High efficiency oxygen/air separation system

• US 5,706,675 A
• Filed: 08/18/1995
• Issued: 01/13/1998
• Est. Priority Date: 08/18/1995
• Status: Expired due to Fees

• Current Assignee: G & A Associates
• Original Assignee: G & A Associates
• Inventors: Manikowski, Ambrose F. Jr.
• Primary Examiner(s): KILNER, CHRISTOPHER B
• Application Number:
  US08/516,554
• Time in Patent Office: 879 Days
• Field of Search: 62/645, 62/902, 62/903, 62/939, 62/940, 62/911, 62/904
• US Class Current: 62/645
• CPC Class Codes: F25J 2240/80 Hot exhaust gas turbine combustion engine
• CPC Class Codes: F25J 2245/02 Recycle of a stream in general, e.g. a by-pass stream
• CPC Class Codes: F25J 2280/02 Control in general, load changes, different modes ("runs"), measurements
• CPC Class Codes: F25J 2290/10 Mathematical formulae, modeling, plot or curves; Design methods
• CPC Class Codes: F25J 2290/42 Modularity, pre-fabrication of modules, assembling and erection, horizontal layout, i.e. plot plan, and vertical arrangement of parts of the cryogenic unit, e.g. of the cold box
• CPC Class Codes: F25J 2290/44 Particular materials used, e.g. copper, steel or alloys thereof or surface treatments used, e.g. enhanced surface
• CPC Class Codes: F25J 3/04018 of main feed air
• CPC Class Codes: F25J 3/0406 of nitrogen
• CPC Class Codes: F25J 3/0409 of oxygen
• CPC Class Codes: F25J 3/04115 characterised by the type of prime driver, e.g. hot gas expander
• CPC Class Codes: F25J 3/04127 Gas turbine as the prime mechanical driver
• CPC Class Codes: F25J 3/04139 Combination of different types of drivers mechanically coupled to the same compressor, possibly split on multiple compressor casings
• CPC Class Codes: F25J 3/04296 Claude expansion, i.e. expanded into the main or high pressure column
• CPC Class Codes: F25J 3/04381 using work extraction by mechanical coupling of compression and expansion so-called companders
• CPC Class Codes: F25J 3/044 using a single pressure main column system only F25J3/0446, F25J3/04624, F25J3/04636 take precedence
• CPC Class Codes: F25J 3/04533 for the direct combustion of fuels in a power plant, so-called "oxyfuel combustion"
• CPC Class Codes: F25J 3/04581 Hot gas expansion of indirect heated nitrogen
• CPC Class Codes: F25J 3/04612 Heat exchange integration with process streams, e.g. from the air gas consuming unit
• CPC Class Codes: F25J 3/04618 for cooling an air stream fed to the air fractionation unit
• CPC Class Codes: F25J 3/04872 Vertical layout of cold equipments within in the cold box, e.g. columns, heat exchangers etc.
• CPC Class Codes: F25J 3/04969 : Retrofitting or revamping of an existing air fractionation unit
• CPC Class Codes: F25J 3/04975 : adapted for special use of the air fractionation unit, e.g. transportable devices by truck or small scale use
• CPC Class Codes: F25J 5/002 : for continuously recuperating cold, i.e. in a so-called recuperative heat exchanger
• CPC Class Codes: Y10S 62/903 : Heat exchange structure
• CPC Class Codes: Y10S 62/904 : Coiled heat exchanger
• CPC Class Codes: Y10S 62/911 : Portable

Abstract

A high efficiency oxygen/air separation system uses waste heat produced by an internal combustion engine to produce pure or enriched oxygen for combustion in the internal combustion engine. Nitrogen is eliminated from the combustion process, thus preventing the formation of nitrogen oxides. The formation of other particulates is also reduced as the exhaust gases are repeatedly burned. The separation system includes a manifold heat exchanger, a vane compressor/expander, a spent nitrogen heat exchanger and an insulated container. Air is first compressed in the integrated vane compressor/expander. Compression energy is provided from the expansion of the spent nitrogen after that nitrogen has been heated to exhaust manifold temperatures. High efficiency is achieved through simultaneous expansion and compression. The compressed air is cooled through a spent nitrogen heat exchanger and enters the insulated container, where the oxygen separation takes place. The insulated container includes a regenerative heat exchanger, an expander and a separator column. The compressed air is delivered to the regenerative heat exchanger and is cooled by the separated gas streams that include a mixture of (1) oxygen/argon and (2) nitrogen. The cooled air stream is expanded in the expander where oxygen/argon condenses in the gas stream. The expanded air stream is delivered to a separation column which separates the liquid oxygen/argon mixture from the nitrogen gas by gravity. Nitrogen gas is released and the liquid oxygen/argon mix is returned to the regenerative heat exchanger to cool the incoming compressed air.

Claims

1. An oxygen/air separation apparatus comprising a first compressor/expander, a first heat exchanger, a manifold heat exchanger and an insulated container, wherein the first compressor/expander compresses input air and expands high pressure, high temperature spent nitrogen from the manifold heat exchanger, wherein the first heat exchanger cools the compressed input air from the first compressor/expander and heats high pressure nitrogen from the insulated container, wherein the manifold heat exchanger heats the heated high pressure nitrogen from the first heat exchanger and cools engine exhaust, further comprising a second heat exchanger provided in the insulated container for further cooling the cooled, compressed input air from the first heat exchanger, a separator in the insulated container for separating the further cooled compressed input air into oxygen and nitrogen, and a second compressor in the insulated container for compressing the nitrogen to obtain said high pressure nitrogen.

2. The apparatus of claim 1, wherein the second heat exchanger is a regenerative heat exchanger, the second compressor is a second compressor/expander and the separator is a separator column, wherein the regenerative heat exchanger cools the cooled, compressed input air from the first heat exchanger, heats the liquified oxygen, and heats the high pressure nitrogen, wherein the second compressor/expander expands the cooled, compressed air from regenerative heat exchanger and compresses the separated nitrogen, and wherein the separator column separates the cooled, expanded air from the second compressor/expander into nitrogen and liquid oxygen components.

3. The apparatus of claim 2, wherein the regenerative heat exchanger has a spiral configuration that spirals around the separator column, the exchanger further comprising multiple sheets stacked and bonded together, each sheet having side walls and a groove milled between the side walls, the sheet spiralled such that small passages are formed between the walls of adjacent sections of the sheet as the sheet is spiralled, and an air tube positioned in the groove of the sheet between the side walls for carrying high pressure air.

4. The apparatus of claim 3, wherein the sheet is made of titanium, and wherein the tube is made of a material selected from the group consisting of titanium, stainless steel and aluminum.

5. The apparatus of claim 1, further comprising a power source connected to the first compressor/expander for supplementing the compression of the input air.

6. The apparatus of claim 2, further comprising a power source connected to the second compressor/expander for supplementing the compression of the nitrogen stream.

9. The apparatus of claim 1, further comprising a trap positioned after the first heat exchanger and prior to the insulated container for trapping water, carbon dioxide and other foreign material present in the cooled, compressed input air from the first heat exchanger.

7. An insulated container for separating oxygen from air comprising a regenerative heat exchanger, a compressor/expander and a separator column, wherein the regenerative heat exchanger cools compressed input air, heats liquified oxygen from the separator column, and heats high pressure nitrogen from the compressor/expander, wherein the compressor/expander expands the cooled, compressed air from regenerative heat exchanger and compresses separated nitrogen from the separator column, and wherein the separator column separates the cooled, expanded air from the compressor/expander into nitrogen gas and liquid oxygen components.

8. The apparatus of claim 7, wherein the regenerative heat exchanger has a spiral configuration that spirals around the separator column, the exchanger further comprising multiple sheets stacked and bonded together, each sheet having side walls and a groove milled between the side walls, the sheet spiralled such that small passages are formed between the walls of adjacent sections of the sheet as the sheet is spiralled, and an air tube positioned in the groove of the sheet between the side walls for carrying high pressure air.

10. A method for separating oxygen from air comprising the steps of inputting air to a compressor/expander, compressing the input air, cooling the compressed air from the compressor/expander in a heat exchanger, introducing the cooled air from the heat exchanger into an insulated container, separating oxygen from the air introduced into the container, releasing purified oxygen from the container, recycling warm nitrogen gas out from the insulated container, heating the warm nitrogen outside of the insulated container, expanding the heated nitrogen in the compressor/expander, and releasing the spent nitrogen.

11. The method of claim 10, wherein the step of heating the spent nitrogen outside of the insulated container further comprises running the warm nitrogen through the heat exchanger through which the compressed air from the compressor/expander is cooled.

12. The method of claim 10, further comprising the step of heating the heated nitrogen in a manifold heat exchanger prior to expanding the heated nitrogen.

13. The method of claim 12, wherein the step of heating the heated nitrogen in a manifold heat exchanger further comprises running a stream of exhaust through the manifold heat exchanger and cooling the exhaust.

14. The method of claim 12, further comprising applying a ceramic coating to a diesel engine combustion chamber for increasing a combustion temperature capability of the engine, thereby yielding two-fold improvements in thermal efficiency of the diesel engine and power out derived from expansion of spent nitrogen in the oxygen separator cycle, essentially eliminating a need to extract shaft power from the engine to drive the oxygen/air separation.

15. The method of claim 10, wherein the step of separating oxygen from the air introduced into the container further comprises cooling the introduced air in a regenerative heat exchanger, expanding the cooled air from the regenerative heat exchanger, separating liquid oxygen from nitrogen gas in the expanded air using a separator column, draining the liquid oxygen from the separator, heating the liquid oxygen from the separator in the regenerative heat expander, forming the purified oxygen, compressing the separated nitrogen gas, and heating the compressed nitrogen gas in the regenerative heat exchanger, forming warm nitrogen gas.

16. The method of claim 15, wherein the steps of compressing separated nitrogen gas and expanding the cooled air from the regenerative heat exchanger are simultaneously performed using an integrated compressor/expander such that the energy of expansion drives the compression.

17. The method of claim 10, further comprising trapping water, carbon dioxide or other foreign materials present in the cooled air delivered from the first heat exchanger prior to the introducing of the cooled air into the insulated container.

18. A method for separating oxygen from air comprising the steps of inputting air into an integrated compressor/expander, compressing the air to about 20 atmospheres, cooling the compressed air in a first heat exchanger to a temperature of about 300°

K, introducing the cooled air from a first heat exchanger into an insulated container, separating the oxygen from the air in the container, releasing separated oxygen gas from the insulated container at about 5 atmospheres and about 290°

K, releasing separated nitrogen gas from the insulated container at about 8-10 atmospheres and about 290°

K, heating the nitrogen gas in the first heat exchanger to about 600°

K, thereby facilitating the cooling of the compressed air, heating the nitrogen gas from the first heat exchanger in a second heat exchanger to 780°

K, expanding the heated nitrogen gas from the second heat exchanger to a pressure of 1 atmosphere, and driving the compressing of the input air using energy of expansion.

19. The method of claim 18, wherein the step of separating the oxygen from the air in the container further comprises cooling the introduced air in a regenerative heat exchanger to a cryogenic temperature of about 120°

K, compressing the cooled air from the regenerative heat exchanger to about 5 atmospheres, separating the air in a separator column such that liquid oxygen falls to a bottom of the separator column and nitrogen gas rests at a top of the separator column, heating the separated liquid oxygen to a gas at 410°

R, compressing the nitrogen gas to about 13 atmospheres, and heating the compressed nitrogen gas in the regenerative heat exchanger to about 410°

R.

20. The method of claim 19, wherein compressing the separated nitrogen gas and expanding the cooled air from the regenerative heat exchanger are simultaneously performed using an integrated compressor/expander such that the energy of expansion drives the compression.

21. The method of claim 19, wherein the step of compressing input air further comprises expanding the heated nitrogen from the second heat exchanger and driving compression of the input air using energy from expansion, the expanding and compressing being simultaneous steps performed using an integrated compressor/expander.

22. The method of claim 21, further comprising transferring shaft power from an engine to the compressor/expander for providing further power for compression.