Patent Description:
The following relates to system for waste heat recovery, and more specifically to embodiments of a system and method for using waste heat from a drive unit to assist in powering a compressor and/or other auxiliary systems.

Gas turbines are a common choice as a compressor driver in regions where electrical power is not readily available. Compressors driven by gas turbines, which include types such as piston, barrel or integrally geared centrifugal compressors, are often used to facilitate the transport of gas in pipelines. In this installation scheme, the gas turbine uses some of the gas from the pipeline as fuel for the gas turbine that powers the compressor to re-pressurize the pipeline gas to overcome the losses that occur due to the transportation process.

Although gas turbine manufacturers have done their best to capture as much energy as possible from the combustion process, all gas turbines inherently produce waste heat. In some cases, a Heat Recovery through Steam Generation (HRSG) system is employed to convert this waste heat to electricity (this is also known as a form of Cogeneration in the power industry). In other cases, the waste heat is used directly, such for HVAC heating. However, most of the gas turbines used to drive compressors are located in remote regions where there often is no use for either electricity or HVAC; thus, the waste heat is thrown away, representing a permanent loss.

Thus, a need exists for a system and method that can capture the waste heat from the gas turbine and use the waste heat to assist in driving the compressor.

<CIT> describes a combined cycle power plant with a gas turbine, a shaft connecting a compressor to a turbine and a first generator, a heat recovery steam generator fluidly connected to the exhaust of the gas turbine.

<CIT> describes a method and a system for supplying compressed air to a process plant using a combustor-turbine unit directly coupled to a bull gear meshing with pinion on which are mounted gas compression stages and expansion stages. Direct energy transfers and intercooling and aftercooling after compression stages enhance the efficiency of the system.

<CIT> describes a high speed centrifugal compressor which is closely directly coupled to the power turbine of a two-shaft gas turbine having a gas generator section separate fromits power turbine. Through the direct close coupling and centerline mounting of the gas turbine exhaust casing for free and uniform heat expansion, alignment between stationary and rotating parts of the power turbine and compressor is maintained free from mechanical problems.

<CIT> describes a geared turbomachine having a gear unit, a drive unit, and output units integrated into a machine train, a central large gear with a large gear shaft and at least two pinions with at least two pinion shafts meshing with the large gear. The geared turbomachine has a drive unit coupled to a first pinion shaft of the gear unit via a first clutch. A first output unit is a main compressor processes a first process gas. The first output unit is coupled to the first pinion shaft via a second clutch such that the first output unit is directly operationally connected to the drive unit with transmission of the gear unit remaining the same.

<CIT> describes a power plant comprising an integrally geared vapor compressor arrangement, comprised of a bull gear and a compressor shaft with a pinion meshing with the bull gear. The plant further comprises a vapor source, fluidly connectable with an inlet of the integrally geared vapor compressor arrangement. A vapor turbine arrangement is fluidly connectable with an outlet of the integrally geared vapor compressor arrangement for receiving a stream of compressed and superheated vapor from the integrally geared vapor compressor arrangement. An electric generator driven by the vapor turbine arrangement converts mechanical power produced by the vapor turbine arrangement into electric power.

The invention relates to a waste heat recovery system according to claim <NUM> and to a method of using waste heat recovery to assist in driving/powering a compression system according to claim <NUM>.

The foregoing and other features of construction and operation will be more readily understood and fully appreciated from the following detailed disclosure, taken in conjunction with accompanying drawings.

Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:.

A detailed description of the hereinafter described embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. Although certain embodiments are shown and described in detail, it should be understood that various changes and modifications may be made without departing from the scope of the appended claims. The scope of the present disclosure will in no way be limited to the number of constituting components, the materials thereof, the shapes thereof, the relative arrangement thereof, etc., and are disclosed simply as an example of embodiments of the present disclosure.

As a preface to the detailed description, it should be noted that, as used in this specification and the appended claims, the singular forms "a", "an" and "the" include plural referents, unless the context clearly dictates otherwise.

Referring to the drawings, <FIG> depicts embodiments of a waste heat recovery system <NUM>. Embodiments of the waste heat recovery system <NUM> may use a waste heat such as but not exclusively the exhaust gas <NUM> from a drive unit <NUM>, in the form of a gas turbine, that is used to drive a compressor <NUM> or other auxiliary systems related to the train, such as an oil pump, cooling fan(s), cooling water pump, a seal system compression, etc., to heat a working fluid in a closed loop system that produces mechanical power. Although embodiments of the present invention may be described with respect to a waste heat source of a drive unit <NUM>, the waste heat <NUM> may also be utilized from one or more other heat sources that is part of the cycle, which may be in addition to the drive unit <NUM>. The waste heat <NUM> may be eventually used to power directly or to assist in powering, driving, and/or running the compression process of the compressor <NUM>. Utilizing the waste heat <NUM> to assist in powering the compressor <NUM> or other components or auxiliary systems may eliminate many limiting factors of the typical waste heat recovery scenarios. Moreover, embodiments of the waste heat recovery system <NUM> may use the power directly to assist in a drive train shaft power, thereby creating many advantages to one or more existing arrangements. These advantages include a reduced complexity due to elimination of a generator and all associated switchgear and wiring, and a greater efficiency due to direct use of the power without the losses associated with converting the mechanical power into electricity, transmission losses, and further losses when converting the electricity back to mechanical power.

In an exemplary embodiment of the waste heat recovery system <NUM>, an Organic Rankine Cycle (ORC) may be used to convert the waste heat <NUM> from the drive unit <NUM> or other heat source to a mechanical power transmitted through a pinion shaft <NUM> to the compressor <NUM>. The mechanical power transmitted to the compressor <NUM> through implementation of the waste heat recovery system <NUM> may reduce a power required directly from the drive unit <NUM> to drive/power the compressor <NUM>, thereby increasing overall system efficiency. For example, embodiments of the waste heat recovery system <NUM> may result in the drive unit <NUM> requiring less fuel/gas, and therefore producing fewer emissions, which are both highly desirable outcomes. In some embodiments, employing the waste heat recovery system <NUM> may allow the use of a smaller drive unit/gas turbine (compared to a size required if the waste heat is not converted to power used by the compressor).

While exemplary embodiments may use an Organic Rankine Cycle (ORC), other working fluids, such as water (steam) or even different thermodynamic cycles may be used. Further, there are a number of different ways in which the power derived from the waste heat <NUM> can be used for assisting the powering of the compressor <NUM>. For instance, the power may be fed to a pinion, such as a pinion that connects to a drive gear in the compressor <NUM>, and this pinion may or may not also have an impeller, or the power may be fed directly to one or more compressor stages. Exemplary embodiments of the waste heat recovery system <NUM> are shown and described below with reference to <FIG>.

With continued reference to <FIG>, embodiments of the waste heat recovery system <NUM> include a driving unit <NUM>, a waste heat recovery cycle <NUM>, and a compressor <NUM>. Embodiments of the waste heat recovery system <NUM> include a drive unit <NUM>, the drive unit <NUM> having a drive shaft <NUM>, a compressor <NUM>, the compressor <NUM> operably coupled to the drive shaft <NUM>, wherein operation of the drive unit <NUM> drives the compressor <NUM>, and a waste heat recovery cycle <NUM>, the waste heat recovery cycle <NUM> coupled to the drive unit <NUM> and the compressor <NUM>, wherein a waste heat <NUM> of the drive unit <NUM> powers the waste heat recovery cycle <NUM>, such that the waste heat recovery cycle <NUM> transmits a mechanical power to the compressor <NUM>. In an exemplary embodiment, the waste heat recovery system <NUM> may convert, utilize, harness, use, utilize, etc. waste or exhaust heat (e.g. exhaust gas) from a turbine, engine, piston, driver, drive unit into shaft power. For example, waste heat, such as warm and/or hot exhaust gas may be recovered, captured, etc. and used to add shaft power to a compressor unit.

Embodiments of the waste heat recovery system <NUM> include a driving unit <NUM>. In an exemplary embodiment, the driving unit <NUM> may be a gas turbine, a gas engine, a piston, a driver, and the like, or any device that is configured to perform work and give off heat. Embodiments of the drive unit <NUM> include a drive shaft <NUM>. The drive shaft <NUM> is driven by the drive unit <NUM>. Embodiments of the drive unit <NUM> or driving source, such as a gas turbine, may drive, rotate, or otherwise transmit torque to the drive shaft <NUM> or other shaft or armature of a machine. When the drive shaft <NUM> is acted upon by the drive unit <NUM>, the drive unit <NUM> interfaces with the compressor <NUM> to actuate/operate one or more compressor stages. In an embodiment where the compressor <NUM> is an integrally geared compressor, the drive unit <NUM> may cooperate with a drive gear <NUM> of the compressor <NUM>, which meshes with or otherwise mechanically engages a plurality of pinions, such as a first pinion <NUM>, a second pinion <NUM>, and a third pinion <NUM>. Accordingly, the plurality of pinions <NUM>, <NUM>, <NUM> are rotated in response to the rotation of the drive shaft <NUM> and drive gear <NUM>, which is rotated by the drive unit <NUM>.

As a result of the drive unit <NUM> operating to rotate the drive shaft <NUM>, hot exhaust gases, such as waste heat <NUM>, are given off by the drive unit <NUM>. The waste heat <NUM> of the drive unit <NUM> is received by the waste heat recovery cycle <NUM>. For instance, waste heat <NUM> may be received, collected, accepted, obtained, recovered by the waste heat recovery cycle <NUM>, or otherwise introduced into the waste heat recovery cycle <NUM>. In other words, the waste heat recovery cycle <NUM> may be powered by the hot waste heat exhaust <NUM> from the drive unit <NUM>, such as a gas turbine. Embodiments of the waste heat recovery cycle <NUM> are operably connected to the drive unit <NUM>. In an exemplary embodiment, the waste heat recovery cycle <NUM> may be in fluid communication with the drive unit <NUM>. In another embodiment, the waste heat recovery cycle <NUM> may be connected to the drive unit <NUM> by one or more pipes, lines, pipelines, ducts, tubes, or other means for passing a fluid from a first component to a second component. The waste heat <NUM> may travel from the drive unit <NUM> through one or more pipes to the waste heat recovery cycle <NUM>. Embodiments of the waste heat recovery cycle <NUM> may be an organic rankine cycle, or other thermodynamic cycle, that may convert heat into work. The organic rankine cycle may include a working fluid, the working fluid being various, known working fluids associated with the organic rankine cycle. In other thermodynamic cycles, a working fluid may be water (steam). The cycle <NUM> may be a closed loop cycle, wherein the waste heat <NUM> of the drive unit <NUM> is supplied externally to the closed loop. In further embodiments, the waste heat <NUM> may be indirectly transferred to the waste heat recovery loop <NUM> (e.g. to the evaporator <NUM>) through an additional transfer medium, such as employing a thermal oil loop.

Embodiments of the waste heat recovery cycle <NUM> may include an evaporator <NUM>, an expansion mechanism <NUM>, a condenser <NUM>, and a pump <NUM>. The components of the cycle <NUM> may be operably connected to each other in a closed loop. Embodiments of the evaporator <NUM> may be a heat exchanger, configured to evaporate a working fluid, such as a high pressure liquid flowing through the closed loop cycle <NUM>. For instance, the hot exhaust gasses from the drive unit <NUM> may flow through the evaporator <NUM> to evaporate the working fluid of the cycle <NUM>. By operation of the waste heat <NUM> flowing through the evaporator <NUM>, the working fluid of the cycle <NUM> may be evaporated to a gaseous form/phase, and the gas may be directed to the expansion mechanism <NUM>, thus generating power that may be transmitted to the compressor <NUM> through a coupling between the expansion mechanism <NUM> and the compressor <NUM>, wherein the coupling may be a shaft, a rotating shaft, pinion shaft etc., depicted as pinion shaft <NUM> in <FIG>. Embodiments of the expansion mechanism <NUM> may be operably connected to the evaporator <NUM> via one or more lines, pipes, etc. to transfer or otherwise direct the evaporated working fluid to the expansion mechanism <NUM>.

Embodiments of the expansion mechanism <NUM> may be an expansion device, an expander, a turboexpander, and the like, configured to remove or otherwise harness energy from the high-pressured gas from the evaporator <NUM> to produce mechanical power. Specifically, embodiments of the expansion mechanism <NUM> may be an expansion turbine, screw, tooth, scroll, and the like. Moreover, embodiments of the expansion mechanism <NUM> are operably connected to the compressor <NUM>. In exemplary embodiments, the expansion mechanism <NUM> may be mechanically coupled to the compressor <NUM> via a pinion shaft <NUM>. For example, the expansion mechanism <NUM> may be mechanically coupled to one end of the pinion shaft <NUM>. The opposing end of the pinion shaft <NUM> may be operably mechanically coupled to the compressor <NUM>. In one embodiment, the opposing end of the pinion shaft <NUM> may be operably connected to the second pinion <NUM> associated with a second compressor stage <NUM> of the compressor <NUM>. In other embodiments, the expansion mechanism <NUM> may be connected to or otherwise mounted on a pinion that runs closest to an ideal speed for the expansion mechanism <NUM> and such pinion does not have a compressor stage mounted on it. Accordingly, embodiments of the expansion mechanism <NUM>, through receiving the gas from the evaporator <NUM> may turn, rotate, or otherwise act upon the pinion shaft <NUM> to assist the operating/powering of the compressor <NUM>, which may be in addition to the drive/power supplied by the drive unit <NUM>.

Embodiments of the compressor <NUM> may be an integrally geared compressor, a piston compressor, a barrel compressor, a portable compressor, and the like. Compressor <NUM> may be used for various gas compression applications. Embodiments of compressor <NUM> may be a centrifugal compressor having of one or more centrifugal compressor stages <NUM>, <NUM>, <NUM>. In some embodiments, the integrated compressor stages <NUM>, <NUM>, <NUM> may be arranged in a single gearbox, or housing. System requirements may determine a configuration of the compressor <NUM> and/or a number of compression stages. For example, embodiments of compressor <NUM> may be a multistage compressor, wherein system requirements may dictate a number of centrifugal compression stages. Moreover, compressor <NUM> includes a gear system. Embodiments of the gear system may be integrated into or arranged in a single housing. The housing may be a gearbox that houses, receives, supports, accommodates, etc., the components of the gear system of the compressor <NUM>. Embodiments of the gear system of the compressor <NUM> may include a drive shaft <NUM> that is driven by the drive unit <NUM>, a drive gear <NUM>, a first pinion shaft <NUM>, a first pinion <NUM>, a second pinion shaft <NUM>, a second pinion <NUM>, a third pinion shaft <NUM>, and a third pinion <NUM>. In one embodiment of the geared compressor, three pinions mesh with the drive gear (or bull gear), wherein one pinion is on each side of the drive gear and one pinion on the top of the drive gear. Further, an idler gear may be disposed between the drive gear and the compressor.

Embodiments of the gear system of the compressor <NUM> include a drive shaft <NUM> and a drive gear <NUM>. The drive gear <NUM> is operably mounted to the drive shaft <NUM>. For instance, the drive gear <NUM> may be fastened to the drive shaft <NUM>, wherein rotation of the drive shaft <NUM> translates to rotation of the drive gear <NUM>. In other embodiments, the drive gear <NUM> may be structurally integral with the drive shaft <NUM>. The drive shaft <NUM> may protrude from a front face of the drive gear <NUM> along a central axis of the drive gear <NUM>, and may also protrude from a back face of the drive gear <NUM> along the central axis of the drive gear <NUM>. Embodiments of the drive gear <NUM> may include teeth along an outer, circumferential surface of the drive gear <NUM>. The gear teeth of drive gear <NUM> may have various spacing, thickness, pitch, size, and the like. Similarly, a size of the drive gear <NUM> may vary to accomplish different desired speeds, ratios, torque transmission, and the like, of the gear system. Embodiments of the drive gear <NUM> may be disposed in the housing of the compressor <NUM>. Actuation of the drive gear <NUM> may result in rotation of the pinions <NUM>, <NUM>, <NUM>, which may then result in rotation of an impeller that may be operably attached to pinion shafts <NUM>, <NUM>, <NUM>.

Furthermore, a compressor stage <NUM>, <NUM>, <NUM> is operably connected to each end of the pinion shafts <NUM>, <NUM>, <NUM>. Embodiments of a compressor stage <NUM>, <NUM>, <NUM> may be an impeller of a centrifugal compressor that is directly mounted to an end of the pinion shafts <NUM>, <NUM>, <NUM>, wherein a gas is drawn in to be compressed by the compressor <NUM>. In an exemplary embodiment, a centrifugal compressor disposed at the end of the first pinion shaft <NUM> may be a first stage of compression <NUM>, a centrifugal compressor disposed at the end of the second pinion shaft <NUM> may be a second stage of compression <NUM>, and a centrifugal compressor disposed at the end of the third pinion shaft <NUM> may be a third stage of compression <NUM>. However, in further embodiments, additional compression stages may be disposed at other ends of the pinion shafts <NUM>, <NUM>, <NUM>.

Referring still to <FIG>, embodiments of the expansion mechanism <NUM> may cooperate with a component of the compressor <NUM>, such as pinion shaft <NUM>, to assist the driving/powering of the compressor <NUM>. The operation of the expansion mechanism <NUM> may result in exhaust gas, which may be directed to a condenser <NUM> of the waste heat recovery cycle <NUM>. For instance, the gas leaving the expansion mechanism <NUM> may travel though one or more lines or pipes from the expansion mechanism <NUM> to a condenser <NUM>, where the gas is condensed by the condenser <NUM>. Embodiments of the condenser <NUM> may be configured to condense the exhaust gas to a liquid form. The gas may be condensed to a liquid form as a result of the ambient air, or by cooling water, or other means known in the art. In an exemplary embodiment, the condenser <NUM> may condense the gas to a liquid, which may then be used as and/or combined with the working fluid of the waste heat recovery cycle <NUM>. A pressure of the liquid as a result of the condenser <NUM> may be increased by one or more pumps <NUM>. Embodiments of the pump <NUM> may be configured to increase the pressure of the condensed liquid within the cycle <NUM> between the condenser <NUM> and the evaporator <NUM>, as well as cause the liquid to flow back to the evaporator <NUM>.

In one exemplary embodiment, depicted by <FIG>, embodiments of the waste heat recovery system <NUM> includes an integrally geared centrifugal compressor <NUM> that includes a first compressor stage <NUM>, a second compressor stage <NUM>, and a third compressor stage <NUM>. Each of the compressor stages <NUM>, <NUM>, <NUM> may be mounted on respective pinions <NUM>, <NUM>, <NUM> which meshes with a central driving gear <NUM>. Embodiments of the expansion mechanism <NUM> may be mounted on an end of a pinion shaft, such as pinion shaft <NUM>, associated with the second pinion <NUM>. Although <FIG> depicts the expansion mechanism <NUM> mounted to a shaft associated with the second pinion <NUM>, an expansion mechanism <NUM> may be mounted to any of the pinions <NUM>, <NUM>, <NUM> (or pinion shafts thereof) that may have a free end (e.g. no compressor stage) therein may be mounted on a pinion that is not associated with a compressor stage. In further embodiments, some heat recovery situations may require multiple stages of expansion to best match the cycle used with the available waste heat and system conditions, and these stages may be mounted on one or more pinions. Likewise, while compressor stages <NUM>, <NUM>, <NUM> are mounted only on one end of each pinion shafts <NUM>, <NUM>, <NUM>, compressor stages may be mounted on each end, and/or expander stages may be mounted on each end, and/or expander stages may be mounted on one end without a compressor stage on the other. The number of pinions may vary with the application, from as few as just one to as many as can be mounted with the gear.

The compressor <NUM> may also include idler gears, such as idler gear <NUM>. Such idler gears may be disposed between two pinions as shown in <FIG>, or may be between the drive gear and one or more pinions; i.e. an idler gear may drive multiple pinions. The addition of any number of idler gears disposed in any location is within the scope of this invention. The drive gear may directly drive all pinions, or may drive one or more idler gears, or any combination thereof.

With continued reference to the drawings, <FIG> depicts an example of a waste heat recovery system <NUM>. Examples of the waste heat recovery system <NUM> may share the same or substantially the same structure and/or function as the waste heat recovery system <NUM> described above. For instance, examples of the waste heat recovery system <NUM> may include a drive unit, a compressor, and a waste heat recovery cycle. Examples of the waste heat recovery cycle <NUM> may operate in the same or substantially the same manner as the waste heat recovery cycle <NUM> described in association with <FIG>. However, examples of the waste heat recovery system <NUM> may include an expansion mechanism <NUM> mounted to a shaft <NUM> of the compressor <NUM> that is located external to the housing of the integrally geared compressor <NUM>.

<FIG> depicts an example of the waste heat recovery system <NUM> having an integrally geared centrifugal compressor <NUM> that has four compressor stages <NUM>, <NUM>, <NUM>, <NUM>, wherein the first compression stage <NUM>, the second compression stage <NUM>, and the third compression stage <NUM> may be mounted on pinions which mesh with a central driving gear, such as gear <NUM>. Examples of the fourth compressor stage <NUM> may be mounted on a shaft <NUM> that may include an expansion mechanism <NUM> mounted on an end of the shaft <NUM>. The shaft <NUM> may be separate from a gearbox of the compressor <NUM>, in an arrangement that may be referred to as a compander. Use of a compander may allow the waste heat recovery system <NUM> to be conveniently utilized in fairly standard design practices. In similar examples where a compander is used for waste heat recovery, the expansion mechanism <NUM> may be connected to the compressor stage that runs closest to the ideal speed for the turbine. Thus any compressor stage may be driven by the waste heat recovery turbine; it is not necessary have the turbine drive the last compression stage. In further examples, some heat recovery situations may require multiple stages of expansion to best match the cycle used with the available waste heat and system conditions, so multiple companders may be used or these stages may be mounted on one or more pinions of the compressor <NUM>. Likewise, while compressor stages <NUM>, <NUM>, <NUM>, <NUM> are mounted only on one end of each pinion shafts <NUM>, <NUM>, <NUM>, <NUM>, compressor stages may be mounted on each end, and/or expander stages may be mounted on each end, and/or expander stages may be mounted on one end without a compressor stage on the other. In addition, shaft <NUM> along with expansion mechanism <NUM> and compressor <NUM> may be mounted in the gearbox of the compressor <NUM> without connecting with either drive gear <NUM> or idler gear <NUM>.

Accordingly, examples of the waste heat recovery system <NUM> may utilize waste heat <NUM> from the drive unit <NUM> to assist in powering the compressor <NUM>. The waste heat <NUM> may be received by the waste heat recovery cycle <NUM> by the evaporator <NUM>. The evaporator <NUM> may utilize the waste heat <NUM> to evaporate a working fluid of the cycle <NUM>, which may then be delivered to the expansion mechanism <NUM>. Examples of the expansion mechanism <NUM> may be operably positioned at an end of the shaft <NUM>, which may be located external to a gearbox of a compressor <NUM>, which may include multiple compression stages. An operation of the expansion mechanism <NUM> may act upon a compression stage that is a part of the compression process but is independent of drive unit <NUM>.

Referring again to the drawings, <FIG> depicts an embodiment of waste heat recovery system <NUM>. Embodiments of the waste heat recovery system <NUM> may share the same or substantially the same structure and/or function as the waste heat recovery system <NUM>, <NUM> described above. For instance, embodiments of the waste heat recovery system <NUM> may include a drive unit, a compressor, and a waste heat recovery cycle. Embodiments of the waste heat recovery cycle <NUM> may operate in the same or substantially the same manner as the waste heat recovery cycle <NUM>, <NUM> described in association with <FIG> and <FIG>. However, embodiments of the waste heat recovery system <NUM> may include a barrel compressor <NUM> operably coupled to the drive unit <NUM>, with an expansion mechanism <NUM> mounted at one end of a shaft connected to the drive unit <NUM>.

<FIG> depicts an embodiment of the waste heat recovery system <NUM> having a barrel-type centrifugal compressor <NUM> that has multiple compressor stages, <NUM>, <NUM>, <NUM>. An expansion mechanism <NUM> may be mounted at one end of the compressor shaft <NUM>. For instance, one end of the compressor shaft <NUM> may be operably coupled to drive shaft <NUM> that may also be operably coupled to the drive unit <NUM>, while the opposing end of the compressor shaft <NUM> may be operably coupled to the expansion mechanism <NUM>. In an alternative embodiment, the expansion mechanism <NUM> may be directly coupled to the drive unit <NUM>. In yet another embodiment, additional expander stages may be integrated into the barrel compressor <NUM>. Moreover, embodiments of the compressor <NUM> may be any type of shaft driven positive or dynamic compressor; including but not limited to reciprocating, rotary screw, rotary vane, rolling piston, scroll, centrifugal, mixed-flow, or axial compressors. Some heat recovery situations may require multiple stages of expansion to best match the cycle used with the available waste heat and system conditions.

Accordingly, embodiments of the waste heat recovery system <NUM> utilize waste heat <NUM> from the drive unit <NUM> to assist in powering the compressor <NUM>. The waste heat <NUM> may be received by the waste heat recovery cycle <NUM> by the evaporator <NUM>. The evaporator <NUM> may utilize the waste heat <NUM> to evaporate a working fluid of the cycle <NUM>, which may then be delivered to the expansion mechanism <NUM>. Embodiments of the expansion mechanism <NUM> may be operably positioned at an end of the compressor shaft <NUM> of the compressor <NUM>. An operation of the expansion mechanism <NUM> may act upon the drive shaft <NUM>, which may assist the drive unit <NUM> in rotating the drive shaft <NUM> to power the compressor <NUM>.

Each of the waste heat recovery systems <NUM>, <NUM>, <NUM> may harness or otherwise use the waste heat from a drive unit <NUM>, such as a gas turbine, as a power source in a waste heat recovery cycle <NUM>, <NUM>, <NUM>, such as an organic rankine cycle. Embodiments of the waste heat recovery cycle <NUM>, <NUM>, <NUM> may include an expansion mechanism <NUM>, <NUM>, <NUM>, and the power, such as a mechanical power, generated from the expansion mechanism <NUM>, <NUM>, <NUM> may be transmitted or transferred to a compressor stage <NUM> or to a compressor <NUM>, <NUM>, <NUM> to assist in driving or otherwise powering the compressor stage <NUM> or to a compressor <NUM>, <NUM>, <NUM>. Thus, the compressor <NUM>, <NUM>, <NUM> may be driven at one or more locations and/or by two driving sources, which can reduce the work or load required by a single drive unit <NUM>. The transmission/transfer of the power from the expansion mechanism <NUM>, <NUM>, <NUM> may be direct, or may involve one or more gears to accommodate various types of gas compression applications, and multiple types of compressors.

With reference to <FIG>, a method of using waste heat recovery to assist in driving/powering a compression system include the steps of incorporating or coupling a waste heat recovery cycle <NUM>, <NUM>, <NUM> to a drive unit <NUM> and a compressor <NUM>, <NUM>, <NUM>, and delivering a mechanical power from the waste heat recovery cycle <NUM>, <NUM>, <NUM> to the compressor.

Claim 1:
A waste heat recovery system for assisting in driving/powering a compressor (<NUM>, <NUM>) comprising:
a drive unit (<NUM>), the drive unit (<NUM>) having a drive shaft (<NUM>), wherein the drive unit (<NUM>) is a gas turbine;
the compressor(<NUM>) having multiple compression stages (<NUM>, <NUM>, <NUM>, <NUM>) and comprising a gear system comprising a drive gear (<NUM>) which mechanically engages a plurality of pinions (<NUM>, <NUM>, <NUM>) each respectively associated with a compression stage (<NUM>, <NUM>, <NUM>, <NUM>), the drive gear (<NUM>) operably mounted to the drive shaft(<NUM>) such that the plurality of pinions (<NUM>, <NUM>, <NUM>) is rotated in response to a rotation of the drive shaft (<NUM>) and the drive gear (<NUM>), wherein operation of the drive unit (<NUM>) drives the compressor (<NUM>) by the rotation of the drive shaft (<NUM>);
characterized in that the waste heat recovery system (<NUM>) further comprises:
a waste heat recovery cycle (<NUM>) comprising an expansion mechanism (<NUM>) for producing mechanical power, the waste heat recovery cycle (<NUM>) coupled to the drive unit (<NUM>) and further comprising a rotating shaft (<NUM>, <NUM>) mechanically coupled to one of the plurality of the pinions (<NUM>, <NUM>,<NUM>);
wherein a waste heat (<NUM>) of the drive unit (<NUM>) powers the expansion mechanism (<NUM>), such that the waste heat recovery cycle (<NUM>) transmits a mechanical power to the compressor (<NUM>) through the rotating shaft (<NUM>, <NUM>).