FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10, rule 13)
1. Title of the invention: APPARATUS FOR REMOVAL OF SULPHUR OXIDES FROM
MARINE EXHAUST GAS
2. Applicant(s)
NAME NATIONALITY ADDRESS
HINDUSTAN PETROLEUM CORPORATION LIMITED Indian Hindustan Petroleum Corporation Ltd., Petroleum House, 17, Jamshedji Tata Road, Churchgate, Mumbai 400020, India
3. Preamble to the description
COMPLETE SPECIFICATION
The following specification particularly describes the invention and the manner in which it
is to be performed.

TECHNICAL FIELD
[0001] The present subject matter relates, in general, to marine exhaust gas purification, and in particular relates to apparatuses for removal of sulphur oxides from marine exhaust gas.
BACKGROUND
[0002] Maritime transport includes transport by cargo ships and cruise ships. Maritime transport accounts for 80% of all world trade as it is considered to be a cheap form of long distance cargo transport. Generally, cargo ships and cruise ships are run on heavy fuel oil. Heavy fuel oil, typically, has high sulphur content with an average of 2.7% by weight. Therefore, exhaust emission from maritime transport comprises SOx (sulphur oxides). SOx are air pollutants and contributors to acid rain. To reduce environmental discharge of SOx, cargo ships and cruise ships may be fitted with exhaust gas purification systems, such as scrubbers, electrostatic precipitators, and the like.
BRIEF DESCRIPTION OF DRAWINGS
[0003] The detailed description is described with reference to the accompanying
figures. In the figures, the left-most digit(s) of a reference number identifies the figure
in which the reference number first appears. The same numbers are used throughout
the drawings to reference like features and components.
[0004] Fig. 1 illustrates an example apparatus for removal of sulphur oxides from
marine exhaust gas, in accordance with an implementation of the present subject
matter.
[0005] Fig. 2 illustrates an example Rotating Bed Scrubber (RBS) unit, in accordance
with an implementation of the present subject matter.
[0006] Fig. 3 illustrates a rotor of the RBS unit, in accordance with an implementation
of the present subject matter.

[0007] Fig. 4(a) illustrates another example apparatus for removal of sulphur oxides
from marine exhaust gas, in accordance with an implementation of the present subject
matter.
[0008] Fig. 4(b) illustrates a process layout diagram of the example apparatus as shown
in Fig. 4(a), in accordance with an implementation of the present subject matter.
[0009] Fig. 5(a) illustrates another example apparatus for removal of sulphur oxides
from marine exhaust gas, in accordance with an implementation of the present subject
matter.
[0010] Fig. 5(b) illustrates a process layout diagram of the example apparatus as shown
in Fig. 5(a), in accordance with an implementation of the present subject matter.
[0011] Fig. 6(a) illustrates another example apparatus for removal of sulphur oxides
from marine exhaust gas, in accordance with an implementation of the present subject
matter.
[0012] Fig. 6(b) illustrates a process layout diagram of the example apparatus as shown
in Fig. 6(a), in accordance with an implementation of the present subject matter.
DETAILED DESCRIPTION
[0013] The present subject matter relates to an apparatus for removal of sulphur oxides
(SOx) from marine exhaust gas. The apparatus includes a Rotating Bed Scrubber (RBS)
unit to contact a feed gas stream comprising the marine exhaust gas with a solvent to
obtain a treated exhaust gas, and thereby, purify marine exhaust gas.
[0014] Generally, cargo ships and cruise ships are fueled by heavy fuel oil. Heavy fuel
oils comprise sulphur as a component. Due to combustion of the heavy fuel oils,
sulphur is oxidized to sulphur oxides (SOx) which are then discharged as part of exhaust
of ships. SOx are air pollutants and contribute to acid rain.
[0015] Typically, SOx in marine exhaust gas can be reduced by reducing content of
sulphur in fuels used to run the ships. International Maritime Organization (IMO) has

passed the Marine Pollution (MARPOL) Regulations where sulphur concentration in marine fuels were revised to 0.1 – 0.5 % by weight.
[0016] Another method for reducing SOx discharged into the environment is by using exhaust gas purification systems. Conventionally used exhaust gas purification systems use devices, such as quenchers, scrubbers, and combinations thereof, for removing pollutants from exhaust gases. However, conventional exhaust gas purification devices are generally not efficient in removing SOx in marine exhaust gas. Further, conventional exhaust gas purification devices have high capital investment with low throughput.
[0017] Currently, technologies for removal of SOx from marine exhaust gas employ vertical scrubber columns using suitable solvents. The type of columns generally used in the vertical scrubber columns are open spray tower, packed bed, venturi, and the like. Depending on the marine vessel capacity, height of such scrubbers can vary between 7 – 15 meters. Continuous undulating movement experienced in marine vessels due to swaying, rolling, heaving, and yawing motions can cause low mass transfer rates. However, such undulating movements are inevitable during marine vessel movements. The low mass transfer rates can also be attributed to problems, such as channeling, dumping, flooding, and the like, that may arise in vertical scrubber columns. Low mass transfer rates contribute to poor SOx removal efficiency of the scrubber.
[0018] The present subject matter provides an apparatus for removal of sulphur oxides from marine exhaust gas. The apparatus can comprise a Rotating Bed Scrubber (RBS) unit and a filtration unit coupled downstream of the RBS unit. The RBS unit can be used to contact a feed gas stream comprising the marine exhaust gas with a first solvent to obtain a treated exhaust gas and a residual solvent. The filtration unit can receive the residual solvent from the RBS unit and recover the first solvent from the residual solvent.

[0019] In one implementation, the RBS unit can comprise a rotor vessel that houses a rotor and has a gas inlet nozzle to receive the feed gas stream. The rotor can comprise a first plate, a second plate, and a plurality of sets of rings concentrically interposed between the first plate and the second plate. Each set of rings can further comprise a plurality of rings arranged cylindrically. Each ring can comprise a plurality of packing elements for enhancing mass transfer between the feed gas stream and the first solvent. [0020] A liquid inlet and gas outlet pipe assembly can be coupled to the rotor at one of the first plate and the second plate. The liquid inlet and gas outlet pipe assembly can comprise a gas outlet pipe to expel the treated exhaust gas from the rotor and a liquid inlet pipe to form a region to affect inflow of the first solvent into the rotor. A shaft may be coupled to the other of the first plate and the second plate to rotate the rotor. Rotation of the rotor helps in enhanced contact of the feed gas stream with the first solvent to extract sulphur oxides from the feed gas stream into the first solvent. [0021] The RBS unit uses centrifugal forces as driving force for contacting the feed gas stream with the first solvent as opposed to gravitational force used in conventional exhaust gas purification systems. Thus, the RBS unit can operate without being affected by any undulating movements occurring due to marine vessel movements leading to high separation efficiency and superior performance. In view of the high mass transfer rates and low Height Equivalent to the Theoretical Plate (HETP) due to the ring packing elements, the height of RBS unit can also be significantly lower than conventional scrubber. In one example, the height of the RBS unit may be lower than that of a vertical column scrubber by up to 10 times. In addition to the operational efficiency, this can also lead to benefits of a smaller carbon foot print, lower capital cost, higher safety, and ease of maintenance.
[0022] In an example, the feed gas stream received by the RBS unit can be one of: quenched marine exhaust gas and unquenched marine exhaust gas. The apparatus can comprise a quenching unit coupled upstream to the RBS unit to receive unquenched marine exhaust gas and a second solvent may be used to quench the unquenched marine

exhaust gas to obtain quenched marine exhaust gas. The obtained quenched marine exhaust gas can be supplied by the quenching unit to the RBS unit as the feed gas stream.
[0023] In an example, the quenching unit is one of: a quenching column and a Rotating Quench (RQ) unit. The RQ unit can have a rotor having a first plate, a second plate, packing elements, and shaft, similar to the RBS unit.
[0024] In one example, a vortex separator can be coupled downstream of the RBS unit. The vortex separator can receive the treated exhaust gas from the RBS unit and separate an entrained solvent from the treated exhaust gas.
[0025] In operation, marine exhaust gas as part of the feed gas stream may be introduced into the apparatus. The marine exhaust gas may be quenched by the quenching unit and supplied as the feed gas stream to the RBS unit. In the RBS unit, the feed gas stream is contacted with the first solvent. The first solvent can be sea-water, alkali treated sea-water, fresh water, alkali treated fresh water, and combinations thereof. Thus, SOx from the feed gas stream can be extracted into the first solvent. [0026] The present subject matter mitigates the need for conventionally used two-column scrubber systems. Further, the RBS unit of the apparatus is compact, helps in achieving a smaller carbon footprint, has lower capital investment, higher safety, and improved operability with improved SOx removal efficiency.
[0027] The above and other features, aspects, and advantages of the subject matter will be better explained with regard to the following description and accompanying figures. It should be noted that the description and figures merely illustrate the principles of the present subject matter along with examples described herein and, should not be construed as a limitation to the present subject matter. It is thus understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and examples thereof, are intended to encompass

equivalents thereof. Further, for the sake of simplicity, and without limitation, the same numbers are used throughout the drawings to reference like features and components. [0028] Fig. 1 illustrates an example apparatus 100 for removal of sulphur oxides from marine exhaust gas, in accordance with an implementation of the present subject matter. The apparatus 100 can comprise a Rotating Bed Scrubber (RBS) unit 102 and a filtration unit 104. The filtration unit 104 can be coupled downstream to the RBS unit 102. The RBS unit 102 can comprise a rotor which is explained later with reference to Fig. 2 and Fig. 3. Rotation of the rotor helps in contacting a feed gas stream, illustrated by stream 106, with a first solvent, illustrated by stream 107, for extraction of sulphur oxides from the feed gas stream 106 into the first solvent 107.
[0029] The feed gas stream 106 can comprise the marine exhaust gas. The marine exhaust gas may be obtained from a main exhaust chamber, which may be coupled upstream of the RBS unit 102. The main exhaust chamber can be used to collect exhaust gas from at least one of a main engine, an auxiliary engine, and a waste heat boiler of the marine vessel. In another example, the feed gas stream 106 can be supplied to the apparatus 100 directly from one or more of the main engine, the auxiliary engine, and the waste heat boiler.
[0030] The feed gas stream 106 can be contacted with the first solvent 107 to obtain a treated exhaust gas, illustrated as stream 108, and a residual solvent, illustrated as stream 110, from the RBS unit 102. In an example, the first solvent 107 is one of: sea-water, alkali treated sea-water, fresh water, alkali treated fresh water, and combinations thereof.
[0031] When the feed gas stream 106 is contacted with the first solvent 107, the sulphur oxides in the feed gas stream 106 get absorbed into the first solvent 107. The residual solvent 110 can, therefore, comprise a mixture of sulphur compounds that may be suspended as precipitates in the first solvent 107. The precipitates are hereinafter referred to as solids. The residual solvent 110 can be filtered by the filtration unit 104 to recover the first solvent from the residual solvent 110. The solids separated from the

residual solvent 110 is illustrated as stream 114. The treated exhaust gas 108 can be discharged into the atmosphere.
[0032] In an example, the first solvent 107 recovered from the residual solvent 110 can be stored, treated, and discharged into the sea. In another example, the first solvent 107 recovered from the residual solvent 110 can be stored and treated for re-contacting with the feed gas stream 106 in the RBS unit 102, as illustrated by stream 112. The RBS unit 102 is explained with reference to Fig. 2 and Fig. 3.
[0033] Fig. 2 illustrates the RBS unit 102 comprising a rotor 200, in accordance with an implementation of the present subject matter. The RBS unit 102 can comprise a rotor vessel 201 enclosing the rotor 200. The rotor vessel 201 can comprise a gas inlet nozzle (not shown) provided in the rotor vessel 201 to receive the feed gas stream 106. The RBS unit 102 can comprise a Rotating Packed Bed (RPB) unit 202 and a motor 204. The RPB unit 202 facilitates mass transfer between the feed gas stream 106 and the first solvent 107. In an example, the RPB unit 202 includes a shaft 206 and the rotor 200.
[0034] The rotor 200 can comprise a first plate 208-1 and a second plate 208-2. The first plate 208-1 and the second plate 208-2 can be metallic plates. In an example, the first plate 208-1 and the second plate 208-1 may be circular in shape. A plurality of set of rings 210 may be concentrically interposed between the first plate 208-1 and the second plate 208-2. Each set of rings 210 can comprise a plurality of rings arranged cylindrically. Each ring can comprise a plurality of packing elements. The packing elements may be selected from at least one of stainless steel, nickel, nichrome, iron, silicon carbide, aluminum, carbon, and wire mesh. In an example, the plurality of set of rings 210 may be aligned in a manner such that a center of each set is aligned along an imaginary straight axis. The rotor 200 may also include one or more sets of metallic rings (not shown in this figure). In an implementation, the sets of metallic rings may be placed in between the plurality of set of rings 210 of the concentric rings at regular or variable intervals. Placement of the metallic rings in between the plurality of set of

rings 210 of the concentric rings helps in achieving a desired stiffness or mechanical strength of the rotor 200. As a result, fatigue in the rotor 200 is reduced. [0035] In an example, one of the first plate 208-1 and the second plate 208-2 may have a gap 214 for facilitating inflow of the first solvent 107 and the outflow of the treated exhaust gas 108 and the other of the first plate 208-1 and the second plate 208-2 can be coupled to the shaft 206. The shaft 206 may be a low weight metallic hollow drive shaft. As shown in Fig. 2, the shaft 206 is coupled to the first plate 208-1 and the second plate 208-2 comprises the gap 214. A liquid inlet and gas outlet pipe assembly 216 can be coupled at the gap 214 as will be explained later with reference to Fig. 3. [0036] In an example, a first end of the shaft 206 is connected to one of the first plate 208-1 and the second plate 208-2 and a second end of the shaft 206 is connected to the motor 204 through one or more removable couplings 218. As shown in Fig. 2, the first end of the shaft 206 is coupled to the first plate 208-1. The motor 204 facilitates rotation of the shaft 206 and thereby rotation of the rotor 200. On the other end, the shaft 206 may be connected to one of the first plate 208-1 and the second plate 208-2 through a flange (not shown in figure).
[0037] Fig. 3 illustrates the rotor 200 in greater detail, in accordance with an implementation of the present subject matter. The liquid inlet and gas outlet pipe assembly 216 may be coupled to the rotor 200 at one of the first plate 208-1 and second plate 208-2. As shown in Fig. 3, the liquid inlet and gas outlet pipe assembly 216 is coupled to the second plate 208-2. The liquid inlet and gas outlet pipe assembly 216 can facilitate inflow of the first solvent 107 in the rotor 200 and exit of the treated exhaust gas 108 from the rotor 200. In an example, the liquid inlet and gas outlet pipe assembly 216 may be connected to the rotor 200 through the gap 214 (as shown in Fig. 2).
[0038] The liquid inlet and gas outlet pipe assembly 216 may comprise a central hollow pipe, hereinafter referred to as the gas outlet pipe, which affects expulsion of the treated exhaust gas 108 from the rotor 200 due to pressure differential. Surrounding the gas

outlet pipe is a liquid inlet pipe to facilitate the inflow of the first solvent 107 into the rotor 200. The first solvent 107 can enter the rotor 200 through an annular space between the gas outlet pipe and the liquid inlet pipe, for example, through liquid distributor pipes (not shown).
[0039] In operation, with reference to Fig(s). 1, 2, and 3, the feed gas stream 106 may be introduced inside the rotor vessel 201 through the gas inlet nozzle provided in the rotor vessel 201. In an example, the feed gas stream 106 may be forced radially inward to the rotor 200. The feed gas stream 106 may be distributed inside the rotor vessel 201 in a homogenous manner by using a gas impingement plate (not shown). In an example, the gas impingement plate may be made of metal and may have one or more holes on its surface. The gas impingement plate may be provided on an inner surface of the rotor vessel 201 and may be suitably aligned with the gas inlet nozzle. The first solvent 107 may be introduced into the rotor 200 through the liquid inlet pipe of the liquid inlet and gas outlet pipe assembly 216.
[0040] The motor 204 rotates the shaft 206, either in clockwise or anti-clockwise direction, and thereby, in turn, rotates the rotor 200. The feed gas stream 106 and the first solvent 107 interact with each other over the surface of the packing elements and mass transfer occurs between the two. Due to the centrifugal acceleration produced due to the rotation of the rotor 200, the first solvent 107 is driven radially outwards of the rotor 200. Further, the treated exhaust gas 108 exits the rotor 200 through the gas outlet pipe of the liquid inlet and gas outlet pipe assembly 216.
[0041] By contacting the feed gas stream 106 with the first solvent 107, the sulphur oxides get captured in the first solvent 107 to obtain the treated exhaust gas 108. The filtration unit 104 can receive the residual solvent 110 from the RBS unit 102. The filtration unit 104 can separate the precipitated solids and recover the first solvent 107 from the residual solvent 110.
[0042] In an example, the apparatus 100 can be operated in an open-loop mode. In this example, the apparatus 100 can comprise a sludge tank and a liquid effluent discharge

tank coupled downstream of the filtration unit 104. The sludge tank and the liquid effluent discharge tank are explained further with reference to Fig(s). 4(b), 5(b), and 6(b). In the open-loop mode, the solvent recovered from the filtration unit 104 is collected in the liquid effluent discharge tank and discharged into the sea. [0043] In another example, the apparatus 100 may be operated in a close-loop mode. In this example, a solvent tank may be coupled downstream of the filtration unit 104 to receive the solvent recovered by the filtration unit 104. In this example, the apparatus 100 can comprise a fresh water storage tank coupled to the solvent tank to supply fresh water to the solvent recovered by the filtration unit 104. In the closed-loop mode, the solvent recovered by the filtration unit 104, which is suitably treated, can be re¬circulated within the apparatus 100. The solvent tank and the fresh water storage tank are explained further with reference to Fig(s). 4(b), 5(b), and 6(b). [0044] In an example, the feed gas stream 106 may be one of: quenched marine exhaust and unquenched marine exhaust gas. In this example, a quenching unit can be coupled upstream of the RBS unit 102. The quenching unit can receive unquenched marine exhaust gas and a second solvent to quench the unquenched marine exhaust gas to obtain the quenched marine exhaust gas. The quenching unit can supply the obtained quenched marine exhaust gas to the RBS unit 102 as the feed gas stream 106. [0045] The quenching unit can be one of: a Rotating Quench (RQ) unit and a quenching column. In one example, as will be explained later with reference to Fig. 4(a) and Fig. 4(b), the quenching unit is the RQ unit. In another example, as will be explained later with reference to Fig. 5(a) and Fig. 5(b), the quenching unit is a quenching column.
[0046] In one example, to further process the treated exhaust gas 108, the apparatus 100 can also comprise a vortex separator coupled downstream of the RBS unit 102, as explained with reference to Fig. 6(a) and Fig. 6(b). The vortex separator can receive the treated exhaust gas 108 from the RBS unit 102 and can separate an entrained solvent from the treated exhaust gas 108.

[0047] In an example, the apparatus 100 can comprise a sea-water tank coupled upstream of the RBS unit 102 to store sea-water which may be used as the first solvent 107. The sea-water tank can supply sea-water as the first solvent 107 to the RBS unit 102 for contacting the feed gas stream 106 with the first solvent 107. [0048] In an example, the apparatus 100 can comprise an alkali dosage unit coupled to at least one of: the RBS unit 102, the solvent tank, and the sea-water tank. The alkali dosage unit can be used to dose at least one of: the first solvent and the solvents recovered by the filtration unit 104 to a basic pH prior to contacting the feed gas stream 106 with at least one of the first solvent and the solvents recovered by the filtration unit 104. The sea-water tank and the alkali dosage unit are explained later with reference to Fig(s). 4(b), 5(b), and 6(b).
[0049] Fig. 4(a) illustrates another example apparatus 400 for removal of sulphur oxides from marine exhaust gas, in accordance with an implementation of the present subject matter. As shown in Fig. 4(a), the example apparatus 400 can comprise a Rotating Quench (RQ) unit 403 upstream of the RBS unit 102 to quench the marine exhaust gas, represented by stream 405, and supply the quenched marine exhaust gas as feed gas stream 106 to the RBS unit 102. In an example, the RQ unit 403 can receive the marine exhaust gas 405and a second solvent, illustrated with stream 409, to quench the marine exhaust gas 405. In an example, the second solvent 409 is one of: sea-water, alkali treated sea-water and the solvents recovered by the filtration unit 104. However, it is to be understood that any other coolant may be used as the second solvent 409 to quench the marine exhaust gas 405.
[0050] In an example, the RQ unit 403 has a configuration similar to that of RBS unit 102 explained earlier with reference to Fig. 2 and Fig. 3. Accordingly, the RQ unit 403 can comprise the first plate 208-1, second plate 208-2, and rotor 200. However, to facilitate co-current flow of the marine exhaust gas 405 and the second solvent 409, the liquid inlet and gas outlet pipe assembly 216 can be replaced with a gas inlet and gas outlet pipe assembly in the gap 214. Therefore, the marine exhaust gas 405 and the

second solvent 409 are introduced and flow in a co-current pattern within the RQ unit 403. The rotor 200 of the RQ unit 403 can also comprise the packing elements as explained with respect to Fig. 2 and Fig. 3.
[0051] Fig. 4(b) illustrates a process layout diagram of the example apparatus 400 as shown in Fig. 4(a), in accordance with an implementation of the present subject matter. Exhaust gases from a main engine 402, an auxiliary engine 404, and a waste heat boiler 406 may be collected in a main exhaust chamber 408 and fed to the RQ unit 403. In another example, exhaust gases from the main engine 402, the auxiliary engine 404, and the waste heat boiler 406 may be directly fed to the RQ unit 403. [0052] As previously explained with reference to Fig. 4(a), in the RQ unit 403, the marine exhaust gas 405 can be contacted with the second solvent 409. The marine exhaust gas 405 and the second solvent 409 can be contacted in a co-current pattern. The second solvent 409 can enter the RQ unit 403 through a liquid inlet pipe of the gas inlet and liquid inlet assembly of the RQ unit 403. The gas inlet and liquid inlet assembly of the RQ unit 403 can be provided with liquid distributor designed for disintegration of the second solvent 409 into droplets. Further, the liquid distributor can be designed to optimize size of the droplets, which can then be sprayed on an inner surface of the RQ unit 403. The RQ unit can comprise a rotor vessel and a gas inlet and liquid inlet assembly. The unquenched marine exhaust gas 405 received at a gas inlet pipe of the gas inlet and liquid inlet assembly and the second solvent 409 received at a liquid inlet pipe of the gas inlet and liquid inlet assembly are contacted in a co-current pattern in the RQ unit 403.
[0053] The marine exhaust gas 405 traverses along with the second solvent 409 flow through the packed bed section of the RQ unit 403. The packed bed section, as will be understood, comprises the packing elements (not shown). Throughout the flow, the marine exhaust gas 405 and the second solvent 409 interact due to rotation of the rotor 200 in the RQ unit 403 and as a result, temperature of the marine exhaust gas 405 gets reduced from about 150 – 400 oC to less than 60oC.

[0054] The quenched gas stream exits through the gas outlet pipe of the RQ unit 403 and a residual second solvent, indicated by stream 411, exits radially outwards from the rotor vessel 201. Apart from cooling the marine exhaust gas 405, the second solvent 409 can also remove solids from the marine exhaust gas 405. The particulate matter on contact with the second solvent 409 tends to settle down and is carried along with the residual second solvent 411. About 5 to 50% SOx removal may be achieved in the RQ unit 403.
1. The quenched marine exhaust gas, as feed gas stream 106, enters the RBS unit
102. The first solvent 107 may enter the RBS unit 102 at the liquid inlet pipe and be distributed in the RBS unit 102 by the liquid distributor which may be provided on the liquid inlet and gas inlet pipe assembly 216 (shown in Fig. 2 and Fig. 3) of the RQ unit 403. In an example, the apparatus 400 can comprise a sea-water tank 407 to store sea-water and supply the sea water as the first solvent 107 and the second solvent 409 to the RQ unit 403 and the RBS unit 102. The feed gas stream 106 received by the gas inlet nozzle and the first solvent 107 received at the liquid inlet pipe are contacted in a counter-current pattern in the RBS unit 102.
[0055] The RBS unit 102 can induce centrifugal force that may be over hundred to thousand times of the gravitational force. This enhances gas side (feed gas stream 106) and liquid side (first solvent 107) mass transfer coefficients, thereby, increasing overall mass transfer. This further reduces the residence time required for contact in the RBS unit 102, thus, increasing throughput to the apparatus 400. This also contributes to reduction in Height Equivalent Theoretical Plate (HETP) by 10 to 100 times. [0056] The treated exhaust gas 108 can exit from gas outlet pipe and the residual solvent 110 can exit the RBS unit 102 radially from the rotor vessel 201 (shown in Fig. 2 and Fig. 3). The treated exhaust gas 108 can comprise sulphur oxide concentration of less than 10 – 100 ppm. Residual second solvent from the RQ unit 403 (illustrated as stream 411) and the RBS unit 102 (illustrated as stream 110) can be routed to the

filtration unit 104 where the solids can be separated to recover the first solvent 107 and the second solvent 409.
[0057] As mentioned previously, the apparatus 400 as shown in Fig. 4(b) can be operated in open loop mode and closed loop mode based on parameters, such as requirement and area of operation of ship, for example, in emission control zone area, non-emission control zone area, and the like.
[0058] When operated in open loop mode, a sludge tank 418 and a liquid effluent discharge tank 419 can be coupled downstream of the filtration unit 104. The sludge tank 418 can receive the solids from the residual solvent 110 and residual second solvent 411 and the liquid effluent discharge tank 419 can receive recovered first and second solvent from filtration unit 104. The recovered solvents from the filtration unit 104 can be treated in the liquid effluent discharge tank 419 to meet discharge specifications and then be discharged into the sea. The solids stored in a sludge tank 418 may be unloaded off shore, post cruise.
[0059] When operated in closed loop mode, the apparatus 400 can comprise a solvent tank 420 coupled downstream of the filtration unit 104 to receive the first solvent and second solvent recovered from the filtration unit 104. The apparatus 400 can comprise a fresh water storage tank 422 coupled to the solvent tank 420 to supply fresh water to the solvents recovered by the filtration unit 104. In the closed-loop mode, the solvents recovered by the filtration unit 104 can be re-circulated within the apparatus 400. As shown in Fig. 4(b), the solvent recovered from the filtration unit 104 can be pumped to the RQ unit 403 to quench the marine exhaust gas 405.
[0060] In an example, the apparatus 400 can comprise an alkali dosage unit 423 coupled to at least one of: the RBS unit 102, the solvent tank 420 and the sea-water tank 407. The alkali dosage unit 423 can be used to dose at least one of: the first solvent and the solvents recovered by the filtration unit 104 to a basic pH prior to contacting the feed gas stream 106 with at least one the first solvent, the first solvents recovered

by the filtration unit 104, and the second solvent. Other example apparatuses are as
shown in Fig(s). 5(a)-(b) and 6(a) and 6(b).
[0061] Fig. 5(a) illustrates another example apparatus 500 for removal of sulphur
oxides from marine exhaust gas, in accordance with an implementation of the present
subject matter. As shown in Fig. 5(a), the example apparatus 500 can comprise a
quenching column 502 upstream of the RBS unit 102 to quench the marine exhaust
gas, represented by stream 405, and supply the quenched marine exhaust gas as feed
gas stream 106 to the RBS unit 102.
[0062] In an example, the quenching column 502 can receive the marine exhaust gas
405 and the second solvent 409 to quench the marine exhaust gas 405. In an example, the second solvent 409 is one of: sea-water, alkali treated sea-water, and the solvents recovered by the filtration unit 104. However, it is to be understood that any other coolant may be used as the second solvent to quench the marine exhaust gas 405. [0063] Fig. 5(b) illustrates a process layout diagram of the example apparatus 500 as shown in Fig. 5(a), in accordance with an implementation of the present subject matter. Exhaust gases from a main engine 402, an auxiliary engine 404, and a waste heat boiler
406 may be collected in a main exhaust chamber 408 and fed to the quenching column 502. In an example, exhaust gases from the main engine 402, the auxiliary engine 404, and the waste heat boiler 406 may be directly fed to the quenching column 502. [0064] In an example, the quenching column 502 may be an open chamber where the marine exhaust gas 405 can be contacted with the second solvent, shown as stream 409, in a counter-current pattern. The second solvent 409 may flow from top to bottom of the quenching column 502. The second solvent 409 may be, for example, pumped into a plurality of liquid distributors 504. The plurality of liquid distributors 504 may include nozzles for spraying droplets of the second solvent. Spraying the second solvent helps in improving surface area for gas liquid contact.
[0065] The marine exhaust gas 405 can enter the quenching column 502 through a bottom gas distribution grid 506 which may comprise multiple nozzles to disperse the

marine exhaust gas 405 into the quenching column 502 for better contact with the
droplets of the second solvent 409. The marine exhaust gas 405 may enter the
quenching column 502 at a temperature of 150 – 400oC. When the marine exhaust gas
405 and the second solvent 409 contact each other, temperature of the marine exhaust
gas 405 may be reduced to less than 60oC. In addition to cooling the marine exhaust
gas 405, the second solvent 409 can also remove solids, such as particulate matter, from
the marine exhaust gas 405. The solids on contact with the second solvent 409 tends to
settle down and can be carried along with the residual second solvent 411. About 5 to
30% SOx removal may be achieved in the quenching column 502.
2. The quenched marine exhaust gas, as feed gas stream 106, can enter the RBS
unit 102 via gas inlet nozzles. The first solvent, illustrated by stream 107, may enter the RBS unit 102 through at the liquid inlet pipe and be distributed in the RBS unit 102 by the liquid distributor which may be provided on the liquid inlet and gas outlet pipe assembly 216 (as shown in Fig(s). 2 and 3) of the RBS unit 102. The feed gas stream 106 received by the gas inlet nozzle and the first solvent 107 received at the liquid inlet pipe are contacted in a counter-current pattern in the RBS unit 102. [0066] The RBS unit 102 can induce centrifugal force that may be over hundred to thousand times of the gravitational force. This enhances gas side (feed gas stream 106) and liquid side (first solvent 107) mass transfer coefficients, thereby, increasing overall mass transfer. This further reduces the residence time required for contact in the RBS unit 102, thus, increasing throughput to the apparatus 500. This also contributes to reduction in Height Equivalent Theoretical Plate (HETP) by 10 to 100 times. In an example, the apparatus 500 can comprise a sea-water tank 407 to store sea-water and supply the sea water as the first solvent 107 and the second solvent 409 to the quenching column 502 and the RBS unit 102.
[0067] The treated exhaust gas 108 can exit from gas outlet pipe and the residual solvent 110 can exit the RBS unit 102 radially. The treated exhaust gas 108 can comprise sulphur oxide concentration of less than 10 – 100 ppm. Residual second

solvent 411 from the quenching column 502 and the RBS unit 102 can be routed to the filtration unit 104 where the solids can be separated to recover the first solvent 107 and the second solvent 409.
[0068] As mentioned previously, the apparatus 500 as shown in Fig. 5(b) can be operated in open loop mode and closed loop mode based on parameters, such as requirement and area of operation of ship, for example, in emission control zone area, non-emission control zone area, and the like.
[0069] When operated in open loop mode, a sludge tank 418 and a liquid effluent discharge tank 419 can be coupled downstream of the filtration unit 104. The sludge tank 418 can receive the solids from the residual solvent 110 and the residual second solvent 411 and the liquid effluent discharge tank 419 can receive the recovered solvent from filtration unit 104. The recovered solvent from filtration unit 104 can be treated in the liquid effluent discharge tank 419 to meet discharge specification and then be discharged into the sea. The solids stored in the sludge tank 418 may be unloaded off shore, post cruise.
[0070] When operated in closed loop mode, the apparatus 500 can comprise a solvent tank 420 coupled downstream of the filtration unit 104 to receive the solvents recovered from the filtration unit 104. The apparatus 500 can comprise a fresh water storage tank 422 coupled to the solvent tank 420 to supply fresh water to the solvents recovered by the filtration unit 104. In the closed-loop mode, the solvents recovered by the filtration unit 104 can be re-circulated within the apparatus 500. As shown in Fig. 5(b), the solvents recovered from the filtration unit 104 can be pumped to the quenching column 502 and the RBS unit 102 to quench the marine exhaust gas 405. [0071] In an example, the apparatus 400 can comprise an alkali dosage unit 423 coupled to at least one of: the RBS unit 102, the solvent tank 420, and the sea-water tank 407. The alkali dosage unit 423 can be used to dose at least one of: the first solvent and the solvents recovered by the filtration unit 104 to a basic pH prior to contacting the feed gas stream 106 with at least one the first solvent, the solvents recovered by the

filtration unit 104, and the second solvent. Other example apparatuses are as shown in Fig(s). 6(a) and 6(b).
[0072] Fig. 6(a) illustrates another example apparatus 600, in accordance with an implementation of the present subject matter. In the apparatus 600 as shown in Fig. 6(a), a vortex separator 602 may be provided downstream of the RBS unit 102 and upstream of the filtration unit 104. The vortex separator 602 can receive the treated exhaust gas 108 from the RBS unit 102 and separate an entrained solvent from the treated exhaust gas 108. The entrained solvent can be further provided to the filtration unit 104, to recover the first solvent from the entrained solvent.
[0073] Fig. 6(b) illustrates a process layout diagram of the example apparatus 600 as shown in Fig. 6(a), in accordance with an implementation of the present subject matter. Exhaust gases from a main engine 402, an auxiliary engine 404, and a waste heat boiler 406 may be collected in a main exhaust chamber 408 and fed to the RBS unit 102. In an example, exhaust gases from the main engine 402, the auxiliary engine 404, and the waste heat boiler 406 may be directly fed to the RBS unit 102.
3. The feed gas stream 106, comprising the marine exhaust gas, can enter the RBS
unit 102 via gas inlet nozzles. The first solvent 107 may enter the RBS unit 102 at the liquid inlet pipe and be distributed in the RBS unit 102 by the liquid distributor which may be provided on the liquid inlet and gas outlet pipe assembly 216 (not shown) of the RBS unit 102. In an example, the apparatus 600 can comprise a sea-water tank 407 to store sea-water and supply the sea water as the first solvent 107 to the RBS unit 102. The feed gas stream 106 received by the gas inlet nozzle and the first solvent 107 received at the liquid inlet pipe are contacted in a counter-current pattern in the RBS unit 102.
[0074] The RBS unit 102 can induce centrifugal force that may be over hundred to thousand times of the gravitational force. This enhances gas side (feed gas stream 106) and liquid side (first solvent 107) mass transfer coefficients, thereby, increasing overall mass transfer. This further reduces the residence time required for contact in the RBS

unit 102, thus, increasing throughput to the apparatus 600. This also contributes to reduction in Height Equivalent Theoretical Plate (HETP) by 10 to 100 times. [0075] The treated exhaust gas 108 can exit from gas outlet pipe and the residual solvent 110 can exit the RBS unit 102 radially from the rotor vessel 201. The treated exhaust gas 108 can comprise sulphur oxide concentration of less than 10 – 100 ppm. Residual solvent 110 from RBS unit 102 can be routed to the filtration unit 104 where the solids can be separated to recover the first solvent 107.
[0076] The treated exhaust gas 108 may be further routed to the vortex separator 602 to separate entrained liquid carried from the marine exhaust gas 405. In the vortex separator 602, a tangential entry for the treated exhaust gas 108 may be provided and cyclonic motion inside the vortex separator 602 may help in settling the entrained liquid carried over and solids, such as particular matter carried over. The entrained liquid can be provided to the filtration unit 104 for recovering the first solvent 107. [0077] As mentioned previously, the apparatus 600 as shown in Fig. 6(b) can be operated in open loop mode and closed loop mode based on parameters, such as requirement and area of operation of ship, for example, in emission control zone area, non-emission control zone area, and the like.
[0078] When operated in open loop mode, a sludge tank 418 and a liquid effluent discharge tank 419 can be coupled downstream of the filtration unit 104. The sludge tank 418 can receive the solids from the residual solvent and the liquid effluent discharge tank 419 can receive the solvents recovered from filtration unit 104. The solvents recovered from filtration unit 104 can be treated in the liquid effluent discharge tank 419 to meet discharge specification and then be discharged into the sea. The solids stored in a sludge tank 418 may be unloaded off shore, post cruise. [0079] When operated in closed loop mode, the apparatus 600 can comprise a solvent tank 420 coupled downstream of the filtration unit 104 to receive the solvents recovered from the filtration unit 104. The apparatus 600 can comprise a fresh water storage tank 422 coupled to the solvent tank 420 to supply fresh water to the solvents recovered by

the filtration unit 104. In the closed-loop mode, the first solvents recovered by the filtration unit 104 can be re-circulated within the apparatus 600. As shown in Fig. 6(b), the solvents recovered from the filtration unit 104 can be pumped to the RBS unit 102 for re-contacting with the feed gas stream 106.
[0080] In an example, the apparatus 600 can comprise an alkali dosage unit 423 coupled to at least one of: the RBS unit 102, the solvent tank 420, and the sea-water tank 407. The alkali dosage unit 423 can be used to dose at least one of: the first solvent, the solvents recovered by the filtration unit 104, and the sea-water stored in the sea-water tank 407 to a basic pH prior to contacting the feed gas stream 106 with at least one the first solvent and the solvents recovered by the filtration unit 104. [0081] By using the RBS unit 102 as described the need for conventionally used two-column scrubber system is mitigated. Further, using the RBS unit 102 also helps in in achieving lower footprint, lower capital investment, safety and improved operability with improved SOx removal efficiency.
[0082] Although the subject matter has been described in considerable detail with reference to certain examples and implementations thereof, other implementations are possible. As such, the present disclosure should not be limited to the description of the preferred examples and implementations contained therein.

I/We Claim:
1. An apparatus for removal of sulphur oxides from marine exhaust gas, the apparatus comprising:
a Rotating Bed Scrubber (RBS) unit to contact a feed gas stream comprising the marine exhaust gas with a first solvent to obtain a treated exhaust gas and a residual solvent, wherein the RBS unit comprises a rotor vessel, wherein the rotor vessel comprises:
a gas inlet nozzle provided in the rotor vessel to receive the feed gas stream;
a rotor, wherein the rotor comprises: a first plate; a second plate; and
a plurality of sets of rings concentrically interposed between the first plate and the second plate, wherein each set of rings comprises a plurality of rings arranged cylindrically, wherein each ring comprises a plurality of packing elements; a liquid inlet and gas outlet pipe assembly coupled to the rotor at one of the first plate and the second plate, the liquid inlet and gas outlet pipe assembly comprising:
a gas outlet pipe to affect expulsion of the treated exhaust gas from the rotor; and
a liquid inlet pipe to form a region to affect inflow of the first solvent into the rotor; and
a shaft coupled to the other of the first plate and the second plate of the rotor to rotate the rotor, wherein rotation of the rotor is to contact the feed gas stream with the first solvent; and

a filtration unit coupled downstream to the RBS unit to receive the residual solvent from the RBS unit, wherein the filtration unit is to recover solvents from the residual solvent.
2. The apparatus as claimed in claim 1, wherein the feed gas stream is one of: quenched marine exhaust gas and unquenched marine exhaust gas.
3. The apparatus as claimed in claim 1, wherein the apparatus comprises a quenching unit coupled upstream of the RBS unit to:
receive unquenched marine exhaust gas and a second solvent to quench the unquenched marine exhaust gas to obtain quenched marine exhaust gas; and
supply the obtained quenched marine exhaust gas to the RBS unit as the feed gas stream.
4. The apparatus as claimed in claim 3, wherein the quenching unit is one of: a quenching column and a Rotating Quench (RQ) unit.
5. The apparatus as claimed in claim 1, wherein the apparatus comprises a vortex separator coupled downstream of the RBS unit, wherein the vortex separator is to receive the treated exhaust gas from the RBS unit and separate an entrained solvent from the treated exhaust gas.
6. The apparatus as claimed in claim 1, wherein the first solvent is one of sea-water, alkali treated sea-water, fresh water, alkali treated fresh water, and combinations thereof.
7. The apparatus as claimed in claim 3, wherein the second solvent is one of sea-water, alkali treated sea-water, and the solvents recovered by the filtration unit.

8. The apparatus as claimed in claim 1, comprising a sludge tank and a liquid
effluent discharge tank are coupled downstream of the filtration unit, wherein:
the sludge tank is to receive solids separated from the residual solvent; and
the liquid effluent discharge tank is to receive the solvents recovered by the filtration unit.
9. The apparatus as claimed in claim 1, wherein a solvent tank is coupled
downstream of the filtration unit to receive solvents recovered by the filtration unit.
10. The apparatus as claimed in claim 9, wherein the apparatus comprises a fresh
water storage tank coupled to the solvent tank to supply fresh water to the solvents
recovered by the filtration unit.
11. The apparatus as claimed in claim 1, wherein the apparatus comprises a sea-water tank coupled upstream of the RBS unit to supply and store sea-water.
12. The apparatus as claimed in any of claims 9 or 11, wherein the apparatus comprises an alkali dosage unit coupled to at least one of: the RBS unit, the solvent tank and the sea-water tank, wherein the alkali dosage unit is to dose at least one of: the first solvent, the solvents recovered by the filtration unit, a second solvent, and combinations thereof to a basic pH.
13. The apparatus as claimed in claim 1, wherein the feed gas stream received by the gas inlet nozzle and the first solvent received at the liquid inlet pipe are contacted in a counter-current pattern in the RBS unit.
14. The apparatus as claimed in claim 4, wherein the RQ unit comprises a rotor vessel and a gas inlet and liquid inlet assembly, wherein unquenched marine exhaust gas received at a gas inlet pipe of the gas inlet and liquid inlet assembly and the second

solvent received at a liquid inlet pipe of the gas inlet and liquid inlet assembly are contacted in a co-current pattern in the RQ unit.