CN110080971B - Gas start method suitable for supercritical carbon dioxide compression system - Google Patents

Gas start method suitable for supercritical carbon dioxide compression system Download PDF

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Publication number
CN110080971B
CN110080971B CN201910278723.0A CN201910278723A CN110080971B CN 110080971 B CN110080971 B CN 110080971B CN 201910278723 A CN201910278723 A CN 201910278723A CN 110080971 B CN110080971 B CN 110080971B
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valve
compression system
stage
gas
pressure
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CN110080971A (en
Inventor
秦飞虎
刘勇
何伟
杨金
***
姚俊
罗智勇
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China National Petroleum Corp
CNPC Jichai Power Co Ltd
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Chengdu Compressor Plant of CNPC Jichai Power Equipment Co
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B08—CLEANING
    • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
    • B08B7/00—Cleaning by methods not provided for in a single other subclass or a single group in this subclass
    • B08B7/0021—Cleaning by methods not provided for in a single other subclass or a single group in this subclass by liquid gases or supercritical fluids
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B35/00—Piston pumps specially adapted for elastic fluids and characterised by the driving means to their working members, or by combination with, or adaptation to, specific driving engines or motors, not otherwise provided for
    • F04B35/04—Piston pumps specially adapted for elastic fluids and characterised by the driving means to their working members, or by combination with, or adaptation to, specific driving engines or motors, not otherwise provided for the means being electric
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B39/00—Component parts, details, or accessories, of pumps or pumping systems specially adapted for elastic fluids, not otherwise provided for in, or of interest apart from, groups F04B25/00 - F04B37/00
    • F04B39/02—Lubrication
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B39/00—Component parts, details, or accessories, of pumps or pumping systems specially adapted for elastic fluids, not otherwise provided for in, or of interest apart from, groups F04B25/00 - F04B37/00
    • F04B39/06—Cooling; Heating; Prevention of freezing
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
    • F04B49/02—Stopping, starting, unloading or idling control
    • F04B49/022—Stopping, starting, unloading or idling control by means of pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
    • F04B49/02—Stopping, starting, unloading or idling control
    • F04B49/03—Stopping, starting, unloading or idling control by means of valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
    • F04B49/02—Stopping, starting, unloading or idling control
    • F04B49/03—Stopping, starting, unloading or idling control by means of valves
    • F04B49/035—Bypassing

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Control Of Positive-Displacement Pumps (AREA)
  • Rotary Pumps (AREA)

Abstract

The invention discloses a gas start method suitable for a supercritical carbon dioxide compression system, which belongs to the technical field of gas compression and comprises the following steps: the gas pressure in the system is maintained at 0.2-0.5Mpa by controlling the opening and closing of the purge valve, and the operations of purging, pre-lubricating and warming up are carried out in sequence under the condition, after the warming up is finished, the pressure in the system is raised to the rated intake pressure in stages, and then loading is carried out. The supercritical carbon dioxide compression system is started after being cleaned and pre-lubricated in a low-pressure environment of 0.2-0.5Mpa, so that the abrasion of precision parts of a compressor caused by starting a motor in a high-pressure environment is avoided; the cleaning time is set reasonably, so that the cleaning time is prevented from being overlong and the starting time is prevented from being wasted while thorough cleaning is ensured.

Description

Gas start method suitable for supercritical carbon dioxide compression system
Technical Field
The invention relates to the field of gas compression, in particular to a gas start method suitable for a supercritical carbon dioxide compression system.
Background
CO2Is a colorless, odorless, tasteless and nontoxic gas, can be dissolved in water at 25 deg.CThe solubility was 0.144g/100g water and the density was about 1.5 times that of air. For 100% pure carbon dioxide, CO is present at a pressure above the critical pressure (7.38MPa) and at a temperature above the critical temperature (31.4 ℃ C.)2In a supercritical state between a gas phase and a liquid phase, the density of supercritical carbon dioxide is very high, close to that of liquid, but the diffusion coefficient is close to that of gas; when the pressure is higher than the critical pressure (7.38MPa) and the temperature is lower than the critical temperature (31.4 ℃), CO2The carbon dioxide is in a dense phase liquid state, the carbon dioxide is very corrosive, the carbon dioxide expands in volume with the reduction of pressure, the temperature is reduced, and the temperature of the carbon dioxide is sharply reduced due to the rapid reduction of the pressure, so that dry ice is formed.
Supercritical CO2The gas injection compression system is CO2Core equipment for gas-driven oil production, which uses CO2The gas is compressed and temperature controlled from conventional gas state step by step to make its temperature higher than critical temperature and pressure higher than critical pressure to reach critical state, then injected into underground to raise oil recovery rate. If liquid phase medium enters the compressor, the compressor has a great corrosion risk, abnormal phenomena such as cylinder jacking and the like occur, and the pipeline is blocked by the formation of dry ice until the pipeline is frozen to crack. Based on the supercritical carbon dioxide compression system, the safe and stable start-up is the basis of the stable operation of the whole compression system.
The patent with the patent number of CN201310228409.4 for a starting method of a reciprocating piston type compressor discloses that a compressor with a larger machine type is preheated and lubricated before starting, and the whole machine is put into operation after the compressor is fully prepared, so that the service life of a key stress part of a compression system can be effectively prolonged, and the stability of the whole system can be improved; however, the limiting condition whether the cleaning operation is executed is the air suction pressure value, when the air suction pressure is higher than the set value, the motor is directly started, the pressure environment in the compression system before starting is not clearly limited, and the clear set value parameters are not disclosed, so that the method is not suitable for starting the supercritical carbon dioxide multistage compression system.
Disclosure of Invention
The invention aims to: in view of the compression requirement of the supercritical carbon dioxide gas, the invention provides a high-stability gas start method suitable for a supercritical carbon dioxide compression system.
The invention specifically adopts the following technical scheme for realizing the purpose: a gas start method suitable for a supercritical carbon dioxide compression system is characterized by comprising the following steps:
the method comprises the following steps: compressor energization
The control system controls the air inlet valve, the cleaning valve, the main exhaust valve, the emptying valve, the bypass switch valve, the final-stage bypass valve and the grading bypass valve to be in a closed state;
step two: opening an emptying valve, and discharging gas in the system from the emptying valve;
step three: monitoring the gas pressure behind the cleaning valve to determine whether the pressure behind the valve is lower than the pressure set value of 0.2-0.5MPa required by cleaning, if the pressure is lower than 0.2-0.5MPa, opening the cleaning valve to supplement air, and if the pressure is higher than 0.2-0.5MPa, closing the cleaning valve to maintain the gas pressure in the supercritical carbon dioxide compression system at 0.2-0.5MPa, and sequentially performing the following operations:
(1) synchronously executing cleaning and pre-lubricating operations, and executing a warming operation after the pre-lubricating operation is finished:
wherein the cleaning operation comprises:
keeping all valve positions unchanged, namely, keeping an air inlet valve, a main exhaust valve, a bypass switch valve, a final-stage bypass valve and a staged bypass valve in a closed state, and opening an emptying valve; carrying out first cleaning, and keeping 100-;
opening a bypass switch valve, a final-stage bypass valve and a grading bypass valve, and cleaning for the second time, wherein the cleaning time is kept between 50 and 70 seconds;
closing the emptying valve;
wherein the pre-lubrication operation comprises:
starting a pre-lubricating oil pump and an oil heater to heat lubricating oil in a crankcase and pre-lubricate bearings of a main engine of the compressor,
monitoring the temperature and pressure of oil temperature, starting a main exhaust valve when the oil temperature and the oil pressure reach set values required by pre-lubrication, and executing warming operation;
(2) warming-up operation
Starting the motor;
monitoring the oil temperature of the compressor, and executing small-cycle operation when the temperature is increased to the rated temperature required by the warming machine;
step four: small cycle operation
Controlling the opening and closing of the cleaning valve, supplementing the air inlet pressure to a rated air inlet pressure value in three stages, supplementing the air inlet pressure to one third of the air inlet pressure in the first stage, supplementing the air inlet pressure to two thirds of the air inlet pressure in the second stage, and supplementing the air inlet pressure to the rated value of the air inlet pressure in the third stage;
monitoring the temperature of a crankcase, and executing loading operation after the temperature of the crankcase oil is raised to a rated temperature required by a small circulation;
step five: load operation
And opening an air inlet valve, closing the cleaning valve, sequentially closing the bypass switch valve and the final-stage bypass valve, closing each stage bypass valve according to the degradation sequence, gradually increasing the exhaust pressure, and performing normal operation on the compressor.
Preferably, each time interval of the staged air supplement in the small circulation flow path is 10S.
Preferably, the first wash hold 130S; the second wash maintains 70S.
Preferably, the air inlet valve is a valve connected to a main air inlet pipeline of the supercritical carbon dioxide compression system and used for carrying out ventilation control on the supercritical carbon dioxide compression system;
the cleaning valve is a valve which is arranged on the air inlet process pipeline and is connected with the air inlet valve in parallel, and is used for throttling and depressurizing the inlet air and performing air replacement in the unit before the unit is started;
the main exhaust valve is a valve connected to a main exhaust pipeline of the supercritical carbon dioxide compression system and used for controlling final exhaust to a user;
the emptying valve is a valve connected to the air outlet end of the final stage compression system of the supercritical carbon dioxide compression system, and the air outlet of the emptying valve is communicated to an emptying pipeline and used for emptying the gas of the supercritical carbon dioxide compression system;
the bypass switch valve is a valve connected to the gas outlet end of the final stage compression system of the supercritical carbon dioxide compression system, and the gas outlet of the bypass switch valve is communicated to the gas inlet end of the primary compression system and used for controlling the backflow of gas from the final stage to the primary stage;
the last-stage bypass valve is also a valve connected to the gas outlet end of the last-stage compression system of the supercritical carbon dioxide compression system, and the gas outlet of the last-stage bypass valve is communicated with the gas inlet end of the last-stage compression system and used for controlling the backflow of gas from the last stage to the last stage;
the grading bypass valve is a valve which is respectively connected with the air inlet end of each stage of compression system of the supercritical carbon dioxide compression system, the air outlets of the grading bypass valve are all communicated with the air inlet end of the previous stage of compression system of the compression system where the grading bypass valve is located, and the grading bypass valve is used for controlling backflow of gas from a high stage to the previous stage step by step.
The pre-lubricating oil pump is used for pressurizing pre-lubricating oil, and the oil heater is used for heating the lubricating oil.
The invention has the following beneficial effects:
1. the invention firstly discharges the gas in the system before cleaning to avoid the gas residue in the system, then controls the switch of the cleaning valve to maintain the gas pressure in the system at 0.2-0.5Mpa, then carries out cleaning replacement and pre-lubrication, starts the motor after cleaning pre-lubrication, the motor is started under the low-pressure environment, the load is close to no-load, can avoid the loss caused by overlarge instant stress of key parts, in the process, the low-pressure starting value of the motor is repeatedly tried and found, the process time is excessively consumed when the gas pressure of the gas compression system is reduced to 0.2Mpa before starting, and when the compressor is directly started under the environment with the pressure higher than 0.5Mpa, the precision parts in the compressor can be impacted, therefore, the motor is started under the pressure of 0.2-0.5Mpa of the system, thereby effectively protecting the precision parts of the compressor, the starting time cannot be consumed too much;
1. the main gas pipeline is cleaned firstly during cleaning, then the bypass is opened to clean the whole system pipeline, the system is ensured to finish whole gas replacement in a stable low-pressure environment before starting, the pressure in the system is not increased, and no impurity gas is remained, and the first cleaning time is kept at 100 plus materials 130S and the second cleaning time is kept at 50-70S after field verification, so that the starting time waste caused by overlong cleaning time can be avoided on the premise of ensuring thorough cleaning;
2. in the process of pre-lubrication, warming and small circulation, the rise of oil temperature and the increase of pressure are synchronous, the increase of pressure is a prerequisite condition that whether the temperature of the oil temperature reaches a set value, and the air inlet pressure is gradually increased after the oil temperature reaches the set condition, so that the full lubrication is ensured and the stable starting is realized;
3. in the small-cycle operation of the invention, the bypass valves are all in an open state, gas circulates and flows back in the system, the pressure cannot be suddenly increased, the intake pressure is increased to a rated value in stages in the state, the intake pressure is stably increased to a rated intake pressure value under the condition of not greatly increasing the load, and the stable starting and pressurization of the system are further ensured; and after the pressurization is finished, the bypass is closed step by step, so that the compressor enters normal step by step compression and exhaust, the whole process is stable and reliable, and the stability of the system is effectively improved.
Drawings
FIG. 1 is a schematic gas flow diagram of a supercritical carbon dioxide compression system of the present invention;
fig. 2 is a schematic view of the air start process of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures. Furthermore, the terms "first," "second," and the like are used merely to distinguish one description from another, and are not to be construed as indicating or implying relative importance.
In the description of the embodiments of the present invention, it should be noted that the terms "inside", "outside", "upper", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings or orientations or positional relationships conventionally arranged when products of the present invention are used, and are only used for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the devices or elements indicated must have specific orientations, be constructed in specific orientations, and operated, and thus, cannot be construed as limiting the present invention.
Example 1
Referring to fig. 1, before describing a gas start method of a supercritical carbon dioxide compression system, the supercritical carbon dioxide compression system is briefly introduced, which comprises a multistage compression system and a temperature control system, wherein the multistage compression system is sequentially connected in series from a primary stage to a final stage, the temperature control system is used for controlling the temperature of gas compressed by each stage of compression cylinder, the gas inlet of the primary compression cylinder is communicated with a main gas inlet through a vent pipeline, the gas outlet of the final compression cylinder is sequentially communicated with the temperature control system and a main gas outlet through a vent pipeline, the gas outlet of the final compression cylinder is also communicated with a gas outlet assembly comprising a plurality of gas channels, the supercritical carbon dioxide compression system further comprises a bypass control system, a vent control system and a staged pressure regulating system, the staged pressure regulating system can gradually return gas from the gas outlet of the final compression cylinder to, the emptying control system is communicated with the grading pressure regulating system. The stepped pressure regulating system comprises a final-stage bypass valve, an air inlet end of the final-stage bypass valve is communicated with an air outlet assembly, an air outlet end of the final-stage bypass valve is communicated with an air inlet of a last-stage compression cylinder of a final-stage compression cylinder, and a stepped bypass valve is communicated between the air inlet of each other stage of compression cylinder except the final-stage compression cylinder and the primary compression cylinder and the air inlet of the last-stage compression cylinder through a return pipeline. The bypass control system comprises a bypass switch valve, the air inlet end of the bypass switch valve is communicated with the air outlet assembly, the air outlet end of the bypass switch valve is communicated with the air inlet of the primary compression cylinder, the emptying control system comprises an emptying valve and an emptying pipeline, the air inlet end of the emptying valve is communicated with the air outlet assembly, and the air outlet end of the emptying valve is communicated with the emptying pipeline; the main air inlet is communicated with an air inlet control system, the main air outlet is communicated with an air outlet control system, the air inlet control system comprises an air inlet valve and a cleaning valve, the air inlet valve is connected with the main air inlet in series, the cleaning valve is connected with the air inlet valve in parallel, and the air outlet control system comprises an air outlet check valve and an air outlet valve which are sequentially connected with the main air outlet in series along the air outlet direction.
The air inlet valve is used for carrying out ventilation control on the supercritical carbon dioxide compression system; the cleaning valve is used for throttling and depressurizing the inlet air, and air in the system is replaced before the system is started; the exhaust valve is used for controlling final exhaust to a user; the gas outlet of the emptying valve is communicated to an emptying pipeline and is used for emptying the gas of the supercritical carbon dioxide compression system; the bypass switch valve is used for controlling the backflow of gas from the final stage to the primary stage; the last-stage bypass valve is used for controlling the backflow of gas from the last stage to the previous stage; and each stage of grading bypass valve is used for controlling backflow of gas from a high stage to the upper stage thereof step by step.
As shown in fig. 2, the present embodiment provides a gas start method suitable for the above supercritical carbon dioxide compression system:
firstly, electrifying a compression system, and controlling a control system of the compression system in an intervention manner (the structure of the control system and a controller thereof is a technical means which is not described any more), wherein at the moment, a main air inlet valve, a cleaning valve, a main exhaust valve, an emptying valve, a bypass switch valve, a final-stage bypass valve and a staged bypass valve are all in a closed state;
step two: opening a vent valve, and discharging residual gas in the system from the vent valve;
step three: monitoring the pressure of gas after cleaning the valve (namely the pressure of gas in an air inlet pipeline of the supercritical carbon dioxide compression system) to determine whether the pressure after cleaning the valve is lower than a pressure set value 0.5Mpa required by cleaning, if the pressure of gas in the air inlet pipeline of the supercritical carbon dioxide compression system is lower than the set value 0.5Mpa, opening the cleaning valve, enabling the gas to enter the compression system through the cleaning valve to supplement gas in the system, and if the pressure of gas in the air inlet pipeline of the supercritical carbon dioxide compression system is higher than the set value 0.5Mpa, closing the cleaning valve to stop supplementing gas, circulating the gas, and keeping the pressure of gas in the supercritical carbon dioxide compression system in a low-pressure state of 0.5Mpa all the time, and sequentially performing the:
(1) and (2) synchronously executing cleaning and pre-lubricating operations, wherein the pre-lubricating time is longer than that of the cleaning operation, so that the cleaning operation is finished after the pre-lubricating, and the warming-up operation is executed after the pre-lubricating is finished:
wherein the cleaning operation comprises:
keeping all valve positions unchanged, namely keeping a main air inlet valve, a main exhaust valve, a bypass switch valve, a final-stage bypass valve and a staged bypass valve in a closed state, opening and closing a cleaning valve according to the pressure change in the system, and regulating pressure, and opening an emptying valve; gas enters the compression system from the cleaning valve, is discharged from the emptying valve, replaces air in the system, performs primary cleaning under the pressure state of 0.5Mpa, keeps 150 seconds, then opens the bypass switch valve, the last-stage bypass valve and the grading bypass valve, performs secondary cleaning, performs air replacement on all pipelines in the whole system, keeps 70 seconds, closes the emptying valve after cleaning is completed, and completes constant-pressure cleaning of the system; at this moment, because the filler leaks, the purge valve still opens and closes according to system internal pressure and supplements the gas, keeps system internal pressure at 0.5Mpa, and up to this moment, each other valve position state is: the main air inlet valve, the main exhaust valve and the emptying valve are in closed states, and the bypass switch valve, the final-stage bypass valve and the stepped bypass valve are in open states;
the pre-lubrication operation is performed while the washing operation is started, that is: starting a pre-lubricating oil pump and an oil heater, heating lubricating oil of a crankcase, pre-lubricating bearings of a compressor main machine, gradually increasing oil temperature and oil pressure, monitoring oil temperature and oil pressure, starting a main exhaust valve when the oil temperature and the oil pressure reach set values required by pre-lubrication, and executing warming operation; at this time, except that the cleaning valve is in the open-close switching air supply state, the states of other valve positions are as follows: the main air inlet valve and the emptying valve are in a closed state, and the bypass switch valve, the final-stage bypass valve, the stepped bypass valve and the main exhaust valve are in an open state.
After the exhaust valve is opened, warming operation is executed, the motor is started, the valve position is unchanged, the cleaning valve is still in an opening-closing switching air supplementing state, the gas pressure is maintained at 0.5Mpa, the load of the compressor is small, and the motor is stably started; meanwhile, the gas pressure in the system is very low and does not reach the high-pressure exhaust value, so that the gas is not exhausted from the main exhaust port, but flows back through the bypass switch valve, the last-stage bypass valve and the staged bypass valve and circulates in the compressor; in the process, the oil temperature of the crankcase of the compressor is gradually increased, the oil temperature of the compressor is monitored, and when the temperature is increased to 25 ℃ of the rated temperature required by the warming machine, the small-cycle operation is executed;
when the small-cycle operation is performed, the gas pressure in the supercritical carbon dioxide compression system is raised in stages by controlling the opening and closing of the purge valve, the gas pressure in the supercritical carbon dioxide compression system is supplemented in stages to a pressure set value required for the small-cycle (the intake pressure set value in the embodiment is 2 Mpa), and for the purpose of stably starting the system, the gas pressure is supplemented to 0.7Mpa in 10S in the first stage, 1.4Mpa in 10S in the second stage, and 2.0Mpa in 10S in the third stage. Monitoring the temperature of a crankcase, and after the temperature of the crankcase oil rises to a rated temperature required by a small circulation, preferably, the temperature of the crankcase oil rises to a rated temperature of more than 38 ℃ and the loading operation is executed after the temperature of the crankcase oil is more than 38 ℃ in order to ensure that the supercritical carbon dioxide compression system is stably started and does not interfere the phase change of the supercritical carbon dioxide compression system; when loading, the main air inlet valve is opened, the cleaning valve is closed, the bypass switch valve and the last-stage bypass valve are closed in sequence, the staged bypass valves are closed in a degrading sequence, the exhaust pressure is gradually increased, and the compressor is in a normal operation state. During pre-lubrication, warm-up and small-cycle operation, along with the gradual rise of the oil temperature, the load of the motor is gradually increased step by step, the condition that the oil temperature is low and the load is high is avoided, each bearing is damaged, and along with the rise of the oil temperature, the load is gradually increased, so that the compression system stably enters a normal working state.

Claims (4)

1. A gas start method suitable for a supercritical carbon dioxide compression system is characterized by comprising the following steps:
the method comprises the following steps: compressor energization
The control system controls the air inlet valve, the cleaning valve, the main exhaust valve, the emptying valve, the bypass switch valve, the final-stage bypass valve and the grading bypass valve to be in a closed state;
step two: opening an emptying valve, and discharging gas in the system from the emptying valve;
step three: monitoring the gas pressure behind the cleaning valve to determine whether the pressure behind the valve is lower than the pressure set value of 0.2-0.5MPa required by cleaning, if the pressure is lower than 0.2-0.5MPa, opening the cleaning valve to supplement air, and if the pressure is higher than 0.2-0.5MPa, closing the cleaning valve to maintain the gas pressure in the supercritical carbon dioxide compression system at 0.2-0.5MPa, and sequentially performing the following operations:
(1) synchronously executing cleaning and pre-lubricating operations, and executing a warming operation after the pre-lubricating operation is finished:
wherein the cleaning operation comprises:
keeping all valve positions unchanged, namely, keeping an air inlet valve, a main exhaust valve, a bypass switch valve, a final-stage bypass valve and a staged bypass valve in a closed state, and opening an emptying valve; carrying out first cleaning, and keeping 100-;
opening a bypass switch valve, a final-stage bypass valve and a grading bypass valve, and cleaning for the second time, wherein the cleaning time is kept between 50 and 70 seconds;
closing the emptying valve;
wherein the pre-lubrication operation comprises:
starting a pre-lubricating oil pump and an oil heater to heat lubricating oil in a crankcase and pre-lubricate bearings of a main engine of the compressor,
monitoring the temperature and pressure of oil temperature, starting a main exhaust valve when the oil temperature and the oil pressure reach set values required by pre-lubrication, and executing warming operation;
(2) warming-up operation
Starting the motor;
monitoring the oil temperature of the compressor, and executing small-cycle operation when the temperature is increased to the rated temperature required by the warming machine;
step four: small cycle operation
Controlling the opening and closing of the cleaning valve, supplementing the air inlet pressure to a rated air inlet pressure value in three stages, supplementing the air inlet pressure to one third of the air inlet pressure in the first stage, supplementing the air inlet pressure to two thirds of the air inlet pressure in the second stage, and supplementing the air inlet pressure to the rated value of the air inlet pressure in the third stage;
monitoring the temperature of a crankcase, and executing loading operation after the temperature of the crankcase oil is raised to a rated temperature required by a small circulation;
step five: load operation
And opening an air inlet valve, closing the cleaning valve, sequentially closing the bypass switch valve and the final-stage bypass valve, closing each stage bypass valve according to the degradation sequence, gradually increasing the exhaust pressure, and performing normal operation on the compressor.
2. The gas start method for the supercritical carbon dioxide compression system according to claim 1, wherein: and each time interval of the air supplement in stages in the small circulation flow is 10S.
3. The gas start method for the supercritical carbon dioxide compression system according to claim 1, wherein: a first cleaning hold 130S; the second wash maintains 70S.
4. The gas start method for the supercritical carbon dioxide compression system according to claim 1, wherein:
the air inlet valve is a valve connected to a main air inlet pipeline of the supercritical carbon dioxide compression system and is used for carrying out ventilation control on the supercritical carbon dioxide compression system;
the cleaning valve is a valve which is arranged on the air inlet process pipeline and is connected with the air inlet valve in parallel, and is used for throttling and depressurizing the inlet air and performing air replacement in the unit before the unit is started;
the main exhaust valve is a valve connected to a main exhaust pipeline of the supercritical carbon dioxide compression system and used for controlling final exhaust to a user;
the emptying valve is a valve connected to the air outlet end of the final stage compression system of the supercritical carbon dioxide compression system, and the air outlet of the emptying valve is communicated to an emptying pipeline and used for emptying the gas of the supercritical carbon dioxide compression system;
the bypass switch valve is a valve connected to the gas outlet end of the final stage compression system of the supercritical carbon dioxide compression system, and the gas outlet of the bypass switch valve is communicated to the gas inlet end of the primary compression system and used for controlling the backflow of gas from the final stage to the primary stage;
the last-stage bypass valve is also a valve connected to the gas outlet end of the last-stage compression system of the supercritical carbon dioxide compression system, and the gas outlet of the last-stage bypass valve is communicated with the gas inlet end of the last-stage compression system and used for controlling the backflow of gas from the last stage to the last stage;
the grading bypass valve is a valve which is respectively connected with the air inlet end of each stage of compression system of the supercritical carbon dioxide compression system, the air outlets of the grading bypass valve are all communicated with the air inlet end of the previous stage of compression system of the compression system where the grading bypass valve is positioned, and the grading bypass valve is used for carrying out backflow control on gas from the high stage to the previous stage step by step;
the pre-lubricating oil pump is used for pressurizing pre-lubricating oil, and the oil heater is used for heating the lubricating oil.
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EP2146154A1 (en) * 2008-07-18 2010-01-20 Valeo Systemes Thermiques Device for controlling a fixed-capacity compressor
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