METHOD AND SYSTEM FOR PROVIDING AUXILIARY REFRIGERATION TO AN AIR SEPARATION PLANT

Description

Field of the Invention

[0001] The present invention relates to a method and system for cryogenic air separation involving production of liquid products by using an integrated refrigeration system comprising a primary refrigeration circuit and an auxiliary refrigeration circuit. More particularly, the present invention relates to an auxiliary refrigeration circuit that can be easily tied-in to an existing cryogenic air separation plant and its existing refrigeration system.

Background

[0002] Oxygen, nitrogen and argon are separated from air through cryogenic rectification in an air separation plant. Typically, gaseous and/or liquid products are produced for on-site customers or pipeline customers, with any excess products often converted to merchant liquid products for nearby customers. For some cryogenic air separation plants, the on-site or pipeline customer demand for gaseous products, such as gaseous oxygen or gaseous nitrogen, may decrease over time either on a long-term basis or perhaps on a more temporary or mid-term basis. To satisfy the lower gaseous product requirements, the cryogenic air separation plant may be operated so as to vent some of the unneeded gaseous product which is economically inefficient as such venting ultimately wastes the power/energy costs used to produce the vented gaseous products. Alternatively, the air separation plant may be operated in a turn-down mode which produces less gaseous product but at less than full plant capacity and separation efficiency. A third option is to adjust the product slate of the cryogenic air separation plant to produce more liquid products in lieu of the lowered gaseous product requirement.

[0003] There have been numerous prior art cryogenic air separation processes designed to address this third option of making additional liquid products to offset decreased requirements of gaseous products. See for example, United States Patent Nos. 6,125,656; 6,666,048; 6,945,076; and 8397535; as well as United States Patent Application Publication Nos. 2010-0058805; 2013-0192301; 2007-0101763; and European Patent Publication EP1544559 A1. As seen in these prior art references, refrigeration must be supplied to offset ambient heat leakage, warm end heat exchange losses and to allow the extraction or production of the liquid products, including liquid oxygen, liquid nitrogen, or liquid argon from one or more air separation units. The conventional or main source of refrigeration for a cryogenic rectification plant is typically supplied by a turbine-based refrigeration system capable of expanding part of the feed air stream or a waste stream to generate a refrigeration stream that is then introduced into the main heat exchanger or the distillation column system of the cryogenic air separation plant. Supplemental refrigeration required to produce additional liquid products may be supplied with an additional turbine-based refrigeration source. Such additional turbine-based refrigeration systems involve additional capital costs and are often not optimized or fully integrated with the main source of refrigeration for a cryogenic air separation plant.

[0004] What is needed, is an improvement to these prior art supplemental liquid make solutions that allows the additional liquid make system to be configured as an add-on feature to the air separation plant that can be easily added to the cryogenic air separation plant/unit after initial plant construction. Such add-on supplemental liquid-make feature should be integrated with the main source of refrigeration for the cryogenic air separation plant and must also be both efficient and operationally flexible. In other words, the supplemental or auxiliary refrigeration system should be capable of and allow the plant to switch easily between a high liquid make cycle and the original high gaseous product make cycle. Finally, the add-on supplemental or auxiliary refrigeration system should be portable, and preferably skid-mounted.

[0005] JP 2009/052807 A and DE 32 16 502 A1 relate to examples of cryogenic air separation units comprising a first refrigeration circuit and an auxiliary refrigeration circuit including an auxiliary heat exchanger.

Summary of the Invention

[0006] The present invention relates to a method of separating air in an air separation unit as defined in claim 1.

[0007] The present invention also relates to an air separation unit configured to produce at least one liquid product stream as defined in claim 10.

[0008] In some embodiments, the first refrigeration circuit may include a compressor for further compressing the first portion of the compressed and purified feed air stream; a cooling means such as an aftercooler and/or main heat exchanger configured to cool the further compressed first portion of the compressed and purified feed air stream; and a first turbo-expander disposed within the first refrigeration circuit and configured to expand the further compressed first portion of the compressed and purified feed air stream to produce the first refrigeration stream. Similarly, the auxiliary refrigeration circuit may also include an auxiliary compressor and cooling means.

[0009] Finally, in some embodiments that employ a multi-stage compression system within the booster air compression circuit, the diversion of the fraction of the further compressed feed air stream to the auxiliary refrigeration circuit preferably includes further includes diverting one or more fractions of the third portion of the compressed and purified feed air stream from one or more interstage locations of the plurality of compression stages to the auxiliary refrigeration circuit. One or more flow control valves are disposed between the booster air compression circuit and the second turbo-expander in the auxiliary refrigeration circuit to control the flow of the diverted one or more fractions and the inlet pressure to the second turbo-expander in the auxiliary refrigeration circuit.

Brief Description of the Drawings

[0010] While the present invention concludes with claims distinctly pointing out the subject matter that Applicants regard as their invention, it is believed that the invention will be better understood when taken in connection with the accompanying drawings in which:

Fig. 1 is a schematic process flow diagram of a cryogenic air separation plant integrated with an add-on supplemental or auxiliary refrigeration circuit not in accordance with the present invention; and

Fig. 2 is a schematic process flow diagram of a cryogenic air separation plant integrated with an embodiment of the add-on supplemental or auxiliary refrigeration circuit in accordance with the present invention.

Detailed Description

[0011] In reference to Figs. 1-2, an air separation unit 10 generally includes an incoming air compression and purification train or circuit (not shown); a primary refrigeration circuit 20; a booster air compression train or circuit 30; a main heat exchanger 40; and a distillation column system 50.

[0012] In the incoming air purification and compression train or circuit, the incoming feed air is compressed in a multi-stage, intercooled, main air compressor arrangement to a pressure that can be between about 5 bar(a) and about 15 bar(a). This main air compressor arrangement may be an integrally geared compressor or a direct drive compressor arrangement. The compressed air feed is then purified in a pre-purification unit to remove high boiling contaminants from the incoming feed air. A pre-purification unit, as is well known in the art, typically contains beds of alumina and/or molecular sieve operating in accordance with a temperature and/or pressure swing adsorption cycle in which moisture and other impurities, such as carbon dioxide, water vapor and hydrocarbons, are adsorbed.

[0013] As described in more detail below, the compressed and purified feed air stream 12 is divided into a plurality of portions which are further compressed and/or cooled. The different portions of the compressed and purified air stream are then separated into oxygen-rich, nitrogen-rich, and argon-rich fractions in a plurality of distillation columns that comprise the distillation column system 50. The distillation column system 50 includes thermally linked higher pressure column 54 and lower pressure column 56, as well as an optional argon rectification column 58.

[0014] Prior to such distillation however, portions of the compressed and purified feed air stream 12 may be further compressed in a booster air compression train or circuit 30 and/or cooled to temperatures suitable for rectification within a primary or main heat exchanger 40. The cooling is typically achieved using refrigeration from the various oxygen, nitrogen and/or argon streams produced by the air separation unit 10 as well as refrigeration generated by one or more refrigeration circuits often as a result of turbo-expansion of various air streams in an upper column turbine (UCT) arrangement, a lower column turbine (LCT) arrangement, and/or a warm recycle turbine (WRT) arrangement as known to persons skilled in the art.

Air Separation Unit with Primary and Auxiliary Refrigeration Circuits

[0015] Turning now to Fig. 1, an exemple which is not covered by the present invention is illustrated that includes a plurality of divided portions of the compressed and purified feed air stream. A first portion 13 of the compressed and purified feed air stream, resulting from the compression and pre-purification of the incoming feed air, is diverted to a first or primary refrigeration circuit 20 shown as an upper column turbine (UCT) arrangement that is configured to produce a first cooled refrigeration stream 22. Preferably, within the first or primary refrigeration circuit 20, the first portion 13 of the compressed and purified feed air stream is further compressed in compressor 24 and cooled in an aftercooler 25 and/or main heat exchanger 40. The compressed and cooled (or partially cooled) stream is then expanded in the first turbo-expander 26 to produce the first refrigeration stream 22. A portion of the first refrigeration stream is directed to the lower pressure column while a second portion of the first refrigeration stream is diverted to the auxiliary or second refrigeration circuit 60 as described in more detail below.

[0016] A second portion 15 of the compressed and purified feed air stream is directed or diverted to the main heat exchanger 40 to cool this portion of the compressed and purified feed air stream. The resulting cooled second portion 42 of the compressed and purified feed air stream is then directed to the higher pressure column 54 of the distillation column system 50 as generally known in the art and practiced in many cryogenic air separation units.

[0017] In addition, a third portion 17 of the compressed and purified feed air stream is diverted to a booster air compression circuit 30 configured to produce a further compressed, high pressure feed air stream 32. As illustrated, the booster air compression circuit 30 employs a booster air compressor arrangement 33 having a plurality of compression stages with intercoolers and aftercoolers 31 and forms a high pressure air stream 32 that is fed to the main heat exchanger 40. The high pressure air stream forms a liquid phase or a dense fluid if its pressure exceeds the critical pressure after cooling in the main heat exchanger. This liquid air stream 34 is then split into two portions 35, 36, with a first portion 35 being directed through an expansion valve 37 and into the higher pressure column 54 of the distillation column system 50 and a second portion 36 is expanded through another expansion valve 38 and introduced into the lower pressure column 56 of distillation column system 50.

[0018] As seen in Fig. 1, a fraction 62A, 62B of the third portion 17 of the compressed and purified feed air stream is further diverted from the booster air compression circuit 30 to an auxiliary refrigeration circuit 60 configured to produce a second refrigeration stream 66. The auxiliary refrigeration circuit 60 preferably includes an auxiliary compressor 63, a second turbo-expander 64, and an auxiliary heat exchanger 65. This fraction 62A, 62B of the further compressed feed air stream from the booster air compression circuit 30 is diverted via one or more flow control valves 67A, 67B, to the auxiliary compressor 63 where the diverted fraction stream is further compressed (as stream 61), optionally cooled or partially cooled and then expanded in a turbo-expander 64. After expansion in the turbo-expander 64, the diverted fraction stream is then cooled in the auxiliary heat exchanger 65 via indirect heat exchange with one or more cooling streams, preferably a diverted portion of the first refrigeration stream 28, to produce the cooled second refrigeration stream 66 exiting the auxiliary heat exchanger 65 and a warmed stream 29. The cooled second refrigeration stream 66 is then combined with the cooled second portion 34 of the compressed and purified feed air stream and the resulting combined stream 68 is then directed to the higher pressure column 54 to impart another or second portion of the refrigeration required by the distillation column system 50. As briefly discussed above, part of the first refrigeration stream 22 is diverted as a cooling stream 28 to the auxiliary heat exchanger 65 where it cools the diverted fraction 62A, 62B of the further compressed feed air stream in the auxiliary refrigeration circuit 60. The remaining portion of the first refrigeration stream 22 is directed to the lower pressure column 56 to impart a portion of the refrigeration required by the distillation column system 50. In this arrangement the supplemental refrigeration created by the expansion of the first portion 13 of the compressed and purified air stream in the first or primary refrigeration circuit 20 is thus imparted partly to the lower pressure column 56 and partly to the auxiliary heat exchanger 65 thereby alleviating some of the cooling duty of the primary heat exchanger 40.

[0019] The present example also shows a fourth portion 19 of the compressed and purified feed air stream that may also be diverted from the incoming air purification and compression circuit (not shown) as a carrier fluid to the auxiliary heat exchanger 65 where it is cooled and subsequently directed to the higher pressure column 54 of the distillation column system 50 so as to capture the auxiliary refrigeration. As illustrated, this cooled fourth portion 69 of the compressed and purified feed air stream may be combined with the warmed second refrigeration stream 66 and/or the cooled second portion 42 of the compressed and purified feed air stream exiting the main heat exchanger 40 with the resulting combined stream 68 then directed to the higher pressure column 54.

[0020] In a preferred embodiment, the first portion of the compressed and purified feed air stream directed to the primary refrigeration circuit represents roughly 8% to 20% of the incoming feed air stream. Of this first portion, up to 12% of the incoming feed air stream is diverted as the second portion to the auxiliary heat exchanger to balance the temperatures in the auxiliary heat exchanger. Varying the amount of diverted air from the first refrigeration circuit to the auxiliary refrigeration circuit enables the air separation unit to readily switch between a high gaseous product make cycle and a high liquid product make cycle.

[0021] The third portion of the compressed and purified feed air stream represents roughly 25% to 32% of the incoming feed air stream with roughly 5% to 10% of the incoming feed air stream being diverted to the auxiliary refrigeration circuit.

[0022] The second portion and fourth portion of the compressed and purified feed air stream combined represents the remainder roughly of the incoming feed air stream 48% to 67% of the incoming feed air stream. The exact split between the second portion and fourth portion of the compressed and purified feed air stream depends on the heat exchange duties in the main heat exchanger and auxiliary heat exchanger.

[0023] The main heat exchanger 40 and auxiliary heat exchanger 65 are preferably a brazed aluminum plate-fin type heat exchanger. Such heat exchangers are advantageous due to their compact design, high heat transfer rates and their ability to process multiple streams. They are manufactured as fully brazed and welded pressure vessels. The brazing operation involves stacking corrugated fins, parting sheets and end bars to form a core matrix. The matrix is placed in a vacuum brazing oven where it is heated and held at brazing temperature in a clean vacuum environment. For small plants, a heat exchanger comprising a single core may be sufficient. For higher flows, a heat exchanger may be constructed from several cores which may be connected in parallel or series.

[0024] The turbo-expanders 26 and 64 are preferably linked with booster air compressors 24 and 63 respectively, either directly or by appropriate gearing. Although not shown, the turbo-expanders may also to be connected or operatively coupled to a generator. Such generator loaded turbo-expander arrangement allows the speed of the turbo-expander to be maintained constant even at very high or low loads. This arrangement is desirable in some applications because the speed of the turbo-expander would remain generally constant at the ideal efficiency across the entire operating envelope. In such arrangements, the generator load may be connected to the turbo-expander by means of a high speed generator. Alternatively, the generator load may be connected to the turbo-expander by means of a high speed coupling connected to an internal or external gearbox and with a low speed coupling from the gearbox to the generator.

[0025] The distillation column system 50 includes a thermally linked higher pressure column 54 and lower pressure column 56 as well as an optional argon rectification column 58. Within the columns, vapor and liquid are counter-currently contacted in order to affect a gas/liquid mass-transfer based separation of the respective feed streams. Such columns will preferably employ structured packing or trays or combinations thereof. The higher pressure column 54 typically operates in the range from between about 20 bar(a) to about 60 bar(a) whereas the lower pressure column 56 typically operates at pressures between about 1.1 bar(a) to about 1.5 bar(a).

[0026] As indicated above, the higher pressure column 54 and the lower pressure column 56 are linked in a heat transfer relationship such that a nitrogen-rich vapor column overhead, extracted from the top of higher pressure column as a stream 71, is condensed within a main condenser-reboiler 55 located in the base of lower pressure column 56 against boiling an oxygen-rich liquid column bottoms 72. The boiling of oxygen-rich liquid column bottoms 72 initiates the formation of an ascending vapor phase within lower pressure column 56. The condensation produces a liquid nitrogen containing stream 73 that is divided into streams 74 and 75A/B that reflux the higher pressure column 54 and the lower pressure column 56, respectively to initiate the formation of descending liquid phases in such columns. If liquid nitrogen product is required, stream 76 may also be recovered.

[0027] Streams 34, 66, and 69 are introduced into the higher pressure column 54 along with the expanded liquid air stream 39 for rectification by contacting an ascending vapor phase of such mixture within a plurality of mass transfer contacting elements with a descending liquid phase that is initiated by reflux stream 74. This produces a crude liquid oxygen column bottoms 77, also known as kettle liquid and the nitrogen-rich column overhead 78. A stream 91 representing a portion of the nitrogen-rich column overhead 78 may be directed to the main heat exchanger 40 to provide refrigeration to the feed air streams. In addition, a stream 101 of the crude liquid oxygen column bottoms 77 may be directed to the argon column 58 to as a reflux to aid in the recovery of argon product 93. Alternatively, although not shown, a stream of the crude liquid oxygen column bottoms may be expanded in an expansion valve to the pressure at or near that of the lower pressure column and introduced into the lower pressure column for further rectification.

[0028] Lower pressure column 56 is also provided with a plurality of mass transfer contacting elements that can be trays or structured packing or random packing or other known elements in the art of cryogenic air separation. As stated previously, the separation produces an oxygen-rich liquid 80 and a nitrogen-rich vapor column overhead 82 that is extracted as a nitrogen product stream 84. Additionally, a waste stream 85 is also extracted to control the purity of nitrogen product stream 84. Both nitrogen product stream 84 and waste stream 85 are passed through a subcooling unit 90 designed to subcool the reflux stream 75A/B. A portion of the reflux stream may optionally be taken as a liquid product stream 76 and the remaining portion (shown as stream 75B) may be introduced into lower pressure column 56 after passing through expansion valve 99.

[0029] After passage through subcooling unit 90, nitrogen vapor product stream 84 and waste stream 85 are fully warmed within main heat exchanger 40 to produce a warmed nitrogen product stream 94 and a warmed waste stream 95. Although not shown, the warmed waste stream 95 may be used to regenerate the adsorbents within pre-purification unit. In addition, an oxygen-rich liquid stream 80 is extracted from the oxygen-rich liquid column bottoms 72 near the bottom of the lower pressure column 56. Oxygen-rich liquid stream 80 can be pumped by a pump 83 to form a pumped product stream as illustrated by pumped liquid oxygen stream 86. Part of the pumped liquid oxygen stream 86 can optionally be taken directly as a liquid oxygen product stream 88, with the remainder, namely stream 87, being directed to the main heat exchanger 40 where it is warmed and vaporized to produce a pressurized oxygen product stream 97. Although only one such stream is shown, there could be a plurality of such streams that are fed into the main heat exchanger 40. Pumped liquid oxygen stream 86 can be pressurized to above or below the critical pressure so that oxygen product stream 97 when discharged from main heat exchanger 40 will be a supercritical fluid. Alternatively, the pressurization of pumped liquid oxygen stream 86 could be lower to produce an oxygen product stream 97 in a vapor form.

[0030] Turning now to the embodiment illustrated in Fig. 2, there is shown an embodiment of the add-on supplemental or auxiliary refrigeration circuit 60. Fig. 2 differs from Fig. 1 in that a portion of the partially cooled, expanded working fluid 27 in the auxiliary refrigeration circuit 60 is recycled back to the first refrigeration circuit 20 at a location upstream of the first turbo-expander 26. In this manner, the working fluid 27 undergoes two stages of expansion in a serial arrangement. In other words, the turbo-expander 64 of the auxiliary refrigeration circuit 60 is arranged in series with the turbo-expander 26 of the first refrigeration circuit 20 with the resulted expanded working fluid being directed to the lower pressure column 56 and/or the auxiliary heat exchanger 65.

[0031] Another difference between the embodiment shown in Fig. 2 and the example of Fig. 1 is found in the auxiliary refrigeration circuit 60. In the example of Fig. 2, all or a portion of the diverted fraction stream may optionally bypass the auxiliary compressor 63 and go directly to the second turbo-expander 64 and on to the auxiliary heat exchanger 65. When flow control valve 67C is open and flow control valve 67D is closed, the combined streams 62A and 62B are further compressed in auxiliary compressor 63, then expanded in second turbo-expander 64 and warmed in auxiliary heat exchanger 65. Conversely, when flow control valve 67C is closed and flow control valve 67D is open, the combined working fluid streams 62A and 62B bypass the auxiliary compressor 63 and directed to the second turbo-expander 64 and then warmed in auxiliary heat exchanger 65. This arrangement allows for adjusting the pressure of the working fluid in the auxiliary refrigeration circuit 60.

Integrating the Auxiliary Refrigeration Circuit with the Air Separation Unit

[0032] As indicated above, air separation unit 10 is capable of producing liquid products, namely, nitrogen-rich liquid stream 76 and liquid oxygen product stream 88. In order to increase the production of such liquid products, additional refrigeration is supplied by an add-on or auxiliary refrigeration circuit. In the presently disclosed air separation unit or air separation plant, the add-on refrigeration circuit is the auxiliary refrigeration circuit 60 that is preferably configured to be added to or bolted on the cryogenic air separation unit 10 after initial plant construction. Thus, the design of the auxiliary refrigeration circuit 60 is tailored for such late add-on or retrofit application and the tie-in points to the cryogenic air separation unit 10 are minimized.

[0033] In the illustrated embodiment, there are five key tie-in points between the cryogenic air separation unit 1 and auxiliary or second refrigeration circuit 60. The first tie-in point 110 preferably occurs downstream of the main air compression train or circuit where the fourth portion 19 of the compressed and purified feed air stream 12 is diverted to the auxiliary or second refrigeration circuit, and more particularly, to the auxiliary heat exchanger 65. This first tie in point 110 is configured to provide the carrier fluid (i.e. compressed and purified air) to which the auxiliary refrigeration from the auxiliary refrigeration circuit 60 is provided.

[0034] The second tie-in point 120 is within the booster air compression circuit 30 and is configured to divert a fraction of the further compressed third portion of the compressed and purified stream as compressed stream s 62A, 62B to the auxiliary refrigeration circuit 60. This second tie in point 110 provides a working fluid (i.e. boosted compressed air) that is to be expanded to provide a portion of the auxiliary refrigeration from the auxiliary refrigeration circuit 60.

[0035] The third tie-in point 130 is located within the distillation column system 50 and is configured to return the cooled carrier fluid 69 (i.e. compressed and purified air) as well as the warmed working fluid 66 (i.e. fully warmed, expanded working fluid) to the higher pressure column 54.

[0036] The fourth tie-in point 140 is located within the first refrigeration circuit 20 and is configured to divert a portion 28 of the first refrigeration stream 22 to the auxiliary refrigeration circuit 60 where it provides further cooling or refrigeration to the carrier stream 19 via indirect heat exchange in the auxiliary heat exchanger 65.

[0037] A fifth tie in point 150 is also required in the embodiment shown in Fig. 2. This fifth tie-in point 150 is also located within the first refrigeration circuit 20 and configured to return a portion of the partially cooled, expanded working fluid 27 back to the first refrigeration circuit 20 upstream of the first turbo-expander 26.

[0038] Preferably, the supplemental or auxiliary refrigeration system is configured and constructed as a portable, skid-mounted refrigeration system that can be easily added to the cryogenic air separation plant/unit after initial plant construction in a manner that minimizes cold-box entry. The preferred skid-mounted supplemental or auxiliary refrigeration system would include: (i) one or more auxiliary compressors 63; (ii) the warm second turbo-expander 64; (iii) the auxiliary heat exchanger 65; (iv) associated piping to facilitate the above-identified four or five tie-in points; and (v) one or more control valves 67A, 67B, 67C, and 67D configured to control the air stream flows to the one or more auxiliary compressors 63, second turbo-expander 64, and auxiliary heat exchanger 65 as described above with reference to Figs. 1 and 2. In some embodiments, some of the flow control valves 67A, 67B, 67C, and 67D configured to control the air stream flows to the one or more auxiliary compressors 63, second turbo-expander 64, and auxiliary heat exchanger 65 may be configured as part of the cryogenic air separation plant and where the skid-mounted supplemental or auxiliary refrigeration system is tied-in downstream of such control valves.

[0039] By controlling the flow to the supplemental or auxiliary refrigeration circuit via the one or more flow control valves, the presently disclosed system can easily switch between a high gaseous product cycle - when the flow control valves are closed and a high liquid make cycle where the flow control valves are operated to produce an increased amount of refrigeration and associated liquid product make.

[0040] An advantage of the present system and method for providing auxiliary refrigeration to a cryogenic air separation plant is the ability to increase the amount of refrigeration and associated liquid product make in a cost-effective manner. The amount of refrigeration produced and amount of liquid make is adjusted by varying the warm turbine inlet pressure and flow in the supplemental or auxiliary refrigeration circuit. Adjustments to the warm turbine inlet pressure and flow are effected by selectively opening and/or closing the one or more flow control valves 67A, 67B, 67C, and 67D. The discharge flow from the warm second turbo-expander is passed through the auxiliary heat exchanger and then directed to the higher pressure column along with the main air (i.e. cooled second portion of the of the compressed and purified feed air stream) and the fourth portion of the of the compressed and purified feed air stream exiting the auxiliary heat exchanger.

[0041] An additional advantage presented by the present system and method is that by diverting a portion of the first refrigeration stream from the primary refrigeration circuit to the auxiliary refrigeration circuit and thus bypassing the lower pressure column separation, the gaseous oxygen product produced by the distillation column system is reduced but the argon recovery within the distillation column system can be maintained or possibly enhanced.

[0042] Also, diverting a portion of the first refrigeration stream to the auxiliary refrigeration circuit is preferably controlled to balance the temperatures in auxiliary heat exchanger and preserve recovery in the auxiliary booster-turbine arrangement. The flow and pressure ratio within the primary refrigeration circuit is maximized. In this fashion, the upper column turbine arrangement is used more as a heat pump to improve liquid making capability of the cryogenic air separation plant.

Claims

1. A method of separating air in an air separation unit (10) comprising a main heat exchanger (40) configured to cool a compressed and purified feed air stream to a temperature suitable for the rectification and a distillation column system (54, 56, 58) configured to rectify the compressed, purified and cooled air stream to produce at least one liquid product stream (76, 88), the method comprising the steps of:

compressing and purifying a feed air stream to produce the compressed and purified feed air stream (12);

diverting a first portion (13) of the compressed and purified feed air stream to a first refrigeration circuit (20) configured to produce a first cooled refrigeration stream (22);

diverting a second portion (15) of the compressed and purified feed air stream to the main heat exchanger to cool the second portion of the compressed and purified feed air stream and wherein the cooled second portion of the compressed and purified feed air stream is subsequently directed to the higher pressure column (54) of the distillation column system;

diverting a third portion (17) of the compressed and purified feed air stream to a booster air compression circuit (30) configured to produce a further compressed feed air stream and wherein a first part (32) of the further compressed feed air stream is directed to the main heat exchanger where the further compressed feed air stream is cooled to produce a liquid air stream (34) that is directed to the distillation column system;

diverting a second part (62A, 62B) of the further compressed feed air stream from the booster air compression circuit to an auxiliary refrigeration circuit (60) configured to produce a second refrigeration stream (66), the auxiliary refrigeration circuit comprising a second turbo-expander (64) and an auxiliary heat exchanger (65);

diverting a fourth portion (19) of the compressed and purified feed air stream to the auxiliary heat exchanger;

diverting a part (28) of the first refrigeration stream from the first refrigeration circuit to the auxiliary heat exchanger and warming the diverted portion of the first refrigeration stream in the auxiliary heat exchanger via indirect heat exchange with the diverted fourth portion of the compressed and purified feed air stream and with the second refrigeration stream to cool the second refrigeration stream;

directing the fourth portion of the compressed and purified feed air stream exiting the auxiliary heat exchanger to the distillation column system;

directing a remaining part of the first refrigeration stream to a lower pressure column (56) of the distillation column system to impart a first portion of the refrigeration required by the distillation column system; and

directing a cooled portion (68) of the second refrigeration stream to the higher pressure column of the distillation column system to impart a second portion of the refrigeration required by the distillation column system

diverting a portion (27) of the second refrigeration stream from the auxiliary refrigeration circuit to the first refrigeration circuit; and

combining (150) the diverted portion of the second refrigeration stream with the first portion of the compressed and purified feed air stream in the first refrigeration circuit.

2. The method of claim 1 further comprising the steps of:

further compressing the first portion (13) of the compressed and purified feed air stream (12) within the first refrigeration circuit (20);

cooling the further compressed first portion of the compressed and purified feed air stream; and

expanding the further compressed first portion of the compressed and purified feed air stream in a first turbo-expander (26) disposed within the first refrigeration circuit to produce the first refrigeration stream (22).

3. The method of claim 2 wherein the step of cooling the further compressed first portion (13) of the compressed and purified feed air stream further (12) comprises cooling the further compressed first portion of the compressed and purified feed air stream in an aftercooler.

4. The method of claim 2 wherein the step of cooling the further compressed first portion (13) of the compressed and purified feed air stream (12) further comprises partially cooling the further compressed first portion of the compressed and purified feed air stream in the main heat exchanger (40).

5. The method of claim 1 wherein in the step of directing the cooled fourth portion (69) of the compressed and purified feed air stream (12) to the distillation column system (54, 56, 58) the cooled fourth portion of the compressed and purified feed air stream is directed to the higher pressure column (54) of the distillation column system.

6. The method of claim 2 wherein the step of directing a cooled portion of the second refrigeration stream (66) to the higher pressure column (54) comprises diverting a portion of the second refrigeration stream that is partially cooled from the auxiliary heat exchanger (65) in the auxiliary refrigeration circuit (60) to the first refrigeration circuit (20); and
wherein the step of combining the diverted portion of the second refrigeration stream with the first portion (13) of the compressed and purified feed air stream (12) in the first refrigeration circuit
comprises combining the diverted portion of the second refrigeration stream with the first portion of the compressed and purified feed air stream in the first refrigeration circuit upstream of the first turbo-expander (26) disposed within the first refrigeration circuit.

7. The method of claim 1 wherein the step of diverting a fraction of the further compressed feed air stream from the booster air compression circuit (30) to the auxiliary refrigeration circuit (60) further comprises:

further compressing the third portion (17) of the compressed and purified feed air stream (12) in a plurality of compression stages (33); and

diverting a first fraction (62A, 62B) of the third portion of the compressed and purified feed air stream from an interstage location of the plurality of compression stages to the auxiliary refrigeration circuit.

8. The method of claim 1 wherein the step of diverting a fraction of the further compressed feed air stream from the booster air compression circuit (30) to the auxiliary refrigeration circuit (60) further comprises:

further compressing the third portion (17) of the compressed and purified feed air stream (12) in a plurality of compression stages (33); and

diverting one or more fractions (62A, 62B) of the third portion of the compressed and purified feed air stream from one or more interstage locations of the plurality of compression stages to the auxiliary refrigeration circuit (60);

controlling the flow of the diverted one or more fractions of the third portion of the compressed and purified feed air stream with one or more flow control valves (67A, 67B, 67C, 67D) disposed between the booster air compression circuit and the second turbo-expander (64) in the auxiliary refrigeration circuit;

wherein the inlet pressure to the second turbo-expander in the auxiliary refrigeration circuit is controlled by adjusting the one or more flow control valves which in turn controls the second portion of the refrigeration required by the distillation column system (54, 56, 58).

9. The method of claim 1 wherein the auxiliary refrigeration circuit (60) further comprises an auxiliary compressor (63), and wherein the method further comprises the steps of:

diverting the fraction of the further compressed feed air stream from the booster air compression circuit (30) to the auxiliary compressor;

further compressing the diverted fraction of the compressed feed air stream from the booster air compression circuit in the auxiliary compressor (63);

partially cooling the further compressed diverted fraction in the auxiliary heat exchanger via indirect heat exchange with the diverted portion (28) of the first refrigeration stream (22);

expanding the partially cooled further compressed diverted fraction in the second turbo-expander;

further cooling the expanded diverted fraction in the auxiliary heat exchanger via indirect heat exchange with the diverted portion of the first refrigeration stream to produce the cooled second refrigeration stream (66); and

directing the cooled second refrigeration stream to the higher pressure column (54) of the distillation column system to impart the second portion of the refrigeration required by the distillation column system.

10. An air separation unit configured to produce at least one liquid product stream (76, 88), the air separation unit (10)comprising:

an incoming air compression and purification train configured to produce a compressed and purified feed air stream (12);

a primary refrigeration circuit (20) having a first turbo-expander (26), the primary refrigeration circuit operatively coupled to the incoming air compression and purification train and configured to receive a first portion (13) of the compressed and purified feed air stream and expand the first portion of the compressed and purified feed air stream in the first turbo-expander to produce a first cooled refrigeration stream (22);

a main heat exchanger (40) operatively coupled to the incoming air compression and purification train and configured to receive a second portion (15) of the compressed and purified feed air stream and to cool the second portion of the compressed and purified feed stream to a temperature suitable for the rectification of the compressed and purified feed air stream;

a booster air compression circuit (30) operatively coupled to the incoming air compression and purification train and the main heat exchanger, the booster air compression circuit configured to receive a third portion (17) of the compressed and purified feed air stream, further compress the third portion and direct a first part (32) of the further compressed third portion to the main heat exchanger to produce a liquid air stream (34);

a second turbo-expander (64) configured to receive a second part (62A; 62B) of the further compressed third portion and expand the fraction of the further compressed third portion to produce a second refrigeration stream; and

an auxiliary heat exchanger (65) operatively coupled to the incoming air compression and purification train, the booster air compression circuit and the primary refrigeration circuit, the auxiliary heat exchanger configured to receive a fourth portion (19) of the compressed and purified feed air stream and cool the fourth portion of the compressed and purified feed air stream and the second refrigeration stream via indirect heat exchange with a diverted portion (28) of the first refrigeration stream;

a distillation column system (54, 56, 58) operatively coupled to the primary refrigeration circuit, the booster air compression circuit and the auxiliary heat exchanger, the distillation column system configured to rectifying some of the first refrigeration stream, and some or all of the second refrigeration stream, the liquid air stream, and the cooled second portion of the compressed and purified feed air stream by a cryogenic rectification process to produce the at least one liquid product stream; and

a recycle circuit connecting the auxiliary heat exchanger with the primary refrigeration circuit wherein a portion of the second refrigeration stream is recycled to the first refrigeration circuit.

11. The air separation unit of claim 10 wherein the primary refrigeration circuit (20) further comprises a compressor (24) configured for further compressing the first portion (13) of the compressed and purified feed air stream (12) within the primary refrigeration circuit (20); and wherein the compressor is operatively coupled to the main heat exchanger (40) such that the further compressed the first portion of the compressed and purified feed air stream is partially cooled in the main heat exchanger.

12. The air separation unit of claim 10 wherein the distillation column system comprises a higher pressure column and the cooled fourth portion (69) of the compressed and purified feed air stream (12) exiting the auxiliary heat exchanger (65) is directed to the higher pressure column (54) of the distillation column system.

13. The air separation unit of claim 10 wherein the portion of the second refrigeration stream recycled to the first refrigeration circuit (20) is partially cooled within the auxiliary heat exchanger (65) and is recycled to a location in the first refrigeration circuit upstream of the first turbo-expander (26).

14. The air separation unit of claim 10 further comprising an auxiliary refrigeration circuit (60) that includes an auxiliary compressor (63) configured to receive the fraction (62A, 62B) of the further compressed feed air stream diverted from the booster air compression circuit (30), the second turbo-expander configured to receive a compressed air stream (61) from the auxiliary compressor and expand the compressed air stream, and the auxiliary heat exchanger (65) configured to receive the expanded air stream from the second turbo-expander.

15. The air separation unit of claim 14 wherein the booster air compression circuit (30) further comprises a plurality of compression stages (33) and a diversion circuit for diverting one or more fractions (6A, 62B) of the further compressed feed air stream from one or more interstage locations of the plurality of compression stages to the auxiliary refrigeration circuit (60).

Ansprüche

1. Verfahren zum Trennen von Luft in einer Lufttrenneinheit (10), umfassend einen Hauptwärmetauscher (40), der dazu konfiguriert ist, einen verdichteten und gereinigten Luftzufuhrstrom auf eine Temperatur zu kühlen, die zur Rektifikation geeignet ist, und ein Destillationskolonnensystem (54, 56, 58), das dazu konfiguriert ist, den verdichteten, gereinigten und gekühlten Luftstrom zu rektifizieren, um mindestens einen Flüssigproduktstrom (76, 88) zu erzeugen, wobei das Verfahren die Schritte umfasst:

Verdichten und Reinigen eines Luftzufuhrstroms, um den verdichteten und gereinigten Luftzufuhrstrom (12) zu erzeugen;

Umleiten eines ersten Teils (13) des verdichteten und gereinigten Luftzufuhrstroms zu einem ersten Kühlkreislauf (20), der dazu konfiguriert ist, einen ersten gekühlten Kühlstrom (22) zu erzeugen;

Umleiten eines zweiten Teils (15) des verdichteten und gereinigten Luftzufuhrstroms zu dem Hauptwärmetauscher, um den zweiten Teil des verdichteten und gereinigten Luftzufuhrstroms zu kühlen, und wobei der gekühlte zweite Teil des verdichteten und gereinigten Luftzufuhrstroms nachfolgend zu der Hochdruckkolonne (54) des Destillationskolonnensystems geleitet wird;

Umleiten eines dritten Teils (17) des verdichteten und gereinigten Luftzufuhrstroms zu einem Kreislauf (30) zur verstärkten Luftverdichtung, der dazu konfiguriert ist, einen weiter verdichteten Luftzufuhrstrom zu erzeugen, und wobei ein erster Teil (32) des weiter verdichteten Luftzufuhrstroms zu dem Hauptwärmetauscher geleitet wird, wobei der weiter verdichtete Luftzufuhrstrom gekühlt wird, um einen Flüssigluftstrom (34) zu erzeugen, der zu dem Destillationskolonnensystem geleitet wird;

Umleiten eines zweiten Teils (62A, 62B) des weiter verdichteten Luftzufuhrstroms von dem Kreislauf zur verstärkten Luftverdichtung zu einem Zusatzkühlkreislauf (60), der dazu konfiguriert ist, einen zweiten Kühlstrom (66) zu erzeugen, wobei der Zusatzkühlkreislauf einen zweiten Turboexpander (64) und einen Zusatzwärmetauscher (65) umfasst;

Umleiten eines vierten Teils (19) des verdichteten und gereinigten Luftzufuhrstroms zu dem Zusatzwärmetauscher;

Umleiten eines Teils (28) des ersten Kühlstroms von dem ersten Kühlkreislauf zu dem Zusatzwärmetauscher und Erwärmen des umgeleiteten Teils des ersten Kühlstroms in dem Zusatzwärmetauscher durch indirekten Wärmeaustausch mit dem umgeleiteten vierten Teil des verdichteten und gereinigten Luftzufuhrstroms und mit dem zweiten Kühlstrom, um den zweiten Kühlstrom zu kühlen;

Leiten des vierten Teils des verdichteten und gereinigten Luftzufuhrstroms, der den Zusatzwärmetauscher verlässt, zu dem Destillationskolonnensystem;

Leiten eines verbleibenden Teils des ersten Kühlstroms zu einer Unterdruckkolonne (56) des Destillationskolonnensystems, um einen ersten Teil der von dem Destillationskolonnensystem erforderlichen Kühlung zu übertragen; und

Leiten eines gekühlten Teils (68) des zweiten Kühlstroms zu der Unterdruckkolonne des Destillationskolonnensystems, um einen zweiten Teil der von dem Destillationskolonnensystem erforderlichen Kühlung zu übertragen;

Umleiten eines Teils (27) des zweiten Kühlstroms von dem Zusatzkühlkreislauf zu dem ersten Kühlkreislauf; und Kombinieren (150) des umgeleiteten Teils des zweiten Kühlstroms mit dem ersten Teil des verdichteten und gereinigten Luftzufuhrstroms in dem ersten Kühlkreislauf.

2. Verfahren nach Anspruch 1, ferner umfassend die Schritte:

Weiterverdichten des ersten Teils (13) des verdichteten und gereinigten Luftzufuhrstroms (12) innerhalb des ersten Kühlkreislaufs (20);

Kühlen des weiter verdichteten ersten Teils des verdichteten und gereinigten Luftzufuhrstroms; und

Expandieren des weiter verdichteten ersten Teils des verdichteten und gereinigten Luftzufuhrstroms in einem ersten Turboexpander (26), der innerhalb des ersten Kühlkreislaufs angeordnet ist, um den ersten Kühlstrom (22) zu erzeugen.

3. Verfahren nach Anspruch 2, wobei der Schritt eines Kühlens des weiter verdichteten ersten Teils (13) des verdichteten und gereinigten Luftzufuhrstroms (12) ferner ein Kühlen des weiter verdichteten ersten Teils des verdichteten und gereinigten Luftzufuhrstroms in einem Nachkühler umfasst.

4. Verfahren nach Anspruch 2, wobei der Schritt eines Kühlens des weiter verdichteten ersten Teils (13) des verdichteten und gereinigten Luftzufuhrstroms (12) ferner ein teilweises Kühlen des weiter verdichteten ersten Teils des verdichteten und gereinigten Luftzufuhrstroms in dem Hauptwärmetauscher (40) umfasst.

5. Verfahren nach Anspruch 1, wobei der gekühlte vierte Teil des verdichteten und gereinigten Luftzufuhrstroms bei dem Schritt des Leitens des gekühlten vierten Teils (69) des verdichteten und gereinigten Luftzufuhrstroms (12) zu dem Destillationskolonnensystem (54, 56, 58) zu der Hochdrucckolonne (54) des Destillationskolonnensystems geleitet wird.

6. Verfahren nach Anspruch 2, wobei der Schritt eines Leitens eines gekühlten Teils des zweiten Kühlstroms (66) zu der Hochdruckkolonne (54) ein Umleiten eines Teils des zweiten Kühlstroms, der teilweise von dem Zusatzwärmetauscher (65) in dem Zusatzkühlkreislauf (60) gekühlt wird, zu dem ersten Kühlkreislauf (20) umfasst;
und
wobei der Schritt eines Kombinierens des umgeleiteten Teils des zweiten Kühlstroms mit dem ersten Teil (13) des verdichteten und gereinigten Luftzufuhrstroms (12) in dem ersten Kühlkreislauf ein Kombinieren des umgeleiteten Teils des zweiten Kühlstroms mit dem ersten Teil des verdichteten und gereinigten Luftzufuhrstroms in dem ersten Kühlkreislauf, der dem ersten Turboexpander (26) vorgeschaltet ist, der innerhalb des ersten Kühlkreislaufs angeordnet ist, umfasst.

7. Verfahren nach Anspruch 1, wobei der Schritt eines Umleitens eines Bruchteils des weiter verdichteten Luftzufuhrstroms von dem Kreislauf (30) zur verstärkten Luftverdichtung zu dem Zusatzkühlkreislauf (60) ferner umfasst:

Weiterverdichten des dritten Teils (17) des verdichteten und gereinigten Luftzufuhrstroms (12) in einer Vielzahl von Verdichtungsstufen (33);

und

Umleiten eines ersten Bruchteils (62A, 62B) des dritten Teils des verdichteten und gereinigten Luftzufuhrstroms von einer Zwischenstufenstelle der Vielzahl von Verdichtungsstufen zu dem Zusatzkühlkreislauf.

8. Verfahren nach Anspruch 1, wobei der Schritt eines Um leitens eines Bruchteils des weiter verdichteten Luftzufuhrstroms von dem Kreislauf (30) zur verstärkten Luftverdichtung zu dem Zusatzkühlkreislauf (60) ferner umfasst:

Weiterverdichten des dritten Teils (17) des verdichteten und gereinigten Luftzufuhrstroms (12) in einer Vielzahl von Verdichtungsstufen (33); und

Umleiten eines oder mehrerer Bruchteile (62A, 62B) des dritten Teils des verdichteten und gereinigten Luftzufuhrstroms von einer oder mehreren Zwischenstufenstellen der Vielzahl von Verdichtungsstufen zu dem Zusatzkühlkreislauf(60);

Regeln der Strömung oder des umgeleiteten einen oder der umgeleiteten mehreren Bruchteile des dritten Teils des verdichteten und gereinigten Luftzufuhrstroms mit einem oder mehreren Stromregelventilen (67A, 67B, 67C, 67D), die zwischen dem Kreislauf zur verstärkten Luftverdichtung und dem zweiten Turboexpander (64) in dem Zusatzkühlkreislauf angeordnet sind;

wobei der Eingangsdruck zu dem zweiten Turboexpander in dem Zusatzkühlkreislauf durch Einstellen des einen oder der mehreren Stromregelventile geregelt wird, was wiederum den zweiten Teil der von dem Destillationskolonnensystem (54, 56, 58) erforderlichen Kühlung regelt.

9. Verfahren nach Anspruch 1, wobei der Zusatzkühlkreislauf (60) ferner einen Zusatzverdichter (63) umfasst und wobei das Verfahren ferner die Schritte umfasst:

Umleiten des Bruchteils des weiter verdichteten Luftzufuhrstroms von dem Kreislauf (30) zur verstärkten Luftverdichtung zu dem Zusatzverdichter;

Weiterverdichten des umgeleiteten Bruchteils des verdichteten Luftzufuhrstroms von dem Kreislauf zur verstärkten Luftverdichtung in dem Zusatzverdichter (63);

teilweises Kühlen des weiter verdichteten umgeleiteten Bruchteils in dem Zusatzwärmetauscher durch indirekten Wärmeaustausch mit dem umgeleiteten Teil (28) des ersten Kühlstroms (22);

Expandieren des teilweise gekühlten weiter verdichteten umgeleiteten Bruchteils in dem zweiten Turboexpander;

Weiterkühlen des expandierten umgeleiteten Bruchteils in dem Zusatzwärmetauscher durch indirekten Wärmeaustausch mit dem umgeleiteten Teil des ersten Kühlstroms, um den gekühlten zweiten Kühlstrom (66) zu erzeugen; und

Leiten des gekühlten zweiten Kühlstroms zu der Hochdruckkolonne (54) des Destillationskolonnensystems, um den zweiten Teil der von dem Destillationskolonnensystem erforderlichen Kühlung zu übertragen.

10. Lufttrenneinheit, die dazu konfiguriert ist, mindestens einen Flüssigproduktstrom (76, 88) zu erzeugen, wobei die Lufttrenneinheit (10) umfasst:

eine Eingangsluftverdichtungs- und -reinigungskette, die dazu konfiguriert ist, einen verdichteten und gereinigten Luftzufuhrstrom (12) zu erzeugen;

einen primären Kühlkreislauf (20), aufweisend einen ersten Turbo-expander (26), wobei der primäre Kühlkreislauf betriebsmäßig an die Eingangsluftverdichtungs- und -reinigungskette gekoppelt ist und dazu konfiguriert ist, einen ersten Teil (13) des verdichteten und gereinigten Luftzufuhrstroms aufzunehmen und den ersten Teil des verdichteten und gereinigten Luftzufuhrstroms in dem ersten Turboexpander zu expandieren, um einen ersten gekühlten Kühlstrom (22) zu erzeugen;

einen Hauptwärmetauscher (40), der betriebsmäßig an die Eingangsluftverdichtungs- und -reinigungskette gekoppelt ist und dazu konfiguriert ist, einen zweiten Teil (15) des verdichteten und gereinigten Luftzufuhrstroms aufzunehmen und den zweiten Teil des verdichteten und gereinigten Luftzufuhrstroms auf eine Temperatur zu kühlen, die zur Rektifikation des verdichteten und gereinigten Luftzufuhrstroms geeignet ist;

Kreislauf (30) zur verstärkten Luftverdichtung, der betriebsmäßig an die Eingangsluftverdichtungs- und -reinigungskette und den Hauptwärmetauscher gekoppelt ist, wobei der Kreislauf zur verstärkten Luftverdichtung dazu konfiguriert ist, einen dritten Teil (17) des verdichteten und gereinigten Luftzufuhrstroms aufzunehmen, den dritten Teil weiter zu verdichten und einen ersten Teil (32) des weiter verdichteten dritten Teils zu dem Hauptwärmetauscher zu leiten, um einen Flüssigluftstrom (34) zu erzeugen;

einen zweiten Turboexpander (64), der dazu konfiguriert ist, einen zweiten Teil (62A; 62B) des weiter verdichteten dritten Teils aufzunehmen und den Bruchteil des weiter verdichteten dritten Teils zu expandieren, um einen zweiten Kühlstrom zu erzeugen; und

einen Zusatzwärmetauscher (65), der betriebsmäßig an die Eingangsluftverdichtungs- und -reinigungskette, den Kreislauf zur verstärkten Luftverdichtung und den primären Kühlkreislauf gekoppelt ist, wobei der Zusatzwärmetauscher dazu konfiguriert ist, einen vierten Teil (19) des verdichteten und gereinigten Luftzufuhrstroms aufzunehmen und den vierten Teil des verdichteten und gereinigten Luftzufuhrstroms und den zweiten Kühlstrom durch indirekten Wärmeaustausch mit einem umgeleiteten Teil (28) des ersten Kühlstroms zu kühlen;

ein Destillationskolonnensystem (54, 56, 58), das betriebsmäßig an die Eingangsluftverdichtungs- und -reinigungskette, den Kreislauf zur verstärkten Luftverdichtung und den Zusatzwärmetauscher gekoppelt ist, wobei das Destillationskolonnensystem dazu konfiguriert ist, etwas von dem ersten Kühlstrom und etwas von dem oder den gesamten zweiten Kühlstrom, den Flüssigluftstrom und den gekühlten zweiten Teil des verdichteten und gereinigten Luftzufuhrstroms durch ein kryogenes Rektifikationsverfahren zu rektifizieren, um den mindestens einen Flüssigproduktstrom zu erzeugen; und

einen Rückführungskreislauf, der den Zusatzwärmetauscher mit dem primären Kühlkreislauf verbindet, wobei ein Teil des zweiten Kühlstroms zu dem ersten Kühlkreislauf zurückgeführt wird.

11. Lufttrenneinheit nach Anspruch 10, wobei der primäre Kühlkreislauf (20) ferner einen Verdichter (24) umfasst, der zum Weiterverdichten des ersten Teils (13) des verdichteten und gereinigten Luftzufuhrstroms (12) innerhalb des primären Kühlkreislaufs (20) konfiguriert ist; und wobei der Verdichter betriebsmäßig an den Hauptwärmetauscher (40) gekoppelt ist, sodass der weiter verdichtete erste Teil des verdichteten und gereinigten Luftzufuhrstroms teilweise in dem Hauptwärmetauscher gekühlt wird.

12. Lufttrenneinheit nach Anspruch 10, wobei das Destillationskolonnensystem eine Hochdruckkolonne umfasst und der gekühlte vierte Teil (69) des verdichteten und gereinigten Luftzufuhrstroms (12), der den Zusatzwärmetauscher (65) verlässt,
zu der Hochdruckkolonne (54) des Destillationskolonnensystems geleitet wird.

13. Lufttrenneinheit nach Anspruch 10, wobei der Teil des zweiten Kühlstroms, der in den ersten Kühlkreislauf (20) zurückgeführt wird, teilweise innerhalb des Zusatzwärmetauschers (65) gekühlt wird und zu einer Stelle in dem ersten Kühlkreislauf, die dem ersten Turboexpander (26) vorgeschaltet ist, zurückgeführt wird.

14. Lufttrenneinheit nach Anspruch 10, ferner umfassend einen Zusatzkühlkreislauf (60), der einen Zusatzverdichter (63) einschließt, der dazu konfiguriert ist, den Bruchteil (62A, 62B) des weiter verdichteten Luftzufuhrstroms von dem Kreislauf (30) zur verstärkten Luftverdichtung aufzunehmen, wobei der zweite Turboexpander dazu konfiguriert ist, einen verdichteten Luftstrom (61) von dem Zusatzverdichter aufzunehmen und den verdichteten Luftstrom zu expandieren und der Zusatzwärmetauscher (65) dazu konfiguriert ist, den expandieren Luftstrom von dem zweiten Turboexpander aufzunehmen.

15. Lufttrenneinheit nach Anspruch 14, wobei der Kreislauf (30) zur verstärkten Luftverdichtung ferner eine Vielzahl von Verdichtungsstufen (33) und einen Umleitungskreislauf zum Umleiten einer oder mehrerer Bruchteile (6A, 62B) des weiter verdichteten Luftzufuhrstroms von einer oder mehreren Zwischenstufenstellen der Vielzahl von Verdichtungsstufen zu dem Zusatzkühlkreislauf (60) umfasst.

Revendications

1. Procédé de séparation d'air dans une unité de séparation d'air (10) comprenant un échangeur thermique principal (40) configuré pour refroidir un courant d'air d'alimentation comprimé et purifié à une température appropriée pour la rectification et un système de colonne de distillation (54, 56, 58) configuré pour rectifier le courant d'air comprimé, purifié et refroidi pour produire au moins un courant de produit liquide (76, 88), le procédé comprenant les étapes consistant à :

comprimer et purifier un courant d'air d'alimentation pour produire le courant d'air d'alimentation comprimé et purifié (12) ;

dévier une première portion (13) du courant d'air d'alimentation comprimé et purifié vers un premier

circuit de réfrigération (20) configuré pour produire un premier courant de réfrigération refroidi (22) ;

dévier une deuxième portion (15) du courant d'air d'alimentation comprimé et purifié vers l'échangeur thermique principal

pour refroidir la deuxième portion du courant d'air d'alimentation comprimé et purifié et dans lequel la deuxième portion refroidie du courant d'air d'alimentation comprimé et purifié est ensuite dirigée vers la colonne à haute pression (54) du système de colonne de distillation ;

dévier une troisième portion (17) du courant d'air d'alimentation comprimé et purifié vers un circuit de compression d'air d'appoint (30) configuré pour produire un courant d'air d'alimentation davantage comprimé et dans lequel une première partie (32) du courant d'air d'alimentation davantage comprimé est dirigée vers l'échangeur thermique principal où le courant d'air d'alimentation davantage comprimé est refroidi pour produire un courant d'air liquide (34) qui est dirigé vers le système de colonne de distillation ;

dévier une deuxième partie (62A, 62B) du courant d'air d'alimentation davantage comprimé depuis le circuit de compression d'air d'appoint vers un circuit de réfrigération auxiliaire (60) configuré pour produire un deuxième courant de réfrigération (66), le circuit de réfrigération auxiliaire comprenant un deuxième turbo-détendeur (64) et un échangeur thermique auxiliaire (65) ;

dévier une quatrième portion (19) du courant d'air d'alimentation comprimé et purifié vers l'échangeur thermique auxiliaire ;

dévier une partie (28) du premier courant de réfrigération depuis le premier circuit de réfrigération vers

l'échangeur thermique auxiliaire et réchauffer la portion déviée du premier courant de réfrigération dans l'échangeur thermique auxiliaire par l'intermédiaire d'un échange thermique indirect avec la quatrième portion déviée du courant d'air d'alimentation comprimé et purifié et avec le deuxième courant de réfrigération pour refroidir le deuxième courant de réfrigération ;

diriger la quatrième portion du courant d'air d'alimentation comprimé et purifié quittant l'échangeur thermique auxiliaire vers le système de colonne de distillation ;

diriger une partie restante du premier courant de réfrigération vers une colonne à plus basse pression (56) du système de colonne de distillation pour communiquer une première portion de la réfrigération requise par le système de colonne de distillation ; et

diriger une portion refroidie (68) du deuxième courant de réfrigération vers la colonne à plus haute pression du système de colonne de distillation pour communiquer une deuxième portion de la réfrigération requise par le système de colonne de distillation

dévier une portion (27) du deuxième courant de réfrigération depuis le circuit de réfrigération auxiliaire vers le premier circuit de réfrigération ; et combiner (150) la portion déviée du deuxième courant de réfrigération avec la première portion du courant d'air d'alimentation comprimé et purifié dans le premier circuit de réfrigération.

2. Procédé selon la revendication 1, comprenant en outre les étapes consistant à :

comprimer davantage la première portion (13) du courant d'air d'alimentation comprimé et purifié (12) au sein du premier circuit de réfrigération (20) ;

refroidir la première portion davantage comprimée du courant d'air d'alimentation comprimé et purifié ; et

détendre la première portion davantage comprimée du courant d'air d'alimentation comprimé et purifié dans un premier turbo-détendeur (26) disposé au sein du premier circuit de réfrigération pour produire le premier courant de réfrigération (22).

3. Procédé selon la revendication 2 dans lequel l'étape de refroidissement de la première portion davantage comprimée (13) du courant d'air d'alimentation comprimé et purifié comprend en outre (12) le refroidissement de la première portion davantage comprimée du courant d'air d'alimentation comprimé et purifié dans un postrefroidisseur.

4. Procédé selon la revendication 2 dans lequel l'étape de refroidissement de la première portion davantage comprimée (13) du courant d'air d'alimentation comprimé et purifié (12) comprend en outre le refroidissement partiel de la première portion davantage comprimée du courant d'air d'alimentation comprimé et purifié dans l'échangeur thermique principal (40).

5. Procédé selon la revendication 1 dans lequel dans l'étape consistant à diriger la quatrième portion refroidie (69) du courant d'air d'alimentation comprimé et purifié (12) vers le système de colonne de distillation (54, 56, 58) la quatrième portion refroidie du courant d'air d'alimentation comprimé et purifié est dirigée vers la colonne à plus haute pression (54) du système de colonne de distillation.

6. Procédé selon la revendication 2 dans lequel l'étape consistant à diriger une portion refroidie du deuxième
courant de réfrigération (66) vers la colonne à plus haute pression (54) comprend la déviation d'une portion du deuxième courant de réfrigération qui est partiellement refroidie depuis l'échangeur thermique auxiliaire (65) dans le circuit de réfrigération auxiliaire (60) vers le premier circuit de réfrigération (20) ; et
dans lequel l'étape de combinaison de la portion déviée du deuxième courant de réfrigération avec la première portion (13) du courant d'air d'alimentation comprimé et purifié (12) dans le premier circuit de réfrigération
comprend la combinaison de la portion déviée du deuxième courant de réfrigération avec la première portion du courant d'air d'alimentation comprimé et purifié dans le premier circuit de réfrigération en amont du premier turbo-détendeur (26) disposé au sein du premier circuit de réfrigération.

7. Procédé selon la revendication 1 dans lequel l'étape de déviation d'une fraction du courant d'air d'alimentation davantage comprimé depuis le circuit de compression d'air d'appoint (30) vers le circuit de réfrigération auxiliaire (60) comprend en outre :

le fait de comprimer davantage la troisième portion (17) du courant d'air d'alimentation comprimé et purifié (12)

dans une pluralité d'étages de compression (33) ; et

la déviation d'une première fraction (62A, 62B) de la troisième portion du courant d'air d'alimentation comprimé et purifié depuis un emplacement entre étages de la pluralité d'étages de compression vers le circuit de réfrigération auxiliaire.

8. Procédé selon la revendication 1 dans lequel l'étape de déviation d'une fraction du courant d'air d'alimentation davantage comprimé depuis le circuit de compression d'air d'appoint (30) vers le circuit de réfrigération auxiliaire (60) comprend en outre :

le fait de comprimer davantage la troisième portion (17) du courant d'air d'alimentation comprimé et purifié (12) dans une pluralité d'étages de compression (33) ; et

la déviation d'une ou plusieurs fractions (62A, 62B) de la troisième portion du courant d'air d'alimentation comprimé et purifié depuis un ou plusieurs emplacements entre étages de la pluralité d'étages de compression vers le circuit de réfrigération auxiliaire (60) ;

la commande de l'écoulement de la ou des fractions déviées de la troisième portion du

courant d'air d'alimentation comprimé et purifié avec une ou plusieurs vannes de régulation de débit (67A, 67B, 67C, 67D) disposées entre le circuit de compression d'air d'appoint et le deuxième turbo-détendeur (64) dans le circuit de réfrigération auxiliaire ;

dans lequel la pression d'entrée au deuxième turbo-détendeur dans le circuit de réfrigération auxiliaire est commandée en réglant la ou les vannes de régulation de débit ce qui à son tour commande la deuxième portion de la réfrigération requise par le système de colonne de distillation (54, 56, 58),

9. Procédé selon la revendication 1 dans lequel le circuit de réfrigération auxiliaire (60) comprend en outre un compresseur auxiliaire (63), et dans lequel le procédé comprend en outre les étapes consistant à :

dévier la fraction du courant d'air d'alimentation davantage comprimé depuis le circuit de compression d'air

d'appoint (30) vers le compresseur auxiliaire ;

comprimer davantage la fraction déviée du courant d'air d'alimentation comprimé provenant du circuit de compression d'air d'appoint dans le compresseur auxiliaire (63) ;

refroidir partiellement la fraction déviée davantage comprimée dans l'échangeur thermique auxiliaire par l'intermédiaire d'un échange thermique indirect avec la portion déviée (28) du premier courant de réfrigération (22) ;

détendre la fraction déviée davantage comprimée partiellement refroidie dans le deuxième turbo-détendeur ;

refroidir davantage la fraction déviée détendue dans l'échangeur thermique auxiliaire par l'intermédiaire d'un échange thermique indirect avec la portion déviée du premier courant de réfrigération pour produire le deuxième courant de réfrigération refroidi (66) ; et

diriger le deuxième courant de réfrigération refroidi vers la colonne à plus haute pression (54) du système de colonne de distillation pour communiquer la deuxième portion de la réfrigération requise par le système de colonne de distillation.

10. Unité de séparation d'air configurée pour produire au moins un courant de produit liquide (76, 88), l'unité de séparation d'air (10) comprenant :

une chaîne de compression et de purification d'air entrant configurée pour produire un courant d'air d'alimentation comprimé et purifié (12) ;

un circuit de réfrigération primaire (20) ayant un premier turbo-détendeur (26), le circuit de réfrigération primaire couplé fonctionnellement à la chaîne de compression et de purification d'air entrant et configuré pour recevoir une première portion (13) du courant d'air d'alimentation comprimé et purifié et détendre la première portion du courant d'air d'alimentation comprimé et purifié dans le premier turbo-détendeur pour produire un premier courant de réfrigération refroidi (22) ;

un échangeur thermique principal (40) couplé fonctionnellement à la chaîne de compression et de purification d'air entrant et configuré pour recevoir une deuxième portion (15) du courant d'air d'alimentation comprimé et purifié et pour refroidir la deuxième portion du courant d'alimentation comprimé et purifié à une température appropriée pour la rectification du courant d'air d'alimentation comprimé et purifié ;

un circuit de compression d'air d'appoint (30) couplé fonctionnellement à la chaîne de compression et de purification d'air entrant et à l'échangeur thermique principal, le circuit de compression d'air d'appoint configuré pour recevoir une troisième portion (17) du courant d'air d'alimentation comprimé et purifié, comprimer davantage la troisième portion et diriger une première partie (32) de la troisième portion davantage comprimée vers l'échangeur thermique principal pour produire un courant d'air liquide (34) ;

un deuxième turbo-détendeur (64) configuré pour recevoir une deuxième partie (62A ; 62B) de la troisième portion davantage comprimée et détendre la fraction de la troisième portion davantage comprimée pour produire un deuxième courant de réfrigération ; et

un échangeur thermique auxiliaire (65) couplé fonctionnellement à la chaîne de compression et de purification d'air entrant, au circuit de compression d'air d'appoint et au circuit de réfrigération primaire, l'échangeur thermique auxiliaire configuré pour recevoir une quatrième portion (19) du courant d'air d'alimentation comprimé et purifié et refroidir la quatrième portion du courant d'air d'alimentation comprimé et purifié et le deuxième courant de réfrigération par l'intermédiaire d'un échange thermique indirect avec une portion déviée (28) du premier courant de réfrigération ;

un système de colonne de distillation (54, 56, 58) couplé fonctionnellement au circuit de réfrigération primaire, au circuit de compression d'air d'appoint et à l'échangeur thermique auxiliaire, le système de colonne de distillation configuré pour rectifier une partie du premier courant de réfrigération, et une partie ou la totalité du deuxième courant de réfrigération, du courant d'air liquide et de la deuxième portion refroidie du courant d'air d'alimentation comprimé et purifié par un processus de rectification cryogénique pour produire l'au moins un courant de produit liquide ; et

un circuit de recyclage raccordant l'échangeur thermique auxiliaire au circuit de réfrigération primaire dans laquelle une portion du deuxième courant de réfrigération est recyclée vers le premier circuit de réfrigération.

11. Unité de séparation d'air selon la revendication 10 dans laquelle le circuit de réfrigération primaire (20) comprend en outre un compresseur (24) configuré pour comprimer davantage la première portion (13) du courant d'air d'alimentation comprimé et purifié (12) au sein du circuit de réfrigération primaire (20) ; et dans laquelle le compresseur est couplé fonctionnellement à l'échangeur thermique principal (40) de telle sorte que la première portion davantage comprimée du courant d'air d'alimentation comprimé et purifié est partiellement refroidie dans l'échangeur thermique principal.

12. Unité de séparation d'air selon la revendication 10 dans laquelle le système de colonne de distillation comprend une colonne à plus haute pression et la quatrième portion refroidie (69) du
courant d'air d'alimentation comprimé et purifié (12) quittant l'échangeur thermique auxiliaire (65) est dirigée vers la
colonne à plus haute pression (54) du système de colonne de distillation.

13. Unité de séparation d'air selon la revendication 10 dans laquelle la portion du deuxième courant de réfrigération recyclée vers le premier circuit de réfrigération (20) est partiellement refroidie au sein de l'échangeur thermique auxiliaire (65) et est recyclée vers un emplacement dans le premier circuit de réfrigération en amont du premier turbo-détendeur (26).

14. Unité de séparation d'air selon la revendication 10 comprenant en outre un circuit de réfrigération auxiliaire (60) qui inclut un compresseur auxiliaire (63) configuré pour recevoir la fraction (62A, 62B) du courant d'air d'alimentation davantage comprimé déviée depuis le circuit de compression d'air d'appoint (30), le deuxième turbo-détendeur configuré pour recevoir un courant d'air comprimé (61) depuis le compresseur auxiliaire et détendre le courant d'air comprimé, et l'échangeur thermique auxiliaire (65) configuré pour recevoir le courant d'air détendu depuis le deuxième turbo-détendeur.

15. Unité de séparation d'air selon la revendication 14 dans laquelle le circuit de compression d'air d'appoint (30) comprend en outre une pluralité d'étages de compression (33) et un circuit de déviation pour dévier une ou plusieurs fractions (6A, 62B) du courant d'air d'alimentation davantage comprimé depuis un ou plusieurs emplacements entre étages de la pluralité d'étages de compression vers le circuit de réfrigération auxiliaire (60).

Drawing