ARGON AND POWER PRODUCTION BY INTEGRATION WITH POWER PLANT

Abstract

A method for producing power and argon is provided by providing a residual gas stream, purifying the residual gas stream in a front-end purification unit to remove carbon dioxide, thereby forming a purified residual gas stream, and introducing the purified residual gas stream to a cold box, wherein the purified residual gas stream is cooled and expanded within the cold box to produce power and then fed to a distillation column system for separation therein, thereby forming an argon-enriched stream and optionally a nitrogen-enriched stream and/or an oxygen-enriched stream, wherein the residual gas stream is sourced from a retentate stream of a cold membrane having oxygen, nitrogen, carbon dioxide, and argon.

Claims

1. A method for producing power and argon, the method comprising the steps of: providing a residual gas stream, wherein the residual gas stream is sourced from a retentate stream of a cold membrane, wherein the residual gas stream comprises nitrogen, argon, oxygen, and carbon dioxide; purifying the residual gas stream in a front-end purification unit to remove carbon dioxide, thereby forming a purified residual gas stream; and introducing the purified residual gas stream to a cold box, wherein the purified residual gas stream is cooled and expanded within the cold box and then fed to a distillation column system for separation therein, thereby forming an argon-enriched stream, wherein the purified residual gas stream is expanded in at least one turbine that is configured to produce power.

2. The method of claim 1, wherein the residual gas stream is derived from a flue gas stream from a power plant.

3. The method of claim 1, wherein the at least one turbine comprises a warm turbine, wherein the step of introducing the purified residual gas stream to a cold box further comprises expanding the purified residual gas stream in the warm turbine prior to cooling in a heat exchanger.

4. The method of claim 3, wherein the step of introducing the purified residual gas stream to a cold box further comprises, after expanding in the warm expander, fully cooling a first portion of the purified residual gas stream in the heat exchanger before subsequently expanding said first portion in a Joule-Thompson valve prior to feeding the first portion to the distillation column system.

5. The method of claim 3, wherein the at least one turbine further comprises a cold turbine, wherein the step of introducing the purified residual gas stream to a cold box further comprises, after expanding in the warm expander, partially cooling a second portion of the purified residual gas stream in the heat exchanger and then cold expanding said second portion in the cold turbine prior to feeding the second portion to the distillation column system.

6. The method of claim 3, wherein the method further comprises: withdrawing a nitrogen-enriched stream and an oxygen-enriched stream from the distillation column system; and warming the nitrogen-enriched stream and the oxygen-enriched stream in the heat exchanger.

7. The method of claim 6, further comprising regenerating the front-end purification unit using a stream selected from the group consisting of the nitrogen-enriched stream, the oxygen-enriched stream, and combinations thereof.

8. The method of claim 1, wherein the argon-enriched stream is produced in a net positive energy environment, such that more electricity is produced than is consumed.

9. The method of claim 1, wherein the residual gas stream is at a pressure above 13 bara.

10. The method of claim 1, wherein the method comprises an absence of providing external refrigeration such that the separation of nitrogen, oxygen, and argon within the distillation column system is effected without cooling other than that provided by the expansion of streams derived from the residual gas stream.

11. A method for producing power and argon, the method comprising the steps of: providing a residual gas stream, wherein the residual gas stream is sourced from a retentate stream of a cold membrane, wherein the residual gas stream comprises nitrogen, argon, oxygen, and carbon dioxide, wherein the residual gas stream is derived from a flue gas stream from a power plant; purifying the residual gas stream in a front-end purification unit to remove carbon dioxide, thereby forming a purified residual gas stream; expanding the purified residual gas stream in a warm turbine to produce an expanded purified residual gas stream and export power; introducing the expanded purified residual gas stream to a heat exchanger; fully cooling a first portion of the expanded purified residual gas stream in the heat exchanger before subsequently expanding said first portion in a Joule-Thompson valve prior to feeding the first portion to a distillation column system for separation therein; partially cooling a second portion of the purified residual gas stream in the heat exchanger and then cold expanding said second portion in a cold turbine prior to feeding the second portion to the distillation column system, wherein the cold turbine produces a second amount of export power; and withdrawing a nitrogen-enriched stream, an oxygen-enriched stream, and an argon-enriched stream from the distillation column system.

12. The method of claim 11, further comprising regenerating the front-end purification unit using a stream selected from the group consisting of the nitrogen-enriched stream, the oxygen-enriched stream, and combinations thereof.

13. The method of claim 11, wherein the method comprises an absence of providing external refrigeration such that the separation of nitrogen, oxygen, and argon within the distillation column system is effected without cooling other than that provided by the expansion of streams derived from the residual gas stream.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

[0026] FIG. 1 is a process flow diagram of an existing power plant and carbon dioxide cold capture; and

[0027] FIG. 2 is a process flow diagram of an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0028] Referring to FIG. 2, pressurized residue stream 10, which contains nitrogen, oxygen, argon, and carbon dioxide and is preferably at a pressure of at least 15 bara, is sent to front-end purification unit 30 to remove components such as carbon dioxide that would freeze at cryogenic temperatures (e.g., below −40° C.). Purified stream 32 is then expanded to a medium pressure, for example, about 9 bara, in warm expander 40 to form expanded stream 42. The expanded stream 42 is then cooled in heat exchanger 50, wherein it is preferably split into two streams, with first portion 52 being fully cooled and then expanded in valve 55 prior to being introduced to distillation column system 70 for separation therein. Second portion 54 is only partially cooled before expanding to a low pressure in cold expander 60 to form cold expanded stream 56, which is also introduced in the distillation column system 70 for separation therein. The expansion provides the majority of the refrigeration for the cold separation within the distillation column system 70.

[0029] Oxygen 74 and nitrogen 76 are produced by distillation column system 70 and heated in heat exchanger 50. In addition to collection as product streams, oxygen 74 and/or nitrogen 76 can be used as regeneration gases in front-end purification unit 30, with the regenerated gas 34, which now contains the desorbed carbon dioxide, being sent back to the flue gas vent stack.

[0030] Argon product 72 is recovered from distillation column system.

WORKING EXAMPLE

[0031] A simulation was run using the embodiment shown in FIG. 2. 456 mt/h of pressurized residue stream 10 containing 93.7% nitrogen, 3.3% oxygen, 1.1% argon, and 1.9% CO2 and at 15 bara was expanded to 9 bara in warm expander 40. The second portion 54 was expanded to about 6 to 7 bara pressure. Approximately 165 mtpd liquid argon 72 was produced, while the two turbines also generated a combined 4.7 MW power (4 MW and 0.7 MW, respectively).

[0032] Consequently, embodiments of the current invention allow a user to utilize the pressurized residue stream of a cold membrane separator to produce both power and valuable argon.

[0033] Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

[0034] The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step or reversed in order.

[0035] The singular forms “a”, “an” and “the” include plural referents, unless the context clearly dictates otherwise.

[0036] “Comprising” in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing (i.e., anything else may be additionally included and remain within the scope of “comprising”). “Comprising” as used herein may be replaced by the more limited transitional terms “consisting essentially of” and “consisting of” unless otherwise indicated herein.

[0037] “Providing” in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary a range is expressed, it is to be understood that another embodiment is from the one.

[0038] Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

[0039] Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such particular value and/or to the other particular value, along with all combinations within said range.

[0040] All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited.