A method for improving energy efficiency of key dynamic equipment in LNG receiving station

Abstract

The present invention relates to a method for improving the energy efficiency of key dynamic equipment of an LNG receiving station. According to the on-site historical operation data, a prediction model and an energy efficiency optimization model are established to predict the energy consumption of key dynamic equipment of the LNG receiving station, including a low-pressure pump in a tank, a BOG compressor, a high-pressure pump for external transmission and a seawater pump. The start-stop combination and the logistics load distribution scheme between the low-pressure pump in a tank, the BOG compressor, the high-pressure pump for external transmission and the seawater pump are optimized to achieve energy saving and consumption reduction optimization of the key dynamic equipment of the receiving station.

Description

Technical Field

[0001] The present invention relates to the technical field of liquefied natural gas, and in particular to a method for improving the energy efficiency of key moving equipment of an LNG receiving station. Background Art

[0002] As the world's energy becomes increasingly scarce, the environmental problems caused by coal and oil are becoming more and more serious. Liquefied natural gas (LNG) has gradually become a new hot spot in the world's oil and gas industry due to its advantages of cleanliness, high efficiency, and ease of use. LNG receiving stations will produce a large amount of flash gas (BOG) under unloading and cold storage cycle conditions, affecting the safe operation of the receiving station. The BOG recondensation system extracts BOG from the storage tank, pressurizes it, recondenses it, and recycles it, and merges it with the LNG from the low-pressure pump in the tank. The high-pressure pump in the gasification and external transmission system pressurizes the combined LNG to the gasifier for external transmission. The main moving equipment involved in the LNG process system are the low-pressure pump in the tank, the BOG compressor, the external high-pressure pump, and the seawater pump, and the main energy consumption is the electricity consumed by the moving equipment.

[0003] In order to reduce the process cost of LNG receiving stations and improve the energy efficiency of equipment operation, there is a real need to fully understand the operating performance of a single device, the parallel relationship between the same type of equipment, and the matching and optimization of the front and back series relationship of different equipment. At present, the operation and start-stop control of on-site equipment have the following problems: 1. To determine the matching optimization plan, we should first obtain the performance curves and energy consumption of low-pressure pumps, high-pressure pumps and seawater pumps under different working conditions, and the BOG processing capacity and energy consumption of BOG compressors under different loads. The site lacks continuous monitoring and data analysis of the operating performance and efficiency of a single device, and the matching operation of low-pressure pumps, BOG compressors and high-pressure pumps should not only grasp the actual operating performance of each device under historical working conditions on site based on historical data, but also be able to predict the actual processing capacity of BOG compressors under different loads.

[0004] 2. The BOG compressor can achieve five-level adjustment of 0%~25%~50%~75%~100% through clearance adjustment and unloading valve adjustment, but load adjustment is generally not used on site, and non-full-load operating conditions are rare. There is a lack of systematic guidance, and it is impossible to conduct actual data analysis of BOG flow, energy consumption and economy under variable load conditions.

[0005] 3. Under different working conditions, the actual flow distribution in the pipeline when multiple low-pressure pumps, high-pressure pumps or seawater pumps are running in parallel is also one of the important factors affecting the pump start and stop plan. At present, the site is still under experience guidance in these aspects and lacks systematic matching optimization plan guidance.

[0006] Therefore, under the premise of fully understanding the actual operating performance of the equipment, the matching optimization of the main dynamic equipment of the LNG receiving station, including the low-pressure pump in the tank, BOG compressor, high-pressure pump and seawater pump, is to include the equipment start-stop and load distribution into the optimization strategy at the same time, which is difficult to achieve with classical mathematical analysis. At present, the optimization operation of the above dynamic equipment is still in the stage of empirical exploration in various receiving stations, and more scientific and effective technical methods and solutions need to be explored. Summary of the invention

[0007] In view of the above problems, the purpose of the present invention is to provide a method for improving the energy efficiency of key dynamic equipment of an LNG receiving station, which can predict the energy consumption of key dynamic equipment of the LNG receiving station including a low-pressure pump in the tank, a BOG compressor, an external high-pressure pump and a seawater pump, and an energy efficiency optimization model, optimize the start-stop combination and logistics load distribution plan between the low-pressure pump in the tank, the BOG compressor, the external high-pressure pump and the seawater pump, and realize energy saving and consumption reduction optimization of key dynamic equipment of the receiving station.

[0008] To achieve the above object, the present invention adopts the following technical solutions: The method for improving energy efficiency of key moving equipment of an LNG receiving station according to the present invention comprises the following steps: Obtain the historical data of relevant structural parameters and operating parameters of key dynamic equipment of LNG receiving stations, and pre-process the historical data of operating parameters using big data analysis; Based on the relevant structural parameters of the key dynamic equipment of the LNG receiving station and the historical data of the pre-processed operating parameters, an energy consumption prediction model for the key dynamic equipment of the LNG receiving station is established; Based on the established energy consumption prediction model of key dynamic equipment of LNG receiving station, the energy efficiency optimization model of key dynamic equipment of LNG receiving station process system is established by using particle swarm optimization algorithm and mixed integer nonlinear optimization method, and the corresponding relationship between operating parameters and energy efficiency indicators of LNG receiving station process system is constructed; The operating parameters of the key dynamic equipment of the LNG receiving station are substituted into the energy efficiency optimization model of the process system of the LNG receiving station, and the energy efficiency optimization values ​​of the process system of the LNG receiving station under different dynamic equipment combinations are calculated. The minimum energy consumption and control scheme of the process system of the LNG receiving station under different LNG output volumes are obtained, and the energy consumption cost required for the process system of the LNG receiving station is determined accordingly.

[0009] The method for improving energy efficiency of key moving equipment of the LNG receiving station, preferably, the key moving equipment of the LNG receiving station includes a low-pressure pump in the tank, a BOG compressor, an external high-pressure pump and a seawater pump; The relevant structural parameters of the key dynamic equipment of the LNG receiving station include BOG exhaust volume, cylinder inner diameter, piston rod diameter, piston stroke, clearance volume, rotation speed, etc. in the BOG compressor, slip coefficient, impeller inlet and outlet diameter, number of blades and blade inlet displacement coefficient in the low-pressure pump in the tank and the high-pressure pump for external transmission; The historical data of the operating parameters of the key dynamic equipment of the LNG receiving station include BOG composition, external LNG composition, LNG inlet and outlet temperature, pressure, flow rate and speed in the low-pressure pump in the tank, BOG inlet and outlet temperature, pressure, flow rate, speed and motor power in the BOG compressor, LNG inlet and outlet temperature, pressure, flow rate and speed in the external high-pressure pump, and operating parameters of the inlet and outlet temperature, pressure, flow rate and speed in the seawater pump.

[0010] The method for improving energy efficiency of key moving equipment of the LNG receiving station is preferably such that the energy consumption prediction model of key moving equipment of the LNG receiving station is a prediction model established by adopting an RBF neural network model, a mechanism model or a hybrid model integrating the RBF neural network model and the mechanism model.

[0011] The method for improving energy efficiency of key dynamic equipment of the LNG receiving station, preferably, the operating parameters of the process system of the LNG receiving station include BOG components, external LNG components, LNG inlet and outlet temperatures, pressures and flow rates in the low-pressure pump in the tank, BOG inlet and outlet temperatures, pressures and flow rates in the BOG compressor, LNG inlet and outlet temperatures, pressures and flow rates in the external high-pressure pump, and inlet and outlet temperatures, pressures and flow rate operating parameters in the seawater pump.

[0012] The energy efficiency indicators of the LNG receiving station process system include the unit energy consumption of the low-pressure pump in the tank, the unit energy consumption of the BOG compressor, the unit energy consumption of the external high-pressure pump, the unit energy consumption of the seawater pump and the comprehensive energy consumption during the operation period.

[0013] The method for improving the energy efficiency of key dynamic equipment of the LNG receiving station is preferably an optimization model established by using a particle swarm optimization algorithm and a mixed integer nonlinear programming method, and the specific establishment steps are as follows: On the basis of meeting the LNG flow demand and minimum pressure demand of the entire site, the total energy consumption is minimized by adjusting the combination of different pumps and compressors. The optimization process first determines the required LNG export volume, and calculates the total number of pumps that need to be turned on based on this demand. Then, the actual flow and operating power of each pump in the parallel pump unit are determined by the following formula: Assuming that there are n pumps working in parallel, the characteristic equation of the submersible pump obtained from the pump parameter model is as follows: (1) In the formula, a 1 、a 2、a n , b 1 、b 2 、b n 、c 1 、c 2. c n are model coefficients, all calculated based on the particle swarm optimization algorithm; is the flow rate of the nth pump; H 1 is the head of the first pump; H 2 is the head of the second pump; H n is the head of the nth pump; When multiple submersible pumps are operated in parallel, they provide flow to a common pipeline system; the outlet of each pump is connected to the shared main pipeline, resulting in the sum of the flow through each pump being equal to the total system flow, and the head provided by each pump being equal, equal to the total system head. This relationship is expressed by the following equation: (2) In the formula, Q tot is the total flow; H tot is the total lift; Knowing the coefficients, the total flow rate Q tot It has been determined that the purpose is to solve the flow rate and head of each pump. By integrating the above equations, a set of equations about the flow rate Q of each pipe section is constructed. n And the nonlinear equations of head H: (3) In the formula, H tot is the total lift; Q n is the flow rate of the nth pump; Let equation (3) be expressed as , expressed as: (4) In the formula, f ( x )for F ( X ), x1~x n+1 Corresponding to the equations (3) Q 1. Q 2.…… H ; The solution is: (5) like The second-order partial derivatives with respect to the independent variable are continuous in the region under discussion and are based on the Taylor formula in Expanding it and ignoring terms above the second order gives: (6) make (7) When the matrix When it is non-singular, the solution of the equation exists and is unique. Take the solution and make k+1 approximations, then: (8) By using Newton's iteration method to solve this set of equations, the actual flow rate of each pump in the parallel pump unit can be obtained; Calculate the minimum power under different pump unit combination conditions. Finally, based on these calculation results, provide an operation optimization plan for the LNG receiving station pump unit. Since a single pump has constraints on the allowable operating flow range, and the same type of pumps at the LNG receiving station are all operated in parallel, when the total external flow is determined, the number of operating pumps is determined, and the actual flow of each pump is solved by the above method; Total power of pumping stations in combined operation P tot Minimum is the objective function: (9) in: Only 0 and 1 are taken, 0 means i The pump is out of service, 1 means i The pump is running; Q i Indicates i Flow rate of the pump, m 3 / h; f i ( Q i ) indicates power P i It is traffic Q i Function of Since a single pump has limitations on the allowable operating flow range and pressure range, the flow constraint and pressure constraint of the pump unit are expressed as: (10) In the formula, Q i For the i The flow rate of the pump; p i For the i The pressure of the pump; Due to the limitation of the flow range allowed for a single pump and the requirement to meet the total external output of the LNG receiving station, the number of various pumps opened at the receiving station and the total flow rate Q tot There is a certain functional relationship: (11) in: Only 0 and 1 are taken, 0 means i The pump is out of service, 1 means i The pump is running; Q i Indicates i The flow rate of the pump; Q tot is the total flow, m 3 / h; Under the premise of not extracting LNG from low tank liquid level for external transmission, the total head should be equal to the head required by external transmission pressure minus the pipe resistance loss: (12) In the formula, H i is the tank liquid level, m; H i is the required head of external transmission pressure, m; is the pipe resistance loss coefficient; Q i For the i Flow rate of the pump, m 3 / h; The penalty function method is used to solve the specific constraint problems in the proposed optimization model. The penalty function method transforms the various constraint problems in the actual operation of the pumping station into partial constraint or unconstrained problems by introducing penalty factors, so as to facilitate the solution. According to the different constraint conditions in the model, the corresponding penalty functions are designed, including the single pump flow penalty function and the tank liquid level penalty function. For a single pump, the flow constraint can be expressed as follows: (13) In the formula, W Ti is the single pump flow penalty function; Q i For the i Flow rate of the pump, m 3 / h; Q beq is the flow rate at the highest efficiency point, m 3 / h; The tank level penalty function is set to avoid the low-pressure pump from extracting LNG from the low-level tank for external transmission. The tank level penalty function can be expressed by the following mathematical expression: (14) In the formula,W cHi Tank level penalty function; H i is the tank liquid level, m; α is a positive constant; In order to prevent the LNG from being exported when the internal LNG level approaches the minimum safe level of the tank, a tank level penalty function mechanism based on an inverse proportional function is adopted. In this mechanism, a positive constant is set. α , when the liquid level inside the tank drops to close to its minimum allowable level, the value of the liquid level penalty function will increase sharply to infinity; In the method for improving energy efficiency of key moving equipment of the LNG receiving station, preferably, the optimization model of the high-pressure pump in the key moving equipment is as follows: Total operating power of LNG high pressure pump station P tot The minimization of the objective function is the optimization model, and the energy consumption optimization fitness function is shown as follows: (15) In the formula, P tot The total operating power of the high-pressure pump station; is the weight coefficient of the high-pressure pump flow penalty function; W Ti is the pump flow penalty function; The constraints of pump station operation are introduced, including flow constraint, outlet pressure constraint and the number of pump stations to be opened. The constraints are: (16) In the method for improving energy efficiency of key moving equipment of the LNG receiving station, preferably, the optimization model of the low-pressure pump in the key moving equipment is as follows: Consistent with the high-pressure pump unit, the LNG low-pressure pump unit operates at a total power of P tot The minimum is the objective function, and the energy consumption optimization fitness function is shown as follows: (17) In the formula, is the weight coefficient of the low-pressure pump flow penalty function; W Ti is the pump flow penalty function; is the weight coefficient of the penalty function of the low-pressure pump tank level; W cHi Tank level penalty function; The low-pressure pump flow constraint has an operating flow range constraint, but due to the different LNG liquid levels in each storage tank, the actual flow of the low-pressure pump in different storage tanks varies greatly, and the low-pressure pump is allowed to operate in a wide range of flow. This does not hold true for the low-pressure pump unit, so the constraint is: (18) In the formula, Only 0 and 1 are taken, 0 means i The pump is out of service, 1 means i The pump is running; Q i Indicates i The flow rate of the pump; Q tot is the total flow, m 3 / h; In the method for improving energy efficiency of key moving equipment of the LNG receiving station, preferably, the optimization model of the seawater pump in the key moving equipment is as follows: Since the pump pool liquid level fluctuates with the seawater tide, the flow rate of the seawater pump unit will change with the liquid level fluctuation within a day. Therefore, the seawater pump unit cannot operate at a certain flow rate. The minimum is the objective function, which should be the minimum daily operating total power. The energy consumption optimization fitness function is shown as follows: (19) in For j Time period sea water pump i flow; For j Time period sea water pump i power; To calculate the length of time; The seawater pump and high-pressure pump at the LNG receiving station are operated in a one-to-one manner, that is, one seawater pump is matched with one high-pressure pump, and the constraints are: (20) in, Only 0 and 1 are taken, 0 means i The pump is out of service, 1 means i The pump is running; Q totS is the total flow rate of the seawater pump, m 3 / h; Q tot is the total LNG flow, m 3 / h; Q i Indicates i Flow rate of the pump, m 3 / h; It is the total number of seawater pumps in operation.

[0014] The method for improving energy efficiency of key moving equipment of LNG receiving station, preferably, the optimization model of BOG compressor in the key moving equipment is as follows By determining the inlet pressure, temperature, flow rate and outlet pressure of the BOG compressor, the compression load can be calculated, and the startup combination of the BOG compressor unit and the flow rate allocated to each unit can be solved, so that the energy consumption of the entire compressor unit per unit time is minimized; therefore, the energy consumption objective function of the compressor can be expressed as: (twenty one) in, P tot is the total power of the compressor unit, kW; Only 0 and 1 are taken, 0 means i The compressor is out of service, 1 means i The compressor is running; P comp,i For the i Power of compressor; Due to the limitations of the inlet temperature, pressure, flow rate and power of a single compressor, the constraints are: (twenty two) In the formula, Only 0 and 1 are taken, 0 means i The pump is out of service, 1 means i The pump is running; Q i Indicates i Flow rate of compressor, Nm 3 / h; Q comp Indicates the total flow of the compressor unit, Nm 3 / h; p si,comp 、p di,comp Respectively represent the compressor inlet and outlet pressure, MPag; T si,comp 、T di,comp Respectively represent the compressor inlet and outlet temperatures, °C; P comp,i For the i Power of compressor, kW.

[0015] The present invention adopts the above technical solution, which has the following advantages: (1) By integrating historical data mining technology and equipment operation mechanism, a key equipment energy consumption prediction model is established, which can accurately reflect and predict the actual operating characteristics of a single key equipment, and clarify the actual processing capacity and actual power consumption of each BOG compressor, and the actual power consumption of each low-pressure pump, high-pressure pump and seawater pump under different working conditions. This is the key energy consumption information of equipment that is currently lacking on site and needs to be mastered.

[0016] (2) The energy efficiency optimization model of key dynamic equipment of the LNG receiving station, which includes all key equipment, is established by using methods such as particle swarm optimization algorithm and mixed integer nonlinear programming method. It can give clear start-up plans and load distribution of each key equipment under different LNG export volumes, which is better than empirical operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Throughout the accompanying drawings, the same reference numerals are used to represent the same components. In the accompanying drawings: Figure 1 It is a technical route flow chart of the present invention. DETAILED DESCRIPTION

[0018] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0019] The present invention provides a method for improving the energy efficiency of key dynamic equipment of an LNG receiving station. According to the on-site historical operation data, a prediction model and an energy efficiency optimization model are established to predict the energy consumption of key dynamic equipment of the LNG receiving station, including a low-pressure pump in the tank, a BOG compressor, a high-pressure pump for external transmission and a seawater pump. The start-stop combination and the logistics load distribution plan between the low-pressure pump in the tank, the BOG compressor, the high-pressure pump for external transmission and the seawater pump are optimized to achieve energy saving and consumption reduction optimization of the key dynamic equipment of the receiving station.

[0020] like Figure 1 As shown, the method for improving energy efficiency of key moving equipment of an LNG receiving station provided by the present invention comprises the following steps: S1. Obtain the historical data of relevant structural parameters and operating parameters of key dynamic equipment of the LNG receiving station, and pre-process the historical data of operating parameters using big data analysis; S2. Establish an energy consumption prediction model for key moving equipment of the LNG receiving station based on the relevant structural parameters of key moving equipment of the LNG receiving station and the historical data of pre-processed operating parameters; S3. Based on the established energy consumption prediction model of key dynamic equipment of LNG receiving station, the energy efficiency optimization model of key dynamic equipment of LNG receiving station process system is established by using particle swarm optimization algorithm and mixed integer nonlinear optimization method, and the corresponding relationship between operating parameters and energy efficiency indicators of LNG receiving station process system is constructed; S4. Substitute the operating parameters of the key dynamic equipment of the LNG receiving station into the energy efficiency optimization model of the process system of the LNG receiving station, calculate the energy efficiency optimization value of the process system of the LNG receiving station under different dynamic equipment combination operating conditions, obtain the minimum energy consumption and control scheme of the process system of the LNG receiving station under different LNG output volumes, and thereby determine the energy consumption cost required for the process system of the LNG receiving station.

[0021] In the above embodiment, preferably, the key dynamic equipment of the LNG receiving station includes a low-pressure pump in the tank, a BOG compressor, an external high-pressure pump and a seawater pump; The relevant structural parameters of the key dynamic equipment of the LNG receiving station include BOG exhaust volume, cylinder inner diameter, piston rod diameter, piston stroke, clearance volume, rotation speed, etc. in the BOG compressor, slip coefficient, impeller inlet and outlet diameter, number of blades and blade inlet displacement coefficient in the low-pressure pump in the tank and the high-pressure pump for external transmission; The historical data of the operating parameters of the key dynamic equipment of the LNG receiving station include BOG composition, external LNG composition, LNG inlet and outlet temperature, pressure, flow rate and speed in the low-pressure pump in the tank, BOG inlet and outlet temperature, pressure, flow rate, speed and motor power in the BOG compressor, LNG inlet and outlet temperature, pressure, flow rate and speed in the external high-pressure pump, and operating parameters of the inlet and outlet temperature, pressure, flow rate and speed in the seawater pump.

[0022] In the above embodiment, preferably, the energy consumption prediction model of key dynamic equipment of the LNG receiving station is a prediction model established by adopting an RBF neural network model, a mechanism model or a hybrid model integrating the RBF neural network model and the mechanism model.

[0023] In the above embodiment, preferably, the operating parameters of the process system of the LNG receiving station include BOG components, external LNG components, LNG inlet and outlet temperatures, pressures and flow rates in the low-pressure pump in the tank, BOG inlet and outlet temperatures, pressures and flow rates in the BOG compressor, LNG inlet and outlet temperatures, pressures and flow rates in the external high-pressure pump, and inlet and outlet temperatures, pressures and flow rates in the seawater pump; The energy efficiency indicators of the LNG receiving station process system include the unit energy consumption of the low-pressure pump in the tank, the unit energy consumption of the BOG compressor, the unit energy consumption of the external high-pressure pump, the unit energy consumption of the seawater pump and the comprehensive energy consumption during the operation period.

[0024] In the above embodiment, preferably, the energy efficiency optimization model of the LNG receiving station process system is an optimization model established by using a particle swarm optimization algorithm and a mixed integer nonlinear programming method, and the specific establishment steps are as follows: On the basis of meeting the LNG flow demand and minimum pressure demand of the entire site, the total energy consumption is minimized by adjusting the combination of different pumps and compressors. The optimization process first determines the required LNG export volume, and calculates the total number of pumps that need to be turned on based on this demand. Then, the actual flow and operating power of each pump in the parallel pump unit are determined by the following formula: Assuming that there are n pumps working in parallel, the characteristic equation of the submersible pump obtained from the pump parameter model is as follows: (1) In the formula, a 1 ~a n , b 1 ~b n 、c 1 ~c n are model coefficients, all calculated based on the particle swarm optimization algorithm; is the flow rate of the nth pump, m 3 / h; H 1 is the head of the first pump; H 2 is the head of the second pump; H n is the head of the nth pump, m; When multiple submersible pumps are operated in parallel, each pump provides flow to a common pipeline system; the outlet of each pump is connected to the shared main pipeline, resulting in the sum of the flow through each pump being equal to the total system flow, and the head provided by each pump is equal, equal to the total system head. This relationship can be expressed by the following equation: (2) In the formula, Q tot is the total flow; H tot is the total lift; Knowing the coefficients, the total flow Q tot It has been determined that the purpose is to solve the flow rate and head of each pump. By integrating the above equations, a set of equations about the flow rate of each pipe section is constructed. Q n And the nonlinear equations of head H: (3) In the formula, H tot is the total head, m; Q n is the flow rate of the nth pump, m 3 / h; Let equation (3) be expressed as , expressed as: (4) In the formula, f ( x )for F ( X ), x1~x n+1 Corresponding to the equations (3) Q 1. Q 2.…… H ; The solution is: (5) like The second-order partial derivatives with respect to the independent variable are continuous in the region under discussion and are based on the Taylor formula in Expanding it and ignoring terms above the second order gives: (6) make (7) When the matrix When it is non-singular, the solution of the equation exists and is unique. Take the solution and make k+1 approximations, then: (8) By using Newton's iteration method to solve this set of equations, the actual flow rate of each pump in the parallel pump unit can be obtained; Calculate the minimum power under different pump unit combinations. Finally, based on these calculation results, provide an operation optimization plan for the LNG receiving station pump unit. Since a single pump has constraints on the allowable operating flow range, and the same type of pumps at the LNG receiving station are all operated in parallel, when the total external flow is determined, the number of operating pumps is determined, and the actual flow of each pump can be solved by the above method. Total power of pumping stations in combined operation P tot Minimum is the objective function: (9) in: Only 0 and 1 are taken, 0 means i The pump is out of service, 1 means i The pump is running;Q i Indicates i Flow rate of the pump, m 3 / h; f i ( Q i ) indicates power P i It is traffic Q i Function of Since a single pump has limitations on the allowable operating flow range and pressure range, the flow constraint and pressure constraint of the pump unit can be expressed as: (10) In the formula, Q i For the i Flow rate of the pump, m 3 / h; p i For the i The pressure of the pump, kPag; Due to the limitation of the flow range allowed for a single pump and the requirement to meet the total external output of the LNG receiving station, the number of various pumps opened at the receiving station and the total flow rate Q tot There is a certain functional relationship: (11) in: Only 0 and 1 are taken, 0 means i The pump is out of service, 1 means i The pump is running; Q i Indicates i The flow rate of the pump; Q tot is the total flow, m 3 / h; Under the premise of not extracting LNG from low tank liquid level for external transmission, the total head should be equal to the head required by external transmission pressure minus the pipe resistance loss: (12) In the formula, H i is the tank liquid level, m; H i is the required head of external transmission pressure, m; is the pipe resistance loss coefficient; Q i For the i Flow rate of the pump, m 3 / h; The penalty function method is used to solve the specific constraint problems in the proposed optimization model. The penalty function method transforms the various constraint problems in the actual operation of the pumping station into partial constraint or unconstrained problems by introducing penalty factors, so as to facilitate the solution. According to the different constraint conditions in the model, the corresponding penalty functions are designed, including the single pump flow penalty function and the tank liquid level penalty function. For a single pump, the flow constraint can be expressed as follows: (13) In the formula, W Ti is the single pump flow penalty function; Q i For the i Flow rate of the pump, m 3 / h; Q beq is the flow rate at the highest efficiency point, m 3 / h; The tank level penalty function is set to avoid the low-pressure pump from extracting LNG from the low-level tank for external transmission. The tank level penalty function can be expressed by the following mathematical expression: (14) In the formula, W cHi Tank level penalty function; H i is the tank liquid level, m; α is a positive constant; In order to prevent the LNG from being exported when the internal LNG level approaches the minimum safe level of the tank, a tank level penalty function mechanism based on an inverse proportional function is adopted. In this mechanism, a positive constant is set. α , when the liquid level inside the tank drops to close to its minimum allowable level, the value of the liquid level penalty function will increase sharply to infinity; In the above embodiment, preferably, the high-pressure pump optimization model in the key moving equipment is as follows: Total operating power of LNG high pressure pump station P tot The minimization of the objective function is the optimization model, and the energy consumption optimization fitness function is shown as follows: (15) In the formula, P tot The total operating power of the high-pressure pump station; is the weight coefficient of the high-pressure pump flow penalty function; W Ti is the pump flow penalty function; The constraints of pump station operation are introduced, including flow constraint, outlet pressure constraint and the number of pump stations to be opened. The constraints are: (16) In the above embodiment, preferably, the optimization model of the low-pressure pump in the key moving equipment is as follows: Consistent with the high-pressure pump unit, the LNG low-pressure pump unit operates at a total power of P tot The minimum is the objective function, and the energy consumption optimization fitness function is shown as follows: (17) In the formula, is the weight coefficient of the low-pressure pump flow penalty function; W Ti is the pump flow penalty function; is the weight coefficient of the penalty function of the low-pressure pump tank level; W cHi Tank level penalty function; The low-pressure pump flow constraint has an operating flow range constraint, but due to the different LNG liquid levels in each storage tank, the actual flow of the low-pressure pump in different storage tanks varies greatly, and the low-pressure pump is allowed to operate in a wide range of flow. This does not hold true for the low-pressure pump unit, so the constraint is: (18) In the formula, Only 0 and 1 are taken, 0 means i The pump is out of service, 1 means i The pump is running; Q i Indicates i The flow rate of the pump; Q tot is the total flow, m 3 / h.

[0025] In the above embodiment, preferably, the seawater pump optimization model in the key moving equipment is as follows: Since the pump pool liquid level fluctuates with the seawater tide, the flow rate of the seawater pump unit will change with the liquid level fluctuation within a day. Therefore, the seawater pump unit cannot operate at a certain flow rate. The minimum is the objective function, which should be the minimum daily operating total power. The energy consumption optimization fitness function is shown as follows: (19) in For j Time period sea water pump i flow; For j Time period sea water pumpi power; To calculate the length of time; The seawater pump and high-pressure pump at the LNG receiving station are operated in a one-to-one manner, that is, one seawater pump is matched with one high-pressure pump, and the constraints are: (20) in, Only 0 and 1 are taken, 0 means i The pump is out of service, 1 means i The pump is running; Q totS is the total flow rate of the seawater pump, m 3 / h; Q tot is the total LNG flow, m 3 / h; Q i Indicates i Flow rate of the pump, m 3 / h; It is the total number of seawater pumps in operation.

[0026] In the above embodiment, preferably, the optimization model of the BOG compressor in the key dynamic equipment is as follows: By determining the inlet pressure, temperature, flow rate and outlet pressure of the BOG compressor, the compression load can be calculated, and the startup combination of the BOG compressor unit and the flow rate allocated to each unit can be solved, so that the energy consumption of the entire compressor unit per unit time is minimized; therefore, the energy consumption objective function of the compressor can be expressed as: (twenty one) in, P tot is the total power of the compressor unit, kW; Only 0 and 1 are taken, 0 means i The compressor is out of service, 1 means i The compressor is running; P comp,i For the i Power of compressor; Due to the limitations of the inlet temperature, pressure, flow rate and power of a single compressor, the constraints are: (twenty two) In the formula, Only 0 and 1 are taken, 0 means i The pump is out of service, 1 means i The pump is running; Q i Indicates i Flow rate of compressor, Nm 3 / h;Q comp Indicates the total flow of the compressor unit, Nm 3 / h; p si,comp 、p di,comp Respectively represent the compressor inlet and outlet pressure, MPag; T si,comp 、T di,comp Respectively represent the compressor inlet and outlet temperatures, ℃; P comp,i For the i Power of compressor, kW.

[0027] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving the energy efficiency of key moving equipment in an LNG receiving station, characterized in that: The steps include: Obtain the historical data of relevant structural parameters and operating parameters of key dynamic equipment of the LNG receiving station, and pre-process the historical data of operating parameters using big data analysis; Based on the relevant structural parameters of the key dynamic equipment of the LNG receiving station and the historical data of the pre-processed operating parameters, an energy consumption prediction model for the key dynamic equipment of the LNG receiving station is established; Based on the established energy consumption prediction model of key dynamic equipment of LNG receiving station, the energy efficiency optimization model of key dynamic equipment of LNG receiving station process system is established by using particle swarm optimization algorithm and mixed integer nonlinear optimization method, and the corresponding relationship between operating parameters and energy efficiency indicators of LNG receiving station process system is constructed; The operating parameters of the key dynamic equipment of the LNG receiving station are substituted into the energy efficiency optimization model of the process system of the LNG receiving station, and the energy efficiency optimization values ​​of the process system of the LNG receiving station under different dynamic equipment combinations are calculated. The minimum energy consumption and control scheme of the process system of the LNG receiving station under different LNG output volumes are obtained, and the energy consumption cost required for the process system of the LNG receiving station is determined accordingly.

2. The method for improving energy efficiency of key moving equipment of an LNG receiving station according to claim 1 is characterized in that: The key dynamic equipment of the LNG receiving station includes low-pressure pumps in the tank, BOG compressors, high-pressure pumps for external transmission and seawater pumps; The relevant structural parameters of the key dynamic equipment of the LNG receiving station include BOG exhaust volume, cylinder inner diameter, piston rod diameter, piston stroke, clearance volume, rotation speed, etc. in the BOG compressor, slip coefficient, impeller inlet and outlet diameter, number of blades and blade inlet displacement coefficient in the low-pressure pump in the tank and the high-pressure pump for external transmission; The historical data of the operating parameters of the key dynamic equipment of the LNG receiving station include BOG composition, external LNG composition, LNG inlet and outlet temperature, pressure, flow rate and speed in the low-pressure pump in the tank, BOG inlet and outlet temperature, pressure, flow rate, speed and motor power in the BOG compressor, LNG inlet and outlet temperature, pressure, flow rate and speed in the external high-pressure pump, and operating parameters of the inlet and outlet temperature, pressure, flow rate and speed in the seawater pump.

3. The method for improving energy efficiency of key moving equipment of an LNG receiving station according to claim 1 is characterized in that: The energy consumption prediction model for key dynamic equipment of the LNG receiving station is a prediction model established by adopting a RBF neural network model, a mechanism model or a hybrid model integrating the RBF neural network model and the mechanism model.

4. The method for improving energy efficiency of key moving equipment of an LNG receiving station according to claim 1 is characterized in that: The operating parameters of the process system of the LNG receiving station include BOG components, LNG components for external transmission, LNG inlet and outlet temperatures, pressures and flow rates in the low-pressure pump in the tank, BOG inlet and outlet temperatures, pressures and flow rates in the BOG compressor, LNG inlet and outlet temperatures, pressures and flow rates in the high-pressure pump for external transmission, and inlet and outlet temperatures, pressures and flow rates in the seawater pump; The energy efficiency indicators of the LNG receiving station process system include the unit energy consumption of the low-pressure pump in the tank, the unit energy consumption of the BOG compressor, the unit energy consumption of the external high-pressure pump, the unit energy consumption of the seawater pump and the comprehensive energy consumption during the operation period.

5. The method for improving energy efficiency of key moving equipment of an LNG receiving station according to claim 4 is characterized in that: The energy efficiency optimization model of the LNG receiving station process system is an optimization model established by using a particle swarm optimization algorithm and a mixed integer nonlinear programming method. The specific establishment steps are as follows: On the basis of meeting the LNG flow demand and minimum pressure demand of the entire site, the total energy consumption is minimized by adjusting the combination of different pumps and compressors. The optimization process first determines the required LNG export volume, and calculates the total number of pumps that need to be turned on based on this demand. Then, the actual flow and operating power of each pump in the parallel pump unit are determined by the following formula: Assuming that there are n pumps working in parallel, the characteristic equation of the submersible pump obtained from the pump parameter model is as follows: (1) In the formula, a 1 、a 2 、a n , b 1 、b 2 、b n 、c 1 、c 2. c n are model coefficients, all calculated based on the particle swarm optimization algorithm; is the flow rate of the nth pump; H 1 is the head of the first pump; H 2 is the head of the second pump; H n is the head of the nth pump; When multiple submersible pumps are operated in parallel, they provide flow to a common pipeline system; the outlet of each pump is connected to the shared main pipeline, resulting in the sum of the flow through each pump being equal to the total system flow, and the head provided by each pump being equal, equal to the total system head. This relationship is expressed by the following equation: (2) In the formula, Q tot is the total flow; H tot is the total lift; Knowing the coefficients, the total flow rate Q tot It has been determined that the purpose is to solve the flow rate and head of each pump. By integrating the above equations, a set of equations about the flow rate Q of each pipe section is constructed. n And the nonlinear equations of head H: (3) In the formula, H tot is the total lift; Q n is the flow rate of the nth pump; Let equation (3) be expressed as , expressed as: (4) In the formula, f ( x )for F ( X ), x1~x n+1 Corresponding to the equations (3) Q 1. Q 2.…… H ; The solution is: (5) like The second-order partial derivatives with respect to the independent variable are continuous in the region under discussion and are based on the Taylor formula in Expanding it and ignoring terms above the second order gives: (6) make (7) When the matrix When it is non-singular, the solution of the equation exists and is unique. Take the solution and make k+1 approximations, then: (8) By using Newton's iteration method to solve this set of equations, the actual flow rate of each pump in the parallel pump unit can be obtained; Calculate the minimum power under different pump unit combination conditions. Finally, based on these calculation results, provide an operation optimization plan for the LNG receiving station pump unit. Since a single pump has constraints on the allowable operating flow range, and the same type of pumps at the LNG receiving station are all operated in parallel, when the total external flow is determined, the number of operating pumps is determined, and the actual flow of each pump is solved by the above method; Total power of pumping stations in combined operation P tot Minimum is the objective function: (9) in: Only 0 and 1 are taken, 0 means i The pump is out of service, 1 means i The pump is running; Q i Indicates i Flow rate of the pump, m 3 / h; f i ( Q i ) indicates power P i It is traffic Q i Function of Since a single pump has limitations on the allowable operating flow range and pressure range, the flow constraint and pressure constraint of the pump unit are expressed as: (10) In the formula, Q i For the i The flow rate of the pump; p i For the i The pressure of the pump; Due to the limitation of the flow range allowed for a single pump and the requirement to meet the total external output of the LNG receiving station, the number of various pumps opened at the receiving station and the total flow rate Q tot There is a certain functional relationship: (11) in: Only 0 and 1 are taken, 0 means i The pump is out of service, 1 means i The pump is running; Q i Indicates i The flow rate of the pump; Q tot is the total flow, m 3 / h; Under the premise of not extracting LNG from low tank liquid level for external transmission, the total head should be equal to the head required by external transmission pressure minus the pipe resistance loss: (12) In the formula, H i is the tank liquid level, m; H i is the required head of external transmission pressure, m; is the pipe resistance loss coefficient; Q i For the i Flow rate of the pump, m 3 / h; The penalty function method is used to solve the specific constraint problems in the proposed optimization model. The penalty function method transforms the various constraint problems in the actual operation of the pumping station into partial constraint or unconstrained problems by introducing penalty factors, so as to facilitate the solution. According to the different constraint conditions in the model, the corresponding penalty functions are designed, including the single pump flow penalty function and the tank liquid level penalty function. For a single pump, the flow constraint can be expressed as follows: (13) In the formula, W Ti is the single pump flow penalty function; Q i For the i Flow rate of the pump, m 3 / h; Q beq is the flow rate at the highest efficiency point, m 3 / h; The tank level penalty function is set to avoid the low-pressure pump from extracting LNG from the low-level tank for external transmission. The tank level penalty function can be expressed by the following mathematical expression: (14) In the formula, W cHi Tank level penalty function; H i is the tank liquid level, m; α is a positive constant; In order to prevent the LNG from being exported when the internal LNG level approaches the minimum safe level of the tank, a tank level penalty function mechanism based on an inverse proportional function is adopted. In this mechanism, a positive constant is set. α , when the liquid level inside the tank drops to close to its minimum allowable level, the value of the liquid level penalty function will increase sharply to infinity.

6. The method for improving energy efficiency of key moving equipment of an LNG receiving station according to claim 5 is characterized in that: The optimization model of the high-pressure pump in the key dynamic equipment is as follows: Total operating power of LNG high pressure pump station P tot The minimization of the objective function is the optimization model, and the energy consumption optimization fitness function is shown as follows: (15) In the formula, P tot The total operating power of the high-pressure pump station; is the weight coefficient of the high-pressure pump flow penalty function; W Ti is the pump flow penalty function; The constraints of pump station operation are introduced, including flow constraint, outlet pressure constraint and the number of pump stations to be opened. The constraints are: (16)。 7. The method for improving energy efficiency of key moving equipment of an LNG receiving station according to claim 5 is characterized in that: The optimization model of the low-pressure pump in the key dynamic equipment is as follows: Consistent with the high-pressure pump unit, the LNG low-pressure pump unit operates at a total power of P tot The minimum is the objective function, and the energy consumption optimization fitness function is shown as follows: (17) In the formula, is the weight coefficient of the low-pressure pump flow penalty function; W Ti is the pump flow penalty function; is the weight coefficient of the penalty function of the low-pressure pump tank level; W cHi Tank level penalty function; The low-pressure pump flow constraint has an operating flow range constraint, but due to the different LNG liquid levels in each storage tank, the actual flow of the low-pressure pump in different storage tanks varies greatly, and the low-pressure pump is allowed to operate in a wide range of flow. This does not hold true for the low-pressure pump unit, so the constraint is: (18) In the formula, Only 0 and 1 are taken, 0 means i The pump is out of service, 1 means i The pump is running; Q i Indicates i The flow rate of the pump; Q tot is the total flow.

8. The method for improving energy efficiency of key moving equipment of an LNG receiving station according to claim 5 is characterized in that: The optimization model of the seawater pump in the key dynamic equipment is as follows: Since the pump pool liquid level fluctuates with the seawater tide, the flow rate of the seawater pump unit will change with the liquid level fluctuation within a day. Therefore, the seawater pump unit cannot operate at a certain flow rate. The minimum is the objective function, which should be the minimum daily operating total power. The energy consumption optimization fitness function is shown as follows: (19) in For j Time period sea water pump i flow; For j Time period sea water pump i power; To calculate the length of time; The seawater pump and high-pressure pump at the LNG receiving station are operated in a one-to-one manner, that is, one seawater pump is matched with one high-pressure pump, and the constraints are: (20) in, Only 0 and 1 are taken, 0 means i The pump is out of service, 1 means i The pump is running; Q totS is the total flow rate of the seawater pump, m 3 / h; Q tot is the total LNG flow, m 3 / h; Q i Indicates i Flow rate of the pump, m 3 / h; It is the total number of seawater pumps in operation.

9. The method for improving energy efficiency of key moving equipment of an LNG receiving station according to claim 5 is characterized in that: The optimization model of the BOG compressor in the key dynamic equipment is as follows By determining the inlet pressure, temperature, flow rate and outlet pressure of the BOG compressor, the compression load can be calculated, and the startup combination of the BOG compressor unit and the flow rate allocated to each unit can be solved, so that the energy consumption of the entire compressor unit per unit time is minimized; therefore, the energy consumption objective function of the compressor can be expressed as: (21) in, P tot is the total power of the compressor unit, kW; Only 0 and 1 are taken, 0 means i The compressor is out of service, 1 means i The compressor is running; P comp,i For the i Power of compressor; Due to the limitations of the inlet temperature, pressure, flow rate and power of a single compressor, the constraints are: (22) In the formula, Only 0 and 1 are taken, 0 means i The pump is out of service, 1 means i The pump is running; Q i Indicates i Flow rate of compressor, Nm 3 / h; Q comp Indicates the total flow of the compressor unit, Nm 3 / h; p si,comp 、p di,comp Respectively represent the compressor inlet and outlet pressure, MPag; T si,comp 、T di,comp Respectively represent the compressor inlet and outlet temperatures, °C; P comp,i For the i Power of compressor, kW.

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