Control method and device for liquefied natural gas receiving station

Abstract

The invention discloses a control method and device for a liquefied natural gas receiving station, and relates to the technical field of liquefied natural gas receiving stations. Based on the difference value between the pressure of the liquefied natural gas in front of an inlet regulating valve of the current high-pressure pump and the target pressure value, the opening degree of an outlet valve of the current low-pressure pump is determined; according to the total volume flow output by all the high-pressure pumps, the adjusting quantity of an inlet adjusting valve of the current high-pressure pump is determined; starting the current high-pressure pump; when the current volume flow output by the high-pressure pump is in the normal range, the opening degrees of an inlet adjusting valve and an inlet throttling valve of the high-pressure pump are adjusted on the basis of the bottom pressure of the after-condenser and the opening degree of the inlet throttling valve of the high-pressure pump; and starting the current vaporizer. The opening of each device of the receiving station is automatically controlled according to the sequence, and the opening of each valve is adjusted before opening, so that one-key opening control is realized, manual participation is reduced, and the working efficiency of the receiving station is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of liquefied natural gas receiving stations, and in particular to a control method and device for a liquefied natural gas receiving station. Background Art

[0002] As the "dual carbon" goal continues to advance, my country's natural gas consumption continues to grow, the total loading and unloading capacity of LNG receiving stations across the country continues to increase, and the operating load rate of receiving stations has been maintained above 70% for a long time. In order to reduce the workload of on-site operators and greatly reduce the workload of operators, it is necessary to improve the automation control level of the vaporization and export production line of the receiving station and realize the one-button automatic start and stop of the vaporization and export production line. However, since the outlet of the low-pressure pump in the one-button start-stop process is a butterfly valve, the regulating valve from the LNG at the bottom of the recondenser to the inlet of the high-pressure pump is a butterfly valve with a pipe diameter of DN500 and manual control, the pressure behind the valve is controlled by a PID regulator to control the shut-off valve of its bypass to achieve the regulation of the pressure behind the valve. The diameter of the shut-off valve is small and it is easy to exceed its adjustment range, which affects the automatic start and stop of the liquefied natural gas receiving station. Summary of the invention

[0003] The purpose of the present invention is to provide a control method and device for a liquefied natural gas receiving station, which automatically controls the opening of various devices of the receiving station in sequence, and adjusts the opening of each valve before opening, so as to realize one-key opening control, reduce manual participation, and improve the working efficiency of the receiving station.

[0004] In order to solve the above technical problems, the present invention provides a control method for a liquefied natural gas receiving station, wherein the storage tank of the liquefied natural gas receiving station is used to output liquefied natural gas to a low-pressure pump, output natural gas to a recondenser, and the recondenser outputs liquefied natural gas to a high-pressure pump. The liquefied natural gas passes through a low-pressure pump, an inlet throttle valve and an inlet regulating valve, a high-pressure pump and a vaporizer in sequence and is converted into natural gas. The control method for the liquefied natural gas receiving station comprises:

[0005] Start the current low-pressure pump;

[0006] Determine the difference between the pressure of the liquefied natural gas before the inlet regulating valve of the current high-pressure pump and the target pressure value, and determine the opening of the outlet valve of the current low-pressure pump based on the difference;

[0007] Determining a total volume flow rate output by all high-pressure pumps, and determining a regulation amount of an inlet regulating valve of the current high-pressure pump according to the total volume flow rate;

[0008] Starting the current high-pressure pump;

[0009] When the volume flow rate output by the current high-pressure pump is within a normal range, adjusting the opening of the inlet regulating valve and the inlet throttle valve of the current high-pressure pump based on the bottom pressure of the recondenser and the opening of the inlet throttle valve of the high-pressure pump;

[0010] Start the current carburetor.

[0011] On the other hand, the liquefied natural gas receiving station further comprises a seawater pump, which is used to output seawater to the vaporizer to provide heat for vaporization of the natural gas;

[0012] Before starting the current low-pressure pump, also include:

[0013] Starting the current seawater pump and determining the starting state of the current seawater pump;

[0014] When the outlet valve of the current seawater pump is in an open state and the motor of the current seawater pump is in a started state, entering the step of starting the current low-pressure pump;

[0015] When the outlet valve of the current seawater pump is not in the open state or the motor of the current seawater pump is not in the started state, the first preset time is delayed and the process returns to the step of determining the start state of the current seawater pump.

[0016] On the other hand, start the current low-pressure pump, including:

[0017] Starting the current low-pressure pump, and obtaining the opening of the outlet valve of the current low-pressure pump or the outlet flow of the current low-pressure pump;

[0018] When the opening of the outlet valve of the current low-pressure pump is greater than a first preset opening or the outlet flow rate of the current low-pressure pump is greater than a first preset flow rate, determining a start-up state of the motor of the current low-pressure pump;

[0019] When the outlet flow of the current low-pressure pump is greater than the second preset flow and the motor of the current low-pressure pump is in a starting state, determining that the current low-pressure pump is started successfully, and the second preset flow is less than the first preset flow;

[0020] When the outlet flow of the current low-pressure pump is not greater than the second preset flow or the motor of the current low-pressure pump is not in the starting state, and the starting time of the current low-pressure pump does not exceed the second preset time, delaying the first preset time and returning to the step of determining the starting state of the motor of the current low-pressure pump;

[0021] If the current start-up time of the low-pressure pump exceeds the second preset time, the start-up of the liquefied natural gas receiving station is stopped.

[0022] On the other hand, the liquefied natural gas receiving station further comprises a pressure detector, which is used to detect the pressure of the liquefied natural gas before the inlet regulating valve of the high-pressure pump;

[0023] Determining the opening of the outlet valve of the current low-pressure pump based on the difference includes:

[0024] Determine whether the pressure collected by the current pressure detector is lower than the lower limit of the low-pressure pipe network pressure;

[0025] If it is lower than the lower limit of the low-pressure pipe network pressure, determining whether the difference between two adjacent pressures collected by the pressure detector is less than a first preset pressure;

[0026] If the difference between two adjacent pressures is not less than the first preset pressure, controlling the opening of the outlet valve of the current low-pressure pump to increase by a first percentage;

[0027] If the difference between two adjacent pressures is less than the first preset pressure, the opening of the outlet valve of the current low-pressure pump is controlled to increase by a second percentage, wherein the second percentage is greater than the first percentage;

[0028] If it is not lower than the network pressure lower limit, then judging whether the pressure collected by the pressure detector is higher than the low-pressure network pressure upper limit;

[0029] If it is higher than the upper limit of the low-pressure pipe network pressure, determining whether the difference between two adjacent pressures collected by the pressure detector is less than a first preset pressure;

[0030] If the difference between two adjacent pressures is not less than the first preset pressure, controlling the opening of the outlet valve of the current low-pressure pump to decrease by a second percentage;

[0031] If the difference between two adjacent pressures is less than the first preset pressure, controlling the opening of the outlet valve of the current low-pressure pump to decrease by a first percentage;

[0032] Determining whether the opening of the outlet valve of the current low-pressure pump is greater than the maximum opening limit;

[0033] If it is greater than the maximum opening limit, the current opening of the outlet valve of the current low-pressure pump is maintained;

[0034] If it is not greater than the maximum opening limit, the third preset time is delayed, and the process returns to the step of determining whether the pressure collected by the pressure detector is lower than the lower limit of the low-pressure pipe network pressure.

[0035] On the other hand, the liquefied natural gas receiving station further includes an inlet isolation valve of a high-pressure pump and a compressor. The inlet isolation valve of the high-pressure pump is arranged between the outlet of the low-pressure pump and the condensation port of the recondenser. The compressor is arranged between the gas outlet of the storage tank and the inlet of the recondenser. The outlet of the recondenser is connected to the outlet of the inlet regulating valve. The compressor is used to compress the gas output from the storage tank and output it to the recondenser.

[0036] Before starting the current high-pressure pump, the method further includes:

[0037] Setting the opening of the inlet isolation valve of the current high-pressure pump according to the number of all high-pressure pumps started in the liquefied natural gas receiving station;

[0038] When the opening of the inlet isolation valve of the current high-pressure pump is within a preset opening range centered on the set opening, entering a step of determining the adjustment amount of the inlet regulating valve of the current high-pressure pump according to the total volume flow;

[0039] Starting the current high pressure pump, comprising:

[0040] Determining whether the inlet regulating valve meets the opening condition of the high-pressure pump after adjustment;

[0041] If satisfied, start the current high-pressure pump;

[0042] Determining whether the output volume flow rate of the current high-pressure pump is greater than a third preset flow rate and whether the motor of the current high-pressure pump is in a starting state;

[0043] If the output volume flow rate is greater than a third preset flow rate and the motor of the current high-pressure pump is in a starting state, determining that the current high-pressure pump is started successfully;

[0044] If the output volume flow rate is not greater than the third preset flow rate and the motor of the current high-pressure pump is not in the started state, the preset time is delayed and the process returns to the step of determining whether the output volume flow rate of the current high-pressure pump is greater than the third preset flow rate and whether the motor of the high-pressure pump is in the started state.

[0045] On the other hand, determine the total volume flow rate delivered by all high-pressure pumps, including:

[0046] Get the starting state of the motor of the i-th high-pressure pump and the output volume flow L i ;

[0047] When the motor of the high-pressure pump is in a starting state, if the volume flow rate output by the i-th high-pressure pump is not within the starting state volume flow rate range, a volume flow rate less than a lower limit value of the starting state volume flow rate range is set as a lower limit value, and a volume flow rate greater than an upper limit value of the starting state volume flow rate range is set as an upper limit value;

[0048] When the motor of the high-pressure pump is in an unstarted state, if the volume flow rate output by the i-th high-pressure pump is not within the unstarted state volume flow rate range, a volume flow rate less than a lower limit value of the unstarted state volume flow rate range is set as a lower limit value, and a volume flow rate greater than an upper limit value of the unstarted state volume flow rate range is set as an upper limit value;

[0049] Determine the total volume flow rate output by all high-pressure pumps, the expression for the total volume flow rate is:

[0050] L sum =ΣL i +ΔL;

[0051] Among them, L sum is the total volume flow rate, L i is the volume flow rate output by the i-th high-pressure pump, ΔL is the preset volume flow rate change value when the high-pressure pump is started or stopped, i∈[1,2,3,…,n], there are n high-pressure pumps in total;

[0052] Determining the adjustment amount of the inlet regulating valve of the current high-pressure pump according to the volume flow includes:

[0053] Determine the total mass flow rate output by the recondenser, the total mass flow rate is expressed as:

[0054] L m =1000×L 4 +L 5 ;

[0055] Determine the theoretical volume flow and relative volume flow through the inlet regulating valve. The expression of the theoretical volume flow is L 2 =L sum -L m / ρ, the relative volume flow rate expression is L 3 =L 2 / (L max / ρ)×100;

[0056] Among them, L m is the total mass flow rate of the recondenser output, L 4 is the mass flow rate of liquefied natural gas input to the recondenser, L 5 is the mass flow rate of evaporated natural gas input to the recondenser, L 2is the theoretical volume flow rate, L 3 is the relative volume flow rate, ρ is the density of liquefied natural gas, L max is the maximum mass flow rate passing through the inlet regulating valve;

[0057] Divide the flow interval into left-closed and right-open intervals that increase in sequence and do not overlap, namely, a first flow interval, a second flow interval, a third flow interval, and a fourth flow interval;

[0058] If the total volume flow rate is within the first flow rate interval, then determine y=a 1 L 3 2 +a 2 L 3 +a 3 ;

[0059] If the total volume flow is in the second flow interval or the fourth flow interval, then y=a is determined. 4 L 3 2 +a 5 L 3 +a 6 ;

[0060] If the total volume flow rate is within the third flow rate interval, then y=a is determined. 7 L 3 2 +a 8 L 3 +a 9 ;

[0061] Determine the theoretical increase in opening ΔA of the inlet regulating valve 3 , the theoretical increase in opening degree is expressed as ΔA 3 =yA 4 ;

[0062] Determine the actual increase in opening ΔA of the inlet regulating valve 2 , the actual increase in opening degree is expressed as ΔA 2 =KΔA 3 +ΔB;

[0063] Wherein, y is the opening of the inlet regulating valve that needs to be adjusted to maintain the bottom pressure of the recondenser stable at the current flow rate, A 4 is the current opening of the inlet regulating valve, K is the weight coefficient, ΔB is the correction parameter, a 1 ,a 2 ,a 3 ,…,a 9 All are adjustment coefficients;

[0064] Determining whether the actually increased opening is within the actually required increased opening range of the inlet regulating valve;

[0065] If the actual increased opening is not within the actually required increased opening range, and the actual increased opening is less than the lower limit of the actually required increased opening range, the actual increased opening is set to the lower limit of the actually required increased opening range; if the actual increased opening is not less than the lower limit of the actually required increased opening range, the actual increased opening is set to the upper limit of the actually required increased opening range;

[0066] Determine the opening A that the inlet regulating valve needs to reach 2 , the relationship between the opening degree to be achieved is:

[0067] A 2 =ΔA 2 +A 4 .

[0068] On the other hand, adjusting the opening of the inlet regulating valve and the inlet throttle valve of the current high-pressure pump based on the bottom pressure of the recondenser and the opening of the inlet throttle valve of the high-pressure pump comprises:

[0069] Obtaining the opening of the inlet throttle valve;

[0070] controlling the opening of the inlet regulating valve based on a deviation between the opening of the inlet throttle valve and a set opening of the inlet throttle valve;

[0071] Obtaining the bottom pressure of the recondenser;

[0072] The opening degree of the throttle-in valve is controlled based on a deviation of a bottom pressure of the recondenser from a set bottom pressure of the recondenser.

[0073] On the other hand, before starting the current carburetor, it also includes:

[0074] Controlling the current high-pressure pump to perform pressure equalization so that the difference between the pressure of the outlet pipeline of the current high-pressure pump and the pressure of the inlet pipeline of the current vaporizer is lower than a preset pressure difference;

[0075] Determining whether the outlet valve of the high-pressure pump is open;

[0076] If it is on, the process proceeds to the step of starting the current carburetor;

[0077] If not, delay for a first preset time and return to the step of determining whether the outlet valve of the high-pressure pump is open.

[0078] On the other hand, it also includes:

[0079] Determine the difference between the pressure of the liquefied natural gas before the inlet regulating valve of the current high-pressure pump and the target pressure value, and determine the opening of the outlet valve of the current low-pressure pump based on the difference;

[0080] Turn off the current high-pressure pump;

[0081] Determining a total volume flow rate output by all high-pressure pumps, and determining a regulation amount of an inlet regulating valve of the current high-pressure pump according to the total volume flow rate;

[0082] When the volume flow rate output by the current high-pressure pump is within a normal range, adjusting the opening of the inlet regulating valve and the inlet throttle valve of the current high-pressure pump based on the bottom pressure of the recondenser and the opening of the inlet throttle valve of the high-pressure pump;

[0083] Turn off the current low-pressure pump;

[0084] The current carburetor is turned off.

[0085] In order to solve the above technical problems, the present invention also provides a control device for a liquefied natural gas receiving station, comprising:

[0086] Memory for storing computer programs;

[0087] The processor is used to implement the steps of the control method of the liquefied natural gas receiving station when executing the computer program.

[0088] The present application provides a control method and device for a liquefied natural gas receiving station, which relates to the technical field of liquefied natural gas receiving stations, including: starting the current low-pressure pump; determining the opening of the outlet valve of the current low-pressure pump based on the difference between the pressure of the liquefied natural gas before the inlet regulating valve of the current high-pressure pump and the target pressure value; determining the adjustment amount of the inlet regulating valve of the current high-pressure pump according to the total volume flow rate output by all high-pressure pumps; starting the current high-pressure pump; when the volume flow rate output by the current high-pressure pump is within the normal range, adjusting the opening of the inlet regulating valve and the inlet throttle valve of the current high-pressure pump based on the bottom pressure of the recondenser and the opening of the inlet throttle valve of the high-pressure pump; starting the current vaporizer. Automatically control the opening of each device of the receiving station in sequence, and adjust the opening of each valve before opening, so as to realize one-key opening control, reduce manual participation, and improve the working efficiency of the receiving station. BRIEF DESCRIPTION OF THE DRAWINGS

[0089] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the prior art and the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0090] Figure 1 A flow chart of a control method for a liquefied natural gas receiving station provided by the present invention;

[0091] Figure 2 A structural schematic diagram of a liquefied natural gas receiving station provided by the present invention;

[0092] Figure 3 A flowchart of a one-key start provided by the present invention;

[0093] Figure 4 A flow chart of an intelligent control strategy provided by the present invention;

[0094] Figure 5 A flowchart of an agile control strategy provided by the present invention;

[0095] Figure 6 A flow chart of a complex control strategy provided by the present invention;

[0096] Figure 7 A flowchart of a one-key shutdown provided by the present invention;

[0097] Figure 8 A schematic structural diagram of a control device for a liquefied natural gas receiving station provided by the present invention. DETAILED DESCRIPTION

[0098] The core of the present invention is to provide a control method and device for a liquefied natural gas receiving station, which automatically controls the opening of various devices in the receiving station in sequence, and adjusts the opening of each valve before opening, realizing one-button opening control, reducing manual participation and improving the working efficiency of the receiving station.

[0099] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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.

[0100] Figure 1 A flow chart of a control method for a liquefied natural gas receiving station provided by the present invention, Figure 2 A structural schematic diagram of a liquefied natural gas receiving station provided by the present invention;

[0101] The storage tank of the liquefied natural gas receiving station is used to output liquefied natural gas to a low-pressure pump, output natural gas to a recondenser, and the recondenser outputs liquefied natural gas to a high-pressure pump. The liquefied natural gas passes through the low-pressure pump, the inlet throttle valve and the inlet regulating valve, the high-pressure pump and the vaporizer in sequence and is converted into natural gas. The control method of the liquefied natural gas receiving station includes:

[0102] S11: Start the current low-pressure pump;

[0103] S12: determining the difference between the pressure of the liquefied natural gas before the inlet regulating valve of the current high-pressure pump and the target pressure value, and determining the opening of the outlet valve of the current low-pressure pump based on the difference;

[0104] S13: determining the total volume flow rate output by all high-pressure pumps, and determining the adjustment amount of the inlet regulating valve of the current high-pressure pump according to the total volume flow rate;

[0105] S14: Start the current high-pressure pump;

[0106] S15: When the volume flow rate output by the current high-pressure pump is within a normal range, adjusting the opening of the inlet regulating valve and the inlet throttle valve of the current high-pressure pump based on the bottom pressure of the recondenser and the opening of the inlet throttle valve of the high-pressure pump;

[0107] S16: Start the current carburetor.

[0108] It should be noted that the pressure of the low-pressure pump is lower than the pressure of the high-pressure pump, and the specific pressures of the low-pressure pump and the high-pressure pump can be set according to actual needs.

[0109] The whole station process simulation includes the tank area, recondenser, high pressure pump area, open rack vaporizer (ORV) area and the cold storage cycle of the LNG (Liquefied Natural Gas) receiving station. NG is Natural Gas, liquefied natural gas, and BOG is Boil Off Gas.

[0110] (1) Tank area simulation:

[0111] The storage tank is fully contained, with a single effective volume of 160,000m3. The LNG space in the storage tank is divided into gas phase and liquid phase. The key to storage is to maintain the balance of gas and liquid phase pressure in the storage tank. When unloading, LNG is fed into the storage tank from the feed pipeline. Depending on the composition and density, it is selected to feed from the bottom or top of the storage tank. The storage tank is equipped with a built-in low-pressure pump to extract LNG from the storage tank and send it to the downstream device or circulate it in the tank. Each tank is equipped with 4 low-pressure pumps, 3 of which are in use and 1 is in reserve. The BOG gas inside the storage tank enters the BOG main pipe and goes to the BOG compressor.

[0112] Each pump outlet pipeline is equipped with a flow control valve, which is a butterfly valve, used to adjust the outlet flow of each running pump and cut off the output in an emergency. To protect the low-pressure pump, a minimum flow control valve is also installed on the outlet pipeline of each pump for pump reflux operation to ensure that the minimum output flow of the low-pressure pump is 280m³ / h to prevent the pump from being blocked.

[0113] (2) Recondenser simulation:

[0114] The recondenser has two working modes: recondenser recovers BOG and recondenser does not recover BOG.

[0115] The gas from the BOG main first enters the desuperheater of the BOG compressor inlet unit, and exchanges heat with a stream of LNG from the low-pressure LNG main to reduce the temperature of the BOG, thereby effectively reducing the temperature of the compressor inlet and outlet. Small LNG droplets are taken out of the desuperheater along with the gas and separated in the inlet separator. The pressure of BOG after compression is about 0.76MPaG, and it enters the recondenser from the top, directly contacts and fully exchanges heat with the LNG from the low-pressure LNG main, and is completely condensed into LNG, and then discharged from the bottom of the recondenser into the manifold leading to the high-pressure pump.

[0116] When the recondenser does not recover BOG, the BOG gas is compressed by the BOG compressor and then transmitted to the outside.

[0117] The recondenser has level, pressure and flow controllers.

[0118] Recondenser liquid level control: The recondenser liquid level is controlled at 50%-75%. When the recondenser liquid level is low, reduce the BOG compressor load or increase the amount of LNG entering the recondenser to increase the recondenser liquid level; in the case of high liquid level, the liquid level controller directly acts on the liquid level regulating valve to introduce high-pressure external gas from the high-pressure external main pipe into the top of the recondenser to reduce the container liquid level.

[0119] Recondenser top pressure control: When the pressure at the top of the recondenser increases, the pressure is adjusted by the pressure controller, and the excess gas is released to the BOG main pipe through the pressure valve. The set value of the pressure controller is 0.76MPaG, the controlled variable is the recondenser top pressure, and the manipulated variable is the pressure valve opening.

[0120] Recondenser bottom pressure control: Pressure control during normal operation: The recondenser bottom pressure (high-pressure pump suction pressure) is controlled by the controller of the LNG to high-pressure pump regulating valve. The LNG to recondenser regulating valve and its stop valve are set on the recondenser bypass, of which the large butterfly valve is manually adjusted and the stop valve is automatically adjusted. After the butterfly valve is manually set to a certain opening, the stop valve is controlled by the pressure controller to adjust the pressure after the LNG to high-pressure pump regulating valve. The pressure setting value is 0.75MPaG.

[0121] Recondenser LNG flow control: When the recondenser is in automatic mode, the amount of LNG entering the recondenser for recondensing BOG is controlled by the controller to ensure that the BOG is completely condensed while maintaining the recondenser liquid level at 55%-75%.

[0122] (3) High-pressure pump and open-frame vaporizer (ORV) area:

[0123] LNG enters the inlet of the high-pressure pump from the low-pressure manifold, is pressurized by the high-pressure pump, and enters the open rack vaporizer (ORV) manifold through the high-pressure pump outlet pipeline. It is vaporized in the open rack vaporizer (ORV) and then transmitted out.

[0124] During the operation of the high-pressure pump, there is a flow controller on the outlet pipeline, which adjusts the flow of the pump back to the storage tank by controlling the opening of the regulating valve on the minimum flow return pipeline to ensure that the high-pressure pump operates above the minimum flow, which is 280m³ / h. The output flow of the high-pressure pump is controlled by the open-frame vaporizer (ORV) inlet flow controller and its regulating valve to ensure the smooth operation of the high-pressure pump and the external transmission requirements.

[0125] During the shutdown of the high-pressure pump, close the high-pressure pump outlet valve and open the return valve to a certain degree to maintain the high-pressure pump cold cycle, so that the high-pressure pump is in standby mode. The circulating cold LNG is passed from the high-pressure pump inlet through the pump barrel to the zero output pipeline to keep the high-pressure pump cold.

[0126] (4) LNG receiving station cold storage cycle:

[0127] The cold storage cycle of the LNG receiving station can be put into use by opening the cold storage flow control valve of the LNG receiving station. The liquefied natural gas used for cold storage of the LNG receiving station is provided by the low-pressure pump in the LNG storage tank, and this part of LNG is returned to the low-pressure main pipe through the cold storage circulation pipeline. The cold storage circulation flow can be set in the simulation.

[0128] Establish the steady-state and dynamic mechanism model of the LNG receiving station; then, design the control scheme of the pressure before and after the LNG to high-pressure pump regulating valve during the one-button start-stop line process, take the pressure stability before and after the LNG to high-pressure pump inlet regulating valve as the optimization goal, and stabilize the pressure before and after the LNG to high-pressure pump inlet regulating valve near the set value by controlling the low-pressure pump outlet butterfly valve, reflux valve and LNG to high-pressure pump inlet regulating valve; finally, write the one-button start-stop line sequence control scheme and apply the pressure control scheme to the pressure control system of the low-pressure pipeline network during the one-button start-stop line process. Reduce the workload of on-site operators, improve the efficiency and safety of pressure control, shorten the time for low and high-pressure pumps to maintain reflux, and improve the economic benefits of the enterprise.

[0129] During the opening process, start the low-pressure pump, high-pressure pump and carburetor in sequence. The high-pressure pump can only be started after the low-pressure pump and the pressure between the low-pressure pump and the high-pressure pump are adjusted to the right position. The carburetor can only be started after the high-pressure pump is started and the pressure between the high-pressure pump and the carburetor is adjusted to the right position. Starting in sequence can avoid affecting the vaporization due to the wrong starting sequence.

[0130] Based on the above embodiments:

[0131] Figure 3 A flowchart of a one-key start provided by the present invention;

[0132] In some embodiments, the liquefied natural gas receiving station further comprises a seawater pump, the seawater pump being used to output seawater to the vaporizer to provide heat for vaporization of the natural gas;

[0133] Before starting the current low-pressure pump, also include:

[0134] Start the current seawater pump and determine the startup status of the current seawater pump;

[0135] When the outlet valve of the current seawater pump is in an open state and the motor of the current seawater pump is in a started state, entering the step of starting the current low-pressure pump;

[0136] When the outlet valve of the current seawater pump is not in the open state or the motor of the current seawater pump is not in the started state, the first preset time is delayed and the process returns to the step of determining the start state of the current seawater pump.

[0137] The seawater pump outputs normal temperature seawater. After the vaporizer vaporizes the liquid natural gas into natural gas, the normal temperature seawater becomes low temperature seawater. The specific normal temperature setting temperature is set according to the actual situation.

[0138] Therefore, the process of controlling the start of the seawater pump is:

[0139] Pre-select seawater pump, open frame vaporizer (ORV), low pressure pump and high pressure pump.

[0140] After the preselection is successful, it is detected that the "one-key line start" button is pressed (the one-key line start procedure begins).

[0141] Continue to detect whether the "One-key startup forced termination" button is pressed (forced to stop the one-key startup program). If not detected, keep the detection status.

[0142] Start the sea water pump.

[0143] Execution judgment: the seawater pump outlet valve is in the open state and the seawater pump motor is in the starting state (seawater pump startup is completed).

[0144] If the conditions are met, the delay is 10s and the delay is completed.

[0145] If the conditions are not met, the judgment is executed: the judgment timer is less than 125s (waiting for the seawater pump to start). If the conditions are met, the execution is delayed by 1s.

[0146] In some embodiments, starting the current low-pressure pump includes:

[0147] Start the current low-pressure pump and obtain the opening of the outlet valve of the current low-pressure pump or the outlet flow of the current low-pressure pump;

[0148] When the opening of the outlet valve of the current low-pressure pump is greater than the first preset opening or the outlet flow rate of the current low-pressure pump is greater than the first preset flow rate, determining the startup state of the motor of the current low-pressure pump;

[0149] When the outlet flow of the current low-pressure pump is greater than the second preset flow and the motor of the current low-pressure pump is in a starting state, it is determined that the current low-pressure pump is started successfully and the second preset flow is less than the first preset flow;

[0150] When the outlet flow of the current low-pressure pump is not greater than the second preset flow or the motor of the current low-pressure pump is not in the starting state, and the starting time of the current low-pressure pump does not exceed the second preset time, delay the first preset time and return to the step of determining the starting state of the motor of the current low-pressure pump;

[0151] If the current start-up time of the low-pressure pump exceeds the second preset time, the liquefied natural gas receiving station is stopped.

[0152] Wait for the low-pressure pump outlet valve feedback opening > 5% or the low-pressure pump outlet flow rate > 300m 3 / h.

[0153] Execution judgment: low pressure pump outlet flow> 200m 3 / h and the low-pressure pump motor is in the starting state (the judgment condition for the successful start of the low-pressure pump is that the outlet flow rate> 200m 3 / h and the low-pressure pump motor is in the started state).

[0154] If the conditions are met, the execution will be delayed for 10 seconds;

[0155] Otherwise, execute judgment: judgment timer < 25s (wait for low-pressure pump to start). If the condition is met, delay 1s.

[0156] In some embodiments, the liquefied natural gas receiving station further comprises a pressure detector, the pressure detector being used to detect the pressure of the liquefied natural gas before the inlet regulating valve of the high-pressure pump;

[0157] Based on the difference, the opening degree of the outlet valve of the current low-pressure pump is determined, including:

[0158] Determine whether the pressure collected by the current pressure detector is lower than the lower limit of the low-pressure pipe network pressure;

[0159] If it is lower than the lower limit of the low-pressure pipe network pressure, it is determined whether the difference between two adjacent pressures collected by the pressure detector is less than the first preset pressure;

[0160] If the difference between two adjacent pressures is not less than the first preset pressure, the opening of the outlet valve of the current low-pressure pump is controlled to increase by a first percentage;

[0161] If the difference between two adjacent pressures is less than the first preset pressure, the opening of the outlet valve of the current low-pressure pump is controlled to increase by a second percentage, where the second percentage is greater than the first percentage;

[0162] If it is not lower than the lower limit of the network pressure, then determine whether the pressure collected by the pressure detector is higher than the upper limit of the low-pressure network pressure;

[0163] If it is higher than the upper limit of the low-pressure pipe network pressure, it is determined whether the difference between two adjacent pressures collected by the pressure detector is less than the first preset pressure;

[0164] If the difference between two adjacent pressures is not less than the first preset pressure, the opening of the outlet valve of the current low-pressure pump is controlled to decrease by a second percentage;

[0165] If the difference between two adjacent pressures is less than a first preset pressure, the opening of the outlet valve of the current low-pressure pump is controlled to decrease by a first percentage;

[0166] Determine whether the current opening of the outlet valve of the low-pressure pump is greater than the maximum opening limit;

[0167] If it is greater than the maximum opening limit, the current opening of the outlet valve of the current low-pressure pump is maintained;

[0168] If it is not greater than the maximum opening limit, the third preset time is delayed, and the process returns to the step of determining whether the pressure collected by the pressure detector is lower than the lower limit of the low-pressure pipe network pressure.

[0169] like Figure 4 As shown, Figure 4 A flow chart of an intelligent control strategy provided by the present invention;

[0170] The LNG storage tank delivers LNG to the downstream low-pressure pipeline network through a low-pressure pump. The intelligent control strategy includes a main control unit and a pressure detector I. The pressure detector I is used to detect the liquid pressure before the LNG to high-pressure pump inlet regulating valve. The main control unit includes a low-pressure pump outlet valve and an expert controller. The pressure detector I is connected to the intelligent controller, and the intelligent controller is connected to the low-pressure pump outlet valve to control the opening and closing of the low-pressure pump outlet valve. The specific steps of the intelligent controller are as follows:

[0171] Step 1: Determine whether the pressure value of pressure detector I is lower than 1.15MPaG (lower limit of low-pressure pipe network pressure). If it is lower than 1.15MPaG, proceed to step 2. Otherwise, proceed to step 5 (perform operation steps according to the deviation between actual pressure and target pressure).

[0172] Step 2: Determine whether the pressure difference of the pressure detector I before and after is ≥-0.02MPaG (pressure difference ≥-0.02MPaG indicates that the pressure of the low-pressure pipe network is lower than the target pressure and the pressure is restored in time, and the opening of the low-pressure pump outlet valve will be slightly increased, i.e. 1%). If ≥-0.02MPaG, execute step 3. Otherwise, execute step 4 (pressure difference <-0.02MPaG indicates that the pressure of the low-pressure pipe network is lower than the target pressure and the pressure is not restored in time, and the opening of the low-pressure pump outlet valve needs to be greatly increased, i.e. 1.5%).

[0173] Step 3: Increase the opening of the low-pressure pump outlet valve by 1%. Go to step 9.

[0174] Step 4: Increase the opening of the low-pressure pump outlet valve by 1.5%. Go to step 9.

[0175] Step 5: Check whether the pressure value of the pressure detector I is higher than 1.3MPaG (low-pressure pipe network pressure upper limit). If it is higher than 1.3MPaG (low-pressure pipe network pressure upper limit), go to step 6. Otherwise, go to step 9.

[0176] Step 6: Check whether the pressure difference of detector I before and after is ≥0.02MPaG (pressure difference ≥0.02MPaG indicates that the pressure of the low-pressure pipe network is higher than the target pressure and the pressure recovery is not timely, and the opening of the low-pressure pump outlet valve will be greatly reduced, that is, 1.5%). If it is ≥0.02MPaG, execute step 7. Otherwise, execute step 8 (pressure difference <0.02MPaG indicates that the pressure of the low-pressure pipe network is higher than the target pressure and the pressure recovery is timely, and the opening of the low-pressure pump outlet valve needs to be slightly reduced, that is, 1.5%).

[0177] Step 7: Control the opening of the low-pressure pump outlet valve to decrease by 1.5%. Go to step 9.

[0178] Step 8: Control the opening of the low-pressure pump outlet valve to decrease by 1%. Go to step 9.

[0179] Step 9: Determine whether the opening of the low-pressure pump outlet valve is ≤35% (the maximum opening limit of the low-pressure pump outlet valve). If the condition is met, execute step 11, otherwise execute step 10.

[0180] Step 10: Keep the current opening and proceed to step 11.

[0181] Step 11: Delay for 3 seconds (wait for the low-pressure pipe network pressure response). After the delay is over, execute step 1.

[0182] In some embodiments, the liquefied natural gas receiving station further includes an inlet isolation valve of a high-pressure pump and a compressor, wherein the inlet isolation valve of the high-pressure pump is arranged between the outlet of the low-pressure pump and the condensation port of the recondenser, the compressor is arranged between the gas outlet of the storage tank and the inlet of the recondenser, the outlet of the recondenser is connected to the outlet of the inlet regulating valve, and the compressor is used to compress the gas output from the storage tank and output it to the recondenser;

[0183] Before starting the high pressure pump, also include:

[0184] Before starting the current high pressure pump, also include:

[0185] The opening degree of the inlet isolation valve of the current high-pressure pump is set according to the number of all high-pressure pumps started in the liquefied natural gas receiving station;

[0186] When the opening of the inlet isolation valve of the current high-pressure pump is within a preset opening range centered on the set opening, entering a step of determining the adjustment amount of the inlet regulating valve of the current high-pressure pump according to the total volume flow;

[0187] Start the current high pressure pump, including:

[0188] Determine whether the inlet regulating valve meets the opening condition of the high-pressure pump after adjustment;

[0189] If satisfied, the current high-pressure pump is started;

[0190] Determining whether the current output volume flow rate of the high-pressure pump is greater than a third preset flow rate and whether the motor of the current high-pressure pump is in a starting state;

[0191] If the output volume flow rate is greater than the third preset flow rate and the motor of the current high-pressure pump is in a starting state, it is determined that the current high-pressure pump is started successfully;

[0192] If the output volume flow rate is not greater than the third preset flow rate and the motor of the current high-pressure pump is not in the started state, the preset time is delayed and the step of determining whether the output volume flow rate of the current high-pressure pump is greater than the third preset flow rate and whether the motor of the high-pressure pump is in the started state is returned.

[0193] Set the opening of the isolation valve according to the number of high-pressure pumps started. 1 %. End condition: Wait for the isolation valve to feedback the opening (a 1 -2)~(a 1 +2)% (the valve feedback signal has a deviation of ±2%).

[0194] Call the control valve agile control program. The initial opening of the control valve is set.

[0195] Execution judgment: the pressure after the regulating valve is ≥0.80MPaG or the valve feedback opening is -0.8<(A2 -A 4 )<0.8 (prerequisite for starting the high pressure pump).

[0196] If the condition is not met: the judgment is executed, and the judgment timer is less than 25s (waiting for the pressure after the regulating valve to be greater than or equal to 0.80MPaG or the valve feedback opening -0.8<(A 2 -A 4 )<0.8), if the condition is met, the execution is delayed for 1s, and it is judged again whether the prerequisite for starting the high-pressure pump is met.

[0197] Start the high-pressure pump when conditions are met.

[0198] Execution judgment: The high-pressure pump output volume flow is normal> 200m 3 / h and the high-pressure pump motor is in the starting state (the judgment condition for the normal start of the high-pressure pump is that the output volume flow of the high-pressure pump is normal> 200m 3 / h and the high-pressure pump motor is in the started state).

[0199] If the condition is not met, execute step 25, then execute judgment: judgment timer < 25s (wait for the high pressure pump to start). If the condition is met, execute delay 1s, and re-judge the high pressure pump output volume flow rate to be normal > 200m 3 / h and the high-pressure pump motor is in the started state.

[0200] In some embodiments, determining the total volume flow rate output by all high pressure pumps includes:

[0201] Get the starting state of the motor of the i-th high-pressure pump and the output volume flow L i ;

[0202] When the motor of the high-pressure pump is in the starting state, if the volume flow rate output by the ith high-pressure pump is not within the starting state volume flow rate range, the volume flow rate less than the lower limit value of the starting state volume flow rate range is set to the lower limit value, and the volume flow rate greater than the upper limit value of the starting state volume flow rate range is set to the upper limit value;

[0203] When the motor of the high-pressure pump is in an unstarted state, if the volume flow rate output by the i-th high-pressure pump is not within the unstarted state volume flow rate range, a volume flow rate less than a lower limit value of the unstarted state volume flow rate range is set as a lower limit value, and a volume flow rate greater than an upper limit value of the unstarted state volume flow rate range is set as an upper limit value;

[0204] Determine the total volume flow rate output by all high-pressure pumps. The expression for the total volume flow rate is:

[0205] L sum =ΣL i +ΔL;

[0206] Among them, L sum is the total volume flow rate, L i is the volume flow rate output by the i-th high-pressure pump, ΔL is the preset volume flow rate change value when the high-pressure pump is started or stopped, i∈[1,2,3,…,n], there are n high-pressure pumps in total;

[0207] Determine the adjustment amount of the inlet regulating valve of the current high-pressure pump according to the volume flow, including:

[0208] Determine the total mass flow rate of the recondenser output. The expression for the total mass flow rate is:

[0209] L m =1000×L 4 +L 5 ;

[0210] Determine the theoretical volume flow and relative volume flow through the inlet control valve. The expression for the theoretical volume flow is L 2 =L sum -L m / ρ, the expression of relative volume flow rate is L 3 =L 2 / (L max / ρ)×100;

[0211] Among them, L m is the total mass flow rate of the recondenser output, L 4 is the mass flow rate of liquefied natural gas input to the recondenser, L 5 is the mass flow rate of evaporated natural gas input to the recondenser, L 2 is the theoretical volume flow rate, L 3 is the relative volume flow rate, ρ is the density of liquefied natural gas, L max is the maximum mass flow rate passing through the inlet regulating valve;

[0212] Divide the flow interval into left-closed and right-open intervals that increase in sequence and do not overlap, namely, a first flow interval, a second flow interval, a third flow interval, and a fourth flow interval;

[0213] If the total volume flow rate is in the first flow interval, then determine y=a 1 L 3 2 +a 2 L 3 +a 3 ;

[0214] If the total volume flow rate is in the second flow interval or the fourth flow interval, then y=a 4 L 3 2 +a 5 L 3 +a6 ;

[0215] If the total volume flow rate is in the third flow rate interval, then determine y=a 7 L 3 2 +a 8 L 3 +a 9 ;

[0216] Determine the theoretical increase in opening ΔA of the inlet control valve 3 , the theoretical increase in opening is related to ΔA 3 =yA 4 ;

[0217] Determine the actual increase in opening of the inlet control valve ΔA 2 , the actual increase in opening is related to ΔA 2 =KΔA 3 +ΔB;

[0218] Where y is the opening of the inlet regulating valve to maintain the bottom pressure of the recondenser stable at the current flow rate, A 4 is the current opening of the inlet regulating valve, K is the weight coefficient, and ΔB is the correction parameter;

[0219] Determine whether the actual increase in opening is within the actual required increase in opening range of the inlet regulating valve;

[0220] If the actual increase in opening is not within the range of the opening that actually needs to be increased, and the actual increase in opening is less than the lower limit of the range of the opening that actually needs to be increased, the actual increase in opening is set to the lower limit of the range of the opening that actually needs to be increased; if the actual increase in opening is not less than the lower limit of the range of the opening that actually needs to be increased, the actual increase in opening is set to the upper limit of the range of the opening that actually needs to be increased;

[0221] Determine the opening degree that the inlet regulating valve needs to reach. The relationship between the opening degree that needs to be reached is:

[0222] A 2 =ΔA 2 +A 4 .

[0223] like Figure 5 As shown, Figure 5 A flow chart of an agile control strategy provided by the present invention.

[0224] There is an LNG to high-pressure pump inlet regulating valve on the pipeline from the storage tank to the high-pressure pump area, which is responsible for controlling the LNG pressure at the high-pressure pump inlet at 0.75MPaG. The agile control method includes a main control unit and a flow detector. The flow detector is used to detect the volume flow rate of the liquid output by the high-pressure pump. The main control unit includes a regulating valve and an agile controller. The agile controller is connected to the regulating valve to control the opening and closing of the regulating valve. When the output flow of the high-pressure pump area changes within a large range, the regulating valve opening is controlled in real time to quickly adjust the high-pressure pump inlet pressure to 0.75MPaG. The specific steps of agile control are as follows:

[0225] Step 1: Determine the status of all high-pressure pump motors. If the motor is enabled, proceed to step 2; if not, proceed to step 4.

[0226] Step 2: Determine whether the output volume flow rate of the high-pressure pump (starting state) is 150m 3 / h—480m 3 / h (the output volume flow rate of the high-pressure pump in the normal startup state is between 150m 3 / h—480m 3 / h. If the output volume flow rate of the high-pressure pump is not in this range, the output volume flow rate data of the high-pressure pump is obtained according to the situation). If the conditions are met, execute step 6, otherwise execute step 3.

[0227] Step 3: If the high pressure pump output volume flow rate is ≤150m 3 / h (the output volume flow rate of the high-pressure pump in normal startup state is not less than 150m 3 / h), then the volume flow rate of this high-pressure pump is L i =150, if the high pressure pump output volume flow ≥480m 3 / h (the output volume flow rate of the high-pressure pump in normal startup state is not higher than 480m 3 / h), then the volume flow rate of this high-pressure pump is L i =480m 3 / h. Go to step 7.

[0228] Step 4: Determine whether the volume flow rate of the high-pressure pump (stop state) is 0m 3 / h—30m 3 / h (the output volume flow rate of the high-pressure pump in the normal stop state is 0m 3 / h—30m 3 / h. If the output volume flow rate of the high-pressure pump is not within this range, the output volume flow rate data of the high-pressure pump is obtained according to the situation). If the conditions are met, execute step 6, otherwise execute step 5.

[0229] Step 5: If the high pressure pump output volume flow is ≤ 0m 3 / h (the output volume flow rate of the high-pressure pump in normal stop state is not less than 0m 3 / h), then the volume flow rate of this high-pressure pump is L i =0, if the output volume flow of the high-pressure pump is ≥30m3 / h (the output volume flow of the high-pressure pump in the normal stop state is not higher than 30m3 / h), then the volume flow of this high-pressure pump L i =30m 3 / h. Go to step 7.

[0230] Step 6: Output volume flow rate L of this high pressure pump i The data of the volume flow detection instrument. Go to step 8.

[0231] Step 7: Calculate the total volume flow rate of the high-pressure pump area: L sum =∑L i +ΔL.

[0232] Among them, L sum is the total volume flow rate of the high-pressure pump output, L i is the volume flow rate output by each high-pressure pump, and ΔL is the preset volume flow rate change value when the high-pressure pump is started or stopped, which is used as the feedforward adjustment of the LNG to the high-pressure pump inlet regulating valve, so that the high-pressure pump inlet pressure can be quickly adjusted to around 0.75MPaG when the high-pressure pump is started or stopped. Execute step 8.

[0233] Step 8: Calculate the total mass flow of liquid phase output in the recondenser zone: L m =1000×L 4 +L 5 .

[0234] Among them, L m is the total mass flow rate of the recondenser output, L 4 is the LNG mass flow rate input to the recondenser, L 5 Enter the BOG mass flow rate for the recondenser. Go to step 9.

[0235] Step 9: Calculate the theoretical LNG volume flow rate through the control valve: L 2 =L sum -L m / ρ.

[0236] Among them, L 2 is the volume flow through the regulating valve; ρ is the density of LNG, ρ=425kg / m 3 . Go to step 10.

[0237] Step 10: Calculate the relative flow through the control valve: L 3 =L 2 / (L max / ρ)×100;

[0238] wherein, L 3 is the relative volume flow rate through the regulating valve; L max is the maximum mass flow rate through the regulating valve. Perform Step 11.

[0239] Step 11: Calculate the additional opening ΔA required for the regulating valve according to the working flow characteristic curve formula of the regulating valve 2 .

[0240] The calculation process is as follows: (affected by the actual working conditions, the working flow characteristic curve of the regulating valve changes significantly with the change of the passing flow rate. In this patent, the working flow characteristic curve of the regulating valve is divided into three segments according to the passing flow rate, that is, 0 ≤ L sum < 400, 400 ≤ L sum ≤ 800 or 2000 ≤ L sum < 2400 and 800 < LSUM < 2000):

[0241] If 0 ≤ L sum < 400:

[0242] y = a 1 L 32 + a 2 L 3 + a 3 ;

[0243] If else 400 ≤ L sum ≤ 800 or 2000 ≤ LSUM < 2400:

[0244] y = a 4 L 32 + a 5 L 3 + a 6 ;

[0245] else 800 < L sum < 2000:

[0246] y = a 7 L 32 + a 8 L 3 + a 9 ;

[0247] where a 1 , a 2 , a 3 , …, a 9 are adjustment coefficients, and the adjustment coefficients are the coefficients identified from the data and model of the working flow characteristic curve of the regulating valve;

[0248] The additional opening required for the regulating valve through theoretical calculation is ΔA3 :

[0249] ΔA 3 = y - A 4

[0250] where A 4 is the current opening of the regulating valve; ΔA 3 is the opening that the regulating valve needs to increase through theoretical calculation.

[0251] The actual opening that the regulating valve needs to increase is ΔA 2 :

[0252] ΔA 2 = KΔA 3 + ΔB

[0253] where K is the weight coefficient, and its value range is: 0 ≤ K ≤ 1, with the initial K = 1; ΔB is the manual correction parameter, and its value range is: -6 ≤ ΔB ≤ 6, with the initial ΔB = 0. After the calculation is completed, step 12 is executed.

[0254] Step 12: Execute the judgment program: Min ≤ ΔA 2 ≤ Max (Min is the lower limit of the actual opening increase required for the regulating valve, and Max is the upper limit of the actual opening increase required for the regulating valve. This step is to prevent excessive single - time changes in the opening of the regulating valve). If the condition is met, step 16 is executed; otherwise, step 13 is executed.

[0255] Step 13: Execute the judgment program: ΔA 2 < Min (when the actual opening increase required for the regulating valve is not within the upper and lower limit intervals, take the upper limit value or the lower limit value). If the condition is met, step 14 is executed; otherwise, step 15 is executed.

[0256] Step 14: ΔA 2 = Min, and step 16 is executed.

[0257] Step 15: ΔA 2 = Max, and step 16 is executed.

[0258] Step 16: Retain ΔA 2 . Execute step 17.

[0259] Step 17: Calculate the opening A that the regulating valve needs to reach 2 : A 2 = ΔA 2 + A 4 ;

[0260] where A 2 is the opening that the regulating valve needs to reach after the current calculation process.

[0261] Execute the judgment program: A2 <40 (the maximum opening limit of the regulating valve is 40), if the condition is met, execute step 19, otherwise execute step 18.

[0262] Step 18: Set the desired opening of the control valve as the upper limit of the valve opening.

[0263] A 2 =Upper_limit.

[0264] Where Upper_limit is the maximum opening of the control valve. Go to step 19.

[0265] Step 19: Adjust the regulating valve opening to A 2 .

[0266] The working flow characteristic curve of the LNG to high-pressure pump inlet regulating valve is calculated by the method of data and mechanism fusion. The working flow characteristic curve of the valve describes the relationship between the valve opening and the flow rate. This curve is usually affected by many factors, including the design of the valve itself, the characteristics of the pipeline system, and the properties of the fluid. Traditional physical models may not be completely accurate or difficult to capture all complex nonlinear effects, and the data and mechanism fusion-driven method can provide more accurate description and prediction capabilities through a large amount of actual operation data. The specific steps are as follows: data acquisition, data preprocessing, establishment of data-driven model, establishment of mechanism model, fusion of mechanism model and data model and parameter optimization, and model verification and adjustment.

[0267] Control valve opening and flow historical data set , x n is the opening of the regulating valve DF01, V n It is the volume flow through the regulating valve DF01 at the current opening.

[0268] Calculate relative flow data set and , where x n is the relative opening of the regulating valve DF01, X n is the current opening of the regulating valve DF01, X max It is the maximum valve opening when the regulating valve DF01 reaches the upper limit of the flow capacity under the pressure difference of 425~450kPa. n To adjust the relative flow rate of DF01, V max is the current volume flow through the control valve, V max It is the maximum volume flow rate that the regulating valve can pass under a pressure difference of 425~450kPa.

[0269] The relationship between the relative opening of the control valve DF01 and the corresponding relative flow rate can form a data set: .

[0270] According to the working characteristic curve of the butterfly valve, the fitting function is selected in the form of Y=C+bx. The goal is to minimize the error square sum S. .

[0271] Take the partial derivatives of C and b and set them to 0, and get the regularized equation ;

[0272] Solving the above equations gives the estimated values ​​of C and b, where C is the intercept of the fitting function, b is the slope of the fitting function, and Y n Substitute C into a=e for the actual measured value of the flow rate. C To obtain the final fitting parameter a and obtain the valve working flow characteristic curve , y is the fitted flow value, and x is the actual relative opening of the valve. Due to the distortion of the valve flow characteristics, the flow characteristic curve is divided into different stages through historical data for data fitting to obtain the complete working flow characteristic curve of the valve.

[0273] In some embodiments, adjusting the opening of the inlet regulating valve and the inlet throttle valve of the current high-pressure pump based on the bottom pressure of the recondenser and the opening of the inlet throttle valve of the high-pressure pump includes:

[0274] Get the opening of the inlet throttle valve;

[0275] controlling the opening of the inlet regulating valve based on a deviation between the opening of the inlet throttle valve and a set opening of the inlet throttle valve;

[0276] Get the bottom pressure of the recondenser;

[0277] The opening degree of the throttle-in valve is controlled based on a deviation of the bottom pressure of the recondenser from a set bottom pressure of the recondenser.

[0278] like Figure 6 As shown, Figure 6 A flow chart of a complex control strategy provided by the present invention.

[0279] The LNG storage tank delivers LNG to the downstream pipeline network through a low-pressure pump. A branch of the LNG main pipe is diverted to the recondenser, and the other branch is used as a bypass of the recondenser. The bypass is equipped with an LNG to high-pressure pump inlet regulating valve and its bypass throttle valve. Two PID loops are designed. PID-I and PID-II form a complex pressure control after the high-pressure pump inlet regulating valve.

[0280] The process value PV of PID-II is the LNG pressure at the bottom of the recondenser, the set value SP is 0.75MPaG, the controller is set to reverse action, and the operating variable is the throttle opening of the LNG to high-pressure pump inlet. The principle is that when the LNG pressure at the bottom of the recondenser deviates from the set value, the LNG flow rate at the bottom of the recondenser is changed by adjusting the throttle opening of the LNG to high-pressure pump inlet, which directly acts on the pressure at the bottom of the recondenser, so as to achieve the purpose of maintaining the pressure at the bottom of the recondenser at about 0.75MPaG within the adjustable range of the throttle valve at the inlet of the LNG to high-pressure pump, and maintaining the internal liquid level of the recondenser stable.

[0281] The PID-I process value PV is the throttle valve opening from LNG to the high-pressure pump inlet, the set value SP is 40%, the controller is set to positive action, and the operating variable is the opening of the regulating valve from LNG to the high-pressure pump inlet. The principle is that when the throttle valve opening from LNG to the high-pressure pump inlet deviates from the set value, the LNG flow rate at the bottom of the recondenser is changed by adjusting the opening of the regulating valve from LNG to the high-pressure pump inlet, which directly acts on the pressure at the bottom of the recondenser. At this time, PID-II will adjust the throttle valve opening from LNG to the high-pressure pump inlet to maintain the pressure at the bottom of the recondenser at 0.75MPaG. Until the throttle valve opening reaches about 40%, the regulating valve will no longer act, achieving the purpose of indirectly maintaining the throttle valve opening at 40% and maintaining the throttle valve's maximum adjustment capacity.

[0282] PID-I and PID-II are put into operation at the same time, which can not only keep the bottom pressure of the recondenser stable at 0.75MPaG, but also maintain the maximum adjustment capacity of the throttle valve from LNG to the inlet of the high-pressure pump. The block diagram of the PID-I and PID-II control loop is as follows: Figure 6 shown.

[0283] In some embodiments, before starting the current vaporizer, the method further includes:

[0284] Controlling the current high-pressure pump to equalize the pressure so that the difference between the pressure of the outlet pipeline of the current high-pressure pump and the pressure of the inlet pipeline of the current vaporizer is lower than a preset pressure difference;

[0285] Determine whether the outlet valve of the high-pressure pump is open;

[0286] If it is on, the process proceeds to the step of starting the current carburetor;

[0287] If not, the first preset time is delayed and the process returns to the step of determining whether the outlet valve of the high-pressure pump is open.

[0288] Perform pressure equalization with the high-pressure pump. Wait until the pressure difference between the high-pressure pump outlet pipeline and the ORV inlet pipeline is less than 2MPa.

[0289] Execution judgment: whether the high-pressure pump outlet valve is open (a prerequisite for ORV startup).

[0290] If the conditions are met.

[0291] Otherwise, the judgment is executed: the judgment timer is less than 25s. If the condition is met, the execution delay is 1s, otherwise the execution delay is 10s.

[0292] In some embodiments, it also includes:

[0293] Determine the difference between the pressure of the liquefied natural gas before the inlet regulating valve of the current high-pressure pump and the target pressure value, and determine the opening of the outlet valve of the current low-pressure pump based on the difference;

[0294] Turn off the current high-pressure pump;

[0295] Determine the total volume flow rate output by all high-pressure pumps, and determine the adjustment amount of the inlet regulating valve of the current high-pressure pump according to the total volume flow rate;

[0296] When the volume flow rate output by the current high-pressure pump is within a normal range, adjusting the opening of the inlet regulating valve and the inlet throttle valve of the current high-pressure pump based on the bottom pressure of the recondenser and the opening of the inlet throttle valve of the high-pressure pump;

[0297] Turn off the current low-pressure pump;

[0298] Turn off the current carburetor.

[0299] Figure 7 A flowchart of a one-key shutdown provided by the present invention;

[0300] like Figure 7 As shown in the figure, a sequential control scheme for stopping the vaporization and export production line of an LNG receiving station with one button is shown. First, the high-pressure pump and the open-rack vaporizer (ORV) are linked to stop the high-pressure pump from exporting and adjust it to the reflux state, and the open-rack vaporizer (ORV) maintains the seawater input. Then, the high-pressure pump is stopped; then, the low-pressure pump is stopped; and finally, the seawater pump is stopped.

[0301] Step 1: Pre-select seawater pump, open rack vaporizer (ORV), low pressure pump and high pressure pump. If pre-selection is successful, proceed to step 2.

[0302] Step 2: Detect that the "one-key stop line" button is pressed (start the one-key stop line procedure), and execute steps 3 and 4.

[0303] Step 3: Continue to detect whether the "One-key line stop forced termination" button is pressed (forcibly stop the one-key line stop program). If detected, execute step 31. Otherwise, keep the detection status.

[0304] Step 4: Call the regulating valve upstream pressure expert control program (flag (1)) and proceed to step 13.

[0305] Step 5: Call the complex control program of the pressure after the regulating valve (flag position (1)).

[0306] Step 6: Stop the high-pressure pump. After detecting that the high-pressure pump outlet valve is fully closed, suspend the complex control program of the pressure after the regulating valve (flag bit (0)), and call the agile control program of the regulating valve. After a delay of 10s, stop the high-pressure pump and execute step 7.

[0307] Step 7: Execute the judgment procedure: The output volume flow of the high-pressure pump is less than 100m³ / h, and the high-pressure pump motor is in the off state (the judgment condition for the high-pressure pump to stop is that the output volume flow of the high-pressure pump is less than 100m³ / h, and the high-pressure pump motor is in the off state). If the condition is met, execute step 10; otherwise, execute step 8.

[0308] Step 8: Execute the judgment procedure: timer < 25s (wait for the high pressure pump to stop). If the condition is met, execute step 9, otherwise execute step 31.

[0309] Step 9: Delay for 1 second. After the delay is over, execute step 7.

[0310] Step 10: Delay for 10 seconds. After the delay is over, execute steps 11 and 12.

[0311] Step 11: Set the opening of the isolation valve to a1% according to the number of high-pressure pumps started. End condition: Wait for the valve feedback opening (a1-2)~(a1+2)% (the valve feedback signal has a deviation of ±2%). Execute step 13.

[0312] Step 12: Call the complex control program of the pressure after the regulating valve (flag (1)). Go to step 19.

[0313] Step 13: Exit the expert control program for the pressure before the regulating valve (flag bit (0)). Go to step 14.

[0314] Step 14: Stop the low-pressure pump. Go to step 15.

[0315] Step 15: Execute the judgment procedure: the output volume flow of the low-pressure pump is less than 100m 3 / h and the low-pressure pump motor is in the off state (the judgment condition for the low-pressure pump to stop is that the output volume flow of the low-pressure pump is less than 100m 3 / h and the low-pressure pump motor is in the off state). If the conditions are met, proceed to step 18; otherwise, proceed to step 16.

[0316] Step 16: Execute the judgment procedure: timer < 25s (wait for the low-pressure pump to stop), if the condition is met, execute step 18, otherwise execute step 31.

[0317] Step 17: Delay for 1 second. After the delay is over, execute step 15.

[0318] Step 18: Exit the post-regulator pressure control program (flag (0)). Go to step 19.

[0319] Step 19: Execute the judgment procedure: whether to stop the first line (the seawater pump needs to be stopped after the first line is stopped). If the condition is met, execute step 20, otherwise execute step 21.

[0320] Step 20: Execute the delay procedure: Delay for 30 minutes (wait for all LNG in the ORV to be gasified). Execute step 22.

[0321] Step 21: Stop the seawater pump and proceed to step 26.

[0322] Step 22: Stop the seawater pump and proceed to step 23.

[0323] Step 23: Execute the judgment procedure: the pressure of the seawater pump outlet valve is less than 0.05MPaG and the seawater pump motor is in the off state (the judgment condition for the seawater pump to stop is that the pressure of the seawater pump outlet valve is less than 0.05MPaG and the seawater pump motor is in the off state). If the condition is met, execute step 31, otherwise execute step 24.

[0324] Step 24: Execute the judgment procedure: the judgment timer is less than 25s (waiting for the seawater pump to stop). If the condition is met, execute step 25, otherwise execute step 31.

[0325] Step 25: Delay for 1 second. After the delay is over, execute step 23.

[0326] Step 26: Execute the judgment procedure: the pressure of the seawater pump outlet valve is less than 0.05MPaG and the seawater pump motor is in the off state (the judgment condition for the seawater pump to stop is that the pressure of the seawater pump outlet valve is less than 0.05MPaG and the seawater pump motor is in the off state). If the condition is met, execute step 29, otherwise execute step 27.

[0327] Step 27: Execute the judgment procedure: Timer < 25s. If the condition is met, execute step 28, otherwise execute step 31.

[0328] Step 28: Delay for 1 second. After the delay is over, execute step 26.

[0329] Step 29: Open the seawater inlet motorized valve for the preselected open rack vaporizer (ORV). Go to Step 30.

[0330] Step 30: Open the seawater inlet regulating valve to the preselected open rack vaporizer (ORV) to 5%. Go to Step 31.

[0331] Step 31: Exit the expert control program for the pressure before the regulating valve (flag bit (0)), and exit the complex control program for the pressure after the regulating valve (flag bit (0)). Go to step 32.

[0332] Step 32: Exit the one-key shutdown program and release the control authority of all controlled valves.

[0333] Figure 8 The present invention provides a schematic diagram of the structure of a control device for a liquefied natural gas receiving station. The control device for the liquefied natural gas receiving station includes:

[0334] A memory 21, used for storing computer programs;

[0335] The processor 22 is used to implement the steps of the control method of the liquefied natural gas receiving station when executing the computer program.

[0336] For an introduction to the control device of the liquefied natural gas receiving station provided in the present application, please refer to the above-mentioned embodiment, which will not be described in detail here.

[0337] It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0338] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0339] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A control method for a liquefied natural gas receiving station, characterized in that: The storage tank of the liquefied natural gas receiving station is used to output liquefied natural gas to a low-pressure pump, output natural gas to a recondenser, and the recondenser outputs liquefied natural gas to a high-pressure pump. The liquefied natural gas passes through a low-pressure pump, an inlet throttle valve, an inlet regulating valve, a high-pressure pump, and a vaporizer in sequence and is converted into natural gas. The control method of the liquefied natural gas receiving station includes: Start the current low-pressure pump; Determine the difference between the pressure of the liquefied natural gas before the inlet regulating valve of the current high-pressure pump and the target pressure value, and determine the opening of the outlet valve of the current low-pressure pump based on the difference; Determining a total volume flow rate output by all high-pressure pumps, and determining a regulation amount of an inlet regulating valve of the current high-pressure pump according to the total volume flow rate; Starting the current high-pressure pump; When the volume flow rate output by the current high-pressure pump is within a normal range, adjusting the opening of the inlet regulating valve and the inlet throttle valve of the current high-pressure pump based on the bottom pressure of the recondenser and the opening of the inlet throttle valve of the high-pressure pump; Start the current carburetor.

2. The control method of the liquefied natural gas receiving station according to claim 1, characterized in that: The liquefied natural gas receiving station further comprises a seawater pump, which is used to output seawater to the vaporizer to provide heat for vaporization of the natural gas; Before starting the current low-pressure pump, also include: Starting the current seawater pump and determining the starting state of the current seawater pump; When the outlet valve of the current seawater pump is in an open state and the motor of the current seawater pump is in a started state, entering the step of starting the current low-pressure pump; When the outlet valve of the current seawater pump is not in the open state or the motor of the current seawater pump is not in the started state, the first preset time is delayed and the process returns to the step of determining the start state of the current seawater pump.

3. The control method of the liquefied natural gas receiving station according to claim 1, characterized in that: Start the current low pressure pump, including: Starting the current low-pressure pump, and obtaining the opening of the outlet valve of the current low-pressure pump or the outlet flow of the current low-pressure pump; When the opening of the outlet valve of the current low-pressure pump is greater than a first preset opening or the outlet flow rate of the current low-pressure pump is greater than a first preset flow rate, determining a start-up state of the motor of the current low-pressure pump; When the outlet flow of the current low-pressure pump is greater than the second preset flow and the motor of the current low-pressure pump is in a starting state, determining that the current low-pressure pump is started successfully, and the second preset flow is less than the first preset flow; When the outlet flow of the current low-pressure pump is not greater than the second preset flow or the motor of the current low-pressure pump is not in the starting state, and the starting time of the current low-pressure pump does not exceed the second preset time, delaying the first preset time and returning to the step of determining the starting state of the motor of the current low-pressure pump; If the current start-up time of the low-pressure pump exceeds the second preset time, the start-up of the liquefied natural gas receiving station is stopped.

4. The control method of the liquefied natural gas receiving station according to claim 1, characterized in that: The liquefied natural gas receiving station further comprises a pressure detector, which is used to detect the pressure of the liquefied natural gas before the inlet regulating valve of the high-pressure pump; Determining the opening of the outlet valve of the current low-pressure pump based on the difference includes: Determine whether the pressure collected by the current pressure detector is lower than the lower limit of the low-pressure pipe network pressure; If it is lower than the lower limit of the low-pressure pipe network pressure, determining whether the difference between two adjacent pressures collected by the pressure detector is less than a first preset pressure; If the difference between two adjacent pressures is not less than the first preset pressure, controlling the opening of the outlet valve of the current low-pressure pump to increase by a first percentage; If the difference between two adjacent pressures is less than the first preset pressure, the opening of the outlet valve of the current low-pressure pump is controlled to increase by a second percentage, wherein the second percentage is greater than the first percentage; If it is not lower than the network pressure lower limit, then judging whether the pressure collected by the pressure detector is higher than the low-pressure network pressure upper limit; If it is higher than the upper limit of the low-pressure pipe network pressure, determining whether the difference between two adjacent pressures collected by the pressure detector is less than a first preset pressure; If the difference between two adjacent pressures is not less than the first preset pressure, controlling the opening of the outlet valve of the current low-pressure pump to decrease by a second percentage; If the difference between two adjacent pressures is less than the first preset pressure, controlling the opening of the outlet valve of the current low-pressure pump to decrease by a first percentage; Determining whether the opening of the outlet valve of the current low-pressure pump is greater than the maximum opening limit; If it is greater than the maximum opening limit, the current opening of the outlet valve of the current low-pressure pump is maintained; If it is not greater than the maximum opening limit, the third preset time is delayed, and the process returns to the step of determining whether the pressure collected by the pressure detector is lower than the lower limit of the low-pressure pipe network pressure.

5. The control method of the liquefied natural gas receiving station according to claim 1, characterized in that: The liquefied natural gas receiving station further includes an inlet isolation valve of a high-pressure pump and a compressor. The inlet isolation valve of the high-pressure pump is arranged between the outlet of the low-pressure pump and the condensation port of the recondenser. The compressor is arranged between the gas outlet of the storage tank and the inlet of the recondenser. The outlet of the recondenser is connected to the outlet of the inlet regulating valve. The compressor is used to compress the gas output from the storage tank and output it to the recondenser. Before starting the current high-pressure pump, the method further includes: Setting the opening of the inlet isolation valve of the current high-pressure pump according to the number of all high-pressure pumps started in the liquefied natural gas receiving station; When the opening of the inlet isolation valve of the current high-pressure pump is within a preset opening range centered on the set opening, entering a step of determining the adjustment amount of the inlet regulating valve of the current high-pressure pump according to the total volume flow; Starting the current high pressure pump, comprising: Determining whether the inlet regulating valve meets the opening condition of the high-pressure pump after adjustment; If satisfied, start the current high-pressure pump; Determining whether the output volume flow rate of the current high-pressure pump is greater than a third preset flow rate and whether the motor of the current high-pressure pump is in a starting state; If the output volume flow rate is greater than a third preset flow rate and the motor of the current high-pressure pump is in a starting state, determining that the current high-pressure pump is started successfully; If the output volume flow rate is not greater than the third preset flow rate and the motor of the current high-pressure pump is not in the started state, the preset time is delayed and the process returns to the step of determining whether the output volume flow rate of the current high-pressure pump is greater than the third preset flow rate and whether the motor of the high-pressure pump is in the started state.

6. The control method of a liquefied natural gas receiving station according to claim 1, characterized in that: Determine the total volume flow rate delivered by all high pressure pumps, including: Get the starting status of the motor of the i-th high-pressure pump and the output volume flow L i ; When the motor of the high-pressure pump is in a starting state, if the volume flow rate output by the i-th high-pressure pump is not within the starting state volume flow rate range, a volume flow rate less than a lower limit value of the starting state volume flow rate range is set as a lower limit value, and a volume flow rate greater than an upper limit value of the starting state volume flow rate range is set as an upper limit value; When the motor of the high-pressure pump is in an unstarted state, if the volume flow rate output by the i-th high-pressure pump is not within the unstarted state volume flow rate range, a volume flow rate less than a lower limit value of the unstarted state volume flow rate range is set as a lower limit value, and a volume flow rate greater than an upper limit value of the unstarted state volume flow rate range is set as an upper limit value; Determine the total volume flow rate output by all high-pressure pumps, the expression for the total volume flow rate is: L sum =ΣL i +ΔL; Among them, L sum is the total volume flow rate, L i is the volume flow rate output by the i-th high-pressure pump, ΔL is the preset volume flow rate change value when the high-pressure pump is started or stopped, i∈[1,2,3,…,n], there are n high-pressure pumps in total; Determining the adjustment amount of the inlet regulating valve of the current high-pressure pump according to the volume flow includes: Determine the total mass flow rate output by the recondenser, the total mass flow rate is expressed as: L m =1000×L4+L5; Determine the theoretical volume flow and relative volume flow through the inlet regulating valve, the expression of the theoretical volume flow is L2=L sum -L m / ρ, the relative volume flow rate expression is L3=L2 / (L max / ρ)×100; Among them, L m is the total mass flow rate output by the recondenser, L4 is the mass flow rate of the liquefied natural gas input to the recondenser, L5 is the mass flow rate of the evaporated natural gas input to the recondenser, L2 is the theoretical volume flow rate, L3 is the relative volume flow rate, ρ is the density of the liquefied natural gas, and L max is the maximum mass flow rate passing through the inlet regulating valve; Divide the flow interval into left-closed and right-open intervals that increase in sequence and do not overlap, namely, a first flow interval, a second flow interval, a third flow interval, and a fourth flow interval; If the total volume flow rate is within the first flow rate interval, then determine y=a1L3 2 +a2L3+a3; If the total volume flow is in the second flow interval or the fourth flow interval, then y=a4L3 is determined. 2 +a5L3+a6; If the total volume flow is in the third flow interval, then y=a7L3 is determined. 2 +a8L3+a9; Determine the theoretical increase in opening ΔA3 of the inlet regulating valve, wherein the relationship of the theoretical increase in opening is ΔA3=y-A4; Determine the actual increase in opening ΔA2 of the inlet regulating valve, wherein the relationship of the actual increase in opening is ΔA2=KΔA3+ΔB; Wherein, y is the opening of the inlet regulating valve that needs to be adjusted to maintain the bottom pressure of the recondenser stable at the current flow rate, A4 is the current opening of the inlet regulating valve, K is the weight coefficient, ΔB is the correction parameter, and a1, a2, a3, ..., a9 are all adjustment coefficients; Determining whether the actually increased opening is within the actually required increased opening range of the inlet regulating valve; If the actual increased opening is not within the actually required increased opening range, and the actual increased opening is less than the lower limit of the actually required increased opening range, the actual increased opening is set to the lower limit of the actually required increased opening range; if the actual increased opening is not less than the lower limit of the actually required increased opening range, the actual increased opening is set to the upper limit of the actually required increased opening range; Determine the opening degree A2 that the inlet regulating valve needs to reach. The relationship between the opening degree that needs to be reached is: A2=ΔA2+A4.

7. The control method of a liquefied natural gas receiving station according to claim 1, characterized in that: Adjusting the opening of the inlet regulating valve and the inlet throttle valve of the current high-pressure pump based on the bottom pressure of the recondenser and the opening of the inlet throttle valve of the high-pressure pump comprises: Obtaining the opening of the inlet throttle valve; controlling the opening of the inlet regulating valve based on a deviation between the opening of the inlet throttle valve and a set opening of the inlet throttle valve; Obtaining the bottom pressure of the recondenser; The opening degree of the throttle-in valve is controlled based on a deviation of a bottom pressure of the recondenser from a set bottom pressure of the recondenser.

8. The control method of a liquefied natural gas receiving station according to claim 1, characterized in that: Before starting the current carburetor, also include: Controlling the current high-pressure pump to perform pressure equalization so that the difference between the pressure of the outlet pipeline of the current high-pressure pump and the pressure of the inlet pipeline of the current vaporizer is lower than a preset pressure difference; Determining whether the outlet valve of the high-pressure pump is open; If it is on, the process proceeds to the step of starting the current carburetor; If not, delay for a first preset time and return to the step of determining whether the outlet valve of the high-pressure pump is open.

9. The control method of a liquefied natural gas receiving station according to any one of claims 1 to 8, characterized in that: Also includes: Determine the difference between the pressure of the liquefied natural gas before the inlet regulating valve of the current high-pressure pump and the target pressure value, and determine the opening of the outlet valve of the current low-pressure pump based on the difference; Turn off the current high-pressure pump; Determining a total volume flow rate output by all high-pressure pumps, and determining a regulation amount of an inlet regulating valve of the current high-pressure pump according to the total volume flow rate; When the volume flow rate output by the current high-pressure pump is within a normal range, adjusting the opening of the inlet regulating valve and the inlet throttle valve of the current high-pressure pump based on the bottom pressure of the recondenser and the opening of the inlet throttle valve of the high-pressure pump; Turn off the current low-pressure pump; The current carburetor is turned off.

10. A control device for a liquefied natural gas receiving station, characterized in that: include: Memory for storing computer programs; A processor, configured to implement the steps of the control method for a liquefied natural gas receiving station as claimed in any one of claims 1 to 9 when executing the computer program.

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