Anti-surge system of centrifugal compressor and control method

Abstract

The invention discloses an anti-surge system device of a centrifugal compressor and a control method, and particularly relates to the technical field of anti-surge. A first pressure transmitter; a first temperature transmitter; a second pressure transmitter; a second temperature transmitter; a branch pipeline; an anti-surge return valve; an anti-surge reflux cooler; a temperature control valve; a third temperature transmitter; the invention provides an anti-surge control system. According to the invention, an anti-surge backflow method of throttling first and then cooling is adopted, and temperature control is set at the outlet of the cooler, so that the problems of cooling first, pressure reduction second and carrying of a large amount of liquid after pressure reduction in the anti-surge backflow process are effectively solved, the guarantee of stable work is provided, and the economic benefit is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of anti-surge, and more particularly to an anti-surge system and a control method for a centrifugal compressor. Background Art

[0002] When a centrifugal compressor is running, if the suction flow rate is reduced to a certain value, the compressor will experience an unstable working phenomenon, and its suction flow rate and outlet pressure will fluctuate rapidly and continuously, which may be accompanied by high vibration, rapid changes in temperature rise and axial thrust, causing the compressor to vibrate strongly and produce huge noise. This phenomenon is called compressor surge, which may damage the compressor. In order to prevent the occurrence of surge, a surge line and a surge control line are usually set in the performance curve of the compressor, and the surge control line is used to control the compression system. The manufacturer or designer of the compression system sets the surge line where surge occurs by conducting theoretical analysis and multiple experiments on the compression system, and sets the surge control line by pre-setting a 10% safety margin.

[0003] In the prior art, the surge control line can be kept away from by adjusting the ratio (pressure ratio) of the pressure of the process medium at the inlet and outlet of the compressor, the fluid flow rate or other controllable parameters. Conventionally, the discharge pressure of the compressor is adjusted by controlling the opening of the inlet guide vane set in the compressor, or the return valve at the outlet of the compressor is opened, so that some process medium discharged from the compressor returns to the inlet side of the compressor, so as to achieve the purpose of keeping away from the surge line and preventing the compressor from surging. When the process medium of the compressor is methanol and DMC, the process gas inlet of the compressor works in a saturated state of the working medium, and liquid is easily precipitated. During the anti-surge reflux process of the compressor when starting, the reflux carries too much liquid due to the mismatch of temperature and pressure, which will reduce the inlet flow of the compressor, causing the compressor to be damaged by surge. If the gas carries too much liquid and the liquid separation is not timely, the liquid will enter the compressor, which will also cause damage to the impeller. Summary of the invention

[0004] In order to overcome the above-mentioned defects of the prior art, the present invention provides an anti-surge system and control method for a centrifugal compressor.

[0005] To achieve the above object, the present invention provides the following technical solution: an anti-surge system for a centrifugal compressor, comprising a compressor, and further comprising:

[0006] A gas-liquid separator is arranged at the inlet of the compressor, connected to the inlet pipeline of the compressor, and used to measure the inlet pressure of the compressor;

[0007] A first pressure transmitter, disposed on the inlet pipe of the compressor, for measuring the inlet temperature of the compressor;

[0008] A first temperature transmitter is provided on the inlet pipe of the compressor and is used to measure the outlet pressure of the compressor;

[0009] A second pressure transmitter is provided on the outlet pipe of the compressor and is used to measure the outlet pressure of the compressor;

[0010] A second temperature transmitter is provided on the outlet pipe of the compressor and is used to measure the outlet temperature of the compressor;

[0011] A branch pipeline connecting the outlet pipeline of the compressor and the inlet pipeline of the compressor;

[0012] an anti-surge reflux valve, which is located on the branch line pipeline and is used to adjust the reflux flow from the outlet pipeline of the compressor through the branch line pipeline and the reflux cooler to the inlet pipeline of the compressor;

[0013] A reflux cooler, which is located on the branch pipeline and arranged after the anti-surge reflux valve, is used to reduce the reflux temperature of the process medium to avoid iterative temperature increase during the compressor cycle;

[0014] A third temperature transmitter, which is located on the branch pipeline and arranged after the reflux cooler, is used to monitor the temperature of the process medium outlet of the reflux cooler;

[0015] a temperature control valve, which is located on the cooling water outlet pipe of the reflux cooler and is controlled by transmitting the third temperature transmitter signal to the temperature controller;

[0016] The anti-surge control system includes an anti-surge controller, which controls the opening of the anti-surge reflux valve by receiving flow, pressure and temperature signals input by a throttling device, a first pressure transmitter, a second pressure transmitter, a first temperature transmitter and a first flow transmitter.

[0017] As a further preferred embodiment of the present invention, the control method adopted by the anti-surge system of the centrifugal compressor comprises:

[0018] S1. Anti-surge method: When the anti-surge reflux valve is opened, the process medium on the compressor outlet pipeline flows back to the compressor inlet pipeline through the branch pipeline, thereby increasing the intake flow rate of the compressor inlet pipeline;

[0019] S2, anti-surge reflux valve control method: calculate the pressure ratio of the compressor according to the pressure signals input by the first pressure transmitter and the second pressure transmitter, and define the pressure ratio of the compressor as the first measurement value; the actual flow value calculated by the flow signal of the first pressure transmitter, the first temperature transmitter and the throttling device is the second measurement value; according to the surge line calculated after the thermal calculation of the compressor, a 10% margin is reserved as the anti-surge line, and this anti-surge line is used as the control index of the opening of the anti-surge reflux valve. When the points obtained by the first and second measurement values ​​on the surge curve are more than 10% to the right of the surge line, the anti-surge reflux valve opening signal is not output; when the points obtained by the first and second measurement values ​​on the surge curve are less than 10% to the right of the surge line, the anti-surge reflux valve opening signal is output;

[0020] S3, anti-reflux liquid method, the process medium after reflux is firstly depressurized by an anti-surge reflux valve, then cooled by an anti-surge reflux cooler, and finally the temperature of the cooled process medium is monitored at the outlet of the reflux cooler, and the monitored temperature value is used for the temperature control valve at the water side outlet of the anti-surge reflux cooler to control the flow rate of cooling water, and the temperature control of the process medium is achieved by controlling the flow rate of cooling water, thereby preventing the reflux gas from being lower than the gas saturation value in temperature and pressure, thereby achieving the purpose of preventing the gas from carrying liquid.

[0021] As a further preferred embodiment of the present invention, the control method of the temperature control valve is as follows: the dew point temperature curve is input into the temperature controller, the monitoring value of the first pressure transmitter on the compressor inlet pipe is taken as the third measurement value, the third temperature transmitter after the reflux cooler is taken as the fourth measurement value, the fourth measurement value is compared with the dew point temperature curve based on the third measurement value; when the fourth measurement value is higher than the gas dew point temperature curve by more than 20°C, the temperature control valve is slowly opened; when the fourth measurement value is lower than the gas dew point temperature by less than 20°C, the temperature control valve is slowly closed to facilitate precise control of the temperature control valve.

[0022] As a further preferred embodiment of the present invention, the process medium at the compressor inlet is in a saturated state, which not only meets the working requirements but also facilitates gas-liquid conversion and helps heat exchange.

[0023] Technical effects and advantages of the invention:

[0024] The object of the present invention is to provide an anti-surge system and control method for a centrifugal compressor, in which the reflux gas is first depressurized by an anti-surge reflux valve, then cooled by an anti-surge reflux cooler, and finally the temperature of the cooled process medium at the outlet of the reflux cooler is monitored. The monitored temperature value is used for the temperature control valve at the water side outlet of the anti-surge reflux cooler to control the flow rate of cooling water, thereby preventing the temperature of the reflux gas from being lower than the dew point temperature of the gas at the pressure, thereby achieving the purpose of preventing the gas from carrying liquid, and effectively solving the problem of first cooling and then reducing the pressure in the anti-surge reflux process, and carrying a large amount of liquid after reducing the pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The figure is a schematic diagram of an anti-surge system of a centrifugal compressor according to the present invention.

[0026] Figure 2 It is the control curve diagram of the temperature control valve in the present invention.

[0027] Figure 3 It is a control curve diagram of the anti-surge return valve in the present invention.

[0028] The accompanying drawings are marked as: 1. compressor; 2. first pressure transmitter; 3. first temperature transmitter; 4. throttling device; 5. anti-surge controller; 6. gas-liquid separator; 7. second pressure transmitter; 8. second temperature transmitter; 9. anti-surge reflux valve; 10. reflux cooler; 11. temperature control valve; 12. temperature controller; 13. third temperature transmitter. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] See attached Figure 1 As shown, an anti-surge system of a centrifugal compressor 1 includes a compressor 1, wherein the process medium at the inlet of the compressor 1 is in a saturated state, which not only meets the working requirements but also facilitates gas-liquid conversion and helps heat exchange;

[0031] A gas-liquid separator 6 is arranged at the inlet of the compressor 1 and is connected to the inlet pipeline of the compressor 1 to measure the inlet pressure of the compressor 1;

[0032] A first pressure transmitter 2, arranged on the inlet pipe of the compressor 1, for measuring the inlet temperature of the compressor 1;

[0033] A first temperature transmitter 3, arranged on the inlet pipe of the compressor 1, for measuring the outlet pressure of the compressor 1;

[0034] A second pressure transmitter 7, arranged on the outlet pipe of the compressor 1, for measuring the outlet pressure of the compressor 1;

[0035] A second temperature transmitter 8 is provided on the outlet pipe of the compressor 1 and is used to measure the outlet temperature of the compressor 1;

[0036] A branch pipeline connecting the outlet pipeline of the compressor 1 and the inlet pipeline of the compressor 1;

[0037] an anti-surge reflux valve 9, which is located on the branch pipeline and is used to adjust the reflux flow from the outlet pipeline of the compressor 1 through the branch pipeline and the reflux cooler 10 to the inlet pipeline of the compressor 1;

[0038] A reflux cooler 10, which is located on the branch pipeline and arranged after the anti-surge reflux valve 9, is used to reduce the reflux temperature of the process medium to avoid iterative temperature increase during the circulation of the compressor 1;

[0039] A third temperature transmitter 13, which is located on the branch pipeline and arranged after the reflux cooler 10, and is used to monitor the temperature of the process medium outlet of the reflux cooler 10;

[0040] A temperature control valve 11, which is located on the cooling water outlet pipe of the reflux cooler 10 and is controlled by transmitting a signal from the third temperature transmitter 13 to the temperature controller 12;

[0041] The anti-surge control system includes an anti-surge controller 5, which controls the opening of the anti-surge reflux valve 9 by receiving flow, pressure and temperature signals input by the throttling device 4, the first pressure transmitter 2, the second pressure transmitter 7, the first temperature transmitter 3 and the first flow transmitter.

[0042] As a further preferred embodiment of the present invention, the control method adopted by the anti-surge system of the centrifugal compressor 1 includes:

[0043] like Figure 1 As shown, in the embodiment of the present invention, the anti-surge method is that when the anti-surge return valve 9 is opened, the process medium on the outlet pipeline of the compressor 1 flows back to the inlet pipeline of the compressor 1 through the branch pipeline, thereby increasing the intake flow rate of the inlet pipeline of the compressor 1;

[0044] like Figure 3As shown, in the embodiment of the present invention, the control method of the anti-surge reflux valve 9 is to calculate the pressure ratio of the compressor 1 according to the pressure signals input by the first pressure transmitter 2 and the second pressure transmitter 7, and the pressure ratio of the compressor 1 is defined as the first measurement value; the actual flow value calculated by the flow signal of the first pressure transmitter 2, the first temperature transmitter 3 and the throttling device 4 is the second measurement value; according to the surge line calculated after the thermal calculation of the compressor 1, a 10% margin is reserved as the anti-surge line, and this anti-surge line is used as the control index of the opening of the anti-surge reflux valve 9. When the points obtained by the first and second measurement values ​​on the surge curve are more than 10% on the right side of the surge line, the opening signal of the anti-surge reflux valve 9 is not output; when the points obtained by the first and second measurement values ​​on the surge curve are less than 10% on the right side of the surge line, the opening signal of the anti-surge reflux valve 9 is output;

[0045] The calculation principle of the above surge line is based on the mass flow formula where qm

[0046] is the mass flow rate; c is the discharge coefficient, which is a constant; β is the diameter ratio, i.e. d / D; ε is the expandability coefficient; ρ is the fluid density; △p is the pressure difference; and according to qv=qm / ρ2, the second measurement value is obtained, wherein qv is the volume flow rate, i.e. the actual flow rate of the compressor, i.e. the second measurement value, qm is the mass flow rate; ρ2 is the fluid density at the temperature and pressure when the volume flow rate is measured; the first measurement value is the pressure ratio of the pressure signals input by the first pressure transmitter and the second pressure transmitter, which can be calculated through the NREC software to obtain the surge line.

[0047] like Figure 2As shown, in the embodiment of the present invention, the anti-backflow liquid method is that the process medium after the backflow is first depressurized by the anti-surge reflux valve 9, and then cooled by the anti-surge reflux cooler 10, and finally the temperature of the cooled process medium is monitored at the outlet of the reflux cooler 10, and the monitored temperature value is used for the temperature control valve 11 at the water side outlet of the anti-surge reflux cooler 10 to control the flow of cooling water. The control method of the temperature control valve 11 is as follows: the dew point temperature curve is input into the temperature controller 12, the monitoring value of the first pressure transmitter 2 on the inlet pipe of the compressor 1 is taken as the third measurement value, and the third temperature transmitter 13 after the reflux cooler 10 is taken as the fourth measurement value. The fourth measurement value is compared with the dew point temperature curve based on the third measurement value; when the fourth measurement value is higher than the gas dew point temperature curve by more than 20°C, the temperature control valve 11 is slowly opened; when the fourth measurement value is higher than the gas dew point temperature by less than 20°C, the temperature control valve 11 is slowly closed, so as to facilitate the precise control of the temperature control valve 11. The temperature of the process medium is controlled by controlling the cooling water flow rate, thereby preventing the return gas from being lower than the gas saturation value in temperature and pressure, thereby preventing the gas from carrying liquid. In addition, the safety margin can be changed according to the needs of the designer or user. The dew point temperature line of different process media is different. The dew point temperature line is a line connected by the dew point lines of the process media of each component, where P1 is the pressure of the first pressure transmitter 2.

[0048] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

[0049] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An anti-surge system for a centrifugal compressor, comprising a compressor, characterized in that: Also includes: A gas-liquid separator is arranged at the inlet of the compressor and is connected to the inlet pipeline of the compressor; A first pressure transmitter is arranged on the inlet pipe of the compressor; A first temperature transmitter is arranged on the inlet pipe of the compressor; A second pressure transmitter is arranged on the outlet pipe of the compressor; A second temperature transmitter is arranged on the outlet pipe of the compressor; A branch pipeline connecting the outlet pipeline of the compressor and the inlet pipeline of the compressor; an anti-surge backflow valve, which is located on the branch pipeline; a reflux cooler, which is located on the branch pipeline and arranged after the anti-surge reflux valve; a third temperature transmitter, which is located on the branch pipeline and arranged after the reflux cooler; a temperature control valve, which is located on the cooling water outlet pipe of the reflux cooler and is controlled by transmitting the third temperature transmitter signal to the temperature controller; The anti-surge control system includes an anti-surge controller, which controls the opening of the anti-surge reflux valve by receiving flow, pressure and temperature signals input by a throttling device, a first pressure transmitter, a second pressure transmitter, a first temperature transmitter and a first flow transmitter.

2. The control method used in the anti-surge system of a centrifugal compressor according to claim 1, characterized in that: include: S1. Anti-surge method: When the anti-surge reflux valve is opened, the process medium on the compressor outlet pipeline flows back to the compressor inlet pipeline through the branch pipeline, thereby increasing the intake flow rate of the compressor inlet pipeline; S2, anti-surge reflux valve control method: calculate the pressure ratio of the compressor according to the pressure signals input by the first pressure transmitter and the second pressure transmitter, and define the pressure ratio of the compressor as the first measurement value; the actual flow value calculated by the flow signal of the first pressure transmitter, the first temperature transmitter and the throttling device is the second measurement value; according to the surge line calculated after the thermal calculation of the compressor, a 10% margin is reserved as the anti-surge line, and this anti-surge line is used as the control index of the opening of the anti-surge reflux valve. When the points obtained by the first and second measurement values ​​on the surge curve are more than 10% to the right of the surge line, the anti-surge reflux valve opening signal is not output; when the points obtained by the first and second measurement values ​​on the surge curve are less than 10% to the right of the surge line, the anti-surge reflux valve opening signal is output; S3, anti-reflux liquid method, the process medium after reflux is firstly depressurized by an anti-surge reflux valve, then cooled by an anti-surge reflux cooler, and finally the temperature of the cooled process gas is monitored at the outlet of the reflux cooler. The monitored temperature value is used for the temperature control valve at the water side outlet of the anti-surge reflux cooler to control the flow of cooling water, and the temperature control of the process gas is achieved by controlling the flow of cooling water.

3. The control method used in the anti-surge system of a centrifugal compressor according to claim 2, characterized in that: The control method of the temperature control valve is as follows: the dew point temperature curve is input into the temperature controller, the monitoring value of the first pressure transmitter on the compressor inlet pipe is taken as the third measurement value, the third temperature transmitter after the reflux cooler is taken as the fourth measurement value, the fourth measurement value is compared with the dew point temperature curve based on the third measurement value; when the fourth measurement value is higher than the gas dew point temperature curve by more than 20°C, the temperature control valve is slowly opened; when the fourth measurement value is lower than the gas dew point temperature by less than 20°C, the temperature control valve is slowly closed.

4. The anti-surge system for a centrifugal compressor according to claim 1, characterized in that: The process gas medium at the compressor inlet is in a saturated state.

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