steps:

a) adding exhaust gas through the inlet channel,

b) injecting washing liquid through a first liquid injection device in the first washing section co-currently to the exhaust gas and

subsequently removing a bulk portion of the injected washing liquid by the first washing liquid collector,

c) injecting washing liquid to the washed exhaust gas entering the second washing section from the first washing section through the second liquid injection device and

subsequently removing a bulk portion of the injected washing liquid by the second washing liquid collector, and

d) reinjecting the removed washing liquid of the second washing liquid collector from the second washing section into the first liquid injection device. In a further aspect the method further comprises the following step:

e) guiding the washing liquid removed via the first washing liquid collector to a reservoir at least partly surrounding the inlet channel or to the exterior of the scrubber via a washing liquid outlet channel. In an yet further aspect the method further comprises the following steps

f) injecting washing liquid through a third liquid injection device arranged in a third washing section to the washed exhaust gas entering from the second washing section and

subsequently removing a bulk portion of the injected washing liquid by a third washing liquid collector within the third washing section, and g) reinjecting the removed washing liquid from the third washing section into the liquid injection device of the second washing section. A person skilled in the art will understand that the scrubber may comprise more than the three mentioned washing sections, and thus the method may comprise further method steps.

In another aspect the present invention involves a sequential washing

tower/scrubber comprising a vertical co-current washing system having a plurality of sequences/sequential steps/washing sections wherein each sequence involves adding water to the gas stream, separating and removing a bulk portion of the added washing liquid/water before adding a new amount of water to the gas entering the next sequence. Water is removed by rotation and internal water collectors, thereby making it possible to have a high gas velocity through the tower/scrubber without risking any water accumulation. Water which has been removed from a sequence higher up in the tower/scrubber can by the aid of the drop and optionally a water seal be reinjected into a preceding sequence in a lower part of the tower/scrubber such that water having little pollution from the upper part can be utilized as wash water in a lower more polluted sequence earlier in the washing process. Dividing the cleaning process into a plurality of sequences also allows for separation of highly polluted wash water from less polluted water, which also simplifies the water treatment and further allows for clean water to be added at the end of the process without increasing the total amount wash water. The scrubber comprises an outer vertical cylindrical pipe and an inner vertical cylindrical pipe arranged in coaxially within the outer cylinder, and one or more spirals arranged between the inner and the outer cylindrical pipe. The inner cylindrical pipe may be fastening the spirals thereto, and may be used as a bypass of the wash water process when problems arise within the nozzle/wash water area/washing liquid injection device by the aid of a simple safety valve/device mounted at the top of the inner cylindrical pipe.

The scrubber may comprise a plurality of washing sections/sequences arranged in series to increase the cleaning efficiency.

In another aspect, the scrubber comprises a plurality of spirals arranged in parallel having a common axis of rotation and arranged vertically displaced from each other. The inner cylindrical pipe may be used as a bypass of the washing area by the aid of a simple valve arrangement mounted at the top of the pipe which will close due to its own weight or by the aid of a spring. The valve can be designed as a simple combined self-opening safety valve with the possibility for manual operation, and which opens when the pressure inside the inner cylinder extends a preset value with regard to the outer cylinder.

The term "bulk portion" should be understood as from 50 to 100% of the total amount/portion, preferably from 60 to 100%, even more preferably from 70 to 100% and most preferably from 80 to 100%. The term "clean washing liquid" should be understood as washing liquid having a high absorption capacity and which has not or barely reacted with the exhaust gas.

The term "polluted washing liquid" should be understood as washing liquid having low/little absorption capacity and which has reacted with exhaust gas. The term "clean exhaust gas" should be understood as exhaust gas which has been washed and wherein all or almost all the oil, particles and/or noxious gases to be washed off are removed from the exhaust gas. In a preferred aspect the clean exhaust gas comprises less than 30 ppm of noxious gases, more preferably less than 20 ppm, even more preferably less than 15 ppm. The term "polluted exhaust has" should be understood as exhaust gas which has not been washed and comprises oil, particles and/or noxious gases .

The term "fluid" should be understood as a mixture of gas and liquid.

The term "plurality" should be understood as at least two.

The term "protruding inward" means that the protrusion protrudes towards the centre of the outer cylindrical pipe.

Brief description of the drawings

The present invention will be described in further detail with reference to the enclosed figures wherein

Figure 1 schematically illustrates a perspective view of an exemplary embodiment of the washing tower/scrubber according to the present invention, where the pipes and other elements are drawn as translucent for illustrative purposes.

Figure 2 schematically illustrates a cross-sectional top view of the scrubber in figure 1,

Figure 3a, 3b and 3c schematically illustrate a detailed perspective view of exemplary embodiments of a part of the scrubber,

Figure 4 schematically illustrates an exemplary embodiment of the lower part of the scrubber,

Figure 5a schematically illustrates an exemplary embodiment of the scrubber having two spirals, and Figure 5b schematically illustrates an exemplary embodiment of the scrubber having three spirals. Detailed description of the invention

In the figures the same reference number is used for the same elements in the different embodiments.

Figure 1 illustrates an exemplary embodiment of a vertical washing/tower scrubber 10 comprising an upper part 12, a lower part 13, an outer cylindrical pipe 11 and an inner cylindrical pipe 9 arranged in the centre of the outer cylindrical pipe. The lower part 13 of the scrubber comprises an inlet 23 for guiding exhaust gas to be washed within the scrubber 10. In the space between the outer cylindrical pipe 11 and the inner cylindrical pipe 9 a spiral 8 is arranged for guiding the exhaust gas flow 5 upwards in a rotational flow. The spiral 8 extends from the lower part 13 to the upper part 12 providing a single rotational flow path. At the upper part 12 of the scrubber 10 washed exhaust gas is guided out of the scrubber 10 through outlet 24.

As shown in figure 1, the exhaust gas enters the spiral 8 at the lower part 13 of the scrubber 10 and rotates around the inner cylindrical pipe 9 when guided upwards in the scrubber 10. The exhaust gas is guided through the three separately arranged washing liquid injection device 1 ,4,26 having a plurality of nozzles inject washing liquid to the exhaust gas. The washing liquid is guided co-currently with the gas flow 5 within the scrubber 10 and passes through three separately arranged washing sections arranged in series. The thick black arrows indicate the direction of the exhaust gas flow 5 within the scrubber 10. The washing liquid added through the injection devices 1,4,26 absorbs inter alia oil, particles and S0 ₂ from the exhaust gas. Due to the spiral 8 the fluid flow is rotating and the washing liquid within the fluid flow is forced outwards due to centrifugal forces, alongside the inner surface of the outer cylindrical vertical pipe 11. During operation of the scrubber 10 in figure 1, the exhaust gas enters the scrubber through the gas inlet channel 23 in the lower part 13 of the scrubber 10. The exhaust gas flow 5 is thereafter guided into a rotational path provided by the spiral 8. The exhaust gas then enters the first washing section (shown in figure 2) having a first washing injection device 1 injecting washing liquid to the exhaust gas flow 5. The exhaust gas is thereby mixes and the washing liquid at absorbs inter alia SO2 from the exhaust gas. The fluid flows approximately 180° within the rotating path before the coalescence washing liquid flowing along the inner surface of the outer cylindrical vertical pipe 11 is collected by a first washing liquid collector 3. The washing liquid collector has a vertical fluid barrier 17 protruding inward from the inner surface of the outer cylindrical vertical pipe 11 and a deflector 18 arranged on the spiral 8 in proximity of, and upstream of, the washing liquid collector 3. The highly polluted washing liquid which has absorbed inter alia SO2 from the exhaust gas can then be removed from the scrubber by a channel (not shown) . The at least partly washed exhaust gas upwards, will follow the rotational path into the second washing section (shown in figure 2) having a second washing injection device 4 injecting washing liquid to the at least partly washed exhaust gas for further washing. The fluid flows

approximately 180° within the rotating path before the coalescence washing liquid flowing along the inner surface of the outer cylindrical vertical pipe 11 is collected by a second washing liquid collector 7 having a vertical fluid barrier and a deflector. The collected washing liquid is then guided by a guiding channel 16, having a liquid seal 20, into the washing injection device 1 of the first washing section. The partly washed exhaust gas which is flowing upwards, will follow the rotational path into the third washing section having a third washing liquid injection device 26 injecting washing liquid to the partly washed exhaust gas for further washing. The fluid flows approximately 180° within the rotating path before the coalescence washing liquid flowing along the inner surface of the outer cylindrical vertical pipe 11 is collected by a third washing liquid collector 27 having a vertical fluid barrier and a deflector. The collected washing liquid is then guided by a guiding channel 16, having a liquid seal 20, into the washing injection device 4 of the second washing section. The washed exhaust will be guided out of the scrubber 10 through gas outlet channel 24 in the upper part 12 of the scrubber.

The washing liquid being injected to the exhaust gas flow from the first injection device 1 of the scrubber 10 is has already been used for washing in the second washing section and has been collected by the second washing liquid collector 7. However, the washing liquid collected in the second washing section will most probably still have a relatively high absorption capacity, and will when reinjected into the first washing liquid injection device wash the exhaust gas in the first washing section. From the figure it can be seen that the washing liquid entering the third injection device 26 of the third washing section in the upper part 12 of the scrubber 10 is unused, meaning that the washing liquid is not reinjected from another washing section. This unused washing liquid will have a high absorption capacity. The gas entering this third washing section has already been washed in the two previous washing sections. The washing liquid collected by the third washing liquid collector 27 will therefore most probably still have a high absorption capacity, and is therefore reinjected into the second washing liquid injection device for washing the exhaust gas in the second washing section. Further, the unused washing liquid injected to the exhaust gas will due to its high absorption capacity remove nearly all or all the oil, particles and/or noxious gases from the exhaust gas before the washed exhaust gas is guided out of the scrubber 10.

At the lower part 13 of the scrubber a washing liquid reservoir 25 is shown for collecting washing liquid and a reservoir outlet 29, see figure 4. A bypass valve 19 is arranged at the upper end of the inner cylindrical vertical pipe

9. Thus, if any problems occur within the rotational path configured by the spiral 8, the exhaust gas can be lead through the inner cylindrical pipe 9 by opening the valve 19 allowing the exhaust gas to pass through the scrubber without being washed.

In other words, the vertical scrubber 10 comprises an outer cylindrical pipe 1 1 and an inner cylindrical pipe 9 arranged in the centre of the outer cylindrical pipe 11. At least one spiral 8 is arranged between the outer cylindrical pipe 11 and the inner cylindrical pipe 9 extending from the lower part of the scrubber 10 to the upper part of the scrubber 10. The spiral 8 is attached to the inner cylindrical pipe 9 and this inner cylindrical pipe 9 can be used as a bypass for exhaust gas if problems occur in the nozzle/washing area of a washing section.

The scrubber 10 further comprises an exhaust gas inlet 23 arranged in the lower part 13, and a washed exhaust gas outlet 24 arranged in the upper part 12 of the scrubber 10. Washing liquid/water is added to the scrubber 10 via a nozzle arrangement 1,4 arranged at least in the upper and lower part of the scrubber and/or between the upper and lower part 12, 13. The gas entering through inlet 23 is put into rotation due to the spiral 8. Water entering/injected from the nozzle arrangements 1,4 is being mixed, and a mixing element, such as a lattice or a layer of packing material (see figure 2) can be arranged downstream the nozzles to increase the absorption surface. The water from the nozzles are transported together with the gas co- currently, and swirls along the inner surface 1 Γ of the outer cylindrical pipe 1 1 due to the rotational forces, and the water is extracted from the scrubber 10 via inner vertical angles/collectors 3,7, 17 and are directed through collecting pipes 16,22 for each collecting step/section. The extracted water can be recycled back to the scrubber 10 via a nozzle arrangement 1 further down due to the drop and optionally a water seal 20. Fairly clean water extracted from the upper part 12 of the scrubber

10, at the end of the scrubbing process, can therefore be reinjected to the beginning of the washing process. This water recycling allows for considerably reduction in the consumption of wash water and amount of wash water for waste treatment, and the cleaning process before discharging is considerably downscaled.

Figure 2 illustrates a cross-section of the scrubber 10 in figure 1 , showing the first and second washing section 14,15 arranged in series as mentioned above. Due to the spiral 8, the second washing section 15 is displaced upward relative to the first washing section 14. As already mentioned above the exhaust first enters the first washing section 14 having a first washing injection device 1 injecting washing liquid to the exhaust gas flow. After the washing liquid has been injected to the gas flow, the fluid, which is a mixture of exhaust gas and washing liquid, is passed through a mixing element 2 which increases the absorption surface of the washing liquid thereby increasing the absorption capacity of the washing liquid. Thereafter the fluid flows approximately 180° within the rotating path before the coalescence washing liquid flow 21 , flowing along the inner surface of the outer cylindrical vertical pipe 11 , is collected by the first washing liquid collector 3. The washing liquid collector 3 has a vertical fluid barrier 17 protruding inward from the inner surface 1 Γ of the outer cylindrical vertical pipe 11 and a deflector (not shown). The highly polluted washing liquid which has absorbed inter alia S0 ₂ from the exhaust gas can then be removed from the scrubber by washing liquid outlet channel 22. The at least partly washed exhaust gas which is flowing upwards will follow the rotational path into the second washing section 15 having a second washing injection device 4 injecting washing liquid to the at least partly washed exhaust gas for further washing. After the washing liquid has been injected to the gas flow, the fluid is passed through the mixing element 6 which increases the absorption surface of the washing liquid. The fluid flows approximately 180° within the rotating path before the washing liquid flow 21 flowing along the inner surface 1 Γ of the outer cylindrical vertical pipe 1 1 is collected by a second washing liquid collector 7 having a vertical fluid barrier and a deflector. The collected washing liquid is then guided by a guiding channel 16, into the washing injection device 1 of the first washing section.

Figure 3a, 3b and 3c illustrate a detailed perspective view of the guiding channel 16, washing liquid collector 7,27 and the washing liquid injection device 1,4.

In figure 3a the washing liquid collector 7,27 comprises a vertical fluid barrier 17 protruding inward from the inner surface of the outer cylindrical vertical pipe and a deflector 18. The deflector 18 has a protruding wing-shape, protruding co current upwards from the upper surface of the spiral 8. In this exemplary embodiment the guiding channel 16 is arranged on the upper surface of the spiral 8 downstream and in proximity of the deflector 18 allowing the washing liquid to flow into the guiding channel 16 after being collected by the vertical fluid barrier 17 and deflected by the deflector 18. The guiding channel 16 has a liquid seal 20 configured as a u-bend compensating for the different static pressure between the two washing sections to avoid backflow of gas through guiding channel 16. The fluid injection device 1,4 comprises a plurality of nozzles 28.

In figure 3b the washing liquid collector 7,27 is having a vertical fluid barrier 17 and a deflector 18 as shown in figure 3 a. However, in this exemplary embodiment the guiding channel 16 is arranged within the spiral 8 creating a hole therein, and the guiding channel is arranged downstream and in proximity of the deflector 18 allowing the washing liquid to flow into the guiding channel 16 after being collected by the vertical fluid barrier 17. The guiding channel 16 has a u-bend 20 and the fluid injection device 1,4 comprises a plurality of nozzles 28 as also seen in figure 3a. In figure 3c the washing liquid collector 7,27 is having a vertical fluid barrier 17 and a deflector 18 as shown in figures 3a and 3b. As in figure 3b, the guiding channel 16 is arranged within the spiral 8 creating a hole therein, and the guiding channel is arranged downstream and in proximity of the deflector 18 allowing the washing liquid to flow into the guiding channel 16 after being collected by the vertical fluid barrier 17. However, the guiding channel 16 does not have a u-bend liquid seal 20 and guiding the washing liquid directly to the fluid injection device 1 ,4. The fluid injection device 1,4 comprises a plurality of nozzles 28.

Figure 4 illustrates a detailed perspective view of the lower part 13 of the scrubber. The exhaust gas enters the scrubber via gas inlet channel 23 which in this exemplary embodiment provides a rotational gas flow before the gas flow enters the path provided by the spiral 8 within the scrubber. Since the gas inlet channel 23 provides for a rotational gas flow 5, the gas flow 5 mainly maintains its velocity when entering the rotational path provided by the spiral 8. The lower part 13 of the scrubber in figure 5 further shows the washing liquid reservoir 25 for collecting washing liquid which may run downwards from spiral 8. The reservoir may also collect washing liquid arriving from a liquid outlet channel guiding the washing liquid to the reservoir from a washing liquid collector of a washing section. The washing liquid reservoir comprises an outlet 29 for guiding the washing fluid to the exterior of the scrubber.

Figure 5a illustrates an exemplary embodiment of scrubber 10 of the invention having two spirals 8,8'making two parallel gas flow paths within the scrubber 10, and figure 5b illustrates another exemplary embodiment of the scrubber having three spirals 8, 8 ', 8 " making three parallel gas flow paths within the scrubber 10.

List of reference numerals / letters

1 first washing liquid injection device

2 mixing element

3 first washing liquid collector

4 second washing liquid injection device

5 gas flow

6 mixing element

7 second washing liquid collector 8, 8', 8 " spiral

9 inner cylindrical vertical pipe

10 scrubber/washing tower

1 1 outer cylindrical vertical pipe

12 upper part of the scrubber

13 lower part of the scrubber

14 first washing section

15 second washing section

16 guiding channel

17 vertical fluid barrier

18 deflector

19 valve/bypass valve/closing device

20 washing liquid seal/u-bend

21 washing liquid flow

22 Washing liquid outlet channel 23 gas inlet channel

24 gas outlet channel

25 washing liquid reservoir

26 third washing liquid injection device

27 third washing liquid collector

28 nozzle/jet

29 outlet