A control method and apparatus for a liquefied natural gas receiving terminal

Abstract

The application discloses a kind of liquefied natural gas receiving station control method and device, it is related to liquefied natural gas receiving station technical field, comprising: starting current low pressure pump;Based on the difference between the pressure of liquid natural gas before current high pressure pump's inlet regulating valve and target pressure value, the opening of the outlet valve of current low pressure pump is determined;According to the total volume flow of all high pressure pump outputs, the regulating amount of the inlet regulating valve of current high pressure pump is determined;Start current high pressure pump;When the volume flow of current high pressure pump output is in normal range, based on the bottom pressure of recondenser and the opening of high pressure pump's inlet throttle valve, the opening of the inlet regulating valve and inlet throttle valve of current high pressure pump is adjusted;Start current vaporizer.Open according to sequence automatically control the opening of each device of receiving station, and adjust the opening of each valve before opening, realize one-key opening control, reduce the participation of artificial, improve the work efficiency of receiving station.

Description

Technical Field

[0001] This invention relates to the field of liquefied natural gas (LNG) receiving station technology, and in particular to a control method and apparatus for an LNG receiving station. Background Technology

[0002] To reduce the workload of on-site operators, it is necessary to improve the automation control level of the vaporization and export production line at the receiving station, enabling one-button automatic start and stop. However, during the one-button start / stop process, the low-pressure pump outlet is a butterfly valve, and the regulating valve from the bottom of the condenser to the high-pressure pump inlet is also a butterfly valve with a pipe diameter of DN500 and manual control. The pressure after this valve is regulated by a PID controller that controls the bypass shut-off valve. The shut-off valve has a small pipe diameter, making it easy to exceed its regulation range, thus affecting the automatic start and stop of the liquefied natural gas receiving station. Summary of the Invention

[0003] The purpose of this invention is to provide a control method and device for a liquefied natural gas receiving station, which automatically controls the opening of each device in the receiving station in sequence, and adjusts the opening degree of each valve before opening, realizing one-button opening control, reducing manual intervention and improving the working efficiency of the receiving station.

[0004] To solve the above-mentioned technical problems, the present invention provides a control method for a liquefied natural gas (LNG) receiving station. The LNG receiving station's storage tanks are used to output LNG to a low-pressure pump, output natural gas to a re-condenser, and the re-condenser outputs LNG to a high-pressure pump. The LNG sequentially passes through a low-pressure pump, an inlet throttle valve and an inlet regulating valve, a high-pressure pump, and a vaporizer to be converted into natural gas. The control method for the LNG receiving station includes:

[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 degree of the outlet valve of the current low-pressure pump based on the difference;

[0007] Determine the total volumetric flow rate of all high-pressure pumps, and determine the adjustment amount of the inlet regulating valve of the current high-pressure pump based on the total volumetric flow rate;

[0008] Start the current high-pressure pump;

[0009] When the volumetric flow rate output by the current high-pressure pump is within the normal range, the opening of the inlet regulating valve and the inlet throttle valve of the current high-pressure pump are adjusted 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 vaporizer.

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

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

[0013] Start the current seawater pump and determine the startup status of the current seawater pump;

[0014] When the outlet valve of the current seawater pump is open and the motor of the current seawater pump is running, proceed to the step of starting the current low-pressure pump;

[0015] If the outlet valve of the current seawater pump is not open or the motor of the current seawater pump is not started, delay for a first preset time and return to the step of determining the start-up status of the current seawater pump.

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

[0017] Start the current low-pressure pump and obtain the opening degree of the outlet valve of the current low-pressure pump or the outlet flow rate of the current low-pressure pump;

[0018] When the opening degree of the outlet valve of the current low-pressure pump is greater than the first preset opening degree or the outlet flow rate of the current low-pressure pump is greater than the first preset flow rate, the starting state of the motor of the current low-pressure pump is determined.

[0019] When the outlet flow rate of the current low-pressure pump is greater than the second preset flow rate and the motor of the current low-pressure pump is in the starting state, it is determined that the current low-pressure pump has started successfully, and the second preset flow rate is less than the first preset flow rate.

[0020] If the outlet flow rate of the current low-pressure pump is not greater than the second preset flow rate or the motor of the current low-pressure pump is not in the start state, and the start time of the current low-pressure pump does not exceed the second preset time, delay for the first preset time and return to the step of determining the start state of the motor of the current low-pressure pump.

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

[0022] On the other hand, the liquefied natural gas receiving station also includes a pressure detector for detecting the pressure of the liquefied natural gas before the inlet regulating valve of the high-pressure pump;

[0023] Based on the difference, the opening degree of the outlet valve of the current low-pressure pump is determined, including:

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

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

[0026] If the pressure difference between two consecutive pressures is not less than the first preset pressure, then the opening of the outlet valve of the current low-pressure pump is increased by a first percentage.

[0027] If the pressure difference between two consecutive pressures is less than the first preset pressure, the opening of the outlet valve of the current low-pressure pump is increased by a second percentage, where the second percentage is greater than the first percentage.

[0028] If the pressure 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.

[0029] If the pressure is higher than the upper limit of the low-pressure pipeline, then it is determined whether the difference between two adjacent pressures collected by the pressure detector is less than the first preset pressure.

[0030] If the pressure difference between two consecutive pressures is not less than the first preset pressure, then the opening of the outlet valve of the current low-pressure pump is reduced by a second percentage.

[0031] If the difference between two consecutive pressures is less than the first preset pressure, then the opening of the outlet valve of the current low-pressure pump is reduced by a first percentage.

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

[0033] If the opening exceeds the maximum opening limit, then maintain the current opening of the outlet valve of the current low-pressure pump.

[0034] If the pressure is not greater than the maximum opening limit, then delay for a third preset time and return to the step of determining whether the pressure collected by the pressure detector is lower than the low-pressure pipeline network pressure limit.

[0035] On the other hand, the liquefied natural gas receiving station also includes an inlet isolation valve for a high-pressure pump and a compressor. The inlet isolation valve for the high-pressure pump is located between the outlet of the low-pressure pump and the condensation port of the recondenser. The compressor is located 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 following steps are also included:

[0037] 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;

[0038] When the opening degree of the inlet isolation valve of the current high-pressure pump is within a preset opening degree range centered on the set opening degree, the step of determining the adjustment amount of the inlet regulating valve of the current high-pressure pump based on the total volume flow rate is initiated.

[0039] Starting the current high-pressure pump includes:

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

[0041] If the conditions are met, then start the current high-pressure pump;

[0042] Determine 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 current high-pressure pump is in the start state;

[0043] 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 the starting state, then it is determined that the current high-pressure pump has been successfully started.

[0044] If the output volumetric flow rate is not greater than the third preset flow rate and the motor of the current high-pressure pump is not in the start state, then delay for a preset time and return to the step of determining whether the output volumetric 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 start state.

[0045] On the other hand, determine the total volumetric flow rate output of all high-pressure pumps, including:

[0046] Obtain the starting status of the motor and the output volumetric flow rate L of the i-th high-pressure pump. i ;

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

[0048] When the motor of the high-pressure pump is not started, if the volumetric flow rate output by the i-th high-pressure pump is not within the volumetric flow rate range of the not started state, then the volumetric flow rate less than the lower limit of the volumetric flow rate range of the not started state is set as the lower limit value, and the volumetric flow rate greater than the upper limit of the volumetric flow rate range of the not started state is set as the upper limit value.

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

[0050] L sum =ΣL i +ΔL;

[0051] Among them, L sum L represents the total volumetric flow rate. i Let ΔL be the volumetric flow rate output by the i-th high-pressure pump, and let ΔL be the preset change in volumetric flow rate when the high-pressure pump starts or stops. i∈[1,2,3,…,n], and there are n high-pressure pumps in total.

[0052] Determining the adjustment amount of the inlet regulating valve of the current high-pressure pump based on the volumetric flow rate includes:

[0053] The total mass flow rate output from the recondenser is determined, and the expression for the total mass flow rate is:

[0054] L m =1000×L4+L5;

[0055] Determine the theoretical volumetric flow rate and relative volumetric flow rate through the inlet regulating valve. The expression for the theoretical volumetric flow rate is L2 = L sum -L m / ρ, the expression for the relative volumetric flow rate is L3=L2 / (L max / ρ)×100;

[0056] Among them, L m L1 is the total mass flow rate output from the recondenser, L4 is the mass flow rate of liquefied natural gas input to the recondenser, L5 is the mass flow rate of evaporated natural gas input to the recondenser, L2 is the theoretical volumetric flow rate, L3 is the relative volumetric flow rate, ρ is the density of liquefied natural gas, and L... max The maximum mass flow rate passing through the inlet regulating valve;

[0057] The flow range is divided into left-closed and right-open intervals that increase in size and do not overlap, namely the first flow range, the second flow range, the third flow range and the fourth flow range;

[0058] If the total volumetric flow rate is within the first flow rate range, then y = a1L3 is determined. 2 +a2L3+a3;

[0059] If the total volumetric flow rate falls within the second or fourth flow rate interval, then y = a4L3 is determined. 2 +a5L3+a6;

[0060] If the total volumetric flow rate is within the third flow rate range, then y = a7L3 is determined. 2 +a8L3+a9;

[0061] The theoretical increase in opening degree ΔA3 of the inlet regulating valve is determined, and the relationship of the theoretical increase in opening degree is ΔA3=y-A4;

[0062] The actual increase in opening degree ΔA2 of the inlet regulating valve is determined, and the relationship of the actual increase in opening degree is ΔA2=KΔA3+ΔB;

[0063] Where y is the opening degree that the inlet regulating valve needs to be adjusted to maintain the bottom pressure of the recondenser under the current flow rate, A4 is the current opening degree of the inlet regulating valve, K is the weighting coefficient, ΔB is the correction parameter, and a1, a2, a3, ..., a9 are all adjustment coefficients;

[0064] Determine whether the actual increase in opening degree is within the range of the actual required increase in opening degree of the inlet regulating valve;

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

[0066] The required opening degree A2 of the inlet regulating valve is determined, and the relationship for the required opening degree is as follows:

[0067] A2 = ΔA2 + A4.

[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 includes:

[0069] Obtain the opening degree of the inlet throttle valve;

[0070] The opening of the inlet regulating valve is controlled based on the deviation between the opening degree of the inlet throttle valve and the set opening degree of the inlet throttle valve.

[0071] Obtain the bottom pressure of the recondenser;

[0072] The opening degree of the inlet throttle valve is controlled based on the deviation between the bottom pressure of the recondenser and the set bottom pressure of the recondenser.

[0073] On the other hand, before starting the current vaporizer, the following also applies:

[0074] Control the current high-pressure pump to equalize the pressure so that the pressure difference between the outlet pipe of the current high-pressure pump and the inlet pipe of the current vaporizer is lower than a preset pressure difference;

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

[0076] If opened, the process will proceed to start the current vaporizer;

[0077] If it is not opened, the process is delayed for a first preset time and then returns 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 degree of the outlet valve of the current low-pressure pump based on the difference;

[0080] Shut down the current high-pressure pump;

[0081] Determine the total volumetric flow rate of all high-pressure pumps, and determine the adjustment amount of the inlet regulating valve of the current high-pressure pump based on the total volumetric flow rate;

[0082] When the volumetric flow rate output by the current high-pressure pump is within the normal range, the opening of the inlet regulating valve and the inlet throttle valve of the current high-pressure pump are adjusted based on the bottom pressure of the recondenser and the opening of the inlet throttle valve of the high-pressure pump.

[0083] Shut down the current low-pressure pump;

[0084] The current vaporizer is shut down.

[0085] To address the aforementioned technical problems, the present invention also provides a control device for a liquefied natural gas receiving station, comprising:

[0086] Memory, used to store computer programs;

[0087] A processor is used to execute the computer program to implement the steps of the control method for the liquefied natural gas receiving station described above.

[0088] This application provides a control method and apparatus for a liquefied natural gas (LNG) receiving station, relating to the field of LNG receiving station technology. The method includes: starting the current low-pressure pump; determining the opening degree of the outlet valve of the current low-pressure pump based on the difference between the pressure of 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 based on the total volumetric flow rate output by all high-pressure pumps; starting the current high-pressure pump; adjusting the opening degree 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 degree of the inlet throttle valve of the high-pressure pump when the volumetric flow rate output by the current high-pressure pump is within the normal range; and starting the current vaporizer. This automatically controls the opening of each component of the receiving station in sequence, and adjusts the opening degree of each valve before opening, achieving one-button opening control, reducing manual intervention, and improving the working efficiency of the receiving station. Attached Figure Description

[0089] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the prior art and embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

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

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

[0092] Figure 3 A flowchart for one-click start provided by the present invention;

[0093] Figure 4 A flowchart 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 flowchart of a complex control strategy provided by the present invention;

[0096] Figure 7 A flowchart for one-click shutdown provided by the present invention;

[0097] Figure 8 This is a schematic diagram of the structure of a control device for a liquefied natural gas receiving station provided by the present invention. Detailed Implementation

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

[0099] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0100] Figure 1 This invention provides a flowchart of a control method for a liquefied natural gas receiving station. Figure 2 This is a schematic diagram of the structure of a liquefied natural gas receiving station provided by the present invention;

[0101] The liquefied natural gas (LNG) receiving terminal's storage tanks are used to output LNG to a low-pressure pump, then to a recondenser, and finally to a high-pressure pump. The LNG then sequentially passes through the low-pressure pump, inlet throttle valve and inlet regulating valve, high-pressure pump, and vaporizer to be converted into natural gas. The control method for this LNG receiving terminal includes:

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

[0103] S12: 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 based on the difference, determine the opening degree of the outlet valve of the current low-pressure pump.

[0104] S13: Determine the total volumetric flow rate of all high-pressure pumps, and determine the adjustment amount of the inlet regulating valve of the current high-pressure pump based on the total volumetric flow rate;

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

[0106] S15: When the current volumetric flow rate output by the high-pressure pump is within the normal range, adjust the opening of the current high-pressure pump's inlet regulating valve and inlet throttle valve based on the bottom pressure of the recondenser and the opening of the high-pressure pump's inlet throttle valve.

[0107] S16: Start the current carburetor.

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

[0109] The full-site process simulation includes the tank farm, recondenser, high-pressure pump area, open-frame vaporizer (ORV) area, and the refrigeration cycle of the LNG (Liquefied Natural Gas) receiving terminal. NG stands for Natural Gas, and BOG stands for Boil Off Gas.

[0110] (1) Tank farm simulation:

[0111] The storage tanks are fully enclosed, with a single unit having an effective volume of 160,000 m³. The LNG space within the tank is divided into a gas phase and a liquid phase; maintaining pressure balance between these phases is crucial for successful storage. During unloading, LNG is fed into the tanks via the feed pipeline, with the feed point selected from either the bottom or top of the tank depending on the composition and density. Each tank has a built-in low-pressure pump that extracts LNG from the tank and delivers it to downstream units or for internal circulation. Four low-pressure pumps are installed in each tank, with three in operation and one on standby. BOG gas from inside the tank enters the BOG manifold and proceeds to the BOG compressor.

[0112] Each pump is equipped with a flow control valve, which is a butterfly valve, on its outlet pipeline. This valve is used to regulate the outlet flow of each operating pump and to cut off the output in case of emergency. To protect the low-pressure pump, a minimum flow control valve is also installed on the outlet pipeline of each pump. This valve is used for pump backflow operation to ensure that the minimum output flow of the low-pressure pump is 280 m³ / h, preventing pump stalling.

[0113] (2) Recondenser simulation:

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

[0115] Gas from the BOG (Bottle-Off Gas) manifold first enters the desuperheater at the BOG compressor inlet unit. After heat exchange with a stream of LNG from the low-pressure LNG manifold, the BOG temperature is reduced, effectively lowering the compressor inlet and outlet temperatures. Small LNG droplets are carried out of the desuperheater with the gas and separated in the inlet separator. After compression, the BOG reaches a pressure of approximately 0.76 MPaG and enters the recondenser from the top. There, it comes into direct contact with the LNG from the low-pressure LNG manifold, undergoing thorough heat exchange and complete condensation into LNG. This LNG is 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 exported.

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

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

[0119] Recondenser top pressure control: When the recondenser top pressure increases, the pressure is regulated by the pressure controller, and excess gas is released to the BOG main through the pressure valve. The pressure controller setpoint is 0.76 MPaG, 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. An LNG to recondenser regulating valve and its shut-off valve are installed on the recondenser bypass. The large butterfly valve is manually adjustable, while the shut-off valve is automatically adjustable. After the butterfly valve is manually set to a certain opening degree, the shut-off valve is controlled by the pressure controller to regulate the pressure after the LNG to high-pressure pump regulating valve. The pressure setpoint is 0.75 MPaG.

[0121] LNG flow control for recondenser: In automatic mode, the amount of LNG required to recondense BOG in the recondenser is controlled by the controller, ensuring that the BOG is completely condensed while maintaining the liquid level in the recondenser at 55%-75%.

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

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

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

[0125] During high-pressure pump shutdown, close the high-pressure pump outlet valve and open the return valve to a certain degree to maintain the high-pressure pump's cooling cycle, keeping the high-pressure pump in standby mode. The circulating cooling LNG flows from the high-pressure pump inlet through the pump cylinder to the zero-output pipeline for high-pressure pump cooling.

[0126] (4) Cooling cycle of LNG receiving terminal:

[0127] Opening the LNG receiving terminal's cooling circulation flow control valve will activate the LNG receiving terminal's cooling circulation system. The liquefied natural gas used for cooling in the LNG receiving terminal is supplied by a low-pressure pump within the LNG storage tank. This LNG is then returned to the low-pressure mains via the cooling circulation pipeline. The cooling circulation flow rate can be set in the simulation.

[0128] A steady-state and dynamic mechanism model of the LNG receiving terminal was established. Then, a control scheme for the pressure before and after the LNG to high-pressure pump regulating valve during the one-button start-stop process was designed. The optimization objective was to stabilize the pressure before and after the LNG to high-pressure pump inlet regulating valve. This was achieved by controlling the low-pressure pump outlet butterfly valve, the reflux valve, and the LNG to high-pressure pump inlet regulating valve, stabilizing the pressure before and after the LNG to high-pressure pump inlet regulating valve near the set value. Finally, a one-button start-stop sequence control scheme was developed and applied to the low-pressure pipeline pressure control system during the one-button start-stop process. This reduces the workload of on-site operators, improves the efficiency and safety of pressure control, shortens the reflux time of the low- and high-pressure pumps, and improves the company's economic benefits.

[0129] During startup, the low-pressure pump, high-pressure pump, and vaporizer should be started in that order. The high-pressure pump can only be started after the pressure between the low-pressure pump and the high-pressure pump has been adjusted to the correct levels. Similarly, the vaporizer can only be started after the high-pressure pump has started and the pressure between the high-pressure pump and the vaporizer has been adjusted to the correct levels. Starting them in the correct order prevents vaporization from being affected by incorrect startup sequence.

[0130] Based on the above embodiments:

[0131] Figure 3 A flowchart for one-click start provided by the present invention;

[0132] In some embodiments, the liquefied natural gas receiving terminal also includes a seawater pump for discharging seawater to the vaporizer to provide heat for the vaporization of natural gas;

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

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

[0135] When the outlet valve of the current seawater pump is open and the motor of the current seawater pump is running, proceed to the step of starting the current low-pressure pump.

[0136] If the outlet valve of the current seawater pump is not open or the motor of the current seawater pump is not started, delay for a first preset time and return to the step of determining the start status of the current seawater pump.

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

[0138] Therefore, the procedure for controlling the start of the seawater pump is as follows:

[0139] Pre-selected seawater pumps, open-frame vaporizers (ORVs), low-pressure pumps, and high-pressure pumps.

[0140] After successful pre-selection, the system detects that the "One-Click Start" button has been pressed (starting the one-click start program).

[0141] Continuously check whether the "One-Click Startup Forced Termination" button is pressed (forcefully stop the one-click startup program). If it is not detected, continue the detection state.

[0142] Start the seawater pump.

[0143] Execution judgment: The seawater pump outlet valve is in the open state and the seawater pump motor is in the start state (seawater pump start-up complete).

[0144] If the condition is met, the delay will last for 10 seconds, after which the delay will end.

[0145] If the condition is not met, then execute the following judgment: check if the timer is less than 125s (wait for the seawater pump to start). If the condition is met, execute a 1s delay.

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

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

[0148] When the opening degree of the outlet valve of the current low-pressure pump is greater than the first preset opening degree or the outlet flow rate of the current low-pressure pump is greater than the first preset flow rate, determine the starting status of the motor of the current low-pressure pump.

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

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

[0151] If the current low-pressure pump starts up after a second preset time, the liquefied natural gas receiving station will be stopped from starting.

[0152] Wait for feedback from the low-pressure pump outlet valve opening >5% or the low-pressure pump outlet flow rate >300 m³ / h3 / h.

[0153] Execution judgment: Low-pressure pump outlet flow rate > 200 m³ / h 3 / h and the low-pressure pump motor is in the starting state (the condition for successful low-pressure pump startup is that the outlet flow rate is >200m³ / h). 3 / h and the low-pressure pump motor is running).

[0154] If the conditions are met, the execution will be delayed by 10 seconds.

[0155] Otherwise, perform the following judgment: check if the timer is less than 25 seconds (wait for the low-pressure pump to start). If the condition is met, delay for 1 second.

[0156] In some embodiments, the liquefied natural gas receiving station further includes a pressure detector for detecting the pressure of liquefied natural gas upstream of the inlet regulating valve of the high-pressure pump;

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

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

[0159] If the pressure is lower than the lower limit of the low-pressure pipeline network, 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 pressure difference between two consecutive pressures is not less than the first preset pressure, then the opening of the outlet valve of the current low-pressure pump is increased by the first percentage.

[0161] If the pressure difference between two consecutive pressures is less than the first preset pressure, the opening of the outlet valve of the current low-pressure pump is increased by a second percentage, which is greater than the first percentage.

[0162] If the pressure 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 the pressure is higher than the upper limit of the low-pressure pipeline network, then determine whether the difference between two adjacent pressures collected by the pressure detector is less than the first preset pressure.

[0164] If the pressure difference between two consecutive pressures is not less than the first preset pressure, then the opening of the outlet valve of the current low-pressure pump is reduced by a second percentage.

[0165] If the pressure difference between two consecutive pressures is less than the first preset pressure, the opening of the outlet valve of the current low-pressure pump is reduced by a first percentage.

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

[0167] If the opening exceeds the maximum limit, maintain the current opening of the outlet valve of the low-pressure pump.

[0168] If the pressure is not greater than the maximum opening limit, then delay for a third preset time and return to the step of determining whether the pressure collected by the pressure detector is lower than the low pressure limit of the low pressure pipeline.

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

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

[0171] Step 1: Determine if the pressure value of pressure detector I is lower than 1.15 MPaG (lower limit of low-pressure pipeline pressure). If it is lower than 1.15 MPaG, proceed to Step 2. Otherwise, proceed to Step 5 (execute the operating steps based on the deviation between the actual pressure and the target pressure).

[0172] Step 2: Determine if the pressure difference between the two pressure detectors I is ≥ -0.02 MPaG (a pressure difference ≥ -0.02 MPaG indicates that the low-pressure pipeline pressure is lower than the target pressure and the pressure recovers in time; the opening of the low-pressure pump outlet valve will be increased slightly, i.e., 1%). If ≥ -0.02 MPaG, proceed to Step 3. Otherwise, proceed to Step 4 (a pressure difference < -0.02 MPaG indicates that the low-pressure pipeline pressure is lower than the target pressure and the pressure recovers slowly; the opening of the low-pressure pump outlet valve needs to be increased significantly, i.e., 1.5%).

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

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

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

[0176] Step 6: Check if the pressure difference between the two detectors I is ≥0.02 MPaG (a pressure difference ≥0.02 MPaG indicates that the low-pressure pipeline pressure is higher than the target pressure and the pressure recovery is not timely, so the opening of the low-pressure pump outlet valve will be significantly reduced, i.e., 1.5%). If it is ≥0.02 MPaG, proceed to Step 7. Otherwise, proceed to Step 8 (a pressure difference <0.02 MPaG indicates that the low-pressure pipeline pressure is higher than the target pressure and the pressure recovery is timely, so the opening of the low-pressure pump outlet valve needs to be slightly reduced, i.e., 1.5%).

[0177] Step 7: Reduce the opening of the low-pressure pump outlet valve by 1.5%. Proceed to Step 9.

[0178] Step 8: Reduce the opening of the low-pressure pump outlet valve by 1%. Proceed to Step 9.

[0179] Step 9: Determine if 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, proceed to step 11; otherwise, proceed to step 10.

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

[0181] Step 11: Delay for 3 seconds (wait for the low-pressure pipeline network to respond). After the delay, proceed to Step 1.

[0182] In some embodiments, the liquefied natural gas receiving station further includes an inlet isolation valve for a high-pressure pump and a compressor. The inlet isolation valve for the high-pressure pump is located between the outlet of the low-pressure pump and the condenser port of the recondenser. The compressor is located 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.

[0183] Before starting the high-pressure pump, the following also applies:

[0184] Before starting the current high-pressure pump, the following also applies:

[0185] Set the opening degree 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 terminal;

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

[0187] To start the current high-pressure pump, including:

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

[0189] If the conditions are met, then start the current high-pressure pump;

[0190] Determine whether the current output volumetric flow rate of the high-pressure pump is greater than the third preset flow rate and whether the motor of the current high-pressure pump is in the start state;

[0191] If the output volumetric flow rate is greater than the third preset flow rate and the motor of the current high-pressure pump is in the starting state, then the current high-pressure pump is determined to be successfully started.

[0192] If the output volumetric flow rate is not greater than the third preset flow rate and the motor of the high-pressure pump is not currently running, then delay for a preset time and return to the step of determining whether the output volumetric flow rate of the high-pressure pump is greater than the third preset flow rate and whether the motor of the high-pressure pump is currently running.

[0193] Set the isolation valve opening degree a1 according to the number of high-pressure pumps started. End condition: wait for the isolation valve to feedback the opening degree (a1-2)~(a1+2)% (the valve feedback signal has a deviation of ±2%).

[0194] The control valve's agile control program has been invoked. The initial opening of the control valve has been set.

[0195] Execution judgment: The pressure after the regulating valve is ≥0.80MPaG or the valve feedback opening is -0.8 < (A2-A4) < 0.8 (prerequisite for starting the high-pressure pump).

[0196] If the condition is not met: execute the judgment, and judge the timer < 25s (wait for the pressure after the regulating valve to be ≥ 0.80MPaG or the valve feedback opening degree -0.8 < (A2-A4) < 0.8). If the condition is met, execute the delay for 1s and judge again whether the prerequisite for starting the high-pressure pump is met.

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

[0198] Judgment: High-pressure pump output volumetric flow rate is normal >200m³ / h 3 / h and the high-pressure pump motor is in the starting state (the judgment condition for normal start of the high-pressure pump is that the output volumetric flow rate of the high-pressure pump is normally >200m³ / h). 3 / h and the high-pressure pump motor is running).

[0199] If the condition is not met, proceed to step 25, then perform a judgment: check if the timer is <25s (wait for the high-pressure pump to start). If the condition is met, delay for 1s and re-judge the high-pressure pump output volumetric flow rate as normal >200m³. 3 / h and the high-pressure pump motor is running.

[0200] In some embodiments, determining the total volumetric flow rate of all high-pressure pump outputs includes:

[0201] Obtain the starting status of the motor and the output volumetric flow rate L of the i-th high-pressure pump. i ;

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

[0203] When the motor of the high-pressure pump is not started, if the volume flow rate output by the i-th high-pressure pump is not within the volume flow rate range of the non-started state, the volume flow rate that is less than the lower limit of the volume flow rate range of the non-started state is set as the lower limit value, and the volume flow rate that is greater than the upper limit of the volume flow rate range of the non-started state is set as the upper limit value.

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

[0205] L sum =ΣL i +ΔL;

[0206] Among them, L sum For the total volumetric flow rate, L i Let ΔL be the volumetric flow rate output by the i-th high-pressure pump, and let ΔL be the preset change in volumetric flow rate when the high-pressure pump starts or stops. i∈[1,2,3,…,n], and there are n high-pressure pumps in total.

[0207] The adjustment amount of the inlet regulating valve of the current high-pressure pump is determined based on the volumetric flow rate, including:

[0208] The total mass flow rate output from the recondenser is determined by the following expression:

[0209] L m =1000×L4+L5;

[0210] Determine the theoretical volumetric flow rate and relative volumetric flow rate through the inlet regulating valve. The expression for the theoretical volumetric flow rate is L2 = L sum -L m The expression for the relative volumetric flow rate is L3 = L2 / (L / ρ). max / ρ)×100;

[0211] Among them, L m L1 is the total mass flow rate output from the recondenser, L4 is the mass flow rate of liquefied natural gas input to the recondenser, L5 is the mass flow rate of evaporated natural gas input to the recondenser, L2 is the theoretical volumetric flow rate, L3 is the relative volumetric flow rate, ρ is the density of liquefied natural gas, and L... max The maximum mass flow rate passing through the inlet control valve;

[0212] The flow range is divided into left-closed and right-open intervals that increase in size and do not overlap, namely the first flow range, the second flow range, the third flow range and the fourth flow range;

[0213] If the total volumetric flow rate is in the first flow rate interval, then y = a1L3 is determined. 2 +a2L3+a3;

[0214] If the total volumetric flow rate is in the second or fourth flow range, then y = a4L3 is determined. 2 +a5L3+a6;

[0215] If the total volumetric flow rate is within the third flow rate interval, then y = a7L3 is determined. 2 +a8L3+a9;

[0216] The theoretical increase in opening of the inlet regulating valve is determined by ΔA3, and the theoretical increase in opening is expressed by the formula ΔA3 = y - A4.

[0217] Determine the actual increase in opening degree ΔA2 of the inlet regulating valve. The relationship for the actual increase in opening degree is ΔA2 = KΔA3 + ΔB.

[0218] Where y is the opening degree that the inlet regulating valve needs to be adjusted to maintain the bottom pressure of the recondenser under the current flow rate, A4 is the current opening degree of the inlet regulating valve, K is the weighting coefficient, and ΔB is the correction parameter.

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

[0220] If the actual increase in opening is not within the range of the actual required increase in opening, and the actual increase in opening is less than the lower limit of the range of the actual required increase in opening, then the actual increase in opening is set to the lower limit of the range of the actual required increase in opening. If the actual increase in opening is not less than the lower limit of the range of the actual required increase in opening, then the actual increase in opening is set to the upper limit of the range of the actual required increase in opening.

[0221] The required opening degree of the inlet regulating valve is determined by the following formula:

[0222] A2 = ΔA2 + A4.

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

[0224] The pipeline from the LNG storage tank to the high-pressure pump area includes an LNG-to-high-pressure pump inlet regulating valve, responsible for controlling the LNG inlet pressure at 0.75 MPaG. The agile control method includes a main control unit and a flow detector. The flow detector detects the volumetric flow rate of the liquid output from 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 and controls its opening and closing. When the output flow rate in the high-pressure pump area varies over a wide range, it controls the valve opening in real time to quickly adjust the high-pressure pump inlet pressure to 0.75 MPaG. 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; otherwise, proceed to Step 4.

[0226] Step 2: Determine if the output volumetric flow rate of the high-pressure pump (in startup state) is within 150 m³ / s. 3 / h—480m 3 The output volumetric flow rate of the high-pressure pump is between / h (under normal startup conditions, the output volumetric flow rate of the high-pressure pump is 150m³ / h). 3 / h—480m 3 If the output volumetric flow rate of the high-pressure pump is not within this range (between / h), then obtain the output volumetric flow rate data of the high-pressure pump as appropriate. If the condition is met, proceed to step 6; otherwise, proceed to step 3.

[0227] Step 3: If the output volumetric flow rate of the high-pressure pump is ≤150m³ 3 / h (The output volumetric flow rate of the high-pressure pump under normal starting conditions is not less than 150m³ / h) 3 If the volumetric flow rate L of this high-pressure pump is / h), then i =150, if the output volumetric flow rate of the high-pressure pump is ≥480m³ 3 / h (Under normal startup conditions, the output volumetric flow rate of the high-pressure pump is no higher than 480m³ / h) 3 If the volumetric flow rate L of this high-pressure pump is / h), then i =480m 3 / h. Proceed to step 7.

[0228] Step 4: Determine if the volumetric flow rate of the high-pressure pump (in a stopped state) is 0 m³ / s. 3 / h—30m 3 / h (the output volumetric flow rate of the high-pressure pump in normal shutdown state is 0m³ / h) 3 / h—30m 3 If the output volumetric flow rate of the high-pressure pump is not within this range (between / h), then obtain the output volumetric flow rate data of the high-pressure pump as appropriate. If the condition is met, proceed to step 6; otherwise, proceed to step 5.

[0229] Step 5: If the high-pressure pump outputs a volumetric flow rate ≤ 0 m³ / s when it is stopped 3 / h (The output volumetric flow rate of the high-pressure pump in normal shutdown state is not less than 0m³) 3 If the volumetric flow rate L of this high-pressure pump is / h), then i =0, if the output volumetric flow rate of the high-pressure pump is ≥30m³ / h (the output volumetric flow rate of the high-pressure pump in normal shutdown state is not higher than 30m³ / h), then the volumetric flow rate L of this high-pressure pump is 0. i =30m 3 / h. Proceed to step 7.

[0230] Step 6: Output volumetric flow rate L of this high-pressure pump i For the volumetric flow rate measurement instrument, proceed to step 8.

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

[0232] Among them, L sum For the total volumetric flow rate output by the high-pressure pump, L i ΔL represents the volumetric flow rate output by each high-pressure pump, and ΔL is the preset change in volumetric flow rate during pump startup or shutdown. This change is used as feedforward regulation of the LNG to the high-pressure pump inlet regulating valve, enabling rapid adjustment of the high-pressure pump inlet pressure to approximately 0.75 MPaG during pump startup or shutdown. Proceed to step 8.

[0233] Step 8: Calculate the total mass flow of liquid phase output from the recondenser zone: L m =1000×L4+L5.

[0234] Among them, L m L4 is the total mass flow rate output from the recondenser, L5 is the LNG mass flow rate input to the recondenser, and L6 is the BOG mass flow rate input to the recondenser. Proceed to step 9.

[0235] Step 9: Calculate the theoretical LNG volumetric flow rate through the regulating valve: L2 = L sum -L m / ρ.

[0236] Where L2 is the volumetric flow rate through the regulating valve; ρ is the LNG density, ρ = 425 kg / m³ 3 Proceed to step 10.

[0237] Step 10: Calculate the relative flow rate through the regulating valve: L3 = L2 / (L max / ρ)×100;

[0238] Where L3 is the relative volumetric flow rate through the regulating valve; L max The maximum mass flow rate through the control valve. Proceed to step 11.

[0239] Step 11: Calculate the required increase in valve opening ΔA2 based on the formula of the working flow characteristic curve of the control valve.

[0240] The calculation process is as follows: (Due to the influence of actual working conditions, the working flow characteristic curve of the control valve changes significantly with the change of the flow rate. This patent divides the working flow characteristic curve of the control valve into three segments according to the flow rate, namely 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=a1L 32 +a2L3+a3;

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

[0244] y=a4L 32 +a5L3+a6;

[0245] else 800 < L sum <2000:

[0246] y=a7L 32 +a8L3+a9;

[0247] In the formula, a1, a2, a3, ..., a9 are adjustment coefficients, which are coefficients identified by the working flow characteristic curve of the control valve based on data and models;

[0248] Theoretically calculated, the required increase in valve opening is ΔA3.

[0249] ΔA3=y-A4

[0250] Where A4 is the current opening degree of the control valve; ΔA3 is the opening degree that the control valve needs to increase according to theoretical calculations.

[0251] The actual increase in valve opening required is ΔA2:

[0252] ΔA2=KΔA3+ΔB

[0253] Where K is the weighting coefficient, with a value range of 0 ≤ K ≤ 1, and an initial K = 1; ΔB is a manually adjusted parameter, with a value range of -6 ≤ ΔB ≤ 6, and an initial ΔB = 0. After calculation, proceed to step 12.

[0254] Step 12: Execute the judgment program: Min ≤ ΔA2 ≤ Max (Min is the lower limit of the actual required opening increase of the regulating valve, and Max is the upper limit of the actual required opening increase of the regulating valve. This step is to prevent excessive single - change of the regulating valve opening). If the condition is met, execute Step 16; otherwise, execute Step 13.

[0255] Step 13: Execute the judgment program: ΔA2 < Min (when the actual required opening increase of 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, execute Step 14; otherwise, execute Step 15.

[0256] Step 14: ΔA2 = Min, and execute Step 16.

[0257] Step 15: ΔA2 = Max, and execute Step 16.

[0258] Step 16: Retain ΔA2. Execute Step 17.

[0259] Step 17: Calculate the opening A2 that the regulating valve needs to reach: A2 = ΔA2 + A4;

[0260] Among them, A2 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 opening that the regulating valve needs to reach to the upper limit value of valve opening.

[0263] A2 = Upper_limit.

[0264] Among them, Upper_limit is the maximum opening of the regulating valve. Execute Step 19.

[0265] Step 19: Adjust the opening of the regulating valve to A2.

[0266] The working flow characteristic curve of the regulating valve for the LNG inlet to the high - pressure pump is calculated by the method of data - 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 non - linear effects, while the data - 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 pre - processing, establishing a data - driven model, establishing a mechanism model, fusing the mechanism model and the data model, parameter optimization, and model verification and adjustment.​​Control valve opening and flow history dataset x n To adjust the opening of valve DF01, V n This represents the volumetric flow rate through regulating valve DF01 at the current opening degree.

[0268] Calculate relative flow dataset and , where x n To adjust the relative opening of valve DF01, X n To adjust the current opening degree of valve DF01, X max This refers to the maximum valve opening of control valve DF01 when it reaches its upper limit of flow capacity under a pressure difference of 425~450kPa. n To adjust the relative flow rate of DF01, V max V is the current volumetric flow rate through the regulating valve. max This refers to the maximum volumetric flow rate that the regulating valve can pass under a pressure difference of 425~450kPa.

[0269] The relationship between the relative opening degree of control valve DF01 and the corresponding relative flow rate can be used to form a dataset: .

[0270] Based on the butterfly valve's operating characteristic curve, the fitting function is chosen to be Y=C+bx, with the objective of minimizing the sum of squared errors S. .

[0271] Taking the partial derivatives with respect to C and b and setting them to 0, we obtain the regularized equation. ;

[0272] Solving the above equations yields estimates of C and b, where C is the intercept of the fitted function, b is the slope of the fitted function, and Y... n Substitute C into a=e for the actual measured flow rate. C To obtain the final fitting parameter 'a', and to obtain the valve's working flow characteristic curve. Here, y represents the fitted flow rate value, and x represents the actual relative valve opening. Due to the distortion of valve flow characteristics, the flow characteristic curve is divided into different stages using historical data for data fitting, thus obtaining the complete working flow characteristic curve of the valve.

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

[0274] Obtain the opening degree of the inlet throttle valve;

[0275] The opening of the inlet regulating valve is controlled based on the deviation between the opening degree of the inlet throttle valve and the set opening degree of the inlet throttle valve.

[0276] Obtain the bottom pressure of the recondenser;

[0277] The opening degree of the inlet throttle valve is controlled based on the deviation between the bottom pressure of the recondenser and the set bottom pressure of the recondenser.

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

[0279] LNG storage tanks deliver LNG to the downstream pipeline network via low-pressure pumps. One branch of the LNG main pipeline flows into the recondenser, while the other branch serves as a bypass for the recondenser. The bypass branch 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, to control the pressure downstream of the high-pressure pump inlet regulating valve.

[0280] The process value PV of the PID-II is the LNG pressure at the bottom of the recondenser, the setpoint SP is 0.75 MPaG, the controller is set to reverse action, and the operating variable is the opening of the LNG to high-pressure pump inlet throttle valve. Its principle is that when the LNG pressure at the bottom of the recondenser deviates from the setpoint, the LNG flow rate at the bottom of the recondenser is changed by adjusting the opening of the LNG to high-pressure pump inlet throttle valve, directly affecting the pressure at the bottom of the recondenser. This achieves the goal of maintaining the pressure at the bottom of the recondenser at approximately 0.75 MPaG within the adjustable range of the LNG to high-pressure pump inlet throttle valve, thus maintaining a stable liquid level inside the recondenser.

[0281] The PID-I process value PV represents the opening of the LNG-to-high-pressure pump inlet throttle valve, with a setpoint SP of 40%. The controller is set to positive action, and the operated variable is the opening of the LNG-to-high-pressure pump inlet regulating valve. The principle is that when the opening of the LNG-to-high-pressure pump inlet throttle valve deviates from the setpoint, adjusting the opening of the regulating valve changes the LNG flow rate at the bottom of the recondenser, directly affecting the pressure at the bottom of the recondenser. At this time, PID-II adjusts the opening of the LNG-to-high-pressure pump inlet throttle valve to maintain the recondenser bottom pressure at 0.75 MPaG. This adjustment continues until the throttle valve opening reaches approximately 40%, at which point the regulating valve stops operating, indirectly maintaining the throttle valve opening at 40% and ensuring the throttle valve maintains its maximum regulating capacity.

[0282] Simultaneous operation of PID-I and PID-II can maintain the bottom pressure of the recondenser at a stable 0.75 MPaG, and also maintain the maximum regulating capacity of the LNG to high-pressure pump inlet throttle valve. The block diagram of the PID-I and PID-II control loops is as follows: Figure 6 As shown.

[0283] In some embodiments, prior to activating the current vaporizer, the method further includes:

[0284] Control the current high-pressure pump to equalize the pressure so that the pressure difference between the outlet pipe of the current high-pressure pump and the inlet pipe of the current vaporizer is lower than the preset pressure difference.

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

[0286] If opened, the process will proceed to start the current vaporizer;

[0287] If it is not opened, delay for a first preset time and return to the step of determining whether the outlet valve of the high-pressure pump is open.

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

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

[0290] If the conditions are met.

[0291] Otherwise, perform a conditional check: Check if the timer is less than 25 seconds. If the condition is met, delay for 1 second; otherwise, delay for 10 seconds.

[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 based on the difference, determine the opening degree of the outlet valve of the current low-pressure pump;

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

[0295] Determine the total volumetric flow rate of all high-pressure pumps, and determine the adjustment amount of the inlet regulating valve of the current high-pressure pump based on the total volumetric flow rate;

[0296] When the current volumetric flow rate output by the high-pressure pump is within the normal range, adjust the opening of the current high-pressure pump's inlet regulating valve and inlet throttle valve based on the bottom pressure of the recondenser and the opening of the high-pressure pump's inlet throttle valve.

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

[0298] Shut down the current carburetor.

[0299] Figure 7 A flowchart for one-click shutdown provided by the present invention;

[0300] like Figure 7As shown, a sequential control scheme for one-click shutdown of the vaporization and export production line at an LNG receiving terminal is described. First, the high-pressure pump and the open-frame vaporizer (ORV) are linked to stop the high-pressure pump's export and adjust it to a reflux state, while the ORV maintains the seawater input. Then, the high-pressure pump is stopped; subsequently, the low-pressure pump is stopped; and finally, the seawater pump is stopped.

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

[0302] Step 2: Detecting that the "One-Click Stop" button has been pressed (starting the one-click stop procedure), proceed to steps 3 and 4.

[0303] Step 3: Continuously check if the "One-Click Stop Connection Forced Termination" button is pressed (forcefully stop the one-click stop connection program). If detected, proceed to step 31. Otherwise, maintain the detection state.

[0304] Step 4: Call the expert control program for the pressure before the regulating valve (flag bit (1)) and execute step 13.

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

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

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

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

[0309] Step 9: Delay for 1 second. After the delay, proceed to step 7.

[0310] Step 10: Delay for 10 seconds. After the delay, proceed to steps 11 and 12.

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

[0312] Step 12: Call the complex control program for the pressure after the regulating valve (flag bit (1)). Execute step 19.

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

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

[0315] Step 15: Execute the judgment procedure: Low-pressure pump output volumetric flow rate < 100m³ 3 / h and the low-pressure pump motor is in the off state (the condition for stopping the low-pressure pump is that the output volumetric flow rate of the low-pressure pump is <100m³ / h). 3 (and the low-pressure pump motor is off). If the condition is met, proceed to step 18; otherwise, proceed to step 16.

[0316] Step 16: Execute the judgment program: if the timer is less than 25 seconds (wait for the low-pressure pump to stop), proceed to step 18; otherwise, proceed to step 31.

[0317] Step 17: Delay for 1 second. After the delay, proceed to step 15.

[0318] Step 18: Exit the pressure control program after the regulating valve (flag bit (0)). Proceed to step 19.

[0319] Step 19: Execute the judgment procedure: Is the first line shut down? (The seawater pump needs to be stopped after the first line is shut down.) If the condition is met, proceed to step 20; otherwise, proceed to step 21.

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

[0321] Step 21: Stop the seawater pump. Proceed to Step 26.

[0322] Step 22: Stop the seawater pump. Proceed to Step 23.

[0323] Step 23: Execute the judgment procedure: The seawater pump outlet valve pressure is <0.05MPaG and the seawater pump motor is in the off state (the judgment condition for stopping the seawater pump is that the seawater pump outlet valve pressure is <0.05MPaG and the seawater pump motor is in the off state). If the condition is met, proceed to step 31; otherwise, proceed to step 24.

[0324] Step 24: Execute the judgment procedure: Check if the timer is <25s (wait for the seawater pump to stop). If the condition is met, proceed to step 25; otherwise, proceed to step 31.

[0325] Step 25: Delay for 1 second. After the delay, proceed to step 23.

[0326] Step 26: Execute the judgment procedure: The seawater pump outlet valve pressure is <0.05MPaG and the seawater pump motor is in the off state (the judgment condition for stopping the seawater pump is that the seawater pump outlet valve pressure is <0.05MPaG and the seawater pump motor is in the off state). If the condition is met, proceed to step 29; otherwise, proceed to step 27.

[0327] Step 27: Execute the judgment program: timer < 25s. If the condition is met, proceed to step 28; otherwise, proceed to step 31.

[0328] Step 28: Delay for 1 second. After the delay, proceed to step 26.

[0329] Step 29: Open the seawater inlet electric valve of the pre-selected open rack vaporizer (ORV). Proceed to Step 30.

[0330] Step 30: Open the seawater inlet regulating valve of the pre-selected open rack vaporizer (ORV) to 5%. Proceed to Step 31.

[0331] Step 31: Exit the pre-regulator pressure expert control program (flag (0)) and exit the post-regulator pressure complex control program (flag (0)). Proceed to step 32.

[0332] Step 32: Exit the one-click shutdown program and release control permissions for all controlled valves.

[0333] Figure 8 This is a schematic diagram of the structure of a control device for a liquefied natural gas (LNG) receiving station provided by the present invention. The control device for the LNG receiving station includes:

[0334] Memory 21 is used to store computer programs;

[0335] The processor 22 is used to execute computer programs to implement the steps of the control method for the liquefied natural gas receiving station described above.

[0336] The description of the control device for the liquefied natural gas receiving station provided in this application is similar to that in the above embodiments and will not be repeated here.

[0337] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0338] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0339] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily 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 invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded 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 liquefied natural gas (LNG) receiving terminal's storage tanks are used to output LNG to a low-pressure pump, then to a re-condenser, and finally to a high-pressure pump. The LNG sequentially passes through a low-pressure pump, an inlet throttle valve and an inlet regulating valve, a high-pressure pump, and a vaporizer, converting it into natural gas. The control method for the LNG receiving terminal 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 degree of the outlet valve of the current low-pressure pump based on the difference; Determine the total volumetric flow rate of all high-pressure pumps, and determine the adjustment amount of the inlet regulating valve of the current high-pressure pump based on the total volumetric flow rate; Start the current high-pressure pump; When the volumetric flow rate output by the current high-pressure pump is within the normal range, the opening of the inlet regulating valve and the inlet throttle valve of the current high-pressure pump are adjusted based on the bottom pressure of the recondenser and the opening of the inlet throttle valve of the high-pressure pump. Start the current vaporizer.

2. The control method for a liquefied natural gas receiving station as described in claim 1, characterized in that, The liquefied natural gas receiving terminal also includes a seawater pump, which is used to output seawater to the vaporizer to provide heat for the vaporization of the natural gas; Before starting the current low-pressure pump, the following also applies: Start the current seawater pump and determine the startup status of the current seawater pump; When the outlet valve of the current seawater pump is open and the motor of the current seawater pump is running, proceed to the step of starting the current low-pressure pump; If the outlet valve of the current seawater pump is not open or the motor of the current seawater pump is not started, delay for a first preset time and return to the step of determining the start-up status of the current seawater pump.

3. The control method for a liquefied natural gas receiving station as described in claim 1, characterized in that, Start the current low-pressure pump, including: Start the current low-pressure pump and obtain the opening degree of the outlet valve of the current low-pressure pump or the outlet flow rate of the current low-pressure pump; When the opening degree of the outlet valve of the current low-pressure pump is greater than the first preset opening degree or the outlet flow rate of the current low-pressure pump is greater than the first preset flow rate, the starting state of the motor of the current low-pressure pump is determined. When the outlet flow rate of the current low-pressure pump is greater than the second preset flow rate and the motor of the current low-pressure pump is in the starting state, it is determined that the current low-pressure pump has started successfully, and the second preset flow rate is less than the first preset flow rate. If the outlet flow rate of the current low-pressure pump is not greater than the second preset flow rate or the motor of the current low-pressure pump is not in the start state, and the start time of the current low-pressure pump does not exceed the second preset time, delay for the first preset time and return to the step of determining the start state of the motor of the current low-pressure pump. If the start-up time of the current low-pressure pump exceeds the second preset time, the start-up of the liquefied natural gas receiving station shall be stopped.

4. The control method for a liquefied natural gas receiving station as described in claim 1, characterized in that, The liquefied natural gas receiving station also includes 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; Based on the difference, the opening degree of the outlet valve of the current low-pressure pump is determined, including: Determine whether the pressure collected by the current pressure detector is lower than the lower limit value of the low-pressure pipeline network; If the pressure is lower than the lower limit of the low-pressure pipeline network, it is determined whether the difference between two adjacent pressures collected by the pressure detector is less than the first preset pressure. If the pressure difference between two consecutive pressures is not less than the first preset pressure, then the opening of the outlet valve of the current low-pressure pump is increased by a first percentage. If the pressure difference between two consecutive pressures is less than the first preset pressure, the opening of the outlet valve of the current low-pressure pump is increased by a second percentage, where the second percentage is greater than the first percentage. If the pressure 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. If the pressure is higher than the upper limit of the low-pressure pipeline, then it is determined whether the difference between two adjacent pressures collected by the pressure detector is less than the first preset pressure. If the pressure difference between two consecutive pressures is not less than the first preset pressure, then the opening of the outlet valve of the current low-pressure pump is reduced by a second percentage. If the difference between two consecutive pressures is less than the first preset pressure, then the opening of the outlet valve of the current low-pressure pump is reduced by a first percentage. Determine whether the opening degree of the outlet valve of the current low-pressure pump is greater than the maximum opening limit; If the opening exceeds the maximum opening limit, then maintain the current opening of the outlet valve of the current low-pressure pump. If the pressure is not greater than the maximum opening limit, then delay for a third preset time and return to the step of determining whether the pressure collected by the pressure detector is lower than the low-pressure pipeline pressure limit.

5. The control method for a liquefied natural gas receiving station as described in claim 1, characterized in that, The liquefied natural gas receiving station also includes an inlet isolation valve for a high-pressure pump and a compressor. The inlet isolation valve for the high-pressure pump is located between the outlet of the low-pressure pump and the condenser port of the recondenser. The compressor is located 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 following steps are also included: 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; When the opening degree of the inlet isolation valve of the current high-pressure pump is within a preset opening degree range centered on the set opening degree, the step of determining the adjustment amount of the inlet regulating valve of the current high-pressure pump based on the total volume flow rate is initiated. Starting the current high-pressure pump includes: Determine whether the inlet regulating valve meets the opening conditions of the high-pressure pump after adjustment; If the conditions are met, then the current high-pressure pump is started; Determine 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 current high-pressure pump is in the start state; 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 the starting state, then it is determined that the current high-pressure pump has been successfully started. If the output volumetric flow rate is not greater than the third preset flow rate and the motor of the current high-pressure pump is not in the start state, then delay for a preset time and return to the step of determining whether the output volumetric 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 start state.

6. The control method for a liquefied natural gas receiving station as described in claim 1, characterized in that, Determine the total volumetric flow rate of all high-pressure pumps, including: Obtain the starting status of the motor and the output volumetric flow rate L of the i-th high-pressure pump. i ; When the motor of the high-pressure pump is in the starting state, if the volumetric flow rate output by the i-th high-pressure pump is not within the volumetric flow rate range of the starting state, then the volumetric flow rate less than the lower limit of the volumetric flow rate range of the starting state is set as the lower limit value, and the volumetric flow rate greater than the upper limit of the volumetric flow rate range of the starting state is set as the upper limit value. When the motor of the high-pressure pump is not started, if the volumetric flow rate output by the i-th high-pressure pump is not within the volumetric flow rate range of the not started state, then the volumetric flow rate less than the lower limit of the volumetric flow rate range of the not started state is set as the lower limit value, and the volumetric flow rate greater than the upper limit of the volumetric flow rate range of the not started state is set as the upper limit value. Determine the total volumetric flow rate output by all high-pressure pumps, the expression for which is: L sum =ΣL i +ΔL; Among them, L sum L represents the total volumetric flow rate. i Let ΔL be the volumetric flow rate output by the i-th high-pressure pump, and let ΔL be the preset change in volumetric flow rate when the high-pressure pump starts or stops. i∈[1,2,3,…,n], and there are n high-pressure pumps in total. Determining the adjustment amount of the inlet regulating valve of the current high-pressure pump based on the volumetric flow rate includes: The total mass flow rate output from the recondenser is determined, and the expression for the total mass flow rate is: L m =1000×L4+L5; Determine the theoretical volumetric flow rate and relative volumetric flow rate through the inlet regulating valve. The expression for the theoretical volumetric flow rate is L2 = L sum -L m / ρ, the expression for the relative volumetric flow rate is L3=L2 / (L max / ρ)×100; Among them, L m L1 is the total mass flow rate output from the recondenser, L4 is the mass flow rate of liquefied natural gas input to the recondenser, L5 is the mass flow rate of evaporated natural gas input to the recondenser, L2 is the theoretical volumetric flow rate, L3 is the relative volumetric flow rate, ρ is the density of liquefied natural gas, and L... max The maximum mass flow rate passing through the inlet regulating valve; The flow range is divided into left-closed and right-open intervals that increase in size and do not overlap, namely the first flow range, the second flow range, the third flow range and the fourth flow range; If the total volumetric flow rate is within the first flow rate range, then y = a1L3 is determined. 2 +a2L3+a3; If the total volumetric flow rate falls within the second or fourth flow rate interval, then y = a4L3 is determined. 2 +a5L3+a6; If the total volumetric flow rate is within the third flow rate range, then y = a7L3 is determined. 2 +a8L3+a9; The theoretical increase in opening degree ΔA3 of the inlet regulating valve is determined, and the relationship of the theoretical increase in opening degree is ΔA3=y-A4; The actual increase in opening degree ΔA2 of the inlet regulating valve is determined, and the relationship of the actual increase in opening degree is ΔA2=KΔA3+ΔB; Where y is the opening degree that the inlet regulating valve needs to be adjusted to maintain the bottom pressure of the recondenser under the current flow rate, A4 is the current opening degree of the inlet regulating valve, K is the weighting coefficient, ΔB is the correction parameter, and a1, a2, a3, ..., a9 are all adjustment coefficients; Determine whether the actual increase in opening degree is within the range of the actual required increase in opening degree of the inlet regulating valve; If the actual increase in opening is not within the range of the actual required increase in opening, and the actual increase in opening is less than the lower limit of the range of the actual required increase in opening, then the actual increase in opening is set to the lower limit of the range of the actual required increase in opening; if the actual increase in opening is not less than the lower limit of the range of the actual required increase in opening, then the actual increase in opening is set to the upper limit of the range of the actual required increase in opening. The required opening degree A2 of the inlet regulating valve is determined, and the relationship for the required opening degree is as follows: A2 = ΔA2 + A4.

7. The control method for a liquefied natural gas receiving station as described in claim 1, characterized in that, Adjusting the opening of the current high-pressure pump's inlet regulating valve and inlet throttle valve based on the bottom pressure of the recondenser and the opening of the high-pressure pump's inlet throttle valve includes: Obtain the opening degree of the inlet throttle valve; The opening of the inlet regulating valve is controlled based on the deviation between the opening degree of the inlet throttle valve and the set opening degree of the inlet throttle valve. Obtain the bottom pressure of the recondenser; The opening degree of the inlet throttle valve is controlled based on the deviation between the bottom pressure of the recondenser and the set bottom pressure of the recondenser.

8. The control method for a liquefied natural gas receiving station as described in claim 1, characterized in that, Before starting the current vaporizer, the following also applies: Control the current high-pressure pump to equalize the pressure so that the pressure difference between the outlet pipe of the current high-pressure pump and the inlet pipe of the current vaporizer is lower than a preset pressure difference; Determine whether the outlet valve of the high-pressure pump is open; If opened, the process will proceed to start the current vaporizer; If it is not opened, the process is delayed for a first preset time and then returns to the step of determining whether the outlet valve of the high-pressure pump is open.

9. The control method for a liquefied natural gas receiving station as described in 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 degree of the outlet valve of the current low-pressure pump based on the difference; Shut down the current high-pressure pump; Determine the total volumetric flow rate of all high-pressure pumps, and determine the adjustment amount of the inlet regulating valve of the current high-pressure pump based on the total volumetric flow rate; When the volumetric flow rate output by the current high-pressure pump is within the normal range, the opening of the inlet regulating valve and the inlet throttle valve of the current high-pressure pump are adjusted based on the bottom pressure of the recondenser and the opening of the inlet throttle valve of the high-pressure pump. Shut down the current low-pressure pump; The current vaporizer is shut down.

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

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