A system and control method for improving the reliability of a centrifugal compressor unit

Abstract

The present invention provides a system and a control method for improving the reliability of a centrifugal compressor unit. Among them, the outlet header is communicated with one end of the shaft end seal gas supply pipe, and the other end of the shaft end seal gas supply pipe is connected to the input ends of a plurality of gas purifiers connected in parallel. After the input ends of the plurality of gas purifiers converge, they are connected to the intake ends of a plurality of supercharging cylinders connected in parallel. After the outlet ends of the plurality of supercharging cylinders connected in parallel converge, they are connected to one end of an intake pipe with a heater, and the other end of the intake pipe is connected to a plurality of beside-the-machine systems, and each beside-the-machine system is connected to a corresponding centrifugal compressor; a bypass provided with a check valve is also connected in parallel to the plurality of supercharging cylinders connected in parallel; each beside-the-machine system includes four subsystems, namely a primary seal gas supply subsystem, a primary leakage gas discharge subsystem, an isolation gas supply subsystem, and a secondary leakage gas discharge subsystem. The present invention improves the reliability of the shaft end seal of a multi-machine parallel centrifugal compressor unit.

Description

Technical Field

[0001] The present invention belongs to the field of turbine compressors, and relates to a centrifugal compressor unit, and specifically to a system and control method for improving the reliability of a centrifugal compressor unit. Background Art

[0002] Single-shaft turbine centrifugal compressors are widely used in the process industry, and are characterized by mature technology, stable operation, and high reliability.

[0003] In the process industry, the media for centrifugal compressors to work include two categories. One category is non-toxic, non-flammable, and non-explosive media. For this type of media, the sealing system required for compressor operation is relatively simple, and there is no need to worry too much about the leakage of the media gas to the environment. However, most of the gases in the devices in the fields of petrochemical, coal chemical, and natural gas are flammable and explosive media, and these media often contain solid or liquid impurities, which require high reliability for the compressor unit, especially the reliability of the sealing system during the operation of the unit. The basic requirement is to reliably and permanently achieve the goal of zero leakage beside the machine.

[0004] The shaft end sealing system of centrifugal compressors has undergone a transformation from traditional oil seals to gas seals. Compared with traditional oil seals, gas seals at the shaft end reduce the risk of oil leakage. At the same time, since the dynamic and static rings of the sealing body do not contact during operation and there is no friction, the reliability of the shaft end sealing system is improved. This makes the application range of centrifugal compressor units wider and wider.

[0005] However, to ensure the reliable operation of the shaft seals at both ends of the rotor of a single-shaft centrifugal compressor, a complete set of gas supply and control systems needs to be provided for this sealing system and perfect control logic needs to be provided. With the continuous change of the process conditions for the application of the unit, the traditional known and publicly available general sealing gas supply and control systems can no longer meet the operation reliability of new units. For example, in a process device where multiple centrifugal compressor units are operated in parallel, the shaft end sealing systems and control schemes of these units need to be studied and developed to improve the operation reliability of the compressor unit and create benefits for customers. Summary of the Invention

[0006] Aiming at the deficiencies existing in the prior art, the purpose of the present invention is to provide a system and control method for improving the reliability of a centrifugal compressor unit, and solve the technical problems that there is no special shaft end sealing system for multi-unit parallel units with such media containing solids or liquids or the operation reliability of the sealing system is poor in the prior art.

[0007] To solve the above technical problems, the present invention adopts the following technical solutions to achieve:

[0008] A system for improving the reliability of a centrifugal compressor unit, wherein the centrifugal compressor unit includes a plurality of parallel centrifugal compressors. The process gas inlet pipe of each centrifugal compressor is connected to an inlet header, and the process gas outlet pipe of each centrifugal compressor is connected to an outlet header;

[0009] Axial seals are respectively arranged at both ends of each centrifugal compressor. A condensate drain port and a pressure tapping port are arranged on the axial seal. An inlet for primary seal gas, an outlet for primary leakage gas, an inlet for isolating gas supply, and an outlet for secondary leakage gas are also arranged on the axial seal;

[0010] A backflush gas return port is communicated on the process gas inlet pipe of each centrifugal compressor, and an inlet for primary seal gas is communicated on the process gas outlet pipe of each centrifugal compressor;

[0011] The outlet header is communicated with one end of an axial seal gas supply pipe. The other end of the axial seal gas supply pipe is connected to the input ends of a plurality of parallel gas purifiers. After the input ends of the plurality of gas purifiers converge, they are connected to the intake ends of a plurality of parallel booster cylinders. After the outlet ends of the plurality of parallel booster cylinders converge, they are connected to one end of an inlet pipe with a heater. The other end of the inlet pipe is connected to a plurality of on-site systems, and each on-site system is connected to a corresponding centrifugal compressor;

[0012] A bypass with a check valve is also connected in parallel on the plurality of parallel booster cylinders;

[0013] Each of the on-site systems includes four subsystems, namely a primary seal gas supply subsystem, a primary leakage gas discharge subsystem, an isolating gas supply subsystem, and a secondary leakage gas discharge subsystem;

[0014] The primary seal gas supply subsystem includes two first input pipes, two first output pipes, and one filter condensate return branch pipe. One first input pipe is connected to the other end of the inlet pipe, and the other first input pipe is connected to the inlet for primary seal gas. The two first output pipes are respectively connected to the inlets for primary seal gas at both ends of the centrifugal compressor. The other end of the filter condensate return branch pipe is communicated with the backflush gas return port;

[0015] The primary leakage gas discharge subsystem includes two second input pipes and two second output pipes. The two second input pipes are respectively connected to the outlets for primary leakage gas at both ends of the centrifugal compressor. The two second output pipes lead the gas to a high point outdoors for venting;

[0016] The isolating gas supply subsystem includes one third input pipe and two third output pipes. The third input pipe is connected to an external gas source. The two third output pipes are respectively connected to the inlets for isolating gas supply at both ends of the centrifugal compressor;

[0017] The described secondary leakage gas venting subsystem includes two fourth input pipes and two fourth output pipes. The two fourth input pipes are respectively connected to the secondary leakage gas venting ports at both ends of the centrifugal compressor, and the two fourth output pipes lead the gas to be vented at a high point outdoors.

[0018] The present invention further includes the following technical features:

[0019] On the two first input pipes of the described primary sealing gas supply subsystem, a cut-off valve and a check valve are sequentially arranged respectively. After the two first input pipes converge, they are also sequentially connected with a double parallel filter, a differential pressure control regulating valve, and an electric heater. The input end of the electric heater is connected to one end of the two first output pipes, and a flow meter and a cut-off valve are respectively arranged on the two first output pipes;

[0020] The output end of the described differential pressure control regulating valve is communicated with the pressure tapping port, and a differential pressure transmitter is arranged between the two;

[0021] The described double parallel filter is connected to one end of the filter condensate return branch pipe, and a check valve, a cut-off valve, and an orifice plate are sequentially arranged on the filter condensate return branch pipe.

[0022] The described double parallel filter, differential pressure control regulating valve, and electric heater are also connected to the drain pipe.

[0023] On the two second input pipes of the described primary leakage venting subsystem, a pressure transmitter and a check valve are sequentially arranged respectively. After the two second input pipes converge, they are connected to a second output pipe provided with a flame arrester;

[0024] One spare vent pipe is connected in parallel to each of the described check valves. On the two spare vent pipes, an orifice plate, a pre-valve constant pressure regulating valve, a flow meter, and a check valve are sequentially arranged respectively. After the two spare vent pipes converge, they are connected to another second output pipe provided with a flame arrester.

[0025] The third input pipe of the described isolation gas supply subsystem is sequentially connected to a filter, a post-valve pressure regulating valve, and a pressure transmitter, and then connected to the two third output pipes. An orifice plate and a check valve are sequentially arranged on the two third output pipes.

[0026] On the two second input pipes of the described secondary leakage venting subsystem, a pressure transmitter and a flow meter are sequentially arranged respectively. Flame arresters are respectively arranged on the two second output pipes.

[0027] The present invention also protects a control method for improving the reliability of a centrifugal compressor unit. This method uses the system for improving the reliability of a centrifugal compressor unit as described above.

[0028] A manifold differential pressure transmitter is arranged between the described inlet manifold and the outlet manifold;

[0029] An inlet pressure transmitter is provided on the process gas inlet pipe described above;

[0030] An inlet and outlet differential pressure transmitter is provided between the process gas inlet pipe and the process gas outlet pipe of each centrifugal compressor described above;

[0031] The cut-off valve provided on one of the first input pipes connected to the other end of the inlet pipe in the primary seal gas supply subsystem described above is a pneumatic cut-off valve.

[0032] This method specifically includes the opening and closing control method of the pneumatic cut-off valve and the opening and closing control method of the booster cylinder;

[0033] The opening and closing control method of the pneumatic cut-off valve described above includes opening conditions and closing conditions;

[0034] Step S11, the opening conditions of the pneumatic cut-off valve:

[0035] When the gas flow rates detected by the flow meters in the two first output pipes in the primary seal gas supply subsystem are both ≤ 300 Nm 3 / h, and the pressure difference value between the process gas inlet pipe and the process gas outlet pipe detected by the inlet and outlet differential pressure transmitter is ≤ 0.5 MPa;

[0036] And when the pressure value in the process gas inlet pipe detected by the inlet pressure transmitter is ≥ 0.5 MPa, open the pneumatic cut-off valve in the primary seal gas supply subsystem corresponding to the centrifugal compressor;

[0037] Step S12, the closing conditions of the pneumatic cut-off valve:

[0038] When the gas flow rates detected by the flow meters in the two first output pipes in the primary seal gas supply subsystem are both ≥ 400 Nm 3 / h, and the pressure difference value between the process gas inlet pipe and the process gas outlet pipe detected by the inlet and outlet differential pressure transmitter is ≥ 1.0 MPa;

[0039] Or when the pressure value in the process gas inlet pipe detected by the inlet pressure transmitter is ≤ 0.3 MPa, close the pneumatic cut-off valve in the primary seal gas supply subsystem corresponding to the centrifugal compressor;

[0040] The opening and closing control method of the booster cylinder described above includes opening conditions and closing conditions;

[0041] Step S21, the opening conditions of the booster cylinder:

[0042] When the pneumatic cut-off valve corresponding to at least one centrifugal compressor is in the open state, and when the gas flow rate detected by the flow meter in at least one of the two first output pipes in the primary seal gas supply subsystem is ≤ 150 Nm 3When it is [specific time] per hour, or when the pressure difference between the process gas inlet pipe and the process gas outlet pipe detected by the inlet and outlet pressure difference transmitter ≤ 0.2 MPa, or when the pressure value in the process gas inlet pipe detected by the inlet pressure transmitter > 0.3 MPa, delay for 2 s and start one supercharging cylinder. After the supercharging cylinder starts for 30 s, continue to judge. If the above-mentioned supercharging cylinder opening conditions are still met, continue to start the unstarted supercharging cylinders among multiple supercharging cylinders until all supercharging cylinders are started;

[0043] When all supercharging cylinders are in the open state, the gas is supplied to the primary seal gas supply subsystem after being supercharged by the supercharging cylinder;

[0044] Step S22, the closing conditions of the supercharging cylinder:

[0045] When all the pneumatic cut-off valves corresponding to the centrifugal compressors are in the closed state, the supercharging cylinder is in the closed state, and the outlet header does not need to supply gas to the primary seal gas supply subsystem;

[0046] Or when at least one pneumatic cut-off valve corresponding to the centrifugal compressor is in the open state, and when the pressure difference between the inlet header and the outlet header detected by the header pressure difference transmitter > 0.5 MPa, or when the pressure values in the process gas inlet pipes detected by all the inlet pressure transmitters corresponding to the centrifugal compressors are all < 0.3 MPa, close all supercharging cylinders. The outlet header needs to supply gas to the primary seal gas supply subsystem, and the gas directly supplies gas to the primary seal gas supply subsystem through the bypass provided with a check valve.

[0047] Compared with the prior art, the present invention has the following technical effects:

[0048] (Ⅰ) The system of the present invention is the shaft end seal system of the centrifugal compressor unit, which is applied to the field of flammable, explosive and toxic medium gas, especially for the multi-parallel centrifugal compressor unit with these dangerous media not very clean and containing solid or liquid impurities. It improves the reliability of the shaft end seal of the multi-parallel centrifugal compressor unit.

[0049] (II) The on-site system in the system of the present invention is divided into four independent subsystems, and the shaft end seal of the centrifugal compressor is sealed through the four independent subsystems, so that the reliability of the seal is significantly improved. Specifically, the filter condensate return branch pipe provided in the primary seal gas supply subsystem solves the problems of freezing blockage or liquid entering the seal body caused by untimely manual operation in a low-temperature environment. The electric heater provided in the primary seal gas supply subsystem solves the problem that the temperature drop effect of the pressure reducing valve may cause secondary generation of condensate. The pneumatic cut-off valve provided in the air intake branch pipe of the booster cylinder in the primary seal gas supply subsystem can solve the problem of automatically putting into use the air source of the booster cylinder. Combined with the setting of the one-way valve, the full-automatic switching of the primary seal gas air source is realized. In the isolation gas supply subsystem, three pressure transmitters further improve the stability of the isolation gas control, so as to stop the vehicle in time when the pressure is insufficient and avoid greater losses, etc.

[0050] (III) The control method of the present invention can improve the reliability and automation level of the switching control of the primary seal gas air source (from the air source of the booster cylinder and the air source of the outlet pipeline of the compressor unit), realize the requirement of unattended operation, improve the operation stability of the booster cylinder inside the system, and avoid misoperation; improve the efficiency of removing the liquid precipitated due to temperature drop in the system, and reduce the damage to the body caused by possible liquid entering the body. Description of the Drawings

[0051] Figure 1 is the overall structural schematic diagram of the system for improving the reliability of the centrifugal compressor unit of the present invention.

[0052] Figure 2 is the structural schematic diagram of the shaft end seal of the compressor.

[0053] Figure 3 is the structural schematic diagram of the primary seal gas supply subsystem.

[0054] Figure 4 is the structural schematic diagram of the primary leakage gas venting subsystem.

[0055] Figure 5 is the structural schematic diagram of the isolation gas supply subsystem.

[0056] Figure 6 is the structural schematic diagram of the secondary leakage gas venting subsystem.

[0057] The meanings of the reference numerals in the figure are as follows: 1 - centrifugal compressor, 2 - inlet header, 3 - outlet header, 4 - shaft end seal, 5 - shaft end seal gas supply pipe, 6 - gas purifier, 7 - booster cylinder, 8 - heater, 9 - inlet pipe, 10 - beside - machine system, 11 - primary seal gas supply subsystem, 12 - primary leakage gas bleed subsystem, 13 - isolating gas supply subsystem, 14 - secondary leakage gas bleed subsystem, 15 - header differential pressure transmitter, 16 - check valve; 17 - inlet pressure transmitter, 18 - inlet - outlet differential pressure transmitter, 19 - pressure transmitter, 20 - shut - off valve, 21 - double - parallel filter, 22 - differential pressure control regulating valve, 23 - electric heater, 24 - flowmeter, 25 - orifice plate, 26 - non - return valve, 27 - flame arrester, 28 - constant - pressure regulating valve before valve, 29 - regulating valve after valve, 30 - differential pressure transmitter, 31 - pneumatic shut - off valve;

[0058] 101 - process gas inlet pipe, 102 - process gas outlet pipe, 103 - back - blowing gas return port, 104 - primary seal gas supply port;

[0059] 401 - primary seal gas charging port, 402 - primary leakage gas bleed port, 403 - isolating gas supply charging port, 404 - secondary leakage gas bleed port, 405 - drain port, 406 - pressure tapping port;

[0060] 1101 - first input pipe, 1102 - first output pipe, 1103 - filter condensate return branch pipe, 1104 - drain pipe;

[0061] 1201 - second input pipe, 1202 - second output pipe, 1203 - standby gas discharge pipe;

[0062] 1301 - third input pipe, 1302 - third output pipe;

[0063] 1401 - fourth input pipe, 1402 - fourth output pipe;

[0064] X represents the serial number of the centrifugal compressor.

[0065] The following further elaborates on the specific content of the present invention in conjunction with embodiments. Specific Embodiments

[0066] It should be noted that all components and materials in the present invention, without special instructions, are those known in the art.

[0067] The following specific embodiments of the present invention are given. It should be noted that the present invention is not limited to the following specific embodiments, and any equivalent transformation based on the technical solution of this application falls within the protection scope of the present invention.

[0068] Embodiment 1:

[0069] This embodiment provides a system for improving the reliability of a centrifugal compressor unit, as Figures 1 to 6 shown. The centrifugal compressor unit includes a plurality of parallel centrifugal compressors 1. The process gas inlet pipe 101 of each centrifugal compressor 1 is connected to the inlet header 2, and the process gas outlet pipe 102 of each centrifugal compressor 1 is connected to the outlet header 3;

[0070] Axial seals 4 are respectively arranged at both ends of each centrifugal compressor 1. A drain port 405 and a pressure tapping port 406 are arranged on the axial seal 4. An inlet port 401 for primary seal gas, a bleed port 402 for primary leakage gas, an inlet port 403 for isolation gas supply, and a bleed port 404 for secondary leakage gas are also arranged on the axial seal 4;

[0071] A back purge gas return port 103 is communicated with the process gas inlet pipe 101 of each centrifugal compressor 1, and a primary seal gas supply port 104 is communicated with the process gas outlet pipe 102 of each centrifugal compressor 1;

[0072] The outlet header 3 is communicated with one end of the axial seal gas supply pipe 5. The other end of the axial seal gas supply pipe 5 is connected to the input ends of a plurality of parallel gas purifiers 6. After the input ends of the plurality of gas purifiers 6 converge, they are connected to the intake ends of a plurality of parallel booster cylinders 7. After the outlet ends of the plurality of parallel booster cylinders 7 converge, they are connected to one end of an inlet pipe 9 with a heater 8. The other end of the inlet pipe 9 is connected to a plurality of near-machine systems 10, and each near-machine system 10 is connected to a corresponding centrifugal compressor 1;

[0073] A bypass with a check valve 16 is also connected in parallel to the plurality of parallel booster cylinders 7; it can ensure that when the booster cylinders 7 do not need to work, the gas automatically bypasses the booster cylinders 7 and enters the inlet pipe 9 through the check valve 16.

[0074] Each near-machine system 10 includes four subsystems, namely a primary seal gas supply subsystem 11, a primary leakage gas bleed subsystem 12, an isolation gas supply subsystem 13, and a secondary leakage gas bleed subsystem 14;

[0075] The primary seal gas supply subsystem 11 includes two first input pipes 1101, two first output pipes 1102, and one filter condensate return branch pipe 1103. One first input pipe 1101 is connected to the other end of the inlet pipe 9, and the other first input pipe 1101 is connected to the primary seal gas supply port 104. The two first output pipes 1102 are respectively connected to the primary seal gas inlet ports 401 at both ends of the centrifugal compressor 1, and the other end of the filter condensate return branch pipe 1103 is communicated with the back purge gas return port 103;

[0076] The primary leakage gas venting subsystem 12 includes two second input pipes 1201 and two second output pipes 1202. The two second input pipes 1202 are respectively connected to the primary leakage gas venting ports 402 at both ends of the centrifugal compressor 1, and the two second output pipes 1202 lead the gas to a high point outdoors for venting.

[0077] The seal gas supply subsystem 13 includes one third input pipe 1301 and two third output pipes 1302. The third input pipe 1301 is connected to an external gas source, and the two third output pipes 1302 are respectively connected to the seal gas supply and inflation ports 403 at both ends of the centrifugal compressor 1.

[0078] The secondary leakage gas venting subsystem 14 includes two fourth input pipes 1401 and two fourth output pipes 1402. The two fourth input pipes 1401 are respectively connected to the secondary leakage gas venting ports 404 at both ends of the centrifugal compressor 1, and the two fourth output pipes 1402 lead the gas to a high point outdoors for venting.

[0079] In the present invention, at both ends of the centrifugal compressor 1, one end is the driving end and the other end is the non - driving end. When any one centrifugal compressor 1 operates, the header can establish pressure to meet the demand for the primary seal gas pressure of the remaining centrifugal compressors 1 to be started. It has obvious advantages compared with taking gas from the centrifugal compressor outlet pipeline.

[0080] In the present invention, each gas purifier 6 can meet the gas purification demand of one centrifugal compressor 1. The three gas purifiers are in standby for each other. The inlet and outlet manual valves of the gas purifier can be operated for removal and on - line maintenance. The function of the gas purifier is to remove liquid and solid particles from the gas once.

[0081] In the present invention, the working gas volume of each booster cylinder 7 can meet the demand of one centrifugal compressor 1. The three booster cylinders are set to be in standby for each other. Cut - off valves are arranged at the inlet and outlet of the booster cylinder and are removed from the gas pipeline system when maintenance is required.

[0082] In the present invention, the numbers of the centrifugal compressor 1, the gas purifier 6 and the booster cylinder 7 are equal. More than one means more than one. Preferably three.

[0083] In the present invention, the function of the heater 8 is to prevent secondary precipitation of liquid due to too low gas temperature. The set target temperature value for heating by the heater is 80 °C, and the control range is taken as 40 - 100 °C. Alarms are given when it is lower or higher.

[0084] As a preferred solution of this embodiment, a cut-off valve 20 and a check valve are sequentially arranged on each of the two first input pipes 1101 of the primary sealing gas supply subsystem 11. After the two first input pipes 1101 converge, they are sequentially connected with a double parallel filter 21, a differential pressure control regulating valve 22, and an electric heater 23. The input end of the electric heater 23 is connected to one end of the two first output pipes 1102. A flowmeter 24 and a cut-off valve are respectively arranged on the two first output pipes 1102;

[0085] The output end of the differential pressure control regulating valve 22 is communicated with the pressure tapping port 406, and a differential pressure transmitter 30 is arranged between the two;

[0086] One end of the double parallel filter 21 is connected to one end of the filter condensate return branch pipe 1103. A check valve, a cut-off valve, and an orifice plate 25 are sequentially arranged on the filter condensate return branch pipe 1103.

[0087] Preferably, the double parallel filter 21 is a double parallel filter with one standby and online switching.

[0088] When the primary sealing gas supply subsystem 11 is in use, when the unit is operating normally, gas is taken from the primary sealing gas supply port 104 of the unit outlet pipeline. When the gas in the unit outlet pipeline cannot meet the flow rate and differential pressure requirements of the primary sealing gas, the gas source from the booster cylinder 7 is switched to. When the unit starts up, shuts down, or operates at no load, gas is taken from the booster cylinder 7.

[0089] The filter condensate return branch pipe 1103 is to reduce the possible condensate accumulation in the filter and convey the filtered liquid back to the compressor inlet pipeline in real time. The function of the filter condensate return branch pipe is that in a low-temperature environment, such as in winter in the north, it can keep the filter condensate in a continuous small gas volume return state and return to the inlet pipeline, thus avoiding the freeze blockage caused by the stay and accumulation of the filter condensate. It is very difficult to avoid this kind of freeze blockage by constantly opening the drain valve manually in the traditional way. At the same time, the manual operation amount is large.

[0090] The main function of the differential pressure control regulating valve 22 is to reduce pressure and limit flow to meet the requirements of the primary sealing gas for gas flow rate and sealing differential pressure.

[0091] The purpose of the electric heater 23 is to avoid the temperature drop of the primary sealing gas caused by the pressure reduction effect of the differential pressure control regulating valve. Excessive temperature drop will cause secondary precipitation of condensate in the gas, and to avoid the condensate precipitating again and entering the sealing body to cause damage. The set parameter of the electric heater is 50°C PID regulation, and when the set gas temperature is lower than 25°C or higher than 70°C, a low alarm or a high alarm is given respectively.

[0092] The flowmeter 24 is used to monitor the flow rate of the primary sealing gas at both ends of the seal, and an alarm is given when it is lower than 300 Nm3 / h.

[0093] Furthermore, the double parallel filters 21, the differential pressure control regulating valve 22, and the electric heater 23 are also connected to the drain pipe 1104.

[0094] As a preferred solution of this embodiment, a pressure transmitter 19 and a check valve 26 are sequentially arranged on each of the two second input pipes 1201 of the primary leakage and venting subsystem 12. After the two second input pipes 1201 converge, they are connected to a second output pipe 1202 provided with a flame arrester 27. Among them, preferably three pressure transmitters 19 are provided;

[0095] A spare vent pipe 1203 is connected in parallel to each check valve 26. A throttle orifice plate, a pre-valve constant pressure regulating valve 28, a flowmeter, and a one-way valve are sequentially arranged on each of the two spare vent pipes 1203. After the two spare vent pipes 1203 converge, they are connected to another second output pipe 1202 provided with a flame arrester 27.

[0096] As a preferred solution of this embodiment, the third input pipe 1301 of the isolation gas supply subsystem 13 is sequentially connected to a filter 32, a post-valve pressure regulating valve 29, and a pressure transmitter, and then connected to two third output pipes 1302. A throttle orifice plate and a one-way valve are sequentially arranged on the two third output pipes 1302. Among them, the filter 32 is a group of parallel-connected filters, and preferably three pressure transmitters are provided. The main function of the isolation gas supply subsystem 13 is to supply gas for sealing, preventing lubricating oil from entering the dry gas seal body and damaging the dry gas seal.

[0097] As a preferred solution of this embodiment, a pressure transmitter and a flowmeter are sequentially arranged on each of the two fourth input pipes 1401 of the secondary leakage and venting subsystem 14. Flame arresters are provided on each of the two fourth output pipes 1402. Among them, preferably one pressure transmitter is provided.

[0098] As a preferred solution of this embodiment, all the booster cylinders 7 in the present invention adopt piston cylinders. All the flowmeters 24 in the present invention adopt orifice flowmeters.

[0099] When the system for improving the reliability of the centrifugal compressor unit of the present invention is in use, the primary seal gas supply subsystem 11, the primary leakage gas venting subsystem 12, the isolation gas supply subsystem 13, and the secondary leakage gas venting subsystem 14 are used to seal the shaft end seal 4 of the centrifugal compressor 1. The primary seal gas supply subsystem 11 takes gas from two positions, namely the outlet header 3 and the process gas outlet pipe 102 of the centrifugal compressor 1, according to process requirements. The gas obtained from the outlet header 3 is purified by the gas purifier 6, and after being optionally pressurized by the booster cylinder 7 or not, it is heated by the heater 8 and then enters the inlet pipe 9 and is used for the shaft end seal of the centrifugal compressor 1.

[0100] Embodiment 2:

[0101] This embodiment provides a control method for improving the reliability of a centrifugal compressor unit, and this method adopts the system for improving the reliability of a centrifugal compressor unit as in Embodiment 1.

[0102] Specifically, a manifold differential pressure transmitter 15 is provided between the inlet manifold 2 and the outlet manifold 3.

[0103] An inlet pressure transmitter 17 is provided on the process gas inlet pipe 101.

[0104] An inlet and outlet differential pressure transmitter 18 is provided between the process gas inlet pipe 101 and the process gas outlet pipe 102 of each centrifugal compressor 1.

[0105] The cut-off valve provided on one of the first input pipes 1101 connected to the other end of the inlet pipe 9 in the primary seal gas supply subsystem 11 is a pneumatic cut-off valve 31.

[0106] Specifically, this method specifically includes the opening and closing control method of the pneumatic cut-off valve 31 and the opening and closing control method of the booster cylinder 7.

[0107] The opening and closing control method of the pneumatic cut-off valve 31 includes the opening condition and the closing condition.

[0108] Step S11, the opening condition of the pneumatic cut-off valve 31:

[0109] When the gas flow rates detected by the flow meters 24 in the two first output pipes 1102 in the primary seal gas supply subsystem 11 are both ≤ 300 Nm 3 / h, and the pressure difference between the process gas inlet pipe 101 and the process gas outlet pipe 102 detected by the inlet and outlet differential pressure transmitter 18 is ≤ 0.5 MPa;

[0110] And when the pressure value in the process gas inlet pipe 101 detected by the inlet pressure transmitter 17 is ≥ 0.5 MPa, the pneumatic cut-off valve 31 in the corresponding primary seal gas supply subsystem 11 of the centrifugal compressor 1 is opened.

[0111] Step S12, the closing condition of the pneumatic cut-off valve 31:

[0112] When the gas flow rates detected by the flow meters 24 in the two first output pipes 1102 in the primary seal gas supply subsystem 11 are both ≥ 400 Nm 3 / h, and the pressure difference between the process gas inlet pipe 101 and the process gas outlet pipe 102 detected by the inlet and outlet differential pressure transmitter 18 is ≥ 1.0 MPa;

[0113] Or when the pressure value in the process gas inlet pipe 101 detected by the inlet pressure transmitter 17 ≤ 0.3 MPa, close the pneumatic cut-off valve 31 in the first-stage seal gas supply subsystem 11 corresponding to the centrifugal compressor 1;

[0114] The opening and closing control method of the booster cylinder 7 includes opening conditions and closing conditions;

[0115] Step S21, the opening condition of the booster cylinder 7:

[0116] When at least one pneumatic cut-off valve 31 corresponding to the centrifugal compressor 1 is in the open state, and when the gas flow rate detected by the flow meter 24 in at least one of the two first output pipes 1102 in the first-stage seal gas supply subsystem 11 ≤ 150 Nm 3 / h, or when the pressure difference value between the process gas inlet pipe 101 and the process gas outlet pipe 102 detected by the inlet and outlet pressure difference transmitter 18 ≤ 0.2 MPa, or when the pressure value in the process gas inlet pipe 101 detected by the inlet pressure transmitter 17 > 0.3 MPa, delay for 2 s, start one booster cylinder 7, and continue to judge 30 s after the booster cylinder 7 starts. If the foregoing opening condition of the booster cylinder is still met, continue to start the booster cylinders 7 that have not been started among multiple booster cylinders 7 until all booster cylinders 7 are started;

[0117] When all the booster cylinders 7 are in the open state, the gas is pressurized by the booster cylinders 7 and supplies gas to the first-stage seal gas supply subsystem 11;

[0118] Step S22, the closing condition of the booster cylinder 7:

[0119] When all the pneumatic cut-off valves 31 corresponding to the centrifugal compressor 1 are in the closed state, the booster cylinder 7 is in the closed state, and the outlet header 3 does not need to supply gas to the first-stage seal gas supply subsystem 11;

[0120] Or when at least one pneumatic cut-off valve 31 corresponding to the centrifugal compressor 1 is in the open state, and when the pressure difference value between the inlet header 2 and the outlet header 3 detected by the header pressure difference transmitter 15 > 0.5 MPa, or when the pressure values in the process gas inlet pipes 101 detected by all the inlet pressure transmitters 17 corresponding to the centrifugal compressors 1 are all < 0.3 MPa, close all the booster cylinders 7. The outlet header 3 needs to supply gas to the first-stage seal gas supply subsystem 11, and the gas directly supplies gas to the first-stage seal gas supply subsystem 11 through the bypass provided with the check valve 16.

[0121] It should be noted that when the condition of the pneumatic cut-off valve 31 is in the buffer condition area between the opening condition and the closing condition, it remains in the previous state.

[0122] Application example:

[0123] For a centrifugal compressor unit project in a natural gas pipeline transmission compressor station, there are 3 centrifugal compressor units arranged in parallel in the station. The designed operating parameters of the units are: designed inlet pressure 9 MPa (G), designed discharge pressure 11 MPa (G). The original preliminary design scheme of the unit was to compare with similar projects, with each compressor having an independent shaft end seal control system. Later, during the design review process, through communication with on-site personnel with rich operation experience, it was found that this independent configuration scheme could not be used as a backup for each other. Once the booster cylinder of a certain compressor unit was damaged, the entire compressor could not operate. At the same time, it was proposed that in the initial stage of the station operation, there were significant differences between the inlet and outlet parameters of the compressor and the designed values, and the operation plan in the initial stage of production needed to be considered. Secondly, the gas source medium contained moisture and other impurities, and the moisture content was relatively high, which was extremely likely to freeze and cause blockage due to temperature drop in winter.

[0124] According to the feedback from the communication, the entire seal system was redesigned and optimized: the redundancy of the booster pump operation was redesigned and considered. At the same time, in order to eliminate the risk of condensate due to temperature drop, through process simulation digital analysis and calculation and combined with a large amount of product test data, improvement schemes such as adding an electric heater after the differential pressure control valve of the primary seal gas were adopted. The original designed control scheme achieved the expected goals through on-site trial operation and adjustment and optimization, and solved well the problems of unstable control of the booster cylinder, frequent start-stop and inability to be used as a backup for each other brought by the existing mature control scheme for similar process devices, and avoided the problem of blockage of the filter in the subsystem 1 beside the machine. The reliability of the centrifugal compressor unit was improved.

Claims

1. A system for improving the reliability of a centrifugal compressor unit, the centrifugal compressor unit comprising a plurality of parallel centrifugal compressors (1), wherein the process gas inlet pipe (101) of each centrifugal compressor (1) is connected to an inlet manifold (2), and the process gas outlet pipe (102) of each centrifugal compressor (1) is connected to an outlet manifold (3); Axial seals (4) are respectively arranged at both ends of each centrifugal compressor (1), and a condensate drain port (405) and a pressure tapping port (406) are arranged on the axial seal (4). It is characterized in that, The shaft end seal (4) is further provided with a first-level sealing gas charging port (401), a first-level leakage gas venting port (402), an isolation gas supply charging port (403) and a second-level leakage gas venting port (404); The process gas inlet pipe (101) of each centrifugal compressor (1) is connected to a back-blowing gas return port (103), and the process gas outlet pipe (102) of each centrifugal compressor (1) is connected to a first-level sealing gas supply port (104); The outlet manifold (3) is connected to one end of the shaft-end sealed gas source pipe (5), the other end of the shaft-end sealed gas source pipe (5) is connected to the input ends of multiple parallel gas purifiers (6), the input ends of the multiple gas purifiers (6) are connected to the air inlet ends of multiple parallel booster cylinders (7), the outlet ends of the multiple parallel booster cylinders (7) are connected to one end of an air inlet pipe (9) with a heater (8), the other end of the air inlet pipe (9) is connected to multiple machine-side systems (10), and each machine-side system (10) is connected to a corresponding centrifugal compressor (1); The plurality of parallel-connected boost cylinders (7) are also connected in parallel with a bypass equipped with a one-way valve (16); Each of the machine-side systems (10) includes four subsystems, namely a first-level sealing gas supply subsystem (11), a first-level leakage gas release subsystem (12), an isolation gas supply subsystem (13) and a second-level leakage gas release subsystem (14); The first-stage sealing gas supply subsystem (11) comprises two first input pipes (1101), two first output pipes (1102) and a filter condensate return branch pipe (1103), wherein one first input pipe (1101) is connected to the other end of the air inlet pipe (9), the other first input pipe (1101) is connected to the first-stage sealing gas supply port (104), the two first output pipes (1102) are respectively connected to the first-stage sealing gas charging ports (401) at both ends of the centrifugal compressor (1), and the other end of the filter condensate return branch pipe (1103) is connected to the back-blowing gas return port (103); The first-stage leakage gas venting subsystem (12) comprises two second input pipes (1201) and two second output pipes (1202), wherein the two second input pipes (1201) are respectively connected to the first-stage leakage gas venting ports (402) at both ends of the centrifugal compressor (1), and the two second output pipes (1202) lead the gas to a high point outdoors for venting; The isolation gas supply subsystem (13) includes a third input pipe (1301) and two third output pipes (1302), wherein the third input pipe (1301) is connected to an external gas source, and the two third output pipes (1302) are respectively connected to the isolation gas supply and charging ports (403) at both ends of the centrifugal compressor (1); The described secondary leakage gas venting subsystem (14) includes two fourth input pipes (1401) and two fourth output pipes (1402). The two fourth input pipes (1401) are respectively connected to the secondary leakage gas venting ports (404) at both ends of the centrifugal compressor (1), and the two fourth output pipes (1402) lead the gas to a high point outdoors for venting.

2. The system for improving the reliability of a centrifugal compressor unit according to claim 1, characterized in that, On the two first input pipes (1101) of the described primary sealing gas supply subsystem (11), a shut-off valve (20) and a check valve are sequentially arranged. After the two first input pipes (1101) converge, they are also sequentially connected to a double parallel filter (21), a differential pressure control regulating valve (22), and an electric heater (23). The input end of the electric heater (23) is connected to one end of two first output pipes (1102), and a flow meter (24) and a shut-off valve are respectively arranged on the two first output pipes (1102); The output end of the differential pressure control regulating valve (22) is communicated with the pressure tapping port (406), and a differential pressure transmitter (30) is arranged between them; The double parallel filter (21) is connected to one end of the filter condensate return branch pipe (1103). A check valve, a shut-off valve, and an orifice plate (25) are sequentially arranged on the filter condensate return branch pipe (1103).

3. The system for improving the reliability of a centrifugal compressor unit according to claim 2, characterized in that, The double parallel filter (21), the differential pressure control regulating valve (22), and the electric heater (23) are also connected to the drain pipe (1104).

4. The system for improving the reliability of a centrifugal compressor unit according to claim 1, wherein, On the two second input pipes (1201) of the described primary leakage gas venting subsystem (12), a pressure transmitter (19) and a check valve (26) are sequentially arranged. After the two second input pipes (1201) converge, they are connected to a second output pipe (1202) provided with a flame arrester (27); One spare vent pipe (1203) is connected in parallel to each check valve (26). A throttle orifice plate, a pre-valve constant pressure regulating valve (28), a flow meter, and a check valve are sequentially arranged on the two spare vent pipes (1203). After the two spare vent pipes (1203) converge, they are connected to another second output pipe (1202) provided with a flame arrester (27).

5. The system for improving the reliability of a centrifugal compressor unit according to claim 1, characterized in that, The third input pipe (1301) of the described isolation gas supply subsystem (13) is sequentially connected to a filter (32), a post-valve pressure regulating valve (29), and a pressure transmitter, and then connected to two third output pipes (1302). A throttle orifice plate and a check valve are sequentially arranged on the two third output pipes (1302).

6. The system for improving the reliability of a centrifugal compressor unit as described in claim 1, wherein On the two fourth input pipes (1401) of the described secondary leakage gas venting subsystem (14), a pressure transmitter and a flow meter are sequentially arranged, and flame arresters are respectively arranged on the two fourth output pipes (1402).

7. A control method for improving the reliability of a centrifugal compressor unit, which uses the system for improving the reliability of a centrifugal compressor unit as described in any one of claims 1 to 6.

8. The control method for improving the reliability of a centrifugal compressor unit according to claim 7, characterized in that, A manifold differential pressure transmitter (15) is arranged between the described inlet manifold (2) and the outlet manifold (3); An inlet pressure transmitter (17) is arranged on the process gas inlet pipe (101); An inlet and outlet differential pressure transmitter (18) is provided between the process gas inlet pipe (101) and the process gas outlet pipe (102) of each centrifugal compressor (1) described above; The cut-off valve provided on a first input pipe (1101) of a path of the primary seal gas supply subsystem (11) connected to the other end of the inlet pipe (9) is a pneumatic cut-off valve (31).

9. The control method for improving the reliability of a centrifugal compressor unit according to claim 8, wherein, This method specifically includes the opening and closing control method of the pneumatic cut-off valve (31) and the opening and closing control method of the booster cylinder (7); The opening and closing control method of the pneumatic cut-off valve (31) described above includes opening conditions and closing conditions; Step S11, the opening condition of the pneumatic cut-off valve (31): When the gas flow rates detected by the flow meters (24) in the two first output pipes (1102) of the primary seal gas supply subsystem (11) are both ≤ 300 Nm 3 / h, and the pressure difference value detected by the inlet and outlet differential pressure transmitter (18) between the process gas inlet pipe (101) and the process gas outlet pipe (102) is ≤ 0.5 MPa; And when the pressure value in the process gas inlet pipe (101) detected by the inlet pressure transmitter (17) ≥ 0.5 MPa, open the pneumatic cut-off valve (31) in the primary seal gas supply subsystem (11) corresponding to the centrifugal compressor (1); Step S12, the closing condition of the pneumatic cut-off valve (31): When the gas flow rates detected by the flow meters (24) in the two first output pipes (1102) of the primary seal gas supply subsystem (11) are both ≥ 400 Nm 3 / h, and the pressure difference value detected by the inlet and outlet differential pressure transmitter (18) between the process gas inlet pipe (101) and the process gas outlet pipe (102) is ≥ 1.0 MPa; Or when the pressure value in the process gas inlet pipe (101) detected by the inlet pressure transmitter (17) ≤ 0.3 MPa, close the pneumatic cut-off valve (31) in the primary seal gas supply subsystem (11) corresponding to the centrifugal compressor (1); The opening and closing control method of the booster cylinder (7) described above includes opening conditions and closing conditions; Step S21, the opening condition of the booster cylinder (7): When at least one pneumatic cut-off valve (31) corresponding to the centrifugal compressor (1) is in the open state, and when the gas flow rate detected by the flow meter (24) in at least one of the two first output pipes (1102) in the primary seal gas supply subsystem (11) ≤ 150 Nm 3 / h, or when the pressure difference value between the process gas inlet pipe (101) and the process gas outlet pipe (102) detected by the inlet and outlet pressure difference transmitter (18) ≤ 0.2 MPa, or when the pressure value in the process gas inlet pipe (101) detected by the inlet pressure transmitter (17) > 0.3 MPa, delay for 2 s and start a supercharging cylinder (7). After the supercharging cylinder (7) has been started for 30 s, continue to judge. If the foregoing supercharging cylinder opening conditions are still met, continue to start the supercharging cylinders (7) that have not been started among multiple supercharging cylinders (7) until all supercharging cylinders (7) have been started; When all the booster cylinders (7) are in the open state, the gas is boosted by the booster cylinders (7) and supplied to the primary seal gas supply subsystem (11); Step S22, the closing condition of the booster cylinder (7): When the pneumatic cut-off valves (31) corresponding to all the centrifugal compressors (1) are in the closed state, the booster cylinders (7) are in the closed state, and the outlet header (3) does not need to supply gas to the primary seal gas supply subsystem (11); Or when the pneumatic cut-off valves (31) corresponding to at least one centrifugal compressor (1) are in the open state, and when the pressure difference between the inlet header (2) and the outlet header (3) detected by the header differential pressure transmitter (15) > 0.5 MPa, or when the pressure values in the process gas inlet pipes (101) detected by the inlet pressure transmitters (17) corresponding to all the centrifugal compressors (1) are all < 0.3 MPa, close all the booster cylinders (7), and the outlet header (3) needs to supply gas to the primary seal gas supply subsystem (11), then the gas is directly supplied to the primary seal gas supply subsystem (11) through the bypass provided with the check valve (16).

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