CN-116917022-B - Method and system for treating a vapor condensate generated by a high pressure generator of a carbon dioxide absorbing solution

CN116917022BCN 116917022 BCN116917022 BCN 116917022BCN-116917022-B

Abstract

The present disclosure relates to a method for treating steam condensate generated by a high pressure regenerator (57) operating at a pressure in the range of 1.0 to 1.2kg/cm 2 for regenerating a carbon dioxide absorbing solution. The method comprises the steps of a) capturing carbon dioxide in a carbon dioxide absorption (56) unit using a carbon dioxide absorption solution, b) feeding the carbon dioxide absorption solution comprising absorbed carbon dioxide and generated in step a) to a high pressure regenerator (57), and c) supplying low pressure steam to a steam reboiler (58) at a pressure in the range of 3.2 to 3.5kg/cm 2 for supplying heat to the high pressure regenerator (57) for producing steam condensate and regenerated carbon dioxide absorption solution, and is characterized by further comprising the step of d) supplying the steam condensate produced in step c) to a deaerator (59) for producing an aqueous solution suitable for producing steam having an oxygen content in the range of 7ppb to less than 20 ppb. The present disclosure further relates to a system for performing the method of the present disclosure and to the use of the system in performing the method of the present disclosure. The present disclosure further relates to a method for retrofitting a system further comprising a process condensate stripper and a water demineralization unit to the disclosed system.

Inventors

Udapal Singh

Assignees

亚拉国际有限公司

Dates

Publication Date: 20260508
Application Date: 20220302
Priority Date: 20210506

Claims (15)

1. A method for treating steam condensate generated by a high pressure regenerator (57) operating at a pressure in the range of 1.0 to 1.2 kg/cm 2 for regenerating a carbon dioxide absorbing solution, the method comprising the steps of: a) Capturing carbon dioxide in a carbon dioxide absorbing unit (56) using a carbon dioxide absorbing solution; b) Feeding the high pressure regenerator (57) comprising absorbed carbon dioxide and the carbon dioxide absorbing solution produced in step a) to a heat exchange system comprising the high pressure regenerator (57) comprising the solution to be regenerated and a steam reboiler (58), and C) Supplying low pressure steam to a steam reboiler (58) at a pressure in the range of 3.2 to 3.5 kg/cm 2 for supplying heat to the high pressure regenerator (57), wherein in the steam reboiler the carbon dioxide absorbing solution comprising absorbed carbon dioxide is heated by exchange of heat by the steam with the carbon dioxide absorbing solution comprising absorbed carbon dioxide, thereby producing steam condensate and a regenerated carbon dioxide absorbing solution, wherein the regenerated carbon dioxide absorbing solution leaving the high pressure regenerator is further treated in a low pressure regenerator operating at a pressure below 0.2 kg/cm 2; Wherein the method further comprises the steps of: d) The steam condensate produced in step c) is directly supplied to a deaerator (59) to produce an aqueous solution suitable for producing steam having an oxygen content of less than 20 ppb.
2. The method of claim 1, wherein the aqueous solution suitable for producing steam has an oxygen content ranging from 7ppb to less than 20 ppb.
3. The method according to any one of claims 1 to 2, further comprising the step of: e) Reusing the regenerated carbon dioxide absorbing solution produced in step c) for absorbing additional carbon dioxide in the carbon dioxide absorbing unit (56).
4. The method according to any one of claims 1 to 2, further comprising the step of: 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 absorbing solution comprises 30% potassium carbonate, optionally partially or fully converted to potassium bicarbonate.
6. The method of claim 5, wherein the carbon dioxide absorbing 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 step of: g) Desulfurizing in a desulfurization unit (11) from a feed of natural gas for producing a feed of natural gas substantially free of sulfur; h) Converting the essentially 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 two-stage reformer (53), oxygen is used to increase the conversion of the essentially sulfur-free natural gas feed in step h) to a mixture of carbon monoxide and hydrogen effected in the one-stage reformer (19); j) Converting the mixture of carbon monoxide and hydrogen obtained in step h) or optionally in step i) into a mixture of carbon dioxide and hydrogen in a shift unit (24); k) Feeding the gaseous mixture of carbon dioxide and hydrogen produced in step j) to the carbon dioxide absorption unit (56) to produce hydrogen substantially free of carbon dioxide, and L) feeding said hydrogen produced in step k) to a methanation unit (32) for converting the remaining amounts of carbon monoxide and carbon dioxide into methane.
8. The method of claim 7, further comprising the step of: m) feeding the mixture of hydrogen and methane obtained from step l) to an ammonia synthesis column (36).
9. A system for treating steam condensate generated by a high pressure regenerator for regenerating a carbon dioxide absorbing solution, the system comprising: a decarbonation unit (28) comprising: A 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 of steam in the steam reboiler (58) with the carbon dioxide absorbing solution containing absorbed carbon dioxide in the high pressure regenerator (57); Low pressure regenerator, and A deaerator (59) for producing an aqueous solution having an oxygen content of less than 20 ppb, said deaerator comprising a first inlet (69) and a first outlet (70), Wherein the high pressure regenerator (57) is operable at a pressure in the range of 1.0 to 1.2 kg/cm 2 for regenerating a carbon dioxide absorbing solution comprising absorbed carbon dioxide; Wherein the low pressure regenerator is operated at a pressure of less than 0.2 kg/cm2 for treating regenerated carbon dioxide exiting the high pressure regenerator (57); Wherein the steam reboiler (58) comprises a second inlet (60) for supplying low pressure steam to the high pressure regenerator (57) at a pressure in the range of 3.2 to 3.5 kg/cm 2 and a second outlet (61) for steam condensate produced by heat exchange of steam in the steam reboiler with the high pressure regenerator, and Wherein the first inlet (69) of the deaerator (59) is in direct fluid communication with the second outlet (61) of the steam reboiler (58).
10. The system of claim 9, further comprising means for recycling regenerated carbon dioxide absorbing solution regenerated in the high pressure regenerator (57).
11. The system according to any one of claims 9 to 10, further comprising means (62) for producing steam having an oxygen content ranging from 7 ppb to less than 20 ppb from the aqueous solution produced in the deaerator (59), wherein means (62) for producing steam is in direct fluid communication with the deaerator (59).
12. The system of any of claims 9 to 10, wherein the system is a hydrogen production portion of an ammonia production unit (71), further comprising: A desulfurization unit (11) for desulfurizing from a feed of natural gas; a primary reformer (19) for converting a feed of substantially sulfur-free natural gas into a mixture of carbon monoxide and hydrogen; optionally, a two-stage reformer (53) for increasing the conversion of the essentially sulfur-free natural gas feed to a mixture of carbon monoxide and hydrogen effected in the one-stage reformer (19), and A shift unit (24) for shifting the mixture of carbon monoxide and hydrogen produced in the primary reformer (19) or optionally in the secondary reformer (53), and A methanation unit (32) for converting the remaining amounts of carbon monoxide and carbon dioxide into methane; Wherein: -said desulfurization unit (11) is in direct fluid communication with said primary reformer (19); The primary reformer (19) is in direct fluid communication with the shift unit (24) in the absence of a secondary reformer (53) and in direct fluid communication with the secondary reformer in the presence of a secondary reformer (53); the two-stage reformer (53), when present, is in direct fluid communication with the shift unit (24), and The shift 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 shift unit (24).
13. The system of claim 12, further comprising an ammonia synthesis column (36) in direct fluid communication with the methanation unit (32).
14. Use of the system according to any one of claims 9 to 13 for recovering heat in performing the method according to any one of claims 1 to 7 for recovering heat.
15. An existing system for recovering heat would include the following: a decarbonation unit (28) comprising: A carbon dioxide absorption unit (56); A heat exchange system comprising a high pressure regenerator (57) for regenerating a carbon dioxide absorbing solution comprising absorbed carbon dioxide, and a steam reboiler (58) comprising a second inlet (60) and a second outlet (61) for exchanging heat of steam in the steam reboiler (58) with the carbon dioxide absorbing solution comprising absorbed carbon dioxide in the high pressure regenerator (57) to produce a steam condensate and a regenerated carbon dioxide absorbing solution; a low pressure regenerator operable at a pressure of less than 0.2 kg/cm2 for further processing the regenerated carbon dioxide absorbing 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 comprising 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 demineralization 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 deaerator (59) for producing an aqueous solution having an oxygen content of less than 5ppm, in particular less than 20 ppb, said deaerator comprising a first inlet (69) in direct fluid communication with the fourth outlet (68) of the water demineralization unit (64) and a first outlet (70); A method retrofitted into a system according to any of claims 8 to 13, said method comprising the steps of: (I) Fluidly disconnecting the second outlet (61) of the steam reboiler (58) from the third inlet (65) of the process condensate stripper (63); (II) fluidly disconnecting the fourth inlet (67) of the water demineralization unit (64) from the third outlet (66) of the process condensate stripper (63), and (III) fluidly connecting the second outlet (61) of the steam reboiler (58) with the first inlet (69) of the deaerator (59).

Description

Method and system for treating a vapor condensate generated by a high pressure generator of a carbon dioxide absorbing solution Technical Field The present disclosure relates to a method and system for carbon dioxide absorption, and more particularly, to a method and system for treating steam condensate generated by a high pressure generator for regeneration of a carbon dioxide absorption solution. Background Carbon dioxide has many uses. For example, carbon dioxide is used for the production of urea, for 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 the treatment of industrial waste and process water as a substitute for sulfuric acid to control pH levels. Other uses include drinking water treatment, environmentally friendly pesticides and air additives in greenhouses for promoting vegetable growth. Generally, carbon dioxide is produced by purifying a waste stream that is a byproduct of an organic or inorganic chemical process. The waste stream containing high concentrations of carbon dioxide is subjected to multiple stages of condensation and purification, and then distilled to produce product grade carbon dioxide. The increase in carbon dioxide concentration in the feed may be performed in a number of ways. A particularly preferred method is to chemisorb carbon dioxide from the crude carbon dioxide feed into an alkanolamine based absorbent. The resulting carbon dioxide loaded absorbent is then subjected to separation into a carbon dioxide product for recovery and an alkanolamine-containing absorbent, which may be recycled within the recovery system for reuse. Recovery of carbon dioxide is particularly important in ammonia processes for separating hydrogen from carbon dioxide, in which the mixture of hydrogen and carbon dioxide produced by the shift unit, hydrogen cannot be used in an ammonia synthesis column for ammonia production unless it is substantially free of carbon dioxide. In GB996543a it is described how a gas containing carbon dioxide is scrubbed with an aqueous solution of alkanolamine in a column (18), wherein the solution having absorbed carbon dioxide is discharged from the column (18) and regenerated in a column (32), indirectly heated by the steam of a waste heat boiler (2) and stripped by the steam of a waste heat boiler (9). In DE102018210921A1 a unit and a related process for producing synthesis gas containing hydrogen is described, which comprises at least (a) a reformer (1), (b) a carbon monoxide (CO) synthesis column (2), (c) a synthesis gas condenser (4), (d) a scrubber unit (3) with regenerated carbon dioxide (CO 2), characterized in that the synthesis gas condenser (4) is connected to a deaerator (5) and that the deaerator (5) is connected to a reformer burner (6) and/or a combustion-assisted steam boiler (7). In CN107866134a, it is disclosed to provide heat to a regenerator operating under reflux conditions of the solution to be regenerated, and also to heat the solution to be treated in the regenerator with rich and lean liquids and also with heat from the CO 2/steam mixture produced in the regenerator. In addition, the steam condensate after heat is supplied to the regenerator is heated by the steam. The prior art thus describes the regeneration of carbon dioxide absorbing solutions by heating with steam and condensation of synthesis gas and subsequent treatment in deaerators. The prior art does not provide any teaching as to how to treat condensate from steam used to regenerate a solution that has absorbed carbon dioxide. The regeneration of the steam for regenerating the solution having absorbed carbon dioxide is important from the point of view of energy recovery and should be performed in an energy-saving manner. At the same time, the process condensate resulting from the use of steam should be treated and used in this way for regenerating steam, the equipment in the unit not being corroded. The present 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 equipment in the unit is not corroded. Disclosure of Invention In one aspect of the present disclosure, a method for treating steam condensate generated by a high pressure regenerator operating at a pressure in the range of 1.0 to 1.2kg/cm2 for regenerating a carbon dioxide absorbing solution is disclosed. The method comprises the following steps: a) Capturing carbon dioxide in a carbon dioxide absorbing unit using a carbon dioxide absorbing solution; b) Feeding an absorption solution comprising absorbed carbon dioxide and carbon dioxide generated in step a) to a high pressure regenerator, and C) Supplying low pressure steam to a steam reboiler at a pressure in the range of 3.2 to 3.5kg/cm 2 for supplying heat to a high pressure regenerator to produc