Apparatus for the production of low pressure gaseous oxygen

Abstract

An apparatus for the production of low pressure gaseous oxygen includes a heat exchanger and a system of columns comprised of an auxiliary column, a higher pressure column and a lower pressure column. The LP column and the HP column are thermally integrated via a top reboiler/condenser disposed on top of the HP column. The system of columns is configured to separate a cooled air stream into oxygen and nitrogen. The auxiliary column comprises a distillation section and a first and second reboiler. One of the reboilers is driven by the cooled air stream and the other reboiler is driven by a pressurized nitrogen stream. The first and second reboilers boil their fluids at the same pressure as the auxiliary column.

Claims

1. An apparatus for the production of low pressure gaseous oxygen, the apparatus comprising: a) a heat exchanger having a warm end, a cold end, and an intermediate section; b) an auxiliary column in fluid communication with the cold end of the heat exchanger, the auxiliary column further comprising distillation media, a first reboiler and a second reboiler both disposed below the distillation media of the auxiliary column, wherein the first reboiler is configured to use a fluid consisting essentially of air as a reboiling fluid for the first reboiler, wherein the second reboiler is configured to use a pressurized nitrogen stream as a reboiling fluid for the second reboiler; c) a higher pressure (HP) column in fluid communication with the heat exchanger and the auxiliary column, wherein the HP column is configured to receive at least a first portion of air from the first reboiler of the auxiliary column, wherein the HP column is configured to receive at least a first portion of the pressurized nitrogen stream from the second reboiler of the auxiliary column; d) a lower pressure (LP) column in fluid communication with the heat exchanger and the HP column, wherein the LP column is configured to receive a bottoms liquid comprising oxygen from the HP column; and e) a cold compressor in fluid communication with a top portion of the HP column, such that the compressor is configured to receive and pressurize at least a first portion of a nitrogen-rich fluid from the HP column to form the pressurized nitrogen stream.

2. The apparatus as claimed in claim 1, wherein the first reboiler and the second reboiler are disposed in a vertical arrangement with each other.

3. The apparatus as claimed in claim 1, wherein the first reboiler is disposed above the second reboiler within the auxiliary column.

4. The apparatus as claimed in claim 1, wherein the first reboiler is disposed in the same horizontal plane as the second reboiler within the auxiliary column.

5. The apparatus as claimed in claim 1, wherein the LP column is in fluid communication with the auxiliary column, wherein the LP column is configured to receive at least a second portion of air from the first reboiler of the auxiliary column, wherein the LP column is configured to receive at least a second portion of the pressurized nitrogen stream from the second reboiler of the auxiliary column.

6. The apparatus as claimed in claim 1, further comprising a nitrogen expander having an inlet and an outlet, wherein the inlet is in fluid communication with the intermediate section of the heat exchanger, and the outlet of the nitrogen expander is in fluid communication with the cold end of the heat exchanger, wherein the heat exchanger is configured to warm a first portion of nitrogen-rich fluid of the nitrogen-rich fluid from the HP column.

7. The apparatus as claimed in claim 1, wherein the auxiliary column is configured to operate at a pressure higher than an operating pressure of the LP column.

8. An apparatus for the production of low pressure gaseous oxygen comprising: a heat exchanger; and a system of columns comprised of an auxiliary column, a higher pressure (HP) column and a lower pressure (LP) column, wherein the LP column and the HP column are thermally integrated via a top condenser disposed on top of the HP column, wherein the system of columns is configured to separate a cooled air stream into oxygen and nitrogen, wherein the auxiliary column comprises distillation media and a first reboiler and second reboiler, wherein both the first and second reboilers are disposed below the distillation media of the auxiliary column, wherein the first reboiler is driven by the cooled air stream and the second reboiler is driven by a pressurized nitrogen stream, wherein the first reboiler and the second reboiler boil fluid at the same pressure as the auxiliary column.

9. The apparatus as claimed in claim 8, wherein the first reboiler and the second reboiler are disposed in a vertical arrangement with each other.

10. The apparatus as claimed in claim 8, wherein the first reboiler is disposed directly above the second reboiler within the auxiliary column.

11. The apparatus as claimed in claim 8, wherein the first reboiler is disposed in the same horizontal plane as the second reboiler within the auxiliary column.

12. The apparatus as claimed in claim 8, wherein the auxiliary column is configured to operate at a pressure higher than an operating pressure of the LP column.

13. The apparatus as claimed in claim 8, wherein the auxiliary column is configured to produce gaseous oxygen at a delivery pressure of the oxygen product.

14. The apparatus as claimed in claim 8, wherein the first reboiler and the second reboiler are disposed within the auxiliary column such that the first reboiler and the second reboiler operate at the same temperatures.

15. The apparatus as claimed in claim 8, wherein there is an absence of the distillation media disposed below the first reboiler, wherein there is an absence of the distillation media disposed below the second reboiler.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, claims, and accompanying drawings. It is to be noted, however, that the drawings illustrate only several embodiments of the invention and are therefore not to be considered limiting of the invention's scope as it can admit to other equally effective embodiments.

(2) FIG. 1 provides an embodiment of the prior art.

(3) FIG. 2 shows an embodiment of the present invention.

DETAILED DESCRIPTION

(4) While the invention will be described in connection with several embodiments, it will be understood that it is not intended to limit the invention to those embodiments. On the contrary, it is intended to cover all the alternatives, modifications and equivalence as may be included within the spirit and scope of the invention defined by the appended claims.

(5) FIG. 2 represents an embodiment of the present invention. In this embodiment, compressed and purified air 2 from a booster air compressor (not shown) is cooled in heat exchanger 10 and then used to provide reboiling duties for air driven reboiler 23, thereby condensing at least a portion of the air to form partially condensed air 3. In a preferred embodiment, all of the air is condensed. First air portion 6 is reduced in pressure by a valve and then introduced into a middle section of higher pressure (HP) column 40 for separation therein. In the embodiment shown, second air portion 8 is reduced in pressure by a valve before being introduced to a middle section of lower pressure (LP) column 80 for separation therein. In an optional embodiment, all of the air is sent to HP column 40.

(6) In an optional embodiment not shown, partially condensed air 3 can be sent to a liquid gas separator, whereby a gaseous air fraction is withdrawn from the top and introduced to a middle section of HP column 40, and a condensed air fraction is withdrawn from the bottom and a first portion is introduced to the middle section of HP column 40 at a point below the gaseous air fraction. Additionally, the second air portion 8 can be cooled in an auxiliary heat exchanger prior to being sent to a second liquid gas separator, wherein a gaseous air fraction is withdrawn from the top and introduced to the middle section of the LP column 80, and a condensed air fraction is withdrawn from the bottom and is introduced to the middle section of the LP column 80 at a point below the gaseous air fraction.

(7) Air from adsorbers 4 is split into first portion 4a and second portion 4b. First portion 4a is compressed in air booster 103 of air turbine/booster 100 to form compressed air 102, which preferably is at a pressure between 4 bara and 5.5 bara, more preferably between 4.5 bara and 5 bara. Compressed air 102 is then partially cooled in heat exchanger 10 and withdrawn from an intermediate location of heat exchanger 10 and then expanded in air turbine 105 of turbine/booster 100 to form expanded air 107, before being introduced to LP column 80 for separation therein. After expansion, expanded air 107 is preferably at the substantially same pressure as LP column 80 (except to account for pressure drops within the lines). Second portion of air from adsorbers 4b is then fully cooled in heat exchanger 10 and sent to a bottom section of HP column 40 for separation therein.

(8) HP column 40 is configured to operate under conditions effective to separate the air into nitrogen and oxygen. Crude oxygen stream 42 is removed from the bottom of HP column 40, optionally cooled in auxiliary heat exchanger (not shown), reduced in pressure via a valve and introduced to a middle section of LP column 80 for separation therein. In an optional embodiment not shown, following expansion in the valve, crude oxygen stream 42 can be introduced to a gas liquid separator. Gaseous overheads can be withdrawn from the top and introduced to the middle section of LP column 80 and liquid bottoms can be withdrawn from the bottom and introduced to the middle section of LP column 80 at a point below gaseous overheads.

(9) Within HP column 40, nitrogen vapor rises towards the top and ultimately are condensed in the reboiler 41 before being reintroduced to the top of HP column 40 as liquid. Nitrogen-rich gas 46 is then withdrawn from a top portion of HP column 40 and split into two streams: first portion of nitrogen-rich gas 46a and second portion of nitrogen-rich gas 46b. First portion of nitrogen-rich gas 46a is partially warmed in heat exchanger 10 before being expanded in nitrogen turbine 93 of nitrogen turbine/booster 90. The resulting low pressure nitrogen is then warmed in heat exchanger 10 to become LP gaseous nitrogen 86, that can be used to regenerate the adsorbers. Second portion of nitrogen-rich gas 46b is compressed in nitrogen compressor 95 of nitrogen turbine/booster 90 to form pressurized nitrogen 92, which is then introduced to an intermediate portion of heat exchanger 10 and cooled. Pressurized nitrogen 92 is then used to provide reboiling duties for nitrogen driven reboiler 25 to form cooled nitrogen 94, which is preferably fully condensed. Cooled nitrogen 94 is then split into two streams, with first portion of cooled nitrogen 94a going to the top portion of HP column 40 and second portion of cooled nitrogen 94b going to the top portion of LP column 80. In one embodiment, all of the cooled nitrogen is introduced to the HP column.

(10) Oxygen-rich liquid 82 is withdrawn from a bottom portion of LP column 80, and pumped by second pump P2 to the reboiler that is fixed atop of HP column 40. In the embodiment shown, the two columns are shown side by side; however, in an alternative embodiment, the two columns may be part of a traditional stacked double column. In the embodiment using a stacked column, second pump P2 would not be used. In the embodiment shown, second pump P2 is preferably used in order to overcome the static pressure. The oxygen-rich liquid introduced to the reboiler provides the refrigeration necessary to condense the nitrogen vapor coming from HP column 40. During the course of operation, the heat provided by the nitrogen vapor causes some of the oxygen-rich liquid to vaporize. Oxygen-rich gas 44 is withdrawn from the top of the reboiler and introduced to the bottom portion of LP column 80 for further separation therein. Oxygen-rich liquid 48 is withdrawn from a bottom part of the reboiler, pressurized in first pump P1 and then sent to a top portion of auxiliary column 20 for further separation therein. In one embodiment, auxiliary column 20 operates at a pressure that is higher than the operating pressure of the LP column.

(11) Auxiliary column 20 contains two reboilers: air driven reboiler 23 and nitrogen driven reboiler 25. In a preferred embodiment, air driven reboiler 23 and nitrogen driven reboiler 25 are arranged in a stacked, vertical fashion. In one embodiment, air driven reboiler 23 is located above nitrogen driven reboiler 25. In another embodiment, the two reboilers are arranged in the same horizontal plane. It is preferable; however, to have the two reboilers arranged in a stacked, vertical fashion such that the overall diameter of auxiliary column 20 can be minimized. In one embodiment, air driven reboiler 23 is smaller in size as compared to nitrogen driven reboiler 25. In one embodiment, air driven reboiler 23 and nitrogen driven reboiler 25 operate at nearly the same temperatures.

(12) Oxygen-rich liquid accumulates in the bottom portion of auxiliary column 20 (e.g., the portion below the distillation section). As noted previously, compressed and purified air 2 provides reboiling duty for air driven reboiler 23 and pressurized nitrogen 92 provides reboiling duty for nitrogen driven reboiler 25, which causes some of the oxygen-rich liquid (as well as any other impurities such as nitrogen) to boil off and travel through the distillation media and is ultimately withdrawn from the top of auxiliary column 20 as oxygen overheads 22 before being expanded through a valve and then introduced to the bottom portion of LP column 80.

(13) Low pressure gaseous oxygen (LP GOX) 24 is withdrawn from auxiliary column 20 and split into two streams: first portion of LP GOX 24a and second portion of LP GOX 24b. Second portion of LP GOX 24b is heated in heat exchanger 10 to produce second LP GOX product. First portion of LP GOX 24a is reduced in pressure via a valve, heated in heat exchanger 10 to produce first LP GOX product 26a.

(14) Waste nitrogen 84 is withdrawn from the top portion of LP column 80 and then introduced to heat exchanger 10 to capture some of its refrigeration. In an optional embodiment, following heating in heat exchanger 10, waste nitrogen 84 can be used for precooling elsewhere in the process.

EXAMPLES

(15) Simulations were conducted in order to compare the results of an embodiment from the prior art (FIG. 1) vs. an embodiment of the present invention (FIG. 2). Pressure, temperature, flow rates, and compositions of various streams of FIG. 1 can be found in Table I below:

(16) TABLE-US-00001 TABLE I Data for Embodiment of the Prior Art TEMP. PRESSURE FLOW N.sub.2 AR O.sub.2 STREAM C. BARA NM.sup.3/Hr MOL % MOL % MOL % 3 179.8 3.468 316348 78.11% 0.93% 20.96% 6 182.0 3.344 51452 78.11% 0.93% 20.96% 8 182.0 3.344 65850 78.11% 0.93% 20.96% 22 184.0 1.257 58276 34.24% 4.30% 61.45% 27 181.0 1.273 93039 0.07% 3.43% 96.50% 42 180.0 3.468 212109 62.68% 1.43% 35.89% 44 184.3 1.252 160062 36.76% 4.09% 59.15% 47 183.7 3.438 92911 99.38% 0.24% 0.38% 49 184.3 1.252 151315 13.23% 3.77% 83.00% 82 186.5 1.249 311377 25.32% 3.93% 70.74% LPGOX 17.7 1.570 93039 0.07% 3.43% 96.50%

(17) Pressure, temperature, flow rates, and compositions of various streams for the embodiment shown in FIG. 2 can be found in Table II below:

(18) TABLE-US-00002 TABLE II Data for Embodiment of the Present Invention TEMP. PRESSURE FLOW N.sub.2 AR O.sub.2 STREAM C. BARA NM.sup.3/Hr MOL % MOL % MOL % 2 21.2 5.150 77615 78.11% 0.93% 20.96% 3 176.8 5.057 77615 78.11% 0.93% 20.96% 4 20.6 3.490 356295 78.11% 0.93% 20.96% 4a 20.6 3.490 48235 78.11% 0.93% 20.96% 4b 20.6 3.490 308060 78.11% 0.93% 20.96% 6 176.8 5.057 48409 78.11% 0.93% 20.96% 8 176.8 5.057 29206 78.11% 0.93% 20.96% 22 181.6 1.672 54839 39.41% 3.07% 57.51% 24 177.9 1.693 92162 0.66% 2.84% 96.50% 24a 177.9 1.693 73554 0.66% 2.84% 96.50% 24b 177.9 1.693 18608 0.66% 2.84% 96.50% 26a 18.0 1.300 73554 0.66% 2.84% 96.50% 26b 18.0 1.570 18608 0.66% 2.84% 96.50% 42 179.4 3.351 166066 54.42% 1.53% 44.05% 44 184.6 1.249 93958 40.52% 3.06% 56.42% 46 183.9 3.321 228000 98.90% 0.40% 0.70% 46a 183.9 3.321 100552 98.90% 0.40% 0.70% 46b 183.9 3.321 127448 98.90% 0.40% 0.70% 48 184.6 1.249 147879 15.03% 2.92% 82.05% 82 186.4 1.249 241837 24.93% 2.97% 72.09% 84 194.0 1.221 244910 99.00% 0.42% 0.58% 86 18.0 1.079 100552 98.90% 0.40% 0.70% 92 164.0 5.974 127448 98.90% 0.40% 0.70% 94 176.8 5.934 127448 98.90% 0.40% 0.70% 94a 176.8 5.934 37598 98.90% 0.40% 0.70% 94b 184.0 3.321 89850 98.90% 0.40% 0.70% 102 21.2 4.450 52827 78.11% 0.93% 20.96% 107 180.6 1.249 52827 78.11% 0.93% 20.96%

(19) As shown in Table I and Table II above, an embodiment of the present invention can produce a low pressure oxygen product of similar quality (96.5% oxygen) and flow rate (92,162 Nm.sup.3/hr vs. 93,039 Nm.sup.3/hr) while eliminating auxiliary vaporizer 30 and the associated piping and valves. As such, embodiments of the current invention provide an improvement over the prior art in terms of simplicity and lower capital expenditures.

(20) In addition to the elimination of auxiliary vaporizers and their related piping and valves, other advantages of operating in accordance with various embodiments of the present invention include an approximately 42% reduction in size of the main reboiler (e.g., reboiler 41) and approximately 2% reduction in size of the auxiliary column 20.

(21) The terms nitrogen-rich and oxygen-rich will be understood by those skilled in the art to be in reference to the composition of air. As such, nitrogen-rich encompasses a fluid having a nitrogen content greater than that of air. Similarly, oxygen-rich encompasses a fluid having an oxygen content greater than that of air. While FIG. 2 shows the higher pressure and lower pressure columns being side by side, in an alternate embodiment, the columns can also be stacked in a typical double column configuration. Advantageously, the embodiment shown in FIG. 2 allows for improved operating pressures, since the HP column can be operated at a lower pressure than if the two columns were stacked due to the absence of having to overcome static pressure losses.

(22) As used herein, an auxiliary vaporizer is a vaporizer that is located outside of the distillation columns and operates at a pressure other than those of the distillation columns.

(23) While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. 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.

(24) The singular forms a, an and the include plural referents, unless the context clearly dictates otherwise.

(25) 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.

(26) 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.

(27) 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.

(28) Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.

(29) 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.