A system and method of cleaning a gas

Abstract

A system and a method of cleaning a gas having one or more pollutants, where the method comprises the steps of providing a closed-loop circulation system having at least one absorber having a absorber fluid input from the closed-loop circulation system and an absorber fluid output into the closed-loop circulation system, providing a first cleaning liquid in the closed-loop circulation system, providing a first water treatment device having a first treatment fluid input receiving a first cleaning liquid from the closed-loop circulation system and a first treatment fluid output for returning a part of the first cleaning liquid into the closed-loop circulation system and a second treatment fluid output for discharging pollutants from the closed-loop circulation system, providing a first liquid-receiving tank holding polluted liquid in the closed-loop circulation system that has a first tank output that is arranged upstream of the water treatment device and a first tank input in fluid connection with the absorber fluid output, providing a filter device having a first filter input receiving polluted liquid from a second tank output of the first liquid-receiving tank and a first filter output discharging filtered liquid into the closed-loop circulation system, providing a first filter pump having a first pump input receiving liquid from the second tank output and a first pump output pumping liquid to the first filter input, and providing a first liquid pressure on the filter input.

Description

[0001] A system and method of cleaning a gas

[0002] Technical field

[0003] A system and method of cleaning a gas having one or more pollutants, where the method comprises the steps of providing a closed-loop circulation system having at least one absorber having an absorber fluid input from the closed-loop circulation system and an absorber fluid output into the closed-loop circulation system.

[0004] Description

[0005] A number of different industries are reliant on energy production which emits flue gasses, and currently there are no alternative energy sources viable to replace these energy sources. One of these industries is the shipping industry, where fossil fuel engines are utilized for propulsion and energy production aboard ships. However, as such energy production relies on the release of flue gasses into the atmosphere, a variety of different approaches are being used to reduce the content of harmful particles or harmful components in the flue gas to reduce pollution.

[0006] One of the methods of reducing pollutants is to utilize Closed Loop systems, which is becoming increasingly important for the successful operation of exhaust gas cleaning systems (EGCS) that are compliant with zero discharge, NOx reduction systems based on exhaust gas recirculation, engines powered by green fuels (such as ammonia) and carbon capture systems.

[0007] The use of a closed-loop system on a ship is becoming increasingly complicated where there are complex water treatment system requirements, which are often unreliable, require high maintenance and accordingly create handling difficulties for system operators (crew).

[0008] Traditionally, the water treatment system of a closed-loop system may be handling two processes simultaneously, which are oily / dirt sludge removal and fine filtration to allow cleaned water to be discharged at sea. Such water treatment systems often involve high investment and operating costs as well as complicated operation as simultaneous handling of the two processes causes changing operational conditions of the treatment system, which contradict optimal operation of the systems.

[0009] One way of attempting to remove impurities and / or pollutants from closed-loop systems on ships has been disclosed in WO 2014 / 181029, where a purification device comprising

[0010] P2939PC00a band filter having a moving inclined filter band removes impurities from the purification device. However, as the system relies on the impurities to precipitate prior to removal, a precipitation agent must be introduced into the purification device to allow the impurities to precipitate. For the system to function properly, the concentration of the precipitation agent must be monitored and manually kept at the right level, which requires constant monitoring by highly skilled support staff to adjust the concentration, which is very costly.

[0011] Thus, there is a need to simplify the operations of a closed-loop system as well as reduce the cost of closed-loop systems for flue gasses.

[0012] In accordance with the invention, there is provided a method of cleaning a gas having one or more pollutants, where the method comprises the steps of:

[0013] - providing a closed-loop circulation system having at least one absorber having an absorber fluid input from the closed-loop circulation system and an absorber fluid output into the closed-loop circulation system,

[0014] - providing a first cleaning liquid in the closed-loop circulation system

[0015] - providing a first water treatment device having a first treatment fluid input receiving a first cleaning liquid from the closed-loop circulation system and a first treatment fluid output for returning a part of the first cleaning liquid into the closed-loop circulation system and a second treatment fluid output for discharging pollutants from the closed-loop circulation system,

[0016] - providing a first liquid-receiving tank holding polluted liquid in the closed-loop circulation system that has a first tank output arranged upstream of the water treatment device and a first tank input in fluid connection with the absorber fluid output,

[0017] - providing a filter device having a first filter input receiving polluted liquid from a second tank output of the first liquid-receiving tank and a first filter output discharging filtered liquid into the closed-loop circulation system, and

[0018] - providing a first filter pump having a first pump input receiving liquid from the second tank output and a first pump output pumping liquid to the first filter input, and providing a first liquid pressure on the filter input.

[0019] The closed-loop circulation system is utilized to cool the gasses and to clean pollutants from gasses, where the pollutants extracted from the gasses build up in the closed-loop circulation system. The pollutants in the gasses may be various, where some of the pollutants cannot be released back into the environment, and where other components

[0020] P2939PC00of the gas may be released into the environment and are natural parts of e.g. a marine ecosystem or a local land-based eco system. A water treatment system is a quite good way of removing harmful pollutants from the cleaning liquid, where the water treatment system is capable of either returning the clean liquid back into the closed-loop system, or of allowing a part of the clean liquid to be released into the environment.

[0021] However, when a closed-loop circulation system is utilized to clean e.g. flue gasses, a large buildup of harmful pollutants may be generated in the closed-loop system over time, where an increased concentration of the harmful pollutants may reduce the efficiency of the water treatment system. Thus, there may be a need to clean the first cleaning liquid before it is fed to the water treatment system in order to ensure that the water treatment system does not clog and reduce or block the capacity of the water treatment system to perform the cleaning operation. A water treatment system may be a system using membranes, centrifuges, setting / floatation, or other types of particle removal to remove impurities from the cleaning liquid. A water treatment system may be provided with membranes for ultra or nanofiltration of the liquid, where forces such as pressure or concentration gradients lead to separation through a semipermeable membrane. Suspended solids and solutes of high molecular weight are retained in the so-called retentate, while water and low-molecular-weight solutes pass through the membrane in the permeate (filtrate). Thus, the choice of an ultra- or a nanofiltration membrane for the water treatment system may affect the ability of the system to remove solids and will certainly affect which pollutants are removed from the cleaning liquid. As the system is a closed-loop system, the system is dependent on removing pollutants from the cleaning liquid in order to have a cleaning liquid that is capable of absorbing the pollutants from the gasses.

[0022] However, when providing a method in accordance with the present disclosure it is possible to simplify the method of cleaning a gas, where the first cleaning liquid will reduce the load of the water treatment system by removing a large part of the pollutants from the cleaning liquid before it is introduced into the water treatment system. This may be obtained by pumping an amount of cleaning liquid from a tank in the circulation system, where the cleaning liquid has pollutants, and into a filter device that is capable of removing at least a part of the pollutants from the cleaning liquid before returning the cleaning liquid back to the closed-loop circulation system. Thus, the filter device is capable of removing an amount of pollutants from the cleaning liquid in order to reduce the amount of pollutants from the cleaning liquid before the cleaning liquid enters the water treatment device. In that way, the filter device is capable of filtering out a large

[0023] P2939PC00part of the pollutants from the water, thereby reducing the concentration of pollutants in the closed-loop circulation system, and thereby reducing the load on the water treatment system in order to minimize the risk of the water treatment system being clogged up and needing maintenance by a skilled worker.

[0024] A water treatment system is an advanced system, where the servicing and / or maintenance of the system requires a skilled worker or at least a user who is trained to service the system to be able to clean or replace the filters of the system. When a closed-loop system is present on a ship, the crew must be able to operate and service the water treatment system, while still maintaining the cleaning of the flue gas coming from the ship engines. Thus, by reducing the need for maintenance and servicing of the water treatment systems it is possible to reduce both the downtime of the water treatment system and the need for training the ship's crew to service the water treatment system.

[0025] Thus, by providing a filter device it is possible to reduce the amount of pollutants in the closed-loop circulation system by way of collecting pollutants in the filter device and removing the pollutants from the filter device by replacing at least part of the filter with a clean filter.

[0026] By having a lower concentration of pollutants in the cleaning liquid when it enters the water treatment device, the load on the water treatment device is reduced, and the service period may be increased, thereby increasing the operating time of the water treatment device, as a high load of particles of pollution has been removed from the cleaning liquid, thus reducing the risk that the particles clog up the water treatment system.

[0027] The filter of the filter device may have a multiple-layer design with a large filter pore size, allowing the filter to catch large particles before entering the water treatment system, and where the water treatment system is configured to catch small particles, e.g. where a membrane has a smaller pore size than the pore size of the filter. During operation, the filter of the filter device may build up a filter cake, so that in the beginning the filter may be configured to capture large particles, where the buildup of the filter cake may allow the filter along with the filter cake to gradually capture finer and finer particles, as the filter cake may operate as an additional filter.

[0028] The flow into the filter may be controlled by a control system, which may be relevant for allowing the filtration to function. In a situation where the filter device has a new

[0029] P2939PC00filter and relatively clean liquid, the control system may pump a high flow of cleaning liquid through the filter, and as the filter cake builds up, the flow may be adjusted to a suitable flow in order to maintain a filter flow. In an exemplary situation where the flow through the filter is maintained as a constant flow, the filter and the filter cake buildup may block up, whereby only a small amount of particles are retained, and where the filter only captures a smaller amount of the very fine particles.

[0030] The system sensors may monitor the condition of the liquid going into the filter, such as density and salt content, as these may affect the filter operation. The filter of the filter device may handle the full spectrum of particle sizes from large to very fine, where the primary advantage is that the load of pollution (dirt load) may be reduced significantly in a cleaning liquid having a high dirt load before the cleaning liquid reaches the water treatment system.

[0031] In one exemplary embodiment, the filter device may be provided with a filter having a first pore size, wherein the water treatment device may be provided with a membrane / filter having a second pore size, where the first pore size is larger than the second pore size.

[0032] The above method may be a method of cleaning a closed-loop circulation liquid in a system for cleaning a gas. The method may be directed to cleaning the cleaning liquid of a closed-loop circulation system used to absorb pollutants from a polluted gas. In one or more embodiments of the present invention, the first cleaning liquid may be an aqueous-based cleaning liquid, where the main components of the cleaning liquid is water.

[0033] In one or more exemplary embodiments, the first liquid-receiving tank may be arranged downstream of the absorber in the closed-loop circulation system, where the cleaning liquid may exit the absorber after absorbing pollutants from the gas, and where the liquid enters the tank. The tank may be a sediment tank, where the tank allows a part of the pollutants in the liquid to sink to the bottom of the tank due to gravity.

[0034] In one or more exemplary embodiments, the first tank outlet may be arranged in a position that is below the liquid level of the first liquid-receiving tank and above 80% of the water level height of the liquid level of the tank. Thus, if the water level height is 100 cm, the first tank output is arranged at a height that is between 80 and 100 cm of the height of the water in the tank. In that way, the first tank outlet may be utilized to withdraw liquids from the tank having less pollutants than the water at a lower part of

[0035] P2939PC00the tank as some of the pollutants have settled near the bottom of the tank due to gravity.

[0036] In one or more exemplary embodiments, the second tank outlet may be arranged in a position that is below the liquid level of the first liquid-receiving tank and below 20% of the water level height of the liquid level of the tank. Thus, if the water level height is 1 m, the second tank output is arranged at a height that is between 0 and 20 cm of the height of the water in the tank. In that way, the second tank outlet may be utilized to withdraw water with pollutants that have settled at the bottom of the tank.

[0037] In one exemplary embodiment, the filter device and the filter pump may be arranged in a first filter loop, where the first filter loop may be a bypass loop allowing liquid to flow from the closed-loop circulation system into the filter device and be returned via the filter loop back into the closed-loop circulation system.

[0038] In one exemplary embodiment, the filter device may be provided with a single-use replaceable filter membrane, where the filter membrane collects the pollutants in a first filter membrane volume. When the filter membrane volume is full or the efficiency of the filter membrane is reduced to a predefined level, the filter membrane may be replaced by removing the filter membrane and the pollutants collected in the filter volume, and replacing the used filter membrane with a new filter membrane. The used filter membrane may be discharged into a filter-collecting volume which is capable of holding a number of used filter membranes.

[0039] In one exemplary embodiment, the filter device may receive the cleaning liquid into the first filter input having a first amount of pollutants, where the filter device may discharge cleaning liquid via the first filter output having a second amount of pollutants that is less than the first amount. The term "amount" may also be used to mean concentration. Thus, the filter device receives cleaning liquid having a higher concentration of pollutants, while the filter device discharges cleaning liquid having a lower concentration of cleaning liquid.

[0040] In one exemplary embodiment, the first filter output may feed filtered cleaning liquid into the first liquid-receiving tank and / or may feed the filtered cleaning liquid into the first water treatment device. Thus, by feeding the filtered cleaning liquid into the first liquid device the filter device may reduce the amount (concentration) of pollutants in the first liquid-receiving tank and thereby reduce the amount of pollutants in the closed-loop circulation system.

[0041] P2939PC00In one exemplary embodiment, the method may further comprise the step of providing a first sensor measuring the pollutant content passing through the first filter pump and providing a controller for controlling the pump pressure and / or the pump flow. The first sensor may be in electrical communication with the controller for controlling the pump, so that feedback from the sensor may control the flow of cleaning liquid through the pump. If the sensor senses a large amount of pollutants in the cleaning liquid, the pump may be configured to pump at a lower flow rate in order to ensure that the filter device is not overloaded with polluted cleaning liquid. However, if the sensor measures that the cleaning liquid has a low amount of pollutants, the flow towards the filter device may be increased as the filter device may be capable of receiving a larger volume of cleaning liquid over a predefined amount of time, while still filtering the pollutants from the cleaning liquid.

[0042] In one exemplary embodiment, the method may also comprise the step of providing a second sensor measuring the liquid flow through the filter device and providing a controller for controlling the pump pressure and / or the pump flow. The second sensor may be used e.g. to measure how effective the filter device is in removing the pollutants from the cleaning liquid. If the second sensor measures a low flow through the filter device, a feedback loop may adjust the pressure of the pump to reduce or increase the flow from the first tank. The second sensor may be utilized to measure the flow through the filter device and may be configured to compare the measurement with the flow rate of the pump to establish whether there is a drop of flow across the filter device. A drop of flow over the filter device may indicate that the filter part of the filter device is spent and has low efficiency and consequently needs to be replaced.

[0043] In one exemplary embodiment, the method may further comprise the step of the filter device collecting the one or more pollutants in a filter volume which is removeable and / or replaceable in the filter device. The filter volume may be defined by a filter part, where the filter part may be a replaceable filter part. The filter part may be in the form of one or more elements that are positioned within the filter device, where the filter part may intersect the flow of cleaning liquid through the filter device, and where the cleaning liquid is configured to pass the filter part. The filter part may be in the form of a mechanical filter, where the filter has a pore size that is configured to remove particles of pollutants from the cleaning liquid. The filter part may further be configured to collect the pollutants in the filter volume, where the cleaning liquid passes through the filter part but traps pollutants in the filter volume. The filter part may be different from one

[0044] P2939PC00application to another; a filter part used for flue gasses in a carbon capture system may be different from a filter part used for flue gasses from a ship engine.

[0045] In one exemplary embodiment, the method may also comprise the step of the first filter outlet discharging the filtered liquid into a second tank inlet of the first liquid-receiving tank and / or into a second treatment fluid input of the water treatment device. The first filter outlet may be in fluid communication with the second tank inlet, where the filtered cleaning liquid is fed from the filter device and may be reintroduced into the first liquidreceiving tank, thereby providing a liquid having a lower amount of pollutants into the first liquid-receiving tank, and thereby reducing the concentration of pollutants in the first liquid-receiving tank. Alternatively, the liquid from the first filter device may be fed directly to the water treatment system, where the cleaned cleaning liquid enters the water treatment device after it has been filtered of pollutants.

[0046] In one or more exemplary embodiments, the first filter outlet may be connected to a valve, where the valve may control the flow of cleaning liquid from the first filter device. The valve may be a valve that can control the flow of liquid from the first filter device and into the liquid-receiving tank and / or into the water treatment device. The valve may also be utilized to stop the flow of cleaning liquid out of the filter device.

[0047] By controlling the concentration of pollutants in the cleaning liquid by way of reducing the concentration of pollutants from the cleaning liquid when it enters the water treatment device, the load on the water treatment device is reduced, and the service period may be increased, thereby increasing the operating time of the water treatment device as a significant amount of particles of pollution have been removed from the cleaning liquid, thus reducing the risk that the particles clog the water treatment system.

[0048] In one exemplary embodiment, the method may further comprise the step of providing a third tank output in fluid communication with the first absorber liquid input. The third tank output may be in fluid communication with the first absorber liquid input, so that the cleaning liquid that is held in the first liquid-receiving tank may be fed back into the absorber to absorb pollutants from the gasses passing through the absorber.

[0049] In one exemplary embodiment, the absorber may be a scrubber. A scrubber (e.g. chemical scrubbers, gas scrubbers) may be an air pollution control device that can be used to remove some particulates and / or gases from industrial exhaust streams, where

[0050] P2939PC00liquids are used to wash unwanted pollutants from a gas stream. Thus, the scrubber may be a wet scrubber.

[0051] In one exemplary embodiment, the method may further comprise a step of providing a second tank having a predefined volume and a secondary first tank outlet which is in fluid communication with the first filter input of the filter device and having a secondary first tank inlet being in fluid communication with the first filter device output and / or in fluid communication with a second water treatment output. The second water treatment output may be an output of the water treatment device, where aqueous pollutants are fed from the water treatment device. Thus, the water treatment device may have a first treatment output where treated water exits the water treatment device and a second treatment output where the removed pollutants are fed from the water treatment device into a second tank. The second tank may be defined as a sludge tank, where the sludge tank is utilized as a buffer tank for cleaning liquid having a high concentration of pollutants. Thus, the second tank may be configured to have a larger concentration of pollutants than the first tank. The secondary first tank outlet may be in fluid communication with the filter device, where a cleaning liquid having a high concentration of pollutants, i.e. in the form of a sludge, is fed to the filter device via the first filter pump, and where the filter device is capable of removing a large amount of pollutants from the sludge before the filtered cleaning liquid is fed from the filter device back into the second tank via a secondary second tank inlet. Thus, the filter device may be utilized to reduce the concentration of pollutants in the second tank by removing pollutants in a filter loop and returning cleaning liquid having a reduced amount of pollutants. Alternatively, the filter output may be fed back into the first tank and / or the first water treatment device, where the flow path or flow direction may be controlled via a valve.

[0052] Existing water treatment systems (WTS) separate a part of the cleaning liquid of e.g. a scrubber system into a clean liquid to be discharged out of the scrubber system and a sludge to be discharged out of the scrubber system.

[0053] In one exemplary embodiment, the method and / or the system may be provided with a first NaOH source, where NaOH may be dosed into the cleaning liquid.

[0054] When a cleaning liquid has a high level of particles, such particles mix chemically with NaOH that may be dosed into the system, which along with a high particle dirt load increases the need to dose NaOH in order to maintain a sufficient cleaning capacity (neutralisation of sulphur). However, the cost of NaOH is high, which means that the

[0055] P2939PC00dosing of NaOH into the cleaning liquid may be expensive and increase the operating cost of the gas cleaning system.

[0056] In many cases, some calcium is present in the process water (may come from the NaOH supplied), and this calcium will bind itself to the NaOH (including CO2) as relatively large particles (compared to sulphur particles, which are dissolved in the liquid).

[0057] When the cleaning liquid is cleaned through a water treatment system, a relatively high content of NaOH may be lost, especially at high particle concentration of the cleaning liquid water, as both the cleaned discharge water of the water treatment system and the sludge carry NaOH particles which may be lost when discharged away from the system tanks and the cleaning system.

[0058] However, by having the filter device of the present disclosure three factors may retain a part of the NaOH and prevent NaOH from being discharged from the system:

[0059] - By keeping the amount of particles in the cleaning liquid (low dirt load), less NaOH is lost to the chemical mixing with the particles of the cleaning liquid. - By filtering the cleaning liquid and sludge in the filter device, the liquid drained from the filter device will contain a high amount of NaOH, where the cleaning liquid having a high concentration of NaOH is returned to the cleaning system. - The water treatment system, when in combination with the filter device, may be operated by having a fine filtration level, as it is only intended to reduce the dirt load (dirt particle concentration) of the cleaning liquid.

[0060] It is known in the art that if there are NaOH calcium particles in the cleaning liquid, these NaOH calcium particles are filtered by the water treatment filter into the sludge, where sulphur in the cleaning liquid is discharged from the water treatment system as dissolved in the cleaned cleaning liquid. By reducing the dirt load of the cleaning liquid, the sludge of the water treatment system may be fed back into the tanks of the cleaning system, thereby returning NaOH to the cleaning process.

[0061] The present disclosure also relates to a system for cleaning a gas (or a closed-loop circulation system for cleaning a gas) having one or more pollutants, where the system comprises:

[0062] a closed-loop circulation system having a first cleaning liquid,

[0063] P2939PC00- an absorber having an absorber fluid input connected to the closed-loop circulation system and an absorber fluid output connected to the closed-loop circulation system,

[0064] - a first water treatment device having a treatment fluid input receiving the first cleaning liquid from the closed-loop circulation system, a first treatment fluid output for returning a part of the first cleaning liquid into the closed-loop circulation system and a second treatment fluid output for discharging pollutants from the closed-loop circulation system,

[0065] - a first liquid-receiving tank arranged upstream from the water treatment device and downstream from the absorber, the first liquid-receiving tank holding a predefined amount of polluted liquid,

[0066] - a filter device (in a first filter loop) having a first filter input receiving polluted liquid (having a first amount of pollutants) from a second tank output of the first liquid-receiving tank and a first filter output configured to discharge filtered liquid (having a second amount of pollutants which is less than the first amount) into the closed-loop circulation system (into the process circulation tank or the first water treatment device), and

[0067] - a first filter pump having a first pump input receiving liquid from the second tank output and a first pump output pumping liquid to the first filter input and providing a first liquid pressure on the filter input.

[0068] In one exemplary embodiment, the system may further comprise a first sensor measuring the pollutant content passing through the first filter pump and providing a controller for controlling the pump pressure and / or the pump flow.

[0069] In one exemplary embodiment, the system may further comprise a second sensor measuring the liquid flow through the filter device and providing a controller for controlling the pump pressure and / or the pump flow.

[0070] In one exemplary embodiment, the filter device may be configured to collect the one or more pollutants in a filter volume which is removeable and / or replaceable in the filter device.

[0071] In one exemplary embodiment, the system may further comprise a first filter outlet discharging the filtered liquid into a second tank inlet of the first liquid-receiving tank and / or into a second treatment fluid input of the water treatment device.

[0072] P2939PC00In one exemplary embodiment, the system may further comprise a third tank output in fluid communication with the first absorber liquid input.

[0073] In one exemplary embodiment, the system may further comprise a second tank having a predefined volume and a secondary first tank fluid outlet which is in fluid communication with the first filter input the filter device (possibly in fluid communication with the first pump inlet) and having a secondary tank first inlet being in fluid communication with the first filter device output and / or in fluid communication with a second water treatment output.

[0074] Brief description of the drawings

[0075] The following is an explanation of exemplary embodiments with reference to the drawings, in which:

[0076] Fig. 1 is a schematical diagram of one embodiment of a system for cleaning a gas, Fig. 2 is a schematic diagram of a second embodiment of a system for cleaning a gas, and

[0077] Fig. 3 is a schematic diagram of an embodiment where a system for cleaning a gas is implemented in an Exhaust Gas Recirculation system (EGRS) of a ship.

[0078] Detailed description

[0079] Various exemplary embodiments and details are described below, with reference to the figures when relevant. It should be noted that the figures may or may not be drawn to scale and that elements of similar structures or functions are represented by like reference numerals throughout the figures. It should also be noted that the figures are only intended to facilitate the description of the embodiments. They are not intended as an exhaustive description of the disclosure or as a limitation on the scope of the disclosure. In addition, an illustrated embodiment needs not have all the aspects or advantages shown. An aspect or an advantage described in conjunction with a particular embodiment is not necessarily limited to that embodiment and can be practiced in any other embodiments even if not so illustrated, or if not so explicitly described.

[0080] Fig. 1 shows a schematic view of a system 1 for cleaning a polluted gas 15, where the system is a closed-loop system 1 having a first cleaning liquid 7. The closed-loop system 1 comprises an absorber 5, where the absorber 5 has an absorber input 9 and an absorber output 11, allowing the cleaning liquid 7 to enter and exit the absorber 5.

[0081] P2939PC00Furthermore the absorber 5 has a first gas input 13 for receiving a polluted gas 15 and a first gas output 17, where cleaned gas 19 exits the absorber 5 having less pollutants than the gas 15 entering the absorber 5.

[0082] The system 1 comprises a first liquid-receiving tank 21 having a first tank input 23 which is in fluid communication with the first absorber output 11 of the absorber 5, where the first liquid-receiving tank 21 is configured to hold a predefined volume of the cleaning liquid 7. The absorber input 9 is in fluid communication with the first liquidreceiving tank 21 via a third tank output 65, where the cleaning liquid 7 may be pumped via an absorber pump 66 to the first absorber input 9.

[0083] The system 1 further comprises a water treatment device 25, where the water treatment device 25 may be configured to remove pollutants from the first cleaning liquid 7, where the first cleaning liquid 7 is fed to a first treatment input 29 of the water treatment device 25 via a first tank output 27 of the first liquid-receiving tank 21. Thus, the cleaning liquid 7 that is collected in the first liquid-receiving tank 21 may be pumped or fed at a different rate from the liquid-receiving tank 21 than the rate at which it enters the tank 21 from the absorber 5. The water treatment device 25 may clean a part of the cleaning liquid 7, where clean liquid 31, i.e. liquid having fewer pollutants than the cleaning liquid 7 entering the system 1, may be let out of the water treatment device 25 via a second treatment fluid output 33 and pumped back into the closed-loop system 1 via a liquid treatment pump 35, where in this embodiment the cleaned liquid 31 is pumped back into a second tank input 63 of the first liquid-receiving tank 21. Alternatively, the clean liquid may be fed into the environment and released from of the closed-loop system 1 via a third fluid treatment output 37. The pollutants that have been removed from the cleaning liquid 7 may be fed out of the water treatment device 25 via a second fluid treatment output 39 into a pollutant tank 41.

[0084] The closed-loop system 1 comprises a filter device 43 having a first filter input 45 being in fluid communication with the first tank 21 via a second tank output 44, where the fluid communication may be controlled by a filter valve 47 and by a filter pump 49 that are arranged in a fluid communication pathway 51 between the tank 21 and the filter device 43. A first sensor 87 measuring the pollutant concentration of the liquid or a second sensor 89 measuring the flow through the filter device 43 may be used to control the pressure and / or flow of the pump 49.

[0085] The filter device 43 may have a filter part 53, where the filter part 53 comprises a filter volume 55 to collect pollutants from the cleaning liquid 7 pumped from the first liquid-

[0086] P2939PC00receiving tank 21, where the second clean liquid 56 is fed out of the filter device 43 via a first filter output 57 back into the closed-loop system 1. Thus, the filter device 43 may be seen as being a filter loop 59 that is capable of reducing the pollutants in the closed-loop system 1. In this embodiment, the first filter output 57 is in fluid communication with a third fluid input 61 of the liquid-receiving tank 21, thereby returning back into the closed-loop system 1 liquid that has a lower concentration of pollutants than when it was fed out of the liquid-receiving tank 21.

[0087] The filter part 53 may be a replaceable filter part, where a used filter part 53 may be replaced by a new filter part 53 when the used filter part 53 has received a predefined amount of pollutants in the first filter volume 55 and is full. When the filter part 53 is to be replaced, the flow from the first liquid-receiving tank 21 may be closed off using the filter valve 47, the filter pump 49 may be shut off, and the filter device 43 may be opened to take out the used filter part 53, discarding the used filter part 53 and replacing the used filter part 53 with a new unused filter part 53. The filter part 53 may be in the form of a single or multi-layered structure, where the cleaning liquid 7 is fed into the filter volume 55 of the filter part 53, and the pollutants that cannot pass through the pores of the layered structure are retained inside the filter volume 55, while the remaining parts of the cleaning liquid 7 pass through the layered structure and thereby have a concentration of pollutants after passing through the layered structure of the filter part 53.

[0088] The filter part 53 may thereby effectively operate similarly to a coffee filter or a vacuum bag, where the pollutants are collected in the filter volume 55, and when the filter volume is full or the efficiency of the filter part 53 is reduced, a user may remove the filter part 53 and replace it with a new unused filter part 53. Thus, the filter parts 53 may be single-use filter parts or may alternatively be cleaned and emptied between uses to be reuseable filter parts 53.

[0089] The second tank output (outlet) 44 may be arranged in a low position in the first liquidreceiving tank 21, so that the second tank output 44 may be utilized to withdraw water containing pollutants that have settled in or near the bottom of the tank. The first tank output 27 may be arranged at a higher position in the liquid-receiving tank 21 where the cleaning liquid 7 that is taken from the first liquid-receiving tank 21 has a lower content of pollutants as the pollutants may have settled or sunk towards the bottom of the first liquid-receiving tank 21.

[0090] P2939PC00Thus, by providing a filter device 43 or a filter loop 59 it is possible to reduce the amount of pollutants in the closed-loop circulation system 1 by way of collecting pollutants in the filter device 43, removing the pollutants from the filter device 43 by replacing at least part 53 of the filter device 43 with a clean filter part 53, thereby reducing the amount of pollutants that are fed to the water treatment device 25 and thereby reducing the need for servicing of the water treatment device and increasing the uptime of the water treatment device when the closed-loop system 1 is needed for absorbing pollutants from the polluted gas 15 entering the absorber 5.

[0091] Fig. 2 shows a schematic view of a system 101 for cleaning a gas, where the system 101 shown in Fig. 2 has all the same elements of the system 1 shown in Fig. 1 and has the same reference numbers and the same functionality. The differences between the two systems 1 and 101 are described below.

[0092] The embodiment shown in Fig. 2 comprises a second tank 67 having a secondary first tank inlet 69 and a secondary second tank inlet 71 as well as a secondary first tank output 79. The second tank 67 may be in the form of a sludge tank 67, where the sludge tank 67 is utilized as a buffer tank for the cleaning liquid 7 having a high concentration of pollutants. Thus, when the water treatment system 25 discharges the pollutants that were separated from the cleaning liquid 7 via a first treatment output 73, the pollutants may be suspended in an aqueous liquid 75, which means that the aqueous liquid 75 has a high concentration of pollutants and may be pumped via a second treatment pump 77 into the sludge tank 67 via the secondary first tank inlet 69, where the polluted aqueous liquid 75 increases the concentration of pollutants in the sludge tank 67. The second tank S may comprise a secondary second tank inlet 71 which is in fluid communication with the first filter output 57 via a first filter valve 81. The first filter valve 81 may be opened or closed, allowing filtered cleaning liquid 83 that has been filtered in the filter device 43 to be introduced into the sludge tank 67. The filtered cleaning liquid 83 may be introduced into the sludge tank 67 to reduce the concentration of pollutants in the sludge tank 67. The secondary first tank output 79 may be in fluid communication with the first filter input 45 and may be controlled by a secondary tank first valve 85 which is capable of opening and closing the fluid communication between the sludge tank 67 and the filter device 43. When the content of the sludge tank 67 is discharged into the filter device 43, the filter pump 49 may be utilized to pump the highly concentrated aqueous liquid from the sludge tank 67 to the filter device 43, and a first sensor 87 measuring the pollutant concentration of the liquid or a second sensor

[0093] P2939PC0089 measuring the flow through the filter device 43 may be used to control the pressure and / or flow of the pump 49.

[0094] In this embodiment, the first filter output 57 may be in fluid communication with the third fluid input 61 of the first liquid-receiving tank 21, where the fluid communication pathway may be controlled by a second filter valve 91 which may be utilized to open and close the pathway between the filter device 43 and the first liquid-receiving tank 21. When the first filter valve 81 is open, the second filter valve 91 may be closed and vice versa to selectively control the flow from the filter device 43 to the sludge tank 67 or the first liquid-receiving tank 21. Alternatively, both valves 81, 91 may be open or closed at the same time to allow liquid to flow into both tanks 21, 67 or to close off fluid communication to both tanks 21, 67 simultaneously.

[0095] Fig. 3 shows a schematic view of a system 201 for cleaning a gas, where the system 201 is arranged on a ship 203 or a marine vessel, and where the system 201 is used for cleaning a gas for a low-pressure Exhaust Gas Recirculation System on the ship 203. The system shown in Fig. 3 has all the same elements as the system 1 shown in Fig. 1 and / or the system 101 shown in Fig. 2 and has the same reference numbers and the same functionality. The differences between the system 101 shown in Fig. 2 and the system 201 shown in Fig. 3 are described below.

[0096] The system shown in Fig. 3 further comprises a third tank 93 having a tertiary tank output 95, where the third tank 93 may be an additive tank 93. The additive in this embodiment may be NaOH, where NaOH may be pumped by an additive pump 97 from the tertiary tank output 95, and where the additive may be added to the cleaning liquid 7 before it enters the absorber input 9 in an additive device 99. The additive may further be fed to the first liquid-receiving tank 21 via a fourth first tank input 105, where the flow may be controlled via an additive valve 107 which may be opened or closed when the additive is to be fed to the first liquid-receiving tank 21.

[0097] In one exemplary embodiment, the method and / or the system may be provided with a drain tank that may be a buffer tank able to receive variable flows of cleaning liquid from engine systems of charge air coolers, etc. Drain tanks may have a certain minimum size in order to have the capacity to receive polluted cleaning liquid, especially during periods where a water treatment system is being maintained or serviced, and the cleaning liquid is not being filtered or treated in the system.

[0098] P2939PC00The system 201 may be provided with a fourth tank 109, where the fourth tank 109 may be a drain tank 109, where the cleaning liquid 7 may be fed from a first tank third output 111 to a quaternary first tank input 113 of the drain tank 109. The drain tank 109 may be provided with a quaternary second tank input 115 which is in fluid communication with a SAC drain and wetting 117, where the flow into the drain tank 109 from the SAC drain and the wetting 117 may be controlled via a first wetting valve 119. Alternatively, the flow from the SAC drain and the wetting 117 may be fed out of the system 201 either overboard or to a holding tank 121 which may be controlled by a second wetting valve 123.

[0099] The drain tank 109 may have a quaternary first tank output 125 which may allow clean cleaning liquid 127 from the drain tank 109 to be pumped either overboard or to a holding tank 121 via a drain pump 129, where the flow out of the drain tank 109 via the first tank output 125 may be controlled by a drain valve 131.

[0100] The third fluid treatment output 37 may further be used to feed the clean cleaning liquid 127 out of the system 201 either overboard or to the holding tank 121.

[0101] In this embodiment, the pollutant tank 41 shown in Fig. 1 and Fig. 2 is not shown but may be present in the embodiment shown in Fig. 3 with the same configuration as shown in Figs. 1 and 2.

[0102] The use of the terms "first", "second", "third" and "fourth", "primary", "secondary", "tertiary", etc., does not imply any particular order, but are included to identify individual elements. Moreover, the use of the terms "first", "second", "third" and "fourth", "primary", "secondary", "tertiary", etc., does not denote any order or importance, but rather the terms "first", "second", "third" and "fourth", "primary", "secondary", "tertiary", etc., are used to distinguish one element from another. Note that the words "first", "second", "third" and "fourth", "primary", "secondary", "tertiary", etc., are used here and elsewhere for labelling purposes only and are not intended to denote any specific spatial or temporal ordering.

[0103] Furthermore, the labelling of a first element does not imply the presence of a second element and vice versa.

[0104] It is to be noted that the word "comprising" does not necessarily exclude the presence of other elements or steps than those listed.

[0105] P2939PC00It is also to be noted that the words "a" or "an" preceding an element do not exclude the presence of a plurality of such elements.

[0106] It should further be noted that any reference signs do not limit the scope of the claims. Although features have been shown and described, it will be understood that they are not intended to limit the claimed invention, and it will be made obvious to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the claimed invention. The specification and drawings are, accordingly, to be regarded in an illustrative rather than restrictive sense. The claimed invention is intended to cover all alternatives, modifications and equivalents.

[0107] P2939PC00List of references

[0108] I Closed-loop system

[0109] 5 Absorber

[0110] 7 First cleaning liquid

[0111] 9 Absorber input

[0112] II Absorber output

[0113] 13 First gas input

[0114] 15 Polluted gas

[0115] 17 First gas output

[0116] 19 Cleaned gas

[0117] 21 First liquid-receiving tank

[0118] 23 First tank input

[0119] 25 Water treatment device

[0120] 27 First tank output

[0121] 29 First treatment input

[0122] 31 Clean liquid

[0123] 33 Second treatment fluid output

[0124] 35 Liquid treatment pump

[0125] 37 Third fluid treatment output

[0126] 39 Second fluid treatment output

[0127] 41 Pollutant tank

[0128] 43 Filter device

[0129] 44 Second tank output

[0130] 45 First filter input

[0131] 47 Filter valve

[0132] 49 Filter pump

[0133] 51 Fluid communication pathway

[0134] 53 Filter part

[0135] 55 First filter volume

[0136] 56 Second clean liquid

[0137] 57 First filter output

[0138] 59 Filter loop

[0139] 61 Third fluid input

[0140] 63 Second tank input

[0141] 65 Third tank output

[0142] 66 Absorber pump

[0143] 67 Second tank

[0144] P2939PC0069 Secondary first tank inlet

[0145] 71 Secondary second tank inlet

[0146] 73 First liquid treatment output

[0147] 75 Aqueous liquid

[0148] 77 Second treatment pump

[0149] 79 Secondary first tank output

[0150] 81 First filter valve

[0151] 83 Filtered cleaning liquid

[0152] 85 Secondary tank first valve

[0153] 87 First sensor

[0154] 89 Second sensor

[0155] 91 Second filter valve

[0156] 93 Third tank

[0157] 95 Tertiary tank output

[0158] 97 Additive pump

[0159] 99 Additive device

[0160] 101 System

[0161] 105 Fourth first tank input

[0162] 107 Additive valve

[0163] 109 Fourth (drain) tank

[0164] 111 First tank third output

[0165] 113 Quaternary first tank input

[0166] 115 Quaternary second tank input

[0167] 117 SAC drain and wetting

[0168] 119 First wetting valve

[0169] 121 Overboard or holding tank

[0170] 123 Second wetting valve

[0171] 125 Quaternary first tank output

[0172] 127 Clean cleaning liquid

[0173] 129 Drain pump

[0174] 131 Drain valve

[0175] 201 System

[0176] 203 Ship

[0177] P2939PC00

Claims

Claims1. A method of cleaning a gas (or cleaning a closed-loop circulation fluid in a system for cleaning a gas) having one or more pollutants, where the method comprises the steps of:- providing a closed-loop circulation system having at least one absorber having an absorber fluid input from the closed-loop circulation system and an absorber fluid output into the closed-loop circulation system,- providing a first cleaning liquid in the closed-loop circulation system- providing a first water (liquid) treatment device having a first treatment fluid input receiving a first cleaning liquid from the closed-loop circulation system and a first treatment fluid output for returning a part of the first cleaning liquid into the closed-loop circulation system, and a second treatment fluid output for discharging pollutants from the closed-loop circulation system,- providing a first liquid-receiving tank holding polluted liquid in the closed-loop circulation system that has a first tank output that is arranged upstream of the water treatment device and a first tank input in fluid connection with the absorber fluid output (arranged downstream of the absorber in the closed-loop circulation system),- providing a filter device (in a first filter loop) having a first filter input receiving polluted liquid (having a first amount of pollutants) from a second tank output of the first liquid-receiving tank and a first filter output discharging filtered liquid (having a second amount of pollutants which is less than the first amount) into the closed-loop circulation system (into the process circulation tank or the first water treatment device), and- providing a first filter pump having a first pump input receiving liquid from the second tank output and a first pump output pumping liquid to the first filter input, and providing a first liquid pressure on the filter input.

2. A method of cleaning a gas in accordance with claim 1, comprising the step of providing a first sensor measuring pollutant content passing through the first filter pump and providing a controller for controlling the pump pressure and / or the pump flow.

3. A method of cleaning a gas in accordance with claim 1 or 2, comprising the step of providing a second sensor measuring the liquid flow through the filter device and providing a controller for controlling the pump pressure and / or the pump flow.P2939PC004. A method of cleaning a gas in accordance with any one of claims 1-3, comprising the step of the filter device collecting the one or more pollutants in a filter volume which is removeable and / or replaceable in the filter device.

5. A method of cleaning a gas in accordance with any one of claims 1-4, comprising the step of the first filter outlet discharging the filtered liquid into a second tank inlet of the first liquid-receiving tank and / or into a second treatment fluid input of the water treatment device.

6. A method of cleaning a gas in accordance with any one of claims 1-5, comprising the step of providing a third tank output in fluid communication with the first absorber liquid input.

7. A method of cleaning a gas in accordance with any one of claims 1-6, comprising the step of providing a second tank having a predefined volume, and a secondary tank first fluid outlet which is in fluid communication with the first filter input of the filter device (possibly in fluid communication with the first pump inlet) and having a secondary tank first inlet being in fluid communication with the first filter device output and / or in fluid communication with a second water treatment output.

8. A system for cleaning a gas (or a closed-loop circulation system for cleaning a gas) having one or more pollutants, where the system comprises:- a closed-loop circulation system having a first cleaning liquid,- an absorber having an absorber fluid input connected to the closed-loop circulation system and an absorber fluid output connected to the closed-loop circulation system,- a first water treatment device having a treatment fluid input receiving the first cleaning liquid from the closed-loop circulation system and a first treatment fluid output for returning a part of the first cleaning liquid into the closed-loop circulation system and a second treatment fluid output for discharging pollutants from the closed-loop circulation system,- a first liquid-receiving tank arranged upstream from the water treatment device and downstream from the absorber, the first liquid-receiving tank holding a predefined amount of polluted liquid,- a filter device (in a first filter loop) having a first filter input receiving polluted liquid (having a first amount of pollutants) from a second tank output of the firstP2939PC00liquid-receiving tank and a first filter output configured to discharge filtered liquid (having a second amount of pollutants which is less than the first amount) into the closed-loop circulation system (into the process circulation tank or the first water treatment device), and- a first filter pump having a first pump input receiving liquid from the second tank output and a first pump output pumping liquid to the first filter input, and providing a first liquid pressure on the filter input.

9. A system for cleaning a gas in accordance with claim 8, wherein the system further comprises a first sensor measuring pollutant content passing through the first filter pump and providing a controller for controlling the pump pressure and / or the pump flow.

10. A system for cleaning a gas in accordance with claim 8 or 9, wherein the system further comprises a second sensor measuring the liquid flow through the filter device and yet further comprises a controller for controlling the pump pressure and / or the pump flow.

11. A system for cleaning a gas in accordance with any one of claims 8-10, wherein the filter device is configured to collect the one or more pollutants in a filter volume which is removeable and / or replaceable in the filter device.

12. A system for cleaning a gas in accordance with any one of claims 8-11, wherein the system further comprises a first filter outlet discharging the filtered liquid into a second tank inlet of the first liquid-receiving tank and / or into a second treatment fluid input of the water treatment device.

13. A system for cleaning a gas in accordance with any one of claims 8-12, wherein the system further comprises a third tank output in fluid communication with the first absorber liquid input.

14. A system for cleaning a gas in accordance with any one of claims 8-13, wherein the system further comprises a second tank having a predefined volume and a secondary tank first fluid outlet which is in fluid communication with the first filter input of the filter device (possibly in fluid communication with the first pump inlet) and having a secondary tank first inlet being in fluid communication with the first filter device output and / or in fluid communication with a second water treatment output.P2939PC00

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