WO2019102318A1

WO2019102318A1 - Integration of waste gas from nitrogen generation unit (ngu) with air separation unit (asu) through main air compressor

Info

Publication number: WO2019102318A1
Application number: PCT/IB2018/059013
Authority: WO
Inventors: Nayef Nazzal AL HUSSAINI; Hamad Mohammed MUDIJ
Original assignee: Sabic Global Technologies B.V.
Priority date: 2017-11-21
Filing date: 2018-11-15
Publication date: 2019-05-31

Abstract

A system and a method for utilizing a by-product of a nitrogen generation process for oxygen production are disclosed. The systems include an integrated nitrogen generation unit and an air separation unit. The method includes separating an air stream, in the nitrogen generation unit, into a nitrogen stream and an oxygen-enriched by-product stream. At least some of the oxygen-enriched by product stream is then fed to the air separation unit along with a second air stream. The combined oxygen-enriched by-product stream and the second air stream is then processed to produce high purity oxygen via the air separation unit.

Description

INTEGRATION OF WASTE GAS FROM NITROGEN GENERATION UNIT (NGU) WITH AIR SEPARATION UNIT (ASU) THROUGH MAIN AIR COMPRESSOR

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of U.S. Provisional Patent Application No. 62/589,482, filed November 21, 2017, which is hereby incorporated by reference in its entirety.

FIELD OF INVENTION

[0002] The present invention generally relates to oxygen production processes. More specifically, the present invention relates to systems and methods for increasing oxygen production by integrating a nitrogen generation unit and an air separation unit.

BACKGROUND OF THE W E M l ON

[0003] A large amount of high grade oxygen is consumed daily in key industries including the refining industry, the steel industry, the chemical industry, the medical industry and the semiconductor industry. As a supporter of combustion and an oxidizer, high concentration of oxygen can reduce fuel consumption rate and increase operating temperature for many industrial processes, thereby improving cost-benefit efficiency for these processes. Generally, high grade oxygen is produced by separation of atmospheric air using air separation units.

[0004] An air separation process typically uses pre-filtered atmospheric air as the feedstock. An air compression unit, often a multi-stage air compressor, compresses the filtered air to reduce the air volume and remove water from the air. The compressed air is further dried via molecular sieve. The dried compressed air can be subsequently liquefied to form liquid air, which is further distilled in a high pressure column and a low pressure column to produce other purified fractions of oxygen, nitrogen and argon. [0005] However, the air separation process is highly energy intensive, leading to high production cost to achieve oxygen with high purity. Furthermore, the production of high grade oxygen from the air separation process is relatively low as the air separation unit generally uses atmospheric air as the feedstock, which contains only about 21 wt.% of oxygen. Therefore, improvements in the field are desired. BRIEF SUMMARY OF THE INVENTION

[0006] A method has been discovered for utilizing a by-product stream from a nitrogen generation unit. The nitrogen generation unit is integrated with an air separation unit that processes atmospheric air. A by-product stream from the nitrogen generation unit is produced by separating the nitrogen from an air stream and flowing the leftover of the air stream as the by-product stream. Notably, the by-product stream has an elevated oxygen content. By feeding the by-product stream that contains primarily oxygen from the nitrogen generation unit and an air stream into the air separation unit, more oxygen can be produced in the cryogenic distillation of the air separation unit, thereby increasing the overall oxygen production and reducing the energy consumption for producing a unit of oxygen. Overall, the production cost of oxygen can be reduced significantly.

[0007] Embodiments of the invention include a method of utilizing a by-product of a nitrogen generation process. The method comprises flowing a first air stream to a nitrogen generation unit. The nitrogen generation unit is adapted for production of nitrogen. The method further includes generating, by the nitrogen generation unit, from the first air stream (1) a first product stream comprising primarily nitrogen and (2) a second product stream comprising primarily oxygen. The method further comprises flowing a second air stream to an air separation unit. The air separation unit is adapted for production of oxygen and nitrogen. At least some of the second product stream is flowed to the air separation unit. The method further still comprises the step of processing, in the air separation unit, the second air stream and at least some of the second product stream such that a majority or all of the oxygen of the second air stream and a majority or all of the oxygen of at least some of the second product stream are comprised in a third product stream flowing from the air separation unit. The third product stream comprises primarily oxygen.

[0008] Embodiments of the invention include a method of utilizing a by-product stream of a nitrogen generation unit. The method comprises flowing a first air stream to the nitrogen generation unit. The nitrogen generation unit comprises one or more cryogenic distillation columns and adsorption equipment for production of nitrogen from an air stream. The method further includes generating, by the nitrogen generation unit, from the first air stream (1) a first product stream comprising primarily nitrogen and (2) a second product stream comprising primarily oxygen. The method further comprises flowing a second air stream to an air separation unit. The air separation unit comprises an air compression unit and one or more cryogenic distillation columns for production of oxygen. The air separation unit is adapted for production of oxygen. At least some of the second product stream is flowed to the air separation unit. The method further still comprises the step of processing, in the air separation unit, the second air stream and the second product stream such that a majority or all of the oxygen of the second air stream and a majority or all of the oxygen of the at least some of the second product stream are comprised in a third product stream flowing from the air separation unit. The third product stream comprises primarily oxygen.

[0009] The following includes definitions of various terms and phrases used throughout this specification. [0010] The terms “about” or“approximately” are defined as being close to as understood by one of ordinary skill in the art. In one non-limiting embodiment the terms are defined to be within 10%, preferably, within 5%, more preferably, within 1%, and most preferably, within 0.5%.

[0011] The terms“wt.%”,“vol.%” or“mol.%” refers to a weight, volume, or molar percentage of a component, respectively, based on the total weight, the total volume, or the total moles of material that includes the component. In a non-limiting example, 10 moles of component in 100 moles of the material is 10 mol.% of component.

[0012] The term“substantially” and its variations are defined to include ranges within

10%, within 5%, within 1%, or within 0.5%. [0013] The terms“inhibiting” or“reducing” or“preventing” or“avoiding” or any variation of these terms, when used in the claims and/or the specification, includes any measurable decrease or complete inhibition to achieve a desired result.

[0014] The term“effective,” as that term is used in the specification and/or claims, means adequate to accomplish a desired, expected, or intended result. [0015] The term“primarily,” as that term is used in the specification and/or claims, means greater than any of 50 wt. %, 50 mol. %, or 50 vol. %. For example,“primarily” may include 50.1 wt. % to 100 wt. % and all values and ranges there between, 50.1 mol. % to 100 mol. % and all values and ranges there between, or 50.1 vol. % to 100 vol. % and all values and ranges there between. [0016] The use of the words“a” or“an” when used in conjunction with the term

“comprising,”“including,”“containing,” or“having” in the claims or the specification may mean“one,” but it is also consistent with the meaning of“one or more,”“at least one,” and “one or more than one.”

[0017] The words“comprising” (and any form of comprising, such as“comprise” and

“comprises”),“having” (and any form of having, such as“have” and“has”),“including” (and any form of including, such as“includes” and“include”) or“containing” (and any form of containing, such as“contains” and“contain”) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0018] The process of the present invention can“comprise,”“consist essentially of,” or“consist of’ particular ingredients, components, compositions, etc., disclosed throughout the specification.

[0019] In the context of the present invention, at least nineteen embodiments are now described. Embodiment 1 is a method of utilizing a by-product stream of a nitrogen generation unit (NGU) in an air separation unit (ASU). The method includes the steps of flowing a first air stream to the nitrogen generation unit, the nitrogen generator unit is adapted for production of nitrogen; generating, by the nitrogen generation unit, from the first air stream, (1) a first product stream containing primarily nitrogen and (2) a second product stream containing primarily oxygen; flowing a second air stream to an air separation unit, the air separation unit adapted for production of oxygen; flowing at least some of the second product stream to the air separation unit; and processing, in the air separation unit, the second air stream and the second product stream such that a majority or all of the oxygen of the second air stream and a majority or all of the oxygen of said at least some of the second product stream are contained in a third product stream flowing from the air separation unit, the third product stream containing primarily oxygen. Embodiment 2 is the method of embodiment 1, wherein the nitrogen generation unit is a cryogenic nitrogen generation plant. Embodiment 3 is the method of embodiment 2, wherein the cryogenic nitrogen generation plant includes one or more cryogenic distillation columns and adsorption equipment adapted to purify the first air stream flowed into the nitrogen generation unit. Embodiment 4 is the method of any of embodiments 1 to 3, wherein the air separation unit includes one or more distillation columns and a compression unit. Embodiment 5 is the method of embodiment 4, wherein the compression unit is a multi-stage compressor. Embodiment 6 is the method of any of embodiments 4 and 5, wherein said at least some of the second product stream is flowed to the compression unit of the air separation unit. Embodiment 7 is the method of any of embodiments 1 to 6, wherein the first product stream contains 95 to 99.99 vol.% nitrogen. Embodiment 8 is the method of any of embodiments 1 to 7, wherein the second product stream contains primarily oxygen and residual nitrogen from the nitrogen generation unit. Embodiment 9 is the method of embodiment 8, wherein the second product stream contains 67 vol.% to 77 vol.% oxygen. Embodiment 10 is the method of any of embodiments 1 to 9, wherein the air separation unit is adapted to separate said at least some of the second product stream and the second air stream into the third product stream containing primarily oxygen and a nitrogen stream contains primarily nitrogen. Embodiment 11 is the method of embodiment 10, wherein the air separation unit is adapted to further separate the second product stream and the second air stream to form an argon stream containing primarily argon. Embodiment 12 is the method of embodiments 1 to 11, wherein the third product stream contains 95 vol.% to 99.99 vol.% oxygen. Embodiment 13 is the method of embodiments 1 to 12, wherein the processing further includes the steps of compressing a combined stream of said at least some of the second product stream and the second air stream to form a combined stream; cooling the combined stream to form a cooled combined stream; liquefying the cooled combined stream to form a liquefied combined stream; and distilling the liquefied combined stream to form the third product stream. Embodiment 14 is the method of embodiments 13, wherein the distilling liquefied combined stream further forms a second nitrogen stream. Embodiment 15 is the method of any of embodiments 13 to 14, wherein the combined stream is compressed to a pressure of 4.5 to 6 bar. Embodiment 16 is the method of any of embodiments 13 to 15, wherein the combined stream is cooled to a temperature in a range of 12 to l6°C. Embodiment 17 is the method of any of embodiments 13 to 16, wherein the distilling is performed using one or more cryogenic distillation columns. Embodiment 18 is the method of any of embodiments 13 and 17, wherein the distilling of the liquefied combined stream is performed at a temperature of -196 to -186 °C and a pressure of 2 to 6 bar.

[0020] Embodiment 19 is a method of utilizing a by-product stream from a nitrogen generation process. The method includes the steps of flowing a first air stream to a nitrogen generation unit, the nitrogen generation unit including one or more cryogenic distillation columns and adsorption equipment; generating, by the nitrogen generation unit, from the first air stream, (1) a first product stream containing primarily nitrogen and (2) a second product stream containing primarily oxygen; flowing a second air stream to a compression unit of an air separation unit, the air separation unit including the compression unit and one or more cryogenic distillation columns; flowing at least some of the second product stream to the air separation unit; processing, in the air separation unit, the second air stream and said at least some of the second product stream such that a majority or all of the oxygen of the second air stream and a majority or all of the oxygen of said at least some of the second product stream are contained in a third product stream flowing from the air separation unit, the third product stream containing primarily oxygen.

[0021] Other objects, features and advantages of the present invention will become apparent from the following figures, detailed description, and examples. It should be understood, however, that the figures, detailed description, and examples, while indicating specific embodiments of the invention, are given by way of illustration only and are not meant to be limiting. Additionally, it is contemplated that changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] For a more complete understanding, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

[0023] FIG. 1 shows a schematic diagram of an integrated system for producing oxygen, according to embodiments of the invention; and [0024] FIG. 2 shows a schematic flowchart of a method of producing oxygen, according to embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0025] A method has been discovered for producing oxygen with an improved oxygen production and a reduced energy consumption per unit of oxygen produced. A first air stream can be processed by a nitrogen generation unit to produce a first product stream comprising primarily nitrogen and a second product stream comprising primarily oxygen. The second product stream then can be flowed to the compression unit of an air separation unit. A nitrogen generation unit generally relies on a cryogenic process for processing atmospheric air through compression, purification, liquefaction and separation to produce high purity of nitrogen gas. In a nitrogen generation unit, waste gas enriched with oxygen is used in regeneration of one or more air purification units (dryer beds). An air separation unit generally relies on a cryogenic process for processing atmospheric air through compression, purification, liquefaction and separation to produce oxygen gas and high purity of nitrogen gas. Nitrogen and argon can be produced from the same air separation unit. The nitrogen generation unit and air separation unit have different degrees of liquefaction and different distillation column configurations such that the nitrogen generation unit produces nitrogen of a higher purity than the purity of the oxygen it produces (usually a mixture of oxygen and nitrogen) and the air separation unit produces both high purity oxygen and high purity nitrogen ( e.g ., 95 to 99.99 wt.%). In other words, for the nitrogen generation unit, the product stream that includes primarily nitrogen has a higher percentage of nitrogen than the percentage of oxygen in any other stream produced by the nitrogen generation unit. For the air separation unit, the product streams include a high purity oxygen stream (e.g., 95 to 99.99 wt.%), a high purity nitrogen stream (e.g, 95 to 99.99 wt.%), and optionally other high purity streams such as a high purity argon stream (e.g, 95 to 99.99 wt.%). By processing a combined stream of the second product stream and a second air stream in the air separation unit, the production of pure oxygen (97 to 99.99 vol.% oxygen) can be improved compared to directly processing atmospheric air by an air separation unit. The energy consumption per unit of oxygen produced can be reduced, thereby reducing the overall production cost for pure oxygen.

[0026] In embodiments of the invention, a system for producing oxygen with an improved oxygen productivity and a reduced energy consumption may include a nitrogen generation unit integrated with an air separation unit. With reference to FIG. 1, a schematic diagram is shown of oxygen production system 100 that is capable of producing high grade oxygen with increased production and reduced energy consumption. Oxygen production system 100 may be an integrated system of a nitrogen generation unit and an air separation unit. According to embodiments of the invention, oxygen production system 100 may include first air compression unit 101 adapted to receive and compress first air stream 11 to form first compressed air stream 12. First compressed air stream 12 may be at a pressure of 5.5 to 7.8 bar and all ranges and values there between including 5.5 to 5.6 bar, 5.6 to 5.8 bar, 5.8 to 6.0 bar, 6.0 to 6.2 bar, 6.2 to 6.4 bar, 6.4 to 6.6 bar, 6.6 to 6.8 bar, 6.8 to 7.0 bar, 7.0 to 7.2 bar, 7.2 to 7.4 bar, 7.4 to 7.6 bar, and 7.6 to 7.8 bar. An exit of first air compression unit 101 may be in fluid communication with chiller 102, which is configured to receive and cool down first compressed air stream 12 to form chilled first air stream 13. In embodiments of the invention, chiller 102 is capable of cooling first compressed air stream 12 to a temperature in a range of 10 to 12 °C and all values and ranges there between including 10.1 °C, 10.2 °C, 10.3 °C, 10.4 °C, 10.5 °C, 10.6 °C, 10.7 °C, 10.8 °C, 10.9 °C, 11.0 °C, 11.1 °C, 11.2 °C, 11.3 °C, 11.4 °C, 11.5 °C, 11.6 °C, 11.7 °C, 11.8 °C, and 11.9 °C.

[0027] An outlet of chiller 102 may be in fluid communication with air purification unit 103 such that chilled first air stream 13 flows from chiller 102 to air purification unit 103. According to embodiments of the invention, air purification unit 103 may be adsorber equipment. Non-limiting example of the adsorber equipment may include a thermal swing adsorber. In embodiments of the invention, thermal swing adsorber may include one or more adsorber reactors ( e.g ., l03a and l03b). Air purification unit 103 may be configured to remove impurities from chilled first air stream 13 to form purified air stream 14. Non limiting examples for the impurities may include residual water, carbon dioxide, and/or hydrocarbons. Each adsorber reactor may include an adsorbent bed. According to embodiments of the invention, the adsorbent bed may include molecular sieves, activated alumina, or a combination thereof. The adsorbent bed may be regenerated by flowing available and cheap dray gases including oxygen-enriched stream at nitrogen generation unit or nitrogen-enriched stream at air separation unit.

[0028] According to embodiments of the invention, second heat exchanger 104 may be installed downstream to an outlet of air purification unit 103 such that purified air stream flows from air purification unit 103 to second heat exchanger 104. Second heat exchanger

104 may be adapted to adjust a temperature of purified air stream 14 from 43 to 46 °C and all values and ranges there between. An outlet of the second heat exchanger 104 may be in fluid communication with a first inlet of coldbox 105 such that purified air stream further flows from second heat exchanger 104 to coldbox 105. In embodiments of the invention, coldbox

105 may be configured to cool purified air stream 14 to a temperature in a range of -150 °C to -175 °C to form partially liquefied air stream 15. Coldbox 105 may be capable of further removing impurities from purified air stream 14. According to embodiments of the invention, partially liquefied air stream 15 may include a combined nitrogen and oxygen of 99.95 to 99.99 wt.% and all ranges and values there between including 99.96 wt.%, 99.97 wt.%, 99.98 wt.%.

[0029] In embodiments of the invention, oxygen production system 100 may further include one or more distillation columns l06a and l06b. In embodiments of the invention, an outlet of coldbox 105 may be in fluid communication with a bottom inlet of distillation column l06a such that liquefied air stream 15 flows from coldbox 105 to distillation column l06a. The bottom inlet of distillation column l06a may be adapted to receive partially liquefied air stream 15. According to embodiments of the invention, distillation columns l06a and l06b are cryogenic distillation columns configured to separate partially liquefied air stream 15 into first product stream 17 exiting from a top outlet of distillation column l06a and second product stream 18 exiting from a top outlet of distillation column l06b. First product stream 17 may include 95 vol.% to 99.99 vol.% nitrogen and all values and ranges there between including ranges of 95 to 95.5 vol.%, 95.5 to 96 vol.%, 96 to 96.5 vol.%, 96.5 to 97 vol.%, 97 to 97.5 vol.%, 97.5 to 98 vol.%, 98 to 98.5 vol.%, 98.5 to 99 vol.%, 99 to

99.5 vol.%, and 99.5 to 99.99 vol.%. Second product stream 18 may include 67 vol.% to 77 vol.% oxygen and all ranges and values there between, including ranges of 67 to 67.5 vol.%,

67.5 to 68 vol.%, 68 to 68.5 vol.%, 68.5 to 69 vol.%, 69 to 69.5 vol.%, 69.5 to 70 vol.%, 70 to 70.5 vol.%, 70.5 to 71 vol.%, 71 to 71.5 vol.%, 71.5 to 72 vol.%, 72 to 72.5 vol.%, 72.5 to 73 vol.%, 73 to 73.5 vol.%, 73.5 to 74 vol.%, 74 to 74.5 vol.%, and 74.5 to 75 vol.%. Second product stream 18 may further include 22 to 24.8 vol.% of nitrogen and all ranges and values there between. In embodiments of the invention, first product stream 17 and/or second product stream 18 may be liquid.

[0030] According to embodiments of the invention, coldbox 105 may include a heat exchanger configured to use first product stream 17 and/or second product stream 18 as cooling medium to cool purified air stream 14. The top outlet of distillation column l06a may be in fluid communication with a second inlet of coldbox 105 such that first product stream 17 flows from distillation column l06a to coldbox 105. The top outlet of distillation column l06b may be in fluid communication with a third inlet of coldbox 105 such that second product stream 18 flows from distillation column l06b to coldbox 105. Vaporizer 107 may be in fluid communication with coldbox 105 such that vaporizer 107 is configured to receive and vaporize, at least some of, second product stream 18 from coldbox 105 and return the at least some of vaporized second product stream to coldbox 105 at a position upstream to the third exit thereof.

[0031] In embodiments of the invention, the second outlet of coldbox 105 may be in fluid communication with nitrogen vaporizer 108 such that first product stream 17 flows from coldbox 105 to nitrogen vaporizer 108. Nitrogen vaporizer 108 may be adapted to receive and vaporize first product stream 17 flowed from the second exit of coldbox 105. Vaporized nitrogen from nitrogen vaporizer 108 may be transported into a storage tank or directly fed to chemical plants that are in need of high purity nitrogen.

[0032] Split valve 109 may be installed downstream to the third outlet of coldbox 105 such that second product stream 18 flows from coldbox 105 to split valve 109. According to embodiments of the invention, split valve 109 may be adapted to split second product stream 18 flowed from third outlet of coldbox 105 into regeneration stream 19, feed stream 20, and vent stream 21. Regeneration stream 19 may be flowed to the one or more adsorber reactors ( e.g ., 103 a and l03b) of thermal swing adsorber. In embodiments of the invention, third heat exchanger 110 may be installed upstream to an inlet of the one or more adsorber reactors for regeneration stream 19 such that at least some second product stream 18 flows from split valve to third heat exchanger 110. Third heat exchanger 110 may be adapted to adjust a temperature of regeneration stream 19 to a regeneration temperature for the adsorbent bed of the adsorber reactors. In embodiments of the invention, the regeneration temperature may be in a range of 190 to 250 °C and all ranges and values there between including ranges of 190 to 193 °C, 193 to 196 °C, 196 to 199 °C, 199 to 202 °C, 202 to 205 °C, 205 to 208 °C, 208 to 211 °C, 211 to 214 °C, 214 to 217 °C, 217 to 220 °C, 220 to 223 °C, 223 to 226 °C, 226 to 229 °C, 229 to 232 °C, 232 to 235 °C, 235 to 238 °C, 238 to 241 °C, 241 to 244 °C, 244 to 247 °C, and 247 to 250 °C. Regeneration stream 19 may be used to regenerate the adsorbent bed of the one or more adsorber reactors when at least one of the adsorber reactors is in regeneration mode. Vent stream 21 is utilized to release at least some of second product stream from third outlet of coldbox 105 to the atmosphere.

[0033] According to embodiments of the invention, feed stream 20, which comprises primarily oxygen, may be fed to an air separation unit. More particularly, in embodiments of the invention, feed stream 20 may be fed to compression unit 112 of the air separation unit such that feed stream 20 and second air stream 22 may form combined stream 23 in compression unit 112. Flow valve 111 may be used to manipulate a flowrate of feed stream 20 from split valve 109 to compression unit 112. Compression unit 112 may be a multi-stage compressor adapted to compress combined stream 23 to a pressure in a range of 4.5 to 6 bar and all ranges and values there between including 4.6 bar, 4.7 bar, 4.8 bar, 4.9 bar, 5.0 bar, 5.1 bar, 5.2 bar, 5.3 bar, 5.4 bar, 5.5 bar, 5.6 bar, 5.7 bar, 5.8 bar, and 5.9 bar. Compression unit 112 may be in fluid communication with one or more distillation unit 113 configured to flow combined stream 23 to distillation unit 113. Distillation unit 113 may be adapted to separate oxygen from combined stream 23 to form third product stream 24. In embodiments of the invention, distillation unit 113 may further separate nitrogen and/or argon from combined stream 23. Distillation unit 113 may include a cooler adapted to cool combined stream 23, a cryogenic high pressure distillation column and a cryogenic low pressure distillation column. Third product stream 24 may include 99.8 to 99.99 vol.% oxygen and all ranges and values there between.

[0034] According to embodiments of the invention, oxygen production system 100 may further include a control system adapted to control the flowrate of feed stream 20 flowing from flow valve 111 to compression unit 112. The control system may be further adapted to control the flow rate of vent stream 21. In embodiments of the invention, the control system may further include a plurality of temperature sensors, pressure sensors, temperature sensors, pressure transmitter, and temperature transmitters, adapted to measure and adjust temperatures and pressures in oxygen production system 100 including the pressures and temperatures of each stream therein.

[0035] In embodiments of the invention, there are provided methods of utilizing a by- product of a nitrogen generation process. The method may be used to produce oxygen. FIG. 2 shows method 200 for utilizing a by-product of a nitrogen generation process to produce oxygen, according to embodiments of the invention. Method 200 may be implemented by oxygen production system 100 as shown in FIG. 1. As shown in block 201, method 200, as implemented by oxygen production system 100, may include flowing first air stream 11 to a nitrogen generation unit of oxygen production system 100. In embodiments of the invention, first air stream 11 is fed to first air compression unit 101.

[0036] According to embodiments of the invention, the nitrogen generation unit may be a cryogenic nitrogen generation plant. The cryogenic nitrogen generation plant may include one or more cryogenic distillation columns ( e.g ., l06a and l06b) and adsorption equipment including thermal swing adsorber (e.g., l03a and l03b).

[0037] As shown at block 202, method 200 may further include generating, by the nitrogen generation unit, from first air stream 11, (1) first product stream 17 comprising primarily nitrogen and (2) second product stream 18 comprising primarily oxygen. As described above, first product stream 17 may include 95 vol.% to 99.99 vol.% nitrogen and all values and ranges there between including ranges of 95 to 95.5 vol.%, 95.5 to 96 vol.%, 96 to 96.5 vol.%, 96.5 to 97 vol.%, 97 to 97.5 vol.%, 97.5 to 98 vol.%, 98 to 98.5 vol.%, 98.5 to 99 vol.%, 99 to 99.5 vol.%, and 99.5 to 99.99 vol.%. Second product stream 18 may include 67 vol.% to 77 vol.% oxygen and all ranges and values there between, including ranges of 67 to 67.5 vol.%, 67.5 to 68 vol.%, 68 to 68.5 vol.%, 68.5 to 69 vol.%, 69 to 69.5 vol.%, 69.5 to 70 vol.%, 70 to 70.5 vol.%, 70.5 to 71 vol.%, 71 to 71.5 vol.%, 71.5 to 72 vol.%, 72 to 72.5 vol.%, 72.5 to 73 vol.%, 73 to 73.5 vol.%, 73.5 to 74 vol.%, 74 to 74.5 vol.%, and 74.5 to 75 vol.%. Second product stream 18 may further include 22 to 24.8 vol.% of nitrogen and all ranges and values there between including ranges of 22 to 22.2 vol.%,

22.2 to 22.4 vol.%, 22.4 to 22.6 vol.%, 22.6 to 22.8 vol.%, 22.8 to 23.0 vol.%, 23.0 to 23.2 vol.%, 23.2 to 23.4 vol.%, 23.4 to 23.6 vol.%, 23.6 to 23.8 vol.%, 23.8 to 24.0 vol.%, 24.0 to

24.2 vol.%, 24.2 to 24.4 vol.%, 24.4 to 24.6 vol.%.

[0038] In embodiments of the invention, the generating at block 202 may include compressing first air stream 11 to form first compressed air stream 12 as shown at block 203, cooling first compressed air stream 12 to a temperature of 44 to 46 °C to form a chilled first air stream 13 as shown at block 204, and purifying chilled first air stream 13 with air purification unit 103 (e.g, thermal swing adsorber) to form purified air stream 14 as shown at block 205. The purifying may be capable of removing residual water, carbon dioxide from chilled first air stream 13. The generating at block 202 may further include cooling purified air stream 14 via coldbox 105 to a temperature in a range of -150 °C to -180 °C and all ranges and values there between, as shown at block 206. The purified air stream 14 may be partially liquefied by the cooling to form partially liquefied air stream 15. The generating at block 202 may further include separating partially liquefied air stream 15 into first product stream 17 and second product stream 18 via distillation columns l06a and l06b as shown at block 207. First product stream 17 and second product stream 18 may be flowed to coldbox 105 as cooling medium for cooling purified air stream 14. At least some of second product stream 18 may be flowed to air purification unit 103 to regenerate at least one of the absorbent beds of the adsorber reactors 103 a and l03b.

[0039] As shown at block 208, method 200 may further include flowing second air stream 22 to the air separation unit of oxygen production system 100. In embodiments of the invention, the air separation unit may include compression unit 112 and distillation unit 113 comprising one or more distillation columns, and/or a cooler. According to embodiments of the invention, second air stream 22 may be flowed to an inlet of compression unit 112. Method 200 may further include flowing, at least some of, or all of, the second product stream to the air separation unit, as shown at block 209.

[0040] In embodiments of the invention, as shown at block 210, method 200 may further still include processing, in the air separation unit, second air stream 22 and at least some of second product stream 18, which forms feed stream 20, such that a majority or substantially all of the oxygen of second air stream 22 and a majority or substantially all of the oxygen of the at least some of second product stream 18 (feed stream 20) are comprised in third product stream 24, which comprises primarily oxygen. In embodiments of the invention, third product stream 24 may include 99.8 to 99.999 vol.% oxygen and all ranges and values there between. Furthermore, processing at block 210 may include separating at least some argon from second air stream 22 and the at least some of second product stream 18 using cryogenic distillation columns.

[0041] According to embodiments of the invention, processing at block 210 may include compressing a combined stream of at least some of second product stream 18 and second air stream 22 to form a combined stream as shown at block 211, cooling the combined stream to form a cooled combined stream as shown at block 212, liquefying, at least some, cooled combined stream to form a liquefied combined stream as shown at block 213, and distilling the liquefied combined stream to form third product stream 24 as shown at block 214. In embodiments of the invention, distilling at block 214 may further form a second nitrogen stream including primarily nitrogen. According to embodiments of the invention, at block 211, combined stream may be compressed to a pressure of 4.5 to 6 bar and all ranges and values there between including 4.6 bar, 4.7 bar, 4.8 bar, 4.9 bar, 5.0 bar, 5.1 bar, 5.2 bar, 5.3 bar, 5.4 bar, 5.5 bar, 5.6 bar, 5.7 bar, 5.8 bar, 5.9 bar. At block 212, the combined stream may be cooled to a temperature of 12 to 16 °C and all ranges and values there between including 13 °C, 14 °C, 15 °C. At block 214, distilling may be performed using one or more cryogenic distillation columns. The distilling may be performed at a temperature of -196 to - 186 °C and all ranges and values there between including -195 °C, -194 °C, -193 °C, -192 °C, -191 °C, -190 °C, -189 °C, -188 °C, and -187 °C. The distillation pressure in distilling at block 214 may be in a range of 2 to 6 bar and all ranges and values there between.

[0042] According to embodiments of the invention, overall, method 200 may be capable of increasing oxygen production rate by 11 to 15% compared to a conventional method that uses only an air separation unit for oxygen production.

[0043] Embodiments of the invention involve a method of utilizing a by-product of a nitrogen generation process. This method can be used for oxygen production. By using an integrated system of a nitrogen generation unit and an air separation unit, an oxygen enriched stream (e.g, second product stream 18) from a nitrogen generation unit can be used to feed into the air separation unit. A combined air stream and the oxygen enriched stream is then processed in the air separation unit to produce high purity oxygen. Therefore, overall, the oxygen productivity of the method is higher than a method that processes air in the air separation unit, reducing production cost for high purity oxygen.

[0044] Although embodiments of the present invention have been described with reference to blocks of FIG. 2, it should be appreciated that operation of the present invention is not limited to the particular blocks and/or the particular order of the blocks illustrated in FIG. 2. Accordingly, embodiments of the invention may provide functionality as described herein using various blocks in a sequence different than that of FIG. 2.

[0045] Although embodiments of the present application and their 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 embodiments 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 above disclosure, 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. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

Claims

1. A method of utilizing a by-product stream of a nitrogen generation unit (NGU) in an air separation unit (ASU), the method comprising: flowing a first air stream to the nitrogen generation unit, the nitrogen generator unit is adapted for production of nitrogen; generating, by the nitrogen generation unit, from the first air stream, (1) a first product stream comprising primarily nitrogen and (2) a second product stream comprising primarily oxygen; flowing a second air stream to an air separation unit, the air separation unit adapted for production of oxygen; flowing at least some of the second product stream to the air separation unit; and processing, in the air separation unit, the second air stream and the second product stream such that a majority or all of the oxygen of the second air stream and a majority or all of the oxygen of said at least some of the second product stream are comprised in a third product stream flowing from the air separation unit, the third product stream comprising primarily oxygen.

2. The method of claim 1, wherein the nitrogen generation unit is a cryogenic nitrogen generation plant.

3. The method of claim 2, wherein the cryogenic nitrogen generation plant comprises one or more cryogenic distillation columns and adsorption equipment adapted to purify the first air stream flowed into the nitrogen generation unit.

4. The method of any of claims 1 to 3, wherein the air separation unit comprises one or more distillation columns and a compression unit.

5. The method of claim 4, wherein the compression unit is a multi-stage compressor.

6. The method of claim 4, wherein said at least some of the second product stream is flowed to the compression unit of the air separation unit.

7. The method of any of claims 1 to 3, wherein the first product stream comprises 95 to 99.99 vol.% nitrogen.

8. The method of any of claims 1 to 3, wherein the second product stream comprises primarily oxygen and residual nitrogen from the nitrogen generation unit.

9. The method of claim 8, wherein the second product stream comprises 67 vol.% to 77 vol.% oxygen.

10. The method of any of claims 1 to 3, wherein the air separation unit is adapted to separate said at least some of the second product stream and the second air stream into the third product stream comprising primarily oxygen and a nitrogen stream comprising primarily nitrogen.

11. The method of claim 10, wherein the air separation unit is adapted to further separate the second product stream and the second air stream to form an argon stream comprising primarily argon.

12. The method of any of claims 1 to 3, wherein the third product stream comprises 95 vol.% to 99.99 vol.% oxygen.

13. The method of any of claims 1 to 3, wherein the processing further includes: compressing a combined stream of said at least some of the second product stream and the second air stream to form a combined stream; cooling the combined stream to form a cooled combined stream; liquefying the cooled combined stream to form a liquefied combined stream; and distilling the liquefied combined stream to form the third product stream.

14. The method of claims 13, wherein the distilling liquefied combined stream further forms a second nitrogen stream.

15. The method of claim 13, wherein the combined stream is compressed to a pressure of 4.5 to 6 bar.

16. The method of claim 13, wherein the combined stream is cooled to a temperature in a range of 12 to 16 °C.

17. The method of claim 13, wherein the distilling is performed using one or more cryogenic distillation columns.

18. The method of claim 13, wherein the distilling of the liquefied combined stream is performed at a temperature of -196 to -186 °C and a pressure of 2 to 6 bar.

19. A method of utilizing a by-product stream from a nitrogen generation process, the method comprising: flowing a first air stream to a nitrogen generation unit, the nitrogen generation unit comprising one or more cryogenic distillation columns and adsorption equipment; generating, by the nitrogen generation unit, from the first air stream, (1) a first product stream comprising primarily nitrogen and (2) a second product stream comprising primarily oxygen; flowing a second air stream to a compression unit of an air separation unit, the air separation unit comprising the compression unit and one or more cryogenic distillation columns; flowing at least some of the second product stream to the air separation unit; processing, in the air separation unit, the second air stream and said at least some of the second product stream such that a majority or all of the oxygen of the second air stream and a majority or all of the oxygen of said at least some of the second product stream are comprised in a third product stream flowing from the air separation unit, the third product stream comprising primarily oxygen.