JP6979977B2 - Compressor surge protection under wet gas conditions - Google Patents

Description

The present disclosure relates to compressor control methods and systems. The embodiments disclosed herein specifically relate to wet gas compressors, particularly centrifugal wet gas compressors, that process gases that can contain liquid phases such as heavy hydrocarbons, water and the like.

Centrifugal compressors are designed to process so-called wet gases, that is, gases that can contain a particular proportion of the liquid phase. Wet gas treatment is often required in the petroleum and gas industry where gas extracted from wells such as submarine wells can contain liquid hydrocarbon phases or water.

The presence and proportion of the liquid phase in the gas can affect the operation of the compressor, especially the surge limits that determine the safe operating range of the compressor. However, usually, the liquid volume fraction in the gas flow on the suction side of the compressor is not known. Flowmeters capable of measuring liquid volume fractions are cumbersome and expensive and may not be suitable for a particular application under extreme environmental conditions.

Therefore, there is a need to reliably and efficiently control the operation of the wet gas compressor, especially as far as surge protection is concerned.

U.S. Patent Application Publication No. 2016/0177958

According to the first aspect, a method for surge protection protection of a compressor under wet gas conditions is disclosed herein. The compressor includes a suction side and a discharge side. The surge protection system is located between the discharge side and the suction side of the compressor. According to the embodiments disclosed herein, this method is:
Steps to calculate the surge limit line in the compression ratio vs. correction power diagram,
The step of determining the compressor operating point in the compression ratio vs. correction power diagram, and
The step of detecting the distance between the operating point and the surge limit line,
If the distance is less than the minimum safe distance, it includes steps that act on the compressor's surge protection system.

According to a further aspect, a wet gas compressor system comprising a compressor having a suction side and a discharge side, a surge prevention control device, and a control unit functionally coupled to the surge prevention control device is described herein. Will be disclosed in. The control unit is configured and arranged to perform the method as described above.

The compression ratio vs. correction power diagram is a diagram in which the compressor performance is expressed as a function of the relationship between the compression ratio on the compressor and the correction power of the compressor.

Features and embodiments are disclosed herein below and are further described in the appended claims. The appended claims form an essential part of the specification. The above brief description is intended to provide a deeper understanding of the following detailed description, and to further assess the contribution of the invention to the art, the features of various embodiments of the invention. It is described. Of course, the present invention has other features, the other features being described below and described in the appended claims. In this regard, prior to elaborating on some embodiments of the invention, various embodiments of the invention are described in the following description or in the drawings in their applications with the details of the configurations and the configurations shown in the drawings. It should be understood that there are no restrictions on the placement of components. Other embodiments are possible and the invention can be practiced and practiced in a variety of ways. It should also be understood that the expressions and terms used herein are for illustration purposes only and should not be considered limiting.

Thus, one of ordinary skill in the art can readily use the concepts under this disclosure as the basis for designing other structures, methods, and / or systems for carrying out some of the objects of the invention. You will understand that you can. Therefore, it is important to consider that the scope of claims includes such an equivalent configuration as long as it does not deviate from the gist and scope of the present invention.

A more complete understanding of the disclosed embodiments of the invention and many of the accompanying advantages of the invention, when considered in connection with the accompanying drawings, may be by reference to the following detailed description. Easily obtained when better understood.

It is a figure which shows the compressor system. It is an operation diagram of a wet gas compressor. It is a flowchart of the method of disclosure in this specification.

In the following detailed description of the exemplary embodiment, reference is made to the accompanying drawings. The same reference numbers in different drawings represent the same or similar elements. Moreover, the drawings are not always drawn to scale. Moreover, the following detailed description does not limit the present invention. Alternatively, the scope of the invention is defined by the appended claims.

References to "one embodiment," "embodiment," or "several embodiments" throughout the specification are subjects in which specific features, structures, or properties are disclosed in connection with certain embodiments. Means to be included in at least one embodiment of. Accordingly, the expressions "in one embodiment," "in an embodiment," or "in some embodiments" that appear in various places throughout the specification do not necessarily refer to the same embodiment (singular and plural). is not it. In addition, specific features, structures or properties may be combined in any suitable manner in one or more embodiments.

FIG. 1 schematically shows a system 1 with a driver 3 and a load 5. The load 5 includes, for example, a compressor 7 which is a centrifugal compressor. The shaft 9 drives the driver 3 to the load 5. The driver 3 can be an electric motor, a gas turbine engine, a steam turbine, or any other suitable driver.

The compressor 7 includes a compressor suction side 7S and a compressor discharge side 7D. The compressor 7 is further provided with a surge prevention system. In the schematic of FIG. 1, the surge protection system comprises a line or duct 11 fluidly coupled to the discharge side 7D and the suction side 7S. Further, the surge protection system includes a surge protection valve 13 arranged on the surge protection line 11. When the operating point of the compressor approaches the surge limit line, the surge prevention valve 13 can be controlled to recirculate the gas from the discharge side 7D of the compressor 7 to the suction side 7S in order to prevent the surge phenomenon in the compressor. Can be opened to.

In some embodiments, the pressure transducer 15 and the temperature transducer 17 are arranged on the suction side 7S of the compressor 7 to measure the gas suction pressure Ps and the gas suction temperature Ts of the gas on the suction side 7S. Further, another pressure transducer 19 and another temperature transducer 21 are arranged on the discharge side 7D of the compressor 7 in order to measure the gas discharge pressure Pd and the gas discharge temperature Td.

System 1 is a control unit that can be functionally coupled to pressure transducers and temperature transducers 15, 17, 19, 21 to collect gas temperature and pressure measurements on the discharge side 7D and suction side 7S of the compressor 7. 23 is further provided. The control unit 23 may be more functionally coupled to an actuator 13A configured and arranged to selectively open and close the surge prevention valve 13. Reference number 25 generally indicates a storage memory resource for the control unit 23, which can store data useful for surge prevention control of the compressor 7, as described in detail below. ..

The control unit 23 may be configured and arranged to receive additional input information such as data about the gas processed by the compressor 7. Block 27 schematically represents a data entry that provides information about, for example, the average molar mass Mw of gas processed by the compressor 7.

Reference numeral 29 refers to additional information such as, for example, the rotational speed N of the compressor 7, the driving force W required to rotate the compressor 7, and any optional information that may be useful or necessary to control the system 1. It schematically shows one or more different process parameter transducers that provide additional information to the control unit 23.

Surge prevention control of the compressor 7 can be performed using the diagram of FIG. The compression ratio, that is, the pressure ratio PR of the compressor 7 is plotted on the vertical axis of the diagram of FIG. The dimensionless parameters that depend on the absorbed power, i.e., the power required to rotate the compressor 7, are plotted on the horizontal axis of the diagram of FIG. The dimensionless parameters are a function of the actual driving force W, the gas suction pressure Ps and the suction temperature Ts, and may further depend on the parameters of the gas being processed and the characteristics of the compressor.

According to some embodiments, the dimensionless correction power Wcorr defined by the following equation is plotted on the horizontal axis of the diagram of FIG.

ここで：
Ｗは、圧縮機７によって吸収された実測動力であり、
Ｐｓ，Ｔｓは、圧縮機７の吸入側のガス圧力および温度であり、
Ｍｗは、圧縮機７によって処理されたガスの平均モル質量であり、
Ｚｓは、圧縮機吸入側でのガスの圧縮率であり、
Ｒは、ガス定数であり、
ｋｖｓは、圧縮機吸入側におけるガスの等エントロピー体積指数であり、
Ｄは、インペラの直径である。

here:
W is the measured power absorbed by the compressor 7.
Ps and Ts are the gas pressure and temperature on the suction side of the compressor 7.
Mw is the average molar mass of the gas processed by the compressor 7.
Zs is the compression rate of the gas on the suction side of the compressor.
R is a gas constant,
kvs is the isentropic volume index of the gas on the suction side of the compressor.
D is the diameter of the impeller.

For a given set of operating parameters, the suction limit line SLL can be plotted in the diagram of FIG. 2, which allows the actual liquid mass fraction (LMF) or gas liquid volume fraction (LVF). That is, it has been found that surge prevention control of the compressor 7 is possible without the need for knowledge of the mass or volume fraction of the liquid phase in the wet gas.

For a given compressor 7, SLL is a function of the gas state at the suction side 7S of the compressor 7, ie the suction temperature Ts and the suction pressure Ps. Further, SLL is a function of the rotation speed of the compressor 7, the average molar mass Mw of the gas on the suction side 7S of the compressor 7, and the compression rate Zs of the gas. Therefore, SLL can be expressed as:
SLL = f (Ts, Ps, Zs, Mw, N) (2)
Some of the parameters appearing in the function defining the surge limit line SLL, specifically the average molar mass Mw and the compressibility Zs on the suction side, depend on the chemical composition of the gas. The chemical composition of the gas processed by the compressor 7 usually changes very slowly over time and can be considered semi-stationary over a relatively long period of time, eg 24 hours. By flowing a portion of the gas through a gas chromatograph, the chemical composition of the gas can be analyzed in-line. In other embodiments, the gas composition can be analyzed offline, for example by taking a gas sample from a gas duct. Regardless of how the gas is analyzed, the average molar mass and the compressibility of the gas can be determined.

The remaining parameters can be detected by the transducer of the system 1 during the operation of the compressor 7.

The surge limit line SLL extends from the first end point corresponding to the dry gas state (liquid mass fraction, LMF = 0%) to the second end point corresponding to the maximum liquid content (LMF = LMFmax).

Therefore, during the operation of the system 1, the current SLL is determined based on the characteristics of the compressor, the parameters of the gas to be processed, and the operating parameters of the system 1, which are detected by the transducer functionally coupled to the control unit 23. Can be decided. The control unit 23 is based on the detected values of suction pressure (Ps), suction temperature (Ts), angular velocity (N), average molar mass (Mw) and compression rate (Zs), for example, in data stored in a table format. Based on and / or by interpolation, the current inhalation limit line SLL is calculated. The data for the calculation of SLL can be stored in the storage memory resource 25. Further, based on the above data and the actual power W currently absorbed by the compressor 7, the correction power Wcorr is calculated by equation (1). The actual operating point of the compressor 7 is determined, and the operating point becomes the coordinates [Wcorr; PR = Pd / Ps] of the diagram of FIG. The distance between the actual operating point and the calculated SLL is then determined. Based on the distance, if necessary, a surge protection control routine is initiated to control the opening of the surge protection valve. Surge protection valves can be controlled according to current technical methods. Generally, when the distance is smaller than the safe value, the surge protection valve 13 is opened. If this distance is equal to or greater than the safety value, the surge prevention valve 13 is maintained in the closed state.

The control methods described so far are summarized in the flowchart of FIG. The last block in the flow chart represents surge protection valve control.

The disclosed embodiments of the subject matter described herein are shown in the drawings and have been described in detail and in detail above in connection with some exemplary embodiments, but with many modifications. Modifications and omissions are possible to those skilled in the art without significantly departing from the advantages of the new teachings, principles, and concepts described herein, as well as the subject matter set forth in the appended claims. It will be obvious. Therefore, the appropriate scope of the disclosed innovations should only be defined by the broadest interpretation of the appended claims, including all such modifications, changes, and omissions. Also, the order or sequence of any method or method step may be modified or reordered by alternative embodiments.

1 System 3 Driver 5 Load 7 Compressor 7D Compressor Discharge side 7S Compressor suction side 9 Shaft 11 Surge prevention line, duct 13 Surge prevention valve 13A Actuator 15 Pressure transducer 17 Temperature transducer 19 Pressure transducer 21 Temperature transducer 22 Control unit 25 Storage Memory resource Mw Average molar mass N Rotation speed PR Pressure ratio Pd Gas discharge pressure Ps Gas suction pressure SLL Surge limit line, suction limit line Td Gas discharge temperature Ts Gas suction temperature W Driving force, power Wcorr Non-dimensional correction power Zs Compressor rate R Gas constant kvs equal entropy volume index D Impeller diameter

Claims (7)

A method for surge protection protection of a compressor (7) under moist gas conditions, wherein the compressor (7) comprises a suction side (7S), a discharge side (7D), and a surge protection system. The method is
The step of specifying the rotation speed (N) of the compressor (7) and
A step of specifying the suction temperature (Ts) and suction pressure (Ps) of the gas on the suction side (7S) of the compressor (7), and
The step of specifying the average molar mass (Mw) of the gas and
A step of specifying the compressibility (Zs) of the gas on the suction side (7S) of the compressor (7), and
The surge limit line (SSL) is a function of the rotation speed (N), the suction temperature (Ts), the suction pressure (Ps), the average molar mass (Mw), and the compressibility (Zs). And the steps to calculate
The driving force (W) required to drive the compressor (7), the suction temperature (Ts), the suction pressure (Ps), the average molar mass (Mw), and the compression rate (Zs). ) and, calculating a corrected dynamic forces as a function of,
The step of specifying the operating point of the compressor (7) in the compression ratio vs. correction power diagram, and
The step of detecting the distance between the operating point and the surge limit line (SSL) in the compression ratio pair correction power diagram, and
A method comprising the step of acting on the surge protection system of the compressor (7) if the distance is less than the minimum safe distance. The method according to claim 1, wherein the correction power is a dimensionless parameter. The method of claim 1 or 2, wherein the surge limit line (SSL) extends from a first endpoint corresponding to the dry gas state to a second endpoint corresponding to the maximum liquid content. The correction power includes the driving force (W) required to drive the compressor (7), the suction temperature (Ts), the suction pressure (Ps), and the average molar mass (Mw). A function of the compression rate (Zs), the isotropic volume index (kvs) of the gas on the suction side (7S) of the compressor (7), and the diameter (D) of the impeller of the compressor (7). The method according to any one of claims 1 to 3. The correction power is calculated as follows,

Where W is the driving force necessary to drive the compressor (7),
Ps and Ts are the suction pressure and the suction temperature of the gas on the suction side (7S) of the compressor (7).
Mw is the average molar mass of the gas processed by the compressor (7).
Zs is the compressibility of the gas in the suction side (7S) of the compressor (7),
R is a gas constant,
kvs is the isentropic volume index of the gas on the suction side (7S) of the compressor (7).
D is the diameter of the impeller,
The method according to claim 4. The surge protection system comprises a surge protection valve (13) that is opened when a step acting on the surge protection system is performed, and the gas is discharged from the discharge side (7D) of the compressor (7). The method according to any one of claims 1 to 5 , which is recirculated to the suction side (7S). A compressor (7) having a suction side (7S) and a discharge side (7D),
Surge protection system and
A control unit (23) functionally coupled to the surge prevention system,
Wet gas compressor system (1) equipped with
The control unit (23) is configured and arranged to perform the method according to any one of claims 1 to 6.
Wet gas compressor system (1).

Images