Integrated process for removing carbon dioxide from a ship or offshore floating vessel using a rotary filling device

Abstract

A method for purifying exhaust gas, the method comprising providing a rotating packed bed device on board a ship or vessel that generates the exhaust gas, and supplying an absorbent together with the exhaust gas to the rotating packed bed to remove carbon dioxide.

Description

Technical Field

[0001] The present invention relates to an improved method and system for removing carbon dioxide from exhaust gas on board a ship or other marine floating vessel using a rotating packed bed device.

Background Art

[0002] Decarbonization in the marine sector requires the installation of exhaust gas reduction treatment equipment on board. On ships, movement, limited installation area, weight, and other constraints can pose challenges, making decarbonization one of the most difficult areas. Conventional technologies available for reducing CO2 in onshore environments, such as packed towers, are not ideal solutions for the marine environment as they are too bulky. These may need to be oversized and have their structures reinforced to withstand the forces of movement that occur in the marine environment due to their large size.

[0003] Rotating packed bed technology (RPB) has advantages for the marine environment in that it is low-profile, low-weight, and has a small installation area, requires less inventory of absorbent liquid, and is more cost-effective for carbon dioxide capture. Furthermore, since RPB technology relies on centrifugal force to improve the mass transfer process, it is less affected by movement and orientation and has the operational advantage of being suitable for marine applications. The turndown ratio of RPB is 10%, making it suitable for various engine loads.

[0004] The marine environment is unstable, and conventional scrubbers are prone to gas leakage and unstable performance due to waves, wind, and other forces that can cause movement. The movement on board a ship is often unstable and unpredictable, making it difficult to maintain effective contact between the exhaust gas and the liquid or solid used for exhaust gas purification. As a result, conventional exhaust gas purification systems need to be overdesigned, increasing one or more of cost, weight, height, and installation area.

[0005] Conventional exhaust gas purification systems, such as systems using a fluidized bed or packed bed spray scrubber, were very large and heavy. Conventional systems were also difficult to retrofit onto existing ships.

[0006] There is a need for improved methods and systems for removing pollutants, including carbon dioxide, from exhaust gas on board a ship. There is a need for an improved system for more efficiently removing exhaust gas pollutants.

[0007] Conventional attempts to remove pollutants from exhaust gas have targeted SOx removal on board ships using an open system that utilizes seawater and discharges the used seawater back into the sea. Amines or other commercially produced chemical solvents are harmful and cannot be discharged into the sea. Further attempts to remove CO2 from the feed gas have targeted natural gas or the like that is available at a much higher pressure than the exhaust gas. There is a need for a CO2 capture system or CO2 capture process that avoids the release of harmful chemical solvents into the sea and addresses the ambient pressure of the exhaust gas, as described herein.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

[0009] Embodiments of the present invention are a closed-loop process for removing CO2 from exhaust gas, including a venturi quench that processes and cools high-temperature exhaust gas from a ship.

[0010] Another embodiment is to supply the cooled exhaust gas to one or more rotating packed bed devices (RPB devices) and bring it into contact with a purification fluid, which is selected for CO2 capture, for example, normal amines (MEA, DEA, and MDEA), advanced amines including activated MDEA and combinations of piperazine and MDEA, ionic liquids, or switchable polarity fluids (SPFs).

[0011] Another embodiment is an integrated system for the purification fluid that includes two tanks, one of which holds unused liquid and the other collects the spent fluid that has reacted with CO2.

[0012] A further embodiment is one or more RPB devices disposed within the hull or stack of a marine vessel, the one or more RPB devices comprising a rotating shaft and a porous medium and configured to mix the exhaust gas and the CO2 capture liquid in an external direction at a gas / liquid ratio sufficient to reduce the CO2 concentration in the exhaust gas to a desired level. The supply of exhaust gas / liquid to the outside of the RPB can be co-current, which allows for a maximum pressure increase of 50 kPa from the internal region to the external region of the RPB, overcoming the upper pressure limit of the exhaust gas.

[0013] Another embodiment of the present invention is to add another RPB to regenerate the spent fluid on board and store the desorbed CO2 in an on-board tank. Another option is to regenerate the spent fluid at a shore facility while in port.

Brief Description of the Drawings

[0014]

Figure 1

Modes for Carrying Out the Invention

[0015] This specification describes a process and a closed system for removing CO2 from exhaust gases generated from a ship or vessel without using seawater. The process and system perform CO2 capture on board using one or more RPB devices in combination with a chemical reaction between CO2 and an advanced solvent such as an amine, an ionic liquid, or a switchable polarity solvent (SPS).

[0016] A "ship" is a large seagoing vessel that travels the world's seas and other sufficiently deep waterways by one or more engines that emit exhaust gases or CO2-containing gases, transporting passengers or goods, or responding to special missions such as defense, survey, and fishing. A "marine ship" is a ship that operates in the sea or seawater.

[0017] "Exhaust gas" is the gas that exits into the atmosphere through an exhaust stack, which is a pipe or channel for transporting exhaust gas from a furnace, engine, oven, stove, boiler, or steam generator. Exhaust gas can refer to, for example, combustion exhaust gas generated by an engine. "Total suspended solids" (TSS) is the dry weight of particles captured by a filter. This is a water quality parameter and is used, for example, to evaluate the water quality of sewage after treatment in a sewage treatment plant. TSS is listed as a conventional pollutant in the US Clean Water Act. "Heavy fuel oil" (HFO) represents fuel used to generate motion and / or fuel used to generate heat, which have particularly high viscosity and density. It can be defined as heavy oil by either a density exceeding 900 kg / m3 at 15°C or a kinematic viscosity exceeding 180 mm2 / s at 50°C. Heavy oil can have a large proportion of heavy molecules such as long-chain hydrocarbons and aromatic compounds with long branched side chains and can be black.

[0018] "Centrifugal force" is an inertial force in the direction away from the axis of rotation that appears to act on all objects when viewed in a rotating reference frame. The radial force generated by a rotating rotor is expressed relative to the gravity of the Earth and is thus known as relative centrifugal force (RCF) or "g-force". The g-force acting on a particle is an exponential function of the rotational speed (defined as revolutions per minute (RPM)). The function between these two parameters is as follows (r is in millimeters): RCF = 1.2r(RPM / 1000)(RPM / 1000).

[0019] "Turn-down ratio" refers to the width of the operating range of a device and is defined as the ratio of the maximum operating capacity to the minimum operating capacity. For example, a device with a maximum output of 10 units and a minimum output of 2 units has a turn-down ratio of 5.

[0020] "Antiscalant" is a family of chemical products designed to inhibit the formation and precipitation of scale-forming crystalline inorganic salts.

[0021] In the context of the present invention, sufficient centrifugal force may be an RCF sufficient to promote good gas-liquid contact and prevent leakage of the exhaust gas 15 during operation of the rotating packed bed device 4. In one embodiment, the RCF may be greater than 1, for example at least greater than 4 and at most 10,000. Gas leakage may be caused by movement on a ship or a floating offshore vessel and may be very difficult to prevent using a conventional scrubber for the exhaust gas 15.

[0022] The removal of CO2 from the exhaust gas is initiated by supplying the exhaust gas to a venturi quench to treat and cool the hot exhaust gas from the ship, and then supplying the cooled exhaust gas to an RPB device to contact it with a purification fluid, also referred to herein as a liquid absorbent. The purification fluid includes CO2 capture fluids known to those skilled in the art and is preferably selected from normal amines (MEA, DEA, and MDEA), higher amines (activated MDEA, a combination of piperazine and MDEA), aqueous potassium carbonate itself, or aqueous potassium carbonate activated with piperazine, ionic liquids, or switchable polarity fluids (SPs). The process described herein can remove up to 92% of the CO2 from the exhaust gas and up to 100% of the CO2 when multiple RPBs are implemented.

[0023] Table 1 below shows examples of good CO2 removal at various flow rates of CO2 and methyl ethanolamine (MEA).

Table 1

[0024] An embodiment of the present invention is an integrated system for the purification fluid that includes two tanks, one of which holds the unused liquid and the other collects the used fluid that has reacted with CO2.

[0025] Further embodiments regenerate the spent fluid by feeding it to one or more rotating packed bed devices and store the desorbed CO2 in on-board or shipboard tanks or regenerate the spent fluid at a shore facility while in port. Regeneration is effected by applying a temperature in excess of 212°F (100°C) to the spent fluid to release the CO2. The purified fluid is free of or partially free of CO2 and can recapture CO2 in the absorption cycle. Such regeneration may be effected by any convenient method and may use a regenerator for regenerating a solution containing a high level of impurities. The regenerator is optionally operably connected, for example, to a flash drum and a rotating packed bed absorber. In this way, a liquid containing a high level of impurities can be delivered to the second (or plural) rotating packed bed regenerator used for regeneration. The specific equipment of the regenerator can vary depending on the particular process, other equipment, and available space. For example, the regenerator can include, by way of example, heaters such as a reboiler and a condenser, one or more additional rotating packed bed regenerators having one or more rotatable packing rings, or any combination thereof. Optionally, the heating unit or the reboiler unit can be external to the rotating packed bed chamber or can be partially or wholly integrated, i.e., can be inside the rotating packed bed chamber. In some embodiments, the regenerator can include a packed tower.

[0026] A further embodiment is an RPB device disposed within the hull or stack of a marine vessel, the one or more RPB devices comprising a rotating shaft and a porous medium, and configured to mix exhaust gas and a CO2 capture liquid in an outward direction at a gas / liquid ratio sufficient to reduce the CO2 concentration in the exhaust gas to a desired level. By the co-current supply of exhaust gas / liquid to the exterior of the RPB, a pressure increase of up to 50 kPa from the interior region to the exterior region of the RPB is possible, overcoming the pressure ceiling of the exhaust gas. An additional pressure increase to overcome the pressure ceiling of the exhaust gas, e.g., a pressure increase exceeding 50 kPa, can be brought about by increasing the rotational speed of the RPB. A current mode is also an embodiment of the present invention. Both co-current mode and counter-current mode are described in U.S. Patent No. 11,491,441, which is incorporated herein by reference, and the fluid utilized is not seawater.

[0027] In the context of the present invention, sufficient centrifugal force can be the RCF sufficient to promote good gas-liquid contact and prevent leakage of the exhaust gas 15 during operation of the rotating packed bed device 4. In one embodiment, the RCF can be greater than 1, e.g., at least greater than 4 and at most 10,000. Gas leakage can be caused by movement on board a ship or a floating marine vessel and can be very difficult to prevent using conventional scrubbers for the exhaust gas 15. In one embodiment, due to sufficient centrifugal force, the rotating packed bed device 4 retains a liquid of less than 1 wt%, such as 0.01 - 0.50 wt%. The low liquid retention rate results in a weight reduction and efficient use of the porous material within the rotating packed bed device 4. For example, in one embodiment, the rotating packed bed device 4 comprises one or more rotatable packing rings 4A of a porous material, and when these operate under sufficient centrifugal force, the rotating packed bed device 4 retains 0.01 - 0.50 wt% of the liquid.

[0028] In one embodiment, the rotating packed bed device 4 includes a porous material having a high surface area per unit volume, for example, exceeding 150 m2 / m3, or from about 200 m2 / m3 to about 6,000 m2 / m3. In one embodiment, the rotating packed bed device 4 includes one or more rotatable packing rings 4A that include a porous material having a high surface area per unit volume. In one embodiment, the rotating packed bed device 4 includes one or more rotatable packing rings 4A that include a porous material.

[0029] The rotating packed bed devices described in International Publication No. WO 2018 / 229589 and U.S. Patent No. 11,491,441, which are incorporated herein by reference, can be used with the systems and processes for removing CO2 from the exhaust gas described herein.

[0030] Embodiments of the present invention are RPB devices disposed within the hull of a marine vessel or a chimney, the one or more RPB devices comprising a rotating shaft and a porous medium, configured to mix exhaust gas and a CO2 capture liquid in an outward direction at a gas / liquid ratio sufficient to reduce the CO2 concentration in the exhaust gas to a desired level. The co-current supply of exhaust gas / liquid to the outside of the RPB enables a pressure increase of up to 50 kPa from the inner region to the outer region of the RPB, overcoming the pressure upper limit of the exhaust gas. In a preferred embodiment, gas and liquid are simultaneously supplied through the annular portion of the RPB to overcome the pressure drop of the exhaust gas.

[0031] Regarding the internal and external regions of the RPB, referring to the exemplary embodiment of FIG. 1 and the description of the RPB from U.S. Patent No. 11,491,441, the method disclosed herein can utilize a system including a rotating packed bed device, as shown. In this embodiment, the rotating packed bed device includes one or more rotatable packing rings disposed in a housing. The one or more rotatable packing rings can typically have the shape of a thick cylindrical disk having a hollow central axis portion or space, also referred to herein as the internal region. The rotatable packing ring surrounding the internal region defines the internal region. The rotatable packing ring is housed in the space inside the housing. This space is the external region within the rotating packed bed device and is not labeled in FIG. 1. Further, a venturi quench, not labeled in FIG. 1, is configured to receive and cool the high-temperature exhaust gas from the ship in the system and then supply the cooled exhaust gas to the RPB device to contact with the purification fluid, as described herein. In one embodiment, a pressure increase is formed between the internal region of the rotating packed bed device 4 and the external region of the rotating packed bed device. The pressure increase is 0 kPa or more, such as greater than 2 kPa or 3 kPa, and can be, for example, from 0 kPa to 50 kPa. This pressure increase can function like a blower and can help push the low-pressure exhaust gas 15 from the engine through the rotating packed bed device 4. The pressure increase can significantly reduce or prevent an undesirable backpressure on the engine of the ship or offshore floating vessel. This can be highly desirable when treating the low-pressure exhaust gas 15. In one embodiment, the maximum allowable backpressure that the engine of the ship can withstand is 981 Pa, and the rotating packed bed device 4 is configured to prevent the backpressure on the engine of the ship.

[0032] The high gravity generated by the centrifugal force of the rotatable packing ring 4A enables the use of a unique packing material having a very high surface area and fine pore diameters. The rotatable packing ring 4A can be formed from a variety of suitable materials, including, for example, metal foams, plastics, composites, stainless steel, titanium, super duplex stainless steel alloys, porous materials including metallic or non-metallic wire meshes, knitted fabrics, and glass fibers. In one embodiment, the rotatable packing ring 4A comprises a porous material having a surface area per unit volume (specific surface area) of about 200 m 2 / m 3 ~ about 6,000 m 2 / m 3 . In one embodiment, the rotatable packing ring 4A comprises a porous material that is a metal foam, a metal mesh, a fiberglass, a polymer, or a composite thereof. In one embodiment, the porous material has an average pore diameter of 100 to 10,000 micrometers. In one embodiment, the porous material is a metal foam having a porosity of at least about 90% and an average pore diameter of 250 to 2,500 micrometers. In one embodiment, the metal foam is a RECEMAT® metal foam (RMF). RECEMAT is a registered trademark of RECEMAT BV based in the Netherlands. RMF is one of the commercially available metal foams and is a continuous cell polyurethane foam metallized using an electrodeposition technique excellent in controlling the cell size. In one embodiment, the RMF has a nickel microstructure, a nickel-chromium (NC) microstructure, or a nickel-chromium extra foam (NCX) microstructure. In one embodiment, the metal foam has a thickness of 1.6 to 20 mm and a pore diameter of 0.4 to 2.3 mm. In one embodiment, the metal foam has the name of NCX0610, NCX1116, NCX1723, NCX2733, or NCX4753. The typical properties of these types of metal foams are summarized in Table 2.

Table 2

[0033] The foregoing processes and systems can be advantageous for a number of independent reasons. For example, when using an integrated process and system that performs absorption and / or regeneration in a rotating packed bed, often the capital costs are reduced and the compact nature of the rotating packed bed reduces the weight and / or footprint (especially vertical) of the equipment. Further, these processes and systems typically result in an improvement in safety due to a reduction in the required inventory of liquids, an improvement in operability due to a reduced likelihood of foaming, and often a high turndown ratio. Further, with respect to movement, the fact that the rotating packed bed is largely unaffected can be advantageous for ships and vessels that generate exhaust gas. Yet another advantage can be when transporting and installing in remote locations. Typically, in conventional ships, the loading of amines is limited due to concerns about corrosion. However, the more compact nature of the rotating packed bed allows the use of more expensive materials such as alloys, enabling the adoption of a richer, i.e., higher concentration, increased loading of amines, which can result in a lower circulation rate and thus a reduction in operating costs.

Claims

1. A method for removing carbon dioxide from exhaust gas in a ship or vessel that generates exhaust gas, the method comprising: (a) Supplying the CO2-containing exhaust gas to a venturi quencher to treat and cool the high-temperature exhaust gas from the ship; (b) Supplying the cooled exhaust gas to a rotating packed bed device (RPB device); (c) Contacting with a purification fluid to form a used fluid having bound CO2. The method as described above.

2. The method according to claim 1, wherein the rotating packed bed device comprises one or more rotatable packing rings, and the one or more rotatable packing rings define an internal region and an external region within the rotating packed bed device.

3. The method according to claim 2, wherein the pressure increase from the internal region to the external region of the rotating packed bed device is from 0 kPa to 50 kPa.

4. The method according to claim 3, wherein the purification fluid is selected from the group consisting of normal amines (MEA, DEA, and MDEA), higher amines (activated MDEA, combination of piperazine and MDEA), aqueous potassium carbonate, ionic liquids, or switchable polarity fluids.

5. The method according to claim 1, wherein the used fluid is regenerated by being supplied to one or more of the rotating packed bed devices, and the desorbed CO2 is stored in a tank on board the ship or vessel, or the used fluid is regenerated at a land-based facility.

6. An integrated system for purifying marine exhaust gas of a ship on board, the system comprising: i) A high-temperature exhaust gas inlet for supplying the marine exhaust gas at a temperature exceeding 180 °C from the engine of the ship; b) The rotating packed bed device; The rotating packed bed device comprises iii) A stationary gas distributor disposed along the outer periphery of the rotary packed bed device and connected to the Venturi quencher, the stationary gas distributor configured to receive the cooled exhaust gas and uniformly distribute the quenched marine exhaust gas along the outer periphery of the rotary packed bed device; iv) A stationary liquid distributor having a plurality of liquid rings and disposed in the center of the rotary packed bed device, wherein the plurality of liquid rings are attached with spray nozzles, and these spray a liquid absorbent supplied together with the cooled exhaust gas into the ring of the rotary packed bed device; the stationary liquid distributor; An integrated system having the same.

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