Turbine-powered air compressor assembly for a system for dehydrogenation of a hydrocarbon

Abstract

The present disclosure provides a turbine-powered air compressor assembly, which includes a gas turbine having a first dual-end power shaft and a startup motor having a second dual-end power shaft with a power shaft end facing the gas turbine and a power shaft end distal from the gas turbine. The assembly also includes a first air compressor, the gas turbine being drivingly connected to the first air compressor. The power shaft end distal from the gas turbine of the startup motor is drivingly connected to a second air compressor. The disclosure also provides a system for dehydrogenation of a hydrocarbon, which includes a dehydrogenation reactor comprising a catalyst bed in fluid communication with a hydrocarbon feed source; and a regeneration air source in fluid communication with the dehydrogenation reactor, wherein the regeneration air source is the turbine-powered air compressor assembly described above.

Description

TURBINE-POWERED AIR COMPRESSOR ASSEMBLY FOR A SYSTEM FOR DEHYDROGENATION OF A HYDROCARBONTECHNOLOGICAL FIELD

[0001] The present disclosure relates to a turbine-powered air compressor assembly, and related methods of use in systems and processes for dehydrogenation of a hydrocarbon.BACKGROUND

[0002] Fixed bed dehydrogenation units are used for production of olefins and / or alkynes from alkanes and / or olefins. Generally, a fixed bed dehydrogenation unit comprises three or more parallel fixed bed reactors and a catalyst regeneration system. When the fixed bed dehydrogenation unit is in operation, one or more reactors are on line (in dehydrogenation mode), and one or more fixed bed reactors are in regeneration mode.

[0003] A fixed bed reactor in dehydrogenation mode first dehydrogenates the hydrocarbon feed for a period of time. Then, the fixed bed reactor is purged with steam. In a subsequent regeneration mode, heated air is blown through to decoke the catalyst disposed in the fixed bed reactor. The reactor is in turn evacuated and the catalyst in the reactor undergoes reduction. After catalyst reduction, the reactor is placed back online for dehydrogenation reactions. The same sequence is repeated automatically for each fixed bed reactor using a programmable logic controller (PLC) to ensure continuous production of the entire dehydrogenation unit.

[0004] There is a desire to increase hydrocarbon flow to the dehydrogenation reactors to increase production, but without concomitant increases in regeneration air supply, the air to hydrocarbon ratio in the process is reduced. This results in wider temperature swings within the catalyst beds, which can decrease production. There remains a need in the art to increase the air supply to the dehydrogenation reactors in an efficient way while minimizing capital costs.BRIEF SUMMARY

[0005] Example implementations of the present disclosure are directed to a turbine- powered air compressor assembly useful for supplying regeneration air fordehydrogenation of a hydrocarbon. The air compressor assembly utilizes a startup motor (e.g., a turbine), typically already present in the plant, to aid in startup of a gas turbine for driving a primary regeneration air compressor, to drive a second regeneration air compressor. In a conventional system arrangement, the startup turbine is used to drive the power shaft of the gas turbine until the gas turbine reaches an rpm suitable for independent turbine operation and is thereafter idled. In the present disclosure, the startup turbine can be used to drive additional regeneration air into a dehydrogenation reactor rather than remain idle for the long periods of time between gas turbine startups.

[0006] The present disclosure includes, without limitation, the following embodiments.

[0007] Embodiment 1 : A system for dehydrogenation of a hydrocarbon, comprising: i) a dehydrogenation unit (100) comprising a catalyst bed reactor in fluid communication with a hydrocarbon feed (11) source; and ii) a regeneration air source in fluid communication with the dehydrogenation unit, wherein the regeneration air source is the turbine-powered air compressor assembly (82) comprising: a) a gas turbine (60) comprising: i. a first dual-end power shaft axially extending through the gas turbine and ii. a first power shaft end (52) and iii. a second power shaft end (54) iv. a startup motor comprising: 1. a second dual-end power shaft axially extending through the startup motor and 2. a power shaft end facing the gas turbine and 3. a power shaft end distal from the gas turbine, wherein the power shaft end facing the gas turbine is drivingly connected to the first power shaft end (52) of the gas turbine (60) via a clutch that enables coupling and decoupling of the startup motor from the gas turbine; b) a first air compressor (40), the second power shaft end (54) of the gas turbine (60) being drivingly connected to the first air compressor such that the first air compressor is positioned on a side of the gas turbine opposite the startup motor; and c) a second air compressor (80), the power shaft end distal from the gas turbine of the startup motor being drivingly connected to the second air compressor such that the second air compressor is positioned on a side of the startup motor opposite the gas turbine..

[0008] Embodiment 2: The system of Embodiment 1, further comprising a clutch between the second air compressor and the startup motor that enables coupling and decoupling of the startup motor from the second air compressor.

[0009] Embodiment 3: The system of Embodiment 1 or 2, wherein the startup motor is a steam turbine.

[0010] Embodiment 4: The system of any one of Embodiments 1 to 3, wherein the power output of the startup motor, in MW, is about 30% or less of the power output of the gas turbine.

[0011] Embodiment 5: The system of any one of Embodiments 1 to 4, wherein the first air compressor outputs about 550 to about 820 t / hr of air and the second air compressor outputs about 120 to about 220 t / hr of air.

[0012] Embodiment 6: A system for dehydrogenation of a hydrocarbon, comprising: a dehydrogenation reactor comprising a catalyst bed in fluid communication with a hydrocarbon feed source; and a regeneration air source in fluid communication with the dehydrogenation reactor, wherein the regeneration air source is the turbine-powered air compressor assembly of any one of Embodiments 1 to 5.

[0013] Embodiment 7: The system of Embodiment 6, further comprising a reducing gas source in fluid communication with the dehydrogenation reactor and / or a steam purge gas source in fluid communication with the dehydrogenation reactor.

[0014] Embodiment 8: The system of Embodiment 6 or 7, wherein the hydrocarbon feed source provides a hydrocarbon selected from the group consisting of propane, isobutane, pentane, isopentane, n-butane, 1 -butene, and combinations thereof.

[0015] Embodiment 9: A method for hydrogenation of a hydrocarbon in a dehydrogenation reactor, comprising: a turbine-powered air compressor assembly which at least includes:a gas turbine; a startup motor; dual end power shaft;a first air compressor and a second air compressor, the method comprises at least the following steps: i) coupling the startup motor to the gas turbine prior to gas turbine startup; ii) operating the startup motor to drive the first dual-end power shaft until the gas turbine reaches an rpm suitable for gas turbine operation; iii) decoupling the startup motor from the gas turbine; iv) operating the gas turbine to drive power to the first air compressor; v) coupling the startup motor to the second air compressor; and vi) operating the startup motor to drivepower to the second air compressor wherein, the method further comprises a following step: passing air from the first air compressor and the second air compressor into a dehydrogenation reactor comprising a catalyst bed for regeneration of the catalyst bed..

[0016] Embodiment 10: The method of Embodiment 9, further comprising passing air from the first air compressor and the second air compressor into a dehydrogenation reactor comprising a catalyst bed for regeneration of the catalyst bed.

[0017] These and other features, aspects, and advantages of the present disclosure will be apparent from a reading of the following detailed description together with the accompanying figures, which are briefly described below. The present disclosure includes any combination of two, three, four or more features or elements set forth in this disclosure, regardless of whether such features or elements are expressly combined or otherwise recited in a specific example implementation described herein. This disclosure is intended to be read holistically such that any separable features or elements of the disclosure, in any of its aspects and example implementations, should be viewed as combinable, unless the context of the disclosure clearly dictates otherwise.

[0018] It will therefore be appreciated that this Brief Summary is provided merely for purposes of summarizing some example implementations so as to provide a basic understanding of some aspects of the disclosure. Accordingly, it will be appreciated that the above described example implementations are merely examples and should not be construed to narrow the scope or spirit of the disclosure in any way. Other example implementations, aspects and advantages will become apparent from the following detailed description taken in conjunction with the accompanying figures which illustrate, by way of example, the principles of some described example implementations.BRIEF DESCRIPTION OF THE FIGURES

[0019] Having thus described aspects of the disclosure in the foregoing general terms, reference will now be made to the accompanying figures, which are not necessarily drawn to scale, and wherein:

[0020] FIG. l is a schematic representation of a dehydrogenation reactor system according to an example implementation of the present disclosure;

[0021] FIG. 2 is a schematic representation of an example embodiment of a turbine- powered air compressor assembly according to an example implementation of the present disclosure; and

[0022] FIG. 3 is another schematic representation of an example embodiment of a turbine-powered air compressor assembly according to an example implementation of the present disclosure.DETAILED DESCRIPTION

[0023] Some implementations of the present disclosure will now be described more fully hereinafter with reference to the accompanying figures, in which some but not all implementations of the disclosure are shown. Indeed, various implementations of the disclosure may be embodied in many different forms and should not be construed as limited to the implementations set forth herein; rather, these example implementations are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Like reference numerals refer to like elements throughout.

[0024] Unless specified otherwise or clear from context, references to first, second or the like should not be construed to imply a particular order. A feature described as being above another feature (unless specified otherwise or clear from context) may instead be below, and vice versa; and similarly, features described as being to the left of another feature else may instead be to the right, and vice versa. Also, while reference may be made herein to quantitative measures, values, geometric relationships or the like, unless otherwise stated, any one or more if not all of these may be absolute or approximate to account for acceptable variations that may occur, such as those due to engineering tolerances or the like.

[0025] All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other (e.g., ranges of “up to 25 wt. %, or, more specifically, 5 wt. % to 20 wt. %”, is inclusive of the endpoints and all intermediate values of the ranges of “5 wt. % to 25 wt. %,” etc.). “Combination” is inclusive of blends, mixtures, alloys, reaction products, and the like.

[0026] As used herein, unless specified otherwise or clear from context, the “or” of a set of operands is the “inclusive or” and thereby true if and only if one or more of the operands is true, as opposed to the “exclusive or” which is false when all of the operands are true. Thus, for example, “[A] or [B]” is true if [A] is true, or if [B] is true, or if both [A] and [B] are true. Further, the articles “a” and “an” mean “one or more,” unless specified otherwise or clear from context to be directed to a singular form.

[0027] The present disclosure provides a turbine-powered air compressor assembly useful for any process or system that includes a startup turbine or other startup motor / engine that is idled during most of its life, and which can be more efficiently utilized as a power source. However, the present disclosure is particularly well-adapted for use in a dehydrogenation process where regeneration air supply is often a limiting factor.Dehydrogenation Process and System

[0028] Accordingly, the present disclosure relates to a potential improvement for a dehydrogenation process used to convert alkanes to alkenes over, for example, a chromium-alumina catalyst. The dehydrogenation process takes place in fixed bed reactors that operate on a cyclic basis to permit continuous flow of the major process streams. In one cycle, hydrocarbon vapors are dehydrogenated and the reactor is then purged with steam and blown with air to burn off coke. These steps are followed by an evacuation and reduction and then another cycle starts.

[0029] In a typical fixed bed dehydrogenation process, an aliphatic hydrocarbon (e.g., propane, isobutane, n-butane, 1 -butene, or isopentane) passes through a dehydrogenation catalyst bed and is dehydrogenated to a complementary olefin. The olefin is then flushed from the catalyst bed, the catalyst is regenerated and reduced, and the cycle is repeated. The product (dehydrogenated hydrocarbon) of the fixed bed dehydrogenation unit may comprise, for example, propylene, isobutylene, pentene, isoprene, butadiene, orcombinations thereof. The dehydrogenation reactions may include reactions (i) and / or (ii) as follows, where “n” in reactions (i) and (ii) is the number of carbon atoms in a hydrocarbon molecule, and “n” is less than 5:

[0030] C IIH2II 2^CHH2II+H2 (i), and / or

[0031] CnH2n^CnH2n-2+H2(ii).

[0032] This process can be run as an adiabatic, cyclic process. Each cycle includes a catalyst reduction step and a dehydrogenation step, and typically further includes a step to purge the remaining hydrocarbon from the reactor, and finally a regeneration step with air. Following this, the cycle begins again with the catalyst reduction step.

[0033] The reactors in dehydrogenation processes operate under vacuum. The evacuation of the reactors is accomplished using a reactor evacuation ejector, and conventionally, MP steam is used as the motive fluid.

[0034] With reference to FIG. 1, a process schematic diagram for an example implementation of a fixed bed dehydrogenation unit 100 is shown, with different reactors at different points in the process cycle. The fixed bed dehydrogenation unit 100 may include a fixed bed reactor 101 in purge mode, a fixed bed reactor 102 in dehydrogenation mode, and a fixed bed reactor 103 in regeneration mode. Each of the fixed bed reactors comprises a catalyst bed. The catalyst may include, for example, Cr / Al (chromium oxide over alumina), Sn-Pt / Al (tin-platinum over alumina), or combinations thereof.

[0035] The inlet of fixed bed reactor 102 in dehydrogenation mode may be connected to a heater 110 that is configured to heat a hydrocarbon feed to a reaction temperature, and the outlet of fixed bed reactor 102 in dehydrogenation mode may be connected to a heat exchanger 108 to cool down the effluent from fixed bed reactor 102 in dehydrogenation mode. The combined hydrocarbon stream 13, which is a combination of hydrocarbon feed stream 11 and a recycled hydrocarbon stream 12, may be vaporized and heated to a reaction temperature by heater 110. The reaction temperature is typically about 540 °C to about 750 °C. The reaction pressure is typically in a range of about 0.2 to about 1.2 bar.

[0036] Fixed bed dehydrogenation unit 100 may further include a regeneration air system comprising an air compressor 104 configured to blow air into fixed bedreactor 103 in regeneration mode, a regeneration air heater 105 configured to heat the air from air compressor 104, a fuel injector 106 configured to inject fuel gas into fixed bed reactor 103 in regeneration mode, and a heat exchanger 107 configured to cool down the effluents from fixed bed reactor 103 in regeneration mode and fixed bed reactor 101 in purge mode. Fuel injector 106 may be disposed between air compressor 104 and air heater 105. A stream 16 leaving fixed bed reactor 103 in regeneration mode may be used for generating steam via heat exchanger 107. The regenerating conditions can include a regenerating pressure of, for example, about 0.1 to about 10 bar. The regenerating conditions can include a regenerating period that is typically in a range of about 7 to about 18 minutes.

[0037] The fixed bed dehydrogenation unit 100 may further include a compression and recovery system 109 to recover and purify a dehydrogenated hydrocarbon obtained from fixed bed reactor 102 in dehydrogenation mode. Specifically, an effluent stream 14 from fixed bed reactor 102 in dehydrogenation mode may be cooled, recovered, and purified through compression and recovery system 109. Purified dehydrogenated hydrocarbon may flow in a stream 17. Recovered unreacted hydrocarbons may be recycled back to combined hydrocarbon stream 13 via recycled hydrocarbon stream 12.

[0038] The fixed bed dehydrogenation unit 100 may further include a purge gas source 20 (e.g., steam) in fluid communication with each reactor for use in the purge step and a reducing gas source 22 (e.g., hydrogen) in fluid communication with each reactor.

[0039] The process sequence can be controlled, for example, using programmable logic controllers. See, for example, the programmable logic controllers set forth in US Pat. No. 11,370,729 to Ansari et al. and US Pat. Publ. No. 2022 / 0055002 to Bodas et al, which are incorporated by reference herein in their entirety.Turbine-Powered Air Compressor Assembly

[0040] According to the present disclosure, an air compressor assembly is provided that can be used, for example, as the air compressor 104 of FIG. 1. An example implementation of an air compressor assembly is shown in FIG. 2 at reference number 30. As shown, a startup turbine 50 is positioned between a gas turbine 60 and a first air compressor 40. Startup turbine 50 has a dual-end power shaft axially extending throughthe turbine and having a first power shaft end 52 facing gas turbine 60 and a second power shaft end 54 facing first air compressor 40. The power shaft of startup turbine 50 is adapted for connection to the drive shaft of both gas turbine 60 and first air compressor 40 for providing power to both components. The connection of startup turbine 50 to each of gas turbine 60 and first air compressor 40 is typically coupleable and decouplable via a clutch, 42a and 42b, respectively.

[0041] Gas turbine 60 also comprises a dual-end power shaft adapted for connection to both startup turbine 50 as described above and a second air compressor 80. In a conventional dehydrogenation plant, second air compressor 80 driven by gas turbine 60 is the sole source of regeneration air in the process and startup turbine 50 remains idle except during startup of the gas turbine. In the present disclosure, startup turbine 60 is used more efficiently to drive an air compressor, which will increase the regeneration air supply available for use in, for example, a dehydrogenation process.

[0042] Atypical gas turbine design is also shown in FIG. 2, which illustrates gas turbine 60 comprising an internal compressor 62 receiving air from an inlet 64 and producing a pressurized effluent 66. Pressurized effluent 66 is in fluid communication with an internal combustor 68, with the internal combustor also receiving a combustible fuel 70. The combustor effluent 72 enters an internal turbine 74 that produces work from the energy of the gas. The exhaust 76 from the gas turbine 60 can be fed to a waste heat boiler (not shown). Gas turbine 60 is used to drive an external regeneration air compressor such as second air compressor 80, which, for example, produces regeneration air to be passed to a dehydrogenation reactor, such as those shown in FIG. 1.

[0043] FIG. 3 illustrates another schematic representation of an example embodiment of the present disclosure. As shown, a turbine-powered air compressor assembly 82 includes a startup steam turbine 84 that is coupleable / decouplable from a first air compressor 86 via a clutch 88. Startup steam turbine 84 is also coupleable / decouplable to a gas turbine 90 via a clutch 92. Gas turbine 90 drives a second air compressor 94. US9309810B2 relates to an arrangement for liquefying natural gas with a gas turbine unit, a steam turbine unit and compressors. US2006042259A1 relates to combined-cycle power plant and a steam thermal power plant, which are installed near medium- or small- scaled gas fields and oil fields.

[0044] Operating the air compressor assembly of the present disclosure would typically involve coupling the startup motor to the gas turbine prior to gas turbine startup and operating the startup motor to drive the dual-end power shaft of the gas turbine until the gas turbine reaches a rotational speed (rpm) suitable for gas turbine operation. Thereafter, the startup motor would be decoupled from the gas turbine, which following startup would be used to drive power to the second air compressor described above. The startup motor is then coupled to the first air compressor described above and used to drive power to the first air compressor.

[0045] The regeneration gas demand in a dehydrogenation system is generally quite high, requiring use of a gas turbine to drive a regeneration air compressor. Example gas turbines for use in driving a regeneration air compressor include GE MS5001 available from General Electric, as well as SGT 750 and SGT 700 available from Siemens. Typically, such gas turbines have a multi-stage internal axial combustion air compressor.

[0046] A typical startup turbine is significantly smaller in power output (expressed inMW) as compared to the gas turbine, often about 30% or less (e.g., about 15 to about 25%) of the power output of the gas turbine. Such startup turbines are often steam turbines, which extract thermal energy from pressurized steam to drive the power shaft. The amount of additional regeneration air provided to a dehydrogenation process will be proportional to the power of the startup turbine, meaning if the startup turbine has a power output of 15-25% of the gas turbine driving the main air compressor, the startup turbine can power the production of an additional 15-25% of regeneration air when used as shown in the present disclosure. In certain embodiments, the air compressor driven by the gas turbine outputs about 550 to about 820 t / hr of air (e.g., about 680 t / hr) and the air compressor driven by the startup turbine outputs about 120 to about 220 t / hr of air (e.g., about 150 t / hr).

[0047] Although the startup system for a gas turbine typically uses a steam turbine, the present disclosure is not limited to such systems. Any startup motor utilized to produce power for startup of a gas turbine, and which includes a dual-end power shaft, could be adapted for use in the present disclosure. For example, a startup motor could be in the form of a turbine, an electric motor, or an internal combustion engine.

[0048] The type of air compressor used in the present disclosure can vary. Example types of air compressors include reciprocating air compressors, rotary air compressors, centrifugal air compressors, and axial air compressors. The type of clutch used to couple / decouple the power shaft of the startup turbine is also not limiting. Atypical clutch will include a flywheel, friction discs, a pressure plate, and a spring and release lever. Example clutch types include friction clutches, hydraulic clutches, centrifugal clutches, and single plate and multi-plate clutches.

[0049] In general, the invention may alternately comprise, consist of, or consist essentially of, any appropriate components herein disclosed. The invention may additionally, or alternatively, be formulated so as to be devoid, or substantially free, of any components, materials, ingredients, adjuvants or species used in the prior art compositions or that are otherwise not necessary to the achievement of the function and / or objectives of the present invention.

[0050] Many modifications and other implementations of the disclosure will come to mind to one skilled in the art to which this disclosure pertains having the benefit of the teachings presented in the foregoing descriptions and the associated figures. Therefore, it is to be understood that the disclosure is not to be limited to the specific implementations disclosed herein and that modifications and other implementations are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

WHAT IS CLAIMED IS:

1. A system for dehydrogenation of a hydrocarbon, comprising: i) a dehydrogenation unit (100) comprising a catalyst bed reactor in fluid communication with a hydrocarbon feed (11) source; and ii) a regeneration air source in fluid communication with the dehydrogenation unit, wherein the regeneration air source is the turbine-powered air compressor assembly (82) comprising: a) a gas turbine (60) comprising: i. a first dual-end power shaft axially extending through the gas turbine and ii. a first power shaft end (52) and iii. a second power shaft end (54) iv. a startup motor comprising:

1. a second dual-end power shaft axially extending through the startup motor and2. a power shaft end facing the gas turbine and3. a power shaft end distal from the gas turbine, wherein the power shaft end facing the gas turbine is drivingly connected to the first power shaft end (52) of the gas turbine (60) via a clutch that enables coupling and decoupling of the startup motor from the gas turbine; b) a first air compressor (40), the second power shaft end (54) of the gas turbine (60) being drivingly connected to the first air compressor such that the first air compressor is positioned on a side of the gas turbine opposite the startup motor; and c) a second air compressor (80), the power shaft end distal from the gas turbine of the startup motor being drivingly connected to the second air compressor such that the second air compressor is positioned on a side of the startup motor opposite the gas turbine.

2. The system according to claim 1, further comprising a clutch between the second air compressor and the startup motor that enables coupling and decoupling of the startup motor from the second air compressor.

3. The system according to claim 1 or claim 2, wherein the startup motor is a steam turbine.

4. The system according to any one of claims 1 to 3, wherein the power output of the startup motor, in MW, is about 30% or less of the power output of the gas turbine.

5. The system according to any one of claims 1 to 4, wherein the first air compressor outputs about 550 to about 820 t / hr of air and the second air compressor outputs about 120 to about 220 t / hr of air.

6. A system for dehydrogenation of a hydrocarbon, comprising: i) a dehydrogenation reactor comprising a catalyst bed in fluid communication with a hydrocarbon feed source; and ii) a regeneration air source in fluid communication with the dehydrogenation reactor, wherein the regeneration air source is the turbine-powered air compressor assembly of any one of claims 1 to 5.

7. The system of claim 6, further comprising a reducing gas source in fluid communication with the dehydrogenation reactor and / or a steam purge gas source in fluid communication with the dehydrogenation reactor.

8. The system of claim 6 or claim 7, wherein the hydrocarbon feed source provides a hydrocarbon selected from the group consisting of propane, isobutane, pentane, isopentane, n-butane, 1 -butene, and combinations thereof.

9. A method for hydrogenation of a hydrocarbon in a dehydrogenation reactor, comprising: a turbine-powered air compressor assembly which at least includes:• a gas turbine;• a startup motor;• dual end power shaft;• a first air compressor and• a second air compressor the method comprises at least the following steps: i) coupling the startup motor to the gas turbine prior to gas turbine startup; ii) operating the startup motor to drive the first dual-end power shaft until the gas turbine reaches an rpm suitable for gas turbine operation; iii) decoupling the startup motor from the gas turbine; iv) operating the gas turbine to drive power to the first air compressor; v) coupling the startup motor to the second air compressor; and vi) operating the startup motor to drive power to the second air compressor wherein, the method further comprises a following step: passing air from the first air compressor and the second air compressor into a dehydrogenation reactor comprising a catalyst bed for regeneration of the catalyst bed.

10. The method of claim 9, further comprising passing air from the first air compressor and the second air compressor into a dehydrogenation reactor comprising a catalyst bed for regeneration of the catalyst bed.

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