Patent Application
20220389831
The subject matter within this disclosure describes turbo expanders.
In gas processing, liquefied and/or high pressure gas (e.g., hydrocarbons, hydrogen, or nitrogen) is depressurized prior to refining. To harness a pressure differential in the processing stream to generate power or electricity, a turbo expander can be used. A turbo expander includes an impeller that acts as a turbine. The turbo expander receives the gas and used the impeller to remove energy from the fluid (e.g., liquid, gas, or a combination) primarily in the form of pressure. In some instances, the turbo expander impeller acts as a driver for other processes. For example, the impeller can drive a pump, compressor, or generator.
This disclosure described technologies relating to regulating flow through turbo expanders.
An example implementation of the subject matter described within this disclosure is a turbo expander with the following features. An impeller is configured to be rotated by a flowing fluid. A fluid stator includes a fixed ring parallel to a plane of rotation of the impeller. The fixed ring has a center in-line with a center of rotation of the impeller. A rotatable ring is rotatable relative to, and parallel to, the fixed ring. The rotatable ring has a center in-line with a center of rotation of the impeller. Stator vanes extend between the fixed ring and the rotatable ring. The stator vanes define an inlet cross sectional area upstream of the impeller. The cross sectional area is dependent upon a relative position of the fixed ring and the rotatable ring. An actuator is configured to rotate the rotatable ring. An electric rotor is coupled to, and configured to rotate in unison with, the impeller. An electric stator encircles the electric rotor. The electric stator includes coil windings.
Aspects of the example turbo expander, which can be combined with the example turbo expander alone or in combination with other aspects, include the following. A gear train includes a rack and a pinion. The rotatable ring includes gear teeth to define the pinion. The actuator is coupled to the rack and configured to move the rack.
Aspects of the example turbo expander, which can be combined with the example turbo expander alone or in combination with other aspects, include the following. A gear train includes a worm gear and a pinion. The rotatable ring includes gear teeth to define the pinion. The actuator is coupled to the worm gear to rotate the worm gear.
Aspects of the example turbo expander, which can be combined with the example turbo expander alone or in combination with other aspects, include the following. A linkage includes a single pin coupled to the actuator and a slot defined by a portion of the rotatable ring. The slot receives the pin and to transfer movement from the pin to the rotatable ring.
Aspects of the example turbo expander, which can be combined with the example turbo expander alone or in combination with other aspects, include the following. A two-part linkage is connected by pins. The two-part linkage includes two arms translatable in a same plane connected by the pins. The two-part linkage provides sufficient coupling to transfer movement from the actuator to the rotatable ring. The two-part linkage provides adequate clearance to prevent binding of the linkage during actuation.
Aspects of the example turbo expander, which can be combined with the example turbo expander alone or in combination with other aspects, include the following. A linkage includes an extension fixed to the rotatable ring and a pin coupled to the actuator. The linkage is of an adequate length to prevent binding of the linkage during actuation.
Aspects of the example turbo expander, which can be combined with the example turbo expander alone or in combination with other aspects, include the following. The actuator is a linear actuator or a rotary motor.
Aspects of the example turbo expander, which can be combined with the example turbo expander alone or in combination with other aspects, include the following. Each and every stator vane is rotatably fixed to either the fixed ring or the rotatable ring.
Aspects of the example turbo expander, which can be combined with the example turbo expander alone or in combination with other aspects, include the following. Each and every stator vane is rotatable and slidably coupled to the other of the fixed ring or the rotatable ring that the each and every stator vane is not rotatably fixed.
Aspects of the example turbo expander, which can be combined with the example turbo expander alone or in combination with other aspects, include the following. Being slidably coupled includes slot and a pin retained within the slot.
Aspects of the example turbo expander, which can be combined with the example turbo expander alone or in combination with other aspects, include the following. The slot is defined by the each of the stator vanes.
Aspects of the example turbo expander, which can be combined with the example turbo expander alone or in combination with other aspects, include the following. The electric rotor and the impeller share a common, hermetically sealed housing that defines a flow path from an inlet at the turbo expander to an outlet downstream of the electric rotor.
Aspects of the example turbo expander, which can be combined with the example turbo expander alone or in combination with other aspects, include the following. An active magnetic bearing supports the impeller or the electric rotor.
An example implementation of the subject matter described within this disclosure is a method of controlling a turbo expander. The method includes the following features. An impeller wheel is rotated by a flowing fluid. An electric rotor is rotated by the rotating impeller. A flow condition of the fluid is adjusted by at least the following steps. A rotatable ring is rotated relative to a stationary ring. The rotatable ring is parallel to a fixed ring that is parallel to a plane of rotation of the rotating impeller. A cross sectional area of an inlet nozzle of the impeller is adjusted by stator vanes extending between the stationary ring and the rotatable ring.
Aspects of the example method, which can be combined with the example method alone or in combination with other aspects, include the following. The method of claim 14, further comprising generating electric current by an electric stator encircling the electric rotor responsive to rotating the electric rotor.
Aspects of the example method, which can be combined with the example method alone or in combination with other aspects, include the following. The electric rotor is supported by a magnetic bearing.
Aspects of the example method, which can be combined with the example method alone or in combination with other aspects, include the following. Rotating the rotatable ring includes rotating by a linear actuator.
Aspects of the example method, which can be combined with the example method alone or in combination with other aspects, include the following. Rotating the rotatable ring includes rotating by a rotational motor and a gear train.
Aspects of the example method, which can be combined with the example method alone or in combination with other aspects, include the following. The impeller is supported by an active magnetic bearing.
Aspects of the example method, which can be combined with the example method alone or in combination with other aspects, include the following. The flowing fluid includes a hydrocarbon gas expanded responsive to rotating the impeller.
An example implementation of the subject matter described within this disclosure is a turbo expander system with the following features. A turbo expander includes an impeller configured to be rotated by a flowing fluid. A fluid stator includes a fixed ring parallel to the impeller. The fixed ring has a center in-line with a center of rotation of the impeller. A rotatable ring is rotatable relative to, and parallel to, the fixed ring. The rotatable ring has a center in-line with a center of rotation of the impeller. Stator vanes extend between the fixed ring and the rotatable ring. The stator vanes define an inlet cross sectional area upstream of the impeller. An actuator is configured to rotate the rotatable ring. An electric rotor is coupled to, and configured to, rotate in unison with the impeller. An electric stator encircles the electric rotor. A controller is configured to control the turbo expander. The controller is separate from the turbo expander. A cable connects the controller to the turbo expander.
Aspects of the example turbo expander system, which can be combined with the example turbo expander system alone or in combination with other aspects, include the following. An active magnetic bearing supports the impeller or the electric rotor.
Aspects of the example turbo expander system, which can be combined with the example turbo expander system alone or in combination with other aspects, include the following. The cable includes a first conductor configured to filtered a pulse width modulated actuating signals to the active magnetic bearing. The first conductor is electrically shielded. A second conductor connects the controller to the active magnetic bearing. The second conductor is configured to exchange a DC current between the controller and the active magnetic bearing.
Aspects of the example turbo expander system, which can be combined with the example turbo expander system alone or in combination with other aspects, include the following. The first conductor and the second conductor are over 500 feet in length.
Aspects of the example turbo expander system, which can be combined with the example turbo expander system alone or in combination with other aspects, include the following. A hydrocarbon or process gas source feeds the turbo expander. The gas drives the impeller and is depressurized by the turbo expander.
The details of one or more implementations of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the subject matter described herein will be apparent from the description and drawings, and from the claims.
Like reference symbols in the various drawings indicate like elements.
In gas processing, turbo expanders can be used to depressurize gas and/or liquefied natural gas, for example, where a processing plant receives hydrocarbon fluids from a pipeline or other transport. In some instances, for example, when hydrocarbon fluids are being processed at high pressures and/or extreme temperatures, the process fluids are hazardous if they come in direct contact with personnel. As turbo expanders include rotating components, dynamic seals, which are prone to failure, are relied upon to isolate personnel from hydrocarbons. In addition, turbo expanders are often “dumb”, passive pieces of equipment. That is, the turbo expander is often not a self-regulated piece of kit, relying instead upon surrounding processes to regulate flows and pressures through the turbo expander. For example, flow and pressure through a turbo expander can be regulated by a pressure regulator upstream or downstream of the turbo expander.
This disclosure describes a turbo expander with an adjustable stator that includes a fixed ring parallel to a plane of rotation of an impeller, and a rotatable ring rotatable relative to, and parallel to, the fixed ring. Stator vanes extend between the fixed ring and the rotatable ring. The stator vanes define an inlet cross sectional area upstream of the impeller. The cross sectional area is dependent upon a relative position of the fixed ring and the rotatable ring. The rotatable ring is adjusted and rotated by an actuator controlled by a controller. An electric rotor is coupled to, and is configured to rotate in unison with, the impeller. An electric stator encircles the electric rotor
An electric rotor 106 is coupled to, and configured to rotate in unison with, the impeller 102. The electric rotor 106 can include an inductive rotor (e.g. squirrel cage or armature wound rotor), a permanent magnet rotor, a wound field synchronous rotor, or any other type of electric rotor. While illustrated and described as being directly coupled to rotate in unison, a gearbox and/or magnetic coupling can be used to couple the electric rotor 106 and the impeller 102 without departing from this disclosure. An electric stator 108 encircles the electric rotor 106. The electric stator 108 includes a coiled windings 112 through which electric current can flow. In operation, the field interaction between the electric rotor and the electric stator 108 can produce electric current and/or can be used to regulate a speed of an electric rotor 106, and therefore the impeller 102. For example, the electric rotor 106 and electric stator 108 can act as a generator, and an adjustable electric load can be used to regulate a rotational speed of the electric rotor. Such a variable load can be included with and/or controlled by a controller 110.
In some implementations, the electric rotor 106 and the impeller 102 share a common, hermetically sealed housing 114 that defines a flow path from an of the turbo expander 100 toward an outlet downstream of the electric rotor. In such implementations, an annulus, defined by an outer surface of the electric rotor 106 and an inner surface of the stator windings 112, exposed to the process fluid. In some implementations, a second annulus defined by an inner surface of a housing 114 and an outer surface of the stator can be similarly exposed to the process fluid. Regardless, such a hermetically sealed housing 114 arrangement reduces the risk of personnel exposure to the process fluid as eliminating dynamic seals eliminates them as a failure point as well.
In some implementations, the turbo expander 100 includes an active magnetic bearing 116 supporting the impeller 102 and/or the electric rotor 106. In such an implementation, the shaft of the electric rotor and/or impeller do not directly come in contact with a bearing surface attached to the housing 114. Such implementations can include active bearing control monitored and controlled by the controller 110. While primarily described and illustrated as using active magnetic bearings, other bearing types can be used without departing from this disclosure. For example, passive magnetic bearings can be used. Alternatively or in addition, anti-friction bearings can be used (e.g., ball bearings or roller bearings). Similarly, journal bearing can be used. In some implementations, types of bearings can be mixed, for example, an antifriction bearing and an active magnetic bearing can be used simultaneously.
In some implementations, the controller 110 can be located some distance from the turbo expander 100. For example, the controller can be 500 feet from the turbo expander, 1000 feet from the turbo expander, or 2000 feet from the turbo expander. The controller 110 is connected to the turbo expander by a cable 118. In some implementations, the cable 118 includes a first conductor 120 and a second conductor 122. The first conductor 120 is configured to filtered a pulse width modulated actuating signals to the active magnetic bearing 116. In some implementations, the first conductor is electrically shielded. The second conductor connects the controller to the active magnetic bearing 116. The second conductor 122 is configured to exchange a direct current between the controller 110 and the active magnetic bearing 116.
Multiple stator vanes 206 extend between the fixed ring 202 and the rotatable ring 204. The stator vanes 206 define an inlet cross sectional area upstream of the impeller 102. In the illustrated implementations, the flow goes from the outside radius of the impeller 102 towards a center of the impeller 102; however, other arrangements are feasible without departing from this disclosure. For example, the flow direction can be from the center of the impeller to the outer radius of the impeller while the stator vanes define an outlet cross sectional area downstream (outlet) of the impeller 102. Regardless of the arrangement, the cross sectional area is dependent upon a relative position of the fixed ring 202 and the rotatable ring 204. That is, the rotational position of the rotatable ring 204 determines the cross sectional flow area 208. In some implementations, the rotatable ring can include an extension or tab 210 to be coupled to an actuator and/or linkage such that the actuator is configured to rotate the rotatable ring 204 to a desired position, setting a flowrate through the turbo expander 100;
Each and every one of stator vanes 206 is rotatably fixed to either the fixed ring 202 or the rotatable ring 204. That is, each of the stator vanes is coupled to one of the rings such that the vane is capable of pivoting around a fixed point of that ring without being able to translate. In the illustrated implementation, the vanes 206 are rotably fixed to the fixed ring 202; however, the vanes 206 could be similarly fixed to the rotatable ring 204 without departing from this disclosure.
Each and every one of stator vanes 206 are also rotatable and slidably coupled to the other of the fixed ring or the rotatable ring that the each and every stator vane is not rotatably fixed. In other words, each of the stator vanes 206 includes a pivot point coupled to one of the rings (202 or 204) and a pivotable/translatable connection coupled to the other ring. In some implementations, being slidably coupled can include a slot 212 and a pin 214 retained within the slot 212. In such implementations, the slot can defined by the each of the stator vanes, or each slot can be defined by a ring, as illustrated in
The first linkage 402 is a gear train that includes a rack 410 and a pinion 412. In such an implementation, the rotatable ring 414 includes gear teeth 416 to define the pinion 412. A linear actuator (not shown) is coupled to the rack 410 and is configured to linearly move the rack 410. This implementation can be made to allow for a large degree of movement between a fully open position of the stator vanes 206 and a fully closed position of the stator vanes 206. A wider operational range can be useful in plants that experience large variations in hydrocarbon flowrates. This implementation can be driven by a motor, rotating actuator, or other drive arrangement.
The second linkage 404 includes a single pin coupled to an actuator, and a slot 420 defined by a portion of the rotatable ring 414, for example, a tab 418. The slot 420 receives the pin 422 and to transfer movement from the pin 422 to the rotatable ring 414. The slot 420 allows for the linear movement of the actuator to be continuously transferred to the circular rotatable ring 414 without creating a significant force moment (greater than that caused by misalignments inherent in standard manufacturing environments) on the actuator. Such an implementation is relatively easy to manufacture. This implementation can be driven by linear actuators, or other drive arrangements.
The third linkage is a two-part linkage 406 connected by pins 422. The two-part linkage 406 includes two arms 424 translatable in a same plane connected by the pins 422. The two-part linkage provides sufficient coupling to transfer movement from the actuator to the rotatable ring. That is, the two-part linkage 406 provides adequate clearance to prevent binding of the linkage 406 during actuation. Such an implementation accomplishes such a feat by allowing for the linear movement of the actuator to be continuously transferred to the circular rotatable ring 414 without creating a significant force moment (greater than that caused by misalignments inherent in standard manufacturing environments) on the actuator. Such an implementation is relatively easy to manufacture, and allows for a greater range of motion than the linkage 404 previously described.
The fourth linkage 408 is an extension 426 fixed to the rotatable ring 414, and a pin 422 coupled to the actuator. The linkage 408 is of an adequate length to prevent binding of the linkage during actuation. In such implementations, a moment is present on the actuator and/or linkage as the linear motion is coupled to a rotational movement. Such a moment can be mitigated by flexing of the linkage 408, or by adding an additional pin 422 to the actuator itself.
In some implementations, the entire actuator (for example, the rotary motor 502) can be completely encased within the hermetically sealed housing 510. In some implementations, the actuator can be positioned on the outside of the housing, and various sealing elements can be used to isolate the actuator from the process fluid. For example, such sealing elements can include dynamic seals that contact the linkage.
In operation, the turbo expander works as follows. Some or all of the steps described within this disclosure can be performed by the controller 110. Hydrocarbon gas (or other high pressure gasses) are fed into the inlet of the turbo expander 100, rotating an impeller wheel by the fluid flow. Responsive to rotating the impeller the flowing fluid is expanded. That is, the pressure of the fluid is decreased. The rotating impeller 102 further rotates the electric rotor 106. Responsive to rotating the electric rotor, electric current is generated by the electric stator 108 encircling the electric rotor 106. In some implementations, the electric rotor and/or the impeller are supported by a magnetic bearing. Such a magnetic bearing can be a passive magnetic bearing or an active magnetic bearing.
To maintain a desired feed rate of fluid, a flow-rate of the fluid can be adjusted by adjusting a cross sectional area of an inlet nozzle (fluid stator) of the impeller 102 by a set of stator vanes extending between the stationary ring and the rotatable ring. Adjusting the stator vanes involves rotating the rotatable ring relative to the stationary ring. The rotatable ring can be rotated by an actuator connected to the rotatable ring by a linkage and/or gear train.
A number of implementations of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, a cross sectional area of an outlet or a turbo expander can be adjusted without departing from this disclosure. Accordingly, other implementations are within the scope of the following claims.
