Method and system for treating steam condensate generated by a high pressure generator from a carbon dioxide absorption solution

Abstract

This disclosure relates to a method for treating substances ranging from 1.0 to 1.2 kg / cm³. 2 A method for regenerating a carbon dioxide absorbent solution using vapor condensate generated by a high-pressure regenerator (57) operating under pressure. The method includes the steps of: a) capturing carbon dioxide in a carbon dioxide absorption (56) unit using the carbon dioxide absorbent solution; b) feeding the absorbed carbon dioxide and the carbon dioxide absorbent solution generated in step a) into the high-pressure regenerator (57); and c) applying a vapor condensate at a pressure ranging from 3.2 to 3.5 kg / cm³. 2 Low-pressure steam is supplied to a steam reboiler (58) under pressure to provide heat to the high-pressure regenerator (57), thereby producing steam condensate and regenerated carbon dioxide absorbent solution; and is characterized by further comprising the step of: d) supplying the steam condensate produced in step c) to a degasser (59) to produce an aqueous solution suitable for producing steam with an oxygen content ranging from 7 ppb to less than 20 ppb. This disclosure further relates to a system for performing the methods of this disclosure and to the use of the system in performing the methods of this disclosure. This disclosure further relates to a method for modifying a system further comprising a process condensate stripper and a water demineralization unit to a disclosed system.

Description

Technical Field

[0001] This disclosure relates to a method and system for carbon dioxide absorption, and more particularly to a method and system for treating vapor condensate generated by a high-pressure generator for the regeneration of a carbon dioxide absorption solution. Background Technology

[0002] Carbon dioxide has many uses. For example, it is used in the production of urea, in carbonated beverages, for cooling, freezing, and packaging seafood, meat, poultry, baked goods, fruits, and vegetables, and for extending the shelf life of dairy products. It is an important environmental component in industrial waste and process water treatment, and is used as a substitute for sulfuric acid to control pH levels. Other uses include drinking water treatment, environmentally friendly pesticides, and air additives used in greenhouses to promote vegetable growth.

[0003] Generally, carbon dioxide is produced by purifying waste streams that are byproducts of organic or inorganic chemical processes. Waste streams containing high concentrations of carbon dioxide undergo multi-stage condensation and purification, followed by distillation to produce product-grade carbon dioxide.

[0004] The concentration of carbon dioxide in the feed can be increased in several ways. A particularly preferred method is to chemically absorb carbon dioxide from the crude carbon dioxide feed into an alkanolamine absorbent. The resulting carbon dioxide-loaded absorbent then undergoes separation into carbon dioxide products for recovery and an alkanolamine-containing absorbent, which can be recycled within the recovery system for reuse.

[0005] Carbon dioxide recovery is particularly important in ammonia processes where hydrogen and carbon dioxide are separated, in a mixture of hydrogen and carbon dioxide produced by the shift unit: hydrogen cannot be used for ammonia production in the ammonia synthesis tower unless it is essentially free of carbon dioxide.

[0006] GB996543A describes how to wash a gas containing carbon dioxide in a column (18) with an aqueous solution of alkanolamine, wherein the solution that has absorbed carbon dioxide is discharged from the column (18) and regenerated in the column (32), indirectly heated by steam from the waste heat boiler (2) and stripped by steam from the waste heat boiler (9).

[0007] DE102018210921A1 describes a unit and related process for producing a hydrogen-containing syngas, comprising at least: (a) a converter (1); (b) a carbon monoxide (CO) synthesis tower (2); (c) a syngas condenser (4); and (d) a carbon dioxide (CO2) scrubber unit (3) with regeneration; characterized in that the syngas condenser (4) is connected to a degasser (5), and the degasser (5) is connected to a converter burner (6) and / or a combustion-assisted steam boiler (7).

[0008] CN107866134A discloses providing heat to a regenerator operating under reflux conditions for the solution to be regenerated, and also using heat from the rich and lean solutions, as well as from the CO2 / steam mixture produced within the regenerator, to heat the solution to be treated in the regenerator. Furthermore, the steam condensate after the heat supply to the regenerator is heated by steam.

[0009] Therefore, the prior art describes the regeneration of a carbon dioxide absorbent solution by heating with steam and condensing the syngas, as well as its subsequent treatment in a degasser. The prior art does not provide guidance on how to treat the condensate from the steam used to regenerate the carbon dioxide-absorbed solution.

[0010] From an energy recovery perspective, the regeneration of steam used to regenerate solutions that have absorbed carbon dioxide is important and should be carried out in an energy-efficient manner. Simultaneously, the process condensate generated from the use of steam should be treated and used in a way that prevents corrosion of the equipment in the unit.

[0011] This disclosure provides a method and system for utilizing the full heat content of the steam condensate generated by a high-pressure regenerator while ensuring that the equipment in the unit is not corroded. Summary of the Invention

[0012] In one aspect of this disclosure, a method is disclosed for treating vapor condensate generated by a high-pressure regenerator operating at a pressure ranging from 1.0 to 1.2 kg / cm² for regenerating a carbon dioxide absorbent solution. The method includes the following steps:

[0013] a) Use a carbon dioxide absorption solution to capture carbon dioxide in a carbon dioxide absorption unit;

[0014] b) Feed the absorbent carbon dioxide and the carbon dioxide absorbent solution generated in step a) into the high-pressure regenerator; and

[0015] c) In the range of 3.2 to 3.5 kg / cm 2 Low-pressure steam is supplied to the steam reboiler under pressure to provide heat to the high-pressure regenerator, thereby producing steam condensate and regenerated carbon dioxide absorbent solution.

[0016] Furthermore, it is characterized by including the following steps:

[0017] d) The steam condensate produced in step c) is supplied to a degasser to produce an aqueous solution suitable for producing steam with an oxygen content of less than 20 ppb.

[0018] Surprisingly, the inventors discovered that the method disclosed herein allows for the utilization of the full heat content of the steam condensate generated by the high-pressure regenerator, while ensuring that the equipment in the unit is not corroded, as it is processed energy-efficiently in the degasser. Furthermore, the use of low-pressure steam to supply the high-pressure regenerator results in the maximum heat content of the steam used, thereby maximizing energy recovery in the system.

[0019] In one embodiment of the method according to this disclosure, the aqueous solution suitable for producing steam has an oxygen content ranging from 7 ppb to less than 20 ppb.

[0020] In one embodiment of the method according to this disclosure, the method further includes the following steps:

[0021] e) The regenerated carbon dioxide absorption solution produced in step c) is reused in the carbon dioxide absorption unit to absorb additional carbon dioxide.

[0022] In one embodiment of the method according to this disclosure, the carbon dioxide absorption solution contains about 30% potassium carbonate, optionally partially or completely converted to potassium bicarbonate.

[0023] In one embodiment of the method according to this disclosure, the carbon dioxide absorption solution comprises about 30% potassium carbonate, about 5% potassium bicarbonate, about 0.5% diethanolamine and about 0.5% glycine.

[0024] In one embodiment of the method according to this disclosure, the method further includes the following steps:

[0025] f) Producing steam from the aqueous solution produced in step d).

[0026] In one embodiment of the method according to this disclosure, the method further includes the following steps:

[0027] g) Desulfurize the natural gas feed in the desulfurization unit to produce a feed that is essentially sulfur-free natural gas;

[0028] h) In a primary converter, steam is used to convert the feed of essentially sulfur-free natural gas obtained in step g) into a mixture of carbon monoxide and hydrogen.

[0029] i) Optionally, in the two-stage converter, oxygen is used to increase the conversion rate of the essentially sulfur-free natural gas feed to a mixture of carbon monoxide and hydrogen achieved in step h) in the one-stage converter.

[0030] j) In the conversion unit, the mixture of carbon monoxide and hydrogen obtained in step h) or optionally in step i) is converted into a mixture of carbon dioxide and hydrogen; and

[0031] k) Feeding the gaseous mixture of carbon dioxide and hydrogen generated in step j) to the carbon dioxide absorption unit to produce hydrogen that is substantially free of carbon dioxide; and

[0032] l) The hydrogen produced in step k) is fed into the methanation unit to convert the remaining carbon monoxide and carbon dioxide into methane.

[0033] In one embodiment of the method according to this disclosure, the method further includes the following steps:

[0034] m) The mixture of hydrogen and methane obtained in step l) is fed into the ammonia synthesis tower for the production of ammonia.

[0035] In another aspect of this disclosure, a method for recovering substances ranging from 1.0 to 1.2 kg / cm³ is disclosed. 2 A system for regenerating carbon dioxide absorbent solution using the heat content of the steam condensate generated by a high-pressure regenerator operable under pressure. The system includes:

[0036] • A carbon dioxide removal unit, comprising:

[0037] o Carbon dioxide absorption unit;

[0038] a high-pressure regenerator, used to regenerate a carbon dioxide absorption solution containing absorbed carbon dioxide; and

[0039] o Steam reboiler, comprising: for use in the range of 3.2 to 3.5 kg / cm³ 2 The inlet supplies heat to the high-pressure regenerator under pressure, and the outlet is for steam condensate, which is produced through heat exchange between steam in the steam reboiler and the high-pressure regenerator; and

[0040] • A degasser for producing aqueous solutions with an oxygen content of less than 5 ppm, especially less than 20 ppb, comprising an inlet and an outlet;

[0041] Furthermore, it is characterized in that the inlet of the degasser is in fluid communication with the outlet of the steam reboiler.

[0042] In one embodiment of the system according to this disclosure, the system further includes means for recycling the regenerated carbon dioxide absorbent solution regenerated in a high-pressure regenerator.

[0043] In one embodiment of the system according to the present disclosure, the system further includes means for producing steam with an oxygen content ranging from 7 ppb to less than 20 ppb from an aqueous solution produced in the degasser, wherein the means for producing steam is in direct fluid communication with the degasser.

[0044] In one embodiment of the system according to this disclosure, the system is a front end of an ammonia production unit and further includes:

[0045] • Desulfurization unit, which is used to desulfurize the natural gas feed;

[0046] • A primary converter, used to convert a feed of essentially sulfur-free natural gas into a mixture of carbon monoxide and hydrogen;

[0047] Optionally, a two-stage reformer for improving the conversion rate of the substantially sulfur-free natural gas feed to a mixture of carbon monoxide and hydrogen, achieved in the first-stage reformer; and

[0048] • A conversion unit for converting a mixture of carbon monoxide and hydrogen produced in a single-stage converter or optionally in a two-stage converter;

[0049] in:

[0050] • The desulfurization unit is directly fluid-connected to the first-stage converter;

[0051] • The primary converter is in direct fluid communication with the conversion unit in the absence of a secondary converter, and is in direct fluid communication with the secondary converter in the presence of a secondary converter;

[0052] • When the two-stage converter is present, the two-stage converter is directly fluidly connected to the conversion unit;

[0053] The conversion unit and the carbon dioxide absorption unit are directly fluidly connected; and

[0054] • Methanation unit, which is used to convert the remaining carbon monoxide and carbon dioxide into methane, wherein the methanation unit is in direct fluid communication with the conversion unit.

[0055] In one embodiment of the system according to this disclosure, the front end is fluidly connected to an ammonia synthesis tower for producing ammonia.

[0056] In another aspect of this disclosure, the use of the system for recovering heat disclosed herein for performing the method for recovering heat disclosed herein is disclosed.

[0057] In another aspect of this disclosure, a system for recovering heat includes the following:

[0058] • A carbon dioxide removal unit, comprising:

[0059] o Carbon dioxide absorption unit;

[0060] a high-pressure regenerator, used to regenerate a carbon dioxide absorption solution containing absorbed carbon dioxide; and

[0061] A steam reboiler, comprising an inlet and an outlet for supplying heat to a high-pressure regenerator to produce steam condensate and a regenerated carbon dioxide absorbent solution; and

[0062] • A process condensate stripper for stripping condensate produced by a steam reboiler, the steam reboiler including an inlet and an outlet that are in direct fluid communication with the outlet of the steam reboiler.

[0063] • A water-based mineral processing unit, comprising an inlet and an outlet in direct fluid communication with the outlet of a process condensate stripper; and

[0064] • A degasser for producing aqueous solutions with an oxygen content of less than 5 ppm, comprising an inlet and an outlet that are in direct fluid communication with the outlet of the water demineralization unit;

[0065] A method for modifying a system according to the present disclosure, the method comprising the following steps:

[0066] (I) Fluidly disconnect the outlet of the steam reboiler from the inlet of the process condensate stripper;

[0067] (II) Fluidly disconnect the inlet of the water demineralization unit from the outlet of the process condensate stripper; and

[0068] (III) Connect the outlet of the steam reboiler to the inlet of the degasser in a fluid manner. Attached Figure Description

[0069] Figure 1 A schematic diagram illustrating the novel process of this disclosure and its differences from conventional systems in the prior art is shown.

[0070] Figure 2 A schematic diagram of an ammonia production process is shown, in which the process disclosed herein can be integrated.

[0071] Explanation of Figure Numbers

[0072]

[0073] Detailed Implementation

[0074] Before describing the systems and methods of this disclosure, it should be understood that this disclosure is not limited to the specific systems, methods, or combinations described, as such systems, methods, and combinations can certainly vary. It should also be understood that the terminology used herein is not intended to be limiting, as the scope of this disclosure will be limited only by the appended claims.

[0075] As used in this article, the singular forms “a,” “one,” and “the” include both the singular and plural indicators, unless the context clearly indicates otherwise.

[0076] The terms “comprising / comprises” and “comprised of” as used herein are synonymous with “including / includes” or “containing / contains” and are inclusive or open-ended, and do not exclude additional, non-narrative members, elements, or method steps. It should be understood that the terms “comprising,” “including,” and “comprised of” as used herein include the terms “comprised of,” “compose,” and “composed of.”

[0077] The numerical values ​​listed with the aid of the accompanying figures include all values ​​and fractions within those ranges, as well as the referenced endpoint values. The term "from...to...", used when referring to a range of measurable values ​​(such as parameters, quantities, time periods, and similar values), is intended to include limitations associated with the disclosed range.

[0078] As used herein, “about” or “approximately” when referring to a measurable value, such as a parameter, quantity, duration, etc., means including the specified value and a variation of + / - 10% or less from the specified value, preferably + / - 5% or less, more preferably + / - 1% or less, and even more preferably + / - 0.1% or less, provided that such variation is suitable for performance in the disclosed disclosure. It should be understood that the value referred to by the modifier “about” or “approximately” is itself specifically and preferably disclosed.

[0079] Although the terms “one or more” or “at least one”, such as one or more or at least one member of a group of members, are clear by themselves, by further example, the term covers references to any one of the members, or to any two or more of the members, such as, for example, any ≥3, ≥4, ≥5, ≥6 or ≥7 members, and up to all the members.

[0080] Reference Figure 1 In one aspect of this disclosure, a method is disclosed for treating the steam condensate generated by a high-pressure regenerator (57) for regenerating a carbon dioxide absorbent solution. The high-pressure regenerator is defined herein as operating in the range of 1.0 kg / cm³. 2 Up to 1.2 kg / cm 2 The regenerator operates under pressure. The method includes the following steps: a) capturing carbon dioxide in a carbon dioxide absorption (56) unit using a carbon dioxide absorption solution; b) feeding the absorbed carbon dioxide and the carbon dioxide absorption solution generated in step a) into a high-pressure regenerator (57); and c) operating at a pressure of 3.2 kg / cm². 2 Up to 3.5 kg / cm 2The low-pressure steam is supplied to the steam reboiler (58) under pressure to supply heat (57) to the high-pressure regenerator, thereby producing steam condensate and regenerated carbon dioxide absorbent solution; and is characterized by further comprising the following steps: d) supplying the steam condensate produced in step c) to the degasser (59) to produce an aqueous solution suitable for producing steam with an oxygen content of less than 20 ppb.

[0081] As defined herein, a carbon dioxide absorption unit is any unit that absorbs gaseous carbon dioxide from a gas mixture into a liquid known as a carbon dioxide absorption solution. Due to this absorption, a carbon dioxide absorption solution containing the absorbed carbon dioxide is generated, and thus, carbon dioxide is purified from the gas mixture from which it has been separated. Since reusing the carbon dioxide solution is economically advantageous, a technological solution is needed to regenerate the solution after it has absorbed carbon dioxide. In other words, it is necessary to desorb the carbon dioxide after absorption, so that the carbon dioxide absorption solution is regenerated and has the capacity to absorb additional carbon dioxide. The desorbed carbon dioxide can, for example, be used in processes that consume carbon dioxide, such as urea production.

[0082] Carbon dioxide is typically regenerated by heating a solution containing absorbed carbon dioxide in a heat exchange system. A known example of such a heat exchange system is one that includes a high-pressure regenerator (57) containing the solution to be regenerated and a steam reboiler (58) that exchanges steam with the solution. Due to the heat exchange process, the absorbed carbon dioxide in the solution to be regenerated is evaporated, making the solution suitable for reuse in a carbon dioxide absorption unit (56). On the reboiler (58) side, after the steam heat exchange, a process condensate is produced. Specifically, in the context of this application, in such a heat exchange system, in the reboiler (58), the carbon dioxide-containing solution to be regenerated is heated and low-pressure steam is condensed into a liquid. Therefore, the condensation of the low-pressure steam contributes the heat required for the regeneration of the carbon dioxide absorbent solution and the evaporation of carbon dioxide in the high-pressure regenerator (57). In some embodiments, the regenerated carbon dioxide absorbent solution leaving the high-pressure regenerator may be further processed in a low-pressure regenerator (not shown), typically below 0.2 kg / cm³. 2 Operating under pressure, such as approximately 0.1 kg / cm². 2 Operating under pressure, the carbon dioxide absorption solution is further evaporated and removed before being reused in the CO2 absorption tower.

[0083] Typically, in existing systems, process condensate is treated in a process condensate stripper (63) to strip any gas. In the stripper, the condensate to be stripped comes into contact with steam and the gas dissolved in the condensate is stripped, allowing water with a suitable gas content to be recovered and used to produce additional steam. Typically, the stripped condensate is then treated in a water demineralization unit (64) to further purify the water before it is used to produce steam. In addition, the softened water needs to be treated in a degasser to reduce the oxygen content to below 20 ppb: reducing the oxygen level is necessary to prevent corrosion of the equipment, in which steam is generated from the water and subsequently used for heat exchange.

[0084] The presence and use associated with the presence of the process condensate stripper (63) and the water demineralization unit (64) implies high energy consumption. The inventors of this disclosure have determined that the presence of such a process condensate stripper and demineralization unit (64) is not necessary for treating the condensate generated in the steam reboiler (58). Instead of treating the process condensate from the steam reboiler (58) via the process condensate stripper (63) and the water demineralization unit (64), the process condensate can be directly fed to the deaerator. In this way, energy is saved not only by avoiding actual chemical treatment of the process condensate in the process condensate stripper (63) and the water demineralization unit (64), but also by avoiding the pumping of an equivalent amount of softened water to the deaerator (59). All that is required is to supply the process condensate directly to the degasser (59), with the process condensate outlet (61) of the reboiler (58) connected to the inlet (69) of the degasser (59), specifically via a direct connection between the reboiler (58) and the degasser (59). This significantly simplifies the equipment in the process, greatly reduces the system footprint, and consequently lowers the costs associated with the system and its operation. Furthermore, the use of low-pressure steam and its condensation into liquid results in the maximum heat content of the steam used to supply heat to the high-pressure regenerator (57), maximizing energy recovery within the system.

[0085] In one embodiment of the method according to this disclosure, the aqueous solution suitable for producing steam obtained in step d) has an oxygen content ranging from 7 ppb to less than 20 ppb.

[0086] In one embodiment of the method according to this disclosure, the method further includes the step e): reusing the regenerated carbon dioxide absorbent solution produced in step c) to absorb additional carbon dioxide in the carbon dioxide absorbent unit (56). As described above, this allows for a reduction in the amount of absorbent solution used to absorb a defined amount of carbon dioxide.

[0087] In one embodiment of the method according to this disclosure, the carbon dioxide absorption solution contains about 30% potassium carbonate, optionally partially or completely converted to potassium bicarbonate.

[0088] In one embodiment of the method according to this disclosure, the carbon dioxide absorption solution comprises about 30% potassium carbonate, about 5% potassium bicarbonate, about 0.5% diethanolamine and about 0.5% glycine.

[0089] In one embodiment of the method according to this disclosure, the method further includes the step of: f) producing steam from the aqueous solution produced by step d). Steam can be produced using water having an oxygen content of less than 20 ppb, particularly in the range of 7 ppb to 20 ppb, and can be supplied to, for example, a steam reboiler (58) for regenerating additional amounts of a carbon dioxide absorption solution containing absorbed carbon dioxide in a high-pressure regenerator (57).

[0090] Reference Figure 2 In one embodiment of the method according to this disclosure, the method is performed in the front end (or hydrogen production section) of an ammonia production unit (71) and further includes the following steps: g) desulfurizing the natural gas feed in a desulfurization unit (11) for the production of a substantially sulfur-free natural gas feed; h) converting the substantially sulfur-free natural gas feed obtained in step g) into a mixture of carbon monoxide and hydrogen using steam in a primary reformer (19); i) optionally, in a secondary reformer (53), using oxygen to enhance the sulfur content achieved in the primary reformer (19) in step h). The conversion rate of the feed of essentially sulfur-free natural gas to a mixture of carbon monoxide and hydrogen; j) in the conversion unit (24), the mixture of carbon monoxide and hydrogen obtained in step h) or optionally in step i) is converted to a mixture of carbon dioxide and hydrogen; k) the gaseous mixture of carbon dioxide and hydrogen generated in step j) is fed to the carbon dioxide absorption unit (56) to produce hydrogen that is substantially free of carbon dioxide; and l) the hydrogen produced in step k) is fed to the methanation unit (32) for converting the remaining amount of carbon monoxide and carbon dioxide into methane.

[0091] Therefore, this disclosure provides the possibility of applying the methods of this disclosure to the carbon dioxide removal unit (28) in the "front end" (i.e., hydrogen production section) of an ammonia production system (71).

[0092] In one embodiment of the method according to the present disclosure, the method further includes the following steps: m) feeding the mixture of hydrogen and methane obtained from step l) into an ammonia synthesis tower (36).

[0093] Therefore, this disclosure not only provides the possibility of applying the method of this disclosure to the decarbon dioxide unit (28) in the "front end" (i.e., the hydrogen production section) of an ammonia production system, but also allows the produced hydrogen to react with nitrogen in the ammonia synthesis tower. Thus, ammonia can be produced while saving energy from the decarbon dioxide unit (28).

[0094] Reference Figure 1 In another aspect of this disclosure, a method for recycling substances ranging from 1.0 to 1.2 kg / cm³ is disclosed. 2 The system utilizes the heat of steam condensate generated by a high-pressure regenerator (57) operable under pressure for regenerating a carbon dioxide absorbent solution. The system includes: a degasser (59) for producing an aqueous solution with an oxygen content below 20 ppb, particularly in the range of 7 ppb to 20 ppb, the degasser including an inlet and an outlet; and a decarbon dioxide unit (28) including a carbon dioxide absorption unit (56); a high-pressure regenerator (57) for regenerating a carbon dioxide absorbent solution containing absorbed carbon dioxide; and a steam reboiler (58) including: a system for regenerating a solution with a pressure range of 3.2 to 3.5 kg / cm³. 2 The degasser (59) has an inlet (60) supplying heat to the high-pressure regenerator (57) under pressure and an outlet (61) for steam condensate, which is produced by heat exchange between the steam in the steam reboiler and the high-pressure regenerator (such as by heat exchange between the steam in the steam reboiler and a carbon dioxide absorption solution containing absorbed carbon dioxide); and is characterized in that the inlet (60) of the degasser (59) is in direct fluid communication with the outlet (61) of the steam reboiler (58). In other words, the inlet (60) of the degasser (59) is connected to the outlet (61) of the steam reboiler (58).

[0095] As described above, in conjunction with the developed method, the inventors of this disclosure have determined that the presence of the process condensate stripper (63) and the demineralization unit (64) is not necessary for treating the condensate generated in the steam reboiler. Because instead of treating the process condensate from the steam reboiler (58) via the process condensate stripper (63) and the water demineralization unit (64), the process condensate can be directly fed to the degasser, greatly simplifying the equipment in the process, significantly reducing the system footprint, and thus lowering the associated costs. Furthermore, the use of low-pressure steam and its condensation into liquid results in the maximum heat content of the steam used to supply heat to the high-pressure regenerator (57), maximizing energy recovery within the system.

[0096] In some embodiments, the system further includes a low-pressure regenerator (not shown) located downstream of the high-pressure regenerator (57) for further removing CO2 from the regenerated carbon dioxide absorbent solution.

[0097] In one embodiment of the system according to this disclosure, the system further includes means for recycling the regenerated carbon dioxide absorbent solution regenerated in a high-pressure regenerator (57) or a low-pressure regenerator. As described above, such a system allows the regenerated carbon dioxide absorbent solution produced in step a) to be subsequently reused to absorb additional carbon dioxide in the carbon dioxide absorption unit (56). Thus, this system allows for a reduction in the amount of absorbent solution used to absorb a defined amount of carbon dioxide.

[0098] In one embodiment of the system according to the present disclosure, the system further includes means (62) for producing steam with an oxygen content ranging from 7 ppb to less than 20 ppb from an aqueous solution produced in a degasser (59), wherein the means (62) for producing steam is in direct fluid communication with the degasser (59).

[0099] Reference Figure 2 In one embodiment of the system according to this disclosure, the system is: a front end of an ammonia production unit (71) or a hydrogen production section, and further includes a desulfurization unit (11) for desulfurizing the natural gas feed; a primary reformer (19) for converting a substantially sulfur-free natural gas feed into a mixture of carbon monoxide and hydrogen; optionally, a secondary reformer (53) for improving the conversion rate of the substantially sulfur-free natural gas feed to the mixture of carbon monoxide and hydrogen achieved in the primary reformer (19); and a conversion unit (24) for converting the mixture of carbon monoxide and hydrogen produced in the primary reformer (19) or optionally in the secondary reformer (53) into a mixture of carbon monoxide and hydrogen. The conversion unit (32) is used to convert the remaining carbon monoxide and carbon dioxide into methane. The desulfurization unit (11) is in direct fluid communication with the primary converter (19). The primary converter (19) is in direct fluid communication with the shift unit (24) in the absence of the secondary converter (53) and in the presence of the secondary converter (53). When the secondary converter (53) is present, the secondary converter is in direct fluid communication with the shift unit (24). The shift unit (24) is in direct fluid communication with the carbon dioxide absorption unit (56). The methanation unit (32) is in direct fluid communication with the shift unit (24).

[0100] Therefore, this disclosure provides not only a carbon dioxide removal unit (28), but also a "front end" (i.e., hydrogen production section) of an ammonia production system.

[0101] In one embodiment of the system according to the present disclosure, the system further includes an ammonia synthesis tower (36) in direct fluid communication with the methanation unit (32).

[0102] Therefore, this disclosure not only provides a decarbonization unit (28) and a "front end" (i.e., a hydrogen production section) of an ammonia production system, but also provides an ammonia synthesis tower for the reaction of produced hydrogen with nitrogen in the ammonia synthesis tower. Thus, ammonia can be produced from the decarbonization unit (28) while saving energy.

[0103] In another aspect of this disclosure, the use of the system for recovering heat disclosed herein for performing the method for recovering heat disclosed herein is disclosed.

[0104] Reference Figure 1 In another aspect of this disclosure, a method is disclosed for converting an existing system comprising: a process condensate stripper (63) for stripping condensate produced by a steam reboiler (58), the steam reboiler including an inlet (65) and an outlet (66) in direct fluid communication with an outlet (61) of the steam reboiler (58); a water demineralization unit (64) including an inlet (67) and an outlet (68) in direct fluid communication with an outlet (66) of the process condensate stripper (63); and a method for producing low oxygen content... A degasser (59) for an aqueous solution of 20 ppb, comprising an inlet (69) and an outlet (70) in direct fluid communication with the outlet (68) of a water demineralization unit (64); a decarbonation unit (28) comprising a carbon dioxide absorption unit (56); a high-pressure regenerator (57) for regenerating a carbon dioxide absorption solution containing absorbed carbon dioxide; and a steam reboiler (58) comprising an inlet (60) and an outlet (61) for supplying heat (57) to the high-pressure regenerator to produce steam condensate and a regenerated carbon dioxide absorption solution.

[0105] The method for modification includes the following steps: (I) fluidly disconnecting the outlet (61) of the steam reboiler (58) from the inlet (65) of the process condensate stripper (63); (II) fluidly disconnecting the inlet (67) of the water demineralization unit (64) from the outlet (66) of the process condensate stripper (63); and (III) fluidly connecting the outlet (61) of the steam reboiler (58) to the inlet (69) of the degasser (59).

[0106] By implementing this modification method, a system based on the prior art can be converted into a system disclosed in this disclosure, thereby removing the process condensate stripper (63) and the water demineralization unit (64), as described in connection with the system of this disclosure. As a result, the equipment in the process is greatly simplified, the system footprint is greatly reduced, and thus the costs associated with the system are reduced.

Claims

1. A method for treating substances ranging from 1.0 to 1.2 kg / cm³ 2 A method for regenerating a carbon dioxide absorbent solution using vapor condensate generated by a high-pressure regenerator (57) operating under pressure, the method comprising the following steps: a) Carbon dioxide is captured in the carbon dioxide absorption unit (56) using a carbon dioxide absorption solution; b) Feeding the absorbed carbon dioxide and the carbon dioxide absorption solution generated in step a) into the high-pressure regenerator (57) of the heat exchange system, the heat exchange system comprising: the high-pressure regenerator (57) containing the solution to be regenerated and a steam reboiler (58); and c) The range is 3.2 to 3.5 kg / cm² 2 Low-pressure steam is supplied to a steam reboiler (58) under pressure to supply heat to the high-pressure regenerator (57), wherein the carbon dioxide absorbent containing absorbed carbon dioxide is heated by heat exchange between the steam and the carbon dioxide absorbent containing absorbed carbon dioxide, thereby producing steam condensate and regenerated carbon dioxide absorbent; wherein the regenerated carbon dioxide absorbent leaving the high-pressure regenerator is further processed in a low-pressure regenerator operating at a pressure below 0.2 kg / cm². The method further includes the following steps: d) The steam condensate produced in step c) is directly supplied to the degasser (59) to produce an aqueous solution suitable for producing steam with an oxygen content of less than 20 ppb.

2. The method according to claim 1, wherein the aqueous solution suitable for producing steam has an oxygen content ranging from 7 ppb to less than 20 ppb.

3. The method according to any one of claims 1 to 2, further comprising the following steps: e) The regenerated carbon dioxide absorption solution produced in step c) is reused to absorb additional carbon dioxide in the carbon dioxide absorption unit (56).

4. The method according to any one of claims 1 to 2, further comprising the following steps: f) Producing steam from the aqueous solution produced in step d).

5. The method according to any one of claims 1 to 2, wherein the carbon dioxide absorption solution comprises 30% potassium carbonate, optionally partially or completely converted to potassium bicarbonate.

6. The method according to claim 5, wherein the carbon dioxide absorption solution comprises 30% potassium carbonate, 5% potassium bicarbonate, 0.5% diethanolamine and 0.5% glycine.

7. The method according to any one of claims 1 to 2, further comprising the following steps: g) Desulfurize the natural gas feed in the desulfurization unit (11) for use as a feed for producing essentially sulfur-free natural gas; h) In a primary converter (19), steam is used to convert the feed of the substantially sulfur-free natural gas obtained in step g) into a mixture of carbon monoxide and hydrogen; i) Optionally, in the two-stage converter (53), oxygen is used to increase the conversion rate of the substantially sulfur-free natural gas feed to a mixture of carbon monoxide and hydrogen achieved in step h) in the one-stage converter (19); j) In the conversion unit (24), the mixture of carbon monoxide and hydrogen obtained in step h) or optionally in step i) is converted into a mixture of carbon dioxide and hydrogen; k) The gaseous mixture of carbon dioxide and hydrogen generated in step j) is fed into the carbon dioxide absorption unit (56) to produce hydrogen that is substantially free of carbon dioxide; as well as l) The hydrogen produced in step k) is fed into the methanation unit (32) to convert the remaining carbon monoxide and carbon dioxide into methane.

8. The method of claim 7, further comprising the following steps: m) The mixture of hydrogen and methane obtained in step l) is fed into the ammonia synthesis tower (36).

9. A system for treating vapor condensate generated by a high-pressure regenerator for regenerating a carbon dioxide absorbent solution, the system comprising: A carbon dioxide removal unit (28) comprising: Carbon dioxide absorption unit (56); A heat exchange system comprising: a high-pressure regenerator (57) containing the solution to be regenerated and a steam reboiler (58) for exchanging heat between steam in the steam reboiler (58) and the carbon dioxide absorption solution containing absorbed carbon dioxide in the high-pressure regenerator (57). Low-voltage regenerator; and A degasser (59) for producing aqueous solutions with an oxygen content of less than 20 ppb, the degasser comprising a first inlet (69) and a first outlet (70), The high-pressure regenerator (57) described therein has a voltage range of 1.0 to 1.2 kg / cm². 2 It can be operated under pressure to regenerate carbon dioxide absorption solutions containing absorbed carbon dioxide; The low-pressure regenerator operates at a pressure below 0.2 kg / cm² to process the regenerated carbon dioxide exiting the high-pressure regenerator (57); The steam reboiler (58) described herein includes components for operating at pressures ranging from 3.2 to 3.5 kg / cm³. 2 A second inlet (60) for supplying low-pressure steam to the high-pressure regenerator (57) under pressure, and a second outlet (61) for steam condensate, the steam condensate being produced through heat exchange between steam in the steam reboiler and the high-pressure regenerator; and The first inlet (69) of the degasser (59) is in direct fluid communication with the second outlet (61) of the steam reboiler (58).

10. The system of claim 9, further comprising: A device for recycling the regenerated carbon dioxide absorbent solution that has been regenerated in the high-pressure regenerator (57).

11. The system according to any one of claims 9 to 10, further comprising: An apparatus (62) for producing steam with an oxygen content ranging from 7 ppb to less than 20 ppb from the aqueous solution produced in the degasser (59), wherein the apparatus (62) for producing steam is in direct fluid communication with the degasser (59).

12. The system according to any one of claims 9 to 10, wherein the system is a hydrogen production section of an ammonia production unit (71), further comprising: A desulfurization unit (11) is used to desulfurize the natural gas feed; A first-stage converter (19) is used to convert a feed of essentially sulfur-free natural gas into a mixture of carbon monoxide and hydrogen; Optionally, a second-stage converter (53) is used to improve the conversion rate of the feed of the substantially sulfur-free natural gas to a mixture of carbon monoxide and hydrogen, which is achieved in the first-stage converter (19); as well as A conversion unit (24) is used to convert the mixture of carbon monoxide and hydrogen produced in the first-stage converter (19) or optionally in the second-stage converter (53); as well as Methanation unit (32) is used to convert the remaining carbon monoxide and carbon dioxide into methane; in: The desulfurization unit (11) is in direct fluid communication with the first-stage converter (19); The first-stage converter (19) is in direct fluid communication with the conversion unit (24) in the absence of the second-stage converter (53), and is in direct fluid communication with the second-stage converter (53) in the presence of the second-stage converter (53); The two-stage converter (53), when present, is in direct fluid communication with the conversion unit (24); and The conversion unit (24) is in direct fluid communication with the carbon dioxide absorption unit (56); and The methanation unit (32) is in direct fluid communication with the conversion unit (24).

13. The system according to claim 12, further comprising an ammonia synthesis tower (36) in direct fluid communication with the methanation unit (32).

14. Use of the system for recovering heat according to any one of claims 9 to 13 in performing the method for recovering heat according to any one of claims 1 to 7.

15. An existing system for recovering heat, comprising: A carbon dioxide removal unit (28) comprising: Carbon dioxide absorption unit (56); A heat exchange system comprising: a high-pressure regenerator (57) for regenerating a carbon dioxide absorbent solution containing absorbed carbon dioxide; and a steam reboiler (58) comprising a second inlet (60) and a second outlet (61) for exchanging heat between steam in the steam reboiler (58) and the carbon dioxide absorbent solution containing absorbed carbon dioxide in the high-pressure regenerator (57) to produce steam condensate and regenerated carbon dioxide absorbent solution. A low-pressure regenerator, operable at pressures below 0.2 kg / cm², is used for further processing of the regenerated carbon dioxide absorption solution exiting the high-pressure regenerator; A process condensate stripper (63) for stripping the condensate produced by the steam reboiler (58), the process condensate stripper including a third inlet (65) and a third outlet (66) in direct fluid communication with the second outlet (61) of the steam reboiler (58). A water-based mineralization unit (64) comprising a fourth inlet (67) and a fourth outlet (68) in direct fluid communication with the third outlet (66) of the process condensate stripper (63); and A degasser (59) for producing an aqueous solution with an oxygen content of less than 5 ppm, particularly less than 20 ppb, the degasser comprising a first inlet (69) and a first outlet (70) in direct fluid communication with the fourth outlet (68) of the water demineralization unit (64); A method for modifying a system according to any one of claims 8 to 13, the method comprising the following steps: (I) Fluidly disconnect the connection between the second outlet (61) of the steam reboiler (58) and the third inlet (65) of the process condensate stripper (63); (II) Fluidly disconnect the fourth inlet (67) of the water demineralization unit (64) from the third outlet (66) of the process condensate stripper (63); and (III) Connect the second outlet (61) of the steam reboiler (58) to the first inlet (69) of the degasser (59) in fluid.

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