A catalyst integrated wave rotor as a device for cracking a gas

Abstract

The present disclosure concerns a wave rotor system as a device for cracking a gas. The wave rotor system comprises one or more wave rotors (10), arranged in series or in parallel, each wave rotor being composed of a rotating body comprising a plurality of channels (12) arranged cylindrically around a rotating axis (11) of the rotating body, each one of the extremities of the channels (12) being closed by a respective plate, the plate comprising ports for the passage of a fluid from respective inlet conduits to the channels or from the channels to respective outlet conduits, wherein the wave rotor system is integrated with a catalytic section and optionally with one or more compressors.

Description

A catalyst integrated wave rotor as a device for cracking a gasDescriptionTECHNICAL FIELD[1] The present disclosure concerns a wave rotor system as a device for cracking a gas. Embodiments disclosed herein specifically concern a wave rotor system integrated with a catalytic section wherein the pressure difference between a driver gas and a driven gas creates pressure waves to heat the driven gas and crack at least a portion of the driven gas. More in particular, embodiments disclosed herein specifically concern a wave rotor system wherein a catalytic section is integrated to the system in order to improve the yield of the cracking reaction, in particular in a system for CO2-free hydrogen production via pyrolysis of methane or ammonia.BACKGROUND ART[2] Thermal decomposition of a chemical compound to obtain simpler molecules is commonly used in the treatment of organic materials. This technology is known as pyrolysis or thermal cracking. In particular, cracking is the process whereby complex organic molecules such as long-chain hydrocarbons are broken down into simpler molecules such as light hydrocarbons, by the breaking of carbon-carbon bonds in the precursors. Thermal decomposition can also be applied to non-organic molecules.[3] In particular, thermal decomposition of methane from natural gas or ammonia is recently getting more and more importance as a technology to produce hydrogen. For example, with reference to the thermal decomposition of methane into carbon and hydrogen (CH4 + Heat → C + 2H2) with trace quantities of other hydrocarbons, this process (methane pyrolysis or methane cracking) is based on the heating of methane to temperatures in which the kinetics of the reaction produce high conversions in a reasonable time. The governing reaction is endothermic, thus the necessary energy input should be provided from an energy source. A main characteristic of this process is the absence of oxygen, which eliminates CO2 and CO by-products. Additionally, no water is consumed, and the produced carbon may have qualities that can be marketed and used in a variety of traditional and novel applications, or it can be securely stored for future use.[4] Recently, shock-wave compression has been proposed as an energy source or temperature multiplier for direct thermal methane decomposition [Akbari, P., Copeland, C. D., Tüchler, S., Davidson, M., and Mahmoodi-Jezeh, S. V, “Shock Wave Heating: A Novel Method for Low-Cost Hydrogen Production” ASME Paper IMECE2021-69775, 2021]. In this approach, a wave rotor [Akbari, P., Nalim, M. R., and Müller, N., “A Review of Wave Rotor Technology and Its Applications,” ASME Journal of Engineering for Gas Turbines and Power, Vol. 128, No. 4, 2006, pp. 717-735] is used to generate shock and rarefaction waves for exchanging energy between fluid streams. This technology is considered very promising in order to produce hydrogen without any undesirable by-product, such as in particular carbon dioxide. In particular, this technology is favorably applicable to produce hydrogen to be used as feedstock for a gas turbine operating as the driver of a compressor in a booster station for natural gas pipelines, in order to counteract the pressure drop of the natural gas along the pipeline [Pejman et al, “The Use of Wave Machinery for Power Generation and Production of Hydrogen as Gas Turbine Fuel”, AIAA Scitech Forum, 29 December 2021]. This solution allows the wave rotor to use a little fraction of the natural gas from the pipeline to produce hydrogen to be used as fuel for the gas turbine, by leveraging the pressure already present in the natural gas pipeline to use the natural gas as the driver gas of the wave rotor. At the same time, the low-pressure natural gas at the driver gas outlet of the wave rotor is sent back to the wave rotor as the driven gas, being heated up to the cracking temperature, to obtain hydrogen.[5] More in general, the possibility of using wave rotors to increase the temperature of a gas up to its thermal decomposition can be applied to different kind of gases. However, the use of wave rotors to heat a gas stream up to its decomposition temperature can still be improved in order to increase the reaction conversion rate, which is according to the prior art, still relatively low.[6] Therefore, there is a need for improved designs of a wave rotor based cracking system that can address these challenges and provide efficient and reliable performance in various industrial applications.[7] Accordingly, an improved wave rotor-based gas cracking system to address the issues of conversion rate of the systems of the current art would be beneficial and would be welcomed in the technology. SUMMARY[8] In one aspect, the subject matter disclosed herein is directed to a wave rotor system for cracking a gas, the wave rotor system comprising one or more wave rotors, wherein the wave rotor system is integrated with a catalytic section.[9] In one aspect, the disclosure concerns a wave rotor system for cracking a gas wherein a catalytic section can be arranged inside at least one wave rotor, upstream the wave rotor and / or downstream the wave rotor and / or inside a casing of the wave rotor. Namely, when the catalytic section is arranged inside the wave rotor, it can be arranged inside all the channels of the wave rotor or only inside some of the channels of the wave rotor, so that both the driver gas and the driven gas are contacted with the catalyst. In particular, the catalytic section inside the channels of the wave rotor can comprise a solid bulk catalyst filling at least part of the channel or channels and / or a catalytic metal foam expanded within at least part of the channel or channels and / or a catalytic coating of the walls of the channel or channels. In one aspect, the catalytic section is implemented in the casing of the wave rotor.

[10] In one aspect, the catalytic section is a coating on the internal surface of the channels and casing of the wave rotors and internal surface of the piping connected different elements such as compressor and wave rotor and surface of the compressor exposing to the feedstock at elevated temperature.

[11] In another aspect, the disclosure concerns a wave rotor system for cracking a gas wherein a catalytic section is obtained in the form of a monolith catalyst of at least one wave rotor.

[12] In another aspect, the disclosure concerns a wave rotor system for cracking a gas integrated with a catalytic section and comprising one or more compressors upstream one or more wave rotors, to compress a gas to be directed to the wave rotor. Conveniently, at least one of the one or more compressors and / or at least one of the one or more wave rotors are mounted on a same shaft. Alternatively, at least one of the one or more compressors and / or at least one of the one or more wave rotors are coupled with an integrally geared rotating system. Preferably, the integrally geared rotating system comprises a gearbox, or a bull gear.

[13] In still another aspect, the disclosure concerns a wave rotor system for cracking a gas integrated with a catalytic section and comprising separating means, arranged downstream the wave rotor, to separate the products of the cracking reaction. Namely, the separating means can include one or more of a membrane, a catalytic membrane, a pressure swing adsorber and a temperature swing adsorber.BRIEF DESCRIPTION OF THE DRAWINGS

[14] A more complete appreciation of the disclosed embodiments of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:Fig.1 illustrates a wave rotor system for cracking a gas, according to a first embodiment;Fig.2 illustrates a wave rotor system for cracking a gas, according to a second embodiment;Fig.3 illustrates a wave rotor system for cracking a gas, according to a third embodiment;Fig.4 illustrates a wave rotor system for cracking a gas, according to a fourth embodiment;Fig.5 illustrates a wave rotor system for cracking a gas, according to a fifth embodiment;Fig.6 illustrates a wave rotor system for cracking a gas, according to a sixth embodiment;Fig. 7 illustrates a wave rotor system for cracking a gas, according to a seventh embodiment, andFig. 8 illustrates a wave rotor system for cracking a gas, according to a eighth embodiment.DETAILED DESCRIPTION OF EMBODIMENTS

[15] According to one aspect, the present subject matter is directed to a wave rotor system for cracking a gas, the wave rotor system being integrated with a catalytic section. In operation, the wave rotor system is fed with a stream of a gas to be cracked and causes an increase of its temperature. The catalytic section allows to obtain cracking of the components of the gas with higher conversion rates and / or at a lower temperature than in normal conditions. The system can further comprise components configured to combine with the wave rotor to increase efficiency and rate of conversion of the cracking reaction, such as compressors arranged upstream the wave rotors, at least one of the compressors being mounted on the same shaft of at least one of the wave rotors, separating means arranged downstream or inside the wave rotors, energy recovery means (such as an expander) configured to recover energy after cracking and provide such energy in the form of heat to the cracking reactor and / or electricity to the wave rotors and / or the compressors. Advantageously, the wave rotors and / or the compressors of the system can be integrated in an integrally geared rotating system.

[16] Reference now will be made in detail to embodiments of the disclosure, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the disclosure, not limitation of the disclosure. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit of the disclosure. Reference throughout the specification to “one embodiment” or “an embodiment” or “some embodiments” means that the particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrase “in one embodiment” or “in an embodiment” or “in some embodiments” in various places throughout the specification is not necessarily referring to the same embodiment(s). Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.

[17] When introducing elements of various embodiments, the articles “a”, “an”, “the”, and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including”, and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[18] Referring now to the drawings, Fig.1 shows a schematic of an exemplary wave rotor system for cracking a gas, the wave rotor system comprising a rotating cylinder 10, i.e. a wave rotor 10, configured to rotate around a shaft 11 and comprising a plurality of channels 12. A gas to be pyrolyzed is directed to the channels 12 of the wave rotor 10, at one end of the channels 12 of the wave rotor 10, through a feed line (not shown), and exit at the opposite end. In the embodiment shown with reference to Fig. 1, a catalyst is arranged inside one or more of the channels 12 of the wave rotor 10. The rotation of the wave rotor can be provided by external means, in particular, the shaft 11 can be connected to a motor or turbine configured to rotate the shaft 11. Inside the channels of the wave rotor shock and rarefaction waves are generated for exchanging energy between fluid streams, with generation of heat. By way of example, ammonia or methane are fed to the wave rotor to react and produce hydrogen according to the following reactions:NH3 N2 + H2 ΔH = 46,4 kJ / molCH4 C(S) + 2H2 ΔH = 74,6 kJ / molThis technology is considered very interesting to produce hydrogen because it allows to avoid the production of carbon oxides as by-products or as a result of combustion reactions used to generate heat to be provided to the pyrolysis reaction. In fact, heat necessary to the reaction is provided by the shock waves and compression. Hydrogen production yield is improved by the catalyst and the short residence time caused by the rapid heating and temperature rise of the gas mixture inside the wave rotor. Moreover, the wave rotor system of the present disclosure allows for easy startup and shutdown procedures without extensive pretreatment. In addition to the production of hydrogen, this technology can also be used in other cracking reactions to obtain different kind of compounds, such as olefins.

[19] Several embodiments of possible wave rotor system arrangements will be described below with reference to the following Figs 2, 3, 4, 5, 6, 7 and 8.

[20] In particular, with continuing reference to Fig.1, Fig.2 illustrates a second embodiment of a wave rotor system of the present disclosure. In Fig. 2, the same reference numbers designate the same or corresponding parts, elements or components already illustrated in Fig.1 and described above, and which will not be described again. According to this exemplary embodiment, a fixed solid catalyst casing 13 is provided around the wave rotor 10. A fixed spacer 14 separates the rotating body of the wave rotor 10 from the fixed solid catalyst casing 13, to avoid friction and allow the stream exiting from the channels 12 to reach the surface of the fixed solid catalyst casing 13. In particular, the fixed solid catalyst casing 13 can be a monolith catalyst or a metal foam catalyst.

[21] With continuing reference to Fig. 1, a further embodiment of a wave rotor system is shown in Fig. 3. The same reference numbers designate the same or corresponding parts, elements or components already illustrated in Fig. 1 and described above, and which will not be described again. The wave rotor system of Fig. 3 differs from the wave rotor system of Fig. 1 in that it further comprises a compressor 15, mounted on the same shaft 11 of the wave rotor 10. The compressor 15 is arranged upstream the wave rotor 10, to pressurize the gas to be reacted at the pressure required by the wave rotor 10. Alternatively, the cracking reaction can initiate inside the compressor if the process fluid is further accelerated to the supersonic velocity and then decelerated to subsonic velocity in the statoric part of the compressor, which brings the fluid to its thermal cracking conditions. The heat required for the pyrolysis reaction is supplied by the system composed by the compressor 15 and the wave rotor 10, without the need for external heating sources.

[22] With continuing reference to Figs. 1 and 3, Fig. 4 illustrates a further embodiment of a wave rotor system. The same reference numbers used in Figs. 1 and 3 are used in Fig. 4 to designate the same or corresponding parts, components or elements, which will not be described again. The embodiment of Fig. 4 differs from the embodiment of Fig. 3 mainly in that a catalytic reactor 16 is arranged downstream the wave rotor 10. Further, means for recovering energy, such as an expander 17, and separating means to separate the products of the cracking reaction, such as a pressure swing adsorber 18, are arranged downstream the catalytic reactor 16. According to this embodiment, a gas to be pyrolyzed is fed to the compressor 15 through the feed line 19. The compressor 15 increases the pressure of the gas, and correspondingly its temperature, before it is fed as a driver gas to the wave rotor 10 through the line 20. A portion of the low-pressure stream 19 is delivered as a driven gas directly to the wave rotor 10 through a by-pass line 19’. Additional flexibility of the compressor 15 allows to integrate the compressor 15 into an integrally geared rotating system. The high temperature and high pressure gas from the wave rotor 10 is directed to the catalytic reactor 16 through the line 21. According to this embodiment, the compressor 15 and the wave rotor 10 can be used to simply compress the gas to be pyrolyzed or also to perform a pre-cracking of the gas, which is subsequently completed by the catalytic reactor 16. The catalytic reactor 16 can be a fixed or fluidized bed reactor. In case the catalytic reactor 16 is a fixed bed catalytic reactor, it can be filled with solid catalyst or catalytic metal foams or monolith or with catalytic membrane for in situ separation / purification of the desired products which further improves the yield of the reaction or moderate the reaction temperature for a given conversion rate. As already disclosed with reference to Figs. 1-3, the catalyst can be integrated also in the compressor 15 and / or in the wave rotor 10, for example, as metal foams or monolith or coatings. The external catalytic reactor 16 can be operated adiabatically without external heating sources. Alternatively, it can be operated isothermally using external sources such as electrical heaters or plasma or microwave or exhaust stream of a gas turbine or other high temperature fluid streams. The pyrolyzed gas from the catalytic reactor 16 is then directed, through the line 22, to the expander 17. In particular, the expander 17 is implemented for energy recovery, the recovered energy 23 being supplied to the wave rotor 10 in the form of heat through the heat line 23’ and / or to the compressor 15 through the power line 23” and / or to the catalytic reactor 16 through the heat line 23’”. The gas downstream the expander 17 is directed to the pressure swing adsorber 18. In case the gas to be pyrolyzed by the wave rotor system is cracked into two gas products in addition to a fraction of unreacted gas, then the pressure swing adsorber 18 is composed of two sections, to respectively separate a first and a second gas product, non-reacted gas being recycled back to either compressor inlet or low-pressure side of the wave rotor. In particular, according to Fig. 4, the gas to be cracked can be for example ammonia, the pyrolyzed gas containing hydrogen, nitrogen and unreacted ammonia, the first section of the pressure swing absorber 18 separating a stream 24 of hydrogen, the second section separating a stream 25 of nitrogen, unreacted ammonia being recycled to the wave rotor 10 through a recirculation line 26. According to alternative embodiments, different types of separating means can be used in place of the pressure swing adsorber, such as a temperature swing adsorber or a membrane.

[23] Referring to Fig.5, with continuing reference to Figs. 1, 2, 3 and 4, a further embodiment of the wave rotor system is disclosed. The same reference numbers used in Figs. 1, 2, 3 and 4 are used in Fig. 5 to designate the same or corresponding parts, components or elements, which will not be described again. The embodiment of Fig. 5 differs from the embodiment of Fig. 4 mainly is that a membrane 27 is arranged downstream the wave rotor 10, instead of a catalytic reactor. According to this embodiment, the compressor 15 and the wave rotor 10 are used to compress and heat the gas to be pyrolyzed up to the cracking temperature of the gas, which is subsequently directed to the membrane 27. The membrane 27 separates the pyrolyzed gas into two streams, by way of example, always in case the gas to be pyrolyzed being ammonia, a hydrogen stream 24’ and a mixed stream of nitrogen and unreacted ammonia, directed to the expander 17. Since the membrane 27 does not need to be heated, the energy 23 recovered by the expander 17 is supplied in the form of heat for the catalytic reaction or in the form of electricity for driving the rotation through an electric motor only to the wave rotor 10 through the heat line 23’ and / or to the compressor 15 through the power line 23”. The pressure swing adsorber 18’ downstream the expander 17 only separates a stream 25 of nitrogen, while unreacted ammonia is recycled to the wave rotor 10 through the recirculation line 26. According to alternative embodiments, different types of separating means can be used in place of the pressure swing adsorber, such as a temperature swing adsorber or a membrane.

[24] With continuing reference to Figs. 1, 2, 3, 4 and 5, a further embodiment of the wave rotor system is disclosed in Fig. 6. The same reference numbers used in Figs. 1, 2, 3, 4 and 5 are used in Fig. 6 to designate the same or corresponding parts, components or elements, which will not be described again. The embodiment of Fig. 6 differs from the embodiment of Fig. 5 mainly in that a stream 28 of gas to be pyrolyzed at high pressure being present in addition to the low-pressure stream 19 of gas to be pyrolyzed at low pressure. The high-pressure gas to be pyrolyzed and the low-pressure gas to be pyrolyzed are delivered directly to the wave rotor 10. According to this embodiment, a catalytic membrane 27’ is arranged downstream the wave rotor 10, to separate a first product through the line 24’ and a temperature swing adsorber 18” is arranged downstream the expander 17. The energy 23 recovered by the expander 17 is delivered in the form of heat to the catalyst being present, into the wave rotor 10, the catalytic membrane 27’ and the temperature swing adsorber 18”.

[25] Referring to Fig.7, with continuing reference to Figs. 1, 2, 3, 4, 5 and 6, a further embodiment of the wave rotor system is disclosed. The same reference numbers used in Figs. 1, 2, 3, 4, 5 and 6 are used in Fig. 7 to designate the same or corresponding parts, components or elements, which will not be described again. The embodiment of Fig. 7 differs from the embodiment of Fig. 4 mainly in that a catalytic reactor 29 is arranged along the line 20 connecting the outlet of the compressor 15’ to the inlet of the wave rotor 10, in order to obtain a preliminary cracking of the high temperature and pressure gas to be cracked downstream the compressor 15’. The stream at the outlet of the catalytic reactor 29 is directed to the wave rotor 10 through the line 30. The pressure swing absorber 18’ downstream the expander 17 separates a product stream mixed stream 25’, by way of example a mixed stream of hydrogen and nitrogen obtained by cracking an ammonia stream, while unreacted ammonia is recycled at low-pressure as a driven gas stream to the wave rotor 10 through the recirculation line 26. A portion of the low-pressure stream 19 (as driven gas) is delivered directly to the wave rotor 10 through a by-pass line 19’, to provide a low pressure driven stream to the wave rotor 10 allowing the compressor 15’ to be operated flexibly. Additional flexibility of the compressor 15’ allows to integrate the compressor 15’ into a rotating system, together with other rotating equipment, such as compressors and turbines. The rotating system can be an integrally geared rotating system and can comprise a gearbox. In particular, in case the speed ratio is greater than 7, the gearbox comprises a bull gear.

[26] Referring to Fig. 8, an integrally geared rotating system is disclosed, integrating the compressor 15’ and two wave rotors 10 according to the present disclosure through a common bull gear 31. Additional compressors 32 and / or turbines 33 can also be integrated into the integrally geared rotating system. Conveniently, one or more of the compressors of the integrally geared rotating system are overhung-impeller centrifugal compressors.

[27] The various arrangements illustrated in Figs. 1 to 8 can be variously combined to one another. For instance, a catalytic reactor 16 and a two sections pressure swing adsorber 18 or a two section temperature swing adsorber can be provided in the embodiments of Fig. 5 and 6, by replacing the membrane 27, 27’ and the single pressure swing adsorber 18’ or the single temperature swing adsorber 18”.

[28] While aspects of the invention have been described in terms of various specific embodiments, it will be apparent to those of ordinary skill in the art that many modifications, changes, and omissions are possible without departing form the spirt and scope of the claims. In addition, unless specified otherwise herein, the order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments.

Claims

1. A wave rotor system for catalytic cracking of a gas, the wave rotor system comprising one or more wave rotors (10), each wave rotor being composed of a rotating body comprising a plurality of channels (12) arranged cylindrically around the rotating axis (11) of the rotating body, each one of the extremities of the channels (12) being closed by a respective plate, the plate comprising ports for the passage of a fluid from respective inlet conduits to the channels or from the channels to respective outlet conduits, wherein the wave rotor system is integrated with a catalytic section, at least partially made of a catalytic material.

2. The wave rotor system of claim 1, wherein the catalytic section is arranged upstream and / or downstream of the one or more wave rotors (10).

3. The wave rotor system of claim 2, wherein the catalytic section is arranged inside at least one of the inlet conduits and / or the outlet conduits of the one or more wave rotors (10) and / or inside one or more catalytic reactors (29) arranged upstream the one or more wave rotors (10) and / or downstream the one or more wave rotors (10).

4. The wave rotor system of any of the preceding claims, wherein the wave rotor system comprises two or more wave rotors (10) connected in series or in parallel.

5. The wave rotor system of claim 4, wherein the catalytic section is arranged amongst the wave rotors (10).

6. The wave rotor system of claim 5, wherein the catalytic section is arranged inside the conduits connecting the wave rotors (10) and / or inside one or more catalytic reactors (29) along the conduits connecting the wave rotors (10).

7. The wave rotor system of any of the preceding claims, wherein the catalytic section is arranged inside at least one wave rotor (10) of the one or more wave rotors (10).

8. The wave rotor system of claim 7, wherein the catalytic section is arranged inside at least a portion of one or more of the channels (12) of the at least one wave rotor (10) and / or inside all the channels (12) of the at least one wave rotor and / or is comprised of a solid bulk catalyst filling at least part of the channel or channels (12) and / or is a monolith catalyst forming at least part of the channel or channels (12) and / or is comprised of catalytic metal foams expanded within at least part of the channel or channels (12) and / or is comprised of a catalytic coating of at least part of the walls of the channel or channels (12).

9. The wave rotor system of claim 7, wherein the catalytic section is a catalyst casing (13) around at least one of the one or more wave rotors (10).

10. The wave rotor system of claim 9, wherein the catalyst casing (13) is a monolith catalyst (13) and / or is comprised of catalytic metal foams and / or is at least partially coated with a catalytic coating.

11. The wave rotor system of any of the preceding claims, wherein the wave rotor system comprises one or more compressors (15, 15’) upstream the one or more wave rotors (10) or between two wave rotors (10).

12. The wave rotor system of claim 11, wherein at least one of the one or more compressors (15, 15’) and at least one of the one or more wave rotors (10) are mounted on the same shaft (11).

13. The wave rotor system of any of claim 11 or 12, wherein the catalytic section is arranged inside one or more of the compressors (15, 15’) and / or inside the conduits connecting the compressors (15, 15’) and the wave rotors (10).

14. The wave rotor system of any of the preceding claims, wherein the wave rotor system comprises one or more separating apparatuses (18, 18’, 18”, 27, 27’) downstream the one or more wave rotors (10) or between two wave rotors (10).

15. The wave rotor system of claim 14, wherein the separating apparatuses (18, 18’, 18”, 27, 27’) comprise a pressure swing adsorber (18, 18’, 18”) and / or a temperature swing adsorber and / or a membrane (27, 27’), preferably a catalytic membrane (27’).

16. The wave rotor system of claim 15, wherein the wave rotor system further comprises one or more pressure swing adsorbers (18, 18’, 18”), arranged downstream the membrane (27, 27’).

17. The wave rotor system of claim 15 or 16, wherein the wave rotor system further comprises one or more temperature swing adsorbers (18, 18’, 18”), arranged downstream the membrane (27, 27’).

18. The wave rotor system of any of the preceding claims, wherein the wave rotor system comprises an expander (17), arranged downstream the wave rotors (20) and configured to recover energy from the stream of cracked gas.

19. The wave rotor system of claim 18, wherein the expander is configured to deliver recovered energy to the catalytic section and / or to at least one of the one or more wave rotors (10) and / or to at least one of the one or more compressors (15, 15’).

20. The wave rotor system of claim 11 or 12, wherein at least one of the one or more compressors (15, 15’) is part of an integrally geared rotating system.

21. The wave rotor system of any of the preceding claims, wherein at least one of the one or more wave rotors (10) is part of an integrally geared rotating system.

22. The wave rotor system of claim 20 or 21, wherein the integrally geared rotating system comprises a gearbox.

23. The wave rotor system of claim 22, wherein the integrally geared rotating system comprises a bull gear.

24. The wave rotor system of any of claims 21-23, wherein the compressor coupled with the integrally geared rotating system is an overhung-impeller centrifugal compressor system. 

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