Method and system for converting heat exchange network flow chart into multistage superstructure

Abstract

The invention discloses a method and system for converting a heat exchange network flow chart into a multi-stage superstructure, and belongs to the technical field of petrochemical engineering in the process industry. According to the method, the initial cold material flow level and the initial hot material flow level of each heat exchanger are determined, so that the process of converting the heat exchange network flow chart into the multi-level superstructure is strictly based on the actual process logistics logic; then, the heat exchange network flow chart is divided into an area above a pinch point and an area below the pinch point according to the pinch point which is a key boundary in thermodynamics, and then the initial cold material flow level and the initial hot material flow level of the heat exchanger in each area are updated; a cold material flow final stage and a hot material flow final stage which are used for solving the multi-stage superstructure can be accurately and effectively constructed; by calculating the superstructure parameters and the superstructure total series, it is ensured that the generated multi-stage superstructure has the minimum series, redundant variables and constraints of the multi-stage superstructure are reduced to the maximum extent, and the conversion efficiency and the solving efficiency of the multi-stage superstructure are improved.

Description

Technical Field

[0001] This invention belongs to the field of process industry and petrochemical technology, and in particular relates to a method and system for converting heat exchanger network flow diagrams into multi-stage superstructures. Background Technology

[0002] In the process industries, particularly in the petrochemical sector, the design and optimization of heat exchanger networks (HENs) are crucial for improving energy efficiency and reducing production costs. Heat exchanger network flowcharts, as a tool for intuitively representing the heat exchange relationships between process streams, visually demonstrate the matching relationship between cold and hot streams, as well as various related distribution data of the heat exchangers and the flow distribution of process streams. Multi-stage superstructure topology discretizes the entire heat exchange process into several consecutive stages, using mathematical programming methods (such as MINLP and NLP) to simultaneously optimize within a framework covering all potential stream matching and arrangement possibilities. Multi-stage superstructure topology can systematically and comprehensively encompass all possible stream combinations and heat exchange sequences in the heat exchanger network (HEN), effectively ensuring that no potentially superior solutions are overlooked during the optimization process. Therefore, it is widely used in the comprehensive optimization and retrofitting of heat exchanger networks.

[0003] In practical industrial applications, the model size grows exponentially with the increase in the amount of process flow, leading to a sharp increase in solution complexity and severely limiting the application of hyperstructure models in the industrial field. Existing methods either rely on manual mapping based on human experience, which is inefficient and error-prone, and struggles to handle flow structures involving complex branching, mixing, and crossing of pinch points; or they use simple sequential mapping rules, which cannot ensure that the transformed topology is strictly equivalent to the heat exchange logic of the original flow diagram, potentially introducing a large number of redundant variables and constraints, significantly increasing the difficulty of solving multi-level hyperstructures, and may even make it impossible to find a feasible solution due to the expansion of the problem size. Summary of the Invention

[0004] This invention aims to provide a method and system for converting heat exchanger network flowcharts into multi-level superstructures to solve the aforementioned technical problems. It constructs initial cold and hot stream stages using stream temperature data, and calculates the final stages of cold and hot streams by dividing the region into areas above and below the pinch points. This process then constructs superstructure parameters and the total number of superstructure stages, thereby realizing the conversion of heat exchanger network flowcharts into multi-level superstructures and improving the accuracy and efficiency of this conversion.

[0005] To address the aforementioned technical problems, this invention provides a method for converting a heat exchanger network flowchart into a multi-level superstructure, comprising: acquiring a heat exchanger network flowchart; determining the initial cold stream stage and initial hot stream stage for each heat exchanger based on the stream temperature data of each heat exchanger in the heat exchanger network flowchart; dividing the heat exchanger network flowchart into a region above the pinch point and a region below the pinch point; updating the initial cold stream stage and initial hot stream stage for each heat exchanger in the region above the pinch point; determining the final cold stream stage and final hot stream stage for each heat exchanger in the region above the pinch point; and further determining the superstructure in the region above the pinch point. The system parameters are updated for each heat exchanger in the region below the pinch point, including the initial cold flow stage and initial hot flow stage. The final cold flow stage and final hot flow stage of each heat exchanger in the region below the pinch point are determined. Based on the final cold flow stage and final hot flow stage of the heat exchanger, the superstructure parameters of the region below the pinch point and the total number of superstructure stages of the multi-level superstructure are determined. Based on the final cold flow stage and final hot flow stage of each heat exchanger, and combining the superstructure parameters of the region below the pinch point, the superstructure parameters of the region above the pinch point, and the total number of superstructure stages of the multi-level superstructure, the heat exchange network flowchart is converted into a multi-level superstructure.

[0006] Understandably, compared to existing technologies, this invention determines the initial cold stream stage and initial hot stream stage of each heat exchanger by using the stream temperature data of each heat exchanger in the heat exchanger network flowchart. This ensures that the process of converting the heat exchanger network flowchart into a multi-level superstructure is strictly based on the actual process stream logic, and that the generated multi-level superstructure can be equivalently converted to the heat exchanger network flowchart. Then, using the pinch point—a key thermodynamic boundary—the heat exchanger network flowchart is divided into regions above and below the pinch point. The initial cold stream stage and initial hot stream stage of the heat exchanger in each region are then updated, accurately and effectively constructing the final cold stream stage and final hot stream stage for solving the multi-level superstructure. By calculating the superstructure parameters and the total number of stages of the multi-level superstructure, the generated multi-level superstructure has a minimum number of stages, thereby minimizing redundant variables and constraints in the multi-level superstructure and improving the conversion and solution efficiency.

[0007] Accordingly, this invention provides a system for converting a heat exchanger network flowchart into a multi-level superstructure, comprising: a heat exchanger initial stage determination module, a final stage determination module for the material flow in the region above the pinch point, a final stage determination module for the material flow in the region below the pinch point, a superstructure parameter determination module, and a multi-level superstructure conversion module; the heat exchanger initial stage determination module is used to acquire a heat exchanger network flowchart, and based on the material flow temperature data of each heat exchanger in the heat exchanger network flowchart, determine the initial cold material stage and the initial hot material stage of each heat exchanger; and divide the heat exchanger network flowchart into a region above the pinch point and a region below the pinch point; the final stage determination module for the material flow in the region above the pinch point is used to update the initial cold material stage and the initial hot material stage of each heat exchanger in the region above the pinch point, and determine the final stage of the cold material flow in the region above the pinch point. The heat flow final stage is determined, thereby determining the superstructure parameters of the region above the pinch point; the heat flow final stage determination module for the region below the pinch point is used to update the initial cold flow stage and initial hot flow stage of each heat exchanger in the region below the pinch point, and determine the cold flow final stage and hot flow final stage of each heat exchanger in the region below the pinch point; the superstructure parameter determination module is used to determine the superstructure parameters of the region below the pinch point and the total number of superstructure stages of the multi-level superstructure based on the cold flow final stage and hot flow final stage of the heat exchanger; the multi-level superstructure conversion module is used to convert the heat exchange network flowchart into a multi-level superstructure based on the cold flow final stage and hot flow final stage of each heat exchanger, combined with the superstructure parameters of the region below the pinch point, the superstructure parameters of the region above the pinch point, and the total number of superstructure stages of the multi-level superstructure.

[0008] Understandably, compared to existing technologies, this system determines the initial cold stream stage and initial hot stream stage of each heat exchanger by using the stream temperature data of each heat exchanger in the heat exchanger network flowchart. This ensures that the process of converting the heat exchanger network flowchart into a multi-level superstructure is strictly based on the actual process stream logic, guaranteeing that the generated multi-level superstructure and the heat exchanger network flowchart can be equivalently converted. Then, using the pinch point—a key thermodynamic boundary—the heat exchanger network flowchart is divided into regions above and below the pinch point. The initial cold stream stage and initial hot stream stage of the heat exchanger in each region are then updated, accurately and effectively constructing the final cold stream stage and final hot stream stage for solving the multi-level superstructure. By calculating the superstructure parameters and the total number of stages in the multi-level superstructure, the system ensures that the generated multi-level superstructure has the minimum number of stages, thereby minimizing redundant variables and constraints in the multi-level superstructure and improving the conversion and solution efficiency. Attached Figure Description

[0009] Figure 1This is a flowchart illustrating the steps of a method for converting a heat exchanger network flowchart into a multi-stage superstructure, as provided in an embodiment of the present invention. Figure 2 A schematic diagram of the initial hot flow stage and the initial cold flow stage provided in an embodiment of the present invention; Figure 3 A schematic diagram illustrating a type of cold logistics and a type of hot logistics provided in an embodiment of the present invention; Figure 4 This is a schematic diagram illustrating the updating of a non-grip region above a gripping point, provided by an embodiment of the present invention. Figure 5 This is an updated schematic diagram of the non-splitting cold flow in the clamp region above the clamp provided in an embodiment of the present invention; Figure 6 An updated schematic diagram of cold flow diversion in the clamp region above the clamp provided in an embodiment of the present invention; Figure 7 This is an updated schematic diagram of a non-splitting cold flow in the pinch region below the pinch point, provided as an embodiment of the present invention. Figure 8 This is a schematic diagram of the updated flow of cold material in the pinch area below the pinch provided in an embodiment of the present invention; Figure 9 This is a schematic diagram of a multi-level superstructure provided in an embodiment of the present invention; Figure 10 This is a schematic diagram of a system for converting a heat exchange network flow chart into a multi-stage superstructure, provided as an embodiment of the present invention. Detailed Implementation

[0010] 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, and 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.

[0011] Example 1 Please refer to Figure 1 , Figure 1 The flowchart of a method for converting a heat exchanger network flowchart into a multi-stage superstructure provided in an embodiment of the present invention includes steps S101 to S105.

[0012] Step S101: Obtain the heat exchanger network flowchart; based on the material temperature data of each heat exchanger in the heat exchanger network flowchart, determine the initial cold material stage and the initial hot material stage of each heat exchanger; and divide the heat exchanger network flowchart into a region above the pinch point and a region below the pinch point.

[0013] In this embodiment, obtaining the heat exchanger network flowchart, based on the material temperature data of each heat exchanger in the heat exchanger network flowchart, determines the initial cold material stage and the initial hot material stage of each heat exchanger; and divides the heat exchanger network flowchart into a region above the pinch point and a region below the pinch point, includes: obtaining the heat exchanger network flowchart and determining the material temperature data of each heat exchanger in the heat exchanger network flowchart, wherein the material temperature data includes: the hot material inlet temperature and the cold material inlet temperature of each heat exchanger; and determining the heat exchange of each heat exchanger in its respective hot material based on the hot material inlet temperature of each heat exchanger. The heat exchange sequence is determined based on the cold stream inlet temperature of each heat exchanger; the initial hot stream stage of each heat exchanger is determined based on the heat exchange sequence of each heat exchanger in the hot stream; the initial cold stream stage of each heat exchanger is determined based on the heat exchange sequence of each heat exchanger in the cold stream; the heat exchange network flowchart is divided into a region above the pinch point and a region below the pinch point, wherein the region above the pinch point includes: a non-pinch point region above the pinch point and a pinch point region above the pinch point; the region below the pinch point includes: a non-pinch point region below the pinch point and a pinch point region below the pinch point.

[0014] Before describing specific embodiments, the meanings of the parameters involved in the embodiments of the present invention will first be explained; firstly, , and All of these represent hot logistics, among which , for Alternative name; Represents a collection of thermal fluids (dimensionless); , and All of these refer to cold chain logistics, among which , for Alternative name; Represents a set of cold chain logistics (dimensionless); , , , Both refer to heat exchangers, among which , , for Alternative name; This represents a collection of heat exchangers (dimensionless). Indicates hot logistics and cold chain logistics In the heat exchanger The heat exchange generated in the process (kW); Indicates heat exchanger cold chain logistics Inlet temperature (°C); Indicates heat exchanger cold chain logistics Outlet temperature (°C); Indicates heat exchanger Hot logistics Inlet temperature (°C); Indicates heat exchanger Hot logistics Outlet temperature (°C); Indicates the thermal flow in the region above the pinch point. Temperature before shunting (°C); Cold logistics in the region above the pinch point The mixing temperature (°C) of each tributary; Indicates the thermal flow in the pinch region below the pinch point. The mixing temperature (°C) of each tributary; Indicates cold logistics in the pinch area below the pinch point. Temperature before shunting (°C); Indicates hot logistics The initial temperature (°C); Indicates hot logistics Target temperature (°C); Indicates cold chain logistics The initial temperature (°C); Indicates cold chain logistics Target temperature (°C); and The number of stages in a heat exchanger (dimensionless) includes the initial cold flow stage, initial hot flow stage, first cold flow stage, or first hot flow stage before the final stage of the cold or hot flow is determined. After the final stage of the cold or hot flow is determined, it represents the final stage of the cold or hot flow. Represents the collection of thermal fluids in the region above the pinch point (dimensionless). Represents the set of cold flow items in the region above the clamp point (dimensionless). Indicates the heat exchange sequence of the heat exchanger on the corresponding cold or hot stream (dimensionless). Indicates the thermal flow in the region above the pinch point. and cold chain logistics In the heat exchanger The heat exchange generated in the process (kW); The temperature (°C) indicates the cold pinch point. Represents the set of thermal fluids in the non-clamp region above the clamp point (dimensionless). Represents the set of cold flow items in the non-clamp region above the clamp point (dimensionless). Indicates the heat capacity flow rate (kW / ℃) of cold or hot logistics. Indicates hot logistics In the heat exchanger Heat flow rate (kW / ℃); Indicates cold chain logistics In the heat exchanger Heat flow rate (kW / ℃); Indicates the pinch point temperature (°C); Represents the collection of thermal fluids in the region above the pinch point (dimensionless). This represents the set of cold flow items in the region above the clamp point (dimensionless). Indicates the diversion of hot flow The maximum value of the initial cold flow stage of the heat exchanger (dimensionless). Indicates the diversion of cold chain logistics The maximum value of the initial heat flow stage of the heat exchanger (dimensionless). Indicates heat exchanger Converted to a multi-stage superstructure heat exchanger The blank level parameter (kW) corresponding to the initial value of the variable in the middle; Indicates heat exchanger cold chain logistics Inlet temperature conversion to multi-stage superstructure heat exchanger The blank level parameter (°C) corresponding to the initial value of the variable; This indicates a heat exchanger in the case of split cold flow. cold chain logistics Inlet temperature conversion to multi-stage superstructure heat exchanger The blank level parameter (°C) corresponding to the initial value of the variable; Indicates heat exchanger cold chain logistics The outlet temperature is converted to a multi-stage superstructure heat exchanger. The blank level parameter (°C) corresponding to the initial value of the variable; Used to indicate cold chain logistics The parameters (dimensionless) for the position of the leftmost heat exchanger; Indicates heat exchanger Hot logistics Inlet temperature conversion to multi-stage superstructure heat exchanger The blank level parameter (°C) corresponding to the initial value of the variable; Indicates hot logistics Parameters (dimensionless) for the leftmost heat exchanger position; This indicates a heat exchanger in the case of a split heat flow. Hot logistics Inlet temperature conversion to multi-stage superstructure heat exchanger The blank level parameter (°C) corresponding to the initial value of the variable; Indicates hot logistics The heat flow outlet temperature (°C) of the rightmost heat exchanger. Indicates heat exchanger Hot logistics The outlet temperature is converted to a multi-stage superstructure heat exchanger. The blank level parameter (°C) corresponding to the initial value of the variable; Indicates cold chain logistics The Level and First The temperature between levels is converted into blank level parameters (°C) of the initial values ​​of the multi-level hyperstructure correlation variables; Indicates hot logistics The Level and First The temperature between levels is converted into blank level parameters (°C) of the initial values ​​of the multi-level hyperstructure correlation variables; Indicates the diversion of cold chain logistics The tributary in the heat exchanger The heat capacity flow rate is converted into a superstructure heat exchanger. Blank level parameters (kW / ℃) corresponding to the initial values ​​of the variables; Indicates the diversion of hot flow The tributary in the heat exchanger The heat capacity flow rate is converted into a superstructure heat exchanger. Blank level parameters (kW / ℃) corresponding to the initial values ​​of the variables; Indicates cold chain logistics In the heat exchanger The heat capacity flow rate is converted into a superstructure heat exchanger. Blank level parameters (kW / ℃) corresponding to the initial values ​​of the variables; Indicates hot logistics In the heat exchanger The heat capacity flow rate is converted into a superstructure heat exchanger. Blank level parameters (kW / ℃) corresponding to the initial values ​​of the variables; This indicates that the logistics of cold utility engineering is in the heat exchanger The heat capacity flow rate is converted into a superstructure heat exchanger. Blank level parameters (kW / ℃) corresponding to the initial values ​​of the variables; This indicates the flow of heat in the heat exchanger in the thermal utility project. The heat capacity flow rate is converted into a superstructure heat exchanger. Blank level parameters (kW / ℃) corresponding to the initial values ​​of the variables; This indicates that the tributary of the cold utility logistics is located in the heat exchanger. The heat capacity flow rate is converted into a superstructure heat exchanger. Blank level parameters (kW / ℃) corresponding to the initial values ​​of the variables; This indicates the tributary of the thermal utility's logistics flow in the heat exchanger. The heat capacity flow rate is converted into a superstructure heat exchanger. Blank level parameters (kW / ℃) corresponding to the initial values ​​of the variables; Indicates the thermal flow in the region below the pinch point. and cold chain logistics In the heat exchanger The heat exchange generated in the process (kW); This represents the collection of thermal fluids in the region below the pinch point (dimensionless). This represents the set of cold flow items in the region below the pinch point (dimensionless). This represents the set of thermal fluids in the region below the pinch point (dimensionless). This represents the set of cold flow items in the region below the pinch point (dimensionless). This represents the set of thermal fluids in the non-pinch region below the pinch point (dimensionless). This represents the set of cold flow materials in the non-clamp region below the clamp point (dimensionless). The number of stages of the heat exchanger in the non-pinch region below the pinch point (dimensionless). The flow rate (kW / ℃) represents the flow rate with the highest heat capacity. Used to represent the heat flow with the maximum heat capacity (dimensionless). Used to represent cold streams with the maximum heat capacity (dimensionless). Indicates cold chain logistics Required thermal utilities (kW); This represents the total thermal utilities (kW) required for all cold chain logistics. and To facilitate the calculation of the intermediate parameters (dimensionless) introduced in this embodiment; Indicates the thermal flow in the region above the pinch point. The number of tributaries (dimensionless); Indicates hot logistics Required cold utilities; This represents the total cooling utilities (kW) required for all hot flow processes. The total number of superstructure levels in a multi-level superstructure is dimensionless. This represents the maximum value (dimensionless) of the final stage of the heat flow in all heat exchangers. This represents the maximum value (dimensionless) of the final stage of the cold flow in all heat exchangers. Indicates heat exchanger The area is converted into a superstructure heat exchanger Blank level parameter (m) corresponding to the initial value of the variable 2 ); Indicates heat exchanger Hot-end temperature difference converted into superstructure heat exchanger Blank level parameter (°C) for initial values ​​of associated variables; Indicates heat exchanger Cold end temperature difference converted into superstructure heat exchanger Blank level parameter (°C) for initial values ​​of associated variables; Indicates heat exchanger Temperature difference can be converted into a superstructure heat exchanger Blank level parameter (°C) for initial values ​​of associated variables; This represents the level in a multi-level superstructure. Represents the set of series in a multi-level superstructure; Indicates thermal utilities; Indicates cold public works; This represents the maximum value operator; This is an operator used to return the index of an element in a set. This is an operator used to return the number of elements in a set; This is the summation operator.

[0015] In an optional embodiment, cold chain logistics is set as or ,Right now and This indicates two different cold logistics streams, with the hot logistics stream set as... or ,Right now and This represents two different heat streams; the heat exchanger is defined as... or ,same and Indicates different heat exchangers; sets the heat exchanger Hot logistics is Cold chain logistics is Therefore, the inlet temperature of the hot stream of this heat exchanger is expressed as The inlet temperature of the cold logistics is expressed as Setting up hot flow and cold chain logistics In the heat exchanger The heat exchange that occurs in is ; A value greater than 0 indicates that heat exchange occurs between the cold and hot streams in the heat exchanger, which also proves the existence of the heat exchanger; under the premise of satisfying formula (1), for any cold stream... The heat exchange sequence of each heat exchanger on the cold stream is shown in the following formula (2). For any hot stream... The heat exchange sequence of each heat exchanger on the hot stream is shown in formula (3). Therefore, the initial hot stream stage of the heat exchanger is solved based on the heat exchange sequence of its hot stream, as shown in formula (4). The initial cold stream stage of the heat exchanger is solved based on the heat exchange sequence of its cold stream, as shown in formula (5). This represents the set of all heat exchangers; Represents a collection of hot fluids; Indicates a collection of cold chain logistics; The conditional control symbol indicates that the conditional statement in formula (2) means that the inlet temperature of each heat stream entering the heat exchanger is compared. The size determines the heat exchange sequence; the conditional statement in formula (3) means that by comparing the inlet temperature of each cold stream entering the heat exchanger... The size determines the heat exchange sequence; (1); (2); (3); (4); (5); For further details, please refer to Figure 2 , Figure 2 A schematic diagram of the initial hot flow stage and the initial cold flow stage provided in an embodiment of the present invention; Figure 2 include Figure 2 (a) and Figure 2 (b); Figure 2 (a) A schematic diagram of the initial cold flow stage of a heat exchanger provided in an embodiment of the present invention; Figure 2 (b) A schematic diagram of the initial heat flow stages of a heat exchanger provided in an embodiment of the present invention; for Figure 2 (a) and Figure 2 (b), where the red line represents the hot stream, the blue line represents the cold stream, and the arrow indicates the direction of the hot or cold stream; two blue spheres connected by a dashed line represent a heat exchanger; since there is no heat exchanger with a higher inlet temperature than the leftmost heat exchanger, based on formulas (2) and (3), the heat exchange sequence of the leftmost heat exchanger in both the hot and cold streams is 0. Through formulas (4) and (5), the initial cold stream stage and the initial hot stream stage of the leftmost heat exchanger are both 1, i.e. Figure 2 As shown in “①”, for the second heat exchanger from left to right of each stream, the heat exchange sequence obtained is 1, so the initial cold stream stage or initial hot stream stage calculated is 2. And so on, the initial cold stream stage and initial hot stream stage of each heat exchanger can be obtained.

[0016] This embodiment determines the heat exchange sequence of the hot and cold streams in the heat exchanger by using the inlet temperatures of the hot and cold streams, respectively. This, in turn, determines the initial cold stream and initial hot stream stages of the heat exchanger, accurately reflecting the actual heat exchange path of the streams in the flow diagram. This ensures that the process of converting the heat exchanger network flow diagram into a multi-stage superstructure is strictly based on the actual process flow logic, guaranteeing that the generated multi-stage superstructure and the heat exchanger network flow diagram can be equivalently converted. Furthermore, by further subdividing the regions above and below the pinch points into non-pinch and pinch regions, the position and function of the heat exchanger in the streams can be more accurately reflected. This provides an accurate basis for subsequent updates to the number of heat exchanger stages in different regions, helping to improve the accuracy and effectiveness of the entire conversion method and better addressing problems caused by inaccurate stage determination and unreasonable region division in heat exchanger network optimization.

[0017] Please refer to Figure 3 , Figure 3 This is a schematic diagram illustrating a type of cold logistics and a type of hot logistics provided in an embodiment of the present invention; as shown. Figure 3 As shown in the diagram, common heat exchanger network flow charts typically include two types of pinch points: cold pinch points and hot pinch points. Figure 3 As shown in (a), it is a schematic diagram of a cold logistics type provided by an embodiment of the present invention. The cold logistics type includes: a first cold logistics type (i.e. Figure 3 (a) in (I)), the second type of cold chain logistics (i.e. Figure 3 (a) in (II)), the third type of cold chain logistics (i.e. Figure 3 (a) in (III)), the fourth type of cold chain logistics (i.e. Figure 3 (a) in (IV)), the fifth type of cold chain logistics (i.e. Figure 3 (V) in (a)); Figure 3 (b) A schematic diagram of a type of thermal fluid provided in an embodiment of the present invention, the type of thermal fluid including: a first type of thermal fluid (i.e. Figure 3 (b) in (I)), the second type of hot flow (i.e. Figure 3 (b) in (II)), the third type of hot flow (i.e. Figure 3 (b) in (III)), the fourth type of hot flow (i.e. Figure 3 (b) in (IV)), the fifth type of hot flow (i.e. Figure 3(b) (V)); furthermore, the initial temperature of the cold stream of the first cold stream type and the target temperature of the hot stream of the first hot stream type are both higher than the pinch point, that is, the entire stream is above the pinch point; the initial temperature of the cold stream of the second cold stream type and the target temperature of the hot stream of the second hot stream type are exactly at the pinch point; the initial temperature and target temperature of the cold stream of the third cold stream type are respectively on both sides of the pinch point; the initial temperature and target temperature of the hot stream of the third hot stream type are respectively on both sides of the pinch point; the target temperature of the cold stream of the fourth cold stream type and the initial temperature of the hot stream of the fourth hot stream type are exactly at the pinch point; the target temperature of the cold stream of the fifth cold stream type and the initial temperature of the hot stream of the third hot stream type are both below the pinch point.

[0018] Step S102: Update the initial cold flow stage and initial hot flow stage of each heat exchanger in the region above the pinch point, determine the final cold flow stage and final hot flow stage of each heat exchanger in the region above the pinch point, and then determine the superstructure parameters of the region above the pinch point.

[0019] In this embodiment, updating the initial cold stream stage and initial hot stream stage of each heat exchanger in the region above the pinch point, determining the final cold stream stage and final hot stream stage of each heat exchanger in the region above the pinch point, and then determining the superstructure parameters of the region above the pinch point, includes: the region above the pinch point includes: a non-pinch region above the pinch point and a pinch region above the pinch point; screening a plurality of first heat exchangers in the non-pinch region above the pinch point, determining the final cold stream stage and final hot stream stage of each first heat exchanger in the non-pinch region above the pinch point based on the initial cold stream stage and initial hot stream stage of each first heat exchanger; screening a plurality of third heat exchangers in the pinch region above the pinch point, and determining the cold stream diversion result and hot stream diversion result of each third heat exchanger. The flow diversion results are as follows: Based on the cold flow diversion results and hot flow diversion results of each of the third heat exchangers, the initial cold flow stage and initial hot flow stage of each of the third heat exchangers are updated to determine the final cold flow stage and final hot flow stage of each of the third heat exchangers in the pinch region above the pinch point; the final cold flow stage and final hot flow stage of each of the first heat exchangers, as well as the final cold flow stage and final hot flow stage of each of the third heat exchangers, are taken as the final cold flow stage and final hot flow stage of each of the heat exchangers in the pinch region above the pinch point; based on the final cold flow stage and final hot flow stage of each of the heat exchangers in the pinch region above the pinch point, combined with the flow temperature data of each of the heat exchangers in the pinch region above the pinch point, the superstructure parameters of the pinch region above the pinch point are determined.

[0020] This embodiment divides the region above the pinch point into a non-pinch region above the pinch point and a pinch region above the pinch point. For the first heat exchanger in the non-pinch region above the pinch point, it directly updates based on the initial stage, which can efficiently solve for the final stages of cold and hot streams. For the possible stream diversion in the pinch region above the pinch point, it solves for the final stages of cold and hot streams using the results of cold and hot stream diversion, which can handle stream structures with complex diversion, mixing, and crossing of pinch points. This ensures that in actual industrial processes with stream branching and merging, the converted multi-stage superstructure topology can still accurately reflect the energy exchange relationship and network connectivity of the original process, improving the accuracy and efficiency of converting heat exchanger network flow diagrams into multi-stage superstructures.

[0021] In this embodiment, the step of screening a plurality of first heat exchangers located in the non-pinch region above the pinch point, and determining the final stage of the cold flow and the final stage of the hot flow for each first heat exchanger located in the non-pinch region above the pinch point based on the initial cold flow stage and the initial hot flow stage of each first heat exchanger, includes: screening a plurality of first heat exchangers located in the non-pinch region above the pinch point based on the cold flow inlet temperature data of each heat exchanger, and determining a plurality of first cold flows located in the non-pinch region above the pinch point based on the first heat exchangers; marking the first heat exchangers on each first cold flow based on a preset flow direction, and determining the initial update heat exchanger for each first cold flow; iteratively updating the initial cold flow stage and the initial hot flow stage of the first heat exchangers on each first cold flow based on the initial update heat exchanger for each first cold flow, until each first heat exchanger on each first cold flow has determined its own final stage of the cold flow and the final stage of the hot flow; wherein, in each first cold flow... In each update of the flow, several second heat exchangers on the first cold flow path of the initially updated heat exchanger that need to be updated are selected; the initial cold flow stage and the initial hot flow stage of the initially updated heat exchanger are compared; if the initial hot flow stage of the initially updated heat exchanger is greater than or equal to the initial cold flow stage, the initial cold flow stage of the initially updated heat exchanger is updated, thereby determining the final cold flow stage and the final hot flow stage of the initially updated heat exchanger; and the initial cold flow stage and the initial hot flow stage of each second heat exchanger are updated; after the update of each second heat exchanger is completed, the next second heat exchanger of the initially updated heat exchanger is used as the initial update heat exchanger for the next update; if the initial hot flow stage of the initially updated heat exchanger is less than the initial cold flow stage, the final cold flow stage and the final hot flow stage of the initially updated heat exchanger are determined based on the initial cold flow stage and the initial hot flow stage; and the next second heat exchanger of the initially updated heat exchanger is used as the initial update heat exchanger for the next update.

[0022] In an optional embodiment, before updating the non-pinch region above the pinch, it is necessary to determine whether the cold flow above the pinch requires a thermal utility using formula (6). If a thermal utility is required, the thermal utility must be in the first stage of the superstructure. Therefore, the initial stage of all heat exchangers on the cold flow must be moved one stage backward, and thus 1 must be added, as shown in formula (7). This indicates the cold flow at the pinch point above the pinch point. Mixing temperature of each tributary Indicates cold chain logistics The target temperature; further, in order to facilitate the subsequent heat exchanger update in the non-pinch region above the pinch point, as shown in equations (8) and (9), this embodiment introduces two parameters, which are also used to represent the initial cold flow stage and the initial hot flow stage in the non-pinch region above the pinch point after the thermal utility judgment has been implemented. This indicates cold logistics in the area above the clamping point; This indicates the thermal flow in the area above the pinch point; (6); (7); (8); (9); Furthermore, the cold pinch point temperature is set to... If the cold stream inlet temperature of a heat exchanger is greater than the cold pinch temperature, then the heat exchanger is marked as the first heat exchanger in the non-pinch region above the pinch. The cold stream containing the first heat exchanger is also marked as the first cold stream. The stream direction is set from left to right; therefore, the initial updated heat exchanger for each first cold stream is the leftmost heat exchanger in each first cold stream. Then, the initial cold stream stage and initial hot stream stage of the first heat exchanger in each first cold stream are iteratively updated. In each iteration, the initial updated heat exchangers are compared. Initial cold chain level and initial thermal flow stage If, as shown in formula (10), the initial hot stream level of the initial heat exchanger is greater than or equal to the initial cold stream level, then according to formula (11), the initial cold stream level of the initial heat exchanger is updated with the larger initial hot stream level, and the final cold stream level and the final hot stream level of the initial heat exchanger are determined. At the same time, formulas (12), (13), and (14) are used to screen several second heat exchangers that need to be updated on the first cold stream where the initial heat exchanger is located. Formulas (12) and (13) are used to screen the initial heat exchangers. All heat exchangers at the rear (i.e., the right side), formula (14) is used to filter out heat exchangers in the non-pinch region above the pinch point, thereby obtaining the second heat exchanger. ; (10); (11); (12); (13); (14); The initial cold stream and initial hot stream of the second heat exchanger are updated, again following a left-to-right order. Specifically, if the requirements of formula (15a) are met, the initial cold stream of the second heat exchanger is updated according to formula (15b). After updating the initial cold stream of the second heat exchanger, the magnitudes of the updated initial cold stream and initial hot stream are compared. If formula (16a) is met, the initial hot stream of the second heat exchanger is updated according to formula (16b). If formula (17a) is met, the initial cold stream of the second heat exchanger is updated again according to formula (17b). The process of updating the first heat exchanger is repeated, thus completing the update of the second heat exchanger. This process is repeated for all second heat exchangers following the initial updated heat exchanger. The first second heat exchanger following the initial updated heat exchanger is then used as the initial updated heat exchanger for the next update. If the initial hot stream level of the initial updated heat exchanger is less than the initial cold stream level, then the initial hot stream level of the initial updated heat exchanger is used as the final hot stream level, and the initial cold stream level of the initial updated heat exchanger is used as the final cold stream level. The next second heat exchanger following the initial updated heat exchanger is then used as the initial updated heat exchanger for the next update. (15a); (15b); (16a); (16b); (17a); (17b).

[0023] Please refer to Figure 4 , Figure 4 This is a schematic diagram illustrating the updating of the non-pinch region above the pinch point, as provided in an embodiment of the present invention. As shown by the solid lines in the figure, it is assumed that the rightmost heat exchanger for the hot stream has 3 stages, while the leftmost heat exchanger for the cold stream has a preliminary stage. or The value is 1. Therefore, the distance between the second heat exchanger and the first heat exchanger in the cold flow is 1, which is the distance between the two heat exchangers. and The difference is represented here. The indicator... This indicates the location of another heat exchanger on the cold flow path (different from the current location). The stage of the updated second heat exchanger can be represented by the left side of equation (15a), and the updated stage is compared with the original stage. The values ​​are compared, and the larger value is taken as the final determined level, as shown in equations (15a) and (15b).

[0024] This embodiment updates the initial cold flow stage by identifying the thermal utility requirements, then updates the heat exchanger based on the preset flow direction marker, and performs iterative updates. In each update, different operations are performed according to the size of the first cold flow stage and the first hot flow stage of the initially updated heat exchanger. This fully considers the mutual influence between heat exchangers in the cold flow, and thus reasonably adjusts the number of stages according to the actual situation. This ensures that the final stages of the cold and hot flows can accurately reflect the heat exchange sequence and position of the heat exchangers in the cold flow, improving the accuracy and rationality of determining the final stages of the cold and hot flows, and thus improving the accuracy of converting the heat exchange network flowchart into a multi-stage superstructure.

[0025] In this embodiment, the process of screening several third heat exchangers located in the pinch region above the pinch point and determining the cold flow diversion result and hot flow diversion result for each third heat exchanger; updating the initial cold flow stage and initial hot flow stage for each third heat exchanger based on the cold flow diversion result and hot flow diversion result for each third heat exchanger, and determining the final cold flow stage and final hot flow stage for each third heat exchanger located in the pinch region above the pinch point, includes: screening several third heat exchangers located in the pinch region above the pinch point and determining the cold flow diversion result and hot flow diversion result for each third heat exchanger; wherein, the cold flow diversion result includes: diverted cold flow and non-diverted cold flow; the hot flow diversion result includes: diverted hot flow and non-diverted hot flow; if the cold flow of the third heat exchanger is non-diverted cold flow and the hot flow is diverted hot flow, determining several first branch heat exchangers corresponding to the third heat exchanger based on the diverted hot flow of the third heat exchanger; based on the first branch heat exchangers The initial cold flow stage of the third heat exchanger is updated, and the initial hot flow stage of the third heat exchanger is determined. If the cold flow of the third heat exchanger is a branched cold flow and the hot flow is a non-branched hot flow, several second branch heat exchangers corresponding to the third heat exchanger are determined based on the branched cold flow. The initial cold flow stage of the third heat exchanger is updated based on the initial hot flow stage of the second branch heat exchanger, and the final cold flow stage of the third heat exchanger is determined. If the cold flow of the third heat exchanger is a branched cold flow and the hot flow is a branched hot flow, several first branch heat exchangers of the third heat exchanger are determined based on the branched hot flow. The initial hot flow stage of the second branch heat exchanger is updated based on the initial cold flow stage of the second branch heat exchanger, and the common flow stage of the third heat exchanger is determined. The final hot flow stage and final cold flow stage of the third heat exchanger are determined based on the common flow stage.

[0026] In one alternative embodiment, please refer to Figure 5 , Figure 5 This is an updated schematic diagram of the non-splitting cold flow in the pinch region above the pinch point provided in an embodiment of the present invention; as shown. Figure 5 As shown, Figure 5 include Figure 5 (a) and Figure 5(b) Type i represents a flow that does not split, and type ii represents a flow that splits; further, if the cold flow of the third heat exchanger is a non-splitting cold flow and the hot flow is a splitting hot flow, then the heat exchanger that satisfies formula (18) is a heat exchanger on the cold flow and above the pinch point region; the heat exchanger that satisfies formula (19) represents a cold flow that does not split; the heat exchanger that satisfies formula (20) is a heat exchanger on the hot flow and above the pinch point region; the heat exchanger that satisfies formula (21) is a non-splitting hot flow; where, This is the cold pinch point temperature; Indicates cold chain logistics In the heat exchanger inlet temperature; Indicates cold chain logistics In the heat exchanger The heat flow rate; Indicates cold chain logistics The heat flow rate; For thermal logistics In the heat exchanger The outlet temperature; Indicates the temperature of the heat pinch point; Indicates hot logistics In the heat exchanger The heat flow rate; Indicates hot logistics The heat flow rate; (18); (19); (20); (twenty one); According to formulas (18) to (21), select several third heat exchangers located in the pinch region above the pinch point, and determine the cold flow diversion result and hot flow diversion result for each of the third heat exchangers; as... Figure 5 (a) is indicated by symbol ii, at which point the hot flow... A diversion occurred, and cold chain logistics... No diversion occurs; in this case, the hot flow is represented by formula (22). It is a diversionary logistics process, and formula (23) determines the hot logistics process. The third heat exchanger in the pinch region above the pinch point; the heat flow is determined using formula (24). The heat exchangers of the other branches (i.e., the first branch heat exchanger) are ensured by formula (25); after obtaining the first branch heat exchanger, since the heat exchangers on all stream branches must be located at the same level in the superstructure, this constraint is expressed by formula (26); index for It is an alternative name for other cold chain logistics. and for It is an alternative name for other heat exchangers; This indicates cold logistics in the area above the clamp point; (twenty two); (twenty three); (twenty four); (25); (26); Then, the maximum value of the initial cold stream stage for all first-branch heat exchangers was selected. That is, as shown in formula (27); then the formula (27) obtained The initial hot stream level of the first branch heat exchanger is compared with that of the first branch heat exchanger, as described in formulas (28a) and (29a), and the smaller value is updated with the larger value, as shown in formulas (28b) and (29b). After the initial hot stream level of all the first branch heat exchangers has been compared and updated, the initial hot stream level of the third heat exchanger is updated synchronously due to the constraint of formula (26), so that the updated initial hot stream level of the third heat exchanger is taken as the final hot stream level of the third heat exchanger, while the final cold stream level of the third heat exchanger is directly determined by the initial cold stream level. At the same time, as shown in formulas (28a) and (29a), the initial hot stream level of the third heat exchanger is updated synchronously, and the updated initial hot stream level of the third heat exchanger is taken as the final hot stream level of the third heat exchanger, while the final cold stream level of the third heat exchanger is directly determined by the initial cold stream level. Figure 5 As shown in (b), the cold stream in the first branch heat exchanger may be a split cold stream, using the final... Update the initial cold stream stages of all first-branch heat exchangers, i.e., Equation (30); (27); (28a); (28b); (29a); (29b); (30); In one alternative embodiment, please refer to Figure 6 , Figure 6 This is an updated schematic diagram of the cold flow distribution in the clamp region above the clamp provided in an embodiment of the present invention; as shown. Figure 6 As shown, Figure 6 include Figure 6 (a) and Figure 6 (b) Type i represents logistics that does not split, and type ii represents logistics that splits. If the cold stream in the third heat exchanger is a split cold stream and the hot stream in the third heat exchanger is a non-split hot stream, such as Figure 6 As shown in (a), cold chain logistics A diversion occurred, and the heat flow that exchanged heat with it... and No diversion occurred; therefore, the hot stream was determined by formula (38). The heat exchanger is located in the pinch region above the pinch point. Formula (39) is used to determine that the hot stream is not split. The stream that satisfies formula (31) is the split cold stream. Then, formulas (32) to (34) are used to determine each heat exchanger on the split cold stream. Formula (32) represents the heat exchanger of each branch on the split cold stream. Formula (33) is used to determine that the heat exchanger is located in the pinch region above the pinch point. Formula (34) is used to indicate that the heat exchanger exists. Formula (35) is used to determine the maximum level of the initial hot stream stage of each heat exchanger on the split cold stream. Then, formulas (36a) and (37a) are used to compare the results obtained from formula (35). The initial cold stream level of the second branch heat exchanger is updated with a larger value, as shown in formulas (36b) and (37b); thus, the initial cold stream level of the heat exchangers on each branch of the cold stream is updated and unified; after the update, the initial hot stream level of the heat exchangers on each branch of the cold stream can be expressed by formula (40); furthermore, since the heat exchangers on all stream branches must be located at the same level in the superstructure, the values ​​of the final hot stream level and the final cold stream level of the third heat exchanger can be expressed by formula (40). To express.

[0027] (31); (32); (33); (34); (35); (36a); (36b); (37a); (37b); (38); (39); (40)

[0028] In an optional embodiment, if the cold stream in which the third heat exchanger is located is a split cold stream and the hot stream in which it is located is a split hot stream, such as Figure 6 As shown in (b), the thermal flow is determined based on formula (41). Diversion, formula (42) determines the hot flow. The heat exchanger is located in the pinch region above the pinch point. Formula (43) is used to ensure the existence of the heat exchanger. Based on formulas (42) and (43), several first branch heat exchangers of the third heat exchanger can be determined. Similarly, the initial hot stream level of the first branch heat exchanger needs to be unified based on formula (44). Then, the maximum value of the initial cold stream level of the first branch heat exchanger is solved based on formula (45). Then, the initial hot stream level of the first branch heat exchanger is updated and unified based on formulas (46a) to (47b). If formula (46a) is satisfied, then formula (46b) is executed. If formula (47a) is satisfied, then formula (47b) is executed. Similarly, for the second branch heat exchanger on the cold stream of the third heat exchanger, referring to the contents of formulas (31) to (37b) above, the same result can be obtained. Then, based on formulas (48a) to (49b), the common stage of the material flow end of the third heat exchanger is determined; if formula (48a) is satisfied, then (48b) is executed; if formula (49a) is satisfied, then (49b) is executed. Since after executing (48b) or (49b), Therefore, this embodiment uses [the term] here. As a common stage for the logistics end; then, the final stages of cold and hot logistics of the third heat exchanger are calculated using formulas (50a) to (53); specifically, formula (50a) is used to determine the cold logistics stage. Above and heat exchanger Other heat exchangers in parallel branches; Formula (50b) is used to determine the pinch region above the pinch point where the heat exchanger is located; Formula (50c) is used to ensure the existence of the heat exchanger; Formula (51) is used to unify the initial heat flow level of the first branch heat exchanger on the branch heat flow where the third heat exchanger is located; Formula (52a) is used to determine all branches on the branch cold flow where the third heat exchanger is located; Formula (52b) is used to ensure that the branch cold flow where the third heat exchanger is located has a heat exchanger; Formula (53) is used to make the initial cold flow level of the second branch heat exchanger on the branch cold flow where the third heat exchanger is located the same. Since formula (51) has updated the initial hot stream level of the first branch heat exchanger on the hot stream of the third heat exchanger, formula (53) has updated the initial cold stream level of the second branch heat exchanger on the cold stream of the third heat exchanger. Since all heat exchangers on the stream branches must be located at the same level in the superstructure, the initial cold stream level and initial hot stream level of the third heat exchanger will also be updated. The updated initial cold stream level of the third heat exchanger will be used as its final cold stream level, and the updated initial hot stream level of the third heat exchanger will be used as its final hot stream level.

[0029] (41); (42); (43); (44); (45); (46a); (46b); (47a); (47b); (48a); (48b); (49a); (49b); (50a); (50b); (50c); (51); (52a); (52b); (53)

[0030] In an optional embodiment, based on the cold and hot flow final stages of each heat exchanger located in the region above the pinch point, and combined with the flow temperature data of each heat exchanger in the region above the pinch point, the superstructure parameters of the region above the pinch point are determined, including: after determining the cold and hot flow final stages of each heat exchanger in the region above the pinch point, their structures are transformed to generate the heat exchanger. Levels in a superstructure Simultaneously, the superstructure parameters of the region above the pinch point: heat exchanger Converted to a multi-stage superstructure heat exchanger Blank level parameters corresponding to the initial values ​​of the variables Heat exchanger Hot logistics Inlet temperature conversion to multi-stage superstructure heat exchanger Blank level parameters corresponding to the initial values ​​of the variables Heat exchanger Hot logistics The outlet temperature is converted to a multi-stage superstructure heat exchanger. Blank level parameters corresponding to the initial values ​​of the variables Heat exchanger cold chain logistics Inlet temperature conversion to multi-stage superstructure heat exchanger Blank level parameters corresponding to the initial values ​​of the variables Heat exchanger cold chain logistics The outlet temperature is converted to a multi-stage superstructure heat exchanger. Blank level parameters corresponding to the initial values ​​of the variables Hot logistics In the heat exchanger The heat capacity flow rate is converted into a superstructure heat exchanger. Blank level parameters corresponding to the initial values ​​of the variables and logistics In the heat exchanger The heat capacity flow rate is converted into a superstructure heat exchanger. Blank level parameters corresponding to the initial values ​​of the variables The result is obtained by formulas (54) to (60) below. Since the initial cold stream stage and the initial hot stream stage have been updated, this embodiment uses formulas (54) to (60) to calculate... Indicates heat exchanger The final stage of thermal logistics. The superstructure parameters of the region above the pinch point are used to initialize the multi-stage superstructure.

[0031] (54); (55); (56); (57); (58); (59); (60)

[0032] This embodiment defines cold stream diversion results as including diverted cold streams and non-diverted cold streams, and hot stream diversion results as including diverted hot streams and non-diverted hot streams. By updating the final cold stream and hot stream stages of the third heat exchanger using the initial stage information (initial cold stream stage and initial hot stream stage) of the branch heat exchangers on the diversion branches, it accurately reflects the process logic of the diversion structure in the heat exchange network. It fully considers the impact of diversion on the number of heat exchanger stages, making the determined final cold stream and hot stream stages more consistent with reality. This ensures that in networks with diversion, the topology of multi-stage superstructures can accurately depict the heat transfer sequence before and after the stream branch, maintaining the energy and topological continuity of the streams before and after the diversion point. Thus, it maintains the logical equivalence of the conversion even under complex structures, improving the accuracy of the heat exchange network superstructure in the pinch area above the pinch point, and consequently improving the accuracy of the multi-stage superstructure conversion in the heat exchange network flowchart.

[0033] Step S103: Update the initial cold stream stage and initial hot stream stage of each heat exchanger in the region below the pinch point, and determine the final cold stream stage and final hot stream stage of each heat exchanger in the region below the pinch point.

[0034] In this embodiment, updating the initial cold flow stage and initial hot flow stage of each heat exchanger in the region below the pinch point, and determining the final cold flow stage and final hot flow stage of each heat exchanger in the region below the pinch point, includes: the region below the pinch point includes: a non-pinch region below the pinch point and a pinch region below the pinch point; screening a plurality of fourth heat exchangers in the pinch region below the pinch point, and determining the cold flow diversion result and hot flow diversion result of each fourth heat exchanger; based on the cold flow diversion result and hot flow diversion result of each fourth heat exchanger, determining the final cold flow stage and final hot flow stage of each fourth heat exchanger in the pinch region below the pinch point; screening a plurality of fifth heat exchangers in the non-pinch region below the pinch point, and determining the cold flow type and hot flow type of each fifth heat exchanger; based on the fourth heat exchangers, combined with the cold flow type and hot flow type of each fifth heat exchanger, determining the final cold flow stage and final hot flow stage of each fifth heat exchanger in the non-pinch region below the pinch point.

[0035] This embodiment divides the region below the pinch point into a non-pinch region below the pinch point and a pinch region below the pinch point. First, based on the cold flow diversion results and the hot flow diversion results, the fourth heat exchanger in the pinch region below the pinch point is processed. Then, based on the processing of the fifth heat exchanger in the non-pinch region below the pinch point, the information of the heat exchangers in the pinch region below the pinch point can be fully utilized to provide a reference for determining the number of heat exchanger stages in the non-pinch region below the pinch point. This makes the determination of the number of heat exchanger stages in the entire pinch region more reasonable and accurate, and helps to improve the accuracy of the heat exchange network superstructure in the pinch region below the pinch point.

[0036] In this embodiment, the step of screening a plurality of fourth heat exchangers located in the pinch region below the pinch point and determining the cold flow diversion result and hot flow diversion result of each fourth heat exchanger; based on the cold flow diversion result and hot flow diversion result of each fourth heat exchanger, determining the final stage of the cold flow and the final stage of the hot flow of each fourth heat exchanger located in the pinch region below the pinch point includes: screening a plurality of fourth heat exchangers located in the pinch region below the pinch point and determining the cold flow diversion result and hot flow diversion result of each fourth heat exchanger; wherein, the cold flow diversion result includes: diverted cold flow and non-diverted cold flow; the hot flow diversion result includes: diverted hot flow and non-diverted hot flow; based on the Based on the cold stream inlet temperature and hot stream outlet temperature of the third heat exchanger, determine the preceding cold stream side heat exchanger and the preceding hot stream side heat exchanger for each of the fourth heat exchangers; based on the preceding cold stream side heat exchanger and the preceding hot stream side heat exchanger, update the initial cold stream stage and the initial hot stream stage for each of the fourth heat exchangers, and determine the first cold stream stage and the first hot stream stage for each of the fourth heat exchangers; if the cold stream and hot stream of the fourth heat exchanger are both non-split cold streams, compare the magnitudes of the first cold stream stage and the first hot stream stage of the fourth heat exchanger, and determine the final cold stream stage and the final hot stream stage of the fourth heat exchanger based on the comparison result, and based on the... The final stage of the cold stream and the final stage of the hot stream of the fourth heat exchanger are updated. The first cold stream stage of the other fourth heat exchangers located in the cold stream or the first hot stream stage of the other fourth heat exchangers located in the hot stream of the fourth heat exchanger are updated. If the cold stream of the fourth heat exchanger is a non-splitting cold stream and the hot stream of the fourth heat exchanger is a split hot stream, several third branch heat exchangers corresponding to the fourth heat exchanger are determined based on the split hot stream of the fourth heat exchanger. The maximum stage of the cold stream side corresponding to the fourth heat exchanger is determined based on the initial cold stream stage of the third branch heat exchanger. The final stage of the cold stream and the final stage of the hot stream of the fourth heat exchanger are determined based on the maximum stage of the cold stream side and the first hot stream stage corresponding to the fourth heat exchanger. If the cold stream in which the fourth heat exchanger is located is a branched cold stream and the hot stream in which it is located is a non-branched hot stream, then based on the branched cold stream in which the fourth heat exchanger is located, several fourth branch heat exchangers corresponding to the fourth heat exchanger are determined; based on the initial hot stream stage of the fourth branch heat exchanger, the maximum cold stream stage corresponding to the fourth heat exchanger is determined, and based on the maximum cold stream stage and the first cold stream stage corresponding to the fourth heat exchanger, the final cold stream stage and the final hot stream stage of the fourth heat exchanger are determined; if the cold stream in which the fourth heat exchanger is located is a branched cold stream and the hot stream in which it is located is a branched hot stream, then based on the branched hot stream in which the fourth heat exchanger is located, several fifth branch heat exchangers corresponding to the fourth heat exchanger are determined.Based on the initial cold stream stage of the fifth branch heat exchanger, the maximum cold stream stage and the maximum hot stream stage of the fourth heat exchanger are determined. Then, based on the maximum cold stream stage and the maximum hot stream stage of the fourth heat exchanger, the final cold stream stage and the final hot stream stage of the fourth heat exchanger are determined.

[0037] In an alternative embodiment, firstly by A fourth heat exchanger located in the pinch region below the pinch point is selected; then, the preceding cold flow side heat exchanger of the fourth heat exchanger on the cold flow is determined by formulas (61a) to (61c), wherein formula (61a) is used to determine the pinch region above the pinch point and located in the cold flow through the cold flow inlet temperature of the third heat exchanger. The third heat exchanger; formula (61b) is used to search for other third heat exchangers; in formula (61c) Used to represent hot flow and cold chain logistics In the heat exchanger The heat exchange at the point is used to indicate the presence of the heat exchanger; after confirming the pre-cold flow side heat exchanger of the fourth heat exchanger, the final stage of the cold flow of the pre-cold flow side heat exchanger is incremented by 1 to obtain the first cold flow stage of the fourth heat exchanger, as shown in formula (62); similarly, the pre-hot flow side heat exchanger of the fourth heat exchanger is obtained through formulas (63a) to (63b), wherein, if the hot flow outlet temperature of the third heat exchanger satisfies formula (63a), and its heat exchange is... If formula (63b) is satisfied, then it is the heat exchanger on the front side of the fourth heat exchanger. Similarly, as shown in formula (64), by adding 1 to the final stage of the heat flow in the front heat flow heat exchanger, the first stage of the heat flow in the fourth heat exchanger is obtained. In the following formula, and These represent the hot and cold streams located in the region below the pinch point, respectively. and These represent the hot and cold logistics flows in the pinch region below the pinch point, respectively.

[0038] (61a); (61b); (61c); (62); (63a); (63b); (64); Please refer to Figure 7 , Figure 7 This is an updated schematic diagram of a non-splitting cold flow in the pinch region below the pinch point, provided as an embodiment of the present invention. Figure 7 (a) shows a schematic diagram illustrating the update process between non-splitting cold and hot materials; Figure 7 (b) shows a schematic diagram of the update between non-diverted cold flow and diverted hot flow; where i represents non-diverted cold flow or non-diverted hot flow; ii represents diverted hot flow.

[0039] In an alternative embodiment, such as Figure 7 As shown in (a), if the cold stream in the fourth heat exchanger is a non-splitting cold stream and the hot stream in the fourth heat exchanger is a non-splitting hot stream, then in the region below the pinch point, if formula (65) is satisfied, the cold stream is a non-splitting cold stream; if formula (66) is satisfied, the hot stream is a non-splitting hot stream; if formula (66a) is satisfied, then the cold stream is a non-splitting hot stream. initial temperature Temperatures below the cold pinch point are considered cold streams in the region below the pinch point; Formula (66b) indicates that the hot stream in the region below the pinch point is a non-splitting hot stream; Formula (66c) indicates that the cold stream in the region below the pinch point is a non-splitting cold stream; thus, based on formulas (65) to (66c), and combined with... A fourth heat exchanger can be identified as having a non-splitting cold stream and a non-splitting hot stream. The magnitudes of the first cold stream stage and the first hot stream stage of the fourth heat exchanger are compared. The comparison results fall into two categories: the first is that the first cold stream stage of the fourth heat exchanger is greater than or equal to the first hot stream stage, as shown in formulas (67a) to (67d). If the first cold stream stage of the fourth heat exchanger is greater than or equal to the first hot stream stage, then the first hot stream stage is updated using the first cold stream stage of the fourth heat exchanger, as shown in formula (67b), thereby determining the final cold stream stage and the final hot stream stage of the fourth heat exchanger. Then, as shown in formula (67c), if the first hot stream stage of the other fourth heat exchangers in the hot stream of the fourth heat exchanger satisfies formula (67c), then the fourth heat exchanger is adjusted based on formula (67d). The first hot stream stage of the remaining fourth heat exchangers on the hot stream of the heat exchanger is updated; the second case is that the first hot stream stage of the fourth heat exchanger is greater than the first cold stream stage as shown in formulas (68a) to (70). If the first hot stream stage of the fourth heat exchanger is greater than the first cold stream stage as shown in formula (68a), then the first cold stream stage is updated with the first hot stream stage of the fourth heat exchanger as shown in formula (68b), thereby determining the final cold stream stage and the final hot stream stage of the fourth heat exchanger; then, other heat exchangers remaining behind the cold stream of the fourth heat exchanger that satisfy formulas (68c) and (68d) are selected. If other heat exchangers remaining behind the cold stream of the fourth heat exchanger satisfy formula (69), then the first cold stream stage of other heat exchangers remaining behind the cold stream of the fourth heat exchanger is updated based on formula (70).

[0040] (65); (66); (66a); (66b); (66c); (67a); (67b); (67c); (67d); (68a); (68b); (68c); (68d); (69); (70)

[0041] In an alternative embodiment, such as Figure 7 As shown in (b), if the cold stream of the fourth heat exchanger is a non-splitting cold stream and the hot stream is a splitting hot stream, the splitting hot stream is screened by formula (71), and the third branch heat exchanger of each branch on the splitting hot stream is determined by formula (72); formula (73) indicates that the third branch heat exchanger exists; similarly, formula (74) is used to unify the initial hot stream stage of the third branch heat exchanger and the first hot stream stage of the fourth heat exchanger; then the third branch heat exchanger is screened based on formula (75). The maximum value of the initial cold flow stage is taken as the maximum cold flow stage corresponding to the fourth heat exchanger. Then, the maximum cold flow stage corresponding to the fourth heat exchanger is compared with the first hot flow stage. The first case is shown in formulas (76a) to (77d). If the first hot flow stage of the fourth heat exchanger shown in formula (76a) is greater than or equal to the maximum cold flow stage, then the maximum cold flow stage corresponding to the fourth heat exchanger is updated based on formula (76b). At this time, the first cold flow stage of the fourth heat exchanger is the final cold flow stage. The first hot stream level is the final hot stream level. Then, the remaining fourth heat exchangers on the cold stream of the fourth heat exchanger are selected by formulas (77a) and (77b). Then, it is determined whether the first cold stream level of the remaining fourth heat exchangers on the cold stream of the fourth heat exchanger satisfies formula (77c). If it satisfies formula (77c), then the first cold stream level of the remaining fourth heat exchangers on the cold stream of the fourth heat exchanger is updated by formula (77d). The second case is as shown by formulas (78a) to (79b). If the maximum level of the cold stream side of the fourth heat exchanger as shown by formula (78a) is greater than or equal to the first hot stream level, then the first hot stream level of the fourth heat exchanger is updated based on formula (78b). At this time, the updated first hot stream level of the fourth heat exchanger is taken as the final hot stream level of the fourth heat exchanger, and the first cold stream level is taken as the final cold stream level. Then, the initial hot stream level of the third branch heat exchanger is updated according to formula (79a), and the initial cold stream level of the third branch heat exchanger is updated according to formula (79b). (71); (72); (73); (74); (75); (76a); (76b); (77a); (77b); (77c); (77d); (78a); (78b); (79a); (79b).

[0042] Please refer to Figure 8 , Figure 8 This is a schematic diagram of the updated flow of cold material in the pinch area below the pinch provided in an embodiment of the present invention; Figure 8 include Figure 8 (a) and Figure 8 (b), where, Figure 8 (a) shows a schematic diagram of heat exchange between the split cold stream and the non-split hot stream. Figure 8 (b) shows a schematic diagram of heat exchange between the split cold flow and the split hot flow; the following embodiments are described based on this.

[0043] In an alternative embodiment, such as Figure 8 As shown in (a), if the cold stream in the fourth heat exchanger is a split cold stream and the hot stream is a non-split hot stream, then the cold stream that satisfies formula (80) is... This refers to the diversion of cold flow and the hot flow that satisfies formula (84). That is, the non-diverted hot flow; then the diverted cold flow is located using formula (81). The fourth branch heat exchanger of each branch; at the same time, it is also necessary to unify the initial cold flow stage and the first cold flow stage of the fourth branch heat exchanger through formula (82); then, the maximum value of the initial hot flow stage of the fourth branch heat exchanger is selected through formula (83) as the maximum stage of the cold flow side of the fourth heat exchanger; then, the maximum stage of the cold flow side of the fourth heat exchanger is compared with the first cold flow stage. The first case is as shown in formulas (85a) to (86d). If the first cold flow stage of the fourth heat exchanger is greater than or equal to the maximum stage of the cold flow side as shown in formula (85a), then the maximum stage of the cold flow side of the fourth heat exchanger is updated with the first cold flow stage based on formula (85b). At this time, the first cold flow stage of the fourth heat exchanger is directly used as its final cold flow stage, and the first hot flow stage is used as its final hot flow stage; then, through formula (86a) (86b) Identify the heat exchanger behind the fourth heat exchanger on the hot stream; if the heat exchanger behind the fourth heat exchanger on the hot stream satisfies formula (86c), then update the initial hot stream stage of the heat exchanger behind the fourth heat exchanger on the hot stream according to formula (86d); the second case is as shown in formulas (87a) to (88b); if the maximum stage of the cold stream side of the fourth heat exchanger is greater than the first cold stream stage as shown in formula (87a), then update the first cold stream stage of the fourth heat exchanger according to formula (87b), at this time the updated first cold stream stage of the fourth heat exchanger is taken as the final cold stream stage of the fourth heat exchanger, and the first hot stream stage is taken as its final hot stream stage; then update the initial cold stream stage of all fourth branch heat exchangers according to formula (88a), and update the initial hot stream stage of all fourth branch heat exchangers according to formula (88b). (80); (81); (82); (83); (84); (85a); (85b); (86a); (86b); (86c); (86d); (87a); (87b); (88a).

[0044] In an alternative embodiment, such as Figure 8 As shown in (b), if the cold stream in the fourth heat exchanger is a split cold stream and the hot stream in the fourth heat exchanger is a split hot stream, as shown in formula (89), it represents the heat exchanger. Hot flow To divert the hot stream; then, the corresponding fifth branch heat exchangers for the fourth heat exchanger are determined by formula (90); similarly, the initial hot stream stage of the fifth branch heat exchanger and the first hot stream stage of the fourth heat exchanger need to be synchronized by formula (91); then, the maximum value of the initial cold stream stage of the fifth branch heat exchanger is selected according to formula (92) as the maximum stage of the hot stream side of the fourth heat exchanger; similarly, the maximum stage of the cold stream side of the fourth heat exchanger is obtained according to formulas (80) to (83) above; then, the maximum stage of the cold stream side of the fourth heat exchanger and the maximum stage of the hot stream side of the fourth heat exchanger are unified according to formulas (93a) to (94b). If the fourth heat exchanger is as shown in formula (93a) If the maximum level of the cold flow side of the heat exchanger is greater than or equal to the maximum level of the hot flow side, then the maximum level of the hot flow side is updated to the maximum level of the cold flow side according to (93b); if the maximum level of the cold flow side of the fourth heat exchanger is less than the maximum level of the hot flow side as shown in formula (94a), then the maximum level of the cold flow side is updated to the maximum level of the hot flow side according to formula (94b); then the initial cold flow level of all branches of the cold flow in which the fourth heat exchanger is located is updated according to formula (95), and thus the first cold flow level of the fourth heat exchanger is updated simultaneously. Therefore, the updated first cold flow level of the fourth heat exchanger is taken as its final cold flow level, and the first hot flow level is taken as its final hot flow level. (89); (90); (91); (92); (93a); (93b); (94a); (94b); (95).

[0045] This embodiment determines the front-side cold flow heat exchanger and the front-side hot flow heat exchanger, considering the influence of the region above the pinch point on the number of stages in the region below the pinch point, and then updates the first cold flow stage and the first hot flow stage. Then, based on the flow splitting situation, the final stage of the cold flow and the final stage of the hot flow are calculated. It fully considers various flow splitting situations and the influence of the front-side heat exchanger on the number of stages, and can accurately determine the final stage of the cold flow and the final stage of the hot flow heat exchanger according to the actual situation, improving the accuracy and rationality of the determination of the number of heat exchanger stages in the pinch point region below the pinch point.

[0046] In this embodiment, the step of screening a plurality of fifth heat exchangers located in the non-pinch region below the pinch point and determining the cold flow type and hot flow type of each fifth heat exchanger; based on the fourth heat exchanger, and in combination with the cold flow type and hot flow type of each fifth heat exchanger, determining the final stage of the cold flow and the final stage of the hot flow of each fifth heat exchanger located in the non-pinch region below the pinch point includes: screening a plurality of fifth heat exchangers located in the non-pinch region below the pinch point and determining the cold flow type and hot flow type of each fifth heat exchanger; if the cold flow type of the fifth heat exchanger is a preset third cold flow type or a preset fourth cold flow type, determining the fourth heat exchanger corresponding to the fifth heat exchanger based on the cold flow of the fifth heat exchanger, and determining the number of non-splitting heat exchangers between the fifth heat exchanger and the corresponding fourth heat exchanger on the cold flow of the fifth heat exchanger; based on the fifth heat exchanger to The final stage of the cold stream of the fifth heat exchanger is determined based on the corresponding final stage of the fourth heat exchanger and the number of non-split heat exchangers. If the heat stream type of the fifth heat exchanger is a preset third heat stream type or a preset fourth heat stream type, the fourth heat exchanger corresponding to the fifth heat exchanger is determined based on the heat stream in which the fifth heat exchanger is located, and the number of non-split heat exchangers between the fifth heat exchanger and the corresponding fourth heat exchanger in the heat stream in which the fifth heat exchanger is located is determined. The final stage of the heat stream of the fifth heat exchanger is determined based on the final stage of the heat stream of the fourth heat exchanger corresponding to the fifth heat exchanger and the number of non-split heat exchangers. If the cold stream type of the fifth heat exchanger is a preset fifth cold stream type or the heat stream type is a preset fifth heat stream type, the initial cold stream stage and the initial heat stream stage of the fifth heat exchanger are compared, and the final stage of the heat stream and the final stage of the cold stream of the fifth heat exchanger are determined based on the comparison result.

[0047] In an alternative embodiment, such as Figure 3 As shown, if the cold flow type of the fifth heat exchanger is a preset third cold flow type or a preset fourth cold flow type; then the fourth heat exchanger corresponding to the fifth heat exchanger is determined by formulas (96), (96a), and (96b). Formula (96) is used to locate the heat exchanger on the cold flow in the clamping area below the clamping point, and formula (96a) is used to represent the heat exchanger. Cold chain logistics For split or non-split flow; Formula (96b) is used to represent cold flow. The heat exchangers in the non-pinch region below the pinch point; then, as in formula (96c), calculate the number of non-split heat exchangers between the fifth heat exchanger and the corresponding fourth heat exchanger on the cold stream where the fifth heat exchanger is located. Specifically, This indicates the number of heat exchangers between the fifth heat exchanger and the corresponding fourth heat exchanger, plus... This can be defined as a non-split heat exchanger; therefore, as shown in formula (96c), the final stage of the cold flow of the fourth heat exchanger and the number of non-split heat exchangers are added together to obtain the final stage of the cold flow of the fifth heat exchanger; if the heat flow type of the fifth heat exchanger is a preset third heat flow type or a preset fourth heat flow type, then the fourth heat exchanger corresponding to the fifth heat exchanger is determined by formulas (96d), (97a), and (97b). Formula (96d) is used to locate the heat exchanger on the heat flow in the pinch area below the pinch point; (97a) is used to represent the heat exchanger. The hot flow For diverting or non-diverting; (97b) for locating hot flow streams The heat exchangers in the non-pinch region below the pinch point; then, as in formula (97c), calculate the number of non-split heat exchangers between the fifth heat exchanger and the corresponding fourth heat exchanger on the heat stream where the fifth heat exchanger is located. Specifically, This indicates the number of heat exchangers between the fifth heat exchanger and the corresponding fourth heat exchanger on the heat stream in which the fifth heat exchanger is located, plus... This can be defined as a non-split heat exchanger; therefore, as shown in formula (97c), the final stage of the heat flow of the fourth heat exchanger and the number of the non-split heat exchangers are added together to obtain the final stage of the heat flow of the fifth heat exchanger. (96); (96a); (96b); (96c); (96d); (97a); (97b); Thus, the final stages of cold and hot flows of the heat exchangers on the third hot flow type, the fourth hot flow type, the third cold flow type, and the fourth cold flow type are confirmed; then, the cold flow type is confirmed to be the preset fifth cold flow type or the hot flow type is the preset fifth hot flow type; further, if the cold flow type of the fifth heat exchanger is the preset fifth cold flow type or the hot flow type is the preset fifth hot flow type, since the flows of the fifth cold flow type and the fifth hot flow type are completely located below the pinch point, they only exchange heat with the flows in the non-pinch area below the pinch point. Therefore, the heat exchangers on the third cold flow type, the fourth cold flow type, the third hot flow type, and the fourth hot flow type in the non-pinch area below the pinch point can be determined by formula (98); the fifth heat exchanger on the flows of the fifth cold flow type and the fifth hot flow type can be determined by formula (99); combining formulas (98) and (99), the fifth heat exchanger with the cold flow type being the preset fifth cold flow type or the hot flow type being the preset fifth hot flow type can be obtained; further, in order to facilitate subsequent calculations, two intermediate parameters are introduced here. and , and They are used to represent and Its specific values ​​are shown in formulas (100) and (101); (98); (99); (100); (101); There are still two cases. The first case is that the initial hot stream level of the fifth heat exchanger is greater than or equal to the initial cold stream level, as shown in formulas (102) to (102e). If the initial hot stream level of the fifth heat exchanger is greater than or equal to the initial cold stream level as shown in formula (102), then the initial cold stream level of the fifth heat exchanger is updated based on formula (102a). At this time, the updated initial cold stream level of the fifth heat exchanger is taken as its final cold stream level, and its initial hot stream level is taken as its final hot stream level. Then, according to formula (102b), all heat exchangers on the right side of the cold stream where the fifth heat exchanger is located are selected. Then, according to formula (102c), the heat exchangers on the right side of the cold stream where the fifth heat exchanger is located are selected as being in the non-pinch region below the pinch point. Then, according to formula (102d), the heat exchangers on the right side of the cold stream where the fifth heat exchanger is located and are in the non-pinch region below the pinch point are determined. If formula (102d) is satisfied, then the initial cold stream level is updated according to formula (102e). The second case is that the initial cold stream level of the fifth heat exchanger is greater than the initial hot stream level, as shown in formulas (103) to (103d). If the initial cold stream level of the fifth heat exchanger is greater than the initial hot stream level according to formula (103), then the initial hot stream level of the fifth heat exchanger is updated according to formula (103a). At this time, the updated initial hot stream level of the fifth heat exchanger is taken as its final hot stream level, and its initial cold stream level is taken as its final cold stream level. Then, according to formula (103b), the heat exchanger in the non-pinch region below the pinch point on the hot stream of the fifth heat exchanger is located, and it is determined whether it meets the requirements of formula (103c). If it does, then the heat exchanger in the non-pinch region below the pinch point on the hot stream of the fifth heat exchanger is updated according to formula (103d). (102); (102a); (102b); (102c); (102d); (102e); (103); (103a); (103b); (103c); (103d).

[0048] This embodiment calculates the final stages of the hot and cold streams of the fifth heat exchanger by combining the cold stream type, cold stream diversion result, hot stream type, and hot stream classification result of the fifth heat exchanger with the fourth heat exchanger in the corresponding stream direction. This greatly improves the efficiency and accuracy of stage determination and avoids complex global calculations for each heat exchanger individually. It ensures that in the non-pinch region below the pinch point, the final stages of the hot and cold streams of the fifth heat exchanger can extend accurately and orderly from the pinch region below the pinch point, maintaining the continuity and consistency of the superstructure topology in the entire region below the pinch point, thereby improving the accuracy of the heat exchange network flowchart conversion to a multi-stage superstructure.

[0049] Step S104: Based on the final stage of the cold flow and the final stage of the hot flow of the heat exchanger, determine the superstructure parameters of the region below the pinch point and the total number of superstructure stages of the multi-stage superstructure.

[0050] In this embodiment, determining the superstructure parameters and the total number of superstructure levels in the region below the pinch point based on the final stages of the cold and hot streams of the heat exchanger includes: determining virtual heat exchanger hot stream stages based on the heat capacity flow rate of each hot stream in the heat exchanger network flowchart; determining virtual heat exchanger cold stream stages based on the heat capacity flow rate of each cold stream in the heat exchanger network flowchart; filling blank-level parameters for each cold stream based on the final stage of the cold stream of each heat exchanger on each cold stream; filling blank-level parameters for the leftmost heat exchanger on each cold stream based on the final stage of the cold stream of the leftmost heat exchanger on each cold stream; filling blank-level parameters for each hot stream based on the final stage of the cold stream of each heat exchanger on each hot stream; and filling blank-level parameters for the leftmost heat exchanger on each hot stream. For the final stage of the hot flow path, blank level parameters are filled for the leftmost heat exchanger in each hot flow path; based on the blank level parameters, the superstructure parameters of the region below the pinch point are determined; the number of cold utilities in the heat exchange network flowchart is obtained, and the total number of superstructure levels is determined based on the number of cold utilities to determine the problem type, wherein the problem type for determining the total number of superstructure levels includes: pinch problem and threshold problem; if the problem type for determining the total number of superstructure levels is pinch problem, then the blank level parameters of the hot and cold flows are refilled to redetermine the superstructure parameters of the region below the pinch point, and then the total number of superstructure levels of the multi-level superstructure is determined based on the maximum value of the final stage of the hot flow path of the heat exchanger; if the problem type for determining the total number of superstructure levels is threshold problem, then the total number of superstructure levels of the multi-level superstructure is determined based on the maximum value of the final stage of the hot flow path of the heat exchanger.

[0051] In an alternative embodiment, where there are no heat exchangers in certain stages, the variable and All relevant parameters are uniformly expressed using the fluid stream corresponding to the maximum heat capacity flow rate (i.e., the heat fluid stream with the maximum heat capacity flow rate). and cold flow with the highest heat capacity Specifically, the heat flow rate of each heat stream in the virtual heat exchanger is determined using formulas (104a) to (104c). Formula (104a) represents the location of the hot stream with the maximum heat capacity flow rate by summation, sum[ [1] indicates any logistics Meet other logistics needs heat capacity flow rate If the quantity exceeds this value, add 1; Formula (104b) indicates that the sum of Formula (104a) is 0, meaning that a hot stream is located in Formula (104b). heat capacity flow rate Maximum, i.e., locking the heat stream; formula (104c) represents setting the virtual heat exchanger heat stream level. This represents the hot stream with the maximum heat capacity flow rate; similarly, the cold stream stages of the virtual heat exchanger are determined using formulas (105a) to (105c); where formula (105a) is used to find the cold stream with the maximum heat capacity flow rate, sum[ [1] indicates any logistics Meet other logistics needs When the heat capacity flow rate is greater than that of the material, add 1; Formula (105b) means that the sum of Formula (105a) is 0, that is, a material is located in Formula (105a). The maximum heat capacity flow rate is achieved by locking in the cold stream; formula (105c) represents the virtual heat exchanger cold stream stage. This indicates the cold flow with the highest heat capacity.

[0052] (104a); (104b); (104c); (105a); (105b); (105c).

[0053] In an optional embodiment, blank-level parameter filling is performed on each cold stream based on the final stage of the cold stream for each heat exchanger on each cold stream, specifically including: First, the cold flow in the region above the pinch point is processed. For the second and third types of cold flow in the region above the pinch point, formula (106) is used to locate the heat exchanger position on the split or non-split flow, and formula (106a) is used to locate the heat exchanger in the pinch point region above the pinch point. Then, the heat exchanger is represented by formula (107a). Cold logistics inlet temperature Cold flow corresponding to the pinch point above the pinch point Mixing temperature of each tributary Therefore, the cold chain flow rate of each cold chain in the region above the pinch point can be obtained using formulas (106), (106a), and (107a). The heat exchanger on the far right Meanwhile, to facilitate subsequent calculations, this embodiment introduces intermediate parameters through formula (107b). This indicates a heat exchanger. The outlet temperature of the cold logistics; at this time, if it is cold logistics heat exchanger on cold chain logistics final stage With heat exchanger cold chain logistics final stage If formula (108) is satisfied, then at this time, by using formulas (109a), (109b), and (109c), combined with the virtual heat exchanger cold flow stage, Fill the blank stage between these two heat exchangers, where formula (109a) is used to calculate the heat exchanger. With heat exchanger Parameters between ; This indicates that the conditions within the parentheses must be met; `ord()` returns the index of the element in the collection. The representation level is located at and between; Indicates cold chain logistics In the Level and The interstage temperature is converted into blank stage parameters of the superstructure correlation variables initial values; formula (109b) is used to calculate the heat exchanger. With heat exchanger Parameters between ; This indicates that the conditions within the parentheses must be met. express For a heat stream with the maximum heat capacity flow rate, "and" indicates that it must simultaneously satisfy the following conditions. The representation level is located at and between; This indicates that the cold flow branch passes through the heat exchanger. The temperature is then converted to a superstructure heat exchanger. Blank-level parameters corresponding to the initial values ​​of the corresponding variables; Formula (109c) is used to calculate the heat exchanger. With heat exchanger Parameters between For the meaning of the formula statements in formula (109c), please refer to the descriptions of formulas (109b) and (109a); Indicates cold chain logistics The tributary in the heat exchanger The heat capacity flow rate is converted into a superstructure heat exchanger. Blank-level parameters corresponding to the initial values ​​of the corresponding variables; after completing the calculation of the heat exchanger With heat exchanger After filling in the blank stage parameters, it is considered a heat exchanger. Switch to cold chain logistics The leftmost end; for the needs of subsequent calculations, the cold flow in the region above the clamp point is here. The rightmost heat exchanger has been renamed It is defined by formula (110); formula (111a) indicates the presence of a heat exchanger. This allows the heat exchanger to satisfy the equation (111b). The inlet temperature of the cold stream is equal to that of the heat exchanger. The cold stream outlet temperature; after obtaining the heat exchanger Then, it is necessary to use formula (111c) to... The value is iterated for the heat exchanger The cold stream outlet temperature; then, based on formula (112), the heat exchanger temperature is determined. and heat exchanger Are they adjacent? If not, calculate the blank stage parameters between the two heat exchangers. , and ; , and Calculate using formulas (113a), (113b), and (113c); then repeat the process from formulas (110) to (113c) until there are no non-adjacent heat exchangers on the cold stream; (106); (106a); (107a); (107b); (108); (109a); (109b); (109c); (110); (111a); (111b); (111c); (112); (113a); (113b); (113c); Next, it is necessary to determine whether the cold flow of the second and third cold flow types in the area above the clamp point is a hot utility. If it requires a heating utility As described by formula (114), the leftmost heat exchanger on the cold flow is determined by formulas (115a) and (115b), where formula (115a) is used to locate the cold flow. The leftmost heat exchanger position is shown above; sum[] represents the summation formula; $() represents the dollar signifier, which is a conditional statement. This indicates that for any fixed inlet temperature As long as there is a temperature higher than this inlet temperature If the value is greater than the inlet temperature, then add 1; if two values ​​are greater than this inlet temperature, add 2, and so on. Formula (115b) is used to indicate that formula (115a) is 0, that is, it is located at the inlet temperature of a certain heat exchanger. The value of formula (115a) is 0, which means that the inlet temperature is at its maximum at this time, thus indicating that the cold chain logistics is being located. The position of the leftmost heat exchanger is determined; then, formula (116) is used to determine whether the final stage of the cold stream from the leftmost heat exchanger is the second stage. A value greater than 2 indicates no, because the thermal utility must be located in the first stage; if it is not the second stage, then the blank stage parameters between the thermal utility and the leftmost heat exchanger on the cold stream are calculated based on formulas (117a), (117b), and (117c); formula (117a) is used to calculate the blank stage parameters between the thermal utility and the leftmost heat exchanger. Parameters at each level Formula (117b) is used to calculate the thermal utility and the leftmost heat exchanger. Parameters at each level Formula (117c) is used to calculate the thermal utility and the leftmost heat exchanger. Parameters at each level The target temperature for this cold chain logistics is then defined as follows: So, in the first stage (heat utility) of this cold chain logistics... The value is shown in formula (118); (114); (115a); (115b); (116); (117a); (117b); (117c); (118); If it does not require thermal utilities As shown in formula (119), the leftmost heat exchanger is still determined by formulas (115a) and (115b). At this time, formula (120) is used to determine whether it is the first stage. If the final value of the cold flow of the leftmost heat exchanger is greater than 1, it means no. If it is not the first stage, the blank stage parameters between the leftmost heat exchanger and the first stage are calculated by formulas (121a), (121b), and (121c). Formula (121a) is used to calculate the final stage of the cold flow of the leftmost heat exchanger. Parameters between the first level The meaning of the $() statement is from the first level to the second level. Between heat exchanger stages, because of cold flow No utilities are required, so the target temperature has been reached. That is, the value is equal to Formula (121b) is used to calculate the final stage of the cold stream in the leftmost heat exchanger. Parameters between the first level As mentioned above, this embodiment specifies that in the heat exchanger of the blank stage... In For the hot stream with the maximum heat capacity flow rate, (since there is no heat exchanger, but complete superstructure parameters are required for model initialization optimization calculations, the parameters for the missing heat exchanger also need to be completed), the parameter values ​​are all... Formula (121c) is used to calculate the final stage of the cold stream in the leftmost heat exchanger. Parameters between the first level As mentioned above, this embodiment specifies that in the heat exchanger of the blank stage... In For the hot stream with the maximum heat capacity flow rate, since there is no branching in these stages, it is equal to ; (119); (120); (121a); (121b); (121c); Next, for the first type of cold logistics in the area above the clamping point... Its rightmost heat exchanger Determined by formulas (122a) and (122b); formula (122a) is used to locate the rightmost heat exchanger position of logistics j by introducing parameters. Formula (122b) is used to locate cold chain logistics. The rightmost heat exchanger; and the rightmost heat exchanger Adjacent heat exchangers Through the rightmost heat exchanger cold chain outlet temperature The parameters are determined using formula (123a) and then updated using formula (123b). The value of is used for the next iteration calculation, until the parameter Reach the leftmost heat exchanger; then determine the rightmost heat exchanger using formula (124). adjacent heat exchanger Whether the final stages of the cold flow are adjacent; if the difference between the final stages of the cold flow is greater than 1, it means they are not adjacent; at this time, the blank stage parameters between the two heat exchangers are calculated using formulas (125a), (125b), and (125c); further, if it is a cold flow of the first cold flow type... In the application of thermal utilities, the parameters between the leftmost heat exchanger and the first stage are... , and It can be calculated by equations (115a)–(117c). Conversely, if no thermal utility is used, the parameters between the leftmost heat exchanger and the first stage are... , and It can be calculated by equations (120)–(121c).

[0054] (122a); (122b); (123a); (123b); (124); (125a); (125b); (125c); After processing the cold flow in the region above the pinch point, the cold flow in the region below the pinch point is processed first. The third and fourth types of cold flow are processed first, and the heat exchanger is then redefined. This represents the leftmost heat exchanger in the cold flow path, and also introduces parameters. The parameters are calculated using formulas (126a) and (126b). Used to assist in positioning adjacent heat exchangers; and heat exchangers Adjacent heat exchangers Determined by equation (127a), and adjusted by equation (127b). The adjacent heat exchanger is located; then, according to formula (128), it is determined whether the final stages of the cold flow of the two heat exchangers are adjacent. If the value is greater than 1, it means that the heat exchanger stages are not adjacent; if they are not adjacent, the blank stage parameters of the two heat exchangers are calculated according to formulas (129a), (129b), and (129c). , and ; (126a); (126b); (127a); (127b); (128); (129a); (129b); (129c); In particular, for the third type of cold logistics, since it crosses the pinch point, it needs to be processed again. First, the heat exchanger in the pinch point region above the pinch point is determined based on formula (130). The heat exchanger adjacent to it on its right side in the pinch region below the pinch point Whether the distribution is in an interleaved state is determined by whether the difference between their final cold flow stages is greater than 1. In this case, the gap stage parameter between the two is calculated based on formulas (131a), (131b), and (131c). , and If the difference between their final cold logistics stages satisfies formula (132), i.e., the difference equals 1, then the distribution is not in an interleaved state; at this time, the blank stage parameter between the two is calculated based on formulas (133a), (133b), and (133c). , and ; (130); (131a); (131b); (131c); (132); (133a); (133b); (133c); After processing the cold streams of the third and fourth cold stream types in the region below the pinch point, the cold stream of the fifth cold stream type is processed. First, the leftmost heat exchanger on the cold stream of the fifth cold stream type is identified using formulas (134a) and (134b). Formula (134a) is used to locate cold chain logistics. The leftmost heat exchanger position, sum[] represents the summation function, Indicates cold chain logistics The cold flow inlet temperature of any heat exchanger For the remaining cold stream inlet temperatures of the heat exchangers As long as there is a temperature ratio If the value is large, the increment is 1; at the same time, a parameter is introduced through formula (134b). Make it equivalent to a heat exchanger The cold flow inlet temperature; then the heat exchanger is redefined using formula (135b). This indicates cold chain logistics. The heat exchanger on the far left The outlet temperature of the cold stream through the heat exchanger is then defined according to formula (136a). The heat exchanger on the far left Adjacent heat exchangers Simultaneously, the parameters also need to be updated synchronously using formula (136b). The value; then, the heat exchanger is determined according to formula (137). With heat exchanger If the final stages of the cold flow are adjacent, then they are not adjacent; if the difference between the final stages of the cold flow is greater than 1, then the heat exchanger is calculated according to formulas (138a), (138b), and (138c). With heat exchanger The blank level parameters between , and Then repeat formulas (135a) to (138c) until the parameter... Locate the heat exchanger on the far right; (134a); (134b); (135a); (135b); (136a); (136b); (137); (138a); (138b); (138c); Based on the final stage of the cold flow of the heat exchanger located on the leftmost side of each cold flow, blank stage parameters are filled for the heat exchanger located on the leftmost side of each cold flow. This part can be referred to the content of subsequent formulas (165) to (166); in this embodiment, the hot flow is described first.

[0055] In an alternative embodiment, for the hot flow in the region above the clamp, the region above the clamp is processed first, and the hot flow is determined by formula (139). The rightmost heat exchanger The rightmost heat exchanger The heat exchanger on the left Defined by equation (139a); in equation (139) This represents the number of branches of each hot stream above the pinch point, in formula (139a). Indicates the thermal flow in the region above the pinch point. The temperature before the split; similarly, parameters are introduced through formula (139b). Used to define the positions of adjacent heat exchangers; then the heat exchanger is determined according to formula (140). With heat exchanger The final stages of the heat flow streams are considered to be adjacent. If the difference between their final stages is greater than 1, they are considered not adjacent. Then, the heat exchanger is calculated according to formulas (140a), (140b), and (140c). With heat exchanger The blank level parameters between , and For the non-pinch region above the pinch point, the rightmost heat exchanger on each heat stream is defined by formula (141). Furthermore, formula (142a) ensures the existence of the adjacent heat exchanger of the rightmost heat exchanger; formula (142b) determines the adjacent heat exchanger of the rightmost heat exchanger. It also needs to be updated using formula (142c). The value is used to locate the position of the adjacent heat exchanger in the next iteration; then the heat exchanger is determined by formula (143). With heat exchanger If the final stages of the hot flow are adjacent, then they are not adjacent. In this case, the blank stage parameters between them are calculated based on formulas (143a), (143b), and (143c). , and Then repeat formulas (141) to (143c) until... The value is for the leftmost heat exchanger on the hot stream; (139); (139a); (139b); (140); (140a); (140b); (140c); (141); (142a); (142b); (142c); (143); (143a); (143b); (143c); Furthermore, thermal logistics in the non-pinch region above the pinch point. The leftmost heat exchanger is named It is determined by equations (144), (145a), and (145b); equation (144) is used to represent the heat exchanger. The formula (145a) is used to locate the thermal flow. Maximum inlet temperature of the upper heat exchanger Indicates hot logistics Above, for any heat stream inlet temperature passing through the heat exchanger As long as any hot flow inlet temperature exists Greater than The cumulative increment is 1; formula (145b) is used to calculate the thermal flow. The maximum heat flow inlet temperature of the heat exchanger is 0, which means that no inlet temperature higher than this has been found; then, formula (146) is used to determine the leftmost heat exchanger. Whether the final stage of the heat flow is the first stage; if the final stage of the heat flow is greater than 1, it indicates that it is not in the first stage; in this case, the leftmost heat exchanger needs to be calculated using formulas (146a), (146b), and (146c). The blank level parameter between the first level and the second level; (144); (145a); (145b); (146); (146a); (146b); (146c); Specifically, for the first type of hot flow, the leftmost heat exchanger... Determined by formulas (147a) and (147b), wherein formula (147a) is used to determine the heat stream of the first heat stream type. The leftmost heat exchanger sum[] represents the summation function. Indicates the inlet temperature of the hot stream for any heat exchanger. As long as any Higher than That is, cumulatively add 1; formula (147b) is used to locate the hot flow. The leftmost heat exchanger on top, A value of 0 indicates that there is no specific heat exchanger. The heat exchanger with the highest inlet temperature for the hot flow is located at the leftmost position; then, parameters are introduced using formula (148a). This is used to locate the positions of adjacent heat exchangers during iterative calculations; simultaneously, as shown in formula (149a), the leftmost heat exchanger is named heat exchanger. Then, the leftmost heat exchanger is set according to formula (149b). The adjacent heat exchanger on the right is As shown in formula (150), if it is a heat exchanger With heat exchanger The final stages of the heat exchanger are not adjacent; that is, if the difference between the final stages of the heat exchanger is greater than 1, they are not adjacent. If they are not adjacent, the heat exchanger is calculated using formulas (151a), (151b), and (151c). With heat exchanger blank level parameters , and ; (147a); (147b); (148a); (148b); (149a); (149b); (150); (151a); (151b); (151c); In particular, for the third type of hot stream, since it crosses the pinch point, the heat exchangers on both sides of the pinch point also require special treatment; firstly, the heat exchangers on both sides of the pinch point are determined using formulas (152a) to (152d); whereby the heat exchanger in the pinch point region above the pinch point is defined as The heat exchanger in the pinch region below the pinch point is defined as Then, the heat exchanger is determined according to formula (153). With heat exchanger The heat exchanger is determined by whether the final stages of the heat flow are adjacent. If they satisfy formula (153), then they are not adjacent. In this case, the heat exchanger is calculated based on formulas (154a), (154b), and (154c). With heat exchanger The blank level parameters between , and If formula (155) is satisfied, it indicates that they are adjacent. In this case, the heat exchanger is calculated based on formulas (156a), (156b), and (156c). With heat exchanger The blank level parameters between , and ; (152a); (152b); (152c); (152d); (153); (154a); (154b); (154c); (155); (156a); (156b); (156c); Next, the hot flow in the region below the pinch point is processed. First, the hot flow in the region below the pinch point is determined by formula (157a). heat exchanger at the mixing position Meanwhile, parameters are introduced through formula (157b). Used to locate adjacent heat exchangers; then the heat flow is defined. The heat exchanger in the pinch region below the pinch point is Therefore, the heat exchanger is judged based on formula (158). With heat exchanger The final stages of the heat exchangers are determined by whether they are adjacent. If the difference between their final stages is greater than 1, they are considered not adjacent. Then, the heat exchanger is calculated according to formulas (159a), (159b), and (159c). With heat exchanger The blank level parameters between , and For the non-pinch region below the pinch point, the heat exchanger is adjusted using formula (160a). Rename Then, the heat exchanger is positioned using formula (160b). Adjacent heat exchanger on the right heat exchanger The inlet temperature of the hot flow is equal to that of the heat exchanger. The hot stream outlet temperature; then the parameters are updated using formula (160°C). To position the heat exchanger Then, the heat exchanger is determined according to formula (161). With heat exchanger If the final stages of the hot flow are adjacent, then they are not adjacent. In this case, the blank stage parameters between them are calculated based on formulas (162a), (162b), and (162c). , and Then repeat formulas (160c) to (162c) until... It is positioned as the rightmost heat exchanger on this heat flow path; (157a); (157b); (158); (159a); (159b); (159c); (160a); (160b); (160c); (161); (162a); (162b); (162c).

[0056] In an optional embodiment, based on the final stage of the heat flow of the leftmost heat exchanger in each heat flow, blank stage parameters are filled for the leftmost heat exchanger in each heat flow, as shown in formulas (163a) to (164c); the heat flow is defined by formula (163a). The leftmost heat exchanger The leftmost heat exchanger is determined using formula (163b). Is the final stage of thermal logistics the first stage? A value greater than 1 indicates that it is not in the first stage; in this case, the leftmost heat exchanger is calculated based on formulas (164a), (164b), and (164c). Blank level parameters between the first level and the first level , and Based on the final stage of the cold flow from the leftmost heat exchanger in each cold flow path, blank stage parameters are filled for the leftmost heat exchanger in each cold flow path, as shown in formulas (165a) to (166c). The cold flow path is defined by formula (165a). The leftmost heat exchanger The leftmost heat exchanger is determined using formula (165b). Is the final stage of cold chain logistics the first stage? A value greater than 1 indicates that it is not in the first stage; in this case, the leftmost heat exchanger is calculated based on formulas (166a), (166b), and (166c). Blank level parameters between the first level and the first level 、 and ; (163a); (163b); (164a); (164b); (164c); (165a); (165b); (166a); (166b); (166c).

[0057] In an alternative embodiment, after determining the aforementioned superstructure parameters, the maximum number of orders of the HEN structure designed by the M-INI model is determined. It remains uncertain. For pinch or threshold problems, the parameter distribution of each stage from the rightmost heat exchanger to the target temperature can only be determined by specifying the total number of stages in the superstructure. Furthermore, the case where the outlet temperature of the rightmost heat exchanger equals the target temperature is also included in these problems. Specifically, the cold utility quantities of the heat exchanger network flow diagram need to be obtained. If the amount of cold public works If the value is greater than 0, it indicates that a cold utility project is required, and the problem type for determining the total superstructure level is a pinch problem; otherwise, the problem type for determining the total superstructure level is a threshold problem. If the problem type for determining the total number of superstructure stages is a pinch problem, i.e., it satisfies formula (167); then, according to formula (168a), the maximum value of the final stage of the heat flow in all heat exchangers is obtained. At this point, the total number of levels in the multi-level superstructure is... As shown in formula (168b), the calculation is obtained; furthermore, it is necessary to fill the blank level parameters for the rightmost heat exchanger on each of the cold streams and the rightmost heat exchanger on each of the hot streams, in order to redetermine the superstructure parameters of the region below the pinch point. For the pinch point problem, the heat exchange process of the hot stream includes three possible cases: (1) stream Heat exchange with cold logistics systems without public utilities means logistics (2) Logistics (3) If heat exchange with cold logistics fails to reach the target temperature, cold utility engineering needs to be introduced; The target temperature is achieved solely through refrigeration utilities.

[0058] In cases (1) and (2), the rightmost heat exchanger on the hot stream is first determined based on formulas (169a) and (169b). (Outlet temperature of non-utility heat exchanger) ;in, Indicates hot logistics Required thermal utilities (unit: kW); furthermore, to ensure feasibility calculation, a minimum number is introduced through formulas (170a) and (170b). heat exchanger outlet temperature Numerical processing was performed to determine the rightmost heat exchanger. The position; if it is the rightmost heat exchanger as shown in formula (171) The final stage of the thermal flow is less than the maximum value of the final stage of the thermal flow across all heat exchangers. Based on formulas (171a), (171b), and (171c), the calculation of the rightmost heat exchanger is performed. The maximum value of the final stage of the thermal flow and the final stage of the thermal flow of all heat exchangers. The blank level parameters between , , This allows for the filling of blank stage parameters for the rightmost heat exchanger in each of the aforementioned cold streams; in the case of (3), formula (172) is used to express that the hot stream only exchanges heat with the cold utility stream to reach the target temperature, then for this hot stream, the blank stage parameters within each stage (from the first stage to the last stage) are... , and The parameters can be calculated using formulas (172a), (172b), and (172c); formula (173) represents the cold flow that exchanges heat only with the thermal engineering flow to reach the target temperature; then formulas (173a), (173b), and (173c) are used to calculate the blank stage parameters within each stage of the cold flow (from the first stage to the last stage). , , This allows for the redetering of the hyperstructure parameters of the region below the pinch point; (167); (168a); (168b); (169a); (169b); (170a); (170b); (171); (171a); (171b); (171c); (172); (172a); (172b); (172c); (173); (173a); (173b); (173c); If the problem type for determining the total number of superstructure levels is a threshold problem, as shown in formula (174), then based on formula (168a), we obtain... The total number of superstructure levels in a multi-level superstructure is obtained as shown in formula (174a).

[0059] (174); (174a).

[0060] This embodiment introduces virtual heat exchangers and fills in blank level parameters. By determining the hot and cold stream stages of the virtual heat exchanger through heat capacity flow rate, it provides a positional reference for streams in the heat exchanger network flow diagram that do not pass through the heat exchanger within the multi-level superstructure. Filling in blank level parameters ensures that each stream has a clearly defined variable across all levels in the final multi-level superstructure, enabling the multi-level superstructure to be used to construct MINLP / NLP models. Subsequently, by using cold utility quantities, the solution to the total number of superstructure stages is divided into pinch problems or threshold problems, and different total stage determination strategies are used accordingly. This ensures that the generated multi-level superstructure has a minimum number of stages, thereby minimizing redundant variables and constraints in the multi-level superstructure and improving the conversion and solution efficiency of the multi-level superstructure.

[0061] Step S105: Based on the final stage of cold flow and the final stage of hot flow of each heat exchanger, and combining the superstructure parameters of the region below the pinch point, the superstructure parameters of the region above the pinch point, and the total number of superstructure stages of the multi-level superstructure, the heat exchange network flowchart is converted into a multi-level superstructure.

[0062] It should be noted that hot streams are divided into hot process streams and hot utility streams. Hot utility streams refer to the heat medium with a stable high temperature, generated and supplied by an external system through external equipment in the heat exchanger network flow diagram. Their purpose is to transfer heat to the cold process streams that need heating through heat exchange. Cold streams are divided into cold process streams and cold utility streams. Cold utility streams refer to a cooling medium with a stable low temperature, supplied by an external system. Their purpose is to absorb unrecoverable heat from the hot process streams through heat exchange. In steps S101 to S104 above, both hot process streams and hot utility streams can be considered hot streams, thus applicable to the corresponding processing in steps S101 to S104. Similarly, both cold process streams and cold utility streams can be considered cold streams, thus applicable to the corresponding processing in steps S101 to S104. However, after converting the heat exchanger network flow diagram into a multi-level superstructure, the blank level parameters of the multi-level superstructure need to be processed so that the multi-level superstructure can be applied to subsequent mathematical programming and other applications.

[0063] In one optional embodiment, the first and last stages of the material flow in the multi-stage superstructure are processed first; specifically, for the cold material flow in the multi-stage superstructure... The cold chain logistics is determined by formula (175). If the heat exchanger on the far right holds true, then the cold flow path has been found. The heat exchanger on the far right indicates that the cold flow is flowing. The cold flow final stage of the heat exchanger located on the far right. Since there is no heat exchanger between the total number of stages and the superstructure, blank stage parameters need to be filled between them. , and Due to cold chain logistics The cold flow final stage of the heat exchanger located on the far right. Since there is no heat exchanger between the superstructure and the total number of stages, this embodiment specifies the heat flow path. For hot streams with maximum heat capacity flow rate; at this time, the blank stage parameters are filled. , and As calculated using formulas (176a), (176b), and (176c). Formula (176a) is used to calculate the multi-level superstructure in the (… , The blank level parameter between ] Its value is cold logistics starting temperature Similarly, formula (176b) is used to calculate the multi-level superstructure in which the ( , The blank level parameter between ] Its value is cold logistics starting temperature In a multi-level superstructure, the position of ( , The blank level parameter between ] Equivalent to cold chain logistics heat capacity flow rate .

[0064] (175); (176a); (176b); (176c); Next, regarding hot logistics In the last level of the multi-level superstructure (i.e. There are situations where cold public works exist; in this case, for the last level (i.e. At this point, it is necessary to set the blank level parameter for the last level. , and Determined by formulas (177a) to (177c); while for cold chain logistics In the case of a thermal utility heat exchanger in the first stage of a multi-stage superstructure, a cold flow path needs to be configured. Temperature upon entering the first stage (blank stage parameter) As shown in formula (178a), it is set as a cold flow. The temperature before entering the heat exchanger of a thermal utility, i.e. At the same time, the blank level parameters of the first level need to be adjusted. and Configure it as shown in formula (178b). Set as cold chain logistics Target temperature As shown in formula (178c), Set as cold chain logistics heat capacity flow rate .

[0065] After addressing situations involving either cold or hot utilities, it is necessary to re-determine the blank level parameters for cold and hot flows at the first and last stages; specifically, for hot flows... As shown in formula (179a), the blank stage parameter of its first stage is equal to that of the heat flow. starting temperature As shown in formula (179b), the blank stage parameter of its last stage is equal to that of the heat flow. Target temperature For cold chain logistics As shown in formula (180a), the blank stage parameter of its first stage is equal to that of the cold flow. Target temperature As shown in formula (180b), the blank stage parameter of its last stage is equivalent to that of cold flow. starting temperature ; (177a); (177b); (177c); (178a); (178b); (178c); (179a); (179b); (180a); (180b); Therefore, through the calculations and organization above, the processing of the first and last stages of hot and cold streams in a multi-stage superstructure has been completed. Now, for the heat exchanger in the multi-stage superstructure, its relevant blank stage parameters... , , , , and It can be calculated using formulas (181a) to (182c).

[0066] (181a); (181b); (181c); (182a); (182b); (182c); Due to the existence of utility logistics, after completing the processing of the first and last stages of hot and cold logistics in the multi-level superstructure, it is still necessary to process the first and last stages of utility logistics. First, the cold logistics requiring hot utility is determined by formula (183). ; and then for cold logistics requiring thermal utilities The corresponding thermal utility logistics set For thermal public works logistics collection thermal logistics The blank level parameters of the first level in the superstructure are determined by formula (183a). The value of each level in the superstructure from the first to the last level is determined by formula (183b). As shown in formula (183c), since the utility stream participates in heat exchange as a branch in each stage and then no longer mixes until the target temperature of the utility stream is reached, the heat stream... After passing the blank level parameters of the first level Equal to hot logistics Target temperature As shown in formula (183d), the thermal flow The blanking level parameters of each level from the first level to the last level. This is also equivalent to hot logistics. Target temperature As shown in formula (183e), the thermal flow... Blank level parameters for each level from the first to the last level Based on the law of heat conservation, this embodiment sets the initial temperature of the thermal utility logistics flow to 1200℃ and the target temperature to 900℃. The blank stage parameters for each stage from the first to the last stage are obtained through calculation. Afterwards, thermal logistics blank level parameters It can also be solved using formula (183f); (183); (183a); (183b); (183c); (183d); (183e); (183f); Formulas (183) to (183f) above determine all blank level parameters for the thermal utility logistics. Then, formulas (184) to (184f) below determine all blank level parameters for the cold utility logistics. First, formula (184) is used to determine the thermal logistics requiring cold utility. This allows for the determination of the heat flow required for cold utilities. Corresponding cold chain logistics For cold chain public works logistics Cold chain logistics Its position in the superstructure after the last stage is determined by formula (184a) (i.e. Blank level parameter Since the utility stream participates in heat exchange as a branch in each stage and then no longer mixes until the target temperature of the utility stream is reached, therefore, as shown in formula (184b), in each stage between the first and last stages (i.e. Blank level parameter Equivalent to cold chain logistics Target temperature Similarly, as shown in formula (184c), the blank level parameter in the last level... Equivalent to cold chain logistics Target temperature Furthermore, regulations for cold chain logistics are stipulated. Heat exchangers in each stage between the first and last stages The corresponding hot stream has the maximum heat capacity flow rate, then its blank stage parameters It is calculated using formula (184d); where This refers to the hot stream with the maximum heat capacity flow rate; and as shown in formula (184e), each stage between the first and last stages (i.e. Blank level parameter Based on the law of conservation of heat, this embodiment sets the initial temperature of the cold utility logistics to 20 ℃ and the target temperature to 30 ℃; the blank stage parameters for each stage from the first stage to the last stage are obtained by solving. Afterwards, cold chain logistics blank level parameters It can also be solved using formula (184f); (184); (184a); (184b); (184c); (184d); (184e); (184f); After processing all blank-level parameters for both thermal and cold utility logistics, it is necessary to determine the required cold logistics for thermal utilities using formula (183). The blank level parameters of the corresponding thermal utility logistics , , and The calculation process is shown in formulas (185a) to (185d); similarly, the heat flow of the required cold utility needs to be determined for formula (184). The corresponding blank level parameters of cold utility logistics. , , and The calculation is performed as shown in formulas (185a) to (185d).

[0067] First, the cold flow required for the thermal utility is determined using formula (185a). cold chain logistics Heat exchange occurs in the first stage of the thermal utility system, and its heat exchange... Should be equal to This allows us to determine the relevant blank level parameters in the first level; then, the cold flow rate is calculated using formula (185b) and the heat conservation formula. First-level blank level parameters Calculate cold flow using formula (185c) First-level blank level parameters ; Calculate cold flow using formula (185d) First-level blank level parameters Next, the heat flow required for the cold utility is determined using formula (186a). hot logistics Heat exchange occurs in the final stage of the cooling utility system, and its heat exchange... Should be equal to This allows us to determine the relevant blank stage parameters in the last stage; then, the heat flow is calculated using formula (186b) and the heat conservation formula. The last level of blank level parameters The thermal flow is calculated using formula (186c). The last level of blank level parameters ; Calculate the heat flow using formula (186d) The last level of blank level parameters .

[0068] (185a); (185b); (185c); (185d); (186a); (186b); (186c); (186d); Thus, all blank-level parameters for cold streams (cold process streams and cold utility streams) and hot streams (hot process streams and hot utility streams) in the multi-level superstructure have been processed. To further improve the comprehensiveness and accuracy of the parameter representation of the heat exchanger network flow diagram by the multi-level superstructure, it is necessary to convert the hot-end temperature difference and cold-end temperature difference of the heat exchanger in the heat exchanger network flow diagram, as well as the available temperature difference and heat exchanger area, into blank-level parameters in the multi-level superstructure. Simultaneously, to ensure the non-negativity constraints of the subsequent superstructure model, enabling its application in practical process solutions, negative values ​​need to be eliminated using formulas (190a) to (192b). First, the hot-end temperature difference of the heat exchanger is converted into blank-level parameters in the multi-level superstructure using formula (187). The cold-end temperature difference of the heat exchanger is converted into blank stage parameters in the multi-stage superstructure using formula (188). Then, the heat exchanger area is converted into blank stage parameters in the multi-stage superstructure by calculating the average value of formula (189) (or by using the logarithmic mean temperature difference). Then, negative values ​​are eliminated using formulas (190a) to (192b). Formula (190a) indicates that if... If the value is negative, then it will be calculated using formula (190b). Set to 0; Formula (191a) indicates if If the value is negative, then it will be determined using formula (191b). Set to 0; Formula (192a) indicates that if If the value is negative, then it will be determined using formula (192b). Set to 0; finally, convert the heat exchanger area into blank stage parameters in the multi-stage superstructure using formula (193). .

[0069] (187); (188); (189); (190a); (190b); (191a); (191b); (192a); (192b); (193); This embodiment uses formulas (175) to (193) to make the converted multi-level superstructure more consistent with the actual operating conditions of the heat exchanger network flowchart, thereby improving the accuracy and comprehensiveness of the conversion of the heat exchanger network flowchart into a multi-level superstructure.

[0070] Please refer to Figure 9 , Figure 9 This diagram illustrates a multi-level superstructure provided by an embodiment of the present invention, showcasing a HEN topology for a petrochemical atmospheric and vacuum distillation unit under a minimum heat transfer temperature difference of 14°C, corresponding to a hot pinch temperature of 275°C and a cold pinch temperature of 261°C. This topology comprises 16 hot streams (hot process streams i1 to i15 and hot utility stream i16) and 11 cold streams (cold process streams j1–j10 and cold utility stream j11). The numbers on either side of the streams represent the starting and ending temperatures of the cold and hot streams, respectively. This structure is derived from a flowchart designed based on the M-INI model using the conversion method proposed in this invention. It includes 52 heat exchangers, including 38 process stream heat exchangers and 14 utility heat exchangers (i.e., hot and cold utilities, specifically 2 heaters and 12 air coolers), with utility consumption consistent with theoretical calculations. Figure 9 As shown, this multi-level superstructure can clearly express cold and hot streams, as well as their flow patterns.

[0071] This embodiment determines the initial cold stream stage and initial hot stream stage of each heat exchanger by using the stream temperature data of each heat exchanger in the heat exchanger network flowchart. This ensures that the process of converting the heat exchanger network flowchart into a multi-stage superstructure is strictly based on the actual process stream logic, and that the generated multi-stage superstructure can be equivalently converted to the heat exchanger network flowchart. Then, using the pinch point, a key thermodynamic boundary, the heat exchanger network flowchart is divided into regions above and below the pinch point. The initial cold stream stage and initial hot stream stage of the heat exchanger in each region are then updated respectively, which can accurately and effectively construct the final cold stream stage and final hot stream stage for solving the multi-stage superstructure. By calculating the superstructure parameters and the total number of stages of the multi-stage superstructure, the generated multi-stage superstructure has the minimum number of stages, thereby minimizing the redundant variables and constraints of the multi-stage superstructure and improving the conversion efficiency and solution efficiency of the multi-stage superstructure.

[0072] Please refer to Figure 10 , Figure 10 A schematic diagram of a system for converting a heat exchanger network flowchart into a multi-stage superstructure according to an embodiment of the present invention includes: a heat exchanger initial stage determination module 201, a final stage determination module 202 for the material flow in the region above the pinch point, a final stage determination module 203 for the material flow in the region below the pinch point, a superstructure parameter determination module 204, and a multi-stage superstructure conversion module 205. The heat exchanger initial stage determination module 201 is used to acquire a heat exchanger network flowchart, and based on the material flow temperature data of each heat exchanger in the heat exchanger network flowchart, determine the initial cold material stage and the initial hot material stage of each heat exchanger; and divide the heat exchanger network flowchart into a region above the pinch point and a region below the pinch point. The final stage determination module 202 is used to update the initial cold material stage and the initial hot material stage of each heat exchanger in the region above the pinch point, and determine the final stage of each heat exchanger in the region above the pinch point. The module 203 for determining the final stage of cold and hot streams in the region below the pinch point is used to update the initial cold and hot stream stages of each heat exchanger in the region below the pinch point, and determine the final stage of cold and hot streams in each heat exchanger in the region below the pinch point. The module 204 for determining the superstructure parameters in the region below the pinch point and the total number of superstructure stages in the multi-level superstructure is used based on the final stages of cold and hot streams of the heat exchangers. The module 205 for converting the heat exchange network flowchart into a multi-level superstructure based on the final stages of cold and hot streams of each heat exchanger, combined with the superstructure parameters in the region below the pinch point, the superstructure parameters in the region above the pinch point, and the total number of superstructure stages in the multi-level superstructure.

[0073] This invention, through the material temperature data of each heat exchanger in the heat exchanger network flowchart, determines the initial cold material stage and the initial hot material stage of each heat exchanger. This ensures that the process of converting the heat exchanger network flowchart into a multi-stage superstructure is strictly based on the actual process material logic, guaranteeing that the generated multi-stage superstructure and the heat exchanger network flowchart can be equivalently converted. Then, using the pinch point—a key thermodynamic boundary—the heat exchanger network flowchart is divided into regions above and below the pinch point. The initial cold material stage and the initial hot material stage of the heat exchanger in each region are then updated, accurately and effectively constructing the final cold material stage and the final hot material stage for solving the multi-stage superstructure. By calculating the superstructure parameters and the total number of stages of the multi-stage superstructure, the generated multi-stage superstructure has a minimum number of stages, thereby minimizing redundant variables and constraints in the multi-stage superstructure and improving the conversion and solution efficiency.

[0074] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A method for converting a heat exchanger network flow chart into a multi-stage superstructure, characterized in that, include: Obtain a heat exchanger network flowchart, and based on the material temperature data of each heat exchanger in the heat exchanger network flowchart, determine the initial cold material stage and the initial hot material stage of each heat exchanger; and divide the heat exchanger network flowchart into a region above the pinch point and a region below the pinch point. The initial cold stream stage and initial hot stream stage of each heat exchanger in the region above the pinch are updated to determine the final cold stream stage and final hot stream stage of each heat exchanger in the region above the pinch, thereby determining the superstructure parameters of the region above the pinch. The initial cold stream stage and initial hot stream stage of each heat exchanger in the region below the pinch are updated to determine the final cold stream stage and final hot stream stage of each heat exchanger in the region below the pinch. Based on the final stage of the cold flow and the final stage of the hot flow of the heat exchanger, the superstructure parameters of the region below the pinch point and the total number of superstructure stages of the multi-level superstructure are determined. Based on the final stage of cold and hot flow of each heat exchanger, and combining the superstructure parameters of the region below the pinch point, the superstructure parameters of the region above the pinch point, and the total number of superstructure stages of the multi-stage superstructure, the heat exchange network flowchart is converted into a multi-stage superstructure.

2. The method for converting a heat exchanger network flow chart into a multi-stage superstructure as described in claim 1, characterized in that, The process of obtaining the heat exchanger network flowchart involves determining the initial cold stream stage and the initial hot stream stage for each heat exchanger based on the stream temperature data of each heat exchanger in the flowchart. The heat exchange network flowchart is divided into a region above the pinch point and a region below the pinch point, including: Obtain the heat exchanger network flowchart and determine the material flow temperature data of each heat exchanger in the heat exchanger network flowchart, wherein the material flow temperature data includes: the hot material inlet temperature and the cold material inlet temperature of each heat exchanger; Based on the inlet temperature of the hot stream for each heat exchanger, the heat exchange sequence of each heat exchanger in its respective hot stream is determined. Based on the cold stream inlet temperature of each heat exchanger, the heat exchange sequence of each heat exchanger in the cold stream is determined. The initial heat flow stage of each heat exchanger is determined based on the heat exchange sequence of the heat flow in which each heat exchanger is located. The initial cold stream stage of each heat exchanger is determined based on the heat exchange sequence of the cold stream in which each heat exchanger is located. The heat exchange network flow chart is divided into a region above the pinch point and a region below the pinch point. The region above the pinch point includes: a non-pinch region above the pinch point and a pinch region above the pinch point; the region below the pinch point includes: a non-pinch region below the pinch point and a pinch region below the pinch point.

3. The method for converting a heat exchanger network flow chart into a multi-stage superstructure as described in claim 1, characterized in that, The process of updating the initial cold stream stage and initial hot stream stage of each heat exchanger in the region above the pinch point, determining the final cold stream stage and final hot stream stage of each heat exchanger in the region above the pinch point, and further determining the superstructure parameters of the region above the pinch point includes: The region above the clamp includes: the non-clamp region above the clamp and the clamp region above the clamp; Select a number of first heat exchangers located in the non-pinch region above the pinch point, and determine the final stage of cold flow and the final stage of hot flow for each of the first heat exchangers located in the non-pinch region above the pinch point based on the initial cold flow stage and the initial hot flow stage of each first heat exchanger. Select several third heat exchangers located in the pinch region above the pinch point, and determine the cold flow diversion result and hot flow diversion result for each third heat exchanger; based on the cold flow diversion result and hot flow diversion result of each third heat exchanger, update the initial cold flow stage and initial hot flow stage of each third heat exchanger, and determine the final cold flow stage and final hot flow stage of each third heat exchanger located in the pinch region above the pinch point; The cold flow final stage and hot flow final stage of each of the first heat exchangers, and the cold flow final stage and hot flow final stage of each of the third heat exchangers, are taken as the cold flow final stage and hot flow final stage of each of the heat exchangers located in the region above the pinch point. Based on the cold and hot flow final stages of each heat exchanger located in the region above the pinch point, and in conjunction with the flow temperature data of each heat exchanger located in the region above the pinch point, the superstructure parameters of the region above the pinch point are determined.

4. The method for converting a heat exchanger network flow chart into a multi-stage superstructure as described in claim 3, characterized in that, The process of screening a plurality of first heat exchangers located in the non-pinch region above the pinch point, and determining the final stage of the cold flow and the final stage of the hot flow for each first heat exchanger located in the non-pinch region above the pinch point based on the initial cold flow stage and the initial hot flow stage of each first heat exchanger, includes: Based on the cold flow inlet temperature data of each heat exchanger, a number of first heat exchangers in the non-pinch region above the pinch point are selected, and a number of first cold flow items in the non-pinch region above the pinch point are determined based on the first heat exchangers. Based on the preset logistics direction, the first heat exchanger on each first cold chain is marked to determine the initial replacement heat exchanger for each first cold chain. Based on the initial updated heat exchanger of each first cold stream, the initial cold stream stage and initial hot stream stage of the first heat exchanger on each first cold stream are iteratively updated until each first heat exchanger on each first cold stream determines its own cold stream final stage and hot stream final stage. In each update of the first cold stream, several second heat exchangers on the first cold stream where the initial updated heat exchanger is located are selected that need to be updated; the initial cold stream level and the initial hot stream level of the initial updated heat exchanger are compared; if the initial hot stream level of the initial updated heat exchanger is greater than or equal to the initial cold stream level, the initial cold stream level of the initial updated heat exchanger is updated, thereby determining the final cold stream level and the final hot stream level of the initial updated heat exchanger; and the initial cold stream level and the initial hot stream level of each second heat exchanger are updated; after the update of each second heat exchanger is completed, the next second heat exchanger of the initial updated heat exchanger is used as the initial updated heat exchanger for the next update; if the initial hot stream level of the initial updated heat exchanger is less than the initial cold stream level, the final cold stream level and the final hot stream level of the initial updated heat exchanger are determined based on the initial cold stream level and the initial hot stream level of the initial updated heat exchanger; and the next second heat exchanger of the initial updated heat exchanger is used as the initial updated heat exchanger for the next update.

5. The method for converting a heat exchanger network flow chart into a multi-stage superstructure as described in claim 3, characterized in that, The process involves screening several third heat exchangers located in the pinch region above the pinch point, and determining the cold flow diversion result and hot flow diversion result for each of the third heat exchangers. Based on the cold stream diversion results and hot stream diversion results of each of the third heat exchangers, the initial cold stream stage and initial hot stream stage of each of the third heat exchangers are updated, and the final cold stream stage and final hot stream stage of each of the third heat exchangers located in the pinch region above the pinch point are determined, including: Select several third heat exchangers located in the pinch region above the pinch point, and determine the cold flow diversion result and hot flow diversion result for each third heat exchanger; wherein, the cold flow diversion result includes: diverted cold flow and non-diverted cold flow; the hot flow diversion result includes: diverted hot flow and non-diverted hot flow. If the cold stream of the third heat exchanger is a non-splitting cold stream and the hot stream is a split hot stream, then based on the split hot stream of the third heat exchanger, determine a number of first branch heat exchangers corresponding to the third heat exchanger; based on the initial cold stream stage of the first branch heat exchanger, update the initial hot stream stage of the third heat exchanger, and then determine the final cold stream stage and the final hot stream stage of the third heat exchanger. If the cold stream in which the third heat exchanger is located is a split cold stream and the hot stream in which it is located is a non-split hot stream, then based on the split cold stream in which the third heat exchanger is located, several second branch heat exchangers corresponding to the third heat exchanger are determined; based on the initial hot stream stage of the second branch heat exchanger, the initial cold stream stage of the third heat exchanger is updated, and then the final cold stream stage and the final hot stream stage of the third heat exchanger are determined. If the cold stream of the third heat exchanger is a split cold stream and the hot stream of the third heat exchanger is a split hot stream, then based on the split hot stream of the third heat exchanger, a number of first branch heat exchangers of the third heat exchanger are determined; based on the initial cold stream stage of the second branch heat exchanger, the initial hot stream stage of the second branch heat exchanger is updated, and the common stream stage of the third heat exchanger is determined; and based on the common stream stage, the final hot stream stage and the final cold stream stage of the third heat exchanger are determined.

6. The method for converting a heat exchanger network flow chart into a multi-stage superstructure as described in claim 3, characterized in that, The step of updating the initial cold stream stage and initial hot stream stage of each heat exchanger in the region below the pinch point, and determining the final cold stream stage and final hot stream stage of each heat exchanger in the region below the pinch point, includes: The region below the grip includes: the non-grip region below the grip and the grip region below the grip; Select several fourth heat exchangers located in the pinch region below the pinch point, and determine the cold flow diversion result and hot flow diversion result for each of the fourth heat exchangers; based on the cold flow diversion result and hot flow diversion result of each of the fourth heat exchangers, determine the final stage of cold flow and the final stage of hot flow for each of the fourth heat exchangers located in the pinch region below the pinch point. Select several fifth heat exchangers located in the non-pinch region below the pinch point, and determine the cold flow type and hot flow type of each fifth heat exchanger; based on the fourth heat exchanger, and in combination with the cold flow type and hot flow type of each fifth heat exchanger, determine the final stage of the cold flow and the final stage of the hot flow for each fifth heat exchanger located in the non-pinch region below the pinch point.

7. The method for converting a heat exchanger network flow chart into a multi-stage superstructure as described in claim 6, characterized in that, The process involves screening several fourth heat exchangers located in the pinch region below the pinch point, and determining the cold flow diversion result and hot flow diversion result for each of the fourth heat exchangers. Based on the cold stream diversion results and hot stream diversion results of each of the fourth heat exchangers, the final stage of the cold stream and the final stage of the hot stream of each of the fourth heat exchangers located in the pinch region below the pinch point are determined, including: Select several fourth heat exchangers located in the pinch region below the pinch point, and determine the cold flow diversion result and hot flow diversion result for each fourth heat exchanger; wherein, the cold flow diversion result includes: diverted cold flow and non-diverted cold flow; the hot flow diversion result includes: diverted hot flow and non-diverted hot flow. Based on the cold flow inlet temperature and hot flow outlet temperature of the third heat exchanger, the preceding cold flow side heat exchanger and the preceding hot flow side heat exchanger of each of the fourth heat exchangers are determined; based on the preceding cold flow side heat exchanger and the preceding hot flow side heat exchanger, the initial cold flow stage and the initial hot flow stage of each of the fourth heat exchangers are updated to determine the first cold flow stage and the first hot flow stage of each of the fourth heat exchangers. If the cold stream and the hot stream of the fourth heat exchanger are both non-splitting cold streams, then the size of the first cold stream stage and the first hot stream stage of the fourth heat exchanger are compared, and the final cold stream stage and the final hot stream stage of the fourth heat exchanger are determined based on the comparison result. Based on the final cold stream stage and the final hot stream stage of the fourth heat exchanger, the first cold stream stage of the other fourth heat exchangers located in the cold stream or the first hot stream stage of the other fourth heat exchangers located in the hot stream of the fourth heat exchanger are updated. If the cold stream in which the fourth heat exchanger is located is a non-splitting cold stream and the hot stream in which it is located is a split hot stream, then based on the split hot stream in which the fourth heat exchanger is located, several third branch heat exchangers corresponding to the fourth heat exchanger are determined; based on the initial cold stream stage of the third branch heat exchanger, the maximum cold stream stage corresponding to the fourth heat exchanger is determined; based on the maximum cold stream stage and the first hot stream stage corresponding to the fourth heat exchanger, the final cold stream stage and the final hot stream stage of the fourth heat exchanger are determined. If the cold stream in which the fourth heat exchanger is located is a split cold stream and the hot stream in which it is located is a non-split hot stream, then based on the split cold stream in which the fourth heat exchanger is located, several fourth branch heat exchangers corresponding to the fourth heat exchanger are determined; based on the initial hot stream stage of the fourth branch heat exchanger, the maximum cold stream stage corresponding to the fourth heat exchanger is determined; and based on the maximum cold stream stage and the first cold stream stage corresponding to the fourth heat exchanger, the final cold stream stage and the final hot stream stage of the fourth heat exchanger are determined. If the cold stream in which the fourth heat exchanger is located is a branch cold stream and the hot stream in which it is located is a branch hot stream, then based on the branch hot stream in which the fourth heat exchanger is located, several fifth branch heat exchangers corresponding to the fourth heat exchanger are determined; based on the initial cold stream stage of the fifth branch heat exchanger, the maximum stage on the cold stream side and the maximum stage on the hot stream side of the fourth heat exchanger are determined, and then based on the maximum stage on the cold stream side and the maximum stage on the hot stream side of the fourth heat exchanger, the final stage on the cold stream side and the final stage on the hot stream side of the fourth heat exchanger are determined.

8. The method for converting a heat exchanger network flow chart into a multi-stage superstructure as described in claim 7, characterized in that, The process of screening several fifth heat exchangers located in the non-pinch region below the pinch point and determining the cold flow type and hot flow type of each fifth heat exchanger; based on the fourth heat exchanger, and in conjunction with the cold flow type and hot flow type of each fifth heat exchanger, determining the final stage of the cold flow and the final stage of the hot flow for each fifth heat exchanger located in the non-pinch region below the pinch point, includes: Select several fifth heat exchangers located in the non-pinch region below the pinch point, and determine the cold flow type and hot flow type of each fifth heat exchanger; If the cold flow type of the fifth heat exchanger is a preset third cold flow type or a preset fourth cold flow type, the fourth heat exchanger corresponding to the fifth heat exchanger is determined based on the cold flow in which the fifth heat exchanger is located, and the number of non-split heat exchangers between the fifth heat exchanger and the corresponding fourth heat exchanger in the cold flow in which the fifth heat exchanger is located is determined; the final stage of the cold flow of the fifth heat exchanger is determined based on the final stage of the cold flow of the fourth heat exchanger corresponding to the fifth heat exchanger and the number of non-split heat exchangers; If the heat flow type of the fifth heat exchanger is a preset third heat flow type or a preset fourth heat flow type, the fourth heat exchanger corresponding to the fifth heat exchanger is determined based on the heat flow in which the fifth heat exchanger is located, and the number of non-split heat exchangers between the fifth heat exchanger and the corresponding fourth heat exchanger in the heat flow in which the fifth heat exchanger is located is determined; the final stage of the heat flow of the fifth heat exchanger is determined based on the final stage of the heat flow of the fourth heat exchanger corresponding to the fifth heat exchanger and the number of non-split heat exchangers; If the cold stream type of the fifth heat exchanger is a preset fifth cold stream type or the hot stream type is a preset fifth hot stream type, then the initial cold stream stage and the initial hot stream stage of the fifth heat exchanger are compared, and based on the comparison result, the final hot stream stage and the final cold stream stage of the fifth heat exchanger are determined.

9. The method for converting a heat exchanger network flow chart into a multi-stage superstructure as described in claim 7, characterized in that, The determination of the superstructure parameters and the total number of superstructure levels in the region below the pinch point, based on the final stages of the cold and hot streams of the heat exchanger, includes: Based on the heat capacity flow rate of each hot stream in the heat exchanger network flowchart, the virtual heat exchanger hot stream stage is determined; based on the heat capacity flow rate of each cold stream in the heat exchanger network flowchart, the virtual heat exchanger cold stream stage is determined. Based on the final stage of the cold flow for each heat exchanger in each cold flow, blank level parameters are filled for each cold flow; based on the final stage of the cold flow for the leftmost heat exchanger in each cold flow, blank level parameters are filled for the leftmost heat exchanger in each cold flow. Based on the final stage of the cold flow of each heat exchanger in each hot flow, blank level parameters are filled for each hot flow; based on the final stage of the hot flow of the leftmost heat exchanger in each hot flow, blank level parameters are filled for the leftmost heat exchanger in each hot flow. Based on the blank level parameters, determine the superstructure parameters of the region below the grip point; Obtain the number of cold utilities in the heat exchanger network flowchart, and determine the total number of superstructure levels based on the number of cold utilities to determine the problem type. The problem types for determining the total number of superstructure levels include: pinch problem and threshold problem. If the problem type for determining the total number of superstructure levels is a pinch problem, then the blank level parameters for hot and cold streams are refilled to redetermine the superstructure parameters in the region below the pinch. Then, based on the maximum value of the final stage of the hot stream in the heat exchanger, the total number of superstructure levels of the multi-stage superstructure is determined. If the problem type for determining the total number of superstructure levels is a threshold problem, then the total number of superstructure levels of the multi-level superstructure is determined based on the maximum value of the final stage of the heat flow in the heat exchanger.

10. A system for converting heat exchanger network flow charts into multi-stage superstructures, characterized in that, include: The heat exchanger initial stage determination module, the final stage logistics determination module for the region above the pinch point, the final stage logistics determination module for the region below the pinch point, the superstructure parameter determination module, and the multi-stage superstructure conversion module; The heat exchanger initial stage determination module is used to obtain the heat exchange network flowchart, and based on the material temperature data of each heat exchanger in the heat exchange network flowchart, determine the initial cold material stage and the initial hot material stage of each heat exchanger; and divide the heat exchange network flowchart into a region above the pinch point and a region below the pinch point. The final stage determination module for the logistics in the region above the pinch is used to update the initial cold flow stage and the initial hot flow stage of each heat exchanger in the region above the pinch, determine the final stage of the cold flow stage and the final stage of the hot flow stage of each heat exchanger in the region above the pinch, and then determine the superstructure parameters of the region above the pinch. The final stage determination module for the logistics in the region below the pinch is used to update the initial cold flow stage and the initial hot flow stage of each heat exchanger in the region below the pinch, and to determine the final stage of the cold flow stage and the final stage of the hot flow stage of each heat exchanger in the region below the pinch. The superstructure parameter determination module is used to determine the superstructure parameters of the region below the pinch point and the total number of superstructure stages of the multi-stage superstructure based on the final stage of the cold flow and the final stage of the hot flow of the heat exchanger. The multi-level superstructure conversion module is used to convert the heat exchange network flowchart into a multi-level superstructure based on the final stage of the cold flow and the final stage of the hot flow of each heat exchanger, combined with the superstructure parameters of the region below the pinch point, the superstructure parameters of the region above the pinch point, and the total number of superstructure stages of the multi-level superstructure.

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