Thermal integration temperature balancing of air separation unit and power generation system

Abstract

A method of temperature balancing for thermal integration of an air separation unit with an oxycombustion power generation system, including compressing air, routing a first stage compressed air stream through a first heat exchanger in heat exchange communication with a subsequent stage compressed air stream, taking the heated first stage compressed air stream and routing the heated first stage compressed air stream through a second heat exchanger in heat exchange communication with a first fluid going to the power generation system, routing the further cooled, first stage compressed air stream to a subsequent compression stage, routing the subsequent compressed air stream exiting from the heat exchanger to a third heat exchanger in heat exchange communication with the first and / or a second fluid going to the power generation system to cool the subsequent air stream exiting from the heat exchanger.

Description

BACKGROUND

[0001] For power generation systems with oxy-combustion, the oxygen is usually supplied by an air separation unit (ASU) nearby. It is possible to envision some thermal integration between the power generation system and warm air coming from one or several uncooled or partially cooled Main Air Compressor(s) (MAC) or / and Booster Air Compressor(s) (BAC) of the ASU. Some power plants can require some heat to be transferred. This heat can be supplied via the warm air with a minimum and / or maximum temperature as well as a minimum and / or maximum pressure from the ASU to the power plant. Some of those constraints can be difficult to achieve as it must stay within the capabilities of the turbomachinery as well as the pressure and temperature requirements of the ASU.SUMMARY

[0002] A method of temperature balancing for thermal integration of an air separation unit with an oxycombustion power generation system, including compressing air, routing a first stage compressed air stream through a first heat exchanger in heat exchange communication with a subsequent stage compressed air stream, taking the heated first stage compressed air stream and routing the heated first stage compressed air stream through a second heat exchanger in heat exchange communication with a first fluid going to the power generation system, routing the further cooled, first stage compressed air stream to a subsequent compression stage, routing the subsequent compressed air stream exiting from the heat exchanger to a third heat exchanger in heat exchange communication with the first and / or a second fluid going to the power generation system to cool the subsequent air stream exiting from the heat exchanger.BRIEF DESCRIPTION OF THE FIGURES

[0003] For a further understanding of the nature and objects for the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein:

[0004] FIG. 1 is a schematic representation of a method for thermal integration heat balancing as known in the art.

[0005] FIG. 2 is another schematic representation of a method for thermal integration heat balancing as known in the art.

[0006] FIG. 3 is a schematic representation of a method for thermal integration heat balancing in accordance with one embodiment of the present invention.ELEMENT NUMBERS101=inlet air stream

[0008] 102=first compressor

[0009] 103=first compressed air stream

[0010] 104=first heat exchanger

[0011] 105=first cooled compressed air stream

[0012] 106=second heat exchanger

[0013] 107=further cooled first air stream

[0014] 108=second compressor

[0015] 109=second compressed air stream

[0016] 110=heated second compressed air stream

[0017] 111=third heat exchanger

[0018] 112=cooled second compressed air stream

[0019] 113=precoolers and dryers

[0020] 114=cooled compressed air (to main heat exchanger)

[0021] 115=first fluid to be heated

[0022] 116=heated first fluid

[0023] 117=second fluid to be heated

[0024] 118=heated second fluid

[0025] 201=inlet air stream

[0026] 202=first compressor

[0027] 203=first compressed air stream

[0028] 204=first heat integration heat exchanger

[0029] 205=first cooled compressed air stream

[0030] 206=first heat exchanger

[0031] 207=further cooled first air stream

[0032] 208=second compressor

[0033] 209=second compressed air stream

[0034] 210=second heat exchanger

[0035] 211=cooled second compressed air stream

[0036] 212=second heat integration heat exchanger

[0037] 213=further cooled second compressed air stream

[0038] 214=cold first heat integration stream

[0039] 215=warm first heat integration stream

[0040] 216=cold second heat integration stream

[0041] 217=warm second heat integration stream

[0042] 301=inlet air stream

[0043] 302=first compressor

[0044] 303=first compressed air stream

[0045] 304=first heat exchanger

[0046] 305=first warmed compressed air stream

[0047] 306=second heat exchanger

[0048] 307=cooled first air stream

[0049] 308=second compressor

[0050] 309=second compressed air stream

[0051] 310=warmed second compressed air stream

[0052] 311=third heat exchanger

[0053] 312=cooled second compressed air stream

[0054] 313=precoolers and dryers

[0055] 314=cooled compressed air (to main heat exchanger and / or to booster compressor)

[0056] 315=first fluid to be heated

[0057] 316=heated first fluid

[0058] 317=second fluid to be heated

[0059] 318=heated second fluidDescription of Preferred Embodiments

[0060] Illustrative embodiments of the invention are described below. While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

[0061] It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

[0062] Turning to FIG. 1, a thermal integration system as discussed in U.S. Pat. No. 10,712,088, the entirety of which is incorporated by reference herein,\is presented. Inlet air stream 101 is introduced into first compressor 102, thereby producing first compressed air stream 103. First compressed air stream 103 has a temperature of T1. First compressed air stream 103 is introduced into first heat exchanger 104, wherein it exchanges heat with second compressed air stream 109, thereby producing first cooled compressed air stream 105. First cooled compressed air stream 105 has a temperature of T2, wherein T2 is lower than T1.

[0063] First cooled compressed air stream 105 is introduced into second heat exchanger 106, wherein it exchanges heat with first fluid to be heated 115, thereby producing further cooled first air stream 107 and first heated fluid 116. Further cooled first air stream 107 has a temperature of T3, wherein T3 is lower than T2, and T3 is lower than T1. Further cooled first air stream 107 is introduced into second compressor 108, thereby producing second compressed air stream 109. Second compressed air stream 109 has a temperature of T4, wherein T4 is lower than T2.

[0064] Second compressed air stream 109 is introduced into first heat exchanger 104, thereby producing heated second compressed air stream 110. Heated second compressed air stream 110 has a temperature of T5, wherein T5 is greater than T4. The overall system heat balance should be adjusted such that T2 is as close to T5 as possible, thereby optimizing the heat integration. Heated second compressed air stream 110 is introduced into third heat exchanger 111, wherein it exchanges heat with second fluid to be heated 117, thereby producing cooled second compressed air stream 112 and second heated fluid 118. Cooled second compressed air stream 112 is then typically introduced into a system of precoolers and dryers 113, thereby producing a cool, dry compressed air stream that is then sent to the main heat exchanger of the air separation unit.

[0065] Turning to FIG. 2, another thermal integration system as is known in the art is presented. Inlet air stream 201 is introduced into first compressor 202, thereby producing first compressed air stream 203. First compressed air stream 203 has a temperature of T1. First compressed air stream 203 is introduced into first heat integration heat exchanger 204, wherein it exchanges heat with cold first heat integration stream 214, thereby producing first cooled compressed air stream 205 and warm first heat integration stream 215. First cooled compressed air stream 205 has a temperature of T2, wherein T2 is lower than T1.

[0066] First cooled compressed air stream 205 is introduced into first heat exchanger 206, thereby producing further cooled first air stream 207. Further cooled first air stream 207 has a temperature of T3, wherein T3 is lower than T2, and T3 is lower than T1. Further cooled first air stream 207 is introduced into second compressor 208, thereby producing second compressed air stream 209. Second compressed air stream 209 has a temperature of T4, wherein T3 is lower than T4.

[0067] Second compressed air stream 209 is introduced into second heat exchanger 210, thereby producing cooled second compressed air stream 211. Cooled second compressed air stream 211 has a temperature of T5, wherein T4 is greater than T5.

[0068] The overall system heat balance should be adjusted such that T5 is as close to T1 as possible, thereby optimizing the heat integration. Cooled second compressed air stream 211 is introduced into second heat integration heat exchanger 212, wherein it exchanges heat with cold second heat integration stream 216, thereby producing further cooled second compressed air stream 213 and warm second heat integration stream 217.

[0069] Turning to FIG. 3, one embodiment of a thermal integration system in accordance with the present invention is presented. Inlet air stream 301 is introduced into first compressor 302, thereby producing first compressed air stream 303. First compressed air stream 303 has a temperature of T1. First compressed air stream 303 is introduced into first heat exchanger 304, wherein it exchanges heat with second compressed air stream 309, thereby producing first warmed compressed air stream 305. First warmed compressed air stream 305 has a temperature of T2, wherein T2 is higher than T1.

[0070] First warmed compressed air stream 305 is introduced into second heat exchanger 306, wherein it exchanges heat with first fluid to be heated 315, thereby producing cooled first air stream 307 and first heated fluid 316. Cooled first air stream 307 has a temperature of T3, wherein T3 is lower than T2. Cooled first air stream 307 is introduced into second compressor 308, thereby producing second compressed air stream 309. Second compressed air stream 309 has a temperature of T4. The present invention addresses the operating condition wherein T4 is higher than T2. In one non-limiting example, second compressor 308 has a higher compression ratio than first compressor 302.

[0071] Second compressed air stream 309 is introduced into first heat exchanger 304, thereby producing cooled second compressed air stream 310. Cooled second compressed air stream 310 has a temperature of T5, wherein T5 is less than T4. The overall system heat balance should be adjusted such that T2 is as close to T5 as possible, thereby optimizing the heat integration. Cooled second compressed air stream 310 is introduced into third heat exchanger 311, wherein it exchanges heat with second fluid to be heated 317, thereby producing cooled second compressed air stream 312 and second heated fluid 318. Cooled second compressed air stream 312 is then typically introduced into a system of precoolers and dryers 313, thereby producing a cool, dry compressed air stream that is then sent to the main heat exchanger of the air separation unit.

[0072] It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above.

Claims

1. A method of temperature balancing for thermal integration of an air separation unit with an oxycombustion power generation system, the method comprising the steps of:a) compressing air through a plurality of compression stages,b) routing a first stage compressed air stream through a first heat exchanger in heat exchange communication with a subsequent stage compressed air stream thereby increasing the first stage compressed air stream temperature and decreasing the temperature of a subsequent stage compressed air stream,c) taking the heated first stage compressed air stream from step b) and routing the heated first stage compressed air stream through a second heat exchanger in heat exchange communication with a first fluid going to the power generation system to further cool the cooled, first stage compressed air stream and increase the temperature of the first fluid going to the power generation system,d) routing the further cooled, first stage compressed air stream to a subsequent compression stage to produce the subsequent air stream that is further compressed and heated from the compression,e) routing the subsequent compressed air stream exiting from the heat exchanger in step b) to a third heat exchanger in heat exchange communication with the first and / or a second fluid going to the power generation system to cool the subsequent air streamexiting from the heat exchanger.

2. The method of claim 1, further comprising routing the cooled subsequent air stream of step e) to precooling and drying steps and then to a main heat exchanger of the air separation unit.

3. The method of claim 1, wherein the first stage compression is a MAC producing the first stage compressed air stream at less than about 10 bar.

4. The method of claim 1, wherein the temperatures of the heated first stage compressed air stream exiting from the heat exchanger in step b) and the subsequent compressed air stream exiting from the heat exchanger in step b), are within twenty degrees Celsius of each other.

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