EA046434B1 - COMPRESSOR AND METHOD FOR REMOVING LIQUID FROM COMPRESSOR - Google Patents

Description

Scope of the invention

Embodiments of the subject matter described herein relate to centrifugal compressors and motorized centrifugal compressors, as well as methods for operating such compressors and motorized compressors. In particular, embodiments of the present disclosure relate to liquid-stable compressors, such as vertical centrifugal compressors, and methods for removing liquid from a compressor upon startup.

Prerequisites for creating the invention

Compressors are used to increase the pressure in a gas stream. Dynamic compressors, which include axial compressors and centrifugal compressors, the latter also called radial compressors, increase fluid pressure by adding kinetic energy to the continuous flow of fluid through the rotor. The kinetic energy is then converted to static pressure by slowing the flow of gas through the diffuser.

The compressors are designed to process gaseous fluids. However, in some applications the gas stream may also contain a liquid phase in the form of small droplets. Compressors designed to be liquid-resistant are sometimes called liquid-tolerant compressors. Typical applications in which a mixture of liquid and gaseous phases can be processed through compressors are in the oil and gas field.

The liquid is collected and removed from the compressor. External drainage systems are usually provided for this purpose. These systems increase the complexity and cost of the compressor. They can be prone to malfunction, which can become critical, especially in subsea installations where maintenance or repair operations can be complex. US 2019/0048895 describes a centrifugal compressor with an integrated motor that does not require an external drainage system.

Although the above compressor represents a significant improvement in the field of liquid-tolerant compressors, there is still room for further improvements, especially in terms of liquid drainage efficiency.

Summary of the invention

Described herein is a centrifugal compressor comprising a casing, a rotor disposed in the casing to rotate about a vertical axis of rotation. The housing contains a gas inlet channel located in the lower region of the compressor, and a gas outlet channel located at a level above the gas inlet channel. The rotor contains at least one impeller. In some embodiments, the compressor includes a plurality of impellers arranged in a line or in any other suitable configuration, such as a twin configuration. The compressor also includes a gas flow path extending from the gas inlet channel to the gas outlet channel.

The compressor further includes an inlet chamber extending from the gas inlet passage to the suction side of the impeller and surrounding the rotor bearing. To facilitate the removal of liquid collected in the lower region of the compressor, in accordance with the embodiments described herein, a suction tube is provided having a lower suction end located at the lower part of the inlet chamber. The suction tube runs up to the suction side of the compressor impeller. If the compressor has more than one impeller, the suction tube may go to the suction side first, i.e. the outermost upstream impeller. The low gas pressure generated by the rotating impeller on the suction side of the impeller spreads through the suction tube and facilitates the removal of liquid collected at the bottom of the inlet chamber.

To improve the absorption of liquid through the suction tube, the discharge end of the suction tube can be located in front of the suction side of the impeller, as close as possible to the leading edges of the impeller blades.

According to some currently preferred embodiments, the suction tube is positioned opposite the gas inlet passage relative to the axis of rotation of the compressor rotor. In this case, a deposition chamber may be formed, preferably adjacent to the bottom of the inlet chamber. The velocity of the incoming gas in the deposition chamber is low and can be almost zero. In this way, a higher pressure difference can be established between the inlet and outlet ends of the suction tube, which helps remove liquid stagnating at the bottom of the inlet chamber.

In accordance with some embodiments, the inlet chamber may be divided into two inlet chamber sections by a dividing rib located approximately opposite the gas inlet channel. The deposition chamber may be formed by a rib. The suction tube may be located in or formed by the rib.

To further improve the efficiency of the above-described suction device, some embodiments may provide an ejector configured to promote fluid flow in the suction tube. The ejector can be driven by a gas flow at a pressure higher than the gas pressure in the inlet chamber. For example, gas flow may

- 1 046434 be diverted from a point in the gas flow channel downstream of the impeller. If there is more than one impeller, the pressurized gas may be removed from a point in the gas flow path downstream of one of the compressor impellers, for example downstream of the last impeller.

The compressor may include one or more drain passages configured to collect liquid in the compressor. Liquid may be collected at the bottom of the compressor, such as in an inlet chamber and/or in a liquid collection chamber extending at least partially below the bottom of the inlet chamber and in fluid communication with the inlet chamber. The liquid collection chamber may be in fluid communication with a source of pressurized gas such that the pressure in the liquid collection chamber is maintained above the pressure in the inlet chamber to promote movement of liquid from the liquid collection chamber into the inlet chamber.

The centrifugal compressor can be designed as a compressor with a built-in motor, comprising an electric motor coupled to the compressor rotor and housed in the same compressor housing.

Also described herein is a method for removing liquid from a liquid-stable centrifugal compressor. The method includes the step of collecting liquid in the inlet chamber of the compressor. The method further allows liquid to be aspirated from the inlet chamber through at least one suction tube having a lower suction end at the bottom of the inlet chamber and extending upward from the suction end to the discharge end towards the suction side of the first compressor impeller.

Additional features and embodiments of the compressor and method of the present invention are described in the detailed description below and set forth in the accompanying claims.

Brief description of graphic materials

The described embodiments of the invention and the many attendant advantages thereof may be more fully appreciated and understood by reference to the following detailed description taken in conjunction with the accompanying drawings, wherein:

in fig. 1 is a cross-sectional view of a compressor with an integrated motor according to the present description, taken in an axial plane;

in fig. 2 is an enlarged view of a section of the integrated motor compressor shown in FIG. 1;

in fig. 3 is a cross-sectional view along line III-III shown in FIG. 1;

in fig. 4 is an enlarged view of detail IV shown in FIG. 2; and in fig. 5 is a flow diagram of the method in accordance with the present description.

Detailed description

Described herein is a new and useful centrifugal compressor in which liquid collected in the lower region of the compressor is removed more efficiently. The compressor can be designed as a single unit with the engine, i.e. made in the form of a compressor with a built-in engine, having a common housing in which both the engine and the compressor are located.

The compressor includes a gas inlet channel and a gas outlet channel, as well as a gas flow channel extending from the gas inlet channel to the gas outlet channel. The gas flow is processed through one or more impellers and one or more diffusers. Gas is compressed by adding kinetic energy to it through a rotating impeller(s) and then slowing down the gas flow in a stationary diffuser(s). The compressor is designed as a vertical compressor, and (when the compressor is installed and during operation) the rotor rotates around a vertical axis. The gas inlet duct is located in the lower region of the compressor, and the gas outlet duct is located at a level above the gas inlet duct. An inlet chamber is provided between the gas inlet channel and the impeller, or the first impeller if there is more than one impeller. Liquid, possibly present in the gas flow, accumulates at the bottom of the inlet chamber. To improve drainage of the liquid phase from the inlet chamber, at least one suction tube is provided which extends upward from the bottom of the inlet chamber to the suction side of the impeller (or preferably the first impeller if there is more than one impeller). Thus, the suction generated by the impeller is distributed through the suction tube towards the bottom of the inlet chamber, where the suction end of the suction tube is located. Thus, liquid from the lower part of the inlet chamber is effectively removed by suction from the lower part of the inlet chamber, and its movement through the gas flow channel is stimulated, for example, to remove the liquid phase collected in the lower region of the compressor.

As mentioned above, and as will be apparent from the detailed description below, the present description relates to a vertical compressor, i.e. a compressor having a rotor configured to rotate around a vertical axis during operation of the compressor. In the present description, reference is made to the spatial relationships of the various parts of the compressor. The terms upper, higher, lower, upper part, lower part, above, below, below, up, down, etc. refer to the position of various components when the compressor is operating, i.e. with axis of rotation in vertical direction

- 2 046434 position, unless otherwise indicated. As used herein, the terms upstream and downstream refer to the direction of fluid flow through the compressor unless otherwise noted.

Further, with reference to graphic materials, Fig. 1 illustrates a cross-sectional view of a compressor 1 with a built-in motor, taken along a plane containing the rotation axis AA of the compressor. The compressor 1 with a built-in engine contains a housing 2, in which a section 3 of the engine and a section 5 of the compressor are located. The housing 2 may in turn comprise a top cover 2.1, an upper housing section 2.2, a lower housing section 2.3 and a lower cover 2.4.

Section 3 of the engine houses the drive for the compressor. Specifically, in the illustrated embodiment, the motor section 3 houses an electric motor 7 having a rotor supported to rotate in the housing 2 about a rotation axis AA. The rotor of the motor 7 may be supported by suitable bearings 9, 11. In some embodiments, the bearings 9 and 11 may be active magnetic bearings. More specifically, the motor rotor 7 may have an upper shaft end 7.1 rotatably positioned in an upper bearing 9 and a lower shaft end 7.2 rotatably positioned in a lower bearing 11.

The compressor section 5 houses a compressor 13. The compressor 13 includes a stationary portion, commonly referred to as a compressor tube, generally designated 15 (see also FIG. 2). The stationary section 15 of the compressor 13 contains one or more diffusers for one or more impellers. The diffusers are marked with reference numbers 15.1, 15.2 and 15.3. The compressor 13 further includes a rotor 16 configured to rotate around a rotation axis AA. The rotor contains a shaft 17 and a plurality of impellers 16.1, 16.2, 16.3 and 16.4. The number of impellers and diffusers is given as an example, and those skilled in the art will understand that several advantages of the compressor described herein can also be achieved in single-stage compressors, i.e. compressors with a single impeller.

The shaft 17 of the compressor 13 is connected with the ability to transmit driving force to the shaft 7.2 of the engine 7 and can be supported by a bearing 11, and its lower end can be supported by a lower bearing 21 located under the rotor 16.

Each impeller has a suction side impeller and a discharge side impeller. In fig. 2, the suction side of the impeller 16.1 is designated by reference numeral 23, and the corresponding discharge side of the impeller is designated by 25. The discharge side of the impeller is fluidly connected to the first diffuser 15.1.

The outermost downstream impeller 16.4 is in fluid communication with the volute chamber 27, which in turn is in fluid communication with the gas outlet channel 29 of the compressor 13.

The compressor 13 further includes an inlet chamber 31 that extends from the gas inlet passage 28 to the suction side of the first impeller 16.1. The inlet chamber 31 extends from the lower part 31.1 to the upper part of the inlet chamber located in front of the suction side 23 of the impeller 16.1. As can be better understood from FIG. 3, the inlet chamber 31 extends circumferentially around the rotation axis AA of the built-in motor compressor 1 and has a conical cross-sectional shape with a narrower transverse dimension at the top and a larger transverse dimension at the bottom.

In some embodiments, the outer boundary of the inlet chamber 31 is formed by the stationary portion 15 of the compressor 13, and the inner boundary of the inlet chamber 31 is formed between an axial inner body 33A that forms the hub of the inlet chamber 31 and a casing 33B that surrounds the inner main body 33A. The inner main body 33A and the casing 33B are connected to each other by spacers 35. As shown in FIG. 2, the struts 35 may have an aerodynamic profile, such as a wing profile, to reduce the head loss in the gas flowing through the inlet chamber 31.

As mentioned above, the inlet chamber 31 is in fluid communication with the inlet channel 28 for gas. Opposite the gas inlet channel 28, a fin 31 may be provided in the inlet chamber 37. The fin 37 divides the inlet chamber 31 into two sections and forms a so-called deposition area, or deposition chamber 39, at the bottom 31.1 of the inlet chamber 31 for purposes that will be described. below.

Thus, in the compressor 1 with a built-in engine, a gas flow channel is formed, and the gas flow channel contains an inlet gas channel 28, an inlet chamber 31, impellers 16.1, 16.2, 16.3, 16.4 and corresponding diffusers 15.1, 15.2, 15.3, a spiral chamber 27 and output channel 29 for gas.

The inner main body 33A, which radially defines the inner surface and the lower surface of the inlet chamber 31, also defines a seat in which the lower bearing 21 is located. The lower bearing 21 may be an active magnetic bearing, similar to the bearings 9 and 11.

The inner body 33A has an inner cavity, and a liquid collection chamber 41 is formed inside and below the inner body 33A between this latter member and the lower

- 3 046434 cover 2.4 of the housing 2. The liquid collection chamber 41 can be configured to collect liquid under the influence of gravity from the remaining areas of the compressor 5 through drainage channels, one of which is shown as an example in FIG. 2 and is designated by reference numeral 43.

The liquid collection chamber 41 may be in fluid communication with the inlet chamber 31. The lower portion of the liquid collection chamber 41, i.e. its lowest point may be located below the bottom of the inlet chamber 31, as shown in FIG. 1 and fig. 2. In some embodiments, a fluid connection between the liquid collection chamber 41 and the inlet chamber 31 may be established through at least one communication channel 45. The communication channel 45 has a lower inlet channel 45.1 in the liquid collection chamber 41 and an upper outlet channel 45.2 in the inlet chamber 31. In preferred embodiments, the upper outlet channel 45.2 is located at a level below the bearing 21. Thus, effective aspiration of liquid from the inlet chamber 31 in the manner described below, the liquid level inside the liquid collection chamber 41 will always remain below the bearing 21, preventing the bearing 21 from flooding.

As used herein, the terms aspiration and aspirate mean removal or removal by suction.

To encourage fluid flow from fluid collection chamber 41 upward toward the bottom of inlet chamber 31, in some embodiments, pressure line 42 places fluid collection chamber 41 in fluid communication with a pressure source, such as a pressurized or partially pressurized source. process gas pressure. The pressurized or partially pressurized process gas can be withdrawn from the gas flow passage of the compressor 5 downstream of the first impeller 16.1. As shown in FIG. 2, for example, pressure line 42 may be in fluid communication with volute chamber 27. In other embodiments, the inlet end of pressure line 42 may be connected to gas outlet passage 29 or any other portion of the gas flow path where gas pressure is higher. than in the inlet chamber 31. For example, the inlet end of the pressure line 42 may be located between the first or any subsequent impeller 16.1, 16.2, 16.3 and the downstream impeller, or at any point between the outermost downstream impeller 16.4 and the outlet passage 29 for gas.

In some embodiments, the pressure line 42 may extend through one of the spacers 35 that connect the inner body 33A to the housing 33B.

With the above arrangement, the liquid contained in the fluid processed through the compressor is collected by gravity in the liquid collection chamber 41 and possibly in the lower part of the inlet chamber 31, especially during periods of inactivity of the motorized compressor 1. When starting, the liquid phase should be removed from the bottom of the compressor 13 (inlet chamber 31 and liquid collection chamber 41).

During installation or after a long period of inactivity, the level of liquid collected at the bottom of compressor section 5 may rise, subsequently filling the first and subsequent impellers 16.1, 16.2, 16.3, 16.4. When the compressor starts, the rotor 16 will rotate at low speed and liquid will be pumped through the impellers, with the compressor 13 acting as a pump. This pumping effect will reduce the liquid level below the suction side 23 of the first impeller 16.1. The speed of rotation of the rotor 16 will increase, and the decrease in pressure above the free liquid level in combination with the gas flow from the gas inlet channel 28 will cause liquid to be sucked into the impeller 16.1.

However, removing liquid from the inlet chamber 31 becomes more difficult as the liquid level in the inlet chamber 31 drops.

To ensure efficient suction of liquid from the bottom of the inlet chamber 31, in the embodiment shown in the drawings, a suction tube 51 is provided which has a first lower suction end 51.1 and a second upper discharge end 51.2. As shown in particular in FIG. 2, the lower suction end 51.1 is located at the lower portion 31.1 of the inlet chamber 31. As understood herein, the term "lower" means that the suction end 51.1 may be located at the lowest location within the inlet chamber 31 or above the lowest location, but preferably in the lower half of the inlet chamber 31. The suction tube 51 extends upward to the suction side 23 of the first impeller 16.1, and its second upper discharge end 51.2 may be located immediately in front of or at a distance from the inlet channel of the first impeller 16.1. In any case, the upper discharge end 51.2 of the suction tube 51 is located in a position in which, when the compressor 13 is operated, a gas pressure is established that is lower than the pressure at the first lower suction end 51.1 of the suction tube 51, thereby aspirating liquid from the inlet chamber 31.

In effect, the suction tube 51 distributes the pressure present at or near the suction side of the impeller 16.1 towards the bottom of the inlet chamber 31. If there is liquid at the bottom of the inlet chamber 31, causing stagnation therein, suction through the suction tube 51 causes said liquid to be transported through the suction tube

- 4 046434 to suction side 23 of impeller 16.1. Thus, effective removal of stagnant liquid will be achieved through suction.

In some embodiments, more than one suction tube 51 may be provided.

In the embodiment shown in FIG. 1 and fig. 2, the lower part 31.1 of the inlet chamber 31 has a variable height. More specifically, the lower part 31.1 of the inlet chamber 31 is at a lower level in the region in the gas inlet channel 28 and at a higher level in the opposite region, i.e. at the location of the suction tube 51. In other words, the cross-section of the inlet chamber 31 along the planes containing the axis of rotation of the compressor 13 varies around the axis. With this shape of the lower part 31.1 of the inlet chamber 31, the energy of the incoming gas can be used to resist stagnation of liquid in the lowermost part of the inlet chamber 31 towards the suction tube 51.

To stimulate the suction efficiency of the suction tube 51, the lower end 51.2 of the suction may be located in a settling chamber 39 formed, for example, by a cavity in the rib 37. As used herein, the term settling chamber or settling area refers to the volume filled with fluid entering the compressor. 13 through the gas inlet channel 28, and the fluid velocity decreases and can reach almost zero. Thus, the kinetic energy of the fluid flow is converted into pressure energy, which facilitates the suction of liquid through the suction tube 51.

In the embodiment shown in FIG. 1, 2 and 3, the suction tube 51 is formed inside the rib 37 so that the number of components of the compressor 13 is reduced and the suction tube 51 is always maintained in the correct position inside the inlet chamber 31 opposite the gas inlet passage 28.

In some embodiments, to further promote fluid suction from the bottom portion 31.1 of the inlet chamber 31, an ejector (i.e., an ejector pump) may be provided in or at the inlet end of the suction tube 51. The ejector is actuated by discharging a pressurized fluid (e.g., pressurized or partially pressurized process gas) at the first, lower suction end 51.1 or at any suitable position along the suction tube 51. The pressurized gas may be removed from the main gas stream along the gas flow path. For example, the same pressure line 42 described above can be used for such a purpose. However, in the illustrated embodiment, a separate pressure line 55 is provided for supply to the ejector. Pressure line 55 may be in fluid communication with the high pressure portion of the gas flow passage, for example downstream of one of the impellers 16.1, 16.2, 16.3 and 16.4 or downstream of one of the diffusers 15.1, 15.2, 15.3. In other embodiments, pressure line 55 is in fluid communication with volute chamber 27, as shown in FIG. 2, or with outlet channel 29 for gas.

The pressure line 55 may be in fluid communication with an ejector 57 (see extension in FIG. 4) located in the suction tube 51 or at its suction end 51.1.

When increased suction is required to remove liquid from the bottom 31.1 of the inlet chamber 31, pressure line 55 may be opened to force pressurized gas into ejector 57. If pressurized gas is not required, pressure line 55 may be closed, for example by means of an adjustable valve. 59 (Fig. 2). This will improve the overall efficiency of compressor 13.

In the above-described built-in motor compressor 1, a method for removing liquid from the compressor 13 and starting it can be performed as follows. The motorized compressor 1 is started when the compressor 13 is at least partially filled with liquid. For example, liquid may be present in one or more of the following areas of the compressor 13: liquid collection chamber 41; entrance chamber 31; one, some or all impellers 16.1, 16.2, 16.3, 16.4.

If the liquid present exceeds the level of the upper discharge end 51.2 of the suction tube 51, the liquid is pumped out through the impellers. The suction generated at the suction side of the impeller 16.1 is distributed through the suction tube 51 to stimulate the suction of liquid from the bottom 31.1 of the inlet chamber 31 and from the liquid collection chamber 41 through the communication channel 45.

The liquid collected in the lower portion of the compressor 13 is gradually removed until the entire gas flow path is substantially free of liquid. The liquid still contained in the compressor 13 can be collected in the chamber 41 to collect liquid remaining below the level of the first lower suction end 51.1 of the suction tube 51. The method is summarized in the flow diagram of FIG. 5.

During operation of the motorized compressor 1, a liquid phase may be present in the gas entering the compressor 13 through the gas inlet passage 28, for example, in the form of small droplets, or may be condensed in the gas flow along the gas flow passage. The compressor 13 may include elements (known as such) configured to separate a liquid phase from a gaseous phase such that such liquid phase is collected under the influence of gravity into a

Claims (16)

41 to collect liquid and can be sucked through the suction tube 51. Thus, effective removal of liquid is achieved both during startup and during normal operation of the compressor 1 with a built-in motor. Although the invention has been described in terms of various specific embodiments, it will be apparent to those skilled in the art that many modifications, variations and exceptions are possible without departing from the spirit and scope of the claims. In addition, unless otherwise indicated, the order or sequence of any steps of the process or method may be varied or rearranged in accordance with alternative embodiments. CLAIM 1. Centrifugal compressor (5, 13), containing: a housing (2) containing a gas inlet channel (28) located in the lower region of the compressor, and a gas outlet channel (29) located at a level above the gas inlet channel; a rotor (16) located in the housing (2) and configured to rotate around a vertical axis of rotation, said rotor (16) comprising at least one impeller (16.1) having a suction side (23) of the impeller and a side (25) ) impeller discharge; a gas flow channel extending from the gas inlet channel (28) to the gas outlet channel (29), characterized in that it contains an inlet chamber (31) in the housing (2) extending from the gas inlet channel (28) to suction side (23) of the impeller and surrounding the rotor bearing (21); and at least one suction tube (51) having a suction lower end (51.1) and an upper discharge end (51.2); wherein the lower end (51.1) of the suction is located in the lower part of the inlet chamber (31); and wherein the suction tube (51) extends upward to the suction side (23) of the impeller. 2. The centrifugal compressor according to claim 1, wherein the discharge end (51.2) of the at least one suction tube (51) is located in front of the suction side (23) of the impeller. 3. Centrifugal compressor according to claim 1 or 2, in which said at least one suction tube (51) is located opposite the gas inlet channel (28) relative to the axis of rotation. 4. The centrifugal compressor according to claim 1 or 2 or 3, wherein the lower suction end (51.1) is located in a settling chamber (39) located at the bottom of the inlet chamber (31). 5. The centrifugal compressor according to claim 4, in which the inlet chamber is divided into two sections of the inlet chamber (31) by a dividing rib (37) located opposite the inlet channel (28) for gas; and wherein the deposition chamber (39) is formed by a rib. 6. The centrifugal compressor according to claim 5, wherein at least one suction tube (51) is formed in the rib (37). 7. The centrifugal compressor according to one or more of the preceding claims, further comprising an ejector (57) configured to stimulate fluid flow in the suction tube (51). 8. The centrifugal compressor according to claim 7, wherein the ejector (57) is fluidly connected to a gas flow channel downstream of said at least one impeller (16.1). 9. The centrifugal compressor according to claim 8, further comprising a channel (55) for gas under pressure connecting the ejector (57) with the channel for gas flow, and a closing element (59) configured to selectively close and open the channel (55) for gas under pressure. 10. The centrifugal compressor according to one or more of the preceding claims, further comprising at least one drainage channel configured to collect liquid in the compressor (5). 11. The centrifugal compressor according to claim 10, wherein said at least one drainage channel extends through the spacer (35) through the entire inlet chamber (31). 12. The centrifugal compressor according to claim 10 or 11, further comprising a liquid collection chamber (41) at least partially extending under the bottom of the inlet chamber (31) and fluidly connected to the inlet chamber (31); and wherein said at least one drainage channel is fluidly connected to a chamber (41) for collecting liquid. 13. The centrifugal compressor according to claim 12, wherein the liquid collection chamber (41) is partially surrounded by an inlet chamber (31). 14. Centrifugal compressor according to claim 12 or 13, in which the rotor bearing (21) is located in the chamber (41) for collecting liquid. 15. The centrifugal compressor according to claim 14, wherein the liquid collection chamber (41) is in fluid communication with the inlet chamber (31) through at least one communication channel (45) terminating in the inlet chamber (31) at a level below the rotor bearing (21). 16. Centrifugal compressor according to one of claims 14, 15, in which the liquid collection chamber (41) is in fluid communication with a source of pressurized gas. -