Methods and systems for washing flue gas

Abstract

A method for washing a flue gas to remove solvent present in the flue gas, the method comprises the steps of feeding a solvent rich flue gas to a first Rotary Packed Bed (RPB). A first inlet aqueous p

Description

The present invention relates to methods and systems for washing flue gas to remove solvent present in the flue gas. BACKGROUND OF THE INVENTION Flue gases from power plants and other industrial activities include pollutants, for example greenhouse gases. One such greenhouse gas is CO2 (carbon dioxide). Emissions of CO2 to the atmosphere from industrial activities are of increasing concern to society and are therefore becoming increasingly regulated. To reduce the amount of CO2 being released into the atmosphere, CO2 capture technology can be applied. The selective capture of CO2 not only minimizes the amount of CO2 released into the atmosphere, but also allows CO2 to be re-used or geographically sequestered. CO2 capture methods can be applied to CO2 capture from flue gases and industrial gases, e.g., emissions from plants that bum hydrocarbon fuel. CO2 capture methods are also applicable to CO2 capture from coal, gas and oil-fired boilers, combined cycle power plants, coal gasification, hydrogen plants, biogas plants, waste to energy plants, steel plants, refineries, cement kilns, blast furnaces, or any other plant which produces a flue gas. CO2 capture methods can be divided into physical adsorbents and chemical absorbents (commonly referred to as carbon capture solvents). For CO2 capture methods, the carbon capture solvent removes CO2from one or more gas streams. The CO2 in the gas streams selectively reacts with components in the solvent, resulting in CO2 being removed from the gas phase and absorbed by the solvent to form a CO2rich solvent. The CO2rich solvent is then heated resulting in CO2 being released back into the gas phase and the CO2 rich solvent being depleted of its CO2 content resulting in the formation of a CO2 lean solvent. The CO2 lean solvent is recycled within the system to capture additional CO2. Figure 1 illustrates a block diagram 100 of a conventional process for capturing CO2 from flue gases. CO2 is separated from a mixture of gases, using a solvent which selectively reacts with the CO2. After the CO2 has reacted with the solvent (the “absorption step”), the solvent can be regenerated using heat to release the CO2 and regenerate the solvent for further CO2 processing. A flue gas 102 containing CO2 is contacted with a liquid solvent in a static packed column 104 (absorber column). The liquid solvent is cascaded over a top of the static packed column 104 and falls under gravity to a bottom where it is collected in a sump. A second static packed column 106 (wash column) having structured packing comprises wash stages to remove traces of the solvent and volatile chemicals. A gaseous mixture depleted of CO2 passes through the wash stages to remove traces of the solvent and volatile chemicals formed through degradation reactions of the solvent components. Thus, the flue gas 108 depleted of CO2 is released from the top of the static packed column 104. All of the wash stages occur in similar static structured packing and use water or acid for washing. The solvent is fed into a top section of a stripper column 112 and allowed to fall under gravity over a packing material to a bottom of the stripper column 112. At the bottom, the solvent is drawn into a reboiler 114. Inside the reboiler 114, the solvent is heated to a temperature so that at an operating pressure of the stripper column 112, water present in the solvent gets vaporized to steam. The steam and the CO2 rise to a top of the stripper column 112 where a condenser cools the steam and gas to around 40°C. This condenses the steam into water 116 and gaseous CO2118. The condensed water 116 is returned to the top of the stripper column via reflux drum 120 and the gaseous CO2118 used for downstream processes while the solvent at the bottom of the stripper is recycled to an absorber as a lean solvent via the heat exchanger 110, ready to repeat the absorption process again. A problem with the conventional process for capturing CO2 from flue gases is that the wash stages can be inefficient at preventing solvent emissions in the form of aerosols. Solvent aerosols can be formed by contaminants in the inlet flue gas, or can arise from suboptimal operating conditions or aerosols already present in the inlet flue gas. To reduce aerosolised solvent emissions in the conventional process, it would be necessary to include a demister (such as a vane or wire mesh demister) in the static packed column. However, the use of demisters can contribute to pressure loss in the system. Such pressure loss causes a decrease in process efficiency of the conventional process because it becomes necessary to apply more pressure to the inlet flue gas to counteract the pressure loss. Increasing the pressure of the inlet flue gas would require further energy, increasing the overall cost ($ / ton) to capture CO2 from flue gases. The conventional process is also relatively poor at preventing non-aerosolised solvent emissions. Therefore, overall solvent removal and recovery by the wash stages of the conventional process for capturing CO2 from flue gases is suboptimal. However, environmental regulation may require that the concentration of solvent in a flue gas emitted to the atmosphere is below a defined level. In addition, any solvent not recovered must be replaced to ensure that there is enough solvent to effectively remove of CO2 during the absorption step. Replacement of solvent increases the cost ($ / ton) and material requirements to capture CO2 from flue gases. There is a need for methods for washing a flue gas that is more effective at removing solvent present in the flue gas. SUMMARY OF THE INVENTION Representative features of the present invention are set out in the following clauses, which stand alone or may be combined, in any combination, with one or more features disclosed in the text and / or figures of the specification. The present invention is as set out in the following clauses: 1. A method for washing a flue gas to remove solvent present in the flue gas, the method comprising the steps of: feeding a solvent rich flue gas to a first Rotary Packed Bed (RPB) rotating circularly, wherein a first inlet aqueous phase provided through an inner radius of the first RPB moves towards an outer radius of the first RPB, and wherein the first inlet aqueous phase contacts with the solvent rich flue gas in a counter-current flow to remove solvent present in the solvent rich flue gas and form a solvent semi-lean flue gas and first outlet aqueous phase; feeding the solvent semi-lean flue gas to a second RPB rotating circularly, wherein a second inlet aqueous phase provided through an inner radius of the second RPB moves towards an outer radius of the second RPB, and wherein the second inlet aqueous phase contacts the solvent semi-lean flue gas in a counter-current flow to remove solvent present in the solvent semi-lean flue gas and form a solvent lean flue gas and second outlet aqueous phase; and, wherein a first portion of the first outlet aqueous phase is cooled to a temperature of from 15 to 50 °C then fed to the inner radius of the first RPB such that the first inlet aqueous phase comprises all or some of the cooled first portion of the first outlet aqueous phase. 2. The method of clause 1, wherein the solvent rich flue gas is introduced from the outer radius of the first RPB. 3. The method of clause 1 or clause 2, wherein the solvent semi-lean flue gas is introduced from the outer radius of the second RPB. 4. The method of any one of clauses 1 to 3, wherein the first portion of the first outlet aqueous phase is cooled to a temperature of from 25 to 40 °C. 5. The method of any one of clauses 1 to 4, wherein a first portion of the second outlet aqueous phase is cooled to a temperature of from 15 to 50 °C then fed to the inner radius of the second RPB such that the second inlet aqueous phase comprises all or some of the cooled first portion of the second outlet aqueous phase. 6. The method of clause 5, wherein the first portion of the second outlet aqueous phase is cooled to a temperature of from 30 to 45 °C. 7. The method of any one of clauses 1 to 6, wherein the rotational speed of the first RPB and / or the second RPB is from 100 to 1500 RPM. 8. The method of clause 7, wherein the rotational speed of the first RPB and / or the second RPB is from 100 to 600 RPM. 9. The method of any one of clauses 1 to 8, wherein the solvent lean flue gas is fed through an acid wash to remove traces of solvent, and wherein the acid wash comprises reacting an acid phase with the solvent lean flue gas in a counter-current flow to remove traces of solvent present in the solvent lean flue gas. 10. The method of clause 9, wherein the temperature of the acid phase is the temperature of the solvent lean flue gas ± 5 °C. 11. The method of clause 9 or clause 10, wherein the acid wash comprises feeding the solvent lean flue gas to a third rotating bed rotating circularly, wherein an acid phase is provided through an inner radius of the third rotating bed and moves towards the outer radius of the third rotating bed. 12. The method of clause 11, wherein the solvent lean flue gas is introduced from the outer radius of the third rotating bed. 13. The method of clause 11 or clause 12, wherein the third rotating bed is a RPB or a Rotating Zig-Zag Bed (RZB). 14. The method of any one of clauses 1 to 13, wherein the weight ratio of liquid to gas in the first and / or second RPB is from 1 to 5 kg / kg. 15. The method of any one of clauses 11 to 14, wherein the weight ratio of liquid to gas of the third rotating bed is from 1 to 10 kg / kg. 16. The method of any one of clauses 1 to 15, wherein the rotational speed of the third rotating bed is from 100 to 1500 RPM. 17. The method of clause 16, wherein the rotational speed of the third rotating bed is from 100 to 600 RPM. 18. The method of any one of clauses 1 to 17, wherein the first inlet aqueous phase is thermally independent with (not in thermal communication with) the second inlet aqueous phase. 19. A method for washing a flue gas to remove solvent present in the flue gas, the method comprising the steps of: feeding a solvent rich flue gas to a first Rotary Packed Bed (RPB) rotating circularly, wherein a first inlet aqueous phase provided through an inner radius of the first RPB moves towards an outer radius of the first RPB, and wherein the first inlet aqueous phase contacts with the solvent rich flue gas in a counter-current flow to remove solvent present in the flue gas and form a solvent semi-lean flue gas and first outlet aqueous phase; feeding the solvent semi-lean flue gas to a second RPB rotating circularly, wherein a second inlet aqueous phase provided through an inner radius of the RPB moves towards an outer radius of the RPB, and wherein the second inlet aqueous phase contacts the solvent semi-lean flue gas in a counter-current flow to remove solvent present in the flue gas and form a solvent lean flue gas and second outlet aqueous phase; wherein a first portion of the second outlet aqueous phase is cooled to a temperature of from 15 to 50 °C then fed to the inner radius of the second RPB such that the second inlet aqueous phase comprises all or some of the cooled first portion of the second outlet aqueous phase; wherein a second portion of the second outlet aqueous phase is fed to the inner radius of the first RPB such that the first inlet aqueous phase comprises all or some of the second portion of the second outlet aqueous phase; and, wherein the weight ratio of liquid to gas in the first RPB is from 0.01 to 0.5 kg / kg. 20. The method of clause 19, wherein the solvent rich flue gas is introduced from the outer radius of the first RPB. 21. The method of clause 19 or clause 20, wherein the solvent semi-lean flue gas is introduced from the outer radius of the second RPB. 22. The method of any one of clauses 19 to 21, wherein the first portion of the second outlet aqueous phase is cooled to a temperature of from 25 to 40 °C. 23. The method of any one of clauses 19 to 22, wherein the weight ratio of liquid to gas in the first RPB is from 0.02 to 0.15 kg / kg. 24. The method of any one of clauses 19 to 23, wherein the rotational speed of the first RPB and / or the second RPB is from 100 to 1500 RPM. 25. The method of clause 24, wherein the rotational speed of the first RPB and / or the second RPB is from 100 to 600 RPM. 26. The method of any one of clauses 19 to 25, wherein the solvent lean flue gas is fed through an acid wash to remove traces of solvent, and wherein the acid wash comprises reacting an acid phase with the solvent lean flue gas in a counter-current flow to remove traces of solvent present in the solvent lean flue gas. 27. The method of clause 26, wherein the temperature of the acid phase is the temperature of the solvent lean flue gas ± 5 °C. 28. The method of clause 26 or clause 27, wherein the acid wash comprises feeding the solvent lean flue gas to a third rotating bed rotating circularly, wherein the acid phase is provided through an inner radius of the third rotating bed and moves towards the outer radius of the third rotating bed. 29. The method of clause 28, wherein the solvent lean flue gas is introduced from the outer radius of the third rotating bed. 30. The method of clause 28 or clause 29, wherein the third rotating bed is a RPB or a Rotating Zig-Zag Bed (RZB). 31. The method of any one of clauses 19 to 30, wherein the ratio of liquid to gas in the second RPB is from 1 to 5 kg / kg. 32. The method of any one of clauses 28 to 31, wherein the weight ratio of liquid to gas in the third rotating bed is from 1 to 10 kg / kg. 33. The method of any one of clauses 19 to 32, wherein the rotational speed of the third rotating bed is from 100 to 1500 RPM. 34. The method of clause 33, wherein the rotational speed of the third rotating bed is from 100 to 600 RPM. 35. The method of any one of clauses 19 to 34, wherein the axis about which the second RPB rotates is horizontal. 36. A method for washing a flue gas to remove solvent present in the flue gas, the method comprising the steps of: feeding a solvent rich flue gas to a first Rotary Packed Bed (RPB) rotating circularly, wherein a first inlet aqueous phase provided through an inner radius of the first RPB moves towards an outer radius of the first RPB, and wherein the first inlet aqueous phase contacts with solvent rich flue gas in a counter-current flow to remove solvent present in the flue gas and form a first solvent semi-lean flue gas and first outlet aqueous phase; feeding the first solvent semi-lean flue gas to a second Rotary Packed Bed (RPB) rotating circularly, wherein a second inlet aqueous phase provided through an inner radius of the second RPB moves towards an outer radius of the second RPB, and wherein the second inlet aqueous phase contacts with the first solvent semi-lean flue gas in a counter-current flow to remove solvent present in the flue gas and form a second solvent semi-lean flue gas and second outlet aqueous phase; feeding the second solvent semi-lean flue gas to a third RPB rotating circularly, wherein a third inlet aqueous phase provided through an inner radius of the third RPB moves towards an outer radius of the third RPB, and wherein the third inlet aqueous phase contacts with second solvent semi-lean flue gas in a counter-current flow to remove solvent present in the flue gas and form a solvent lean flue gas and third outlet aqueous phase; wherein a first portion of the third outlet aqueous phase is cooled to a temperature of from 15 to 50 °C then fed to the inner radius of the third RPB such that the third inlet aqueous phase comprises all or some of the cooled first portion of the third outlet aqueous phase; and, wherein the weight ratio of liquid to gas in the second RPB is from 0.01 to 0.5 kg / kg. 37. The method of clause 36, wherein a second portion of the third outlet aqueous phase is fed to the inner radius of the second RPB such that the second inlet aqueous phase comprises all or some of the second portion of the third outlet aqueous phase. 38. The method of clause 36 or clause 37, wherein the solvent rich flue gas is introduced from the outer radius of the first RPB. 39. The method of any one of clauses 36 to 38, wherein the first solvent semilean flue gas is introduced from the outer radius of the second RPB. 40. The method of any one of clauses 36 to 39, wherein the second solvent semilean flue gas is introduced from the outer radius of the third RPB. 41. The method of any one of clauses 36 to 40, wherein the first portion of the third outlet aqueous phase is cooled to a temperature of from 25 to 40 °C. 42. The method of any one of clauses 36 to 41, wherein the weight ratio of liquid to gas in the second RPB is from 0.02 to 0.15 kg / kg. 43. The method of any one of clauses 36 to 42, wherein a first portion of the first outlet aqueous phase is cooled to a temperature of from 15 to 50 °C then fed to the inner radius of the first RPB such that the first inlet aqueous phase comprises all or some of the cooled first portion of the first outlet aqueous phase. 44. The method of clause 43, wherein the first portion of the first outlet aqueous phase is cooled to a temperature of from 30 to 45 °C. 45. The method of any one of clauses 36 to 44, wherein a second portion of the first outlet aqueous phase is fed to the inner radius of the second RPB such that the second inlet aqueous phase comprises all or some of the cooled second portion of the first outlet aqueous phase. 46. The method of any one of clauses 36 to 45, wherein the rotational speed of any one or more of the first RPB, the second RPB, and / or the third RPB is from 100 to 1500 RPM. 47. The method of clause 46, wherein the rotational speed of any one or more of the first RPB, the second RPB, and / or the third RPB is from 100 to 600 RPM. 48. The method of any one of clauses 36 to 47, wherein the solvent lean flue gas is fed through an acid wash to remove traces of solvent, and wherein the acid wash comprises reacting an acid phase with the solvent lean flue gas in a counter-current flow to remove traces of solvent present in the solvent lean flue gas and form an solvent ultra-lean flue gas and a used acid phase. 49. The method of clause 48, wherein the temperature of the acid phase is the temperature of the solvent lean flue gas ± 5 °C. 50. The method of clause 48 or clause 49, wherein the acid wash comprises feeding the solvent lean flue gas to a fourth rotating bed rotating circularly, wherein the acid phase is provided through an inner radius of the fourth rotating bed and moves towards the outer radius of the fourth rotating bed. 51. The method of clause 50, wherein the solvent lean flue gas is introduced from the outer radius of the fourth rotating bed. 52. The method of any one of clauses 50 to 51, wherein the fourth rotating bed is a RPB or a Rotating Zig-Zag Bed (RZB). 53. The method of any one of clauses 36 to 52, wherein the weight ratio of liquid to gas in the first RPB and / or third RPB is from 1 to 5 kg / kg. 54. The method of any one of clauses 50 to 53, the weight ratio of liquid to gas in the fourth rotating bed is from 1 to 10 kg / kg. 55. The method of any one of clauses 50 to 54, wherein the rotational speed of the fourth rotating bed is from 100 to 1500 RPM. 56. The method of clause 55, wherein the rotational speed of the fourth rotating bed is from 100 to 600 RPM. 57. The method of any one of clauses 36 to 56, wherein the axis about which the second RPB rotates is horizontal. 58. A method for washing a flue gas to remove solvent present in the flue gas, the method comprising the steps of: feeding a solvent rich flue gas to a first Rotary Packed Bed (RPB) rotating circularly, wherein a first inlet aqueous phase provided through an inner radius of the first RPB moves towards an outer radius of the first RPB, and wherein the first inlet aqueous phase contacts with solvent rich flue gas in a counter-current flow to remove solvent present in the flue gas and form a first solvent semi-lean flue gas and first outlet aqueous phase; feeding the first solvent semi-lean flue gas to a second RPB rotating circularly, wherein a second inlet aqueous phase provided through an inner radius of the second RPB moves towards an outer radius of the second RPB, and wherein the second inlet aqueous phase contacts with the solvent semi-lean flue gas in a counter-current flow to remove solvent present in the flue gas and form a second solvent semi-lean flue gas and second outlet aqueous phase; wherein the weight ratio of liquid to gas in the first RPB is from 0.01 to 0.5 kg / kg; feeding the second solvent semi-lean flue gas at to a third RPB rotating circularly, wherein a third inlet aqueous phase provided through an inner radius of the third RPB moves towards an outer radius of the third RPB, and wherein the third inlet aqueous phase contacts with the second solvent semi-lean flue gas in a countercurrent flow to remove solvent present in the flue gas and form a solvent lean flue gas and third outlet aqueous phase; wherein a first portion of the second outlet aqueous phase is cooled to a temperature of from 15 to 50 °C then fed to the inner radius of the second RPB such that the second inlet aqueous phase comprises all or some of the cooled first portion of the second outlet aqueous phase. 59. The method of clause 58, wherein a second portion of the second outlet aqueous phase is fed to the inner radius of the first RPB such that the first inlet aqueous phase comprises all or some of the first portion of the second outlet aqueous phase. 60. The method of clause 58 or clause 59, wherein the solvent rich flue gas is introduced from the outer radius of the first RPB. 61. The method of any one of clauses 58 to 60, wherein the first solvent semilean flue gas is introduced from the outer radius of the second RPB. 62. The method of any one of clauses 58 to 61, wherein the second solvent semilean flue gas is introduced from the outer radius of the third RPB. 63. The method of any one of clauses 58 to 62, wherein the first portion of the second outlet aqueous phase is cooled to a temperature of from 25 to 40 °C. 64. The method of any one of clauses 58 to 63, wherein the weight ratio of liquid to gas in the first RPB is from 0.02 to 0.15 kg / kg. 65. The method of any one of clauses 58 to 64, wherein a first portion of the third outlet aqueous phase is cooled to a temperature of from 15 to 50 °C then fed to the inner radius of the third RPB such that the third inlet aqueous phase comprises all or some of the cooled first portion of the third outlet aqueous phase. 66. The method of clause 65, wherein first portion of the third outlet aqueous phase is cooled to a temperature of from 30 to 45 °C. 67. The method of any one of clauses 58 to 66, wherein the rotational speed of any one or more of the first RPB, the second RPB, and / or the third RPB is from 100 to 1500 RPM. 68. The method of clause 67, wherein the rotational speed of any one or more of the first RPB, the second RPB, and / or the third RPB is from 100 to 600 RPM. 69. The method of any one of clauses 58 to 68, wherein the solvent lean flue gas is fed through an acid wash to remove traces of solvent, and wherein the acid wash comprises reacting an acid phase with the solvent lean flue gas in a counter-current flow to remove traces of solvent present in the solvent lean flue gas. 70. The method of clause 69, wherein the temperature of the acid is the temperature of the solvent lean flue gas ± 5 °C. 71. The method of clause 69 or clause 70, wherein the acid wash comprises feeding the solvent lean flue gas to a fourth rotating bed rotating circularly, wherein an acid phase is provided through an inner radius of the fourth rotating bed and moves towards the outer radius of the fourth rotating bed. 72. The method of any one of clauses 69 to 71, wherein the solvent lean flue gas is introduced from the outer radius of the fourth rotating bed. 73. The method of any one of clauses 69 to 72, wherein the fourth rotating bed is a RPB or a Rotating Zig-Zag Bed (RZB). 74. The method of any one of clauses 58 to 73, wherein the weight ratio of liquid to gas in the second and / or third RPB is from 1 to 5 kg / kg. 75. The method of any one of clauses 71 to 74, the ratio of liquid to gas in the fourth rotating bed is from 1 to 10 kg / kg. 76. The method of any one of clauses 71 to 75, wherein the rotational speed of the fourth rotating bed is from 100 to 1500 RPM. 77. The method of clause 76, wherein the rotational speed of any one or more of the fourth rotating bed is from 100 to 600 RPM. 78. The method of any one of clauses 58 to 77, wherein the axis about which the first RPB rotates is horizontal. The present invention also relates to systems for carrying out the method of any one of clauses 1 to 78. In some embodiments, the system of the present invention is as set out in clauses 1 A, 2A, 3A or 4A: 1 A. A system for washing a flue gas to remove solvent present in the flue gas, the system comprising: a first Rotary Packed Bed (RPB) configured to rotate circularly, wherein when the first RPB rotates circularly a first inlet aqueous phase provided through an inner radius of the first RPB moves towards an outer radius of the RPB, and wherein the first inlet aqueous phase contacts solvent rich flue gas in a counter-current flow to remove solvent present in the solvent rich flue gas and form a solvent semi-lean flue gas and first outlet aqueous phase; a second RPB configured to rotate circularly, wherein when the second RPB rotates circularly a second inlet aqueous phase provided through an inner radius of the second RPB moves towards an outer radius of the second RPB, and wherein the second inlet aqueous phase contacts the solvent semi-lean flue gas in a countercurrent flow to remove solvent present in the solvent semi-lean flue gas and form a solvent lean flue gas and second outlet aqueous phase; and, a cooler, wherein the cooler is configured to cool a first portion of the first outlet aqueous phase to a temperature of from 15 to 50 °C, and wherein the cooled first portion is fed to the inner radius of the first RPB such that the first inlet aqueous phase comprises all or some of the cooled first portion; optionally, further comprising the features of any one of clauses 2 to 18. 2A. A system for washing a flue gas to remove solvent present in the flue gas, the system comprising: a first Rotary Packed Bed (RPB) configured to rotate circularly, wherein when the first RPB rotates circularly a first inlet aqueous phase provided through an inner radius of the first RPB moves towards an outer radius of the first RPB, wherein the first inlet aqueous phase contacts solvent rich flue gas in a counter-current flow to remove solvent present in the solvent rich flue gas and form a solvent semi-lean flue gas and first outlet aqueous phase, and wherein the weight ratio of liquid to gas in the first RPB is from 0.01 to 0.5 kg / kg; a second RPB configured to rotate circularly, wherein when the second RPB rotates circularly a second inlet aqueous phase provided through an inner radius of the second RPB moves towards an outer radius of the second RPB, and wherein the second inlet aqueous phase contacts the solvent semi-lean flue gas in a countercurrent flow to remove solvent present in the solvent semi-lean flue gas and form a solvent lean flue gas and second outlet aqueous phase; a cooler, wherein the cooler is configured to cool a first portion of the second outlet aqueous phase to a temperature of from 15 to 50 °C, and wherein the cooled first portion is fed to the inner radius of the second RPB such that the second inlet aqueous phase comprises all or some of the cooled first portion; and, wherein a second portion of the second outlet aqueous phase is fed to the inner radius of the first RPB such that the first inlet aqueous phase comprises all or some of the second portion; optionally, further comprising the features of any one of clauses 20 to 35. 3A. A system for washing a flue gas to remove solvent present in the flue gas, the system comprising: a first Rotary Packed Bed (RPB) configured to rotate circularly, wherein when the first RPB rotates circularly a first inlet aqueous phase provided through an inner radius of the first RPB moves towards an outer radius of the RPB, and wherein the first inlet aqueous phase contacts solvent rich flue gas in a counter-current flow to remove solvent present in the solvent rich flue gas and form a solvent semi-lean flue gas and first outlet aqueous phase; a second RPB configured to rotate circularly, wherein when the second RPB rotates circularly a second inlet aqueous phase provided through an inner radius of the second RPB moves towards an outer radius of the second RPB, and wherein the second inlet aqueous phase contacts the solvent semi-lean flue gas in a countercurrent flow to remove solvent present in the solvent semi-lean flue gas and form a solvent lean flue gas and second outlet aqueous phase and wherein the weight ratio of liquid to gas in the second RPB is from 0.01 to 0.5 kg / kg; a third Rotary Packed Bed (RPB) configured to rotate circularly, wherein when the third RPB rotates circularly a third inlet aqueous phase provided through an inner radius of the third RPB moves towards an outer radius of the RPB, and wherein the third inlet aqueous phase contacts solvent semi-lean flue gas in a counter-current flow to remove solvent present in the solvent semi-lean flue gas and form a solvent lean flue gas and third outlet aqueous phase; and, a cooler, wherein the cooler is configured to cool a first portion of the third outlet aqueous phase to a temperature of from 15 to 50 °C, and wherein the cooled first portion is fed to the inner radius of the third RPB such that the third inlet aqueous phase comprises some or all of the cooled first portion; optionally, further comprising the features of any one of clauses 37 to 57. 4A. A system for washing a flue gas to remove solvent present in the flue gas, the system comprising: a first Rotary Packed Bed (RPB) configured to rotate circularly, wherein when the first RPB rotates circularly a first inlet aqueous phase provided through an inner radius of the first RPB moves towards an outer radius of the first RPB, wherein the first inlet aqueous phase contacts solvent rich flue gas in a counter-current flow to remove solvent present in the solvent rich flue gas and form a solvent semi-lean flue gas and first outlet aqueous phase, and wherein the weight ratio of liquid to gas in the first RPB is from 0.01 to 0.5 kg / kg; a second RPB configured to rotate circularly, wherein when the second RPB rotates circularly a second inlet aqueous phase provided through an inner radius of the second RPB moves towards an outer radius of the second RPB, and wherein the second inlet aqueous phase contacts the solvent semi-lean flue gas in a countercurrent flow to remove solvent present in the solvent semi-lean flue gas and form a solvent lean flue gas and second outlet aqueous phase; a cooler, wherein the cooler is configured to cool a first portion of the second outlet aqueous phase to a temperature of from 15 to 50 °C, and wherein the cooled first portion is fed to the inner radius of the second RPB such that the second inlet aqueous phase comprises all or some of the cooled first portion; and, a third Rotary Packed Bed (RPB) configured to rotate circularly, wherein when the third RPB rotates circularly a third inlet aqueous phase provided through an inner radius of the third RPB moves towards an outer radius of the RPB, and wherein the third inlet aqueous phase contacts solvent semi-lean flue gas in a counter-current flow to remove solvent present in the solvent semi-lean flue gas and form a solvent lean flue gas and third outlet aqueous phase; optionally, further comprising the features of any one of clauses 59 to 78. DETAILED DESCRIPTION Embodiments of the invention are described below with reference to the accompanying drawings. The accompanying drawings illustrate various embodiments of systems, methods, and embodiments of various other aspects of the disclosure. Any person with ordinary skills in the art will appreciate that the illustrated element boundaries (e.g., boxes, groups of boxes, or other shapes) in the figures represent one example of the boundaries. It may be that in some examples one element may be designed as multiple elements or that multiple elements may be designed as one element. In some examples, an element shown as an internal component of one element may be implemented as an external component in another and vice versa. Furthermore, elements may not be drawn to scale. Nonlimiting and non-exhaustive descriptions are described with reference to the following drawings. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating principles. Figure 1 is a block diagram 100 of a conventional method and system for capturing CO2 from flue gases, where a static packed column is used to remove traces of solvent from a flue gas. Figure 2 is a block diagram 200 of a system used to remove traces of solvent from a flue gas according to the present invention, using two RPBs in series. Figure 3 is a block diagram 300 of a system used to remove traces of solvent from a flue gas according to the present invention, using two RPBs in series and where one RPB uses a low weight ratio of liquid to gas. Figure 4 is a block diagram 400 of a system used to remove traces of solvent from a flue gas according to the present invention, using three RPBs in series and where one RPB uses a low weight ratio of liquid to gas. Figure 5 is a graph showing the relative scrubbing rate and volumetric mass transfer coefficient for an RPB and a static packed column when used to remove solvent from a flue gas. Figure 6 is a graph showing the modelled relative solvent concentration in the outlet flue gases at each stage (each RPB) of method and system 200 and at each stage of an equivalent static packed column design. Figure 7 is a graph showing the modelled relative solvent concentration in the outlet flue gases at each stage (each RPB) of method and system 300 and at each stage of an equivalent static packed column design. Figure 8 is a graph showing the modelled relative solvent concentration in the outlet flue gases at each stage (each RPB) of method and system 400 and at each stage of an equivalent static packed column design. Embodiments of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings in which like numerals represent like elements throughout the several figures, and in which example embodiments are shown. Embodiments of the claims may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. The words "comprising," "having," "containing," and "including," and other forms thereof, are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. It must also be noted that as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Although any systems and methods similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present disclosure, the preferred systems and methods are now described. Some of the terms used to describe the present invention are set out below: “Flue gas” is a gas exiting to the atmosphere via a pipe or channel that acts as an exhaust from a boiler, furnace or a similar environment, for example a flue gas may be the emissions from power plants and other industrial activities that bum hydrocarbon fuel such as coal, gas and oil-fired power boilers, combined cycle power plants, coal gasification, hydrogen plants, biogas plants, waste to energy plants, steel plants, refineries, cement kilns, blast furnaces, or any other plant which produces a flue gas. A carbon dioxide rich flue gas is a flue gas that comprises carbon dioxide from 2.5 volume % to 51 volume %. “Solvent rich flue gas” refers to a gas comprising solvent. For example, the “solvent rich flue gas” can have a concentration of solvent of from greater than 100 ppmv to less than 1000 ppmv. “Solvent semi-lean flue gas” refers to a gas with a lower concentration of solvent than the “solvent rich flue gas” (on a volume basis). For example, at the steady state the concentration of solvent of the semi-lean flue gas may be from 50 ppmv to 100 ppmv. “Solvent lean flue gas” refers to a gas with a lower concentration of solvent than the “solvent semi-lean flue gas” (on a volume basis). For example, at the steady state the concentration of solvent of the solvent lean flue gas may be from 1 ppmv to 10 ppmv. “Solvent ultra-lean flue gas” refers to a gas with a lower concentration of solvent than the “solvent lean flue gas” (on a volume basis). For example, at the steady state the concentration of solvent of the solvent lean flue gas may be lower than 1 ppbv. “Rotary Packed Bed” (RPB) refers to an absorber or a regenerator where the packing is housed in a rotatable disk (rather than in a static bed, as in a static column), which can be rotated at high speed to generate a high gravity centrifugal force within the RPB. A “Rotating Zig-Zag Bed” (RZB) is the same as an RPB, except that the housing contains baffles instead of packing. An “inlet aqueous phase” refers to a fluid comprising water entering a method or system according to the present disclosure, at an inlet. The “inlet aqueous phase” can comprise solvent. An “outlet aqueous phase” refers to a fluid comprising water and an increased amount of solvent relative to the respective “inlet aqueous phase” on a total mass basis. “Acid phase” refers to any fluid having a pH of less than 7. The pH may be from 2 to 6.5. The acid phase may be an organic acid. Examples of organic acid include oxalic acid, formic acid, or acetic acid. The acid phase may be an inorganic acid. Examples of inorganic acid include sulphuric acid, nitric acid, or phosphoric acid. “Solvent” refers to an absorbent. The solvent may be liquid. The solvent may be an intensified solvent. “Intensified solvent” refers to a solvent that can achieve a high CO2 loading (optionally >3.0 mol / L) and forms a greater proportion of bicarbonate salts than carbamate salts. Examples of intensified solvents are included in US 2017 / 0274317 A1, the disclosure of which is incorporated herein by reference. An intensified solvent, in some embodiments, comprises: an alkanolamine, a reactive amine and a carbonate buffer. Optionally, the solvent is CDRMax as sold by Carbon Clean Solutions Limited. CDRMax, as sold by Carbon Clean Solutions Limited, has the following formulation: from 15 to 25 weight % 2-amino-2-methyl propanol (CAS number 124-68-5); from 15 to 25 weight % 1-(2-ethylamino)piperazine (CAS number 140-31-8); from 1 to 3 weight % 2-methylamino-2-methyl propanol (CAS number 27646-80-6); from 0.1 to 1 weight % potassium carbonate (584-529-3); and, the balance being deionised water (CAS number 7732-18-5). “Counter-current flow” refers to a fluid moving in an opposite direction to another fluid. The fluids can be the same fluids or different fluids. The term “fluid” includes “vapours”. EXAMPLES The following are non-limiting examples that discuss, with reference to tables and figures, the advantages of the present invention. The examples set forth herein are merely examples among other possible examples. System 200: Removal of solvent from a flue gas by using two RPBs in series According to a first aspect of the present disclosure, there is provided a system and method for removing solvent from a flue gas. In particular, the method and system uses two RPBs in series to remove solvent from a flue gas. Figure 2 illustrates a block diagram of system 200 according to a first aspect of the present invention. In Figure 2, a solvent rich flue gas 201 enters system 200 at a temperature of from 45 to 70 °C and a pressure of from 90 to 110 kPa. The solvent rich flue gas 200 is fed through an outer radius of a first RPB 202. A first inlet aqueous phase 207 is fed through an inner radius of the first RPB 202. The temperature of the inlet aqueous phase 207 is equal to or lower than the temperature of the solvent rich flue gas 201. In some embodiments, the temperature of the inlet aqueous phase 207 is from 15 to 50 °C. In some embodiments, the first RPB 202 rotates at a rotational speed of from 100 to 1500 RPM. In some embodiments, the first RPB 202 rotates at a rotational speed of 100 to 600 RPM. The weight ratio of liquid to gas in the first RPB 202 is from 1 to 5 kg / kg. As the first RPB 202 rotates circularly, the first inlet aqueous phase 207 flows towards the outer radius of the first RPB 202 under a centrifugal force. The first inlet aqueous phase 207 contacts the solvent rich flue gas 201 in a countercurrent flow, transferring solvent from the solvent rich flue gas 201 to the to the first inlet aqueous phase 207. In this way, the circular rotation of the first RPB 202 results in a solvent semi-lean flue gas 211 and first outlet aqueous phase 203. Contact of the first inlet aqueous phase 207 with the solvent rich flue gas 201 also cools the solvent rich flue gas 201 to a desired temperature of from 30 to 45 °C, condensing water and / or solvent. The temperature of the first outlet aqueous phase 203 as it leaves the first RPB 202 is therefore higher than the temperature of the first inlet aqueous phase 207 as it enters the first RPB 202 because heat is transferred to the first aqueous phase 207 as it contacts the solvent rich flue gas 201. The first outlet aqueous phase 203 passes to first sump tank 204. A portion of the first outlet aqueous phase 203 is diverted via valve 204b to first cooler 206 where, if desired, it is cooled to form a cooled first portion 207a. All or some of the cooled first portion 207a may be fed back to inner radius of first RPB 202 such that the first inlet aqueous phase 207 can comprise the cooled first portion 207a. In this way, first cooler 206 makes it possible to maintain a desired temperature of the first inlet aqueous phase 207. In some embodiments, the temperature of the cooled first portion 207a is from 15 to 50 °C. In some embodiments, the temperature of the cooled first portion 207a is from 25 to 40 °C. Advantageously, a temperature of from 25 to 40 °C leads to a lower cooling duty, aiding process economics. In order to maintain the volume of liquid in the sump tank, level control 204a of sump tank 204 actuates valve 204b so that the flow of a second portion 205 of first outlet aqueous phase 203 is increased or decreased as necessary in the direction of the solvent loop of the main CO2 capture process (not shown). The solvent semi-lean flue gas 211 is fed through an outer radius of a second RPB 212. A second inlet aqueous phase 217 is fed through an inner radius of the second RPB 212. The temperature of the second inlet aqueous phase 217 is equal to or lower than the temperature of the solvent semi-lean flue gas 211. In some embodiments, the temperature of the second inlet aqueous phase 217 is from 15 to 50 °C. In some embodiments, the rotational speed of the second RPB 212 will be from 100 to 1500 RPM. In some embodiments, the rotational speed of second RPB 212 will be from 100 to 600 RPM. The weight ratio of liquid to gas in the second RPB 212 is from 1 to 5 kg / kg. As the second RPB 212 rotates circularly, the second inlet aqueous phase 217 flows towards the outer radius of the second RPB 212 under a centrifugal force. The second inlet aqueous phase 217 contacts the solvent semi-rich flue gas 211 in a counter-current flow, transferring solvent from the solvent rich flue gas 211 to the to the second inlet aqueous phase 217. In this way, the circular rotation of the second RPB 212 results in a solvent lean flue gas 221 and second outlet aqueous phase 213. In some embodiments, there is no, or minimal (e.g. 1 °C), cooling of the solvent semilean flue gas 211 by the second inlet aqueous phase 217. This means that the solvent semi-lean flue gas 211 and the solvent lean flue gas 221 are approximately isothermal. In other embodiments, contact of the second inlet aqueous phase 217 with the solvent semi-lean flue gas 211 also cools the solvent semi-lean flue gas 211 to a desired temperature of from 30 to 45 °C, condensing water and / or solvent. The temperature of the second outlet aqueous phase 213 as it leaves the second RPB 212 is therefore higher than the temperature of the second inlet aqueous phase 217 as it enters the second RPB 212 because heat is transferred to the second inlet aqueous phase 217 as it contacts the solvent semi-lean flue gas 211. The second outlet aqueous phase 213 passes to second sump tank 214. A portion of second outlet aqueous phase 213 is diverted via valve 214b to second cooler 216 where, if desired, it can be cooled to form a cooled first portion 217a. All or some of the first portion 217a is fed back to the inner radius of the second RPB 212 such that second inlet aqueous phase 217 can comprise the cooled first portion 217a. In this way, second cooler 216 makes it is possible to maintain a desired temperature of the second inlet aqueous phase 217. In some embodiments, the temperature of the cooled first portion 217a is from 15 to 50 °C. In some embodiments, the temperature of the cooled first portion 217a is from 30 to 45 °C. Advantageously, a temperature of from 30 to 45 °C leads to a lower cooling duty, aiding process economics. In order to maintain the volume of liquid in the sump tank, level control 214a of sump tank 214 actuates valve 214b so that the flow of a second portion 215 of first outlet aqueous phase 213 is increased or decreased as necessary in the direction of the solvent loop of the main CO2 capture process (not shown). In some embodiments, the first inlet aqueous phase 207 is thermally independent with (not in thermal communication with) the second inlet aqueous phase 217. The temperature of the aqueous phase is a factor in the condensation of water from the flue gas. Advantageously, thermal independence allows for control over the location in which (i.e. first RPB or second RPB) condensation from the flue gases happens. Advantageously, the use of RPBs results in an improved rate of transfer of solvent from the flue gases to the aqueous phases compared to if a static packed column was used. Near complete (or at least greater than 99%) recovery of solvent from the flue gas is possible using the disclosed system. The present invention therefore reduces the need to replace solvent lost by emissions in the main CO2 capture process, and reduces the CO2 capture cost ($ / ton). Advantageously, the RPBs can themselves act as demisters. In this way, the present invention significantly reduces aerosolised solvent emissions. The use of RPBs therefore negates the need for conventional demisters in addition to the unit operation and thereby negates the need to apply additional pressure to the inlet flue gas. Consequently, the present invention is more efficient than the conventional process employing static packed columns, and reduces the CO2 capture cost ($ / ton). Advantageously, the present system can maintain its maximum rate of solvent removal from a flue gas for a longer duration compared to a traditional system including two static packed columns (or a system using a single RPB). This is attributed to the effect of solvent concentration in the aqueous phase. An aqueous phase having a low concentration of solvent is more effective at removing solvent from a gas than the same aqueous phase having a high concentration of solvent. In the present system, the concentration of solvent in the solvent semi-rich flue gas 211 entering the second RPB 212 will be lower than that leaving the first static packed bed column of a system including two static packed bed columns. A lower concentration of solvent in the solvent semi-rich flue gas 211 entering the second RPB 212 means that the concentration of the solvent in the second inlet aqueous phase 217 will increase more slowly than in the traditional system. By maintaining relatively lower concentrations of solvent in the second inlet aqueous phase 217 for a relatively longer duration, the maximum efficiency of the second RPB 212 and system 200 as a whole is maintained for a longer duration. In some embodiments, solvent lean flue gas 221 is washed with an acid phase (not shown). The temperature of the acid phase is controlled so that the acid phase wash process is approximately isothermal (within ± 5 °C). Advantageously, washing with acid phase results in a solvent ultra-lean flue gas. In some embodiments, the washing of the solvent lean flue gas 221 with a temperature-controlled acid phase occurs in a third RPB 222a or a Rotating Zig-Zag Bed (RZB) 231b (not shown). The operation of the third RPB 222a or the RZB 222b occurs in a manner consistent with the operation of the first RPB 202 or second RPB 212, except that aqueous phase is replaced with an acid phase (at a temperature as described above) and in that the weight ratio of liquid to gas is from 1 to 10 kg / kg. Advantageously, the use of an RPB or RZB results in an improved reaction of solvent with acid phase compared to when a static packed column is used. System 300: Removal of solvent from a flue gas by using two RPBs in series where one RPB uses a low weight ratio of liguid to gas According to a second aspect of the present disclosure, there is provided a system and method for removing solvent from a flue gas. In particular, the method and system uses two RPBs in series to remove solvent from a flue gas. Advantageously, one RPB uses a low weight ratio of liquid to gas. Figure 3 illustrates a block diagram of system 300 according to a second aspect of the present invention. In Figure 3, a solvent rich flue gas 301 enters system 300 at a temperature of from 45 to 70 °C and a pressure of from 90 to 110 kPa. The solvent rich flue gas 301 is fed through an outer radius of a first RPB 302. A first inlet aqueous phase 315 is fed through an inner radius of the first RPB 302. The temperature of the inlet aqueous phase 315 is equal to or lower than the temperature of the solvent rich flue gas 301. In some embodiments, the temperature of the inlet aqueous phase 315 is from 15 to 50 °C. In some embodiments, the first RPB 302 rotates at a rotational speed of from 100 to 1500 RPM. In some embodiments, the first RPB rotates at a rotational speed of from 100 to 600 RPM. As the first RPB 302 rotates circularly, the first inlet aqueous phase 315 flows towards the outer radius of the first RPB 302 under a centrifugal force. The first inlet aqueous phase 315 contacts the solvent rich flue gas 301 in a countercurrent flow, transferring solvent from the solvent rich flue gas 301 to the first inlet aqueous phase 315. In this way, the circular rotation of the first RPB 302 results in a solvent semi-lean flue gas 311 and first outlet aqueous phase 303. In some embodiments, there is no, or minimal (e.g. 1 °C), cooling of the solvent rich flue gas 301 by the first inlet aqueous phase 315. Put differently, the solvent rich flue gas 301 and the solvent semi-lean flue gas 311 are approximately isothermal. The degree of cooling here is not under direct control and is instead dependent on the other process conditions (such as the temperature of the solvent lean flue gas 321, the temperature of solvent rich flue gas 301 and the weight ratio of liquid to gas in the second RPB 312). In some embodiments, the weight ratio of liquid to gas in the first RPB 302 is from 0.01 to 0.5 kg / kg. In some embodiments, the weight ratio of liquid to gas in the first RPB 302 is from 0.02 to 0.15 kg / kg. However, the exact operating liquid to gas ratio in the first RPB 302 is dependent on the several factors. For example, one factor in the choice of liquid to gas ratio in the first RPB 302 is the temperature of the solvent semi-lean flue gas 311 as it enters second RPB 312. This is because the amount of water that the solvent semi-lean flue gas 311 can hold increases with an increase in its temperature (assuming that the solvent semi-lean flue gas 311 always has a relative humidity of over 85%). Therefore, the amount of liquid water condensing into sump tank 314 when the solvent semi-lean flue gas 311 undergoes cooling in second RPB 312 increases with an increase in temperature of the solvent semi-lean gas flue 311. In practise, this means that the weight ratio of liquid to gas in the first RPB 302 will be higher where the temperature of the solvent semilean flue gas 311 is higher (but within the 0.01 to 0.5 kg / kg range). For similar reasons, other factors in the liquid to gas ratio in the first RPB 302 include the temperature of the second inlet aqueous phase 317 and the initial water content of the solvent rich flue gas 301. Advantageously, a weight ratio of liquid to gas ratio of from 0.01 to 0.5 kg / kg results in a more efficient transfer of solvent components from the solvent rich flue gas 301 to the first inlet aqueous phase 315 during operation of the first RPB 302. Further, such low weight ratios are not generally feasible when a traditional static packed bed column is used in place of an RPB. This is because at such weight ratios the distribution of liquid across the packing is poor, causing poor levels of liquid-gas contact and poor solvent removal from the gas. In some embodiments, the major axis of the first RPB 302 is horizontal. In other words, the axis about which the first RPB 302 rotates is horizontal. This means that the force of gravity acts on the liquid in a direction parallel to the plane in which the liquid rotates. The centrifugal force on the liquid in the first RPB 302 acts evenly in all axial directions. Advantageously, as a result the liquid has an improved (more even) distribution over the packing in the first RPB 302 compared to RPBs having other orientations. The first outlet aqueous phase 303 is fed to a solvent loop of the main CO2 capture process (not shown). The solvent semi-lean flue gas 311 is fed through an outer radius of a second RPB 312. A second inlet aqueous phase 317 is fed through an inner radius of the second RPB 312. The temperature of the second inlet aqueous phase 317 is equal to or lower than the temperature of the solvent semi-lean flue gas 311. In some embodiments, the temperature of the second inlet aqueous phase 317 is from 15 to 50 °C. In some embodiments, the second RPB 312 rotates at a rotational speed of from 100 to 1500 RPM. In some embodiments, the second RPB 312 rotates at a rotational speed of from 100 to 600 RPM. The weight ratio of liquid to gas in the second RPB 312 is from 1 to 5 kg / kg. As the second RPB 312 rotates circularly, the second aqueous phase 317 flows towards the outer radius of the second RPB 312 under a centrifugal force. The second inlet aqueous phase 317 contacts the solvent semi-lean flue gas 311 in a counter-current flow, transferring solvent from the solvent semi-lean flue gas 311 to the second inlet aqueous phase 317. In this way, the circular rotation of the second RPB 312 results in a solvent lean flue gas 321 and second outlet aqueous phase 313. Contact of the second inlet aqueous phase 317 with the solvent semi-lean flue gas 311 cools the solvent semi-lean flue gas 311 to a desired temperature of from 30 to 45 °C, condensing water and / or solvent. The temperature of the second outlet aqueous phase 313 as it leaves the second RPB 312 is therefore higher than the temperature of the second inlet aqueous phase 317 as it enters the second RPB 312 because heat is transferred to the second inlet aqueous phase 317 as it contacts the solvent semi-lean flue gas 311. The second outlet aqueous phase 313 passes to sump tank 314. A portion of second outlet aqueous phase 313 is then diverted via valve 314b to second cooler 316 where it is cooled to form a cooled first portion 317a of second outlet aqueous phase 313. All or some of the cooled first portion 317a may be fed back to the inner radius of the second RPB 312 such that second inlet aqueous phase 317 can comprise cooled first portion 317a. In this way, second cooler 316 makes it is possible to maintain a desired temperature of the second inlet aqueous phase 317. In some embodiments, the temperature of the cooled first portion 317a is from 15 to 50 °C. In some embodiments, the temperature of the cooled first portion 317a is from 25 to 40 °C. Advantageously, a temperature of from 25 to 40 °C leads to a lower cooling duty, aiding process economics. Level control 314a of sump tank 314 actuates valve 314b so that a second portion 315 of second outlet aqueous phase 313 is diverted to the inner radius of the first RPB 302. In some embodiments, the flow rate of the second portion 315 sent to the inner radius of the first RPB 302 is equal to the flow rate of water condensed in the second RPB 312 during operation. In some embodiments, the major axis of the second RPB 312 is horizontal. In other words, the axis about which the second RPB 312 rotates is horizontal. This means that the force of gravity acts on the liquid in a direction parallel to the plane in which the liquid rotates. The centrifugal force on the liquid in the second RPB 312 acts evenly in all axial directions. Advantageously, as a result the liquid has an improved (more even) distribution over the packing in the second RPB 312 compared to RPBs having other orientations. Advantageously, the use of RPBs results in an improved rate of transfer of solvent from the flue gas to the aqueous phase compared to if a static packed column was used. Near complete (or at least greater than 99%) recovery of solvent from the flue gas is possible using the disclosed system. The present invention therefore reduces the need to replace solvent lost by emissions in the main CO2 capture process, and reduces the CO2 capture cost ($ / ton). Advantageously, the RPBs can themselves act as demisters. In this way, the present invention significantly reduces aerosolised solvent emissions. The use of RPBs therefore negates the need for conventional demisters in addition to the unit operation and thereby negates the need to apply additional pressure to the inlet flue gas. Consequently, the present invention is more efficient than the conventional process employing static packed columns, and reduces the CO2 capture cost ($ / ton). Advantageously, the present system can maintain its maximum rate of solvent removal from a flue gas for a longer duration compared to a traditional system including two static packed columns (or a system using a single RPB). This is attributed to the effect of solvent concentration in the aqueous phase. An aqueous phase having a low concentration of solvent is more effective at removing solvent from a gas than the same aqueous phase having a high concentration of solvent. In the present system, the concentration of solvent in the solvent semi-rich flue gas 311 entering the second RPB 312 will be lower than that leaving the first static packed bed column of a system including two static packed bed columns. A lower concentration of solvent in the solvent semi-rich flue gas 311 entering the second RPB 312 means that the concentration of the solvent in the second inlet aqueous phase 317 will increase more slowly than in the traditional system. By maintaining relatively lower concentrations of solvent in the second inlet aqueous phase 317 for a relatively longer duration, the maximum efficiency of the second RPB 312 and system 300 as a whole is maintained for a longer duration. Advantageously, the present system has a smaller size footprint than other systems for removing solvent from a flue gas since the present system requires fewer components. In this way, the present system can be employed in a wider variety of contexts than the other systems. In addition, by using fewer components the installation and operational costs are reduced. In some embodiments, solvent-lean flue gas 321 is washed with an acid phase (not shown). The temperature of the acid phase is controlled so that the acid phase wash process is approximately isothermal (within ± 5 °C). Advantageously, washing with acid phase results in a solvent ultra-lean flue gas. In some embodiments, the washing of the solvent lean flue gas 321 with a temperature-controlled acid phase occurs in a third RPB 322a or a Rotating Zig-Zag Bed (RZB) 322b (not shown). The operation of the third RPB 322a or the RZB 322b occurs in a manner consistent with the operation of the second RPB 312, except that aqueous phase is replaced with an acid phase (at a temperature as described above) and in that the weight ratio of liquid to gas is from 1 to 10 kg / kg. Advantageously, the use of an RPB or RZB results in an improved rate of transfer of solvent from the flue gases to the aqueous phases over the use of a static column or a static packed bed. System 400: Removal of solvent from a flue gas by using three RPBs where one RPB uses a low weight ratio of liguid to gas According to a third aspect of the present disclosure, there is provided a system and method for removing solvent from a flue gas. In particular, the method and system uses three RPBs to remove solvent from a flue gas. Advantageously, one RPB uses a low weight ratio of liquid to gas. Figure 4 illustrates a block diagram of system 400 according to a third aspect of the present invention. In Figure 4, a solvent rich flue gas 401 enters system 400 at a temperature of from 45 to 70 °C and a pressure of from 90 to 110 kPa. The solvent rich flue gas 401 is fed through an outer radius of a first RPB 402. A first inlet aqueous phase 407 is fed through an inner radius of the first RPB 402. The temperature of the first inlet aqueous phase 407 is equal to or lower than the temperature of the solvent rich flue gas 401. In some embodiments, the temperature of the inlet aqueous phase 407 is from 15 to 50 °C. In some embodiments, the first RPB 402 rotates at a rotational speed of from 100 to 1500 RPM. In some embodiments, the first RPB 402 rotates at a rotational speed of from 100 to 600 RPM. The weight ratio of liquid to gas in the first RPB 402 is from 1 to 5 kg / kg. As the first RPB 402 rotates circularly, the first inlet aqueous phase 407 flows towards the outer radius of the first RPB 402 under a centrifugal force. The first inlet aqueous phase 407 contacts the solvent rich flue gas 401 in a countercurrent flow, transferring solvent from the solvent rich flue gas 401 to the first inlet aqueous phase 407. In this way, the circular rotation of the first RPB 402 results in a first solvent semi-lean flue gas 411 and first outlet aqueous phase 403. In some embodiments, there is no cooling of the solvent rich flue gas 401 by the first inlet aqueous phase 407. This means that the solvent rich flue gas 401 and the first solvent semi-lean flue gas 411 are approximately isothermal. In other embodiments, contact of the first inlet aqueous phase 407 with the first solvent rich flue gas 401 also cools the solvent rich flue gas 401 to a desired temperature of from 30 to 45 °C, condensing water and / or solvent. The temperature of the first outlet aqueous phase 403 as it leaves the first RPB 402 is therefore higher than the temperature of the first inlet aqueous phase 407 as it enters the first RPB 402 because heat is transferred to the first aqueous phase 407 as it contacts the solvent rich flue gas 401. The first outlet aqueous phase 403 passes to first sump tank 404. A portion of first outlet aqueous phase 403 is then diverted via valve 404b to first cooler 406 where, if desired, it can be cooled to form a cooled first portion 407a. All or some of the cooled first portion 407a may be fed back to the inner radius of the first RPB 402 such that first inlet aqueous phase 407 can comprise cooled first portion 407a. In this way, first cooler 404 makes it is possible to maintain a desired temperature of the first inlet aqueous phase 407. In some embodiments, the temperature of the cooled first portion 407a is from 15 to 50 °C. In some embodiments, the temperature of the cooled first portion 407a is from 30 to 45 °C. Advantageously, a temperature of from 30 to 45 °C leads to a lower cooling duty, aiding process economics. If the volume of liquid in the first sump tank 404 becomes too high, level control 404a of first sump tank 404 actuates valve 404b to enable the flow of a second portion 405 of first outlet aqueous phase 403 to a solvent loop of the main CO2 capture process (not shown) via valve 494i. In some embodiments, valve 494i and valve 494j are actuated so that the second portion 405 of first outlet aqueous phase 403 is fed to the inner radius of a second RPB 412 (in addition to or in place of being sent to the solvent loop). In this way, second inlet aqueous phase 425 can comprise second portion 405. The first solvent semi-lean flue gas 411 is fed through an outer radius of a second RPB 412. A second inlet aqueous phase 425 is fed through an inner radius of the second RPB 412. The temperature of the second inlet aqueous phase 425 is equal to or lower than the temperature of the first solvent semi-lean flue gas 411. In some embodiments, the temperature of the second inlet aqueous phase 425 is from 15 to 50 °C. In some embodiments, the second RPB 412 rotates at a rotational speed of from 100 to 1500 RPM. In some embodiments, the second RPB 412 rotates at a rotational speed of from 100 to 600 RPM. As the second RPB 412 rotates circularly, the second inlet aqueous phase 425 flows towards the outer radius of the second RPB 412 under a centrifugal force. The second inlet aqueous phase 425 contacts first solvent semi-lean flue gas 411 in a counter-current flow, transferring solvent from the first solvent semi-lean flue gas 411 to the second inlet aqueous phase 425. In this way, the circular rotation of the second RPB 412 results in a second solvent semi-lean flue gas 421 and second outlet aqueous phase 413. The second outlet aqueous phase 413 is fed to a solvent loop of the main CO2 capture process (not shown). In some embodiments, there is no, or minimal (e.g. 1 °C), cooling of the first solvent semi-lean flue gas 411 by the second inlet aqueous phase 425. Put differently, the first solvent semi-lean flue gas 411 and the second solvent semi-lean flue gas 421 are approximately isothermal. The degree of cooling here is not under direct control and is instead dependent on the other process conditions (such as the temperature of the solvent lean flue gas 431, the temperature of solvent rich flue gas 401, the weight ratio of liquid to gas in the second RPB 412). In some embodiments, the weight ratio of liquid to gas in the second RPB 412 is from 0.01 to 0.5 kg / kg. In some embodiments, the weight ratio of liquid to gas in the second RPB 412 is from 0.02 to 0.15 kg / kg. However, the exact chosen liquid to gas ratio in the second RPB 412 is dependent on the several factors. For example, one factor in the choice of liquid to gas ratio in the second RPB 412 is the temperature of the second solvent semi-lean gas 421 as it enters third RPB 422 (see below). This is because the amount of water that the second solvent semi-lean gas 421 can hold increases with an increase in its temperature (assuming that the second solvent semi-lean gas 421 has a relative humidity of over 85%). Therefore, the amount of liquid water condensing into sump tank 424 when the second solvent semilean gas 421 undergoes cooling in third RPB 422 (see below) increases with an increase in temperature of the second solvent semi-lean gas 421. In practise, this means that the chosen weight ratio of liquid to gas in the second RPB 412 will be higher where the temperature of the second solvent semi-lean gas 421 is higher. For similar reasons, other factors in the choice of liquid to gas ratio in the second RPB 412 include the temperature of the third inlet aqueous phase 427 (see below) and the initial water content of the solvent rich flue gas 401. Advantageously, a weight ratio of liquid to gas ratio of from 0.01 to 0.5 kg / kg results in a more efficient transfer of solvent components from the first solvent semi-lean flue gas 411 to the second inlet aqueous phase 425 during operation of the second RPB 412 (compared to if a higher weight ratio was used). Further, such low weight ratios are not generally possible when a traditional static packed bed column is used in place of an RPB. This is because at such weight ratios the distribution of liquid across the packing is poor, causing poor levels of liquid-gas contact and poor solvent removal from the gas. In some embodiments, the major axis of the second RPB 412 is horizontal. In other words, the axis about which the second RPB 412 rotates is horizontal. This means that the force of gravity acts on the liquid in a direction parallel to the plane in which the liquid rotates. The centrifugal force on the liquid in the second RPB 412 acts evenly in all axial directions. Advantageously, as a result the liquid has an improved (more even) distribution over the packing in the second RPB 412 compared to RPBs having other orientations. The second solvent semi-lean flue gas 421 is fed through an outer radius of a third RPB 422. A third inlet aqueous phase 427 is fed through an inner radius of the third RPB 422. The temperature of the third inlet aqueous phase 427 is equal to or lower than the temperature of the second solvent semi-lean flue gas 421. In some embodiments, the temperature of the third inlet aqueous phase 427 is from 15 to 50 °C. In some embodiments, the third RPB 422 rotates at a rotational speed of from 100 to 1500 RPM. In some embodiments, the third RPB 422 rotates at a rotational speed of from 100 to 600 RPM. The weight ratio of liquid to gas in the third RPB 422 is from 1 to 5 kg / kg. As the third RPB 422 rotates circularly, the third inlet aqueous phase 427 flows towards the outer radius of the third RPB 422 under a centrifugal force. The third inlet aqueous phase 427 contacts the second solvent semi-lean flue gas 421 in a counter-current flow, transferring solvent from the second solvent semi-lean flue gas 421 to the to the third inlet aqueous phase 427. In this way, the circular rotation of the third RPB 422 results in a solvent lean flue gas 431 and a third outlet aqueous phase 423. Contact of the third inlet aqueous phase 427 with the second solvent semi-lean flue gas 421 cools the second solvent semi-lean flue gas 421 to a desired temperature of from 30 to 45 °C, condensing water and / or solvent. The temperature of the third outlet aqueous phase 423 as it leaves the third RPB 422 is therefore higher than the temperature of the third inlet aqueous phase 427 because heat is transferred to the third inlet aqueous phase 427 as it contacts the second solvent semi-lean flue gas 421. The third outlet aqueous phase 423 passes to second sump tank 424. A portion of third outlet aqueous phase 423 is diverted via valve 424b to second cooler 426 where it is cooled to form a cooled first portion 427a. All or some of the cooled first portion 427a may be fed back to the inner radius of the third RPB 422 such that the third inlet aqueous phase 427 can comprise cooled first portion 427a. In this way, second cooler 426 makes it is possible to maintain a desired temperature of the third inlet aqueous phase 427. In some embodiments, the temperature of the cooled first portion 427a is from 15 to 50 °C. In some embodiments, the temperature of the cooled first portion 427a is from 25 to 40 °C. Advantageously, a temperature of from 25 to 40 °C leads to a lower cooling duty, aiding process economics. Level control 424a of second sump tank 424 may actuate valve 424b to enable the flow of a second portion 425a of third outlet aqueous phase 423 to a solvent loop of the main CO2 capture process (not shown) via valve 494k. In some embodiments, valve 494k and valve 494j are actuated so that some or all of second portion 425a is fed to the inner radius of a second RPB 412 (in addition to or in place of being sent to the solvent loop). In this way, second inlet aqueous phase 425 can comprise second portion 425a. In some embodiments, the flow rate of the second portion 425a sent to the inner radius of the second RPB 412 is equal to the flow rate of water condensed in the third RPB 422 during operation. Advantageously, the use of RPBs results in an improved rate of transfer of solvent from the flue gases to the aqueous phases over the use of a static packed column. Near complete (or at least 99.9%) recovery of solvent from the flue gas is possible using the disclosed system. The present invention therefore reduces the need to replace solvent lost by emissions in the main CO2 capture process, and reduces the CO2 capture cost ($ / ton). Advantageously, the RPBs can themselves act as demisters. In this way, the present invention significantly reduces aerosolised solvent emissions. The use of RPBs therefore negates the need conventional demisters in addition to the unit operation and thereby negates the need to apply additional pressure to the inlet flue gas. Consequently, the present invention is more efficient than the conventional process employing static packed columns, and reduces the CO2 capture cost ($ / ton). Advantageously, a system using multiple RPBs can maintain its maximum rate of solvent removal from a flue gas for a longer duration compared to a traditional system including two static packed columns (or a system using a single RPB). This is particularly true for the present system, including at least three RPBs. The effect is attributed to the effect of solvent concentration in the aqueous phase. An aqueous phase having a low concentration of solvent is more effective at removing solvent from a gas than the same aqueous phase having a high concentration of solvent. In the present system, the concentration of solvent in the solvent semi-rich flue gas 411 entering the second RPB 412 may be lower than that leaving the first static packed bed column of a system including two static packed bed columns. A lower concentration of solvent in the solvent semi-rich flue gas 411 entering the second RPB means that the concentration of the solvent in the second inlet aqueous phase 417 will increase more slowly than in the traditional system. The concentration of the solvent in third inlet aqueous phase 427 increases even more slowly. By maintaining relative lower concentrations of solvent in the inlet aqueous phases for a relatively longer duration, the maximum efficiency of the RPBs and system 400 as a whole is maintained for a longer duration. In some embodiments, solvent lean flue gas 431 is washed with an acid phase (not shown). The temperature of the acid phase is controlled so that the acid phase wash process is approximately isothermal (within ± 5 °C). Advantageously, washing with acid phase results in a solvent ultra-lean flue gas. In some embodiments, the washing of the solvent lean flue gas 431 with a temperature-controlled acid phase occurs in a fourth RPB 442a or a Rotating Zig-Zag Bed (RZB) 442b (not shown). The operation of the fourth RPB 442a or the RZB 442b occurs in a manner consistent with the operation of the second RPB 412, except that aqueous phase is replaced with an acid phase (at a temperature as described above) and in that the weight ratio of liquid to gas is from 1 to 10 kg / kg. Advantageously, the use of an RPB or RZB results in an improved rate of transfer of solvent from the flue gases to the aqueous phases over the use of a static packed column. In the foregoing description of method and system 400, it is the second RPB 412 that employs a low weight ratio of liquid to gas (of from 0.01 to 0.5 kg / kg). However, in an alternative embodiment the RPB employing a low weight ratio of liquid to gas could instead be the first RPB 402. Experimental comparison of static packed column and rotary packed bed Experiments were carried out to study the efficacy of the use of an RPB in a method for removing solvent from a flue gas by water washing. Flue gas from a gas-fired furnace was cooled by a direct contact cooler then fed at a temperature of 40 °C and a pressure of 108 kPa to either a first system (comparative example) or a second system. The first and second systems were modified versions of conventional system 100. The flue gas was rich in amine-based CO2 capture solvent. The pilot plant in which the experiments were performed was able to capture 1 tonne of CO2 per day (TPD). The first system (comparative example) was based on the conventional system 100, differing in that the wash column (second static packed column 106) was physically separate from the absorber column (first static packed column 104). The flue gas depleted of CO2 from the absorber column was fed directly to the wash column to be washed with water fed at a variable temperature to achieve an outlet gas temperature of 40 °C. The weight ratio of liquid to gas in the wash column was 4.5 kg / kg. The concentration of solvent in the flue gas (inlet and outlet) and water (inlet and outlet) were measured for the wash column. Using this data, the volumetric mass transfer coefficient (Kca) and the solvent scrubbing rate (rs) for the wash column were calculated (following to the equations below). For the second system, the flue gas depleted of CO2 from the absorber column was fed directly to an RPB, to be washed. The outlet gas of the RPB was then fed to the wash column. In detail, the flue gas depleted of CO2 from the absorber column (first static packed column 104) was fed to an RPB rotating at 400 RPM. The weight ratio of liquid to gas in the RPB was about 1.5 kg / kg. The flue gas depleted of CO2 was fed through an outer radius of the RPB, contacting water fed at a variable temperature to achieve a outlet gas temperature of 40 °C. The water was fed through an inner radius of the RPB in a counter-current flow to the flue gas. The concentration of solvent in the flue gas (inlet and outlet) and water (inlet and outlet) was measured for the RPB. Using this data, the volumetric mass transfer coefficient (Kca) and the solvent scrubbing rate (rs) for the RPB were calculated, (following the equations below). Once washed, the outlet flue gas from the RPB was passed to a wash column (a static packed column) to be washed with water fed at a temperature of 40 °C. The weight ratio of liquid to gas in the wash column was 4.5 kg / kg. The volume of packing in the RPB was approximately half the volume of packing in the wash column. The volume of packing in the wash column (static packed column) was the same in the first and second systems. Equation 1 - volumetric mass transfer coefficient: KGa = —ln(—~) v cG,o Where Kca is the volumetric mass transfer coefficient (s-1), Qg is the volumetric flow rate of the inlet flue gas (m3s_1), V is the volume of packing in the static column or RPB (m3), Cgj and Cg.o are the respective concentrations of the amine solvent in the inlet flue gas and outlet flue gas for the wash column or RPB (ppmv). Equation 2 - solvent scrubbing rate: r t ^solv I Solvit Jo Where hsoiv is the molar flow rate of solvent (mol / hr), nsoiv is the amount in moles of solvent in the recirculating water stream at time t. Figure 5 shows the volumetric mass transfer coefficient and the solvent scrubbing rate for the wash column of the first system (comparative example) and for the RPB of the second system. The data provided is relative to the calculated values for the RPB. The figure demonstrates that the RPB had an improved solvent scrubbing rate over the wash column (static packed column). This is despite the volume of the wash column (static packed column) being approximately twice the volume of the RPB. Partly because of the difference in volume, the volumetric mass transfer coefficient for the RPB was three times higher than for the wash column. In summary, the experiments show that an RPB was more efficient at removing solvent from a flue gas despite having a substantially smaller packing volume. Process modelling Computational process modelling was utilised to extrapolate the impact of the experimental observations onto methods and systems of removing solvent from a flue gas according to the present invention. The simulations were conducted using proprietary modelling software. Before use in the present simulations, the modelling software had undergone significant validation with experimental data for each aspect of the CO2 capture process. The primary focus of the simulations was the wash stage of a CO2 capture process. The wash stage plays a crucial role in removing residual solvent from the treated flue gas to reduce solvent losses and minimise environmental emissions. Changes to other aspects of the CO2 capture process, such as absorption and regeneration, were not considered here. The model used was based on a static packed column, with modifications made to simulate an RPB. The changes adjusted mass transfer properties to reflect the RPB performance enhancement evidenced by the earlier experimental findings. The solvent modelled was an amine-based solvent that selectively reacted with CO2. The aim of the simulations was to explore how the different methods and systems for removing solvent from a flue gas according to the present invention affected removal of solvent from the CO2 depleted flue gas. The properties of the solvent rich flue gas (201, 301, 401) were chosen to be representative of a typical flue gas leaving an absorber column. For instance, control parameters included temperature, pressure, flow rate and the concentrations of gases like CO2, water vapor, and amine solvent. The concentration of solvent was the same for each system. The temperature of the outlet gas for each RPB was obtained after completing the simulations. Table 1 shows some of the control parameters for the solvent rich flue gas, along with the temperature of the outlet flue gas obtained from the simulations. Table 1: Selected control parameters for the solvent rich flue gas. Also shown is the temperature of the outlet gases for each RPB (output by the simulations). Solvent rich flue gas Outlet gases System of the present invention Temperature (°C) Concentration (mol.%) Flow rate (kg / hr) Temperature (°C) CO2 O2 H2O First RPB Second RPB Third RPB 200 55 1 6 13.74 200 40 40 n / a 300 54 40 n / a 400 50 50 40 The properties of the inlet aqueous phases were also chosen to be representative of operating conditions in a pilot plant. For instance, control parameters included temperature, pressure and solvent concentration. Inlet aqueous phase flow rate was set for an optimal weight ratio of liquid to gas in each RPB. The solvent concentration for each inlet and outlet aqueous phase were obtained from the simulations. Table 2 shows some of the control parameters for the inlet aqueous phase for each RPB. Table 2: selected control parameters for the inlet aqueous phases. Inlet aqueous phases System of the present invention Temperature (°C) Flow rate (kg / hr) First RPB Second RPB Third RPB First RPB Second RPB Third RPB 200 40 40 n / a 600 600 n / a 300 50 40 n / a 9.59 600 n / a 400 50 49 40 600 10.23 600 Table 3 shows the weight ratio of liquid to gas for each RPB. Table 3: weight ratio of liquid to gas for each RPB System of the present invention Weight ratio of liquid to gas First RPB Second RPB Third RPB 200 3.00 3.00 n / a 300 0.04795 3.00 n / a 400 3.00 0.05115 3.00 Figure 6 shows relative solvent concentration in the outlet flue gas for each RPB of method and system 200. The relative solvent concentration is a ratio of the concentration of solvent in the outlet flue gas to the concentration of the solvent in the solvent rich flue gas (201, 301, 401). The relative concentrations shown relate to those in the solvent semi-lean flue gas 211 (“after one stage”) and in the solvent lean flue gas 221 (“after two stages”). A comparison is made to an equivalent design having static packed columns. At each stage of the equivalent static packed column design, the same operating conditions were used as for the respective RPB. The relative concentration of solvent in the solvent semi-lean flue gas 211 (“after one stage”) and in the solvent lean flue gas 221 (“after two stages”) was no more than 33% of the respective relative concentrations for the equivalent static packed column system. In other words, at each stage the RPB was at least three times more effective at removing solvent from the flue gas than a static packed column. Therefore, the present method and system 200 was substantially more effective at removing solvent from a flue gas than an equivalent method or system using static packed columns. Figure 7 shows relative solvent concentration in the outlet flue gas for each RPB of method and system 300. The relative concentrations shown relate to those in the solvent semi-lean flue gas 311 (“after one stage”) and in the solvent lean flue gas 321 (“after two stages”). A comparison is made to the equivalent design with static packed columns. At each stage of the equivalent static packed column design, the same operating conditions (e.g. temperature, pressure and weight ratio of liquid to gas) were used as for the respective RPB. The relative solvent concentration in the solvent semi-lean flue gas 311 (“after one stage”) was no more than a 44% of the relative concentration in the outlet gas for the first stage of the equivalent static packed column system. In other words, after the first stage the RPB was at least twice as effective at removing solvent from the flue gas than the equivalent static packed column. The improvement of the RPB-based system is even more stark in the second stage. The relative solvent concentration in the solvent lean flue gas 321 (“after two stages”) was no more than 5% of the relative solvent concentration for the second stage of the equivalent static packed column system. In other words, after the second stage the RPBs were over twenty times as effective at removing solvent from the flue gas than the equivalent static packed columns. Therefore, the present method and system 300 was substantially more effective at removing solvent from a flue gas than an equivalent method or system using static packed columns. Figure 8 shows relative solvent concentration in the outlet flue gas for each RPB of method and system 400. The relative concentrations shown relate to those of the first solvent semi-lean flue gas 411 (“after one stage”), second solvent semi-lean flue gas 421 (“after two stages”) and the solvent lean flue gas 431 (“after three stages”). A comparison is made to the equivalent design with static packed columns. At each stage of the equivalent static packed column design, the same operating conditions were used as for the respective RPB. The relative solvent concentration in the first solvent semi-lean flue gas 411 (“after one stage”) was no more than 72% of the relative concentration of the outlet gas for the first stage of the equivalent static packed column system. In other words, after the first stage the RPB was at least 1.4 times as effective at removing solvent from the flue gas than an equivalent static packed column. The relative solvent concentration in the second solvent semi-lean flue gas 421 (“after two stages”) was no more than a 50% of the relative concentration of the outlet gas for the second stage of the equivalent static packed column system. In other words, after the second stage the RPBs were at least twice as effective at removing solvent from the flue gas than the equivalent static packed columns. The relative solvent concentration in the solvent lean flue gas 431 (“after three stages”) was no more than 4% of the relative solvent concentration of the of the outlet gas for the third stage of the equivalent static packed column system. In other words, after the third stage the RPBs were over twenty-five times as effective at removing solvent from the flue gas than the equivalent static packed columns. Therefore, the present method and system 400 was substantially more effective at removing solvent than an equivalent method or system using static packed columns. The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilized for realizing the invention in diverse forms thereof. Although certain example aspects of the invention have been described, the scope of the appended claims is not intended to be limited solely to these examples. The claims are to be construed literally, purposively, and / or to encompass equivalents.

Claims

1. A method for washing a flue gas to remove solvent present in the flue gas, the method comprising the steps of:feeding a solvent rich flue gas to a first Rotary Packed Bed (RPB) rotating circularly, wherein a first inlet aqueous phase provided through an inner radius of the first RPB moves towards an outer radius of the first RPB, and wherein the first inlet aqueous phase contacts with the solvent rich flue gas in a counter-current flow to remove solvent present in the solvent rich flue gas and form a solvent semi-lean flue gas and first outlet aqueous phase;feeding the solvent semi-lean flue gas to a second RPB rotating circularly, wherein a second inlet aqueous phase provided through an inner radius of the second RPB moves towards an outer radius of the second RPB, and wherein the second inlet aqueous phase contacts the solvent semi-lean flue gas in a counter-current flow to remove solvent present in the solvent semi-lean flue gas and form a solvent lean flue gas and second outlet aqueous phase; and,wherein a first portion of the first outlet aqueous phase is cooled to a temperature of from 15 to 50 °C then fed to the inner radius of the first RPB such that the first inlet aqueous phase comprises all or some of the cooled first portion of the first outlet aqueous phase.

2. The method of claim 1, wherein the solvent rich flue gas is introduced from the outer radius of the first RPB.

3. The method of claim 1 or claim 2, wherein the solvent semi-lean flue gas is introduced from the outer radius of the second RPB.

4. The method of any one of claims 1 to 3, wherein the first portion of the first outlet aqueous phase is cooled to a temperature of from 25 to 40 °C.

5. The method of any one of claims 1 to 4, wherein a first portion of the second outlet aqueous phase is cooled to a temperature of from 15 to 50 °C then fed to the inner radius of the second RPB such that the second inlet aqueous phase comprises all or some of the cooled first portion of the second outlet aqueous phase.

6. The method of claim 5, wherein the first portion of the second outlet aqueous phase is cooled to a temperature of from 30 to 45 °C.

7. The method of any one of claims 1 to 6, wherein the rotational speed of the first RPB and / or the second RPB is from 100 to 1500 RPM.

8. The method of claim 7, wherein the rotational speed of the first RPB and / or the second RPB is from 100 to 600 RPM.

9. The method of any one of claims 1 to 8, wherein the solvent lean flue gas is fed through an acid wash to remove traces of solvent, and wherein the acid wash comprises reacting an acid phase with the solvent lean flue gas in a counter-current flow to remove traces of solvent present in the solvent lean flue gas.

10. The method of claim 9, wherein the temperature of the acid phase is the temperature of the solvent lean flue gas ± 5 °C.

11. The method of claim 9 or claim 10, wherein the acid wash comprises feeding the solvent lean flue gas to a third rotating bed rotating circularly, wherein an acid phase is provided through an inner radius of the third rotating bed and moves towards the outer radius of the third rotating bed.

12. The method of claim 11, wherein the solvent lean flue gas is introduced from the outer radius of the third rotating bed.

13. The method of claim 11 or claim 12, wherein the third rotating bed is a RPB or a Rotating Zig-Zag Bed (RZB).

14. The method of any one of claims 1 to 13, wherein the weight ratio of liquid to gas in the first and / or second RPB is from 1 to 5 kg / kg.

15. The method of any one of claims 11 to 14, wherein the weight ratio of liquid to gas of the third rotating bed is from 1 to 10 kg / kg.

16. The method of any one of claims 1 to 15, wherein the rotational speed of the third rotating bed is from 100 to 1500 RPM.

17. The method of claim 16, wherein the rotational speed of the third rotating bed is from 100 to 600 RPM.

18. The method of any one of claims 1 to 17, wherein the first inlet aqueous phase is thermally independent with (not in thermal communication with) the second inlet aqueous phase.

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